Multi-layer composite chinlon fabric and preparation method thereof

Abstract

The invention relates to the technical field of chinlon fabrics, and discloses a multi-layer composite chinlon fabric and a preparation method thereof. The multi-layer composite chinlon fabric comprises an inner layer, an antibacterial layer and an outer layer, the inner layer is prepared by blending polyamide fibers and cotton fibers, the antibacterial layer is prepared by weaving antibacterial fibers, and the outer layer is prepared by weaving modified polyamide fibers; wherein a composite antibacterial agent, sodium alginate and chitin are introduced into the antibacterial fibers, and the antibacterial performance, the moisture absorption performance and the air permeability of the fabric are improved through the synergistic effect of the composite antibacterial agent, the sodium alginate and the chitin; sulfonic acid groups with extremely high hydrophilicity are introduced into the modified polyamide fibers, so that the hydrophilicity of the fibers is improved, and the breathability and hygroscopicity of the fabric are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of nylon fabrics, and in particular to a multi-layer composite nylon fabric and a preparation method thereof. Background Art

[0002] Nylon fabric, also known as polyamide fabric, has good abrasion resistance, elasticity, corrosion resistance and other advantages, so it is made into clothing, textiles, etc. However, with the continuous advancement of textile technology and the improvement of people's living standards, the market's performance requirements for clothing fabrics are becoming increasingly diversified. Although traditional single-layer nylon fabric has good abrasion resistance and elasticity, it is insufficient in anti-static, quick-drying, breathable and other properties, and it is difficult to meet the needs of modern consumers for high-performance and multifunctional fabrics.

[0003] For example, traditional nylon fabrics are not good at wicking moisture, which can easily lead to discomfort when wearing; they do not have antibacterial properties, and cannot effectively kill existing bacteria, inhibit the growth and reproduction of bacteria, and thus reduce the spread and infection of viruses and bacteria. Therefore, according to people's different needs, a nylon fabric with multiple layers of different functional fabrics can be designed to meet people's requirements for antibacterial, moisture absorption, breathability, etc. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a multi-layer composite nylon fabric and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A multi-layer composite nylon fabric, comprising an inner layer, an antibacterial layer and an outer layer from top to bottom; the inner layer is woven by mixing nylon fiber and cotton fiber in a ratio of 2:1; the antibacterial layer is formed by interweaving antibacterial fibers; the outer layer is woven by modified nylon fibers; The antibacterial fiber is composed of the following raw materials in parts by weight: 40-60 parts of polyamide solution, 3-6 parts of sodium alginate, 5-10 parts of composite antibacterial agent, and 1-4 parts of chitin; The composite antibacterial agent is prepared by the following steps: Step A1, ultrasonically dispersing cellulose in a 1-2 wt% acetic acid solution, stirring at 40-50° C. for 3-5 h, filtering, washing, and drying to obtain pre-treated cellulose; Further, in step A1, the mass ratio of cellulose to acetic acid solution is 1:10; Step A2, the pretreated cellulose and 2,3-dimercaptosuccinic acid are mixed and stirred in DMF (N,N-dimethylformamide), p-toluenesulfonic acid is added, and the mixture is reacted under nitrogen at 120-140° C. for 1 hour, and then under vacuum conditions for 1.5-2.5 hours, and then acetone and n-hexane are added and stirred, and the mixture is distilled under reduced pressure to obtain modified cellulose; Furthermore, in step A2, the usage ratio of pre-treated cellulose, 2,3-dimercaptosuccinic acid, DMF, p-toluenesulfonic acid, acetone, and n-hexane is 2-5 g: 1-3 g: 100 mL: 0.005-0.015 g: 50 mL: 20 mL; Step A3, under nitrogen conditions, add modified cellulose to DMF and mix and stir evenly, slowly dropwise add 0.15-0.25 mol / L copper nitrate solution, and adjust the solution pH to 8-9, raise the temperature to 40°C, react for 1-3h, distill under reduced pressure, and dry to obtain a composite antibacterial agent; Furthermore, in step A3, the usage ratio of modified cellulose, DMF and copper nitrate solution is 3-5 g: 50 mL: 20 mL.

