Enhanced flame retardant masterbatch material and preparation method

Abstract

The present invention relates to the field of plastic masterbatches and provides an enhanced flame-retardant masterbatch material and preparation method. The masterbatch comprises a core-shell flame retardant, polypropylene, a compatibility modifier, a lubricating and dispersing aid, a surfactant, an anti-aging stabilizer, and ethanol. The core-shell flame retardant is composed of bimetallic layered hydroxide microspheres with a hollow structure and a nanoscale corrugated surface coated with melamine phosphate. The flame retardant is prepared by ultrasonic impregnation, and the microspheres are synthesized by hydrothermal reaction. The structure is controlled by regulating the Mg / Al molar ratio, pH value, filling degree, and reaction conditions. The resulting masterbatch is prepared through premixing, melt extrusion, cooling granulation, and post-processing steps. It has excellent flame retardant properties, thermal stability, and dispersion compatibility, and is suitable for flame retardant enhancement applications of polyolefin-based materials.

Description

Technical Field

[0001] The present invention relates to the field of plastic masterbatches, and in particular to an enhanced flame retardant masterbatch material and a preparation method thereof. Background Art

[0002] Safety and cost advantages are widely used in the manufacture of various structural parts and functional components. However, with the continuous improvement of safety standards and increasingly stringent environmental regulations, polyolefin materials are faced with the dual performance requirements of higher flame retardancy and structural strength in practical applications, especially in high-temperature electrical environments, automotive interior systems or long-term load scenarios. The material not only needs to have excellent flame retardancy to reduce the risk of fire, but also needs to ensure good mechanical strength to maintain structural stability and service life. Therefore, the development of a modified masterbatch material with both high flame retardancy and enhanced performance can not only meet the stringent requirements of high-end application scenarios for the comprehensive performance of materials, but also improve the safety and reliability of products, and broaden the application boundaries of polyolefin materials. More importantly, achieving performance synergy between flame retardancy and enhancement through the coordinated design and structural regulation of functional additives is a key way to promote the development of flame retardant materials towards high efficiency, lightweight and green, and has important engineering practice significance and industrial application value.

[0003] Despite extensive research on polyolefin flame-retardant masterbatches, and the availability of numerous market-proven modification schemes based on inorganic fillers, phosphorus-nitrogen compounds, or synergistic flame-retardant systems, significant deficiencies remain in balancing strength and flame retardancy. For example, Chinese patent publication number CN104419166A discloses a PC flame-retardant masterbatch. While this improves the flame retardancy of the material to a certain extent, it often results in a decrease in the strength of the matrix material under high-filling conditions, making it difficult to meet the requirements for applications with high mechanical performance requirements. These issues primarily stem from poor interfacial compatibility between the flame-retardant component and the polymer matrix, uneven particle size distribution, or a lack of synergy in the structural design. In particular, the lack of precise control of the additive structure and functional integration leads to performance conflicts between the flame-retardant mechanism and the reinforcement mechanism. Furthermore, the easy migration and poor dispersibility of the flame retardants used in some process pathways further limit their application in high-performance flame-retardant products. Therefore, how to enhance the mechanical strength of the masterbatch while maintaining flame retardancy remains a key challenge in current research on high-performance polyolefin flame-retardant masterbatches, and systematic breakthroughs in structural design, interface control, and preparation methods are urgently needed. Summary of the Invention

[0004] (1) Technical problems solved

[0005] The purpose of the present invention is to provide an enhanced flame retardant masterbatch material and a preparation method to solve the problem that the current masterbatch is insufficient in strength and flame retardancy.

[0006] (2) Technical solution

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A reinforced flame retardant masterbatch material comprises the following raw materials in parts by weight: 20-40 parts of a core-shell structure flame retardant, 100-200 parts of polypropylene, 5.0-8.0 parts of a compatibility modifier, 2.0-4.5 parts of a lubricating and dispersing aid, 1.0-3.5 parts of a surfactant, 0.5-2.0 parts of an anti-aging stabilizer 1010, and 10.0-30.0 parts of ethanol;

[0009] The core-shell flame retardant is composed of porous bimetallic layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres;

[0010] The surface of the porous double metal hydroxide microspheres has a nanoscale wrinkled structure;

[0011] The double metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide.

[0012] Furthermore, the preparation method of the core-shell structure flame retardant is as follows: 20 to 40 parts by weight of porous double metal hydroxide microspheres are dispersed in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 1:1 to 3:1, and ultrasonic dispersion treatment time is 10 to 30 minutes, and the ultrasonic power is 200 to 500 W; 10 to 30 parts by weight of melamine phosphate are added to the dispersion, and an impregnation method is used, at an impregnation temperature of 40 to 70° C. and an impregnation time of 120 to 360 minutes, during which slow stirring at 50 to 150 rpm is maintained to promote penetration; after the impregnation is completed, the solid and liquid phases are separated by vacuum filtration, and the filter cake is washed with deionized water 3 to 5 times, and then the temperature is programmed to 50 to 80° C. at a heating rate of 2 to 5° C. / min under a vacuum degree of -0.08 to -0.1 MPa and dried for 180 to 420 minutes, to finally obtain the core-shell structure flame retardant.

[0013] Furthermore, the preparation method of the porous double metal hydroxide microspheres is as follows: in parts by weight, 40.0-60.0 parts of magnesium source magnesium nitrate hexahydrate and aluminum source aluminum nitrate nonahydrate are dissolved in 200.0-300.0 parts of deionized water at a total mass ratio of Mg / Al of 3.5-4.0:1 to form a homogeneous solution, 8.0-15.0 parts of morphology control agent sodium citrate, 2.0-6.0 parts of sodium gluconate and 1.5-2.5 parts of surfactant hexadecyltrimethylammonium bromide are added in sequence at a stirring rate of 500-700 rpm, stirring continuously until the mixture is uniformly mixed, and then the pH value is adjusted to 10.0-10.5 using 0.1 mol / L NaOH solution. The current stirring rate is maintained and the reaction is continued for 15-30 min, and then the mixture is treated with an ultrasonic device with a frequency of 40-60 kHz for 15-25 min. min, the resulting precursor solution was transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 70% to 80%, and hydrothermally reacted at 160 to 180 ° C for 12 to 18 hours and then naturally cooled to 25 ° C. The free ions and small molecular organic matter in the reaction system that did not participate in the crystallization were removed with the centrifugal supernatant at 10000 to 12000 rpm after 5 to 10 minutes. The collected precipitate was washed with deionized water 3 to 5 times until the filtrate conductivity was lower than 50 μS / cm to completely remove soluble impurities. Subsequently, the temperature was increased to 350 ° C at 5 ° C / min under nitrogen protection and calcined for 2 hours to completely decompose the organic template and form a stable hollow structure. Finally, the hollow double hydroxide microspheres with nanoscale surface wrinkles were obtained by vacuum drying at 60 to 80 ° C for 12 to 16 hours.

