High-strength antibacterial bio-based composite yarn and preparation method thereof

Abstract

The invention belongs to the technical field of textile materials, and provides a high-strength antibacterial bio-based composite yarn and a preparation method thereof.The preparation method comprises the steps that S1, chitosan is dissolved in an acetic acid aqueous solution to form a spinning solution, supercritical CO 2 drying is conducted after wet spinning, coagulating bath forming and solvent replacement, and chitosan aerogel fibers are obtained; s2, the chitosan aerogel fibers and lyocell fibers are subjected to opening and mixing, and non-crosslinked composite yarns are spun through a ring spinning technology; and S3, pretreating the non-crosslinked composite yarn by using a CA aqueous solution, cleaning and drying, then carrying out a crosslinking reaction by using an EGDE aqueous solution, and cleaning and drying to obtain the high-strength antibacterial bio-based composite yarn. The chitosan aerogel fibers and the lyocell fibers are subjected to composite spinning and then subjected to multi-step cross-linking treatment, the mechanical property is improved, meanwhile, the antibacterial performance is reserved and enhanced, collaborative optimization of the material performance is achieved, and the tensile strength, the antibacterial durability and the wearing comfort of the composite yarn can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of textile materials technology, specifically relating to a high-strength antibacterial bio-based composite yarn and its preparation method. Background Technology

[0002] Chitosan is a natural polysaccharide with excellent biocompatibility, antibacterial properties, and biodegradability, and is widely used in biomedicine, environmental protection, and food packaging. However, pure chitosan fibers have poor mechanical properties (strength generally below 2 cN / dtex) and high cost, limiting their application in textiles and medical materials. Common methods to improve yarn performance include: The chitosan / cotton composite yarn reported in the Tianjin Textile Technology's "Spinning Process and Antibacterial Properties of Chitosan / Cotton Blended Yarn" exhibits poor spinnability of pure chitosan, and chitosan-cotton blended products have short antibacterial duration, insufficient strength, and complex processing. The wool textile technology report "Research Progress on Antibacterial Yarn" indicates that when the blending ratio of antibacterial polyester to chitin is 70 / 30, the breaking strength is the highest at 32.969 cN / tex, with a coefficient of variation (CV) of 8.33%, and the antibacterial rate against Staphylococcus aureus is only 88.7%.

[0003] Existing technologies primarily focus on improving fiber strength, with few applications of post-treatment to enhance mechanical properties of the yarn. Furthermore, there are virtually no reports on performance improvements achieved through blending chitosan with lyocell. Currently used chemical cross-linking agents for improving fiber mechanical properties are mostly glutaraldehyde and epoxy resins. While cross-linking chitosan fibers can increase strength, it often leads to fiber embrittlement or decreased biocompatibility. The closest existing technology involves blending chitosan fibers with cotton fibers to obtain yarns with some antibacterial properties, but this lacks systematic cross-linking reinforcement, resulting in low tensile strength and a decline in antibacterial performance with increasing washing cycles.

[0004] The existing yarns have the following drawbacks: insufficient mechanical properties, which cannot meet the application requirements of high-strength textiles; short-lasting antibacterial properties, especially after being wet or used repeatedly; complex or costly processing technology, such as electrospinning which requires special equipment and has low production capacity; and a single cross-linking method which can easily lead to fiber embrittlement or functional degradation.

[0005] The reasons for the above-mentioned shortcomings of existing yarns are: weak inter-chain forces of chitosan molecules, low crystallinity, and loose fiber structure; the antibacterial mechanism relies on the binding of amino groups in chitosan molecules to bacterial cell walls, but this is easily lost in the water environment; existing composite processes have failed to achieve a systematic improvement in the interfacial strength between fibers; and the selection or treatment of crosslinking agents is too simplistic, failing to form a stable three-dimensional network structure. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a composite yarn with high strength, long-lasting antibacterial properties, and good biocompatibility, as well as its preparation method. This method involves using chitosan aerogel fibers and lyocell fibers to form a composite yarn, followed by a multi-step crosslinking process, to solve the problems of existing chitosan fiber composite materials mentioned in the background art.

