A composite chitosan fiber and a preparation method thereof

Abstract

This invention discloses a composite chitosan fiber and its preparation method. The preparation method includes: dissolving chitosan in acetic acid solution to obtain a chitosan solution; dissolving soybean protein in water to obtain a soybean protein solution; dissolving polyvinyl alcohol in water to obtain a polyvinyl alcohol solution; stirring the chitosan solution and soybean protein solution until fully mixed; then adding the polyvinyl alcohol solution, continuously stirring, and vacuum degassing to obtain a spinning solution; spinning the spinning solution, followed by coagulation bath, drawing, oiling, and drying to obtain a semi-finished fiber; and acetalizing the semi-finished fiber to obtain the composite chitosan fiber. The composite chitosan fiber of this invention has low overall cost and strong mechanical and elongation properties.

Description

Technical Field

[0001] This invention relates to the field of fiber technology, specifically to a composite chitosan fiber and its preparation method. Background Technology

[0002] Global concerns about the environment are growing daily, and bio-products have recently gained widespread popularity due to increased public attention to environmental issues. Chitosan is a product of chitin after deacetylation. Chitin is an abundant organic renewable resource in nature, mainly derived from the shells of shrimp, crabs, and other arthropods. Chitosan fiber is a functional biomass regenerated fiber with a certain strength, prepared through spinning using chitosan as the main raw material. Currently, chitosan fibers on the market have relatively low strength and are mainly used in medical and hygiene clothing. To explore new application areas, modification and blending with other polymers can effectively improve the mechanical properties of the fibers.

[0003] Chinese patent application CN112064144A discloses a nanocomposite fiber, comprising: dissolving chitosan in an aqueous acetic acid solution to prepare a chitosan solution with a concentration of 5.5%-5.9%; adding 11%-15% polyvinyl alcohol solution to the chitosan solution, mixing, ultrasonically dispersing evenly, and allowing to stand to degas to obtain a spinning solution, wherein the chitosan solution comprises 85-120 parts and the polyvinyl alcohol solution comprises 28-45 parts. The application provides the weight ratio of chitosan solution to polyvinyl alcohol solution, which yields nanocomposite fibers with smooth morphology and strong interactions. Improved process parameters enhance the spinning performance of chitosan and improve the morphology of the nanocomposite fibers; however, it cannot be wet-spun, and the resulting fiber strength is still unsatisfactory.

[0004] Chinese patent application CN105597575A discloses a bio-based biodegradable high-efficiency air filtration fiber membrane material. This air filtration fiber membrane uses bio-based high-molecular-weight soybean protein and polyvinyl alcohol as the main materials, and one or more water-soluble natural polymer derivatives such as methylcellulose, chitosan, and hydroxyethylcellulose as auxiliary materials, prepared by electrospinning. The nanofibers have a diameter of 100-1000 nm, a membrane thickness of 20 μm-100 μm, a porosity of over 65%, a pore size of 10-100 nm, and a filtration efficiency of over 90%. This bio-based biodegradable air filtration membrane can be processed for various applications such as masks, window screens, and air purifiers, and is safe, reliable, and low-cost. Furthermore, the preparation method is simple, requires minimal equipment, has low production costs, and the resulting air filtration membrane has good purification effect, strong adsorption capacity, and is biodegradable and recyclable, showing good market prospects. However, since it uses soybean protein and polyvinyl alcohol as the main materials, the fiber performance is not ideal. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a composite chitosan fiber with low overall cost, strong mechanical properties and elongation properties, and a method for preparing the same.

[0006] The present invention solves the above-mentioned technical problems through the following technical means:

[0007] A method for preparing composite chitosan fibers includes the following steps:

[0008] S1. Chitosan is dissolved in acetic acid solution to obtain chitosan solution; soybean protein is dissolved in water to obtain soybean protein solution; polyvinyl alcohol is dissolved in water to obtain polyvinyl alcohol solution;

[0009] S2. Stir the chitosan solution and soybean protein solution until they are fully mixed; then add the polyvinyl alcohol solution and continue stirring. Vacuum degassing is then performed to obtain the spinning solution.

[0010] S3. Spinning the defoamed spinning solution, followed by coagulation bath, stretching, oiling, and drying to obtain semi-finished fiber.

