Flame-retardant foamed polypropylene composite material and preparation method thereof

Abstract

The invention belongs to the technical field of polypropylene composite materials, and relates to a flame-retardant foamed polypropylene composite material and a preparation method thereof. The flame-retardant polypropylene composite material comprises polypropylene, polystyrene, an ethylene-octylene copolymer, tris (2, 3-dibromopropyl) isocyanurate, a flame-retardant synergist, a cross-linking agent, a compatilizer, a lubricant, an antioxidant, an anti-ultraviolet absorbent, expanded microspheres and a nucleating agent. The flame retardant synergist is a mixture of polymethylsiloxane, tris (2, 2, 2-trifluoroethyl) phosphate, melamine cyanurate and melamine polyphosphate. The polystyrene and the ethylene-octylene copolymer are added to improve the foaming effect and mechanical property of the material, the flame retardant synergist and the main flame retardant are added to achieve a synergistic effect, the flame retardant property of the material is improved, the expanded microspheres are added for physical foaming, and the nucleating agent is added to improve the foaming efficiency and quality. The foamed polypropylene composite material with high flame retardant property and excellent foaming property and mechanical property is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of polypropylene composite materials and relates to a flame retardant foamed polypropylene composite material and a preparation method thereof. Background Art

[0002] Since the 1990s, China's foam plastics industry has experienced a rapid development stage, and three major categories of products have appeared in the market: polyurethane soft and hard foam plastics, polystyrene foam plastics and polyethylene foam plastics. Although these materials have played an important role in their respective fields, they also have obvious disadvantages. For example, polyurethane foam will have isocyanate residues that are harmful to the human body during the foaming process, and the foaming material cannot be recycled; and the production process of polystyrene foam plastics usually requires the use of chlorofluorocarbon compounds or butane as a foaming agent, which not only pollutes the environment, but also its product degradation cycle is extremely long, posing a threat to the natural ecology; although polyethylene foam plastics have good flexibility and cushioning properties, their rigidity is poor, and the maximum operating temperature is limited to 80°C, which limits its application in high temperature environments.

[0003] In contrast, polyolefins, especially polypropylene foam materials, have attracted widespread attention due to their unique advantages. Polypropylene foam materials not only have good thermal stability and chemical resistance, but also show high toughness and strength, while the processing cost is relatively low. More importantly, this material has little impact on the environment during production and post-disposal treatment, which meets the requirements of sustainable development. Therefore, polypropylene foam materials are considered to be an important direction for the development of the foam plastics industry in the future, and have gradually become a hot topic of concern. For example, Chinese patent CN114015186A discloses a foamed polypropylene material and a preparation method thereof, comprising the following components in parts by weight: 100 parts of polypropylene, 0.5 to 1 part of a foaming agent, 1 to 5 parts of an elastomer, and 1 to 5 parts of a cross-linking agent. A foamed polypropylene material is prepared by mixing and extrusion granulation, and has excellent mechanical and dielectric properties and high temperature resistance. Another example is Chinese patent CN116041855A, which discloses a high melt strength micro-foamed polypropylene composite material and its preparation method, which adopts hydrogenated polybutadiene (not completely hydrogenated) grafted onto the main chain of polypropylene to prepare polypropylene with long chain branches, so that the polypropylene has a higher melt strength and is easy to control foaming. However, none of the above patents modify the flame retardancy of polypropylene, and polypropylene itself is a flammable material, which poses a safety hazard in daily life. Therefore, it is particularly necessary to study the effective flame retardant modification of polypropylene.

[0004] For example, Chinese patent CN118271747A discloses a halogen-free and fluorine-free flame-retardant polypropylene composite material, its preparation method and application. By adding phosphate flame retardants, melamine flame retardants and piperazine flame retardants, a halogen-free and fluorine-free flame-retardant polypropylene composite material with excellent fluidity and flame retardant properties is obtained. Another example is Chinese patent CN118240298A discloses a low-smoke, halogen-free and highly flame-retardant polypropylene composite material and its preparation method, which includes the following components calculated by mass percentage: polypropylene resin 5-30wt%, magnesium hydroxide 50-80wt%, toughening agent 5-20wt%, wollastonite 0-5wt%, montmorillonite 0-5wt%, antioxidant 0.1-1wt% and lubricant 0.1-1wt%, and the low-smoke, halogen-free and highly flame-retardant polypropylene composite material is prepared by high-speed mixing and extrusion granulation. However, the above patents do not foam polypropylene, resulting in the lack of light weight, high strength and good resilience of the material, which limits its application range in certain fields.

[0005] Although some achievements have been made in polypropylene foam materials and flame retardant modification, how to effectively combine these two properties to make polypropylene foam materials have excellent mechanical properties and flame retardancy remains the focus of future research. Summary of the invention

[0006] The present invention aims at the deficiencies in the prior art and provides a flame retardant foamed polypropylene composite material and a preparation method thereof.

[0007] One object of the present invention is achieved by the following technical solutions: A flame retardant foamed polypropylene composite material comprises the following components in parts by weight: 100 parts of polypropylene resin, 10-15 parts of polystyrene resin, 10-15 parts of ethylene-octene copolymer, 20-25 parts of tris(2,3-dibromopropyl)isocyanurate, 10-20 parts of flame retardant synergist, 0.2-0.8 parts of crosslinking agent, 2-4 parts of compatibilizer, 2-5 parts of lubricant, 0.4-0.8 parts of antioxidant, 0.4-0.8 parts of anti-ultraviolet absorber, 1-3 parts of expanded microspheres, and 5-10 parts of nucleating agent.

