Process for mixed fabric rejuvination

Abstract

The invention pertains to a method for mixed fabric fiber rejuvenation, wherein the method comprises the steps of adding ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C trough vapour injection to a fabric fibre material comprising polyester and natural fibre material, whereby at least partly depolymerising the polyester material to monomeric and oligomeric polyester residues, the monomeric and oligomeric polyester residues being dissolved in condensed, excess of liquid EG; optionally adding liquid phase EG, recovering a solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, and an essentially polyester-free natural fibre as a solid product; and optionally separating the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, from the solid product, comprising essentially polyester-free natural fibre. Further is provided a system 100 for mixed fabric fiber rejuvenation of a mixed fabric fibre material comprising polyester and natural fibre material.

Description

[0001] PROCESS FOR MIXED FABRIC REJUVINATION

[0002] Field of the Invention

[0003] This invention pertains in general to the field of recycling of mixed fiber fabrics. More specifically, the invention pertains to a method for mixed fabric fiber rejuvenation, wherein the mixed fabric fiber material comprises polyester and natural fiber material, and where the polyester is reacted with ethylene glycol EG. Further, the invention pertains to a system for such a mixed fabric fiber rejuvenation.

[0004] Background of the Invention

[0005] One of the main problems for recycling mixed fiber fabrics is the difficulty in separating and sorting the different types of fibers. Mixed fiber fabrics are often made up of a blend of different materials, such as cotton, polyester, nylon, and others. These fibers may have different properties and require different recycling processes. The challenge lies in effectively and efficiently separating these fibers to obtain high-quality recycled materials.

[0006] The recycling process typically involves shredding the fabric into smaller pieces and then using mechanical or chemical methods to break down the fibers. However, when different fibers are mixed together, it becomes more challenging to achieve a uniform and consistent output.

[0007] Another issue is the difference in melting points and chemical properties of various fibers. During the recycling process, the fibers may be subjected to high temperatures and chemical treatments, which can lead to variations in the quality and properties of the resulting recycled materials. Some fibers may melt or degrade faster than others, affecting the overall quality of the recycled materials.

[0008] Moreover, the presence of contaminants, such as dyes, finishes, or other additives, in mixed fiber fabrics can further complicate the recycling process. These contaminants may interfere with the recycling process or affect the quality of the recycled materials.

[0009] As for the quality of the recycled materials obtained from mixed fiber fabric recycling, it can vary. Achieving high-quality recycled materials from mixed fiber fabrics is more challenging compared to recycling single-fiber materials. The different fibers may have varying degrees of degradation, leading to differences in the strength, color, and other properties of the recycled materials. Therefore, recycled materials from mixed fiber fabric recycling may also have limited applications. For instance, they may be suitable for certain lower-grade products, such as insulation or non-woven materials, rather than higher-value applications like textile or apparel production.

[0010] Efforts are being made to develop improved recycling technologies and processes to address these challenges. Innovations in fiber sorting, chemical treatments, and mechanical processes are being explored to enhance the quality and efficiency of recycling mixed fiber fabrics. This is especially important, since textile waste is a significant environmental issue. According to the Ellen MacArthur Foundation, the equivalent of one garbage truck full of textiles is landfilled or burned every second globally. This figure includes various types of textiles, including mixed fiber fabrics. The United Nations Environment Programme (UNEP) estimates that the global fashion industry produces approximately 92 million tons of textile waste annually.

[0011] Since mixed fiber fabrics form a significant portion of textile waste streams, and are commonly found in clothing, home textiles, and other textile products, there is a great need for improved methods for achieve high-quality recycled materials from these complex mixed fabric textile waste streams.

[0012] Summary of the Invention

[0013] Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems by providing a method for mixed fabric fiber rejuvenation, wherein the method comprises the steps of: - adding ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C trough vapour injection to a fabric fibre material comprising polyester and natural fibre material, whereby at least partly depolymerising the polyester material to monomeric and oligomeric polyester residues, the monomeric and oligomeric polyester residues being dissolved in condensed, excess of liquid EG; - optionally adding liquid phase EG, - recovering a solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, and an essentially polyester-free natural fibre as a solid product; and - optionally separating the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, from the solid product, comprising essentially polyester-free natural fibre.

[0014] Further, is provided the method wherein the monomeric polyester residues are bis(hydroxy ethyl) terephthalate (BHET). Also, is provided the method wherein the natural fibre material comprises fibers that are more hygroscopic than polyester fibers.

[0015] Further, is provided the method wherein the natural fibre material are selected from the group consisting of plant-based materials, such as cotton, linen, bamboo, and jute, manmade cellulosic fibers, such as viscose and lyocell, animal-based fibers, such as silk and wool; preferably the natural fiber material is cotton.

[0016] Also, is provided the method wherein a gas phase is withdrawn, and separating any non-EG components in the gas phase from EG and reintroducing the separated EG to the fabric fibre material comprising polyester and natural fibre material, whereby the EG in the gas phase is recycled.

