A process for preparing chitosan fibers based on the method of cross-linking in spinning

Abstract

The application discloses a process for preparing chitosan fibers based on a pre-spinning cross-linking method and belongs to the technical field of natural polymer fiber preparation, processing and application. Alkaline solvents are used to dissolve chitosan, a pre-spinning cross-linking process is adopted, namely, a cross-linking agent is added into the chitosan solution after dissolution to perform cross-linking, and the solution obtained after the cross-linking reaction is used as a spinning solution; then, a wet spinning process is adopted to prepare chitosan fibers. Since there is a chemical cross-linking action between the chitosan molecular chains in the chitosan fibers, the chitosan fibers still have certain acid resistance under an acidic condition and will not be dissolved, which has important significance for the practical application of the chitosan fibers in the field of textiles and garments.

Description

Technical Field

[0001] This invention relates to a process for preparing chitosan fibers, and more particularly to a process for preparing chitosan fibers based on a pre-spinning crosslinking method, belonging to the technical field of preparation, processing and application of natural polymer fibers. Background Technology

[0002] Chitosan is the only alkaline natural polysaccharide found in nature. It is a derivative obtained by deacetylation of chitin, the second most abundant natural polymer after cellulose. Chitosan is not only safe and non-toxic, but also has good biocompatibility, biodegradability, and antibacterial properties, making it a promising candidate for biomedical applications.

[0003] Traditional methods for preparing chitosan fibers involve dissolving the chitosan raw material in a dilute acid solution (such as dilute acetic acid or dilute hydrochloric acid), then regenerating it in an alkaline coagulation bath (such as NaOH solution), and finally using wet spinning to produce chitosan fibers. However, the pure chitosan fibers obtained in this way can still be dissolved in acidic solutions and do not possess acid resistance. This means that pure chitosan fibers have certain limitations in their applications, especially in the textile and apparel industry. To solve this technical problem, cross-linking agents are typically used for post-treatment of the shaped fibers. While this can address the acid resistance issue of chitosan fibers to some extent, the post-treatment process using cross-linking agents significantly increases production costs and time.

[0004] The existing technology "CN103993380A A method for preparing high-strength chitosan fiber" discloses that: after mixing chitosan solution and polyvinyl alcohol solution, a crosslinking agent is added, the mixture is stirred evenly, and vacuum degassing is performed for 24 hours to obtain a spinning solution. Although this technology uses a pre-spinning crosslinking method, the crosslinking agents used are sodium alginate oxide, genipin, and glutaraldehyde. The crosslinking mechanism of sodium alginate oxide is ionic crosslinking with the amino groups on chitosan, while the crosslinking mechanisms of genipin and glutaraldehyde are crosslinking through the aldehyde groups with the amino groups on chitosan. Regardless of the crosslinking mechanism, the crosslinking reaction between the crosslinking agent and the amino groups is very rapid. When the crosslinking agent comes into contact with the chitosan solution, a crosslinking reaction occurs immediately, leading to gelation of the solution, i.e., a stable spinning solution cannot be obtained. Summary of the Invention

[0005] To address the technical problems of chitosan fibers being susceptible to acid damage and the high production costs and long production cycles caused by the use of crosslinking agents in post-processing, a process for preparing chitosan fibers based on pre-spinning crosslinking is proposed.

[0006] In this technical solution, chitosan is dissolved using an alkaline solvent, and a pre-spinning crosslinking process is employed. This involves adding a crosslinking agent to the dissolved chitosan solution to induce crosslinking, and using the resulting solution as the spinning solution. Then, a wet spinning process is used to prepare chitosan fibers. Because of the chemical crosslinking between the chitosan molecular chains in these fibers, they maintain good acid resistance even under acidic conditions, meaning they do not dissolve directly (the crosslinking agent reacts with the chitosan molecules, inhibiting the electrostatic repulsion of chitosan to some extent, resulting in swelling rather than dissolution under acidic conditions). This is of great significance for their practical application in the textile and apparel industry.

[0007] In addition, the entire preparation method is simple and has a short process, which can be used for large-scale industrial production.