[0014] The present invention adopts the design / preparation of a core-shell structure flame retardant mainly for enhancing the mechanical properties and flame retardant properties of plastic masterbatch. The flame retardant is composed of a porous bimetallic layered hydroxide microsphere with a hollow structure and a melamine phosphate coated in its inner cavity. Through the synergistic construction of structure and components, it aims to achieve a comprehensive improvement in thermal stability, mechanical strength and flame retardant efficiency in a polymer matrix. The bimetallic hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide, and the surface of the microsphere has a nanoscale wrinkled structure. This morphological feature not only significantly increases the specific surface area, which is beneficial to the adsorption and loading of subsequent functional components, but also enhances its physical intercalation and interfacial bonding in the polymer matrix. The microsphere structure with hollow and wrinkled characteristics is regulated and formed by the synergistic action of sodium citrate and hexadecyltrimethylammonium bromide, ensuring the uniformity and stability of the microstructure. After the above-mentioned microspheres are dispersed in an ethanol-water mixed solution, they are impregnated and coated with melamine phosphate as a functional component. Melamine phosphate can achieve effective confinement within the hollow structure of the microspheres, improving their release timing and spatial stability under thermal stimulation. By controlling the ultrasonic power, impregnation time, temperature and stirring rate, melamine phosphate is fully penetrated into the inner cavity of the microspheres to form core-shell flame retardant particles with a dense structure and uniform distribution. During the drying process, programmed temperature is combined with vacuum control to effectively avoid structural damage and component migration, ensuring the thermal stability and dispersibility of the obtained particles in subsequent processing. This core-shell structure flame retardant can not only provide a synergistic flame retardant effect in the polymer matrix, but also improve the mechanical properties of the matrix through its structural characteristics, reflecting the functional complementarity and structural synergy between the filler and the functional component, breaking through the bottleneck of traditional flame retardant materials that are difficult to balance flame retardancy and reinforcement, and showing significant performance advantages and broad application potential in the modification of thermoplastics such as polyolefins.

[0015] Furthermore, the mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide is (5.3~6.0):1.

[0016] Furthermore, the mass ratio of the porous double metal hydroxide microspheres to the melamine phosphate in the core-shell flame retardant is (2.0-3.5):1.

[0017] Furthermore, the average size of the core-shell structure flame retardant is 200-600 nm.

[0018] Furthermore, the compatibility modifier is maleic anhydride grafted modified polypropylene;

[0019] The lubricating and dispersing auxiliary agent is zinc stearate;

[0020] The surfactant is sodium lauryl sulfate;

[0021] The anti-aging stabilizer is antioxidant 1010.

[0022] The technical solution of the present invention aims to improve the flame retardant properties and mechanical properties of plastic masterbatch by constructing a synergistic core-shell flame retardant system. The starting point of the design is to optimize and balance the overall performance of the material by utilizing a multi-component synergistic strategy with integrated structure and function. The core-shell flame retardant is composed of porous double metal hydroxide microspheres with a hollow structure and melamine phosphate coated in its inner cavity, wherein the double metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide, and the surface of the microspheres has a nanoscale wrinkled structure, which helps to increase the specific surface area and enhance the interfacial bonding ability with the polymer matrix. In the process of preparing microspheres, by introducing the morphology control agent sodium citrate and the surfactant hexadecyltrimethylammonium bromide, and controlling their mass ratio within the range of (5.0~6.0):1, the particle size distribution and surface structure of the microspheres can be effectively regulated to ensure that the obtained microspheres have good dispersibility and structural integrity. During the core-shell structure construction process, by coating melamine phosphate in the inner cavity of double metal hydroxide microspheres at a mass ratio of (2.0~3.5):1, both the effective confinement of the flame retardant component and the migration and failure of the flame retardant component during polymer processing are achieved. The particle size of the resulting coating structure is controlled at 200~600nm, which is conducive to the formation of a uniformly distributed microstructure in the polypropylene matrix, thereby enhancing the mechanical stability of the material while improving the flame retardant performance. In addition, the present invention further improves the compatibility and processing stability between the components by introducing maleic anhydride grafted modified polypropylene as a compatibility modifier, zinc stearate as a lubricating dispersing aid, sodium lauryl sulfate as a surfactant, and antioxidant 1010 as an anti-aging stabilizer. Overall, through structural control and optimization of component ratios, a stable and effective synergistic effect is formed between the hollow porous microspheres and melamine phosphate, which not only enhances the distribution uniformity and interfacial bonding strength of the flame retardant system in the resin matrix, but also achieves a synergistic improvement in flame retardant efficiency and mechanical properties, reflecting the unified strategy of structural regulation and functional integration in material design.