[0011] S4. The semi-finished fiber is acetalized to obtain the composite chitosan fiber.

[0012] Preferably, in S2, the mass ratio of chitosan in the chitosan solution, soybean protein in the soybean protein solution, and polyvinyl alcohol in the polyvinyl alcohol solution is 6.75-7.5:1-8:1-4.5.

[0013] Preferably, in step S1, the mass-to-volume ratio of chitosan to acetic acid solution is 6.75-7.5g:150-250ml; the mass-to-volume ratio of soybean protein to water is 5-10g:50-100ml; the mass-to-volume ratio of polyvinyl alcohol to water is 10-15g:100ml; the volume ratio of chitosan solution, soybean protein solution, and polyvinyl alcohol solution is 150-250:10-50:10-30; and the mass fraction of acetic acid solution is 2%.

[0014] Preferably, in S2, the mass ratio of chitosan in the chitosan solution, soybean protein in the soybean protein solution, and polyvinyl alcohol in the polyvinyl alcohol solution is 6.75:8:4.5.

[0015] Preferably, in step S2, the chitosan solution and soybean protein solution are stirred at 30-40°C until fully mixed; then, a polyvinyl alcohol solution is added, and the mixture is stirred continuously at 30-40°C for 1-5 hours until the solution viscosity no longer increases, and the solution is degassed under vacuum to obtain the spinning solution.

[0016] Preferably, in S2, the vacuum degassing time is 5-10 hours.

[0017] Preferably, in S3, the method for preparing the coagulation bath includes the following steps: weighing alkaline components to prepare an alkaline solution, dissolving sodium sulfate in the alkaline solution to obtain a mixed solution, and mixing the mixed solution with an ethanol solution to obtain a three-component coagulation bath.

[0018] Preferably, the alkaline component comprises one or a mixture of two of sodium hydroxide and sodium carbonate.

[0019] Preferably, in S4, the acetalization temperature is 55-85°C and the time is 1-2 hours; the aldehyde used for acetalization is one or a mixture of formaldehyde, acetaldehyde, propionaldehyde, and glyoxal.

[0020] Preferably, the aldehyde used in the acetalization is formaldehyde.

[0021] The present invention also proposes a composite chitosan fiber, which is prepared by the aforementioned method for preparing composite chitosan fibers.

[0022] The advantages of this invention are:

[0023] In this invention, chitosan is a typical polycationic electrolyte, and soy protein isolate is a multi-component globular protein, a typical amphoteric polyelectrolyte. It ionizes in solution and has a large number of charges on its surface, which can achieve electrostatic interaction with chitosan to form soluble self-assemblies, thus improving the stability of the system. Polyvinyl alcohol molecules have strong hydrogen bonding with chitosan molecules and can graft copolymerize with soy protein, increasing the solution viscosity. This greatly improves the stability and spinnability of the spinning solution. Moreover, soy protein is widely available and inexpensive, which can reduce production costs.

[0024] This invention provides a composite chitosan fiber containing soybean protein, polyvinyl alcohol and chitosan. Compared with pure chitosan fiber, this composite fiber has advantages such as low overall cost, enhanced fiber mechanical properties and elongation properties, and can be used in the fields of pharmaceuticals, food and textiles.

[0025] The composite chitosan fiber prepared by the method of the present invention uses chitosan as the main component, with polyvinyl alcohol and soybean protein added as auxiliary components. Through the physical and chemical combination of the three, a mixed spinning solution with higher viscosity and stability and simple spinning is obtained. It is produced by wet spinning technology and has high fiber strength. After testing, the fineness is 1-4 dtex, the dry breaking strength is 5.6-6.1 CN / dtex, and the dry breaking elongation is 10-40%. Attached Figure Description

[0026] Figure 1 The image shows the morphology of the composite fiber prepared in Example 1 of this invention under a transmission electron microscope. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0029] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0030] Chitosan in the examples and comparative examples was purchased from Jiangsu Jinke Biomedical Technology Co., Ltd., with a molecular weight of 200,000; soybean protein: food grade, purchased from Henan Wanbang Chemical Technology Co., Ltd.; polyvinyl alcohol was polyvinyl alcohol 1799, purchased from Aladdin.

