Textile product recycling methods and plants

Abstract

This provides a safe, low-cost, easy, and environmentally friendly method for recycling waste polyester cotton fiber products. [Solution] A method for recycling waste blended textile products, comprising the steps of a) supplying a waste blended textile product containing cellulose fibers 40 and polyester fibers; b) mechanically opening the waste blended textile product to form fiber tufts; c) supplying the fiber tufts into a reaction chamber 10; d) supplying a basic depolymerization solution 3 according to a bath ratio of 1 / 2 to 1 / 20 of the weight of the fiber tufts to the weight of the solution; e) circulating the amount of depolymerization solution through the fiber tufts to depolymerize the polyester and remove the monomers from the fiber tufts; and f) removing the depolymerization solution from the reaction chamber, wherein the solution in c) is at 101 to 160°C, and the solution is circulated through the static fiber tufts to obtain treated fiber tufts 5 containing cellulose staple fibers that do not contain polyester.

Description

Technical Field

[0001] The present invention relates to a method for recycling textile products and a plant. More specifically, the present invention relates to a method for recycling textile products containing cellulosic short fibers and polyester. By the method of the present invention, polyester can be removed from waste textile products such as polyester blend fiber products, that is, fabrics, clothes, yarns, fibers, etc. containing polyester long fibers or polyester fibers and cellulosic short fibers, especially cotton short fibers, and the cellulosic short fibers can be recovered and recycled. The cotton fibers and cellulosic fibers recovered by the method of the present invention are suitable for use as short fibers for yarn production without being dissolved and regenerated into artificial cellulosic fibers.

Background Art

[0002] In the textile industry, the recycling of waste textile products, especially waste textile products such as fabrics and used clothing and apparel, has become a major issue in the textile industry. Waste textile products include fabrics, clothing items, scraps generated in the manufacturing process of yarns, yarns, or long fibers, pre-use fabrics and defective fibers such as yarns, and used textile products such as used or defective clothing items and fabrics derived from interior decorations. New and efficient methods for recycling these waste textile products are being actively studied.

[0003] One of the objectives of the present invention is to recycle textile products and textile products that contain both polyester and cotton and are generally known as polycotton or polyester-cotton fiber products. The object of the present invention is to recover cellulosic short fibers, especially cotton fibers of yarns, contained in waste textile products and recycle them in a form of short fibers suitable for further use as secondary raw materials for spinning, and to remove the polyester contained in the blend fiber products and textile products of waste textile products, that is, polycotton fabrics, and recover them as corresponding monomers. Polycotton fabrics contain yarns containing cellulosic short fibers and polyester long fibers or fibers. The blended fabrics as defined in this application may include yarns comprising cotton yarn and polyester yarn, and / or combinations of polyester yarn without polyester and polyester yarn without cotton fibers. The yarns are woven or knitted to form a fabric structure. Discarded garments processed according to the present invention may also include non-fabric elements, such as zippers, rivets, and labels, which are typically made of metal or plastic materials.

[0004] Methods for recycling polyester-containing fabrics are known in the art. Some methods involve depolymerizing the polyester component in the fabric to obtain the starting monomers terephthalic acid (TPA) and ethylene glycol (EG). These known recycling methods require the fabric to be pre-cut into fragments or sheets before treatment with the depolymerization solution. The final product includes cellulose pulp, TPA, and EG, the TPA and EG of which can be used in the manufacture of polyester or for other applications.

[0005] Patent Document 1 discloses a method and system for recycling polycotton fiber products, in which fiber product pieces obtained by cutting the fiber product are treated in an aqueous solution with a pH of 10 to 14 at a temperature of 105°C to 190°C and a pressure of 40 to 300 psi under subcritical conditions for 0 to 90 minutes. The polyester component is depolymerized into TPA and EG, and the cotton fibers are broken down into cellulose pulp, which is then recycled into artificial cellulose fibers, i.e., regenerated cellulose materials such as rayon, viscose, lyocell, and cellulose acetate through further processing. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] WO2019 / 140245A1 [Overview of the project] [Problems that the invention aims to solve]

[0007] The aforementioned known methods focus on recovering the polyester content from waste textile materials, and therefore have the drawback of significantly degrading the quality of the cotton fibers after processing. For example, if recycled cotton fibers need to be dyed with a dye different from the dye used in the original waste textile product, the strength, length, and dyeability of the resulting fibers are significantly reduced.

[0008] Therefore, one of the objectives of the present invention is to solve the above-mentioned drawbacks of known methods for recycling polyester cotton textile products and to provide a method for recycling waste polyester cotton textile products, i.e., fabrics, clothing, yarn (and optionally fibers as well), in a safe, low-cost, easy, and environmentally friendly manner, by recovering cotton (or cellulosic) fibers in waste textile products in a state identical or as close as possible to the properties of the original unused cotton fibers, thereby providing cotton fibers that are suitable for use as they are, i.e., staple fibers, in the manufacture of yarn. In other words, one of the objectives of the present invention is to recycle cotton fibers from waste textile products into cotton fibers suitable for further use in yarn production through a fiber-to-fiber recycling process.

[0009] Another object of the present invention is to provide a method for easily handling recycled fibers during the process, even when processing large quantities of fibers. A further object of the present invention is to provide a fully automated method. Another object of the present invention is to provide a method for obtaining cellulosic fibers (i.e., cotton fibers) that can be easily and effectively dyed, even with dyes different from the dyes used in the original waste textile product. [Means for solving the problem]

[0010] The above-mentioned object of the present invention is achieved by the invention described in one or more of the claims of this application. In particular, the present invention relates to one or more independent claims relating to methods, plants, and related products, and preferred embodiments are described in each dependent claim.

[0011] These methods are intended for the recycling of waste "blended textile products," that is, waste "blended textile products" containing both polyester and cotton, such as so-called "polycotton" fibers, or waste "blended textile products" containing other cellulosic fibers other than polyester and cotton. Typically, polyester exists in the form of long fibers in fabrics and clothing, but it can also exist in the form of short fibers (e.g., yarn). Polyester may also be in the form of sewing thread used to join parts of the garment being treated. Since the objective of the present invention is to recover valuable cotton in a reusable form, preferably the amount of polyester in the textile product according to the present invention is 1% to 75% by weight of the weight of the textile product, and more preferably the amount of polyester is 4% to 50% by weight.

[0012] According to one embodiment of the present invention, the method of the present invention can be applied to waste textile products with a polyester content of 0 to 100%. The method of the present invention can also be used to remove dye from waste textile tufts in the case of 100% cotton textile products. In fact, one object of the present invention is to provide a method for decolorizing waste textile products.

[0013] According to one embodiment of the present invention, the method of the present invention is directed toward the recycling of textile products such as cloths and clothing, and includes the step of mechanically opening such textile products (e.g., yarn, cloth, clothing) to obtain a fiber tuft containing or substantially consisting of cellulosic fibers, i.e., cotton fibers and polyester fibers, or consisting of cellulose fibers. Next, the fiber tuft is treated with a depolymerization solution to remove any polyester, dyes, and pigments that may be present in the tuft. After a bleaching step (optional), the fiber tuft is dried to become a cotton material suitable for processing into yarn.

[0014] Methods for mechanically opening fibers in textile products are known in the art. In the so-called tearing step or defibration step, a machine known as a tearing machine is commonly used for such operations. Suitable tearing machines are available from manufacturers such as Laroche (a subsidiary of the Andritz Group, France), Dell'Orco & Villani (Italy), and Trutzschler (Germany).

[0015] A preferred tearing machine comprises a series of rotating cylinders or drums covered with opening means such as saw wires or steel pins for tearing textile products, thereby gradually tearing the textile product structure into bundles of fibers or tufts of fibers. Therefore, the terms “tuft,” “fiber tuft,” and “fiber tuft” refer to a known fiber state in which a textile product is transformed into a bundle of fibers obtained by a tearing machine that processes the fibers using a series of rotating drums equipped with tearing means such as steel pins. Therefore, fiber tufts obtained by known machines are no longer in the form of yarn, but rather aggregates or bundles of fibers in a physical state similar to that of raw cotton and absorbed cotton after ginning.

[0016] The fiber tuft can be cut into strips by carding. The fibers of the fiber tuft obtained by the method of the present invention are stretched to a length suitable for use in the spinning process and may be used in combination with other fibers. The fiber tufts used in the present invention preferably have the fibers disclosed above as the main component. It is noted that the reduction in the length of cotton fibers in the final product by the method of the present invention is extremely small compared to the initial fiber tufts. The micronaire of this fiber tuft is preferably 3 to 5, more preferably 3.5 to 4.5 when measured by TexTechno Fibrotest according to ASTM (American Society for Testing and Materials) D5867-12. This value applies to the fineness and maturity of the fibers, which are extremely important in spinning.

[0017] As used herein, the terms "treated tuft", "treated fiber tuft", and "treated tuft of fibers" refer to the material obtained after the tuft has been treated according to the method of the present invention, and include cellulose-based fibers, preferably cotton fibers, or consist essentially of cellulose fibers, or refer to an agglomerate of cellulose fibers. Regarding fiber tufts, for example, it is described in "Tearing of Used Cotton T-Shirts and Jeans with Different Degrees of Wear" by Julia Aronsson and Anders Persson (DOI: 10.1177 / 1558925020901322), and is also described in the pamphlet regarding the tearing machine provided by the manufacturer of the machine, and is available, for example, from the following address.