[0023] The present invention also discloses a method for preparing an enhanced flame retardant masterbatch material, comprising the following steps:

[0024] S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic device, add ethanol and heat to 30-40°C, slowly add surfactant while stirring at 200-400 rpm, and dissolve for 15-30 min; then add core-shell flame retardant, and use intermittent ultrasonication with a power of 300-600 W, with an operating cycle of 3-5 s and a pause of 1-2 s, during which mechanical stirring is coordinated and dispersed for 30-60 min; add anti-aging stabilizer and lubricating dispersing aid in sequence, and mix in stages at 40-60°C and 250-800 rpm for 30-45 min; finally, dry at 60-70°C and a vacuum degree of 0.05-0.1 MPa for 5-8 h to obtain flame retardant additive composite;

[0025] S2: Pretreatment and compounding of the matrix resin: Preheat the polypropylene resin at 80-100°C for 2-4 hours, then mix it with the compatibility modifier at 110-130°C and 600-1000 rpm for 15-25 minutes. Then, mix the flame retardant additive compound obtained in S1 with the matrix resin and mix at 50-60°C and 500-800 rpm for 10-20 minutes to form a homogeneous premix.

[0026] S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder with a screw speed of 80-120 rpm, a temperature gradient from the feed port to the die head of 160-200°C, and a residence time of 2-4 min. The extruded melt was cooled in a water bath at 20-30°C for 1-3 min and solidified, and then pelletized to obtain primary particles of 3-5 mm.

[0027] S4: Post-processing and finished product preparation: The primary granules are dehydrated by centrifugation at 800-1200 rpm for 2-5 min, and then air-dried at 70-80°C for 30-45 min. A 40-60 mesh vibrating screen is used with a frequency of 20-30 Hz for 10-15 min. Finally, the granules are sealed and packaged under a vacuum of 0.05-0.08 MPa to obtain a finished product with a moisture content of <0.1%.

[0028] (3) Beneficial technical effects

[0029] 1. This invention uses hollow wrinkled microspheres and melamine phosphate to synergistically construct a core-shell structure, significantly improving the flame retardancy and mechanical properties of the masterbatch, solving the problem of traditional systems that are difficult to achieve both strength and flame retardancy. It has excellent dispersibility and interfacial compatibility and is suitable for the modification of high-performance polyolefin materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The morphology of the porous double metal hydroxide microspheres prepared in Example 1 of the present invention was obtained.

[0031] Figure 2 This is a morphology diagram of the core-shell structure flame retardant prepared in Example 1 of the present invention.

[0032] Figure 3 This is a physical picture of the flame retardant masterbatch prepared in Example 1 of the present invention.

[0033] Figure 4 The porous double metal hydroxide microspheres are prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Example 1

[0035] A reinforced flame retardant masterbatch material, comprising the following raw materials in parts by weight: 20 parts of a core-shell structure flame retardant, 100 parts of polypropylene, 5.0 parts of maleic anhydride grafted modified polypropylene, 2.0 parts of zinc stearate, 1.0 part of sodium lauryl sulfate, 0.5 parts of an antioxidant 1010, and 10.0 parts of ethanol;

[0036] The core-shell flame retardant consists of porous double-metal layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres; the surface of the porous double-metal hydroxide microspheres has a nanoscale wrinkled structure; and the double-metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide.

[0037] The preparation method of the core-shell structure flame retardant of this embodiment is as follows: 26 parts by weight of porous double metal hydroxide microspheres are dispersed in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 1.6:1, and ultrasonic dispersion treatment is performed for 16 minutes at an ultrasonic power of 290 W; 16 parts by weight of melamine phosphate are added to the dispersion, and an impregnation method is adopted at an impregnation temperature of 49° C. and an impregnation time of 192 minutes, during which slow stirring at 80 rpm is maintained to promote penetration; after the impregnation is completed, the solid and liquid phases are separated by vacuum filtration, and the filter cake is washed four times with deionized water, and then the temperature is programmed to 59° C. at a heating rate of 3° C. / min under a vacuum degree of -0.09 MPa and dried for 252 minutes, thereby obtaining a core-shell structure flame retardant.

[0038] The preparation method of the porous double hydroxide microspheres of this embodiment is as follows: in parts by weight, 40.0 parts of magnesium nitrate hexahydrate as a magnesium source and aluminum nitrate nonahydrate as an aluminum source are dissolved in 200.0 parts of deionized water at a Mg / Al molar ratio of 3.5:1 to form a homogeneous solution; 8.0 parts of morphology control agent sodium citrate, 2.0 parts of sodium gluconate and 1.5 parts of surfactant cetyltrimethylammonium bromide are added in sequence at a stirring rate of 500 rpm; after continuous stirring until the mixture is uniformly mixed, the pH value is adjusted to 10.0 with a 0.1 mol / L NaOH solution; the current stirring rate is maintained and the reaction is continued for 15 minutes; then, the mixture is transferred to an ultrasonic device with a frequency of 40 kHz for 15 minutes; the resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 70%; the reaction is hydrothermally reacted at 160° C. for 12 hours, and then naturally cooled to 25° C. The free ions and small molecular organic matter in the reaction system that do not participate in crystallization are separated with the centrifugal supernatant at 10,000 rpm for 5 minutes. The collected precipitate was removed after 30 min, and the collected precipitate was washed three times with deionized water until the conductivity of the filtrate was less than 50 μS / cm to completely remove soluble impurities. It was then heated to 350°C at 5°C / min under nitrogen protection and calcined for 2 h to completely decompose the organic template and form a stable hollow structure. Finally, it was vacuum dried at 60°C for 12 h to obtain hollow double hydroxide microspheres with nanoscale surface wrinkles.

[0039] The mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide in this embodiment is 5.3:1.

[0040] The mass ratio of the porous double hydroxide microspheres to the melamine phosphate in the core-shell flame retardant of this embodiment is 2.5:1.

[0041] The average size of the core-shell structure flame retardant of this embodiment is 320 nm.

[0042] A method for preparing an enhanced flame retardant masterbatch material according to this embodiment includes the following steps:

[0043] S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic devices, ethanol was added and the temperature was raised to 30°C. The surfactant was slowly added with stirring at 200 rpm and the dissolution time was 15 minutes. Then, the core-shell flame retardant was added and intermittent ultrasonication at 300 W power was used, with an operation time of 3 seconds and a pause time of 1 second, during which mechanical stirring and dispersion were coordinated for 30 minutes. The anti-aging stabilizer and lubricating dispersing additive were added in sequence and mixed in stages at 40°C and 250 rpm for 30 minutes. Finally, the flame retardant additive composite was dried at 60°C and 0.05 MPa vacuum for 5 hours to obtain.

