PROCESS AND PLANT FOR RECYCLING TEXTILES

Abstract

A process of treatment of waste blend textiles comprising polyester fibers and cotton fibres depolymerizes polyester in a controlled environment to obtain treated textile comprising cotton staple fibers suitable to be recycled into cotton yarns.

Claims

1. A process for recycling waste blend textiles comprising polyester and cellulosic fibers, the process including depolymerization of the polyester in a basic aqueous solution, said process comprising the following steps: a) providing an amount of said waste blend textiles, comprising cellulosic fibers (40) and polyester fibers (4), said cellulosic fibers (40) comprising or consisting entirely of cotton staple fibers; b) mechanically opening said waste blend textiles into fiber tufts (1) comprising at least said cellulosic fibers (40) and said polyester fibers (4); c) providing said fiber tufts (1) in a reaction chamber (10); d) providing an amount of a basic depolymerization solution (3) according to a bath ratio ranging from 1/2 to 1/20 by weight of said fiber tufts to weight of solution; e) circulating said amount of said basic depolymerization solution (3) through said fiber tufts (1), to depolymerize said polyester of said polyester fibers (4) into corresponding polyester monomers and to remove said polyester monomers from said fiber tufts; and f) removing said basic depolymerizing solution (3) from said reaction chamber (10), wherein the temperature of said basic depolymerizing solution in step c) is in the range between 101 C. and 160 C., and wherein the basic depolymerization solution is circulated through said fiber tufts, said fiber tufts being in a still condition, to provide treated fiber tufts (5) comprising said cellulosic staple fibers (40), substantially free from polyester material.

2. The process according to claim 1, wherein said step of mechanically opening is carried out via a tearing machine comprising a plurality of tearing cylinders configured to gradually open said waste blend textiles.

3. The process according to claim 1, wherein said fiber tufts are compressed before said step e) of circulating, to increase their bulk density (g/L).

4. The process according to claim 1, wherein said basic depolymerization solution is an alkaline solution comprising 50 g/L to 500 g/L of a solution of sodium hydroxide having a Baum degree ( Be) in the range of 43 to 50 Be.

5. The process according to claim 1, wherein said bath ratio is in the range of 1/2 to 1/8.

6. The process according to claim 1, wherein the temperature of said basic depolymerization solution in said step e) is in the range of 120 to 160 C.

7. The process according to claim 1, wherein pressure inside said chamber (10) in said step e) is in the range of 1.05 bar to 7.0 bar.

8. The process according to claim 1, wherein said step e) is carried out for a time in a range of 30 minutes to 240 minutes.

9. The process according to claim 1, wherein said treated fiber tufts are free of dye.

10. The process according to claim 1, wherein said treated fiber tufts further comprise residual indigo dye, said process further comprising a step of bleaching said fiber tufts (5) obtained after step [5)] e) in said chamber (10) by circulating a bleaching solution (30) comprising an oxidizing agent through said fiber tufts in said chamber (10), said bleaching solution (30) provided in a bath ratio in the range of 1/2 to 1/20 by weight of fiber tufts to bleaching solution.

11. The process according to claim 1, wherein said fiber tufts are compressed in said chamber to a bulk density of 100 to 350 g/L expressed as weight of textile material per volume occupied by said material in said reaction chamber.

12. The process according to claim 10, further comprising a step of washing the treated fiber tufts (5) by means of a washing solution (80) comprising dispersing agents to remove remaining terephthalic acid (TPA) salts, wherein the bath ratio is in the range of 1/2 to 1/20 by weight of fiber tufts to washing solution.

13. The process according to claim 1, wherein a number of cycles the basic depolymerization solution is fed through said fiber tufts is in the range of 30 to 480 cycles per hour.

14. The process according to claim 1, wherein the waste blend textiles comprise fabric, and further comprising cutting the fabric into clippings before said step of mechanically opening said waste blend textiles into fiber tufts.

15. The process according to claim 1, wherein said waste blend textiles are garments comprising non-textile elements, wherein said non-textile elements are detached and removed from said garments before or during said step of mechanically opening said waste blend textiles.

16. The process according to claim 12, wherein said basic depolymerization solution, and/or said bleaching solution and/or washing solution is adjusted to its initial concentration of NaOH, bleaching agents and dispersing agents, respectively, and is re-used 1 to 100 times in a subsequent depolymerizing, bleaching or washing cycle of a new batch of fiber tufts.

17. The process according to claim 1, wherein the micronaire of the fiber tufts used in said step c), measured according to ASTM D5867-12 is between 3 and 5.