[0008] The polypropylene resin of the present invention is preferably a high melt strength polypropylene, the melt strength of the polypropylene resin is 5-50 cN, and the test conditions are: using a melt strength meter to test, extrusion temperature 200 ° C, tensile acceleration 20 mm / S 2. The temperature difference between the melting point and the micropores that begin to break of ordinary polypropylene is small, and its viscosity is low and its solubility is poor. It cannot retain the gas generated by the decomposition of the foaming agent, so it cannot be used directly for foaming. High melt strength polypropylene has higher melt strength, which enables it to maintain the stability of the gas during the melt foaming process, thereby forming a uniform and controllable pore structure. At the same time, high melt strength polypropylene can also improve the mechanical properties and processability of composite materials.

[0009] More preferably, the melt strength of the polypropylene resin is 10-20 cN.

[0010] Preferably, the weight average molecular weight of the polystyrene resin is 1*10 4 ~9*10 6 , Mw / Mn is 1-1.4. The invention adds polystyrene to the polypropylene resin to significantly improve the overall foaming performance of the material. The molecular weight and distribution of polystyrene will affect its melt viscosity and foaming performance. An appropriate molecular weight can provide sufficient melt strength to support the bubbles formed during the foaming process, and a uniform molecular weight distribution is helpful to obtain a uniform cell structure.

[0011] Preferably, the melt index of the ethylene-octene copolymer is 15-30 g / 10 min, and the test conditions are: temperature 190° C., die 2.095 mm, load 2.16 kg. Ethylene-octene copolymer with high melt index has good compatibility with PP. The addition of this material not only makes the composite material have excellent toughness and resilience; it also improves the dispersion effect between the filler and the matrix resin, and further improves the comprehensive properties of the composite material, such as flame retardancy; in addition, it can also improve the processing fluidity of the material and increase the foaming efficiency of the composite material.

[0012] More preferably, the melt index of the ethylene-octene copolymer is 20-25 g / 10 min.

[0013] Preferably, the flame retardant synergist is a mixture of polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate, and melamine polyphosphate.

[0014] More preferably, the flame retardant synergist is a mixture of polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate, and polyphosphate melamine in a mass ratio of 1:(1-1.5):(2-2.5):(2-2.5).

[0015] The flame retardant in the present invention is a composite flame retardant with tris(2,3-dibromopropyl)isocyanurate (CAS NO: 52434-90-9) as the main flame retardant, and a mixture of polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate, and polyphosphate melamine as flame retardant synergists. Tris(2,3-dibromopropyl)isocyanurate is a highly efficient bromine-nitrogen intumescent flame retardant. In this system, in combination with other flame retardants, tris(2,3-dibromopropyl)isocyanurate not only has good flame retardant effect, but also has the characteristics of low volatility, good compatibility, durability, water resistance and non-toxicity. Tris(2,3-dibromopropyl)isocyanurate decomposes into hydrogen bromide when heated at high temperature. Hydrogen bromide captures the active free radicals (such as OH•, O•, H•) that transmit the combustion chain reaction, generating less active bromine free radicals, causing the combustion to slow down or terminate. At the same time, the generated hydrogen bromide gas has a high density and is difficult to burn. It can not only dilute the oxygen in the air, but also cover the surface of the material to isolate the air, causing the material's combustion rate to slow down or self-extinguish, achieving the purpose of flame retardancy. Polymethylsiloxane can form a dense non-combustible silicon-carbon layer during the combustion process, effectively isolating oxygen and heat, thereby achieving the purpose of flame retardancy. In addition, polymethylsiloxane can promote the carbonization process and increase the amount of carbonization. In addition, the addition of polymethylsiloxane can also increase the processing fluidity and mold release smoothness of the material, and improve the overall processability of the material. The phosphorus element in tri(2,2,2-trifluoroethyl) phosphate can produce non-combustible compounds at high temperatures to cover the surface of the material and block combustion. In addition, when it decomposes at high temperatures, it produces hydrogen fluoride gas that can react with free radicals in the flame to replace hydrogen atoms or form hydrofluoric acid, thereby destroying the flame chain reaction and slowing down or inhibiting the spread of flames. In addition, when tri(2,2,2-trifluoroethyl) phosphate decomposes at high temperatures, it will form a non-combustible protective film on the surface of the material to prevent flame combustion and has a significant anti-burning dripping effect. Melamine cyanurate and polyphosphate melamine are expandable nitrogen-based flame retardants. When they decompose at high temperatures, they will form a dense carbon foam layer on the surface of the material to cover the polymer surface, which plays a role in heat insulation and oxygen isolation. In addition, when it decomposes, it produces non-combustible gases, such as (nitrogen, carbon dioxide). These gases can dilute oxygen and absorb heat, thereby reducing the temperature of the material surface and achieving the purpose of flame retardancy. In summary, the present invention utilizes the synergistic effect between multiple flame retardants to improve the flame retardant efficiency of the polymer, reduce the content of certain components in the flame retardant system, ensure the processability and flowability of the material while meeting high flame retardant requirements, and can well control costs, thereby achieving low-amount and high-efficiency flame retardants.

[0016] Preferably, the crosslinking agent is one or more of an aromatic divinyl compound, a diacrylate compound, a multifunctional crosslinking agent, and a diol compound. Aromatic divinyl compounds may be listed as divinylbenzene and / or divinylnaphthalene; diacrylate compounds may be listed as one or more of ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, and tetraethylene glycol diacrylate; multifunctional crosslinking agents may be listed as one or more of pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, and tetramethylolmethane tetramethacrylate; and glycol compounds may be listed as one or more of butanediol, ethylene glycol, and 1,5-pentanediol.