[0006] The modified nylon fiber is prepared by the following steps: Step B1, add 5-aminoisophthalic acid to N, N-dimethylacetamide, mix and stir evenly, transfer to an ice water bath and let stand for 10-20 minutes, add triethylamine, then add undecylenic acid chloride three times, and stir at 0-5°C for 30 minutes, then transfer to an oil bath, and heat to 55-75°C, react for 4-8 hours, precipitate, wash, dry, recrystallize, and dry twice to obtain a carboxyl-terminated product; Further, in step B1, the usage ratio of 5-aminoisophthalic acid, N,N-dimethylacetamide, triethylamine and undecenoyl chloride is 0.1-0.3 mol: 100 mL: 2.3-7 mL: 0.1-0.3 mol; Step B2, the carboxyl-terminated product, anhydrous sodium sulfite and sodium nitrate are mixed and stirred evenly in a flask containing DMF, the temperature is raised to reflux, and the sodium bisulfite solution is slowly added dropwise for 1 hour, and then the temperature is maintained at 90-105° C. for continuous reaction for 8-10 hours, chromatography, washing and drying to obtain the sulfonated product; Further, in step B2, the amount ratio of the terminal carboxyl product, anhydrous sodium sulfite, sodium nitrate, DMF and sodium bisulfite solution is 1.7-5.1 g: 0.095-0.285 g: 0.07-0.21 g: 100 mL: 21.5-24.6 g, and the sodium bisulfite solution is prepared by mixing and stirring sodium bisulfite and deionized water in a mass ratio of 1.56-4.68: 20; Step B3, dispersing the sulfonated product and hexamethylenediamine in equal amounts of ethanol to form a sulfonated product solution and a hexamethylenediamine solution, then adding the sulfonated product solution dropwise to the hexamethylenediamine solution, heating to 50-70°C and stirring for reaction for 1-3h, filtering and drying, collecting the sulfonated product-hexamethylenediamine salt; then mixing caprolactam, the sulfonated product-hexamethylenediamine salt and deionized water and stirring evenly, transferring to a reactor, replacing the gas in the reactor with nitrogen three times, heating to 100°C, starting stirring, then heating to 230-250°C, and maintaining the pressure at 0.5-0.6MPa for reaction for 2-4h, adjusting the pressure in the reactor to normal pressure, introducing nitrogen, continuing the reaction for 4-6h, evacuating, continuing the reaction for 30-60min, standing for 10min, discharging, casting, and pelletizing to obtain hydrophilic polyamide slices, and then melt spinning to obtain modified nylon fiber; Furthermore, the mass ratio of the sulfonated product in step B3, hexamethylenediamine and caprolactam is 1-2: 0.26-0.52: 47.48-48.74, and deionized water accounts for 4-5% of the total mass of the reactants.

[0007] A method for preparing a multi-layer composite nylon fabric comprises the following steps: Step S1, weighing raw materials by weight, mixing polyamide solution, sodium alginate, composite antibacterial agent and chitosan, and then melt spinning to obtain antibacterial fibers, and then interweaving the antibacterial fibers to form an antibacterial layer; Step S2, mixing nylon fiber and cotton fiber in a ratio of 2:1 to form an inner layer, and weaving modified nylon fiber to form an outer layer; Step S3: stacking, aligning and compounding the inner layer, the antibacterial layer and the outer layer from top to bottom in sequence to obtain a multi-layer composite nylon fabric.

[0008] Beneficial effects of the present invention: The multi-layer composite nylon fabric of the present invention comprises an inner layer, an antibacterial layer and an outer layer; the inner layer is prepared by mixing nylon fibers and cotton fibers, the antibacterial layer is woven from the antibacterial fibers, and the outer layer is prepared by weaving modified nylon fibers; wherein composite antibacterial agents, sodium alginate and chitosan are introduced into the antibacterial fibers, and the synergistic effect of the three improves the antibacterial, moisture absorption and air permeability of the fabric; and the modified nylon fibers are introduced with extremely hydrophilic sulfonic acid groups to improve the hydrophilicity of the fibers, thereby improving the air permeability and moisture absorption of the fabric.

