A finishing method for chitosan fiber and chitosan fiber prepared thereby

Abstract

The application discloses a finishing method of chitosan fiber and chitosan fiber prepared by the method, and comprises the following steps: preparing an acid aqueous solution of an anionic polyelectrolyte, adding a crosslinking agent and stirring uniformly, pre-crosslinking, and obtaining a pre-crosslinked chitosan fiber finishing solution; immersing formed chitosan fiber into the pre-crosslinked chitosan fiber finishing solution for soaking, drying and heat-crosslinking, and immersing into ethanol, and obtaining finished chitosan fiber. The application utilizes the property that chitosan fiber is activated into a cationic electrolyte under an acid condition, and an anionic polyelectrolyte is strongly adsorbed on the surface of the chitosan fiber through electrostatic interaction, effectively solves the problem that the interaction force between a sizing agent and other finishing agents and the chitosan fiber is weak, and effectively avoids the problem that the mechanical property of the chitosan fiber is poor due to the falling-off of the finishing agents and the sizing agent during use.

Description

Technical Field

[0001] This invention belongs to the field of textile engineering technology, specifically relating to a method for finishing chitosan fibers and the resulting chitosan fibers. Background Technology

[0002] Chitin, a biomass polysaccharide compound, is abundant in crustaceans such as shrimp and crab. Through deacetylation, chitin can yield a cationic polysaccharide polyelectrolyte, chitosan. Chitosan possesses fiber-forming, antibacterial, biocompatible, and biodegradable properties. Chitosan fiber materials have broad application prospects not only in textiles and clothing but also in the biomedical field. Chitosan can degrade into harmless products such as glucosamine in vivo, thus showing significant application potential in surgical sutures, hemostatic materials, wound dressings, and regenerative tissue engineering.

[0003] Currently, the tensile strength of chitosan fibers prepared using traditional wet spinning processes ranges from 0.53 to 2.2 cN / dtex. The tensile strength of conventional chitosan fibers prepared using dilute acetic acid as a solvent is 1.07 cN / dtex. The generally poor mechanical properties of chitosan fibers significantly limit their applications. Blending chitosan fibers with other fibers is the most common and readily available method to improve their mechanical properties. However, the presence of blended fibers significantly impacts the biocompatibility of chitosan fibers, especially in medical fields where high antibacterial and biocompatibility requirements are necessary. The strong intramolecular and intermolecular hydrogen bonds in chitosan make it difficult to dissolve in common organic solvents.

[0004] In recent years, researchers have conducted a series of studies on chitosan dissolution systems to improve the mechanical properties of chitosan fibers. These systems can be categorized into three types: acid systems, ionic liquid systems, and alkali / urea systems. Chitosan fibers prepared using ionic liquids and alkali / urea systems as solvents exhibit higher mechanical strength compared to those prepared using acetic acid systems. However, the synthesis of ionic liquids and the freeze-thaw cycle process of alkali / urea systems are time-consuming, energy-intensive, and costly.

[0005] Currently, most mature production processes for chitosan fibers use acetic acid as a solvent. Building upon this acetic acid-based process, researchers have chemically cross-linked the prepared chitosan fibers to improve their mechanical properties.

[0006] Patent CN 201510182592.8 discloses a medium-temperature textile sizing method. The method involves preparing a sizing agent, adding the required amount of water to a mixing tank, starting the stirring, adding the dried sizing agent to the mixing tank, adding ordinary unmodified starch to the mixing tank, stirring, adding more dried sizing agent, continuing stirring, then starting steam heating, stopping the steam supply after heating, maintaining the temperature and stirring for 30 minutes, pumping the mixture to a sizing tank, and starting the sizing machine to begin sizing. The sizing agent can significantly improve the mechanical properties of the yarn, but due to the weak intermolecular forces, the enhancement of the fiber's mechanical properties is limited.

[0007] To address the limited improvement in fiber mechanical properties due to weak intermolecular forces between sizing agents, patent CN201810387628.X discloses a method for preparing carboxymethyl chitosan-sized chitosan fibers. The method involves axially stretching wet-spun chitosan fibers in a swelling agent, washing, and drying to obtain reinforced chitosan fibers. Then, carboxymethyl chitosan is dissolved in water and subjected to vacuum degassing to obtain a crosslinked carboxymethyl chitosan sizing agent. The reinforced chitosan fibers are then immersed in the crosslinked carboxymethyl chitosan sizing agent for uniform sizing and drying. Finally, the sized reinforced chitosan fibers are immersed in a crosslinking agent solution for crosslinking and then dried to obtain carboxymethyl chitosan-sized chitosan fibers. The tensile strength of these fibers is increased by 88.4–114.5% compared to the finished chitosan fibers. Although using a crosslinking sizing agent can increase the mechanical properties of chitosan fibers, the current crosslinking modification process is performed before the sizing step. The increased sizing concentration during crosslinking is detrimental to subsequent sizing.