[0017] The addition of crosslinking agent increases the connection points between molecules by changing the connection mode and structure of material molecules, forming a tighter spatial network structure, thereby improving the mechanical strength, wear resistance and other mechanical properties of the material. In addition, in this system, mild crosslinking can also improve the foaming stability of the material.

[0018] More preferably, the crosslinking agent is one or more of divinylbenzene, 1,5-pentanediol, and pentaerythritol triacrylate.

[0019] Preferably, the compatibilizer is one or more of hydrogenated styrene-butadiene-styrene terblock copolymer, styrene-isoprene-styrene terblock copolymer, and styrene-butadiene-styrene terblock copolymer.

[0020] The compatibilizer used in the present invention can, on the one hand, improve the interfacial compatibility of different matrix resins when melted at high temperature, and on the other hand, can also increase the compatibility between the inorganic filler and the polymer resin, so that the inorganic phase can be evenly distributed in the polymer phase, effectively avoiding the separation and mutual repulsion between different materials, thereby perfectly reflecting the various properties of the material.

[0021] Preferably, the expanded microspheres are expanded microspheres formed by using a thermoplastic polymer as the outer shell and carbon dioxide and nitrogen as the core material in a volume ratio of 1:0.5-2.

[0022] More preferably, the particle size of the expanded microspheres is 10 to 50 μm, and more preferably 30 to 40 μm.

[0023] Unlike traditional chemical foaming agents, expanded microspheres are a core-shell structure with a thermoplastic polymer shell and a low-boiling point gas enclosed. This core-shell structure allows the microspheres to expand when heated. When the expanded microspheres are heated to a certain temperature, their shells soften and become plastic. At the same time, the low-boiling point core material in the microspheres is heated and vaporized, generating internal pressure, causing the microsphere shell to expand, thereby achieving a foaming effect. The use of expanded microspheres eliminates the risk of residual foaming agent during the foaming process of traditional chemical foaming agents, which leads to reduced overall material performance and environmental non-compliance.

[0024] Preferably, the nucleating agent is a mixture of nano calcium silicate and nano basic zinc carbonate.

[0025] The present invention uses a mixture of nano calcium silicate and nano basic zinc carbonate as a nucleating agent, which can improve the polypropylene crystallization rate, accelerate the crystallization process, increase the number of crystal nuclei, make the polymer resin phase crystallization in the system more perfect and more evenly stressed, thereby improving the impact strength and surface strength of the final composite material and improving its overall mechanical properties. On the other hand, the nucleating agent can provide enough tiny cores in the system of the present invention, accelerate the generation of bubbles in the foaming process, thereby improving the foaming effect, and the tiny core provided by the nucleating agent can also optimize the cell structure, make the cells evenly distributed, and avoid the situation of insufficient or too high local density. In addition, the nucleating agent can also reduce the foaming temperature and pressure, shorten the foaming time, and improve the foaming efficiency.

[0026] More preferably, the nucleating agent is a mixture of nano calcium silicate and nano basic zinc carbonate in a mass ratio of (1-2):(2-3).

[0027] Preferably, the particle size of the nucleating agent is 1 to 50 nm, more preferably 10 to 20 nm.

[0028] Lubricants can improve the processing properties of materials during processing, reduce the internal and external friction of materials during high-temperature extrusion, and thus improve the processing flow properties of materials. The types of lubricants of the present invention are not particularly limited, but any substance that can improve the processing properties of materials is within the protection scope of the present invention. Preferably, the lubricant is one or more of fatty acid lubricants, fatty acid salt lubricants, hydrocarbon lubricants, fatty amide lubricants, and silicone lubricants. Fatty acid lubricants can be listed as one or more of saturated fatty acids, unsaturated fatty acids, and hydroxy fatty acids; fatty acid salt lubricants can be listed as one or more of fatty acid potassium, fatty acid sodium, and fatty acid ethanolamine; hydrocarbon lubricants can be listed as one or more of paraffin, polyethylene wax, and halogenated hydrocarbons; fatty amide lubricants can be listed as one or more of ethylene bisstearamide, fatty acid amide, and alkylene bisfatty acid amide; silicone lubricants can be listed as polysiloxanes.

[0029] The invention adds an antioxidant and an anti-ultraviolet absorber into the polypropylene composite material to improve the light resistance and weather resistance of the polypropylene composite material.

[0030] Polypropylene molecules are very sensitive to photooxidation, mainly because there are tertiary carbon atoms in their molecular unit structure. The hydrogen on the tertiary carbon atoms is very unstable and easily oxidized, causing the accelerated degradation of polypropylene. Adding antioxidants can use the active groups in them to capture free radicals, prevent polypropylene from oxidizing and extend its service life.

[0031] Preferably, the antioxidant can be selected from one or more of phenolic antioxidants, thiol antioxidants, phosphites, and pentaerythritol ester antioxidants. The present invention does not make any special requirements on the specific selection of antioxidants, and any phenolic antioxidants, thiol antioxidants, amide antioxidants, and pentaerythritol ester antioxidants that can play an antioxidant role are within the protection scope of the present invention. As an example, phenolic antioxidants include one or more of butylated hydroxytoluene, butylated hydroxyanisole, tert-butylhydroquinone, and antioxidant 1076; thiol antioxidants include one or more of tetrapropionic acid disulfide, lipoic acid, acetylcysteine, cysteine, and glutathione; phosphite antioxidants include one or more of tris(2,4-di-tert-butylphenol)phosphite, dioctadecyl pentaerythritol diphosphite, and bis(3,5-di-tert-butylphenol)pentaerythritol diphosphite; pentaerythritol ester antioxidants include one or more of pentaerythritol diphosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and pentaerythritol tetrakis(3-laurylthiopropionate).

