Method suitable for recycling textile waste

Abstract

The present invention relates to a method suitable for recovering textile waste comprising a polyester yarn containing a dye, the method comprising: a first step in which the polyester yarn is treated with a solvent to extract a portion of the dye from the polyester yarn; a second step in which the solvent-treated polyester yarn is subjected to a process in which the polyester is depolymerized into an oligoester consisting on average of between 3 and 30 monomeric units wherein the remainder of the dye is removed from the oligoester by adsorption to particulate matter in a mixture with the oligoester; and a third step in which the oligoester is separated from the particulate matter comprising the adsorbed dye, thereby providing a decolorized oligoester suitable for repolymerization, consisting on average of between 3 and 30 monomeric units.

Description

Technical Field

[0001] This invention relates to the field of recycling dyed textile waste, particularly materials including semi-crystalline polyesters (such as, for example, polyethylene terephthalate (PET)). Background Technology

[0002] Polyesters (such as PET, commonly used in soda bottles, and yarn materials used in textile production) are typically recycled. The post-consumer polyester recycling industry began due to environmental pressures to improve waste management. Another driving force behind the polyester recycling industry is the slow rate of natural decomposition of polyester products. Many polyesters are non-degradable plastics under normal conditions because there are no known organisms that can consume their relatively large molecules. Making polyester biodegrade requires complex and expensive procedures.

[0003] The world's first recycling effort for polyester waste (i.e., post-consumer polyester objects or materials) occurred in the 1970s, but the development of comprehensive recycling methods has evolved rapidly. For example, in 2000, Australia's total PET consumption was 88,258 tonnes, of which 28,113 tonnes were recycled, indicating a recycling rate of approximately 32%. Many researchers have reported that PET flakes should meet specific minimum requirements for successful PET recycling. The main factor affecting the suitability of post-consumer PET flakes for recycling is the level and nature of contaminants present in the flakes. Minimizing the amount of these contaminants leads to better rPET (i.e., recycled PET) quality. Due to the use of PET bottles for storing these substances, PET is contaminated with many substances, such as acid-producing contaminants, water, coloring contaminants, acetaldehyde, and other contaminants (such as detergents, fuels, pesticides, etc.).

[0004] Various different methods have been applied to recycle polyester waste, each with its own advantages and disadvantages.

[0005] Extensive applications are so-called energy recovery methods, such as pyrolysis and carbonization. Pyrolysis of polyester waste was first described in the early 1980s. It is an alternative to PET disposal in landfills. Generally, polyester waste is pyrolyzed without further purification of the plastic waste. Most pyrolysis is carried out to produce aliphatic and aromatic hydrocarbons as alternatives to fossil fuels or as sources of chemicals. Carbonization is a second method for pyrolyzing polyester waste. Next, only the polyester waste is sorted, and the sorted material is then used as an additive in stone mastic asphalt, binders, mortars, or concrete composites.

[0006] In recent years, the chemical recycling of polyester has been developed and applied in practice. In chemical recycling (chemical decomposition) methods, polyester waste is recovered by depolymerization into monomers and / or oligomers. This can be divided into many subcategories depending on the type of reactants used in the chemical decomposition. Examples include the use of ionic liquids or castor oil for depolymerization. Furthermore, polyester polymers can be degraded by enzymes, as first described in the 1970s. Compared to conventional chemical recycling methods, this biochemical method, using ionic liquids and castor oil, has been developed to provide an environmentally friendly process for polymer recycling. However, it is quite inefficient compared to the complete depolymerization of polyester, and therefore, quantitatively recovering homogeneous reaction products for reuse is not possible.

[0007] Alcohololysis for the depolymerization of PET was first described in the early 1990s. This method was developed to avoid the drawbacks of acidic and alkaline hydrolysis (pollution problems) and to provide polymers with a renewable and more environmentally friendly degradative agent. Typically, polyesters are polymerized using excess alcoholysis to produce corresponding esters of the corresponding acid and ethylene glycol. Among alcoholysis methods, the reaction with methanol has gained particular importance due to methanol's low price and availability. Furthermore, ethylene glycol (a diol, whose uses are sometimes separately classified as "glycolysis," although it belongs to the alcoholysis category) is primarily used in reactive extrusion to produce low molecular weight oligomers.

[0008] Because amine groups are more reactive than hydroxyl groups or alcohols used in the alcoholysis of polyesters, aminolysis and ammonolysis have been developed for polyester recycling. However, for alcoholysis, a metal catalyst is still required.

[0009] Finally, controlled depolymerization of polyester using a defined amount of depolymerizing agent to block chain scission provides an alternative to chemical recycling of polyester. Compared to existing chemical methods (such as alcoholysis), this method produces polyester oligomers with well-defined molecular weights over a wider range. However, this method requires sorted polyester material that must be free of contaminants.

[0010] All chemical recycling methods require the removal of any dyes from the polymer to ensure high-end reuse of the recycled material. In the art, numerous methods are described for achieving (almost complete) removal of dyes from polymeric materials, particularly from polyester yarns derived from textile materials.

[0011] US Patent 2015 / 0059103 (transferred to Far Eastern New Century Corporation of Taiwan) discloses a method for decolorizing dyed polyester yarn. The method includes providing dyed polyester yarn stained with a dye and a solvent capable of completely dissolving the dye. In this method, the solvent is heated to generate fresh vapor at a relatively high temperature, within the range between the glass transition temperature and melting point of the polyester. The fresh vapor is then condensed to form a condensed fluid of the solvent, and the dyed polyester yarn is subsequently contacted with the condensed fluid of the solvent to dissolve the dye, thereby extracting the dye from the yarn to form an easily separable dye-containing solution and decolorized polyester yarn. It is difficult to find a solvent that can completely decolorize the yarn without causing chemical decomposition of the polyester.

[0012] US Patent 2022 / 0169786 (granted to Sintech Corporation and Jeplan Inc., both Japanese companies) discloses a method for producing decolorized polyester using a decolorizing agent containing a glycol ether-type compound having a boiling point of 160°C or higher at atmospheric pressure. The method includes the steps of removing dye by contacting the decolorizing agent with the dyed polyester at least once while heating the decolorizing agent to a temperature equal to or below the melting point of the polyester, thereby obtaining decolorized polyester. Depending on the type of decolorizing agent, this method can be efficient, but at the cost of very high energy consumption and carries a serious risk of polyester chemical decomposition.

