Shrimp shell biochar composite flame-retardant antibacterial agent as well as preparation method and application thereof

Abstract

The invention discloses a shrimp shell biochar composite flame-retardant antibacterial agent as well as a preparation method and application thereof, and relates to the fields of high-value utilization of biomass resources and functional polymer materials. The preparation method comprises the steps that waste seafood shrimp shells serve as raw materials, porous nitrogen-doped biochar is prepared through decalcification, activation and pyrolysis, transition metal (copper, zinc and silver) phytate nanoparticles are loaded on the biochar based on an in-situ coprecipitation method, and the composite material rich in carbon, phosphorus and transition metal is formed. The material has the following functions: the nitrogen-doped biochar provides a carbon source, the phytate provides a phosphorus source, and the nitrogen-doped biochar and the phytate have a synergistic effect to realize an efficient flame-retardant effect; transition metal ions and phytic acid form a stable complex which is encapsulated in a three-dimensional porous structure of the biochar, so that the slow release of the transition metal ions is realized, and the antibacterial aging is prolonged. The material can be used for preparing plastics such as polyvinyl chloride, polyurethane, epoxy resin and the like with flame-retardant and antibacterial functions.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, and also relates to the high-value utilization of biomass resources and functional polymer materials. Specifically, it relates to a shrimp shell biochar composite flame-retardant and antibacterial agent material, its preparation method, and its application. This material, based on the synergistic effect of the high phosphorus content of phytate and biochar, endows the polymer matrix with highly efficient flame retardancy; based on the efficacy of transition metals in the stable phytate-metal complex, it endows the polymer matrix with long-lasting antibacterial properties. This material is suitable for fields with high safety and hygiene requirements, such as electronic packaging materials, medical catheters, and fire-retardant coatings for buildings. This invention specifically solves the technical problems in existing technologies, such as the difficulty in simultaneously achieving flame retardant and antibacterial functions, poor compatibility of the filler-matrix interface, explosive release of metal ions, and environmental health risks. Background Technology

[0002] In applications such as medical, electronic packaging, and building fire protection, polymer materials need to possess both highly efficient flame retardancy and broad-spectrum antibacterial properties, but traditional solutions have significant drawbacks: 1. Limitations of flame retardants Halogenated flame retardants (such as decabromodiphenyl ethane involved in patent CN119752046A) have excellent flame retardant efficiency, but they release highly toxic gases such as dioxins during combustion, causing serious environmental pollution and posing a threat to human health. Therefore, their use has been strictly restricted in the EU and other regions. Inorganic flame retardants (represented by aluminum hydroxide) are environmentally friendly, but require extremely high addition levels (>60 wt%) to achieve ideal flame retardant effects, which seriously affects the performance and application of the substrate polymer. Phosphorus-based flame retardants exert their flame retardant effect through condensed phase flame retardancy and gas-phase flame retardancy by capturing combustion free radicals. They are currently commonly used flame retardant materials. Generally, they can better exert their flame retardant function by combining with carbon source compounds to quickly form an inorganic carbon protective layer to isolate oxygen. Transition metal phytates, as an emerging flame retardant, have attracted much attention due to their unique "synergistic catalytic char formation" mechanism. However, transition metal phytates face the bottleneck of poor dispersibility in practical applications. They are prone to agglomeration in polymer matrices, affecting the full realization of flame retardant efficiency.

[0003] 2. Insufficient antibacterial agents Transition metal antibacterial agents: Transition metals such as silver, zinc and copper ions or elements have good antibacterial properties and are widely used in antibacterial applications in medical devices, textiles and coatings. However, when used as ions, they are subject to rapid release and their antibacterial properties are easily lost. When used as nano-elements, transition metal antibacterial agents face the problems of oxidation, aggregation and inactivation.

[0004] Quaternary ammonium salt antibacterial agents: Quaternary ammonium salt antibacterial agents (such as benzalkonium chloride, hexadecyltrimethylammonium bromide, etc.) have the advantages of broad-spectrum antibacterial activity, low concentration, stable properties, and low corrosivity, and are suitable for disinfection in medical, household, and industrial fields. However, their disadvantages are also obvious: the antibacterial spectrum is limited, and the effect on Gram-negative bacteria, spores, and some viruses is poor. Long-term use may induce drug resistance. The bactericidal effect is easily affected by organic matter, hard water, and pH value. When mixed with polymer substrates, they are prone to precipitation and inactivation.

