Process and plant for removing dyes from waste textiles

Abstract

To provide a process of recycling waste textile containing or based on polyester, or a process of recycling a waste textile comprising or consisting in dyed cotton fibers comprising indigo or indigoid dyes.SOLUTION: In a process for recycling waste fabric comprising dyed polyester fibers or dyed cellulosic fibers, a polar solvent is caused to flow through the waste fabric in an extraction chamber to remove the dyes. The polar solvent is evaporated in an evaporation chamber and condensed to be sent to a solvent collection tank or back to the extraction chamber. All elastomeric materials present in the waste textile are dissolved by the polar solvent during the treatment.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a process and a plant for removing dyes from waste textiles in order to recycle textile materials such as fabrics, yarns, filaments, and clothing. More specifically, the present invention relates to a process for recovering polyester materials from waste fabrics containing polyester fibers and filaments, dyes, and optionally elastomeric materials, and from clothing. The present invention also relates to a process for recycling waste textiles containing dyed cotton fibers or consisting of dyed cotton fibers, including indigo dyes or indigoid dyes.

Background Art

[0002] The recycling of used fabrics, also known as "waste fabrics", is a major target in the textile industry, and new efficient processes for recycling are being actively studied. One of the goals is to recycle the polyester fibers and filaments contained in widely used fabrics. Another goal is to recycle cotton fabrics and cellulose fabrics.

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

[0004] Patent Document 1 discloses recycling waste polyester materials including waste textiles by dissolving polyester in a solution containing hexafluoroisopropyl alcohol and chlorinated hydrocarbons and / or aromatic hydrocarbons. Prior to dissolution, a pretreatment with dichloromethane (DCM) is performed to remove color and impurities from PET bottles and waste textile materials. In this method, dyes cannot be removed effectively and completely.

[0005] Patent Document 2 describes a method for producing decolorized polyester by removing a colorant from polyester while heating a decolorizing agent containing a glycol ether compound having a boiling point of 160°C or higher under atmospheric pressure to a temperature not higher than the melting point of the polyester.

[0006] Patent Document 3 discloses a method and a system for decolorizing textile waste dyed with disperse dyes using a magnetically charged dye adsorbent in a hot water environment. The textile material is treated under self-generated pressure as obtained when heated to about 100°C to 170°C with stirring in a decolorization reactor containing water and magnetic activated carbon as the dye adsorbent. An ultrasonic generator (9) is activated to accelerate the release of dye molecules from the textile material into water. The dye released from the polyester fiber is adsorbed by the magnetic activated carbon collected by activating a magnetic field at the end of this process.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] Generally, in known methods, polyester materials or cotton fibers are partially deteriorated. When operating under mild conditions to reduce the deterioration, only part of the dye is removed. The deterioration of the polymer may have an adverse effect on the recyclability of the recovered polyester material. Similarly, the deterioration of cotton fibers may impair the mechanical properties of the yarn produced from the recycled cotton fibers and may in some cases impair the appearance.

[0009] In particular, a process that can remove all decorations and dyes, i.e., disperse dyes, from dyed or printed polyester clothing, or a process that can remove indigo dyes and indigoid dyes from cotton clothing without degrading the fabric and clothing, would be very useful. The thus-treated and decolorized clothing can then be dyed again in a different color or printed to apply a new print or decoration.

[0010] A further problem is that polyester-based fabrics and clothing often contain polyurethane materials, either as elastane-type filaments in the fabric yarns or as layers printed on the clothing as decorations such as in sports clothing. When recycling polyester fibers, the presence of elastomeric materials can be a problem. The same problem exists with cotton-based fabrics and clothing.

Means for Solving the Problems

[0011] An object of the present invention is to solve the above problems and provide a recycling process for waste fabrics containing or based on polyester, or a recycling process for waste fiber products containing or consisting of dyed cotton fibers containing indigo dyes or indigoid dyes, and to provide a safe, easy, and environmentally clean method of recovering polyester materials or cotton materials from the waste fiber products by removing the dyes from the waste fiber products without or with reduced degradation of the polyester materials or cotton materials in the waste fiber products.

[0012] The decolorized polyester material can then be further recycled by methods known per se, for example, by decomposing cellulose fibers (if present), by depolymerizing the polyester, or by recovering the polyester as staple fibers.

[0013] Similarly, the decolorized cotton or cellulose material can be recycled by methods known per se, for example, by mechanically adding cotton or cellulose staple fibers that can be processed into yarns.

[0014] In particular, in the case of pre-consumer materials consisting of clothing or fabrics, the clothing or fabric can be decolorized to the gray state (undyed) and then recycled by dyeing or printing, or both, of the treated clothing.

[0015] This problem is solved by the process according to claim 1 and the plant according to claim 10.

[0016] Accordingly, the present invention relates to a process for recycling waste fiber products comprising or consisting of polyester fibers containing a disperse dye for polyester fibers, or waste fiber products comprising or consisting of dyed cotton fibers containing indigo dye or indigoid dye, by removing said dye from said waste fiber products, said process comprising: a) introducing a certain amount of said waste fiber products into an extraction chamber and heating said extraction chamber; b) circulating a solvent suitable for removing said dye from said waste fiber products through said extraction chamber and said waste fiber products; c) returning the solvent discharged from said extraction chamber to said extraction chamber in order to increase the amount of said dye removed from said waste fiber products; d) evaporating at least a part of the solvent obtained in step c) in an evaporation chamber; e) condensing the evaporated solvent in at least one condensation chamber.

[0017] According to one aspect of the present invention, this process further comprises: f) supplying at least a part of the condensed solvent directly or indirectly to said extraction chamber; and g) repeating steps b) to f) until the dye is removed.

[0018] According to one aspect of the present invention, there is provided a process for recycling waste textile articles containing polyester fibers and a dye, namely a disperse dye, the process comprising circulating (i.e., flowing) said solvent through the waste textile articles in an extraction chamber using a solvent selected from dimethylformamide (DMF) and dimethylacetamide (DMAC) until the dye is removed, thereby removing the disperse dye from the waste textile articles. Advantageously, if a polyurethane material is present, it is removed from the waste textile articles.

[0019] According to one aspect of the present invention, there is provided a process for recycling waste textile articles containing cotton and / or cellulose fibers and a dye, namely indigo dye or indigoid dye, the process comprising circulating (i.e., flowing) said solvent through the waste textile articles in an extraction chamber using a solvent selected from dimethylformamide (DMF) and dimethylacetamide (DMAC) until the dye is removed, thereby removing the indigo dye or indigoid dye from the waste textile articles. Advantageously, if a polyurethane material is present, it is removed from the waste textile articles.

[0020] As will be disclosed in more detail in the following description, the solvent is fed to an extraction chamber (which is static and contains the waste textile articles), the solvent is flowed through the textile material and the extraction chamber, and preferably, the solvent (i.e., DMF or DMAC) is circulated by returning the solvent exiting the extraction chamber to the extraction chamber at least once and flowing it through the textile articles, in order to increase the content of the dye removed from the textile articles. In the following description and claims, the term "solvent" means dimethylformamide (DMF) or dimethylacetamide (DMAC).

[0021] Advantageously, at least a portion of the solvent (including the dye removed from the fabric) is fed to an evaporation chamber for distillation, the evaporated solvent is condensed, and at least a portion of the condensed solvent is fed back to the extraction chamber, thereby being reused in this process. The content of the dye (and optionally the elastomeric material) in the waste fabric decreases each time the solvent passes through the waste fabric. At the same time, the content of the dye in the evaporation chamber, i.e., the disperse dye and indigo / indigoid dye, and optionally the elastomeric material present, increases over time.

[0022] Finally, the solvent containing the concentrated dye and optionally the elastomeric material can be recovered by distillation from the evaporation chamber or another vessel, and after removal of the solvent, the dye and optionally the elastomeric material present remain as solids.

[0023] In this process, textile materials such as fabrics, clothing, and fibers are contained within a stationary, i.e., static, extraction chamber. The textile materials are in a stationary, i.e., static, state except for any movement that may be caused by the flow of the solvent circulated through the static extraction chamber and the textile materials by means of a pump or the like.

[0024] Fabrics that can be recycled by the claimed process include polyester sports apparel, such as T-shirts and clothing with a thin layer or film of polyurethane material applied to the clothing and having decorations printed thereon. The polyurethane layer is dissolved by the solvent together with the ink forming the decorative elements (logos, numbers, etc.).

[0025] In the following description, reference is made to "polyurethane material" or PU material, but this term encompasses elastomeric materials (such as elastane or spandex) used in yarns (usually the core of the yarn) and other polyurethane materials that may be present on or within the fabric as part of a decoration (such as a printed decoration) as described above.

[0026] In the following description, the polyester fiber is referred to as including all fibers in any state, such as staple fibers and polyester continuous filaments in any state (for example, textured, POY, FDY).

[0027] In the following description, cotton fibers and cotton fibers generally including cellulose-based fibers are referred to.

[0028] By circulating the solvent through the extraction chamber and the waste fiber product, that is, repeatedly circulating or flowing it, the contact time of the waste fiber product with the solvent can be increased. By increasing this time, the amount of solvent used can be reduced, and as a result, the overall time required to remove the dye from the waste fiber product is shortened.

[0029] Advantageously, the ratio of waste fiber (weight, kg) to solvent (volume, liter) is 1:8 to 1:12, preferably 1:10. This ratio can reduce the environmental impact of the recycling process.