[0008] To achieve the above technical objectives, the following technical solution is proposed:

[0009] A process for preparing chitosan fibers based on pre-spinning crosslinking includes the following steps:

[0010] X. Preparation of spinning solution

[0011] X1: Chitosan raw material with a viscosity of 450-550 mPa·s and a degree of deacetylation of 87.2% is added to an alkali / urea solvent system, mixed thoroughly, and dissolved to obtain a chitosan dispersion; the chitosan dispersion is frozen to below -30°C for 4 hours, and then thawed and dissolved by mechanical stirring at room temperature; then, it is frozen to below -30°C again for 4 hours, and then thawed and dissolved by mechanical stirring at room temperature. This freezing and thawing cycle is repeated 1-2 times. After centrifugation, a transparent chitosan solution with a viscosity of 20000-30000 mPa·s is obtained.

[0012] The alkali / urea solvent system is a KOH / LiOH / urea system, which provides an alkaline environment for the dissolution of chitosan raw materials and ensures the stability of the solution. More specifically, the chitosan solution contains 3.0–3.5% chitosan, 13–17% alkali (6–8% KOH and 7–9% LiOH), and 8–11% urea.

[0013] X2: A crosslinking agent (specifically, a crosslinking agent with an epoxy structure, such as epichlorohydrin, polyethylene glycol diglycidyl ether, etc., preferably epichlorohydrin) is added to the chitosan solution. The crosslinking reaction is carried out at -5℃ with stirring for 15 minutes to obtain a chitosan pregel solution with a viscosity of 30,000–50,000 mPa·s. This ensures good spinnability of the resulting spinning solution during subsequent spinning while maintaining the performance of the subsequent filaments. The viscosity of the solution is related to the viscosity of the chitosan raw material and the concentration of the chitosan solution. The pregel solution obtained after adding the crosslinking agent will have a higher viscosity than the original chitosan solution. However, excessively high viscosity will lead to filtration difficulties and also affect the spinning process. Therefore, the viscosity of the prepared chitosan pregel solution is controlled to be 30,000–50,000 mPa·s.

[0014] Among them, the mass ratio between the amount of crosslinking agent with epoxy structure added and chitosan is controlled to be 1:100 to 1000;

[0015] X3: Degas and filter the chitosan pregel solution to remove impurities, and then store it in a jacketed low-temperature storage tank, controlling the storage temperature to ≤5℃ (with 5℃ condensate flowing through the jacket), to obtain the spinning solution for spinning.

[0016] Among them, the degassing is carried out by centrifugation, with a speed of ≥10000rpm, a degassing time of 10 min, and a degassing temperature of 5℃;

[0017] The filter uses a filter screen with a pore size of 15μm;

[0018] Y. Spinning process

[0019] Spinning produces filaments;

[0020] Equipment: Uses acid and alkali resistant nozzles, such as large-aperture platinum nozzles (30 holes) with a nozzle diameter of 0.078 mm. The nozzle material is platinum:gold = 4:6. The nozzle orifice size is related to the thickness of the spun filaments, so the corresponding nozzle can be selected according to actual needs.

[0021] Control conditions: Spinning speed 5-10 m / min, total draft 15-25%;

[0022] Spinning bath: citric acid content 5-10 wt% and sodium citrate content 15-20 wt%, spinning bath temperature 30-60℃, filament immersion length 500-1000 mm;

[0023] Z. Post-processing

[0024] The obtained filaments are wound into bundles using a winding device, and then stretched, washed, oiled and dried to obtain chitosan fibers.

[0025] The beneficial technical effects of adopting this technical solution are as follows:

[0026] I. In this invention, a crosslinking agent is added to the raw material chitosan solution to carry out a crosslinking reaction. The pre-gel solution after the crosslinking reaction is used as the spinning solution, and chitosan fibers are prepared by wet spinning. Compared with the prior art of directly treating chitosan fibers after crosslinking, the steps involved in this invention are simpler and more practical. Furthermore, the introduction of the crosslinking agent does not adversely affect the performance of the chitosan fibers, and it has good acid resistance.