[0008] To address the problem of increased sizing viscosity due to cross-linking occurring before sizing, which hinders the fiber sizing process, patent CN 201810385932.0 discloses a method for processing chitosan fibers. The method involves axially stretching the finished chitosan fiber in a swelling agent, washing, and drying to obtain reinforced chitosan fibers. These reinforced chitosan fibers are then immersed in a sizing agent for uniform sizing, followed by drying and cross-linking to obtain starch-sized chitosan fibers. Compared to finished chitosan fibers, the tensile strength is increased by 74.8–108.1%. The introduction of a sizing agent and the cross-linking reaction improve the strength of the chitosan fibers. However, the interaction between the sizing agent and the chitosan fibers is weak, resulting in the fiber product's mechanical properties failing to meet long-term application requirements.

[0009] Therefore, it is of great significance to develop a low-cost, simple process that has strong interaction between the sizing agent and chitosan fiber, and between the sizing agents themselves, and is compatible with existing wet spinning processes to improve the mechanical properties of chitosan fibers. Summary of the Invention

[0010] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0011] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0012] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for finishing chitosan fibers.

[0013] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for finishing chitosan fibers, comprising,

[0014] Anionic polyelectrolyte was prepared into an acidic aqueous solution, and a crosslinking agent was added and stirred evenly to perform pre-crosslinking, thereby obtaining a pre-crosslinked chitosan fiber finishing solution.

[0015] After immersing the shaped chitosan fibers in a pre-crosslinked chitosan fiber finishing solution, they are dried and thermally crosslinked, then immersed in ethanol to obtain the finished chitosan fibers.

[0016] As a preferred embodiment of the finishing method described in this invention, the shaped chitosan fiber comprises wet or dry shaped chitosan fiber prepared by wet spinning.

[0017] In a preferred embodiment of the finishing method described in this invention, the chitosan fiber finishing solution is prepared from the following raw material formulation in parts by weight:

[0018] Anionic polyelectrolytes: 1–30 parts;

[0019] Crosslinking agent: 0.4–12 parts;

[0020] Water: 100-300 parts.

[0021] In a preferred embodiment of the finishing method described in this invention, the anionic polyelectrolyte is prepared into an acidic aqueous solution, wherein the acid is selected from one or more of formic acid, acetic acid, adipic acid, citric acid, butanetetracarboxylic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid, hydrochloric acid, and phytic acid; the anionic polyelectrolyte includes one or more of carboxymethyl cellulose, carboxymethyl dextran, carboxymethyl starch, carboxymethyl chitosan, carboxymethyl cyclodextrin, and polyglutamic acid; and the crosslinking agent is one or more of ethylene glycol diglycidyl ether, epichlorohydrin, polyethylene glycol glycidyl ether, glyoxal, glutaraldehyde, maleic anhydride, and mixed anhydrides.

[0022] In a preferred embodiment of the finishing method described in this invention, the pre-crosslinking reaction temperature is 30–60°C and the time is 1–2 h.

[0023] As a preferred embodiment of the finishing method of the present invention, the step of immersing the shaped chitosan fiber in the pre-crosslinked chitosan fiber finishing solution is to soak for 1 to 15 minutes.

[0024] In a preferred embodiment of the finishing method described in this invention, the drying thermal crosslinking is performed at a temperature of 40–80°C for a time of 0.5–2 hours.

[0025] In a preferred embodiment of the finishing method described in this invention, the immersion in ethanol is carried out for a duration of 5 to 20 minutes.

[0026] In a preferred embodiment of the finishing method described in this invention, the pH value of the pre-crosslinked chitosan fiber finishing solution is 5.5 to 6.5.

[0027] Another objective of this invention is to overcome the shortcomings of the prior art and provide a chitosan fiber prepared by a chitosan fiber finishing method.

[0028] Beneficial effects of this invention:

[0029] (1) This invention utilizes the property of chitosan fiber to be activated into cationic electrolyte under acidic conditions, and strongly adsorbs anionic polyelectrolytes on its surface by electrostatic interaction. This effectively solves the problem of weak interaction between sizing agents and other finishing agents and chitosan fiber, and effectively avoids the problem of poor mechanical properties of chitosan fiber caused by the shedding of finishing agents and sizing agents during use.

[0030] (2) The present invention modifies the fiber by combining pre-crosslinking and thermal crosslinking, making the crosslinked network structure formed by the anionic electrolyte adsorbed on the surface of the chitosan fiber more compact and firm, greatly enhancing the interaction between molecular chains and effectively improving the mechanical properties of the chitosan fiber.