[0018] [Numeral 1] https: / / web.archive.org / web / 2 / https: / / www.truetzschler.com / en / spinning / products / tearing-lines / . <000008, According to a preferred embodiment, the content of unopened fibers in the fiber tuft is less than 20% of the weight of the starting material. In other words, the content of unopened fibers is expressed as the percentage of the weight of unopened fiber pieces with respect to the weight of the starting material. The amount of unopened fibers can be evaluated manually or using an apparatus such as the TexTechno Fibrotest. The content of unopened fibers obtained from the machine may be given as a yarn piece by the machine.

[0020] As one solution, the tufts obtained from the tearing machine are further processed with another opening machine. This other opening machine is called a so-called fine opener. In particular, according to one aspect, tufts with an unopened fiber content exceeding 20% can be sent to a further opening process such as a fine opener machine in order to reduce the content of unopened fibers.

[0021] In this specification, the term "agglomerate" refers to a mass of a substance without a definite shape (especially fibers, and in some cases fragments of yarn). The term "fiber product" refers to both fabrics and clothing before and after use by consumers. The fabric is a fiber product, a knitted fabric, or a non-woven fabric. Clothing includes all kinds of clothing items such as T-shirts, trousers, jeans, jackets, shirts, sportswear, etc.

[0022] In an embodiment of the present invention, the waste clothing may be used in the process as it is. That is, the waste clothing may include non-fiber elements such as zippers, rivets, buttons (these elements are usually made of metal or plastic), and labels. The non-fiber elements are removed from the fiber material before the fibers are fed into the tearing machine line. The removal of the non-fiber elements is carried out by a method known per se in the art when the waste is preliminarily subjected to a cutting step.

[0023] Fabrics and garments may contain polycotton yarn. An exemplary polycotton yarn is a core-spun yarn having a polyester core and a cotton sheath containing cotton staples. Blended nonwovens may contain polyester nonwoven filaments on a cotton or cellulose substrate. Waste textile products may also contain yarn in some embodiments. A suitable starting waste textile product is fabric known as “hard waste” and “hard waste textile product.”

[0024] The term "cellulose fibers" defines cotton fibers, particularly virgin cotton fibers, modified cotton fibers, and other fibers commonly used in yarn, such as linen fibers, flax fibers, jute fibers, hemp fibers, ramie fibers, kenaf fibers, sisal fibers, and Heneken fibers. Cotton and cellulose fibers contained in textile products subject to recycling are typically in the form of short, thread-like fibers. Viscose and other cellulose-based synthetic fibers fall under the definition of cellulose fibers in this application. The following discussion will focus on cotton fibers, the primary cellulose-based product recovered from waste textile products. However, starting blends may also include other cellulose fibers besides cotton, such as viscose, rayon, and lyocell.

[0025] In either case, the cotton or cellulosic fibers are recovered as they are (for example, in their original form as staple fibers in yarn) rather than being turned into pulp. As an example, a polycotton fiber product made from cotton and polyester fibers and processed according to the method of the present invention ultimately yields a fiber tuft in which only cotton fibers remain at the end of the method, while the polyester is depolymerized during the process to disodium salts of TPA and EG by a depolymerization solution and removed from the fiber tuft, leaving the cotton fibers behind.

[0026] The term "bath ratio" is intended to define the ratio of the dry weight of the textile product to be recycled to the weight of the solution used to process the textile product, where, depending on the stage of the method of the present invention, the solution is either a depolymerization solution, or a bleaching solution or a washing solution, used in a further step of the method, as described below.

[0027] With respect to polyester, the terms “dissolve” or “melt” are intended to define the result of polyester being depolymerized into its monomers, so that after the method of the present invention, the treated fiber tuft will no longer contain, or substantially no, polyester filaments or fibers.

[0028] The term “circulation” in relation to the depolymerization solution (and other solutions used in the method of the present invention) is intended to define that the solution is subjected to a flow through the textile product, i.e., polycotton fiber tufts, and the reaction chamber in which the fiber tufts are held. This flow is preferably generated by a pump that supplies the solution to the reaction chamber through the textile product and the reaction chamber. The solution leaves the reaction chamber and is then returned to it, circulating the fiber tufts and the reaction chamber again. The bleaching solution and washing solution also circulate the tuft aggregates multiple times, similar to the depolymerization solution. A plant for carrying out the method of the present invention typically includes a fluid circuit that includes an inlet and an outlet to the reaction chamber.

[0029] The fiber tuft is held in a stationary, or static, state within the reaction chamber. The term "stationary" or "static" state defines the fiber tuft as being contained within the reaction chamber, while the depolymerization solution (or bleaching or washing solution) is supplied to and discharged from the reaction chamber through the tuft. The fiber tuft fills the reaction chamber and does not move with the solution, i.e., it does not move with the flow of the solution. Preferably, the tuft within the reaction chamber is in a compressed state.

[0030] In a preferred embodiment, the fiber tuft is contained in at least one cage or basket permeable to a flow of solution. This cage, preferably multiple cages, i.e., baskets, is placed in the reaction chamber to carry out the method of the present invention. As described above, the tuft is compressed. That is, the tuft is placed in the basket (or cage) and compressed until it reaches a bulk density of 100 to 350 g / L, preferably 240 to 320 g / L, more preferably 280 to 300 g / L, and most preferably 300 g / L. In some cases, the bulk density may be as low as about 100 g / L, but preferably it is greater than 240 g / L. Thus, the bulk density of the fiber tuft in the reaction chamber is within the above range. The fact that the fibers are filled into the reaction chamber, preferably in a compressed state, also offers the advantage of significantly improving the productivity of the method. In other words, embodiments in which the fibers are agitated or moved in the depolymerization solution using a rotating drum in a washing machine, for example, are not part of the present invention.

[0031] Such compression may be wet compression, meaning the fiber tuft is preferably moistened with water before compression. This promotes fiber fluidity and accelerates the compression step. When using wet compression, the bulk density of the fiber tuft is preferably 130-460 g / L, more preferably 240-350 g / L, and even more preferably 280-350 g / L. In particular, good results have been found when the bulk density is around 300 g / L. The weight of the tuft mentioned above is the weight of the tuft in a dry state.

[0032] In particular, the present invention relates to a method for recycling waste blend textile products containing polyester and cellulosic fibers, preferably cotton fibers, the method comprising the depolymerization of polyester in a basic aqueous solution, and the step being: a) A method for supplying a fixed amount of the waste blended textile product, wherein the waste blended textile product is selected from fabrics, garments, and yarns; b) Mechanically opening the waste blended fiber product to form a fiber tuft (1) containing or substantially consisting of cellulosic fibers (40) and polyester fibers (4); c) The step of supplying the fiber tuft (1) into the reaction chamber (10); d) A step of supplying an amount of basic depolymerization solution (3) according to a bath ratio of 1 / 2 to 1 / 20 of the weight of the fiber tuft relative to the weight of the solution; e) The step of circulating the above amount of depolymerization solution (3) through the fiber tuft (1) to depolymerize the polyester (4) to the corresponding monomer and remove the polyester monomer from the fiber tuft; and f) The step of removing the depolymerization solution (3) from the reaction chamber (10), The temperature of the depolymerization solution in step e) is in the range of 101°C to 160°C. The fiber tuft is in a stationary, i.e., static state, and the flow of the solution circulates through the tuft. This method provides a treated fiber tuft that is substantially free of polyester material, preferably free of polyester material, and contains cellulosic staple fibers, preferably cotton staple fibers.

[0033] The method of the present invention has the advantage of easily processing large quantities of waste textile products to be recycled, even when there are multiple textile products to be processed. In fact, the starting material is in the form of fiber tufts, which can be compressed into baskets (cages) and then easily supplied to the reaction chamber.

[0034] As disclosed below, the method of the present invention can be automated as a whole. In embodiments, fiber opening (i.e., the step of reducing stiff waste textile products into tufted fibers) is carried out in parallel with the depolymerization step. In embodiments, the fiber opening step is carried out separately, the tufts are compressed into bales, and the bales are transported to a depolymerization plant. There the bales are opened and supplied to the depolymerization plant. After completion of this step, the resulting fiber tufts can be formed into bales again.

[0035] Furthermore, the method of the present invention makes it possible to obtain cotton fibers that are substantially free of dye molecules, or completely free of them. Therefore, the need for further treatment of the fibers to completely remove the dye is avoided or significantly reduced. This method has the advantage of supplying a depolymerization solution to the reaction chamber to depolymerize the polyester fibers of the tuft, and maintaining the fiber tuft in a static state under mild reaction conditions within the reaction chamber. This decomposes the ester bonds of the polyester into monomers, disodium terephthalate (Na2TP), and ethylene glycol (EG), significantly reducing the alteration and depolymerization of the cellulosic staple fibers.

[0036] As shown in Figures 1, 2, and 5, and as described below, the flow of the depolymerization solution passes through the compressed fiber tuft aggregate, i.e., the "tuft," exits the reaction chamber, returns to the reaction chamber, passes through the fiber tuft again, and is supplied into the reaction chamber several times, depolymerizing the polyester present in the tuft. The number of cycles, i.e., the number of times the solution is supplied through the tuft, can be adjusted according to the amount of polyester in the fiber tuft, for example, the amount of polyester in the waste textile product being processed. The number of times the depolymerization solution is supplied to the fiber product, i.e., the number of cycles, is suitable to be in the range of 30 to 480 cycles per hour, preferably 50 to 400 cycles per hour, more preferably 60 to 300 cycles per hour, and most preferably 70 to 200 cycles per hour. In other words, a certain amount of solution is supplied to the reaction chamber containing the tuft at a flow rate that yields the above-mentioned number of cycles.

