An antibacterial nylon fiber and its preparation method

Abstract

This invention relates to the field of nylon fiber technology and discloses an antibacterial nylon fiber and its preparation method. In the molecular structure of hyperbranched quaternary ammonium salt polyamide, the quaternary ammonium salt carries a positive charge. When bacteria come into contact with it, through electrostatic interaction, the negatively charged bacteria are attracted by the quaternary ammonium salt cations, inhibiting bacterial respiration and causing "contact death." In addition, the large molecular weight of hyperbranched polyamide hinders its diffusion and penetration into the cell wall, resulting in a long-lasting antibacterial effect and easy storage. The molecular structure of hyperbranched quaternary ammonium salt polyamide contains structural units similar to those of nylon. According to the principle of "like dissolves like," the two have good interfacial compatibility and a tighter bond. At the same time, the imidazole, triazole, and other heterocyclic structures and benzene rings in the molecular structure of hyperbranched quaternary ammonium salt polyamide can effectively inhibit the movement and rotation of molecular chains, thereby improving the heat resistance of nylon fiber.

Description

Technical Field

[0001] This invention relates to the field of nylon fiber technology, specifically to an antibacterial nylon fiber and its preparation method. Background Technology

[0002] Nylon fiber is one of the most widely used and high-performance synthetic fibers. Due to its high strength and abrasion resistance, it is widely used in clothing, carpet decoration, and medical fabrics, especially in underwear, socks, automotive interiors, and curtain fabrics. However, the chemical structure and porous nature of nylon fiber textiles facilitate the attachment of microorganisms and make them susceptible to infection by most bacteria and viruses. Under certain conditions, they can even provide a breeding ground for bacteria, threatening human health. With increasing demands for environmental health and hygiene, higher requirements are being placed on the antibacterial properties of nylon fibers. Therefore, developing durable antibacterial fibers is of great practical significance.

[0003] Currently, the main methods for solving the antibacterial problem of nylon fibers include blending and modifying small-molecule organic antibacterial agents with polyamides. However, small-molecule organic antibacterial agents have drawbacks such as easy migration, easy water solubility, and poor thermal stability. Other technologies use antibacterial agents such as zeolite, natural minerals, and nanoparticles for antibacterial modification, but these have weak antibacterial properties, require large quantities, and are difficult to process at high temperatures, thus severely affecting the mechanical properties of the fibers. Antibacterial fibers are widely used and in high demand, but existing technologies cannot effectively solve the problems of high functional component addition, difficulty in dispersion, and challenges in high-temperature processing. Problems such as low production yield in stable and continuous production have prevented antibacterial fibers from being effectively mass-produced, making it difficult to meet the broad market demand. Patent No. CN113502660B discloses a cool antibacterial mosquito net fabric and its preparation method, which introduces alkyl diguanidine salt into the polyamide molecular chain to synthesize a self-made nylon fiber with a macromolecular chain. Then, a finishing agent is sprayed onto the fiber, which has the effects of water resistance and long-lasting antibacterial effect. However, this technology is complicated to operate, the antibacterial components are unevenly distributed and the amount added is large, and a finishing process is required to ensure the antibacterial effect. Moreover, the function is relatively simple.

[0004] The main methods to achieve antibacterial properties in fibers are through surface modification and blending modification techniques. This invention improves the antibacterial properties of nylon fibers by synthesizing hyperbranched polyamides with structures similar to nylon and introducing quaternary ammonium salt structures into the polymer matrix. It also improves the heat resistance of nylon fibers by introducing heat-resistant groups such as triazole groups and benzene rings, thereby further improving the overall performance of nylon fibers. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an antibacterial nylon fiber and its preparation method, which solves the problem of poor antibacterial performance of existing nylon fibers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing an antibacterial nylon fiber is carried out according to the following steps:

[0008] (1) Under a nitrogen atmosphere, add the following structural formula to the reaction flask: 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide, triazidotriacetic acid glycerol, and N,N-dimethylformamide were stirred until homogeneous. Then, N,N,N',N'',N''-pentamethyldiethylenetriamine and cuprous bromide were added and stirred to react. After the reaction was completed, diethyl ether was added for precipitation and purification to obtain hyperbranched quaternary ammonium salt polyamide.