[0032] Polypropylene has a weak resistance to ultraviolet rays and is easily affected by ultraviolet radiation, causing oxidation, discoloration, and deterioration, which leads to a decrease in the performance of the material. Adding ultraviolet absorbers can absorb ultraviolet rays and prevent them from corroding polypropylene, thereby extending the service life of polypropylene.

[0033] Preferably, the anti-ultraviolet absorber can be one or more of benzotriazole anti-ultraviolet absorbers, hindered amine anti-ultraviolet absorbers, and benzophenone anti-ultraviolet absorbers.

[0034] The present invention does not make any special requirements for the selection of anti-ultraviolet absorbers. Any benzotriazole anti-ultraviolet absorbers, hindered amine anti-ultraviolet absorbers, and benzophenone anti-ultraviolet absorbers that can play an anti-ultraviolet role are within the protection scope of the present invention. Benzotriazole anti-ultraviolet absorbers may include one or more of 2-(2-hydroxy 3,5-di-tert-butyl)-5-chloro-benzotriazole, 2-(2-hydroxy 5-methyl-benzotriazole, and 2-(2-hydroxy-3-tert-butyl-5-methyl)-5-chloro-benzotriazole; hindered amine anti-ultraviolet absorbers may be selected from bis-1,2,2,6,6-pentamethylpiperidinol sebate, bis-1-octyloxy-, 2,2,6,6-tetramethylpiperidinol sebate, and bis-1-octyloxy-, 2,2,6,6-tetramethylpiperidinol sebate. One or more of methyl piperidine alcohol ester, poly (1-octyloxy)-, 2,2,6,6-tetramethyl piperidine alcohol sebacate, poly (4-hydroxy-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate; benzophenone anti-ultraviolet absorbers can be listed as one or more of 2-hydroxy-4-n-octyloxy benzophenone (ultraviolet absorber UV-531), ultraviolet absorber UV-9, and ultraviolet absorber UV-284.

[0035] Another object of the present invention is achieved by the following technical solutions: A method for preparing a flame retardant foamed polypropylene composite material comprises the following steps: (1) Weighing polypropylene resin, polystyrene resin, ethylene-octene copolymer, tris(2,3-dibromopropyl)isocyanurate, flame retardant synergist, crosslinking agent, compatibilizer, lubricant, antioxidant, and anti-ultraviolet absorber in parts by weight and mixing to obtain component A; weighing expanded microspheres and nucleating agent in parts by weight and mixing to obtain component B; (2) Component A is added through a front feeding device of an extruder, and component B is added through a side feeding device of the extruder, and the flame-retardant foamed polypropylene composite material is obtained by extrusion granulation.

[0036] Preferably, the mixing in step (1) is carried out at 5-40° C. for 5-30 min.

[0037] Preferably, the front feeding device is located in the feeding section of the extruder, and the side feeding device is located in the melting section of the extruder.

[0038] Preferably, the temperature of each section of the extruder is: 155-180°C in the feeding section, 170-190°C in the conveying section, 180-215°C in the melting section, and 180-210°C in the die.

[0039] Preferably, the main engine speed of the extruder is 10-50 rpm, the feeding speed of the front feeding device is 10-20 rpm, and the feeding speed of the side feeding device is 2-5 rpm.

[0040] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adds a certain amount of polystyrene resin and ethylene-octene copolymer to polypropylene with high melt strength. The addition of polystyrene resin within a certain range is beneficial to improving the foaming efficiency and mechanical properties of the material and improving the processing flowability; and the addition of ethylene-octene copolymer can also improve the mechanical properties, flame retardancy, foaming effect and flow processing performance of the composite material.

[0041] 2. The present invention adds a mixture of polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate, and polyphosphate melamine in a mass ratio of 1:(1-1.5):(2-2.5):(2-2.5) as a flame retardant synergist and compounded with the main flame retardant tris(2,3-dibromopropyl) isocyanurate, and utilizes the synergistic flame retardant effect between the flame retardants to achieve low-amount and high-efficiency flame retardants.

[0042] 3. The present invention adopts a multi-system physical foaming method to prepare a low-density flame-retardant polypropylene composite material. The obtained composite material has excellent foaming effect and avoids the problem of high chemical foaming agent residue in traditional foaming materials.

[0043] 4. The present invention uses a mixture of nano calcium silicate and basic zinc carbonate as a nucleating agent. The synergistic effect of the two is not only conducive to the foaming of the material, but also can improve the mechanical properties of the material.

[0044] 5. The flame retardant foamed polypropylene composite material provided by the present invention has the following properties: elongation at break is 18-30%, tensile strength is 20-30 MPa (test standard GB / T16421-1996); oxygen index is 31-34% (test standard GB / T5454-1997); impact strength is 10-15 kj / m 2 (Test standard GB / T1843-2008); Color fastness level reaches level 5 and above (Test standard GB / T8427-2008); Density is 0.6~0.8g / cm 3 (Test standard GB / T 6343-2009); melt index is 5-7g / min (test temperature 190°C, die 2.095mm, load 2.16Kg). The polypropylene composite material prepared by the present invention not only has good flame retardant properties, but also has good foaming effect, low density, and excellent mechanical properties, processing properties and weather resistance.