[0031] Example 1

[0032] A method for preparing composite chitosan fibers includes the following steps:

[0033] (1) Preparation of spinning solution

[0034] Weigh 7.5g of chitosan powder and add it to 250ml of 2% acetic acid solution. Stir and swell for 10 minutes. Maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours. After complete dissolution, chitosan solution is obtained.

[0035] Weigh 10g of soy protein powder and add it to 100mL of water. Stir at 60℃ for 1 hour until completely dissolved to obtain a soy protein solution.

[0036] Weigh 10g of polyvinyl alcohol and add it to 100mL of water. Stir and dissolve the solution in an oil bath at 95℃ for 2 hours until completely dissolved.

[0037] Measure 50 mL of soybean protein solution and add it to the chitosan solution above. Place the mixture in a water bath at 30°C and stir for 30 minutes. After stirring until homogeneous, add 30 mL of polyvinyl alcohol solution and continue stirring for 1 hour until the blend solution is homogeneous. Place the resulting blend solution in a vacuum drying oven and degas at 40°C for 10 hours to obtain the blend spinning solution.

[0038] (2) Preparation of coagulation bath

[0039] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution to make the sodium sulfate mass fraction of 7% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0040] (3) Wet spinning

[0041] The blending spinning solution is added to a wet spinning solution tank, and spinning is performed using a 0.05mm spinneret. The fiber passes through a coagulation bath, where the solvent and coagulation bath components form a double diffusion, and the nascent fiber gradually coagulates from a gel state. It is then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules achieve a certain degree of orientation. The fiber is then washed, oiled, and dried at 85°C. After acetalization, chitosan / soybean protein / polyvinyl alcohol blended fiber is obtained, which is the composite chitosan fiber. The acetalization treatment is performed at 70°C for 1.5 hours, and formaldehyde is used as the aldehyde. Figure 1 The image shows the morphology of the composite fiber prepared in Example 1 under a transmission electron microscope.

[0042] Example 2

[0043] A method for preparing composite chitosan fibers includes the following steps:

[0044] (1) Preparation of spinning solution

[0045] Weigh 6.75g of chitosan powder and add it to 150ml of 2% acetic acid solution. Stir and swell for 10 minutes, maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours until completely dissolved to obtain chitosan solution.

[0046] Weigh 5g of soy protein powder and add it to 50mL of water. Stir at 60℃ for 1 hour until completely dissolved to obtain a soy protein solution.

[0047] Weigh 10g of polyvinyl alcohol and add it to 100mL of water. Stir and dissolve the solution in an oil bath at 95℃ for 2 hours until completely dissolved.

[0048] Measure 10 mL of soybean protein solution and add it to the chitosan solution above. Place the mixture in a water bath at 30°C and stir for 30 minutes. After stirring until homogeneous, add 10 mL of polyvinyl alcohol solution and continue stirring for 1 hour until the blend solution is homogeneous. Place the blend solution obtained at a volume ratio of chitosan solution (CS): soybean protein solution (SPI): polyvinyl alcohol solution (PVA) of 15:1:1 in a vacuum drying oven and degas at 40°C for 10 hours to obtain the blended spinning solution.

[0049] (2) Preparation of coagulation bath

[0050] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution to make the sodium sulfate mass fraction of 5% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0051] (3) Wet spinning

[0052] The blending spinning solution is added to a wet spinning solution tank, and spinning is performed using a 0.05mm spinneret. The fiber passes through a coagulation bath, where the solvent and coagulation bath components form a double diffusion, and the nascent fiber gradually coagulates from a gel state. It is then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules achieve a certain degree of orientation. The fiber is then washed, oiled, and dried at 85°C. After acetalization, chitosan / soybean protein / polyvinyl alcohol blended fiber is obtained, which is the composite chitosan fiber. The acetalization treatment is performed at a temperature of 60°C for 1 hour, and formaldehyde is used as the aldehyde.

[0053] Example 3

[0054] A method for preparing composite chitosan fibers includes the following steps:

[0055] (1) Preparation of spinning solution

[0056] Weigh 6.75g of chitosan powder and add it to 150ml of 2% acetic acid solution. Stir and swell for 10 minutes, maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours until completely dissolved to obtain chitosan solution.