[0031] (3) This invention forms a dense cross-linked network structure on the fiber surface through the dual effects of electrostatic interaction and chemical cross-linking, which improves the mechanical strength of chitosan fiber and achieves the purpose of fiber surface modification. The whole process is simple, energy-saving, and low-cost. It can be realized in the existing chitosan wet spinning finishing process. The finished chitosan fiber has a wide range of uses and can be used in medical sutures, medical wound dressings, medical tissue engineering, etc. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0033] Figure 1 This is a photograph of the chitosan fibers obtained in Example 4 of the present invention. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0037] Mechanism of this invention:

[0038] This invention involves immersing wet or dry chitosan fibers in an acidic finishing solution containing anionic polyelectrolytes. In the acidic finishing solution, a large number of amino groups on the chitosan fiber molecular chains are activated and combine with ionized hydrogen ions in the acidic finishing solution, transforming the chitosan fibers into cationic polyelectrolytes. This disrupts the hydrogen bond structure on the fiber surface, causing the molecular chains to untangle to a certain extent, forming a swollen body with a positive charge on the fiber surface.

[0039] Positively charged chitosan fibers can form polyelectrolyte complexes when they encounter anionic polyelectrolytes in the finishing solution.

[0040] The finishing agent used in this invention is an anionic polyelectrolyte that can electrostatically interact with chitosan fibers. By utilizing the electrostatic interaction between activated chitosan fibers and the anionic polyelectrolyte, the adhesion between the sizing agent or finishing liquid and the chitosan fibers is enhanced, thus solving the problem of no interaction between the sizing agent and chitosan fibers in the prior art.

[0041] Anionic polyelectrolytes undergo a pre-crosslinking reaction in an acidic solution containing a crosslinking agent to form a weakly crosslinked network. This negatively charged weakly crosslinked network adsorbs onto the surface of chitosan fibers under acidic conditions through electrostatic interactions. During the drying process, the fibers adsorbed on the chitosan fiber surface undergo further thermal crosslinking, forming a denser crosslinked network structure. This crosslinked network structure not only improves the mechanical properties of the fibers but also firmly binds the polyelectrolyte complex to the fiber surface.

[0042] This invention is the first to use a combination of pre-crosslinking and thermal crosslinking to modify fibers. Pre-crosslinking ensures that the crosslinking reaction occurs in a liquid environment and prevents the sizing agent from becoming too viscous, making sizing difficult. Meanwhile, the thermal crosslinking during the subsequent fiber drying process further promotes the crosslinking reaction, resulting in complete crosslinking network formation, enhanced intermolecular forces, and improved fiber strength.

[0043] The combined effect of the electrostatic interaction between chitosan fibers and anionic polyelectrolytes, and the cross-linked network structure of anionic polyelectrolytes on the fiber surface, significantly improves the mechanical properties of chitosan fibers, avoiding the problem of affecting the mechanical properties of chitosan fibers due to slurry shedding during use.

[0044] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies. Carboxymethyl cellulose (molecular weight 90,000) was purchased from the Aladdin Chemical Reagents website.

[0045] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples:

[0046] (1) Mechanical properties (including breaking strength and elongation at break) were measured by a universal tensile testing machine (refer to national standard GB / T 14344).

[0047] (2) The fracture strength improvement rate is calculated using the following formula:

[0048]

[0049] In the formula, the breaking strength (after finishing) refers to the breaking strength of chitosan fibers after finishing with the technology of this invention; the breaking strength (before finishing) refers to the breaking strength of chitosan fibers before finishing with the technology of this invention.

[0050] (3) The increase in elongation at break is calculated using the following formula:

[0051]

[0052] In the formula, the elongation at break (after finishing) refers to the elongation at break of chitosan fibers obtained after finishing with the technology of this invention; the elongation at break (before finishing) refers to the elongation at break of chitosan fibers before finishing with the technology of this invention.

[0053] (4) The chitosan fibers and related experimental materials used in the following examples were obtained by the following preparation methods:

[0054] Prepare a 2% (v / v) dilute acetic acid solution;

[0055] Chitosan powder was slowly added to a dilute acetic acid solution to prepare a chitosan spinning solution with a mass fraction of 4 wt%. After vacuum degassing, a homogeneous and stable chitosan solution was formed.

[0056] Chitosan spinning solution is injected into sodium hydroxide / ethanol aqueous solution for wet spinning. A portion of the formed chitosan fibers are washed with water but not dried to obtain wet chitosan fibers.

[0057] A portion of the shaped chitosan fibers is dried in an oven to obtain dry chitosan fibers.

