Method and apparatus for removing dyes from waste textiles

Abstract

In a method of recovering a waste fabric comprising dyed polyester fibers or dyed cellulosic fibers, a polar solvent flows through the waste fabric in an extraction chamber to remove dye; the solvent is evaporated and condensed in the evaporation chamber to be sent to the solvent collection tank or sent back to the extraction chamber; during treatment, any elastic material present in the waste fabric is dissolved by a solvent.

Description

Technical Field

[0001] The present invention relates to methods and plants for removing dyes from waste textiles to recover textile materials such as fabrics, yarns, filaments, and garments. More specifically, the present invention relates to a method for recovering polyester materials from waste fabrics and garments containing polyester fibers and filaments, dyes, and possibly elastic materials. The present invention also relates to a method for recovering waste textiles comprising dyed cotton fibers containing indigo or indigo-like dyes or consisting of dyed cotton fibers containing indigo or indigo-like dyes. Background Art

[0002] Recycling old fabrics, also known as "waste fabrics", has become a major goal of the textile industry; new and efficient recycling methods are currently being actively studied. One goal is to recover the polyester fibers and filaments present in widely used fabrics. Another goal is to recycle cotton and cellulose fabrics.

[0003] One problem in recycling polyester or cotton fabrics is removing dyes from the polyester or cotton fibers and filaments of the fabrics.

[0004] WO2022118244 discloses a method for recovering waste polyester materials (including waste textiles) by dissolving polyester in a solution containing hexafluoroisopropanol and a chlorinated hydrocarbon and / or an aromatic hydrocarbon. Before dissolution, pretreatment is carried out with dichloromethane (DCM) to remove colors and impurities in PET bottles and waste textile materials. This method cannot effectively and thoroughly remove dyes.

[0005] US2022169786 describes a method for producing decolorized polyester by removing a colorant from polyester with a decolorizing agent containing an ethylene glycol ether compound having a boiling point of 160°C or higher at atmospheric pressure while heating the decolorizing agent to a temperature equal to or lower than the melting point of polyester.

[0006] EP3699355 discloses a method and system for decolorizing textile waste dyed with disperse dyes using a magnetic dye adsorption material in a hydrothermal environment. In a decolorization reactor containing water and magnetic activated carbon as a dye absorption material, the textile material is treated under stirring at the autogenous pressure obtainable when heated to about 100°C to 170°C. An ultrasonic generator (9) is activated to accelerate the release of dye molecules from the textile material into the water. The dye released from the polyester fibers is adsorbed by the magnetic activated carbon, and the magnetic activated carbon is collected by activating a magnetic field at the end of the process. Summary of the Invention

[0007] Generally, known methods result in partial degradation of polyester materials or cotton fibers. If operations are to be carried out under mild conditions to reduce degradation, only part of the dye can be removed. The degradation of the polymer may be unfavorable for the reuse of recycled polyester materials. Similarly, the degradation of cotton fibers also endangers the mechanical properties of the yarns produced from recycled cotton fibers and may also affect their appearance.

[0008] In particular, if there is a method to remove all decorations and dyes, i.e., disperse dyes, from dyed or printed polyester garments, or to remove indigo and indigo-like dyes from cotton garments without degrading the fabric and the garment, then the treated decolorized garments can be dyed with other colors or printed with new patterns or decorations again, which would be very useful.

[0009] Another problem is that polyester-based fabrics and garments usually may contain polyurethane materials, which can be in the form of elastane-type filaments in the fabric yarns or can be layers as decorations printed on the garments (such as sportswear). The presence of elastic materials may be a problem when recycling polyester fibers. The same problem also exists for cotton fabrics and garments.

[0010] The object of the present invention is to solve the above problems and to provide a method for recycling waste fabrics containing polyester or polyester-based, or for recycling waste textiles containing dyed cotton fibers or consisting of dyed cotton fibers, said dyed cotton fibers containing indigo or indigo-like dyes, said method providing a safe, simple and environmentally friendly method for recycling polyester materials or cotton materials in waste textiles by removing dyes from the waste textiles without or with reduced degradation of the polyester materials or cotton materials in the waste textiles.

[0011] The decolorized polyester materials can be further recycled in a manner known per se, for example by digesting cellulose fibers (if present) or by depolymerizing the polyester, or by recycling the polyester as short fibers.

[0012] Similarly, the decolorized cotton or cellulose materials can also be recycled in a manner known per se, for example by mechanically providing cotton or cellulose short fibers that can be processed into yarns.

[0013] Especially for pre-consumer materials consisting of garments or fabrics, said garments or fabrics can be decolorized to the greige state (undyed) and recycled by subsequently dyeing and / or printing the treated garments.

[0014] The problems are solved by the method according to claim 1 and the device according to claim 10.

