Antibacterial flame-retardant polypropylene material and preparation method

Abstract

The application relates to the technical field of high polymer foaming materials, and particularly discloses an antibacterial and flame-retardant polypropylene material and a preparation method. The antibacterial and flame-retardant polypropylene material comprises the following raw materials in parts by weight: polypropylene resin 65-88 parts, layered silicate 5-20 parts, phosphorus-nitrogen halogen-free flame retardant 3-7 parts, PP-g-MAH 3-5 parts, foam stabilizing aid 2-5 parts, composite antibacterial system 0.5-3.0 parts, composite weather-resistant system 0.8-3.5 parts, silane coupling agent 0.3-1.5 parts and antioxidant 0.1-0.5 part. The application can improve the antibacterial performance and long-term weather resistance of the flame-retardant polypropylene material in an outdoor long-term exposure scene.

Description

Technical Field

[0001] This invention relates to the technical field of polymer foam materials, and in particular to an antibacterial flame-retardant polypropylene material and its preparation method. Background Technology

[0002] Polypropylene foam materials have been widely used in automotive interiors, packaging, and building insulation due to their excellent properties such as lightweight, thermal insulation, and energy absorption. Foamed polypropylene is a high-performance foaming resin that, after being foamed 5 to 50 times through physical or chemical methods, possesses advantages such as lightweight, material saving, energy efficiency, environmental friendliness, and impact resistance, making it widely used in building insulation, automotive parts, and other fields.

[0003] In related technologies, Chinese patent CN115073854A discloses a high-temperature resistant and flame-retardant polypropylene foam material, which uses polypropylene resin, silicate, and polyphosphate to achieve UL94V0 flame retardancy and a temperature resistance performance of less than 0.2% dimensional shrinkage rate at 110℃.

[0004] However, when used in outdoor environments with long-term exposure, the aforementioned high-temperature flame-retardant polypropylene foam material is highly susceptible to becoming a breeding ground for bacteria and mold when soaked in rainwater, leading to discoloration, odor, and deterioration of mechanical properties on the material surface. Under outdoor sunlight, the aforementioned high-temperature flame-retardant polypropylene foam material is prone to photo-oxidative degradation, resulting in surface cracking, powdering, and a sharp decline in mechanical properties, making it difficult for the aforementioned polypropylene foam material to meet the requirements for use in outdoor environments with long-term exposure. Summary of the Invention

[0005] To improve the antibacterial properties and long-term weather resistance of flame-retardant polypropylene materials under long-term outdoor exposure, this application provides an antibacterial flame-retardant polypropylene material and its preparation method.

[0006] Firstly, this application provides an antibacterial and flame-retardant polypropylene material, which adopts the following technical solution: An antibacterial flame-retardant polypropylene material comprises the following raw materials in parts by weight: 65-88 parts polypropylene resin, 5-20 parts layered silicate, 3-7 parts phosphorus-nitrogen halogen-free flame retardant, 3-5 parts PP-g-MAH, 2-5 parts foam stabilizer, 0.5-3.0 parts composite antibacterial system, 0.8-3.5 parts composite weather-resistant system, 0.3-1.5 parts silane coupling agent, and 0.1-0.5 parts antioxidant; wherein the composite antibacterial system comprises a zirconium phosphate silver-loaded composite antibacterial agent, an organic polymer antibacterial agent, and organically modified montmorillonite, and the composite weather-resistant system comprises a hindered amine light stabilizer, an ultraviolet absorber, and an auxiliary antioxidant.

[0007] In one specific implementation, the phosphorus-nitrogen halogen-free flame retardant includes at least one of 3-hydroxyphenylphosphopropionic acid or polyphosphate.

[0008] In one specific implementation, the layered silicate includes one or more of montmorillonite, kaolinite, talc, and mica powder, and the particle size of the layered silicate is 800-4000 mesh.

[0009] In one specific implementation, the foam stabilizer is glyceryl monostearate or glyceryl distearate.

