A method for efficiently preparing chitosan fiber materials

Abstract

This invention relates to the technical field of natural polymers and polymer materials, specifically to a method for efficiently preparing chitosan fiber materials, comprising the following steps: preparing an aqueous solution of KOH, NaOH, or a mixture thereof with a mass concentration of 25 wt% or higher to obtain an alkaline aqueous solution; adding chitosan to the alkaline aqueous solution, stirring to disperse and soaking to obtain an aqueous solution of chitosan / KOH complex, chitosan / NaOH complex, or chitosan / KOH / NaOH complex; adding ice or an ice-water mixture to the obtained solution, stirring until completely dissolved to obtain a chitosan spinning solution; spinning the obtained chitosan spinning solution, and then solidifying it in a coagulation bath to obtain chitosan fiber materials. This invention can improve the dissolution rate of chitosan, achieve dissolution of chitosan at room temperature, is simple to operate, and is suitable for large-scale production. The obtained chitosan fibers are non-toxic and harmless, and have good biodegradability and biocompatibility.

Description

Technical Field

[0001] This invention relates to the technical field of natural polymers and polymer materials, and specifically to a method for efficiently preparing chitosan fiber materials. Background Technology

[0002] Chitosan is produced by deacetylation of chitin. Chitin is the second most abundant natural polymer after cellulose, and it is widely found in chitinous animals such as crab and shrimp shells. It has also been found in squid, earthworms, and some fungi. Due to its excellent broad-spectrum antibacterial properties, biocompatibility, biodegradability, adsorption, film-forming properties, permeability, and hygroscopic properties, chitosan is widely used in biomedicine, food hygiene, and textiles. Furthermore, chitosan also has certain fiber-forming properties. Utilizing this property, it can be dissolved in a suitable solvent to prepare a spinning solution of a certain concentration, which can then be solidified to obtain chitosan fibers. Currently, organic acids (acetic acid, formic acid) and inorganic acids are often used to dissolve chitosan, and alkaline solutions, alcoholic solutions or aqueous solutions are used as coagulation baths. Chitosan fibers are then prepared by stretching, washing and drying. However, these methods have problems such as cumbersome and time-consuming operation, unsatisfactory safety and non-toxicity, and poor mechanical properties of chitosan fibers, which limit the widespread application of chitosan fibers.

[0003] Studies have shown that different alkali metal hydroxides have a good dissolving effect on chitin, and these alkali metal hydroxides also exhibit unique dissolving abilities for chitosan, such as KOH, NaOH, and LiOH. LiOH / KOH / urea aqueous solution can dissolve chitosan by a single freeze-thaw cycle (Duan, J., et al., Macromolecules (2015) 48(8), 2706). If the KOH / urea aqueous solution is controlled at a specific concentration (approximately 16 wt% KOH / 8 wt% urea), chitosan can be completely dissolved by continuous stirring at -5°C for 3 hours, resulting in a transparent chitosan solution (Zhang, Q., et al., Materials Today (2021) 51, 27). This dissolution method is simple to operate and has certain industrialization potential.

[0004] It is worth noting that although chitosan can dissolve in KOH / urea aqueous solution without freezing and thawing, its dissolution temperature is still below 0°C (above the freezing point). This low-temperature condition results in high costs and high energy consumption, hindering economic efficiency. Therefore, increasing the dissolution temperature of chitosan would significantly reduce the cost and energy consumption associated with low-temperature dissolution, making industrial production possible. Maintaining a rapid dissolution rate and efficiency while increasing the temperature, and preparing a high-concentration chitosan solution suitable for subsequent processing, presents a significant challenge for current alkaline chitosan solution systems. The inventors' earlier patents CN109721740A and CN110964129A used a high-temperature deacetylation method to prepare chitin or chitosan with a high degree of deacetylation. Then, by diluting the alkaline solution with water, they could dissolve chitin or chitosan in a one-pot process without separation. However, during the dissolution process, although the dissolution temperature was above the freezing point, it was still relatively low and required the addition of stabilizers such as urea.

