A method for preparing chitosan polyelectrolyte composite fiber

Abstract

The present invention discloses a method for preparing chitosan polyelectrolyte composite fibers, and belongs to the technical field of preparation, processing and application of natural polymer fibers. The present invention adopts an alkaline solvent to dissolve the raw material chitosan. In the alkaline solvent, chitosan shows electrical neutrality and can stably coexist with negatively charged polymers to obtain a uniform and stable mixed solution; a cross-linking agent is added to the mixed solution to obtain a pre-gel solution that can be used for spinning; and then wet spinning is used to regenerate in an acidic coagulation bath to obtain a chitosan-based polyelectrolyte composite fiber. Since the fiber is constructed by hydrogen bond interaction, electrostatic interaction and chemical cross-linking between chitosan and polyanions, the fiber also has the advantages of both chitosan and polyanions, thereby providing a prerequisite for expanding the application range of chitosan polyelectrolyte composite fibers.

Description

Technical Field

[0001] The present invention specifically relates to a method for preparing chitosan polyelectrolyte composite fibers, and belongs to the technical field of preparation, processing and application of natural polymer fibers. Background Art

[0002] Polyelectrolyte complexes (PECs) are macromolecular complexes formed by electrostatic interactions between two oppositely charged polyelectrolytes. In recent years, natural polymer polyelectrolytes derived from renewable biomass resources have been widely used in biomedicine, drug delivery, textiles, and apparel due to their excellent biocompatibility, biodegradability, strong electrostatic interactions, and chelating properties.

[0003] Chitosan (CS) is a positively charged polyelectrolyte that is readily soluble in dilute aqueous acid solutions. It possesses inherent advantages such as good biocompatibility, biodegradability, and nontoxicity. Due to the numerous amino groups in its molecular chain, chitosan can be combined with negatively charged natural polymers such as sodium alginate, hyaluronic acid, carrageenan, and carboxymethyl cellulose through electrostatic interactions to construct polyelectrolyte composites. The most widely used method involves alternately depositing chitosan and polyanions via electrostatic layer-by-layer assembly (LBL) to produce composites such as multilayer films, microcapsules, and core-shell hybrid nanoparticles. However, LBL is not suitable for preparing fiber materials because it requires a uniform spinning solution. In acidic solutions, the protonated amino groups of chitosan carry a large positive charge, which causes flocculation and phase separation when coexisting with polyanions. Consequently, a uniform and stable solution cannot be obtained, making spinning impossible.

[0004] The prior art, "CN108102150A: A Chitosan-Based Polyelectrolyte Composite," aims to address the problem of conventional chitosan-based polyelectrolyte composites, resulting in irregular, flocculent, and non-uniform products, which impact their effectiveness. However, the resulting slurry-like semi-soluble mixture is essentially a dispersion of chitosan powder in a polyanion solution. Due to the significant heterogeneity of chitosan powder particles, uniform dispersion in the polyanion solution is difficult. Furthermore, the subsequent release of acidic gases from the acid solution also makes it difficult to achieve uniform dissolution of the chitosan powder in the polyanion solution. This is because the reaction takes a long time (24 hours) for the gas to penetrate the solution after contact with the surface. Furthermore, upon contact with the acidic liquid, the -NH3 residues on the chitosan molecular chain are immediately protonated, causing the chitosan to dissolve. The dissolved chitosan then immediately combines with the polyanion through electrostatic interactions to form a polyelectrolyte complex. This resulting polyelectrolyte complex, in turn, prevents further contact between the acidic solution and the chitosan, making uniformity difficult throughout the reaction. The resulting hydrogel is only macroscopically uniform; microscopically, it still exhibits a phase-separated structure, resulting in low mechanical strength. The overall preparation process is time-consuming, making it unsuitable for industrial production. The semi-soluble slurry mixture involved cannot be filtered before spinning, making it impossible to prepare composite fibers. "CN102634040A: An alkaline solvent for dissolving chitosan and a method for dissolving chitosan under alkaline conditions" uses a NaOH / urea / cellulose aqueous solution as the solvent. First, the NaOH / urea solvent system cannot be used to prepare a high-concentration chitosan solution unless a very low-molecular-weight chitosan raw material is used, but the technical solution does not provide a detailed description of the raw material. Second, the solvent system contains another high-molecular-weight component, cellulose, so the resulting solution is not a pure chitosan solution, but rather a mixed solution of chitosan and cellulose. The alkaline solvent in "CN101215341 A kind of alkaline solvent for dissolving chitosan and its use" is suitable for dissolving chitosan powder with a deacetylation degree of 40-70% and a molecular weight of 200,000-600,000, but is not suitable for dissolving chitosan raw materials with a high deacetylation degree (deacetylation degree > 80%).