[0005] 3. Dilemmas in integrating existing technologies and bottlenecks in carrier materials Simply mixing flame retardants and antibacterial agents may not only result in poor compatibility and decreased mechanical properties due to the "sea-island structure," but also fail to achieve synergistic functional effects.

[0006] Using porous materials (such as biochar) as a support to load functional molecules is an effective strategy to solve the aforementioned problems of dispersion and synergy. However, existing methods for preparing biochar supports (such as "pyrolysis followed by acid washing") have structural defects: Pore ​​structure is not ideal: Inorganic salt decomposition products during pyrolysis may block the pores, and subsequent acid washing is difficult to completely clear them, resulting in limited specific surface area and poor pore connectivity.

[0007] Low loading efficiency: The above-mentioned structural defects severely limit the loading capacity, dispersion uniformity and bonding strength of functional components (such as transition metal phytates), ultimately affecting the performance of composite materials. Summary of the Invention

[0008] To address the aforementioned problems, the purpose of this invention is to develop a novel composite material with an ideal porous structure, capable of achieving high capacity and high dispersion loading of functional components, and possessing both flame-retardant and antibacterial synergistic properties.

[0009] To achieve the above technical objectives, the present invention adopts the following technical solution: A shrimp shell biochar composite flame retardant and antibacterial agent includes nitrogen-doped porous shrimp shell biochar and transition metal phytate nanoparticles in situ supported in the nitrogen-doped porous shrimp shell biochar.

[0010] A method for preparing a shrimp shell biochar composite flame retardant and antibacterial agent, comprising the following steps: S1. Using calcium-removed shrimp shells as raw materials, the porous nitrogen-doped shrimp shell biochar was prepared by pyrolysis at 700-900℃ for 1-3 hours under potassium hydroxide activation, followed by acid neutralization, washing with water until neutral, and drying. S2. Stable transition metal phytate complexes are formed in situ on the surface and within the pores of porous biochar using a co-precipitation method.

[0011] As a specific embodiment of the present invention, the calcium-removed shrimp shell is prepared by the following method: the shrimp shell is crushed and soaked in an acidic solution to remove calcium, then washed with water until neutral and dried to obtain the final product.

[0012] In one specific embodiment of the present invention, in step S1, the mass ratio of the calcium-removed shrimp shell to KOH is 1:1 to 1:3.

[0013] As a specific embodiment of the present invention, step S2 includes: S21. Phytic acid and transition metal salts are dissolved in water at a molar ratio of phytic acid to transition metal ions of 1.2:1 to 3.0:1 to form a first mixed solution; S22. Add biochar to the first mixed solution and stir continuously to fully impregnate the biochar in the mixed solution to form a second mixed solution. The amount of biochar added is 10% to 100% of the mass of phytic acid. S23. Add alkali to adjust the pH of the second mixed solution to 6.0~7.0, and continue stirring to precipitate the transition metal phytate and load it onto the biochar to form the third mixed solution; S24. Separate the liquid and solid phases in the third mixed solution. The obtained solid phase is then thoroughly washed, dried, and ball-milled in aqueous solution to obtain the shrimp shell biochar-supported transition metal phytate composite flame retardant and antibacterial agent.

[0014] In one specific embodiment of the present invention, the transition metal salt is one or a mixture of copper nitrate, copper sulfate, zinc nitrate, zinc sulfate and silver nitrate.