[0027] Second, in this invention, chitosan raw materials are dissolved using an alkali / urea solvent, rather than the traditional method of dissolving chitosan raw materials with dilute acid aqueous solution. This allows for pre-spinning crosslinking. The crosslinking mechanism is a ring-opening etherification reaction, not the traditional Schiff base reaction. In the alkali / urea solvent system, a crosslinking agent with an epoxy structure is used, which reacts with the hydroxyl groups on the chitosan molecular chain. This not only achieves pre-spinning crosslinking but also ensures that the final fiber's performance is not adversely affected. In contrast, in existing technologies (such as CN103993380A), crosslinking chitosan using glutaraldehyde (and oxidized sodium alginate, genipin) in an acidic system cannot achieve pre-spinning crosslinking, and the resulting chitosan fibers show a significant decrease in elongation and strength.

[0028] Third, in step X1 of this invention, chitosan with a viscosity of 450-550 mPa·s and a degree of deacetylation of 87.2% is selected as the raw material. On the one hand, this is suitable for subsequent processes and control conditions, such as the solubility in the corresponding solvent, i.e., the effect on the spinning solution; on the other hand, it ensures the strength and functionality of the final product - chitosan fiber. The viscosity of the raw material reflects the molecular weight of chitosan, which not only has a significant impact on the strength of the fiber, but also affects the solubility of chitosan, while the degree of deacetylation is related to the antibacterial properties of the fiber.

[0029] An alkali / urea solvent system was selected to ensure effective dissolution of chitosan and improve the stability of the solution. The alkali / urea solvent system dissolves macromolecules primarily by breaking the hydrogen bonds between them. Low temperatures not only facilitate the swelling of macromolecules in an alkaline environment but also further enhance the breaking of hydrogen bonds. Excessive temperature leads to insufficient chitosan dissolution, resulting in a spinning solution with poor solubility and uniformity, causing difficulties in subsequent filtration and spinning, and ultimately reducing the performance of the final product. Therefore, the freezing conditions were limited to "freezing to below -30°C for 4 hours." Repeated freezing and thawing cycles (1-2 times) further improved the solubility of chitosan, resulting in a chitosan solution with a chitosan content of 3.0-3.5%, an alkali content of 13-17%, and a urea content of 8-11%, ensuring a better-dissolving spinning solution for subsequent applications.

[0030] IV. In step X2 of this invention, in order to ensure the product performance after the crosslinking reaction and the cost of the crosslinking agent, this invention selects epichlorohydrin or polyethylene glycol diglycidyl ether, preferably epichlorohydrin with a simpler structure. The crosslinking agent that does not participate in the crosslinking reaction will enter the subsequent coagulation bath, and therefore, it will be separated in the coagulation bath.

[0031] Furthermore, the cross-linking reaction is further specified as "at -5℃ with stirring for 15 minutes." Conducting the cross-linking reaction at a low temperature effectively prevents the chitosan solution from directly cross-linking and solidifying, thus avoiding gelation. If the temperature is too high, the chitosan solution will rapidly undergo a cross-linking reaction, leading to gelation and making subsequent spinning impossible. Stirring ensures the cross-linking agent is evenly dispersed in the chitosan solution; insufficient stirring time will result in uneven cross-linking.

[0032] Furthermore, controlling the amount of crosslinking agent with epoxy structure added to 1 / 1000 to 1 / 100 of the chitosan mass ensures the degree of crosslinking of the chitosan solution, thus achieving better acid resistance. If the amount of crosslinking agent added is too small, the degree of crosslinking of the chitosan fiber will be low, meaning its acid resistance will be poor, and the fiber elongation and wet strength will also be low. On the other hand, if the amount of crosslinking agent added is too large, there may be unreacted crosslinking agent, which not only wastes the crosslinking agent, but also allows the unreacted crosslinking agent to enter the coagulation bath during subsequent water washing, affecting the regeneration of the coagulation bath and generating some wastewater. The treatment of this wastewater containing crosslinking agent may also increase the treatment cost.

[0033] 5. In step X3 of this invention, since tiny bubbles are generated during the stirring process of the crosslinking reaction, and the viscosity of the chitosan solution also increases, degassing is required. Furthermore, a high degassing speed is required; based on the equipment's operating capacity, a centrifugal speed of ≥10000 rpm is adopted. In addition, limiting the centrifugal degassing time achieves better degassing results, which is beneficial for subsequent spinning processes. If the centrifugation time is too short, degassing will be insufficient, leading to filament separation and breakage during subsequent spinning; if the centrifugation time is too long, it will increase equipment operating costs. Similarly, temperature control ensures the stability of the gel solution; if the centrifugation temperature is too high, the pre-gelled solution may gel during centrifugation.