[0007] This invention is achieved through the following technical solution: A method for preparing high-strength antibacterial bio-based composite yarn includes the following steps: S1. Preparation of chitosan aerogel fibers: Chitosan is dissolved in an aqueous acetic acid solution to form a spinning solution. The spinning solution is degassed under vacuum and then loaded into a spinning pump. After being extruded through a spinneret, it enters a coagulation bath containing ethanol and alkali for wet spinning. Wet gel fibers are formed by wet spinning. The wet gel fibers are then removed by solvent replacement with ethanol and dried using a supercritical CO2 drying device to obtain chitosan aerogel fibers with a porous structure. In step S1, the coagulation bath contains ethanol as the main component and a small amount of alkali. The alkali is used to neutralize acetic acid. In the coagulation bath, chitosan precipitates from the solution and forms a shape, while the acetic acid is neutralized, initially forming wet gel fibers. Supercritical CO2 drying avoids the pore collapse caused by surface tension in ordinary drying, ultimately obtaining chitosan aerogel fibers with a nanoscale porous structure and a specific surface area of ​​200-400 m². 2 / g, porosity greater than 85%; S2. Ring spinning preparation of uncrosslinked composite yarn: The chitosan aerogel fibers and lyocell fibers obtained in step S1 are fed into an opening machine for opening and mixing to form a mixed fiber layer. The mixed fiber layer is then spun into a lyocell / chitosan composite yarn through a ring spinning process. The mixed fiber layer is then spun into a lyocell / chitosan composite yarn through a ring spinning process, which is a tightly structured lyocell / chitosan composite yarn with low hairiness and high strength, i.e., an uncrosslinked composite yarn. S3. Multi-step sequential crosslinking strengthening treatment: First, the uncrosslinked composite yarn obtained in step S2 is immersed in a citric acid aqueous solution for pretreatment. Then, the pretreated composite yarn is taken out and cleaned and dried. Next, the pretreated and dried composite yarn is immersed in an ethylene glycol diglycidyl ether aqueous solution for crosslinking reaction. Then, the crosslinked composite yarn is taken out and cleaned and dried to obtain the high-strength antibacterial bio-based composite yarn. In step S3, citric acid (CA) is a polycarboxylic acid. The three carboxyl groups on its molecule can effectively adsorb and wet the fiber. Pretreatment of the uncrosslinked composite yarn with citric acid aqueous solution mainly plays two roles: first, to clean and activate the fiber surface; second, its carboxyl groups can form ester bond precursors with the hydroxyl groups on the fiber (especially cellulose and chitosan), and provide an acidic catalytic microenvironment for the next crosslinking step. After pretreatment, cleaning and drying, citric acid molecules have been initially introduced into the lyocell / chitosan composite yarn, and the hydroxyl groups on the fiber surface have been partially activated. In step S3, ethylene glycol diglycidyl ether (EGDE) is a crosslinking agent containing two epoxy groups. In the weakly acidic environment provided by citric acid in the pretreatment process, the activity of the epoxy groups is enhanced. The crosslinking reaction process is the key to constructing a three-dimensional network. The epoxy groups of EGDE can undergo ring-opening addition reactions with the hydroxyl groups of lyocell cellulose, the hydroxyl and amino groups of chitosan, and the hydroxyl groups of citric acid to form stable ether bonds (-COC-).

[0008] Furthermore, in step S1, the chitosan is chitosan powder with a degree of deacetylation ≥90% and a viscosity of 100~500 mPa•s, the concentration of the acetic acid aqueous solution is 1~3% (v / v), and the concentration of the chitosan is 4.0~6.0% (w / v).

[0009] Furthermore, in step S1, when chitosan is dissolved in an aqueous acetic acid solution, the aqueous acetic acid solution is continuously stirred in a water bath at 40-50°C for 6-8 hours until a uniform, transparent, bubble-free viscous chitosan spinning solution is formed.

[0010] Furthermore, in step S1, the spinneret used in the wet spinning process has an orifice diameter of 0.08~0.12 mm, the alkali contained in the coagulation bath is sodium hydroxide, which is used to neutralize acetic acid, the spinning temperature is 25℃, and the residence time of the spinning solution after being extruded through the spinneret into the coagulation bath is 2~5 minutes, thus initially forming wet gel fibers.

[0011] Furthermore, in step S1, the critical temperature of the supercritical CO2 drying is ≥31℃ and the critical pressure is ≥7.4Mpa. The supercritical CO2 drying under the above parameter settings avoids the pore collapse caused by surface tension in ordinary drying, and finally obtains chitosan aerogel fibers with nanoscale porous structure.