[0015] Accordingly, the present invention relates to a method for recycling waste textiles by removing dyes from the waste textiles, wherein the waste textiles contain polyester fibers or consist of polyester fibers, the polyester fibers contain disperse dyes for the polyester fibers, or the waste textiles contain dyed cotton fibers or consist of dyed cotton fibers, the dyed cotton fibers contain indigo or indigo-like dyes, and is characterized by comprising the following steps:

[0016] a) Providing a quantity of the waste textiles in an extraction chamber and heating the chamber;

[0017] b) Circulating a solvent suitable for removing the dyes from the waste textiles through the extraction chamber and the waste textiles;

[0018] c) Returning the solvent leaving the extraction chamber to the extraction chamber to increase the amount of dyes removed from the waste textiles;

[0019] d) Evaporating at least a portion of the solvent obtained in step c) in an evaporation chamber;

[0020] e) Condensing the evaporated solvent in at least one condensation chamber.

[0021] According to one aspect of the present invention, the method further comprises the following steps: f) Directly or indirectly feeding at least a portion of the condensed solvent into the extraction chamber and g) Repeating steps b)-f) until the dyes are removed.

[0022] According to one aspect of the present invention, there is provided a method for recycling waste textiles containing polyester fibers and dyes (i.e., disperse dyes), the method comprising the steps of: removing the disperse dyes from the waste textiles using a solvent selected from dimethylformamide (DMF) and dimethylacetamide (DMAC), and circulating (i.e., flowing) the solvent through the waste textiles in an extraction chamber until the dyes are removed. Preferably, polyurethane materials (if present) are also removed from the waste textiles.

[0023] According to one aspect of the present invention, there is provided a method for recycling waste textiles containing cotton and / or cellulose fibers and dyes (i.e., indigo or indigo-like dyes), the method comprising the steps of: removing the indigo or indigo-like dyes from the waste textiles using a solvent selected from dimethylformamide (DMF) and dimethylacetamide (DMAC), and circulating (i.e., flowing) the solvent through the waste textiles in an extraction chamber until the dyes are removed. Preferably, polyurethane materials (if present) are also removed from the waste textiles.

[0024] As more fully disclosed in the following description, the recycling of the solvent (i.e., DMF or DMAC) involves feeding the solvent into an extraction chamber (which is static and contains waste textiles), causing the solvent to flow through the textile material and the chamber, and preferably returning the solvent leaving the extraction chamber back to the extraction chamber and passing it through the textile at least once to increase the dye content removed from the textile. In the following description and claims, the term "solvent" is used to denote dimethylformamide (DMF) or dimethylacetamide (DMAC).

[0025] Advantageously, at least a portion of the solvent (containing the dye removed from the fabric) is fed into an evaporation chamber for distillation and recycled in the process by condensing the evaporated solvent and feeding at least a portion of the condensed solvent into the extraction chamber. The content of the dye (and possibly elastic material) in the waste textiles decreases with each pass of the solvent through the waste textiles. At the same time, the content of the dye (i.e., disperse dyes and indigo / indigo-like dyes) and the content of the elastic material (if present) in the evaporation chamber increase over time.

[0026] Finally, the solvent containing the concentrated dye and possibly present elastic material can be recovered from the evaporation chamber or a different container by distillation, and after removing the solvent, the dye and possibly present elastic material remain as solids.

[0027] In this method, textile materials, such as fabrics, garments, or fibers, are accommodated in a stationary (i.e., static) extraction chamber. The textile materials are also in a stationary, i.e., static, state, except for the movement that may be brought about by the circulating solvent flow (e.g., by a pump) through the static extraction chamber and the textiles.

[0028] Fabrics that can be recycled by the claimed method are those polyester sportswear, such as T-shirts and garments with a thin layer or film of polyurethane material applied thereon and printed decorations. The polyurethane layer and the ink forming the decorative elements (such as trademarks or numbers, etc.) are dissolved by the solvent.

[0029] In the following description, the term "polyurethane material" or "PU material" is mentioned; this term includes elastic materials (such as elastane and spandex) used in yarns (usually in the yarn core), and any other polyurethane materials that may be present on or in the fabric, such as part of a decoration (such as a printed decoration), as described above.

[0030] The polyester fibers mentioned in the following description include any fibers, such as staple fibers and polyester continuous filaments in any state (such as textured, POY, FDY, etc.).

[0031] The cotton fibers mentioned in the following description generally include cotton fibers and cellulose fibers.

[0032] The solvent allows an increase in the contact time of the waste textiles by recycling, i.e., repeated circulation or repeated flow, through the extraction chamber and the waste textiles. The increase in time allows a reduction in the amount of solvent used, and thus ultimately a reduction in the total process time required to remove the dye from the waste textiles.