[0017] Further, is provided the method, wherein the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG is separated from the solid product, comprising essentially polyester-free natural fibre, through filtering.

[0018] Also, is provided the method, wherein the recovered solvent phase is cooled down to a temperature of less than 50 °C, such as between 10 to 50 °C, thereby precipitating monomeric and oligomeric polyester residues, and thereafter separating the precipitated monomeric and oligomeric polyester residues from the solvent phase.

[0019] Further, is provided the method wherein the evaporation or distillation takes place at a superatmospheric pressure to generate ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C, and wherein the generated EG vapour is used for vapour injection to the fabric fibre material comprising polyester and natural fibre material.

[0020] Also, is provided the method, wherein the recovered liquid solvent phase is cooled to a temperature of 100° C to 140° C and filtered, whereby contaminants with higher precipitation temperatures than monomeric and oligomeric polyester residues are separated from the solvent phase comprising monomeric and oligomeric polyester residues and EG.

[0021] Further is provided a system for mixed fabric fiber rejuvenation of a mixed fabric fibre material comprising polyester and natural fibre material, the system comprising at least one depolymerization vessel for at least partly depolymerising the polyester to monomeric and oligomeric polyester residues, wherein the depolymerization vessel comprises; at least one feed inlet for feeding a mixed fabric fiber material comprising polyester and natural fiber material to the vessel, at least one EG vapour inlet for injecting EG in gas phase at a temperature of between 190° to 250° C into the vessel, at least one EG liquid inlet for injecting liquid EG into the vessel at least one outlet for recovering monomeric and oligomeric polyester residues, unreacted EG and essentially polyester-free natural fiber material.

[0022] Also, is provided the system further comprising a vapour phase recycling column and a partial condenser for separating any non-EG components in a gas phase from EG by condensing EG, wherein the depolymerization vessel further comprises; at least one gas outlet for removing the gas phase, at least one EG inlet for reintroducing separated liquid EG, whereby the EG in the gas phase is recycled, wherein the vapour phase recycling column comprises; at least one gas inlet connected to the gas outlet of the depolymerization vessel, at least one EG liquid outlet connected to the EG liquid inlet depolymerization vessel, a gas outlet, a liquid inlet, and wherein the partial condenser comprises; at least one gas inlet connected to the gas outlet of the vapour phase recycling column, at least one EG liquid outlet connected to the liquid inlet of the vapour phase recycling column, and at least one non-EG gas outlet for removal of any non-EG components.

[0023] Further, is provided the system further comprising a separation means for separating a solvent phase comprising the monomeric and oligomeric polyester residues and unreacted EG from a solid product comprising an essentially polyester-free natural fiber, the separation means comprising an inlet connected to the outlet of the depolymerization vessel, a solvent outlet and a solids outlet.

[0024] Also, is provided the system further comprising at least one contaminant precipitation vessel for cooling the recovered liquid solvent phase to a temperature of 100° C to 140° C and precipitating contaminants with higher precipitation temperatures than the monomeric and oligomeric polyester residues from the solvent phase, comprising an inlet connected, directly or indirectly, to the solvent outlet of the separation means, a solvent outlet and a precipitant outlet for contaminants with higher precipitation temperatures than the monomeric and oligomeric polyester residues; preferably the contaminant precipitation vessel is arranged downstream of the separation means.

[0025] Further, is provided the system further comprising at least one precipitation and separation vessel, for precipitating monomeric and oligomeric polyester residues, and for separating said precipitated monomeric and oligomeric polyester residues from the solvent phase, the precipitation and separation vessel comprising an inlet connected, directly or indirectly, to the solvent outlet of the precipitation means, a solvent outlet and a precipitant outlet.

[0026] Also, is provided the system further comprising a EG recycling column, for generating EG vapour and concentrating any remaining monomeric and oligomeric polyester residues, comprising a liquid phase inlet, an EG vapour outlet connected to the EG vapour inlet of the depolymerization vessel, and an outlet for concentrated monomeric and oligomeric polyester residues

[0027] Further, is provided the system wherein the liquid phase inlet of the a EG recycling column is connected to the solvent outlet of the filter, or the solvent outlet of the precipitation and separation vessel, or the solvent outlet of the contaminant precipitation vessel.

[0028] Brief Description of the Drawings

[0029] These and other aspects, features and advantages of which the invention is capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which

[0030] Fig- 1 is a schematic representation of a system according to one embodiment of the invention, comprising a depolymerization vessel;

[0031] Fig- 2 is a schematic representation of a system according to one embodiment of the invention, further comprising a vapour phase recycling column and a partial condenser;

[0032] Fig- 3 is a schematic representation of a system according to one embodiment of the invention, further comprising a separation means;

[0033] Fig. 4 is a schematic representation of a system according to one embodiment of the invention, further comprising a precipitation and separation vessel for separating monomeric and oligomeric polyester residues from the solvent phase; and

[0034] Fig. 5 a schematic representation of a system according to one embodiment of the invention, further comprising an EG recycling column.

