Method for preparing a polyester fiber from polyester recycled from a polymer blend

Abstract

In a first aspect, the invention relates to a method for preparing a polyester fiber comprising providing a polymer blend, which comprises (i) a polyester and (ii) one or more component(s) selected from the group consisting of a second polymer, a third polymer, a colorant and a filler, wherein second polymer and third polymer are different from each other and different from the polyester of (i).the method comprising a step (e), wherein a fiber is prepared from a precipitated polyester.

Description

[0001] Method for preparing a polyester fiber from polyester recycled from a polymer blend

[0002] In a first aspect, the invention relates to a method for preparing a polyester fiber comprising providing a polymer blend, which comprises (i) a polyester and (ii) one or more component(s) selected from the group consisting of a second polymer, a third polymer, a colorant and a filler, wherein second polymer and third polymer are different from each other and different from the polyester of (i); the method comprising: (a) providing the polymer blend and providing a solvent system; (b) optionally contacting the polymer blend with the solvent system at a temperature T 1 of < 170 °C, thereby obtaining a solvent system, which is enriched in dissolved second polymer and / or colorant and optionally in the filler or in a part of the filler, and a residue of the polymer blend, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler; (c) contacting the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) with a solvent system at a temperature T2 of > 170 °C, thereby obtaining a solvent system, which is enriched in dissolved polyester compared to the solvent system provided in (a) and comprises optionally the filler or a part of the filler, and optionally a residue of the polymer blend, which is depleted of polyester and comprises optionally the third polymer and optionally the filler or a part of the filler; (d) precipitating the polyester from solvent system, which is enriched in dissolved polyester, obtained in (c), thereby obtaining a precipitated polyester and a solvent system, which is depleted in dissolved polyester and which optionally comprises the filler or a part of the filler; and (e) preparing a fiber from the precipitated polyester obtained in (d). A second aspect of the invention is directed to a polyester fiber, obtained or obtainable from the method of the first aspect; and a third aspect relates to the use of a polyester fiber of the second aspect for preparing a textile. In a fourth aspect, the invention is related to a method for preparing a product comprising (I) providing polyester of the second aspect; and (II) preparing a textile from the polyester provided in (I). A fifth aspect of the invention relates to a method, preferably according to the first aspect, comprising the further step of converting a residue obtainable by or obtained by the process according to the first aspect, to obtain one or more monomer, polymer or polymer product.

[0003] State of the art

[0004] The demand for polymeric materials has drastically increased over the last decades. However, the poor biodegradability has led to large amounts of plastic waste which is in Europe usually incinerated thereby losing valuable materials and generating huge CO2 emissions. Even worse is landfill due to the poor biodegradability. Polymeric materials based on polyesters have been used extensively in the packaging sector, for example, in beverage packaging or food packaging. The vast majority of food and drink today is packaged within plastic bottles and containers, made from, for example, polyester materials comprising polyethylene terephthalate (PET). PET is also a main component of clothing nowadays. As these materials typically have poor biodegradability and are also still valuable products, it is desirable for these plastics to be recovered and recycled.

[0005] Although recycling processes have been adopted to convert the waste materials into new production materials, there are still many problems associated with recycling and recovery of polymeric materials. Waste packaging often includes a mixture of different polymeric materials containing also, for example, colorants. The same applies also for textiles, which also comprise a high amount of colored polymeric materials. Therefore, in order to recycle polymeric materials, it is common to separate polymeric materials based on their color and / or their composition. However, this sorting method is labor intensive and / or requires the use of sorting machines. Regarding removal of colorants, EP 2 784 110 A1 describes the removal of organic colorants from polyethylene terephthalate (PET) flakes from shredded PET bottles by extracting the PET-flakes with ethylene glycol at ambient pressure and at the boiling temperature of the ethylene glycol. US 10,876,240 B2 relates to decolorization of a dyed polyester with gaseous propylene glycol methyl ether. DE 2223466 A1 discloses a method for detaching substances from substrates at elevated temperature with a solvent, wherein the substrate is heated with the aid of the condensing vapor of a liquid, which is miscible with the solvent but does not dissolve the substrate and, subsequently, the heated substrate is treated with the solvent, whereby the substance is separated from the substrate. While several processes are known for removing colorants from polyesters, these processes still suffer disadvantages: Depolymerization or transesterification of colored polymeric material delivers monomers and / or other esters which have to be extensively purified by filtrations, crystallization or distillations. This makes the method very expensive. If decoloration is not achieved, the product quality is low and cannot be re-used in high-value applications. Furthermore, additional components such as further polymers present in a blend are interfering or cannot be removed as the colorant. Further drawbacks are the necessity to use toxic solvents and / or the need to use large quantities of solvents. An approach for recovery of polymeric materials and separation of polymer blends comprising not only polyester but rather further polymers includes the dissolving of the polymeric material combined with precipitation.

[0006] WO 2016 / 12755 A1 discloses an extraction of polyesters from packaging, wherein a first solvent is used for removal of colorants and a second solvent is used to dissolve the polyester. Chen et al. (Wenjun Chen, Yuechao Yang, Xue Lan, Baolong Zhang, Xiaogang Zhang and Tiancheng Mu in Green Chem., 2021 , 23, 4065) describe a method for dissolution and accelerated alkaline hydrolysis of PET. WO 2022 / 221832 A1 describes a method for treatment of a polyethylene terephthalate (PET) stream, wherein a polar solvent is used for dissolution of the PET. The polar solvent is defined based on Hansen parameters, wherein a three dimensional rectangular Hansen room is defined by the parameter for energy from dispersion forces between molecules ( 5D) being in the range of from 15 to 20, the parameter for energy from dipolar intermolecular force between molecules (5P) being in the range of from 4 to 20 and the parameter for energy from hydrogen bonds between molecules (5H) being in the range of from 3 to 10. However, polar solvents were considered as solvents for PET according to said definition, which simply are not suited or are unable to dissolve PET, for example, glycerol triacetate, dimethyl succinate or ethyl levulinate. Thus, even knowing these disclosures, it is still unpredictable therefrom what solvents are precisely suitable to dissolve PET. Furthermore, with an eye on a re-use / re-cycling of the obtained PET, it must be considered detrimental if the PET is degraded during the disso- lution / precipitation steps; however, the state of the art discloses lots of solvents, which, even if some kind of dissolution takes place, are not suited to recover non-degraded PET, meaning that even if some kind of polymeric material was re-obtained, it was degraded, for example, in view of reduced polymer chain lengths, reduced molecular weight etc.

[0007] While all these recycling attempts outlined above were known, it was still not possible to obtain, for example, a textile fiber from such polymer blends, which would be comparable in view of textile properties to a fiber made from a virgin polyester, i.e. a polyester freshly made from the respective monomers via chemical synthesis.

[0008] The technical problem underlying the present invention was thus the provision of a method for recovery of a polyester from a polymeric material, which overcomes these disadvantages, and which especially enables obtaining a fiber therefrom having properties as if made from a virgin polyester.

[0009] In a first aspect, the invention relates to a method for preparing a polyester fiber comprising providing a polymer blend, which comprises

[0010] (i) a polyester and

[0011] (ii) one or more component(s) selected from the group consisting of a second polymer, a third polymer, a colorant and a filler, wherein second polymer and third polymer are different from each other and different from the polyester of (i); the method comprising:

[0012] (a) providing the polymer blend and providing a solvent system;

[0013] (b) optionally contacting the polymer blend with the solvent system at a temperature T1 of < 170 °C, thereby obtaining a solvent system, which is enriched in dissolved second polymer and / or colorant and optionally in the filler or in a part of the filler, and a residue of the polymer blend, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler; (c) contacting the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) with a solvent system at a temperature T2 of > 170 °C, thereby obtaining a solvent system, which is enriched in dissolved polyester compared to the solvent system provided in (a) and comprises optionally the filler or a part of the filler, and optionally a residue of the polymer blend, which is depleted of polyester and comprises optionally the third polymer and optionally the filler or a part of the filler;

[0014] (d) precipitating the polyester from solvent system, which is enriched in dissolved polyester, obtained in (c), thereby obtaining a precipitated polyester and a solvent system, which is depleted in dissolved polyester and which optionally comprises the filler or a part of the filler;

[0015] (e) preparing a fiber from the precipitated polyester obtained in (d).

[0016] It was surprisingly found that the inventive method allows to dissolve and precipitate the polyester and does not have a negative impact on the re-obtained polyester. In particular not only a stop of decrease regarding the Mass average molecular weight Mw of the polyester, which is recovered from the polymer blend, could be achieved but also the number average molecular weight Mn increased. Furthermore, the re-obtained polyester can directly be re-used for fiber preparation wherein the obtained fiber is, for example, in view of its elastic limit in oriented state and Young’s modulus comparable to a fiber obtained from a virgin polyester material. Thus, further processing of the polyester in a, preferably closed, loop recycling method became possible. Preferably, the polymeric material, which preferably comes from textiles, fibers and / or packaging is thus recycled into the same. Naturally, the re-obtained polyester can also be put to any further use without being restricted in this regard. Furthermore, the inventive method allows precipitation of the polyester with minor or no addition of an anti-solvent being favorable in view of solvent recycling.

[0017] “Contacting” in optional step (b) and in step (c) preferably means that the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) is at least partially immersed in the solvent system. Preferably, polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) is at least partially immersed in the solvent system in that at least 60 %, more preferably at least 70 %, more preferably at least 80 %, more preferably at least 90 %, more preferably at least 95 %, more preferably at least 99 % of the surface of the polymer blend provided in (a) or of the residue of the polymer blend optionally obtained in (b) are in contact with the solvent system, based on the total surface of the f the polymer blend provided in (a) or of the residue of the polymer blend optionally obtained in (b) being 100%. Regarding optional step (b), “enriched in second polymer” means that at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, more preferably of the second polymer - if present - comprised in the material provided in (a), are dissolved in the solvent system, based on 100 weight-% of the second polymer - if present- comprised in the material provided in (a). “Depleted of said second polymer” regarding the residue (optionally) obtained in (b) means that < 50 weight-%, preferably < 40 weight-%, more preferably < 30 weight-%, more preferably < 20 weight-%, more preferably < 10 weight-%, more preferably < 5 weight-%, of the second polymer - if present - comprised in the material provided in (a), are still present in the residue, based on 100 weight-% of the second polymer - if present- comprised in the material provided in (a). Regarding optional step (b), “enriched in colorant” means that at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, more preferably at least 95 weight-%, of the colorant - if present comprised in the polyester of the material provided in (a) are dissolved in the solvent system, based on 100 weight-% of the colorant - if present - comprised in the polyester comprised in the material provided in (a). “Depleted of said colorant” regarding the residue (optionally) obtained in (b) means that < 50 weight-%, preferably < 40 weight-%, more preferably < 30 weight-%, more preferably < 20 weight-%, more preferably < 10 weight-%, more preferably < 5 weight-%, of the colorant - if present - comprised in the polyester comprised in the material provided in (a), are still present in the residue, based on 100 weight-% of the colorant - if present - comprised in the polyester comprised in the material provided in (a). This means that colorant, which is comprised in the polyester (i), is comparatively easy removed in step (c), i.e. is dissolved together with the polyester in the solvent system in step (c), whereas colorant being comprised in third polymer - if present- is not easily dissolved but rather remains to a large extend in the third polymer and thus also in the residue comprising said third polymer. Regarding step (c), “solvent system, which is enriched in dissolved polyester compared to the solvent provided in (a)” means that at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight- %, more preferably at least 95 weight-%, of the polyester comprised in the material provided in (a), are dissolved in the solvent system, based on 100 weight-% of the polyester comprised in the material provided in (a). Regarding the optionally obtained residue of the polymer blend of step (c), “depleted of polyester and comprises optionally the third polymer” means that < 50 weight-%, preferably < 40 weight-%, more preferably < 30 weight-%, more preferably < 20 weight-%, more preferably < 10 weight-%, more preferably < 5 weight-%, of the polyester comprised in the material provided in (a), are still present in the residue, based on 100 weight-% of the polyester comprised in the material provided in (a), wherein still at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, more preferably at least 95 weight-%, of the third polymer -if present- comprised in the material provided in (a), are present in the residue, based on 100 weight-% of the third polymer - if present - comprised in the material provided in (a). Regarding step (d), “solvent system, which is depleted in dissolved polyester” means that compared to 100 weight-% of polyester comprised in the solvent obtained in (c), at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, are precipitated and no longer dissolved in the solvent. The expressions “enriched optionally in filler or a part of the filler” regarding the solvent system obtained in (b) and “depleted optionally of the filler or a part of the filler” regarding the residue obtained in (b) mean that, if a filler is present in the polymer blend provided in (a), which is soluble in a solvent system at a temperature T1 , said soluble filler is also dissolved in the solvent system, which is obtained in (b), and, consequently, the residue is depleted thereof. In case that not (only) a filler soluble at T1 is present in the polymer blend provided in (a) but (also) a filler, which is not soluble in a solvent system at a temperature T 1 , said insoluble filler remains in the residue of the polymer blend obtained in (b). If that insoluble filler is then soluble at T2 in a solvent system, said insoluble filler is then dissolved in the solvent system at T2 and, consequently, the solvent system obtained in (c) is enriched in said filler and the residue obtained in (c) is depleted thereof. In cases where the polymer blend provided in (a) comprises only filler(s) soluble in a solvent system at a temperature T1 , no filler remains in the residue of the polymer blend obtained in (b), and consequently, also the residue obtained in (c) does not contain filler(s). In cases where only filler(s) insoluble in in a solvent system at a temperature T2 are contained in the polymer blend provided in (a), all filler(s) remain(s) in the residue of the polymer blend obtained in (b), but are, consequently, then all dissolved in the solvent system at T2 and thus, the residue obtained in (c) does not contain filler. In cases where the polymer blend provided in (a) comprises filler(s) insoluble in in a solvent system at a temperature T1 and filler(s) insoluble in in a solvent system at a temperature T2, these insoluble filler(s) is / are retained in the residue obtained in (c).