[0005] Therefore, although the prior art discloses the use of alkaline solvent systems: NaOH / urea / cellulose aqueous solution and NaOH / potassium hydroxide aqueous solution for dissolving chitosan, they all have certain limitations, such as the inability to dissolve chitosan raw materials with a high degree of deacetylation and the inability to obtain a uniform and stable pure chitosan solution. Summary of the Invention

[0006] In order to solve the problems of uneven spinning solution, flocculation and phase separation in the preparation of composite fibers using chitosan as raw material, a method for preparing chitosan polyelectrolyte composite fibers was proposed.

[0007] In this technical solution, the raw chitosan is dissolved in an alkaline solvent. In this alkaline solvent, chitosan exhibits electrical neutrality, allowing it to stably coexist with negatively charged polymers, resulting in a uniform, stable mixed solution. A crosslinking agent is added to the mixed solution to obtain a pregel solution suitable for spinning. This solution is then regenerated by wet spinning in an acidic coagulation bath to produce a chitosan-based polyelectrolyte composite fiber. Because this composite fiber is constructed through hydrogen bonding interactions, electrostatic interactions, and chemical crosslinking between chitosan and polyanions, it combines the advantages of both chitosan and polyanions, providing a prerequisite for expanding the application range of chitosan-polyelectrolyte composite fibers.

[0008] In order to achieve the above technical objectives, the following technical solutions are proposed:

[0009] A method for preparing chitosan polyelectrolyte composite fiber

[0010] 1. Spinning solution preparation

[0011] 1) Adding a chitosan raw material having a viscosity of 450-550 mPa.s and a degree of deacetylation of 87.2% to an alkali-urea aqueous solution and thoroughly mixing to obtain a chitosan dispersion; freezing the chitosan dispersion to below -30°C for 4 hours; then thawing and dissolving the chitosan dispersion by mechanical stirring at room temperature; repeating this freeze-thaw cycle 1-2 times; and centrifuging to obtain a transparent chitosan solution having a chitosan content of 3.0-4.0%, an alkali content of 13-17% (KOH content of 6-8%, LiOH content of 7-9%), and a urea content of 8-11%;

[0012] Chitosan with a viscosity of 450-550 mPa.s and a degree of deacetylation of 87.2% was selected as the raw material. This not only adapts to subsequent process steps and control conditions, such as solubility in the corresponding solvent, which affects the spinning solution, but also ensures the strength and functionality of the final product, the chitosan polyelectrolyte composite fiber. The viscosity of the raw material reflects the molecular weight of the chitosan and significantly affects not only the fiber's strength but also its solubility. The degree of deacetylation, on the other hand, is related to the antibacterial properties of the composite fiber. The degree of deacetylation is determined by the ratio of amino groups to acetylamino groups on the chitosan molecular chain. Different bases have different affinities for amino and acetylamino groups on chitosan. For example, LiOH has a higher affinity for amino groups, so a higher degree of deacetylation in the chitosan raw material increases the LiOH content in the solvent. KOH, on the other hand, has a higher affinity for acetylamino groups, so a lower degree of deacetylation in the chitosan raw material increases the KOH content in the solvent. The types and proportions of components in the solvent corresponding to chitosan raw materials with different deacetylation degrees may be different. Therefore, the present invention controls the chitosan solution to have a chitosan content of 3.0-4.0%, an alkali content of 13-17% (KOH content of 6-8%, LiOH content of 7-9%), and a urea content of 8-11%, which is just suitable for dissolving the chitosan raw material.