[0033] Advantageously, the ratio of waste textiles (weight, kg) to solvent (volume, liters) is between 1:8 and 1:12, preferably 1:10. This ratio can reduce the environmental impact of the recycling process.

[0034] In one embodiment, the solvent containing the dissolved dye and possibly PU material leaving the extraction chamber is sent back to the extraction chamber at least once to recycle through the waste, thereby increasing the content of the removed dye and polyurethane material in the solvent. Thus, the solvent is recycled (preferably continuously) in the extraction chamber containing the waste textiles, allowing an increase in the contact time of the same solvent with the waste textiles.

[0035] In one embodiment, the solvent leaving the extraction chamber is sent to an evaporation chamber for distillation; the distilled and condensed solvent is sent back to the extraction chamber.

[0036] In a preferred embodiment, a portion of the solvent, preferably after a selected time of recycling, is sent to an evaporation chamber where it is distilled by evaporation and condensation of the solvent. The distilled solvent is sent back to the extraction chamber, or in a preferred embodiment, to a solvent reservoir and ultimately fed back into the extraction chamber from the reservoir when needed.

[0037] According to a preferred aspect of the invention, the solvent leaving the extraction chamber is filtered. Filtering the solvent maximizes the amount of waste textiles remaining in the extraction chamber while keeping the solvent free of solid substances that could endanger the quality of the final product.

[0038] According to a possible embodiment, the solvent is filtered by a filter basket that holds the waste textiles in the extraction chamber. Advantageously, the filter basket can be a rigid structure, such as a metal structure, with filter openings along its surface to allow the solvent to flow through. Holding the waste textiles in the filter basket allows the flow of the solvent through the waste textiles to be restricted to a closed volume without agitating the fabric / textile fragments.

[0039] According to a possible aspect, at least a part of the method, such as steps d) and e), is carried out under reduced pressure, i.e., the evaporation and condensation parts of the equipment are connected to a source of reduced pressure. Since steps d) and e) are carried out under reduced pressure, it is possible to lower the temperature required to evaporate the solvent in the evaporation chamber. The lower evaporation temperature can prevent degradation of the solvent in the equipment or the degradation can be negligible, so the same solvent can be used for multiple processes.

[0040] In one embodiment, the suitable pressure value range in the evaporation chamber (and other parts of the equipment that may be connected to the evaporation chamber) is from 20 to 100 mbar, preferably from 35 to 100 mbar, and most preferably from 40 to 80 mbar.

[0041] According to a possible aspect, the method includes the step of heating the extraction chamber, thereby heating the solvent flowing through the extraction chamber (and the waste textiles). Advantageously, the extraction chamber is heated to a temperature that raises the temperature of the solvent in the extraction chamber to a value that does not cause solvent degradation. The increase in the temperature of the waste textiles and the solvent preferably shortens the time required to dissolve and remove the dyes and any polyurethane materials that may be present in the waste textiles.

[0042] In one embodiment, the solvent is recycled by a pump. Advantageously, recycling the solvent by a pump allows increasing the number of times the same portion of waste textiles comes into contact with a certain volume of solvent, where the waste textiles are subjected to the action of the solvent, thereby accelerating the rate of removing dyes (and PU materials if present) from the waste textiles.

[0043] Furthermore, different from the methods known in the art, the waste textiles remain stationary (i.e., static) in the extraction chamber. For example, the waste textiles are not agitated by, for example, a stirring rotor. Similarly, in a preferred embodiment, the extraction chamber and the filter basket containing the waste textiles can be configured to be stationary and static. For example, the basket does not rotate. In one embodiment, the textiles completely fill the basket in the extraction chamber, so that when the solvent is circulated, that is, pumped into and out of the extraction chamber, the textiles remain in a static state.

[0044] In one embodiment, the waste textiles are compressed in the basket to maximize the use of the volume of the basket; the compression of the waste textiles advantageously improves the productivity of the method.

[0045] Advantageously, the textile material (such as fabric) being in a static state significantly reduces the amount of short fibers (such as cotton fibers and cellulose fibers) that may be present, and these short fibers will loosen or break and fall off from the textile material during processing.

[0046] According to a possible aspect, steps d) and e) are carried out under reduced pressure, and the solvent is heated in the evaporation chamber to a temperature value below the boiling point of the solvent at the selected pressure, preferably below 100 °C, to prevent solvent degradation.

[0047] Suitable solvents are dimethylformamide (DMF) and dimethylacetamide (DMAC). DMF and DMAC are polar solvents, and they are unexpectedly found to be suitable for removing disperse dyes under the process temperature conditions. DMF and DMAC can also dissolve the PU and elastic materials that may be present in or on the waste textiles.