[0005] Because my country started its research on the preparation and functionality of chitosan fibers relatively late, there are still some problems with the spinning technology: the difficulty of the chitosan spinning industry lies in obtaining a stable and uniform spinning solution and a suitable coagulation bath. According to existing reports on wet spinning, chitosan fibers are mostly blended fibers, while pure chitosan fibers cannot realize their economic value due to their poor strength. For example, chitosan solution is obtained by using acetic acid and urea aqueous solution as solvents, and chitosan fibers are prepared by using sodium hydroxide / ethanol aqueous solution as coagulation bath. The chitosan fibers obtained by this method have very low wet strength, making it difficult to stretch and process them. Their dry strength is only 1.98 cN / dtex at most. In addition, there are reports on dissolving chitosan with ionic liquids and spinning them, but the cost is too high, and the quality of dissolved chitosan is also limited, resulting in a relatively low fiber strength (0.8 cN / dtex), and it also faces many problems such as environmental pollution (Kuznik, I., et al., Polymers (2022) 14 (3)). In their previously filed patent CN110129923A, the inventors used a high-temperature deacetylation method to prepare chitin or chitosan with different degrees of deacetylation. Then, by diluting the alkaline solution with water, they were able to dissolve the chitin or chitosan in a one-pot process without separation, producing chitin / chitosan fibers with different degrees of deacetylation. However, the dissolution temperature remained relatively low (around -20°C), requiring the addition of stabilizers such as urea. From an industrial perspective, the power of refrigeration equipment increases as the refrigeration temperature decreases, leading to high costs and energy consumption under these stringent low-temperature conditions. In large-scale production, the refrigeration capacity is enormous, and even a slight increase in the chitosan dissolution temperature can significantly reduce energy consumption. Therefore, increasing the chitosan dissolution temperature would significantly reduce the cost and energy consumption associated with low-temperature dissolution, making industrial production possible. Maintaining a rapid dissolution rate and efficiency while increasing the temperature, and producing a high-concentration chitosan solution suitable for subsequent spinning, are currently significant challenges in preparing chitosan fibers using alkaline solution systems. Summary of the Invention

[0006] The purpose of this invention is to provide an efficient method for preparing chitosan fiber materials, which reduces energy consumption and improves efficiency in the chitosan membrane preparation process. This method promotes the utilization of natural chitosan materials and is simple and suitable for large-scale production.

[0007] The solution adopted by this invention to achieve its objective is: a method for efficiently preparing chitosan fiber materials, comprising the following steps:

[0008] (1) Prepare an aqueous solution of KOH, NaOH or a mixture thereof with a mass concentration of 25 wt% or higher to obtain an alkaline aqueous solution;

[0009] (2) Add chitosan to the alkaline aqueous solution of step (1), stir to disperse and soak to obtain an aqueous solution of chitosan / KOH complex or chitosan / NaOH complex or chitosan / KOH / NaOH complex;

[0010] (3) Add ice or ice-water mixture to the solution obtained in step (2) and stir until completely dissolved to obtain chitosan spinning solution;

[0011] (5) The obtained chitosan spinning solution is spun and then solidified in a coagulation bath to obtain chitosan fiber material.

[0012] Preferably, in step (1), when the alkali solution is a KOH aqueous solution, the concentration is 30wt%-60wt%, and when the alkali solution is a NaOH aqueous solution, the concentration is 25wt%-50wt%.

[0013] The concentrations of KOH and NaOH in step (1) determine the stirring temperature required to obtain chitosan / KOH, chitosan / NaOH, or chitosan / KOH / NaOH complexes in step (2). Higher concentrations of KOH and NaOH in step (1) result in a higher lower limit for the stirring temperature in step (2), lower requirements for refrigeration equipment, and lower energy consumption. When the KOH concentration in step (1) is higher than 40 wt% and the NaOH concentration is higher than 35 wt%, chitosan / KOH, chitosan / NaOH, or chitosan / KOH / NaOH complexes can be formed with chitosan at 10℃ and above.