[0037] It is preferable to raise the temperature of the depolymerization solution in a closed reaction chamber, thereby increasing the pressure accordingly, to a level that allows the polyester to depolymerize while minimizing, and in some cases avoiding, deterioration or alteration of the cotton staple fibers (e.g., a decrease in the degree of polymerization).

[0038] In step e), it is preferable that a selected amount of the depolymerization solution at the requested temperature is circulated, for example, by a pump, throughout step e) of this method, both within the reaction chamber and through the fiber tuft. In other words, a tuft containing, substantially consisting of, or comprising cellulosic fibers, preferably cotton fibers, and polyester fibers, is kept in a static state and brought into contact with the depolymerization solution several times, and the solution is repeatedly passed through the tuft, i.e., circulated, thereby increasing the content of disodium terephthalate (Na2TP), terephthalate ions, or EG, more generally dyes, and products from decomposed polyester in the solution, while keeping the cotton or cellulosic fibers as intact as possible. It was found that by combining the preferably compressed and static state of the fiber tuft with the circulation (flow) of the depolymerization solution through the fiber tuft, the polyester was completely depolymerized, the dye was effectively removed, and at the same time, the depolymerization of the cotton fibers was significantly reduced.

[0039] The technical effect of circulating, i.e., flowing, a depolymerization solution through static, i.e., stationary fiber tufts under mild conditions is preferable because it protects the cellulose polymer chains from degradation and recovers cotton fibers (and other cellulosic fibers, if present) that are suitable for processing into recycled yarn by methods known in the art.

[0040] At the end of this method, the polyester fibers / long fibers are removed from the tuft (by depolymerization), and a treated tuft is obtained, i.e., a treated aggregate containing, or substantially consisting of, cotton or other cellulosic fibers, which is substantially free, preferably free, of dyes and polyester depolymerization products, particularly Na2TP, TPA, and ethylene glycol (EG). The treated tuft obtained by the method of the present invention is made from cotton / cellulose fibers and can be used in cotton fiber recycling methods known in the art. The cotton fibers obtained by the method of the present invention can be used in yarn spinning methods.

[0041] According to one aspect of the present invention, a step is performed in which a textile product is opened into a fiber tuft. This fiber tuft includes, or substantially consists of, cellulosic fibers and polyester fibers. As previously stated, the fiber tuft, i.e., the “tuft,” can be obtained by a technique known in the art by name, “tearing” or “unraveling.” For example, waste fabrics and / or garments (known as “hard waste”) can be mechanically processed by a subsequent step of progressively opening the hard waste textile product. For example, a series of cylinders equipped with tearing means that engage with the textile product, each cylinder performing a partial opening step until the desired degree of opening is reached. Tearing or unraveling can be performed according to techniques and machines known in the art. For example, a suitable machine is currently manufactured and supplied by Andritz Laroche SAS in Cour-la-Ville, France.

[0042] Discarded clothing may contain non-textile elements such as zippers, rivets, buttons (these elements are usually made of metal or plastic), and labels. Such non-textile elements can themselves be removed before or during mechanical processing according to techniques known in the art. For example, non-textile elements can be removed before or during mechanical processing, preferably before cylinder processing with appropriate equipment. Depolymerization

[0043] According to one aspect of the present invention, the depolymerization solution is an alkaline solution, preferably an alkaline solution containing sodium hydroxide or potassium hydroxide. The solution preferably contains a sodium hydroxide solution with a Baume degree of 48°Be in a concentration of 50 g / L to 500 g / L, preferably 50 to 90 g / L. In other words, the sodium hydroxide concentration in the depolymerization solution is in the range of 24 g / L to 237 g / L of NaOH, preferably 24 g / L to 42 g / L of NaOH.

[0044] In possible embodiments, the amount of depolymerization solution used in this method is selected according to the amount of textile product to be processed, for example, the weight of the textile product tuft to be processed. In embodiments, the bath ratio is in the range of 1 / 2 to 1 / 20, preferably 1 / 2 to 1 / 8, and most preferably 1 / 2 to 1 / 5. This bath ratio is the weight ratio between the weight of the textile product to be processed, i.e., the weight of the textile tuft to be processed, and the weight of the depolymerization solution.

[0045] According to possible embodiments in step e), the temperature of the depolymerization solution is in the range of 101°C to 160°C, preferably in the range of 120°C to 160°C. The temperature of the depolymerization solution is in the range of 130°C to 140°C, which has the advantage of minimizing changes in the chemical and mechanical properties of the cotton or cellulosic fibers, such as the length and dimensions of the fibers and the degree of polymerization of cellulose.

[0046] In a possible embodiment, the pressure in the reaction chamber during step c) is in the range of 1.05 bar (0.05 bar) to 7.0 bar (6.0 bar), preferably 2.7 bar (1.7 bar) to 7 bar (6 bar), and more preferably 2.7 bar (1.7 bar) to 5.5 bar (4.5 bar). In a possible embodiment, the depolymerization step e) is carried out for a time in the range of 30 to 240 minutes, preferably 60 to 240 minutes, more preferably 91 to 240 minutes, and most preferably 100 to 150 minutes, i.e., 120 minutes. In a preferred embodiment, step e) is carried out at 130°C for 120 minutes, preferably at a pressure in the range of 2.7 bar (39.16 psi) to 5.5 bar (79.77 psi).

[0047] The method of the present invention has the advantage of resulting in complete or substantially complete depolymerization of polyester fibers. According to one embodiment of the method of the present invention, the depolymerization solution is circulated through the reaction chamber and static fiber tuft in a unidirectional flow, preferably from the center of the reaction chamber toward the sides. In other embodiments, the direction of the flow can be changed during the depolymerization process to alternate between flow from the center of the reaction chamber toward the periphery and flow from the periphery toward the center of the reaction chamber. At the end of the depolymerization of the polyester, the depolymerization solution is cooled to a temperature of 40°C to 80°C.

[0048] As described above, the tuft is held in a static state, and the depolymerization solution is pumped into the reaction chamber containing the fiber tuft, passed through the fiber tuft, and discharged out of the reaction chamber. This is repeated several times, preferably until the polyester is completely depolymerized. The fiber tuft is held in place by appropriate structural elements that fill a portion of the reaction chamber, i.e., the depolymerization reaction chamber, and prevent the tuft from moving within the reaction chamber. Preferably, the fiber tuft is held in a compressed state within at least one basket or cage so as to completely fill the relevant portion of the reaction chamber. This state has the advantage that the depolymerization solution flows through all the stationary fibers in the tuft, resulting in high uniformity and productivity of the method. Dye removal

[0049] An advantage of the present invention is that all or most of the dye is removed from the fibers in the depolymerization step. In fact, reactive dyes, disperse dyes, and dope dyes are also removed from the waste textile product tufts by the depolymerization step. Furthermore, most of the vat dyes are also removed from the fiber tufts in the depolymerization step. Indigo and indigoid dyes have the advantage of being at least partially removed from the fibers, i.e., physically separated as indigo particles, by a flow of depolymerization solution circulating through the fibers. The separated indigo dyes accumulate in the solution and can be recovered in subsequent steps.

[0050] According to this embodiment, particularly when the tuft contains indigo-dyed fibers, the method further includes a step of bleaching the fiber tuft after the depolymerization step. Bleaching is preferably carried out in a reaction chamber with a bleach / decolorizing solution containing an oxidizing agent such as hydrogen peroxide, perborate, percarbonate, preferably hydrogen peroxide. This bleaching step is performed after the depolymerization solution has been removed from the reaction chamber. Typically, some depolymerization solution remains in the fiber tuft even after the solution has been removed. Similar to the depolymerization solution, the bleaching solution is circulated through the stationary tuft, for example, using a pump.

[0051] The bleaching solution has the advantage of being able to remove the color imparted by residual indigo dye from the treated fibers. According to the embodiment, the bleaching solution may also contain stabilizers and wetting agents, preferably a dispersant such as Permulsin FF (Bozzetto Group) and / or a wetting agent such as Sanwet NW2109 (Chemko) and / or a stabilizer for an oxidizing agent such as Sanstabil AI100 (Chemko).

[0052] According to the embodiment, the bleaching solution is supplied in an amount corresponding to the bath ratio, with a weight ratio of 1 / 2 to 1 / 20, preferably 1 / 2 to 1 / 8, and more preferably 1 / 5, of the fiber tuft (dry state) to the bleaching solution. According to the embodiment, there is an advantage that it is not necessary to add an extra amount of sodium hydroxide to the bleaching solution.

