A high flame retardant expandable polystyrene and a method for preparing the same

Abstract

The application relates to the technical field of high polymer materials, and particularly discloses a high-flame-retardant expandable polystyrene and a preparation method thereof.A kind of high-flame-retardant expandable polystyrene, according to weight parts, raw materials include styrene, flame retardant, modified expandable graphite, initiator, foaming agent, dispersant, organic suspending agent, inorganic suspending agent, stabilizer, nucleating agent and water; the modified expandable graphite is a core-shell structure particle with expandable graphite as the core, and the shell layer raw material includes silicon dioxide, zirconium dioxide and aluminum hydroxide.The high-flame-retardant expandable polystyrene of the application realizes the high dispersion stability of carbon-based flame-retardant materials in polystyrene, and significantly improves the flame-retardant performance and mechanical properties of the polystyrene material.

Description

Technical Field

[0001] This application relates to the field of polymer materials technology, and more specifically, to a highly flame-retardant expandable polystyrene and its preparation method. Background Technology

[0002] Expandable polystyrene (EPS), as a lightweight polymer insulation material, is widely used in building insulation, packaging cushioning, cold chain transportation, and other fields due to its excellent thermal insulation performance, low density, impact resistance, and ease of processing and molding. However, EPS has inherent drawbacks such as a low limiting oxygen index (LOI) and a fast burning rate. When burning, it easily releases a large amount of heat, flames, and toxic fumes, posing serious fire safety hazards and severely limiting its application in high-end buildings, rail transportation, and other scenarios with stringent flame retardant requirements.

[0003] Carbon-based materials such as carbon black and graphite have attracted much attention in the flame retardant modification of EPS due to their wide availability, good environmental compatibility, and excellent char-forming properties. These materials can effectively inhibit heat transfer and the release of combustible gases by forming a dense and continuous carbonaceous barrier layer during combustion, thus achieving a flame retardant effect. Compared with traditional halogenated flame retardants, they can effectively avoid the generation of toxic and harmful gases during combustion, which is in line with the development trend of environmentally friendly flame retardants.

[0004] Regarding the aforementioned technologies, the inventors discovered that fillers such as carbon black and graphite have large specific surface areas and high surface energies, resulting in poor compatibility with hydrophobic polystyrene matrices. This makes it difficult to achieve uniform dispersion within the polystyrene matrix, and they are prone to agglomeration in traditional blending or suspension polymerization processes, forming aggregates of micrometer or even larger scales. This not only fails to form a continuous and complete flame-retardant barrier layer, but may also create weak points in combustion due to localized agglomerates, significantly reducing the flame-retardant efficiency of EPS. At the same time, agglomeration also disrupts the continuity of the polystyrene matrix, affecting the foaming performance, mechanical strength, and thermal insulation effect of EPS, thus restricting the industrial application of carbon-based flame-retardant materials in EPS modification. Summary of the Invention

[0005] In order to improve the dispersion uniformity of carbon-based flame retardant materials in polystyrene and enhance the flame retardant efficiency and flame retardant stability of expandable polystyrene, this application provides a highly flame-retardant expandable polystyrene and its preparation method.

[0006] In a first aspect, this application provides a highly flame-retardant expandable polystyrene, employing the following technical solution: A highly flame-retardant expandable polystyrene, comprising, by weight, 90-100 parts styrene, 0.1-0.2 parts flame retardant, 5-10 parts modified expandable graphite, 0.1-0.3 parts initiator, 1-2 parts foaming agent, 0.1-0.2 parts dispersant, 0.0002-0.0004 parts organic suspending agent, 0.05-0.15 parts inorganic suspending agent, 0.002-0.004 parts stabilizer, 0.1-0.2 parts nucleating agent, and 120-140 parts water; wherein the modified expandable graphite is a core-shell structure particle with expandable graphite as the core, and the shell material includes silicon dioxide, zirconium dioxide, and aluminum hydroxide.