[0010] In one specific implementation, the organic polymeric antibacterial agent is a polyhexamethylene guanidine hydrochloride or an organosilicon quaternary ammonium salt antibacterial agent.

[0011] In one specific implementation scheme, the composite antibacterial system comprises a zirconium phosphate silver-loaded composite antibacterial agent, an organic polymeric antibacterial agent, and an organically modified montmorillonite in a weight ratio of 1:(0.1~0.8):(0.1~0.7).

[0012] In one specific implementation, the hindered amine light stabilizer is light stabilizer 944 or light stabilizer UV-3346.

[0013] In one specific implementation, the composite weather-resistant system comprises a hindered amine light stabilizer, an ultraviolet absorber, and an auxiliary antioxidant in a weight ratio of 1:(0.3~1.2):(0.2~0.8).

[0014] Secondly, this application provides a method for preparing an antibacterial and flame-retardant polypropylene material, which employs the following technical solution: A method for preparing an antibacterial and flame-retardant polypropylene material includes the following steps: S1. Weigh the polypropylene resin, layered silicate, polyphosphate, PP-g-MAH, foam stabilizer, composite antibacterial system, composite weather-resistant system, silane coupling agent and antioxidant according to the specified ratio, and mix them evenly to obtain a mixture. S2. The mixture is melt-blended using a twin-screw extruder, extruded into strands, water-cooled, pelletized, dried, and sieved to obtain polypropylene masterbatch. The extrusion process parameters are as follows: main feed rate of the extruder is 50 kg / h; feeding stage temperature is 170~190℃; melting zone temperature is 190~220℃; metering zone temperature is 190~220℃; extrusion temperature is 170~220℃; screw speed is 70~200 rpm; and die pressure is 2~8 MPa. S3. Press the polypropylene masterbatch into sheets using a molding machine, cool and solidify to obtain a pre-foamed polypropylene board. S4. Place the pre-foamed polypropylene board into a constant-temperature mold cavity, fill it with supercritical fluid, and allow it to permeate and swell to an equilibrium state to obtain a homogeneous system. S5. Depressurize and foam at a rate of 20~50MPa / s until the pressure is reduced to 0. The polypropylene pre-foamed board expands and foams to obtain an antibacterial and flame-retardant polypropylene material.

[0015] In one specific implementation scheme, the parameters of the molding equipment are as follows: temperature 200~220℃, pressure 4~6MPa, time 10~15min; the temperature of the constant temperature mold cavity is 155~165℃; the supercritical fluid pressure is 7.2~20MPa, and the equilibrium time is 1~5h.

[0016] In summary, this application has the following beneficial effects: 1. This application employs a ternary compound antibacterial system consisting of a zirconium phosphate-loaded silver composite antibacterial agent, an organic polymeric antibacterial agent, and a carrier-based antibacterial synergist. The synergistic effect of silver and zinc ions achieves a combination of rapid sterilization and long-lasting antibacterial action. The zirconium phosphate-loaded silver composite antibacterial agent exhibits high heat resistance, maintaining activity during high-temperature processing of polypropylene, and demonstrates good sustained-release and long-lasting antibacterial properties. A ternary compound weather-resistant system employing a high-molecular-weight hindered amine light stabilizer, an ultraviolet absorber, and an auxiliary antioxidant significantly inhibits the photo-oxidative degradation of polypropylene through the synergistic effects of free radical capture, ultraviolet shielding, and thermo-oxidative inhibition. The high-molecular-weight hindered amine light stabilizer features low volatility, migration resistance, and high-temperature resistance. A synergistic flame-retardant system using layered silicates and phosphorus-nitrogen halogen-free flame retardants is employed, with the addition of an aminosilane coupling agent further enhancing the material's flame retardancy. The silane coupling agent improves dispersibility, exhibits good compatibility with the polypropylene matrix, and does not affect the foaming process. Therefore, the antibacterial properties and long-term weather resistance of flame-retardant polypropylene materials can be improved in outdoor long-term exposure scenarios.