[0013] US Patent 2020 / 0270790 (granted to Nan Ya Plastics Corporation of Taiwan) discloses a method for decolorizing dyed polyester yarn. The method includes providing an ether alcohol solvent and heating the solvent to its boiling point to continuously generate fresh gas at temperatures ranging from 90°C to 200°C. This allows dye to be extracted from the polyester yarn, forming an extract condensate containing the dye, which can be refluxed back into the ether alcohol solvent. This process must be repeated multiple times to extract all the dye from the polyester yarn. This is a time-consuming and energy-intensive method.

[0014] Nanya Corporation was assigned another recent patent application, US 2023 / 0093536, which involves extracting hydrophobic compounds from polyester yarns in addition to dyes. In this method, a composite solvent containing a mixture of water and acetic acid is used for the extraction process. This extraction process includes permeating the polyester yarn (which may be in the form of an intact fabric) with the composite solvent and extracting the dye and hydrophobic agent. A liquid polycondensation reaction is then carried out on the polyester fabric, increasing the intrinsic viscosity of the polyester fabric and further removing residual impurities.

[0015] Nanya Corporation was assigned another recent patent application, US 2003 / 0080748. This patent application describes the removal of any colorant adhering to the surface of a polymer material, which may be pre-extracted, after which the polymer is broken down into its monomer units, i.e., BHET in the case of polyester. Decomposition into BHET is crucial to this method and ensures that any colorant is released into the fluid material and can be removed using any adsorbent material, such as activated carbon. Especially for dark yarns containing large amounts of colorant, a large amount of activated carbon is required.

[0016] US 7192988 (assigned to Invista) describes a method for depolymerizing PET and subsequently removing any released colorants by a combination of adsorption to particulate matter (such as activated carbon) and solvent extraction. This allows the amount of carbon to be kept to a minimum, ensuring economically viable purification of the monomer.

[0017] JP 200533044 (assigned to IS KK) discloses a method for recovering ester monomers from polyester yarn, comprising the steps of: extracting by contacting the polyester yarn with an ethylene glycol extractant until a low degree of color is achieved, and thereafter depolymerizing and purifying the ester monomers.

[0018] WO 2022 / 003084 (assigned to CURE Technologies) describes a method in which a polymer is broken down into low-viscosity oligomers before any dye is removed, from which the dye can be removed using activated carbon or another particulate material that adsorbs the dye and can be easily mixed through and filtered from the material. However, in addition to the time-consuming and energy-intensive process of separating carbon from the oligomer melt, the recovery of the large amount of activated carbon required for complete dye removal is a serious drawback of this method. Moreover, the combination of a more viscous oligomer material and activated carbon means that the amount of colorant that can be removed in this way is limited.

[0019] There is a need for an improved method for decolorizing polymer yarns to facilitate the recycling of textile waste. In particular, there is a need for decolorizing polymer yarns where the polymer material mass is dyed, and where the purification of any resulting depolymerization products is relatively easy. Summary of the Invention

[0020] To achieve the objectives of this invention, a method has been designed for decolorizing dyed polyester yarn to recover textile waste including such polyester yarn. The method includes: a first step in which the polyester yarn is treated with a solvent to extract a portion of the dye from the polyester yarn; a second step in which the solvent-treated polyester yarn is subjected to a method in which the polyester is depolymerized into a low-polymer consisting of an average of 3 to 30 monomer units, wherein a remaining portion of the dye is removed from the low-polymer by adsorption onto particulate matter mixed with the low-polymer; and a further step in which the low-polymer is separated from the particulate matter including the adsorbed dye. Thus, a decolorized low-polymer, consisting of an average of 3 to 30 monomer units, suitable for repolymerization is provided. This decolorized low-polymer has been found to be ideally suited for repolymerization into high-quality polyester. Surprisingly, even in the polymer bulk, the amount of colorant that can be removed by solvent extraction is so high that it seems unnecessary to depolymerize the remaining material into its monomer units, and the remaining colorant can still be removed at a very high level using particulate adsorbent materials (such as activated carbon).

[0021] It should be noted that the particulate matter can be actively mixed into the low-polyester (or mixed with the polyester before the polyester is depolymerized, so as to produce the desired mixture after the depolymerization), or passively mixed, for example by pumping the low-polyester (which is liquid due to its low level of polymerization) through the bed of the particulate material, or by any other means capable of forming a mixture of particulate matter and low-polyester.

[0022] It should also be noted that the separation step of separating the low-polyester from the particulate matter is not limited to the step of actively separating the low-polyester from the particulate matter. For example, if in this method the low-polyester is pumped through a solid bed of particulate material, separation between the two components inherently occurs at the end of the bed.

[0023] This invention is particularly based on the understanding that by combining two methods (i.e., partial removal of dye with a solvent, and removal of the remainder with a particulate adsorbent after the polyester has been broken down into oligomers), greater operational freedom is provided, while allowing for very high purification of the polymer material without depolymerizing it into its monomer units: the choice of solvent is far less critical because it is not necessary to remove the entire amount of dye by an extraction step. Moreover, a favorable polymer decomposition can be chosen (which is usually not necessary when the aim is to recover the polymer), since the polymer will be broken down into oligomers for repolymerization anyway. Furthermore, the removal of the remaining dye from the oligomers with a particulate adsorbent is less critical because the amount to be removed may be far less than the total amount of dye present in the original polyester yarn. Therefore, for example, a less efficient adsorbent can be chosen as a trade-off for easier (economically advantageous) separation or reactivation, or other methods can be chosen if they are more advantageous in the overall process.

[0024] Crucially, oligomers typically consist of a maximum of 30 monomer units, as otherwise the viscosity would be too high to easily mix and / or separate particulate matter from the oligomer. Nevertheless, a number of monomer units below 3 is also less advantageous due to the need for repolymerization into polyester. If the number of units in the oligomer is less than 3, repolymerization takes too much time. This time not only costs money but also carries the risk of unwanted degradation of the polyester.

[0025] In the first step of this invention, a solvent capable of dissolving dyes is used, such as, for example, alcohols, ethers, ketones, aliphatic and aromatic hydrocarbons, oils, fats, waxes, and chlorinated hydrocarbons. It has been found that not only can colorants adhering to the surface of the yarn be removed, but colorants present in the polymer material bulk can also be removed.