[0013] An alkali-urea aqueous solution, specifically KOH / LiOH / urea aqueous solution, is used to ensure effective dissolution of chitosan while improving the stability of the solution. Alkali-urea aqueous solution dissolves macromolecules primarily by disrupting hydrogen bonds between macromolecules. Low temperatures not only facilitate the swelling of macromolecules in an alkaline environment, but also facilitate the disruption of hydrogen bonds. If the temperature is too high, the chitosan will not dissolve fully, and a spinning solution with good solubility and uniformity cannot be obtained, which will cause difficulties in subsequent filtration and spinning, and the performance of the final product will also be reduced. Therefore, the freezing conditions are limited to "freezing below -30°C for 4 hours." And "repeating the freezing and thawing cycle 1 to 2 times" uses a secondary dissolution method to further enhance the solubility of chitosan. That is, the chitosan solution with a chitosan content of 3.0-4.0%, an alkali content of 13-17%, and a urea content of 8-11% is controlled to obtain, and the subsequent spinning solution with better dissolution effect is guaranteed. Only on the basis of ensuring the full dissolution of chitosan can the stability of the subsequent spinning process and the quality of the product be guaranteed;

[0014] 2) adding the negatively charged natural polymer to an alkali-urea aqueous solution and stirring to dissolve the polymer to obtain a polyanion solution having a mass percentage of 4.0-5.0%;

[0015] The negatively charged natural polymer is one or a mixture of any two or more natural polyelectrolytes such as carboxymethyl cellulose and its potassium and sodium salts, alginic acid and its potassium and sodium salts;

[0016] For the alkali-urea aqueous solution, the same alkali-urea aqueous solution as in step 1) is selected, specifically a KOH / LiOH / urea aqueous solution, to ensure the consistency of the solvent system and avoid gelation of chitosan due to inconsistent system components during mixing of the two solutions, thereby preventing the formation of a uniform and stable mixed solution. The polyanion solution is controlled to have a 4.0-5.0% by weight percentage to ensure that the viscosity of the polyanion solution is not significantly different from that of the chitosan solution. This ensures that the viscosity of the solution system does not change significantly after mixing the two solutions.

[0017] Furthermore, the type of negatively charged polymer is selected to ensure the performance requirements of the final composite fiber. This patent mainly provides a method for preparing polyelectrolyte composite fibers, so no special restrictions are imposed. The selection of natural polyanions is mainly to ensure that the final composite fiber is a natural bio-based fiber. If synthetic polyanions are used, the biological properties of the fiber will be lost.

[0018] 3) mixing the obtained chitosan solution with the obtained polyanion solution, stirring them thoroughly, and controlling the chitosan concentration to be 3.0-4.0 wt % and the polyanion concentration to be 4.0-5.0 wt % to obtain a mixed solution;

[0019] In principle, the higher the concentration of chitosan solution and polyanion solution, the better, so that the performance of the resulting composite fiber will be better. However, if the concentration of the mixed solution is too high, it will cause difficulties in subsequent filtration and will also affect the spinnability. Therefore, on the basis of ensuring the normal progress of the subsequent spinning process, the mixed solution with a chitosan concentration of 3.0-4.0wt% and a polyanion concentration of 4.0-5.0wt% is controlled. If the concentration of the mixed solution is too low, it will affect the performance of the final product (such as strength, elongation, etc.), and will also affect the spinning process, resulting in the occurrence of splitting and breaking of the yarn.

[0020] 4) adding a crosslinking agent (specifically a crosslinking agent with an epoxy structure, such as epichlorohydrin, polyethylene glycol diglycidyl ether, etc., preferably epichlorohydrin) to the mixed solution, stirring, and performing a crosslinking reaction at -5°C for 20 minutes to obtain a composite pregel solution for spinning with a viscosity of 25,000 to 35,000 mPa.s; wherein the weight ratio of the chitosan solution to the polyanion solution is greater than 0.5:1, and the amount of the crosslinking agent added is 10 to 30% of the total weight of the chitosan and polyanion;

[0021] The crosslinking reaction primarily targets the hydroxyl groups on the chitosan and polyanion chains. To ensure product performance after the crosslinking reaction and minimize crosslinker costs, the present invention uses epichlorohydrin or polyethylene glycol diglycidyl ether. Epichlorohydrin, with its simpler structure, is preferred as it better adapts to the alkaline solvent system (alkali-urea aqueous solution) used in the crosslinking reaction. This produces a stable composite pre-gel solution without gelling. Any crosslinker not involved in the crosslinking reaction will enter the subsequent coagulation bath and must therefore be separated from the coagulation bath.