[0035] Fig. 6 a schematic representation of a system according to one embodiment of the invention, further comprising a contaminant precipitation vessel. Description of embodiments

[0036] The following description focuses on an embodiment of the present invention applicable to a method and a system for mixed fabric fiber rejuvenation.

[0037] The invention pertains especially to mixed fiber fabrics comprising a natural fiber and polyester. Several process configurations have been published for glycolysis of PET plastics and polyester fabric material. However, there are several challenges, including:

[0038] (A) In the first step of the general glycolysis process of PET plastics and polyester, the material is contacted with ethylene glycol (EG) and heated to approximately 180-230 °C. In the case glycolysis fabric / textile type material, this material has a low specific density and well as low bulk density when introduced into a reactor and furthermore, the mixture of fibre and liquid becomes highly viscous. This provides a low efficiency for the contact between EG and fabric, and heat transfer to reach the desired dissolving rate and temperature in the reactor. Therefore, it is required to apply excessive heat, sometimes as high as 400 °C, at the reactor walls, in order to reach the desired reaction temperature in the center of the material. Several solutions such as using an extruder, wet milling etc. has been suggested in literature in order to achieve an intimate contact between the polyester and EG and enhance mass and heat transfer. However, if shredded cloth mixtures are mixed while heated up, the viscosity becomes high and mixing shredded cloth and liquid EG may also result in a “sticky ball” of fiber materials, making separation of the different fibers even harder.

[0039] (B) The utilizing fabric textile waste as feedstock provides additional challenges in that the feedstock material will contain water bound to the textile fibers. Specifically post-consumer textile contains significant amounts of cotton, wool etc. apart from the polyester itself and which are highly hygroscopic and results in a variation of water content of the feedstock between 5 and 15 % for post-consumer textiles stored at ambient conditions. This creates a mixture of ethylene glycol and water with a lower boiling point than the required for the dissolving reaction of PET in the dissolving reactor. The boiling point of the mixture can be increased by increasing reactor pressure. Increased operation pressure does however lead to increased capital cost and complexity.

[0040] (C) The recovery of Ethylene glycol is a critical part of the glycolysis process layout. In a process layout where bi s(hydroxy ethyl) terephthalate (BHET) is precipitated from EG by cooling down steam from the dissolving and glycolysis steps, recovery of EG as well as the yield of BEET in the precipitation is critical. In this context the Ethylene glycol filtrate stream containing the majority of the Ethylene glycol will also contain a significant amount of residual BEET. In order to recover the maximum amount of EG and also avoid polymerization of BEET in the bottom of the column, the distillation to separate EG from BEET in the filtrate is therefore performed under vacuum which reduces the temperature of the EG product vapor due to its lower temperature and this results in that the EG vapor is of less value for heat integration and recovery.

[0041] In the invention, it was realized that many of these problems are linked to three main challenges. The first challenge is to separate the materials from each other, the other is to not degrade the different fiber types in the mixed fabric during the separation and chemical recycling process, and the third is to solve the problem the high water content in the mixed fabric.

[0042] In the method for mixed fabric fiber rejuvenation of the invention, the method comprises the steps of adding ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C trough vapour injection to a fabric fibre material comprising polyester and natural fibre material, whereby at least partly depolymerising the polyester material to monomeric and oligomeric polyester residues, the monomeric and oligomeric polyester residues being dissolved in condensed, excess of liquid EG.

[0043] By adding the ethylene glycol as vapour at a desired temperature, the Ethylene glycol can penetrate the mixed fibre textile material and condensates directly on the fabric fiber material, supplying heat, solvent and reactant for the depolymerisation of the polyester material to monomeric and oligomeric polyester residues, such as BEET and oligomers. The method thus solves the problem of efficient heat transfer to the low density mixed textile material. The monomeric and oligomeric polyester residues is transported from the fabric material along with unreacted EG in solvent form, leaving the natural fiber material. Optionally, liquid phase EG may be added, for instance to quickly reach a desired EG:polyester reaction ratio.

[0044] - recovering a solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, and an essentially polyester-free natural fibre as a solid product

[0045] A solvent phase, comprising the monomeric and oligomeric polyester residues, oligomers and unreacted EG, is recovered, and an essentially polyester-free natural fiber as a solid product. Optionally, the solvent phase, comprising the BHET, oligomers and unreacted EG, may be separated from the solid product, comprising essentially polyester-free natural fiber.

[0046] Thus, the method also solves the problem of fiber separation. An example of a system suitable for such a method can be seen in figure 1.

[0047] The polyester may be polyethylene terephthalate) (PET) polyester.

[0048] The resulting polyester monomers and may be bi s(hydroxy ethyl) terephthalate (BHET).

[0049] BHET has active hydroxyl groups that make it useful for synthesizing unsaturated polyester resins, polyethylene terephthalate (PET), and new biocompatible polymer systems.

[0050] The natural fiber material may be defined as comprising fibers that are more hygroscopic than polyester fibers. An example of such fibers are cellulosic fibers.