[0017] 2. The antibacterial and flame-retardant polypropylene foam material of this application is particularly suitable for outdoor applications such as automotive exterior parts, outdoor building insulation, and outdoor facilities. Detailed Implementation

[0018] Unless otherwise specified, all raw materials used in this application were commercially available. Polypropylene resin, brand: Total PPH 9099 (France). Mica powder was calcined mica powder purchased from Shengfei Mineral Products Processing Plant in Lingshou County. Antioxidant was Antioxidant 1010. Silane coupling agent was silane coupling agent KH550. Auxiliary antioxidant was Antioxidant 168. Ultraviolet absorber was benzophenone-based ultraviolet absorber UV-531. Polyphosphate was tripolyphosphate, CAS number 115-86-6, with an active ingredient content of 99%. PP-g-MAH, model: Mitsui Chemicals AT3215E (Japan). Glyceryl monostearate, CAS number 123-94-4, with an active ingredient content of 98%. Zirconium phosphate silver-loaded composite antibacterial agent was purchased from Jinda Nanotechnology (Xiamen) Co., Ltd. Polyhexamethylene guanidine hydrochloride, CAS No. 32289-58-0, source: Mitsui Chemicals, Japan, active ingredient content 99%. Organically modified montmorillonite, model: Nanomer I.44P. 3-Hydroxyphenylphosphopropionic acid, CAS No. 14657-64-8, active ingredient content 99%. Montmorillonite, purity 98%, purchased from Lingshou Jiashuo Building Materials Processing Co., Ltd. Kaolin, purity 98%, purchased from Lingshou Baofeng Mica Processing Co., Ltd. Talc, active ingredient content 90%, purchased from Qingdao Haishengyuan Minerals Co., Ltd. Glyceryl distearate, CAS No. 1323-83-7, active ingredient content 98%. Organosilicon quaternary ammonium salt antibacterial agent, model: MED200W.

[0019] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0020] Example Example 1

[0021] This embodiment provides an antibacterial flame-retardant polypropylene material, comprising the following raw materials: 72 kg of polypropylene resin, 14 kg of layered silicate, 8 kg of polyphosphate, 3 kg of PP-g-MAH, 3.5 kg of glyceryl monostearate, 1.4 kg of composite antibacterial system, 2 kg of composite weather-resistant system, 0.5 kg of silane coupling agent, and 0.2 kg of antioxidant.

[0022] The composite antibacterial system comprises a zirconium phosphate silver-loaded composite antibacterial agent, polyhexamethylene guanidine hydrochloride, and organically modified montmorillonite in a weight ratio of 1:0.5:0.4. The composite weather-resistant system comprises light stabilizer 944, ultraviolet absorber, and auxiliary antioxidant in a weight ratio of 1:0.7:0.5. The layered silicate is mica powder with a particle size between 800 and 4000 mesh.

[0023] This embodiment also provides a method for preparing an antibacterial flame-retardant polypropylene material, comprising the following steps: S1. Weigh the polypropylene resin, layered silicate, polyphosphate, PP-g-MAH, glyceryl monostearate, composite antibacterial system, composite weather-resistant system, silane coupling agent and antioxidant according to the formula, add them to a high-speed mixer and mix evenly to obtain a mixture.

[0024] S2. The mixture is melt-blended using a twin-screw extruder and extruded into strands. The extrusion process parameters are as follows: main feed rate of 50 kg / h; feeding stage temperature of 170~190℃; melting zone temperature of 190~220℃; metering zone temperature of 190~220℃; extrusion temperature of 170~220℃; screw speed of 130 rpm; and die pressure of 5 MPa. The extrudate is then sequentially water-cooled, pelletized, dried, and sieved to obtain polypropylene masterbatch.

