Cellulose fibers and process for their production

Abstract

The present application provides a kind of cellulose fiber and its preparation method, first NMMO aqueous solution is heated and stirred, and cellulose raw material is added to the prepared NMMO aqueous solvent, and heated and stirred;Then the blend after swelling is dissolved by stirring and vacuumizing, and then the obtained cellulose solution is continuously heated and stirred, while adding spinning aid, after stirring, centrifugal spinning dope is obtained, finally the obtained spinning dope is injected into syringe, and cellulose filament is spun at low temperature by push pump.The method can reduce the temperature of cellulose spinning relative to the spinning method of NMMO water system, and can effectively reduce the energy consumption of industrial production of cellulose fiber, and the method is obvious at low cellulose concentration, which has great economic advantage in the differentiation production of lyocell fiber.

Description

Technical Field

[0001] This invention belongs to the technical field of fiber materials, and particularly relates to a low-temperature spinning method for cellulose based on the NMMO system and the cellulose fibers prepared therefrom. Background Technology

[0002] Cellulose is the world's most produced natural polymer and a major component of plant cell walls and marine organism membranes. Global reserves of cellulose currently amount to trillions of tons, and are continuing to grow at a rate of 100-150 billion tons annually. Cellulose and its derivatives are widely used in textiles, food, medicine, and other industries.

[0003] The first step in utilizing cellulose is dissolving it. Numerous patents, both domestic and international, have demonstrated that copper ammonia solution, sodium hydroxide, alkaline urea, acetic anhydride, ionic molten salts, phosphoric acid, and N-methylmorpholine oxide (NMMO) can all be used to dissolve cellulose. However, only copper ammonia solution, cellulose acetate, viscose processes using sodium hydroxide as a representative solvent, and the lyocell process using NMMO as a solvent have achieved industrial-scale production.

[0004] Cuprammonium cellulose was phased out by viscose cellulose due to the high pollution during its production process. While viscose cellulose is less polluting than cuprammonium cellulose, it still inevitably emits waste gases such as carbon disulfide. The lyocell process, which achieved zero emissions, was successfully industrialized in the 1980s and is now considered the most promising new green regenerated cellulose production process to replace viscose cellulose.

[0005] Compared to viscose processes, the dissolution process in the lyocell process is a purely physical one, with a shorter process flow, no waste gas emissions, and recyclable solvents. Unlike viscose production, the lyocell process does not involve aging or curing; the cellulose undergoes minimal degradation from dissolution to spinning, resulting in a higher viscosity spinning solution in the lyocell process.

[0006] Due to the high viscosity of the spinning solution, the lyocell spinning process had to abandon traditional wet spinning and melt spinning methods, instead adopting a dry-wet spinning process that combines the characteristics of both. Simultaneously, to ensure the fluidity of the spinning solution, the spinning temperature was forced to be maintained at 90–100°C. Increasing the temperature not only increased the energy consumption of the lyocell process but also accelerated the degradation of cellulose and the decomposition of N-methylmorpholine oxide. Cellulose decomposition leads to a decline in product quality, while solvent degradation increases the difficulty of subsequent solution recovery. Furthermore, the colored groups produced after solvent decomposition can permanently stain the produced cellulose fibers.

[0007] In summary, the current high-temperature lyocell process in production has excessively high production costs and lacks market competitiveness, necessitating further process improvements to reduce costs. Several methods exist for this, such as the solution in Patent Document 1, which involves mixing NMMO with non-proton-transferring polar solvents like acetone, dimethylformamide, and dimethylacetamide in a specific ratio to prepare a mixed solution that improves the viscosity and stable temperature of cellulose. Alternatively, Patent Document 2 involves adding a low-boiling-point, volatile, polar organic solvent as an additive to the pulp swelling process, mixing it with N-methylmorpholine-N-oxide (NMMO) with a water content of 8-18% to form a mixed solvent that improves pulp swelling while shortening the evaporation and concentration time in traditional processes. However, Patent Document 1 uses a solvent with high toxicity that is difficult to separate from NMMO, increasing the difficulty of subsequent solvent recovery. Patent Document 2, on the other hand, controls the NMMO water content to below 18%, requiring a large amount of organic solvent for dilution, which undoubtedly increases the load on existing equipment. Furthermore, the presence of a large amount of low-boiling-point solvent also increases the risk of reaction complications.