[0034] The impurities involved in filtration and impurity removal include dust, insoluble substances in raw materials, and undissolved gel particles. If filtration and impurity removal are not carried out, it will affect the subsequent spinning, reduce the spinnability, and even cause filament separation and breakage during the spinning process.

[0035] Furthermore, since the pregel solution obtained after the crosslinking reaction accelerates the gelation rate at high temperatures, spinning cannot proceed once gelation occurs. Its gelation rate is slower and more stable at low temperatures; therefore, the storage temperature is controlled to ≤5℃. Temperatures above this will shorten the effective storage time of the pregel solution, and excessively high temperatures can also lead to direct gelation.

[0036] Using a filter screen with a pore size of 15μm can intercept smaller impurities, ensuring thorough removal and improving filtration efficiency, which is beneficial for subsequent spinning. If impurities are not fully removed during filtration, it will significantly impact the spinning process, and may even cause filament breakage and splitting.

[0037] VI. In step Y of this invention, controlling the spinning speed to 5-10 m / min ensures effective forming of the chitosan fibers and prevents filament breakage. Limiting the total draw to 15-25% improves the performance of the chitosan fibers. In this preparation process, below this draw condition will reduce fiber strength but will not affect spinning (draw can be 0%); however, above this draw condition will cause filament breakage during the draw process.

[0038] Furthermore, the spinning bath contains 5-10 wt% citric acid and 15-20 wt% sodium citrate. When the citric acid and the alkali in the chitosan solution undergo a neutralization reaction, the reaction is relatively mild and the reaction rate is slow, which helps to form chitosan fibers.

[0039] Furthermore, the limitation of "spinning bath temperature of 30-60℃ and filament immersion length of 500-1000 mm" ensures that the pre-gelling solution achieves the desired gelation effect. Temperature affects the diffusion rate of molecules in the coagulation bath, thus influencing fiber regeneration and shaping. Immersion length ensures the filament can be fully regenerated and shaped in the coagulation bath. A shorter immersion length will result in insufficient reaction during the shaping process, affecting filament performance; a longer immersion length may cause complete fiber coagulation, potentially impacting subsequent drawing processes and thus filament performance. Additionally, an excessively long immersion length can cause the filament to carry away too much acid from the coagulation bath, affecting subsequent washing processes and potentially leading to insufficient washing.

[0040] VII. In this invention, the chitosan molecular chains in the prepared chitosan fibers have chemical cross-linking effects, thus exhibiting acid resistance under acidic conditions, which is of great significance for their practical application in the textile and apparel industry. Attached Figure Description

[0041] Figure 1 The diagram shows the state of the samples in the comparative examples and examples in hydrochloric acid aqueous solution at pH=2 (where a is the sample in comparative example 1, and bd are the samples in examples 1-3 respectively). Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] 35 g of chitosan raw material with a viscosity of 450 mPa·s was dispersed in 965 g of a mixed aqueous solution containing 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea to obtain a chitosan dispersion. The chitosan dispersion was frozen to -30°C for 4 h until it was completely frozen. Then, it was thawed by mechanical stirring. After 1 to 2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 3.5 wt% and a viscosity of 25300 mPa·s was obtained. The solution was then degassed by centrifugation at 10000 rpm for 10 minutes at 5°C. 1 g of epichlorohydrin, a crosslinking agent, was added to the degassed solution, and a crosslinking reaction was carried out at -5℃ with a stirring time of 15 min and a stirring speed of 300 rpm, resulting in a pregel solution with a viscosity of 31700 mPa·s. The pregel solution after the crosslinking reaction was centrifuged to remove bubbles and filtered through a 15 μm filter screen to obtain the spinning solution for spinning. The spinning solution was pressurized and passed through a spinning machine spinneret with a diameter of 0.078 mm × 30 orifices into a coagulation bath for coagulation. The coagulation bath consisted of a 5 wt% citric acid / 15 wt% sodium citrate aqueous solution, with a bath temperature of 35℃, a spinning speed of 8 m / min, and a draw of 20%. The regenerated fibers were then drawn, washed, oiled, and dried to obtain chitosan fibers.