[0044] S2: Pretreatment and compounding of the matrix resin: After preheating the polypropylene resin at 80°C for 2 hours, it was mixed with the compatibility modifier at 110°C and 600 rpm for 15 minutes. Then, the flame retardant additive compound obtained in S1 was mixed with the matrix resin and mixed at 50°C and 500 rpm for 10 minutes to form a homogeneous premix.

[0045] S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder with a screw speed of 80 rpm, a temperature gradient from the feed port to the die head of 160°C, and a residence time of 2 min. The extruded melt was cooled in a 20°C water bath for 1 min and solidified, and then pelletized to obtain 3 mm primary pellets.

[0046] S4: Post-processing and finished product preparation: The primary particles were dehydrated by centrifugation at 800 rpm for 2 min, and then dried at 70°C for 30 min. A 40-mesh vibrating screen was used with a frequency of 20 Hz for 10 min. Finally, the particles were sealed and packaged under a vacuum of 0.05 MPa to obtain a finished product with a moisture content of <0.1%.

[0047] The structural characteristics and morphology control mechanism of the present invention can be clearly observed through scanning electron microscope image analysis. Figure 1 The porous double hydroxide microspheres prepared in Example 1 are shown. The microspheres exhibit a regular spherical structure and obvious nanoscale wrinkles on the surface. This special surface structure significantly increases the specific surface area of ​​the material, which is beneficial for the subsequent loading and dispersion of the flame retardant. Figure 2 This is the morphology of the core-shell flame retardant prepared in Example 1. It can be observed that melamine phosphate successfully penetrates and encapsulates the interior of the porous double metal hydroxide microspheres, forming a clear core-shell structure while retaining the nanoscale wrinkle features on the surface. This structure is conducive to the formation of a dense carbon layer and the release of flame-retardant gas during combustion. Figure 3 This is a photo of the prepared flame retardant masterbatch. It can be seen that the obtained masterbatch is uniform light gray, with regular particle shape, smooth surface, and no obvious agglomeration. This indicates that the core-shell structure flame retardant is well dispersed in the matrix resin, confirming the effectiveness of the preparation process of the present invention. This flame retardant masterbatch with uniform structure and good dispersion is conducive to subsequent application in various plastic products, and can significantly improve the flame retardant and mechanical properties of the final product. Example 2

[0048] A reinforced flame retardant masterbatch material, comprising the following raw materials in parts by weight: 26 parts of a core-shell structure flame retardant, 130 parts of polypropylene, 5.9 parts of maleic anhydride grafted modified polypropylene, 2.8 parts of zinc stearate, 1.8 parts of sodium lauryl sulfate, 1.0 part of an antioxidant 1010, and 16.0 parts of ethanol;

[0049] The core-shell flame retardant consists of porous double-metal layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres; the surface of the porous double-metal hydroxide microspheres has a nanoscale wrinkled structure; and the double-metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide.

[0050] The preparation method of the core-shell structure flame retardant of this embodiment is as follows: 20 parts by weight of porous double metal hydroxide microspheres are dispersed in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 1:1, and an ultrasonic dispersion treatment time is 10 minutes and an ultrasonic power is 200 W; 10 parts by weight of melamine phosphate is added to the dispersion, and an impregnation method is used at an impregnation temperature of 40° C. and an impregnation time of 120 minutes, during which slow stirring is maintained at 50 rpm to promote penetration; after the impregnation is completed, the solid and liquid phases are separated by vacuum filtration, and the filter cake is washed three times with deionized water, and then the temperature is programmed to 50° C. at a heating rate of 2° C. / min under a vacuum degree of -0.08 MPa and dried for 180 minutes, thereby obtaining a core-shell structure flame retardant.

[0051] The preparation method of the porous double hydroxide microspheres of this embodiment is as follows: in parts by weight, 46.0 parts of magnesium nitrate hexahydrate as a magnesium source and aluminum nitrate nonahydrate as an aluminum source are dissolved in 230.0 parts of deionized water at a Mg / Al molar ratio of 3.7:1 to form a homogeneous solution; 10.1 parts of morphology control agent sodium citrate, 3.2 parts of sodium gluconate and 1.8 parts of surfactant cetyltrimethylammonium bromide are added in sequence at a stirring rate of 560 rpm; the mixture is stirred continuously until uniformly mixed; the pH value is adjusted to 10.2 with a 0.1 mol / L NaOH solution; the reaction is continued at the current stirring rate for 20 minutes; and then the mixture is transferred to an ultrasonic device with a frequency of 46 kHz for 18 minutes; the resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 73%, hydrothermally reacted at 166°C for 14 hours, and then naturally cooled to 25°C; the free ions and small molecular organic matter in the reaction system that do not participate in crystallization are separated along with the centrifugal supernatant at 10600 The collected precipitate was removed after centrifugation at rpm for 7 min, and the collected precipitate was washed four times with deionized water until the conductivity of the filtrate was less than 50 μS / cm to completely remove soluble impurities. It was then heated to 350°C at 5°C / min under nitrogen protection and calcined for 2 h to completely decompose the organic template and form a stable hollow structure. Finally, it was dried in vacuum at 66°C for 13 h to obtain hollow double hydroxide microspheres with nanoscale surface wrinkles.

[0052] The mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide in this embodiment is 5.6:1.

[0053] The mass ratio of the porous double hydroxide microspheres to the melamine phosphate in the core-shell flame retardant of this embodiment is 2.0:1.

[0054] The average size of the core-shell structure flame retardant of this embodiment is 200 nm.

[0055] A method for preparing an enhanced flame retardant masterbatch material according to this embodiment includes the following steps:

[0056] S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic devices, ethanol was added and the temperature was raised to 33°C. The surfactant was slowly added with stirring at 260 rpm and the dissolution time was 20 minutes. Then, the core-shell flame retardant was added and intermittent ultrasonication at 390 W power was used, with an operation time of 4 seconds and a pause time of 1 second, during which mechanical stirring was coordinated and dispersed for 39 minutes. The anti-aging stabilizer and lubricating dispersing additive were added in sequence and mixed in stages at 46°C and 415 rpm for 35 minutes. Finally, the flame retardant additive composite was dried at 63°C and a vacuum degree of 0.07 MPa for 6 hours to obtain the flame retardant additive composite.