[0022] Furthermore, it is further limited to "cross-linking and stirring the reaction at -5°C for 20 minutes". The cross-linking reaction is carried out at a low temperature to effectively prevent the mixed solution from directly cross-linking and curing, which leads to the phenomenon of gelation. For example, if the cross-linking reaction temperature is too high, the chitosan solution will undergo a rapid cross-linking reaction, resulting in solution gelation, and subsequent spinning will be impossible. Among them, the limitation of the cross-linking reaction time allows the cross-linking agent to be evenly dispersed in the chitosan solution. If the cross-linking time is not sufficient, it will lead to uneven cross-linking, which will affect the performance of the final product. If the cross-linking time is too long, it will increase the energy consumption of the equipment. At the same time, if the system temperature rises during the cross-linking process, it will also lead to gelation.

[0023] In addition, the amount of cross-linking agent added is controlled to be 10-30% of the sum of the weights of chitosan and polyanion to ensure the cross-linking degree of the chitosan solution, that is, to achieve better performance of the final product. If the amount of cross-linking agent added is too small, the degree of cross-linking of the chitosan fiber will be low, which means that the performance of the composite fiber will be poor, and the elongation and wet strength of the fiber will be low; and if the amount of cross-linking agent added is too large, there may be unreacted cross-linking agent, which will not only cause waste of cross-linking agent, but also the unreacted cross-linking agent will enter the coagulation bath during the subsequent water washing process, which will affect the regeneration of the coagulation bath, and will also produce a certain amount of wastewater. The treatment of this wastewater containing cross-linking agent may also increase a certain treatment cost.

[0024] 5) Degassing and filtering the pregel solution, wherein the filter screen size is 15 μm, and after filtering and removing impurities, the resulting solution is stored in a low-temperature storage tank with a jacket, and the solution temperature is controlled to be ≤5°C (the jacket is passed through 5°C condensate), to obtain a composite spinning solution;

[0025] The centrifugal degassing method is used, and the centrifugal degassing conditions include: temperature -5 to 10°C, speed 8000 to 10000 rpm, time 5 to 10 minutes;

[0026] Since tiny bubbles will be generated during the stirring process of the cross-linking reaction and the viscosity of the chitosan solution will also increase, degassing treatment is required. In addition, the degassing speed is required to be high. According to the operating capacity of the equipment, a centrifugal speed of 8000 to 10000 rpm is used. In addition, the limitation of the centrifugal degassing time can achieve a better degassing effect, which is beneficial to the subsequent spinning process. If the centrifugation time is too short, the degassing will be insufficient, and the subsequent spinning will be prone to splitting and breaking of the yarns; if the centrifugation time is too long, the operating cost of the equipment will increase. Similarly, the temperature limitation ensures the stability of the glue solution. If the centrifugal temperature is too high, the pre-gel solution will gel during the centrifugation process, etc., so that a stable spinning solution cannot be obtained;

[0027] Impurities involved in filtration and impurity removal include dust, insoluble matter in raw materials, and incompletely dissolved gel particles. If filtration and impurity removal are not performed, subsequent spinning will be affected, causing spinnability to deteriorate and even causing yarn splitting and breakage during the spinning process.

[0028] Furthermore, the pre-gel solution obtained after the cross-linking reaction will accelerate the gelation rate at high temperatures. Once gelation occurs, spinning cannot be carried out. The gelation rate is slow at low temperatures and is relatively stable. Therefore, the storage temperature should be controlled at ≤5°C. If it is higher than this temperature, the effective storage time of the pre-gel solution will be shortened. In addition, excessively high temperatures will directly cause gelation.

[0029] The use of a filter with a pore size of 15μm can intercept smaller impurities, ensure that the impurities are fully removed, improve the filtration effect, and facilitate subsequent spinning. If the impurities are not fully removed during filtration, it will have a significant impact on the spinning process and may even cause the yarn to split or break due to the impurities.