[0053] According to the embodiment, the oxidizing agent is present in the bleaching solution in an amount effective for removing residual indigo dye from the treated fibers. In a preferred embodiment, the bleaching solution contains 1 g / L to 7 g / L, preferably 4 to 7 g / L, and more preferably 5 g / L, of 50% by weight (w / w) hydrogen peroxide solution. In other words, the concentration of H2O2 in the bleaching solution is 0.5 g / L to 3.5 g / L, preferably 2 g / L to 3.5 g / L, and more preferably 2.5 g / L. According to the embodiment, the bleaching solution is heated to a temperature of 100°C to 110°C, preferably 105°C, and held at the said temperature for 80 to 150 minutes, preferably about 90 minutes. At the end of the bleaching step, the bleaching solution may be cooled before being removed from the reaction chamber.

[0054] According to the embodiment, the bleaching solution is preferably maintained at a temperature of 100°C to 110°C in order to minimize alteration and deterioration of cotton or cellulosic fibers. According to the embodiment, the oxidizing agent is gradually poured into the bleaching solution in the reaction chamber for, for example, 2 to 7 minutes, preferably 5 minutes. It is preferable to gradually pour the oxidizing agent into the bleaching solution in order to control the presence of undesirable gaseous contents in the reaction chamber that are generated from the reaction between the bleaching solution and the oxidizing agent. By controlling the gas content in the reaction chamber, it is possible to prevent an unwanted rise in pressure in the reaction chamber and to increase the efficiency of hydrogen peroxide. Cleaning

[0055] According to the embodiment, the method further includes a step of washing the treated fiber tuft with a washing solution preferably containing a dispersant. The concentration of the dispersant is preferably 1 g / L to 5 g / L. In this washing step, any TPA salts and EG that may remain in the treated fiber tuft are removed. Examples of suitable dispersants currently available on the market include palmlucin FF (Bozet Group) or Develope JFR NB (MKS DEVO).

[0056] According to the embodiment, the bath ratio of the washing solution (textile product (kg) / solution (kg)) is in the range of 1 / 2 to 1 / 20, preferably 1 / 2 to 1 / 8, and more preferably 1 / 5 to 1 / 6. Similar to the depolymerization and bleaching steps, the washing step is carried out by a flow of washing solution circulating through static and compressed fiber tufts in the reaction chamber. The washing step is carried out at a solution temperature of less than 100°C, preferably about 90°C.

[0057] According to the embodiment, the treated fibers, after depolymerization and removal of polyester monomers, have a degree of polymerization of 600 to 3500 and contain cotton fibers in which mechanical properties such as length, strength, and elongation can be detected, thereby making the fibers suitable for further use in the manufacture of yarn.

[0058] The degree of polymerization of cellulose in cellulosic fibers can be determined by measuring the relative viscosity with a capillary viscometer, then calculating the corresponding intrinsic viscosity according to the ISO 5351 standard, and finally calculating it according to the following formulas known in the art, such as the "modified Mark-Houwink-Sakurada equation for cellulose-solvent (standard method) systems." In detail, the viscosity can be determined from the following formula, which is also described in Patent Document 1.

[0059] [Math 2][η] = 954xlog[η] rel ]-325

[0060] The dynamic programming (DP) can be derived from the range of the following two equations.

[0061] [Math 3] DP 0.905 = 0.75x[η], DP= 1.9[η]

[0062] According to a preferred embodiment of the method of the present invention (see, for example, Figure 5), the depolymerization solution obtained after the first depolymerization cycle is reused in the next depolymerization cycle of a new batch of fiber tufts to be treated. According to the embodiment, the bleaching solution and / or washing solution can be reused in subsequent bleaching and washing cycles, respectively. This has the advantage of significantly reducing water consumption.

[0063] The applicant found that the depolymerization solution can be used multiple times, for example, at least 20 times, and even more, without losing its properties, provided that the sodium hydroxide content is restored to the initially required amount before reuse in a new processing batch cycle. The applicant also found that the increase in TPA salt and EG content generated in each cycle does not impair the chemical properties or depolymerization capacity of the depolymerization solution.

[0064] The number of times a depolymerization solution can be reused in another depolymerization cycle depends on the initial amount of polyester present in the textile product being treated, and consequently, the amount of polyester present in the textile tuft being treated. In other words, the more polyester present in the textile product being treated, the fewer cycles the depolymerization solution can be reused for. This also applies to bleaching solutions and / or cleaning solutions.

[0065] According to the embodiment, the depolymerization solution, bleaching solution, and washing solution are set to the required initial conditions (e.g., the initial concentration of sodium hydroxide and bleach in the depolymerization solution and bleaching solution, respectively) and can be reused in additional cycles of the method for a range of 1 to 100 times, preferably 10 to 100 times, and more preferably 10 to 40 times.

[0066] An advantage of the present invention is that, unlike conventional techniques in which polyester undergoes complete depolymerization, cotton or cellulosic fibers are not reduced to cellulose pulp after the depolymerization step. According to the present invention, there is the advantage that the decrease in DP (degree of polymerization) and mechanical properties of cellulosic fibers is maintained at a completely acceptable level. In any case, after depolymerization of polyester, and after complete treatment including any bleaching and washing, the cotton fibers can be recovered as staple fibers and recycled, and are suitable for use in the manufacture of yarn and textile products (no chemical pretreatment is required).

[0067] According to the embodiment, if the textile product, i.e., yarn, textile product and garment, contains one or more fluorescent whitening agents, the method may further include a pretreatment step of removing the fluorescent whitening agents from the textile product with a suitable solvent before mechanically opening the fibers and / or garment to form fiber tufts. In this pretreatment step, glossing agents and / or inhibitors and / or quenching agents are removed from the solution, and the removal of glossing agents is carried out with a bath ratio of 1 / 2 to 1 / 20, preferably 1 / 10, at a temperature of 30°C to 40°C, and for a time of 10 to 30 minutes.

[0068] Fluorescent whitening agents are chemical compounds that, when added to fabrics, produce the effect of making the areas where the fluorescent whitening agent is present whiter or brighter compared to areas where the fluorescent whitening agent is not present. Fluorescent whitening agents present in waste textile products should be removed after the fabric and / or garments have been mechanically tufted, thereby obtaining treated cellulosic fibers with uniform decolorization and a uniform level of brightness at the end of the process.

[0069] The pretreatment step to remove the fluorescent whitening agent is preferably carried out using an aqueous solution containing a decolorizing agent for fluorescent whitening agents, such as Fluorex DEL (CHT Group), and preferably a wetting agent, such as Sanwet M30 (Chemko). Preferably, the mass concentration of the decolorizing agent is 0.2 g / L to 1.2 g / L.

[0070] Another subject of the present invention is a plant for recycling fiber tufts containing cellulosic fibers and polyester fibers, or substantially consisting of cellulosic fibers and polyester fibers, or consisting of cellulosic fibers and polyester fibers. The plant comprises a reaction chamber configured to contain fiber tufts, at least one tank containing a depolymerization solution and optionally either a bleaching solution or a washing solution, a pump for supplying and circulating the depolymerization solution from the tank to the reaction chamber, and control means for controlling the temperature of the depolymerization solution in the reaction chamber, the control means typically including heating means and cooling means.

[0071] The reaction chamber is configured to contain the fiber tuft to be processed. Typically, the reaction chamber is made of a material suitable for contact with the depolymerization solution, bleaching solution, and washing solution. Examples of such materials include steel metal, preferably stainless steel, more preferably stainless steel such as AISI316 and AISI316 / 316L.

[0072] Multiple tanks containing the depolymerization solution, bleaching solution, and washing solution are fluidly connected to the reaction chamber to supply and remove solutions from the reaction chamber. Typically, these multiple tanks are made of materials suitable for contact with the depolymerization solution, bleaching solution, and washing solution.

[0073] The pump of the present invention is preferably capable of controlling the flow of depolymerization solution, bleaching solution, and washing solution from multiple tanks to the reaction chamber. Typically, the pump can be selected from centrifugal pumps, positive displacement pumps, axial flow pumps, or similar pumps, with centrifugal pumps being preferred. The device is preferably capable of reversing the direction of the solution flow in the reaction chamber in a known manner, for example, by an alternator switch device connected to the pump.

[0074] As described above, the depolymerization solution is circulated through the fibers (and reaction chamber) by a pump, and this circulation continues until the polyester material in the fibers is completely or substantially removed from the fibers as monomers through depolymerization. The reaction chamber is equipped with a heating means for raising the temperature of the depolymerization solution. This heating means can be installed inside the reaction chamber, for example, at the bottom of the chamber. This heating means may be a coil that supplies superheated steam to heat the depolymerization solution. A cooling means for cooling the solution is also provided, which may be provided in the form of another coil connected to a cooling fluid source, for example, cold water. It is preferable that the same coil be used as both a heating means and a cooling means by selectively connecting it to either a heating fluid source or a cooling fluid source. Typically, the heating and cooling means are connected to a control means, which is also connected to a sensor means that detects the temperature of the depolymerization solution in the reaction chamber.

[0075] According to one embodiment, the reaction chamber comprises one or more cages or baskets suitable for containing the fiber tuft to be processed and passing the solution through them. Typically, the basket is housed in the reaction chamber during processing and removed from the chamber at the end of the process, from which the compressed tuft is extracted. Because the tuft is compressed, it is extracted in the form of a "cake" of processed tuft. The empty basket is then filled with a new batch of tuft to be processed.