[0007] By employing the above-mentioned technical solution, modified expandable graphite with a core-shell structure was prepared. Compared with traditional graphite fillers, the inventors introduced silica, zirconium dioxide, and aluminum hydroxide onto the surface of the expandable graphite, enhancing its polarity and making it easier to interact with specific dispersants and the aqueous phase and suspending agent in the suspension polymerization system. This allows it to remain stably suspended in the aqueous phase from the initial stage of polymerization, encapsulated by monomer droplets, achieving uniform dispersion at the microscale. Furthermore, the rigid core-shell structure acts as a physical barrier, effectively blocking direct contact and van der Waals forces between graphite sheets, effectively suppressing agglomeration caused by high surface energy during processing and polymerization.

[0008] Under high-temperature flame, the core expandable graphite decomposes and produces gas between its layers, forming a worm-like expanded carbon layer that provides efficient heat and material insulation. The outer shell, aluminum hydroxide, is a commonly used flame retardant that decomposes and absorbs heat to generate water vapor. The resulting alumina protective layer helps prevent the transfer of oxygen and heat, inhibiting the combustion reaction. Silica and zirconium dioxide are both high-temperature resistant ceramic phases that can form a stable ceramic protective layer at high temperatures, further enhancing the flame retardant effect. The flame-retardant metal oxide and ceramic mixed protective layer, together with the carbonization barrier effect of graphite, forms a synergistic flame retardant system. This system can form a continuous and dense carbon-ceramic composite flame retardant layer throughout the styrene matrix, significantly improving the limiting oxygen index and flame retardant stability of the material.

[0009] Optionally, the method for preparing the modified expandable graphite includes the following steps: S1: Disperse expandable graphite in ethanol to form a suspension; S2: Tetraethyl orthosilicate is dissolved in anhydrous ethanol, water and catalyst are added, and the mixture is stirred to pre-hydrolyze to obtain a silicon source solution; Zirconium oxychloride is dissolved in a mixture of anhydrous ethanol and acetylacetone to obtain a zirconium source solution; the zirconium source solution is added dropwise to the silicon source solution under stirring, a surfactant template agent is added, and the mixture is stirred to form a SiO2-ZrO2 composite sol. S3: Under ultrasonic conditions, SiO2-ZrO2 composite sol was added dropwise to a suspension, heated and stirred in a water bath, aged, washed and dried, and then calcined at high temperature to obtain SiO2-ZrO2 coated expandable graphite. S4: Dissolve aluminum nitrate in water to form an aluminum source solution. Then add the SiO2-ZrO2-coated expandable graphite to the silicon source solution, add ammonia water, adjust the pH to 8.5-9.5, stir the reaction, centrifuge, wash and dry, and then heat treat to obtain the final product.

[0010] Optionally, the surfactant template agent in step S2 is selected from hexadecyltrimethylammonium bromide, and the high-temperature calcination conditions in step S3 are: heating to 500-600℃ at 2-5℃ / min and holding at that temperature for 2-3 hours.

[0011] By adopting the above technical solution, a SiO2-ZrO2 composite porous shell layer is first coated onto the surface of expandable graphite using a composite sol method. High-temperature calcination transforms the amorphous gel coating layer into a stable ceramic structure, forming a strong chemical bond with the graphite surface. Finally, an aluminum hydroxide coating layer is formed on the outer shell using a pre-deposition method, resulting in core-shell structure modified expandable graphite particles with expandable graphite as the core, the SiO2-ZrO2 composite porous layer as the intermediate buffer layer, and aluminum hydroxide as the shell. The mesoporous SiO2-ZrO2 composite layer provides more anchoring points for the aluminum hydroxide load, improving the strength of the modified expandable graphite. Furthermore, it regulates heat transfer in the early stages of combustion; the porous structure effectively delays heat transfer to the core, allowing more time for the decomposition and heat absorption of the outer aluminum hydroxide layer. This ensures that the expansion of the core expandable graphite occurs after the decomposition of aluminum hydroxide, improving flame retardant efficiency and helping to reduce the rate of heat release and total smoke production.

[0012] Optionally, the dispersant is hydroxyalkyl methacrylate.