[0051] The natural fiber material may be selected from the group consisting of plantbased materials, such as cotton, linen, bamboo, and jute, man-made cellulosic fibers, such as viscose and lyocell, animal-based fibers, such as silk and wool; preferably the natural fiber material is cotton.

[0052] These natural fibers contain significantly higher contents of water compared to polyester. For example, at ambient conditions cotton may contain 8-10 % water whereas polyester would contain 1-1.5 % water.

[0053] The percentage of fibers in the mixed fabric fiber may vary.

[0054] The percentage of natural fiber in the mixed fabric fiber is at least 1 wt.-%, such as at least 5 wt.-%, such as at least 10 wt.-%, such as at least 20 wt.-%, such as at least 50 wt.-%, such as between 1 wt.-% to 99 wt.-%, such as between 5 wt.-% to 95 wt.-%, such as between 1 to 50 wt.% or between 50 wt.-% and 99 wt.-%

[0055] Similarly, the percentage of polyester in the mixed fabric fiber is at least 1 wt.-%, such as at least 5 wt.-%, such as at least 20 wt.-%, such as at least 50 wt.-%, such as from between 1 wt.-% to 99 wt.-%, such as from between 5 wt.-% to 95 wt.-%, such as between 1 to 50 wt.% or between 50 wt.-% and 99 wt.-%.

[0056] The method may include withdrawing a gas phase, and separating any non-EG components in the gas phase from EG. Thereafter, the separated EG may be reintroduced to the fabric fibre material comprising polyester and natural fibre material, whereby the EG in the gas phase is recycled.

[0057] This efficiently deals with the higher water content of a mixed fiber material. The EG vapour evaporates any water into a gas phase from where it can be separated from EG, whereafter the EG is reintroduced. Thus, the problem of obtaining sufficiently high temperature for dissolving polyester in a water containing mixed textile waste feedstock without increasing operating pressure is solved.

[0058] The EG in the gas phase may be continuously recycled. This way, if more mixed fibre fabrics are introduced to the reaction, any non-EG components (i.e. water) will be continuously removed.

[0059] Any non-EG components in the gas phase may be separated from EG by condensation, such as through distillation. An example of a system suitable for such a method can be seen in figure 2.

[0060] There, a gas phase is withdrawn, and separating any non-EG components in the gas phase from EG and reintroducing the separated EG to the fabric fibre material comprising polyester and natural fibre material, whereby the EG in the gas phase is recycled.

[0061] The fiber degeneration is especially tricky to solve. In Krishnamoorthy et.al (Appl Nanosci (2012) 2: 119-126), the thermal stability of a cotton (control) fabric is examined using thermogravimetric analysis (TGA). It is shown that the onset of melting peak for the cotton fibers starts already at 200 °C degrees and arises gradually. After 250 °C, the major decomposition of the control peak starts. Thus, any expose to temperatures over 200 °C will already start to degenerate the cotton fibers, and closer to 250 °C , the degeneration will be rapid, thus degrading the quality and limiting the choice of application for the recycled product.

[0062] The high temperature may lead to weakening of the fiber, which may result in reduced strength and durability of the recycled cotton fibers, affecting the quality of the recycled material. It may also result in loss of fiber length. Longer fibers are desirable for textile production as they contribute to the strength and quality of the fabric and reduce spinning and weaving properties. However, it may also result in changes in fiber properties through chemical and structural changes in the cotton fibers. This can affect the fiber's moisture absorption properties, dyeability, and other characteristics, which limits the potential applications of the recycled cotton material.

[0063] In the invention, the temperature is precisely regulated to a span of 190° to 250° C, or even 195 °C and 240 °C, 195 °C and 230 °C or 197 °C and 220 °C. Thereby the degradation can be significantly reduced compared to present methods for recycling. Thus, the method also solves the problem of natural fiber degradation. In fact, by supplying the heat through the EG vapour, there is no need for heating up the reaction chamber to undesired temperatures, in order to transfer the heat into the fabric. In fact, the heat for the depolymerisation may be provided solely through the injected EG vapour.

[0064] If further heating is applied, for instance through a heat mantle surrounding the reaction, the heating does not have to exceed the temperature of the EG vapour.

[0065] Additional heat may be added through additional heats sources, such as through pre-heating of the mixed fabric fiber and / or optional liquid EG, or through use of an external heat source, such a heat mantle or use of micro-waves.

[0066] The solvent phase, comprising monomeric and oligomeric polyester residues and unreacted EG may be separated from the solid product, comprising essentially polyester-free natural fibre, preferably through filtering. An example of a system suitable for such a method can be seen in figure 3.

[0067] The resulting essentially polyester-free natural fibre may be further washed free of the monomeric and oligomeric polyester residues in order to obtain a purified natural fiber.

[0068] In order to remove contaminants from the solvent phase, the recovered liquid solvent phase may be cooled to a temperature of between 100 °C to 140 °C, whereby contaminants with higher precipitation temperatures than monomeric and oligomeric polyester residues, for example of BHET and oligomers, may be separated from the solvent phase comprising monomeric and oligomeric polyester residues and EG. The precipitate (comprising contaminants) may for instance be filtered away, leaving the solvent phase comprising monomeric and oligomeric polyester residues and EG.