[0026] For the second step in the method of this invention, a highly porous adsorbent with good selectivity is typically used. Activated carbon has demonstrated excellent ability to remove organic compounds such as dyes. Adsorption of dyes onto an adsorbent can be achieved through physical or chemical methods. In physical adsorption mechanisms, dye molecules attach to the adsorbent surface under the influence of van der Waals forces and hydrogen bonds. During chemisorption, dye molecules or ions attach themselves to specific surface functional groups or sites via chemical bonds. Many different dye functional groups can participate in various adsorption attachments over a wide range of available adsorbents.

[0027] definition PolyesterPolyesters are polymers in which monomer units are linked together by ester groups. They are typically formed by polymerizing polyhydric alcohols with polybasic acids and are mainly used in the manufacture of resins, plastics, and textile fibers. Polyesters are well known to be prepared by condensation polymerization, in which monomers providing the "acid component" (including their ester derivatives) react with monomers providing the "hydroxyl component." If desired, polyesters may also include other linking groups, such as, for example, a certain proportion of carbonylamine linking groups -C(=O)-NH- (i.e., amide linking groups) or -C(=O)-NR. 2 - (tertiary amide linkage group). Polyesters used in everyday life can be aliphatic, semi-aromatic, or aromatic. Typical examples are polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate, and condensation products of Vectran®, 4-hydroxybenzoic acid, and 6-hydroxynaphthalene-2-carboxylic acid. Among these PETs, also abbreviated as PETE, or the obsolete PETP or PET-P, it is the most common thermoplastic polymer resin in the polyester family, and the raw material is considered one of the most important engineering polymers of the past few decades. It is considered an excellent material for many applications and is used in clothing fibers, containers for liquids and food, thermoforming, and in combination with glass fiber for engineering resins. It is also mentioned by brand names such as Terylene, Arnite, Eastapac, Mylar, Lavsan, and Dacron. Polyester articles (such as polyester yarns) can contain up to 50% (w / w) of non-polyester polymer chains (e.g., 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%) while still being referred to as polyester articles.

[0028] dye It is a colored substance that is chemically bonded to the substrate to which it is applied. Typically, dyes impart color to the substrate when applied from an aqueous or organic solvent in a solution.

[0029] pigment It is a completely or nearly insoluble colored substance. In contrast, dyes are usually soluble, at least at some stage of their use.

[0030] Post-consumer textile waste Post-consumption fabrics are those that are used at or after the end of their consumption period (i.e., the time during which consumers use them for practical or aesthetic purposes).

[0031] Depolymerization This means reducing the molecular weight by breaking down the original polyester molecules into shorter molecules (e.g., into oligomers).

[0032] Polyurethane Polyurethane refers to a class of polymers composed of organic units linked by carbamate bonds. Polyurethane articles (such as polyurethane fibers or polyurethane adhesive drops) may contain up to 50% (w / w) of non-polyurethane polymer chains (e.g., 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%) while still being referred to as polyurethane articles.

[0033] DGME It is 2-(2-ethoxyethoxy)ethanol, a colorless liquid. It is produced by the ethoxylation of ethanol.

[0034] elastic fibers It is a polymer known as polyurethane, which is a polyether-polyurea copolymer. Elastic fiber fabric is a general term used to describe branded textiles such as Lycra®. This type of fabric is also known as Spandex®, and its main property is its incredible elasticity. Although Lycra®, Spandex®, and elastic fiber are all the same material, the regional variant of the term "elastic fiber" is most commonly used to refer to this type of fabric.

[0035] Quantity of items Part This means less than the total quantity or the complete item.

[0036] oligomers Oligomers are chemically bonded monomer chains with up to 50 subunits. The term oligomer usually refers to a mixture of molecules with different lengths (or different amounts of subunits) and is typically expressed as their average number of subunits.

[0037] Particulate matter This means that the substance includes solid particles, that is, small, localized objects that can be described by several physical or chemical properties, such as volume, density, or mass. Typically, particles are macroscopic particles, such as powders and other granular materials.

[0038] Adsorption To particulate matter means to be bonded to the surface of the matter, which does not exclude the possibility that the surface is, for example, the inner surface of a pore.

[0039] mix The two materials imply the combination or blending of these two materials into a macroscopic mass. This mass is preferably macroscopically homogeneous (i.e., on a 5 mm scale, preferably on a scale of 4 mm, 3 mm, 2 mm, 1 mm or even less than 1 mm).

[0040] Chop It is divided into smaller pieces, for example, by cutting.

[0041] Further embodiments of the present invention In a first further embodiment of the method according to the invention, at least 50% (w / w) of dye is extracted from the polyester yarn in the first step, preferably at least 55%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% up to 99%. The more dye extracted in the first step, the less particulate adsorbent needs to be recovered in the second step.

[0042] In a second further embodiment of the method according to the invention, the particulate matter is selected from activated carbon, zeolite, silica gel, activated alumina, inorganic minerals, chitosan, resin particles, carbon nanotubes and aluminum phosphate molecular sieves, with activated carbon (denoted as AC) being the preferred particulate matter.

[0043] In yet another embodiment of the method according to the invention, the method includes the step of filtering the low-polymer using a filter having a mesh size of less than 20 μm, preferably between 5 μm and 10 μm. Due to the low viscosity of the low-polymer, it can be filtered at low cost and with minimal energy to remove any pigments and any other small particulate matter (if present).

[0044] In yet another embodiment of the method according to the invention, the polyester is depolymerized into a low-polymer consisting of an average of between 5 and 20 monomer units. The lower limit of 5 monomer units is advantageous, considering that the oligomers will eventually repolymerize in a higher molecular weight polyester polymer. This requires less time and energy when the starting material has a slightly higher degree of polymerization. The upper limit of 20 monomer units is advantageous for the step of separating particulate matter from the low-polymer and for the use of small screen filters. Above 20 monomer units, increased adhesion means increased cost for such methods.

[0045] In yet another embodiment of the method according to the invention, the solvent used for extracting dye from polyester yarn is an ester or an ether. These types of solvents have been found to be ideally suited to this method. Given that the extraction itself is incomplete in the first step, the solvent actually used is less critical. Nevertheless, it is advantageous that the solvent has a boiling temperature between 140°C and 250°C, preferably between 150°C and 220°C. Since many different, particularly non-polyester, materials used in the production of polyester textiles have melting points in this range, the solvent can be used to selectively remove these specific materials if desired. This has proven particularly advantageous for post-consumer polyester waste streams, given that polyester waste streams almost invariably also include other polymeric materials. Good examples of effective solvents for the invention are solvents selected from alkyl lactate esters or ethylene glycol ethers, preferably ethyl lactate or diethylene glycol monoethyl ether (DGME).