[0008] In further research, the inventors' patent application (Patent Document 3) filed in 2019 proposed a technical solution involving dissolving NMMO in an alcoholic organic solvent to obtain an NMMO alcohol solution with a mass fraction of 40-80 wt%. Cellulose raw materials were then added to this NMMO alcohol solution for activation and swelling. Under vacuum heating and stirring conditions, the cellulose was rapidly dissolved at a lower temperature, thus rapidly dissolving the cellulose. However, the addition of ethanol only improved the conditions during the dissolution process; the overall process remained a high-temperature system, offering little improvement in production costs compared to the original process. Furthermore, the method required the addition of a large amount of ethanol during implementation, increasing production costs.

[0009] In summary, the production cost of the lyocell process under high temperature conditions is too high, and it lacks market competitiveness. Further process improvements and cost reductions are needed. Existing patents also have certain limitations and need to be improved.

[0010] Patent document 1 mentioned above is Chinese patent with publication number CN101187081A;

[0011] Patent document 2 is: Chinese patent with publication number CN101240461A;

[0012] Patent document 3 is Chinese patent with publication number CN112679756A. Summary of the Invention

[0013] To address the shortcomings of existing technologies, this invention provides a method for preparing cellulose fibers. Preferred alcohols and aprotic polar solvents are added as spinning aids to the spinning solution formed by the NMMO / water system. This method significantly reduces the spinning temperature and viscosity during the lyocell fiber production process, thereby reducing energy consumption and carbon emissions. Simultaneously, the low-temperature conditions effectively prevent the degradation of cellulose and the decomposition of NMMO, which contributes to the production of high-quality cellulose filaments.

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] A method for preparing cellulose fibers, the method comprising the following steps:

[0016] S1. Stir the NMMO aqueous solution and heat it to a certain temperature;

[0017] S2. Add the cellulose raw material to the NMMO aqueous solvent obtained in step S1, heat and stir to allow the cellulose to swell fully; dissolve the swollen blend under vacuum while stirring to obtain a transparent and homogeneous cellulose solution.

[0018] S3. Continue heating and stirring the cellulose solution obtained in step S2, while adding a spinning aid. After stirring for a certain period of time, centrifuge to obtain the spinning solution.

[0019] S4. Inject the spinning solution obtained in step S3 into a syringe, leaving a preset air gap between the needle and the coagulation bath, and spin cellulose filaments at low temperature using a push pump.

[0020] As a further limitation of the present invention, the initial mass concentration of the NMMO aqueous solution is 40-70%.

[0021] As a further limitation of the present invention, the vacuum degree is not higher than 0.01 MPa, and the dissolution time is 10 to 60 min.

[0022] As a further limitation of the present invention, the spinning aid includes, but is not limited to, lower alcohols, lower ethers, and nonproton-transferring polar solvents.

[0023] As a further limitation of the present invention, the stirring time is 0 to 60 minutes.

[0024] As a further limitation of the present invention, the temperature of the heating and stirring is 20 to 50°C.

[0025] As a further limitation of the present invention, in step S4, the air gap is 0 to 60 mm.

[0026] As a further limitation of the present invention, in step S4, the coagulation bath includes, but is not limited to, a mixed solution formed from one or more of water, methanol, ethanol, and diethyl ether.

[0027] As a further limitation of the present invention, the water content of the NMMO is 30-70%.

[0028] In addition, the present invention also provides a cellulose fiber, which is prepared by the above-described preparation method.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1) The method for preparing cellulose fibers provided by this invention involves adding preferred alcohols and aprotic polar solvents as spinning aids to the spinning solution formed in the NMMO / water system. The small-molecule spinning aids act as lubricants in the NMMO / cellulose / water system, promoting intermolecular slippage and reducing the apparent viscosity of the system. Simultaneously, the hydroxyl groups in the spinning aids can compete with the aqueous phase in the system to form hydrogen bonds with NMMO, thereby preventing the formation of NMMO hydrated crystals. This allows the spinning solution to remain in a solution state even at low temperatures, achieving the purpose of low-temperature spinning. This method significantly reduces the spinning temperature and viscosity during the production of lyocell fibers, reducing production energy consumption and carbon emissions. Furthermore, it effectively prevents the degradation of cellulose and the decomposition of NMMO under low-temperature conditions, which helps produce high-quality cellulose filaments.