[0057] S2: Pretreatment and compounding of the matrix resin: After preheating the polypropylene resin at 86°C for 3 hours, it was mixed with the compatibility modifier at 116°C and 720 rpm for 18 minutes. The flame retardant additive compound obtained in S1 was then mixed with the matrix resin and mixed at 53°C and 590 rpm for 13 minutes to form a homogeneous premix.

[0058] S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder at a screw speed of 92 rpm, a temperature gradient from the feed port to the die head of 172°C, and a residence time of 3 min. The extruded melt was cooled in a 23°C water bath for 2 min and solidified, and then pelletized to obtain 4 mm primary pellets.

[0059] S4: Post-processing and finished product preparation: The primary particles were centrifuged and dehydrated at 920 rpm for 3 min, and then air-dried at 73°C for 35 min. A 46-mesh vibrating screen was used with a frequency of 23 Hz for 12 min. Finally, the particles were sealed and packaged under a vacuum of 0.06 MPa to obtain a finished product with a moisture content of <0.1%. Example 3

[0060] A reinforced flame retardant masterbatch material, comprising the following raw materials in parts by weight: 32 parts of a core-shell structure flame retardant, 160 parts of polypropylene, 6.8 parts of maleic anhydride grafted modified polypropylene, 3.5 parts of zinc stearate, 2.5 parts of sodium lauryl sulfate, 1.4 parts of an antioxidant 1010, and 22.0 parts of ethanol;

[0061] The core-shell flame retardant consists of porous double-metal layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres; the surface of the porous double-metal hydroxide microspheres has a nanoscale wrinkled structure; and the double-metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide.

[0062] The preparation method of the core-shell structure flame retardant of this embodiment is as follows: 40 parts by weight of porous double metal hydroxide microspheres are dispersed in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 3:1, and an ultrasonic dispersion treatment time is 30 minutes at an ultrasonic power of 500 W; 30 parts by weight of melamine phosphate are added to the dispersion, and an impregnation method is used at an impregnation temperature of 70° C. and an impregnation time of 360 minutes, during which slow stirring at 150 rpm is maintained to promote penetration; after the impregnation is completed, the solid and liquid phases are separated by vacuum filtration, the filter cake is washed with deionized water 5 times, and then the temperature is programmed to 80° C. at a heating rate of 5° C. / min under a vacuum degree of -0.1 MPa and dried for 420 minutes to finally obtain a core-shell structure flame retardant.

[0063] The preparation method of the porous double hydroxide microspheres of this embodiment is as follows: in parts by weight, 52.0 parts of magnesium nitrate hexahydrate as a magnesium source and aluminum nitrate nonahydrate as an aluminum source are dissolved in 260.0 parts of deionized water at a Mg / Al molar ratio of 3.8:1 to form a homogeneous solution; 12.2 parts of morphology control agent sodium citrate, 4.4 parts of sodium gluconate and 2.1 parts of surfactant cetyltrimethylammonium bromide are added in sequence at a stirring rate of 620 rpm; stirring is continued until the mixture is uniform; the pH value is adjusted to 10.3 with a 0.1 mol / L NaOH solution; the current stirring rate is maintained and the reaction is continued for 24 minutes; then the mixture is transferred to an ultrasonic device with a frequency of 52 kHz for 21 minutes; the resulting precursor solution is transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 76%, hydrothermally reacted at 172°C for 16 hours, and then naturally cooled to 25°C; the free ions and small molecular organic matter in the reaction system that do not participate in crystallization are separated along with the centrifugal supernatant at 11200 rpm. The collected precipitate was removed after centrifugation at rpm for 8 min, and the collected precipitate was washed four times with deionized water until the conductivity of the filtrate was less than 50 μS / cm to completely remove soluble impurities. It was then heated to 350°C at 5°C / min under nitrogen protection and calcined for 2 h to completely decompose the organic template and form a stable hollow structure. Finally, it was vacuum dried at 72°C for 14 h to obtain hollow double hydroxide microspheres with nanoscale surface wrinkles.

[0064] The mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide in this embodiment is 5.8:1.

[0065] The mass ratio of the porous double hydroxide microspheres to the melamine phosphate in the core-shell flame retardant of this embodiment is 3.5:1.

[0066] The average size of the core-shell structure flame retardant of this embodiment is 600 nm.

[0067] A method for preparing an enhanced flame retardant masterbatch material according to this embodiment includes the following steps:

[0068] S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic devices, ethanol was added and the temperature was raised to 36°C. The surfactant was slowly added with stirring at 320 rpm and the dissolution time was 24 minutes. Then, the core-shell structure flame retardant was added and intermittent ultrasonication at 480W power was used, with an operation time of 4 seconds and a pause time of 2 seconds, during which mechanical stirring was coordinated and dispersed for 48 minutes. The anti-aging stabilizer and lubricating dispersing additive were added in sequence and mixed in stages at 52°C and 580 rpm for 39 minutes. Finally, the flame retardant additive composite was dried at 66°C and 0.08 MPa vacuum for 7 hours to obtain.

[0069] S2: Pretreatment and compounding of the matrix resin: After preheating the polypropylene resin at 92°C for 3 hours, it was mixed with the compatibility modifier at 122°C and 840 rpm for 21 minutes. The flame retardant additive compound obtained in S1 was then mixed with the matrix resin and mixed at 56°C and 680 rpm for 16 minutes to form a homogeneous premix.

[0070] S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder with a screw speed of 104 rpm, a temperature gradient from the feed port to the die head of 184°C, and a residence time of 3 min. The extruded melt was cooled in a 26°C water bath for 2 min and solidified, and then pelletized to obtain 4 mm primary pellets.