[0046] The inventors have also recognized that a specific “contamination” of polyester textiles is articles containing polyurethane (PUR), such as PUR yarns (e.g., so-called elastic fibers), adhesives, or foams, and have found it advantageous to remove the PUR articles from the polyester yarns by mechanical and / or chemical methods (which are well known in the art) prior to the depolymerization step of the polyester. This is to prevent the PUR articles or products derived therefrom from interfering with the depolymerization process and potentially ultimately resulting in low-polyester composition. Preferably, the PUR articles are removed by using a PUR solvent. This has been found to be a simple way to remove PUR articles before the start of the depolymerization step. It has even been further found that it is highly advantageous to use the same PUR solvent as a portion of the solvent used to extract the dye from the polyester yarn in the first process step.

[0047] Various solvents can be used for this purpose, but DGME is the most preferred solvent. It should be noted that WO2023044699 (granted to the Hong Kong Textile and Apparel Research Institute Limited) describes a method for separating Spandex® (which is a polyurethane yarn) from textile blends using a biological solvent (such as ethyl lactate). The inventors have found that ethyl lactate is extremely inefficient in extracting Spandex® from textile waste, while DGME (not mentioned in WO2023044699 because it is not a biological solvent) is conversely highly efficient. Even more surprisingly, it has been found that after extracting the dye and polyurethane using DGME, a purified form of the PUR polymer can be obtained by pouring the DGME together with the extracted PUR and dye into water. This has resulted in a high-purity PUR fraction in the aqueous fraction.

[0048] In a further embodiment of the method according to the invention, wherein the textile waste includes cotton articles (such as cotton yarn and the like) in addition to polyester yarn, the method is further improved in that the cotton articles are removed from the polyester yarn by mechanical and / or chemical methods (which are well known in the art) prior to the depolymerization step of the polyester. This is to prevent the cotton articles or products derived therefrom from interfering with the depolymerization process and potentially ultimately resulting in low-polyester composition. Typically, cotton is decolored before it is removed from the textile waste. The method for removing cotton articles can be carried out before or after (or simultaneously with) the removal of dye from the polyester yarn.

[0049] In a preferred embodiment of the method according to the invention, polyester is depolymerized into low-polyester by alcoholysis. This method is known in particular from WO2022 / 003084 (assigned to CURE Technologies) and has been found to be particularly suitable for the present invention. In particular, it has been found advantageous to depolymerize polyester into low-polyester by a two-step process comprising two independent consecutive steps, in which alcohol is added to depolymerize the polyester in both separate consecutive steps. Further, it has been found advantageous that in the first step of the two consecutive steps, polyester is fed into an extruder operating at a temperature above the melting temperature of the polyester, while a first amount of alcohol is co-fed into the extruder to produce a fluid mixture comprising a melt of at least partially depolymerized polyester, and in the second step of the two consecutive steps, the fluid mixture is fed into a continuously stirred tank reactor (CSTR) operating at a temperature above the melting temperature of the polyester, while a second amount of alcohol is co-fed into the CSTR to provide low-polyester.

[0050] In yet another embodiment of the method according to the invention, the polyester is polyethylene terephthalate (PET) and the low polyester comprises more than 50% w / w, preferably more than 60% w / w, 65% w / w, 70% w / w, 75% w / w, 80% w / w, 81% w / w, 82% w / w, 83% w / w, 84% w / w, 85% w / w, 86% w / w, 87% w / w, 88% w / w, 89% w / w, or even 90% w / w, 91% w / w, 92% w / w, 93% w / w, 94% w / w, 95% w / w, 96% w / w, 97% w / w, 98% w / w, 99% w / w, or even 100%. Oligomers of 4 to 16 w / w bis(2-hydroxyethyl) terephthalate (BHET) units, preferably 6 to 14 (BHET) units, and most preferably 8 to 10 BHET units.

[0051] In a further embodiment of the method according to the invention, after the dye is extracted with a solvent, the dye is removed from the solvent in a separate step to provide purified dye and purified solvent. This step is known in the art and may be, for example, a simple concentration step, or may include methods such as membrane diffusion or distillation, all aimed at completely recovering the dye and solvent. Accordingly, after separating the low-polyester from the particulate matter containing the adsorbed dye, the dye is removed from the particulate matter to provide purified dye and purified particulate matter.

[0052] Finally, the invention is embodied in a method preceding one or more steps selected from the group consisting of: 1) removing any decorations (such as buttons, zippers, and labels) from the textile waste; 2) washing the textile waste (e.g., removing any coatings, such as DWR (durable hydrophobic coating), or fine spinning oil, dirt, grease, etc.); and 3) shredding the textile waste into smaller pieces. The order in which these steps (which are well known in the art) are performed is not essential for this embodiment.

[0053] The invention will now be further illustrated using specific examples below. Attached Figure Description

[0054] Figure 1 An outline of the method according to the invention is schematically depicted. Detailed Implementation

[0055] Example 1 provides various embodiments, including a two-stage depolymerization method for polyester.

[0056] Example 2 demonstrates the initial decolorization steps of blue fabric using ethyl lactate.

[0057] Example 3 demonstrates the initial decolorization steps of the same blue fabric using DGME.

[0058] Example 4 is an example of initial decolorization of a green fabric using ethyl lactate, wherein the fabric is coated with DWR and contains a small amount of elastic fiber (PUR) yarn mechanically attached to the polyester yarn.

[0059] Example 5 shows the results of bleaching the same green fabric with ethyl lactate at a lower temperature.

[0060] Example 6 is another example of using DGME to decolorize the same green fabric.

[0061] Example 7 was performed to evaluate the use of this method for textile waste containing relatively high amounts of elastic fibers.

[0062] Example 8 demonstrates the dissolution of compressed elastic fibers.

[0063] Example 9 is a further example of the dissolution of compressed elastic fibers.

[0064] Example 10 demonstrates the dissolution of polyurethane foam as an item in textile waste.

[0065] Example 11 demonstrates the use of xylene to decolorize blue fabric.

[0066] Example 12 briefly describes some comparative examples.