[0058] Example 1

[0059] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0060] Anionic polyelectrolyte (carboxymethyl cellulose): 30 parts;

[0061] Crosslinking agent (ethylene glycol diglycidyl ether): 12 parts;

[0062] Water: 300 servings;

[0063] 30 parts of anionic polyelectrolyte (carboxymethyl cellulose) and 12 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 300 parts of deionized water solution. Formic acid was then added to adjust the pH of the solution to 5.5. The solution was stirred thoroughly and reacted at 60°C for 1 hour to obtain the pre-crosslinked chitosan fiber finishing solution.

[0064] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 10 minutes. The fibers with the finishing solution were taken out and placed in a 60°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 5 minutes to obtain the finished chitosan fibers.

[0065] The properties of the cross-linked chitosan fiber were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fiber obtained in the end had a breaking strength increased by 113.8% and a breaking elongation increased by 23.8%.

[0066] The test results are shown in Table 1.

[0067] Example 2

[0068] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0069] Anionic polyelectrolyte (carboxymethyl cyclodextrin): 5 parts;

[0070] Crosslinking agent (ethylene glycol diglycidyl ether): 1 part;

[0071] Water: 200 servings;

[0072] Five parts of anionic polyelectrolyte (carboxymethyl cyclodextrin) and one part of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 200 parts of deionized water solution. Then, acetic acid was added to adjust the pH of the solution to 6.4. The solution was stirred thoroughly and reacted at 30°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0073] The dried chitosan fibers were immersed in the fiber finishing solution at room temperature for 15 minutes. The fibers, still in the finishing solution, were then removed and placed in an 80°C oven for a thermal crosslinking reaction for 0.5 hours. The dried chitosan fibers were then immersed in ethanol for 8 minutes to obtain the finished chitosan fibers. The properties of the crosslinked chitosan fibers were tested. Compared to the finished chitosan fibers, the final crosslinked chitosan fibers showed a 104.1% increase in breaking strength and a 21.3% increase in elongation at break.

[0074] The test results are shown in Table 1.

[0075] Example 3

[0076] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0077] Anionic polyelectrolyte (carboxymethyl starch): 18 parts;

[0078] Crosslinking agent (ethylene glycol diglycidyl ether): 10 parts;

[0079] Water: 300 servings;

[0080] 18 parts of anionic polyelectrolyte (carboxymethyl starch) and 10 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 300 parts of deionized water solution. Then, adipic acid was added to adjust the pH of the solution to 6.1. The solution was stirred thoroughly and reacted at 60°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0081] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 10 minutes. The fibers with the finishing solution were then removed and placed in a 40°C oven for a thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 6 minutes to obtain the finished chitosan fibers.

[0082] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained had a breaking strength increased by 105.4% and a breaking elongation increased by 20.5%.

[0083] The test results are shown in Table 1.

[0084] Example 4

[0085] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0086] Anionic polyelectrolyte (polyglutamic acid): 20 parts;

[0087] Crosslinking agent (ethylene glycol diglycidyl ether): 8 parts;

[0088] Water: 200 servings;

[0089] 20 parts of anionic polyelectrolyte (polyglutamic acid) and 8 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 200 parts of deionized water solution. Then, acetic acid was added to adjust the pH of the solution to 6.0. The solution was stirred thoroughly and reacted at 50°C for 2 hours to obtain a pre-crosslinked chitosan fiber finishing solution. The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 7 minutes to obtain the finished chitosan fibers.

[0090] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength increased by 121.2% and a breaking elongation increased by 25.8%.

[0091] The test results are shown in Table 1. See the attached image of the obtained chitosan fibers. Figure 1 .

[0092] Example 5

[0093] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0094] Anionic polyelectrolyte (carboxymethyl dextran): 15 parts;

[0095] Crosslinking agent (epoxychloropropane): 5 parts;

[0096] Water: 200 servings;

[0097] 15 parts of anionic polyelectrolyte (carboxymethyl dextran) and 5 parts of crosslinking agent (epoxychloropropane) were slowly added to 200 parts of deionized water solution. Citric acid was then added to adjust the pH of the solution to 5.7. The solution was stirred thoroughly and placed at 50°C for 1.25 h to obtain the pre-crosslinked chitosan fiber finishing solution.

[0098] The dried chitosan fibers were immersed in the fiber finishing solution at room temperature for 12 minutes. The fibers, still containing the finishing solution, were then removed and placed in a 60°C oven for a thermal crosslinking reaction for 1.5 hours. The dried chitosan fibers were then immersed in ethanol for 6 minutes to obtain the finished chitosan fibers. The properties of the crosslinked chitosan fibers were tested. Compared to the finished chitosan fibers, the final crosslinked chitosan fibers showed a 109.4% increase in breaking strength and a 21.4% increase in elongation at break.