[0018] Precipitation in (d) - cooling

[0019] In some embodiments of the method, precipitation in (d) comprises cooling the solvent obtained in (c), which is enriched in dissolved polyester compared to the solvent provided in (a), from T2 to a temperature below 140°C, wherein cooling is done so that the temperature of the solvent system, which is enriched in dissolved polyester, is within the temperature range of from 160 to 145 °C for a period of time of at least 5 minutes, preferably at least 10 minutes, more preferably in the range from 5 to 120 minutes, more preferably in the range of from 10 to 100 minutes, more preferably in the range of from 15 to 100 minutes. In some embodiments of the method, cooling in (d) is done so that the solvent system, which is enriched in dissolved polyester, in the temperature range of from 160 to 145 °C has a viscosity in the range of from 1 to 12 Pa s, more preferably in the range of from 1 to 10 Pa s, determined according to ASTM D445.

[0020] In some embodiments of the method, cooling is done with a cooling rate < 3.0 °C / min, more preferably < 1.5 °C / min, more preferably in the range of from 0.05 to 3.0 °C / min, more preferably in the range of from 0.13 to 3.0 °C / min, more preferably in the range of from 0.15 to 1.5 °C / min, more preferably in the range of from 0.15 to 1.0 °C / min.

[0021] In some embodiments of the method, the cooling of the solvent system in (d) is done from T2 to a temperature below 100°C.

[0022] In some embodiments of the method, the cooling of the solvent system in (d) is done from T2 to a temperature below 100°C using a cooling rate < 3.0 °C / min, preferably < 1.5 °C / min, more preferably in the range of from 0.05 to 3.0 C / min, more preferably in the range of from 0.13 to 3.0 °C / min, more preferably in the range of from 0.15 to 1.5 °C / min, more preferably in the range of from 0.15 to 1.0 °C / min.

[0023] In some embodiments of the method, the cooling of the solvent system in (d) is done without addition of an antisolvent. An “antisolvent” is a solvent having a solubility regarding the polyester < 1 g / kg at a temperature in the range of from 20 to 25 °C. In some embodiments, only a small amount of one or more antisolvent(s) is / are added to and / or is / are present in the solvent system in step (d), wherein a small amount means that less than 5 weight-%, preferably less than 4 weight-%, more preferably less than 3 weight-%, more preferably less than 2 weight-%, more preferably less than 1 weight-% of antisolvent(s) is / are added and / or is / are present based on the total weight of the solvent system including the antisolvent(s) being 100 weight-%.

[0024] Fiber preparation in (e)

[0025] In some embodiments of the method, (e) comprises

[0026] (e.1) optionally melt extrusion of the precipitated polyester obtained in (d), thereby obtaining an extrudate comprising the polyester;

[0027] (e.2) optionally pelletizing the extrudate obtained in (e.1), thereby obtaining an extrusion product comprising the polyester in pellet form;

[0028] (e.3) fiber preparation from the precipitated polyester obtained in (d) or from the extrusion product comprising the polyester in pellet form obtained in (e.2), to give a polyester fiber. The optional step (e.1) optionally comprises vacuum application during melt extrusion, wherein the pressure is preferably in the range of from 1 to 1013 mbar, more preferably in the range of from 5 to 100 mbar. The vacuum is maintained for a period of time in the range of from 1 to 30 minutes. Said vacuum application removes residual water, and results in polymerization, which in turn results in an increase of intrinsic viscosity.

[0029] In some embodiments of the method, melt-extrusion in step (e.1) is done at a temperature of >250 °C, more preferably in the range of from 250 to 300 °C.

[0030] In some embodiments of the method, the extrusion product comprising the polyester in pellet form obtained in (e.2) is dried at a temperature in the range of from 60 to 160 °C, optionally under vacuum.

[0031] In some embodiments of the method, wherein fiber preparation of (e.3) is done by a method selected from the group of melt spinning, electrospinning, wet spinning, matrix spinning and a combination of two or more of these methods, preferably by melt spinning.

[0032] In some embodiments of the method, fiber preparation of (e.3) by melt spinning, comprises (e.3.1) providing precipitated polyester obtained in (d) or the polyester in pellet form obtained in (e.2);

[0033] (e.3.2) melting the polyester provided in (e.3.1) at a temperature in the range of from 250 to

[0034] 300 °C, preferably in an extruder, thereby obtaining melted polyester;

[0035] (e.3.3) optionally filtering the melted polyester, thereby obtaining a filtered melted polyester;

[0036] (e.3.4) extrusion of the melted polyester of (e.3.2) or of the filtered melted polyester obtained in (e.3.3), preferably through a spinning nozzle, thereby obtaining at least one fiber filament.

[0037] In some embodiments of the method, fiber preparation comprises

[0038] (e.3.5) optionally combining two or more fiber filaments obtained in (e.3.4) to obtain a fiber;

[0039] (e.3.6) collecting the at least one fiber filament obtained in (e.3.4) or the fiber obtained in

[0040] (e.3.5) on a ribbon, preferably with a speed of the ribbon of at least 500 m / min, more preferably in the range of from 1000 to 3000 m / min.

[0041] A filament is a continuous and flexible strand that is used in the production of textiles.

[0042] A fiber is an elongated aggregate of polymeric molecules, which are predominantly oriented in one direction of the space. Fibers can be monofilament or can consist of multi-filaments. Fibers have very different lengths but for all fibers, the length is larger than the diameter. The fiber obtained or obtainable from (e), (e.3), (e.3.4) or (e.3.4), preferably from (e.3), (e.3.4) or (e.3.6), has an elastic limit in the oriented state of more than 15 cN / tex, preferably in the range of from 15 to 70 cN / tex, determined according to DIN 53816:1993-02. Furthermore, the Young’s modulus of the fiber in oriented state is in the range of from 400 to 900 cN / tex, determined according to DIN 53834-1:1976-02.

[0043] Intermediate steps

[0044] In some embodiments, the method comprises, if (b) is conducted, after (b) and before (c):

[0045] (v) washing the residue of the polymer blend obtained in (b) with a washing solvent, thereby obtaining a washed residue, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler;

[0046] (w) optionally drying the washed residue obtained in (v).

[0047] Washing in optional step (v) is preferably done with a solvent system having features (s.1 ), (s.2) and (s.3) as defined herein, preferably with a solvent system comprising one or more of the solvents) of any one of the groups defined herein. Preferably, washing in optional step (v) is done with the same solvent system as used for (b). In some embodiments, washing is done with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water or a mixture of two or more of these solvents. In some embodiments, the washing in optional step (v) is done with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water, GVL, or a mixture of two or more of these solvents. Drying in optional step (w) is preferably done under one or more conditions selected from the group consisting of a pressure in the range of from 1 to 1013 mbar; a temperature in the range of from 50 to 210 °C, preferably in the range of from 60 to 180°C, more preferably in the range of from 80 to 160 °C; drying time in the range of from 30 minutes to 24 hours; drying in an atmosphere comprising nitrogen, preferably in an atmosphere having at least 90 volume-%, more preferably 95 volume-%, more preferably at least 98 volume-% nitrogen. Drying is done by one or more methods selected from the group consisting of contact drying, convection drying and radiation drying. Contacting in step (c) is then done based on the washed (and optionally dried) residue obtained in (b).

[0048] In some embodiments, the method comprises, after (c) and before (d)

[0049] (x.1) separating the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, obtained in (c) from the residue of the polymer blend, wherein the separation is preferably done by heated filtration, more preferably by heated filtration at a temperature T3 in the range of from T2 minus 20 °C to T2 plus 20 °C (T3 = T2 ± 20°C), more preferably at a temperature T3 in the range of from T2 minus 10 °C to T2 plus 10 °C (T3 = T2 ± 10°C), thereby obtaining the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, separated;

[0050] (x.2) optionally contacting said residue of the polymer blend obtained in (x.1) with solvent system, preferably at a temperature T3 as defined above in (x.1), followed by filtration, preferably heated filtration at a temperature T3 as defined above in (x.1), thereby obtaining a residue of the polymer blend, which is further depleted of polyester and comprises the third polymer and optionally the filler or a part of the filler; and a solvent system, which contains further amount of the polyester and comprises optionally the filler or a part of the filler;

[0051] (x.3) optionally combining the solvent system, which contains the further amount of the polyester and comprises optionally the filler or a part of the filler obtained in (x.2) with the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, separated in (x.1); wherein precipitation in (d) is done based on the separated solvent system obtained in (x.1) or based on the combined solvent system obtained in (x.3).

[0052] In heated filtration, the solution, filter, and funnel are heated, preferably heated so that each has temperature T3. Other means and methods for the separation in (x.1) are known to the skilled person such as non-heated filtration. In some embodiments, it is preferred that the heated filtration is done under a pressure of >1 bar, more preferably at a pressure in the range of from 1 bar to 30 bar, preferably in the range of from 1 to 10 bar, more preferably in the range of from 1 to 6 bar (heated pressure filtration). Preferably, the filter used in heated filtration is stable, especially does not dissolve or degrade, at the respective conditions and in connection with the respective solvent system. For example, the filter may be made of polyetheretherketone.

[0053] Preferably, the contacting in (x.2) is done in that, especially in cases where heated filtration is used in (x.1), the residue of the polymer blend obtained in (x.1) remains on the filter and is there brought into contact with solvent system, wherein the solvent system, which contains the remaining amount of the polyester and comprises optionally the filler or a part of the filler obtained in (x.2), is separated thereof due to filtration. In some embodiments, the solvent system, which contains the remaining amount of the polyester and comprises optionally the filler or a part of the filler obtained in (x.2) is combined with the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, obtained in (cx.1).

[0054] In some embodiments, the method comprises after (d) and before (e) (y.1) separating the precipitated polyester obtained in (d) from the solvent system, which is depleted in dissolved polyester and comprises optionally the filler or a part of the filler, thereby obtaining a precipitated polyester and the solvent system, which is depleted in dissolved polyester and comprises optionally the filler or a part of the filler;

[0055] (y.2) optionally washing the precipitated polyester obtained in (y.1);

[0056] (y.3) drying the precipitated polyester obtained in (y.1) or the washed precipitated polyester obtained in (y.2), thereby obtaining a dried (washed) precipitated polyester.