[0057] Weigh 10g of soy protein powder and add it to 50mL of water. Stir at 60℃ for 1 hour until completely dissolved to obtain a soy protein solution.

[0058] Weigh 15g of polyvinyl alcohol and add it to 100mL of water. Stir and dissolve the solution in an oil bath at 95℃ for 2 hours until completely dissolved.

[0059] Measure 40 mL of soybean protein solution and add it to the chitosan solution above. Place the mixture in a water bath at 30°C and stir for 30 minutes. After stirring until homogeneous, add 30 mL of polyvinyl alcohol solution and continue stirring for 1 hour until the blend solution is homogeneous. Place the blend solution obtained at a volume ratio of CS:SPI:PVA of 15:4:3 in a vacuum drying oven and degas at 40°C for 10 hours to obtain the blend spinning solution.

[0060] (2) Preparation of coagulation bath

[0061] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution, and the mass fraction of sodium sulfate was 8% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0062] (3) Wet spinning

[0063] The blending spinning solution is added to a wet spinning solution tank, and spinning is performed using a 0.05mm spinneret. The fiber passes through a coagulation bath, where the solvent and coagulation bath components form a double diffusion, and the nascent fiber gradually coagulates from a gel state. It is then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules achieve a certain degree of orientation. The fiber is then washed, oiled, and dried at 85°C. After acetalization, chitosan / soybean protein / polyvinyl alcohol blended fiber is obtained, which is the composite chitosan fiber. The acetalization treatment is performed at 85°C for 1 hour, and formaldehyde is used as the aldehyde.

[0064] Example 4

[0065] A method for preparing composite chitosan fibers includes the following steps:

[0066] (1) Preparation of spinning solution

[0067] Weigh 7.5g of chitosan powder and add it to 150ml of 2% acetic acid solution. Stir and swell for 10 minutes, maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours until completely dissolved to obtain chitosan solution.

[0068] Weigh 10g of soy protein powder and add it to 50mL of water. Stir at 60℃ for 1 hour until completely dissolved to obtain a soy protein solution.

[0069] Weigh 10g of polyvinyl alcohol and add it to 100mL of water. Stir and dissolve the solution in an oil bath at 95℃ for 2 hours until completely dissolved.

[0070] Measure 40 mL of soybean protein solution and add it to the chitosan solution above. Place the mixture in a water bath at 30°C and stir for 30 minutes. After stirring until homogeneous, add 30 mL of polyvinyl alcohol solution and continue stirring for 1 hour until the blend solution is homogeneous. Place the blend solution obtained at a volume ratio of CS:SPI:PVA of 15:4:3 in a vacuum drying oven and degas at 40°C for 10 hours to obtain the blend spinning solution.

[0071] (2) Preparation of coagulation bath

[0072] Weigh an appropriate amount of sodium hydroxide to prepare an alkaline solution with a mass fraction of 5%, and dissolve sodium sulfate in the alkaline solution to obtain a mixed solution with a mass fraction of 7%. Mix the mixed solution with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0073] (3) Wet spinning

[0074] The blending spinning solution is added to a wet spinning solution tank, and spinning is performed using a 0.05mm spinneret. The fiber passes through a coagulation bath, where the solvent and coagulation bath components form a double diffusion, and the nascent fiber gradually coagulates from a gel state. It is then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules achieve a certain degree of orientation. The fiber is then washed, oiled, and dried at 85°C. After acetalization, chitosan / soybean protein / polyvinyl alcohol blended fiber is obtained, which is the composite chitosan fiber. The acetalization treatment is performed at 55°C for 2 hours, and formaldehyde is used as the aldehyde.

[0075] Comparative Example 1

[0076] (1) Preparation of spinning solution

[0077] Weigh 6g of chitosan powder and add it to 150ml of 2% acetic acid solution. Stir and swell for 10 minutes. Maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours. After complete dissolution, obtain chitosan solution. Place in vacuum drying oven and degas at 40℃ for 10 hours to obtain spinning solution.

[0078] (2) Preparation of coagulation bath

[0079] Weigh out an appropriate amount of sodium hydroxide and prepare a 5% (w / w) alkaline solution as a coagulation bath.