[0009] The composite antimicrobial agent first pre-treats cellulose with dilute acid to obtain pre-treated cellulose; then uses esterification reaction to introduce active groups (carboxyl and thiol) into cellulose to obtain modified cellulose; finally, copper nitrate is used as a source of copper ions, and the active groups on the modified cellulose are used to complex copper ions to obtain a composite antimicrobial agent. The composite antimicrobial agent can synergize with natural antimicrobial ingredients (sodium alginate and chitin) to improve the antimicrobial properties of the fiber; the composite antimicrobial agent can not only use the hydroxyl groups in the cellulose molecules to interact with the proteins and lipids of bacteria and viruses, destroy their structure and function, and kill bacteria, but also use its surface metal complexes to release metal copper ions, and use the metal ions to react with the ester bonds and olefin structures in the lipids, resulting in oxidation, rupture and damage of cell membrane lipids, thereby killing bacteria and giving the fiber a lasting antimicrobial effect.

[0010] In addition, the composite antibacterial agent, sodium alginate and chitosan introduced into the antibacterial fiber have good hydrophilicity, which can effectively improve the hydrophilicity of polyamide fiber and improve the air permeability and moisture absorption of the fabric.

[0011] In the modified nylon fiber, 5-aminoisophthalic acid and undecenoyl chloride are first reacted to obtain a terminal carboxyl product; then the double bond in the terminal carboxyl product and sodium bisulfite are subjected to a sulfonation reaction to obtain a sulfonated product; and then the sulfonated product, hexamethylenediamine and caprolactam are used as raw materials to synthesize the modified nylon fiber. Using the modified nylon fiber as the material for the outer layer of the weaving can significantly improve the air permeability and moisture absorption of the fabric. This is because the modified nylon fiber introduces a sulfonic acid group with excellent hydrophilicity, which improves the hydrophilicity of the nylon fiber without reducing the original mechanical properties, and introduces a benzene ring structure into the main chain of the polyamide molecule, which can improve the mechanical properties of the fiber. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] Example 1: The composite antibacterial agent is prepared by the following steps: Step A1, ultrasonically dispersing 10 g of cellulose in 100 g of 1 wt% acetic acid solution, stirring at 40° C. for 3 h, filtering, washing, and drying to obtain pretreated cellulose; Step A2, 2 g of pre-treated cellulose and 1 g of 2,3-dimercaptosuccinic acid were mixed and stirred in 100 mL of DMF, and then 0.005 g of p-toluenesulfonic acid was added, and the mixture was reacted under nitrogen at 120° C. for 1 h, and then reacted under vacuum conditions for 1.5 h, and then 50 mL of acetone and 20 mL of n-hexane were added and stirred, and the mixture was distilled under reduced pressure to obtain modified cellulose; Step A3: Under nitrogen conditions, add 3 g of modified cellulose to 50 mL of DMF and mix and stir evenly, slowly drop 20 mL of 0.15 mol / L copper nitrate solution, adjust the solution pH to 8, heat to 40°C, react for 1 h, distill under reduced pressure, and dry to obtain a composite antibacterial agent.

[0014] The modified nylon fiber is prepared by the following steps: Step B1, add 0.1 mol 5-aminoisophthalic acid to 100 mL N, N-dimethylacetamide, mix and stir evenly, transfer to an ice water bath and let stand for 10 min, add 2.3 mL triethylamine, then add 0.1 mol undecenoyl chloride three times, and stir at 0°C for 30 min, then transfer to an oil bath, heat to 55°C, react for 4 h, precipitate, wash, dry, recrystallize, and dry twice to obtain a carboxyl-terminated product; Step B2, 1.7g of the carboxyl-terminated product, 0.095g of anhydrous sodium sulfite and 0.07g of sodium nitrate were mixed and stirred in a flask containing 100mL DMF, the temperature was raised to reflux, 21.5g of sodium bisulfite solution was slowly added dropwise for 1h, and the temperature was maintained at 90°C for continuous reaction for 8h, chromatography, washing and drying to obtain a sulfonated product, wherein the sodium bisulfite solution was prepared by mixing and stirring sodium bisulfite and deionized water in a mass ratio of 1.56:20; Step B3, 1g of the sulfonated product and 0.26g of hexamethylenediamine were dispersed in 10mL of ethanol to form a sulfonated product solution and a hexamethylenediamine solution, and then the sulfonated product solution was added dropwise to the hexamethylenediamine solution, and the temperature was raised to 50°C and stirred for 1h, filtered and dried, and the sulfonated product-hexamethylenediamine salt was collected; then 48.74g of caprolactam, the sulfonated product-hexamethylenediamine salt and 2g of deionized water were mixed and stirred evenly, transferred to a reactor, nitrogen replaced the gas in the reactor three times, heated to 100°C, started stirring, and then heated to 230°C, and maintained the pressure at 0.5MPa for 2h, adjusted the pressure in the reactor to normal pressure, introduced nitrogen, continued to react for 4-6h, vacuumed, and continued to react for 30-60min, let stand for 10min, unloaded, cast, and pelletized to obtain hydrophilic polyamide slices, and then melt-spun to obtain modified nylon fiber.