[0057] The separation in (y.1) is done by methods and means known to the skilled person, especially solid-liquid separation methods such as filtration, for example, heated pressure filtration, sedimentation or centrifugation (see Handbuch der mechanischen Fest-Flussig-Trennung Taschen- buch - 29. April 2004 von Klaus Luckert (Herausgeber)). Washing in optional step (y.1) is preferably done with a solvent system having features (s.1 ), (s.2) and (s.3) as defined herein, preferably with a solvent system comprising one or more of the solvent(s) of any one of the groups defined above. In some embodiments, a subsequent washing of the washed residue is done with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water or a mixture of two or more of these solvents or with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water, GVL, or a mixture of two or more of these solvents. In some embodiments, washing in optional step (y.2) is preferably done with a solvent system having features (s.1 ), (s.2) and (s.3) as defined herein, preferably with a solvent system comprising one or more of the solvent(s) of any one of the groups defined herein. In some embodiments, a subsequent washing of the washed residue is done with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water or a mixture of two or more of these solvents or with a solvent selected from the group consisting of methanol, ethanol, propanol, isopropanol, acetonitrile, ethyl acetate, acetone, water, GVL, or a mixture of two or more of these solvents. Drying in step (y.3) is preferably done under one or more conditions selected from the group consisting of a pressure in the range of from 1 to 1013 mbar; a temperature in the range of from 50 to 210 °C, preferably in the range of from 60 to 180°C, more preferably in the range of from 80 to 160 °C; drying time in the range of from 30 minutes to 24 hours; drying in an atmosphere comprising nitrogen, preferably in an atmosphere having at least 90 volume-%, more preferably 95 volume-%, more preferably at least 98 vol- ume-% nitrogen. Drying is done by one or more methods selected from the group consisting of contact drying, convection drying and radiation drying.

[0058] In some embodiments, the method comprises

[0059] (y.4) pelletizing the dried (washed) precipitated polyester obtained in (y.3), thereby obtaining a pelletized polyester. “Pelletizing” is the process of compressing or molding a material into the shape of a pellet. Pelletizing can be done as known in the art, for example, by extruding and subsequently pelletizing under water or by strand granulation.

[0060] In some embodiments, the method comprises after (d) and before (e), preferably after (y.3) or after (y.4) and before (e)

[0061] (z) increasing the intrinsic viscosity of the precipitated polyester obtained in (d) or of the dried (washed) precipitated polyester obtained in (y.3) or of the pelletized polyester obtained in (y.4).

[0062] Increasing the intrinsic viscosity according to (z) is done in solid state and / or wherein at least a part of the precipitated polyester is in molten state, wherein increasing the intrinsic viscosity enables to increase molecular weight of the polyester.

[0063] In some embodiments of the method, increasing the intrinsic viscosity in step (z) is carried out at a temperature in the range of from 180 to 230 °C, preferably in the range of from 200 to 230 °C, and / or, preferably and, at a pressure in the range of from 0.1 to 1013 mbar, preferably in the range of from 5 to 1013 mbar, and / or, preferably and, for a time in the range of from 1 to 80 hour(s), preferably in the range of from 2 to 40 hours.

[0064] Solvent system

[0065] In some embodiments of the method, the solvent system comprises one or more solvent(s), wherein

[0066] (s.1) the solvent system has Hansen solubility parameters with respect to energy from dispersion forces between molecules (5DSS), energy from dipolar intermolecular force between molecules (5PSS) and energy from hydrogen bonds between molecules (5HSS), which fullfill equitation 1

[0067] (8.8)2> 4(6Dss-20)2+ (5PSS-11.8)2+ (5Hss-4.5)2

[0068] [equitation 1];

[0069] (s.2) each solvent of the solvent system has a boiling point at 1013 hPa of at least 160 °C; and (s.3) solvents having a functional group selected from the group consisting of hydroxyl (OH), amino (NH2), carboxyl (COOH), and thiol (SH) are excluded.

[0070] The boiling point of a solvent is understood as the boiling point of the solvent at the respective pressure. Any solvent system for which 4(5Dss-20)2+ (5PSS-11.8)2+ (5Hss-4.5)2is larger than (8.8)2(i.e. 77.44) is not suited to dissolve polyester properly and any solvent system for which 4(6Dss-20)2+ (6Pss-11.8)2+ (6Hss-4.5)2is equal to or smaller than (8.8)2(i.e. 77.44) is suitable for dissolving polyester. In case of two or more solvents being part of the solvent system, i.e. n solvents with n being an integer with n>2 and i=1 ... n, the Hansen solubility parameters of the resulting mixture with respect to each of bDss, 6HSSand bPssare calculated, knowing the percentage part of each solvent in the solvent system, as the weighted arithmetic mean from 6DSi, 6HSiand bPsi of each of the n solvents S(i). The Hansen parameters of solvents are to be found in in BIOVIA COSMOquick 2022.

[0071] Considering the three-dimensional form given by equitation 1 in the three-dimensional Hansen space, a sphere is formed which has its center at 5DC= 20, 5PC= 11.8 and 5HC= 4.5 and a radius r of 8.8. The doubling of the dispersion parameter value is required, according to Charles Hansen, for achieving a spherical form. A Hansen sphere, since there are no negative values possible for 5H, can also be considered as a dome, i.e. a half-sphere. PET has Hansen parameters according to the 5thEdition 5.1.03 (2008) of the HANSEN Solubility Parameters in Practice (HSPiP) of 5D = 18.2, 5P = 6.4 and 5H = 6.6 and lies within the sphere but not at its center.

[0072] In some embodiments of the method, at least 90 weight-%, more preferably at least 95 weight- %, more preferably at least 98 weight-%, more preferably at least 99 weight-%, of the solvent system consist of one solvent system, which fulfills equitation 1 , wherein in cases where the solvent system consists of only one solvent system, the temperature T is a temperature at least 7K below the boiling temperature of said one solvent.

[0073] In some embodiments of the method, at least 90 weight-%, more preferably at least 95 weight- %, more preferably at least 98 weight-%, more preferably at least 99 weight-%, of the solvent system consist of two or more solvent(s), wherein the respective mixture fulfill(s) equitation 1.

[0074] In some embodiments of the method, the one or more solvent(s) is / are selected from the group consisting of N,N-dimethylbenzamide, N,N-dimethylphenylacetamide, 1 ,4-benzoquinone, acetophenone, dimethyl terephthalate, 1 ,3,5-trimethoxybenzene, 2-phenylacetophenone, N- methylcaprolactam, methylbenzoate, methyl-4-methoxybenzoate, butylene carbonate, N- ethylpyrrolidone, benzophenone, di-benzyl malonate, N-ethyl-caprolactam, methyl 2-(5-oxotet- rahydrofuran-3-yl)acetate (FAME), methyl 2-(5-oxotetrahydrofuran-2-yl)acetate, propiophenone, N-methoxypropyl-pyrrolidone, 1 ,4-cyclohexanedione, cyclohexane-carbonate, N-methoxyethyl- pyrrolidone, N,N-diethylphenylacetamide, phenyl acetate, 1-(2-hydroxyethyl)pyrrolidin-2-one acetate (HEPAc), N,N-diethylbenzamide, isopropyl-benzoate, cyclohexyl phenyl ketone, phenylacetic acid ethylester, phenylacetat.N-methyl-morpholine, benzyl-propionate, benzylacetate, Ne- opentyl-glycol-dibenzoate, tetrahydrofurfuryl acetate, N-methyl-imidazole, benzyl butyrate, 2- pyrrolidone, 2-phenoxyethanol propionate, 2-phenoxyethyl isobutyrate, N,N-dipropylbenzamide, N,N-dimethylacetamide, N,N-diethylacetamide, dihydrolevoglucosenon (Cyrene), propylenecarbonate, caprolactone, dimethylisosorbide, N-butylpyrrolidone, t-butylpyrrolidone, methyl-1-me- thyl-5-oxopyrrolidine-3-carboxylate (MMOC), gamma-valerolactone (GVL), delta-valerolactone, gamma butyrolactone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polar- clean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, N,N-dimethyl- lactamide (Agnique AMD 3L), 1 ,3-dimethyl-2-imidazolidinone (DMI) and dimethyl sulfoxide (DMSO). In some embodiments of the method, the one or more solvent(s) is / are selected from the group consisting of dihydrolevoglucosenon (Cyrene), propylenecarbonate, caprolactone, dimethylisosorbide, N-butylpyrrolidone, t-butylpyrrolidone, methyl-1-methyl-5-oxopyrrolidine-3-car- boxylate (MMOC), gamma-valerolactone (GVL), Delta-valerolactone, gamma butyrolactone, dimethylsulfoxide, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, propyl benzoate, and dimethyl sulfoxide (DMSO). In some embodiments of the method, the one or more solvent(s) of the solvent system is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t-butylpyrrolidone, methyl-1-methyl-5-oxopyrroli- dine-3-carboxylate (MMOC), Delta-valerolactone, gamma butyrolactone, methyl 5-(dimethyla- mino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), caprolactam, phenethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, propyl benzoate and GVL. In some embodiments of the method, the one or more solvent(s) is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t-butylpyrrolidone, methyl-1- methyl-5-oxopyrrolidine-3-carboxylate (MMOC), Delta-valerolactone, gamma butyrolactone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, and propyl benzoate. In some embodiments of the method, the one or more solvent(s) of the solvent system is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t- butylpyrrolidone, methyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), methyl 5-(dimethyla- mino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), phenethyl acetate, and GVL. In some embodiments of the method, the one or more solvent(s) is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t-butylpyrrolidone, methyl- 1-methyl-5-ox- opyrrolidine-3-carboxylate (MMOC), methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rho- diasolvOPolarclean), and phen ethyl acetate.

[0075] In some embodiments of the method, ethyl benzoate and butyl benzoate are excluded as solvents).

[0076] In some embodiments of the method, (s.3a) solvents having a functional group selected from the group consisting of hydroxyl (OH), amino (NH2), secondary amine (-NH-), carboxyl (COOH), and thiol (SH) are excluded.

[0077] In some embodiments of the method, the solvent system comprises gamma-valerolactone, wherein more preferably at least 50 weight-%, more preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the solvent system consists of gamma-valerolactone, based on the total weight of the solvent system being 100 weight-%.

[0078] In some embodiments of the method, in optional step (b) the same solvent system as in (c) is used.

[0079] Polyester

[0080] In some embodiments of the method, the polyester is based on 1 ,2-ethandiol, more preferably the polyester according to (i) is based on 1 ,2-ethanediol and terephthalic acid (polyethylene terephthalate, PET), wherein more preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the polyester are PET, based on the total weight of the polyester being 100 weight-%.

[0081] Colorant

[0082] In some embodiments of the method, the colorant is selected from the group consisting of dye and optical brightener and mixtures of dye and optical brightener.

[0083] A “colorant” is a substance that cause the change of color impression of material. This comprises dyes, which absorb wavelength intervals of visible light (400 to 780 nm) and optical brighteners, which amplify the light emission of a material through UV light adsorption and emittance of visible light (through fluorescence), i.e. an optical brightener converts radiation that is not visible to the human eye (<400nm) into visible fluorescence radiation of the blue-red spectral range (400 to 600 nm). Colorants usable or used for changing the color impression of polymeric materials are known to the skilled person. In the context of the present invention, the term “dye” means any kind of dye such as dye, pigment, dispersion, wherein a dye is, for example, one or more selected from the group consisting of acid dye, basic dye, direct dye, disperse dye, azoic dye, food dye, solvent dye, organic dye, organic pigment, sulfur dye, mordant dye and vat dye. The term “optical brightener” comprises optical brightening agents, fluorescent brightening agents, and fluorescent whitening agents.