[0048] Advantageously, under the claimed process conditions, the claimed solvent can remove the dyes without causing degradation of the polyester or cotton fibers in the textile or significantly reducing the degradation of the polyester or cotton fibers in the textile. In fact, for polyester, the following results were observed: the IV (intrinsic viscosity) decreased by about 3% (measured according to BS EN ISO 1628-5:2015), and the tensile strength decreased by about 5% (measured according to ASTM D5034-21).

[0049] According to a possible aspect, the extraction chamber is under reduced pressure, and the temperature of the solvent in the extraction chamber is higher than 80 °C, preferably 85 to 100 °C, most preferably 85 to 95 °C.

[0050] Another object of the present invention is to provide a device for implementing the above method, which can recycle waste textiles containing polyester fibers by removing dyes (i.e., disperse dyes), or recycle waste textiles containing cellulose fibers by removing indigo and indigo-like dyes. Advantageously, the PU material that may be present in the fabric is removed.

[0051] According to the present invention, the device includes an extraction chamber configured to accommodate waste textiles including disperse dyes and / or indigo or indigo-like dyes and possibly polyurethane materials, and a solvent selected from DMF and DMAC.

[0052] The extraction chamber preferably includes at least one heater. The device further includes a circulation device for circulating (preferably at least once) the solvent through the extraction chamber; an evaporation chamber configured to collect the solvent containing the dissolved dye and evaporate at least part of the solvent to be re-fed into the extraction chamber; and at least one condensation chamber including a cooling system configured to condense the solvent evaporated in the evaporation chamber and feed the condensed solvent directly or indirectly into the extraction chamber.

[0053] In a possible embodiment, the recovered solvent can be fed into a solvent reservoir, for example, when the process is not running.

[0054] According to a preferred embodiment, the extraction chamber of the device includes a filtering device, preferably a mesh filter basket for accommodating waste textiles. As described above, the filtering device in the extraction chamber allows waste textiles and small fibers that may fall off the textiles to be accommodated in the extraction chamber.

[0055] According to one aspect of the present invention, the device is connected to a reduced-pressure circuit. Preferably, the circuit includes a vacuum pump. Preferably, the extraction chamber and the condensation chamber are connected to or can be connected to the reduced-pressure circuit.

[0056] According to a possible aspect, the decompression circuit of the device is connected to the at least one condensation chamber. Preferably, there are two condensation chambers connected in series to prevent solvent vapors from leaving the device.

[0057] According to a possible aspect, a solvent collection tank, i.e., a solvent reservoir, is connected to the extraction chamber and the condensation chamber via suitable pipelines or conduits. Advantageously, the solvent collection tank can hold the solvent removed from the evaporation chamber.

[0058] Alternatively, the solvent contained in the solvent collection tank can be fed into the extraction chamber before step b), where the solvent circulates through the extraction chamber and the waste textile to dissolve and remove the elastic material from the waste textile. Advantageously, the solvent is contained in the solvent collection tank and fed back into the extraction chamber, whereby the solvent can be provided, which, after the condensation step in at least one condensation chamber, can be recycled through the extraction chamber and the waste textile to dissolve and remove the elastic material from the waste textile.

[0059] According to a possible aspect, the solvent collection tank can be connected to the condensation chamber to selectively receive the condensed solvent.

[0060] According to a possible aspect, the evaporation chamber includes a mixer or agitator for improving the evaporation of at least part of the solvent from the solution of the elastic material in the evaporation chamber to increase the amount of solvent distilled from the evaporation chamber.

[0061] Further aspects and advantages according to the present disclosure will be discussed in more detail with reference to the accompanying drawings, which are given by way of non-limiting examples, wherein:

[0062] - Figure 1 shows a schematic diagram of a device according to a possible embodiment of the present invention;

[0063] - Figure 2 is a flowchart illustrating the extraction method according to the present invention, and

[0064] - Figure 3 shows 15 dyed or printed polyester fabric samples before and after treatment according to the present invention.

[0065] Reference Figure 1Exemplary embodiments, the textile recycling device 100 includes an extraction chamber 4 configured to accommodate waste textiles 2, which are textiles containing polyester fibers 1 dyed with disperse dyes. In one embodiment, the textile contains cellulose fibers, especially cotton fibers, dyed with indigo and indigo-like dyes. The extraction chamber 4 is configured to receive and contain a solvent 3 (DMF or DMAC) suitable for removing the dye 1 and dissolving any PU material that may be present. The extraction chamber 4 is connected to a recirculation loop 42, where the solvent 3 leaving the extraction chamber through the chamber outlet conduit 43 can be recirculated to the extraction chamber 4 via the extraction chamber inlet conduit 44 by means of a circulation device 9. Preferably, the circulation device 9 is a pump. A valve V is located in the loop pipeline to control the flow of the solvent.