[0067] Figure 1 Figure 1 An outline of the method according to the invention is schematically depicted. In the illustrated method, in a first step, a washed and pre-dried mixed polymer waste (in this case, textile waste comprising elastic fibers and dyed PET yarns) is treated with DGME to extract the majority of the dye from the polyester yarns and dissolve all the elastic fiber yarns. Subsequently, the PET is partially separated from the liquid DGME and depolymerized and repolymerized in a continuous process through steps 2 to 8, while removing any remaining dye (and pigment) from the PET. Step 9 is an additional repolymerization step (comprising solid-state polymerization) to achieve an intrinsic viscosity (IV) greater than 0.6.

[0068] The depolymerization method is based on the well-known equilibrium reaction of PET in the alcoholysis of monoethylene glycol (MEG): BHET [PET]x + ½ x MEG By adding MEG to the polyester melt, the equilibrium shifts to the left, resulting in shorter polymer chains, ultimately forming oligomers (less than 100 repeating BHET units, particularly less than 50, 40, 30, 20, or even 10 units) and reducing viscosity. By removing the MEG, for example by using a vacuum or nitrogen, the short chains react with each other to reform the polyester. The viscosity of the material is controlled by controlling the depolymerization rate and thus the oligomer length.

[0069] In step 1, the material is treated with DGME by dispersing the textile waste in DGME and applying continuous mixing. This extracts the majority of the dye from the polyester yarn while completely dissolving the elastic fiber yarn. We refer to a further example below, which demonstrates that DGME is ideally suited for this step compared to other solvents. Next, in step 2, the partially decolorized polyester portion is fed into a conical co-rotating twin-screw extruder. This extruder operates at 280°C to completely melt the polyester. An injection point (indicated by arrow 50) for feeding MEG is provided near the end of the conical twin-screw extruder (at 10% of its length) to achieve the first step of depolymerization, thereby reducing viscosity. For this purpose, approximately 1% MEG (w / w) is fed. The reduction in IV also helps to minimize the pressure differential throughout the first filtration step 3, allowing filtration with an 80-micron sieve size. The filter also acts as a static mixer to homogenize the mixture and distribute it by adding diols and molten polymers to fully react with the shorter polymer chains, thus achieving the molecular weight distribution at equilibrium (dispersion order of approximately 2). Method parameters are selected such that the MEG reacts (almost) completely, and there is no longer (almost none) free MEG.

[0070] In step 4, the partially depolymerized and filtered material is fed into a single-screw extruder. Typically, approximately 3% to 4% MEG is fed into this extruder (indicated by arrow 50'). At the end of the extruder, the viscosity of the melt is measured. The viscosity level is determined by an automatic control loop (in...). Figure 1 (Not specified) The automatic control loop controls the level of MEG fed into the single-screw extruder. This automatic control loop results in a consistent viscosity, typically between 0.1 and 0.2 IV, independent of the starting material's IV. Due to the inherent transesterification reaction occurring in the extruder, polydispersity can be maintained at a low level, preferably around 2 to 3, which depends primarily on the residence time in the extruder (which can be adjusted in this method by controlling the initial feed and extruder speed).

[0071] In step 5, the depolymerized material is filtered a second time. Due to an IV of approximately 0.15, the filter size can be reduced compared to the first filter, preferably to 40 micrometers, while the pressure difference above the filter is not too high.

[0072] In step 6, a material with an IV of approximately 0.15 (0.1 to 0.2) is continuously added to a continuous stirred tank reactor (CSTR). MEG (indicated by arrow 50") is also added to this CSTR to further depolymerize the material to the desired viscosity / oligomer length.

[0073] In the CSTR, further decolorization is performed by adding activated carbon, indicated by arrow 60. Activated carbon can be pre-selected for optimal performance to adsorb any residual colorant (i.e., dye) present in the polyester waste. Following the CSTR, a low-viscosity oligomer / activated carbon mixture is pumped through a three-step microfiltration (20 / 10 / 5 microns) step 7 to remove colorant-loaded carbon particles from the oligomer. The three filters are installed in parallel sets such that if the pressure differential above the filters becomes too high, the melt can be pumped through these parallel sets, while simultaneously cleaning the first filter set.

[0074] After filtration, the melt is still at approximately 250°C. At a high temperature of C, the melt is pumped to a vacuum of 1 mbar at approximately 260°C. A polycondensation reactor operated at temperature C (step 8) to remove MEG results in a rightward shift of the BHET / PET equilibrium to form a PET polymer. Due to the processing conditions, a polyester with an IV between 0.4 and 0.6 is obtained. The polymer is removed from the reactor and pumped through a perforated template, producing polymer strands (polymeric strands). These strands are cooled and cut into amorphous granules to produce new polyester products.

[0075] Example 1 Example 1 describes a two-stage depolymerization method according to the present invention and the overall decolorization of the resulting low-polyester. Specifically, this example provides results achieved through alcoholysis, particularly glycolysis, using MEG as a reactant for the depolymerization of PET in a single-screw extruder in conjunction with CSTR, configured as a continuous process. This method is described in detail in International Patent Application WO 2022 / 003084 (Example 2). Although used in that patent application for recycling carpet and bottle waste, it is equally applicable to textile waste including polyester yarn.

[0076] Reactive extrusion tests were performed using up to 3% w / w MEG and dried PET yarn. The glycolysis process proceeds very rapidly. PET is depolymerized into oligomers within 30 seconds. The dosed MEG reacts almost completely within this timeframe. Over 98% of the dosed MEG has been used in the glycolysis process.

[0077] HPLC analysis confirmed that significant amounts of BHET were converted to tetramers when 12% MEG or more were applied (see Table 1). However, depolymerization has not been necessary so far to enable melt filtration. A viscosity of (IV = ±) 0.1 is sufficient for the filtration method. This corresponds to 8-10 (octadecanoic) oligomers. This would require 5% to 8% MEG w / w.

[0078] Table 1. Analysis of oligomers (relative to pure BHET)

[0079] At this relatively low viscosity (approximately 0.1 IV), it is very easy to remove any remaining colorant by adsorbing residual dye using activated carbon or any other particulate material. Activated carbon itself, as well as any pigment (if present), can be removed by using the methods described above. Figure 1 The described filter is used to remove [the pollutants].