[0069] The recovered solvent phase may be cooled down to a temperature of less than 50 °C, such as between 10 to 50 °C, thereby precipitating monomeric and oligomeric polyester residues, and thereafter separating the precipitated monomeric and oligomeric polyester residues from the solvent phase. An example of a system suitable for such a method can be seen in figure 4.

[0070] The recovery of EG is another critical part of the glycolysis process layout. Efficient EG recovery contributes to resource conservation, cost reduction, environmental benefits, and process efficiency. It also minimizes waste generation.

[0071] A portion of the EG in the recovered solvent phase may be evaporated to generate EG vapour, thereby concentrating the monomeric and oligomeric polyester residues in the solvent phase. Alternatively, a portion of the EG in the recovered solvent phase may be reclaimed through distillation, thereby concentrating monomeric and oligomeric polyester residues in the solvent phase and generating EG vapour.

[0072] Preferably, evaporation or distillation takes place at a superatmospheric pressure to generate ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C (or desired temperature), and wherein the generated EG vapour is used for vapour injection to the fabric fibre material comprising polyester and natural fibre material.

[0073] Once a solvent phase has been separated during recovery, such a recycling of EG may serve as the principal source of EG vapour for the reaction. Similarly, starting the method, EG may be added to the distillation column to generate EG vapour for the reaction. An example of a system suitable for such a method can be seen in figure 5.

[0074] Since the method may have continuous recycling of EG, the method may be run continuously. However, the method may also be run in batches.

[0075] This may simplify certain aspects, such as adding a preferred ratio of EG to the amount of added polyester. The ratio (wt. / wt.) between polyester and EG in may be in the range of 1 :3 to 1 :9, preferably between 1 :3.7 to 1 :6, more preferably between 1 :4 to 1 :5.

[0076] Also, it may simplify the monitoring of the reaction. For instance, the monomeric polyester residue (for example BEET) level in the solvent phase may be monitored. When the depolymerization starts, the monomeric polyester residue level in the solvent phase will rise. Then the monomeric polyester residue:EG ratio has stabilized, this indicates that all polyester has been depolymerized. Thus, the solvent phase and the essentially polyester-free natural fibre in the solid phase may be recovered without exposing the natural fibers to the reaction conditions unnecessarily, thereby minimizing fiber degeneration.

[0077] In the invention, it was found that the reaction could take place in a single chamber reaction chamber for cloth recycling.

[0078] Such a system 100 for mixed fabric fiber rejuvenation of a mixed fabric fibre material comprising polyester and natural fibre material, the system comprising at least one depolymerization vessel 1 for at least partly depolymerising the polyester to monomeric and oligomeric polyester residues. The depolymerization vessel 1 comprises; at least one feed inlet 2 for feeding a mixed fabric fiber material comprising polyester and natural fiber material to the vessel, at least one EG vapour inlet 3 for injecting EG in gas phase at a temperature of between 190° to 250° C into the vessel, at least one EG liquid inlet 4 for injecting liquid EG into the vessel, and at least one outlet 5 for recovering monomeric and oligomeric polyester residues, unreacted EG and essentially polyester-free natural fiber material. An example of such a system can be seen in figure 1.

[0079] In the system 100, the depolymerization vessel 1 may be operated at atmospheric pressure or superatmospheric pressure.

[0080] The system does not have to be limited to a single reaction chamber, but allowing for a single chamber design offers several advantages, such as a simplified process, efficient space utilization and cost-effectiveness. Using the method of the invention, it was found that it also leads to enhanced process control for temperature regulation, leading to improved process efficiency and product quality.

[0081] The EG in gas phase may be provided from a unit for evaporating EG.

[0082] However, in the invention it was found that the EG is preferably recycled, which can be seen in figures 5 and 6.

[0083] The system 100 may further comprise a vapour phase recycling column 6, being connected to the depolymerization vessel 1, for withdrawing a gas phase, and separating any non-EG components in the gas phase from EG, and reintroducing the EG to the to the depolymerization vessel 1. This efficiently deals with the higher water content of a mixed fiber material.

[0084] The system (100) may comprise a vapour phase recycling column 6 and a partial condenser 24 for separating any non-EG components in a gas phase from EG by condensing EG. The depolymerization vessel 1 may further comprise at least one gas outlet 7 for removing the gas phase, at least one EG inlet 8 for reintroducing separated liquid EG, whereby the EG in the gas phase is recycled. The vapour phase recycling column 6 may comprise at least one gas inlet 9 connected to the gas outlet 7 of the depolymerization vessel 1, at least one EG liquid outlet 10 connected to the EG liquid inlet 8 depolymerization vessel 1, a gas outlet 25, a liquid inlet 26. The partial condenser 24 may comprise at least one gas inlet 27 connected to the gas outlet 25 of the vapour phase recycling column 6, at least one EG liquid outlet 28 connected to the liquid inlet 26 of the vapour phase recycling column 6, and at least one non-EG gas outlet 11 for removal of any non-EG components. In figure 2, an example of such a system can be seen. This way, non-EG vapour (i.e. water) may be removed from the EG.