[0066] In Figure 1 In an embodiment, the extraction chamber 4 is connected to an evaporation chamber 6 through a conduit 41. The extraction chamber 4 is connected to a condensation chamber 7 through a conduit 72. The extraction chamber 4 is also connected to a solvent collection tank 20 through a conduit 201. Appropriate valves V are installed on the lead-out conduits to selectively direct the solvent flow to the components required by the device.

[0067] In a possible embodiment, the method of the present invention preferably provides for filtering the solvent containing the extracted dye to remove fibers of other materials other than elastomeric fibers, such as removing cotton fibers. Preferably, the extraction chamber 4 includes a filtering device, such as a mesh filter basket 40, to accommodate the waste textiles 2 containing the dye 1.

[0068] The mesh filter basket 40 is provided with Figure 1 Openings not shown in the figure, which allow the solvent to flow throughout the volume of the extraction chamber 4 while retaining the waste textiles 2 within the mesh filter basket 40. In a preferred embodiment, the filter basket is made of stainless steel or includes a non-woven fabric that acts as a filter inside; the non-woven fabric is resistant to the solvents used in the extraction chamber and can be used alone or fixed to or accommodated by a metal support (such as the filter basket 40) to retain fibers or particles detached from the textile material.

[0069] According to a possible aspect, the extraction chamber 4 includes at least one heater 3. The heater 3 heats the solvent (and the waste textiles 2) in the extraction chamber 4 during the process to facilitate the extraction of the dye and any PU material from the waste textiles.

[0070] The device further includes an evaporation chamber 6. The evaporation chamber 6 is configured to collect (i.e., receive) a solution 3' containing the solvent 3 and the dissolved dye (possible PU material) 1 obtained by circulating the solvent in the chamber 4 and to evaporate at least part of the solvent from the solution 3' to recover the solvent 3 for the extraction step. As previously mentioned, the evaporation chamber 6 is connected to the extraction chamber 4 through a conduit 41.

[0071] According to a possible aspect, the evaporation chamber 6 includes stirring means, such as a mixer 66. Generally, as is known in the art, the mixer 66 includes a rotating rod 61 and a plurality of protrusions 62. The protrusions 62 rotate within the solution 3' to maximize the evaporation of the solvent in the solution 3. The evaporation chamber 6 is also equipped with heating means to heat the solvent therein to the boiling point under reduced pressure, as detailed below.

[0072] To recover the evaporated solvent, the apparatus further includes at least one condensation chamber 7. The evaporation chamber 6 is fluidly connected to the condensation chamber 7 via a pipe 60. In the preferred embodiment shown in the figure, the apparatus is equipped with two condensation chambers 7a, 7b arranged and connected in series.

[0073] The condensation chamber 7 includes a cooling system 10 configured to condense the solvent evaporated from the solution 3' in the evaporation chamber 6 and send the condensed solvent to at least one of the extraction chamber 4 and the solvent collection tank 20 via a conduit 72. In other words, the solvent 3 in the condensation chamber reaches the dew point, allowing the solvent to condense and be sent back to the extraction step in the extraction chamber 4 (if the process is ongoing) or the solvent collection tank 20, or both.

[0074] In the embodiment shown, the apparatus is connected to a reduced-pressure circuit 71 including a vacuum pump 70 and a separation element 75 to collect the solvent 3 that may flow back to the extraction chamber 4 or the solvent collection tank 20 (batch process). Preferably, the vacuum circuit is connected to the condensation chamber, and the condensation chamber is connected to the evaporation chamber. Thus, during the process of the present invention, at least the evaporation chamber 6 and the condensation chamber 7 are maintained under reduced pressure. The vacuum pump is advantageously configured to generate a reduced pressure of 20 mbar to 100 mbar, preferably 35 mbar to 100 mbar, and most preferably 40 mbar to 80 mbar in the evaporation chamber.

[0075] Advantageously, the reduced-pressure circuit 71 is connected to at least one condensation chamber 7 via a conduit 80; in Figure 1 the embodiment including condensation chambers 7 and 7a, the vacuum circuit 71 is connected to the end portion of chamber 7a, so as to condense all of the evaporated solvent in the two chambers before it reaches the end of the condensation chamber system.

[0076] At least the main components of the apparatus, namely the extraction chamber 4, the evaporation chamber 6, the condensation chambers 7, 7a, 7b, and the solvent collection tank 20, are equipped with pipes and valves Av to communicate the apparatus with the atmosphere when decompression is not required within the apparatus.

[0077] As described above, preferably, the apparatus further includes a solvent collection tank 20 for storing the solvent 3. The solvent collection tank 20 is connected to the extraction chamber 4 through conduits 74, 201 and is connected to the evaporation chamber 6 through a conduit 75. According to a possible embodiment, the condensation chamber 7 is connected to the solvent collection tank 20 through a conduit 202, and a valve is provided on the conduit 202 for guiding the solvent to flow to the collection tank 20 or the extraction chamber 4. Preferably, the solvent 3 stored in the solvent collection tank 20 can flow to the extraction chamber 4 through the conduits 74, 201 via a decompression circuit 71 and a vacuum pump 70 under a reduced pressure state.

[0078] The present invention further provides a method for recycling waste textiles 2 containing polyester fibers and disperse dyes, or waste textiles containing cotton / cellulose fibers and indigo or indigo-like dyes; the waste textiles may further contain a PU material, such as an elastic material in the form of fibers; the PU material may also exist in the form of ornaments printed on the fabric, for example, by applying a PU layer on the fabric.

[0079] The fabric can be processed in a known manner, such as being shredded or cut into small pieces, or it can be kept in its original clothing form, such as being a pair of pants or a T-shirt; generally, shredding is carried out after removing parts such as plastic tags or zippers, metal components, etc.

[0080] First, in step a), a certain amount of waste textiles 2 are loaded into the extraction chamber 4. Preferably, the waste textiles are packed and compressed into the basket of the extraction chamber.

[0081] In the subsequent step b), the solvent 3 is fed into the chamber 4 and passes through the extraction chamber and the textiles to dissolve and remove the dye 1 and the possible PU material in the waste textiles 2. Preferred solvents for disperse dyes are DMF and DMAC. In a preferred embodiment, the solvent is fed into the extraction chamber at a controllable flow rate, flows through the waste textiles, and then exits the chamber 4; the flow rate is preferably obtained by a pump 9 that forces the solvent to flow along the desired path.

[0082] In step c), the solvent 3 that leaves the extraction chamber 4 through the outlet pipe 43 is guided along a recirculation circuit 42 and flows back into the extraction chamber 4 through the inlet pipe 44 at least once to extract more dye and increase its content in the solvent. In other words, the recirculation of the solvent through the circuit 42 allows maximizing the concentration of the dissolved dye 1 in the solvent.

[0083] Preferably, a certain volume of the solvent passes through the extraction chamber and the waste textiles at least three times, i.e., three cycles. Usually, in each cycle, the solvent is recirculated for at least 70 minutes, preferably at least 80 minutes, more preferably at least 90 minutes, and possibly up to 150 minutes. After one cycle, preferably, the solvent is fed into the evaporation chamber, and then a clean solvent is used in the next cycle.

[0084] During the extraction process, by connecting the device to the circuit 71, at least a part of the device, namely the evaporation chamber and the condensation chamber, is kept under reduced pressure. The suitable pressure value in the device (i.e., chambers 4, 6, and 7) is about 20 to 100 mbar, preferably 35 to 100 mbar, more preferably 40 to 80 mbar. Advantageously, the reduced pressure will lower the boiling point temperature of the solvent to promote the evaporation of the solvent in step d), thereby reducing or preventing the degradation of the solvent.

[0085] To improve the extraction effect of the dye (and the polyurethane material that may be present), the extraction chamber 4 needs to be heated. According to one aspect, the temperature of the solvent in the extraction chamber 3 is equal to or higher than 80 °C, within the range of 85 to 100 °C, preferably 80 - 90 °C, possibly 81 - 90 °C, that is, 85 °C. The extraction chamber is usually not connected to the reduced pressure circuit 71. In a preferred embodiment, to transfer the solvent containing the extracted dye from the extraction chamber 4 to the evaporation chamber 6, as described above, under reduced pressure, the extraction chamber 4 is connected to the evaporation chamber 6: once the two chambers are connected by the conduit 41, the liquid content in chamber 4 will be transferred to the evaporation chamber 6.

[0086] The solvent can also be transferred from the solvent reservoir 20 to the extraction chamber 4 by temporarily reducing the pressure in the extraction chamber 4 before connecting the extraction chamber 4 to the reservoir 20. Generally, in addition to using the pump 9 to circulate the solvent in and out of the extraction chamber, the pressure difference between the various parts of the device can also be utilized to transfer the polar solvent to the various parts of the device.

[0087] According to a possible aspect, the solvent 3 leaving the extraction chamber 4 is filtered through the mesh filter basket 40. In other words, the filtration can retain the waste textile 2 in the mesh filter basket 40 during step c), only allowing the solvent 3 to leave the extraction chamber 4 through the outlet 43 and the recirculation circuit 42 and flow back into the extraction chamber 3 through the inlet 44, while retaining the waste textile 2 in the extraction chamber 4.

[0088] Once the solvent containing the dye 1 and any polyurethane material extracted in step c) has circulated through the textile material for a sufficient number of times, that is, the total time is long enough to achieve the purpose of extracting the desired elastic material, the dyed solvent is guided to the evaporation chamber 6 through the conduit 41. In the evaporation chamber 6, at least a part of the solvent is evaporated and recovered into the process.