[0009] (2) Nylon 6 chips and hyperbranched quaternary ammonium salt polyamide are blended and melted in a twin-screw extruder, melt-spun in a melt spinning machine, and then stretched in a stretching and twisting machine. The hot plate temperature is 120-130℃, the hot plate temperature is 60-70℃, and the stretching ratio is 2.5-3.5 to obtain antibacterial nylon fiber.

[0010] Furthermore, in step (1), the ratio of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide, triazidotriacetate, N,N,N',N'',N''-pentamethyldiethylenetriamine, and cuprous bromide is (1.5-2) mol: 1 mol: (0.25-0.35) mol: (0.3-0.4) mol.

[0011] Furthermore, in step (1), the reaction temperature is 40-60℃ and the reaction time is 45-60h.

[0012] Furthermore, in step (2), the ratio of nylon 6 chips to hyperbranched quaternary ammonium salt polyamide is 100g: (1-10)g.

[0013] Furthermore, in step (2), the spinning temperature is 255-270℃ and the winding speed is 750-900m / min.

[0014] Furthermore, the preparation method of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide in step (1) is carried out according to the following steps:

[0015] Step S1: Under a nitrogen atmosphere, 5-(1H-imidazol-1-yl)isophthalic acid and N,N-dimethylformamide were added to a reaction flask and stirred until homogeneous. Then, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole were added and dispersed until homogeneous. Propyleneamine was added and the mixture was stirred until the reaction was complete. After the reaction was completed, the mixture was concentrated under reduced pressure, purified by column chromatography, and dried to obtain 5-imidazolyl-1,3-bis(propynyl)isophthalamide.

[0016] Step S2: Under a nitrogen atmosphere, benzyl bromide and toluene are added to a reaction flask and stirred until homogeneous. Then, 5-imidazolyl-1,3-bis(propynyl)-isophthalamide is added and reacted at 60-80°C for 5-10 hours. After cooling to room temperature, dichloromethane is added, and the mixture is concentrated under reduced pressure and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

[0017] Furthermore, in step S1, the ratio of 5-(1H-imidazol-1-yl)isophthalic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, and propargylamine is 1 mol: (2.5-3.5) mol: (2.2-3) mol: (2.4-3.2) mol.

[0018] Furthermore, in step S1, the reaction temperature is 20-35℃ and the reaction time is 8-16h.

[0019] Furthermore, in step S2, the ratio of benzyl bromide to 5-imidazolyl-1,3-bis(propynyl)isophthalamide is 1 mol: (1.05-1.2) mol.

[0020] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0021] This invention first involves an amide condensation reaction between 5-(1H-imidazol-1-yl)isophthalic acid and propargylamine in the presence of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole to obtain 5-imidazolyl-1,3-di(propynyl)isophthalamide. Next, benzyl bromide is reacted with 5-imidazolyl-1,3-di(propynyl)isophthalamide in a quaternization reaction to obtain 5-(benzylimidazolium bromide)-1,3-di(propynyl)isophthalamide. Then, a Click reaction is performed between the alkynyl group of 5-(benzylimidazolium bromide)-1,3-di(propynyl)isophthalamide and the azide group of triazidotriacetate to obtain a hyperbranched quaternary ammonium salt polyamide. Finally, this polyamide is melt-blended with nylon 6 chips, spun, and stretched to obtain antibacterial nylon fibers.

[0022] Hyperbranched polymers possess a three-dimensional branched structure, multiple internal cavities, binding sites, and terminal functional groups, exhibiting significant structural advantages. This invention introduces imidazole quaternary ammonium salt antibacterial groups into the polymer chain through chemical grafting, resulting in hyperbranched quaternary ammonium salt polyamides. The quaternary ammonium salt in its molecular structure carries a positive charge, exhibiting a high relative molecular weight and positive charge density. When bacteria come into contact with hyperbranched quaternary ammonium salt polyamides, the negatively charged bacteria are attracted by the quaternary ammonium salt cations, inhibiting their respiration and resulting in "contact death." Simultaneously, through electrostatic interactions, the higher molecular weight antibacterial molecules come into contact with the negatively charged bacteria more rapidly, causing deformation of the cell wall and cell membrane, leading to leakage of intracellular proteins and other substances, resulting in "bacterial lysis" and death. Furthermore, the large molecular weight of the hyperbranched polyamide hinders its diffusion and penetration through the cell wall. Compared to small-molecule antibacterial agents with the same structure, it exhibits a longer-lasting antibacterial effect and is easier to store.

[0023] Hyperbranched quaternary ammonium salt polyamides contain structures similar to those of nylon 6. According to the principle of "like dissolves like," hyperbranched quaternary ammonium salt polyamides have good interfacial compatibility with nylon 6 and are tightly bound together. Moreover, as an antibacterial polymer, hyperbranched quaternary ammonium salt polyamides do not have the disadvantages of easy migration or easy water solubility, thus enabling the prepared nylon fibers to have highly efficient and long-lasting antibacterial functions. At the same time, the imidazole, triazole and other heterocyclic structures and benzene rings in the molecular structure of hyperbranched quaternary ammonium salt polyamides can effectively inhibit the movement and rotation of molecular chains, making the chemical structure of hyperbranched polymerization stable. They also have structural units similar to nylon, with good compatibility, which gives the molecular chains excellent thermal properties, thereby improving the heat resistance of nylon fibers. Detailed Implementation

[0024] The compounds of the present invention, their preparation methods, and applications are further described in detail below with reference to specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0025] 5-(1H-imidazol-1-yl)isophthalic acid, CAS number 1643586-52-0.

[0026] 1-Ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, CAS No. 25952-53-8.

[0027] 1-Hydroxybenzotriazole, CAS number 2592-95-2.

[0028] Propyleneamine, CAS number 2450-71-7.

[0029] Benzyl bromide, CAS number 100-39-0.

[0030] N,N,N',N'',N''-Pentamethyldiethylenetriamine, CAS number 3030-47-5.

[0031] Glycerol, CAS number 56-81-5.

[0032] Preparation of triazidotriacetic acid glycerol: 7.4 g glycerol, 26.1 g chloroacetic acid, 0.5 g p-toluenesulfonic acid, and 150 mL toluene were added to a reaction flask. The mixture was refluxed at 110 °C until the solvent was clear in the separator. After cooling, the mixture was washed with Na₂CO₃ aqueous solution and deionized water, and dried to obtain trichlorotriacetic acid glycerol. 5 g of trichlorotriacetic acid glycerol, 3.3 g sodium azide, and 30 mL acetone were reacted at 80 °C for 16 h. After cooling, the mixture was extracted with dichloromethane and deionized water. The organic phase was concentrated and dried to obtain triazidotriacetic acid glycerol. The preparation process is as follows:

[0033]

[0034] Example 1

[0035] (1) Under a nitrogen atmosphere, 10 mmol of 5-(1H-imidazol-1-yl)isophthalic acid and 80 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 30 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 25 mmol of 1-hydroxybenzotriazole were added. After even dispersion, 28 mmol of propargylamine was added. The reaction was carried out at 25 °C for 15 h, concentrated under reduced pressure, and purified by column chromatography. The mobile phase consisted of methanol and dichloromethane in a volume ratio of 1:10. After drying, 5-imidazolyl-1,3-bis(propynyl)isophthalamide was obtained. The preparation process is as follows:

[0036]

[0037] (2) Under a nitrogen atmosphere, 25 mmol of benzyl bromide and 250 mL of toluene were added to a reaction flask and stirred until homogeneous. Then, 27.5 mmol of 5-imidazolium-1,3-bis(propynyl)-isophthalamide was added, and the mixture was reacted at 70 °C for 80 h. After cooling to room temperature, dichloromethane was added, and the mixture was concentrated under reduced pressure and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide. The preparation process is as follows:

[0038]

[0039] (3) Under a nitrogen atmosphere, 27 mmol of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide, 15 mmol of triazidotriacetin, and 180 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 4.5 mmol of N,N,N',N'',N''-pentamethyldiethylenetriamine and 5.4 mmol of cuprous bromide were added. The reaction was carried out at 50 °C for 54 h. After precipitation and purification by adding diethyl ether, hyperbranched quaternary ammonium salt polyamide was obtained. The preparation process principle is as follows:

[0040]

[0041] (4) 100g of nylon 6 chips and 1g of hyperbranched quaternary ammonium salt polyamide were melt-blended in a twin-screw extruder at a blending temperature of 170℃, a screw speed of 120r / min, and a blending time of 8min. Then, melt spinning was performed in a melt spinning machine at a spinning temperature of 260℃ and a winding speed of 800m / min. Next, stretching was performed on a stretching and twisting machine at a hot plate temperature of 125℃, a hot plate temperature of 65℃, and a stretching ratio of 3.0 to obtain antibacterial nylon fiber.

[0042] Example 2

[0043] (1) Under a nitrogen atmosphere, 50 mmol of 5-(1H-imidazol-1-yl)isophthalic acid and 250 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 125 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 110 mmol of 1-hydroxybenzotriazole were added. After being evenly dispersed, 120 mmol of propargylamine was added. The reaction was carried out at 35 °C for 8 h. The mixture was concentrated under reduced pressure and purified by column chromatography. The mobile phase consisted of methanol and dichloromethane in a volume ratio of 1:10. After drying, 5-imidazolyl-1,3-bis(propynyl)isophthalamide was obtained.

[0044] (2) Under a nitrogen atmosphere, 30 mmol of benzyl bromide and 240 mL of toluene were added to the reaction flask and stirred until homogeneous. Then, 31.5 mmol of 5-imidazolyl-1,3-bis(propynyl)-isophthalamide was added and reacted at 80 °C for 5 h. After cooling to room temperature, dichloromethane was added, the mixture was concentrated under reduced pressure, and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

[0045] (3) Under a nitrogen atmosphere, 30 mmol of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide, 20 mmol of triazidotriacetic acid glycerol and 200 mL of N,N-dimethylformamide were added to the reaction flask. After stirring evenly, 5 mmol of N,N,N',N'',N''-pentamethyldiethylenetriamine and 6 mmol of cuprous bromide were added. The reaction was carried out at 60 °C for 45 h. Diethyl ether was added to precipitate and purify the product to obtain hyperbranched quaternary ammonium salt polyamide.

[0046] (4) 100g of nylon 6 chips and 3.25g of hyperbranched quaternary ammonium salt polyamide were melt-blended in a twin-screw extruder at a blending temperature of 175℃, a screw speed of 125r / min, and a blending time of 5min. Then, melt spinning was performed in a melt spinning machine at a spinning temperature of 270℃ and a winding speed of 900m / min. Next, stretching was performed on a stretching and twisting machine at a hot plate temperature of 130℃ and a hot plate temperature of 70℃, with a stretching ratio of 3.5, to obtain antibacterial nylon fiber.

[0047] Example 3

[0048] (1) Under a nitrogen atmosphere, 35 mmol of 5-(1H-imidazol-1-yl)isophthalic acid and 350 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 122.5 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 105 mmol of 1-hydroxybenzotriazole were added. After being evenly dispersed, 112 mmol of propargylamine was added. The reaction was carried out at 25 °C for 16 h. The mixture was concentrated under reduced pressure and purified by column chromatography. The mobile phase consisted of methanol and dichloromethane in a volume ratio of 1:10. After drying, 5-imidazolyl-1,3-bis(propynyl)isophthalamide was obtained.

[0049] (2) Under a nitrogen atmosphere, 10 mmol of benzyl bromide and 8-12 mL of toluene were added to the reaction flask and stirred until homogeneous. Then, 12 mmol of 5-imidazolium-1,3-bis(propynyl)-isophthalamide was added and reacted at 60 °C for 10 h. After cooling to room temperature, dichloromethane was added, and the mixture was concentrated under reduced pressure and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

[0050] (3) Under a nitrogen atmosphere, 40 mmol of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide, 20 mmol of triazidotriacetic acid glycerol and 300 mL of N,N-dimethylformamide were added to the reaction flask. After stirring evenly, 7 mmol of N,N,N',N'',N''-pentamethyldiethylenetriamine and 8 mmol of cuprous bromide were added. The reaction was carried out at 40 °C for 60 h. Diethyl ether was added to precipitate and purify the product to obtain hyperbranched quaternary ammonium salt polyamide.

[0051] (4) 100g of nylon 6 chips and 5.5g of hyperbranched quaternary ammonium salt polyamide were melt-blended in a twin-screw extruder at a blending temperature of 165℃, a screw speed of 115r / min, and a blending time of 10min. Then, melt spinning was performed in a melt spinning machine at a spinning temperature of 255℃ and a winding speed of 750m / min. Next, stretching was performed on a stretching and twisting machine at a hot plate temperature of 120℃, a hot plate temperature of 60℃, and a stretching ratio of 2.5 to obtain antibacterial nylon fiber.

[0052] Example 4

[0053] (1) Under a nitrogen atmosphere, 100 mmol of 5-(1H-imidazol-1-yl)isophthalic acid and 950 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 280 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 265 mmol of 1-hydroxybenzotriazole were added. After being evenly dispersed, 310 mmol of propargylamine was added. The reaction was carried out at 30 °C for 10 h. The mixture was concentrated under reduced pressure and purified by column chromatography. The mobile phase consisted of methanol and dichloromethane in a volume ratio of 1:10. After drying, 5-imidazolyl-1,3-bis(propynyl)isophthalamide was obtained.

[0054] (2) Under a nitrogen atmosphere, 80 mmol of benzyl bromide and 880 mL of toluene were added to the reaction flask and stirred until homogeneous. Then, 92 mmol of 5-imidazolyl-1,3-bis(propynyl)-isophthalamide was added and reacted at 75 °C for 8 h. After cooling to room temperature, dichloromethane was added, and the mixture was concentrated under reduced pressure and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

[0055] (3) Under a nitrogen atmosphere, 72 mmol of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide, 45 mmol of triazidotriacetin, and 630 mL of N,N-dimethylformamide were added to the reaction flask. After stirring evenly, 14.4 mmol of N,N,N',N'',N''-pentamethyldiethylenetriamine and 16.2 mmol of cuprous bromide were added. The reaction was carried out at 55 °C for 52 h. Diethyl ether was added to precipitate and purify the product to obtain hyperbranched quaternary ammonium salt polyamide.

[0056] (4) 100g of nylon 6 chips and 7.75g of hyperbranched quaternary ammonium salt polyamide were melt-blended in a twin-screw extruder at a blending temperature of 170℃, a screw speed of 125r / min, and a blending time of 10min. Then, melt spinning was performed in a melt spinning machine at a spinning temperature of 260℃ and a winding speed of 850m / min. Next, stretching was performed on a stretching and twisting machine at a hot plate temperature of 120℃, a hot plate temperature of 65℃, and a stretching ratio of 3.5 to obtain antibacterial nylon fiber.

[0057] Example 5

[0058] (1) Under a nitrogen atmosphere, 60 mmol of 5-(1H-imidazol-1-yl)isophthalic acid and 450 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 171 mmol of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 168 mmol of 1-hydroxybenzotriazole were added. After being evenly dispersed, 174 mmol of propargylamine was added. The reaction was carried out at 35 °C for 12 h. The mixture was concentrated under reduced pressure and purified by column chromatography. The mobile phase consisted of methanol and dichloromethane in a volume ratio of 1:10. After drying, 5-imidazolyl-1,3-bis(propynyl)isophthalamide was obtained.

[0059] (2) Under a nitrogen atmosphere, 35 mmol of benzyl bromide and 280 mL of toluene were added to the reaction flask and stirred until homogeneous. Then, 41.3 mmol of 5-imidazolyl-1,3-bis(propynyl)-isophthalamide was added and reacted at 75 °C for 10 h. After cooling to room temperature, dichloromethane was added, the mixture was concentrated under reduced pressure, and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

[0060] (3) Under a nitrogen atmosphere, 9 mmol of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide, 5 mmol of triazidotriacetin, and 70 mL of N,N-dimethylformamide were added to a reaction flask. After stirring evenly, 1.6 mmol of N,N,N',N'',N''-pentamethyldiethylenetriamine and 1.8 mmol of cuprous bromide were added. The reaction was carried out at 60 °C for 45 h. Diethyl ether was added to precipitate and purify the product to obtain hyperbranched quaternary ammonium salt polyamide.

[0061] (4) 100g of nylon 6 chips and 10g of hyperbranched quaternary ammonium salt polyamide were melt-blended in a twin-screw extruder at a blending temperature of 175℃, a screw speed of 115r / min, and a blending time of 5min. Then, melt spinning was performed in a melt spinning machine at a spinning temperature of 260℃ and a winding speed of 750m / min. Next, stretching was performed on a stretching and twisting machine at a hot plate temperature of 130℃, a hot plate temperature of 65℃, and a stretching ratio of 3.0 to obtain antibacterial nylon fiber.

[0062] Comparative Example 1

[0063] 100g of nylon 6 chips were melt-blended with 1g of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide (prepared in Example 1) in a twin-screw extruder at a blending temperature of 170°C, a screw speed of 120 r / min, and a blending time of 8 min. Then, the mixture was melt-spun in a melt spinning machine at a spinning temperature of 260°C and a winding speed of 800 m / min. Finally, the mixture was stretched in a stretching and twisting machine at a hot plate temperature of 125°C and a hot plate temperature of 65°C, with a stretch ratio of 3.0, to obtain nylon fibers.

[0064] Comparative Example 2

[0065] 100g of nylon 6 chips were melt-blended in a twin-screw extruder at a blending temperature of 170℃, a screw speed of 120r / min, and a blending time of 8min. Then, melt-spinning was performed in a melt spinning machine at a spinning temperature of 260℃ and a winding speed of 800m / min. Subsequently, the fibers were stretched in a stretching and twisting machine at a hot plate temperature of 125℃ and a hot plate temperature of 65℃, with a stretch ratio of 3.0, to obtain nylon fibers.

[0066] Antibacterial performance test: According to the antibacterial test standard GB / T20944.3-2008, Staphylococcus aureus and Escherichia coli were used as test bacteria, and the antibacterial performance of the fabric was measured by the shaking method.

[0067] Bacterial culture and activation: Escherichia coli and Staphylococcus aureus were activated in liquid culture medium, and then the culture was placed in a constant temperature shaker at 37℃ and cultured at a shaking speed of 150 rpm for 24 h; then the nylon fibers to be tested were cut into small pieces of 2cm×2cm, 1g of each fabric sample was weighed, and sterilized at 120℃ for 60 min with Erlenmeyer flasks containing 30mL of liquid culture medium and glassware.

[0068] Test method: The bacterial culture was inoculated into Erlenmeyer flasks containing liquid culture medium, and then the sterilized fiber sample was also placed in the flasks. The flasks were incubated in a constant temperature shaker for 18 hours. After incubation, the bacterial culture in the medium was diluted with PBS buffer to a final concentration of 1.1 × 10⁻⁶. 8 CFU / mL, 100 μL of the diluted solution was dropped onto a solid culture medium, spread evenly, and then incubated in a 37℃ constant temperature and humidity incubator for 24 h. Finally, plate viable counts were performed. The antibacterial rate of nylon fiber was calculated according to the formula: Y (%) = (W1-W2) / W1×100%, where Y represents the antibacterial rate of nylon fiber (%), W1 represents the average number of surviving bacteria (CFU / mL) in the bottle after 18 h of full contact with bacteria from ordinary nylon fiber (the nylon fiber prepared for Comparative Example 2), and W2 represents the average number of surviving bacteria (CFU / mL) in the bottle after 18 h of full contact with bacteria from antibacterial fiber. The average value was calculated from three tests.

[0069]

[0070] The test results in the table above show that as the content of hyperbranched quaternary ammonium salt polyamide in the blend system increases, the antibacterial rate of nylon fiber against different bacteria increases rapidly. Among them, the antibacterial rate against Escherichia coli and Staphylococcus aureus is the highest, reaching 99.99%, demonstrating excellent antibacterial performance. This is because the hyperbranched quaternary ammonium salt polyamide, obtained by grafting imidazole quaternary ammonium salt antibacterial functional groups onto the polymer chain, increases the density of quaternary ammonium salt antibacterial groups. Quaternary ammonium salt molecules carry a positive charge, and after polymerization, their relative molecular mass increases, and the charge density of the positive charge also increases. Meanwhile, the phospholipids on the bacterial surface and inside the cell membrane carry a negative charge. Through electrostatic interaction, the hyperbranched quaternary ammonium salt polyamide comes into contact with the negatively charged bacteria more quickly, causing an imbalance in the cell wall structure. In addition, the large molecular weight of hyperbranched polyamide hinders its diffusion and penetration into the cell wall. Compared with small molecule antibacterial agents with the same structure, the antibacterial effect is long-lasting and easy to store.

[0071] The 5-(benzylimidazolium bromide)-1,3-bis(propynyl)isophthalamide added in Comparative Example 1 has a small molecule quaternary ammonium salt structure and has certain antibacterial effects. However, because it is an organic small molecule structure, it is prone to thermal decomposition at high temperatures, which affects its antibacterial performance.

[0072] Washability test: Pour laundry detergent and water into a beaker with a concentration of 5 g / L. Place the prepared nylon fiber into the washing water and mechanically agitate and wash for 5 minutes. Rinse the washed fiber with clean water for 10 minutes and dry at 70°C. Record the above cycle as one wash. Repeat the washing 50 times. Then, randomly cut a 2 cm × 2 cm sample of the washed fabric. According to the antibacterial test standard GB / T20944.3-2008, use the shaking method to test the antibacterial properties of the washed nylon fiber.

[0073]

[0074] The test results in the table above show that the antibacterial properties of nylon fibers remain excellent after 50 washes. The antibacterial rate after washing is basically unchanged compared to the unwashed fiber. The antibacterial rates against Escherichia coli and Staphylococcus aureus are the highest, both reaching 99.99%. This is because the synthesized hyperbranched quaternary ammonium salt polyamide contains a structure similar to that of nylon 6. According to the principle of "like dissolves like," the hyperbranched quaternary ammonium salt polyamide has good interfacial compatibility with nylon 6 and a tighter bond. Moreover, as an antibacterial polymer structure, the hyperbranched quaternary ammonium salt polyamide does not have the disadvantages of easy migration or easy water solubility, thus enabling the prepared nylon fibers to have a highly efficient and long-lasting antibacterial function.

[0075] Thermal performance test: The test was conducted using a TG tester. 5mg of shredded nylon fiber was placed in an alumina crucible and tested under a nitrogen atmosphere. The temperature range was 50-700℃ and the heating rate was 10℃ / min.