[0085] The system 100 may also comprise means for separating the solvent phase from the solid product. Preferably, a filter 12 is used. Thus, the system 100 may comprise a separation means 12 for separating a solvent phase comprising the monomeric and oligomeric polyester residues and unreacted EG from a solid product comprising an essentially polyester-free natural fiber, the separation means 12 comprising an inlet 13 connected to the outlet 5 of the depolymerization vessel 1, a solvent outlet 14 and a solids outlet 15. The separation means 12 may be a filter. In figure 3, an example of such a system 100 can be seen.

[0086] Alternatively, a separation means 12 could also be part of the depolymerization vessel 1, for instance by having the separation means 12, being a filter, form a floor close to the bottom of the depolymerization vessel 1, such that the solid material can rest on the filter floor and the liquid phase can penetrate the filter by gravity, thereby separating the solids from the solid phase from the liquid phase.

[0087] Thereby, the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG may be separated from the solid product, comprising essentially polyester-free natural fibre.

[0088] The system 100 may further comprise contaminant precipitation vessel 29 for cooling the recovered liquid solvent phase, preferably to a temperature of 100° C to 140° C, and precipitating contaminants with higher precipitation temperatures than the monomeric and oligomeric polyester residues from the solvent phase. The contaminant precipitation vessel 29 may comprise an inlet 30 connected, directly or indirectly, to the solvent outlet 14 of the separation means 12, a solvent outlet 31 and a precipitant outlet 32 for contaminants with higher precipitation temperatures than the monomeric and oligomeric polyester residues. Preferably, the contaminant precipitation vessel 29 is arranged downstream of the separation means 12.

[0089] The contaminant precipitation vessel 29 may further comprise a separation means, such as a filter, for separating the precipitate from the solvent phase.

[0090] Further, the contaminant precipitation vessel 29 may further comprise a cooling means, for speeding up the cooling of the liquid phase.

[0091] The system 100 may also comprise means for precipitation monomeric and oligomeric polyester residues , for example BHET and oligomers, and separating these precipitants from the solvent phase. An example of such a system can be seen in figure 4.

[0092] The system 100 may comprise a precipitation and separation vessel 16, for precipitating monomeric and oligomeric polyester residues, and for separating said precipitated monomeric and oligomeric polyester residues from the solvent phase. The precipitation and separation vessel 16 may comprise an inlet 17 connected, directly or indirectly, to the solvent outlet 14 of the precipitation means 12, a solvent outlet 18 and a precipitant outlet 19.

[0093] By cooling down the recovered solvent phase to a temperature of less than 50 °C, such as between 1 and 49 °C, most of the BHET and oligomers will precipitate, whereafter they can be separated from the EG solvent phase.

[0094] To speed up precipitation, the precipitation and separation vessel 16 may further comprise cooling means.

[0095] In order to facilitate EG recovery, the system 100 may further comprise an EG recycling column 20, for generating EG vapour and concentrating any remaining monomeric and oligomeric polyester residues.

[0096] The EG recycling column 20 may comprise a liquid phase inlet 21, an EG vapour outlet 22 connected to the EG vapour inlet 3 of the depolymerization vessel 1, and an outlet 23 for concentrated monomeric and oligomeric polyester residues.

[0097] The liquid phase inlet 21 of the EG recycling column 20 may be connected to the solvent outlet 14 of the filter 12, or the solvent outlet 18 of the precipitation and separation vessel 16, or the solvent outlet 31 of the contaminant precipitation vessel 29.

[0098] Such a recycling of EG may serve as the principal source of EG vapour for the method of the invention. An example of a system suitable for such a method can be seen in figure 5.

[0099] The EG recycling column 20 may further comprise an EG inlet, where EG can be added to generate EG vapour for the reaction.

[0100] The system 100 may further include several different extra features.

[0101] If further heating is to be applied, a heat mantle may surround all or part of the depolymerization vessel 1.

[0102] Further, the depolymerization vessel 1 may comprise one or several sensors, such as a temperature sensor, and / or a sensor for monitoring the level of BHET in the solvent phase.

[0103] The depolymerization vessel 1 may also comprise agitation means for agitating the mixed fabric fiber, the gas phase and the solvent phase are agitated to ensure an even temperature distribution.

[0104] Example

[0105] The depolymerization step is highly sensitive to operation temperature i.e. at temperatures below 190 °C the depolymerization rate is too low to be feasible in an industrial context whereas temperatures above 240 °C has been shown to cause degradation of cotton (WO 2022 / 118148 Al). It is thus critical to maintain a well- controlled operation temperature and to maintain a uniform temperature throughout the fiber and liquid volume in the depolymerization step while simultaneously ensuring a sufficiently high heating rate of the feedstock. The example below shows that introducing MEG in gaseous form to transfer the required duty by condensation provides efficient heating with minimum excess temperature whereas supplying the equal duty from a heating jacket to the viscous mixture of fiber and liquid results in high excess temperatures which will lead to degradation of the cotton present in the feedstock.

[0106] Although the present invention has been described above with reference to (a) specific embodiment s), it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and, other embodiments than the specific above are equally possible within the scope of these appended claims, e.g. different than those described above.

[0107] In the claims, the term "comprises / comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and / or advantageous. In addition, singular references do not exclude a plurality. The terms "a", "an", “first”, “second” etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

CLAIMS1. A method for mixed fabric fiber rejuvenation, wherein the method comprises the steps of:- adding ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C trough vapour injection to a fabric fibre material comprising polyester and natural fibre material, whereby at least partly depolymerising the polyester material to monomeric and oligomeric polyester residues, the monomeric and oligomeric polyester residues being dissolved in condensed, excess of liquid EG;- optionally adding liquid phase EG,- recovering a solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, and an essentially polyester-free natural fibre as a solid product; and- optionally separating the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG, from the solid product, comprising essentially polyester-free natural fibre.

2. The method according to claim 1, wherein the monomeric polyester residues are bis(hydroxy ethyl) terephthalate (BHET).

3. The method according to any one of claims 1 to 2, wherein the temperature of the EG vapour injection is between 195 °C and 240 °C.

4. The method according to any one of claims 1 to 3, wherein the temperature of the EG vapour injection is between 197 °C and 220 °C.

5. The method according to any one of claims 1 to 4, wherein a gas phase is withdrawn, and separating any non-EG components in the gas phase from EG and reintroducing the separated EG to the fabric fibre material comprising polyester and natural fibre material, whereby the EG in the gas phase is recycled.

6. The method according to claim 5, wherein the EG in the gas phase is continuously recycled.

7. The method according to any one of claims 5 to 6, wherein non-EG components in the gas phase are separated from EG by condensation.

8. The method according to any one of claims 1 to 7, wherein the solvent phase, comprising the monomeric and oligomeric polyester residues and unreacted EG is separated from the solid product, comprising essentially polyester-free natural fibre, preferably through filtering.

9. The method according to any one of claims 1 to 8, wherein the recovered liquid solvent phase is cooled to a temperature of 100° C to 140° C and filtered, whereby contaminants with higher precipitation temperatures than monomeric and oligomeric polyester residues are separated from the solvent phase comprising monomeric and oligomeric polyester residues and EG.

10. The method according to any one of claims 1 to 8, wherein the recovered solvent phase is cooled down to a temperature of less than 50 °C, such as between 10 to 50 °C, thereby precipitating monomeric and oligomeric polyester residues, and thereafter separating the precipitated monomeric and oligomeric polyester residues from the solvent phase.

11. The method according to any one of claims 1 to 10, wherein a portion of the EG in the recovered solvent phase is evaporated to generate EG vapour, thereby concentrating the monomeric and oligomeric polyester residues in the solvent phase.

12. The method according to claim 1 to 11, wherein a portion of the EG in the recovered solvent phase is reclaimed through distillation, thereby concentrating monomeric and oligomeric polyester residues in the solvent phase and generating EG vapour.

13. The method according to claim 11 or 12, wherein the evaporation or distillation takes place at a superatmospheric pressure to generate ethylene glycol (EG) in gas phase at a temperature of between 190° to 250° C, and wherein the generated EG vapour is used for vapour injection to the fabric fibre material comprising polyester and natural fibre material.

14. The method according to any one of claims 1 to 13, wherein the mixed fabric fiber, the gas phase and the solvent phase are agitated to ensure an even temperature distribution during the depolymerization.

15. The method according to any one of claims 1 to 14, wherein the resulting essentially polyester-free natural fibre is washed to remove monomeric and oligomeric polyester residues to obtain a purified natural fiber.

16. The method according to any one of claims 1 to 15, wherein the natural fibre material comprises fibers that are more hygroscopic than polyester fibers.

17. The method according to any one of claims 1 to 16, wherein the natural fibre material are selected from the group consisting of plant-based materials, such as cotton, linen, bamboo, and jute, man-made cellulosic fibers, such as viscose and lyocell, animal-based fibers, such as silk and wool; preferably the natural fiber material is cotton.

18. The method according to any one of claims 1 to 17, wherein the percentage of natural fiber in the mixed fabric fiber is at least 1 wt.-%, such as at least 5 wt.-%, such as at least 10 wt.-%, such as at least 20 wt.-%, such as at least 50 wt.-%, such as between 1 wt.-% to 99 wt.-%, such as between 5 wt.-% to 95 wt.-%, such as between 1 to 50 wt.% or between 50 wt.-% and 99 wt.-%.

19. The method according to any one of claims 1 to 18, wherein the percentage of polyester in the mixed fabric fiber is at least 1 wt.-%, such as at least 5 wt.-%, such as at least 20 wt.-%, such as at least 50 wt.-%, such as from between 1 wt.-% to 99 wt.-%, such as from between 5 wt.-% to 95 wt.-%, such as between 1 to 50 wt.% or between 50 wt.-% and 99 wt.-%.