[0071] S4: Post-processing and finished product preparation: The primary granules were dehydrated by centrifugation at 1040 rpm for 4 min, and then dried at 76°C for 39 min. A 52-mesh vibrating screen was used with a frequency of 26 Hz for 13 min. Finally, the granules were sealed and packaged under a vacuum of 0.07 MPa to obtain a finished product with a moisture content of <0.1%. Example 4

[0072] A reinforced flame retardant masterbatch material, comprising the following raw materials in parts by weight: 40 parts of a core-shell flame retardant, 200 parts of polypropylene, 8.0 parts of maleic anhydride grafted modified polypropylene, 4.5 parts of zinc stearate, 3.5 parts of sodium lauryl sulfate, 2.0 parts of an antioxidant 1010, and 30.0 parts of ethanol;

[0073] The core-shell flame retardant consists of porous double-metal layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres; the surface of the porous double-metal hydroxide microspheres has a nanoscale wrinkled structure; and the double-metal hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide.

[0074] The preparation method of the core-shell structure flame retardant of this embodiment is as follows: 32 parts by weight of porous double metal hydroxide microspheres are dispersed in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 2.2:1, and ultrasonic dispersion treatment is performed for 22 minutes at an ultrasonic power of 380 W; 22 parts by weight of melamine phosphate are added to the dispersion, and an impregnation method is adopted at an impregnation temperature of 58° C. and an impregnation time of 264 minutes, during which slow stirring at 110 rpm is maintained to promote penetration; after the impregnation is completed, the solid and liquid phases are separated by vacuum filtration, and the filter cake is washed four times with deionized water, and then the temperature is programmed to 68° C. at a heating rate of 4° C. / min under a vacuum degree of -0.09 MPa and dried for 324 minutes, thereby obtaining a core-shell structure flame retardant.

[0075] The preparation method of the porous double metal hydroxide microspheres of the present embodiment is as follows: in parts by weight, 60.0 parts of magnesium nitrate hexahydrate as a magnesium source and 4.0:1 of aluminum nitrate nonahydrate as an aluminum source are dissolved in 300.0 parts of deionized water at a Mg / Al molar ratio of 4.0:1 to form a homogeneous solution; 15.0 parts of morphology control agent sodium citrate, 6.0 parts of sodium gluconate and 2.5 parts of surfactant hexadecyltrimethylammonium bromide are added in sequence at a stirring rate of 700 rpm; after continuous stirring until the mixture is uniformly mixed, the pH value is adjusted to 10.5 with a 0.1 mol / L NaOH solution; the current stirring rate is maintained and the reaction is continued for 30 min, and then the mixture is transferred to an ultrasonic device with a frequency of 60 kHz for treatment for 25 min; the obtained precursor solution is transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 80%, and hydrothermally reacted at 180°C for 18 min. After h, it was naturally cooled to 25°C. The free ions and small molecular organic matter in the reaction system that did not participate in crystallization were removed along with the centrifugal supernatant after centrifugation at 12000 rpm for 10 min. The collected precipitate was washed with deionized water five times until the filtrate conductivity was less than 50 μS / cm to completely remove soluble impurities. Subsequently, the temperature was increased to 350°C at 5°C / min under nitrogen protection and calcined for 2 h to completely decompose the organic template and form a stable hollow structure. Finally, the hollow double hydroxide microspheres with nanoscale surface wrinkles were obtained by vacuum drying at 80°C for 16 h.

[0076] In this embodiment, the mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide is 6:1.

[0077] The mass ratio of the porous double hydroxide microspheres to the melamine phosphate in the core-shell flame retardant of this embodiment is 2.9:1.

[0078] The average size of the core-shell structure flame retardant of this embodiment is 440 nm.

[0079] A method for preparing an enhanced flame retardant masterbatch material according to this embodiment includes the following steps:

[0080] S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic devices, ethanol was added and the temperature was raised to 40°C. The surfactant was slowly added while stirring at 400 rpm and the dissolution time was 30 minutes. Then, the core-shell flame retardant was added and intermittent ultrasonication at 600W power was used, with an operating cycle of 5 seconds and a pause of 2 seconds, during which mechanical stirring was coordinated and dispersed for 60 minutes. The anti-aging stabilizer and lubricating dispersing additive were added in sequence and mixed in stages at 60°C and 800 rpm for 45 minutes. Finally, the flame retardant additive composite was dried at 70°C and 0.1 MPa vacuum for 8 hours to obtain the flame retardant additive composite.

[0081] S2: Pretreatment and compounding of the matrix resin: After preheating the polypropylene resin at 100°C for 4 hours, it was mixed with the compatibility modifier at 130°C and 1000 rpm for 25 minutes. Then, the flame retardant additive compound obtained in S1 was mixed with the matrix resin and mixed at 60°C and 800 rpm for 20 minutes to form a homogeneous premix.

[0082] S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder with a screw speed of 120 rpm, a temperature gradient from the feed port to the die head of 200°C, and a residence time of 4 min. The extruded melt was cooled in a 30°C water bath for 3 min and solidified, and then pelletized to obtain 5 mm primary pellets.

[0083] S4: Post-processing and finished product preparation: The primary particles were centrifuged and dehydrated at 1200 rpm for 5 min, and then dried at 80°C for 45 min. A 60-mesh vibrating screen was used with a frequency of 30 Hz for 15 min. Finally, the particles were sealed and packaged under a vacuum of 0.08 MPa to obtain a finished product with a moisture content of <0.1%.

[0084] Comparative Example 1

[0085] The method is basically the same as Example 1, except that a core-shell structure flame retardant is not used. Instead, a simple physical mixture of uncoated porous double metal hydroxide microspheres and melamine phosphate is directly used as the flame retardant, and other components and preparation process parameters remain unchanged.

[0086] Comparative Example 2

[0087] The method is basically the same as Example 1, except that when preparing the core-shell structure flame retardant, the volume ratio of ethanol to water is 0.5:1, which results in an excessively high polarity of the dispersion medium. Other components and preparation process parameters remain unchanged.