[0045] 6. The preparation process of the flame-retardant foamed polypropylene composite material of the present invention is simple and suitable for mass production. DETAILED DESCRIPTION

[0046] The technical scheme of the present invention is further described below by specific embodiments. It should be understood that the specific embodiments described herein are only used to help understand the present invention and are not intended to be used for specific limitations of the present invention. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0047] Example 1 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; Among them, the melt strength of polypropylene resin is 15cN, and the weight average molecular weight of polystyrene resin is 6.5*10 5 , Mw / Mn is 1.2, the melt index of ethylene-octene copolymer is 22g / 10min, the flame retardant synergist is 2.08 parts of polymethylsiloxane, 2.5 parts of tris(2,2,2-trifluoroethyl) phosphate, 5.21 parts of melamine cyanurate, 5.21 parts of polyphosphate melamine (mass ratio is about 1:1.2:2.5:2.5), the crosslinking agent is pentaerythritol triacrylate, the compatibilizer is hydrogenated styrene-butadiene-styrene ternary block copolymer, the lubricant is ethylene bisstearamide, and the antioxidant The agent is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], the anti-ultraviolet agent is 2-hydroxy-4-n-octyloxybenzophenone, the expanded microspheres are expanded microspheres formed by thermoplastic acrylate polymer as the shell and carbon dioxide and nitrogen in a volume ratio of 1:1 as the core material, and the particle size is 30-40μm; the nucleating agent is 3 parts of nano calcium silicate and 5 parts of nano basic zinc carbonate (mass ratio is 1.5:2.5), and the particle size range of nano calcium silicate and nano basic zinc carbonate is 10-20nm.

[0048] The flame retardant foamed polypropylene composite material of this embodiment is prepared by the following method: Weigh polypropylene resin, polystyrene resin, ethylene-octene copolymer, tris(2,3-dibromopropyl)isocyanurate, flame retardant synergist, crosslinker, compatibilizer, lubricant, antioxidant, anti-ultraviolet absorber in parts by weight, mix in a low mixer at 25°C for 13 minutes for standby use, and obtain component A. Weigh expanded microspheres and nucleating agent in parts by weight, mix in a low mixer at 20°C for 10 minutes for standby use, and obtain component B.

[0049] The A component mixture is added to the front feeding device of a parallel co-rotating twin-screw extruder with a side feeding device for melt extrusion, and the B component is added through the side feeding device of the extruder for melt extrusion. The temperature of each section of the screw is: 170°C for the feeding section, 180°C for the conveying section, 200°C for the melting section, 195°C for the die, 24rpm for the main engine, 17rpm for the front feeding device, and 3rpm for the side feeding device. After melt extrusion, the composite material particles are obtained by air cooling and pelletizing.

[0050] Example 2 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 25 parts, flame retardant synergist: 18 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The flame retardant synergist is 2.5 parts of polymethylsiloxane, 3 parts of tri(2,2,2-trifluoroethyl) phosphate, 6.25 parts of melamine cyanurate, and 6.25 parts of polyphosphate melamine (mass ratio is 1:1.2:2.5:2.5). The specific ingredients and their proportions of the other components are the same as in Example 1. The preparation method of the polypropylene composite material is the same as in Example 1.

[0051] Example 3 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 20 parts, flame retardant synergist: 10 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The flame retardant synergist is 1.39 parts of polymethylsiloxane, 1.67 parts of tri(2,2,2-trifluoroethyl) phosphate, 3.47 parts of melamine cyanurate, and 3.47 parts of polyphosphate melamine (the mass ratio is about 1:1.2:2.5:2.5). The specific ingredients and their proportions of the other components are the same as in Example 1. The preparation method of the polypropylene composite material is the same as in Example 1.

[0052] Example 4 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 10 parts; Among them, the flame retardant synergist is 2.3 parts of polymethylsiloxane, 2.3 parts of tri(2,2,2-trifluoroethyl) phosphate, 4.6 parts of melamine cyanurate, and 5.8 parts of polyphosphate melamine (mass ratio is 1:1:2:2.5), the nucleating agent is 3.75 parts of nano calcium silicate and 6.25 parts of nano basic zinc carbonate (mass ratio is 1.5:2.5), the specific ingredients and their proportions of other components are the same as in Example 1, and the preparation method of the polypropylene composite material is the same as in Example 1.

[0053] Example 5 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2.8 parts, nucleating agent: 8 parts; The compatibilizer is a styrene-isoprene-styrene ternary block copolymer, the specific ingredients and their proportions of the other components are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0054] Example 6 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 1.2 parts, nucleating agent: 8 parts; The specific ingredients and their proportions of the components in Example 6 are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0055] Example 7 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.8 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The specific ingredients and their proportions of the components in Example 7 are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0056] Example 8 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 2.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The specific ingredients and their proportions of the components in Example 8 are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0057] Example 9 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 10 parts, ethylene-octene copolymer: 12 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The specific ingredients and their proportions of the components in Example 9 are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0058] Example 10 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 12 parts, ethylene-octene copolymer: 10 parts, tris(2,3-dibromopropyl)isocyanurate: 23 parts, flame retardant synergist: 15 parts, crosslinking agent: 0.5 parts, compatibilizer: 3.5 parts, lubricant: 3.5 parts, antioxidant: 0.5 parts, anti-ultraviolet absorber: 0.5 parts, expanded microspheres: 2 parts, nucleating agent: 8 parts; The specific ingredients and their proportions of each component in Example 10 are the same as those in Example 1, and the preparation method of the polypropylene composite material is the same as that in Example 1.