[0030] 2. Spinning

[0031] Equipment: Use a nozzle that is resistant to acid and alkali corrosion, such as a large-hole yellow platinum nozzle (30 holes) with a nozzle diameter of 0.078 mm. The nozzle material is platinum:gold = 4:6;

[0032] Control conditions: spinning speed 3-8 m / min, total draft 5-10%;

[0033] Spinning bath: citric acid content 5-10 wt%, sodium citrate content 10-15 wt%, spinning bath temperature 25-50°C, filament length 800-1000 mm;

[0034] Control the "spinning speed of 3 to 8 meters per minute" to ensure the effective molding of chitosan fibers and prevent the breakage of the yarns. For example, if the spinning speed is too low, the production efficiency will be low and the production cost will be high; if the spinning speed is too high, it will lead to splitting and breaking of the yarns. Generally, the spinning speed should be increased as much as possible while ensuring the stability of the spinning process. Limiting the "total draft of 5 to 10%" can improve the performance of chitosan fibers. In this preparation process, if the draft is lower than this condition, the fiber strength will be reduced, but it will have no effect on spinning (the draft can be 0%); but if the draft is higher than this condition, the yarns will break during the drafting process.

[0035] In addition, the spinning bath includes 5-10 wt% citric acid and 10-15 wt% sodium citrate. When the citric acid reacts with the alkali in the chitosan solution to neutralize the reaction, the reaction is relatively mild and the reaction rate is slow, which is conducive to the formation of chitosan composite fibers. In addition, the limitation of "the spinning bath temperature is 25-50 ° C, and the filament immersion length is 800-1000 mm" ensures that the pre-gel solution achieves the gelation effect. Among them, the temperature will affect the diffusion rate of molecules in the coagulation bath, which has a certain impact on the regeneration and molding of the fiber; the immersion length ensures that the filament can be fully regenerated and molded in the coagulation bath. If the immersion length is too short, the filament will not react sufficiently during the molding process, affecting the filament performance; if the immersion length is too long, the fiber may be completely coagulated, which may affect the subsequent drawing process, thereby affecting the filament performance. In addition, too long an immersion length will also cause the filament to take away more acid from the coagulation bath, which will affect the subsequent water washing process, that is, it may cause insufficient water washing;

[0036] Finally, the spun filaments are wound into tows through a winding device, and then drawn, washed, oiled and dried to obtain chitosan-polycomposite fibers.

[0037] The beneficial technical effects brought about by adopting this technical solution are:

[0038] 1. The wet spinning method used in the present invention to prepare chitosan polyelectrolyte composite fibers is a brand-new preparation process, and there are no similar reports so far. Among them, the use of alkaline solvents to dissolve chitosan solves the problem that chitosan cannot stably coexist with negatively charged polymers in an acidic solvent system. The dissolution mechanism is to cause dissolution by destroying the hydrogen bonds between the molecular chains, and the -NH3 on the chitosan molecular chain does not undergo protonation. Therefore, in this system, chitosan itself does not carry any charge and exhibits an electrically neutral property. In the alkaline solvent, it has good blending compatibility and can be simply physically blended with negatively charged polymers to obtain a uniform and stable pre-gel solution, which is then filtered through a filter to obtain a spinning solution with good spinnability, and composite fibers are prepared by wet spinning;

[0039] Second, the chitosan polyelectrolyte composite fiber prepared by the present invention has a structure after molding that is maintained by electrostatic interactions, hydrogen bonding, and chemical crosslinking between chitosan and negatively charged polymers. Therefore, it has the advantages of both chitosan and polyanions, which can expand the application range of chitosan polyelectrolyte composite fibers and is of great significance for its practical application in the field of textiles and clothing.

[0040] 3. The chitosan polyelectrolyte composite fiber prepared by the present invention has more practical application value than other forms of polyelectrolyte composite materials such as membranes, hydrogels, microspheres, etc.