[0084] Overviews of colorants for polymeric materials can be found, for example, in “Dyes and Pigments” Metin Agikyildiz, Kubra Gunes, Ahmet Gurses Springer, 2016 (ISBN: 10 : 3319338900); Industrial Organic Pigments - Klaus Hunger, Thomas Heber, Martin II. Schmidt, Friedrich Reisinger, Stefan Wanne Wiley-VCH, 4thedition, 2018 (ISBN: 978-3-527-32608-2); Chemistry and Technology of Natural and Synthetic Dyes and Pigments - Ashis Kumar Samanta, Nasser Awwad, IntechOpen, 2020 (ISBN: 9781789859980, 9781789859973, 9781839687587); Encyclopedia of Color, Dyes, Pigments - Volume 1, Gerhard Pfaff, de Gruyter, 2021 (ISBN: 311058588X); Heinrich Zollinger: Color Chemistry: Syntheses, Properties, and Applications of Organic Dyes and Pigments. 3rdedition. WILEY-VCH Verlag, Weinheim 2003 (ISBN: 3-906390- 23-3); Klaus Hunger (Ed.): Industrial Dyes: Chemistry, Properties, Applications. WILEY-VCH Verlag, Weinheim 2003 (ISBN: 3-662-01950-7); Hermann Rath: Lehrbuch der Textilchemie. ein- schl. der textilchemischen Technologie. 2nd edition. Springer-Verlag, Berlin, Heidelberg 1963 (ISBN: 978-3-662-00065-6); Wilfried Kratzert, Rasmus Peichert: Farbstoffe. Quelle & Meyer, Heidelberg 1981 (ISBN: 3-494-01021-8); Ullmann’s Encyclopedia of industrial chemistry, Wiley- VCH, 2000, sections “dyes and pigments” and “dyes, general survey” (ISBN: 9783527303854).

[0085] Preferably, in step b) only colorant(s) is / are removed from the polymer blend and transferred into the solvent system, which is / are non-covalently bonded to the polyester.

[0086] Second polymer

[0087] In some embodiments of the method, the second polymer is selected from the group consisting of polyurethane (PU), polyethylene glycol (PEG), polytetrahydrofuran (pTHF), mixtures of these polymers and copolymers of these polymers, wherein the second polymer is more preferably PU or a copolymer of PU and PEG and / or pTHF, more preferably Spandex.

[0088] “Spandex” is preferably a copolymer of polyurethane and polyethylene glycol and / or polytetra- hydrofurane, more preferably Spandex is a copolymer of polyurethane and polyethylene glycol or a copolymer of polyurethane with polytetrahydrofurane.

[0089] In some embodiments of the method, the third polymer is selected from polypropylene (PP), polyethylene (PE), polyamide (PA), natural polymer such as cotton, viscose, linen and mixtures of two or more thereof. PA comprises preferably PA6 and PA66; however, in some embodiments PA6 is excluded as third polymer, i.e. the third polymer when being PA is PA66.

[0090] Origin of the polymer blend

[0091] In some embodiments of the method, the polymer blend is a packaging article, more preferably a beverage packaging or food packaging, more preferably a bottle, which has preferably been shredded by mechanical means before (a).

[0092] In some embodiments of the method, the polymer blend is a textile article, more preferably a clothing article, which has preferably been shredded and / or cut by mechanical means before (a).

[0093] Filler

[0094] In some embodiments of the method, the filler is selected from the group consisting of glass fiber, coal fiber, carbon black, inorganic salts (for example, talc, disodium carbonate), adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent.

[0095] In some embodiments of the method, wherein the polyester comprises, preferably is, PET, the filler is one or more selected from the group consisting of glass fiber, coal fiber, carbon black, inorganic salts (for example, talc, disodium carbonate), adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent, preferably the filler one or more selected from adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent.

[0096] In some embodiments, the article provided in (a) comprises titanium dioxide (TiCh). In these preferred embodiments, said TiC>2 is absent in the precipitated polyester obtained in (d) or is present in the_precipitated polyester obtained in (d) in an amount in the range of from 0.001 to 1 .0 weight-%, based on the total precipitated polyester obtained in (d) being 100 weight-%. In these preferred embodiments, said TiC>2, if present, is also present in the fiber prepared in (e).

[0097] Process conditions

[0098] In some embodiments of the method, T1 is a temperature in the range of from 110 to < 170°C, more preferably a temperature in the range of from 110 to 165 °C, more preferably a temperature in the range of from 110 to 160 °C, more preferably a temperature in the range of from 120 to 150 °C, more preferably in the range of from 151 to 160 °C.

[0099] In some embodiments of the method, T2 is a temperature in the range of from > 170°C to 200 °C, more preferably a temperature in the range of from 175 to 190 °C, more preferably a temperature in the range of from 180 to 190 °C.

[0100] Advantageously the use of a solvent system comprising GVL allow energy saving because working at temperatures < 200°C is possible.

[0101] In some embodiments of the method, (a), optionally (b), (c) and (d) are done at a pressure in the range of from 800 to 200,000 hPa.

[0102] In some embodiments of the method, the contacting in (b) is done for a period of time of at least 5 minutes, more preferably in the range of from 5 minutes to 10 hours, more preferably in the range of from 5 minutes to 5 hours, more preferably in the range of from 5 minutes to 4 hours.

[0103] In some embodiments of the method, the contacting in (c) is done for a period of time of at least 0.1 hours, more preferably in the range of from 1 minute to 10 hours, more preferably in the range of from 1 minute to 2 hours, more preferably in the range of from 5 minutes to 1 hour.

[0104] In some embodiments of the method, the contacting in (b) and / or (c) is done with a in mass based ratio solvent system : polymer blend provided in (a) or residue obtained in (b) in the range of 1 : 1 to 100: 1 , more preferably in the range of from 1 :1 to 20: 1.

[0105] In some embodiments of the method, at least steps (b) and (c), more preferably all steps, are done in an inert atmosphere, preferably in the presence of an inert gas, wherein the inert gas is preferably selected from the group consisting of argon, helium, neon, nitrogen and mixtures of two or more of these inert gases, preferably comprises at least nitrogen, more preferably the inert gas is nitrogen. In some embodiments of the method, at least steps (b) and (c), more preferably all steps, are done batch-wise or continuous.

[0106] 2ndaspect - Polyester fiber

[0107] A second aspect of the invention is directed to a polyester fiber, obtained or obtainable from the method of the first aspect. All details, embodiments and preferred embodiments disclosed in the section related to the first aspect apply also for the second aspect.

[0108] In some embodiments, the polyester fiber has an elastic limit in the oriented state of more than 15 cN / tex, more preferably in the range of from 15 to 70 cN / tex, determined according to DIN 53816:1993-02.

[0109] In some embodiments, the polyester fiber has a Young’s modulus of the fiber in oriented state in the range of from 400 to 900 cN / tex, determined according to DIN 53834-1:1976-02.

[0110] 3rdaspect - use of the polyester fiber

[0111] A third aspect of the invention is directed to the use of a polyester fiber according to the second aspect for preparing a textile. All details, embodiments and preferred embodiments disclosed in the sections related to the first aspect and the second aspect apply also for the third aspect.

[0112] 4thaspect - method for preparing a textile

[0113] A fourth aspect of the invention relates to a method for preparing a product comprising

[0114] (I) providing polyester of the second aspect;

[0115] (II) preparing a textile from the polyester provided in (I).

[0116] All details, embodiments and preferred embodiments disclosed in the sections related to the first to third aspect apply also for the fourth aspect.

[0117] 5thaspect - method related to the second polymer

[0118] A fifth aspect of the invention relates to a method of the first aspect, wherein (b) comprises: (b.1) contacting the polymer blend with the solvent system at a temperature T1 of < 170 °C, thereby obtaining a solvent system, which is optionally enriched in colorant, optionally enriched in second polymer and optionally comprises the filler or a part of the filler, and a residue of the polymer blend, which is depleted of said optional colorant and of optional second polymer and comprises the polyester, optionally the third polymer, and optionally the filler or a part of the filler;

[0119] (b.2) separating the solvent system, which is optionally enriched in colorant, optionally enriched in second polymer and optionally comprises the filler or a part of the filler, obtained in (b.1) from the residue, preferably by a physical separation method, thereby obtaining a separated solvent system, which is optionally enriched in colorant, and optionally enriched in second polymer and optionally comprises the filler or a part of the filler, compared to the solvent system provided in (a); and

[0120] (b.3) separating the optional second polymer from the solvent system, thereby obtaining a separated fraction comprising the second polymer.

[0121] All details, embodiments and preferred embodiments disclosed in the sections related to the first to fourth aspect apply also for the fifth aspect.

[0122] In some embodiments, the method comprises the further step: converting a residue obtainable by or obtained by the method according to the first aspect, preferably obtained or obtainable from step (d), more preferably the residue comprising at least third polymer obtainable by or obtained by the method according to according to the first aspect, preferably obtained or obtainable from step (d), to obtain one or more monomer, polymer or polymer product.

[0123] In some embodiments of the method, the monomer is a di- or polyol; preferably butandiol; aldehyde; preferably formaldehyde; di- or polyisocyanate; preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI); amide; preferably caprolactam; alkene; preferably styrene, ethene and norbornene; alkyne, (di)ester; preferably methyl methacrylate; mono or diacid; preferably adipic acid or terephthalic acid; diamine; preferably hexamethylenediamine, nonanediamine; or sulfones; preferably 4,4'-dichlorodiphenyl sulfone.

[0124] In some embodiments of the method, the polymer is and / or the polymer product comprises polyamide (PA); preferably PA 6 or PA 66; polyisocyanate polyaddition product; preferably polyurethane (Pll), thermoplastic polyurethane (TPU), polyurea or polyisocyanurate (PIR); low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polystyrene (PS), poly acrylonitrile butadiene styrene (ABS), poly styrene acrylonitrile (SAN), poly acrylate styrene acrylonitrile (ASA), polytetrafluoroethylene (PTFE), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), polybutadiene (BR, PBD), poly(cis-1 ,4-isoprene), poly(trans-1 ,4-isoprene), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly- butylene adipate coterephthalate (PBAT), polyester (PES), polyether sulfone (PESLI), polyhydroxyalkanoate (PHA), poly-3-hydroxybutyrate (P3HB), poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polylactic acid (PLA), polysulfone (PSU), polyphenylene sulfone (PPSLI), polycarbonate (PC), polyether ether ketone (PEEK), poly(p-phenylene oxide) (PPO), poly(p-phenylene ether) (PPE); or copolymer or mixture thereof.

[0125] In some embodiments of the method, the polymer and / or the polymer product is / are or is / are a part of: a part of a car; preferably cylinder head cover, engine cover, housing for charge air cooler, charge air cooler flap, intake pipe, intake manifold, connector, gear wheel, fan wheel, cooling water box, housing, housing part for heat exchanger, coolant cooler, charge air cooler, thermostat, water pump, radiator, fastening part, part of battery system for electromobility, dashboard, steering column switch, seat, headrest, center console, transmission component, door module, cover for car A, B, C or D pillar, spoiler, door handle, exterior mirror, windscreen wiper, windscreen wiper protection housing, decorative grill, cover strip, roof rail, window frame, sunroof frame, antenna panel, headlight and taillight, engine cover, cylinder head cover, intake manifold, airbag, cushion, or coating; a cloth; preferably shirt, trousers, pullover, boot, shoe, shoe sole, tight or jacket; an electrical part; preferably electrical or electronic passive or active component, circuit board, printed circuit board, housing component, foil, line, switch, plug, socket, distributor, relay, resistor, capacitor, inductor, bobbin, lamp, diode, LED, transistor, connector, regulator, integrated circuit (IC), methodor, controller, memory, sensor, microswitch, microbutton, semiconductor, reflector housing for light-emitting diodes (LED), fastener for electrical or electronic component, spacer, bolt, strip, slide-in guide, screw, nut, film hinge, snap hook (snap-in), or spring tongue; a consumer, agricultural product or pharmaceutical product; preferably tennis string, climbing rope, bristle, brush, artificial grass, 3D printing filament, grass trimmer, zipper, hook and loop fastener, paper machine clothing, extrusion coating, fishing line, fishing net, offshore line and rope, vial, syringe, ampoule, bottle, sliding element, spindle nut, chain conveyor, plain bearing, roller, wheel, gear, roller, ring gear, screw and spring dampers, hose, pipeline, cable sheathing, socket, switch, cable tie, fan wheel, carpet, box or bottle for cosmetics, mattress, cushion, insulation, detergent, dishwasher tabs or powder, shampoo, body wash, shower gel, soap, fertilizer, fungicide, or pesticide; a packaging for the food industry; preferably mono- or multi-layer blown film, cast film (mono- or multi-layer), biaxially stretched film, or laminating film; or a part of a construction; preferably a rotor blade, insulating material, frame, housing, wall, coating, or separating wall. In some embodiments of the method, the content of the third polymer in the monomer, polymer and / or polymer product is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or the content of the third polymer in the monomer, polymer and / or polymer product is 100 weight- % or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.

[0126] The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The method of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The method of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0127] 1 . A method for preparing a polyester fiber comprising providing a polymer blend, which comprises

[0128] (i) a polyester and

[0129] (ii) one or more component(s) selected from the group consisting of a second polymer, a third polymer, a colorant and a filler, wherein second polymer and third polymer are different from each other and different from the polyester of (i); the method comprising:

[0130] (a) providing the polymer blend and providing a solvent system;

[0131] (b) optionally contacting the polymer blend with the solvent system at a temperature T 1 of < 170 °C, thereby obtaining a solvent system, which is enriched in dissolved second polymer and / or colorant and optionally in the filler or in a part of the filler, and a residue of the polymer blend, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler;

[0132] (c) contacting the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) with a solvent system at a temperature T2 of > 170 °C, thereby obtaining a solvent system, which is enriched in dissolved polyester compared to the solvent system provided in (a) and comprises optionally the filler or a part of the filler, and optionally a residue of the polymer blend, which is depleted of polyester and comprises optionally the third polymer and optionally the filler or a part of the filler;

[0133] (d) precipitating the polyester from solvent system, which is enriched in dissolved polyester, obtained in (c), thereby obtaining a precipitated polyester and a solvent system, which is depleted in dissolved polyester and which optionally comprises the filler or a part of the filler;

[0134] (e) preparing a fiber from the precipitated polyester obtained in (d). The method of embodiment 1 , wherein precipitation in (d) comprises cooling the solvent obtained in (c), which is enriched in dissolved polyester compared to the solvent provided in (a), from T2 to a temperature below 140°C, wherein cooling is done so that the temperature of the solvent system, which is enriched in dissolved polyester, is within the temperature range of from 160 to 145 °C for a period of time of at least 5 minutes, preferably at least 10 minutes, more preferably in the range from 5 to 120 minutes, more preferably in the range of from 10 to 100 minutes, more preferably in the range of from 15 to 100 minutes. The method of embodiment 2, wherein cooling in (d) is done so that the solvent system, which is enriched in dissolved polyester, in the temperature range of from 160 to 145 °C has a viscosity in the range of from 1 to 12 Pa s, preferably in the range of from 1 to 10 Pa s, determined according to ASTM D445. The method of embodiment 2 or 3, wherein cooling is done with a cooling rate < 3.0 °C / min, preferably < 1.5 °C / min, more preferably in the range of from 0.05 to

[0135] 3.0 C / min, more preferably in the range of from 0.13 to 3.0 °C / min, more preferably in the range of from 0.15 to 1.5 °C / min, more preferably in the range of from 0.15 to 1.0 °C / min. The method of any one of embodiments 2 to 4, wherein the cooling of the solvent system in (d) is done from T2 to a temperature below 100°C. 6. The method of any one of embodiments 2 to 5, wherein the cooling of the solvent system in (d) is done without addition of an anti-solvent.

[0136] 7. The method of any one of embodiments 1 to 6, wherein (e) comprises

[0137] (e.1) optionally melt extrusion of the precipitated polyester obtained in (d), thereby obtaining an extrudate comprising the polyester;

[0138] (e.2) optionally pelletizing the extrudate obtained in (e.1), thereby obtaining an extrusion product comprising the polyester in pellet form;

[0139] (e.3) fiber preparation from the precipitated polyester obtained in (d) or from the extrusion product comprising the polyester in pellet form obtained in (e.2), to give a polyester fiber.

[0140] 8. The method of any embodiment 7, wherein melt-extrusion in step (e.1) is done at a temperature of >250 °C, preferably in the range of from 250 to 300 °C.

[0141] 9. The method of any embodiment 7 or 8, wherein the extrusion product comprising the polyester in pellet form obtained in (e.2) is dried at a temperature in the range of from 60 to 160 °C, optionally under vacuum.

[0142] 10. The method of any one of embodiments 7 to 9, wherein fiber preparation of (e.3) is done by a method selected from the group of melt spinning, electrospinning, wet spinning, matrix spinning and a combination of two or more of these methods, preferably by melt spinning.

[0143] 11. The method of embodiment 10, wherein fiber preparation of (e.3) by melt spinning, comprises

[0144] (e.3.1) providing precipitated polyester obtained in (d) or the polyester in pellet form obtained in (e.2);

[0145] (e.3.2) melting the polyester provided in (e.3.1) at a temperature in the range of from 250 to 300 °C, preferably in an extruder, thereby obtaining melted polyester;

[0146] (e.3.3) optionally filtering the melted polyester, thereby obtaining a filtered melted polyester;

[0147] (e.3.4) extrusion of the melted polyester of (e.3.2) or of the filtered melted polyester obtained in (e.3.3), preferably through a spinning nozzle, thereby obtaining at least one fiber filament.

[0148] 12. The method of embodiment 11 , wherein fiber preparation comprises (e.3.5) optionally combining two or more fiber filaments obtained in (e.3.4) to obtain a fiber;

[0149] (e.3.6) collecting the at least one fiber filament obtained in (e.3.4) or the fiber obtained in (e.3.5) on a ribbon, preferably with a speed of the ribbon of at least 500 m / min, more preferably in the range of from 1000 to 3000 m / min.

[0150] 13. The method of any one of embodiments 1 to 12, comprising, if (b) is conducted, after (b) and before (c):

[0151] (v) washing the residue of the polymer blend obtained in (b) with a washing solvent, thereby obtaining a washed residue, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler;

[0152] (w) optionally drying the washed residue obtained in (v).

[0153] 14. The method of any one of embodiments 1 to13, comprising after (c) and before (d) (x.1) separating the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, obtained in (c) from the residue of the polymer blend, wherein the separation is preferably done by heated filtration, more preferably by heated filtration at a temperature T3 in the range of from T2 minus

[0154] 20 °C to T2 plus 20 °C (T3 = T2 ± 20°C), more preferably at a temperature T3 in the range of from T2 minus 10 °C to T2 plus 10 °C (T3 = T2 ± 10°C), thereby obtaining the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, separated;

[0155] (x.2) optionally contacting said residue of the polymer blend obtained in (x.1) with solvent system, preferably at a temperature T3 as defined above in (x.1), followed by filtration, preferably heated filtration at a temperature T3 as defined above in (x.1), thereby obtaining a residue of the polymer blend, which is further depleted of polyester and comprises the third polymer and optionally the filler or a part of the filler; and a solvent system, which contains further amount of the polyester and comprises optionally the filler or a part of the filler;

[0156] (x.3) optionally combining the solvent system, which contains the further amount of the polyester and comprises optionally the filler or a part of the filler obtained in (x.2) with the solvent system, which is enriched in dissolved polyester and comprises optionally the filler or a part of the filler, separated in (x.1); wherein precipitation in (d) is done based on the separated solvent system obtained in (x.1) or based on the combined solvent system obtained in (x.3). 15. The method of any one of embodiments 1 to 14 comprising after (d) and before (e)

[0157] (y.1) separating the precipitated polyester obtained in (d) from the solvent system, which is depleted in dissolved polyester and comprises optionally the filler or a part of the filler, thereby obtaining a precipitated polyester and the solvent system, which is depleted in dissolved polyester and comprises optionally the filler or a part of the filler;

[0158] (y.2) optionally washing the precipitated polyester obtained in (y.1);

[0159] (y.3) drying the precipitated polyester obtained in (y.1) or the washed precipitated polyester obtained in (y.2), thereby obtaining a dried (washed) precipitated polyester;

[0160] (y.4) optionally pelletizing the dried (washed) precipitated polyester obtained in (y.3), thereby obtaining a pelletized polyester.

[0161] 16. The method of any one of embodiments 1 to 15 comprising after (d) and before (e), preferably after (y.3) or after (y.4) and before (e)

[0162] (z) increasing the intrinsic viscosity of the precipitated polyester obtained in (d) or of the dried (washed) precipitated polyester obtained in (y.3) or of the pelletized polyester obtained in (y.4).

[0163] 17. The method of embodiment 16, wherein increasing the intrinsic viscosity in step (z) is carried out at a temperature in the range of from 180 to 230 °C, preferably in the range of from 200 to 230 °C, and / or, preferably and, at a pressure in the range of from 0.1 to 1013 mbar, preferably in the range of from 5 to 1013 mbar, and / or, preferably and, for a time in the range of from 1 to 80 hour(s), preferably in the range of from 2 to 40 hours.

[0164] 18. The method of any one of embodiments 1 to 17, wherein the solvent system comprises one or more solvent(s), wherein

[0165] (s.1) the solvent system has Hansen solubility parameters with respect to energy from dispersion forces between molecules (5DSS), energy from dipolar intermolecular force between molecules (5PSS) and energy from hydrogen bonds between molecules (5HSS), which fullfill equitation 1

[0166] (8.8)2> 4(6Dss-20)2+ (5PSS-11.8)2+ (5Hss-4.5)2

[0167] [equitation 1];

[0168] (s.2) each solvent of the solvent system has a boiling point at 1013 hPa of at least

[0169] 160 °C; and

[0170] (s.3) solvents having a functional group selected from the group consisting of hydroxyl (OH), amino (NH2), carboxyl (COOH), and thiol (SH) are excluded. The method of any one of embodiments 1 to 18, wherein at least 90 weight-%, preferably at least 95 weight-%, more preferably at least 98 weight-%, more preferably at least 99 weight-%, of the solvent system consist of one solvent system, which fulfills equitation 1 , wherein in cases where the solvent system consists of only one solvent system, the temperature T is a temperature at least 7K below the boiling temperature of said one solvent. The method of any one of embodiments 1 to 19, wherein at least 90 weight-%, preferably at least 95 weight-%, more preferably at least 98 weight-%, more preferably at least 99 weight-%, of the solvent system consist of two or more solvent(s), wherein the respective mixture fulfill(s) equitation 1. The method of any one of embodiments 1 to 20, wherein the one or more solvent(s) is / are selected from the group consisting of N,N-dimethylbenzamide, N,N-dimethylphenyla- cetamide, 1,4-benzoquinone, acetophenone, dimethyl terephthalate, 1,3,5-trimethoxyben- zene, 2-phenylacetophenone, N-methylcaprolactam, methylbenzoate, methyl-4-methox- ybenzoate, butylene carbonate, N-ethylpyrrolidone, benzophenone, di-benzyl malonate, N-ethyl-caprolactam, methyl 2-(5-oxotetrahydrofuran-3-yl)acetate (FAME), methyl 2-(5- oxotetrahydrofuran-2-yl)acetate, propiophenone, N-methoxypropyl-pyrrolidone, 1,4-cyclo- hexanedione, cyclohexane-carbonate, N-methoxyethyl-pyrrolidone, N,N-diethylphenyla- cetamide, phenyl acetate, 1-(2-hydroxyethyl)pyrrolidin-2-one acetate (HEPAc), N,N-dieth- ylbenzamide, isopropyl-benzoate, cyclohexyl phenyl ketone, phenylacetic acid ethylester, phenylacetat.N-methyl-morpholine, benzyl-propionate, benzylacetate, Neopentyl-glycol- dibenzoate, tetrahydrofurfuryl acetate, N-methyl-imidazole, benzyl butyrate, 2-pyrrolidone, 2-phenoxyethanol propionate, 2-phenoxyethyl isobutyrate, N,N-dipropylbenzamide, N,N- dimethylacetamide, N,N-diethylacetamide, dihydrolevoglucosenon (Cyrene), propylenecarbonate, caprolactone, dimethylisosorbide, N-butylpyrrolidone, t-butylpyrrolidone, me- thyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), gamma-valerolactone (GVL), delta- valerolactone, gamma butyrolactone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polarclean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, N,N-dimethyllactamide (Agnique AMD 3L), 1,3-dimethyl-2-imidazolidinone (DMI) and dimethyl sulfoxide (DMSO). The method of any one of embodiments 1 to 21 , wherein the one or more solvent(s) is / are selected from the group consisting of dihydrolevoglucosenon (Cyrene), propylenecarbonate, caprolactone, dimethylisosorbide, N-butylpyrrolidone, t-butylpyrrolidone, methyl-1- methyl-5-oxopyrrolidine-3-carboxylate (MMOC), gamma-valerolactone (GVL), Delta- valerolactone, gamma butyrolactone, dimethylsulfoxide, methyl 5-(dimethylamino)-2-me- thyl-5-oxopentanoate (RhodiasolvOPolarclean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, propyl benzoate, and dimethyl sulfoxide (DMSO).