[0059] Embodiment 11 The flame retardant foamed polypropylene composite material of this embodiment is composed of the following components in parts by weight: Polypropylene resin: 100 parts, polystyrene resin: 13 parts, ethylene-octene copolymer: 13 parts, tris(2,3-dibromopropyl)isocyanurate: 22 parts, flame retardant synergist: 18 parts, crosslinking agent: 0.3 parts, compatibilizer: 2 parts, lubricant: 3 parts, antioxidant: 0.4 parts, anti-ultraviolet absorber: 0.6 parts, expanded microspheres: 2 parts, nucleating agent: 6 parts; Among them, the melt strength of polypropylene resin is 18cN, and the weight average molecular weight of polystyrene resin is 6.5*10 5 , Mw / Mn is 1.2, the melt index of ethylene-octene copolymer is 25g / 10min, the flame retardant synergist is 3 parts of polymethylsiloxane, 3 parts of tris(2,2,2-trifluoroethyl) phosphate, 6 parts of melamine cyanurate, and 6 parts of polyphosphate melamine (mass ratio is 1:1:2:2), the crosslinking agent is divinylbenzene, the compatibilizer is styrene-isoprene-styrene ternary block copolymer, the lubricant is polyethylene wax, the antioxidant is antioxidant 1076, the anti-ultraviolet agent is ultraviolet absorber UV-9, the expanded microspheres are expanded microspheres formed by thermoplastic acrylate polymer as the shell and carbon dioxide and nitrogen as the core material in a volume ratio of 1:1, and the particle size is 30-40μm; the nucleating agent is 2 parts of nano calcium silicate and 4 parts of nano basic zinc carbonate (mass ratio is 1:2), and the particle size range of nano calcium silicate and nano basic zinc carbonate is 10-20nm.

[0060] Comparative Example 1 The only difference between the components of the polypropylene composite material of Comparative Example 1 and Example 1 is that the flame retardant synergist of Comparative Example 1 is 15 parts of polymethylsiloxane, and the specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0061] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0062] Comparative Example 2 The only difference between the components of the polypropylene composite material of Comparative Example 2 and Example 1 is that the flame retardant synergist of Comparative Example 2 is 15 parts of tris(2,2,2-trifluoroethyl) phosphate, and the specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0063] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0064] Comparative Example 3 The only difference between the components of the polypropylene composite material of Comparative Example 3 and Example 1 is that the flame retardant synergist of Comparative Example 3 is 15 parts of melamine cyanurate, and the specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0065] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0066] Comparative Example 4 The only difference between the components of the polypropylene composite material of Comparative Example 4 and Example 1 is that the flame retardant synergist of Comparative Example 4 is 15 parts of polyphosphate melamine, and the specific components, contents and component ratios of other components are the same as those of Example 1.

[0067] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0068] Comparative Example 5 The only difference between the components of the polypropylene composite material of Comparative Example 5 and Example 1 is that the flame retardant synergist of Comparative Example 5 is a mixture of 2.9 parts of tris(2,2,2-trifluoroethyl) phosphate, 6.05 parts of melamine cyanurate, and 6.05 parts of polyphosphate melamine (mass ratio is about 1.2:2.5:2.5), and the specific ingredients, contents and component ratios of other components are the same as those in Example 1.

[0069] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0070] Comparative Example 6 The only difference between the components of the polypropylene composite material of Comparative Example 6 and Example 1 is that the flame retardant synergist in Comparative Example 6 is 0 parts, and the specific ingredients, contents and proportions of other components are the same as those in Example 1.

[0071] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0072] Comparative Example 7 The only difference between the components of the polypropylene composite material of Comparative Example 7 and Example 1 is that the flame retardant synergist of Comparative Example 7 is 2.5 parts of polymethylsiloxane, 6.25 parts of melamine cyanurate, and 6.25 parts of polyphosphate melamine (mass ratio is 1:2.5:2.5), and the specific ingredients, contents and component ratios of other components are the same as those in Example 1.

[0073] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0074] Comparative Example 8 The only difference between the components of the polypropylene composite material of Comparative Example 8 and Example 1 is that the nucleating agent in Comparative Example 8 is 0 parts, and the specific components, contents and component ratios of other components are the same as those in Example 1.

[0075] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0076] Comparative Example 9 The only difference between the components of the polypropylene composite material of Comparative Example 9 and Example 1 is that 2 parts of AC foaming agent azodicarbonamide are added in Comparative Example 9 instead of expanded microspheres, and the specific components, contents and component ratios of other components are the same as those of Example 1.

[0077] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0078] Comparative Example 10 The only difference between the components of the polypropylene composite material of Comparative Example 10 and Example 1 is that: 0 parts of expanded microspheres are added to Comparative Example 10, and the specific components, contents and component ratios of other components are the same as those of Example 1.

[0079] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0080] Comparative Example 11 The only difference between the components of the polypropylene composite material of Comparative Example 11 and Example 1 is that the nucleating agent of Comparative Example 11 is 5.25 parts of nano calcium silicate, 8.75 parts of nano basic zinc carbonate (mass ratio is 1.5:2.5) and 14 parts, and the specific ingredients, contents and component ratios of other components are the same as those of Example 1.

[0081] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0082] Comparative Example 12 The only difference between the components of the polypropylene composite material of Comparative Example 12 and Example 1 is that the nucleating agent of Comparative Example 12 is 8 parts of nano calcium silicate and does not contain basic zinc carbonate. The specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0083] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0084] Comparative Example 13 The only difference between the components of the polypropylene composite material of Comparative Example 13 and Example 1 is that the nucleating agent of Comparative Example 13 is 8 parts of nano basic zinc carbonate, and does not contain nano calcium silicate. The specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0085] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0086] Comparative Example 14 The only difference between the components of the polypropylene composite material of Comparative Example 14 and Example 1 is that the polystyrene resin in Comparative Example 14 is 0 parts, and the specific ingredients, contents and component ratios of other components are the same as those in Example 1.