[0045] The chitosan fiber prepared in this embodiment has a fineness of 1.41 dtex, a dry breaking strength of 1.46 cN / dtex, a dry breaking elongation of 7.6%, a wet breaking strength of 0.73 cN / dtex, and a wet breaking elongation of 15.1%.

[0046] Example 2

[0047] Based on Example 1, the difference between this example and Example 1 is that the amount of crosslinking agent added to the chitosan solution is 10 g, while the other process conditions and equipment used are the same as in Example 1, and will not be repeated here.

[0048] The chitosan fiber prepared in this embodiment has a fineness of 1.37 dtex, a dry breaking strength of 1.56 cN / dtex, a dry breaking elongation of 7.8%, a wet breaking strength of 0.74 cN / dtex, and a wet breaking elongation of 19.7%.

[0049] Example 3

[0050] Based on Example 1, the difference between this example and Example 1 is that the amount of crosslinking agent added to the chitosan solution is 20 g, while the other process conditions and equipment used are the same as in Example 1, and will not be repeated here.

[0051] The chitosan fiber prepared in this embodiment has a fineness of 1.44 dtex, a dry breaking strength of 1.52 cN / dtex, a dry breaking elongation of 7.9%, a wet breaking strength of 0.78 cN / dtex, and a wet breaking elongation of 22.2%.

[0052] Example 4

[0053] Based on Example 2, the difference between this example and Example 2 is that the spinning speed is 5 meters / minute and the draft is 25%. Other processes and equipment used are the same as in Example 2, and will not be repeated here.

[0054] The chitosan fiber prepared in this embodiment has a fineness of 1.51 dtex, a dry breaking strength of 1.58 cN / dtex, a dry breaking elongation of 7.7%, a wet breaking strength of 0.76 cN / dtex, and a wet breaking elongation of 18.1%.

[0055] Example 5

[0056] Based on Example 2, the difference between this example and Example 2 is that the coagulation bath includes 5 wt% citric acid and 10 wt% sodium citrate aqueous solution. Other processes and equipment used are the same as in Example 2, and will not be repeated here.

[0057] The chitosan fiber prepared in this embodiment has a fineness of 1.43 dtex, a dry breaking strength of 1.49 cN / dtex, a dry breaking elongation of 7.4%, a wet breaking strength of 0.72 cN / dtex, and a wet breaking elongation of 18.9%.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that no cross-linking agent was added to the chitosan solution. Other process conditions and equipment used are the same as in Example 1, and will not be repeated here. Finally, uncross-linked chitosan fibers were obtained.

[0060] The chitosan fibers prepared in this comparative example have a fineness of 1.48 dtex, a dry breaking strength of 1.43 cN / dtex, a dry breaking elongation of 7.3%, a wet breaking strength of 0.61 cN / dtex, and a wet breaking elongation of 13.3%.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that no cross-linking agent was added to the chitosan solution. Instead, the obtained uncross-linked chitosan fibers were immersed in a 1 wt% glutaraldehyde solution, and after a cross-linking reaction of 30 min, they were washed with water and dried. Other process conditions and equipment used were the same as in Example 1, and will not be repeated here. That is, a post-treatment cross-linking process was adopted.

[0063] The chitosan fibers prepared in this comparative example have a fineness of 1.44 dtex, a dry breaking strength of 1.21 cN / dtex, a dry breaking elongation of 5.1%, a wet breaking strength of 0.66 cN / dtex, and a wet breaking elongation of 8.7%.

[0064] The chitosan fibers obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests, including: an acid resistance evaluation test of the chitosan fibers, i.e., immersing the chitosan fibers in a 0.05wt% acetic acid aqueous solution and observing whether dissolution occurred. The results are shown in Table 1 below. Figure 1 As shown.

[0065] Table 1 Performance test results of chitosan fiber

[0066] Table 1 Performance test results of chitosan fiber

[0067]

[0068] Therefore, it can be seen that the addition of cross-linking agent can effectively improve the acid resistance of chitosan fiber, while also having a certain impact on the fiber's performance.

