Modified nylon composite flame retardant and preparation method thereof

Abstract

The invention discloses a modified nylon composite flame retardant and a preparation method thereof, and the preparation method comprises the following steps: mixing agmatine and sulfuric acid according to a ratio of 1: 1, adding ethanol, heating and stirring, and carrying out rotary evaporation to remove a solvent to obtain agmatine sulfate; then, 4, 4 '-diaminodiphenyl sulfone and phenylphosphoryl dichloride are dissolved in acetonitrile, and after a reaction, a phosphorus-sulfur composite flame retardant is obtained; then mixing brominated polystyrene and antimony trioxide according to a ratio of 3: 1, adding a dimethyl sulfoxide solvent, and stirring to obtain a bromine-antimony composite flame retardant; and finally, mixing all the components with the long glass fiber, performing high-speed stirring and twin-screw extrusion melt blending, and performing cooling and pelletizing molding. The agmatine sulfate can provide gas-phase flame retardance, the phosphorus-sulfur composite flame retardant generates a carbon layer to enhance solid-phase flame retardance, and the bromine-antimony composite flame retardant synergistically delays flame propagation, so that the flame retardance stability and durability of the nylon composite flame retardant are improved, and the long-term use safety in a high-temperature environment is ensured.

Description

Technical Field

[0001] The present invention relates to the field of nylon flame retardants, and particularly to a modified nylon composite flame retardant and a preparation method thereof. Background Art

[0002] Nylon PA6 (polycaprolactam), as a widely used engineering plastic, is widely used in fields such as automobiles, electronics, and construction due to its excellent mechanical properties, wear resistance, and processability. However, the flammability of nylon PA6 limits its application in high-temperature environments. To improve the flame retardancy of nylon PA6, some flame retardants are usually used to modify nylon PA6 to enhance its flame retardant performance.

[0003] However, although these flame retardants can improve the flame retardancy of nylon PA6 to a certain extent, with the extension of the use time or repeated exposure under high-temperature conditions, the use effect of the flame retardant will gradually weaken, resulting in a significant decrease in the flame retardant performance of the material. In addition, the addition of the flame retardant will also cause the material to become brittle, thus affecting the mechanical properties and processing performance of the material.

[0004] Therefore, there are defects in the prior art and improvement is needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modified nylon composite flame retardant with good flame retardant effect and excellent mechanical processing performance and a preparation method thereof.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a modified nylon composite flame retardant, comprising the following steps:

[0008] S1. Prepare guanidinium butylamine sulfate: Mix guanidinium butylamine and sulfuric acid according to a mass ratio of 1:1, add an ethanol solution, then heat the mixture to 50-60 °C, stir with a magnetic stirrer, and after the reaction is completed, remove the ethanol solution by rotary evaporation. After cooling to room temperature, crystalline guanidinium butylamine sulfate is obtained;

[0009] S2. Prepare a phosphorus-sulfur composite flame retardant: Dissolve 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine in an acetonitrile solution according to a mass ratio of 1:2. Then place the dissolved reaction mixture in a reactor, stir at a temperature of 90-100 °C, with a stirring rate of 300-500 r / min and a stirring time of 3-5 h. Remove the unreacted impurities by vacuum filtration to obtain a pure phosphorus-sulfur composite flame retardant;

[0010] S3. Preparation of bromine-antimony composite flame retardant: After mixing brominated polystyrene and antimony trioxide in a mass ratio of 3:1, add them to dimethylsulfinamide solvent, then add a dispersant, and stir at a rate of 500 - 1000 r / min for 1 - 2 h. After the reaction is completed, remove the solvent to obtain the bromine-antimony composite flame retardant;

[0011] S4. Mixing and stirring: Place nylon PA6, prepared guanidinobutylamine sulfate, phosphorus-sulfur composite flame retardant, bromine-antimony composite flame retardant, long glass fiber, coupling agent, and plasticizer into a high-speed mixer in a mass ratio of 100:10:10:12:30:0.5:0.5 for mixing to obtain a premix;

[0012] S5. Feed the premix obtained in step S4 into a twin-screw extruder for melt blending. After the extruded composite material is cooled and solidified, it is granulated by a granulator to obtain the modified nylon composite flame retardant.

[0013] Adopting the above technical solution, in step S1, the liquid ratio between the mixture of guanidinobutylamine and sulfuric acid and the ethanol solution is 1:10 - 25 g / mL, and the concentration of ethanol is 50 - 70 wt%;

[0014] The stirring rate of the magnetic stirrer is 200 - 300 r / min, and the stirring time is 2 - 3 h.

[0015] Adopting the above technical solution, in step S2, the liquid ratio between the mixture of 4,4'-diaminodiphenyl sulfone and phenylphosphonic dichloride and the acetonitrile solution is 1:25 - 35 g / mL.

[0016] Adopting the above technical solution, in step S3, the liquid ratio between the mixture of brominated polystyrene and antimony trioxide and the dimethylsulfinamide solvent is 1:8 - 12 g / mL.

[0017] Adopting the above technical solution, in step S3, the dispersant is maleic anhydride-grafted polyolefin, and the addition amount of the dispersant is 1 - 2 wt% of the total mass of brominated polystyrene and antimony trioxide.

[0018] Adopting the above technical solution, in step S4, the coupling agent is γ-aminopropyltriethoxysilane or γ-chloropropyltrichlorosilane;

[0019] The plasticizer is dioctyl phthalate or dioctyl suberate.