18. A plant (100) to carry out a process of recycling waste textiles comprising polyester fibers (4) and cellulosic staple fibers (40) said plant comprising: an opening machine (15) suitable to mechanically open waste textile into fiber tufts, a closable reaction chamber (10) configured to contain said waste textiles in the form of fiber tufts (1); at least one depolymerization solution tank (7) adapted to contain a depolymerization solution and at least one of: a) a plurality of tanks (7a,7b) adapted to contain at least one of a bleaching solution (30); and, b) a washing solution (80); a pump (8) adapted to feed and circulate a basic depolymerization solution (3) from said depolymerization solution tank (7) to and through said chamber (10); a temperature sensor (90; 9a; 9b) to control the temperature of said basic depolymerization solution (3) inside said chamber (10); and a centrifuge (50) to centrifuge fiber tufts after treatment in the reaction chamber (10).

19. The plant according to claim 18, further comprising a filtering basket (6), to house said fiber tufts (1) in said chamber, said filtering basket being removable from said chamber (10), said chamber comprising at least one perforated separation element (60) housed in said basket (6) to maintain the fiber tufts in a still condition.

20. Polyester free cellulosic staple fiber tufts as obtainable according to, wherein said cotton staple fibers in said fiber tufts have a reflectance (RD) greater than 50 measured with ASTM D5867-12 and a degree of polymerization between 600 to 3500.

21. The process according to claim 1, wherein said step e) is carried out for a time in a range of 100 minutes to 150 minutes.

22. The process according to claim 1, wherein said basic depolymerization solution is an alkaline solution comprising a concentration of 24 g/L to 42 g/L of sodium hydroxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Further aspects and advantages in accordance with the present invention will be discussed more in detail with reference to the enclosed drawings, given by way of non-limiting example, wherein:

[0103] FIG. 1 is a schematic view of an embodiment of the plant according to the housing fibers tufts comprising polyester fibres and cellulosic fibres;

[0104] FIG. 2 shows the schematic of the embodiment of FIG. 1 and the treated fiber tufts comprising decolorized cellulosic fibers at the end of the process;

[0105] FIG. 3a shows a perspective view of the section of the filtering basket of FIG. 1;

[0106] FIG. 3b shows a sectional view of the closed reaction chamber and the filtering basket of FIG. 1;

[0107] FIG. 4 shows a perspective view of the perforated separation element of FIG. 1;

[0108] FIG. 5 shows a scheme of an embodiment of the process of the invention comprising the step of mechanically treating garments and/or fabrics to obtain fiber tufts, the depolymerization step, the bleaching step and the washing step and the possible re-use of the respective solutions;

[0109] FIG. 6 shows a perspective view of the heating and cooling element of the plant of FIG. 1;

[0110] FIG. 7 is a photograph showing a plurality of fiber tufts before the process of the invention and

[0111] FIG. 8 is a photograph showing the tufts of FIG. 7 after the process of the invention.

DETAILED DESCRIPTION

[0112] FIG. 1 and FIG. 2 show a plant 100 suitable to carry out the process of the invention on fiber tufts comprising, or substantially consisting of, or consisting of, polyester and cellulosic fibers, preferably cotton fibres. In FIG. 1 the plant is shown at the initial stage of the process: it comprises a chamber 10 filled with the fiber tufts to be treated, said fiber tufts comprising polyester fibres 4 and cotton fibres 40.

[0113] According to the present invention, an amount of waste textiles, selected from fabrics, garments and mixtures thereof (possibly also yarns), is mechanically opened by an opening machine 15 to obtain fiber tufts comprising, or substantially consisting of, or consisting of, cellulosic fibers and polyester fibers, i.e., to obtain a mass comprising, or substantially consisting of, or consisting of, cellulosic fibers and polyester fibers. The fiber tufts can be obtained from, e.g., waste fabrics and/or garments, according to techniques that are, per se, known in the art. For example, waste fabrics and/or garments can be mechanically treated by progressive opening. Progressive opening of the textile can be performed according to techniques and opening machines 15 (in particular tearing machines) known, per se, in the art. For example, suitable machines are those currently produced and supplied by ANDRITZ Laroche SAS, Cours-la-ville, France. Machines for obtaining fiber tufts from waste fabrics and/or garments may be connected to the plant of the invention in a way known, per se, in the art. In an embodiment, one or more machines for obtaining fiber tufts from waste fabrics and/or garments is connected to the plant of the invention so that fiber tufts can be automatically moved from the machines for obtaining fiber tufts to the reaction chamber of the plant of the invention. In another embodiment the tufts are formed into bales that are transported to the depolymerization plant where they are opened and fed into the plant, e.g. they are compressed in the basket.

[0114] If needed, tufts from different bales, or more in general from different sources, may be mixed together to be used in the reaction chamber, so as to reach a desired ratio of polyester vs cellulosic fibers in the reaction chamber.

[0115] Waste garments may comprise non-textile elements such as zippers, rivets, buttons (these elements being typically made of metal or plastic), and labels. Such non-textile elements can be removed before or during the opening step, typically via a tearing machine, according to techniques known, per se, in the art. Known tearing machines are in fact usually provided with a device for separating non textile elements from textile elements.

[0116] Typically, the reaction chamber 10 is cylindrically shaped and includes a side wall, a bottom wall and a lid 91. The closed chamber is configured to withstand pressures generated in the invention process.

[0117] In the shown embodiment, the reaction chamber 10 comprises a basket 6 to house the fiber tufts to be treated. As shown in FIGS. 3a and 3b, basket 6 is in the form of a cylindrical container, usually made of metal, including a perforated lateral wall 64 which allows a flow of a depolymerizing solution 3 within and through chamber 10 and the fiber tufts 1, being housed in basket 6. As shown in FIG. 3b with arrows F1 and F2, the flow of depolymerization solution 3 can be substantially in a first direction F2 from the central axis A through perforated internal wall, or column, 65 towards outer wall 64 or in a second direction F1 from the perforated wall 64 substantially opposite to the first flow direction.

[0118] In other words, the solution inside the chamber 10 can be circulated in a first direction or in a second direction. In the first direction the flow inside the chamber 10 goes from the inner perforated wall 65 of basket 6 and is forced through the fiber tufts 1 to exit basket 6 from the perforated wall 64. In the second circulation direction, the feeding direction is reversed, i.e. the solution is fed to the chamber in correspondence of the outer perforated wall 64 and forced through the fabrics towards the inner perforated portion 65 and towards the central axis A.

[0119] If circulation, i.e. flow, is alternated, according to embodiments, the first recirculation may be preferably carried out in the first direction for 2 to 6 minutes, preferably 4 minutes. In embodiments, the second recirculation may be carried out in the second direction for 4 to 8 minutes, preferably 6 minutes. In embodiments, the flow in the process can be conducted all in the first direction or in the entire process the flow can be conducted in the second direction only.

[0120] Advantageously the flow of the depolymerizing solution 3 through the fabrics, out of the chamber and back into it, in a first radial direction and/or in a second radial direction, allows the depolymerizing solution 3 to reach all the fibers within the fiber tufts 1, that are kept still, i.e. are not stirred in the solution, and to ensure a uniform depolymerization of polyester in a short time. Maximizing the flow injections from the perforated walls of the filtering basket 64 and 65 provides a proper absorption of the depolymerizing solution 3 within the fiber tufts and therefore maximizes the depolymerization of the polyester fibres 4.

[0121] In the shown embodiment, see FIGS. 3b and 4, chamber 10 comprises at least one, preferably a plurality of perforated separation elements 60 housed in basket 6, transversally to central column 65. The diameter of separation element 60 is less than the diameter of basket 6, i.e. less than the distance between the internal surfaces 641 of the lateral wall 64, to allow element 60 to be inserted in the basket without leaving a too wide gap on the side. As visible in FIG. 4 element 60 is provided with a central hole 62 that allows the separation element to slide without mechanical interference along column 65 and inside basket 6. Separation element 60 allows to maximize the filling of basket 6 in chamber 10 with the fiber tufts and to prevent the fibers from moving within the basket. In case more than one separation element 60 is housed in the filtering basket 6 there will be a fiber tufts 1 housed on top of each separation elements 60. Advantageously element 60 comprises a perforated plate 601 such that the flow of the depolymerizing solution 3 is ensured inside chamber 10. FIG. 3b also shows a top retaining element 603.

[0122] The plant 100 further comprises a plurality of tanks, or reservoirs, to contain a depolymerizing solution 3 in tank 7, a bleaching solution 30 in tank 7a and a washing solution 80 in a tank 7b. Said tanks are connected to chamber 10 with respective pipes and through a circulation loop including a pump 8 connected to the reaction chamber 10 by means of conduits 72 and 74 and fluid alternator device 82.

[0123] The depolymerizing solution 3 can flow from tank 7 to chamber 10 through conduit 71, and conduits 72 and 74 according to the direction of the flow as provided by flow alternator 82. As visible in FIGS. 1 and 2, conduit 72 is connected to the inner column 65 of basket 6 so that it may feed the solution to the inner column 65 of basket 6; conduit 74 is connected to the outer portion of the chamber in correspondence to wall 6 of the basket to receive the solution that has been circulated, i.e. flowed, through the fibers and the chamber, in a reversed flow conduit 74 feeds the solution to the chamber.

[0124] The alternator device 82 provides an advantageous alternated circulation of the depolymerizing solution inside chamber 10. After feeding the depolymerizing solution to the chamber 10, valve V2 and valve V1 are positioned such that the depolymerizing solution can be circulated through conduits 72, 74 wherein the recirculation of the depolymerizing solution is in a counter clockwise direction. Alternatively, the direction of the flow can be inverted by means of the alternator device 82 such that the recirculation of the depolymerizing solution through the conduits 72,74 and the chamber 10 is in a clockwise direction.

[0125] The bleaching solution 30 and the washing solution 80 can flow from the plurality of tanks 7a and 7b, respectively, to conduits 72 and 74. Valves V1, V2 and V3 are located on the circuit ducts to control the flow in the conduits. The plant 100 further comprises a plurality of spare chemical tanks 20 to provide reagents to the tank 7 through conduits 21,22 or to the tank 7a through conduits 21,23 or to the tank 7b through conduits 21,24. Reagents can be alkaline solution or alkali, oxidizing agents, wetting agents, dispersing agents, stabilizing agents, decolorizing agents and similar reagents.

[0126] The plant 100 further comprises a heating and cooling element 9a, 9b and a temperature sensor 90 to control the temperature of the depolymerizing solution 3 or the bleaching solution, inside the reaction chamber 10. According to an aspect, the heating and cooling means can be realized with a coil, as an example the one shown in FIG. 6, that is selectively connectable with a source of steam 9a or to a source of cool water 9b to respectively heat or cool the solution in chamber 10.

[0127] Plant 100 may also comprise a centrifuge 50, wherein fiber tufts can be centrifuged. The centrifuge 50 can be connected, in a known manner, not shown in detail, to the circuit feeding the depolymerizing solution to the reaction chamber 10 (but it may be provided with a separate circuit, too). Centrifugation is typically carried out after the washing step, before the fiber tufts are dried; a centrifugation step may also be carried out after the depolymerization step if no bleaching step is required.

[0128] The present invention relates to a process for recycling waste blend textiles comprising polyester and cellulosic fibers, preferably cotton fibres, the process comprising the following steps: a) providing an amount of said textiles, wherein said textiles are selected from fabrics, garments and mixtures thereof; b) mechanically opening said textiles into fiber tufts comprising, or substantially consisting of, or consisting of, cellulosic fibers 40 and polyester fibers 4; c) providing said fiber tufts in a reaction chamber 10; d) providing an amount of basic depolymerization solution 3 according to a bath ratio in the range of 1/2 and 1/20 by weight of fiber tufts over weight of solution; e) circulating said amount of depolymerizing solution 3 through said fiber tufts to depolymerize said polyester into corresponding monomers and to remove said polyester monomers from said fiber tufts; f) removing said depolymerizing solution 3 from said reaction chamber 10; wherein the temperature of the said depolymerizing solution 3 in step e) is in the range between 101 C. and 160 C., and wherein g) the fiber tufts are in a still, i.e. static, condition and the solution 3 is circulated through it to provide a treated fiber tufts comprising cellulosic staple fibers 40, preferably cotton staple fibres, substantially free, preferably free, from polyester material.

[0129] As discussed, the mechanical opening is preferably carried out by a tearing machine, usually provided with cylinders having tearing means acting on the textile, so as to open it and obtain fiber tufts.

[0130] If waste garments comprise non-textile elements such as zippers, rivets, buttons (these elements being typically made of metal or plastic), and labels, such non-textile elements are preferably removed. Techniques known in the art can be used to perform this step. Usually, tearing machines are equipped with means to carry out such a separation preliminary to the step of opening the yarns of the textile into fiber tufts

[0131] In the exemplary embodiment shown in the figures, the fibers tufts are placed in basket 6, possibly with the use of one or more separation elements 60. The basket is preferably completely filled with the fiber tufts to be treated.

[0132] The fiber tufts 1, comprise polyester fibres 4 and cellulosic fibers 40, preferably cotton fibres 40, before the depolymerization step.

[0133] After filling the basket 6 with fiber tufts and compressing the fibers to the above disclosed bulk density, a depolymerizing solution 3 comprising sodium hydroxide or potassium hydroxide, preferably sodium hydroxide is fed to the reaction chamber 10. The solution is prepared by adding to water an amount in the range of 50 g/L to 500 g/L of a NaOH solution that has a Baum degree of 43 to 50 Be, preferably of 48 Be. In a preferred embodiment the amount of said 48 Be solution of NaOH that is added to water is in the range of 50 g/L to 90 g/L of said solution. 50 g/L to 500 g/L of said 48 Baume solution corresponds to about 24 g to 237 g/L of solid (pellet) NaOH.

[0134] The amount of depolymerizing solution 3 is selected to have a bath ratio between 1/2 and 1/20, more preferably the bath ratio of the depolymerizing solution is 1/3 to 1/8 by weight of fibers to bath. Preferred values are 1/5 and 1/6. The depolymerizing solution is preferably heated by means of coil 9 to which steam, namely superheated steam, is fed.

[0135] The temperature of the depolymerizing solution 3 in the chamber 10 is controlled in order to depolymerize the polyester fibres 4 while maintaining as far as possible the original mechanical and chemical characteristics, e.g. the degree of polymerization and the dimensions, of the cotton fibers 40. The temperature of the depolymerization solution 3 in the chamber 10 is controlled via sensor 90 to be maintained in the range of 101 C. and 160 C. preferably 130 to 140 C.

[0136] According to embodiments, the pressure inside chamber 10 in step e) is in the range between 1.05 bar (15.23 psi) to 7.0 bar (101.5 psi), preferably 2.7 bar (39.16 psi) to 7.0 bar (101.5 psi), more preferably between 2.7 bar (39.16 psi) and 5.5 bar (79.77 psi). The pressure inside the closed chamber 10 may change due to a change of temperature of the depolymerizing solution 3.

[0137] According to embodiments, the temperature of the depolymerizing solution 3 in the chamber 10 is kept for a period of time between 30 minutes and 240 minutes, preferably between 100 and 150 minutes, more preferably 120 minutes. After said period of time the depolymerizing solution is cooled to a temperature between 40 C. and 80 C. When the amount of polyester fibers to be depolymerized is low or null, especially when the process is used to decolorize textiles, the process time may be quite short, also of about 20 minutes.

[0138] The depolymerizing solution 3 is then removed from the chamber 10 trough conduits 71,72,74 and controlling valves V1, V2.

[0139] Reactive dyes are hydrolysed by the depolymerization solution 3 to provide non-dyed fibers substantially free, preferably free, from polyester. Vat dyes are partially removed during the depolymerization step. A part of indigo is also removed as indigo from the fibers during the depolymerization step. In other words, if the textiles to be treated, i.e., the fiber tufts, do not comprise indigo dyed fibers, the bleaching step may be omitted.

[0140] After depolymerization and removal of depolymerizing solution 3 from chamber 10, if the fibers still include residual indigo dye, the treated fiber tufts 5 are subjected to a step of bleaching in the chamber 10 by means of a bleaching solution 30. The bleaching solution 30 is provided to the chamber 10 through conduits 73 connected to the pump 8 and through conduits 72, 74, 73.

[0141] The bleaching solution 30 is provided in an amount to give a bath ratio in the range of 1/2 to 1/20, preferably 1/7 to 1/9, more preferably 1/8.

[0142] The concentration of hydrogen peroxide in the bleaching solution is in the range 2 g/L to 7 g/L, preferably 5 g/L and the solution is heated via coil 9 to a temperature in the range between 100 C. to 110 C., preferably 105 C. and kept at said temperature for a period of time in the range between 60 to 150 min, preferably 100 minutes to 150 minutes, more preferably 80 to 90 minutes. After said period of time the depolymerizing solution is cooled to a temperature between 40 C. and 80 C., and discharged back to tank 7a.

[0143] According to embodiments, the oxidizing agent is gradually added to the bleaching solution 30 in the chamber 10 for a period of time in the range of 2 minutes to 7 minutes, preferably about 5 minutes.

[0144] The gradually addition of the oxidizing agent in the bleaching solution 30 is preferred in order to avoid an undesired increase of the pressure inside the closed chamber 10 and to maintain a good efficiency of the oxidizing agent.

[0145] The process further comprises a step of washing the treated fiber tufts 5 after depolymerization or, possibly, bleaching, by means of a washing solution 80 comprising dispersing agents. The washing solution 80 is held in tank 7b and is fed to chamber 10 through conduits 75 connected to pump 8 through conduit 74. The washing solution 80 has a bath ratio in the range of 1/2 to 1/20, preferably 1/2 to 1/8, more preferably 1/5.

[0146] The step of washing treated fiber tufts 5 comprising cellulose fibres 40 can be performed either after step g) above described or after the treated textiles 5 have been subject to the bleaching solution 30. In other words, the step of washing can be performed after the end of the depolymerization of the polyester fibres (when no bleaching is carried out) or after the treated fibers 5 have been subject to the step of bleaching wherein the indigo-type dyes have been removed.

[0147] Advantageously, after step g) the treated fibers 5 comprise cotton fibres with a degree of polymerization that can be as high as 3500. The product of the invention process does not include cellulose pulp, i.e. does not reduce cellulosic fibers into cellulosic pulp. In other words, the fibers obtained from the process of the invention are still in the form of a fiber tufts, although deprived of its initial polyester fibers component and without any initially present dye.

[0148] The treated fibers, preferably after washing, may be dried in a way known per se, e.g. in a tumble dryer, or may be dried in a continuous drier such as, e.g., a belt conveyor drier.

[0149] As previously mentioned, if waste fabrics and/or garments to be treated comprise optical brightening agents, such fabrics and/or garments are subject to a pre-treating step of removing the optical brightening agents with a solvent, before carrying out the depolymerization step, preferably before carrying out the step of mechanically treating said waste fabrics and/or garments to obtain a fiber tufts. Said removal comprises a bath ratio in the range of 1/2 to 1/20, preferably 1/10 at a temperature between 30 C. and 40 C. for a period of time between 10 minutes to 30 minutes.

[0150] According to a preferred embodiment of the invention process, as shown in FIG. 7, the depolymerizing solution obtained after a depolymerization cycle is re-used in a subsequent depolymerization cycle of a fresh batch of fibers. Similarly, the bleaching solution and the washing solution may be stored in tanks 7a and 7b to be used again in further processes with the advantage of greatly reducing the consumption of water.

[0151] According to possible embodiments, after the step of depolymerizing solution (3) through still and compressed fiber tufts 1 (i.e. after step e), and possibly after removing the solution (after step f), the treated fiber tufts are centrifuged. This can be done within the reaction chamber but, in preferred embodiments, the treated fiber tufts 1, which are in the form of a compressed cake, are moved into a centrifuge. During the centrifuge step, a depolymerization solution (3) can be supplied to the fiber tufts. The depolymerization solution (3) is typically the same used during the circulation step. In particular, as discussed, the depolymerizing solution (3) can be re-used in different cycles of the plant. As a result, the depolymerizing used during the circulation step can be re-used during the centrifuging step, or vice-versa. It is also possible that the centrifuging step is fed depolymerizing solution via a different circuit with respect to the one feeding the circulating step. In this case, the depolymerizing solution used for a batch of fiber tufts, can be re-used to treat a different batch of fiber tufts.

[0152] The invention is now further disclosed with reference to the following examples provided for merely illustrative and non-limiting purpose.

Example 1: Depolymerization of Indigo Dyed Fiber Tufts

[0153] Post-consumer waste fabric comprising cotton fibres in the warp yarns and cotton fibres and polyester fibres in the weft yarns are provided. The waste fabrics are dyed with indigo.

[0154] The waste fabrics are mechanically treated using a Laroche post-consumer textile waste recycling machine (Andritz).

[0155] After the mechanical treatment, 2250 Kg of fiber are obtained in the form of a fiber tufts with 4.0% polyester content. The obtained fiber tufts are provided to a closed reactor, and pressed under a pression power of 120 tons.

[0156] The fiber tufts after said compression step have a bulk density of about 300 g/L (+10%); this parameter can be calculated by dividing the kg of tufts by the volume of the basket or of the chamber into which they have been compressed and that is filled by the tufts. The fiber tufts are treated in the closed reactor with 11000 liters of depolymerization solution comprising sodium hydroxide (48 Be) with a concentration of 90 g/L. The depolymerization solution is heated to reach a temperature of 130 C. and kept at said temperature for 120 minutes. The bath ratio is equal to 1/5. The depolymerization solution is circulated through the fibers 70 to 200 times.

[0157] After 120 minutes, the depolymerizing solution is cooled to a temperature of 50 C. After the treatment with the depolymerization solution, polyester fibres have been depolymerized into monomers and separated from the remaining treated cellulosic fibers.

[0158] The thus obtained cellulosic fibers are subsequently treated with a bleaching solution. The bleaching solution comprises hydrogen peroxide with a mass concentration of 5 g/L, stabilizing agents in a concentration of 3.0 g/L, dispersing agents with a concentration of 1 g/L and wetting agents with a concentration of 0.2 g/L.

[0159] Hydrogen peroxide is gradually poured in the bleaching solution after 5 minutes the treated waste fabric is immersed in the bleaching solution. The bleaching solution has a bath ratio of 1/5. The bleaching solutions is then heated to a temperature of 105 C. for 90 minutes and indigo dye is removed from the treated fabric.

[0160] In the final step the treated fiber tufts is treated with a washing solution. The washing solution comprises dispersing agents (e.g. Develope JFR NB-MKS DEVO) with a concentration of 3 g/L. The bath ratio is equal to 1/5.

[0161] The washing solution is heated to a temperature of 95 C. for 30 minutes and the treated fiber tuft is washed. The washed fibers are dried and can be further subjected to recycling processes known, per se, in the art to make yarns in a textile-to-textile circular process.

Example 2: Depolymerization of Indigo Dyed Fabric Clippings

[0162] 2250 Kg post-consumer fabric clippings in different sizes comprising cotton fibres in the warp yarns and cotton fibres and polyester fibres in the weft yarns are provided. Additionally, the waste fabrics comprise 88% cotton and 12% polyester and are dyed with indigo.

[0163] The fabric clippings are treated in the closed reactor with a depolymerization solution comprising sodium hydroxide (48 Be) with a concentration of 90 g/L in bath ratio equal to 1/5. The same process is applied as in Example 1.

[0164] The processed fabric clippings are later mechanically treated using a Laroche post-consumer textile waste recycling machine (Andritz) to form fiber tufts from treated fabric clippings.

[0165] Mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated clippings are analyzed by fiber bundle method with TexTechno Fibrotest machine according to the ASTM D5867-12 standard and given in Table 1.

[0166] After the process, the dried depolymerized, bleached and washed fiber tufts from Example 1, fabric clippings and post-formed fiber tufts from Example 2 are used to measure the viscosity and the Degree of Polymerization (DP) is calculated. The % drop in viscosity for all samples show similarities. When the mechanical properties of treated fiber tufts are compared, the strength shows a 17% decrease after the treatment as fiber tufts form whereas 36% decrease after the treatment as fabric clippings and conversion into fiber tufts.

[0167] The whiteness of the samples after the treatment as in fiber tufts form and clippings form shows a difference. As known, reflectance and yellowing are used to define color grade; the reflectance RD may be used as a way of expressing the whiteness degree.

TABLE-US-00001 TABLE 1 Properties of fiber tufts treated from tufts form and clippings form. Clippings form Fiber tufts after process before after and converted indigo-dyed process process into fiber tufts Composition (%) 4.0% polyester, 100% cotton 100% cotton 96% cotton Moisture content (%) 6.4 9.0 6.4 Fiber length 23.09 21.3 22.04 average (UHML) (mm) Strength (g/tex) 11.31 9.38 7.18 Yellowing (+b) 6.41 6.25 2.51 Reflectance (RD) 15.4 60.5 20.08 Maturity (%) 87.84 94.38 86.04 Micronaire 4.0 3.71 3.68

Example 3: Treatment of Reactive Dyed Cotton Fiber Tufts

[0168] Post-consumer waste fabric comprising 100% cotton fibres are provided. The waste fabrics are dyed with reactive dye in orange color.

[0169] The waste fabrics are mechanically treated using a Laroche post-consumer textile waste recycling machine (Andritz).

[0170] After the mechanical treatment, 500 Kg of fiber are obtained in the form of a fiber tufts.

[0171] The obtained fiber tufts are provided to a closed reactor, after being compressed under a pression power of 120 tons. The fiber tufts under said pressure have a bulk density of about 300 g/L (10%).

[0172] The fiber tufts are treated in the closed reactor with 3000 liters of depolymerization solution comprising sodium hydroxide (48 Be) with a concentration of 90 g/L. The depolymerization solution is heated to reach a temperature of 130 C. and kept at said temperature for 120 minutes. The bath ratio is equal to 1/6. The depolymerization solution is circulated through the fibers 70 to 200 times.

[0173] After 120 minutes, the depolymerizing solution is cooled to a temperature of 50 C. The treated cellulosic fibers are subsequently treated with a washing solution. The washing solution comprises dispersing agents (e.g. Develope JFR NB-MKS DEVO) with a concentration of 1 g/L. The bath ratio is equal to 1/6.

[0174] The washing solution is heated to a temperature of 95 C. for 30 minutes and the treated fiber tuft is washed. The washed fibers are dried and can be further subjected to recycling processes known, per se, in the art. The resulting fibers are free from orange colour. No bleaching is required.

[0175] Mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated clippings are analyzed by fiber bundle method with Tex Techno Fibrotest machine according to the ASTM D5867-12 standard and given in Table 2.

[0176] When the mechanical properties of before and after treatment of fiber tufts are compared; the fiber length shows a 1.7% decrease after the treatment, the % drop in strength (g/tex) is found as 26% while the elongation (%) stays almost the same.