[0089] As described above, due to the action of the decompression circuit 71 and the vacuum pump 70, the evaporation and condensation steps are preferably carried out under reduced pressure. Therefore, the solvent 3 in the evaporation chamber 6 can be heated to a temperature value lower than the boiling point under atmospheric pressure, preferably lower than 100 °C, to prevent solvent degradation. The temperature range of the evaporation chamber is from 75 to 95 °C, preferably from 80 to 90 °C. At the above temperatures, the reduced pressure range in the evaporation chamber is from 20 mbar to 100 mbar, or preferably from 35 to 85 mbar, more preferably from 40 to 80 mbar.

[0090] In step e), the solvent vapor flows along the conduit 60 to the condensation chamber 7, where the vapor is condensed. In Figure 1 the illustrated embodiment, two condensation chambers 7a and 7b arranged and connected in series are provided. The condensed solvent 3 is fed into the extraction chamber 4 through the conduit 72; alternatively, the liquid solvent can be stored in the solvent reservoir 20 through the conduit 202, or pumped back into the extraction chamber 4 through the conduit 74.

[0091] In one possible embodiment, as Figure 2 schematically shown, the DMF solvent is recycled through the extraction chamber until the required reduction in dye is detected (e.g., visually), and then it is sent to the evaporation chamber 6. In one possible embodiment, the solvent is circulated through the fabric at least 3 times, each time for about 90 minutes. Preferably, a cleaning solvent is added to the system in each cycle.

[0092] At the end of the extraction process, a further step can be carried out to remove and recover the solvent from the waste textile, and the solvent recovery step is preferably selected from pressing, squeezing, rotating or centrifuging the solvent-soaked waste textile.

[0093] The present invention will be further explained by referring to the following non-limiting examples.

[0094] Example 1

[0095] 1.5 kg of textile waste was collected, including polyester, polyester - elastane, polyurethane - printed polyester pre - consumer fabric, post - consumer fabric, and fibers. The textile waste was contained in a stainless - steel filter basket. The 1.5 kg of textile waste was placed in an extraction chamber heated to 90 - 95 °C and recycled through 15 liters of DMF three times, 90 minutes each time (3 x 90 minutes, a total of 270 minutes). The sample / DMF ratio (flotte) was 1:10. During the recycling process, the exiting solution was fed into an evaporation chamber and heated at 40 - 80 mbar, 85 ± 5 °C; the solvent was evaporated and stored in a solvent collection tank. After the extraction process, the textile waste was squeezed to remove the residual solvent added to the solution in the evaporation chamber. After complete removal of DMF, the elastomeric material, dyes, and polyurethane prints were separated in solid form. At the end of the process, the mass loss of the waste textiles was 150 grams (10%). No elastane fibers were found in the treated textile waste at the end of the process. It was observed that the prints and colors in the waste were completely removed, forming a white greige fabric.

[0096] Example 2

[0097] 1.8 kg of colored pre - consumer clothing (T - shirts) was collected without cutting or shredding. The clothing was placed in an extraction chamber heated to 90 - 95 °C and recycled through 19 liters of DMF three times, 90 minutes each time (a total of 270 minutes). During the dye extraction process, the exiting solution was fed into an evaporation chamber and heated at 60 - 80 mbar, 85 ± 5 °C; the solvent was evaporated and stored in a solvent collection tank (20) (batch process). After the extraction process, the clothing was pressed to remove the residual solvent added to the solution in the evaporation chamber. After complete removal of DMF, the dyes were separated in solid form. The clothing was in greige state and could be recycled by re - dyeing and / or printing different colors.

[0098] Example 3

[0099] 2 kg of fabric waste was collected. The 2 kg of fabric was placed in an extraction chamber heated to 90 - 95 °C and recycled through DMAC three times, 90 minutes each time (3 x 90 minutes, a total of 270 minutes). During the recycling process, the exiting solution was fed into an evaporation chamber and heated at 40 - 80 mbar, 85 ± 5 °C; the solvent was evaporated and stored in a solvent collection tank (20) (batch process). After the extraction process, the fabric was pressed to remove the residual solvent added to the solution in the evaporation chamber. After complete removal of DMAc from the dye - containing solution, the elastomeric material, dyes, and polyurethane prints were separated in solid form.

[0100] Figure 3Shows the results of applying the method of the present invention to 15 different dyed or printed polyester and cotton fabrics: It is worth noting that the dyes and printing substances on all fabrics have been completely removed, which is clearly visible from the white fabric samples obtained after the method. The obtained white fabrics can be recycled as white polyester or cotton materials.

[0101] Therefore, the claimed method and apparatus can remove disperse dyes from polyester fibers and indigo or indigo-like dyes from cotton fibers. The resulting textiles can be recycled in a manner known per se.