[0014] In step (2), after adding chitosan, stirring and dispersing at 60°C for more than 1 minute yields chitosan / KOH, chitosan / NaOH, or chitosan / KOH / NaOH complexes. The stirring temperature determines the stirring time. The higher the stirring temperature, the shorter the time required to form the complex. Since temperatures above 30°C require the use of heating equipment, and after generating chitosan / KOH, chitosan / NaOH, or chitosan / KOH / NaOH complexes at high temperatures, cooling equipment is needed to lower the system temperature below the gelation temperature to prevent the chitosan solution from gelling. Therefore, operating at near room temperature is more energy-efficient. Preferably, in step (2), the stirring temperature is below 0–10°C, and the stirring time is more than 10 minutes.

[0015] After adding the ice or ice-water mixture in step (3), the mass concentration of KOH and NaOH in the resulting mixture should not be less than 5 wt%. The concentration of KOH and NaOH affects the stability of the chitosan solution. If the concentration of KOH and NaOH is too high or too low, the chitosan solution will gel too quickly at room temperature. Preferably, after adding the ice or ice-water mixture in step (3), the mass concentration of KOH and NaOH in the resulting mixture is 12 wt% to 20 wt%, which makes the chitosan solution more stable.

[0016] Before step (4), the obtained chitosan spinning solution is filtered and degassed. The degasing methods include centrifugal degasing, depressurized static degasing, and continuous degasing.

[0017] Preferably, in step (3), after adding ice or an ice-water mixture, the mass concentration of alkali in the chitosan spinning solution is 5wt%-20wt%.

[0018] Preferably, in step (3), the mass concentration of chitosan in the chitosan spinning solution is 2wt% to 12wt%.

[0019] The source and crystal form of the chitosan raw material are not limited. It can be a product obtained by deacetylation of α-chitin, β-chitin, γ-chitin, regenerated chitin, etc., or it can be low molecular weight chitosan obtained through degradation. The mass concentration of chitosan in the spinning solution is related to the molecular weight of chitosan. The upper limit of the soluble chitosan mass concentration is related to the molecular weight of chitosan. The lower the molecular weight, the higher the concentration of soluble chitosan. However, both excessively low and excessively high chitosan concentrations will affect the mechanical properties of the prepared chitosan fibers.

[0020] Preferably, in step (4), the spinning method includes wet spinning and dry-jet wet spinning.

[0021] Preferably, the spinning process involves passing the chitosan spinning solution through a spinneret with a diameter of 0.05–0.3 mm and then solidifying it into filaments in a coagulation bath at a temperature below the gelation temperature of the chitosan solution for 1–100 seconds.

[0022] Preferably, in step (4), the coagulation bath is a single coagulation bath or a multi-stage coagulation bath, and the coagulation bath is a mixed solution of one or two of water, alcohol, and salt; the concentration of alcohol in the coagulation bath is 0wt% to 100wt%, and the concentration of salt is 0wt% to 60wt%.

[0023] Preferably, the alcohol is selected from at least one of methanol and ethanol, and the salt is selected from at least one of potassium salt, sodium salt, magnesium salt, chloride salt, acetate, nitrate, sulfate, carbonate, and citrate.

[0024] In this invention, the solvent and coagulation bath components are recyclable, and the recycling technology is mature and reliable. The entire process is simple, convenient, safe, environmentally friendly, requires low investment, and is inexpensive, making it suitable for industrial production.

[0025] In the preparation process of the chitosan fiber material, the chitosan spinning solution is coagulated into fibers in a coagulation bath at a temperature below the chitosan gelation temperature. The gelation temperature of the chitosan solution varies depending on the solvent composition, the source of chitosan, and the concentration of the chitosan solution. The temperature of the coagulation bath is between -10℃ and 60℃, preferably between 0℃ and 50℃.

[0026] During the preparation of chitosan fibers, the nascent chitosan fibers can be pre-stretched in the coagulation bath. Multiple coagulation baths supplement the coagulation and pre-stretching functions, making the coagulation and shaping of chitosan fibers more complete, which is beneficial for subsequent stretching and improves the performance of the fibers.

[0027] In the preparation of chitosan fibers, the draw ratio obtained by a single draw is limited, so two or more draws can be used to increase the draw ratio. The draw process can include multiple draw stages such as hot water, boiling water, and steam draw, and can be interleaved with oiling and drying steps. This helps to prevent internal defects in the fiber caused by over-drawing, improves the density of the fiber structure, and further orients the molecules inside the fiber, thereby further improving the mechanical properties of the fiber.

[0028] In the preparation process of the chitosan fiber, the washing process can use multiple washing treatments to gradually remove the solvent from the fiber and reduce the internal voids of the fiber.

[0029] During the preparation of the chitosan fiber, common drying methods can be used, such as natural drying, hot roller drying, and hot air drying.

[0030] Preferably, functional organic or inorganic additives, low-dimensional nanomaterials, natural polymers or synthetic polymers may be introduced during the preparation process; the functional organic or inorganic additives, low-dimensional nanomaterials, natural polymers or synthetic polymers are added through spinning solution or through coagulation bath.

[0031] Preferably, the functional organic or inorganic additive is selected from at least one of plasticizers, reinforcing agents, refractory additives, dyes, optical stabilizers, antibacterial and bacteriostatic agents, conductive materials, and surfactants; the low-dimensional nanomaterial is selected from at least one of graphene and its derivatives, polypyrrole, polyaniline, carbon nanotubes and their derivatives, metal or metal oxide nanoparticles, organic framework compounds, and layered nanomaterials.

[0032] Preferably, the natural or synthetic polymer is selected from at least one of polymer nanofibers, cellulose and its derivatives, chitin, animal protein, plant protein, collagen, alginate, conductive polymers, polyethylene glycol, and polyvinyl alcohol.

[0033] This invention does not limit the source or crystal form of chitosan. The chitosan raw material used for dissolving can be the deacetylated product of α-chitin, β-chitin, γ-chitin, regenerated chitin, etc., or it can be low molecular weight chitosan obtained by degradation. The mass concentration of chitosan in the spinning solution is related to the molecular weight of chitosan.

[0034] The present invention has the following advantages and beneficial effects:

[0035] (1) This invention prepares chitosan / KOH, chitosan / NaOH, or chitosan / KOH / NaOH complexes by mixing chitosan with high-concentration KOH aqueous solution, NaOH aqueous solution, or a mixture of the two. These complexes dissolve in ice or an ice-water mixture within minutes, yielding a transparent chitosan spinning solution. The method of this invention not only improves the dissolution rate of chitosan but also enables the dissolution of chitosan at room temperature, resulting in a high-concentration, high-quality chitosan spinning solution. This significantly reduces energy consumption during chitosan fiber preparation, improves the production efficiency of chitosan fiber materials, and is simple to operate, making it particularly suitable for large-scale production.

[0036] (2) The chitosan fibers obtained by the preparation method of the present invention have excellent mechanical properties, which can reach or even exceed those of chitosan fibers prepared by traditional acid dissolution, alkaline solution, alcohol solution or aqueous solution as coagulation bath. At the same time, the obtained chitosan fibers are non-toxic and harmless, and have good degradability and biocompatibility. Attached Figure Description

[0037] Figure 1 The diagram shows the mechanical properties of the chitosan fiber prepared in Example 11, and compares it with commercially available chitosan fibers. Detailed Implementation

[0038] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0039] Unless otherwise specified, the following examples are taken at room temperature, and the chitosan is obtained by deacetylation of α-chitin.