[0080] Example 2 Example 2 demonstrates the initial decolorization process of blue pure polyester fabric using the solvent ethyl lactate. First, a total of 75 g of blue fabric, typically used as a sofa cover and made of PET fibers, was cut into small pieces and subsequently loaded into a 500 mL glass reactor equipped with a condenser, thermometer, and nitrogen inlet. Next, 450 g of ethyl lactate was added, and the contents of the glass reactor were slowly heated to reflux (150°C to 155°C) using a heating jacket with continuous magnetic stirring. After reaching reflux conditions, the contents of the glass reactor were maintained under these conditions for 60 minutes. During this period, visible removal of the colorant was aided by the ethyl lactate solvent, which is dark green to blue and appears transparent. The less colored fabric pieces were then separated from the dark green to blue solvent containing the colorant removed by standard solid-liquid filtration.

[0081] The fabric sheet from the first colorant removal step was then loaded into the same glass reactor used for the color removal step, followed by 450 g of fresh ethyl lactate. The contents of the glass reactor were slowly heated to reflux (150°C to 155°C) using a heating jacket under continuous magnetic stirring. After reaching reflux conditions, the contents of the glass reactor were maintained under these conditions for 60 minutes. During this period, the visible removal of the colorant was aided by the ethyl lactate solvent, resulting in the fabric sheet exhibiting only a slight green tint and the solvent exhibiting a dark green to blue tint. The slightly green fabric sheet was separated from the dark green to blue solvent containing the colorant removed by standard solid-liquid filtration.

[0082] It is estimated that approximately 60% to 80% of the dye is removed from the fabric by extraction methods.

[0083] Example 3 Example 3 demonstrates the same initial decolorization steps for the polyester blue fabric used in Example 2, but now using diethylene glycol monoethyl ether (DGME) as the solvent. First, a total of 20 g of fabric was cut into small pieces and then loaded into a 500 mL glass reactor equipped with a condenser, thermometer, and nitrogen inlet. Next, 125 g of DGME was added, and the contents of the glass reactor were slowly heated to reflux (200°C to 205°C) with continuous magnetic stirring. During heating, the fabric pieces showed almost complete color removal and were solvent-colored orange to red and appeared transparent. After reaching the reflux conditions, the contents of the glass reactor were held under these conditions for 15 minutes. The decolorized fabric pieces (slightly yellow) were then separated from the orange to red solvent containing the removed colorant by standard solid-liquid filtration.

[0084] It is estimated that approximately 90% to 95% of the dye content is removed from the fabric by extraction methods. This partially decolorized material can be used as input to a depolymerization process, in which activated carbon is used to remove the remaining dye.

[0085] Example 4 Example 4 is an initial example of decolorizing a green fabric with a so-called durable hydrophobic (DWR) coating on its surface using ethyl lactate. This was to evaluate whether dye could be extracted from polyester in the presence of a common coating. First, 1 g of green fabric with a DWR coating on its surface was cut into small pieces. This green fabric was intended for outdoor applications and was primarily made of PET fibers and 2% elastane. Next, 60 g of ethyl lactate was added to a 150 mL glass beaker equipped with a thermometer, and the contents of the beaker were slowly heated to 150°C (slightly below boiling point) with a hot plate under continuous magnetic stirring. When the preset temperature was reached, the fabric pieces were added to the glass beaker, and the resulting mixture was maintained at 150°C for 15 minutes. During this period, visible removal of the colorant was aided by the ethyl lactate solvent, resulting in a slightly green fabric piece and a dark green solvent. The slightly green fabric piece was then separated from the green solvent containing the colorant removed by standard solid-liquid filtration. After drying, a drop of water is applied to the surface of a piece of fabric that has been primarily decolorized. The droplet remains intact and does not spread (wet) above the surface, indicating the presence of a hydrophobic coating on the fabric surface.

[0086] It is estimated that despite the presence of a DWR coating, over 80% w / w of dye is removed from the fabric by extraction methods. This indicates that it is possible to extract dye from polyester articles using solvents, even when a DWR surface coating is present.

[0087] Example 5 This example demonstrates the results of decolorizing green fabric with ethyl lactate at a lower temperature. First, 1 g of the same DWR-coated green fabric used in Example 4 was cut into small pieces. This green fabric is intended for outdoor applications and is primarily composed of PET fibers and 2% elastane. Next, 45 g of ethyl lactate was added to a 150 mL glass beaker equipped with a thermometer, and the contents of the beaker were slowly heated to 185°C with a hot plate under continuous magnetic stirring. When the preset temperature was reached, the fabric pieces were added to the glass beaker, and the resulting mixture was maintained at 85°C for 15 minutes. During this period, only partial removal of the colorant was achieved with the assistance of the ethyl lactate solvent, which imparted a deep green hue to the solvent, while the fabric pieces remained dark. The fabric pieces were then separated from the green solvent containing the decolorized colorant by standard solid-liquid filtration. After drying, a drop of water was applied to the surface of a primarily decolorized piece of fabric. The droplet remained intact and did not spread (wet) above the surface, indicating the presence of a hydrophobic coating on the fabric surface.

[0088] It is estimated that dyes with less than 50% w / w are extracted by solvent extraction.

[0089] Example 6 Example 6 is another example of decolorizing a green fabric containing a small amount of elastic fiber (PUR) yarn mechanically bonded to polyester yarns using diethylene glycol monoethyl ether (DGME). First, a total of 2 g of the same DWR-coated green fabric used in Example 4 was cut into small pieces. This green fabric was intended for outdoor applications and was primarily composed of PET fibers and 2% w / w elastic fibers. Next, 80 g of DGME was added to a 150 mL glass beaker equipped with a thermometer, and the contents of the beaker were slowly heated to 180°C using a hot plate with continuous magnetic stirring. When the preset temperature was reached, the fabric pieces were added to the glass beaker, and the resulting mixture was maintained at 180°C for 15 minutes. The fabric pieces showed almost complete color removal, were solvent-red, and appeared transparent after 5 minutes.

[0090] Next, the almost completely decolorized fabric sheet (light green) was separated from the red solvent containing the removed colorant by standard solid-liquid filtration. After filtration, a white solid material began to form and precipitate in the coloring solvent. This material is assumed to contain or be a polyurethane polymer used to make elastic fiber yarns. After the fabric sheet dried, a drop of water was applied to the surface of a primarily decolorized piece of fabric. The droplet remained intact and did not spread (wet) above the surface, indicating the presence of a hydrophobic coating on the fabric surface.