[0099] The test results are shown in Table 1.

[0100] Example 6

[0101] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0102] Anionic polyelectrolyte (carboxymethyl cellulose): 10 parts;

[0103] Crosslinking agent (maleic anhydride): 2 parts;

[0104] Water: 100 parts;

[0105] 10 parts of anionic polyelectrolyte (carboxymethyl cellulose) and 2 parts of crosslinking agent (maleic anhydride) were slowly added to 100 parts of deionized water solution. Then, citric acid was added to adjust the pH of the solution to 5.5. The solution was stirred thoroughly and reacted at 40°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0106] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 14 minutes. The fibers with the finishing solution were taken out and placed in a 50°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 8 minutes to obtain the finished chitosan fibers.

[0107] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength increased by 118.5% and a breaking elongation increased by 20.8%.

[0108] The test results are shown in Table 1.

[0109] Example 7

[0110] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0111] Anionic polyelectrolyte (polyglutamic acid): 15 parts;

[0112] Crosslinking agent (maleic anhydride): 9 parts;

[0113] Water: 250 portions;

[0114] 15 parts of anionic polyelectrolyte (polyglutamic acid) and 9 parts of crosslinking agent (maleic anhydride) were slowly added to 250 parts of deionized water solution. Then, hydrochloric acid was added to adjust the pH of the solution to 5.8. The solution was stirred thoroughly and reacted at 30°C for 1 hour to obtain a pre-crosslinked chitosan fiber finishing solution. The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 11 minutes. The fibers with finishing solution were taken out and placed in a 65°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 9 minutes to obtain the finished chitosan fibers.

[0115] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength that increased by 103.2% and a breaking elongation that increased by 21.3%.

[0116] The test results are shown in Table 1.

[0117] Example 8

[0118] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0119] Anionic polyelectrolyte (polyglutamic acid): 30 parts;

[0120] Crosslinking agent (maleic anhydride): 10 parts;

[0121] Water: 300 servings;

[0122] 30 parts of anionic polyelectrolyte (polyglutamic acid) and 10 parts of crosslinking agent (maleic anhydride) were slowly added to 300 parts of deionized water solution, and then sulfuric acid was added to adjust the pH of the solution to 5.6. The solution was stirred thoroughly and placed at 30°C for 1.75 h to obtain the pre-crosslinked chitosan fiber finishing solution.

[0123] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 13 minutes. The fibers with the finishing solution were then removed and placed in a 75°C oven for thermal crosslinking reaction for 1.5 hours. The dried chitosan fibers were then immersed in ethanol for 10 minutes to obtain the finished chitosan fibers.

[0124] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained had a breaking strength increased by 115.4% and a breaking elongation increased by 24.6%.

[0125] The test results are shown in Table 1.

[0126] Example 9

[0127] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0128] Anionic polyelectrolyte (carboxymethyl chitosan): 20 parts;

[0129] Crosslinking agent (glutaraldehyde): 10 parts;

[0130] Water: 250 portions;

[0131] 20 parts of anionic polyelectrolyte (carboxymethyl chitosan) and 10 parts of crosslinking agent (glutaraldehyde) were slowly added to 250 parts of deionized water solution, and then phosphoric acid was added to adjust the pH of the solution to 5.5. The solution was stirred thoroughly and reacted at 55°C for 1 hour to obtain the pre-crosslinked chitosan fiber finishing solution.

[0132] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 11 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 10 minutes to obtain the finished chitosan fibers.

[0133] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength increased by 120.2% and a breaking elongation increased by 20.4%.

[0134] The test results are shown in Table 1.

[0135] Example 10

[0136] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0137] Anionic polyelectrolyte (carboxymethyl dextran): 1 part;

[0138] Crosslinking agent (mixed acid anhydrides): 0.4 parts;

[0139] Water: 100 parts;

[0140] One part of anionic polyelectrolyte (carboxymethyl dextran) and 0.4 parts of crosslinking agent (mixed acid anhydride) were slowly added to 100 parts of deionized water solution. Then, p-toluenesulfonic acid was added to adjust the pH of the solution to 5.7. The solution was stirred thoroughly and placed at 60°C for 1.5 h to obtain the pre-crosslinked chitosan fiber finishing solution.

[0141] The wet chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 3 minutes. The fibers with the finishing solution were taken out and placed in an 80°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 12 minutes to obtain the finished chitosan fibers.

[0142] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength increased by 102.4% and a breaking elongation increased by 24.5%.

[0143] The test results are shown in Table 1.