[0030] In one embodiment, the solvent containing the dissolved dye, and optionally the PU material exiting the extraction chamber, are also returned to the extraction chamber at least once and recycled through the waste material, increasing the content of the removed dye and PU material in the solvent. Thus, the solvent is (preferably continuously) recycled within the extraction chamber containing the waste fiber, and the same solvent can increase the contact time with the waste fiber product.

[0031] In one embodiment, the solvent exiting the extraction chamber is sent to an evaporation chamber for distillation, and the distilled and condensed solvent is returned to the extraction chamber.

[0032] In a preferred embodiment, a portion of the solvent is preferably supplied to the evaporation chamber after recycling for a selected time, where it is distilled by evaporation and condensation of the solvent. The distilled solvent is returned to the extraction chamber or, in a preferred embodiment, supplied to a solvent reservoir from which it is ultimately supplied to the extraction chamber as needed.

[0033] According to a preferred embodiment of the present invention, the solvent exiting the extraction chamber is filtered. By filtering the solvent, the amount of waste fiber products remaining in the extraction chamber can be maximized while maintaining a solvent free of solids that would compromise the quality of the final product.

[0034] According to a possible embodiment, the solvent is filtered by a filtration basket that houses the waste fiber products within the extraction chamber. Advantageously, the filtration basket can be a rigid structure, such as a metal structure, provided with filtration openings along its surface to allow the flow of the solvent. By housing the waste fiber products in the filtration basket, the flow of the solvent through the waste fiber products can be restricted within a sealed space without agitating the fabric pieces / fiber pieces.

[0035] According to a possible embodiment, at least a part of this process, for example steps d) and e), is carried out under reduced pressure, i.e., the evaporation section and the condensation section of the plant are connected to a source of reduced pressure. Since steps d) and e) are carried out under reduced pressure, the temperature required to evaporate the solvent in the evaporation chamber can be lowered. When the evaporation temperature is low, the degradation of the solvent within the plant is prevented or reduced to an ignorable level, enabling the same solvent to be used in multiple processes.

[0036] In one embodiment, the appropriate pressure within the evaporation chamber (and optionally other parts of the plant connected to the evaporation chamber) is between 20 and 100 mbar, preferably between 35 and 100 mbar, and most preferably between 40 and 80 mbar.

[0037] According to a possible embodiment, this process includes a step of heating the extraction chamber, thereby heating the solvent flowing through the extraction chamber (and the waste fiber products). Advantageously, the extraction chamber is heated to a temperature at which the solvent within the extraction chamber does not cause degradation of the solvent. The increase in temperature of the waste fiber products and the solvent shortens the time required to preferably dissolve and remove any dyes and any PU materials that may be present in the waste fiber products.

[0038] In one embodiment, the solvent is recycled by a pump. Advantageously, by recycling the solvent by the pump, the waste fiber product is subjected to the action of the solvent, and the number of times the same part of the waste fiber product comes into contact with the volume of the solvent can be increased. As a result, the removal of dyes (and PU materials if present) from the waste fiber product is accelerated.

[0039] Furthermore, unlike the processes known in the art, the waste fiber product is held in a stationary (i.e., static) position within the extraction chamber. For example, the waste fiber product is not agitated by an agitation rotor or the like. Similarly, in a preferred embodiment, the extraction chamber and the filtration basket containing the waste fiber product can be in a stationary static state, for example, such that the filtration basket does not rotate. In one embodiment, the fiber product completely fills the basket within the extraction chamber and maintains a stationary state even when the solvent circulates, i.e., is pumped into or discharged from the extraction chamber.

[0040] In one embodiment, the waste fiber product is compressed within the basket in order to maximize the use of the basket volume. Advantageously, the compression of the waste fiber product improves the productivity of this process.

[0041] Advantageously, by keeping the fiber product material, such as fabric, in a static state, the amount of short fibers, such as cotton fibers and cellulose fibers, that may loosen or break during this process and peel off from the fiber product material is dramatically reduced.

[0042] According to a possible aspect, steps d) and e) are carried out under reduced pressure, and the solvent is heated to a temperature below the boiling point of the solvent at the selected pressure within the evaporation chamber, preferably below 100°C, in order to prevent degradation of the solvent.

[0043] Suitable solvents are dimethylformamide (DMF) and dimethylacetamide (DMAC). DMF and DMAC are polar solvents, and surprisingly, it has been found that the temperature conditions of this process are suitable for removing disperse dyes. DMF and DMAC can also dissolve PU materials and elastomer materials that may be present in or on waste textiles.

[0044] Advantageously, the claimed solvents can remove dyes with no or extremely reduced degradation of polyester or cotton fibers in textiles under the claimed process conditions. In fact, in the case of polyester, results were observed showing a decrease in IV (intrinsic viscosity) of about 3% (measured according to BS EN ISO 1628-5: 2015) and a decrease in tensile strength of about 5% (measured according to ASTM D5034-21).

[0045] According to a possible embodiment, the extraction chamber is under reduced pressure and the solvent temperature in the extraction chamber is higher than 80°C, preferably 85 - 100°C, most preferably 85 - 95°C.

[0046] Another object of the present invention is a plant for performing the above process of recycling waste textiles containing polyester fibers by removing dyes, i.e., disperse dyes, or recycling waste textiles containing cellulose fibers by removing indigo dyes and indigoid dyes, and advantageously removing PU materials that may be present in the fabric.

[0047] According to the present invention, this plant comprises an extraction chamber adapted to contain waste textiles containing disperse dyes and / or indigo dyes or indigoid dyes, and optionally PU materials, and a solvent selected from DMF and DMAC.

[0048] The extraction chamber preferably comprises at least a heater. This plant further comprises circulation means for circulating the solvent through the extraction chamber, preferably at least once, an evaporation chamber for recovering the solvent containing the dissolved dye and evaporating at least a part of the solvent for refeeding it to the extraction chamber, and at least one condensation chamber equipped with a cooling system for condensing the solvent evaporated in the evaporation chamber and supplying the condensed solvent directly or indirectly to the extraction chamber.

[0049] In a possible embodiment, the recovered solvent can be supplied to a solvent reservoir, for example when this process is not operating.

[0050] According to a preferred embodiment, the extraction chamber of this plant comprises filtration means for accommodating waste fibers, preferably a mesh filtration basket. As described above, the filtration means of the extraction chamber can accommodate waste fibers and small fibers that may peel off from the fibers within the extraction chamber.

[0051] According to one aspect of the present invention, this plant is connected to a decompression circuit. Preferably, the decompression circuit includes a vacuum pump. Preferably, the extraction chamber and the condensation chamber are connected to or connectable to the decompression circuit.

[0052] According to a possible aspect, the decompression circuit of this plant is connected to the at least one condensation chamber. Preferably, two condensation chambers are connected in series to prevent the solvent vapor from flowing out of the plant.

[0053] According to a possible aspect, the solvent collection tank, i.e., the solvent reservoir, is connected to the extraction chamber and the condensation chamber by appropriate pipes or conduits. Advantageously, the solvent collection tank can accommodate the solvent removed from the evaporation chamber.

[0054] Alternatively, the solvent stored in the solvent collection tank can be supplied to the extraction chamber before step b) where the solvent circulates through the extraction chamber and the waste fiber product to dissolve and remove the elastomeric material from the waste fiber product. Thus, advantageously, the solvent stored in the solvent collection tank and returned to the extraction chamber can be used as a solvent that can be recycled through the extraction chamber and the waste fiber product to dissolve and remove the elastomeric material from the waste fiber product after undergoing a condensation process in at least one condensation chamber.

[0055] According to a possible embodiment, the solvent collection tank can be connected to the condensation chamber to selectively receive the condensed solvent.

[0056] According to a possible embodiment, the evaporation chamber is equipped with a mixer or agitator for increasing the evaporation of at least a portion of the solvent from the solution of the elastomeric material present in the evaporation chamber so as to increase the amount of solvent distilled from the evaporation chamber.

[0057] Further aspects and advantages according to the present disclosure will be described in more detail with reference to the accompanying drawings, which are shown by way of non-limiting examples.

Brief Description of the Drawings

[0058]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0059] Referring to the exemplary embodiment of FIG. 1, the textile recycling plant 100 comprises an extraction chamber 4 adapted to receive waste textiles 2 which are textiles containing polyester fibers 1 dyed with disperse dyes. In one embodiment, the textiles contain cellulose fibers, particularly cotton fibers, dyed with indigo dyes and indigoid dyes. The extraction chamber 4 is adapted 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 circuit 42 in which the solvent 3 exiting the extraction chamber from the chamber outlet conduit 43 can be recirculated through the extraction chamber inlet conduit 44 into the extraction chamber 4 by means of a circulation means 9. Preferably, the circulation means 9 is a pump. A valve V is arranged on the circuit duct to control the flow of the solvent.

[0060] In the embodiment of FIG. 1, the extraction chamber 4 is connected to an evaporation chamber 6 via a conduit 41. The extraction chamber 4 is connected to a condensation chamber 7 via a conduit 72. The extraction chamber 4 is also connected to a solvent collection tank 20 via a conduit 201. Appropriate valves V are provided in the above conduits to selectively direct the flow of the solvent to the required components of the textile recycling plant 100.

[0061] In a possible embodiment, it is preferred that the process of the present invention filters the solvent containing the extracted dye to remove fibers of materials other than elastomeric fibers, such as cotton fibers. Preferably, the extraction chamber 4 is provided with filtering means, such as a mesh filtration basket 40, for receiving the waste textiles 2 containing the dye 1.

[0062] The mesh filtration basket 40 is provided with an opening not shown in FIG. 1, which allows the solvent to flow through the entire volume of the extraction chamber 4 while retaining the waste fiber product 2 within the mesh filtration basket 40. In a preferred embodiment, the mesh filtration basket 40 is made of stainless steel or includes a non-woven fabric that lines the interior and functions as a filter. This non-woven fabric is resistant to the solvents used in the extraction chamber and may be used alone or fixed to or contained within a metal support such as the mesh filtration basket 40 so as to retain fibers or particles that separate from the fibrous material.

[0063] According to a possible aspect, the extraction chamber 4 comprises at least a heater 8. The heater 8 heats the solvent (and the waste fiber product 2) within the extraction chamber 4 during operation of the process, facilitating the extraction of dyes and any PU materials from the waste fiber product 2.

[0064] The fiber recycling plant 100 further comprises an evaporation chamber 6. The evaporation chamber 6 is adapted to collect, i.e., receive, a solution 3' containing the solvent 3 and the dissolved dye (and optionally PU material) 1 obtained by recirculation of the solvent within the extraction chamber 4, and to evaporate at least a portion of the solvent from the solution 3' to recover the solvent 3 for use in the extraction process. As described above, the evaporation chamber 6 is connected to the extraction chamber 4 by a conduit 41.

[0065] According to a possible aspect, the evaporation chamber 6 comprises stirring means, such as a mixer 66. Usually, as is known in the art, the mixer 66 comprises a rotating rod 61 and a plurality of protrusions 62. The rotation of the protrusions 62 within the solution 3' maximally promotes the evaporation of the solvent 3 from the solution 3'. The evaporation chamber 6 is also provided with heating means for raising the solvent contained therein to its boiling point under reduced pressure, as will be described in detail below.

[0066] To recover the evaporated solvent, the textile recycling plant 100 further comprises at least one condensation chamber 7. The evaporation chamber 6 is fluidly connected to the condensation chamber 7 via a duct 60. In the preferred embodiment shown, the textile recycling plant 100 is provided with two condensation chambers 7a, 7b arranged and connected in series.

[0067] The condensation chamber 7 comprises a cooling system 10 adapted to condense the solvent evaporated from the solution 3' contained in the evaporation chamber 6 and supply the condensed solvent via a conduit 72 to at least one of the extraction chamber 4 and the solvent collection tank 20. In other words, when the solvent 3 in the condensation chamber reaches the dew point, the solvent condenses and this solvent can be returned to the extraction process in the extraction chamber 4 (if the process for recycling this waste textile is operating), or to the solvent collection tank 20, or both.

[0068] In the embodiment shown, the textile recycling plant 100 is connected to a vacuum circuit 71 including a vacuum pump 70 and a separation element 75 to recover the solvent 3 that will return to the extraction chamber 4 or the solvent collection tank 20 (batch process). Preferably, this vacuum circuit 71 is connected to the condensation chamber connected to the evaporation chamber. Thus, during operation of the process for recycling waste textiles of the present invention, at least the evaporation chamber 6 and the condensation chamber 7 are kept under reduced pressure. Advantageously, the vacuum pump is adapted to generate a reduced pressure in the range of 20 mbar to 100 mbar, preferably 35 to 100 mbar, most preferably 40 to 80 mbar in the evaporation chamber 6.

[0069] Advantageously, the vacuum circuit 71 is connected to at least one condensation chamber 7 via a conduit 80. In the embodiment of FIG. 1 including condensation chambers 7a and 7b, the vacuum circuit 71 is connected to the end of the condensation chamber 7a so as to condense all of the solvent evaporated in the two condensation chambers before the evaporated solvent reaches the end of the condensation chamber system.

[0070] If there is no need to reduce the pressure inside the plant, at least the main components of the plant, namely the extraction chamber 4, the evaporation chamber 6, the condensation chambers 7, 7a, 7b and the solvent collection tank 20, are provided with a valve-equipped duct Av for connecting the plant to the atmosphere.

[0071] As described above, preferably, the textile recycling plant 100 further comprises a solvent collection tank 20 for storing the solvent 3. This solvent collection tank 20 is connected to the extraction chamber 4 via conduits 74, 201 and is connected to the evaporation chamber 6 via a separation element 75. According to a possible embodiment, the condensation chamber 7 is connected to the solvent collection tank 20 via a conduit 202 equipped with a valve for guiding the solvent flow to either the solvent collection tank 20 or the extraction chamber 4. Preferably, the solvent 3 stored in the solvent collection tank 20 can be guided to the extraction chamber 4 via conduits 74, 201 under reduced pressure via a decompression circuit 71 and a vacuum pump 70.

[0072] The present invention further provides a process for recycling waste textiles 2 containing polyester fibers and disperse dyes, or a process for recycling waste textiles 2 containing cotton / cellulose fibers and indigo dyes or indigoid dyes. The waste textiles 2 can contain, for example, a PU material as an elastic material in the form of fibers. The PU material can be present, for example, in the form of a decoration printed on the fabric by a PU layer applied to the fabric.