[0031] 2) The cellulose filaments prepared by NMMO and ethanol in this invention can achieve a tensile stress of 152 MPa, which is 46% higher than the tensile strength of cellulose filaments prepared by traditional NMMO water solvent, which is only 108 MPa.

[0032] 3) Compared with the traditional lyocell production process, this invention only requires adding a preferred spinning aid to the final spinning solution to reduce the spinning temperature and improve the viscosity of the system, which greatly reduces the energy consumption in the production process; at the same time, the operation of adding the spinning aid is simple and convenient, and does not require major modifications to the production line.

[0033] 4) The preferred spinning aid described in this invention requires a small amount, is easy to remove, and will not have a significant impact on solvent recovery. Attached Figure Description

[0034] Figure 1 These are optical photographs of cellulose solutions in the traditional NMMO aqueous solvent system and cellulose solutions with added ethanol in the system of this invention, taken at different temperatures.

[0035] Figure 2 (a) and (b) are the surface and cross-sectional morphology characterization results of the cellulose filaments obtained from the solution after fiber dissolution in Example 5, respectively; Figure 2(c) and (d) show the surface and cross-sectional morphology characterization results of the cellulose filaments obtained from the solution after fiber dissolution in Example 3, respectively.

[0036] Figure 3 This is a comparison of the mechanical properties of cellulose filaments obtained from the solutions after fiber dissolution in Examples 3 and 5. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0038] like Figure 1 As shown, the present invention provides a method for preparing cellulose fibers, specifically including the following steps:

[0039] S1. Stir the NMMO aqueous solution and heat it to a certain temperature;

[0040] S2. Add the cellulose raw material to the NMMO aqueous solvent obtained in step S1, heat and stir to allow the cellulose to swell fully; dissolve the swollen blend under vacuum while stirring to obtain a transparent and homogeneous cellulose solution.

[0041] S3. Continue heating and stirring the cellulose solution obtained in step S2, while adding a spinning aid. After stirring for a certain period of time, centrifuge to obtain the spinning solution.

[0042] S4. Inject the spinning solution obtained in step S3 into a syringe, leaving a preset air gap between the needle and the coagulation bath, and spin cellulose filaments at low temperature using a push pump.

[0043] The invention also relates to a cellulose fiber prepared using the aforementioned method for preparing cellulose fibers.

[0044] Example 1

[0045] A method for preparing cellulose fibers includes the following steps:

[0046] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0047] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0048] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0049] S4. Continue heating and stirring the cellulose solution obtained in step S3. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0050] S5. The spinning solution obtained in step S4 is solidified into a block at 35°C, making it impossible to spin.

[0051] In this embodiment, the cellulose solution no longer has fluidity at 35°C and cannot be spun.

[0052] Example 2

[0053] A method for preparing cellulose fibers includes the following steps:

[0054] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0055] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0056] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0057] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 1.36g of methanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0058] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0059] In this embodiment, the cellulose solution remains fluid at 35°C and can be extruded into filaments by a push pump.

[0060] Example 3

[0061] A method for preparing cellulose fibers includes the following steps:

[0062] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0063] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0064] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0065] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 2.72g of methanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0066] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0067] In this embodiment, the cellulose solution has good fluidity at 35°C and can be extruded into filaments by a push pump.

[0068] Example 4

[0069] A method for preparing cellulose fibers includes the following steps:

[0070] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0071] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0072] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0073] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 5.44g of methanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0074] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0075] In this embodiment, the cellulose solution contains tiny gel particles that are fluid at 35°C and can be extruded into filaments by a push pump.

[0076] Example 5

[0077] A method for preparing cellulose fibers includes the following steps:

[0078] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0079] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0080] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0081] S4. Continue heating and stirring the cellulose solution obtained in step S3. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0082] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 80°C.

[0083] In this embodiment, the cellulose solution has good fluidity at 80°C and can be extruded into filaments by a push pump.

[0084] Example 6

[0085] A method for preparing cellulose fibers includes the following steps:

[0086] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0087] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0088] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0089] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 2.72g of methanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0090] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0091] In this embodiment, the cellulose solution has very good fluidity at 80°C and can be extruded into filaments by a push pump.