[0088] Comparative Example 3

[0089] The method is basically the same as Example 1, except that the morphology control agent sodium citrate is not added during the preparation of the porous double hydroxide microspheres, and the magnesium source, aluminum source and surfactant are directly used for synthesis, resulting in the obtained microspheres not having a nanoscale wrinkled structure. The other components and preparation process parameters remain unchanged.

[0090] Figure 4 The sample of Comparative Example 3 shown (without the addition of the morphology control agent sodium citrate) also formed a spherical structure, but the surface was smooth and lacked a wrinkled structure, proving that the morphology control agent sodium citrate played a key role in constructing the nanoscale wrinkled surface morphology. This morphology control mechanism can be attributed to the fact that sodium citrate, as a chelating agent, changes the nucleation and growth dynamics of metal ions, and induces the formation of a wrinkled structure with high surface energy through orderly adsorption on the growing crystal surface, thus laying a structural foundation for the efficient preparation of core-shell flame retardants.

[0091] Comparative Example 4

[0092] The method is basically the same as Example 1, except that the magnesium hydroxide and aluminum hydroxide in the double metal hydroxide are replaced by single aluminum hydroxide, and the other components and preparation process parameters remain unchanged.

[0093] Comparative Example 5

[0094] The method is basically the same as Example 1, except that when the core-shell structure flame retardant is prepared by the impregnation method, the impregnation temperature is 30° C., resulting in insufficient penetration of melamine phosphate. Other components and preparation process parameters remain unchanged.

[0095] Comparative Example 6

[0096] The method is basically the same as Example 1, except that in step S1, continuous ultrasound rather than intermittent ultrasound is used for ultrasonic dispersion of the core-shell structure flame retardant (the intermittent mode of working for 35 seconds / pausing for 12 seconds is not adopted), which leads to excessive heat accumulation during the dispersion process. Other components and preparation process parameters remain unchanged.

[0097] Comparative Example 7

[0098] It is basically the same as Example 1, except that during the preparation of porous double hydroxide microspheres, the mass ratio of the morphology control agent sodium citrate and the surfactant cetyltrimethylammonium bromide is 4.0:1, specifically 8.0 parts of sodium citrate to morphology control agent sodium citrate and 2 parts of 16 parts of surfactant cetyltrimethylammonium bromide, resulting in an excess of surfactant, and the other components and preparation process parameters remain unchanged.

[0099] Comparative Example 8

[0100] The method is basically the same as Example 1, except that the Mg / Al molar ratio is adjusted to 2:1.

[0101] Performance testing:

[0102] Flame retardant properties: The prepared flame retardant masterbatch material was evaluated for combustion grade according to the UL 94 vertical burning test standard (ASTM D3801). The masterbatch was injection molded into a standard specimen measuring 127 mm × 12.7 mm × 3.2 mm. The specimen was suspended vertically and ignited from the bottom for 10 seconds. The flame extinguishing time, the presence of burning dripping matter, and the ignition of the cotton were recorded. The flame retardant properties of the material were evaluated based on the test classification results (HB, V-2, V-1, V-0).

[0103] Limiting Oxygen Index (LOI) test: Referring to the oxygen index test standard (ISO 4589-2), the sample is measured using an oxygen index meter. The flame retardant masterbatch is injection molded into a standard specimen of 120mm×6.5mm×3.2mm. The ratio of oxygen to nitrogen is adjusted in the oxygen index tester to determine the combustion behavior of the material under different oxygen concentrations. Ultimately, the minimum oxygen concentration that can sustain combustion (LOI value) is determined. The higher the LOI value, the better the flame retardant performance.

[0104] Thermal stability test: Based on the GB / T 2406-2009 thermogravimetric analysis standard, a thermogravimetric analyzer (TGA) was used to study the thermal stability and degradation behavior of the samples. Approximately 10 mg of sample was heated from room temperature to 800°C at a heating rate of 10°C / min in a nitrogen and air atmosphere. The curve of sample mass change with temperature was recorded, and parameters such as the initial decomposition temperature (T5%), maximum decomposition rate temperature (Tmax), and residual carbon rate were analyzed to evaluate the thermal stability and flame retardant efficiency of the material.

[0105] Mechanical properties: According to ASTM D638, the tensile properties of the material were tested using a universal material testing machine. The flame retardant masterbatch was used to prepare dumbbell-shaped standard specimens. The test was performed at a tensile rate of 5 mm / min. Parameters such as tensile strength, elongation at break, and elastic modulus were recorded to evaluate the effect of the flame retardant on the mechanical properties of the material.

[0106] The properties of the plastics of Examples 1-4 and Comparative Examples 1-8 are summarized in Table 1. As can be seen from Table 1, the failure to form a core-shell structure or inadequate coating can lead to uneven distribution of the flame retardant components in the matrix, weakening the synergistic effect, thereby reducing flame retardant efficiency and worsening thermal stability. Improper polarity of the dispersion medium or unreasonable ultrasonic method can affect the particle distribution and interfacial intercalation of the flame retardant, resulting in reduced mechanical properties. Insufficient control of the microsphere morphology can reduce the specific surface area and interfacial bonding force, affecting the stable dispersion of the flame retardant in the polymer, resulting in unstable flame retardant properties and thermal stability. Improper component ratio or a single active component can weaken the synergistic effect of multiple mechanisms, resulting in a lack of effective heat shielding, dilution or acid neutralization mechanisms during the combustion process, thereby reducing the overall flame retardant grade and residual carbon rate. In terms of process parameters, too low an impregnation temperature, insufficient amount of morphology control agent, or an unreasonable metal ratio can all affect the formation and stability of the core-shell structure, making it impossible to simultaneously achieve the flame retardant properties, thermal stability, and mechanical properties of the material. In summary, the key role of structural control, interface engineering, and multi-component collaborative design in achieving a good performance balance is demonstrated.