[0040] Example 1

[0041] Prepare a 20g KOH aqueous solution with a mass concentration of 25wt%, add 3g of chitosan derived from shrimp shells, and stir at 30℃ for 5min to obtain a chitosan / KOH complex. Then add 80g ice with a KOH concentration of 5wt%, stir for 5min until the chitosan is completely dissolved. After centrifugation and degassing, a transparent chitosan spinning solution is obtained. Chitosan fiber is prepared from this chitosan solution using a wet spinning process. The chitosan solution is spun into a 20℃ 50wt% ethanol / 2wt% sodium citrate aqueous solution under a pressure of 0.2MPa through a spinneret with a diameter of 0.3mm to solidify into filaments. The solidification bath has a length of 100cm. After removing chemical reagents with deionized water, the obtained filaments are oiled and dried to obtain chitosan fiber. The mechanical properties of the prepared chitosan fiber are tested, and its tensile strength is approximately 90-100MPa, and its elongation at break is approximately 10-15%.

[0042] Example 2

[0043] A 40g KOH aqueous solution with a mass concentration of 30wt% was prepared, and 4g of chitosan derived from crab shells was added. The mixture was stirred at 0℃ for 5 minutes to obtain a chitosan / KOH complex. Then, 60g of an ice-water mixture with a KOH concentration of 12wt% was added, and the mixture was stirred for 10 minutes until the chitosan was completely dissolved. After filtration and settling to remove bubbles, a transparent chitosan spinning solution was obtained. Chitosan fibers were prepared from this chitosan solution using a wet spinning process. The chitosan solution was spun into a 20℃ 50wt% ethanol / 4wt% sodium citrate aqueous solution under a pressure of 0.2MPa through a 0.3mm orifice to solidify into filaments. The solidification bath length was 100cm. After removing chemical reagents with deionized water, the resulting filaments were oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 100–110MPa, and their elongation at break was approximately 12–15%.

[0044] Example 3

[0045] A 40g KOH aqueous solution with a mass concentration of 40wt% was prepared, and 2g of chitosan derived from squid capsid was added. The mixture was stirred at 5℃ for 10min to obtain a chitosan / KOH complex. Then, 60g of ice (KOH concentration of 16wt%) was added, and the mixture was stirred for 20min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 20℃ 75wt% ethanol / 2wt% sodium citrate aqueous solution under a pressure of 0.2MPa through a 0.3mm orifice to solidify into filaments. The solidification bath length was 100cm. After removing chemical reagents with deionized water, the resulting filaments were oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 110–130MPa, and their elongation at break was approximately 14–16%.

[0046] Example 4

[0047] A 40g solution of 50wt% KOH was prepared, and 6g of chitosan was added. The mixture was stirred at 20℃ for 20min to obtain a chitosan / KOH complex. Then, 60g of an ice-water mixture with a KOH concentration of 20wt% was added, and the mixture was stirred for 20min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 30℃ 60wt% potassium acetate / 25wt% ethanol aqueous solution under a pressure of 0.2MPa through a 0.26mm orifice to solidify into filaments. The solidification bath had a depth of 100cm. The resulting filaments were then treated with deionized water to remove chemical reagents, oiled, and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 120–130MPa, and their elongation at break was approximately 14–17%.

[0048] Example 5

[0049] A 40g solution of 50wt% NaOH was prepared, and 7g of chitosan was added. The mixture was stirred at 10℃ for 40min to obtain a chitosan / NaOH complex. Then, 60g of ice (20wt% NaOH) was added, and the mixture was stirred for 30min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 50℃ 20wt% magnesium chloride aqueous solution under a pressure of 0.2MPa through a 0.26mm orifice to solidify into filaments. The solidification bath length was 100cm. The resulting filaments were cleaned with deionized water to remove chemical reagents, then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and the tensile strength was approximately 130–140MPa, and the elongation at break was approximately 18–22%.

[0050] Example 6

[0051] A 32g solution of 50wt% KOH was prepared, and 7g of chitosan was added. The mixture was stirred at 15°C for 30 minutes to obtain a chitosan / KOH complex. Then, 68g of ice (16wt% KOH concentration) was added, and the mixture was stirred for 30 minutes until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 10°C 50wt% ethanol / 40wt% potassium carbonate mixed solution under a pressure of 0.2MPa through a 0.26mm orifice to solidify into filaments. The solidification bath was 100cm long. The resulting filaments were cleaned with deionized water to remove chemical reagents, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and the tensile strength was approximately 140–150MPa, and the elongation at break was approximately 16–20%.