[0092] Example 7

[0093] A method for preparing cellulose fibers includes the following steps:

[0094] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0095] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0096] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0097] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 3.92g of ethanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0098] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0099] In this embodiment, the cellulose solution has good fluidity at 35°C and can be extruded into filaments by a push pump.

[0100] Example 8

[0101] A method for preparing cellulose fibers includes the following steps:

[0102] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0103] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0104] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0105] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 5.27g of ethylene glycol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0106] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0107] In this embodiment, the cellulose solution has a certain fluidity at 35°C and can be extruded into filaments by a push pump.

[0108] Example 9

[0109] A method for preparing cellulose fibers includes the following steps:

[0110] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0111] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0112] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0113] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 7.82g of glycerol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0114] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 35°C.

[0115] In this embodiment, the cellulose solution is fluid at 35°C and can be extruded into filaments by a push pump.

[0116] Example 10

[0117] A method for preparing cellulose fibers includes the following steps:

[0118] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0119] S2. Add 1.24g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0120] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0121] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 2.72g of ethanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0122] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (water) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 30°C.

[0123] In this embodiment, the cellulose solution has good fluidity at 30°C and can be extruded into filaments by a push pump.

[0124] Example 11

[0125] A method for preparing cellulose fibers includes the following steps:

[0126] S1. Stir 40g of an aqueous solution of NMMO with a water content of 50% vigorously and heat it to 60°C.

[0127] S2. Add 0.83g of cellulose to the NMMO aqueous solution prepared in S1, and heat and stir for 15min to allow the cellulose to swell fully.

[0128] S3. Heat the blend obtained in step S2 to 100°C, evacuate to 80 mbar (900 rpm), and dissolve in cellulose solution after 25 min.

[0129] S4. Continue heating and stirring the cellulose solution obtained in step S3, while adding 2.72g of ethanol. After stirring for 5 minutes, centrifuge to obtain the spinning solution.

[0130] S5. Inject the spinning solution obtained in step S4 into a syringe. The air gap between the needle and the coagulation bath (ethanol) is 20 mm. Spin cellulose filaments are produced by pushing the pump at 30°C.

[0131] In this embodiment, the cellulose solution has good fluidity at 30°C and can be extruded into filaments by a push pump.

[0132] The experimental conditions and results obtained in Examples 1-11 are shown in the table below:

[0133] Table 1. Experimental results under different experimental conditions

[0134]

[0135] The results in the table above show that:

[0136] 1) Under the same conditions, spinning solutions without added spinning aids will solidify and crystallize at 35°C, making spinning impossible; spinning solutions with added spinning aids can maintain a certain fluidity at temperatures above 30°C and can be used for spinning (Examples 1, 2, 3, 6, 7, 8, 9).

[0137] 2) When the spinning temperature is 80°C, the spinning solution with added spinning aid has a lower viscosity (Examples 5 and 6), which means that at the same temperature, adding spinning aid can prepare spinning solutions with a higher cellulose content.

[0138] 3) Based on the results of Examples 1 to 11, it can be seen that the present invention can effectively reduce the viscosity and spinning temperature of the spinning solution and improve the spinnability of the solution by adding a spinning aid to the NMMO / cellulose spinning solution.

[0139] Experimental Example 1

[0140] To compare the advantages and disadvantages of the present invention and the traditional NMMO / cellulose / water high-temperature spinning system, the cellulose spinning solutions prepared in Examples 1 and 3 were poured into sample bottles, respectively. The temperature of the spinning solution was measured using an alcohol thermometer, and then photographs were taken to observe and compare the stability of the spinning solution. The results are as follows: Figure 1 As shown.

[0141] As can be seen from the figure, the spinning solution (Example 3) prepared by adding methanol at the same cellulose concentration is more stable and can still maintain good fluidity at 30°C, thus having good spinning conditions; while the spinning solution (Example 1) without methanol begins to solidify at 50°C and is completely solidified at 30°C, making it impossible to spin.

[0142] Experimental Example 2

[0143] The fiber solutions obtained in Examples 5 and 3 were transferred into 20 ml syringes with needles (screw-in, inner diameter 0.84 mm) and fixed to an injection pump. Cellulose gel fibers were prepared by wet spinning at an extrusion speed of 2 mL / min using water as a coagulation bath at room temperature. The obtained gel fibers were then washed with water to obtain wet cellulose fibers. Finally, the wet cellulose fibers were dried at room temperature (temperature 25°C, humidity 74-77%) to obtain dry cellulose fibers.

[0144] The cellulose filaments obtained by the above method were prepared, sputtered with gold, and their surface and cross-sectional morphology were observed on a Phenom desktop scanning electron microscope.

[0145] Figure 2 (a) and (b) show the surface and cross-sectional morphology characterization results of the cellulose filaments obtained in Example 5, respectively. Figure 2 (c) and (d) show the surface and cross-sectional morphology characterization results of the cellulose filaments obtained in Example 3, respectively. As can be seen from the figure, the cross-sections of the fibers prepared by the two dissolution methods of NMMO with ethanol and traditional NMMO aqueous solution are both circular or nearly circular. Moreover, the cross-section of the cellulose filaments prepared by NMMO with ethanol is denser than that of the cellulose filaments prepared by NMMO aqueous solution, which helps to improve the mechanical properties of cellulose filaments.

[0146] Experimental Example 3

[0147] The cellulose filaments obtained in Examples 3 and 5 were tested for their mechanical properties using an Instron 5600 tensile testing machine. The test conditions were: test length 2 cm, test speed 1 cm / min. The test results are shown in Table 2 below. Figure 3 As shown.

[0148] Table 2 Comparison of mechanical properties of cellulose filaments prepared in different embodiments

[0149] 3 152±6 12.13±1 5 104±5 8.97±0.5

[0150] from Figure 3 The results show that the mechanical properties of cellulose prepared by NMMO and ethanol in this invention are significantly higher than those of cellulose prepared by NMMO aqueous solvent. Table 2 shows that the mechanical properties of cellulose filaments prepared by NMMO and ethanol in this invention are 46% higher than those prepared by traditional NMMO aqueous solvent. This is because in traditional high-temperature systems, the spinning solution cools down to solidification time very quickly after leaving the spinneret, resulting in limited fiber orientation time; often, the fibers solidify before achieving significant orientation. In contrast, the spinning solution prepared by this method remains stable at room temperature. Therefore, compared to traditional high-temperature systems, under the same production conditions, the fiber orientation is higher and better, ultimately yielding cellulose filaments with better tensile properties.

[0151] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that any improvements and additions made by those skilled in the art without departing from the method of the present invention should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art using the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing cellulose fibers, characterized in that, Includes the following steps: S1. Stir the NMMO aqueous solution and heat it to a certain temperature; S2. Add the cellulose raw material to the NMMO aqueous solvent obtained in step S1, heat and stir to allow the cellulose to swell fully; dissolve the swollen blend under vacuum while stirring to obtain a transparent and homogeneous cellulose solution. S3. Continue heating and stirring the cellulose solution obtained in step S2, while adding a spinning aid. After stirring for a certain period of time, centrifuge to obtain the spinning solution. S4. Inject the spinning solution obtained in step S3 into a syringe, leaving a preset air gap between the needle and the coagulation bath, and spin cellulose filaments at low temperature using a push pump. In step S3, the spinning aid includes lower alcohols; In step S3, the heating and stirring temperature is 20~50℃.

2. The preparation method according to claim 1, characterized in that, In step S1, the initial mass concentration of the NMMO aqueous solution is 40-70%.

3. The preparation method according to claim 1, characterized in that, In step S2, the vacuum level of the vacuuming is no higher than 0.01 MPa, and the dissolution time is 10~60 min.

4. The preparation method according to claim 1, characterized in that, In step S3, the stirring time is 5 to 60 minutes.

5. The preparation method according to claim 1, characterized in that, In step S4, the air gap is 20~60mm.

6. The preparation method according to claim 1, characterized in that, In step S4, the coagulation bath comprises a mixed solution formed from one or more of water, methanol, ethanol, and diethyl ether.

7. The preparation method according to claim 1, characterized in that, The water content of the NMMO is 30-60%.

8. A cellulose fiber, characterized in that, It is prepared by the preparation method described in claim 1.

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