[0080] (3) Wet spinning

[0081] The spinning solution is added to a wet spinning solution tank, and spinning is performed using a 0.05mm spinneret. The fiber passes through a coagulation bath, where the solvent and coagulation bath components form a double diffusion, and the nascent fiber gradually coagulates from a gel state. It is then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules reach a certain degree of orientation. Finally, the fiber is washed, oiled, and dried at 85℃ to obtain pure chitosan fiber.

[0082] Comparative Example 2

[0083] A method for preparing composite chitosan fibers includes the following steps:

[0084] (1) Preparation of spinning solution

[0085] Chitosan was dissolved in an aqueous solution of acetic acid with a mass fraction of 2% to prepare a chitosan solution with a mass concentration of 5.5%. A polyvinyl alcohol solution with a mass fraction of 11% was added to the chitosan solution and mixed. The mixture was then ultrasonically dispersed and allowed to stand to remove bubbles to obtain a spinning solution. The volume ratio of the chitosan solution to the polyvinyl alcohol solution was 120:28.

[0086] (2) Preparation of coagulation bath

[0087] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution to make the sodium sulfate mass fraction of 5% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0088] (3) Wet spinning

[0089] The spinning solution is added to the wet spinning solution tank, and spinning is carried out using a 0.05mm spinneret. The fiber passes through the coagulation bath, where the solvent and coagulation bath components form a double diffusion, preventing the nascent fiber from fully coagulating and further stretching.

[0090] Comparative Example 3

[0091] A method for preparing composite chitosan fibers includes the following steps:

[0092] (1) Preparation of spinning solution

[0093] 1.68 g of soy protein, 0.46 g of chitosan, 0.46 g of hydroxyethyl cellulose, and 0.46 g of polyvinyl alcohol were dissolved in 20 ml of acetic acid aqueous solution (water volume V / acetic acid volume V = 8 / 2). The solution was stirred to obtain a homogeneous polymer solution. The soy protein accounted for 55 wt% of the total solute, chitosan for 15 wt%, hydroxyethyl cellulose for 15 wt%, and polyvinyl alcohol for 15 wt%. The total solute to solvent ratio was 0.153 g / mL.

[0094] (2) Preparation of coagulation bath

[0095] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution to make the sodium sulfate mass fraction of 5% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0096] (3) Wet spinning

[0097] The polymer solution was added to a wet spinning solution tank, and spinning was performed using a 0.05mm spinneret. The fibers passed through a coagulation bath, where the solvent and coagulation bath components formed a double diffusion process, causing the nascent fibers to gradually coagulate from a gel state. The fibers were then dehydrated by salting out with a 20% sodium chloride solution. After two drawing processes with a draw ratio of 1.25, the fiber macromolecules achieved a certain degree of orientation. The fibers were then washed, oiled, and dried at 85°C. Finally, an acetalization treatment was performed to obtain chitosan / soybean protein / polyvinyl alcohol blend fibers. The acetalization treatment was conducted at 55°C for 2 hours, using formaldehyde as the aldehyde.

[0098] Comparative Example 4

[0099] (1) Preparation of spinning solution

[0100] Weigh 4g of chitosan powder and add it to 150ml of 2% acetic acid solution. Stir and swell for 10 minutes, maintain 30℃ and mechanically stir under nitrogen atmosphere for 2 hours until completely dissolved to obtain chitosan solution.

[0101] Weigh 5g of soy protein powder and add it to 50mL of water. Stir at 60℃ for 1 hour until completely dissolved to obtain a soy protein solution.

[0102] Weigh 10g of polyvinyl alcohol and add it to 100mL of water. Stir and dissolve the solution in an oil bath at 95℃ for 2 hours until completely dissolved.

[0103] Measure 10 mL of soybean protein solution and add it to the chitosan solution above. Place the mixture in a water bath at 30°C and stir for 30 minutes. After stirring until homogeneous, add 10 mL of polyvinyl alcohol solution and continue stirring for 1 hour until the blend solution is homogeneous. Place the blend solution obtained at a volume ratio of CS:SPI:PVA of 15:1:1 in a vacuum drying oven and degas at 40°C for 10 hours to obtain the blend spinning solution.