[0015] Example 2: The composite antibacterial agent is prepared by the following steps: Step A1, ultrasonically dispersing 10 g of cellulose in 100 g of 1.5 wt% acetic acid solution, stirring at 45° C. for 4 h, filtering, washing, and drying to obtain pretreated cellulose; Step A2, 3.5 g of pre-treated cellulose and 2 g of 2,3-dimercaptosuccinic acid were mixed and stirred in 100 mL of DMF, and then 0.01 g of p-toluenesulfonic acid was added, and the mixture was reacted under nitrogen at 130° C. for 1 h, and then under vacuum conditions for 2 h, and then 50 mL of acetone and 20 mL of n-hexane were added and stirred, and the mixture was distilled under reduced pressure to obtain modified cellulose; Step A3: Under nitrogen conditions, add 4 g of modified cellulose to 50 mL of DMF and mix and stir evenly, slowly drop 20 mL of 0.2 mol / L copper nitrate solution, adjust the solution pH to 8.5, heat to 40°C, react for 2 h, distill under reduced pressure, and dry to obtain a composite antibacterial agent.

[0016] The modified nylon fiber is prepared by the following steps: Step B1, add 0.2 mol 5-aminoisophthalic acid to 100 mL N, N-dimethylacetamide, mix and stir evenly, transfer to an ice water bath and let stand for 15 min, add 4.6 mL triethylamine, then add 0.2 mol undecenoyl chloride three times, and stir at 2 ° C for 30 min, then transfer to an oil bath, and heat to 65 ° C, react for 4-8 h, precipitate, wash, dry, recrystallize, and dry twice to obtain a carboxyl-terminated product; Step B2, 3.4g of the carboxyl-terminated product, 0.19g of anhydrous sodium sulfite and 0.14g of sodium nitrate were mixed and stirred in a flask containing 100mL of DMF, the temperature was raised to reflux, 23g of sodium bisulfite solution was slowly added dropwise for 1h, and the temperature was maintained at 100°C for continuous reaction for 9h, chromatography, washing and drying to obtain a sulfonated product, wherein the sodium bisulfite solution was prepared by mixing and stirring sodium bisulfite and deionized water in a mass ratio of 3.12:20; Step B3, 1.5g of the sulfonated product and 0.39g of hexamethylenediamine were dispersed in 10mL of ethanol to form a sulfonated product solution and a hexamethylenediamine solution, and then the sulfonated product solution was added dropwise to the hexamethylenediamine solution, and the temperature was raised to 60°C and stirred for 2h, filtered and dried, and the sulfonated product-hexamethylenediamine salt was collected; then 48.11g of caprolactam, the sulfonated product-hexamethylenediamine salt and 2.3g of deionized water were mixed and stirred evenly, transferred to a reactor, nitrogen replaced the gas in the reactor three times, heated to 100°C, started stirring, and then heated to 240°C, and maintained the pressure at 0.55MPa for 3h, adjusted the pressure in the reactor to normal pressure, introduced nitrogen, continued to react for 5h, vacuumed, and continued to react for 45min, let stand for 10min, unloaded, cast, and pelletized to obtain hydrophilic polyamide slices, and then melt-spun to obtain modified nylon fiber.