[0012] Furthermore, in step S2, before the chitosan aerogel fiber and the lyocell fiber are put into the cotton opener for opening and mixing, they are first equilibrated for 24 hours under standard temperature and humidity conditions of 20±2℃ and 65±3% relative humidity. The lyocell fiber and the chitosan aerogel fiber are mixed in a dry weight ratio range of 9 to 1.

[0013] Furthermore, in step S2, the ring spinning process comprises the following steps: Carding: The mixed fiber layer is separated into individual fibers and short fibers and impurities are removed by a carding machine, and a uniform fiber web is output and bundled into slivers (raw slivers); Drawing: The raw sliver undergoes multiple drawing and stretching processes to make the fibers straighter and parallel, and the mixture more uniform, resulting in a sliver of uniform thickness. Roving: Using a roving frame, a certain twist is applied to draw the sliver into roving with a certain strength; Fine yarn: The roving is further drafted to the target fineness using a ring spinning machine, and the twist is applied by the high-speed rotation of the ring and traveler. The twist coefficient is set at 380~420 to form a lyocell / chitosan composite yarn.

[0014] Furthermore, in step S3, the concentration of the citric acid aqueous solution is 8% (w / v), and the pretreatment process conditions are as follows: the uncrosslinked composite yarn is loosely and uniformly immersed in the citric acid aqueous solution, the bath ratio is 1:30, the water bath is kept at 80°C, and the treatment time is 40 minutes, during which slow oscillation is maintained to ensure uniform treatment.

[0015] Furthermore, in step S3, the concentration of the ethylene glycol diglycidyl ether aqueous solution is 2.5% (v / v), and the crosslinking reaction process conditions are: bath ratio 1:25, constant temperature water bath at 60℃, and reaction time 90 minutes. This temperature and time are sufficient to ensure that the epoxy groups fully open the ring without causing excessive damage to the fibers.

[0016] This application also provides a high-strength antibacterial bio-based composite yarn, which is prepared by the high-strength antibacterial bio-based composite yarn preparation method described above.

[0017] As can be seen from the above technical solution, the high-strength antibacterial bio-based composite yarn and its preparation method provided by the present invention have the following beneficial effects: (1) Chitosan aerogel fiber structure: The chitosan aerogel fiber in this invention has a "porous sponge-like" structure, which is obtained by wet spinning combined with supercritical CO2 drying. It has a nanoscale porous network and a large specific surface area (200~400m²). 2 / g), with high porosity (>85%), currently obtained by direct solidification and drying via conventional wet spinning, resulting in a dense "solid columnar" structure with a small specific surface area (typically <50m²). 2 (g), existing antibacterial technologies rely on limited surface groups, while this invention provides a large number of active sites through a huge inner surface. Existing technologies with dense fibers are not conducive to the penetration of crosslinking agents, while the porous structure of this invention creates conditions for crosslinking agents to penetrate deep into the interior for reaction. (2) Crosslinking system and process: In this invention, CA / EGDE sequential crosslinking is a clear two-step method with synergistic function between the two steps (CA creates optimized conditions for EGDE reaction). First, citric acid (CA) pretreatment (8%, 80℃, 40min) cleans and activates the fiber, providing an acidic microenvironment; then, ethylene glycol diglycidyl ether (EGDE) crosslinking (2.5%, 60℃, 90min) is used. Under the conditions created by CA, its epoxy groups undergo ring-opening addition with the hydroxyl / amino groups of the fiber, mainly forming more stable ether bonds (-COC-) and ester bonds, resulting in a more stable network and better biocompatibility. In contrast, existing methods use single crosslinking or post-treatment, that is, only aldehydes such as glutaraldehyde are used for crosslinking, mainly forming Schiff bases (C=N) or imine bonds, which easily lead to fiber embrittlement, or only citric acid is used for esterification treatment, which has limited reinforcement effect, and the process is mostly a one-step impregnation treatment. (3) This invention provides a composite yarn with high strength, long-lasting antibacterial effect, good biocompatibility and feasible process and its preparation method. By constructing a composite structure of chitosan aerogel fiber and lyocell fiber and adopting a multi-step cross-linking strategy, the mechanical properties are improved while the antibacterial properties are retained and enhanced, realizing the synergistic optimization of material properties, significantly improving the tensile strength, antibacterial durability and wearing comfort of the yarn, which is suitable for medical dressings, functional clothing, environmentally friendly textiles and other fields, and helps to promote its practical application in high-end medical dressings, sportswear and other fields. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0019] Figure 1 This is the first SEM image of yarn 6040 in Embodiment 6 of the present invention.

