A flame-retardant and antibacterial nylon 6 composite material and its preparation method and application

Abstract

The present invention relates to a flame-retardant antibacterial nylon 6 composite material and its preparation method and application, belonging to the technical field of flame-retardant antibacterial material synthesis. The composite material is prepared from nylon 6 slices, Zn@tannic acid (TA), copper pyromellitic acid (HKUST-1) and dimethyl methylphosphonate (DMMP). A Zn@TA@HKUST-1 antibacterial system is constructed by a layer-by-layer self-assembly method, and DMMP is then loaded into the antibacterial system by an immersion method. Wherein, the Zn@TA complex has photosensitivity and can efficiently kill bacteria under the synergistic effect of photodynamic / photothermal forces; HKUST-1 with a porous structure can adsorb smoke and poisonous gases in the early stage of combustion, and the intrinsic copper ions in the structure are slowly released, which, on the one hand, contributes to the efficient killing of bacteria, and on the other hand, can catalyze the carbonization of the material, thereby preventing further combustion of the material; DMMP releases PO· free radicals when thermally decomposed, which can capture H· and HO· free radicals in the combustion process, thereby dehydrating and carbonizing to exert a flame retardant effect.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant and antibacterial material synthesis, and relates to a flame-retardant and antibacterial nylon 6 composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Nylon 6 is widely used in the textile industry in fabrics such as underwear, panties, socks, tights, casual wear, and sportswear. However, prolonged contact between these nylon 6 fabrics and human skin, exposed to sweat, can easily breed bacteria, potentially impacting human health. Furthermore, nylon 6 fibers have poor thermal properties and are easily flammable, resulting in dripping and potentially spreading fires over large areas. With rising living standards and changing consumer attitudes, people are increasingly pursuing safe, environmentally friendly, and healthy textile products. Therefore, the development of flame-retardant and antimicrobial nylon 6 composites is in line with market trends.

[0003] Common nylon 6 flame retardants are categorized as halogen-based and halogen-free. Halogen-based flame retardants typically use organic fluorides and organic bromides, while halogen-free flame retardants typically use red phosphorus, melamine salts, ammonium polyphosphate salts, and polyetheramine salts. Halogen-free flame retardants generate significant smoke during use, releasing corrosive hydrogen halide gas and inevitably producing toxic gases that can affect human metabolism and harm health. Halogen-free flame retardants, while offering advantages such as low toxicity and smoke, also present issues such as low flame retardancy and deterioration in thermal stability and mechanical properties. Common nylon 6 antimicrobial agents include organic (such as zinc pyridine sulfate and monochlorophenol), inorganic (such as nanosilver and titanium dioxide), and natural (such as chitosan). However, organic antimicrobial agents are toxic and have poor heat resistance, limiting their use. Inorganic antimicrobial agents contain heavy metal ions, which also contribute to their toxicity and short-lasting antimicrobial effects. Natural antimicrobial agents, while safe, exhibit limited antimicrobial efficacy. Therefore, in order to solve the problems existing in current flame retardants and antimicrobial agents, more and more researchers have begun to devote themselves to the research and development of new flame retardants and antimicrobial agents. Among them, metal-organic framework compounds (MOFs) have become the focus of researchers due to their special structure.

[0004] CN114479286A discloses a method for preparing low-smoke, halogen-free, flame-retardant polypropylene, wherein diaminoethyl aluminum hypophosphite is grafted onto MOFs or dispersed in the pores or on the surface of MOFs to form a new flame retardant for improving the flame retardancy of polypropylene. CN112931530A discloses a Cu-MOF antibacterial material loaded with nanosilver, which utilizes the thiol groups on the MOF surface to capture anions, and after subsequent chemical reduction, achieves uniform fixation of Ag on the MOF surface, increases the Ag loading, and effectively improves the antibacterial properties of the material. CN113121880A discloses a hybrid nanocomposite flame retardant, its preparation method, and application, which introduces a phosphorus-containing flame-retardant silane into the structure of a silane-modified MOFs material, which not only solves the compatibility problem between MOFs and the polymer matrix, but also achieves efficient flame retardancy for nylon 6 through the synergistic flame retardant effect of MOFs and the phosphorus-containing flame-retardant silane. In order to further expand the selectivity of MOFs-based flame retardants and antibacterial agents, the present application provides a new MOFs-based flame retardant and antibacterial agent to improve the antibacterial and flame retardant properties of nylon 6. Summary of the Invention

[0005] In view of this, one of the objects of the present invention is to provide a method for preparing a flame retardant and antibacterial nylon 6 composite material; a second object of the present invention is to provide a flame retardant and antibacterial nylon 6 composite material; a third object of the present invention is to provide an application of a flame retardant and antibacterial nylon 6 composite material in the preparation of textiles or non-woven products.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] 1. A method for preparing a flame-retardant and antibacterial nylon 6 composite material, the preparation method being as follows:

[0008] (1) Preparation of Zn@TA@HKUST-1: Tannic acid (TA) and a water-soluble zinc salt were dispersed in a Tris-HCl buffer solution with a pH of 8.5 to obtain solution A; copper trimesate (HKUST-1) was dispersed in deionized water to obtain solution B; then, solution A and solution B were mixed and dried at 80-100°C for 12-24 hours;

[0009] (2) Preparation of Zn@TA@HKUST-1@DMMP: The Zn@TA@HKUST-1 described in step (1) was dried at 90-150°C for 10-15 h, then immersed in dimethyl methylphosphonate (DMMP) for 2-5 d, filtered, washed with acetone, and dried at 20-30°C for 10-24 h;

[0010] (3) Preparation of flame-retardant and antibacterial nylon 6 composite materials: The Zn@TA@HKUST-1@DMMP and nylon 6 chips described in step (2) are melt-mixed in a twin-screw extruder, then extruded into a spinning box, and delivered to the spinning assembly through a metering pump. The composite material is obtained by oiling with an oiling system and drawing and winding with a winding device.

[0011] Preferably, the preparation method of HKUST-1 in step (1) is as follows:

[0012] A water-soluble divalent copper salt and trimesic acid are added to N,N-dimethylformamide to form a mixture, and then the mixture is placed in a Teflon autoclave, reacted at 90-150° C. for 18-30 hours, centrifuged, washed with N,N-dimethylformamide and ethanol for 3-5 times, and then vacuum dried at 100-150° C. for 12-20 hours.

[0013] Preferably, the water-soluble divalent copper salt is any one of copper nitrate trihydrate, copper sulfate, copper acetate or copper chloride; and the molar ratio of the water-soluble divalent copper salt to trimesic acid is 6:4.

[0014] Preferably, in step (1), the molar ratio of TA, water-soluble zinc salt and HKUST-1 is 0.25:2.86:2.5; the water-soluble zinc salt is any one of zinc nitrate hexahydrate, zinc chloride, zinc sulfate or zinc acetate.

[0015] Preferably, the mass volume ratio of Zn@TA@HKUST-1 to DMMP in step (2) is 2:15, g:mL.

[0016] Preferably, the mass ratio of Zn@TA@HKUST-1@DMMP and nylon 6 chips in step (3) is 4:96 to 10:90.

[0017] Preferably, the screw speed of the twin-screw extruder in step (3) is 20-40 Hz, the screw heating temperature is 245-260°C; the box temperature of the spinning box is 255-265°C, the side blowing air volume is 15-40m 3 / min; the oiling rate of the oiling system is 2 to 6 wt.%; the winding speed of the winding device is 800 to 2000 m / min.

[0018] 2. The flame-retardant and antibacterial nylon 6 composite material prepared by the method.

[0019] 3. Application of the flame-retardant and antibacterial nylon 6 composite material in the preparation of textile or non-woven products.

[0020] The beneficial effects of the present invention are as follows: the present invention provides a flame-retardant and antibacterial nylon 6 composite material. The composite material is prepared from nylon 6 chips, a Zn@tannic acid complex, copper trimesic acid (HKUST-1), and dimethyl methylphosphonate (DMMP). First, zinc ions are complexed with tannic acid (TA) to form a Zn@TA complex. Then, a layer-by-layer self-assembly method is used to construct a Zn@TA@HKUST-1 antibacterial system through interactions such as electrostatic attraction, hydrogen bonding, and van der Waals forces. Finally, DMMP is loaded into this antibacterial system by an immersion method to form a novel flame-retardant and antibacterial nylon 6 composite material. In this composite material, the complex formed by zinc ions and TA is photosensitizing. Light-induced generation of highly oxidizing reactive oxygen species (ROS) can contact microorganisms and disrupt their cell membranes, causing cytoplasmic leakage and ultimately leading to cell death. HKUST-1, with its porous structure, absorbs smoke and toxic gases during the initial stages of combustion. The intrinsic copper ions in the structure are slowly released, effectively killing bacteria while also catalyzing the material's carbonization, thereby preventing further combustion. DMMP, upon thermal decomposition, releases PO· free radicals that capture H· and HO· free radicals during combustion, dehydrating them into charcoal and exerting a flame retardant effect. Compared to pure nylon 6, this composite material exhibits a peak heat release rate (pHRR) reduction of over 33.6%, a total heat release rate (THR) reduction of over 15.0%, an increase in the limiting oxygen index (LOI) to over 26.3%, and a V-0 rating in the vertical burn test (UL 94). When the Zn@TA@HKUST-1@DMMP content in the composite material exceeds 4 wt.%, the antibacterial rate against Escherichia coli, Staphylococcus aureus, and Candida albicans reaches over 99.99%. Even after 50 washes, the antibacterial rate remains above 99%. This demonstrates that the composite material has excellent flame retardant and antibacterial properties.

[0021] The present invention also provides a method for preparing the flame-retardant and antibacterial nylon 6 composite material. The preparation method is simple, easy to operate, and suitable for large-scale production.

[0022] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0024] Example 1

[0025] A flame-retardant and antibacterial nylon 6 composite material, wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips is 4:96, and the specific preparation method is as follows:

[0026] (1) Preparation of HKUST-1: 1.45 g of copper nitrate trihydrate and 0.85 g of trimesic acid were added to 35 ml of N,N-dimethylformamide (DMF) to obtain a mixture. The mixture was then placed in a Teflon autoclave and reacted at 110°C for 20 h to obtain a reaction product. The reaction product was then centrifuged, washed five times with DMF and five times with ethanol, and finally dried under vacuum at 150°C for 12 h.

[0027] (2) Preparation of Zn@TA@HKUST-1: 0.43 g of tannic acid and 0.85 g of zinc nitrate hexahydrate were dispersed in 50 ml of 10 mmol / L Tris-HCl buffer solution at pH 8.5 to obtain solution A; 1.7 g of HKUST-1 prepared in step (1) was ultrasonically dispersed in 5 ml of deionized water for 30 min to obtain solution B; solution A was injected into solution B, mixed and stirred for 30 min, and then dried in a rotary evaporator at 80°C for 24 h;

[0028] (3) Preparation of Zn@TA@HKUST-1@DMMP: 2.0 g of Zn@TA@HKUST-1 prepared in step (2) was heated in a vacuum drying oven at 100°C for 12 h, then immersed in 15 ml of DMMP for 3 days, filtered, washed with acetone five times, and dried at 25°C for 24 h.