[0091] Example 7 This example was performed to evaluate the use of the method on textile waste containing a relatively high amount of elastic fibers. First, a total of 10 g of black fabric, intended for outdoor applications and made of PET fibers, was cut into small pieces and mechanically bonded by weaving approximately 27% (w / w) elastic fibers. Next, 50 g of diethylene glycol monoethyl ether (DGME) was added to a 150 mL glass beaker equipped with a thermometer, and the contents of the beaker were slowly heated to 180°C with a hot plate under continuous magnetic stirring. When the preset temperature was reached, the fabric pieces were added to the glass beaker, and the resulting mixture was maintained at 180°C for 60 minutes. During this period, visible removal of the colorant was assisted by the DGME solvent, resulting in the fabric pieces appearing gray and the solvent appearing dark gray to black. Furthermore, it was noted that the fabric structure of the pieces changed, as observed by the slightly wrinkled appearance of the pieces and the pieces adhering together. The gray fabric pieces were then separated from the gray to black solvent containing the colorant removed by standard solid-liquid filtration. Next, the gray to black filtrate was poured into a 300 mL glass beaker containing 150 mL of demineralized water. Immediately after pouring, a dark gray suspension formed, with some solid material appearing to float for several hours. The solid material was then separated from the dark gray suspension by standard solid-liquid filtration to produce a dark gray residue that was subsequently dried in a vacuum. Standard analysis of the dried residue revealed a good match with an elastic fiber reference, and the dried residue was obtained in a yield of 2.45 g, indicating almost complete removal and recovery of the polyurethane from the elastic fibers present in the textile waste.

[0092] Example 8 Example 8 demonstrates the dissolution of compressed elastic fibers. First, the elastic fibers were partially cut and hydraulically compressed (10 kN) on a heated plate for 30 minutes, and then the elastic fiber sheet was cut into small pieces. Next, 0.5 g of elastic fiber pellets and 50 g of diethylene glycol monoethyl ether (DGME) were added to a 100 mL glass beaker equipped with a thermometer, and the contents of the beaker were slowly heated to 180°C with continuous magnetic stirring using a heated plate. At the preset temperature, the elastic fiber pellets dissolved after a first stage of swelling at a lower temperature. After 10 minutes, an additional 12 g of elastic fiber pellets were added. The elastic fiber pellets dissolved completely within 10 minutes, resulting in a yellow and transparent solution. Over the next 60 minutes, the solution turned a slightly darker yellow, after which it was cooled to room temperature, becoming slightly opaque.

[0093] Example 9 Example 9 is a further example of the dissolution of compressed elastic fibers. First, the elastic fibers were processed into pellets as in Example 8. Next, 50 g of diethylene glycol monoethyl ether (DGME) was added to a 150 mL glass beaker equipped with a thermometer, and the contents of the glass beaker were slowly heated to 180°C with a heating plate under continuous magnetic stirring. Next, 0.5 g of elastic fiber pellets and 50 g of DGME were added to a 100 mL glass beaker equipped with a thermometer, and the contents of the glass beaker were slowly heated to 180°C with a heating plate under continuous magnetic stirring. At a preset temperature, 2.5 g of elastic fiber pellets were added to the glass beaker, and the temperature of the resulting mixture was maintained at 180°C. The elastic fiber pellets dissolved easily after initial swelling, and the resulting solution appeared slightly yellow and transparent. Next, an additional 2.5 g of elastic fiber pellets was added to the DGME solvent containing the first dissolved portion of the elastic fiber pellets. Similar to the first portion of the elastic fiber pellets, the second portion dissolves readily after initial swelling, resulting in a slightly darker yellow solution. After the second portion of the elastic fiber pellets dissolves, 2.5 g of the third portion of the elastic fiber pellets is loaded into a glass beaker containing both the first and second dissolved portions. Similar to the first and second portions of the elastic fiber pellets, the third portion dissolves readily after initial swelling, resulting in a slightly darker yellow solution compared to the previously dissolved portion.

[0094] A total of 25 g of elastic fiber pellets, representing 40% of the DGME solvent, were loaded into the DGME solvent and dissolved over 2 to 2.5 hours to produce a deep yellow to brown solution. This solution became slightly opaque after loading 15 g of elastic fiber pellets, or 30% of the DGME solvent. The opaque, deep yellow to brown solution, comprising 20 g of the dissolved elastic fiber pellets or 40% of the DGME solvent, was then poured into a 500 mL glass beaker containing 350 mL of demineralized water. Immediately after pouring, a yellow strand formed, which solidified into yellow spherical articles that deposited at the bottom of the glass beaker within minutes. The yellow solid articles were then separated from the slightly opaque demineralized water by standard solid-liquid filtration and dried under vacuum. Almost 20 g of elastic fiber was recovered, indicating that the elastic fiber was almost completely removed.

[0095] Example 10 This example illustrates the dissolution of polyurethane foam, an article found in textile waste. First, a large sheet of yellow, flexible polyurethane foam, intended for use as the interior of a mattress, was cut into smaller pieces. Next, 0.25 g of the cut foam pieces and 50 g of diethylene glycol monoethyl ether (DGME) were added to a 100 mL glass beaker equipped with a thermometer. The contents of the beaker were then slowly heated to 180°C using a hot plate with continuous magnetic stirring. At the preset temperature, the cut foam pieces exhibited an initial swelling phase at a lower temperature before slowly dissolving. After 10 minutes, the foam pieces were completely dissolved, producing a brown, slightly opaque solution. This brown, slightly opaque solution was maintained at the preset temperature for 30 minutes, after which it was cooled to room temperature. After 72 hours, the solution still appeared brown and opaque, showing no sedimentation, indicating the solubility properties of the foam.

[0096] Example 11 This example demonstrates the decolorization of blue fabric using xylene. First, 75 g of blue fabric, intended for use as a sofa cover and made of PET fiber, was cut into small pieces and loaded into a 500 mL glass reactor equipped with a condenser, thermometer, and nitrogen inlet. Next, 450 g of xylene was added, and the contents of the glass reactor were slowly heated to reflux (140°C to 145°C) with continuous magnetic stirring. After reaching reflux conditions, the contents of the reactor were held at this temperature for 60 minutes. During this period, visible removal of the colorant was aided by the xylene solvent, which is deep blue and appears transparent. The less colored fabric pieces were then separated from the solvent containing the decolorized colorant by standard solid-liquid filtration.