[0104] (2) Preparation of coagulation bath

[0105] Sodium hydroxide was weighed and prepared into an alkaline solution with a mass fraction of 5%. Sodium sulfate was dissolved in the alkaline solution to make the sodium sulfate mass fraction of 5% to obtain a mixed solution. The mixed solution was then mixed with a 95% ethanol solution at a volume ratio of 1:1 to obtain a three-component coagulation bath.

[0106] (3) Wet spinning

[0107] The blending spinning solution is added to the wet spinning solution tank, and spinning is carried out using a 0.05mm spinneret. The fiber passes through the coagulation bath, where the solvent and coagulation bath components form a double diffusion, preventing the nascent fiber from fully coagulating and further stretching.

[0108] Test method:

[0109] The properties of the fibers in the examples and comparative examples were determined using a single-fiber strength tester, as shown in the table below:

[0110]

[0111] As shown in the table above, the composite chitosan fiber prepared by the method of the present invention has better performance than pure chitosan fiber.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing composite chitosan fibers, characterized in that: Includes the following steps: S1. Chitosan is dissolved in acetic acid solution to obtain chitosan solution; soybean protein is dissolved in water to obtain soybean protein solution; polyvinyl alcohol is dissolved in water to obtain polyvinyl alcohol solution; S2. Stir the chitosan solution and soybean protein solution until they are fully mixed; then add the polyvinyl alcohol solution and continue stirring. Vacuum degassing is then performed to obtain the spinning solution. The mass ratio of chitosan in the chitosan solution, soybean protein in the soybean protein solution, and polyvinyl alcohol in the polyvinyl alcohol solution is 6.75-7.5:1-8:1-4.5; S3. Spinning the defoamed spinning solution, followed by coagulation bath, stretching, oiling, and drying to obtain semi-finished fiber. S4. The semi-finished fiber is acetalized to obtain the composite chitosan fiber.

2. The method for preparing composite chitosan fibers according to claim 1, characterized in that: In S1, the mass-to-volume ratio of chitosan to acetic acid solution is 6.75-7.5g:150-250ml; the mass-to-volume ratio of soybean protein to water is 5-10g:50-100ml; the mass-to-volume ratio of polyvinyl alcohol to water is 10-15g:100ml; the volume ratio of chitosan solution, soybean protein solution, and polyvinyl alcohol solution is 150-250:10-50:10-30; and the mass fraction of acetic acid solution is 2%.

3. The method for preparing composite chitosan fibers according to claim 1, characterized in that: In S2, the mass ratio of chitosan in the chitosan solution, soybean protein in the soybean protein solution, and polyvinyl alcohol in the polyvinyl alcohol solution is 6.75:8:4.

5.

4. The method for preparing composite chitosan fibers according to claim 1, characterized in that: In S2, the chitosan solution and soybean protein solution are stirred at 30-40℃ until fully mixed; then polyvinyl alcohol solution is added, and the mixture is stirred continuously at 30-40℃ for 1-5 hours until the solution viscosity no longer increases. Vacuum degassing is then performed to obtain the spinning solution.

5. The method for preparing composite chitosan fibers according to claim 1, characterized in that: In S2, the vacuum degassing time is 5-10 hours.

6. The method for preparing composite chitosan fibers according to claim 1, characterized in that: In S3, the preparation method of the coagulation bath includes the following steps: weighing alkaline components to prepare an alkaline solution, dissolving sodium sulfate in the alkaline solution to obtain a mixed solution, and mixing the mixed solution with an ethanol solution to obtain a three-component coagulation bath.

7. The method for preparing composite chitosan fibers according to claim 6, characterized in that: The alkaline component includes one or a mixture of two of sodium hydroxide and sodium carbonate.

8. The method for preparing composite chitosan fibers according to any one of claims 1-7, characterized in that: In S4, the acetalization temperature is 55-85℃ and the time is 1-2 hours; the aldehyde used for acetalization is one or a mixture of formaldehyde, acetaldehyde, propionaldehyde, and glyoxal.

9. A composite chitosan fiber, characterized in that: It is prepared by the method of any one of claims 1-8 for preparing composite chitosan fibers.

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