[0076] The cage or basket preferably consists of a rigid structure (usually cylindrical), such as a metal structure, with fiber openings along its walls, allowing the depolymerization solution to flow through the reaction chamber and the fibers. The cage or basket must withstand the pressure applied to the fiber tuft when it is compressed into a mass within the basket, and reach the required bulk density within the basket. Typically, the tuft is compressed using a device capable of exerting a compressive force of 120 tons. In any case, the final bulk density (expressed as the number of kg of fiber tuft compressed within the basket volume) is in the range of 100 to 350 g / L, preferably 240 to 320 g / L, more preferably 280 to 300 g / L, and most preferably 300 g / L.

[0077] By placing the waste blend cloth in one or more baskets, the fibers within the baskets can be confined during the flow of the solution. In other words, the fiber tufts remain stationary, i.e., static, while the flow of the depolymerization solution is pushed through the fibers in the reaction chamber. According to the embodiment, the fiber tufts fill the entire space of the basket, preferably the fiber tufts are compressed within the basket, and as can be seen from the drawings below, there is empty space in the reaction chamber above the upper basket.

[0078] Preferably, the filtration basket is a rigid container having perforations formed to match the shape of the reaction chamber, comprising a perforated outer wall on the side and a rigid columnar side having perforations positioned along the central axis of the basket, i.e., defining the hollow portion. The depolymerization solution can flow from the rigid column (perforated wall) towards the fiber tuft through the perforated wall on the side, or from the perforated wall on the side towards the fiber through the fiber, thereby preferably enabling uniform and consistent contact between the depolymerization solution and the fiber over time.

[0079] According to the embodiment, if the reaction chamber comprises a basket, at least one, preferably more, perforated separation elements are housed within the basket, arranged along the central column (perforated wall) and extending laterally relative to the central column (perforated wall). The separation element comprises a perforated plate on which fiber tufts can be placed. The perforated plate allows the solution to pass through the pores. The separation element also functions as a holding means to keep the fiber tufts stationary.

[0080] In another embodiment, multiple baskets are provided, each individually filled with fiber tufts compressed to the required bulk density. These baskets are stacked and housed in the reaction chamber.

[0081] The present invention further relates to cotton fiber tufts obtained by the method of the present invention, wherein the cotton fibers have a degree of polymerization of 600 to 3500 and are substantially free of dyes, preferably not containing any dyes. [Brief explanation of the drawing]

[0082] [Figure 1] This is a schematic diagram of a plant for housing fiber tufts containing polyester fibers and cellulosic fibers, illustrating one embodiment of the present invention. [Figure 2] This figure shows the state of the treated fiber tuft, including decolorized cellulose fibers, at the end of processing in the plant according to the embodiment of Figure 1. [Figure 3a] Figure 1 is a perspective view showing a cross-section of the filtration basket. [Figure 3b] Figure 1 is a longitudinal cross-sectional view of the sealed reaction chamber and filtration basket. [Figure 4] Figure 1 is a perspective view of the perforated separation element. [Figure 5] This is a schematic diagram of an embodiment of the method of the present invention, which includes the steps of mechanically treating clothing and / or fabric to obtain fiber tufts, a depolymerization step, a bleaching step, and a washing step, and the possible reuse of each solution. [Figure 6] Figure 1 is a perspective view of the heating and cooling elements of the plant. [Figure 7] This is a photograph showing multiple fiber tufts before carrying out the method of the present invention. [Figure 8] Figure 7 is a photograph showing the state after the method of the present invention has been applied to the tuft. [Modes for carrying out the invention]

[0083] Further embodiments and advantages of the present invention will be discussed in more detail with reference to the accompanying drawings, which are shown as examples not to limit. Figures 1 and 2 show a plant 100 suitable for carrying out the method of the present invention. Specifically, Figures 1 and 2 show a plant 100 suitable for carrying out the method of the present invention on a fiber tuft containing polyester fibers and cellulosic fibers, preferably cotton fibers, or substantially consisting of polyester fibers and cellulosic fibers, or consisting of polyester fibers and cellulosic fibers. Figure 1 shows the plant in the initial stage of processing, and includes a reaction chamber 10 filled with the fiber tuft 1 to be processed, the fiber tuft containing polyester fibers 4 and cotton fibers 40.

[0084] According to the present invention, a certain amount of waste textile product selected from fabrics, garments, and mixtures thereof (and possibly yarn) is mechanically opened by a fiber opener 15 to obtain a fiber tuft containing, or substantially consisting of, cellulosic fibers and polyester fibers. That is, an aggregate containing, or substantially consisting of cellulosic fibers and polyester fibers is obtained. This fiber tuft can be obtained, for example, from waste fabrics and / or waste garments according to techniques known to the extent that waste fabrics and / or waste garments can be mechanically subjected to progressive fiber opening. The progressive opening of textile products can be carried out using known techniques and opening machines (especially tearing machines). For example, a suitable machine is the one currently manufactured and supplied by Andritz Laroche SAS in Cour-la-Ville, France. Machines for obtaining fiber tufts from waste fabrics and / or waste clothing can be connected to the plant of the present invention in ways known by themselves in the art. In one embodiment, one or more machines for obtaining fiber tufts from waste fabrics and / or waste clothing are connected to the plant of the present invention, and the fiber tufts are automatically moved from the machines for obtaining fiber tufts to the reaction chamber of the plant of the present invention. In another embodiment, the fiber tufts are formed into bales, transported to a depolymerization plant, where they are opened and fed into the plant, and compressed, for example, in baskets.

[0085] If necessary, the desired ratio of polyester fibers to cellulosic fibers in the reaction chamber can be achieved by mixing tufts from different bales, or more generally, from different sources, and using them in the reaction chamber. Discarded clothing may contain non-textile elements such as zippers, rivets, buttons (these elements are usually metal or plastic), and labels. Such non-textile elements can be removed before or during the fiber opening step, usually using a tearing machine, according to techniques known in the art. Known tearing machines are, in practice, usually equipped with devices for separating non-textile elements from fibrous elements. Typically, the reaction chamber 10 is cylindrical and includes side walls, a bottom wall, and a lid 91. The sealed chamber is configured to withstand the pressure generated by the method of the present invention.

[0086] In the illustrated embodiment, the reaction chamber 10 includes a basket 6 for containing the fiber tufts to be processed. As shown in Figures 3a and 3b, the basket 6 is cylindrical in shape, usually made of metal, and has perforated side walls 64 that allow the flow of the depolymerization solution 3 through the reaction chamber 10 and the fiber tufts 1 contained in the basket 6. As shown by arrows F1 and F2 in Figure 3b, the flow of the depolymerization solution 3 can substantially flow in a first direction F2 from the central axis A through the inner perforation wall 65 of the basket 6 toward the outer perforation wall 64, or in a second direction F1 from the outer perforation wall 64 toward the second direction substantially opposite to the first flow direction.

[0087] In other words, the solution in the reaction chamber 10 can be circulated in either a first or second direction. In the first direction, the flow in the reaction chamber 10 exits from the inner perforated wall 65 of the basket 6, passes through the fiber tuft 1, and is discharged from the basket 6 via the perforated wall 64. In the second circulation direction, the supply direction is reversed. That is, the solution is supplied to the reaction chamber corresponding to the outer perforated wall 64, passes through the fiber tuft 1, and is discharged toward the inner perforated wall 65 and the central axis A.

[0088] In the case of circulation, i.e., alternating flow, according to one embodiment, the first recirculation is preferably carried out in the first direction for 2 to 6 minutes, preferably 4 minutes. In another embodiment, the second recirculation is preferably carried out in the second direction for 4 to 8 minutes, preferably 6 minutes. In another embodiment, all flow in the process may be carried out in the first direction, or the flow may be carried out in the second direction only throughout the entire method.

[0089] The depolymerization solution 3 flows through the textile product, exiting the reaction chamber and returning to it in a first radial and / or second radial flow, thereby reaching all fibers in the stationary fiber tuft 1 that are not agitated in the solution. That is, it reaches even the fibers that are not agitated in the stationary solution within the fiber tuft 1, which has the advantage of ensuring uniform depolymerization of polyester in a short time. By maximizing the flow rate from the perforated walls 64 and 65 of the filtration basket, appropriate absorption of the depolymerization solution 3 within the fiber tuft is obtained, and thus the depolymerization of the polyester fibers 4 is maximized.

[0090] In the embodiments shown in Figures 3b and 4, the reaction chamber 10 comprises at least one, preferably multiple, perforated separation elements 60 housed within the basket 6 in a direction transverse to the central column (perforated wall) 65. The diameter of these separation elements 60 is smaller than the diameter of the basket 6, i.e., smaller than the distance between the inner surfaces 641 of the side walls 64, so that no excessive gaps are created on the sides when the separation elements 60 are inserted into the basket 6. As shown in Figure 4, the separation element 60 is provided with a central hole 62, which allows the separation element to slide along the central column (perforated wall) 65 and within the basket 6 without mechanical interference. The separation element 60 maximizes the filling of the fiber tuft into the basket 6 in the reaction chamber 10 and prevents the fibers from moving within the basket. When multiple separation elements 60 are housed in the filtration basket 6, the fiber tuft 1 is housed on top of each separation element 60. The separation element 60 preferably includes a perforated plate 601 to ensure the flow of the depolymerization solution 3 within the reaction chamber 10. An upper holding element 603 is also shown in Figure 3b.