Example 4: Treatment of Reactive Dyed Cotton Fabric ClippingsComparison Example

[0177] 500 Kg post-consumer fabric clippings in different sizes comprising 100% cotton fibres in the warp and the weft directions are provided. Additionally, the waste fabrics are dyed with reactive dye in orange color.

[0178] The fabric clippings are treated in the closed reactor with a depolymerization solution comprising sodium hydroxide (48 Be) with a concentration of 90 g/L in bath ratio equal to 1/6. The same process applied as in Example 3.

[0179] The processed fabric clippings are later mechanically treated using a Laroche post-consumer textile waste recycling machine (Andritz) to form fiber tufts from treated fabric clippings.

[0180] Mechanical properties of fiber tufts (before and after treatment) and fiber tufts obtained from treated clippings are analyzed by fiber bundle method with Tex Techno Fibrotest machine according to the ASTM D5867-12 standard and given in Table 2.

[0181] When the mechanical properties are compared; the fiber mean length in the tufts obtained from treated clippings shows a 11% decrease after the treatment compared to a 1.7% of the treated tufts, the % drop in strength (g/tex) in the tufts obtained from treated clippings is found as about 40% compared to 26% in the tufts treated according to the process in example 3.

[0182] Both of the samples after the treatment as in fiber tufts form and clippings form shows similarities in the whiteness degree from reflectance (RD) above 70; the samples treated as fiber tuft form visually have the highest among them.

TABLE-US-00002 TABLE 2 Clippings form Fiber form after process before after and converted reactive-dyed process process into fiber tufts Composition (%) 100% cotton 100% cotton 100% cotton Mean length (mm) 20.2 19.85 17.99 Fiber length 25.34 24.61 23.05 average (UHML) (mm) Strength (g/tex) 7.34 5.4 4.14

[0183] The above data exemplifies how the process of the invention may be used to de-colourize a waste textile. Thus, the invention also refers to a process for removing dyes from dyed waste textiles comprising cellulosic fibres, preferably cotton fibres, and optionally polyester fibers, the process including treatment in a basic aqueous solution, characterized in comprising the following steps: [0184] a) providing an amount of said waste blend textiles, comprising, or substantially consisting of cellulosic fibers (40); [0185] b) mechanically opening said textiles into fiber tufts (1); [0186] c) compressing said fiber tufts (1) in a reaction chamber (10) to a bulk density within the range of 100 to 350 g/L, preferably 240 to 320 g/L, more preferably 280-300 g/L, most preferably 300 g/L; [0187] d) providing an amount of basic solution (3) according to a bath ratio between 1/2 and 1/20 by weight of fiber tufts over weight of solution; [0188] e) circulating said amount of depolymerizing solution (3) through said fiber tufts (1), to remove at least part of said dye from said fiber tufts; [0189] f) removing said solution (3) from said reaction chamber (10); [0190] wherein the temperature of the said depolymerizing solution in step c) is in the range between 101 C. and 160 C., and wherein the solution is circulated through said fiber tufts, said fiber tufts being in a still and compressed condition, to provide a treated fiber tufts (5) comprising cellulosic staple fibres, preferably cotton staple fibres (40), substantially free from dyes.

[0191] The process includes a bleaching step when the dyes are indigo or indigoid dyes. The above disclosure of process features and plant features applies to the decolourizing process here discussed. The fiber tufts are compressed into a basket or other container, or in the reaction chamber, preferably to reach a bulk density of 100 to 350 g/L, preferably 240 to 320 g/L, more preferably 280-300 g/L, most preferably 300 g/L before being treated with the basic aqueous solution. Bulk density is expressed as grams of textile material divided by a known volume occupied by the material in the reactor.

[0192] The tests show that for a same fabric, cut into clippings, the removal of dyes from fiber tufts is more effective than removal from clippings and that at least some of the mechanical properties of the fibers are better when the process is carried out on fiber tufts than when the process is carried out on clippings that are eventually opened into fiber tufts. It is believed that this result is obtained because the process carried out on compressed fiber tufts is more uniform than the same process carried out on compressed fabric clippings.

[0193] In other words, the invention provides for a first step in which the density of the textile is reduced by opening it into fibers as tufts and a further step in which density is reduced because the fiber tufts are compressed. It is noted that the actual bulk density, expressed in grams per Liter of textile material, in the reaction chamber may advantageously be more or less equivalent for fabric clippings and compressed fiber tufts. Typically, by compressing the fiber tufts, a density of the material in the reactor of e.g. 260 g/L can be obtained, the corresponding amount of compressed clippings would provide a bulk density of about 280 g/L, this difference amounting to about 5-7%. The invention makes it possible to process huge amounts of textile in an extremely efficient way resulting in uniformly de-colorized and de-polymerized textile materials.