[0144] Example 11

[0145] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0146] Anionic polyelectrolyte (carboxymethyl dextran): 10 parts;

[0147] Crosslinking agent (maleic anhydride): 4 parts;

[0148] Water: 300 servings;

[0149] 10 parts of anionic polyelectrolyte (carboxymethyl dextran) and 4 parts of crosslinking agent (maleic anhydride) were slowly added to 300 parts of deionized water solution. Then, phytic acid was added to adjust the pH of the solution to 5.6. The solution was stirred thoroughly and reacted at 40°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0150] The wet chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 2 minutes. The fibers with the finishing solution were taken out and placed in an 80°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 13 minutes to obtain the finished chitosan fibers.

[0151] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained in the end had a breaking strength that increased by 99.6% and a breaking elongation that increased by 23.6%.

[0152] The test results are shown in Table 1.

[0153] Example 12

[0154] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0155] Anionic polyelectrolyte (carboxymethyl cellulose): 1 part;

[0156] Crosslinking agent (glyoxal): 0.6 parts;

[0157] Water: 150 portions;

[0158] One part of anionic polyelectrolyte (carboxymethyl cellulose) and 0.6 parts of crosslinking agent (glyoxal) were slowly added to 150 parts of deionized water solution, and then butanetetracarboxylic acid was added to adjust the pH of the solution to 6.4. The solution was stirred thoroughly and reacted at 60°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0159] The wet chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 5 minutes. The fibers with the finishing solution were taken out and placed in an 80°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 15 minutes to obtain the finished chitosan fibers.

[0160] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fiber, the cross-linked chitosan fibers obtained had a breaking strength increased by 92.4% and a breaking elongation increased by 22.2%.

[0161] The test results are shown in Table 1.

[0162] Example 13

[0163] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0164] Anionic polyelectrolyte (polyglutamic acid): 12 parts;

[0165] Crosslinking agent (polyethylene glycol glycidyl ether): 5 parts;

[0166] Water: 150 portions;

[0167] 12 parts of anionic polyelectrolyte (polyglutamic acid) and 5 parts of crosslinking agent (polyethylene glycol glycidyl ether) were slowly added to 150 parts of deionized water solution, and then acetic acid was added to adjust the pH of the solution to 6.2. The solution was stirred thoroughly and placed at 60°C for 1.5 h to obtain the pre-crosslinked chitosan fiber finishing solution.

[0168] The wet chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 1 minute. The fibers with the finishing solution were then removed and placed in an 80°C oven for a thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 14 minutes to obtain the finished chitosan fibers.

[0169] The properties of the cross-linked chitosan fibers were tested. Compared with the finished chitosan fibers, the cross-linked chitosan fibers obtained in the final product showed an increase in breaking strength of 91.5% and an increase in breaking elongation of 20.7%. The test results are shown in Table 1.

[0170] Comparative Example 1

[0171] The method of Example 4 is the same, except that no cross-linking agent is added. Without the addition of a cross-linking agent, there is no subsequent cross-linking reaction. The polyanionic polyelectrolyte is simply adsorbed onto the chitosan fiber by electrostatic force. The resulting chitosan fiber is then tested.

[0172] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0173] Anionic polyelectrolyte (polyglutamic acid): 20 parts;

[0174] Water: 200 servings;

[0175] 20 parts of anionic polyelectrolyte (polyglutamic acid) were slowly added to 200 parts of deionized water solution, and then acetic acid was added to adjust the pH of the solution to 6.0. The solution was stirred thoroughly and reacted at 50°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0176] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 5 minutes to obtain the finished chitosan fibers.

[0177] The properties of the cross-linked chitosan fibers were tested. Compared with the finished chitosan fibers, the cross-linked chitosan fibers obtained in the final product had a 2.3% higher breaking strength and a 0.9% higher elongation at break. The test results are shown in Table 1.

[0178] Comparative Example 2

[0179] The method of Example 4 was followed, except that pre-crosslinking was not performed, and the resulting chitosan fibers were tested.

[0180] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0181] Anionic polyelectrolyte (polyglutamic acid): 20 parts;

[0182] Crosslinking agent (ethylene glycol diglycidyl ether): 8 parts;

[0183] Water: 200 servings;

[0184] 20 parts of anionic polyelectrolyte (polyglutamic acid) and 8 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 200 parts of deionized water solution. Then, acetic acid was added to adjust the pH of the solution to 6.0. The mixture was stirred thoroughly. The dried chitosan fibers were then immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were then removed and placed in a 70°C oven for a thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 5 minutes to obtain the finished chitosan fibers.

[0185] The properties of the cross-linked chitosan fibers were tested. Compared with the finished chitosan fibers, the cross-linked chitosan fibers obtained in the final product had a breaking strength increased by 1.3% and a breaking elongation of 1.1%. The test results are shown in Table 1.

[0186] Comparative Example 3

[0187] The method of Example 4 was followed, except that no acid was added to adjust the pH of the finishing solution. The obtained chitosan fibers were then tested.

[0188] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0189] Anionic polyelectrolyte (polyglutamic acid): 20 parts;

[0190] Crosslinking agent (ethylene glycol diglycidyl ether): 8 parts;

[0191] Water: 200 servings;

[0192] 20 parts of anionic polyelectrolyte (polyglutamic acid) and 8 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 200 parts of deionized water solution and stirred thoroughly. The solution was then placed at 50°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0193] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal crosslinking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 6 minutes to obtain the finished chitosan fibers.

[0194] The properties of cross-linked chitosan fibers were tested. Compared with the finished chitosan fibers, the cross-linked chitosan fibers obtained had a breaking strength increased by 3.1% and a breaking elongation of 1.5%.

[0195] The test results are shown in Table 1.

[0196] Comparative Example 4

[0197] The method of Example 4 was followed, except that the thermal cross-linking process was not performed. The obtained chitosan fibers were then tested.

[0198] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0199] Anionic polyelectrolyte (polyglutamic acid): 20 parts;

[0200] Crosslinking agent (ethylene glycol diglycidyl ether): 8 parts;

[0201] Water: 200 servings;

[0202] 20 parts of anionic polyelectrolyte (polyglutamic acid) and 8 parts of crosslinking agent (ethylene glycol diglycidyl ether) were slowly added to 200 parts of deionized water solution. Then, acetic acid was added to adjust the pH of the solution to 6.0. The solution was stirred thoroughly and reacted at 50°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0203] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and dried at room temperature without baking. The dried chitosan fibers were then immersed in ethanol for 6 minutes to obtain the finished chitosan fibers.

[0204] The properties of the cross-linked chitosan fibers were tested. Compared with the finished chitosan fibers, the cross-linked chitosan fibers obtained in the final product had a breaking strength increased by 4.2% and a breaking elongation of 2.5%. The test results are shown in Table 1.

[0205] Comparative Example 5

[0206] The method is the same as in Example 4, except that no crosslinking agent is added, but the amount of anionic polyelectrolyte added is equivalent to the total amount of anionic polyelectrolyte and crosslinking agent.

[0207] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0208] Anionic polyelectrolyte (polyglutamic acid): 28 parts;

[0209] Water: 200 servings;

[0210] 28 parts of anionic polyelectrolyte (polyglutamic acid) were slowly added to 200 parts of deionized water solution, and then acetic acid was added to adjust the pH of the solution to 6.0. The solution was stirred thoroughly and reacted at 50°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0211] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 5 minutes to obtain the finished chitosan fibers.

[0212] The results are shown in Table 1.

[0213] Comparative Example 6

[0214] The method is the same as in Example 4, except that no anionic polyelectrolyte is added, but the amount of anionic polyelectrolyte added is equivalent to the total amount of anionic polyelectrolyte and crosslinking agent.

[0215] Preparation of the finishing solution: Weigh the following parts by weight of the raw materials to prepare the chitosan fiber finishing solution:

[0216] Crosslinking agent (ethylene glycol diglycidyl ether): 28 parts;

[0217] Water: 200 servings;

[0218] 28 parts of ethylene glycol diglycidyl ether were slowly added to 200 parts of deionized water, and then acetic acid was added to adjust the pH of the solution to 6.0. The mixture was stirred thoroughly and the solution was placed at 50°C for 2 hours to obtain the pre-crosslinked chitosan fiber finishing solution.

[0219] The dried chitosan fibers were immersed in the above fiber finishing solution and soaked at room temperature for 12 minutes. The fibers with the finishing solution were taken out and placed in a 70°C oven for thermal cross-linking reaction for 2 hours. The dried chitosan fibers were then immersed in ethanol for 5 minutes to obtain the finished chitosan fibers.

[0220] The results are shown in Table 1.

[0221] Table 1

[0222] Fracture strength improvement rate (%) Elongation at break increase rate (%) Example 1 113.8 23.8 Example 2 104.1 21.3 Example 3 105.4 20.5 Example 4 121.2 25.8 Example 5 109.4 21.4 Example 6 118.5 20.8 Example 7 103.2 21.3 Example 8 115.4 24.6 Example 9 120.2 20.4 Example 10 102.4 24.5 Example 11 99.6 23.6 Example 12 92.4 22.0 Example 13 91.5 20.7 Comparative Example 1 2.3 0.9 Comparative Example 2 1.3 1.1 Comparative Example 3 3.1 1.5 Comparative Example 4 4.2 2.5 Comparative Example 5 1.2 1.1 Comparative Example 6 0.3 1.2