[0041] 4. The chitosan composite fiber prepared by the present invention is a natural bio-based regenerated fiber with better skin affinity and will not harm human health. It can be used not only in the field of textiles and clothing, but also in the fields of skin care (such as facial masks), and has good industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The mixed solution is obtained by mixing the chitosan solution and the carboxymethyl cellulose solution in Example 1 of the present invention;

[0043] Figure 2 This is a scanning electron microscope surface image of the chitosan-carboxymethyl cellulose composite fiber prepared in Example 1 of the present invention;

[0044] Figure 3 This is a scanning electron microscope cross-sectional view of the chitosan-carboxymethyl cellulose composite fiber prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0045] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. It is obvious that the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0046] Example 1

[0047] 1. Disperse 35 g of chitosan raw material with a viscosity of 450 mPa.s in 965 g of an alkaline solvent (comprising 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea) to obtain a chitosan dispersion. Freeze the chitosan dispersion to -30°C for 4 hours until it is completely frozen. Then, thaw it using mechanical stirring. After 1-2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 4.0 wt% is obtained.

[0048] 2. Disperse 40 g of carboxymethyl cellulose powder in 960 g of an alkaline solvent (including 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea), stir and dissolve uniformly at room temperature to obtain 1000 g of a 4.0 wt% carboxymethyl cellulose solution;

[0049] 3. Mix 900 g of chitosan solution with 100 g of carboxymethyl cellulose solution and stir evenly to obtain a mixed solution (such as Figure 1 );

[0050] 4. Add 10 g of epichlorohydrin dropwise to the mixed solution and stir at -5°C for 20 minutes. Centrifuge the solution at 8000 rpm at -5°C for 5 minutes to degas, and filter to obtain the spinning solution for spinning.

[0051] 5. The spinning solution is pressurized and passed through a spinning machine spinneret with a diameter of 0.078 mm and 30 holes, and then enters a coagulation bath for coagulation. The coagulation bath composition includes 5 wt% citric acid and 10 wt% sodium citrate aqueous solution. The bath temperature is 35°C, the spinning speed is 3 m / min, and the draft is 5%. The regenerated fiber is drafted, washed, oiled, and dried to obtain chitosan-carboxymethyl cellulose composite fiber (such as Figure 2-3 shown).

[0052] The indicators involved in the chitosan-carboxymethyl cellulose composite fiber include: fineness of 1.21 dtex, dry breaking strength of 1.52 cN / dtex, dry breaking elongation of 11.6%, and water absorption of 14 g / g.

[0053] Example 2

[0054] 1. Disperse 35 g of chitosan raw material with a viscosity of 450 mPa.s in 965 g of an alkaline solvent (comprising 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea) to obtain a chitosan dispersion. Freeze the chitosan dispersion to -30°C for 4 hours until it is completely frozen. Then, thaw it using mechanical stirring. After 1-2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 4.0 wt% is obtained.

[0055] 2. Disperse 40 g of carboxymethyl cellulose powder in 960 g of an alkaline solvent (including 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea), stir and dissolve uniformly at room temperature to obtain 1000 g of a 4.0 wt% carboxymethyl cellulose solution;

[0056] 3. Mix 800 g of chitosan solution with 200 g of carboxymethyl cellulose solution and stir evenly to obtain a mixed solution;

[0057] 4. Add 10 g of epichlorohydrin dropwise to the mixed solution and stir at -5°C for 20 minutes. Centrifuge the solution at 8000 rpm at -5°C for 5 minutes to degas, and filter to obtain the spinning solution for spinning.

[0058] 5. The spinning solution was pressurized through a spinning machine spinneret with a diameter of 0.078 mm and 30 holes. The solution then entered a coagulation bath containing 5 wt% citric acid and 10 wt% sodium citrate in water. The bath temperature was 35°C, the spinning speed was 3 m / min, and the draft was 5%. The regenerated fibers were then drawn, washed, oiled, and dried to obtain chitosan-carboxymethyl cellulose composite fibers.

[0059] The indicators involved in the chitosan-carboxymethyl cellulose composite fiber include: fineness of 1.25 dtex, dry breaking strength of 1.33 cN / dtex, dry breaking elongation of 10.1%, and water absorption of 22 g / g.

[0060] Example 3

[0061] 1. Disperse 35 g of chitosan raw material with a viscosity of 450 mPa.s in 965 g of an alkaline solvent (comprising 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea) to obtain a chitosan dispersion. Freeze the chitosan dispersion to -30°C for 4 hours until it is completely frozen. Then, thaw it using mechanical stirring. After 1-2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 4.0 wt% is obtained.