[0013] Optionally, the preparation method of the hydroxyalkyl phosphonate methacrylate includes the following steps: Hydroxyethylphosphonic acid and methacrylic acid were mixed in a molar ratio of 1:(1.1-1.5) and added to toluene as reactants. Then, 0.1-0.4 wt% hydroquinone and 0.5-1 wt% p-toluenesulfonic acid were added. The mixture was heated to 100-110℃ under an inert gas atmosphere and stirred for 6-12 h to obtain a reaction solution. After the reaction solution is cooled, sodium bicarbonate solution is added, stirred to neutralize, allowed to stand and separate into layers, and the organic phase is dried with anhydrous magnesium sulfate. After filtration, it is evaporated under reduced pressure to obtain the final product.

[0014] By adopting the above technical solution, a dispersant prepared from hydroxyethylphosphonic acid and methacrylic acid has a phosphonic acid group at one end and a methacrylate group at the other end. One end of the phosphonic acid group can be chemically anchored to the inorganic shell surface of modified expandable graphite, while the other end can achieve good compatibility with expandable polystyrene matrix during polymerization.

[0015] During suspension polymerization, hydroxyalkyl phosphonates of methacrylate can not only prevent the agglomeration of expandable graphite through steric hindrance, but also anchor to the polystyrene molecular chain through covalent bonding, achieving a strong interfacial bond between expandable graphite and the polymer matrix. This effectively prevents the common problems of weak interfaces and migration after long-term use in physical mixing, ensuring the long-term stability of expandable graphite dispersion in expandable polystyrene matrix.

[0016] Optionally, the organic suspending agent is hydroxyethyl cellulose, and the inorganic suspending agent is active calcium phosphate.

[0017] Secondly, this application provides a method for preparing highly flame-retardant expandable polystyrene, using the following technical solution: A method for preparing highly flame-retardant expandable polystyrene includes the following steps: (1) Mix the modified expandable graphite with the dispersant until a uniform mixture is formed; (2) Add water to the reactor, then add organic suspending agent, inorganic suspending agent and mixture, stir evenly and then add styrene, flame retardant, initiator, stabilizer and nucleating agent to obtain suspension; (3) The suspension is heated to 88-90℃ and kept at that temperature for 5-6 hours to obtain a blend; (4) Add foaming agent to the blend, heat to 118-130℃, react for 3-5 hours, cool down and discharge to obtain the product.

[0018] By adopting the above technical solution, the preparation process of this application is simple. The foaming agent is directly impregnated in the same reactor, which prevents the uniformly dispersed filler from agglomerating again due to external force or drying during the separation and transportation process. This keeps the system in the best dispersion state, making it easy to scale up and achieve continuous industrial production.

[0019] In summary, this application has the following beneficial effects: 1. This application uses expandable graphite as the core, SiO2-ZrO2 composite porous layer as the intermediate buffer, and aluminum hydroxide as the shell to prepare a core-shell structure modified expandable graphite. On the one hand, the introduction of the intermediate layer and the shell improves the surface polarity of expandable graphite, making it easier for particles to interact with specific dispersants and suspension polymerization systems, thereby effectively improving the dispersion uniformity and stability of expandable graphite in polystyrene systems and reducing particle agglomeration.

[0020] 2. The modified expandable graphite prepared in this application has a mixed protective layer of flame-retardant metal oxide and high-temperature resistant ceramic. It can first form a dense and continuous composite flame-retardant system in the early stage of combustion to achieve efficient flame retardancy and smoke suppression. Under the action of high-temperature flame, the core expandable graphite decomposes and produces gas between its layers, forming a worm-like expandable elastic layer, which further ensures the high efficiency and stability of flame retardancy and meets the requirements of GB / T8624 B1 level.