[0223] As shown in Table 1, this invention uses a combination of pre-crosslinking and thermal crosslinking to modify the fibers. Pre-crosslinking ensures that the crosslinking reaction occurs in a liquid environment and prevents the sizing agent from becoming too viscous, making sizing difficult. Meanwhile, the thermal crosslinking during the subsequent fiber drying process further promotes the crosslinking reaction, resulting in complete crosslinking network formation, enhanced intermolecular forces, and improved fiber strength. The dual effects of the electrostatic interaction between chitosan fibers and anionic polyelectrolytes, and the crosslinking network structure of anionic polyelectrolytes on the fiber surface, significantly improve the mechanical properties of chitosan fibers, avoiding the problem of sizing agent shedding affecting the mechanical properties of chitosan fibers during use. Furthermore, the comparative examples show that there is a synergistic effect between anionic polyelectrolytes and crosslinking agents, which jointly improve the mechanical properties of chitosan fibers.

[0224] The purpose of this invention is to address the problems of poor mechanical properties of chitosan fibers and weak interaction between sizing agents and chitosan fibers, as well as among sizing agents themselves, in existing chitosan fiber crosslinking modification technologies. This invention provides a simple, low-cost method that improves the mechanical strength of chitosan fibers. In existing technologies, the crosslinking process occurs before sizing. Excessive viscosity of the sizing agent makes the sizing process difficult, and the lack of interaction between the sizing agent and chitosan fibers easily leads to sizing agent detachment. In existing technologies, the crosslinking process occurs after sizing. Since the crosslinking process needs to be carried out in a liquid environment, i.e., during fiber drying, rapid liquid evaporation leads to incomplete crosslinking, incomplete formation of the crosslinked network, weak intermolecular forces, and poor fiber strength. Chitosan, as the only naturally occurring cationic polysaccharide polyelectrolyte, can form cationic polyelectrolytes with dissociated hydrogen ions under acidic conditions. It can also interact with anionic polyelectrolytes to form polyelectrolyte complexes. Electrostatic interaction can adsorb the pre-crosslinked anionic polyelectrolytes onto the surface of the chitosan fibers, enhancing the interaction between the chitosan fibers and the finishing agent. The anionic polyelectrolytes adsorbed on the surface of chitosan fibers undergo further thermal cross-linking and curing under the action of a cross-linking agent, forming a dense cross-linked network structure. This enhances the intermolecular forces and improves the mechanical strength of the chitosan fibers. The anionic polyelectrolytes on the chitosan surface significantly improve the mechanical properties of chitosan fibers through the dual effects of electrostatic interactions and the cross-linked network structure.

[0225] It should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for finishing chitosan fibers, characterized in that: The method includes preparing an acidic aqueous solution of anionic polyelectrolyte, adding a crosslinking agent and stirring evenly to perform pre-crosslinking, thereby obtaining a pre-crosslinked chitosan fiber finishing solution. The pH value of the pre-crosslinked chitosan fiber finishing solution is 5.5 to 6.

5. The chitosan fiber finishing solution is prepared from the following raw material formula in parts by weight: anionic polyelectrolyte: 1 to 30 parts; Crosslinking agent: 0.4 ~ 12 parts; Water: 100-300 parts; The acid is selected from one or more of formic acid, acetic acid, adipic acid, citric acid, butanetetracarboxylic acid, p-toluenesulfonic acid, phosphoric acid, sulfuric acid, hydrochloric acid, and phytic acid. The anionic polyelectrolyte is one or more of carboxymethyl cellulose, carboxymethyl dextran, carboxymethyl starch, carboxymethyl chitosan, carboxymethyl cyclodextrin, and polyglutamic acid; The crosslinking agent is one or more of the following: ethylene glycol diglycidyl ether, epichlorohydrin, polyethylene glycol diglycidyl ether, glyoxal, glutaraldehyde, maleic anhydride, and mixed anhydrides. The pre-crosslinking reaction temperature is 30–60°C, and the time is 1–2 h; After immersing the shaped chitosan fiber in the pre-crosslinked chitosan fiber finishing solution, it is subjected to drying and thermal crosslinking, and then immersed in ethanol to obtain the finished chitosan fiber. The drying and thermal crosslinking is carried out at a temperature of 40-80°C for 0.5-2 hours.

2. The sorting method as described in claim 1, characterized in that: The shaped chitosan fibers include wet or dry shaped chitosan fibers prepared by wet spinning.

3. The sorting method as described in claim 1, characterized in that: The process involves immersing the shaped chitosan fibers in a pre-crosslinked chitosan fiber finishing solution for 1 to 15 minutes.

4. The sorting method as described in claim 1, characterized in that: The immersion in ethanol is carried out for a period of 5 to 20 minutes.

5. Chitosan fibers prepared by any of the finishing methods described in claims 1 to 4.

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