[0073] The fabric can be processed by known methods, such as cutting into shreds or pieces, or can be left in the form of the original clothing, for example as a pair of trousers or a T-shirt. Usually, shredding is carried out after removing parts such as plastic labels or zippers, metal parts, etc.

[0074] First, in step a), a certain amount of waste textiles 2 are introduced into the extraction chamber 4. Advantageously, the waste textile material is packed and compressed in the basket of the extraction chamber 4.

[0075] In the next step b), the solvent 3 is supplied to the extraction chamber 4, passes through the extraction chamber and the textile, and dissolves and removes the possible dyes 1 and PU materials present in the waste textile 2. Preferred solvents for disperse dyes are DMF and DMAC. In a preferred embodiment, the solvent is supplied to the extraction chamber and flows out of the extraction chamber 4 through the waste fibers in a controlled flow. Such a flow is preferably obtained using a pump 9 that pushes the solvent along the required path.

[0076] In step c), the solvent 3 that exits the extraction chamber 4 through the outlet duct 43 is guided along the recirculation circuit 42, returns to the extraction chamber 4 at least once through the inlet duct 44, extracts more dyes, and increases the dye content in the solvent. In other words, by recirculating the solvent through the recirculation circuit 42, the concentration of the dissolved dye 1 in the solvent can be maximized.

[0077] Preferably, a certain amount of solvent is supplied to the extraction chamber and the waste textile at least 3 times, i.e., 3 cycles. Usually, in each cycle, the solvent is circulated for at least 70 minutes, preferably at least 80 minutes, more preferably at least 90 minutes, and up to 150 minutes if possible. After the cycle is completed, preferably, the solvent is sent to the evaporation chamber, and a clean solvent is used in the next cycle.

[0078] During the extraction process, by connecting the textile recycling plant 100 to the vacuum circuit 71, at least a part of the textile recycling plant 100, i.e., the evaporation chamber and the condensation chamber, is kept under reduced pressure. The appropriate pressure in the plant, i.e., in chambers 4, 6, and 7, is about 20 - 100 mbar, preferably 35 - 100 mbar, more preferably 40 - 80 mbar. Advantageously, under reduced pressure, the boiling point of the solvent decreases, the evaporation of the solvent in step d) is promoted, and the degradation of the solvent is reduced or prevented.

[0079] To facilitate the extraction of the dye (and optionally the PU material present), the extraction chamber 4 is heated. According to one aspect, the temperature of the solvent in the extraction chamber 4 is 80°C or higher, in the range of 85 - 100°C, preferably 80 - 90°C, optionally 81 - 90°C, i.e., 85°C. The extraction chamber 4 is usually not connected to the vacuum circuit 71. In a preferred embodiment, the extraction chamber 4 is connected to the evaporation chamber 6 which is under reduced pressure as described above, in order to transfer the solvent containing the extracted dye from the extraction chamber 4 to the evaporation chamber 6. When the two chambers are connected via the duct 41, the liquid content of the extraction chamber 4 is transferred to the evaporation chamber 6.

[0080] The transfer of the solvent from the solvent reservoir 20 to the extraction chamber 4 can also be done by temporarily reducing the pressure inside the extraction chamber 4 before connecting the extraction chamber 4 to the solvent reservoir. Generally, apart from using the pump 9 to circulate the solvent inside and outside the extraction chamber, the pressure difference between parts of the textile recycling plant 100 can be utilized to transfer the polar solvent to various parts of this textile recycling plant 100.

[0081] According to a possible aspect, the solvent 3 discharged from the extraction chamber 4 is filtered through the mesh filtration basket 40. In other words, during step c), the waste textile 2 can be held inside the mesh filtration basket 40, and with the waste textile 2 held inside the extraction chamber 4, only the solvent 3 can exit the extraction chamber 4 through the outlet 43, through the recirculation circuit 42, and return to the extraction chamber 4 through the extraction chamber inlet conduit 44.

[0082] When the solvent containing the dye 1 and any optional PU material extracted as described in step c) is recirculated through the textile material a sufficient number of times, i.e., for a total time sufficient to effect the required extraction of the elastomeric material, the solvent containing the dye is sent through the conduit 41 to the evaporation chamber 6. In the evaporation chamber 6, at least a part of the solvent evaporates and is recirculated to the process for recycling the waste textile.

[0083] As described above, the evaporation and condensation processes are preferably carried out under reduced pressure by the decompression circuit 71 and the vacuum pump 70. Therefore, the solvent 3 in the evaporation chamber 6 is preferably heated to a temperature below the boiling point at atmospheric pressure, i.e., a temperature below 100°C, in order to prevent deterioration of the solvent. The temperature in the evaporation chamber is 75 to 95°C, preferably 80 to 90°C. The reduced pressure in the evaporation chamber at the above temperature is 20 mbar to 100 mbar, preferably 35 to 85 mbar, and more preferably 40 to 80 mbar.

[0084] In step e), the solvent vapor flows along the conduit 60 into the condensation chamber 7, where the vapor condenses. In the embodiment shown in FIG. 1, two condensation chambers 7a and 7b are provided, arranged and connected in series. The condensed solvent 3 is supplied to the extraction chamber 4 via the conduit 72, or the liquid solvent is supplied to the solvent reservoir 20 via the conduit 202, stored therein, or pumped back to the extraction chamber 4 via the conduit 74.

[0085] In a possible embodiment, as schematically shown in FIG. 2, the DMF solvent is recirculated through the extraction chamber until a necessary reduction of the dye (e.g., visually) is detected before being sent to the evaporation chamber 6. In a possible embodiment, the solvent is circulated through the fabric at least three times, each time for about 90 minutes. Preferably, clean solvent is supplied to the system in each cycle.

[0086] At the end of the extraction process, a further step of removing and recovering the solvent from the waste textile can be carried out. Preferably, the solvent recovery step is selected from pressing, squeezing, rotating, or centrifuging the waste textile immersed in the solvent.

[0087] The present invention will be further described with reference to the following non-limiting examples.

[0088] Example 1 1.5 kg of textile waste containing polyester, polyester elastane, polyurethane printed polyester pre-consumer, post-consumer fabrics, and fibers was collected. This textile waste was placed in a stainless-steel filtration basket. This 1.5 kg of textile waste was put into an extraction chamber heated to 90 - 95°C, and 15 liters of DMF was circulated 3 times for 90 minutes each (for a total of 3 × 90 minutes, i.e., 270 minutes). The sample / DMF float ratio was 1:10. During recirculation, the discharged solution was sent to an evaporation chamber heated to 85 ± 5°C at 40 - 80 mbar, and the solvent evaporated and was stored in a solvent collection tank. At the end of the extraction process, the textile waste was squeezed to remove the remaining solvent and added to the solution in the evaporation chamber. After the DMF was completely removed, the elastomer material, dyes, and polyurethane prints were separated in solid form. The mass loss of the waste textiles at the end of the extraction process was 150 grams (10%). No elastane was found in the treated textile waste after the extraction process. It was confirmed that the prints and colors of the waste were completely removed, resulting in a white - grayish fabric.

[0089] Example 2 1.8 kg of colored pre-consumer clothing (T-shirts) was collected. However, no cutting or shredding was done. The clothing was placed in an extraction chamber heated to 90 - 95°C, and 19 liters of DMF was circulated 3 times for 90 minutes each (for a total of 270 minutes). During dye extraction, the discharged solution was sent to an evaporation chamber heated to 85 ± 5°C at 60 - 70 mbar, and the solvent evaporated and was stored in a solvent collection tank (20) (batch process). At the end of the extraction process, the clothing was compressed to remove the remaining solvent and added to the solution in the evaporation chamber. After the DMF was completely removed, the dyes were separated in solid form. Since the clothing was in a grayish state, it could be recycled by re-dyeing and / or printing with another color.

[0090] Example 3 2 kg of textile waste was collected. This 2 kg of textile was placed in an extraction chamber heated to 90 - 95 °C and subjected to 3 cycles of 90 minutes each (for a total of 3 × 90 minutes, i.e., 270 minutes) of recirculation with DMAC. During recirculation, the discharged solution was sent to an evaporation chamber heated to 85 ± 5 °C at 40 - 80 mbar, where the solvent evaporated and was stored in a solvent collection tank (20) (batch process). At the end of the extraction process, the textile was compressed to remove the remaining solvent and added to the solution in the evaporation chamber. After the DMAC was completely removed from the solution containing the dye, the elastomeric material, the dye, and the polyurethane print were separated in solid form.

[0091] Figure 3 shows the results of applying the process of the present invention to 15 types of dyed or printed polyester and cotton textiles. As is clearly evident from the white textile samples obtained after the process of the present invention, it is noteworthy that the dye and the print have been completely removed from all the textiles. The resulting white textiles can be recycled as white polyester or cotton materials.

[0092] With the claimed process and apparatus, disperse dyes can be removed from polyester fibers and indigo or indigoid dyes can be removed from cotton fibers. The resulting textile products can be recycled by methods known per se.