[0015] In this invention, when preparing calcium-free shrimp shells, the acidic solution can be acetic acid, hydrochloric acid, or sulfuric acid, and the concentration can be selected as needed, such as 0.1 mol / L to 2.0 mol / L. The specific drying method can also be selected as needed, such as vacuum drying. When phytic acid and transition metal salts are dissolved in water, the specific amount of water added can be selected as needed. For example, a 0.05 mol / L to 0.5 mol / L phytic acid solution can be prepared first, and then the transition metal salt can be added. When adjusting the pH value with alkali, the type and concentration of the alkali solution can also be selected as needed, such as a 0.05 mol / L to 2.0 mol / L alkali solution (sodium hydroxide or potassium hydroxide or a mixture thereof). The specific stirring time during the biochar impregnation and transition metal phytate precipitation stages can be adjusted as needed. For example, during the biochar impregnation stage, stirring at room temperature for more than 1 hour is usually sufficient to ensure adequate impregnation. During the transition metal phytate precipitation stage, stirring is usually continued for 3 to 6 hours.

[0016] An application of a shrimp shell biochar composite flame retardant and antibacterial agent involves using the aforementioned shrimp shell biochar composite flame retardant and antibacterial agent as a functional additive for flame retardancy and antibacterial properties of plastics, with an addition amount of 3-30% of the polymer matrix mass. The polymer matrix can be epoxy resin, polyurethane, polyvinyl chloride, etc.

[0017] Typical application solutions include: Epoxy resin system: Disperse shrimp shell biochar composite flame retardant and antibacterial agent in acetone and mix with epoxy resin (such as E-51) and curing agent (such as DDM), and prepare flame retardant and antibacterial epoxy resin by solution casting or compression molding.

[0018] Polyurethane system: Shrimp shell biochar composite flame retardant and antibacterial agent is premixed with polyether polyol, catalyst and chain extender, and then diisocyanate (such as isophorone diisocyanate, diphenylmethane diisocyanate) is added to react and mold to obtain polyurethane elastomer.

[0019] Polyvinyl chloride system: After uniformly mixing shrimp shell biochar composite flame retardant and antibacterial agent with polyvinyl chloride, plasticizer (such as phthalate), and heat stabilizer (such as calcium zinc stabilizer), the mixture is processed into sheets by open milling and then processed by flat vulcanizing machine to obtain polyvinyl chloride soft products.

[0020] In this invention, the prepared porous nitrogen-doped shrimp shell biochar is a porous nitrogen-doped biochar with a high specific surface area (800 m² / g~1500 m² / g). This special structure not only provides a large amount of encapsulation space for functional transition metal phytate complexes, but its own flame-retardant nitrogen-containing biochar also forms a physical barrier effect, rapidly blocking the contact between unburned substrate and oxygen, significantly improving flame retardant performance. Phytic acid is one of the compounds with the highest phosphorus content and has good flame retardant properties. Combined with the flame-retardant nitrogen-doped biochar barrier layer, it can quickly exert its flame-retardant effect. In addition, the 6 phosphate groups and 12 hydroxyl groups on the phytic acid molecule can coordinate with transition metal cations to form stable multidentate chelates, realizing the slow release of transition metal ions and exerting long-lasting antibacterial ability.

[0021] The present invention has the following significant beneficial effects: (1) Dual-function synergistic effect: Flame retardancy: The shrimp shell biochar composite flame retardant and antibacterial agent contains transition metal phytate, which decomposes to produce a phosphate carbon layer (condensed phase flame retardant) and a free radical scavenger (gas phase flame retardant), thus exhibiting flame retardancy. By loading transition metal phytate onto porous shrimp shell biochar, the flame-retardant biochar, together with the carbon layer produced by the decomposition of phytate, quickly forms a dense physical barrier, enhancing the flame retardancy of phytate. Antibacterial properties: The shrimp shell biochar composite flame retardant and antibacterial agent contains transition metal ions, which slowly release and disrupt the cell membranes of microorganisms, exhibiting good antibacterial activity against bacteria such as Escherichia coli and Staphylococcus aureus. Phytic acid has a strong complexing effect on transition metals, preventing the rapid release and loss of the antibacterial components due to the transition metals, thus ensuring long-lasting antibacterial efficacy.

[0022] (2) Environmentally friendly characteristics: Biochar is derived from waste shrimp shells, is renewable, and realizes the high-value utilization of waste biomass; the shrimp shell biochar composite flame retardant and antibacterial agent avoids the use of halogen elements, reducing environmental hazards; the synthesis of transition metal phytates on porous shrimp shell biochar is achieved only by adjusting the solution pH, which is simple, energy-efficient, and produces little pollution. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope and elemental mapping diagram of PA-Cu / BC in Example 1 of the present invention. In the figure, wt.% represents the mass percentage and at.% represents the atomic percentage. Figure 2 The Fourier transform infrared spectrum of PA-Cu / BC in Example 1 of this invention; Figure 3 The X-ray photoelectron spectrum of PA-Cu / BC in Example 1 of this invention; Figure 4 Hardness diagram of epoxy resin + PA-Cu / BC; Figure 5 The figure shows the cone calorimetry curve of the epoxy resin flame retardant sample. In the figure, HRR represents the heat release rate, THR represents the total heat release, and SPR represents the smoke generation rate. Detailed Implementation

[0024] The present invention will be further described below through specific embodiments. These embodiments are preferred implementations of the present invention, but the scope of protection of the present invention is not limited to these embodiments.

[0025] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0026] Example 1 (Shrimp shell biochar supported on copper phytate complex) 1. After drying the shrimp shells (from a local shrimp paste processing plant) (drying temperature 60℃), the shells are processed by a pulverizer to pass through a 100-mesh sieve. The shrimp shell powder is then soaked in 0.5 mol / L acetic acid (soaking for 1 hour), filtered, washed with water until neutral, and further dried until the moisture content is <5% (drying temperature 100℃) to obtain calcium-free shrimp shell powder. 2. Mix calcium-removed shrimp shell powder with potassium hydroxide at a mass ratio of 1:1, place the mixture in a tube furnace, heat it to 750 ℃ ​​at a rate of 5 ℃ / min under a N2 atmosphere, and pyrolyze it for 2 h. The resulting crude shrimp shell biochar product is then soaked in 0.5 mol / L hydrochloric acid to remove impurities such as the activator potassium hydroxide (soaking time 1 h), filtered, washed with water until neutral, and vacuum dried to constant weight (drying temperature 80 ℃) to obtain porous shrimp shell biochar.

[0027] 3. Prepare a 0.2 mol / L phytic acid solution. Add copper chloride to the phytic acid solution, wherein the molar ratio of phytic acid to copper chloride is 2:1. Stir until completely dissolved, then add shrimp shell porous biochar, the amount of biochar added being 50% of the mass of phytic acid. Continue stirring for 1 h.

[0028] 4. Under stirring conditions, add 1.0 mol / L sodium hydroxide solution dropwise to the solution obtained in step 3 until the pH of the solution is 7.0, and continue stirring for 3 h.

[0029] 5. Filter the product obtained in step 4. Rinse the resulting solid product with deionized water more than 3 times to remove soluble components, and then vacuum dry to constant weight (drying temperature is 80℃).

[0030] 6. The sample obtained in step 5 is processed in a ball mill for 2 hours to ensure that the sample is completely pulverized to pass through a 100-mesh sieve, and the shrimp shell biochar-supported copper phytate complex (labeled as PA-Cu / BC) can be obtained.

[0031] The microstructure of PA-Cu / BC was observed using scanning electron microscopy, and its X-ray electron spectrum was recorded. The results are as follows: Figure 1 As shown, PA-Cu / BC is an irregular granular material with a rough surface. In addition to carbon from biochar, its electronic energy spectrum also shows characteristic elements such as oxygen, phosphorus, and copper from copper phytate, proving the successful preparation of PA-Cu / BC.

[0032] The infrared spectrum of PA-Cu / BC was recorded using a Fourier transform infrared spectrometer, such as... Figure 2 As shown, in the range of 2800-3800 cm -1 The stretching vibration of OH in phytic acid was observed within the range of 1500-1760 cm⁻¹. -1 Characteristic peaks belonging to the aromatic ring structure of biochar appear within the range of 900-1350 cm⁻¹. -1 Characteristic peaks attributable to P=O and PO stretching vibrations appear within the range of 500-750 cm⁻¹. -1 Vibrational peaks belonging to Cu-O were observed within the range. These characteristic peaks confirm that the target material is composed of biochar and copper phytate.

[0033] The composition and structure of PA-Cu / BC were analyzed using photoelectron spectroscopy, such as... Figure 3 As shown in Figure a, in the full spectrum, a signal indicating the binding energy of the phosphorus 2p orbital appears at 132.48 eV, the carbon 1s orbital at 298.38 eV, the oxygen 1s orbital at 531.38 eV, and the copper 2p orbital at 936.68 eV. The presence of these signals confirms that the target materials, copper phytate and biochar, are the main components. Further analysis of the high-resolution characteristic peaks of phosphorus and copper, such as... Figure 3 As shown in Figures b and c, the oxidation states of phosphorus and copper are +5 and +2, respectively, indicating that their precipitation on biochar did not undergo redox reactions during the synthesis process.

[0034] Example 2 (Shrimp shell biochar supported on zinc phytate complex) 1. The process for preparing porous shrimp shell biochar is as described in steps 1 and 2 of Example 1; 2. Prepare a 0.2 mol / L phytic acid solution. Add zinc nitrate to the phytic acid solution, where the molar ratio of phytic acid to zinc nitrate is 2:1. Stir until completely dissolved, then add shrimp shell porous biochar, with the amount of biochar added being 50% of the mass of phytic acid. Continue stirring for 1 h.

[0035] 3. Under stirring conditions, add 1.0 mol / L sodium hydroxide solution dropwise to the solution obtained in step 2 until the pH of the solution is 7.0, and continue stirring for 3 h.

[0036] 4. Filter the product obtained in step 3. Rinse the resulting solid product with deionized water more than 3 times to remove soluble components, and then vacuum dry to constant weight (drying temperature is 80℃).

[0037] 5. The sample obtained in step 4 is processed in a ball mill for 2 hours to ensure that the sample is completely pulverized to pass through a 100-mesh sieve, thereby obtaining the shrimp shell biochar-supported zinc phytate complex (labeled as PA-Zn / BC). Example 3 (Shrimp shell biochar supported on silver phytate complex) 1. The process for preparing porous shrimp shell biochar is as described in steps 1 and 2 of Example 1; 2. Prepare a 0.2 mol / L phytic acid solution. Add silver nitrate to the phytic acid solution, where the molar ratio of phytic acid to silver nitrate is 2:1. Stir until completely dissolved, then add shrimp shell porous biochar, with the amount of biochar added being 50% of the mass of phytic acid. Continue stirring for 1 h.

[0038] 3. Under stirring conditions, add 1.0 mol / L strong sodium oxide solution dropwise to the solution obtained in step 2 until the pH of the solution is 7.0, and continue stirring for 3 h.

[0039] 4. Filter the product obtained in step 3. Rinse the resulting solid product with deionized water more than 3 times to remove soluble components, and then vacuum dry to constant weight (drying temperature is 80℃).

[0040] 5. The sample obtained in step 4 is processed in a ball mill for 2 hours to ensure that the sample is completely pulverized to pass through a 100-mesh sieve, thereby obtaining the shrimp shell biochar-supported silver phytate complex (labeled as PA-Ag / BC). Example 4 Ten parts of epoxy resin (2,2'-((1-methylethylidene)bis(4,1-phenyleneformaldehyde))bis(ethylene oxide, E-51)) were mechanically stirred at 80 °C for 30 min. A certain amount of PA-Cu / BC was dispersed in 20 mL of acetone and sonicated for 30 min to ensure uniform dispersion. The resulting dispersion was poured into the above E-51 and stirred continuously for 30 min. The acetone was further removed by treating with a rotary evaporator at 50 °C for 2 h. Then, two parts of curing agent 4,4'-diaminodiphenylmethane (DDM) were added to the above solution and mechanically stirred at 80 °C for 10 min. After vacuum degassing, the mixture was poured into a polytetrafluoroethylene mold and cured under vacuum conditions using a stepwise method of 80 °C / 2 h + 120 °C / 2 h to prepare epoxy resin. By changing the amount of PA-Cu / BC, epoxy resin composites with PA-Cu / BC mass fractions of 0%, 5%, 10%, 15%, and 20% were prepared.

[0041] For comparison, no biochar (BC) was added during the above PA-Cu / BC preparation process (see Example 1). Phytate copper (PA-Cu) was synthesized and epoxy resin composites with PA-Cu mass fractions of 0%, 5%, 10%, 15% and 20% were prepared using the same processing technology.

[0042] The hardness of the prepared sample was tested using a Shore hardness tester of model KL-SS-A (Haibao Instruments). Figure 4 As shown, the addition of PA-Cu / BC did not significantly affect the hardness of the epoxy resin. When the addition amount exceeded 10%, the hardness of the sample was slightly higher than that of the reference sample (without PA-Cu / BC). The limiting oxygen index (LOI) of the prepared epoxy resin was tested using a fully automatic oxygen index tester (JL-LF-5 model, Jionglei Instruments). The results are shown in Table 1. The addition of PA-Cu / BC to the epoxy resin can improve the flame retardancy of the epoxy resin material. With the increase of the addition amount, the LOI value gradually increases until the addition amount reaches 10%. However, further increasing the addition amount of PA-Cu / BC leads to a decrease in the LOI value. This may be because the large amount of copper ions in the system catalyzes the degradation of the epoxy resin polymer, offsetting the barrier effect of biochar.

[0043] Table 1 LOI values ​​of epoxy resin composites The tensile strength of the samples was tested using a UTM-1434 universal testing machine. Table 2 shows that the PA-Cu / BC described in this invention has a significant regulating effect on the tensile strength of epoxy resin: with pure epoxy resin (tensile strength 111.44 MPa) as the baseline, when the amount of PA-Cu / BC added is 5 wt.%, the tensile strength of the composite material increases to 144.18 MPa (an increase of about 29%); as the amount of PA-Cu / BC added continues to increase (10 wt.%~20 wt.%), the tensile strength gradually decreases to 125.47 MPa~83.50 MPa, showing a trend of "increased strength at low addition and decreased strength at high addition".

[0044] The comparison shows that when PA-Cu without biochar is added alone, the tensile strength of the composite material is always lower than that of pure epoxy resin, and it continues to decrease with the increase of the amount added. This is mainly because PA-Cu has poor dispersibility with epoxy resin when added alone. Biochar, as a porous structure carrier, anchors PA-Cu in the pores, avoids agglomeration, and reduces the formation of local defects.

[0045] Table 2 Tensile strength of epoxy resin composites According to the standard for testing the antimicrobial activity of plastic surfaces (ISO 22196: 2007, IDT), Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were used as experimental microorganisms to test the antimicrobial rate of epoxy resin + PA-Cu / BC samples. Table 3 shows that as the PA-Cu / BC addition ratio increased from 0% to 20%, the sterilization rate of the material against both bacteria increased. When the PA-Cu / BC addition was 20%, the sterilization rate against Escherichia coli reached 87.5%, and the sterilization rate against Staphylococcus aureus reached 92.3%, which was significantly better than the control group without PA-Cu / BC (sterilization rates of 0.2% and 4.8%, respectively). The antimicrobial rate was also significantly improved when PA-Cu without biochar was added alone, but the improvement effect was not as good as that of epoxy resin + 0% PA-Cu / BC. The study fully demonstrates that PA-Cu / BC can effectively improve the antimicrobial performance of epoxy resin composites.

[0046] Table 3 Antibacterial rate of epoxy resin composites from Figure 5As can be seen, with increasing time, compared to epoxy resin composites with 0% PA-Cu / BC, those with 10% and 20% PA-Cu / BC showed significantly lower peak values ​​for both heat release rate (HRR) and total heat release rate (THR) with time delay, indicating that the intensity of combustion was effectively suppressed. Simultaneously, the smoke generation rate (SPR) also decreased significantly, demonstrating that the filler possesses excellent smoke suppression and toxic gas reduction capabilities. These phenomena are mainly due to the catalytic formation of a dense carbon layer by PA-Cu / BC in the condensed phase, which plays a crucial role in heat insulation, oxygen isolation, and suppression of combustible material volatilization.

[0047] In summary, the PA-Cu / BC prepared by this invention can simultaneously achieve excellent antibacterial properties (sterilization rate of over 87% for two types of bacteria at 20% addition) and flame retardant properties (heat release and smoke generation are effectively suppressed) in epoxy resin materials with optimized addition amount, thus possessing dual antibacterial and flame retardant functional characteristics.

[0048] Example 5 A one-step method was used to prepare polyurethane foam composite materials. In a plastic beaker, 20 parts of polyether polyol (330N), 0.04 parts of deionized water, 4 parts of silicone oil, 0.04 parts of dibutyltin dilaurate, 0.08 parts of A33, and a certain amount of PA-Cu / BC were added and mechanically stirred at 1000 rpm for 1 minute. Simultaneously, 20 parts of isocyanate (PM-200) were added and stirred thoroughly for 1 minute. The foam was then rapidly poured into a square mold and allowed to foam naturally at room temperature for 24 hours to obtain the polyurethane foam composite material.

[0049] Table 4 shows the limiting oxygen index (LOI) of polyurethane flexible foam composites: as the PA-Cu / BC addition increases from 0% to 10%, the LOI value of the material increases from 17% to 23%, and the flame retardant performance is gradually enhanced.

[0050] Table 4. LOI values ​​of polyurethane flexible foam composites Table 5 shows the antibacterial rate of polyurethane flexible foam composite material: the antibacterial rate is extremely low when no PA-Cu / BC is added (2% for Escherichia coli and 8% for Staphylococcus aureus), while when the addition amount reaches 10%, the antibacterial rate against the two types of bacteria increases to 85.7% and 92.4% respectively, and the antibacterial performance is significantly improved.

[0051] Table 5 Antibacterial rate of polyurethane flexible foam composites Example 6 Ten parts of TPU particles were dissolved in 100 mL of DMF solution and magnetically stirred at 80 °C for 1 h to obtain solution A. A certain amount of PA-Cu / BC material was ultrasonically dispersed in 30 mL of DMF to obtain solution B. Solution B was poured into solution A and mixed thoroughly for 30 min. The mixture was then poured into deionized water for precipitation and filtration. The filtered sample was dried at 80 °C for 48 h. The dried solid was mixed evenly in a mixer and preheated at 170 °C for 3 min and held under pressure for 5 min in a flat vulcanizing machine to obtain thermoplastic polyurethane composites of different sizes. By changing the amount of PA-Cu / BC, thermoplastic polyurethane composites with PA-Cu / BC mass fractions of 0%, 3%, 5%, 7%, and 10% were prepared.

[0052] Table 6 shows the limiting oxygen index (LOI) test results of polyurethane elastomer composites: when the amount of PA-Cu / BC added increases from 0% to 10%, the LOI value of the material increases from 19.3% to 23.5%, indicating that its flame retardant performance gradually improves with the increase of PA-Cu / BC added amount.

[0053] Table 6 LOI values ​​of polyurethane elastomer composites Table 7 shows the antibacterial performance test data of polyurethane flexible foam composite materials: the blank sample without PA-Cu / BC added had an antibacterial rate of only 5% and 7% against Escherichia coli and Staphylococcus aureus, respectively; while when the amount of PA-Cu / BC added reached 10%, the antibacterial rate of the material against the above two types of test bacteria reached 86.4% and 92.3%, respectively, and the antibacterial efficacy was significantly improved.

[0054] Table 7 Antibacterial rate of polyurethane flexible foam composites Example 7 100 parts of polyvinyl chloride (PVC) resin, 40 parts of dioctyl phthalate, 2 parts of calcium stearate (Cast), 4 parts of calcium-zinc heat stabilizer, and a certain amount of PA-Cu / BC were weighed and stirred at room temperature (3-5 min) until homogeneous. The mixture was then added to a mixer (160°C, 105 r / min) for melting. After mixing, the sample was removed, cooled, and pulverized. Finally, the sample was preheated (3-5 min), pressurized (10.0 MPa, 5 min), and cooled (2-3 min) in a flat vulcanizing machine at 160°C to prepare PVC composites of different sizes. By changing the amount of PA-Cu / BC, PVC composites with PA-Cu / BC mass fractions of 0%, 10%, 15%, 20%, and 25% were prepared.

[0055] Table 8 shows the limiting oxygen index (LOI) test results of polyvinyl chloride composite materials: when the amount of PA-Cu / BC added increases from 0% to 25%, the LOI value of the material increases from 25.3% to 27.2%, 30.4%, and 33.0% respectively, and finally reaches 35.9%, indicating that its flame retardant performance shows a continuous optimization trend with the increase of PA-Cu / BC added amount.

[0056] Table 8 LOI values ​​of polyurethane flexible foam composites Table 9 shows the antibacterial performance test data of the composite material: the blank sample without PA-Cu / BC showed antibacterial rates of only 1.2% and 2% against Escherichia coli and Staphylococcus aureus, respectively; while when the amount of PA-Cu / BC added reached 25%, the antibacterial rates of the material against the above two types of test bacteria reached 88.9% and 92.6%, respectively, and the antibacterial efficacy was significantly improved.

[0057] Table 9 Antibacterial rate of polyvinyl chloride composite materials The PA-Cu / BC material prepared by this invention can simultaneously achieve excellent flame retardant properties (LOI value up to 28.9%) and antibacterial properties (antibacterial rates against two types of bacteria up to 88.9% and 92.6%) by optimizing the amount added to polyvinyl chloride, thus possessing dual antibacterial and flame retardant functional characteristics.

[0058] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A shrimp shell biochar composite flame retardant and antibacterial agent, characterized in that, It includes nitrogen-doped porous shrimp shell biochar and transition metal phytate nanoparticles in situ supported in the nitrogen-doped porous shrimp shell biochar.

2. A method for preparing a shrimp shell biochar composite flame retardant and antibacterial agent, used to prepare the shrimp shell biochar composite flame retardant and antibacterial agent according to claim 1, characterized in that, Includes the following steps: S1. Using calcium-removed shrimp shells as raw materials, the porous nitrogen-doped shrimp shell biochar was prepared by pyrolysis at 700-900℃ for 1-3 hours under potassium hydroxide activation, followed by acid neutralization, washing with water until neutral, and drying. S2. Stable transition metal phytate complexes are formed in situ on the surface and within the pores of porous biochar using a co-precipitation method.

3. The preparation method according to claim 2, characterized in that, The calcium-removed shrimp shells are prepared by the following method: the shrimp shells are crushed and soaked in an acidic solution to remove calcium, then washed with water until neutral and dried to obtain the final product.

4. The preparation method according to claim 2, characterized in that, In step S1, the mass ratio of the calcium-removed shrimp shell to KOH is 1:1 to 1:

3.

5. The preparation method according to claim 2, characterized in that, Step S2 includes: S21. Phytic acid and transition metal salts are dissolved in water at a molar ratio of phytic acid to transition metal ions of 1.2:1 to 3.0:1 to form a first mixed solution; S22. Add biochar to the first mixed solution and stir continuously to fully impregnate the biochar in the mixed solution to form a second mixed solution. The amount of biochar added is 10% to 100% of the mass of phytic acid. S23. Add alkali to adjust the pH of the second mixed solution to 6.0~7.0, and continue stirring to precipitate the transition metal phytate and load it onto the biochar to form the third mixed solution; S24. Separate the liquid and solid phases in the third mixed solution. The obtained solid phase is then thoroughly washed, dried, and ball-milled in aqueous solution to obtain a shrimp shell biochar-supported transition metal phytate composite flame retardant and antibacterial agent.

6. The preparation method according to claim 5, characterized in that, The transition metal salt is at least one of copper nitrate, copper sulfate, zinc nitrate, zinc sulfate, and silver nitrate.

7. The application of a shrimp shell biochar composite flame retardant and antibacterial agent, characterized in that, The shrimp shell biochar composite flame retardant and antibacterial agent described in claim 1 is used as a functional additive for flame retardancy and antibacterial properties of plastics, and its addition amount is 3 to 30% of the mass of the polymer matrix.

8. The application of the shrimp shell biochar composite flame retardant and antibacterial agent according to claim 7, characterized in that, The polymer matrix is ​​epoxy resin, polyurethane, or polyvinyl chloride.

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