[0076]

[0077] As shown in the test results above, with the increase of hyperbranched quaternary ammonium salt polyamide content, the weight loss temperature of nylon fiber decreased, but it was still higher than that of pure nylon 6, which improved the heat resistance of nylon fiber. The highest temperature reached was 410.9℃ with a weight loss of 5wt%, and the highest temperature reached was 472.3℃ with a weight loss of 50wt%. This is because the hyperbranched quaternary ammonium salt polyamide structure contains more heterocyclic structural units such as imidazole and triazole, as well as rigid structures such as benzene rings, which have strong heat resistance. This hinders the free rotation of polyamide along the molecular chain direction under heating conditions, making the chemical structure of hyperbranched polymerization stable. At the same time, it has structural units similar to polyamide, with good compatibility, which makes the molecular chain have excellent thermal properties, thereby improving the heat resistance of nylon fiber.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing antibacterial nylon fiber, characterized in that, The preparation method is carried out according to the following steps: (1) Under a nitrogen atmosphere, add the following structural formula to the reaction flask: 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide, triazidotriacetic acid glycerol, and N,N-dimethylformamide were stirred until homogeneous. Then, N,N,N',N'',N''-pentamethyldiethylenetriamine and cuprous bromide were added and stirred to react. After the reaction was completed, diethyl ether was added for precipitation and purification to obtain hyperbranched quaternary ammonium salt polyamide. (2) Nylon 6 chips and hyperbranched quaternary ammonium salt polyamide are blended and melted in a twin-screw extruder, melt-spun in a melt spinning machine, and then stretched in a stretching and twisting machine. The hot plate temperature is 120-130℃, the hot plate temperature is 60-70℃, and the stretching ratio is 2.5-3.5 to obtain antibacterial nylon fiber.

2. The method for preparing antibacterial nylon fiber according to claim 1, characterized in that, The ratio of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide, triazidotriacetate, N,N,N',N'',N''-pentamethyldiethylenetriamine, and cuprous bromide in step (1) is (1.5-2) mol: 1 mol: (0.25-0.35) mol: (0.3-0.4) mol.

3. The method for preparing antibacterial nylon fiber according to claim 1, characterized in that, The reaction temperature in step (1) is 40-60℃ and the reaction time is 45-60h.

4. The method for preparing antibacterial nylon fiber according to claim 1, characterized in that, In step (2), the ratio of nylon 6 chips to hyperbranched quaternary ammonium salt polyamide is 100g: (1-10)g.

5. The method for preparing antibacterial nylon fiber according to claim 1, characterized in that, In step (2), the spinning temperature is 255-270℃ and the winding speed is 750-900m / min.

6. The method for preparing antibacterial nylon fiber according to claim 1, characterized in that, The preparation method of 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide in step (1) is carried out according to the following steps: Step S1: Under a nitrogen atmosphere, 5-(1H-imidazol-1-yl)isophthalic acid and N,N-dimethylformamide were added to a reaction flask and stirred until homogeneous. Then, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1-hydroxybenzotriazole were added and dispersed until homogeneous. Propyleneamine was added and the mixture was stirred until the reaction was complete. After the reaction was completed, the mixture was concentrated under reduced pressure, purified by column chromatography, and dried to obtain 5-imidazolyl-1,3-bis(propynyl)isophthalamide. Step S2: Under a nitrogen atmosphere, benzyl bromide and toluene are added to a reaction flask and stirred until homogeneous. Then, 5-imidazolyl-1,3-bis(propynyl)-isophthalamide is added and reacted at 60-80°C for 5-10 hours. After cooling to room temperature, dichloromethane is added, and the mixture is concentrated under reduced pressure and dried to obtain 5-(benzylimidazolium bromide)-1,3-bis(propynyl)-isophthalamide.

7. The method for preparing antibacterial nylon fiber according to claim 6, characterized in that, In step S1, the ratio of 5-(1H-imidazol-1-yl)isophthalic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, 1-hydroxybenzotriazole, and propargylamine is 1 mol: (2.5-3.5) mol: (2.2-3) mol: (2.4-3.2) mol.

8. The method for preparing antibacterial nylon fiber according to claim 6, characterized in that, In step S1, the reaction temperature is 20-35℃ and the reaction time is 8-16h.

9. The method for preparing antibacterial nylon fiber according to claim 6, characterized in that, In step S2, the ratio of benzyl bromide to 5-imidazolyl-1,3-bis(propynyl)isophthalamide is 1 mol: (1.05-1.2) mol.

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