Explanation of Reference Numerals

[0093] 1 Polyester fiber, dye 2 Waste textile 3 Solvent 3’ Solution 4 Extraction chamber 6 Evaporation chamber 7, 7a, 7b Condensation chamber 8 Heater 9 Circulation means, pump 10 Cooling system 20 Solvent collection tank, solvent reservoir 40 Mesh filtration basket 41 Conduit, duct 42 Recirculation circuit 43 Extraction chamber outlet conduit, outlet duct 44 Extraction chamber inlet conduit, inlet duct 60 Duct, conduit 61 Rotating rod 62 Protrusion 66 Mixer 70 Vacuum pump 71 Vacuum circuit 72, 74, 80 Conduit 75 Separation element 100 Textile recycling plant 201, 202 Conduit Duct with Av valve V valve

Claims

1. A process for removing dyes from waste textile products (2), said waste textile products comprising or consisting of dyed polyester fibres with a disperse dye for polyester fibres (1) or said waste textile products comprising or consisting of dyed cotton fibres with an indigo or indigoid dye, said process comprising: a) placing a quantity of said waste textile products in an extraction chamber (4) and heating said extraction chamber (4); b) circulating a solvent (3) suitable for removing said dyes from said waste textile products through said extraction chamber (4) and said waste textile products (2); c) returning the solvent discharged from the extraction chamber (4) to said extraction chamber in order to increase the amount of the dye removed from the waste textile products; d) evaporating at least a portion of the solvent obtained in step c) in an evaporation chamber (6); e) condensing said evaporated solvent (3) in at least one condensation chamber (7).

2. 2. The process for removing dyes from waste textile products (2) according to claim 1, characterized in that the solvent is selected from dimethylformamide (DMF) and dimethylacetamide (DMAC).

3. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, characterized in that the waste textile products further comprise polyurethane material in the form of filaments or layers.

4. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, characterized in that the textile products and the extraction chamber are stationary during the extraction step.

5. A process for removing dyes from waste textile products (2) according to claim 1 or 2, further comprising: f) feeding at least a portion of the condensed solvent (3) directly or indirectly into the extraction chamber (4); and g) repeating steps b) to f) as necessary until the dye is removed, wherein at least the evaporation step and the condensation steps (d) and (e) are carried out under reduced pressure.

6. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, characterized in that at least in step c), the solvent is circulated by a pump (9) through the waste textile products and the extraction chamber and back to the extraction chamber.

7. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, characterized in that the removed dyes are recovered.

8. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, characterized in that the pressure in the evaporation chamber (6) is between 20 and 85 mbar, preferably between 40 and 80 mbar, and the temperature of the solvent in the evaporation chamber (6) is between 75 and 95°C, preferably between 80 and 90°C.

9. The process for removing dyes from waste textile products (2) according to claim 8, characterized in that the temperature of the solvent in the extraction chamber is between 80 and 100°C, preferably between 80 and 95°C, more preferably about 85°C.

10. 3. The process for removing dyes from waste textile products (2) according to claim 1 or 2, further comprising a step of recovering the solvent from the treated waste textile products, preferably the step of recovering the solvent being selected from pressing, squeezing, spinning or centrifuging the waste textile products.

11. A plant for carrying out the process for removing dyes from waste textile products according to claim 1, characterized in that it comprises an extraction chamber (4), preferably equipped with at least a heater (8) and adapted to accommodate the waste textile products (2), a container for storing a solvent (3) suitable for removing the dyes from the waste textile products, circulation means (9) for circulating the solvent at least once through the waste textile products and the extraction chamber (4), an evaporation chamber (6) adapted to collect the solvent containing the dyes and to evaporate at least a part of the solvent (3), at least one condensation chamber (7) equipped with a cooling system (10) adapted to condense the solvent evaporated in the evaporation chamber (6), and storage means for the condensed solvent.

12. 12. A plant according to claim 11, characterized in that the extraction chamber (4) comprises a filtering means, preferably a mesh filtering basket (40) for containing the waste textile products (2).

13. 13. Plant according to claim 11 or 12, characterized in that at least a part of the plant is connected or connectable to a pressure reduction circuit (71), which comprises a vacuum pump (70) adapted to generate a pressure reduction of preferably between 35 and 100 mbar, and which pressure reduction circuit (71) is connected or connectable to the evaporation chamber, preferably also to at least one condensation chamber (7) connected or connectable to the evaporation chamber.

14. 13. A plant according to claim 11 or 12, characterized in that the circulation means comprise a recirculation circuit (42) and a pump (9) for circulating solvent in and out of the extraction chamber (4).

15. 13. The plant according to claim 11 or 12, further comprising a solvent collection tank (20) for containing the solvent (3), the solvent collection tank (20) being connected or connectable to the extraction chamber (4) and to the condensation chamber (7).

16. 16. A plant according to claim 15, characterized in that the condensation chamber (7) is connectable to the solvent collecting tank (20).

17. 13. Use of a plant according to claim 11 or 12 in a process for removing disperse dyes from dyed polyester textiles.

18. 3. A process for recycling garments comprising or consisting of a fabric comprising polyester yarns dyed with a disperse dye or a fabric comprising cotton yarns dyed with an indigo or indigoid dye, characterized in that the dye is removed from the garment by the process of claim 1 or 2 and the garment is processed to provide a pre-consumer garment.

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