[0025] S3. Press the polypropylene masterbatch into sheets using a flat vulcanizing machine. The molding process temperature is 210℃, the pressure is 5MPa, and the time is 13min. After cooling and shaping, a polypropylene pre-foamed sheet with a thickness of 30mm is obtained.

[0026] S4. Place the polypropylene pre-foamed board into a mold cavity at a constant temperature of 160℃, replace the air in the mold cavity, fill it with carbon dioxide to a supercritical state, control the pressure at 13MPa, maintain the pressure for 3 hours to achieve equilibrium, and obtain a homogeneous system.

[0027] S5. Depressurize the pressure in the mold cavity to 0 at a depressurization rate of 35MPa / s to complete the depressurization foaming. The polypropylene pre-foamed board foams and expands to obtain antibacterial flame-retardant polypropylene material.

[0028] Example 2

[0029] The only difference between this embodiment and Embodiment 1 is that the antibacterial flame-retardant polypropylene material includes the following raw materials: 65 kg of polypropylene resin, 5 kg of layered silicate, 3 kg of polyphosphate, 3 kg of PP-g-MAH, 2 kg of glyceryl monostearate, 0.5 kg of composite antibacterial system, 0.8 kg of composite weather-resistant system, 0.3 kg of silane coupling agent, and 0.1 kg of antioxidant.

[0030] Example 3

[0031] The only difference between this embodiment and Embodiment 1 is that the antibacterial flame-retardant polypropylene material includes the following raw materials: 88 kg of polypropylene resin, 20 kg of layered silicate, 7 kg of polyphosphate, 5 kg of PP-g-MAH, 5 kg of glyceryl monostearate, 3.0 kg of composite antibacterial system, 3.5 kg of composite weather-resistant system, 1.5 kg of silane coupling agent, and 0.5 kg of antioxidant.

[0032] Example 4

[0033] The only difference between this embodiment and Embodiment 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of 3-hydroxyphenylphosphopropionic acid is used to replace polyphosphate.

[0034] Example 5

[0035] The only difference between this embodiment and Embodiment 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, the layered silicate is montmorillonite with a particle size of 800~4000 mesh.

[0036] Example 6

[0037] The only difference between this embodiment and Embodiment 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, the layered silicate is kaolin with a particle size of 800~4000 mesh.

[0038] Example 7

[0039] The only difference between this embodiment and Embodiment 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, the layered silicate is talc powder with a particle size of 800~4000 mesh.

[0040] Example 8

[0041] The only difference between this embodiment and Embodiment 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of glyceryl distearate is used to replace glyceryl monostearate.

[0042] Example 9

[0043] The only difference between this embodiment and Embodiment 1 is that, in the composite antibacterial system, an equal amount of organosilicon quaternary ammonium salt antibacterial agent is used to replace polyhexamethylene guanidine hydrochloride.

[0044] Example 10

[0045] The only difference between this embodiment and Embodiment 1 is that the composite antibacterial system includes a zinc phosphate silver-loaded composite antibacterial agent, polyhexamethylene guanidine hydrochloride, and organically modified montmorillonite in a weight ratio of 1:0.1:0.1.

[0046] Example 11

[0047] The only difference between this embodiment and Embodiment 1 is that the composite antibacterial system includes a zinc phosphate silver-loaded composite antibacterial agent, polyhexamethylene guanidine hydrochloride, and organically modified montmorillonite in a weight ratio of 1:0.8:0.7.

[0048] Example 12

[0049] The only difference between this embodiment and Embodiment 1 is that, in the composite weather-resistant system, an equal amount of light stabilizer UV-3346 is used to replace light stabilizer 944.

[0050] Example 13

[0051] The only difference between this embodiment and Embodiment 1 is that the composite weather-resistant system includes light stabilizer 944, ultraviolet absorber, and auxiliary antioxidant in a weight ratio of 1:0.3:0.2.