[0091] Plant 100 further comprises several tanks or storage tanks, each containing a depolymerization solution 3 in tank 7, a bleaching solution 30 in tank 7a, and a washing solution 80 in tank 7b. These tanks are connected to the reaction chamber 10 by their respective pipes and are connected via a circulating loop that includes a pump 8 connected to the reaction chamber 10 via conduits 72 and 74 and a flow alternator 82. The depolymerization solution 3 can flow from the tank 7 to the reaction chamber 10 through conduits 71, 72, and 74, following the direction of flow supplied by the flow alternator 82. As shown in Figures 1 and 2, conduit 72 is connected to the inner column (perforated wall) 65 of the basket 6 and supplies the solution to the inner column (perforated wall) 65 of the basket 6. Conduit 74 is connected to the outer part of the reaction chamber corresponding to the wall of the basket 6 and receives the solution that has circulated, i.e., flowed through the fibers and the reaction chamber, and supplies the solution to the reaction chamber via this reverse-flow conduit 74.

[0092] The flow alternator 82 has the advantage of providing alternating circulation of the depolymerization solution within the reaction chamber 10. Valves V2 and V1 are arranged so that after supplying the depolymerization solution to the reaction chamber 10, the depolymerization solution circulates through conduits 72 and 74. In this case, the recirculation of the depolymerization solution is counterclockwise. Alternatively, the flow alternator 82 can be used to reverse the direction of flow, so that the recirculation of the depolymerization solution through conduits 72 and 74 and the reaction chamber 10 is clockwise.

[0093] The bleaching solution 30 and the cleaning solution 80 can flow from multiple tanks 7a and 7b into conduits 72 and 74, respectively. Valves V1, V2 and V3 are located on the circuit duct to control the flow rate in the conduits. Plant 100 further includes a number of auxiliary chemical tanks 20 for supplying reagents to tank 7 via conduits 21 and 22, to tank 7a via conduits 21 and 23, or to tank 7b via conduits 21 and 24.

[0094] Plant 100 further includes heating and cooling elements 9 (heating element 9a and cooling element 9b) and a temperature sensor 90 for controlling the temperature of the depolymerization solution 3 or bleaching solution in the reaction chamber 10. According to one aspect of the present invention, the heating and cooling means can be implemented by a coil, for example, as shown in Figure 6, which can be selectively connected to a steam source (heating element) 9a or a cold water source (cooling element) 9b, thereby heating or cooling the solution in the reaction chamber 10, respectively.

[0095] Plant 100 may be equipped with a centrifuge 50 capable of centrifuging the fiber tuft. This centrifuge 50 can be connected to a circuit that supplies the depolymerization solution to the reaction chamber 10 in known ways, although details are not shown (a separate circuit may also be provided). Centrifugation is usually performed after the washing step and before drying the fiber tuft. If the bleaching step is not required, the centrifugation step may be performed after the depolymerization step.

[0096] This invention also relates to a method for recycling waste blended textile products containing polyester fibers and cellulosic fibers, preferably cotton fibers, and this method is a) A step of supplying a predetermined amount of the waste blended textile product, wherein the waste blended textile product is selected from fabrics, garments, and mixtures thereof; b) Mechanically opening the waste blend fiber product to form a fiber tuft containing, or substantially consisting of, cellulosic fibers 40 and polyester fibers 4; c) The step of supplying the fiber tuft into the reaction chamber 10; d) A step of supplying an amount of basic depolymerization solution 3 according to a bath ratio in the range of 1 / 2 to 1 / 20 of the weight of the fiber tuft relative to the weight of the solution; e) The step of circulating the above amount of depolymerization solution 3 through the fiber tuft to depolymerize the polyester to the corresponding monomer and remove the polyester monomer from the fiber tuft; and f) The step of removing the depolymerization solution 3 from the reaction chamber 10, The temperature of the depolymerization solution 3 in step e) is in the range of 101°C to 160°C. moreover, In step g), the fiber tuft is in a stationary, i.e., static state, and solution 3 is circulated therein, and a treated fiber tuft is supplied that is substantially free of polyester material, preferably free of polyester material, and contains cellulosic staple fibers 40, preferably cotton staple fibers.

[0097] As described above, mechanical fiber opening is usually preferably carried out by a tearing machine equipped with a cylinder having a tearing mechanism that acts on the textile product to form fiber tufts. If the discarded clothing contains non-textile elements such as zippers, rivets, buttons (these elements are usually made of metal or plastic), or labels, it is preferable to remove these non-textile elements. Techniques known in the art can be used for this step. Typically, tearing machines are equipped with means for performing such separation before the step of defibrating the fibers into fiber tufts.

[0098] In the exemplary embodiment shown in the figure, the fiber tuft is placed in a basket 6 using one or more separating elements 60. Preferably, the basket is completely filled with the fiber tuft to be processed. The fiber tuft 1 contains polyester fibers 4 and cellulosic fibers 40, preferably cotton fibers 40, prior to the depolymerization step.

[0099] After filling basket 6 with fiber tuft and compressing the fibers to the above bulk density, a depolymerization solution 3 containing sodium hydroxide or potassium hydroxide, preferably sodium hydroxide, is supplied to reaction chamber 10. This solution is prepared by adding a NaOH solution with a Baume degree of 43-50°Be, preferably 48°Be, to water in an amount ranging from 50 g / L to 500 g / L. In a preferred embodiment, the amount of 48°Be NaOH solution added to water is in the range of 50 g / L to 90 g / L per 1 L of the solution. 50 g / L to 500 g / L per 1 L of the 48°Baume solution corresponds to approximately 24 g to 237 g / L of solid (pellet) NaOH.

[0100] The amount of depolymerization solution 3 is selected such that the bath ratio is 1 / 2 to 1 / 20, and more preferably, the bath ratio of the depolymerization solution is 1 / 3 to 1 / 8 of the bath weight relative to the fiber weight. Preferred values ​​are 1 / 5 and 1 / 6. The depolymerization solution is preferably heated by a coil 9 supplied with steam, i.e., superheated steam. The temperature of the depolymerization solution 3 in the reaction chamber 10 is controlled to depolymerize the polyester fibers 4 while maintaining as much of the original mechanical and chemical properties (e.g., degree of polymerization and dimensions) of the cotton fibers 40 as possible. The temperature of the depolymerization solution 3 in the reaction chamber 10 is controlled via a sensor 90 to be maintained in the range of 101°C to 160°C, preferably 130°C to 140°C.

[0101] According to embodiments of the present invention, the pressure inside the reaction chamber 10 in step e) is in the range of 1.05 bar (15.23 psi) to 7.0 bar (101.5 psi), preferably in the range of 2.7 bar (39.16 psi) to 7.0 bar (101.5 psi), and more preferably in the range of 2.7 bar (39.16 psi) to 5.5 bar (79.77 psi). The pressure inside the sealed reaction chamber 10 may change due to temperature changes in the depolymerization solution 3.

[0102] According to the embodiment, the temperature of the depolymerization solution 3 in the reaction chamber 10 is maintained for 30 to 240 minutes, preferably 100 to 150 minutes, and more preferably 120 minutes. After the time has elapsed, the depolymerization solution is cooled to a temperature of 40°C to 80°C. If the amount of polyester fiber to be depolymerized is small or none, especially when this method is used for decolorizing textile products, the method time may be very short, about 20 minutes.

[0103] Next, the depolymerization solution 3 is removed from the reaction chamber 10 via conduits 71, 72, 74 and control valves V1, V2. The reactive dye is hydrolyzed by the depolymerization solution 3 to obtain a substantially polyester-free, preferably polyester-free, undyed fiber. The batt dye is partially removed during the depolymerization step. Also, some of the indigo is removed as indigo from the fiber during the depolymerization step. In other words, if the textile product to be treated, i.e., the fiber tuft, does not contain indigo-dyed fibers, the bleaching step can be omitted.

[0104] After depolymerization and removal of the depolymerization solution 3 from the reaction chamber 10, if the fibers still contain residual indigo dye, the treated fiber tufts 5 are subjected to a bleaching step using bleaching solution 30 in the reaction chamber 10. The bleaching solution 30 is supplied to the reaction chamber 10 via conduits 73 and 72, 74, and 75 connected to the pump 8.

[0105] The bleaching solution 30 is supplied in an amount such that the bath ratio is 1 / 2 to 1 / 20, preferably 1 / 7 to 1 / 9, and more preferably 1 / 8. The concentration of hydrogen peroxide in the bleaching solution is in the range of 2 g / L to 7 g / L, preferably 5 g / L. The solution is heated via coil 9 to a temperature in the range of 100°C to 110°C, preferably 105°C, and held at the temperature for a period of 60 to 150 minutes, preferably 100 to 150 minutes, more preferably 80 to 90 minutes. After the time has elapsed, the depolymerization solution is cooled to a temperature of 40°C to 80°C and returned to tank 7a.

[0106] According to the embodiment, the oxidizing agent is gradually added to the bleaching solution 30 in the reaction chamber 10 over a period of 2 to 7 minutes, preferably about 5 minutes. To avoid an undesirable increase in pressure within the sealed reaction chamber 10 and to maintain good efficiency of the oxidizing agent, it is preferable to gradually add the oxidizing agent to the bleaching solution 30.