[0020] Adopting the above technical solution, in step S4, before adding long glass fibers, they are subjected to solvent impregnation pretreatment; the specific process flow is as follows: The long glass fibers are placed in dichloromethane solvent for impregnation treatment. Among them, the material-liquid ratio between the long glass fibers and the dichloromethane solvent is 1:10 - 15 g / mL, the soaking time is 30 - 60 min, and then the impregnated long glass fibers are dried by a vacuum drying oven or a hot air dryer. The drying temperature is controlled at 50 - 60 °C, and the drying time is 6 - 8 h.

[0021] Adopting the above technical solution, in step S4, an epoxy chain extender ADR-4468 with a mass ratio of 0.3 - 0.8 wt% of nylon PA6 is added to a high-speed mixer, and during the stirring process, through pulsed temperature field regulation, the temperature is alternately switched between 180 - 190 °C / 80 - 100 °C, with each switching interval of 30 - 60 seconds, and a total of 5 - 10 cycles are performed.

[0022] Adopting the above technical solution, in step S5, the screw speed of the twin-screw extruder is 250 - 300 r / min, the feeding zone temperature is 180 - 190 °C, the melting zone temperature is 200 - 220 °C, the mixing zone temperature is 230 - 240 °C, the plasticizing zone temperature is 250 - 260 °C, and the die head zone temperature is 260 - 270 °C.

[0023] This technical solution also provides a modified nylon composite flame retardant, which is prepared by using the preparation method of any one of the above-mentioned modified nylon composite flame retardants.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The guanidinium butylamine sulfate of the present invention provides a gas-phase flame retardant effect through its amino structure. The phosphorus-sulfur composite flame retardant can enhance the solid-phase flame retardant effect by generating a protective carbon layer and inhibiting the release of volatile combustible gases; the bromine-antimony composite flame retardant delays the flame propagation through a synergistic effect, and its flame retardant effect is more persistent. Through this composite flame retardant system, the fire resistance of the material near the fire source is significantly improved, effectively improving the stability and persistence of the flame retardant effect of the material, and is suitable for high-temperature or fire-dangerous environments; long glass fibers can enhance the tensile strength, impact strength and wear resistance of nylon PA6, and the coupling agent can improve the interfacial bonding force between the glass fibers and the nylon PA6 matrix, avoiding the aggregation or uneven dispersion of long glass fibers; the plasticizer can enhance the flexibility and fluidity of the composite material, reduce the glass transition temperature of the material, making the composite material more easily flow during the processing process, and avoiding problems such as brittle fracture and poor flow; in addition, the use of the epoxy chain extender ADR-4468 can improve the thermal stability and melt strength of nylon PA6 through chain extension and branching effects, improve the stability of the composite material at high temperatures, and enhance the impact resistance and toughness of the material. Detailed Embodiments

[0026] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the descriptions of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. below mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms are not necessarily directed to the same embodiment or example. Moreover, the technical features involved in various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0027] The present invention provides a preparation method of a modified nylon composite flame retardant, comprising the following steps:

[0028] S1. Prepare guanidinium butylamine sulfate: After mixing guanidinium butylamine and sulfuric acid in a mass ratio of 1:1, add an ethanol solution, and then heat the mixture to 50-60 °C and stir it with a magnetic stirrer. After the reaction is completed, remove the ethanol solution by rotary evaporation, and obtain crystalline guanidinium butylamine sulfate after cooling to room temperature; As a nitrogen-containing compound, the guanidine structure of guanidinium butylamine has strong thermal stability and can decompose at high temperatures to release substances that can inhibit the spread of flames, thereby providing effective flame retardant protection for nylon PA6 and enhancing the stability and combustion resistance of nylon PA6 at high temperatures.

[0029] S2. Preparation of phosphorus-sulfur composite flame retardant: 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine are added to an acetonitrile solution for dissolution according to a mass ratio of 1:2. Subsequently, the dissolved reaction mixture is placed in a reactor and stirred at a temperature of 90 - 100 °C with a stirring rate of 300 - 500 r / min for 3 - 5 h. Unreacted impurities are removed by vacuum filtration to obtain a pure phosphorus-sulfur composite flame retardant. The phosphorus-based component in the phosphorus-sulfur composite flame retardant isolates oxygen by generating a protective carbon layer during combustion, inhibiting flame spread. The sulfur-based component can provide an additional fire suppression effect at high temperatures, effectively reducing the release of volatile combustible gases from the material, thereby enhancing the flame retardancy of the material. By introducing this composite flame retardant into nylon PA6, the fire resistance of the material near a fire source can be significantly improved, the flame propagation speed can be slowed down, and fire spread can be prevented. In addition, the phosphorus-sulfur composite flame retardant also has good thermal stability and can maintain its good flame retardant effect in a high-temperature environment, avoiding the gradual weakening of the flame retardant performance during use, thus ensuring the long-term use safety of the material. It not only enhances the flame retardancy of the material but also improves the thermal stability, providing stronger protection for nylon PA6 materials applied at high temperatures and ensuring their long-term stability in a high-temperature environment.