[0087] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0088] Comparative Example 15 The only difference between the components of the polypropylene composite material of Comparative Example 15 and Example 1 is that the ethylene-octene copolymer of Comparative Example 15 is 0 part, and the specific ingredients, contents and proportions of the other components are the same as those of Example 1.

[0089] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0090] Comparative Example 16 The only difference between the components of the polypropylene composite material of Comparative Example 16 and Example 1 is that the ethylene-octene copolymer of Comparative Example 16 is 5 parts, and the specific ingredients, contents and proportions of the other components are the same as those of Example 1.

[0091] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0092] Comparative Example 17 The only difference between the components of the polypropylene composite material of Comparative Example 17 and Example 1 is that the cross-linking agent in Comparative Example 17 is 0 parts, and the specific ingredients, contents and proportions of other components are the same as those in Example 1.

[0093] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0094] Comparative Example 18 The only difference between the components of the polypropylene composite material of Comparative Example 18 and Example 1 is that the cross-linking agent in Comparative Example 18 is 1 part, and the specific ingredients, contents and proportions of the other components are the same as those in Example 1.

[0095] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0096] Comparative Example 19 The only difference between the components of the polypropylene composite material of Comparative Example 19 and Example 1 is that the compatibilizer in Comparative Example 19 is 0 parts, and the specific ingredients, contents and proportions of the other components are the same as those in Example 1.

[0097] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0098] Comparative Example 20 The only difference between the components of the polypropylene composite material of Comparative Example 20 and Example 1 is that the polystyrene resin in Comparative Example 20 is 20 parts, and the specific ingredients, contents and component ratios of other components are the same as those in Example 1.

[0099] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0100] Comparative Example 21 The only difference between the components of the polypropylene composite material of Comparative Example 21 and Example 1 is that the melt strength of the polypropylene resin of Comparative Example 21 is 3 cN, and the specific ingredients, contents and proportions of other components are the same as those of Example 1.

[0101] The preparation method of the polypropylene composite material is the same as that in Example 1.

[0102] The polypropylene composite materials of Examples 1-11 and Comparative Examples 1-21 were tested for physical and chemical properties, and the test labels are as follows: oxygen index test standard GB / T5454-1997; light color fastness test standard GB / T8427-2008; impact strength test standard GB / T1843-2008; elongation at break and tensile strength test standard GB / T16421-1996; density test standard GB / T6343-2009; melt index test temperature 190°C, die 2.095mm, load 2.16Kg. The test results are shown in Table 1: Table 1 Physical and chemical properties of polypropylene composite materials of Examples 1-11 and Comparative Examples 1-21

[0103] As can be seen from Table 1, the polypropylene composite material prepared by the present invention not only has good flame retardant properties, but also has good foaming effect, low density, and excellent mechanical properties, processing properties and weather resistance.

[0104] The polypropylene composite material formula system of the present invention adopts multi-system composite flame retardant technology, fully utilizes the multi-mechanism synergistic effect between flame retardants, and makes its flame retardant effect well exerted with the cooperation of compatibilizer. Within a certain range, as the flame retardant component in the system increases, the flame retardant performance of the composite material is improved, see Examples 1, 2, and 3. The flame retardant synergist plays a very obvious synergistic role in the flame retardant performance of the composite material of the present invention. No flame retardant synergist is added or only polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate, polyphosphate melamine or polymethylsiloxane and tris(2,2,2-trifluoroethyl) phosphate components in the flame retardant synergist are added separately, which will affect the flame retardant performance of the material, see Example 1 and Comparative Examples 1-7.

[0105] The present invention adopts a physical foaming method, and the obtained composite material has good foaming effect and low density. The coordinated use of nucleating agent and expanded microspheres makes the composite material have high foaming efficiency, small foaming holes and uniform distribution. Within a certain range, as the expanded microspheres or nucleating agent components in the system increase, the foaming efficiency of the composite material is higher and the density is low, see Examples 1, 4, 5, and 6. No nucleating agent or expanded microspheres are added to the system, or other foaming agents are used to replace expanded microspheres, or there is no basic zinc carbonate component or nano calcium silicate in the nucleating agent, which will significantly affect the foaming performance and other comprehensive properties of the material, see Example 1 and Comparative Examples 8, 9, 10, 12, and 13. The nucleating agent in the system of the present invention not only affects the foaming performance, but also has a certain effect on improving the mechanical properties of the material, see Example 1 and Comparative Example 8. Too much nucleating agent addition will lead to inappropriate compatibility of the material system, resulting in reduced comprehensive properties such as mechanical properties, see Example 1 and Comparative Example 11.

[0106] The polystyrene resin in the present invention plays a positive role in improving the foaming efficiency and increasing the comprehensive performance of the material. The increase in its dosage within a certain range will improve the foaming efficiency and mechanical properties of the material, see Examples 1 and 9. In the absence of polystyrene resin, the mechanical properties and foaming effect of the obtained composite material are significantly reduced, see Example 1 and Comparative Example 14. However, the addition of too much polystyrene resin will make the various component systems of the material uncoordinated, not only affecting the mechanical properties and foaming effect of the composite material, but also reducing its melt index and affecting the processing flowability, see Example 1 and Comparative Example 20.

[0107] The use of high melt strength polypropylene in the present invention is a guarantee for preparing flame-retardant foamed polypropylene composite materials. If low melt strength polypropylene is used, the mechanical properties, foaming and flame retardant effects of the obtained composite materials will be reduced, see Example 1 and Comparative Example 21.