[0020] Figure 2 This is a second SEM image of yarn 6040 of the present invention.

[0021] Figure 3 This is a comparison chart of the antibacterial effects of four types of yarn against Staphylococcus aureus. Detailed Implementation

[0022] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0023] Example 1 A method for preparing high-strength antibacterial bio-based composite yarn mainly includes three stages: preparing chitosan aerogel fibers, ring spinning to prepare lyocell / chitosan composite yarn, and multi-step sequential crosslinking strengthening treatment.

[0024] Phase 1: Preparation of chitosan aerogel fibers Solution preparation: Slowly add chitosan powder with a degree of deacetylation ≥90% and a moderate viscosity (100~500 mPa•s) to a 1~3% (volume percentage concentration v / v) aqueous solution of acetic acid under continuous stirring. Control the final concentration of chitosan to 4.0~6.0% (weight / volume percentage concentration w / v). Continue stirring in a water bath at 40~50℃ for 6~8 hours until a homogeneous, transparent, bubble-free viscous chitosan solution is formed, which is also the spinning solution. Wet spinning: After vacuum degassing, the above spinning solution is loaded into a spinning pump and extruded through a spinneret (orifice diameter 0.08~0.12mm) into a coagulation bath containing ethanol as the main component and a small amount of sodium hydroxide (used to neutralize acetic acid). The spinning temperature is 25℃ and the coagulation bath residence time is about 2~5 minutes. During this process, chitosan precipitates from the solution and forms a shape, acetic acid is neutralized, and wet gel fibers are initially formed. Supercritical drying: The wet aerogel fibers are sequentially replaced with ethanol to completely remove moisture, and then placed in a supercritical CO2 drying apparatus for drying at a temperature (31℃) and pressure (7.4 MPa) above the critical level. This process avoids the pore collapse caused by surface tension in ordinary drying, ultimately obtaining chitosan aerogel fibers with a nanoscale porous structure and a specific surface area of ​​200~400 m². 2 / g, porosity greater than 85%.

[0025] Phase 2: Ring spinning to prepare lyocell / chitosan composite yarn (uncrosslinked composite yarn) Raw material preparation and pretreatment: The chitosan aerogel fiber prepared above and commercially available 1.5D Lyocell fiber were equilibrated for 24 hours under standard temperature and humidity conditions (temperature 20±2℃, relative humidity 65±3%). Opening and mixing: According to the dry weight ratio set by Lyocell: Chitosan aerogel fiber (dry weight ratio range 9~1), the two fibers are put into the cotton opener for full opening and mixing to make a uniformly mixed fiber layer. Ring spinning: Carding: The mixed fiber layer is passed through a carding machine to further separate individual fibers and remove short fibers and impurities, outputting a uniform fiber web and bundling it into slivers (raw slivers); Drawing: After 2 to 3 rounds of drawing and stretching, the fibers are made straighter and parallel, and the mixture is more uniform, resulting in a sliver of uniform thickness; Roving: The sliver is lightly drawn and twisted on a roving frame to produce roving with a certain strength; Fine yarn: Using a ring spinning machine, the roving is further drafted to the target fineness (40 English count, or about 14.8 Tex in this example), and sufficient twist is applied by the high-speed rotation of the ring and traveler (twist coefficient set at 380~420), finally spinning into a lyocell / chitosan composite yarn with a tight structure, less hairiness, and higher strength. The yarn at this stage is called "uncrosslinked composite yarn".