[0030] S3. Preparation of bromine-antimony composite flame retardant: After mixing brominated polystyrene and antimony trioxide according to a mass ratio of 3:1, they are added to a dimethylsulfinamide solvent. Then, a dispersant is added, and the mixture is stirred at a rate of 500 - 1000 r / min for 1 - 2 h. After the reaction is completed, the solvent is removed to obtain a bromine-antimony composite flame retardant. As a bromine-based flame retardant, brominated polystyrene can release bromine radicals during combustion, inhibiting flame spread and significantly enhancing the flame retardant performance of the material. Antimony trioxide, as an inorganic synergistic flame retardant, can enhance the flame retardant effect by absorbing heat and forming a protective carbon layer. The combination of the two makes the effect of the bromine-based flame retardant more persistent, while reducing the volatility of the bromine-based flame retardant and its impact on the environment at high temperatures, thereby improving the stability of the flame retardant performance and the safety of the material. When the mixed brominated polystyrene and antimony trioxide are added to the dimethylsulfinamide solvent, dimethylsulfinamide has excellent solubility and can dissolve and disperse these two relatively insoluble substances, avoiding the phenomenon of uneven dispersion in subsequent steps and ensuring the consistency and stability of the final product.

[0031] S4. Mixing and Stirring: Nylon PA6, prepared guanidinium butyl sulfate, phosphorus-sulfur composite flame retardant, bromine-antimony composite flame retardant, long glass fiber, coupling agent and plasticizer are placed into a high-speed mixer according to a mass ratio of 100:10:10:12:30:0.5:0.5 for mixing to obtain a premix; Nylon PA6 serves as the matrix material, which can provide good mechanical properties and processability. Guanidinium butyl sulfate, phosphorus-sulfur composite flame retardant and bromine-antimony composite flame retardant can respectively provide gas-phase, solid-phase and synergistic flame retardant effects. The combination of the three can effectively enhance the overall flame retardant performance of the material. By mixing these flame retardants in a specific ratio, their synergistic effect can be achieved, avoiding the mutual inhibition of flame retardant effects and ensuring the stability and durability of the flame retardant effect; The addition of long glass fiber can enhance the mechanical properties of Nylon PA6. The addition of a coupling agent can improve the interfacial bonding force between the glass fiber and the Nylon PA6 matrix, thereby enhancing the overall strength and toughness of the composite material, while improving the dispersion of the glass fiber in the resin. The addition of a plasticizer can improve the processability of the composite material, enhance its flexibility and fluidity, and avoid brittle fracture or poor flow during subsequent processing; By mixing all these components in a high-speed mixer, the uniform dispersion of each component in the matrix can be ensured, and the high-speed mixer can provide a high shear force to overcome the dispersion difficulty of long glass fiber and flame retardant, so that they are evenly distributed in Nylon PA6.

[0032] S5. Feed the premix obtained in step S4 into a twin-screw extruder for melt blending. After the extruded composite material is cooled and solidified, it is granulated by a pelletizer to obtain a modified nylon composite flame retardant. In the twin-screw extruder, the material is heated to a molten state at high temperature, so that the Nylon PA6 matrix is completely fused with various flame retardants, long glass fiber, coupling agent and plasticizer and other components. After the melt-blended composite material is extruded, it is cooled and solidified by a cooling system, so that the material is quickly formed and maintains its stable structure. Then, the solidified composite material is cut into particles by a pelletizer, and the particle size of the particles is controlled between 2 - 5 mm for subsequent processing and injection molding.

[0033] Further, in step S1, the material ratio between the mixture of guanidinobutylamine and sulfuric acid and the ethanol solution is 1:10 - 25 g / mL, and the concentration of ethanol is 50 - 70 wt%; the stirring rate of the magnetic stirrer is 200 - 300 r / min, and the stirring time is 2 - 3 h. In the process of preparing guanidinobutylamine sulfate, guanidinobutylamine and sulfuric acid are mixed at a mass ratio of 1:1, and guanidinobutylamine sulfate can be formed through an acid-base reaction; sulfuric acid, as a strong acid, can effectively promote the reaction between the guanidine group in guanidinobutylamine and sulfuric acid to form a water-soluble salt, thereby providing a stable intermediate product for the subsequent reaction; then, an ethanol solution is added. Ethanol, as a solvent, can help guanidinobutylamine and sulfuric acid mix fully and, to a certain extent, help the reactants disperse in the solution, making the reaction more uniform. Subsequently, by heating to 50 - 60 °C, the reaction process can be accelerated while maintaining the solubility of the reactants to ensure that the formed guanidinobutylamine sulfate is not easily crystallized. Using a magnetic stirrer for stirring can ensure that the reactants are fully mixed in the solution, increasing the contact between molecules and making the reaction more complete, thereby improving the yield and purity of the product. After the reaction is completed, the ethanol solvent is removed by rotary evaporation to avoid damaging the product at too high a temperature while retaining the required soluble salt. Finally, after cooling to room temperature, the solid in the guanidinobutylamine sulfate solution will crystallize out to obtain pure guanidinobutylamine sulfate. Setting the material ratio between the mixture of guanidinobutylamine and sulfuric acid and the ethanol solution to 1:10 - 25 g / mL allows the reactants in the reaction process to dissolve fully and promotes the reaction between them.