[0062] 2. Disperse 40 g of carboxymethyl cellulose powder in 960 g of an alkaline solvent (including 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea), stir and dissolve uniformly at room temperature to obtain 1000 g of a 4.0 wt% carboxymethyl cellulose solution;

[0063] 3. Mix 700 g of chitosan solution with 300 g of carboxymethyl cellulose solution and stir evenly to obtain a mixed solution;

[0064] 4. Add 10 g of epichlorohydrin dropwise to the mixed solution and stir at -5°C for 20 minutes. Centrifuge the solution at 8000 rpm at -5°C for 5 minutes to degas, and filter to obtain the spinning solution for spinning.

[0065] 5. The spinning solution was pressurized through a spinning machine spinneret with a diameter of 0.078 mm and 30 holes. The solution then entered a coagulation bath containing 5 wt% citric acid and 10 wt% sodium citrate in water. The bath temperature was 35°C, the spinning speed was 3 m / min, and the draft was 5%. The regenerated fibers were then drawn, washed, oiled, and dried to obtain chitosan-carboxymethyl cellulose composite fibers.

[0066] The indicators involved in the chitosan-carboxymethyl cellulose composite fiber include: fineness of 1.33 dtex, dry breaking strength of 1.09 cN / dtex, dry breaking elongation of 7.8%, and water absorption rate of 39 g / g.

[0067] Example 4

[0068] 1. Disperse 35 g of chitosan raw material with a viscosity of 450 mPa.s in 965 g of an alkaline solvent (comprising 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea) to obtain a chitosan dispersion. Freeze the chitosan dispersion to -30°C for 4 hours until it is completely frozen. Then, thaw it using mechanical stirring. After 1-2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 4.0 wt% is obtained.

[0069] 2. Disperse 40 g of carboxymethyl cellulose powder in 960 g of an alkaline solvent (including 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea), stir and dissolve uniformly at room temperature to obtain 1000 g of a 4.0 wt% carboxymethyl cellulose solution;

[0070] 3. Mix 600 g of chitosan solution with 400 g of carboxymethyl cellulose solution and stir evenly to obtain a mixed solution;

[0071] 4. Add 10 g of epichlorohydrin dropwise to the mixed solution and stir at -5°C for 20 minutes. Centrifuge the solution at 8000 rpm at -5°C for 5 minutes to degas, and filter to obtain the spinning solution for spinning.

[0072] 5. The spinning solution was pressurized through a spinning machine spinneret with a diameter of 0.078 mm and 30 holes. The solution then entered a coagulation bath containing 5 wt% citric acid and 10 wt% sodium citrate in water. The bath temperature was 35°C, the spinning speed was 3 m / min, and the draft was 5%. The regenerated fibers were then drawn, washed, oiled, and dried to obtain chitosan-carboxymethyl cellulose composite fibers.

[0073] The indicators involved in the chitosan-carboxymethyl cellulose composite fiber include: fineness of 1.37 dtex, dry breaking strength of 0.86 cN / dtex, dry breaking elongation of 6.3%, and water absorption rate of 57 g / g.

[0074] Example 5

[0075] 1. Disperse 35 g of chitosan raw material with a viscosity of 450 mPa.s in 965 g of an alkaline solvent (comprising 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea) to obtain a chitosan dispersion. Freeze the chitosan dispersion to -30°C for 4 hours until it is completely frozen. Then, thaw it using mechanical stirring. After 1-2 cycles of freezing and thawing, 1000 g of a chitosan solution with a concentration of 4.0 wt% is obtained.

[0076] 2. Disperse 40 g of carboxymethyl cellulose powder in 960 g of an alkaline solvent (including 7 wt% KOH, 8 wt% LiOH, and 8 wt% urea), stir and dissolve uniformly at room temperature to obtain 1000 g of a 4.0 wt% carboxymethyl cellulose solution;

[0077] 3. Mix 500 g of chitosan solution with 500 g of carboxymethyl cellulose solution and stir evenly to obtain a mixed solution;

[0078] 4. Add 10 g of epichlorohydrin dropwise to the mixed solution and stir at -5°C for 20 minutes. Centrifuge the solution at 8000 rpm at -5°C for 5 minutes to degas, and filter to obtain the spinning solution for spinning.