[0052] Example 7

[0053] A 33.3g KOH aqueous solution with a mass concentration of 60wt% was prepared, and 10g chitosan was added. The mixture was stirred at 5℃ for 30min to obtain a chitosan / KOH complex. Then, 66.7g ice (KOH concentration of 20wt%) was added, and the mixture was stirred for 30min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 40℃ 75wt% ethanol / 20wt% sodium sulfate mixed solution under a pressure of 0.2MPa through a 0.2mm orifice to solidify into filaments. The solidification bath distance was 100cm. The resulting filaments were cleaned with deionized water to remove chemical reagents, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and the tensile strength was approximately 165–185MPa, and the elongation at break was approximately 13–16%.

[0054] Example 8

[0055] A 40g solution of 50wt% KOH was prepared, and 12g of degraded low molecular weight chitosan was added. The mixture was stirred at 5°C for 60min to obtain a chitosan / KOH complex. Then, 60g of ice (20wt% KOH concentration) was added, and the mixture was stirred for 60min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 45wt% sodium acetate aqueous solution at 40°C under a pressure of 0.2MPa through a 0.2mm orifice to solidify into filaments. The solidification bath was 100cm long. The resulting filaments were cleaned with deionized water to remove chemical reagents, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and the tensile strength was approximately 160–175MPa, and the elongation at break was approximately 14–17%.

[0056] Example 9

[0057] Prepare a 32g (50wt%) NaOH aqueous solution, add 8g chitosan, and stir at 5℃ for 30min to obtain a chitosan / NaOH complex. Then add 68g ice (16wt%), stir for 30min until the chitosan is completely dissolved, and centrifuge to remove bubbles to obtain a transparent chitosan solution. This chitosan solution is then used to prepare chitosan fibers via a wet spinning process. The chitosan solution is spun into filaments at 20℃ in a 40wt% sodium citrate aqueous solution under a pressure of 0.2MPa through a 0.2mm orifice. The coagulation bath has a length of 100cm. After passing through a second alcohol-water mixed solution, the resulting filaments are treated with deionized water to remove chemical reagents, then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers are tested; the tensile strength is approximately 160–180MPa, and the elongation at break is approximately 12–16%.

[0058] Example 10

[0059] Prepare a 32g KOH aqueous solution with a mass concentration of 50wt%, add 7g chitosan, and stir at 5℃ for 30min to obtain a chitosan / KOH complex. Then add 68g ice, with a KOH concentration of 16wt%, and stir for 30min until the chitosan is completely dissolved. After centrifugation and degassing, a transparent chitosan solution is obtained. This chitosan solution is used to prepare chitosan fibers through a wet spinning process. The chitosan solution is spun into filaments through a 0.2mm orifice at 0.2MPa and then into a 15℃ 45wt% potassium carbonate aqueous solution at a coagulation bath length of 100cm. A second coagulation bath of 15℃ 25wt% potassium carbonate aqueous solution is then used. After removing chemical reagents with deionized water, the resulting filaments are drawn to a draw ratio of 1-2, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the chitosan fibers prepared above were tested, and their tensile strength was approximately 180–360 MPa, and their elongation at break was approximately 12–16%.

[0060] Example 11

[0061] Prepare a 32g KOH aqueous solution with a mass concentration of 50wt%, add 8g chitosan to it, and stir at 10℃ for 20min to obtain a chitosan / KOH complex. Then add 68g ice, with a KOH concentration of 16wt%, and stir for 30min until the chitosan is completely dissolved. After centrifugation and degassing, a transparent chitosan solution is obtained. This chitosan solution is used to prepare chitosan fibers through a wet spinning process. The chitosan solution is spun into filaments through a 0.2mm orifice at 0.2MPa pressure into a 40℃ 20wt% potassium chloride aqueous solution at a coagulation bath length of 100cm. The filaments then pass through a 40℃ 10wt% potassium chloride aqueous solution as a second coagulation bath. After removing chemical reagents with deionized water, the draw ratio is 1-2. Finally, after oiling and drying, chitosan fibers are obtained. The mechanical properties of the chitosan fibers prepared above were tested, and their tensile strength was approximately 240–400 MPa, and their elongation at break was approximately 10–13%. Figure 1 As shown, the chitosan fiber prepared in this embodiment with a draw ratio of 1.6 has superior mechanical properties compared to commercially available chitosan fibers.

[0062] Example 12

[0063] A 30g KOH / NaOH mixed solution with a mass concentration of 40wt% was prepared, and 4g of chitosan was added. The mixture was stirred at 20℃ for 10min to obtain a chitosan / KOH / NaOH complex. Then, 70g of ice (12wt% alkali concentration) was added, and the mixture was stirred for 10min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 40℃ 20wt% magnesium chloride aqueous solution under a pressure of 0.2MPa through a spinneret with a diameter of 0.2mm to solidify into filaments. The coagulation bath was 100cm long. After passing through a second alcohol-water mixed solution, the resulting filaments were treated with deionized water to remove chemical reagents. The draw ratio was 1–2. After oiling and drying, chitosan fibers were obtained. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 120–250MPa, and their elongation at break was approximately 5–12%.

[0064] Example 13

[0065] A 30g KOH / NaOH mixed solution with a mass concentration of 50wt% was prepared, and 5g of chitosan was added. The mixture was stirred at 20℃ for 10min to obtain a chitosan / KOH / NaOH complex. Then, 70g of ice (15wt% alkali concentration) was added, and the mixture was stirred for 10min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 15℃ methanol solution under a pressure of 0.2MPa through a 0.2mm orifice to solidify into filaments. The solidification bath length was 100cm. The resulting filaments were treated with deionized water to remove chemical reagents, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 120–145MPa, and their elongation at break was approximately 12–18%.

[0066] Example 14

[0067] A 32g solution of 50wt% KOH was prepared, and 7g of chitosan was added. The mixture was stirred at 10℃ for 20min to obtain a chitosan / KOH complex. Then, 68g of ice (16wt% KOH concentration) was added, and the mixture was stirred for 30min until the chitosan was completely dissolved. After centrifugation and degassing, a transparent chitosan solution was obtained. This chitosan solution was used to prepare chitosan fibers via a wet spinning process. The chitosan solution was spun into a 60℃ aqueous solution under a pressure of 0.2MPa through a 0.2mm orifice to solidify into filaments. The solidification bath length was 100cm. The resulting filaments were cleaned with deionized water to remove chemical reagents, and then oiled and dried to obtain chitosan fibers. The mechanical properties of the prepared chitosan fibers were tested, and their tensile strength was approximately 60–90MPa, and their elongation at break was approximately 8–12%.

[0068] Example 15

[0069] Prepare a 32g KOH aqueous solution with a mass concentration of 50wt%, add 7g chitosan, and stir at 20℃ for 10min to obtain a chitosan / KOH complex. Then add 68g ice, making the KOH concentration 16wt%, and simultaneously add 3g polypyrrole, stir for 30min until the chitosan is completely dissolved. After centrifugation and degassing, obtain a chitosan solution containing polypyrrole. This chitosan solution is used to prepare chitosan fibers through a wet spinning process. The chitosan solution is spun into a 10℃ 50wt% potassium carbonate aqueous solution under a pressure of 0.2MPa through a spinneret with a diameter of 0.2mm to solidify into filaments. The solidification bath has a length of 100cm. After removing chemical reagents with deionized water, the resulting filaments are oiled and dried to obtain functional chitosan fibers. The mechanical properties of the chitosan fibers prepared above were tested, and their tensile strength was about 150-170 MPa and their elongation at break was about 16-20%. At the same time, the fibers have certain electrical conductivity and photothermal conversion properties, and are expected to be applied in the fields of sensors, capacitors, and electrode materials.

[0070] Comparative Example 1

[0071] Prepare 100g of 50wt% KOH aqueous solution, add 6g of chitosan to it, and stir at 20℃ for 5h. The chitosan does not dissolve.

[0072] Comparative Example 2

[0073] Prepare 32g of 50wt% KOH aqueous solution, add 6g of chitosan to it, stir at 5℃ for 30min, and after the system cools to room temperature, add 68g of room temperature water and stir for 30min. Only part of the chitosan dissolves.

[0074] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for efficiently preparing a chitosan fiber material, characterized by, The method comprises the following steps: (1) preparing an aqueous alkali solution with a mass concentration of 25 wt% or above, wherein the aqueous alkali solution is prepared by using KOH, NaOH or a mixture of KOH and NaOH; (2) adding chitosan to the aqueous alkali solution prepared in step (1) to obtain a chitosan / KOH complex, a chitosan / NaOH complex or a chitosan / KOH / NaOH complex; (3) adding ice or an ice-water mixture to the solution obtained in step (2) to obtain a chitosan spinning dope; (4) spinning the chitosan spinning dope obtained in step (3) and then solidifying the chitosan spinning dope in a coagulation bath to obtain a chitosan fiber material. In step (1), when the aqueous alkali solution is KOH, the concentration of KOH is 30 wt%-60 wt%; when the aqueous alkali solution is NaOH, the concentration of NaOH is 25 wt%-50 wt%. In step (3), after the ice or the ice-water mixture is added, the mass concentration of the alkali in the chitosan spinning dope is 5 wt%-20 wt%; the mass concentration of chitosan in the chitosan spinning dope is 2 wt%-12 wt%.

2. The method of claim 1, wherein the method is efficient for the preparation of chitosan fibrous material. In step (4), the spinning method comprises wet spinning and dry-jet wet spinning.

3. The method of efficiently preparing chitosan fibrous material according to claim 1, characterized by: In step (4), the coagulation bath is a single coagulation bath or a multi-stage coagulation bath, and the coagulation bath is prepared by using water, an alcohol or a salt or a mixture of water, the alcohol and the salt; the concentration of the alcohol in the coagulation bath is 0 wt%-100 wt%, and the concentration of the salt in the coagulation bath is 0 wt%-60 wt%.

4. The method of efficiently producing chitosan fiber material according to claim 3, characterized by: The alcohol is at least one selected from the group consisting of methanol and ethanol, and the salt is at least one selected from the group consisting of potassium salt, sodium salt, magnesium salt, chloride, acetate, nitrate, sulfate, carbonate and citrate.

5. The method for efficiently preparing chitosan fiber material according to any one of claims 1 to 4, characterized by: Functional organic or inorganic additives, low-dimensional nanomaterials, natural polymers or synthetic polymers are introduced during the preparation process; the functional organic or inorganic additives, the low-dimensional nanomaterials, the natural polymers or the synthetic polymers are added to the chitosan spinning dope or the coagulation bath.

6. The method of efficiently producing chitosan fiber material according to claim 5, characterized by: The functional organic or inorganic additives are at least one selected from the group consisting of plasticizers, reinforcing agents, fireproof material additives, dyes, optical stabilizers, antibacterial and bacteriostatic agents, conductive materials and surfactants; the low-dimensional nanomaterials are at least one selected from the group consisting of graphene, polypyrrole, polyaniline, carbon nanotubes, metal or metal oxide nanoparticles, organic framework compounds and layered nanomaterials.

7. The method of efficiently producing chitosan fiber material according to claim 5, characterized by: The natural polymers or the synthetic polymers are at least one selected from the group consisting of high-molecular nanofibers, cellulose, chitin, animal proteins, plant proteins, collagen, alginates, conductive polymers, polyethylene glycol and polyvinyl alcohol.

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