[0017] Example 3: The composite antibacterial agent is prepared by the following steps: Step A1, ultrasonically dispersing 10 g of cellulose in 100 g of 2 wt% acetic acid solution, stirring at 50° C. for 5 h, filtering, washing, and drying to obtain pretreated cellulose; Step A2, 5 g of pre-treated cellulose and 3 g of 2,3-dimercaptosuccinic acid were mixed and stirred in 100 mL of DMF, and then 0.015 g of p-toluenesulfonic acid was added, and the mixture was reacted under nitrogen at 140° C. for 1 h, and then under vacuum conditions for 2.5 h, and then 50 mL of acetone and 20 mL of n-hexane were added and stirred, and the mixture was distilled under reduced pressure to obtain modified cellulose; Step A3, under nitrogen conditions, add 5 g of modified cellulose to 50 mL of DMF and mix and stir evenly, slowly drop 20 mL of 0.25 mol / L copper nitrate solution, and adjust the solution pH to 9, heat to 40 ° C, react for 3 h, distill under reduced pressure, and dry to obtain a composite antibacterial agent.

[0018] The modified nylon fiber is prepared by the following steps: Step B1, add 0.3 mol 5-aminoisophthalic acid to 100 mL N, N-dimethylacetamide, mix and stir evenly, transfer to an ice water bath and let stand for 20 min, add 7 mL triethylamine, then add 0.3 mol undecenoyl chloride three times, and stir at 5 ° C for 30 min, then transfer to an oil bath, and heat to 75 ° C, react for 8 h, precipitate, wash, dry, recrystallize, and dry twice to obtain a carboxyl-terminated product; Step B2, 5.1g of the carboxyl-terminated product, 0.285g of anhydrous sodium sulfite and 0.21g of sodium nitrate were mixed and stirred in a flask containing 100mL of DMF, the temperature was raised to reflux, 24.6g of sodium bisulfite solution was slowly added dropwise for 1h, and the temperature was maintained at 105°C for continuous reaction for 10h, chromatography, washing and drying to obtain a sulfonated product, wherein the sodium bisulfite solution was prepared by mixing and stirring sodium bisulfite and deionized water in a mass ratio of 4.68:20; Step B3, 2g of the sulfonated product and 0.52g of hexamethylenediamine were dispersed in 10mL of ethanol to form a sulfonated product solution and a hexamethylenediamine solution, and then the sulfonated product solution was added dropwise to the hexamethylenediamine solution, and the temperature was raised to 70°C and stirred for 3h, filtered and dried, and the sulfonated product-hexamethylenediamine salt was collected; then 47.48g of caprolactam, the sulfonated product-hexamethylenediamine salt and 2.5g of deionized water were mixed and stirred evenly, transferred to a reactor, nitrogen replaced the gas in the reactor three times, heated to 100°C, started stirring, and then heated to 250°C, and maintained the pressure at 0.6MPa for 4h, adjusted the pressure in the reactor to normal pressure, introduced nitrogen, continued to react for 6h, vacuumed, and continued to react for 60min, let stand for 10min, unloaded, cast, and pelletized to obtain hydrophilic polyamide slices, and then melt-spun to obtain modified nylon fiber.

[0019] Embodiment 4: A method for preparing a multi-layer composite nylon fabric comprises the following steps: Step S1, weighing raw materials by weight, mixing 40 parts of polyamide solution, 3 parts of sodium alginate, 5 parts of the composite antibacterial agent prepared in Example 1 and 1 part of chitosan, and then melt spinning to obtain antibacterial fibers, and then interweaving the antibacterial fibers to form an antibacterial layer; Step S2, nylon fiber and cotton fiber are mixed and woven in a ratio of 2:1 to form an inner layer, and the modified nylon fiber prepared in Example 1 is woven to form an outer layer; Step S3: stacking, aligning and compounding the inner layer, the antibacterial layer and the outer layer from top to bottom in sequence to obtain a multi-layer composite nylon fabric.

[0020] Embodiment 5: A method for preparing a multi-layer composite nylon fabric comprises the following steps: Step S1, weighing raw materials by weight, mixing 50 parts of polyamide solution, 4.5 parts of sodium alginate, 7.5 parts of the composite antibacterial agent prepared in Example 2 and 2.5 parts of chitosan, and then melt spinning to obtain antibacterial fibers, and then interweaving the antibacterial fibers to form an antibacterial layer; Step S2, nylon fiber and cotton fiber are mixed and woven in a ratio of 2:1 to form an inner layer, and the modified nylon fiber prepared in Example 2 is woven to form an outer layer; Step S3: stacking, aligning and compounding the inner layer, the antibacterial layer and the outer layer from top to bottom in sequence to obtain a multi-layer composite nylon fabric.