[0052] Example 14

[0053] The only difference between this embodiment and Embodiment 1 is that the composite weather-resistant system includes light stabilizer 944, ultraviolet absorber, and auxiliary antioxidant in a weight ratio of 1:1.2:0.8.

[0054] Example 15

[0055] The only difference between this embodiment and Embodiment 1 is that the preparation method of the antibacterial flame-retardant polypropylene material includes the following steps: S1. Weigh the polypropylene resin, layered silicate, polyphosphate, PP-g-MAH, glyceryl monostearate, composite antibacterial system, composite weather-resistant system, silane coupling agent and antioxidant according to the formula, add them to a high-speed mixer and mix evenly to obtain a mixture.

[0056] S2. The mixture is melt-blended using a twin-screw extruder and extruded into strands. The extrusion process parameters are as follows: main feed rate of the extruder is 50 kg / h; feeding stage temperature is 170~190℃; melting zone temperature is 190~220℃; metering zone temperature is 190~220℃; extrusion temperature is 170~220℃; screw speed is 70 rpm; and die pressure is 2 MPa. The extrudate is then sequentially water-cooled, pelletized, dried, and sieved to obtain polypropylene masterbatch.

[0057] S3. Press the polypropylene masterbatch into sheets using a flat vulcanizing machine. The molding process temperature is 200℃, the pressure is 4MPa, and the time is 10min. After cooling and shaping, a polypropylene pre-foamed sheet with a thickness of 30mm is obtained.

[0058] S4. Place the polypropylene pre-foamed board into a mold cavity at a constant temperature of 155℃, replace the air in the mold cavity, fill it with carbon dioxide to a supercritical state, control the pressure at 7.2MPa, maintain the pressure for 1 hour to achieve equilibrium, and obtain a homogeneous system.

[0059] S5. Depressurize the pressure in the mold cavity to 0 at a depressurization rate of 20MPa / s to complete the depressurization foaming. The polypropylene pre-foamed board foams and expands to obtain antibacterial flame-retardant polypropylene material.

[0060] Example 16

[0061] The only difference between this embodiment and Embodiment 1 is that the preparation method of the antibacterial flame-retardant polypropylene material includes the following steps: S1. Weigh the polypropylene resin, layered silicate, polyphosphate, PP-g-MAH, glyceryl monostearate, composite antibacterial system, composite weather-resistant system, silane coupling agent and antioxidant according to the formula, add them to a high-speed mixer and mix evenly to obtain a mixture.

[0062] S2. The mixture is melt-blended using a twin-screw extruder and extruded into strands. The extrusion process parameters are as follows: main feed rate of the extruder is 50 kg / h; feeding stage temperature is 170~190℃; melting zone temperature is 190~220℃; metering zone temperature is 190~220℃; extrusion temperature is 170~220℃; screw speed is 200 rpm; and die pressure is 8 MPa. The extrudate is then sequentially water-cooled, pelletized, dried, and sieved to obtain polypropylene masterbatch.

[0063] S3. Press the polypropylene masterbatch into sheets using a flat vulcanizing machine. The molding process temperature is 220℃, the pressure is 6MPa, and the time is 15min. After cooling and shaping, a polypropylene pre-foamed sheet with a thickness of 30mm is obtained.

[0064] S4. Place the polypropylene pre-foamed board into a mold cavity at a constant temperature of 165℃, replace the air in the mold cavity, fill it with carbon dioxide to a supercritical state, control the pressure at 20MPa, maintain the pressure for 5 hours to achieve equilibrium, and obtain a homogeneous system.

[0065] S5. Depressurize the pressure inside the mold cavity to 0 at a depressurization rate of 50MPa / s to complete the depressurization foaming. The polypropylene pre-foamed board foams and expands to obtain antibacterial flame-retardant polypropylene material.

[0066] Comparative Example Comparative Example 1 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of polypropylene resin is used to replace the layered silicate.

[0067] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of polypropylene resin is used to replace polyphosphate.

[0068] Comparative Example 3 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of polypropylene resin is used to replace glyceryl monostearate.