[0034] Further, in step S2, the material ratio between the mixture of 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine oxide and the acetonitrile solution is 1:25 - 35 g / mL. In the process of preparing the phosphorus-sulfur composite flame retardant, first, 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine oxide are added to the acetonitrile solution at a mass ratio of 1:2 for dissolution. Acetonitrile, as a solvent, has good solubility and can effectively dissolve these two compounds and maintain the stability of the solution. After that, the dissolved reaction mixture is placed in a reactor and reacted at a temperature of 90 - 100 °C to promote the chemical reaction between dichlorophenylphosphine oxide and 4,4'-diaminodiphenyl sulfone to form a preliminary structure of the phosphorus-sulfur composite flame retardant; during the reaction, the stirring rate is set at 300 - 500 r / min to make the components in the reaction mixture disperse evenly, increasing the collision frequency between molecules and promoting the progress of the reaction. Setting the material ratio between the mixture of 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine oxide and the acetonitrile solution to 1:25 - 35 g / mL can ensure that the acetonitrile solution is neither too dilute to the reactants nor too concentrated to ensure their dissolution and reaction are smoother, thereby obtaining a highly efficient and pure phosphorus-sulfur composite flame retardant.

[0035] Further, in step S3, the material-liquid ratio between the mixture of brominated polystyrene and antimony trioxide and the dimethyl sulfinamide solvent is 1:8 - 12 g / mL. Dimethyl sulfinamide, as a solvent, has good solubility. In the set range of the material-liquid ratio, the solvent can fully dissolve the reactants and maintain the fluidity and stability of the solution.

[0036] Further, in step S3, the dispersant is maleic anhydride grafted polyolefin, and the addition amount of the dispersant is 1 - 2 wt% of the total mass of brominated polystyrene and antimony trioxide. Maleic anhydride grafted polyolefin has good compatibility and dispersibility, and can improve the compatibility between polar substances and non-polar matrices. In the solution, maleic anhydride grafted polyolefin can effectively reduce the agglomeration of brominated polystyrene and antimony trioxide, making them evenly dispersed in the solvent, thus avoiding the aggregation between the two particles and ensuring their stability and uniformity in the subsequent processing.

[0037] Further, in step S4, the coupling agent is γ-aminopropyltriethoxysilane or γ-chloropropyltrichlorosilane. As coupling agents, γ-aminopropyltriethoxysilane and γ-chloropropyltrichlorosilane can form a stable interface between the glass fiber and the resin through chemical bonding, strengthening the bonding force between the glass fiber and nylon PA6, thereby improving the mechanical properties of the composite material; the plasticizer is dioctyl phthalate or dioctyl sebacate. Dioctyl phthalate or dioctyl sebacate can lower the glass transition temperature of nylon, thereby enhancing the flexibility of the composite material, making it more fluid during processing, reducing problems such as cracks or deformation during processing, and at the same time improving the low-temperature resistance of the material to avoid embrittlement of the material in a low-temperature environment.

[0038] Further, in step S4, before adding the long glass fiber, it is subjected to solvent impregnation pretreatment. The specific process flow is as follows: The long glass fiber is placed in dichloromethane solvent for impregnation treatment. Among them, the material-liquid ratio between the long glass fiber and the dichloromethane solvent is 1:10 - 15 g / mL, and the soaking time is 30 - 60 min. Subsequently, the impregnated long glass fiber is dried by a vacuum drying oven or a hot air dryer, and the drying temperature is controlled at 50 - 60 °C, and the drying time is 6 - 8 h. As a reinforcing material, the long glass fiber can significantly improve the tensile strength, impact resistance and wear resistance of the composite material. However, due to the poor interfacial compatibility between the long glass fiber and the nylon PA6 matrix, through solvent impregnation pretreatment, the surface of the long glass fiber can be effectively improved, increasing its affinity with the nylon PA6 matrix, thus ensuring the uniform dispersion of the glass fiber, avoiding the agglomeration of the glass fiber in the nylon PA6 matrix, and effectively improving the overall mechanical properties of the composite material.

[0039] Further, in step S4, an epoxy chain extender ADR-4468 with a mass ratio of 0.3-0.8 wt% of nylon PA6 is added to a high-speed mixer, and during the mixing process, the temperature is regulated by a pulsed temperature field, alternately switching between 180-190 °C / 80-100 °C, with a switching interval of 30-60 seconds each time, and a total of 5-10 cycles. As a multi-functional epoxy chain extender, ADR-4468 can react with the amino or carboxyl groups at the ends of nylon PA6 molecules, increasing the polymer molecular weight and the degree of molecular chain entanglement through chain extension or branching, effectively improving the melt strength and thermal stability of the material, while enhancing the impact resistance and toughness of the material; in order to enable the chain extender to fully exert its reactivity during the mixing process, a pulsed temperature field regulation is adopted, that is, the temperature is switched between 180-190 °C and 80-100 °C, with a switching interval of 30-60 seconds each time, and 5-10 cycles, so set, the reaction system promotes the chemical reaction between the chain extender and the polymer at the high temperature stage, while relieving local overheating at the low temperature stage, controlling the reaction rate, inhibiting the occurrence of side reactions, and enhancing the reaction uniformity, thereby constructing a denser and more stable molecular network structure.