[0171] 23. The method of any one of embodiments 1 to 22, wherein the one or more solvent(s) of the solvent system is / are selected from the group consisting of propylenecarbonate, N-bu- tylpyrrolidone, t-butylpyrrolidone, methyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), Delta-valerolactone, gamma butyrolactone, methyl 5-(dimethylamino)-2-methyl- 5-oxopentanoate (RhodiasolvOPolarclean), caprolactam, phenethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, propyl benzoate and GVL.

[0172] 24. The method of any one of embodiments 1 to 23, wherein the one or more solvent(s) is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t-butylpyr- rolidone, methyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), Delta-valerolactone, gamma butyrolactone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodi- asolvOPolarclean), caprolactam, phen ethyl acetate, methyl phenylacetate, benzyl benzoate, phenyl benzoate, methyl benzoate, and propyl benzoate.

[0173] 25. The method of any one of embodiments 1 to 24, wherein the one or more solvent(s) of the solvent system is / are selected from the group consisting of propylenecarbonate, N-bu- tylpyrrolidone, t-butylpyrrolidone, methyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), phenethyl acetate, and GVL.

[0174] 26. The method of any one of embodiments 1 to 25, wherein the one or more solvent(s) is / are selected from the group consisting of propylenecarbonate, N-butylpyrrolidone, t-butylpyr- rolidone, methyl-1-methyl-5-oxopyrrolidine-3-carboxylate (MMOC), methyl 5-(dimethyla- mino)-2-methyl-5-oxopentanoate (RhodiasolvOPolarclean), and phen ethyl acetate.

[0175] 27. The method of any one of embodiments 1 to 26, wherein ethyl benzoate and butyl benzoate are excluded as solvent(s).

[0176] 28. The method of any one of embodiments 1 to 27, wherein

[0177] (s.3a) solvents having a functional group selected from the group consisting of hydroxyl (OH), amino (NH2), secondary amine (-NH-), carboxyl (COOH), and thiol (SH) are excluded. 29. The method of any one of embodiments 1 to 28, wherein the solvent system comprises gamma-valerolactone, wherein more preferably at least 50 weight-%, more preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least

[0178] 80 weight-%, more preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the solvent system consists of gamma-valerolactone, based on the total weight of the solvent system being 100 weight-%.

[0179] 30. The method of any one of embodiments 1 to 29, wherein in optional step (b) the same solvent system as in (c) is used.

[0180] 31. The method of any one of embodiments 1 to 30, wherein the polyester is based on 1 ,2- ethandiol, more preferably the polyester according to (i) is based on 1,2-ethanediol and terephthalic acid (polyethylene terephthalate, PET), wherein more preferably at least

[0181] 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the polyester are PET, based on the total weight of the polyester being 100 weight-%.

[0182] 32. The method of any one of embodiments 1 to 31 , wherein the colorant is selected from the group consisting of dye and optical brightener and mixtures of dye and optical brightener.

[0183] 33. The method of any one of embodiments 1 to 32, wherein the second polymer is selected from the group consisting of polyurethane (Pll), polyethylene glycol (PEG), polytetrahydrofuran (pTHF), mixtures of these polymers and copolymers of these polymers, wherein the second polymer is more preferably Pll or a copolymer of Pll and PEG and / or pTHF, more preferably Spandex.

[0184] 34. The method of any one of embodiments 1 to 33, wherein the third polymer is selected from polypropylene (PP), polyethylene (PE), polyamide (PA), natural polymer such as cotton, viscose, linen and mixtures of two or more thereof.

[0185] 35. The method of any one of embodiments 1 to 34, wherein the polymer blend is a packaging article, preferably a beverage packaging or food packaging, more preferably a bottle, which has preferably been shredded by mechanical means before (a).

[0186] 36. The method of any one of embodiments 1 to 35, wherein the polymer blend is a textile article, preferably a clothing article, which has preferably been shredded by mechanical means before (a). 37. The method of any one of embodiments 1 to 36, wherein the filler is selected from the group consisting of glass fiber, coal fiber, carbon black, inorganic salts (for example, talc, disodium carbonate), adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent.

[0187] 38. The method of embodiment 37, wherein the polyester comprises, preferably is, PET and the filler is one or more selected from the group consisting of glass fiber, coal fiber, carbon black, inorganic salts (for example, talc, disodium carbonate), adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent, preferably the filler one or more selected from adhesive, thickener, antifoam agent, finishing agent (for example water / oil / stain repellent, flame retardant, anticrease agent, biocide), binder, surfactant (for example, softener, scouring agent, antistatic agent), desizing agent, bleaching agent, oxidant, UV filter, emulsionant, fixing agent, washing dispersant, profiling agent.

[0188] 39. The method of any one of embodiments 1 to 38, wherein T1 is a temperature in the range of from 110 to < 170°C, preferably a temperature in the range of from 110 to 165 °C, more preferably a temperature in the range of from 110 to 160 °C, more preferably a temperature in the range of from 120 to 150 °C, more preferably in the range of from 151 to 160°C.

[0189] 40. The method of any one of embodiments 1 to 39, wherein T2 is a temperature in the range of from > 170°C to 200 °C, preferably a temperature in the range of from 175 to 190 °C, more preferably a temperature in the range of from 180 to 190 °C.

[0190] 41 . The method of any one of embodiments 1 to 40, wherein (a), optionally (b), (c) and (d) are done at a pressure in the range of from 800 to 200,000 hPa.

[0191] 42. The method of any one of embodiments 1 to 41 , wherein the contacting in (b) is done for a period of time of at least 5 minutes, preferably in the range of from 5 minutes to 10 hours, more preferably in the range of from 5 minutes to 5 hours, more preferably in the range of from 5 minutes to 4 hours. The method of any one of embodiments 1 to 42, wherein the contacting in (c) is done for a period of time of at least 0.1 hours, preferably in the range of from 1 minute to 10 hours, more preferably in the range of from 1 minute to 2 hours, more preferably in the range of from 5 minutes to 1 hour. The method of any one of embodiments 1 to 43, wherein the contacting in (b) and / or (c) is done with a in mass based ratio solvent system : polymer blend provided in (a) or residue obtained in (b) in the range of 1 :1 to 100:1, preferably in the range of from 1 :1 to 20:1. The method of any one of embodiments 1 to 44, wherein at least steps (b) and (c), preferably all steps, are done in an inert atmosphere, preferably in the presence of an inert gas, wherein the inert gas is preferably selected from the group consisting of argon, helium, neon, nitrogen and mixtures of two or more of these inert gases, preferably comprises at least nitrogen, more preferably the inert gas is nitrogen. The method of any one of embodiments 1 to 45, wherein at least steps (b) and (c), preferably all steps, are done batch-wise or continuous. A polyester fiber, obtained or obtainable from the method of any one of embodiments 1 to 46. The polyester fiber of embodiment 47, having an elastic limit in the oriented state of more than 15 cN / tex, preferably in the range of from 15 to 70 cN / tex, determined according to DIN 53816:1993-02. The polyester fiber of embodiment 47 or 48 having a Young’s modulus of the fiber in oriented state in the range of from 400 to 900 cN / tex, determined according to DIN 53834- 1 :1976-02. Use of a polyester fiber according to any one of embodiments 47 to 49 for preparing a textile. A method for preparing a product comprising

[0192] (I) providing polyester of any one of embodiments 47 to 49;

[0193] (II) preparing a textile from the polyester provided in (I). The method of any one of embodiment 1 to 46, wherein (b) comprises:

[0194] (b.1) contacting the polymer blend with the solvent system at a temperature T1 of < 170 °C, thereby obtaining a solvent system, which is optionally enriched in colorant, optionally enriched in second polymer and optionally comprises the filler or a part of the filler, and a residue of the polymer blend, which is depleted of said optional colorant and of optional second polymer and comprises the polyester, optionally the third polymer, and optionally the filler or a part of the filler;

[0195] (b.2) separating the solvent system, which is optionally enriched in colorant, optionally enriched in second polymer and optionally comprises the filler or a part of the filler, obtained in (b.1) from the residue, preferably by a physical separation method, thereby obtaining a separated solvent system, which is optionally enriched in colorant, and optionally enriched in second polymer and optionally comprises the filler or a part of the filler, compared to the solvent system provided in (a); and

[0196] (b.3) separating the optional second polymer from the solvent system, thereby obtaining a separated fraction comprising the second polymer. Method, preferably according to any one of embodiments 1 to 46 or 52, comprising the further step: converting a residue obtainable by or obtained by the method according to any one of embodiments 1 to 42 or 49, preferably obtained or obtainable from step (d), more preferably the residue comprising at least third polymer obtainable by or obtained by the method according to according to any one of embodiments 1 to 46 or 52, preferably obtained or obtainable from step (d), to obtain one or more monomer, polymer or polymer product. Method according to embodiment 53, wherein the monomer is a di- or polyol; preferably butandiol; aldehyde; preferably formaldehyde; di- or polyisocyanate; preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI); amide; preferably caprolactam; alkene; preferably styrene, ethene and norbornene; alkyne, (di)ester; preferably methyl methacrylate; mono or diacid; preferably adipic acid or terephthalic acid; diamine; preferably hexamethylenediamine, nonanediamine; or sulfones; preferably 4,4'-dichlorodiphenyl sulfone. Method according to embodiment 53 or 54, wherein the polymer is and / or the polymer product comprises polyamide (PA); preferably PA 6 or PA 66; polyisocyanate polyaddition product; preferably polyurethane (Pll), thermoplastic polyurethane (TPU), polyurea or polyisocyanurate (PIR); low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polystyrene (PS), poly acrylonitrile butadiene styrene (ABS), poly styrene acrylonitrile (SAN), poly acrylate styrene acrylonitrile (ASA), polytetrafluoroethylene (PTFE), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), polybutadiene (BR, PBD), poly(cis-1 ,4-isoprene), poly(trans-1 ,4-iso- prene), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutylene adipate coterephthalate (PBAT), polyester (PES), polyether sulfone (PESLI), polyhydroxyalkanoate (PHA), poly-3-hydroxybutyrate (P3HB), poly-4-hy- droxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polylactic acid (PLA), polysulfone (PSU), polyphenylene sulfone (PPSLI), polycarbonate (PC), polyether ether ketone (PEEK), poly(p-phenylene oxide) (PPO), poly(p-phenylene ether) (PPE); or copolymer or mixture thereof. Method according to any one of embodiments 53 to 55, wherein the polymer and / or the polymer product is / are or is / are a part of: a part of a car; preferably cylinder head cover, engine cover, housing for charge air cooler, charge air cooler flap, intake pipe, intake manifold, connector, gear wheel, fan wheel, cooling water box, housing, housing part for heat exchanger, coolant cooler, charge air cooler, thermostat, water pump, radiator, fastening part, part of battery system for electromobility, dashboard, steering column switch, seat, headrest, center console, transmission component, door module, cover for car A, B, C or D pillar, spoiler, door handle, exterior mirror, windscreen wiper, windscreen wiper protection housing, decorative grill, cover strip, roof rail, window frame, sunroof frame, antenna panel, headlight and taillight, engine cover, cylinder head cover, intake manifold, airbag, cushion, or coating; a cloth; preferably shirt, trousers, pullover, boot, shoe, shoe sole, tight or jacket; an electrical part; preferably electrical or electronic passive or active component, circuit board, printed circuit board, housing component, foil, line, switch, plug, socket, distributor, relay, resistor, capacitor, inductor, bobbin, lamp, diode, LED, transistor, connector, regulator, integrated circuit (IC), methodor, controller, memory, sensor, microswitch, microbutton, semiconductor, reflector housing for light-emitting diodes (LED), fastener for electrical or electronic component, spacer, bolt, strip, slide-in guide, screw, nut, film hinge, snap hook (snap-in), or spring tongue; a consumer, agricultural product or pharmaceutical product; preferably tennis string, climbing rope, bristle, brush, artificial grass, 3D printing filament, grass trimmer, zipper, hook and loop fastener, paper machine clothing, extrusion coating, fishing line, fishing net, offshore line and rope, vial, syringe, ampoule, bottle, sliding element, spindle nut, chain conveyor, plain bearing, roller, wheel, gear, roller, ring gear, screw and spring dampers, hose, pipeline, cable sheathing, socket, switch, cable tie, fan wheel, carpet, box or bottle for cosmetics, mattress, cushion, insulation, detergent, dishwasher tabs or powder, shampoo, body wash, shower gel, soap, fertilizer, fungicide, or pesticide; a packaging for the food industry; preferably mono- or multi-layer blown film, cast film (mono- or multi-layer), biaxially stretched film, or laminating film; or a part of a construction; preferably a rotor blade, insulating material, frame, housing, wall, coating, or separating wall.