[0069] Comparative Example 4 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of silver-loaded zirconium phosphate composite antibacterial agent is used to replace the composite antibacterial system.

[0070] Comparative Example 5 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of polyhexamethylene guanidine hydrochloride is used to replace the composite antibacterial system.

[0071] Comparative Example 6 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of light stabilizer 944 is used to replace the composite weather-resistant system.

[0072] Comparative Example 7 The only difference between this comparative example and Example 1 is that, in the raw materials and preparation method of the antibacterial flame-retardant polypropylene material, an equal amount of ultraviolet absorber is used to replace the composite weather-resistant system.

[0073] Performance testing The following performance tests were conducted on Examples 1-16 and Comparative Examples 1-7: Antibacterial performance test: The antibacterial and flame-retardant polypropylene foam materials prepared in each example and comparative example were cut into 50mm × 50mm samples. Borealis WB140HMS foam grade polypropylene material was used as a control sample. *Escherichia coli* (ATCC 8739) and *Staphylococcus aureus* (ATCC 6538P) were selected as standard test strains, prepared at a concentration of 2.5 × 10⁻⁶. 5 ~1.0×10 6 CFU / mL standard bacterial suspension. The standard bacterial suspension was dropped onto the surface of the sample and control samples, and covered with a sterile film to ensure even spread. The inoculated sample and control samples were placed in petri dishes and incubated for 24 hours at 35±1℃ and relative humidity ≥90%. After incubation, the bacteria on the surface of the sample and control samples were eluted and recovered using elution buffer. The number of viable bacteria was counted using a plate count or a spiral inoculator. The result was calculated using the following formula: Antibacterial rate = (Average recovered bacteria count of control sample - Average recovered bacteria count of sample) / Average recovered bacteria count of control sample × 100% The test results are shown in Table 1.

[0074] Flame retardancy rating test: The flame retardancy rating was tested according to UL 94 "Tests on flammability of plastic materials for use in equipment and appliance parts", and the test results are shown in Table 1.

[0075] Long-term weather resistance test: Accelerated aging tests were conducted under the following conditions, referring to GB / T16422.2-2022 "Laboratory Light Source Exposure Test Methods for Plastics - Part 2: Xenon Arc Lamp": Irradiance: 1.10 W / m 2 @420nm; Black label temperature (BPT): 65±3℃; Relative humidity: 50±10%; Internal temperature: 38±3℃; Lighting / spraying cycle: A cycle of 102 minutes of light + 18 minutes of spraying (with water) is adopted; Test duration: 500 hours.

[0076] Record the color difference value after the xenon arc lamp has been aged for 500 hours.

[0077] The material aged under a xenon arc lamp for 500 hours was tested according to the antibacterial performance test procedure, and the antibacterial rate after aging was calculated using the following formula: Antibacterial performance retention rate after aging = (Antibacterial rate against Escherichia coli after aging / Antibacterial rate against Escherichia coli before aging) × 100% The test results are shown in Table 1.

[0078] Table 1

[0079] Combining Example 1 and Comparative Examples 1-7 with Table 1, it can be seen that compared to Example 1, the antibacterial performance retention rate of Comparative Examples 1-7 after aging is lower; the antibacterial rates against Escherichia coli and Staphylococcus aureus of Comparative Examples 1 and 4-5 are lower; the color difference values ​​of Comparative Examples 1-7 after 500 hours of aging are significantly higher; and the flame retardant rating of Comparative Examples 1-2 is worse. This indicates that the raw material ratio and preparation method of Example 1 can improve the antibacterial performance and long-term weather resistance of flame-retardant polypropylene materials under long-term outdoor exposure conditions.