[0029] (4) Preparation of flame-retardant and antibacterial nylon 6 composite materials: According to the percentage by mass, the Zn@TA@HKUST-1@DMMP and nylon 6 chips in step (3) were melt-mixed under the operation of a twin-screw extruder (wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips was 4:96, the screw speed of the twin-screw extruder was 30 Hz, the screw heating temperature was 245°C in zone 1, 250°C in zone 2, 255°C in zone 3, and 260°C in zone 4), and then extruded into a spinning box (the box temperature of the spinning box was 260°C, the side blowing air volume was 20m 3 / min), and then sent to the spinning assembly through a metering pump, oiled by an oiling system (oiling rate is 4wt.%) and drawn by a winding device (winding speed of the winding device is 1200m / min) to obtain a flame retardant and antibacterial nylon 6 composite material.

[0030] Example 2

[0031] A flame-retardant and antibacterial nylon 6 composite material, wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips is 7:93, and the specific preparation method is as follows:

[0032] (1) Preparation of HKUST-1: 2.2 g of copper nitrate trihydrate and 1.26 g of trimesic acid were added to 52 ml of DMF to obtain a mixture. The mixture was then placed in a Teflon autoclave and reacted at 110°C for 20 h to obtain a reaction product. The reaction product was then centrifuged, washed five times with DMF and five times with ethanol, and finally dried under vacuum at 150°C for 12 h.

[0033] (2) Preparation of Zn@TA@HKUST-1: 0.65 g of tannic acid and 1.28 g of zinc nitrate hexahydrate were dispersed in 75 ml of 10 mmol / L Tris-HCl buffer solution at pH 8.5 to obtain solution A; 2.6 g of HKUST-1 prepared in step (1) was ultrasonically dispersed in 75 ml of deionized water for 30 min to obtain solution B; solution A was injected into solution B, mixed and stirred for 30 min, and then dried in a rotary evaporator at 80°C for 24 h;

[0034] (3) Preparation of Zn@TA@HKUST-1@DMMP: 3.0 g of Zn@TA@HKUST-1 prepared in step (2) was heated in a vacuum drying oven at 100°C for 12 h, then immersed in 22.5 ml of DMMP for 3 days, filtered, washed with acetone five times, and dried at 25°C for 24 h.

[0035] (4) Preparation of flame-retardant and antibacterial nylon 6 composite materials: According to the percentage by mass, the Zn@TA@HKUST-1@DMMP in step (3) and nylon 6 chips were melt-mixed under the operation of a twin-screw extruder (wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips was 7:93, the screw speed of the twin-screw extruder was 30 Hz, the screw heating temperature was 245°C in zone 1, 250°C in zone 2, 255°C in zone 3, and 260°C in zone 4), and then extruded into a spinning box (the box temperature of the spinning box was 260°C, the side blowing air volume was 20m 3 / min), and then sent to the spinning assembly through a metering pump, oiled by an oiling system (oiling rate is 4wt.%) and drawn by a winding device (winding speed of the winding device is 1200m / min) to obtain a flame retardant and antibacterial nylon 6 composite material.

[0036] Example 3

[0037] A flame-retardant and antibacterial nylon 6 composite material, wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips is 10:90, and the specific preparation method is as follows:

[0038] (1) Preparation of HKUST-1: 2.9 g of copper nitrate trihydrate and 1.68 g of trimesic acid were added to 70 ml of DMF to obtain a mixture. The mixture was then placed in a Teflon autoclave and reacted at 110°C for 20 h to obtain a reaction product. The reaction product was then centrifuged, washed five times with DMF and five times with ethanol, and finally dried under vacuum at 150°C for 12 h.

[0039] (2) Preparation of Zn@TA@HKUST-1: 0.86 g of tannic acid and 1.70 g of zinc nitrate hexahydrate were dispersed in 100 ml of 10 mmol / L Tris-HCl buffer solution at pH 8.5 to obtain solution A; 3.4 g of HKUST-1 prepared in step (1) was ultrasonically dispersed in 100 ml of deionized water for 30 min to obtain solution B; solution A was injected into solution B, mixed and stirred for 30 min, and then dried in a rotary evaporator at 80°C for 24 h;

[0040] (3) Preparation of Zn@TA@HKUST-1@DMMP: 4.0 g of Zn@TA@HKUST-1 prepared in step (2) was heated in a vacuum drying oven at 100°C for 12 h, then immersed in 30 ml of DMMP for 3 days, filtered, washed with acetone five times, and dried at 25°C for 24 h.