[0197] 57. Method according to any one of embodiments 53 to 56, wherein the content of the third polymer in the monomer, polymer and / or polymer product is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of the third polymer in the monomer, polymer and / or polymer product is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.

[0198] The present invention is further illustrated by the following reference examples, comparative examples, and examples.

[0199] Examples

[0200] Methods

[0201] Determination of viscosity: ASTM D445 Determination of elastic limit: DIN 53816:1993-02

[0202] Determination of Young’s modulus: DIN 53834-1 :1976-02

[0203] GPC (Gel-Permeation Chromatography):

[0204] Sample preparation:

[0205] Approximately 6 mg sample was dissolved in 5 ml eluent (hexafluorisopropanol + 0.05 weight-% trifluoro potassium acetate) over night. All sample solutions were filtered by a Millipore Millex FG (0.2 pm) filtered prior to injection. Sealed sample vials were placed into the auto sampler.

[0206] Experimental conditions:

[0207] An Agilent 1100 HPLC system, consisting of an isocratic pump, vacuum degasser, auto sampler and a column oven (35°C) was used. Furthermore, the Agilent system contained as detectors a Differential Refractive Index (DRI) and a variable Ultra Violet (UVW) Detector. Data acquisition and data processing of conventionally SEC data were done by WinGPC Unichrom, of PSS (Polymer Standard Services). A combination of a PL-HFIP guard (7.5 x 50 mm) column and 2 PL- HFIP Gel columns (7.5 x 300 mm, 9p) of Agilent were put in series. As an eluent, hexafluorisopropanol + 0.05 weight-% trifluoro potassium acetate was used as a flow rate of 1 ml / min. Of each sample solution 50pl was injected. The calibration was obtained by narrow molar mass distributed PM MA standards (Polymer Standard Services) having a molar mass range of M = 800 till M = 2.200.000 g / mol or M= 600 till M = 2.050.000 g / mol. Molar masses outside this range were extrapolated.

[0208] Chemicals

[0209] PET having Hansen parameters according to the 5thEdition 5.1.03 (2008) of the HANSEN

[0210] Solubility Parameters in Practice (HSPiP) of 5D = 18.2, 5P = 6.4 and 5H = 6.6

[0211] Hansen parameter GVL: 5D: 18.50, 5P: 14.17, 5H: 7.93 (from BIOVIA COSMOquick 2022) Reference Example 1 : Separation of PET from polymeric material

[0212] 1.1 : Removal of colorants and / or second polymer (Spandex)

[0213] Polymeric material (in any processing form, e.g. textile, flakes etc.) was cut / shredded into pieces and placed in a reaction vessel (e.g. flask, tube, reaction vessel). GVL was added (in mass based ratio polymeric material : GVL 1 :1 to 1 :100, preferred 1 :1-1 :20) and the mixture was heated by use of a suitable heating system (e.g. oil bath, heating blocks, mini-plant vessels) under inert gas atmosphere to a temperature in the range of from 60 to 160 °C. After 0.5-8 h the mixture was filtered, whereby GVL enriched in colorant and / or Spandex and (optionally colorant depleted) polymeric material pieces were obtained, wherein the later were washed with a small amount of GVL. For an easy removal of GVL and a faster drying method of the (optionally colorant depleted) polymeric material pieces, small amounts of acetone were optionally used in a second washing step. The thus obtained polymeric material pieces were dried (for example in a vacuum compartment dryer).

[0214] 1 .2 Separation of PET

[0215] Polymeric material from Reference Example 1 still comprising PET and cotton and / or PA in shredded form was placed in a reaction vessel (e.g. flask, tube, reaction vessel). Degassed GVL was added (in mass-based ratio GVL: polymeric material 1 :1 to 100:1 , preferred 1 :1-10:1) and the mixture was heated under inert gas atmosphere at 1013 mbar by use of a suitable heating system (e.g. oil bath, heating blocks, mini-plant vessels) to 185 °C so that a mixture was obtained, wherein PET was fully dissolved, but solid particles remained in the mixture. After 5-60 min the mixture was filtered (e.g. heated pressure filtration), whereby a filter cake with undissolved polymeric materials (Cotton and / or PA) and a filtrate with PET were obtained. The filter cake was optionally further washed with a small amount of hot GVL.

[0216] Examples 1 to 5 (E1 to E5): Separation of PET from Cotton and / or PA

[0217] Polymeric material was treated as described in Reference Example 1 - if Spandex and / or colorant were present, according to 1.1 and 1.2 of Reference Example 1 - if no Spandex and / or colorant was present, then according to 1 .2 of Reference Example 1 only.

[0218] The resulting filtrate obtained from Reference Example 1 was cooled down from 185 °C to a temperature below 140 °C, and then further down to a temperature in the range of from 20 to 120 °C, wherein PET precipitated. Cooling was done -without addition of any further solvent or component- so that the filtrate was within the temperature range of from 160 to 145 °C for a period of time of at least 5 minutes, preferably at least 10 minutes, more preferably in the range from 5 to 120 minutes, more preferably in the range of from 10 to 100 minutes. A cooling rate < 3.0 °C / min, preferably

[0219] < 1.5 °C / min, more preferably in the range of from 0.05 to 3.0 C / min, more preferably in the range of from 0.13 to 3.0 °C / min, more preferably in the range of from 0.15 to 1.5 °C / min, more preferably in the range of from 0.15 to 1.0 °C / min, was used.

[0220] During cooling, the viscosity was determined. The experiment (E1) was repeated four times, each with fresh material (E2 to E5), wherein the maximum viscosity data of E1 to E5 are shown below in Table 1.

[0221] Table 1 maximum viscosity during cooling for examples E1 to E5

[0222] It was observed that in the temperature range of from 160 to 145 °C, a high viscous phase occurred with maximum viscosity in the range of from 5 to 12 Pa s, preferably in the range of from 5 to 10 Pa s.

[0223] The precipitate was filtrated and washed with a small amount of GVL. For an easy removal of GVL and a faster drying method of the re-obtained PET powder, small amounts of acetone were optionally used in a second washing step. The filter cake was also washed with a small amount of GVL.

[0224] Drying was done at a temperature of at the outmost 160 °C at a pressure in the range of from 1 to 1013 mbar for a period of time in the range of from 1 to 24 hours.

[0225] Mn and Mw values were determined by GPC analysis of the PET comprised in the starting materials and of re-obtained PET, and are listed below in Table 1a: Table 1a

[0226] Mn and Mw values from GPC analysis

[0227] Example 6 and Comparative Example 1 : Cooling

[0228] Example 1 was repeated twice with the deviation that cooling was done -without addition of any further solvent or component- so that the filtrate was within the temperature range of from 160 to 145 °C for a period of time of less 5 minutes (Comparative Example 1) and so that the filtrate was within the temperature range of from 160 to 145 °C for a period of time of 90 minutes (Example 6). After cooling down to a temperature in the range of from 20 to 120 °C, was completed and the PET had precipitated, the precipitate was filtrated over a pressure filter press with 1 bar nitrogen and the GVL was collected after filtration. The results are shown below in Table 2.

[0229] Table 2

[0230] Different cooling procedures

[0231] It was found that, if the filtrate is cooled so that the filtrate was within the temperature range of from 160 to 145 °C for more than 5 minutes, the fivefold amount of GVL could be recovered after filtration. This was very beneficial in view of solvent recycling. Example 2: Fiber preparation by spinning

[0232] A rPET fiber (rPET means recycled PET, i.e. PET obtained from a polymeric blend material) was produced from the precipitated PET of Example E1-E5 after pelletization and from pelletized virgin PET via melt spinning. “Virgin” PET meant PET not obtained by separation form a polymer blend but rather fresh PET made via chemical synthesis from the respective monomers from fossil source. The rPET granules were melted (temperature range: 250 -300 °C) in an extruder. The melted rPET was first filtered, then dosed via a pump and the filaments produced through a spinning nozzle. From monofilaments the fiber was then obtained. The fiber was then collected on a ribbon with different speeds (from 1000 m / min to 3000 m / min).

[0233] The resulting fiber had an elastic limit in the oriented state of more than 15 cN / tex, preferably in the range of from 15 to 70 cN / tex, determined according to DIN 53816:1993-02. Furthermore, the Young’s modulus of the fiber in oriented state was in the range of from 400 to 900 cN / tex, determined according to DIN 53834-1 :1976-02. Exemplarily, the measured / calculated values of the fiber obtained from E4 in oriented state were as follows:

[0234] Strength: 30.59 cN / text

[0235] Young’s modulus: 739.6 cN / tex

[0236] For comparison, the measured / calculated values of the fiber obtained from virgin PET in oriented state are as follows:

[0237] Strength: 29.79 cN / text

[0238] Young’s modulus: 656.93 cN / tex

[0239] Cited Literature

[0240] EP 2 784 110 A1

[0241] US 10,876,240 B2 DE 2223466 A1 WO 2016 / 12755 A 1

[0242] Wenjun Chen, Yuechao Yang, Xue Lan, Baolong Zhang, Xiaogang Zhang and Tiancheng Mu in Green Chem., 2021 , 23, 4065 WO 2022 / 221832 A 1

[0243] Handbuch der mechanischen Fest-Flussig-Trennung Taschenbuch - 29. April 2004 von Klaus Luckert (Herausgeber)

[0244] 5thEdition 5.1.03 (2008) of the HANSEN Solubility Parameters in Practice (HSPiP) “Dyes and Pigments” Metin Agikyildiz, Kubra Gunes, Ahmet Gurses Springer, 2016 (ISBN: 10

[0245] : 3319338900)

[0246] Industrial Organic Pigments - Klaus Hunger, Thomas Heber, Martin II. Schmidt, Friedrich

[0247] Reisinger, Stefan Wanne Wiley- VCH, 4thedition, 2018 (ISBN: 978-3-527-32608-2)

[0248] Chemistry and Technology of Natural and Synthetic Dyes and Pigments - Ashis Kumar Sa- manta, Nasser Awwad, IntechOpen, 2020 (ISBN: 9781789859980, 9781789859973, 9781839687587)

[0249] Encyclopedia of Color, Dyes, Pigments - Volume 1 , Gerhard Pfaff, de Gruyter, 2021 (ISBN: 311058588X)

[0250] Heinrich Zollinger: Color Chemistry: Syntheses, Properties, and Applications of Organic Dyes and Pigments. 3rdedition. WILEY-VCH Verlag, Weinheim 2003 (ISBN: 3-906390-23-3)

[0251] Klaus Hunger (Ed.): Industrial Dyes: Chemistry, Properties, Applications. WILEY-VCH Verlag, Weinheim 2003 (ISBN: 3-662-01950-7)

[0252] Hermann Rath: Lehrbuch der Textilchemie. einschl. der textilchemischen Technologie. 2nd edition. Springer-Verlag, Berlin, Heidelberg 1963 (ISBN: 978-3-662-00065-6); Wilfried Kratzert, Rasmus Peichert

[0253] Farbstoffe. Quelle & Meyer, Heidelberg 1981 (ISBN: 3-494-01021-8)

[0254] Ullmann’s Encyclopedia of industrial chemistry, Wiley-VCH, 2000, sections “dyes and pigments” and “dyes, general survey” (ISBN: 9783527303854).