[0107] Table 1 Performance summary of plastics in Examples 1 to 4 and Comparative Examples 1 to 8

[0108]

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that any equivalent structural changes made based on the contents of the present invention's description and drawings under the concept of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An enhanced flame retardant masterbatch material, characterized in that: The invention comprises the following raw materials in parts by weight: 20-40 parts of a core-shell structure flame retardant, 100-200 parts of polypropylene, 5.0-8.0 parts of a compatibility modifier, 2.0-4.5 parts of a lubricating and dispersing aid, 1.0-3.5 parts of a surfactant, 0.5-2.0 parts of an anti-aging stabilizer 1010, and 10.0-30.0 parts of ethanol; The core-shell flame retardant is composed of porous bimetallic layered hydroxide microspheres with a hollow structure and melamine phosphate coated in the inner cavity of the microspheres; The surface of the porous bimetallic layered hydroxide microspheres has a nanoscale wrinkled structure; The double metal layered hydroxide is a mixture of magnesium hydroxide and aluminum hydroxide; The core-shell flame retardant is prepared by dispersing 20 to 40 parts by weight of porous bimetallic layered hydroxide microspheres in an ethanol-water mixed solution, wherein the volume ratio of ethanol to water is 1:1 to 3:1, and performing ultrasonic dispersion treatment for 10 to 30 minutes at an ultrasonic power of 200 to 500 W. 10 to 30 parts by weight of melamine phosphate are added to the dispersion, and an immersion method is used at an immersion temperature of 40 to 70° C. for 120 to 360 minutes, during which slow stirring at 50 to 150 rpm is maintained to promote penetration. After the impregnation is completed, the solid and liquid phases are separated by vacuum filtration. The filter cake is washed with deionized water 3 to 5 times, and then the temperature is programmed to 50 to 80°C at a heating rate of 2 to 5°C / min under a vacuum degree of -0.08 to -0.1 MPa and dried for 180 to 420 minutes to obtain a core-shell flame retardant. The preparation method of the porous bimetallic layered hydroxide microspheres is as follows: in parts by weight, 40.0-60.0 parts of magnesium nitrate hexahydrate as a magnesium source and 3.5-4.0:1 of aluminum nitrate nonahydrate as an aluminum source are dissolved in 200.0-300.0 parts of deionized water to form a homogeneous solution, and 8.0-15.0 parts of morphology control agent sodium citrate, 2.0-6.0 parts of sodium gluconate and 1.5-2.5 parts of surfactant cetyltrimethylammonium bromide are added in sequence under a stirring rate of 500-700 rpm. After continuous stirring until the mixture is uniform, a 0.1 mol / L NaOH solution is used to adjust the pH value to 10.0-10.5, the current stirring rate is maintained and the reaction is continued for 15-30 minutes, and then the mixture is treated with an ultrasonic device with a frequency of 40-60 kHz for 15-25 minutes. The resulting precursor solution was transferred to a polytetrafluoroethylene-lined reactor with a volume filling degree of 70%-80%. The reaction was hydrothermally reacted at 160-180°C for 12-18 h and then naturally cooled to 25°C. The free ions and small organic molecules in the reaction system that did not participate in the crystallization were removed with the centrifugal supernatant at 10,000-12,000 rpm for 5-10 min. The collected precipitate was washed with deionized water 3-5 times until the filtrate conductivity was less than 50 μS / cm to completely remove soluble impurities. The product was then heated to 350°C at 5°C / min under nitrogen protection and calcined for 2 h to completely decompose the organic template and form a stable hollow structure. Finally, the product was dried in vacuum at 60-80°C for 12-16 h to obtain porous bimetallic layered hydroxide microspheres with nanoscale surface wrinkles. The mass ratio of the morphology control agent sodium citrate to the surfactant cetyltrimethylammonium bromide is (3.2-6.0):

1.

2. The enhanced flame retardant masterbatch material according to claim 1, characterized in that: The mass ratio of the porous bimetallic layered hydroxide microspheres to the melamine phosphate in the core-shell structure flame retardant is (2.0-3.5):

1.

3. The enhanced flame retardant masterbatch material according to claim 1, characterized in that: The average size of the core-shell structure flame retardant is 200-600 nm.

4. The enhanced flame retardant masterbatch material according to claim 1, characterized in that: The compatibility modifier is maleic anhydride grafted modified polypropylene; The lubricating and dispersing auxiliary agent is zinc stearate; The surfactant is sodium lauryl sulfate; The anti-aging stabilizer is antioxidant 1010.

5. The method for preparing a reinforced flame retardant masterbatch material according to claim 1, characterized in that: The following steps are involved: S1: Preparation of flame retardant additive composite system: In a reactor equipped with mechanical stirring and ultrasonic devices, add ethanol and heat to 30-40°C. Slowly add surfactant while stirring at 200-400 rpm for 15-30 min. Then add core-shell flame retardant and use intermittent ultrasonication at a power of 300-600 W, with an operating cycle of 3-5 s and a pause of 1-2 s, during which mechanical stirring is used for dispersion for 30-60 min. Anti-aging stabilizer and lubricating dispersing aid are added in sequence and mixed in stages at 40-60°C and 250-800 rpm for 30-45 min. Finally, dry at 60-70°C and a vacuum degree of 0.05-0.1 MPa for 5-8 h to obtain the flame retardant additive composite. S2: Pretreatment and compounding of the matrix resin: Preheat the polypropylene resin at 80-100°C for 2-4 hours, then mix it with the compatibility modifier at 110-130°C and 600-1000 rpm for 15-25 minutes. Then, mix the flame retardant additive compound obtained in S1 with the matrix resin and mix at 50-60°C and 500-800 rpm for 10-20 minutes to form a homogeneous premix. S3: Melt extrusion and molding: The premix was fed into a twin-screw extruder with a screw speed of 80-120 rpm, a temperature gradient from the feed port to the die head of 160-200°C, and a residence time of 2-4 min. The extruded melt was cooled in a water bath at 20-30°C for 1-3 min and solidified, and then pelletized to obtain primary particles of 3-5 mm. S4: Post-processing and finished product preparation: The primary granules are dehydrated by centrifugation at 800-1200 rpm for 2-5 min, and then air-dried at 70-80°C for 30-45 min. A 40-60 mesh vibrating screen is used with a frequency of 20-30 Hz for 10-15 min. Finally, the granules are sealed and packaged under a vacuum of 0.05-0.08 MPa to obtain a finished product with a moisture content of <0.1%.

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