[0021] Embodiment 6: A method for preparing a multi-layer composite nylon fabric comprises the following steps: Step S1, weighing raw materials by weight, mixing 60 parts of polyamide solution, 6 parts of sodium alginate, 10 parts of the composite antibacterial agent prepared in Example 3 and 4 parts of chitosan, and then melt spinning to obtain antibacterial fibers, and then interweaving the antibacterial fibers to form an antibacterial layer; Step S2, nylon fiber and cotton fiber are mixed and woven in a ratio of 2:1 to form an inner layer, and the modified nylon fiber prepared in Example 3 is woven to form an outer layer; Step S3: stacking, aligning and compounding the inner layer, the antibacterial layer and the outer layer from top to bottom in sequence to obtain a multi-layer composite nylon fabric.

[0022] Comparative Example 1: This comparative example is a nylon fabric. The difference from Example 6 is that a commercially available quaternary ammonium salt antibacterial agent is used instead of the composite antibacterial agent prepared in Example 3, and the rest are the same.

[0023] Comparative Example 2: This comparative example is a nylon fabric, which differs from Example 6 in that nylon fiber is used instead of the modified nylon fiber prepared in Example 3, and the rest is the same.

[0024] The nylon fabrics prepared in Examples 4-6 and Comparative Examples 1-2 were subjected to performance tests: Antibacterial performance test: According to GB / T 20944.3-2008 "Evaluation of antibacterial properties of textiles Part 3: Oscillation method", the antibacterial rate of each nylon fabric after washing 100 times was analyzed; Air permeability test: GBT5453-1997 "Determination of air permeability of textile fabrics" is used to test the air permeability of nylon fabrics (mm / s); Hygroscopicity test: Determined in accordance with GB / T 21655.1-2008 "Evaluation of moisture absorption and quick-drying properties of textiles Part 1: Single combination test method"; The test results are shown in Table 1: Table 1: Performance test results

[0025] It can be seen from Table 1 that the multi-layer composite nylon fabric prepared by the present invention has excellent antibacterial performance, air permeability and hygroscopicity after being tested for antibacterial performance, air permeability and hygroscopicity.

[0026] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the scope defined by the concept of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A multi-layer composite nylon fabric, characterized in that: From top to bottom, it includes an inner layer, an antibacterial layer and an outer layer; the inner layer is woven by mixing nylon fiber and cotton fiber in a ratio of 2:1; the antibacterial layer is formed by interweaving antibacterial fibers; the outer layer is woven by modified nylon fiber; The antibacterial fiber is composed of the following raw materials in parts by weight: 40-60 parts of polyamide solution, 3-6 parts of sodium alginate, 5-10 parts of composite antibacterial agent and 1-4 parts of chitin.

2. The multi-layer composite nylon fabric according to claim 1, characterized in that: The composite antibacterial agent is prepared by the following steps: Step A1, ultrasonically dispersing cellulose in a 1-2 wt% acetic acid solution, stirring at 40-50° C. for 3-5 h, filtering, washing, and drying to obtain pre-treated cellulose; Step A2, the pretreated cellulose and 2,3-dimercaptosuccinic acid are mixed and stirred in DMF, p-toluenesulfonic acid is added, and the mixture is reacted under nitrogen at 120-140° C. for 1 hour, and then under vacuum conditions for 1.5-2.5 hours, and then acetone and n-hexane are added and stirred, and the mixture is distilled under reduced pressure to obtain modified cellulose; Step A3, under nitrogen conditions, add modified cellulose to DMF and mix and stir evenly, slowly drop 0.15-0.25 mol / L copper nitrate solution, and adjust the solution pH to 8-9, heat to 40°C, react for 1-3h, distill under reduced pressure, and dry to obtain a composite antibacterial agent.

3. The multi-layer composite nylon fabric according to claim 1, characterized in that: The mass ratio of cellulose to acetic acid solution in step A1 is 1:

10.