Claims

Claims1 . A method for preparing a polyester fiber comprising providing a polymer blend, which comprises(i) a polyester and(ii) one or more component(s) selected from the group consisting of a second polymer, a third polymer, a colorant and a filler, wherein second polymer and third polymer are different from each other and different from the polyester of (i); the method comprising:(a) providing the polymer blend and providing a solvent system comprising gamma valerolactone;(b) optionally contacting the polymer blend with the solvent system at a temperature T 1 of < 170 °C, thereby obtaining a solvent system, which is enriched in dissolved second polymer and / or colorant and optionally in the filler or in a part of the filler, and a residue of the polymer blend, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler;(c) contacting the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) with a solvent system at a temperature T2 of > 170 °C, thereby obtaining a solvent system, which is enriched in dissolved polyester compared to the solvent system provided in (a) and comprises optionally the filler or a part of the filler, and optionally a residue of the polymer blend, which is depleted of polyester and comprises optionally the third polymer and optionally the filler or a part of the filler;(d) precipitating the polyester from solvent system, which is enriched in dissolved polyester, obtained in (c), thereby obtaining a precipitated polyester and a solvent system, which is depleted in dissolved polyester and which optionally comprises the filler or a part of the filler, wherein precipitation comprises cooling the solvent system obtained in (c), which is enriched in dissolved polyester compared to the solvent system provided in (a), from T2 to a temperature below 140°C, wherein cooling is done so that the temperature of the solvent system, which is enriched in dissolved polyester, is within the temperature range of from 160 to 145 °C for a period of time of at least 5 minutes;(e) preparing a fiber from the precipitated polyester obtained in (d).

2. The method of claim 1 , wherein precipitation in (d) comprises cooling the solvent obtained in (c), which is enriched in dissolved polyester compared to the solvent provided in (a), from T2 to a temperature below 140°C, wherein cooling is done so that the temperature ofthe solvent system, which is enriched in dissolved polyester, is within the temperature range of from 160 to 145 °C for a period of time of at least 10 minutes, preferably in the range from 5 to 120 minutes, more preferably in the range of from 10 to 100 minutes, more preferably in the range of from 15 to 100 minutes; wherein cooling in (d) is preferably done so that the solvent system, which is enriched in dissolved polyester, in the temperature range of from 160 to 145 °C has a viscosity in the range of from 1 to 12 Pa s, preferably in the range of from 1 to 10 Pa s, determined according to DIN EN ISO 2555 (2018-09).

3. The method of claim 1 or 2, wherein the cooling of the solvent system in (d) is done without addition of an anti-solvent.

4. The method of any one of claims 1 to 3, wherein (e) comprises(e.1) optionally melt extrusion of the precipitated polyester obtained in (d), thereby obtaining an extrudate comprising the polyester;(e.2) optionally pelletizing the extrudate obtained in (e.1), thereby obtaining an extrusion product comprising the polyester in pellet form;(e.3) fiber preparation from the precipitated polyester obtained in (d) or from the extrusion product comprising the polyester in pellet form obtained in (e.2), to give a polyester fiber.

5. The method of claims 4, wherein fiber preparation of (e.3) is done by a method selected from the group of melt spinning, electrospinning, wet spinning, matrix spinning and a combination of two or more of these methods, preferably by melt spinning, herein fiber preparation of (e.3) by melt spinning. Preferably comprises(e.3.1) providing precipitated polyester obtained in (d) or the polyester in pellet form obtained in (e.2);(e.3.2) melting the polyester provided in (e.3.1) at a temperature in the range of from 250 to 300 °C, preferably in an extruder, thereby obtaining melted polyester;(e.3.3) optionally filtering the melted polyester, thereby obtaining a filtered melted polyester;(e.3.4) extrusion of the melted polyester of (e.3.2) or of the filtered melted polyester obtained in (e.3.3), preferably through a spinning nozzle, thereby obtaining at least one fiber filament.

6. The method of claim 5, wherein fiber preparation comprises(e.3.5) optionally combining two or more fiber filaments obtained in (e.3.4) to obtain a fiber;(e.3.6) collecting the at least one fiber filament obtained in (e.3.4) or the fiber obtained in (e.3.5) on a ribbon, preferably with a speed of the ribbon of at least 500 m / min, more preferably in the range of from 1000 to 3000 m / min.

7. The method of any one of claims 1 to 6, comprising, if (b) is conducted, after (b) and before (c):(v) washing the residue of the polymer blend obtained in (b) with a washing solvent, thereby obtaining a washed residue, which is depleted of said second polymer and / or colorant and optionally in the filler or in a part of the filler, and comprises the polyester, optionally the third polymer and optionally the filler or a part of the filler;(w) optionally drying the washed residue obtained in (v).

8. The method of any one of claims 1 to 7, wherein at least 50 weight-%, preferably at least 60 weight-%, more preferably at least 70 weight-%, more preferably at least 80 weight-%, more preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the solvent system consists of gamma-valerolactone, based on the total weight of the solvent system being 100 weight-%.

9. The method of any one of claims 1 to 8, wherein the polyester is based on 1 ,2-ethandiol, more preferably the polyester according to (i) is based on 1 ,2-ethanediol and terephthalic acid (polyethylene terephthalate, PET), wherein more preferably at least 90 weight-%, more preferably at least 95 weight-%, more preferably at least 99 weight-% of the polyester are PET, based on the total weight of the polyester being 100 weight-%; and / or wherein the second polymer is selected from the group consisting of polyurethane (Pll), polyethylene glycol (PEG), polytetrahydrofuran (pTHF), mixtures of these polymers and copolymers of these polymers, wherein the second polymer is more preferably Pll or a copolymer of Pll and PEG and / or pTHF, more preferably Spandex; and / or wherein the third polymer is selected from polypropylene (PP), polyethylene (PE), polyamide (PA), natural polymer such as cotton, viscose, linen and mixtures of two or more thereof.

10. The method of anyone of claims 1 to 9, wherein in (c) the polymer blend provided in (a) or the residue of the polymer blend optionally obtained in (b) is contacted with a solvent system at a temperature T2 of > 170 °C to 200 °C, more preferably a temperature in the range of from 175 to 190 °C.11 . The method of anyone of claims 1 to 10, wherein the solvent system in step (d) comprises less than 5 weight-%, preferably less than 4 weight-%, more preferably less than 3 weight- %, more preferably less than 2 weight-%, more preferably less than 1 weight-%, of anti-solvents) based on the total weight of the solvent system including the anti-solvent(s) being 100 weight-%.

12. A polyester fiber, obtained or obtainable from the method of any one of claims 1 to 11 ; wherein preferably, the polyester fiber has an elastic limit in the oriented state of more than 15 cN / tex, preferably in the range of from 15 to 70 cN / tex, determined according to DIN 53816:1993-02; and / or wherein preferably, the polyester fiber has a Young’s modulus of the fiber in oriented state in the range of from 400 to 900 cN / tex, determined according to DIN 53834-1 :1976-02.

13. Use of a polyester fiber according to claim 12 for preparing a textile.

14. A method for preparing a product comprising(I) providing polyester of claim 12;(II) preparing a textile from the polyester provided in (I).

15. Method according to any one of claims 1 to 11 , comprising the further step: converting a residue obtainable by or obtained by the method according to any one of claims 1 to 11 , preferably obtained or obtainable from step (d), more preferably the residue comprising at least third polymer obtainable by or obtained by the method according to according to any one of claims 1 to 11 , preferably obtained or obtainable from step (d), to obtain one or more monomer, polymer or polymer product; wherein preferably, the monomer is a di- or polyol; preferably butandiol; aldehyde; preferably formaldehyde; di- or polyisocyanate; preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI); amide; preferably caprolactam; alkene; preferably styrene, ethene and norbornene; alkyne, (di)ester; preferably methyl methacrylate; mono or diacid; preferably adipic acid or terephthalic acid; diamine; preferably hexamethylenediamine, nonanediamine; or sulfones; preferably 4,4'-di- chlorodiphenyl sulfone; and / or wherein preferably, the polymer is and / or the polymer product comprises polyamide (PA); preferably PA 6 or PA 66; polyisocyanate polyaddition product; preferably polyurethane (PU), thermoplastic polyurethane (TPU), polyurea or polyisocyanurate (PIR); low-densitypolyethylene (LDPE), high-density polyethylene (HDPE), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polystyrene (PS), poly acrylonitrile butadiene styrene (ABS), poly styrene acrylonitrile (SAN), poly acrylate styrene acrylonitrile (ASA), polytetrafluoroethylene (PTFE), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), polybutadiene (BR, PBD), poly(cis-1,4-isoprene), poly(trans-1,4- isoprene), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polybutylene adipate coterephthalate (PBAT), polyester (PES), polyether sulfone (PESLI), polyhydroxyalkanoate (PHA), poly-3-hydroxybutyrate (P3HB), poly- 4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), polyhydroxyoctanoate (PHO), polylactic acid (PLA), polysulfone (PSU), polyphenylene sulfone (PPSLI), polycarbonate (PC), polyether ether ketone (PEEK), poly(p-phenylene oxide) (PPO), poly(p-phenylene ether) (PPE); or copolymer or mixture thereof; and / or wherein preferably, the polymer and / or the polymer product is / are or is / are a part of: a part of a car; preferably cylinder head cover, engine cover, housing for charge air cooler, charge air cooler flap, intake pipe, intake manifold, connector, gear wheel, fan wheel, cooling water box, housing, housing part for heat exchanger, coolant cooler, charge air cooler, thermostat, water pump, radiator, fastening part, part of battery system for electromobility, dashboard, steering column switch, seat, headrest, center console, transmission component, door module, cover for car A, B, C or D pillar, spoiler, door handle, exterior mirror, windscreen wiper, windscreen wiper protection housing, decorative grill, cover strip, roof rail, window frame, sunroof frame, antenna panel, headlight and taillight, engine cover, cylinder head cover, intake manifold, airbag, cushion, or coating; a cloth; preferably shirt, trousers, pullover, boot, shoe, shoe sole, tight or jacket; an electrical part; preferably electrical or electronic passive or active component, circuit board, printed circuit board, housing component, foil, line, switch, plug, socket, distributor, relay, resistor, capacitor, inductor, bobbin, lamp, diode, LED, transistor, connector, regulator, integrated circuit (IC), methodor, controller, memory, sensor, microswitch, microbutton, semiconductor, reflector housing for light-emitting diodes (LED), fastener for electrical or electronic component, spacer, bolt, strip, slide-in guide, screw, nut, film hinge, snap hook (snap-in), or spring tongue; a consumer, agricultural product or pharmaceutical product; preferably tennis string, climbing rope, bristle, brush, artificial grass, 3D printing filament, grass trimmer, zipper, hook and loop fastener, paper machine clothing, extrusion coating, fishing line, fishing net, offshore line and rope, vial, syringe, ampoule, bottle, sliding element, spindle nut, chain conveyor, plain bearing, roller, wheel, gear, roller, ring gear, screw and spring dampers, hose, pipeline, cable sheathing, socket, switch, cable tie, fanwheel, carpet, box or bottle for cosmetics, mattress, cushion, insulation, detergent, dishwasher tabs or powder, shampoo, body wash, shower gel, soap, fertilizer, fungicide, or pesticide; a packaging for the food industry; preferably mono- or multi-layer blown film, cast film (mono- or multi-layer), biaxially stretched film, or laminating film; or a part of a construction; preferably a rotor blade, insulating material, frame, housing, wall, coating, or separating wall.

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