20. The method according to any one of claims 1 to 19, wherein the heat is provided through the injected EG vapour.

21. The method according to any one of claims 1 to 19, wherein additional heat is added in the method through additional heats sources, such as through pre-heating of the mixed fabric fiber and / or optional liquid EG, or through use of an external heat source, such a heat mantle or use of micro-waves.

22. The method according to any one of claims 1 to 21, wherein the method is run in batches.

23. The method according to any one of claims 1 to 22, wherein the monomeric polyester residue level in the solvent phase is monitored, a stabile monomeric polyester residue:EG ratio in the solvent phase indicating that all polyester has been depolymerized, whereby the solvent phase and the essentially polyester-free natural fibre is recovered.

24. The method according to any one of claims 1 to 23, wherein the mass ratio (wt. / wt.) between polyester and EG is in the range of 1 :3 to 1 :9, preferably 1 :3.7 to 1 :6, more preferably 1 :4 to 1 :5.

25. A system (100) for mixed fabric fiber rejuvenation of a mixed fabric fibre material comprising polyester and natural fibre material, the system comprising at least one depolymerization vessel (1) for at least partly depolymerising the polyester to monomeric and oligomeric polyester residues, wherein the depolymerization vessel (1) comprises; at least one feed inlet (2) for feeding a mixed fabric fiber material comprising polyester and natural fiber material to the vessel, at least one EG vapour inlet (3) for injecting EG in gas phase at a temperature of between 190° to 250° C into the vessel, at least one EG liquid inlet (4) for injecting liquid EG into the vessel, and at least one outlet (5) for recovering monomeric and oligomeric polyester residues, unreacted EG and essentially polyester-free natural fiber material.

26. A system (100) according to claim 25, wherein the depolymerization vessel (1) may be operated at atmospheric pressure or superatmospheric pressure.

27. The system (100) according to claim 25 to 26, further comprising a vapour phase recycling column (6) and a partial condenser (24) for separating any non-EG components in a gas phase from EG by condensing EG, wherein the depolymerization vessel (1) further comprises; at least one gas outlet (7) for removing the gas phase, at least one EG inlet (8) for reintroducing separated liquid EG, whereby the EG in the gas phase is recycled, wherein the vapour phase recycling column (6) comprises; at least one gas inlet (9) connected to the gas outlet (7) of the depolymerization vessel (1), at least one EG liquid outlet (10) connected to the EG liquid inlet(8) depolymerization vessel (1), a gas outlet (25), a liquid inlet (26), and wherein the partial condenser (24) comprises; at least one gas inlet (27) connected to the gas outlet (25) of the vapour phase recycling column (6), at least one EG liquid outlet (28) connected to the liquid inlet(26) of the vapour phase recycling column (6), and at least one non-EG gas outlet (11) for removal of any non-EG components.

28. The system (100) according to any one of claims 25 to 27, further comprising a separation means (12) for separating a solvent phase comprising the monomeric and oligomeric polyester residues and unreacted EG from a solid product comprising an essentially polyester-free natural fiber, the separation means (12) comprising an inlet (13) connected to the outlet (5) of the depolymerization vessel (1), a solvent outlet (14) and a solids outlet (15).

29. The system (100) according to claim 28, wherein the separation means (12) is a filter.

30. The system (100) according to any one of claims 28 to 29, further comprising at least one contaminant precipitation vessel (29) for cooling the recovered liquid solvent phase and precipitating contaminants with higherprecipitation temperatures than the monomeric and oligomeric polyester residues from the solvent phase, comprising an inlet (30) connected, directly or indirectly, to the solvent outlet (14) of the separation means (12), a solvent outlet (31) and a precipitant outlet (32) for contaminants with higher precipitation temperatures than the monomeric and oligomeric polyester residues; preferably the contaminant precipitation vessel (29) is arranged downstream of the separation means (12).

31. The system (100) according to any one of claims 28 to 30, further comprising at least one precipitation and separation vessel (16), for precipitating monomeric and oligomeric polyester residues, and for separating said precipitated monomeric and oligomeric polyester residues from the solvent phase, the precipitation and separation vessel (16) comprising an inlet (17) connected, directly or indirectly, to the solvent outlet (14) of the precipitation means (12), a solvent outlet (18) and a precipitant outlet (19).

32. The system (100) according to any one of claims 28 to 31, further comprising an EG recycling column (20), for generating EG vapour and concentrating any remaining monomeric and oligomeric polyester residues, comprising a liquid phase inlet (21), an EG vapour outlet (22) connected to the EG vapour inlet (3) of the depolymerization vessel (1), and an outlet (23) for concentrated monomeric and oligomeric polyester residues.

33. The system (100) according to claim 31, wherein the liquid phase inlet (21) of the a EG recycling column (20) is connected to the solvent outlet (14) of the filter (12), or the solvent outlet (18) of the precipitation and separation vessel (16), or the solvent outlet (31) of the contaminant precipitation vessel (29).

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