A method for one-bath recovery of cellulose / polyester blended fabrics and preparation of composite fibers

Abstract

The application discloses a method for preparing composite fibers from cellulose / polyester blended fabrics by one-bath recycling, and belongs to the field of textile recycling and reuse. The cellulose / polyester blended fabric is activated by using a NaOH aqueous solution, and then washed with water and dried. The treated fabric is put into a mixed solvent system of LiCl / solvent, and reacted at high temperature and relatively low temperature respectively for a period of time, so that a homogeneous cellulose / polyester mixed solution is obtained. Finally, the regenerated cellulose / polyester composite fibers are prepared by a wet spinning process or a dry-jet wet spinning process. The method can recycle two fiber components simultaneously by using a single solvent, and the obtained solution has uniform texture and meets the spinning requirements. The prepared regenerated composite fibers have good mechanical properties, and the breaking strength can be up to 2.7 cN / dtex, and the breaking elongation can be up to 13.5%.

Description

Technical Field

[0001] This invention relates to the field of textile recycling technology, specifically to a one-bath method for recycling cellulose / polyester blended fabrics and preparing composite fibers. Background Technology

[0002] Polyester, with its wrinkle-resistant, abrasion-resistant, and quick-drying properties, is widely used in clothing and home textiles, commonly used in shirts, trousers, and sportswear, making it one of the most widely used synthetic fibers in the apparel industry. Polylactic acid (PLA) is a biodegradable and environmentally friendly fiber, and its market demand has continued to grow in recent years driven by environmental policies. In the apparel sector, its excellent moisture-wicking and UV-protective properties make it commonly used in yoga wear, cycling apparel, and other garments. Cellulose fibers, due to their softness and moisture absorption, are commonly used in everyday clothing, underwear, and bedding, and also have wide applications in industries such as filter materials and medical gauze. Polyester and cellulose fibers occupy important positions in both the apparel and industrial sectors, while PLA, although used in a relatively smaller proportion, is experiencing rapid growth. Given the increasingly scarce resources, recycling polyester, PLA, and cellulose fibers can reduce the accumulation of waste textiles, effectively reduce deforestation, decrease dependence on natural resources, and thus protect the ecological environment, demonstrating significant environmental and resource utilization value.

[0003] The main methods for recycling polyester (including polyester fiber and polylactic acid) include physical recycling, chemical recycling, and a combination of chemical and physical recycling. Among these, chemical recycling is widely used because it yields high-quality polyester fibers and has better environmental benefits. Chemical recycling utilizes chemical reactions to depolymerize waste polyester materials into monomers or polymerization intermediates, producing products with relatively high purity, clear structures, and fewer varieties. The process involves polymer degradation and the breaking of chemical bonds under specific conditions. Ester bonds in polyester undergo efficient degradation reactions with alcohols, amines, heat, or water under specific conditions, generating all or part of the constituent structural units of the polymer. Although alcoholysis and hydrolysis can efficiently degrade polyester fibers and obtain monomers or monomer fragments with high purity, these methods require the use of excess reaction reagents, and the excess unreacted portion needs to be removed after the reaction, making the process relatively complex and economically inefficient. Cellulose fiber recycling mainly includes physical and chemical recycling. Physical recycling uses mechanical means to decompose waste textiles into short fibers and fragments, which are then processed through washing, carding, and respinning to produce regenerated cellulose fibers. This process is simple and low-cost, but the quality of the recycled fibers is relatively low. Chemical recycling utilizes chemical reagents or solvents to dissolve cellulose from waste textiles. It primarily employs techniques such as the NaOH / urea aqueous solvent system, the NMMO solvent method, and ionic solutions to dissolve the cellulose, which is then processed into cellulose products through spinning and other processes. While the NaOH / urea aqueous solvent system has many advantages, it generates high-salinity wastewater, increasing the difficulty and cost of wastewater treatment. Furthermore, this system exhibits low stability and repeatability. The NMMO system also faces wastewater treatment issues, and its process is relatively complex and energy-intensive. In contrast, ionic solutions demonstrate significant advantages in chemical recycling due to their superior dissolving power, good chemical properties and thermal stability, and environmentally friendly and recyclable characteristics.

[0004] In real life, most waste textiles are composed of blended fibers, with cellulose / polyester blends being the most common. Although cellulose or polyester fibers can be easily recycled, current technologies mostly use physical or chemical methods to separate cellulose and polyester fibers, then process them separately for recycling. These methods typically involve complex processes and numerous side reactions. There are few existing technologies that directly dissolve cellulose / polyester blends and respin them to produce composite fibers. Furthermore, due to the different properties of cellulose and polyester, existing methods often struggle to achieve effective separation and utilization. Even when combining physical and chemical methods to separate them effectively, the properties of the separated fibers are affected, resulting in poor mechanical properties in the prepared blends. Therefore, developing a new method that can recycle cellulose and polyester fibers in one step, upgrading waste textiles into high-value-added products, is particularly necessary. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a one-bath method for recycling cellulose / polyester blended fabrics to prepare composite fibers. This method involves dissolving waste cellulose / polyester blended fabrics in LiCl solvent, combining high-temperature swelling and low-temperature dissolution methods to promote the dissolution of cellulose and polyester, thereby obtaining a homogeneous mixed solution. The mixed solution is then transformed into regenerated cellulose / polyester composite fibers through solution spinning. This method not only simplifies the recycling process but also yields composite fibers with excellent mechanical properties.

[0006] To achieve the above objectives, this invention first discloses a method for preparing composite fibers by recovering cellulose / polyester blended fabrics using a one-bath process, comprising the following steps:

[0007] (1) The cellulose / polyester blended fabric is activated, cleaned and dried to obtain the activated blended fabric;

[0008] (2) The activated blended fabric obtained in step (1) is mixed with a solvent and stirred at high temperature in the first stage to dissolve the polyester component and simultaneously complete the swelling of the cellulose component; LiCl is added to the resulting mixture to form a LiCl / solvent mixed solvent system and stirred at high temperature in the second stage.

[0009] (3) Transfer the reaction system obtained in step (2) to a lower temperature environment and carry out the third stage of stirring to complete the dissolution of cellulose components and form a homogeneous mixed solution;

[0010] (4) The mixed solution obtained in step (3) is used to produce recycled composite fibers through solution spinning process;

[0011] Alternatively, (1) the cellulose / polyester blended fabric is activated, washed and dried to obtain the activated blended fabric;

[0012] (2) The activated blended fabric obtained in step (1) is mixed with the LiCl / solvent mixed solvent system, and the first stage of stirring is carried out at high temperature to dissolve the polyester component and simultaneously complete the swelling of the cellulose component; the second stage of stirring is carried out at high temperature.

[0013] (3) Transfer the reaction system obtained in step (2) to a lower temperature environment and carry out the third stage of stirring to complete the dissolution of cellulose components and form a homogeneous mixed solution;

[0014] (4) The mixed solution obtained in step (3) is used to produce composite fibers by solution spinning.

[0015] In one embodiment of the present invention, the cellulose / polyester blended fabric in step (1) is a cellulose / polyester blended fabric or a cellulose / polylactic acid fiber blended fabric.

[0016] In one embodiment of the present invention, the cellulose / polyester blended fabric in step (1) has a cellulose mass fraction of 35-99%.

[0017] In one embodiment of the present invention, the activation in step (1) refers to activation using an aqueous sodium hydroxide solution with a mass fraction of 5-20%, an activation temperature of 20-80°C, preferably 40-60°C, and an activation time of 1-5 hours, preferably 2-4 hours.

[0018] In one embodiment of the present invention, the cleaning in step (1) refers to cleaning with deionized water and solvent 3 to 5 times in sequence until sodium hydroxide is no longer present. The solvent includes at least one of dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO). The drying temperature is 40 to 50°C and the drying time is 2 to 5 hours.

[0019] In one embodiment of the present invention, the solvent in step (2) includes at least one of DMF, DMAc and DMSO.

[0020] In one embodiment of the present invention, the mass ratio of the activated blended fabric to the LiCl / solvent mixed solvent system in step (2) is 1 to 10:100, and the mass concentration of LiCl in the LiCl / solvent mixed solvent system is 2 to 10%.

[0021] In one embodiment of the present invention, the high temperature in step (2) is 90 to 150°C, and the stirring speed is 30 to 600 r / min.

[0022] In one embodiment of the present invention, the stirring time in the first stage of step (2) is 1 to 2 hours, and the stirring time in the second stage is 1 to 3 hours.

[0023] In one embodiment of the present invention, in step (3), the lower temperature environment refers to an environment with a temperature of 20 to 60°C, the stirring time in the third stage is 1 to 3 hours, and the stirring speed is 30 to 600 r / min.

[0024] In one embodiment of the present invention, the spinning process in step (4) refers to wet spinning or dry-jet wet spinning, and the regenerated composite fiber has a breaking strength of 1.0 to 3.0 cN / dtex and a breaking elongation of 5 to 15%.

[0025] In one embodiment of the present invention, during the solution spinning process in step (4), the temperature of the spinning solution is 80–120°C, and the extrusion pressure is 1–5 kg / cm². 2 The extrusion speed is 1-3 m / min; the spinneret diameter is 0.2 μm; the coagulation bath is carried out in deionized water at 20-40℃; the air gap is 0-1 cm; the total draw ratio is 1-5 times; the drying temperature is 30-50℃; and the winding speed is 1-15 m / min, preferably 1-5 m / min.

[0026] The present invention also provides a composite fiber prepared according to the above method.

[0027] Beneficial effects:

[0028] 1. This invention uses a mixed solvent system of LiCl / solvent as an ionic solution to swell and dissolve cellulose and polyester in cellulose / polyester blended fabrics in steps. By optimizing the dissolution system and reaction conditions, it is possible to dissolve two different components, cellulose and polyester, simultaneously using a single ionic solvent. The resulting solution has a uniform texture and high stability, and can be directly used in solution spinning to produce recycled composite fibers with good mechanical properties.

[0029] 2. The composite fiber components recovered in this invention are regenerated cellulose and polyester. Cellulose has good hydrophilicity, which can improve the hydrophilicity of the composite fiber, and polyester fiber provides a certain strength to the composite fiber.

[0030] 3. The process conditions adopted in this patent do not require the use of strong acids or alkalis, the dissolving system used has low toxicity, the pretreatment process is simple, effectively improving the recycling efficiency of waste blended fabrics, the entire recycling process is carried out under mild conditions (90-150℃, normal pressure), and no side reactions occur, simplifying the recycling process and reducing the complexity of recycling blended fabrics.

[0031] 4. This invention not only achieves full-component recycling of waste blended textiles, but also avoids the resource waste and environmental pollution caused by traditional incineration or landfill methods. Furthermore, it converts waste textiles into high-value recycled composite fibers, significantly improving economic efficiency.

[0032] 5. The method of the present invention can effectively dissolve cellulose and polyester in cellulose / polyester blended fabrics, and the resulting solution has a uniform texture. Spinning the dissolved solution can yield composite fibers with good mechanical properties. The composite fibers prepared by the method of the present invention can have a breaking strength as high as 2.7 cN / dtex and a breaking elongation as high as 13.5%. Detailed Implementation

[0033] The invention will now be described in detail with specific examples.

[0034] Test method:

[0035] The elongation at break and tensile strength of the composite fiber were tested according to the method in standard GB / T 14337, wherein the fiber was in a dry state, the tensile length of the sample was 10 mm, the tensile speed was 5 mm / min, the temperature was room temperature, and the humidity was 65% ± 2%.

[0036] Example 1

[0037] A method for preparing composite fibers by one-bath recycling of cellulose / polyester blended fabrics includes the following steps:

[0038] 1) The cellulose / polylactic acid fabric (35:65) was first mechanically pulverized, then treated with a 17% NaOH aqueous solution at 50°C for 3 hours, washed with deionized water 3 to 5 times, dried at 50°C for 3 to 5 hours until dry, and then washed with DMAc solvent 2 to 3 times and dried at 50°C for 3 to 5 hours until dry to obtain fabric powder.

[0039] 2) Take 3 portions of the fabric powder obtained in step 1), put them into 92 portions of DMAc solvent, and stir them at 90°C for 1 hour at a stirring speed of 300 r / min to dissolve polylactic acid and swell cellulose.

[0040] 3) Add 8 parts of LiCl to the mixed system obtained in step 2) so that the mass fraction of LiCl in the LiCl / DMAc ion solution system is 8%. Continue the second stage of stirring at 90℃ for 2 hours at a stirring speed of 100 r / min. Then transfer the system to 40℃ and carry out the third stage of stirring at 40℃ for 2 hours at a stirring speed of 50 r / min to obtain a homogeneous cellulose / polylactic acid / LiCl / DMAc solution.

[0041] 4) Regenerated cellulose / polylactic acid composite fibers were obtained using a wet spinning method. During the wet spinning process, the temperature of the spinning solution was 100℃ and the extrusion pressure was 3 kg / cm². 2 The extrusion speed is 2 m / min; the spinneret diameter is 0.2 μm; the coagulation bath is in deionized water at 35℃; the total draw ratio is 2 times; the drying temperature is 50℃; and the winding speed is 4 m / min.

[0042] Example 2

[0043] The difference between Example 2 and Example 1 is that the temperature in the first stage of step 2) and the second stage of step 3) is replaced with 110°C.

[0044] Example 3

[0045] The difference between Example 3 and Example 1 is that the temperature in the first stage of step 2) and the second stage of step 3) is replaced with 130°C.

[0046] Example 4

[0047] The difference between Example 4 and Example 1 is that the temperature in the first stage of step 2) and the second stage of step 3) is replaced with 150°C.

[0048] Example 5

[0049] The difference between Example 5 and Example 4 is that step 2) is omitted, and 1 part of the fabric powder is directly added to a LiCl / DMAc ion solution system with a LiCl mass fraction of 8% and stirred at high temperature for 3 hours.

[0050] The dissolution of fibers in the cellulose / polylactic acid / LiCl / DMAc solution obtained in step 3) is shown in Table 1. Table 1 shows that Examples 1-4, which used different high-temperature stirring temperatures, all dissolved the cellulose / polylactic acid blended fabric into a homogeneous and stable solution within the range of 90-150℃. Example 5 involved directly mixing the cellulose / polyester blended fabric with a mixed solvent system composed of LiCl and solvent, followed by both high-temperature and low-temperature stirring. The resulting solution was homogeneous and stable, almost identical to the solutions obtained in Examples 1-4. The tensile properties of the composite fibers obtained in step 4) show that as the temperature increases, the fiber macromolecular chains become straighter, exhibiting better flexibility and making them more suitable for spinning. However, as the temperature rises to 150℃, the cellulose degrades due to the high temperature, leading to a decrease in fiber properties.

[0051] Table 1. Dissolution and fiber properties of fabrics from Examples 1-5 after three-stage stirring.

[0052]

[0053] Example 6

[0054] A method for preparing composite fibers by one-bath recycling of cellulose / polyester blended fabrics includes the following steps:

[0055] 1) The cellulose / polylactic acid fabric (35:65) was first mechanically pulverized, then treated with a 17% NaOH aqueous solution at 50°C for 3 hours, washed with deionized water 3 to 5 times, dried at 50°C for 3 to 5 hours until dry, and then washed with DMAc solvent 2 to 3 times and dried at 50°C for 3 to 5 hours until dry to obtain fabric powder.

[0056] 2) Take 3 portions of the fabric powder obtained in step 1), put them into 90 portions of DMAc solvent, and stir them at 110°C for 1 hour at a stirring speed of 300 r / min to dissolve polylactic acid and swell cellulose.

[0057] 3) Add 10 parts of LiCl to the mixture obtained in step 2) so that the mass fraction of LiCl in the LiCl / DMAc ion solution system is 10%. Continue the second stage of stirring at 110℃ for 1.5h at a stirring speed of 100r / min. Then transfer the system to 40℃ and carry out the third stage of stirring at 40℃ for 2h at a stirring speed of 50r / min to obtain a homogeneous cellulose / polylactic acid / LiCl / DMAc solution.

[0058] 4) Regenerated cellulose / polylactic acid composite fibers were obtained using a wet spinning method. During the wet spinning process, the temperature of the spinning solution was 100℃ and the extrusion pressure was 3 kg / cm². 2 The extrusion speed is 2 m / min; the spinneret diameter is 0.2 μm; the coagulation bath is in deionized water at 35℃; the total draw ratio is 2 times; the drying temperature is 50℃; and the winding speed is 4 m / min.

[0059] Example 7

[0060] The difference between Example 7 and Example 6 is that the stirring time in the second stage of step 3) is replaced with 2 hours.

[0061] Example 8

[0062] The difference between Example 8 and Example 6 is that the stirring time in the second stage of step 3) is replaced with 2.5h.

[0063] Example 9

[0064] The difference between Example 9 and Example 6 is that the stirring time in the second stage of step 3) is replaced with 3 hours.

[0065] Example 10

[0066] The difference between Example 10 and Example 9 is that step 2) is omitted, and 3 parts of fabric powder are directly added to a LiCl / DMAc ion solution system with a LiCl mass fraction of 10% and stirred at high temperature for 4 hours.

[0067] The dissolution of fibers in the cellulose / polylactic acid / LiCl / DMAc solution obtained in step 3) is shown in Table 2. Table 2 shows that Examples 6-9, with different high-temperature stirring times in the second stage, all achieved a homogeneous and stable solution within 1.5-3 hours. Example 10 involved directly mixing the cellulose / polyester blended fabric with a mixed solvent system composed of LiCl and solvent, followed by both high-temperature and low-temperature stirring. The resulting solution was homogeneous and stable, almost identical to the solutions obtained in Examples 6-9. The tensile properties of the composite fibers obtained in step 4) show that with increasing second-stage dissolution time, the solution dissolves more uniformly, resulting in higher performance composite fibers. However, with longer times, degradation also becomes more severe, leading to a decrease in fiber performance.

[0068] Table 2 shows the dissolution and fiber properties of the fabrics from Examples 6-10 after three-stage stirring.

[0069]

[0070]

[0071] Example 11

[0072] A method for preparing composite fibers by one-bath recycling of cellulose / polyester blended fabrics includes the following steps:

[0073] 1) The cellulose / polylactic acid fabric (35:65) was first mechanically pulverized, then treated with a 17% NaOH aqueous solution at 60°C for 2.5 h, washed with deionized water 3 to 5 times, dried at 50°C for 3 to 5 h until dry, and then washed with DMF solvent 2 to 3 times and dried at 50°C for 3 to 5 h until dry to obtain fabric powder;

[0074] 2) Take 1 part of the fabric powder obtained in step 1), put it into 90 parts of DMF solvent, and stir it in the first stage at 110°C for 1.5 hours at a stirring speed of 300 r / min to dissolve polylactic acid and swell cellulose at the same time.

[0075] 3) Add 10 parts of LiCl to the mixture obtained in step 2) so that the mass fraction of LiCl in the LiCl / DMF ion solution system is 10%. Continue the second stage of stirring at 110℃ for 2 hours at a stirring speed of 100 r / min. Then transfer the system to 50℃ and carry out the third stage of stirring at this condition for 1.5 hours at a stirring speed of 50 r / min to obtain a homogeneous cellulose / polylactic acid / LiCl / DMF solution.

[0076] 4) Regenerated cellulose / polylactic acid composite fibers were obtained using a wet spinning method. During the wet spinning process, the temperature of the spinning solution was 100℃ and the extrusion pressure was 3 kg / cm². 2 The extrusion speed is 2 m / min; the spinneret diameter is 0.2 μm; the coagulation bath is in deionized water at 35℃; the total draw ratio is 2 times; the drying temperature is 50℃; and the winding speed is 4 m / min.

[0077] Example 12

[0078] The difference between Example 12 and Example 11 is that the weight of the fabric powder in step 2) is replaced with 3 parts.

[0079] Example 13

[0080] The difference between Example 13 and Example 11 is that the weight of the fabric powder in step 2) is replaced with 5 parts.

[0081] Example 14

[0082] The difference between Example 14 and Example 11 is that the weight of the fabric powder in step 2) is replaced with 7 parts.

[0083] Example 15

[0084] The difference between Example 15 and Example 11 is that the weight of the fabric powder in step 2) is replaced with 9 parts.

[0085] Example 16

[0086] The difference between Example 16 and Example 15 is that step 2) is omitted, and 9 parts of fabric powder are directly added to a LiCl / DMF ion solution system with a LiCl mass fraction of 10% and stirred at high temperature for 3.5 hours.

[0087] The dissolution of fibers in the cellulose / polylactic acid / LiCl / DMF solution obtained in step 3) is shown in Table 3. Table 3 shows that Examples 11-15, with different fabric mass ratios ranging from 1 to 9:100, all resulted in the dissolution of the cellulose / polylactic acid blended fabric into a homogeneous and stable solution. Example 16 involved directly mixing the cellulose / polyester blended fabric with a mixed solvent system composed of LiCl and solvent, followed by high-temperature and low-temperature stirring. The resulting solution was homogeneous and stable, almost identical to the solutions obtained in Examples 11-15. The tensile property data of the composite fibers obtained in step 4) show that as the amount of fabric added increases, the solution dissolves more uniformly, resulting in composite fibers with higher performance after spinning.

[0088] Table 3. Dissolution and fiber properties of fabrics from Examples 11-16 after the third stage of stirring.

[0089]

[0090] Example 17

[0091] A method for preparing composite fibers by one-bath recycling of cellulose / polyester blended fabrics includes the following steps:

[0092] 1) The cellulose / polyester fabric (65:35) is first mechanically crushed, then treated with a 17% NaOH aqueous solution at 70°C for 2 hours, washed with deionized water 3 to 5 times, dried at 50°C for 3 to 5 hours until dry, and then washed with DMSO solvent 2 to 3 times and dried at 50°C for 3 to 5 hours until dry to obtain fabric powder.

[0093] 2) Take 3 parts of the fabric powder obtained in step 1), put it into 90 parts of DMSO solvent, and stir it at 110°C for 1 hour to dissolve the polyester and swell the cellulose.

[0094] 3) Add 10 parts of LiCl to the mixture obtained in step 2) so that the mass fraction of LiCl in the LiCl / DMSO ion solution system is 10%. Continue the second stage of stirring at 110℃ for 1.5 h at a stirring speed of 300 r / min. Then transfer the system to 30℃ and carry out the third stage of stirring at 30℃ for 1.5 h at a stirring speed of 500 r / min to obtain a homogeneous cellulose / polyester / LiCl / solvent solution.

[0095] 4) Regenerated cellulose / polylactic acid composite fibers were obtained using a dry-jet wet spinning method. During the spinning process, the spinning solution temperature was 100℃ and the extrusion pressure was 3 kg / cm². 2 The extrusion speed is 2 m / min, the spinneret diameter is 0.2 μm, the air gap is 1 cm, and the coagulation bath is carried out in deionized water at 35℃; the total draw ratio is 5 times, the drying temperature is 50℃, and the winding speed is 10 m / min.

[0096] Example 18

[0097] A method for preparing composite fibers by one-bath recycling of cellulose / polyester blended fabrics includes the following steps:

[0098] 1) The cellulose / polyester fabric (65:35) is first mechanically crushed, then treated with a 17% NaOH aqueous solution at 70°C for 2 hours, washed with deionized water 3 to 5 times, dried at 50°C for 3 to 5 hours until dry, and then washed with DMSO solvent 2 to 3 times and dried at 50°C for 3 to 5 hours until dry to obtain fabric powder.

[0099] 2) Take 3 parts of the fabric powder obtained in step 1), put them into 96 parts of DMSO solvent, and stir them in the first stage at 110°C for 1 hour at a stirring speed of 300 r / min to dissolve the polyester and swell the cellulose at the same time.

[0100] 3) Add LiCl to the mixture obtained in step 2) so that the mass fraction of LiCl in the LiCl / DMSO ion solution system is 4%. Continue the second stage of stirring at 110℃ for 1.5h at a stirring speed of 100r / min. Then transfer the system to 50℃ and carry out the third stage of stirring at 50r / min for 1.5h to obtain a homogeneous cellulose / polyester / LiCl / DMSO solution.

[0101] 4) Regenerated cellulose / polylactic acid composite fibers were obtained using a dry-jet wet spinning method. The spinning solution temperature was 100℃, and the extrusion pressure was 3 kg / cm². 2 The extrusion speed is 2 m / min, the spinneret diameter is 0.2 μm, the air gap is 1 cm, and the coagulation bath is carried out in deionized water at 35℃; the total draw ratio is 5 times, the drying temperature is 50℃, and the winding speed is 10 m / min.

[0102] Example 19

[0103] The difference between Example 19 and Example 18 is that, in step 3), after adding LiCl, the mass fraction of LiCl in the LiCl / DMSO ion solution system is 6%.

[0104] Example 20

[0105] The difference between Example 20 and Example 18 is that, in step 3), after adding LiCl, the mass fraction of LiCl in the LiCl / DMSO ion solution system is 8%.

[0106] Example 21

[0107] The difference between Example 21 and Example 18 is that, in step 3), after adding LiCl, the mass fraction of LiCl in the LiCl / DMSO ion solution system is 10%.

[0108] Example 22

[0109] The difference between Example 22 and Example 21 is that step 2) is omitted, and 1 part of the fabric powder is directly added to the LiCl / DMSO ion solution system and stirred at high temperature for 2.5 hours.

[0110] The dissolution of fibers in the cellulose / polyester / LiCl / DMSO solution obtained in step 3) is shown in Table 4. Table 4 shows that Examples 17-22, with different LiCl mass fractions ranging from 4% to 10%, all dissolved the cellulose / polyester blended fabric into a homogeneous and stable solution. Example 22 involved directly mixing the cellulose / polyester blended fabric with a mixed solvent system consisting of LiCl and solvent, followed by high-temperature and low-temperature stirring. The resulting solution was homogeneous and stable, almost identical to the solutions obtained in Examples 17-21. Example 17, with low-temperature stirring at 30°C, also yielded a homogeneous solution with good dissolution. The tensile properties of the composite fibers obtained in step 4) show that with increasing LiCl content, the cellulose dissolves more uniformly, resulting in composite fibers with higher performance.

[0111] Table 4. Dissolution and fiber properties of fabrics from Examples 17-22 after the third stage of stirring.

[0112]

[0113] Comparative Example 1

[0114] The difference between Comparative Example 1 and Example 1 is that the stirring temperature in the first stage of step 2) and the second stage of step 3) is replaced with 70°C, and the step of switching to 40°C for the third stage of stirring in step 3) is omitted.

[0115] Comparative Example 2

[0116] The difference between Comparative Example 2 and Example 1 is that the stirring temperature in the first stage of step 2) and the second stage of step 3) is replaced with 70°C.

[0117] Comparative Example 3

[0118] The difference between Comparative Example 3 and Example 1 is that the stirring temperature in the third stage of step 3) is replaced with 90°C.

[0119] Comparative Example 4

[0120] The difference between Comparative Example 4 and Example 3 is that the step of transferring to 30°C for the third stage of stirring in step 3) is omitted.

[0121] Comparative Example 5

[0122] The difference between Comparative Example 5 and Example 6 is that the stirring time in the second stage of step 3) is changed to 1 hour.

[0123] Comparative Example 6

[0124] The difference between Comparative Example 6 and Example 15 is that the weight of the fabric powder in step 2) is changed to 11 parts.

[0125] Comparative Example 7

[0126] The difference between Comparative Example 7 and Example 17 is that, in step 3), LiCl is not added during the second stage of stirring.

[0127] Comparative Example 8

[0128] The difference between Comparative Example 8 and Example 17 is that, in step 3), after adding LiCl, the mass fraction of LiCl in the LiCl / DMSO ion solution system is 11%.

[0129] Table 5 shows the dissolution of fabrics from Comparative Examples 1–8 and Examples 1, 3, 6, 15, and 17 after the third stage of stirring.

[0130]

[0131]

[0132] The dissolution of fibers in the cellulose / polyester / LiCl / solvent solution obtained in step 3) is shown in Table 5. Table 5 shows that the blended fabric cannot be completely dissolved under high-temperature stirring alone, as shown in Comparative Examples 3 and 4. Data from Examples 1 and 3 indicate that even with prolonged stirring at higher temperatures, the fibers cannot be completely dissolved, suggesting that the dissolution of cellulose and polyester requires a combination of high-temperature stirring for swelling and lower-temperature stirring for dissolution. The experimental results from Examples 1 and Comparative Examples 1-2 show that when the high-temperature stirring temperature is below 90°C, the fabric is difficult to swell completely. Even if a seemingly homogeneous solution is obtained after stirring, it will separate into layers after settling. The experimental data from Examples 6 and 5 show that even a short high-temperature swelling time will result in incomplete fabric dissolution, failing to produce a homogeneous mixed solution after settling, thus preventing subsequent spinning. The experimental data from Examples 15 and 6 show that excessively high blended fabric content will prevent the fabric from being completely dissolved. The experimental data from Examples 17 and Comparative Examples 7-8 show that Comparative Example 7 could not completely dissolve the cellulose / polyester fabric using only DMSO solvent, and excessive LiCl could not completely dissolve the fabric either, and even caused the solution to separate into layers after standing.

[0133] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for producing a composite fiber from a cellulose / polyester blended fabric by a one-bath process, characterized by, The method comprises the following steps: (1) activating, washing and drying the cellulose / polyester blended fabric to obtain the activated blended fabric, wherein the activation is performed by using a sodium hydroxide aqueous solution with a mass fraction of 5-20%, the activation temperature is 20-80°C, and the activation time is 1-5h; (2) mixing the activated blended fabric obtained in step (1) with a solvent, and stirring at 90-150°C in a first stage to dissolve the polyester component and swell the cellulose component; adding LiCl into the obtained mixed system to form a LiCl / solvent mixed solvent system, and continuing to stir at 90-150°C in a second stage, wherein the solvent comprises at least one of DMF, DMAc and DMSO, and the mass concentration of LiCl in the LiCl / solvent mixed solvent system is 2-10%; (3) transferring the reaction system obtained in step (2) to an environment with a temperature of 20-60°C, and stirring in a third stage to dissolve the cellulose component and form a uniform mixed solution; (4) preparing a composite fiber through a solution spinning process by using the mixed solution obtained in step (3); alternatively, (1) activating, washing and drying the cellulose / polyester blended fabric to obtain the activated blended fabric, wherein the activation is performed by using a sodium hydroxide aqueous solution with a mass fraction of 5-20%, the activation temperature is 20-80°C, and the activation time is 1-5h; (2) mixing the activated blended fabric obtained in step (1) with a LiCl / solvent mixed solvent system, and stirring at 90-150°C in a first stage to dissolve the polyester component and swell the cellulose component; continuing to stir at 90-150°C in a second stage, wherein the solvent comprises at least one of DMF, DMAc and DMSO, and the mass concentration of LiCl in the LiCl / solvent mixed solvent system is 2-10%; (3) transferring the reaction system obtained in step (2) to an environment with a temperature of 20-60°C, and stirring in a third stage to dissolve the cellulose component and form a uniform mixed solution; (4) preparing a regenerated composite fiber through a solution spinning process by using the mixed solution obtained in step (3).

2. The method of claim 1, wherein, The cellulose / polyester blended fabric in step (1) is a cellulose / polyester blended fabric or a cellulose / poly-lactic acid fiber blended fabric, and the mass fraction of cellulose in the cellulose / polyester blended fabric is 35-99%.

3. The method of claim 1, wherein, The washing in step (1) is performed by using deionized water and a solvent for 3-5 times, respectively, wherein the solvent comprises at least one of DMF, DMAc and DMSO, and the drying temperature is 40-50°C, and the drying time is 2-5h.

4. The method of claim 1, wherein, The mass ratio of the activated blended fabric to the LiCl / solvent mixed solvent system in step (2) is 1-10:

100.

5. The method of claim 1, wherein, The stirring speed in step (2) is 30-600r / min, the first stage stirring time is 1-2h, and the second stage stirring time is 1-3h.

6. The method of claim 1, wherein, In step (3), the third stage stirring time is 1-3 h, and the stirring speed is 30-600 r / min.

7. The method of claim 1, wherein, In step (4), the spinning process is wet spinning or dry-jet wet spinning, and the breaking strength of the regenerated composite fiber is 1.0-3.0 cN / dtex, and the breaking elongation is 5-15%.

8. The method of claim 1, wherein, In the solution spinning process of step (4), the temperature of the spinning solution is 80-120℃, the extrusion pressure is 1-5 kg / cm 2 , the extrusion speed is 1-3 m / min; the spinneret diameter is 0.2 μm, the coagulation bath is performed in deionized water at 20-40℃; the air gap is 0-1 cm, the total draw ratio is 1-5 times, the drying temperature is 30-50℃, and the winding speed is 1-15 m / min.

9. The composite fiber prepared by the method according to any one of claims 1-8.

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