[0021] 3. This application uses hydroxyethylphosphonic acid and methacrylic acid as raw materials to prepare hydroxyalkylphosphonate methacrylate as a dispersant. The phosphonic acid at one end can be anchored on the surface of modified expandable graphite, while the other end can achieve good compatibility with expandable polystyrene matrix during polymerization. This effectively improves the dispersion uniformity and stability of expandable graphite in the polystyrene system, significantly enhances the flame retardant stability of expandable polystyrene, and improves the mechanical properties of the system. Detailed Implementation

[0022] The present application will be further described in detail below with reference to embodiments and comparative examples. Examples of modified expandable graphite preparation 1.1-1.6

[0023] Preparation Example 1.1 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 30 mL of tetraethyl orthosilicate in 60 mL of anhydrous ethanol, add 5 mL of deionized water and 2 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze and obtain silicon source solution; 10g of zirconium oxychloride was dissolved in a mixture of 40mL of anhydrous ethanol and 3mL of acetylacetone, and stirred at 60℃ for 1h to obtain zirconium source solution. Under stirring conditions, zirconium source liquid was added dropwise to silicon source liquid, 2g of hexadecyltrimethylammonium bromide was added, and stirring was continued for 2h to form SiO2-ZrO2 composite sol; S3: The suspension was heated to 50℃, and SiO2-ZrO2 composite sol was added to the suspension under ultrasonic conditions at a dropping rate of 2mL / min. The mixture was heated to 60℃ and stirred in a water bath for 6h. After standing and aging for 12h, the mixture was washed and dried. The temperature was then increased to 500℃ at 2℃ / min and held for 3h to obtain SiO2-ZrO2-coated expandable graphite. S4: Dissolve aluminum nitrate in water to form a 0.3 mol / L aluminum source solution. Under stirring, add SiO2-ZrO2-coated expandable graphite to the silicon source solution at a ratio of 1:30, add ammonia water, adjust the pH to 8.5, stir for 3 hours, centrifuge, wash and dry, and heat treat at 400℃ to obtain the final product.

[0024] Preparation Example 1.2 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 30 mL of tetraethyl orthosilicate in 60 mL of anhydrous ethanol, add 5 mL of deionized water and 2 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze and obtain silicon source solution; 10g of zirconium oxychloride was dissolved in a mixture of 40mL of anhydrous ethanol and 3mL of acetylacetone, and stirred at 60℃ for 1h to obtain zirconium source solution. Under stirring conditions, zirconium source liquid was added dropwise to silicon source liquid, 2g of hexadecyltrimethylammonium bromide was added, and stirring was continued for 2h to form SiO2-ZrO2 composite sol; S3: The suspension was heated to 50℃, and SiO2-ZrO2 composite sol was added dropwise to the suspension under ultrasonic conditions at a dropping rate of 2mL / min. The mixture was heated to 60℃ and stirred in a water bath for 7h. After standing and aging for 12h, the mixture was washed and dried. The temperature was then increased to 600℃ at 5℃ / min and held for 2h to obtain SiO2-ZrO2-coated expandable graphite. S4: Dissolve aluminum nitrate in water to form a 0.3 mol / L aluminum source solution. Under stirring, add SiO2-ZrO2-coated expandable graphite to the silicon source solution at a ratio of 1:40, add ammonia water, adjust the pH to 9.5, stir for 2 hours, centrifuge, wash and dry, and heat treat at 400℃ to obtain the final product.

[0025] Preparation Example 1.3 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 30 mL of tetraethyl orthosilicate in 60 mL of anhydrous ethanol, add 5 mL of deionized water and 2 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze and obtain silicon source solution; 10g of zirconium oxychloride was dissolved in a mixture of 40mL of anhydrous ethanol and 3mL of acetylacetone, and stirred at 60℃ for 1h to obtain zirconium source solution. Under stirring conditions, zirconium source liquid was added dropwise to silicon source liquid, 2g of hexadecyltrimethylammonium bromide was added, and stirring was continued for 2h to form SiO2-ZrO2 composite sol; S3: The suspension was heated to 50℃, and SiO2-ZrO2 composite sol was added dropwise to the suspension under ultrasonic conditions at a dropping rate of 2mL / min. The mixture was heated to 60℃ and stirred in a water bath for 8 hours. After standing and aging for 12 hours, the mixture was washed and dried. The temperature was then increased to 500℃ at a rate of 4℃ / min and held for 3 hours to obtain SiO2-ZrO2-coated expandable graphite. S4: Dissolve aluminum nitrate in water to form a 0.3 mol / L aluminum source solution. