High-performance polyamide flame-retardant composite material based on element synergistic effect and preparation method thereof

Abstract

The invention provides a high-performance polyamide flame-retardant composite material based on element synergistic effect and a preparation method thereof, and belongs to the technical field of polyamide flame-retardant materials. The preparation method comprises the following steps: preparing a phosphorus-nitrogen flame retardant, preparing a surface-modified rare earth-silicon-based material, preparing a mixture, extruding and granulating. The step of preparing the mixture comprises the following steps: uniformly mixing brominated polystyrene (BPS), a phosphorus-nitrogen flame retardant, a rare earth-silicon-based material, glass fibers, an antioxidant 1098, a heat stabilizer diisooctyl phenyl phosphite, nylon 66 and nylon 6 to obtain the mixture; according to the invention, the use of antimony oxide in the traditional bromine-antimony flame-retardant system preparation process is abandoned, and the preparation process is simple, good in repeatability, green, environment-friendly and efficient.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyamide flame-retardant materials, and particularly relates to a high-performance polyamide flame-retardant composite based on element synergy and a preparation method thereof. BACKGROUND

[0002] Polyamide (PA) is an important engineering plastic, which is widely used in the fields of machinery, electronics and electrical appliances, communication, household appliances, automobiles, rail transit, aerospace, etc. due to its excellent mechanical properties, wear resistance, chemical corrosion resistance and good processing performance. After decades of development, it has become the largest, most diverse and most widely used basic material among engineering plastics.

[0003] However, polyamide materials have serious fire hazards, and their flammability and flaming drips during combustion limit their application to some extent. The addition of flame retardants is a key means to improve the flame retardance of polyamide.

[0004] At present, a bromine-antimony flame-retardant system is mainly used. In the formula design process of bromine-based flame-retardant polyamide materials, the excellent flame-retardant performance is mainly achieved by the synergistic effect of bromine-antimony. Although the core problem of the bromine-antimony system is that the synergistic effect of brominated flame retardants (such as polybrominated diphenyl ether PBDEs, decabromodiphenyl ethane DBDPE, and brominated polystyrene BPS) and antimony trioxide (Sb2O3) can effectively inhibit combustion, it produces multiple risks in the life cycle and has the following problems: First, polybrominated dibenzo-p-dioxins (PBDD / Fs) and polybrominated dibenzofurans (PBDFs) are generated under high temperature or combustion conditions, both of which are class I carcinogens, have strong biological accumulation and endocrine interference, and cause great harm to the environment and human health; Second, antimony-containing flame retardants produce antimony tribromide and other gas in the processing process, which has a certain corrosion effect on instruments and equipment; Third, the global antimony ore reserves are only about 2 million tons, the static reserve-production ratio is only 18:1, the resource depletion problem is serious, the price fluctuates greatly and is relatively high.

[0005] Under this background, antimony oxide substitutes have become a research hotspot in the flame-retardant field.

[0006] European and American enterprises (such as BASF and Longsheng) relied on halogen-antimony oxide synergistic system in the early stage, but in recent years, they gradually shifted to phosphorus-nitrogen synergism due to environmental regulations, such as Albemarle's organic phosphorus flame retardant, some products still retain antimony-based synergists; some products of BASF and other enterprises rely on high addition amount, which is limited by environmental protection; zinc borate and hydrotalcite, which replace antimony oxide, are used to partially replace antimony oxide in the early stage, but the flame retardant efficiency is low, the addition amount is high, and the compatibility is poor, which easily leads to a decrease in material performance; Z10R18 flame retardant of Shanghai Shengao Industry can replace 30%-50% of the amount of antimony oxide, significantly reducing the dependence on antimony resources and production costs, but the replacement ratio of antimony oxide is limited, and the highest can only replace 50% of antimony oxide; TMF-077FR flame retardant synergist (silicon stannate) of Huizhou Temagn Huixin Material can replace 50% of antimony oxide, has outstanding thermal stability, and the whiteness is >98%, thereby reducing production costs, but it cannot completely replace antimony oxide.

[0007] It can be seen that in the continuous research and practical application, it is found that the new flame retardant cannot completely get rid of antimony oxide, but can only partially replace it, and the large addition amount will lead to a significant decrease in the processing performance and mechanical properties of the flame-retardant polyamide material.

[0008] At present, the flame retardant for polyamide material on the market is still mainly bromine-antimony type, and with the problems of environmental safety and resource scarcity of antimony oxide, the field of flame-retardant polyamide tends to adopt a new type of polyamide flame-retardant solution that is more efficient, stable and can give the polyamide material excellent physical and mechanical properties.

[0009] In recent years, phosphorus-nitrogen intumescent flame retardant (IFR), silicon-based flame retardant and rare earth elements have attracted attention due to their environmental protection and functional advantages; for example, the phosphorus-nitrogen system compounded by ammonium polyphosphate (APP) and melamine (MEL) can achieve condensed phase flame retardation by catalytic dehydration to form carbon, but its flame-retardant efficiency for polyamide is limited (more than 25% addition amount is required for UL94 V-2 level), and its hygroscopicity leads to a decrease in the electrical insulation performance of the material; nano-silicon dioxide (SiO2) can enhance the stability of the carbon layer through physical barrier effect, but its interface compatibility with polyamide is poor, which easily leads to agglomeration and stress concentration; rare earth elements (such as cerium and lanthanum) exhibit catalytic carbon formation, free radical quenching and smoke suppression functions due to their unique electronic layer structure and surface activity, but existing technologies are mostly limited to simple compounding of rare earth with a single flame-retardant system, and cannot achieve global optimization of multi-element cross-phase synergy.

[0010] Therefore, there is an urgent need for a new preparation scheme, and the field of flame-retardant polyamide tends to adopt a new type of polyamide flame-retardant solution that is more efficient, stable and can give the polyamide material excellent physical and mechanical properties, i.e. it can ensure the synergistic effect of each element, and the preparation process is simple and efficient, avoiding the use of antimony oxide and reducing environmental pollution.

[0011] The new flame retardant developed by utilizing element synergy can solve the problems of high cost and complete replacement of antimony oxide, and can improve the flame retardant efficiency; compared with the traditional bromine-antimony flame retardant, the element synergy has relatively small negative impact on the mechanical properties of the polyamide, and can maintain the tensile strength and impact toughness of the material to some extent, thereby expanding the application of the polyamide in some fields with high requirements on material properties.

[0012] In order to meet the requirements of environmental protection and reduce production cost, it is an important task in the field of flame retardation to develop a new high-performance polyamide flame-retardant composite material and a preparation method thereof, which can improve the flame-retardant performance while ensuring the mechanical properties. SUMMARY

[0013] In order to solve the technical problems existing in the prior art, the present application provides a high-performance polyamide flame-retardant composite material based on element synergy and a preparation method thereof, which is modified by bromine and phosphorus, nitrogen, silicon and rare earth elements, and improves the flame-retardant performance and mechanical properties under the premise of reducing the amount of flame retardant and ensuring the safety and greenness of the reaction process.

[0014] In one aspect, a high-performance polyamide flame-retardant composite material based on element synergy and a preparation method thereof are provided, and the specific operation is as follows: 1. Preparation of phosphorus-nitrogen flame retardant Mixing the phosphorus-based flame retardants zinc diethyl phosphinate and aluminum diisobutyl phosphinate uniformly to obtain FR-P, and then mixing the FR-P and melamine polyphosphate (MPP) uniformly to obtain a phosphorus-nitrogen flame retardant; The zinc diethyl phosphinate and aluminum diisobutyl phosphinate are in a ratio of 1:1-3. The mass ratio of the FR-P to the melamine polyphosphate (MPP) is 3:1-2.

[0015] 2. Preparation of surface-modified rare earth-silicon-based material Mixing tetraethyl orthosilicate, anhydrous ethanol and deionized water to obtain a reaction solution, dropping nitric acid solution to adjust the pH to 2.3-2.6, hydrolyzing at 60-62℃ for 1.0-1.3h, adding rare earth cerium nitrate, stirring for 2.0-2.5h to form a uniform sol, gelling at 70-73℃ for 9-10h, drying at 115-120℃ for 12-14h, cooling to room temperature, and then performing staged calcination, first heating to 270-280℃, and calcining for 2.0-2.5h, then heating to 440-450℃ and calcining for 3.0-3.2h, and cooling to room temperature to obtain rare earth-SiO2; adding the rare earth-SiO2 into a high-speed mixer, setting the rotation speed of the high-speed mixer to 1000-1200rpm, adding silane coupling agent kH550, and stirring at 105-110℃ for 16-20min to obtain a surface-modified rare earth-silicon-based material.

[0016] The molar ratio of the tetraethyl orthosilicate, the anhydrous ethanol and the deionized water is 1:3.5-4:3.5-4; The molar ratio of the tetraethyl orthosilicate and the rare earth cerium nitrate is 1:0.5-1; The mass concentration of the nitric acid solution is 18-22%; The mass ratio of the rare earth-SiO2 and the silane coupling agent kH550 is 500:1.5-2.5.

[0017] 3. Preparing a mixture The brominated polystyrene (BPS), the phosphorus-nitrogen flame retardant and the rare earth-silicon-based material are mixed, the glass fiber is added, then the antioxidant 1098 and the heat stabilizer monophenyl diisooctyl phosphite are added, then the nylon 66 and the nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture; In the mixture, the mass ratio of the brominated polystyrene (BPS), the phosphorus-nitrogen flame retardant, the rare earth-silicon-based material, the glass fiber, the antioxidant 1098, the heat stabilizer monophenyl diisooctyl phosphite, the nylon 66, the nylon 6 is 6-10:5-8:2-5:10-40:0.2-0.5:0.2-0.5:30-50:3-10.

[0018] 4. Extruding and granulating The mixture is put into a double-screw extruder for granulation, the granulation temperature is 1 zone 120-190℃, 2 zone 260-280℃, 3 zone 260-280℃, 4 zone 260-270℃, 5 zone 260-270℃, and after cooling and cutting, the polyamide flame-retardant composite material is obtained by drying in an oven at 105℃ for 2h.

[0019] In another aspect, a high-performance polyamide flame-retardant composite material based on element system action is prepared by the above preparation method.

[0020] The preparation process has small flame retardant addition amount, high flame retardant efficiency, and the existing bromine-based flame retardant synergist is uniformly dispersed and non-toxic, which breaks the bondage of the traditional bromine-antimony flame-retardant system, the reaction process is clean and green, and is suitable for industrialization promotion; the brominated polystyrene (BrPS) in the gas phase releases HBr free radical capture agent, and the PO· free radical generated by the decomposition of melamine polyphosphate (MPP) is combined to generate high-activity PBr3, which significantly improves the gas phase fire extinguishing efficiency; the phosphinate is combined with Ce 3+ / Ce 4+The redox cycle reduces the polyamide dehydrogenation temperature by 50 DEG C, and promotes the low-temperature formation of a dense graphitized carbon layer; the silane coupling agent modified SiO2 is bonded to the polyamide carboxyl group through the amino group of kH-550, so that the SiO2 nano network is distributed in the matrix in a directional manner, which not only enhances the crack resistance of the carbon layer, but also blocks the diffusion of organic degradation products; the five components realize the UL94 V-0 level and no dripping through the three-order synergistic path of gas phase free radical termination (BrPS / MPP), catalytic carbonization (hypophosphite / rare earth), and carbon layer enhancement (SiO2) at 18% addition amount, balance the flame retardant performance and mechanical performance, and enhance the comprehensive performance of the polyamide flame retardant composite.

[0021] Compared with the prior art, the present application has the following beneficial effects: 1. The preparation process of the present application overcomes the problems of excessive addition amount of existing flame retardants, low flame retardant efficiency, and the difficulty of uniform dispersion of existing bromine-based flame retardant synergists and toxicity, can break through the limitations of traditional bromine-antimony flame retardant system, completely replace antimony oxide, and has simple preparation process, no pollution, good repeatability, green environmental protection, and high efficiency; the high-performance polyamide flame retardant composite of the present application can break through the performance bottleneck of traditional flame retardants through multi-element synergy, and has high efficiency, environmental friendliness and engineering applicability; 2. The polyamide flame retardant composite prepared by the present application has a flame retardant level of V-0 in the UL-94 vertical burning test at a thickness of 1.6 mm, and the total combustion time of five tests is 10-28s; 3. The polyamide flame retardant composite prepared by the present application has a simply supported beam impact strength of 25.96-30.50kJ / m 2 , and a tensile strength of 98.45-110.80MPa. DETAILED DESCRIPTION

[0022] In order to more clearly understand the technical features, objects and effects of the present application, the specific embodiments of the present application will be described below.

[0023] Example 1 A preparation method of a high-performance polyamide flame retardant composite based on element synergy, comprising the following steps: 1. Preparation of phosphorus-nitrogen flame retardant According to the mass ratio of 1:2, zinc diethyl hypophosphite and aluminum diisobutyl hypophosphite are mixed uniformly to obtain FR-P02, and then FR-P02 is mixed with MPP according to the mass ratio of 3:1 to obtain a phosphorus-nitrogen flame retardant.

[0024] 2. Preparation of surface modified rare earth-silicon based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:3.5:4 to obtain a reaction solution, 18wt% nitric acid solution is added dropwise to adjust the pH to 2.3, hydrolysis is carried out at 62°C for 1.2h, rare earth cerium nitrate is added, stirring is carried out for 2.5h to form a uniform sol, gelation is carried out at 72°C, the gelation time is 9h, drying is carried out at 115°C for 14h, after cooling to room temperature, step calcination is carried out, first heating to 270°C, calcining for 2.5h, then heating to 440°C and calcining for 3.2h, and cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1200rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 107°C for 18min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:0.5.

[0025] 3. Preparation of the mixture 8wt% BPS, 6.5wt% phosphorus-nitrogen flame retardant and 4wt% rare earth-silicon-based material are mixed, 26wt% glass fiber is added, then 0.3wt% antioxidant 1098 and 0.4wt% heat stabilizer monophenyl diisooctyl phosphite are added, and then 47.2wt% nylon 66 and 7.6wt% nylon 6 are added, and after uniform mixing, a mixture is obtained.

[0026] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 1 zone 170°C, 2 zone 270°C, 3 zone 270°C, 4 zone 265°C, 5 zone 265°C, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0027] Example 2 A preparation method of a high-performance polyamide flame-retardant composite material based on element synergistic effect, comprising the following steps: 1. Preparation of phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed uniformly in a mass ratio of 1:1 to obtain FR-P01, then FR-P01 and MPP are mixed uniformly in a mass ratio of 3:1 to obtain a phosphorus-nitrogen flame retardant.

[0028] 2. Preparation of surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:4 to obtain a reaction solution, 20wt% nitric acid solution is added dropwise to adjust the pH to 2.5, hydrolysis is carried out at 60°C for 1h, rare earth cerium nitrate is added, stirring is carried out for 2h to form a uniform sol, gelation is carried out at 70°C, the gelation time is 10h, drying is carried out at 120°C for 12h, after cooling to room temperature, step calcination is carried out, first heating to 280°C, calcining for 2h, then heating to 450°C and calcining for 3h, cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1000rpm, 1.5g of silane coupling agent kH550 is added, stirring is carried out at 105°C for 20min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:0.5.

[0029] 3. Preparation of the mixture 8wt% BPS, 7wt% phosphorus-nitrogen flame retardant and 3wt% rare earth-silicon-based material are mixed, 30wt% glass fiber is added, then 0.2wt% antioxidant 1098 and 0.2wt% heat stabilizer monoisooctyl phenyl phosphite are added, then 46.4wt% nylon 66 and 5.2wt% nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture.

[0030] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 160°C in zone 1, 265°C in zone 2, 270°C in zone 3, 265°C in zone 4 and 260°C in zone 5, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0031] Example 3 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of phosphorus-nitrogen flame retardant Zinc diethyl phosphinate and aluminum diisobutyl phosphinate are mixed uniformly in a mass ratio of 1:3 to obtain FR-P03, then FR-P03 and MPP are mixed uniformly in a mass ratio of 3:1 to obtain a phosphorus-nitrogen flame retardant.

[0032] 2. Preparation of surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:3.5 to obtain a reaction solution, 22wt% nitric acid solution is added dropwise to adjust the pH to 2.6, hydrolysis is carried out at 60°C for 1.3h, rare earth cerium nitrate is added, stirring is carried out for 2.2h to form a uniform sol, gelation is carried out at 73°C, the gelation time is 10h, drying is carried out at 118°C for 12h, after cooling to room temperature, staged calcination is carried out, first heating to 276°C, calcination at 276°C for 2.3h, then heating to 445°C, calcination at 445°C for 3.0h, and cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1000rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 110°C for 16min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:0.5.

[0033] 3. Preparation of the mixture 7.5wt% BPS, 6wt% phosphorus-nitrogen flame retardant and 4.2wt% rare earth-silicon-based material are mixed, 35wt% glass fiber is added, then 0.3wt% antioxidant 1098 and 0.2wt% heat stabilizer monophenyl diisooctyl phosphite are added, and then 42.8wt% nylon 66 and 4.0wt% nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture.

[0034] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 180°C in zone 1, 275°C in zone 2, 280°C in zone 3, 270°C in zone 4, and 270°C in zone 5, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0035] Example 4 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of a phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed uniformly in a mass ratio of 1:2 to obtain FR-P02, then FR-P02 and MPP are mixed uniformly in a mass ratio of 3:1 to obtain a phosphorus-nitrogen flame retardant.

[0036] 2. Preparation of a surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:3.5:4 to obtain a reaction solution, 18wt% nitric acid solution is added dropwise to adjust the pH to 2.3, hydrolysis is carried out at 62°C for 1.2h, rare earth cerium nitrate is added, stirring is carried out for 2.5h to form a uniform sol, gelation is carried out at 72°C, the gelation time is 9h, drying is carried out at 115°C for 14h, after cooling to room temperature, the material is subjected to staged calcination, first heated to 270°C, calcination is carried out at 270°C for 2.5h, then heated to 440°C, calcination is carried out at 440°C for 3.2h, and the rare earth-SiO2 is obtained after cooling to room temperature; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1200rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 107°C for 18min, and the surface-modified rare earth-silicon-based material is obtained. The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0037] 3. Preparation of the mixture 8.5wt% BPS, 5.5wt% phosphorus-nitrogen flame retardant and 3.5wt% rare earth-silicon-based material are mixed, 28wt% glass fiber is added, then 0.4wt% antioxidant 1098 and 0.3wt% heat stabilizer monophenyl diisooctyl phosphite are added, and then 47.5wt% nylon 66 and 6.3wt% nylon 6 are added, and the mixture is obtained after uniform mixing.

[0038] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 175°C in zone 1, 270°C in zone 2, 273°C in zone 3, 262°C in zone 4, and 260°C in zone 5, and after cooling and cutting, the polyamide flame-retardant composite material is obtained after drying in an oven at 105°C for 2h.

[0039] Example 5 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of the phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed uniformly in a mass ratio of 1:1 to obtain FR-P01, and then FR-P01 and MPP are mixed uniformly in a mass ratio of 3:1 to obtain the phosphorus-nitrogen flame retardant.

[0040] 2. Preparation of the surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:4 to obtain a reaction solution, 20wt% nitric acid solution is added dropwise to adjust the pH to 2.5, hydrolysis is carried out at 60°C for 1h, rare earth cerium nitrate is added, stirring is carried out for 2h to form a uniform sol, gelation is carried out at 70°C, the gelation time is 10h, drying is carried out at 120°C for 12h, after cooling to room temperature, step calcination is carried out, first heating to 280°C, calcining for 2h, then heating to 450°C and calcining for 3h, cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1000rpm, 1.5g of silane coupling agent kH550 is added, stirring is carried out at 105°C for 20min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0041] 3. Preparation of the mixture 6.4wt% BPS, 7.3wt% phosphorus-nitrogen flame retardant and 2.8wt% rare earth-silicon-based material are mixed, 33wt% glass fiber is added, then 0.3wt% antioxidant 1098 and 0.4wt% heat stabilizer monophenyl diisooctyl phosphite are added, then 44.2wt% nylon 66 and 5.6wt% nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture.

[0042] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 165°C in zone 1, 275°C in zone 2, 280°C in zone 3, 267°C in zone 4 and 265°C in zone 5, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0043] Example 6 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of the phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed uniformly in a mass ratio of 1:3 to obtain FR-P03, then FR-P03 and MPP are mixed uniformly in a mass ratio of 3:1 to obtain a phosphorus-nitrogen flame retardant.

[0044] 2. Preparation of the surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:3.5 to obtain a reaction solution, 22wt% nitric acid solution is added dropwise to adjust the pH to 2.6, hydrolysis is carried out at 60°C for 1.3h, rare earth cerium nitrate is added, stirring is carried out for 2.2h to form a uniform sol, gelation is carried out at 73°C, the gelation time is 10h, drying is carried out at 118°C for 12h, after cooling to room temperature, staged calcination is carried out, first heating to 276°C, calcination at 276°C for 2.3h, then heating to 445°C, calcination at 445°C for 3.0h, and cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1000rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 110°C for 16min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0045] 3. Preparation of the mixture 6.7wt% BPS, 7.7wt% phosphorus-nitrogen flame retardant and 4.4wt% rare earth-silicon-based material are mixed, 37wt% glass fiber is added, then 0.4wt% antioxidant 1098 and 0.3wt% heat stabilizer monooctyl diphenyl phosphite are added, then 40wt% nylon 66 and 3.5wt% nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture.

[0046] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 190°C in zone 1, 272°C in zone 2, 275°C in zone 3, 265°C in zone 4, and 262°C in zone 5, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0047] Example 7 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of the phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed in a mass ratio of 1:2 to obtain FR-P02, then FR-P02 and MPP are mixed in a mass ratio of 3:2 to obtain a phosphorus-nitrogen flame retardant.

[0048] 2. Preparation of the surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:3.5:4 to obtain a reaction solution, 18wt% nitric acid solution is added dropwise to adjust the pH to 2.3, hydrolysis is carried out at 62°C for 1.2h, rare earth cerium nitrate is added, stirring is carried out for 2.5h to form a uniform sol, gelation is carried out at 72°C, the gelation time is 9h, drying is carried out at 115°C for 14h, after cooling to room temperature, step calcination is carried out, first heating to 270°C, calcining for 2.5h, then heating to 440°C and calcining for 3.2h, and cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1200rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 107°C for 18min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0049] 3. Preparation of the mixture 8.3wt% BPS, 6.8wt% phosphorus-nitrogen flame retardant and 3.8wt% rare earth-silicon-based material are mixed, 30wt% glass fiber is added, then 0.2wt% antioxidant 1098 and 0.2wt% heat stabilizer monophenyl diisooctyl phosphite are added, and then 45.9wt% nylon 66 and 4.8wt% nylon 6 are added, and after mixing uniformly, a mixture is obtained.

[0050] 4. Extrusion granulation The mixture is placed into a twin-screw extruder for granulation, the granulation temperature is 160°C in zone 1, 268°C in zone 2, 270°C in zone 3, 260°C in zone 4 and 260°C in zone 5, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0051] Example 8 A preparation method of a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of the phosphorus-nitrogen flame retardant Zinc diethylphosphinate and aluminum diisobutylphosphinate are mixed uniformly in a mass ratio of 1:1 to obtain FR-P01, then FR-P01 and MPP are mixed uniformly in a mass ratio of 3:2 to obtain a phosphorus-nitrogen flame retardant.

[0052] 2. Preparation of the surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:4 to obtain a reaction solution, 20wt% nitric acid solution is added dropwise to adjust the pH to 2.5, hydrolysis is carried out at 60°C for 1h, rare earth cerium nitrate is added, stirring is carried out for 2h to form a uniform sol, gelation is carried out at 70°C, the gelation time is 10h, drying is carried out at 120°C for 12h, after cooling to room temperature, step calcination is carried out, first heating to 280°C, calcining for 2h, then heating to 450°C and calcining for 3h, cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotation speed of the high-speed mixer is 1000rpm, 1.5g of silane coupling agent kH550 is added, stirring is carried out at 105°C for 20min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0053] 3. Preparation of the mixture 8.5wt% BPS, 6.2wt% phosphorus-nitrogen flame retardant and 4.5wt% rare earth-silicon-based material are mixed, 25wt% glass fiber is added, then 0.4wt% antioxidant 1098 and 0.4wt% heat stabilizer monophenyl diisooctyl phosphite are added, then 46.8wt% nylon 66 and 8.2wt% nylon 6 are added, and the mixture is uniformly mixed to obtain a mixture.

[0054] 4. Extrusion granulation The mixture is placed in a twin-screw extruder for granulation, the granulation temperature is 1 zone 170°C, 2 zone 264°C, 3 zone 270°C, 4 zone 264°C, 5 zone 260°C, after cooling and cutting, drying is carried out in an oven at 105°C for 2h to obtain a polyamide flame-retardant composite material.

[0055] Example 9 A method for preparing a high-performance polyamide flame-retardant composite material based on element synergy, comprising the following steps: 1. Preparation of phosphorus-nitrogen flame retardant Zinc diethyl phosphinate and aluminum diisobutyl phosphinate are mixed uniformly in a mass ratio of 1:3 to obtain FR-P03, then FR-P03 and MPP are mixed uniformly in a mass ratio of 3:2 to obtain a phosphorus-nitrogen flame retardant.

[0056] 2. Preparation of surface-modified rare earth-silicon-based material The tetraethyl orthosilicate, anhydrous ethanol and deionized water are mixed in a molar ratio of 1:4:3.5 to obtain a reaction solution, 22wt% nitric acid solution is added dropwise to adjust the pH to 2.6, hydrolysis is carried out at 60℃ for 1.3h, rare earth cerium nitrate is added, stirring is carried out for 2.2h to form a uniform sol, gelation is carried out at 73℃, the gelation time is 10h, drying is carried out at 118℃ for 12h, after cooling to room temperature, staged calcination is carried out, first heating to 276℃, calcination for 2.3h, then heating to 445℃ and calcination for 3.0h, cooling to room temperature to obtain a rare earth-SiO2; 500g of the rare earth-SiO2 is added to a high-speed mixer, the rotating speed of the high-speed mixer is 1000rpm, 2.5g of silane coupling agent kH550 is added, stirring is carried out at 110℃ for 16min to obtain a surface-modified rare earth-silicon-based material; The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:1.

[0057] 3. Preparation of a mixture 7wt% BPS, 7.2wt% phosphorus-nitrogen flame retardant and 4wt% rare earth-silicon-based material are mixed, 30wt% glass fiber is added, then 0.3wt% antioxidant 1098 and 0.2wt% heat stabilizer monophenyl diisooctyl phosphite are added, then 44.9wt% nylon 66 and 6.4wt% nylon 6 are added, and after uniform mixing, a mixture is obtained.

[0058] 4. Extrusion and granulation The mixture is placed into a twin-screw extruder for granulation, the granulation temperature is 185℃ in zone 1, 280℃ in zone 2, 280℃ in zone 3, 270℃ in zone 4 and 265℃ in zone 5, after cooling and cutting, drying is carried out in an oven at 105℃ for 2h to obtain a polyamide flame-retardant composite material.

[0059] Comparative Example 1 A preparation method of a polyamide flame-retardant composite material containing brominated polystyrene and antimony trioxide synergistically modified, comprising the following steps: 1. Preparation of a mixture 18wt% BPS, 6wt% antimony trioxide are mixed, 30wt% glass fiber is added, then 0.2wt% antioxidant 1098 and 0.2wt% heat stabilizer monophenyl diisooctyl phosphite are added, then 41wt% nylon 66 and 4.6wt% nylon 6 are added, and after uniform mixing, a mixture is obtained.

[0060] 2. Extrusion and granulation The mixture is placed into a twin-screw extruder for granulation, the granulation temperature is 160℃ in zone 1, 265℃ in zone 2, 270℃ in zone 3, 265℃ in zone 4 and 260℃ in zone 5, after cooling and cutting, drying is carried out in an oven at 105℃ for 2h to obtain a polyamide flame-retardant composite material.

[0061] Comparative Example 2 A method for preparing a polyamide flame-retardant composite of a pure phosphorus-based flame retardant, comprising the following steps: 1. Preparing a mixture 5wt% zinc diethylphosphinate, 10wt% aluminum diisobutylphosphinate were mixed, 30wt% glass fibers were added, then 0.2wt% antioxidant 1098 and 0.2wt% thermal stabilizer monophenyl diisooctyl phosphite were added, and then 49.1wt% nylon 66 and 5.5wt% nylon 6 were added, and after uniform mixing, a mixture was obtained.

[0062] 2. Extrusion granulation The mixture was placed in a twin-screw extruder for granulation, and the granulation temperature was 160℃ in zone 1, 265℃ in zone 2, 270℃ in zone 3, 265℃ in zone 4, and 260℃ in zone 5. After cooling and cutting, the polyamide flame-retardant composite was dried in an oven at 105℃ for 2h.

[0063] Performance test The high-performance polyamide flame-retardant composite prepared in Examples 1-9 and Comparative Examples 1-2 was tested for flame-retardant performance and strength performance, as follows:

[0064] According to the above result analysis, the polyamide flame retardant prepared in Examples 1-9 and Comparative Examples 1 and 2, the 1.6mm flame-retardant bar UL-94 is V-0; The present application has small flame retardant addition amount, high flame retardant efficiency, and uniform dispersion of the existing bromine-based flame retardant synergist, no toxicity, breaking the traditional bromine-antimony flame retardant system, clean and green reaction process, suitable for industrialization promotion; Brominated polystyrene (BrPS) in the gas phase releases HBr free radical traps, and the PO· free radicals generated by the decomposition of melamine polyphosphate (MPP) combine to form high-activity PBr3, significantly improving the gas-phase fire extinguishing efficiency; Ce 3+ / Ce 4+ Oxidation-reduction cycle reduces the dehydrogenation temperature of polyamide by 50℃, promoting the formation of a dense graphitized carbon layer at low temperature; Silane coupling agent modified SiO2 is bonded to the carboxyl group of polyamide through the amino group of kH-550, so that the SiO2 nano network is directionally distributed in the matrix, enhancing the crack resistance of the carbon layer and blocking the diffusion of organic degradation products; the three-stage synergistic path of gas-phase free radical termination (BrPS / MPP), catalytic carbonization (phosphinic acid salt / rare earth), and carbon layer enhancement (SiO2) enables the material to achieve UL94 V-0 level and no dripping at 18% addition amount, balancing the flame-retardant performance and mechanical properties, and enhancing the comprehensive performance of the polyamide flame-retardant composite.

[0065] The bromine-antimony system in Comparative Example 1 relies on brominated polystyrene and Sb2O3 to generate SbBr3 to extinguish fire, but the Sb-Br complex decomposes at the polyamide processing temperature (>260°C) in advance, resulting in yellowing of the material due to thermal oxidation aging, and release of brominated dioxin and other toxic substances (smoke toxicity index ITC >1.5) during combustion; the single phosphorus system in Comparative Example 2 such as aluminum hypophosphite promotes charring, but lacks a gas-phase synergistic mechanism, and the PH3 gas produced by its decomposition can corrode processing equipment (screw wear rate increased by 3 times), and the acidic environment catalyzes polyamide hydrolysis (intrinsic viscosity decreased by 28%), triggering premature degradation of the material.

[0066] Unless otherwise specified, the proportions described in the present application are mass proportions, and the percentages described are mass percentages.

[0067] Finally, it should be noted that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing high performance polyamide flame retardant composite based on synergistic effect of elements, characterized in that, Bromine is modified with phosphorus, nitrogen, silicon and rare earth elements; The preparation method comprises the steps of preparing a phosphorus-nitrogen flame retardant, preparing a surface-modified rare earth-silicon-based material, preparing a mixture, and extruding and granulating. The preparation method comprises the steps of preparing a phosphorus-nitrogen flame retardant, preparing a surface-modified rare earth-silicon-based material, preparing a mixture, and extruding and granulating.

2. The preparation method of the high-performance polyamide flame-retardant composite material based on element synergy according to claim 1, characterized in that, The preparation of the phosphorus-nitrogen flame retardant comprises the steps of uniformly mixing phosphorus-based flame retardants zinc diethyl phosphinate and aluminum diisobutyl phosphinate to obtain FR-P, and then uniformly mixing FR-P and melamine polyphosphate to obtain the phosphorus-nitrogen flame retardant. The zinc diethyl phosphinate and aluminum diisobutyl phosphinate are in a 1:1-3 ratio. The mass ratio of FR-P to MPP is 3:1-2.

3. The preparation method of the high-performance polyamide flame-retardant composite material based on element synergy according to claim 1, characterized in that, The preparation of the surface-modified rare earth-silicon-based material comprises the steps of mixing tetraethyl orthosilicate, anhydrous ethanol and deionized water to obtain a reaction solution, adjusting the pH to 2.3-2.6, hydrolyzing for 1.0-1.3 hours, adding rare earth cerium nitrate, stirring to form a uniform sol, and then performing gelation, drying, and step-by-step calcination, wherein the calcination is performed at 270-280°C for 2.0-2.5 hours, at 440-450°C for 3.0-3.2 hours, and then cooled to room temperature to obtain rare earth-SiO2; mixing the rare earth-SiO2 with silane coupling agent kH550, stirring at 105-110°C for 16-20 minutes to obtain the surface-modified rare earth-silicon-based material. The molar ratio of the tetraethyl orthosilicate, the anhydrous ethanol and the deionized water is 1:3.5-4:3.5-4. The molar ratio of the tetraethyl orthosilicate to the rare earth cerium nitrate is 1:0.5-1. The mass ratio of the rare earth-SiO2 to the silane coupling agent kH550 is 500:1.5-2.

5.

4. The preparation method of the high-performance polyamide flame-retardant composite material based on element synergy according to claim 1, characterized in that, In the preparation of the mixture, the mass ratio of the brominated polystyrene, the phosphorus-nitrogen flame retardant, the rare earth-silicon-based material, the glass fiber, the antioxidant 1098, the heat stabilizer monophenyl diisooctyl phosphite, the nylon 66 and the nylon 6 is 6-10:5-8:2-5:10-40:0.2-0.5:0.2-0.5:30-50:3-10.

5. The preparation method of the high-performance polyamide flame-retardant composite material based on element synergy according to claim 1, characterized in that, The extrusion granulation step is to put the mixture into a double screw extruder for granulation, the granulation temperature is 120-190℃ in zone 1, 260-280℃ in zone 2, 260-280℃ in zone 3, 260-270℃ in zone 4, and 260-270℃ in zone 5, after cooling and cutting, drying in an oven at 105℃ for 2h to obtain the polyamide flame-retardant composite material.

6. The high-performance polyamide flame-retardant composite material based on element system effect prepared by the preparation method according to any one of claims 1-5.

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