[0040] Further, in step S5, the screw speed of the twin-screw extruder is 250-300 r / min, the feeding zone temperature is 180-190 °C, the melting zone temperature is 200-220 °C, the mixing zone temperature is 230-240 °C, the plasticizing zone temperature is 250-260 °C, and the die head zone temperature is 260-270 °C. The feeding zone temperature is controlled at 180-190 °C, slightly higher than the melting point of nylon PA6, which can preheat and soften the material but not immediately melt it, thereby reducing the feeding resistance and avoiding bridging or blocking phenomena caused by premature melting; then it enters the melting zone, and the temperature is raised to 200-220 °C to ensure that nylon PA6 and various flame retardants, glass fibers, coupling agents, etc. are gradually melted and start to contact each other to form a continuous phase; after entering the mixing zone, the temperature rises to 230-240 °C, combined with the strong shear force of the screw, to ensure that the flame retardant is uniformly coated on the nylon PA6 matrix and the glass fibers are evenly distributed in the system, constructing a composite material with a stable structure; the plasticizing zone is raised to 250-260 °C to completely melt the material and eliminate the residual stress during the mixing process. At the same time, through a thermally stable environment, it promotes the orientation of molecular chains and the enhancement of interfacial interactions, making the composite system tend to be structurally homogeneous and continuous, facilitating subsequent molding; finally, the die head zone temperature is set at 260-270 °C. On the one hand, it maintains good fluidity of the material to ensure that there is no gel and no material breakage during the exit molding, and on the other hand, it can provide a stable melt viscosity for particle extrusion to avoid surface defects caused by uneven flow.

[0041] Example 1

[0042] Example 1 of the present invention provides a preparation method of a modified nylon composite flame retardant, including the following steps:

[0043] S1. Preparation of guanidinium butylamine sulfate: Mix guanidinium butylamine and sulfuric acid at a mass ratio of 1:1, then add an ethanol solution. The liquid ratio between the mixture of guanidinium butylamine and sulfuric acid and the ethanol solution is 1:10 g / mL, and the concentration of ethanol is 50 wt%. Subsequently, heat the mixture to 50 °C and stir it with a magnetic stirrer at a stirring rate of 200 r / min for 3 h. After the reaction is completed, remove the ethanol solution by rotary evaporation. After cooling to room temperature, crystalline guanidinium butylamine sulfate is obtained;

[0044] S2. Preparation of phosphorus-sulfur composite flame retardant: Dissolve 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine in an acetonitrile solution at a mass ratio of 1:2. The liquid ratio between the mixture of 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine and the acetonitrile solution is 1:25 g / mL. Subsequently, place the dissolved reaction mixture in a reactor and stir it at a temperature of 90 °C at a stirring rate of 500 r / min for 3 h. Remove the unreacted impurities by vacuum filtration to obtain a pure phosphorus-sulfur composite flame retardant;

[0045] S3. Preparation of bromine-antimony composite flame retardant: Mix brominated polystyrene and antimony trioxide at a mass ratio of 3:1, then add them to a dimethylsulfinamide solvent. The liquid ratio between the mixture of brominated polystyrene and antimony trioxide and the dimethylsulfinamide solvent is 1:8 g / mL. Then add a dispersant, the dispersant is maleic anhydride-grafted polyolefin, and the addition amount of the dispersant is 1 wt% of the total mass of brominated polystyrene and antimony trioxide. Stir at a rate of 500 r / min for 2 h. After the reaction is completed, remove the solvent to obtain a bromine-antimony composite flame retardant;

[0046] S4. Mixing and stirring: Place nylon PA6, prepared guanidinium butylamine sulfate, phosphorus-sulfur composite flame retardant, bromine-antimony composite flame retardant, long glass fiber, coupling agent, and plasticizer into a high-speed mixer according to a mass ratio of 100:10:10:12:30:0.5:0.5 to obtain a premixed material; the coupling agent is γ-aminopropyltriethoxysilane, and the plasticizer is dioctyl phthalate;

[0047] Among them, before adding the long glass fiber, it is pretreated by solvent impregnation. The specific process flow is: Place the long glass fiber in a dichloromethane solvent for impregnation treatment. Among them, the liquid ratio between the long glass fiber and the dichloromethane solvent is 1:10 g / mL, and the soaking time is 60 min. Subsequently, dry the impregnated long glass fiber with a vacuum drying oven or a hot air dryer, and control the drying temperature at 50 °C and the drying time at 8 h;

[0048] In addition, add an epoxy chain extender ADR-4468 with a mass ratio of 0.3 wt% of nylon PA6 to a high-speed mixer, and during the mixing process, regulate the temperature field by pulse, alternately switch the temperature to 180 °C / 80 °C, with an interval of 30 seconds for each switch, and cycle 10 times in total;

[0049] S5. Feed the premixed material obtained in step S4 into a twin-screw extruder for melt blending. The screw speed of the twin-screw extruder is 250 r / min, the temperature of the feeding zone is 180 °C, the temperature of the melting zone is 200 °C, the temperature of the mixing zone is 230 °C, the temperature of the plasticizing zone is 250 °C, the temperature of the die head zone is 260 °C. After the extruded composite material is cooled and solidified, it is granulated by a pelletizer to obtain a modified nylon composite flame retardant.