[0080] This may be because the zirconium phosphate-loaded silver composite antibacterial agent loads silver and zinc ions between the layers through an ion exchange mechanism. During the material's use, the Na+ in the environment... + Ca 2+ Plasma and Ag in the interlayer + / Zn 2+ An exchange reaction occurs, Ag + / Zn 2+ It is slowly released to the material surface. Due to the ion exchange selectivity of zirconium phosphate, the release rate can be maintained at a low level, ensuring a long-term antibacterial effect lasting for months to years. Ag + Zn achieves sterilization by binding to sulfhydryl groups on bacterial cell membranes and disrupting electron transport in the respiratory chain;2+ This method achieves antibacterial effect by interfering with the bacterial enzyme system and competitively inhibiting the activity of metalloenzymes. The synergistic effect of both methods results in a broader antibacterial spectrum and higher bactericidal efficiency. Furthermore, the introduction of zinc ions reduces the total amount of silver ions required, saving costs. The polyhexamethylene guanidine hydrochloride molecule has densely distributed guanidine groups, forming cationic active sites in aqueous solution. These cationic guanidine groups electrostatically adsorb onto the negatively charged bacterial cell surface, penetrate the cell wall, and bind to the phospholipid bilayer on the cell membrane, disrupting membrane integrity and causing intracellular leakage, thus achieving rapid sterilization. The interlayer domain of organically modified montmorillonite can adsorb PHMG molecules through ion exchange, fixing them in the interlayer and slowing down the PHMG dissolution rate. Organically modified montmorillonite exhibits good dispersibility in a polypropylene matrix and can serve as a dispersion anchor for zirconium phosphate-loaded silver-zinc particles, preventing inorganic particle aggregation and ensuring uniform distribution of antibacterial active sites. These three elements form a three-tiered protective layer of rapid sterilization, sustained bacteriostasis, and long-lasting protection. When bacteria come into contact with the material surface, PHMG quickly takes effect, killing most bacteria in a short time; subsequently, Ag... + / Zn 2+ Sustained release inhibits the reproduction of surviving bacteria; the layered structure of zirconium phosphate and montmorillonite controls the release rate, ensuring long-term antibacterial activity for months to years.

[0081] The weather-resistant ternary system, composed of light stabilizer 944, UV absorber, and auxiliary antioxidant, protects the polymer from thermal oxidation damage and maintains its molecular weight during melt processing. During outdoor use, antioxidant 168 supplements the free radical scavenging ability of the UV absorber, decomposing hydroperoxides that are difficult for the UV absorber to directly act upon. The silane coupling agent, through a dual action of chemical anchoring at the inorganic end and physical entanglement at the organic end, firmly anchors the antibacterial components, mica powder, and weather-resistant components within the matrix. This prevents the loss of these components during outdoor use, such as rain and wiping, and avoids the negative impact of inorganic particle agglomeration on the foaming process. The barrier effect of mica powder not only prolongs the penetration path of UV and oxygen but also slows down the release rate of antibacterial components and silver ions, further extending the antibacterial effectiveness. The physical shielding of UV rays by mica powder, combined with the chemical weather-resistant system, forms a dual barrier of physical shielding and chemical protection, significantly attenuating UV rays before they reach the polymer matrix. Polyphosphate esters improve flame retardant properties.

[0082] Therefore, the raw material ratio and preparation method of Example 1 can improve the antibacterial properties and long-term weather resistance of flame-retardant polypropylene materials in outdoor long-term exposure scenarios.

[0083] As can be seen from Examples 1-16 and Table 1, the antibacterial rate of all examples 1-16 reached 99.9%, and the flame retardant rating reached V-0. The color difference values ​​after 500 hours of aging were all small, and the retention rate of antibacterial performance after aging was relatively high. This indicates that using the raw material ratios and preparation methods within the range of Examples 1-16 can improve the antibacterial performance and long-term weather resistance of flame-retardant polypropylene materials under long-term outdoor exposure conditions.