[0069] In conclusion, the following conclusions can be drawn:

[0070] I. By comparing Examples 1-3 and Comparative Example 1, it can be seen that: 1) The addition of crosslinking agent can increase the acid resistance of the fiber. Chitosan fibers without pre-spinning crosslinking cannot exist stably in acid solutions and will dissolve; 2) As the amount of crosslinking agent increases, the acid resistance of the fiber will also improve. When the amount of crosslinking agent added is low, the fiber will partially dissolve in acid solutions; 3) The addition of crosslinking agent can significantly improve the strength and elongation of the fiber in the wet state, but has little effect on the strength and elongation of the fiber in the dry state. In addition, the improvement effect of crosslinking agent on chitosan fiber decreases with the increase of crosslinking agent dosage, which also indicates that the amount of crosslinking agent added in the preparation process of chitosan fiber is not necessarily better the more it is added.

[0071] II. By comparing Examples 2, 4, and 5, it can be seen that: 1) Adjusting the spinning speed and draw ratio will affect the final performance of chitosan fibers. Lowering the spinning speed and increasing the draw ratio can improve the strength of the fibers to a certain extent, but the elongation of the fibers will also decrease; 2) Changes in the composition of the coagulation bath will also affect the final performance of chitosan fibers. Sodium citrate in the coagulation bath helps to slow down the fiber regeneration rate and improve the fiber strength.

[0072] III. By comparing Example 2 and Comparative Examples 1-2, it can be seen that: 1) Regardless of whether pre-spinning crosslinking or post-treatment crosslinking is used, the acid resistance of chitosan fibers is improved; 2) Chitosan fibers prepared by pre-spinning crosslinking process have improved performance compared with uncrosslinked chitosan fibers, especially in terms of strength and elongation under wet conditions; 3) Chitosan fibers prepared by post-treatment crosslinking process have significantly decreased performance compared with uncrosslinked chitosan fibers, with both dry strength and wet strength decreasing, especially the elongation decreasing more significantly.

Claims

1. A process for preparing chitosan fibers based on pre-spinning crosslinking, characterized in that, Includes the following steps: X. Preparation of spinning solution X1: Dissolve Chitosan raw material with a viscosity of 450–550 mPa·s and a degree of deacetylation of 87.2% was added to an alkali / urea solvent system and dissolved to obtain a chitosan dispersion. The chitosan dispersion was frozen and thawed, and then the freezing and thawing were repeated 1 to 2 times. After centrifugation, a chitosan solution with a viscosity of 20,000 to 30,000 mPa·s was obtained. X2: Crosslinking A crosslinking agent with an epoxy structure was added to a chitosan solution, and a crosslinking reaction was carried out at -5℃ to obtain a chitosan pregel solution with a viscosity of 30,000 to 50,000 mPa·s. The amount of crosslinking agent with epoxy structure added is 1 / 1000 to 1 / 100 of the mass of chitosan; X3: Defoaming and filtration The chitosan pregel solution was degassed and filtered, and then stored at a temperature ≤5℃ to obtain a spinning solution for spinning. Y. Spinning Spinning is carried out at a spinning speed of 5-10 m / min and a total draft of 15-25% to obtain filaments; The spinning bath contains 5-10 wt% citric acid and 15-20 wt% sodium citrate, the spinning bath temperature is 30-60℃, and the filament immersion length is 500-1000 mm. Z. Post-processing The obtained filaments are wound into bundles, then stretched, washed, oiled and dried to obtain chitosan fibers.

2. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1, characterized in that, In step X1, the alkali / urea solvent system is a KOH / LiOH / urea system.

3. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1 or 2, characterized in that, The freezing process in step X1 includes freezing the chitosan dispersion to below -30°C for 4 hours.

4. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 3, characterized in that, In step X1, the chitosan solution is controlled to have a chitosan content of 3.0-3.5%, an alkali content of 13-17%, and a urea content of 8-11%.

5. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1, characterized in that, The crosslinking process in step X2 includes: stirring the reaction for 15 minutes.

6. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1, characterized in that, In step X2, the crosslinking agent with an epoxy structure is epichlorohydrin or polyethylene glycol diglycidyl ether.

7. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1, characterized in that, In step X2, the crosslinking agent with the epoxy structure is epichlorohydrin.

8. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1, characterized in that, In step X3, the degassing process includes: centrifugal degassing at a speed of ≥10000 rpm, a degassing time of 10 min, and a degassing temperature of 5℃.

9. The process for preparing chitosan fibers based on pre-spinning crosslinking according to claim 1 or 8, characterized in that, In step X3, the filtration uses a filter screen with a pore size of 15 μm.

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