[0050] Example 2

[0051] Example 2 of the present invention provides a method for preparing a modified nylon composite flame retardant, including the following steps:

[0052] S1. Prepare guanidinium butylamine sulfate: Mix guanidinium butylamine and sulfuric acid in a mass ratio of 1:1, then add an ethanol solution. The liquid ratio between the mixture of guanidinium butylamine and sulfuric acid and the ethanol solution is 1:25 g / mL, and the concentration of ethanol is 70 wt%. Subsequently, heat the mixture to 60 °C and stir it with a magnetic stirrer at a stirring rate of 300 r / min for 2 h. After the reaction is completed, remove the ethanol solution by rotary evaporation, and obtain crystalline guanidinium butylamine sulfate after cooling to room temperature;

[0053] S2. Prepare a phosphorus-sulfur composite flame retardant: Dissolve 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine in an acetonitrile solution in a mass ratio of 1:2. The liquid ratio between the mixture of 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine and the acetonitrile solution is 1:35 g / mL. Subsequently, place the dissolved reaction mixture in a reactor and stir it at a temperature of 100 °C at a stirring rate of 500 r / min for 3 h. Remove the unreacted impurities by vacuum filtration to obtain a pure phosphorus-sulfur composite flame retardant;

[0054] S3. Prepare a bromine-antimony composite flame retardant: Mix brominated polystyrene and antimony trioxide in a mass ratio of 3:1, then add them to a dimethyl sulfinamide solvent. The liquid ratio between the mixture of brominated polystyrene and antimony trioxide and the dimethyl sulfinamide solvent is 1:12 g / mL. Then add a dispersant, and the dispersant is maleic anhydride-grafted polyolefin. The addition amount of the dispersant is 2 wt% of the total mass of brominated polystyrene and antimony trioxide. Stir at a rate of 1000 r / min for 2 h. After the reaction is completed, remove the solvent to obtain a bromine-antimony composite flame retardant;

[0055] S4. Mixing and Stirring: Nylon PA6, prepared guanidinium butyl sulfate, phosphorus-sulfur composite flame retardant, bromine-antimony composite flame retardant, long glass fiber, coupling agent and plasticizer are placed in a high-speed mixer according to a mass ratio of 100:10:10:12:30:0.5:0.5 to obtain a premix; the coupling agent is γ-chloropropyltrichlorosilane, and the plasticizer is dioctyl suberate;

[0056] Among them, before adding the long glass fiber, it is pretreated by solvent impregnation. The specific process flow is as follows: The long glass fiber is placed in dichloromethane solvent for impregnation treatment. Among them, the material-liquid ratio between the long glass fiber and the dichloromethane solvent is 1:15 g / mL, and the soaking time is 60 min. Subsequently, the impregnated long glass fiber is dried by a vacuum drying oven or a hot air dryer, and the drying temperature is controlled at 50 °C, and the drying time is 8 h;

[0057] In addition, an epoxy chain extender ADR-4468 with a mass ratio of 0.8 wt% of nylon PA6 is added to the high-speed mixer, and during the stirring process, the temperature is regulated by a pulsed temperature field, alternately switching the temperature to 190 °C / 100 °C, with each switching interval of 60 seconds, for a total of 10 cycles;

[0058] S5. Feed the premix obtained in step S4 into a twin-screw extruder for melt blending. The screw speed of the twin-screw extruder is 300 r / min, the feeding zone temperature is 190 °C, the melting zone temperature is 220 °C, the mixing zone temperature is 240 °C, the plasticizing zone temperature is 260 °C, the die head zone temperature is 270 °C. After the extruded composite material is cooled and solidified, it is granulated by a granulator to obtain a modified nylon composite flame retardant.

[0059] Comparative Example 1

[0060] In the modified nylon composite flame retardant and its preparation method of this Comparative Example 1, the difference from Example 1 is that: in step S4, the guanidinium butyl sulfate component is not added.

[0061] Comparative Example 2

[0062] In the modified nylon composite flame retardant and its preparation method of this Comparative Example 2, the difference from Example 1 is that: in step S4, the phosphorus-sulfur composite flame retardant component is not added.

[0063] Comparative Example 3

[0064] In the modified nylon composite flame retardant and its preparation method of this Comparative Example 3, the difference from Example 1 is that: in step S4, the bromine-antimony composite flame retardant component is not added.

[0065] Comparative Example 4

[0066] In the modified nylon composite flame retardant and its preparation method of Comparative Example 4, the difference from Example 1 is that in step S4, the long glass fiber component is not added.

[0067] Comparative Example 5

[0068] In the modified nylon composite flame retardant and its preparation method of Comparative Example 5, the difference from Example 1 is that in step S4, before adding the long glass fiber, it is not pretreated by solvent impregnation.

[0069] Comparative Example 6

[0070] In the modified nylon composite flame retardant and its preparation method of Comparative Example 6, the difference from Example 1 is that in step S4, the epoxy chain extender ADR-4468 is not added to the high-speed mixer.

[0071] Comparative Example 7

[0072] In the modified nylon composite flame retardant and its preparation method of Comparative Example 7, the difference from Example 1 is that in step S5, the temperature of each zone of the twin-screw extruder is 260 °C.

[0073] Next, the above Examples 1-2 and Comparative Examples 1-7 were experimented to verify or understand their properties. Among the modified nylon composite flame retardants prepared in the above Examples 1-2 and Comparative Examples 1-7.

[0074]

[0075] Table 1 Comparison table of performance test data of modified nylon composite flame retardants

[0076] As can be seen from Table 1 above: In the modified nylon composite flame retardants prepared in Example 1 and Example 2, guanidinium butylamine sulfate provides a gas-phase flame retardant effect through its amino structure. The phosphorus-sulfur composite flame retardant can enhance the solid-phase flame retardant effect by generating a protective carbon layer and inhibiting the release of volatile combustible gases. The bromine-antimony composite flame retardant delays flame propagation through synergistic effects, and its flame retardant effect is more persistent. Through this composite flame retardant system, the fire resistance of the material near the fire source is significantly improved, effectively enhancing the stability and persistence of the flame retardant effect of the material, and it is applicable to high-temperature or fire-dangerous environments. Long glass fibers can enhance the tensile strength, impact strength, and wear resistance of nylon PA6. The coupling agent can improve the interfacial bonding force between the glass fibers and the nylon PA6 matrix, avoiding the aggregation or uneven dispersion of long glass fibers. The plasticizer can enhance the flexibility and fluidity of the composite material, lower the glass transition temperature of the material, making the composite material flow more easily during the processing, and avoiding problems such as brittle cracking and poor flow. In addition, the use of the epoxy chain extender ADR-4468 can improve the thermal stability and melt strength of nylon PA6 through chain extension and branching effects, enhance the stability of the composite material at high temperatures, and improve the impact resistance and toughness of the material.

[0077] In Comparative Example 1, guanidinium butylamine sulfate, as a nitrogen-containing compound, has strong thermal stability and can decompose at high temperatures to release substances that can inhibit flame spread. Its guanidine structure can effectively react with the fire source during the flame propagation process to form a gas-phase substance that inhibits flame spread, thereby providing effective gas-phase flame retardant protection for the material. Without the participation of guanidinium butylamine sulfate, when the composite material faces a fire source, the lack of this gas-phase flame retardant effect will lead to an accelerated flame spread rate and an increased release of harmful gases during combustion, thus reducing the safety and fire resistance of the material. Especially in a high-temperature environment, guanidinium butylamine sulfate can improve the thermal stability of the material and avoid premature thermal degradation. Therefore, the absence of guanidinium butylamine sulfate will significantly affect the nylon PA6 in terms of flame retardant performance, thermal stability, and combustion resistance, the flame retardant effect cannot be persistent, and the material is more easily ignited by the fire source.

[0078] In Comparative Example 2, the phosphorus-based component of the phosphorus-sulfur composite flame retardant can generate a protective carbon layer during combustion to effectively isolate oxygen, and this carbon layer can prevent the continuous spread of the flame. The sulfur-based component can reduce the volatile combustible gases during combustion, thereby inhibiting the spread of the flame. Without adding the phosphorus-sulfur composite flame retardant, the material will lose this solid-phase flame retardant mechanism, resulting in an accelerated flame spread rate. In addition, the phosphorus-sulfur composite flame retardant also has excellent thermal stability and can maintain a stable flame retardant effect in a high-temperature environment, avoiding a gradual weakening of the flame retardant performance during use.

[0079] In Comparative Example 3, the bromine-antimony composite flame retardant component was not added, which may affect the synergistic flame retardant effect of the composite material. The bromine-antimony composite flame retardant can enhance the flame retardant effect through the synergistic effect between brominated polystyrene and antimony trioxide. Specifically, brominated polystyrene, as a bromine-based flame retardant, can release bromine free radicals during combustion, and these free radicals can effectively inhibit the spread of the flame and reduce the combustion rate of the material. Antimony trioxide, as an inorganic synergistic flame retardant, enhances the flame retardant performance of the material through endothermic action and the formation of a protective carbon layer.

[0080] In Comparative Example 4, the absence of long glass fibers led to a significant reduction in the mechanical properties of the nylon PA6 matrix. Although nylon PA6 itself has a certain strength, it lacks the support of reinforcing materials and is prone to fracture or deformation when subjected to external forces such as tension, bending, and impact. The addition of long glass fibers can enhance the rigidity, strength, and wear resistance of the composite material, effectively improving the mechanical properties of the nylon PA6 composite material.

[0081] In Comparative Example 5, before adding long glass fibers, no solvent impregnation pretreatment was carried out, which would result in poor interfacial bonding force between the long glass fibers and the nylon PA6 matrix, thus affecting the mechanical properties and flame retardant properties of the composite material. The purpose of solvent impregnation pretreatment is to improve the surface properties of long glass fibers, make their surface more compatible with the nylon PA6 matrix, and enhance the interfacial bonding force between the two. Long glass fibers without pretreatment lack sufficient affinity to bond with the nylon PA6 matrix, resulting in an uneven composite material. This will cause the long glass fibers to aggregate or disperse poorly, making the mechanical properties of the composite material unable to reach the best effect. In addition, the poor interfacial bonding force between the long glass fibers and the nylon PA6 matrix will also affect the distribution and effect of the flame retardant, resulting in the inability of the flame retardant to be evenly distributed in the composite material, thus reducing the flame retardant effect.

[0082] In Comparative Example 6, the epoxy chain extender ADR-4468 can undergo a crosslinking reaction with the molecular ends of nylon PA6 through chemical reactions, thereby increasing the molecular weight of the polymer and the degree of entanglement of the molecular chains, and improving the melt strength of nylon PA6; ADR-4468 has multiple functional groups and can react with the amino or carboxyl groups in the nylon PA6 molecule to form an extended or branched structure of the molecular chain. This structure can enhance the intermolecular crosslinking effect and improve the thermal stability of the material. Especially when used at high temperatures, it can effectively prevent the material from undergoing thermal degradation and softening, ensuring its long-term stability in a high-temperature environment; if the epoxy chain extender is not added, the molecular structure of nylon PA6 will be relatively simple, lacking chain extension and crosslinking, resulting in a low melt strength during high-temperature melting, making the material exhibit poor fluidity, poor thermal stability, and uneven processing during the processing process, increasing the processing difficulty; moreover, the untreated nylon PA6 without chain extension also has relatively poor thermal stability and thermal aging resistance, and is prone to performance degradation, such as embrittlement and poor melt fluidity, when exposed to a high-temperature environment for a long time.