[0108] Ethylene-octene copolymer has a great influence on the tensile fracture properties and fluidity of the material. When ethylene-octene copolymer is not added or its addition amount is reduced, the mechanical properties, flame retardancy, foaming effect and flow processing properties of the material will be reduced, see Examples 1, 10 and Comparative Examples 15, 16.

[0109] The compatibilizer used in the present invention can ensure perfect coordination between the materials so that their various properties can be fully exerted. When the compatibilizer is reduced or not added, the various comprehensive properties of the material are reduced because the various components of the composite material cannot be perfectly integrated, see Examples 1, 8 and Comparative Example 19.

[0110] It can also be seen from the above table that the light crosslinking of the composite material of the present invention makes the composite material have a three-dimensional network structure, which not only significantly improves the mechanical properties of the material, but also makes the foaming effect of the material more stable. The mechanical properties and foaming effect of the material are significantly reduced without adding a crosslinking agent, see Examples 1, 7 and Comparative Example 17. Adding too much crosslinking agent will reduce the various properties of the material, see Example 1 and Comparative Example 18.

[0111] The various aspects, embodiments, and features of the present invention should be considered to be illustrative in all aspects and not limiting of the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

[0112] In the preparation method of the present invention, the order of each step is not limited to the order listed. For those skilled in the art, without creative work, the order of each step is also within the protection scope of the present invention. In addition, two or more steps or actions can be performed simultaneously.

[0113] Finally, it should be noted that the specific embodiments described herein are merely examples of the present invention, and are not intended to limit the implementation methods of the present invention. A person skilled in the art of the present invention may make various modifications or supplements to the specific embodiments described, or replace them in a similar manner. It is not necessary and impossible to provide all examples of all implementation methods here. However, these obvious changes or modifications derived from the essential spirit of the present invention still fall within the scope of protection of the present invention, and interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A flame retardant foamed polypropylene composite material, characterized in that: It includes the following components by weight: 100 parts of polypropylene resin, 10-15 parts of polystyrene resin, 10-15 parts of ethylene-octene copolymer, 20-25 parts of tris(2,3-dibromopropyl)isocyanurate, 10-20 parts of flame retardant synergist, 0.2-0.8 parts of crosslinking agent, 2-4 parts of compatibilizer, 2-5 parts of lubricant, 0.4-0.8 parts of antioxidant, 0.4-0.8 parts of anti-ultraviolet absorber, 1-3 parts of expanded microspheres, and 5-10 parts of nucleating agent.

2. The flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The melt strength of the polypropylene resin is 5-50 cN, and the test conditions are: using a melt strength meter for testing, extrusion temperature 200°C, tensile acceleration 20 mm / S 2 ; The weight average molecular weight of the polystyrene resin is 1*10 4 ~9*10 6 , Mw / Mn is 1~1.4; The melt index of the ethylene-octene copolymer is 15-30 g / 10 min, and the test conditions are: temperature 190° C., die 2.095 mm, and load 2.16 kg.

3. The flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The flame retardant synergist is a mixture of polymethylsiloxane, tris(2,2,2-trifluoroethyl) phosphate, melamine cyanurate and polyphosphate melamine.

4. A flame retardant foamed polypropylene composite material according to claim 1 or 3, characterized in that: The flame retardant synergist is a mixture of polymethylsiloxane, tri(2,2,2-trifluoroethyl) phosphate, melamine cyanurate and polyphosphate melamine in a mass ratio of 1:(1-1.5):(2-2.5):(2-2.5).

5. The flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The expanded microspheres are formed by using a thermoplastic polymer as the outer shell and carbon dioxide and nitrogen as the core material in a volume ratio of 1:0.5-2; The particle size of the expanded microspheres is 10-50 μm.

6. The flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The nucleating agent is a mixture of nano calcium silicate and nano basic zinc carbonate.

7. A flame retardant foamed polypropylene composite material according to claim 1 or 6, characterized in that: The nucleating agent is a mixture of nano calcium silicate and nano basic zinc carbonate in a mass ratio of (1-2): (2-3); The particle size of the nucleating agent is 1-50 nm.

8. The flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The crosslinking agent is one or more of an aromatic divinyl compound, a diacrylate compound, a multifunctional crosslinking agent, and a diol compound; The compatibilizer is one or more of hydrogenated styrene-butadiene-styrene terblock copolymer, styrene-isoprene-styrene terblock copolymer, and styrene-butadiene-styrene terblock copolymer.

9. The method for preparing a flame retardant foamed polypropylene composite material according to claim 1, characterized in that: The following steps are involved: (1) Weighing polypropylene resin, polystyrene resin, ethylene-octene copolymer, tris(2,3-dibromopropyl)isocyanurate, flame retardant synergist, crosslinking agent, compatibilizer, lubricant, antioxidant, and anti-ultraviolet absorber in parts by weight and mixing to obtain component A; weighing expanded microspheres and nucleating agent in parts by weight and mixing to obtain component B; (2) Component A is added through a front feeding device of an extruder, and component B is added through a side feeding device of the extruder, and the flame-retardant foamed polypropylene composite material is obtained by extrusion granulation.

10. The preparation method according to claim 9, characterized in that: The front feeding device is located in the feeding section of the extruder, and the side feeding device is located in the melting section of the extruder; The temperature of each section of the extruder is: feeding section 155~180℃, conveying section 170~190℃, melting section 180~215℃, die head 180~210℃; The main engine speed of the extruder is 10~50rpm, the unloading speed of the front feeding device is 10~20rpm; the unloading speed of the side feeding device is 2~5rpm.

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