[0107] This method further includes a step of washing the treated fiber tuft 5 after depolymerization, or optionally after bleaching, with a washing solution 80 containing a dispersant. The washing solution 80 is held in a tank 7b and supplied to the reaction chamber 10 via a conduit 75 connected to a pump 8 via a conduit 74. The bath ratio of the washing solution 80 is 1 / 2 to 1 / 20, preferably 1 / 2 to 1 / 8, more preferably 1 / 5. The step of washing the treated fiber tuft 5 containing the cellulose fibers 40 can be performed after step g) above, or after exposing the treated fiber tuft 5 to the bleaching solution 30. In other words, the washing step can be performed either after the depolymerization of the polyester fibers is complete (if bleaching is not performed), or after the treated fiber tuft 5 has been exposed to the bleaching step to remove the indigo dye.

[0108] After step g), the treated fiber tuft 5 preferably contains cotton fibers whose degree of polymerization can reach 3500. The product of the method of the present invention does not contain cellulose pulp; that is, the cellulosic fibers are not reduced to cellulose pulp. In other words, the fibers obtained from the method of the present invention still retain the shape of a fiber tuft, even though the original polyester fiber components have been removed and the dyes that were originally present are no longer included. The treated fibers may preferably be washed and then dried by a method known to be used, such as a tumble dryer or a continuous dryer such as a belt conveyor dryer.

[0109] As described above, if the waste fabric and / or garment to be processed contains a fluorescent whitening agent, such fabric and / or garment is subjected to a pretreatment step to remove the fluorescent whitening agent with a solvent before carrying out the depolymerization step, preferably before carrying out the step of mechanically processing the waste fabric and / or garment to obtain fiber tufts. The removal includes treatment for 10 to 30 minutes at a temperature of 30°C to 40°C in a bath ratio of 1 / 2 to 1 / 20, preferably 1 / 10.

[0110] According to a preferred embodiment of the method of the present invention, as shown in Figure 7, the depolymerization solution obtained after the depolymerization cycle is reused in the depolymerization cycle of the next new fiber batch. Similarly, the bleaching solution and washing solution can be stored in tanks 7a and 7b and reused in further ways, which has the advantage of significantly reducing water consumption.

[0111] According to possible embodiments, after the step of depolymerizing the statically compressed fiber tuft 1 by passing the solution (3) through it (i.e., after step e), and optionally after removing the solution (after step f), the treated fiber tuft is centrifuged. This can be done in a reaction chamber, but in a preferred embodiment, the compressed cake-like treated fiber tuft 1 is transferred to a centrifuge. During the centrifugal separation step, the depolymerization solution (3) can be supplied to the fiber tuft. The depolymerization solution (3) is usually the same as that used in the circulation step. In particular, as mentioned above, the depolymerization solution (3) can be reused in different cycles of the plant. As a result, the depolymerization solution used in the circulation step can be reused in the centrifugal separation step, and vice versa. It is also possible to supply the depolymerization solution to the centrifugal separation step via a circuit different from the circuit that supplies it to the circulation step. In this case, the depolymerization solution used for one batch of fiber tuft can be reused to process another batch of fiber tuft.

[0112] The present invention is further disclosed with reference to the following examples, which are merely illustrative and not limiting.

[0113] Example 1: Depolymerization of indigo-dyed fiber tufts Used waste fabrics containing cotton fibers for the warp and cotton and polyester fibers for the weft are supplied, and these waste fabrics are indigo dyed. These waste fabrics are processed mechanically using a used textile waste recycling machine (manufactured by Andritz) manufactured by La Roche. After mechanical processing, 2250 kg of fiber tuft with a polyester content of 4.0% is obtained. This obtained fiber tuft is then placed in a closed reactor and pressed under a pressure of 120 tons. The bulk density of the fiber tuft after the compression step is approximately 300 g / L (±10%), and this parameter can be calculated by dividing the weight of the tuft in kg by the volume of the basket or reaction chamber in which the fiber tuft is compressed and filled. The fiber tufts are treated in a sealed reactor using 11,000 liters of depolymerization solution containing 90 g / L of sodium hydroxide (48°Be). The depolymerization solution is heated to 130°C and held at that temperature for 120 minutes. The bath ratio is 1 / 5. The depolymerization solution is circulated through the fibers 70 to 200 times. After 120 minutes, the depolymerization solution is cooled to 50°C. After treatment with the depolymerization solution, the polyester fibers are depolymerized into monomers and separated from the remaining treated cellulosic fibers. The cellulosic fibers thus obtained are then treated with a bleaching solution. The bleaching solution contains hydrogen peroxide at a mass concentration of 5 g / L, a stabilizer at a concentration of 3.0 g / L, a dispersant at a concentration of 1 g / L, and a wetting agent at a concentration of 0.2 g / L. After soaking the treated waste fabric in bleach solution for 5 minutes, hydrogen peroxide is gradually added to the bleach solution. The bleach solution bath ratio is 1:5. Then, the bleach solution is heated at 105°C for 90 minutes to remove the indigo dye from the treated waste fabric. In the final step, the treated fiber tufts are treated with a cleaning solution. The cleaning solution contains a dispersant at a concentration of 3 g / L (e.g., Develop JFR NB-MKS DEVO) and the bath ratio is 1 / 5. The cleaning solution is heated to 95°C for 30 minutes to clean the treated fiber tufts. The cleaned fibers are dried and then subjected to recycling methods known in the art in a fiber-to-fiber recycling process to produce yarn.

[0114] Example 2: Depolymerization of indigo-dyed fabric scraps 2,250 kg of used fabric in various sizes will be supplied, with cotton fibers in the warp and cotton and polyester fibers in the weft. The fabric is treated in a sealed reactor with a depolymerization solution containing 90 g / L sodium hydroxide (48°Be) at a bath ratio of 1 / 5. The same method as in Example 1 is applied. The treated fabric scraps are then mechanically processed using Laroche's used textile waste recycling machine (Andritz) to form fiber tufts from the treated fabric scraps. The mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated cutouts were analyzed by the fiber tufting method using a Tex Techno Fiber Test Machine in accordance with ASTM D5867-12 standard and are shown in Table 1. After processing, the viscosity was measured using the dried, depolymerized, bleached, and washed fiber tufts from Example 1 and the cut and post-formed fiber tufts from Example 2, and the degree of polymerization (DP) was calculated. The viscosity reduction rates across all samples show similarities. Comparing the mechanical properties of the treated fiber tufts, the strength decreases by 17% when fiber tufts are formed after treatment, but decreases by 36% when fabric scraps are converted into fiber tufts. There is a difference in the whiteness of the processed sample between tufted and cut-out samples. As is well known, reflectance and yellowing are used to define color grades, but reflectance RD can be used as a way to express the degree of whiteness.

[0115] [Table 1] Table 1. Characteristics of processed fiber tufts from tuft foam and clipping foam. TIFF2026048596000002.tif87154

[0116] Example 3: Treatment of reactive-dyed cotton fiber tufts We supply used, waste fabric made from 100% cotton. The waste fabric is dyed orange with reactive dyes. The waste fabric is processed mechanically using a used waste fabric recycling machine (manufactured by Andritz) manufactured by La Roche. After mechanical processing, 500 kg of fiber is obtained in the form of fiber tufts. The obtained fiber tufts are compressed under a pressure of 120 tons and then sent to a closed reactor. Under this pressure, the bulk density of the fiber tufts is approximately 300 g / L (±10%). The fiber tufts are treated in a sealed reactor using 3000 liters of a depolymerization solution containing 90 g / L sodium hydroxide (48°Be). The depolymerization solution is heated to 130°C and held at that temperature for 120 minutes. The bath ratio is 1 / 6. The depolymerization solution is circulated through the fibers 70 to 200 times. After 120 minutes, the depolymerization solution is cooled to 50°C. The treated cellulose fibers are then treated with a washing solution. The washing solution contains a dispersant at a concentration of 1 g / L (e.g., Develop JFR NB, MKS DEVO). The bath ratio is 1 / 6. The cleaning solution is heated at 95°C for 30 minutes to wash the treated fiber tufts. The washed fibers are dried and can then be subjected to recycling processes known in the art. The resulting fibers do not exhibit an orange color. Bleaching is not required. The mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated cutouts were analyzed by the fiber tufting method using a TexTechno Fibrotest machine in accordance with the ASTMD5867-12 standard, and are shown in Table 2. Comparing the mechanical properties of the fiber tuft before and after treatment, the fiber length decreased by 1.7% and the strength (g / tex) decreased by 26% after treatment, while the elongation (%) remained almost the same.

[0117] Example 4: Treatment of cut-out cotton fabric dyed using reactive dyeing - Comparative example We will supply 500 kg of used fabric in various sizes, using 100% cotton fibers for both the warp and weft. Furthermore, this waste fabric will be dyed orange with reactive dyes. The waste fabric was treated in a sealed reactor with a depolymerization solution containing 90 g / L sodium hydroxide (48°Be) at a bath ratio of 1 / 6. The same method as in Example 3 was applied. The processed fabric scraps are then mechanically processed using Laroche's used textile waste recycling machine (Andritz) to form fiber tufts from the processed fabric scraps. The mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated cutouts were analyzed by the fiber tufting method using a TexTechno Fibrotest machine in accordance with the ASTMD5867-12 standard and are shown in Table 2. Comparing the mechanical properties, the average fiber length of the tuft obtained from the treated cutout was reduced by 11% compared to 1.7% of the untreated tuft, and the decrease in strength (g / tex) of the tuft obtained from the treated cutout was approximately 40%, compared to 26% of the tuft treated according to the method of Example 3. Both samples, after being processed as fiber tufts and cutouts, show similarities in whiteness, as their reflectance (RD) exceeds 70. However, visually, the sample processed as fiber tufts has the highest whiteness.