4. The multi-layer composite nylon fabric according to claim 1, characterized in that: In step A2, the usage ratio of pre-treated cellulose, 2,3-dimercaptosuccinic acid, DMF, p-toluenesulfonic acid, acetone and n-hexane is 2-5 g: 1-3 g: 100 mL: 0.005-0.015 g: 50 mL: 20 mL.

5. The multi-layer composite nylon fabric according to claim 1, characterized in that: In step A3, the usage ratio of modified cellulose, DMF and copper nitrate solution is 3-5 g: 50 mL: 20 mL.

6. The multi-layer composite nylon fabric according to claim 1, characterized in that: The modified nylon fiber is prepared by the following steps: Step B1, add 5-aminoisophthalic acid to N, N-dimethylacetamide, mix and stir evenly, transfer to an ice water bath and let stand for 10-20 minutes, add triethylamine, then add undecylenic acid chloride three times, and stir at 0-5°C for 30 minutes, then transfer to an oil bath, and heat to 55-75°C, react for 4-8 hours, precipitate, wash, dry, recrystallize, and dry twice to obtain a carboxyl-terminated product; Step B2, the carboxyl-terminated product, anhydrous sodium sulfite and sodium nitrate are mixed and stirred evenly in a flask containing DMF, the temperature is raised to reflux, and the sodium bisulfite solution is slowly added dropwise for 1 hour, and then the temperature is maintained at 90-105° C. for continuous reaction for 8-10 hours, chromatography, washing and drying to obtain the sulfonated product; Step B3, the sulfonated product and hexamethylenediamine are dispersed in equal amounts of ethanol to form a sulfonated product solution and a hexamethylenediamine solution, and then the sulfonated product solution is added dropwise to the hexamethylenediamine solution, and the temperature is raised to 50-70°C and stirred for reaction for 1-3h, filtered and dried, and the sulfonated product-hexamethylenediamine salt is collected; caprolactam, the sulfonated product-hexamethylenediamine salt and deionized water are mixed and stirred evenly, transferred to a reactor, nitrogen is replaced in the reactor three times, the temperature is raised to 100°C, stirring is started, and then the temperature is raised to 230-250°C, and the pressure is maintained at 0.5-0.6MPa for reaction for 2-4h, the pressure in the reactor is adjusted to normal pressure, nitrogen is introduced, the reaction is continued for 4-6h, vacuum is drawn, and the reaction is continued for 30-60min, and the material is discharged, cast, and pelletized to obtain hydrophilic polyamide slices, and then melt-spinning is performed to obtain modified nylon fiber.

7. The multi-layer composite nylon fabric according to claim 6, characterized in that: In step B1, the usage ratio of 5-aminoisophthalic acid, N,N-dimethylacetamide, triethylamine and undecenoyl chloride is 0.1-0.3 mol:100 mL:2.3-7 mL:0.1-0.3 mol.

8. The multi-layer composite nylon fabric according to claim 6, characterized in that: In step B2, the amount ratio of the terminal carboxyl product, anhydrous sodium sulfite, sodium nitrate, DMF and sodium bisulfite solution is 1.7-5.1 g: 0.095-0.285 g: 0.07-0.21 g: 100 mL: 21.5-24.6 g, and the sodium bisulfite solution is prepared by mixing and stirring sodium bisulfite and deionized water in a mass ratio of 1.56-4.68:

20.

9. The multi-layer composite nylon fabric according to claim 6, characterized in that: In step B3, the mass ratio of the sulfonated product, hexamethylenediamine and caprolactam is 1-2: 0.26-0.52: 47.48-48.74, and deionized water accounts for 4-5% of the total mass of the reactants.

10. A method for preparing the multi-layer composite nylon fabric according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step S1, weighing raw materials by weight, mixing polyamide solution, sodium alginate, composite antibacterial agent and chitosan, and then melt spinning to obtain antibacterial fibers, and then interweaving the antibacterial fibers to form an antibacterial layer; Step S2, mixing nylon fiber and cotton fiber in a ratio of 2:1 to form an inner layer, and weaving modified nylon fiber to form an outer layer; Step S3: stacking the inner layer, the antibacterial layer and the outer layer from top to bottom, aligning and compounding them, so as to obtain a multi-layer composite nylon fabric.

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