[0079] 5. The spinning solution was pressurized through a spinning machine spinneret with a diameter of 0.078 mm and 30 holes. The solution then entered a coagulation bath containing 5 wt% citric acid and 10 wt% sodium citrate in water. The bath temperature was 35°C, the spinning speed was 3 m / min, and the draft was 5%. The regenerated fibers were then drawn, washed, oiled, and dried to obtain chitosan-carboxymethyl cellulose composite fibers.

[0080] The indicators involved in the chitosan-carboxymethyl cellulose composite fiber include: fineness of 1.41 dtex, dry breaking strength of 0.74 cN / dtex, dry breaking elongation of 5.7%, and water absorption rate of 68 g / g.

[0081] In summary, Examples 1-5 show that as the concentration of the negatively charged polymer carboxymethyl cellulose component in the spinning solution increases, the resulting chitosan composite fibers exhibit a significant decrease in both strength and elongation. This suggests that, during the preparation of chitosan polyelectrolyte composite fibers, the introduction of polyanions does not improve the mechanical properties of the fibers; rather, it imparts functional properties of the polyanions to the chitosan composite fibers, such as increased water absorption.

Claims

1. A method for preparing chitosan polyelectrolyte composite fiber, characterized in that: The steps include:

1. Spinning solution preparation 1) Adding chitosan raw material with a viscosity of 450-550 mPa.s and a degree of deacetylation of 87.2% to a KOH / LiOH / urea aqueous solution and dissolving the mixture to obtain a chitosan dispersion; The chitosan dispersion is frozen and thawed, and then the freezing and thawing cycles are repeated 1 to 2 times, and the mixture is centrifuged to obtain a chitosan solution having a viscosity of 20,000 to 30,000 mPa.s. The chitosan solution contains: 3.0 to 4.0 wt% chitosan, 6 to 8 wt% KOH, 7 to 9 wt% LiOH, and 8 to 11 wt% urea. 2) adding the negatively charged natural polymer to a KOH / LiOH / urea aqueous solution and dissolving the polymer to obtain a polyanion solution having a mass percentage of 4.0 to 5.0 wt%; The KOH / LiOH / urea aqueous solution is the same as the KOH / LiOH / urea aqueous solution in step 1), and the negatively charged natural polymer is one or a mixture of any two or more of carboxymethyl cellulose and its potassium or sodium salt, and alginic acid and its potassium or sodium salt; 3) mixing the obtained chitosan solution with the obtained polyanion solution to obtain a mixed solution having a chitosan concentration of 3.0 to 4.0 wt % and a polyanion concentration of 4.0 to 5.0 wt %; 4) adding a crosslinking agent with an epoxy structure to the mixed solution, and crosslinking and stirring the reaction at -5°C for 20 minutes to obtain a composite pre-gel solution with a viscosity of 25,000 to 35,000 mPa.s; The cross-linking agent with epoxy structure is epichlorohydrin or polyethylene glycol diglycidyl ether, and the amount of the cross-linking agent with epoxy structure added is 10-30% of the total weight of chitosan and polyanion; 5) degassing and filtering the composite pregel solution, and then storing it at a temperature ≤ 5° C. to obtain a composite spinning solution; 2. Spinning Spinning is performed at a spinning speed of 3 to 8 m / min and a total draft of 5 to 10% to obtain slivers; The spinning bath comprises 5-10 wt% citric acid and 10-15 wt% sodium citrate, the spinning bath temperature is 25-50° C., and the filament length is 800-1000 mm. Finally, the obtained filaments are wound into tows, and then drawn, washed, oiled and dried to obtain chitosan polyelectrolyte composite fibers.

2. The method for preparing chitosan polyelectrolyte composite fiber according to claim 1, characterized in that: In step 1), the freezing process includes: freezing the chitosan dispersion to below -30°C for 4 hours.

3. The method for preparing the chitosan polyelectrolyte composite fiber according to claim 1, characterized in that: In step 5), a centrifugal degassing method is used, and the centrifugal degassing conditions include: temperature of -5 to 10°C, rotation speed of 8000 to 10000 rpm, and time of 5 to 10 min.

4. The method for preparing the chitosan polyelectrolyte composite fiber according to claim 1 or 3, characterized in that: In step 5), filtering is performed using a filter with a pore size of 15 μm.

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