[0118] [Table 2] TIFF2026048596000003.tif52143

[0119] The data above illustrates how the method of the present invention can be used for decolorizing waste textile products. Accordingly, the present invention also refers to a method for removing dyes from dyed waste textile products comprising cellulosic fibers, preferably cotton fibers, and optionally polyester fibers. This method comprises treatment in a basic aqueous solution and is characterized by comprising the following steps: a) A step of supplying a predetermined amount of the waste blend fiber product, which contains or is substantially composed of cellulosic fibers (40); b) A step of mechanically opening the waste blended fiber product to form a fiber tuft (1); c) Compressing the fiber tuft (1) in a reaction chamber (10) to a bulk density in the range of 100 to 350 g / L, preferably 240 to 320 g / L, more preferably 280 to 300 g / L, and most preferably 300 g / L; d) A step of supplying a predetermined amount of basic solution (3) according to a bath ratio of 1 / 2 to 1 / 20 of the weight of the fiber tuft relative to the weight of the solution; e) a step of circulating the depolymerization solution (3) through the fiber tuft (1) to remove at least a portion of the dye from the fiber tuft; and, f) The step of removing the solution (3) from the reaction chamber (10). Here, the temperature of the depolymerization solution in step c) is in the range of 101°C to 160°C, the solution is circulated through the fiber tuft, the fiber tuft is in a stationary compressed state, and a treated fiber tuft (5) is obtained that contains substantially dye-free cellulosic staple fibers, preferably cotton staple fibers (40).

[0120] If the dye is an indigo dye or indigoid dye, the method includes a bleaching step. The above disclosure of method and plant features also applies to the decolorization methods discussed herein. The fiber tuft is compressed in a basket or other container or in the reaction chamber to a bulk density of preferably 100-350 g / L, preferably 240-320 g / L, more preferably 280-300 g / L, and most preferably 300 g / L. The bulk density is expressed as the number of grams of fiber material divided by the known volume occupied by that material in the reactor.

[0121] The test results show that, when the same fabric is cut out, dye removal from the fiber tuft is more effective than removal from the cutout, and that treating the fiber tuft results in superior mechanical properties of at least some of the fibers compared to treating the cutout that will ultimately be opened into fiber tuft. This result is thought to be because the treatment applied to the compressed fiber tuft is more uniform than the same treatment applied to the compressed fabric cutout.

[0122] In other words, the present invention provides a first step of reducing the density of a textile product by opening the fibers into fibrous strands, and a further step of reducing the density by compressing the fiber tuft. Preferably, the actual bulk density (expressed as grams per liter of textile material) in the reaction chamber is approximately the same for the cut fabric and the compressed fiber tuft. Typically, by compressing the fiber tuft, the density of the material in the reactor becomes, for example, 260 g / L, and the corresponding amount of compressed fiber tuft results in a bulk density of approximately 280 g / L, a difference of approximately 5-7%. The present invention makes it possible to process large quantities of textile products very efficiently and to obtain uniformly decolorized and depolymerized textile materials. [Explanation of Symbols]

[0123] 1. Fiber tuft 3. Depolymerization solution 4. Polyester fiber 5 Fiber Tuft 7. Tank of cleaning solution 8 pumps 9 Heating and cooling elements 10 Reaction Chamber 15. Fiber opening machine (tear machine) 20 Reserve chemical tanks 30 Bleach solution 40 Cellulose-based short fibers (cotton fibers) 50 Centrifugal Separators 60 separation elements 80 Cleaning Solution 90 Temperature Sensor 100 plants

Claims

1. A method for recycling waste blended textile products containing polyester and cellulosic fibers, comprising the depolymerization of the polyester in a basic aqueous solution, as a step, a) A predetermined amount of the waste blend fiber product comprising, or substantially consisting thereof, cellulose fibers (40) and polyester fibers (4); b) Mechanically opening the waste blended fiber product to form a fiber tuft (1) containing, or substantially consisting of, cellulosic fibers (40) and polyester fibers (4); c) The step of supplying the fiber tuft (1) into the reaction chamber (10); d) A step of supplying an amount of basic depolymerization solution (3) according to a bath ratio of 1 / 2 to 1 / 20 of the weight of the fiber tuft relative to the weight of the solution; e) The step of circulating the above amount of depolymerization solution (3) through the fiber tuft (1) to depolymerize the polyester (4) to the corresponding monomer and remove the polyester monomer from the fiber tuft; and f) The process includes the step of removing the depolymerization solution (3) from the reaction chamber (10), The temperature of the depolymerization solution in step c) is in the range of 101°C to 160°C. A method for recycling waste blended textile products, characterized in that the fiber tuft is stationary, and the solution is circulated through the fiber tuft to obtain a treated fiber tuft (5) containing cellulose-based short fibers that are substantially free of polyester material.

2. A method for recycling a waste blended fiber product, characterized in that the fiber opening step is performed by a tearing machine equipped with a plurality of tearing cylinders for gradually opening the waste fiber.

3. A method for recycling waste blended fiber products according to claim 1, characterized in that the fiber tuft is compressed before being treated with the depolymerization solution in order to increase its bulk density (g / L).

4. A method for recycling waste blended fiber products, characterized in that the depolymerization solution is an alkaline solution containing 50 g / L to 500 g / L of a sodium hydroxide solution having a Baume degree (°Be) in the range of 43 to 50°Be.

5. A method for recycling waste blended fiber products, characterized in that the bath ratio is in the range of 1 / 2 to 1 / 8, according to the method of claim 1.

6. A method for recycling waste blended fiber products according to claim 1, characterized in that the temperature of the depolymerization solution in step e) is in the range of 120 to 160°C.

7. A method for recycling waste blended fiber products, characterized in that the pressure in the reaction chamber (10) in step e) is in the range of 1.05 bar to 7.0 bar, according to the method of claim 1.

8. A method for recycling waste blended textile products according to claim 1, characterized in that step e) is performed in a range of 30 to 240 minutes.

9. A method for recycling waste blended textile products according to claim 1, characterized in that the treated fiber tuft is substantially free of dye.

10. A method for recycling a waste blended textile product, characterized in that the treated fiber tuft contains residual indigo dye, and the method further includes the step of bleaching the fiber tuft (5) obtained after step e) in the reaction chamber (10) by circulating a bleaching solution (30) containing an oxidizing agent through the fiber tuft in the reaction chamber (10).

11. A method for recycling waste blended fiber products, characterized in that the fiber tuft is compressed in the reaction chamber such that the bulk density, expressed as the weight of the fiber material per unit volume occupied by the fiber material in the reaction chamber, is 100 to 350 g / L.

12. A method for recycling waste blended textile products according to claim 1, comprising the step of washing the treated fiber tuft (5) with a cleaning solution (80) to remove any remaining TPA salts, wherein the bath ratio is 1 / 2 to 1 / 20 in weight ratio of fiber tuft to cleaning solution.

13. A method for recycling waste blended fiber products, characterized in that the number of cycles in which the depolymerization solution is supplied to the fiber tuft is in the range of 30 to 480 cycles per hour, according to the method of claim 1.

14. A method for recycling a waste blended textile product, characterized in that, prior to the step of mechanically opening the waste fibers into fiber tufts, the waste cloth is cut into cutouts.

15. A method for recycling a waste blended textile product according to claim 1, characterized in that the waste blended textile product is clothing, the clothing optionally includes non-textile elements, and the non-textile elements are separated and removed from the clothing before or during the step of mechanically processing the waste textile.

16. A method for recycling waste blended textile products, characterized in that the depolymerization solution and / or the bleaching solution and / or washing solution are adjusted to their initial concentrations of NaOH, bleach, and dispersant, respectively, and are reused 1 to 100 times in subsequent depolymerization, bleaching, or washing cycles of new batches of fiber tufts.

17. A method for recycling waste blended textile products according to claim 1, characterized in that the micronere of the fiber tuft used in step c) is 3 to 5 as measured according to ASTM D5867-12.

18. A plant (100) for carrying out a recycling method for waste textile products comprising polyester fibers (4) and cellulosic staple fibers (40) according to any one of claims 1 to 17, A fiber opening machine (15) suitable for mechanically opening waste textile products into fiber tufts, A retractable reaction chamber (10) configured to contain waste textile products in the form of fiber tufts (1), At least one tank (7) containing the depolymerization solution (3), and at least one of a plurality of tanks (7a, 7b) optionally containing at least one of the bleaching solution (30) and the washing solution (80), A pump (8) supplies and circulates the depolymerization solution (3) from the depolymerization solution tank (7) to the chamber (10), and A plant characterized by having means (90, 9a, 9b) for controlling the temperature of the depolymerization solution (3) inside a chamber (10).

19. A plant according to claim 18, further comprising a filtration basket (6) for housing the fiber tuft (1) in the reaction chamber, wherein the basket is removable from the reaction chamber (10).

20. A polyester-free cotton fiber tuft obtained by the recycling method described in any one of claims 1 to 17, characterized in that the cotton fibers in the fiber tuft have a reflectance (RD) of more than 50 as measured by ASTM D5867-12, and the degree of polymerization is between 600 and 3500.

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