[0026] Phase 3: Multi-step sequential crosslinking strengthening treatment This stage is the core step in improving the performance of this invention, and it consists of two steps: Step 1: Citric Acid (CA) Pretreatment and Activation Pretreatment process: Prepare an 8% (w / v) citric acid aqueous solution, and immerse the "uncrosslinked composite yarn" in the solution in a loose and uniform manner at a liquor ratio of 1:30. Treat in a constant temperature water bath at 80°C for 40 minutes, and maintain slow oscillation during the process to ensure uniform treatment. Post-treatment: After treatment, take out the yarn and wash it thoroughly with deionized water until the washing solution is neutral. Then dry it in an 80℃ oven. After this step, citric acid molecules have been initially introduced into the yarn and the hydroxyl groups on the fiber surface have been partially activated. Step 2: Covalent crosslinking of ethylene glycol diglycidyl ether (EGDE) Crosslinking reaction process: Prepare an EGDE aqueous solution with a concentration of 2.5% (v / v) (a small amount of isopropanol can be added to aid dissolution), immerse the yarn that has been pretreated and dried by CA into the EGDE solution, with a liquor ratio of 1:25, and react in a constant temperature water bath at 60℃ for 90 minutes. This temperature and time are sufficient to ensure that the epoxy groups fully open the ring without causing excessive damage to the fibers. Post-processing: After the reaction is complete, take out the yarn and wash the unreacted EGDE and byproducts thoroughly with warm water and deionized water in sequence. Finally, dry it at 70°C to obtain the final high-strength antibacterial composite yarn.

[0027] Example 2 This application also provides a high-strength antibacterial bio-based composite yarn, which is prepared by the high-strength antibacterial bio-based composite yarn preparation method described in Example 1; The high-strength antibacterial bio-based composite yarn is specifically 6040 yarn, and the SEM image of the 6040 yarn is shown below. Figure 1 and Figure 2 As shown.

[0028] Mechanical property testing of the high-strength antibacterial bio-based composite yarn: The mechanical properties of the high-strength antibacterial bio-based composite yarn prepared by the method described in this invention are shown in the table below: Table 1 Mechanical properties of 6040 yarn (uncrosslinked composite yarn) before multi-step crosslinking treatment Table 2 Mechanical properties of 6040 yarn after multi-step crosslinking treatment The mechanical property test results of the high-strength antibacterial bio-based composite yarn are as follows: (1) Mechanism of mechanical property improvement (approximately 3 times improvement): Untreated composite yarns, due to the low strength of the chitosan aerogel fibers and weak interfacial bonding with lyocell, have overall strength primarily dependent on lyocell, with a tested strength of approximately 1.0~1.2 cN / dtex. After CA / EGDE sequential crosslinking: ① Interfacial reinforcement: EGDE acts as a "molecular bridge", with its two ends bonded to the active groups of lyocell cellulose and chitosan molecules, respectively, transforming the original physical contact into a strong covalent bond, which greatly enhances the interfacial bonding force. ② Network Reinforcement: EGDE not only reacts at the interface but also penetrates into the porous interior of chitosan aerogel fibers and the amorphous regions of lyocell fibers, reacting with numerous molecular chains to form a pervasive, densely cross-linked three-dimensional network within the yarn. This network effectively transfers and disperses stress, preventing crack propagation; ③ Fiber self-strengthening: The cross-linking reaction makes it difficult for the relative slippage between chitosan and cellulose molecular chains, thereby increasing the modulus and strength of the fiber itself.

[0029] Overall results: As shown in Tables 1 and 2, in the preferred embodiment, the breaking strength of the treated composite yarn is stably 3.0~3.5 cN / dtex, which is about 3 times higher than before the multi-step crosslinking treatment, and the breaking elongation is well maintained.

[0030] (2) Mechanism of durable antibacterial properties: The antibacterial properties of traditional chitosan blended yarns decrease rapidly due to the loss of chitosan molecules during washing. In this invention: (1) Chemical fixation: A large number of amino (-NH2) and hydroxyl (-OH) groups on chitosan molecules are firmly fixed in the three-dimensional network through EGDE crosslinking, and cannot migrate or fall off freely; (2) Stable structure: The porous structure of the aerogel is maintained after cross-linking, ensuring long-term effective exposure of the antibacterial surface.

[0031] like Figure 3As shown, from left to right, the yarn is the control yarn, the lyocell yarn, the lyocell / chitosan composite yarn before multi-step cross-linking treatment, and the lyocell / chitosan composite yarn after multi-step cross-linking treatment. The antibacterial effect against Staphylococcus aureus is greater than 90%.

[0032] Therefore, the antibacterial mechanism has shifted from "dissolution type" to "contact type," and its antibacterial performance no longer depends on the loss of chitosan. Experiments show that the high-strength antibacterial bio-based composite yarn exhibits an initial inhibition rate of over 99% against Staphylococcus aureus and Escherichia coli. After 50 washes using standard methods (such as AATCC 61-2020), the inhibition rate remains above 95%, demonstrating excellent durability.