Claims

1. A method for removing dyes from waste textiles (2), wherein the waste textiles contain or consist of dyed polyester fibers, wherein the dyed polyester fibers contain disperse dyes used for the polyester fibers (1), or the waste textiles contain or consist of dyed cotton fibers, wherein the dyed cotton fibers contain indigo or indigo-like dyes, characterized in that The following steps are involved: a) providing a quantity of said waste textile in an extraction chamber (4) and heating said chamber (4), b) circulating a solvent (3) suitable for removing the dye from the waste textiles through the extraction chamber (4) and the waste textiles (2); c) returning the solvent leaving the extraction chamber (4) to the extraction chamber to increase the amount of dye removed from the waste textile; d) evaporating at least a portion of the solvent obtained in step c) in an evaporation chamber (6); e) condensing the evaporated solvent (3) in at least one condensation chamber (7).

2. The method of claim 1, wherein the solvent is selected from dimethylformamide (DMF) and dimethylacetamide (DMAC).

3. The method of any one of claims 1 to 3, wherein the waste textile further comprises a polyurethane material selected from the group consisting of filaments and layers.

4. The method of any one of claims 1 to 4, wherein the textile and the extraction chamber are in a static state during the extraction step.

5. The method according to any one of the preceding claims, further comprising the steps of: f) feeding at least a portion of the condensed solvent (3) directly or indirectly into the extraction chamber (4); g) optionally repeating steps b) to f) until the dye is removed, wherein at least the evaporation and condensation steps (d, e) are carried out under reduced pressure.

6. A method according to any one of the preceding claims, wherein at least in step c) the solvent is circulated through the waste textile and the extraction chamber and is sent back into the chamber by a pump (9).

7. A method as claimed in any preceding claim, wherein the removed dye is recovered.

8. A method as claimed in any one of the preceding claims, wherein The pressure in the evaporation chamber is in the range of 20 to 85 mbar, preferably 40 to 80 mbar, and the temperature of the solvent in the evaporation chamber (6) is in the range of 75 to 95°C, preferably 80 to 90°C.

9. The method of claim 8, wherein the solvent temperature in the extraction chamber ranges from 80 to 100°C, preferably from 80 to 95°C, more preferably about 85°C.

10. The method according to any one of the preceding claims, further comprising a step of recovering solvent from the treated waste textile, preferably the solvent recovery step is selected from pressing, squeezing, spinning or centrifuging the waste textile.

11. An apparatus for carrying out the method for removing dyes from waste fabrics as claimed in any one of the preceding claims, characterized in that: The apparatus comprises an extraction chamber (4) configured to receive waste fabric (2), the extraction chamber (4) preferably comprising at least one heater (8); a container for storing a solvent (3), the solvent (3) being suitable for removing the dye from the waste fabric; a circulation device (9) for circulating the solvent at least once through the textile and the extraction chamber (4); an evaporation chamber (6) configured to collect the solvent containing the dye and evaporate at least part of the solvent (3); at least one condensation chamber (7) comprising a cooling system (10), the cooling system (10) being configured to condense the solvent evaporated in the evaporation chamber (6), and a device for storing the condensed solvent.

12. Apparatus according to claim 11, wherein the extraction chamber (4) comprises filtering means, preferably a filter basket (40) for receiving the waste textile (2).

13. The apparatus of claim 11 or 12, wherein: At least a part of the device is connected or connectable to a decompression circuit (71), which preferably includes a vacuum pump (70), and the vacuum pump (70) is configured to generate a reduced pressure of 35 to 100 mbar, wherein the decompression circuit (71) is connected or connectable to the evaporation chamber, and preferably the decompression circuit (71) is also connected or connectable to at least one condensation chamber (7), and the at least one condensation chamber (7) is connected or connectable to the evaporation chamber.

14. Apparatus according to any one of claims 11 to 13, wherein the circulation means comprises a loop (42) and a pump (9) for circulating solvent into and out of the extraction chamber (4).

15. The apparatus according to any one of claims 11 to 14, further comprising a solvent collecting tank (20) for containing the solvent (3), the solvent collecting tank (20) being connected or connectable to the extraction chamber (4) and the condensation chamber (7).

16. The apparatus according to claim 15, wherein the condensation chamber (7) is connectable to the solvent collection tank (20).

17. Use of the apparatus of any one of claims 11 to 16 in a method for removing disperse dyes from polyester dyed fabrics.

18. A method of recycling garments comprising or consisting of fabrics containing polyester yarns dyed with disperse dyes or containing cotton yarns dyed with indigo or indigo-like dyes, wherein the dyes are removed from the garments by the method of any one of claims 1 to 10 and the garments are treated to provide pre-consumer garments.

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