[0041] (4) Preparation of flame-retardant and antibacterial nylon 6 composite materials: According to the percentage by mass, the Zn@TA@HKUST-1@DMMP and nylon 6 chips in step (3) were melt-mixed under the operation of a twin-screw extruder (wherein the mass ratio of Zn@TA@HKUST-1@DMMP to nylon 6 chips was 10:90, the screw speed of the twin-screw extruder was 30 Hz, the screw heating temperature was 245°C in zone 1, 250°C in zone 2, 255°C in zone 3, and 260°C in zone 4), and then extruded into a spinning box (the box temperature of the spinning box was 260°C, the side blowing air volume was 20m 3 / min), and then sent to the spinning assembly through a metering pump, oiled by an oiling system (oiling rate is 4wt.%) and drawn by a winding device (winding speed of the winding device is 1200m / min) to obtain a flame retardant and antibacterial nylon 6 composite material.

[0042] Heat release tests were performed on the nylon 6 composite materials and pure nylon 6 in Examples 1 to 3. The peak heat release rate (pHRR) at a test time of 60 seconds, the total heat release rate (THR) at a test time of 180 seconds, and the limiting oxygen index (LOI) and vertical burning (UL 94) of the nylon 6 composite materials in Examples 1 to 3 and pure nylon 6 were compared. The experimental results are shown in Table 1.

[0043] Table 1 Comparison of peak heat release rate, total heat release rate, limiting oxygen index and vertical combustion of nylon 6 composite materials and pure nylon 6

[0044]

[0045] As shown in Table 1, by adding 4.0, 7.0, and 10.0 wt.% Zn@TA@HKUST-1@DMMP to pure nylon 6, the peak heat release rate (pHRR) of the composites decreased by 33.6%, 39.8%, and 44.2%, respectively; the total heat release rate (THR) decreased by 15.0%, 19.8%, and 20.5%, respectively; the limiting oxygen index (LOI) increased from 21.0% to 26.3%, 29.8%, and 34.9%, respectively; and the vertical flammability (UL 94) ratings reached V-1, V-0, and V-0, respectively. Compared to pure nylon 6, the peak heat release rate (pHRR) and total heat release rate (THR) of the composites were significantly reduced, the limiting oxygen index (LOI) was significantly improved, and the flame retardancy was enhanced. The lower the peak heat release rate (pHRR) and total heat release rate (THR), the less heat released by the material upon combustion, and the less hazard it poses. A higher limiting oxygen index (LOI) indicates a less flammable material. This indicates that the nylon 6 composites in Examples 1 to 3 exhibit excellent flame retardancy, with increasing amounts of Zn@TA@HKUST-1@DMMP added, further improving the flame retardancy.

[0046] The antibacterial properties of the nylon 6 composite materials in Examples 1 to 3 were tested, and the experimental results are shown in Table 2.

[0047] Table 2 Antibacterial effect of nylon 6 composite materials in Examples 1 to 3 on different bacteria

[0048]

[0049] Table 2 shows that when the addition level of Zn@TA@HKUST-1@DMMP in nylon 6 is 4 wt.% or greater, the antibacterial rate against Escherichia coli, Staphylococcus aureus, and Candida albicans exceeds 99.99%. Experimental results show that the composite material maintains an antibacterial rate exceeding 99% even after 50 washes. This demonstrates that the composite material possesses excellent antibacterial properties.

[0050] In summary, the present invention provides a flame-retardant and antibacterial nylon 6 composite material. This composite material is prepared from nylon 6 chips, Zn@tannic acid complex, copper trimesic acid (HKUST-1), and dimethyl methylphosphonate (DMMP). A Zn@TA@HKUST-1 antibacterial system is constructed using a layer-by-layer self-assembly method, and DMMP is then loaded into this antibacterial system by an immersion method to form a novel flame-retardant and antibacterial nylon 6 composite material. Compared to pure nylon 6, this composite material exhibits significantly reduced peak heat release rate (pHRR) and total heat release rate (THR), significantly improved limiting oxygen index (LOI), and can achieve V-0 rating in the vertical flame test (UL 94). When the Zn@TA@HKUST-1@DMMP content in this composite material exceeds 4 wt.%, the antibacterial rates against Escherichia coli, Staphylococcus aureus, and Candida albicans all reach over 99.99%, and the antibacterial rates remain above 99% after 50 washes. It can be seen that the composite material has excellent flame retardant and antibacterial properties.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a flame-retardant and antibacterial nylon 6 composite material, characterized by: The preparation method is as follows: (1) Preparation of Zn@TA@HKUST-1: Tannic acid and a water-soluble zinc salt were dispersed in a Tris-HCl buffer solution with a pH of 8.5 to obtain solution A; copper trimesic acid was dispersed in deionized water to obtain solution B; the solution A and the solution B were then mixed and dried at 80-100°C for 12-24 hours; the molar ratio of the tannic acid, the water-soluble zinc salt, and the copper trimesic acid was 0.25:2.86:2.5; (2) Preparation of Zn@TA@HKUST-1@DMMP: The Zn@TA@HKUST-1 described in step (1) was dried at 90-150°C for 10-15 h, then immersed in dimethyl methylphosphonate for 2-5 days, filtered, washed with acetone, and dried at 20-30°C for 10-24 h; (3) Preparation of flame-retardant and antibacterial nylon 6 composite materials: The Zn@TA@HKUST-1@DMMP and nylon 6 chips described in step (2) are melt-mixed in a twin-screw extruder, then extruded into a spinning box, and delivered to the spinning assembly through a metering pump. The composite material is obtained by oiling with an oiling system and drawing and winding with a winding device.

2. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 1, characterized in that: The preparation method of copper trimesate described in step (1) is as follows: A water-soluble divalent copper salt and trimesic acid are added to N,N-dimethylformamide to form a mixture, and the mixture is then placed in a Teflon autoclave and reacted at 90-150°C for 18-30 hours. After centrifugation, the mixture is washed with N,N-dimethylformamide and ethanol 3-5 times, respectively, and then vacuum-dried at 100-150°C for 12-20 hours.

3. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 2, characterized in that: The water-soluble divalent copper salt is any one of copper nitrate trihydrate, copper sulfate, copper acetate or copper chloride; the molar ratio of the water-soluble divalent copper salt to trimesic acid is 6:

4.

4. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 1, characterized in that: The water-soluble zinc salt in step (1) is any one of zinc nitrate hexahydrate, zinc chloride, zinc sulfate or zinc acetate.

5. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 1, characterized in that: The mass volume ratio of Zn@TA@HKUST-1 to dimethyl methylphosphonate in step (2) is 2:15, g:mL.

6. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 1, characterized in that: The mass ratio of Zn@TA@HKUST-1@DMMP and nylon 6 chips in step (3) is 4:96~10:

90.

7. The method for preparing a flame-retardant and antibacterial nylon 6 composite material according to claim 1, characterized in that: The screw speed of the twin-screw extruder in step (3) is 20~40Hz, the screw heating temperature is 245~260ºC; the box temperature of the spinning box is 255~265ºC, the side blowing air volume is 15~40m 3 / min; the oiling rate of the oiling system is 2~6wt.%; the winding speed of the winding equipment is 800~2000m / min.

8. The flame-retardant and antibacterial nylon 6 composite material prepared by the method according to any one of claims 1 to 7.

9. Use of the flame-retardant and antibacterial nylon 6 composite material according to claim 8 in the preparation of textile or non-woven products.

Images