[0083] In Comparative Example 7, if the temperature in the feeding zone is too high, it will cause the raw materials to start melting or even undergo local thermal degradation before being fully compacted by the screw, triggering the phenomenon of bridging and blocking the material, reducing the feeding efficiency and affecting the subsequent conveying stability; at the same time, it will also cause the plasticizer and coupling agent to volatilize or decompose prematurely, resulting in a ratio imbalance; secondly, in the melting zone and the mixing zone, although 260 °C can ensure the full melting of PA6, since all the materials are exposed to continuous high temperatures, it will exacerbate the thermal-oxidative degradation of nylon and the thermal decomposition of the flame retardant, rendering the flame retardant ineffective. Especially for inorganic components such as antimony trioxide, they are prone to agglomeration at high temperatures, affecting uniform dispersion and resulting in unstable flame retardancy of the material.

[0084] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of a modified nylon composite flame retardant, characterized in that, It includes the following steps: S1. Prepare guanidinobutylamine sulfate: Mix guanidinobutylamine and sulfuric acid at a mass ratio of 1:1, add an ethanol solution, then heat the mixture to 50 - 60 °C, stir it with a magnetic stirrer, remove the ethanol solution by rotary evaporation after the reaction is completed, and obtain crystalline guanidinobutylamine sulfate after cooling to room temperature; S2. Prepare a phosphorus-sulfur composite flame retardant: Dissolve 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine in an acetonitrile solution at a mass ratio of 1:

2. Then place the dissolved reaction mixture in a reactor, stir it at a temperature of 90 - 100 °C, with a stirring rate of 300 - 500 r / min and a stirring time of 3 - 5 h. Remove the unreacted impurities by vacuum filtration to obtain a pure phosphorus-sulfur composite flame retardant; S3. Prepare a bromine-antimony composite flame retardant: Mix brominated polystyrene and antimony trioxide at a mass ratio of 3:1, add them to a dimethyl sulfinamide solvent, then add a dispersant, and stir at a rate of 500 - 1000 r / min for 1 - 2 h. Remove the solvent after the reaction is completed to obtain a bromine-antimony composite flame retardant; S4. Mixing and stirring: Place nylon PA6, the prepared guanidinobutylamine sulfate, phosphorus-sulfur composite flame retardant, bromine-antimony composite flame retardant, long glass fiber, coupling agent, and plasticizer into a high-speed mixer according to a mass ratio of 100:10:10:12:30:0.5:0.5 to mix and obtain a premix; S5. Feed the premix obtained in step S4 into a twin-screw extruder for melt blending. After the extruded composite material is cooled and solidified, granulate it with a granulator to obtain a modified nylon composite flame retardant.

2. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that In step S1, the liquid ratio between the mixture of guanidinobutylamine and sulfuric acid and the ethanol solution is 1:10 - 25 g / mL, and the concentration of ethanol is 50 - 70 wt%; The stirring rate of the magnetic stirrer is 200 - 300 r / min, and the stirring time is 2 - 3 h.

3. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S2, the liquid ratio between the mixture of 4,4'-diaminodiphenyl sulfone and dichlorophenylphosphine and the acetonitrile solution is 1:25 - 35 g / mL.

4. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S3, the liquid ratio between the mixture of brominated polystyrene and antimony trioxide and the dimethyl sulfinamide solvent is 1:8 - 12 g / mL.

5. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S3, the dispersant is maleic anhydride-grafted polyolefin, and the addition amount of the dispersant is 1 - 2 wt% of the total mass of brominated polystyrene and antimony trioxide.

6. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S4, the coupling agent is γ-aminopropyltriethoxysilane or γ-chloropropyltrichlorosilane; The plasticizer is dioctyl phthalate or dioctyl suberate.

7. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S4, before adding the long glass fiber, it is pretreated by solvent impregnation; The specific process flow is: Place the long glass fiber in a dichloromethane solvent for impregnation treatment. Among them, the liquid ratio between the long glass fiber and the dichloromethane solvent is 1:10 - 15 g / mL, the soaking time is 30 - 60 min, and then dry the impregnated long glass fiber with a vacuum drying oven or a hot air dryer. The drying temperature is controlled at 50 - 60 °C, and the drying time is 6 - 8 h.

8. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S4, an epoxy chain extender ADR-4468 accounting for 0.3-0.8 wt% of nylon PA6 by mass is added to a high-speed mixer, and during the mixing process, the temperature is alternately switched between 180-190 °C and 80-100 °C through pulsed temperature field regulation, with an interval of 30-60 seconds for each switch, and a total of 5-10 cycles are performed.

9. The preparation method of the modified nylon composite flame retardant according to claim 1, characterized in that, In step S5, the screw speed of the twin-screw extruder is 250-300 r / min, the temperature of the feeding zone is 180-190 °C, the temperature of the melting zone is 200-220 °C, the temperature of the mixing zone is 230-240 °C, the temperature of the plasticizing zone is 250-260 °C, and the temperature of the die head zone is 260-270 °C.

10. A modified nylon composite flame retardant, characterized in that, It is prepared by the preparation method of the modified nylon composite flame retardant according to any one of claims 1-9.

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