[0084] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An antibacterial and flame-retardant polypropylene material, characterized in that, The raw materials include the following parts by weight: 65-88 parts polypropylene resin, 5-20 parts layered silicate, 3-7 parts phosphorus-nitrogen halogen-free flame retardant, 3-5 parts PP-g-MAH, 2-5 parts foam stabilizer, 0.5-3.0 parts composite antibacterial system, 0.8-3.5 parts composite weather-resistant system, 0.3-1.5 parts silane coupling agent, and 0.1-0.5 parts antioxidant; the composite antibacterial system includes a zirconium phosphate silver-loaded composite antibacterial agent, an organic polymer antibacterial agent, and organically modified montmorillonite; the composite weather-resistant system includes a hindered amine light stabilizer, an ultraviolet absorber, and an auxiliary antioxidant.

2. The antibacterial flame-retardant polypropylene material according to claim 1, characterized in that, The phosphorus-nitrogen halogen-free flame retardant includes at least one of 3-hydroxyphenylphosphopropionic acid or polyphosphate.

3. The antibacterial flame-retardant polypropylene material according to claim 1, characterized in that, The layered silicate includes one or more of montmorillonite, kaolinite, talc powder, and mica powder, and the particle size of the layered silicate is 800-4000 mesh.

4. The antibacterial flame-retardant polypropylene material according to claim 1, characterized in that, The foam stabilizer is glyceryl monostearate or glyceryl distearate.

5. The antibacterial flame-retardant polypropylene material according to claim 1, characterized in that, The organic polymeric antibacterial agent is a polyhexamethylene guanidine hydrochloride or an organosilicon quaternary ammonium salt antibacterial agent.

6. The antibacterial flame-retardant polypropylene material according to claim 5, characterized in that, The composite antibacterial system comprises a zinc phosphate silver-loaded composite antibacterial agent, an organic polymeric antibacterial agent, and an organically modified montmorillonite in a weight ratio of 1:(0.1~0.8):(0.1~0.7).

7. The antibacterial flame-retardant polypropylene material according to claim 1, characterized in that, The hindered amine light stabilizer is light stabilizer 944 or light stabilizer UV-3346.

8. The antibacterial flame-retardant polypropylene material according to claim 7, characterized in that, The composite weather-resistant system comprises hindered amine light stabilizers, ultraviolet absorbers, and auxiliary antioxidants in a weight ratio of 1:(0.3~1.2):(0.2~0.8).

9. A method for preparing an antibacterial flame-retardant polypropylene material as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Weigh the polypropylene resin, layered silicate, polyphosphate, PP-g-MAH, foam stabilizer, composite antibacterial system, composite weather-resistant system, silane coupling agent and antioxidant according to the specified ratio, and mix them evenly to obtain a mixture. S2. The mixture is melt-blended using a twin-screw extruder, extruded into strands, water-cooled, pelletized, dried, and sieved to obtain polypropylene masterbatch. The extrusion process parameters are as follows: main feed rate of the extruder is 50 kg / h; feeding stage temperature is 170~190℃; melting zone temperature is 190~220℃; metering zone temperature is 190~220℃; extrusion temperature is 170~220℃; screw speed is 70~200 rpm; and die pressure is 2~8 MPa. S3. Press the polypropylene masterbatch into sheets using a molding machine, cool and solidify to obtain a pre-foamed polypropylene board. S4. Place the pre-foamed polypropylene board into a constant-temperature mold cavity, fill it with supercritical fluid, and allow it to permeate and swell to an equilibrium state to obtain a homogeneous system. S5. Depressurize and foam at a rate of 20~50MPa / s until the pressure is reduced to 0. The polypropylene pre-foamed board foams and expands to obtain an antibacterial and flame-retardant polypropylene material.

10. The method for preparing the antibacterial flame-retardant polypropylene material according to claim 9, characterized in that, The parameters of the molding equipment are as follows: temperature 200~220℃, pressure 4~6MPa, time 10~15min; the temperature of the constant temperature mold cavity is 155~165℃; the supercritical fluid pressure is 7.2~20MPa, and the equilibrium time is 1~5h.

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