Claims

1. A method for preparing high-strength antibacterial bio-based composite yarn, characterized in that, Includes the following steps: S1. Preparation of chitosan aerogel fibers: Chitosan is dissolved in an aqueous acetic acid solution to form a spinning solution. The spinning solution is degassed under vacuum and then loaded into a spinning pump. After being extruded through a spinneret, it enters a coagulation bath containing ethanol and alkali for wet spinning. Wet gel fibers are formed by wet spinning. The wet gel fibers are then removed by solvent replacement with ethanol and dried using a supercritical CO2 drying device to obtain chitosan aerogel fibers with a porous structure. S2. Ring spinning to prepare uncrosslinked composite yarn: The chitosan aerogel fiber and lyocell fiber obtained in step S1 are fed into a cotton opener for opening and mixing to form a mixed fiber layer. The mixed fiber layer is then spun into lyocell / chitosan composite yarn through a ring spinning process. S3. Multi-step sequential crosslinking strengthening treatment: First, the uncrosslinked composite yarn obtained in step S2 is immersed in a citric acid aqueous solution for pretreatment. Then, the pretreated composite yarn is taken out and cleaned and dried. Next, the pretreated and dried composite yarn is immersed in an ethylene glycol diglycidyl ether aqueous solution for crosslinking reaction. Then, the crosslinked composite yarn is taken out and cleaned and dried to obtain the high-strength antibacterial bio-based composite yarn.

2. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1, characterized in that: In step S1, the chitosan is chitosan powder with a degree of deacetylation ≥90% and a viscosity of 100~500 mPa•s, the concentration of the acetic acid aqueous solution is 1~3% (v / v), and the concentration of the chitosan is 4.0~6.0% (w / v).

3. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1 or 2, characterized in that: In step S1, when chitosan is dissolved in an aqueous acetic acid solution, the aqueous acetic acid solution is continuously stirred in a water bath at 40-50°C for 6-8 hours until a uniform, transparent, bubble-free viscous chitosan spinning solution is formed.

4. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1, characterized in that: In step S1, the spinneret used in the wet spinning process has an orifice diameter of 0.08~0.12 mm, the alkali contained in the coagulation bath is sodium hydroxide, the spinning temperature is 25℃, and the residence time in the coagulation bath is 2~5 minutes.

5. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1, characterized in that: In step S1, the critical temperature of the supercritical CO2 drying is ≥31℃ and the critical pressure is ≥7.4 MPa.

6. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1, characterized in that: In step S2, before the chitosan aerogel fiber and the lyocell fiber are put into the cotton opener for opening and mixing, they are first equilibrated for 24 hours under standard temperature and humidity conditions of 20±2℃ and 65±3% relative humidity. The lyocell fiber and the chitosan aerogel fiber are mixed in a dry weight ratio range of 9 to 1.

7. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1 or 6, characterized in that, In step S2, the ring spinning process includes the following steps: Carding: The mixed fiber layer is separated into individual fibers and short fibers and impurities are removed by a carding machine, and a uniform fiber web is output and bundled into sliver; Bundling: The process of combining and stretching raw strips to produce cooked strips of uniform thickness; Roving: Roving is produced by drafting sliver using a roving frame; Fine yarn: The roving is further drawn to the target fineness using a ring spinning machine, and the twist is applied by the high-speed rotation of the ring and traveler. The twist coefficient is set at 380~420 to produce lyocell / chitosan composite yarn.

8. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1, characterized in that: In step S3, the concentration of the citric acid aqueous solution is 8% (w / v), and the pretreatment process conditions are: bath ratio 1:30, constant temperature water bath at 80℃, and treatment time 40 minutes.

9. The method for preparing high-strength antibacterial bio-based composite yarn according to claim 1 or 8, characterized in that: In step S3, the concentration of the ethylene glycol diglycidyl ether aqueous solution is 2.5% (v / v), and the crosslinking reaction process conditions are: bath ratio 1:25, constant temperature water bath at 60℃, and reaction time 90 minutes.

10. A high-strength antibacterial bio-based composite yarn, characterized in that: The high-strength antibacterial bio-based composite yarn is prepared by the high-strength antibacterial bio-based composite yarn preparation method according to any one of claims 1 to 9.

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