[0097] The fabric sheet from the first colorant removal step was then loaded into a 500 mL reactor, followed by 450 g of fresh xylene. The contents of the glass reactor were slowly heated to reflux (140°C to 145°C) with continuous magnetic stirring. After reaching reflux, the reactor contents were held at this temperature for 60 minutes. During this period, visible removal of the colorant was aided by the xylene solvent, resulting in a bluish tint to the fabric sheet and a deep blue tint to the solvent. The bluish fabric sheet was separated from the solvent containing the colorant removed by standard solid-liquid filtration.

[0098] The fabric sheet from the second colorant removal step was then reloaded into a 500 mL reactor, followed by 450 g of fresh xylene. The contents of the glass reactor were slowly heated to reflux (140°C to 145°C) with continuous magnetic stirring. After reaching reflux, the reactor contents were held at this temperature for 60 minutes. During this period, visible removal of the colorant was aided by the xylene solvent, resulting in a slightly bluish tint to both the fabric sheet and the solvent. The slightly bluish fabric sheet was then separated from the solvent containing the colorant removed by standard solid-liquid filtration.

[0099] The fabric sheet from the third colorant removal step was then reloaded into a 500 mL reactor, followed by 450 g of fresh xylene. The contents of the glass reactor were slowly heated to reflux (140°C to 145°C) with continuous magnetic stirring. After reaching reflux, the reactor contents were held at this temperature for 60 minutes. During this period, the fabric sheet became almost white while the solvent still appeared bluish. The almost white fabric sheet was obtained by separating the solvent using standard solid-liquid filtration.

[0100] Example 12 Example 12 briefly describes several further comparative examples in which DGME was used to attempt to dissolve another type of polymer besides PUR or PET. Experiments were conducted using waste materials containing high-density polyethylene (HDPE) or polybutylene terephthalate (PBT) in addition to dyed polyesters. HDPE appeared not to dissolve in DGME, at least not in significant quantities. PBT also did not dissolve.

Claims

1. A method for recycling textile waste, the waste comprising polyester yarn containing dyes, the method comprising the following sequential steps: The first step involves treating the polyester yarn with a solvent to extract a portion of the dye from the polyester yarn. The second step involves subjecting the solvent-treated polyester yarn to a method in which the polyester is depolymerized into a low-polyester consisting of an average of 3 to 30 monomer units, wherein any remaining dye is removed from the low-polyester by adsorption of particulate matter mixed with the low-polyester. The third step involves separating the low-polyester from the particulate matter containing the adsorbed dye, thereby providing a decolorized low-polyester suitable for repolymerization, consisting on average of 3 to 30 monomer units.

2. The method according to claim 1, characterized in that, In this first step, at least 50% of the dye is extracted from the polyester yarn, preferably at least 60%, 70%, 80% or even 90%.

3. The method according to any one of the preceding claims, characterized in that, The particulate matter is selected from activated carbon, zeolite, silica gel, activated alumina, inorganic minerals, chitosan, resin particles, carbon nanotubes, and aluminophosphate molecular sieves.

4. The method according to any one of the preceding claims, characterized in that, The method includes the step of filtering the low polyester using a filter with a sieve pore size of less than 20 μm, preferably between 5 μm and 10 μm.

5. The method according to any one of the preceding claims, characterized in that, The polyester is depolymerized into a low-polymer that consists of an average of 5 to 20 monomer units.

6. The method according to any one of the preceding claims, characterized in that, The solvent used to extract the dye from the polyester yarn is an ester or an ether.

7. The method according to claim 6, characterized in that, The solvent has a boiling temperature between 140°C and 250°C, preferably between 150°C and 220°C.

8. The method according to claim 6 or 7, characterized in that, The solvent is selected from alkyl lactate or ethylene glycol ether, preferably ethyl lactate or diethylene glycol monoethyl ether (DGME).

9. The method according to any one of the preceding claims, wherein, in addition to the polyester yarn, the textile waste also includes polyurethane (PUR) articles, such as PUR yarn, adhesives, or foams, characterized in that, Prior to the depolymerization step of the polyester, the PUR article is removed from the polyester yarn by mechanical and / or chemical methods.

10. The method according to claim 9, characterized in that, The PUR item is removed by using a PUR solvent.

11. The method according to claim 10, characterized in that, The PUR solvent is the same solvent used in the first method step to extract a portion of the dye from the polyester yarn.

12. The method according to claim 11, characterized in that, The solvent is DGME.

13. The method according to claim 12, characterized in that, The purified form of the PUR polymer was obtained by pouring the DGME into water.

14. The method according to any one of the preceding claims, wherein, in addition to the polyester yarn, the textile waste also includes cotton articles, such as cotton yarn, characterized in that, Prior to the depolymerization step of the polyester, the cotton article is removed from the polyester yarn by mechanical and / or chemical methods.

15. The method according to any one of the preceding claims, characterized in that, The polyester is depolymerized into low-polyester by alcoholysis.

16. The method according to claim 15, characterized in that, The polyester is depolymerized into a low-polymer by a two-step process comprising two independent consecutive steps, in which alcohols are added to depolymerize the polyester in both separate consecutive steps.

17. The method according to claim 16, characterized in that, In the first step of the two consecutive steps, the polyester is fed into an extruder operating at a temperature above the melt temperature of the polyester, while a first amount of alcohol is co-fed into the extruder to produce a fluid mixture comprising a melt of at least partially depolymerized polyester. In the second step of the two consecutive steps, the fluid mixture is fed into a continuously stirred tank reactor (CSTR) operating at a temperature above the melt temperature of the polyester, while a second amount of alcohol is co-fed into the CSTR to provide the low-polymer polyester.

18. The method according to any one of the preceding claims, wherein the polyester is polyethylene terephthalate (PET), characterized in that, The oligomer comprising more than 50% w / w, preferably more than 60%, 70%, 80%, or even 90% w / w, includes 4 to 16 bis(2-hydroxyethyl) terephthalate (BHET) units, preferably 6 to 14 (BHET) units, and most preferably 8 to 10 BHET units.

19. The method according to any one of the preceding claims, characterized in that, After the dye is extracted with the solvent, the dye is removed from the solvent in a separate step to provide purified dye and purified solvent.

20. The method according to any one of the preceding claims, characterized in that, After separating the low-polyester from the particulate matter containing the adsorbed dye, the dye is removed from the particulate matter to provide purified dye and purified particulate matter.

21. The method according to any one of the preceding claims, characterized in that, The method is preceded by one or more steps selected from the group consisting of: 1) removing any decorations such as buttons, zippers and tags from the textile waste, 2) washing the textile waste, and 3) chopping the textile waste into smaller pieces.

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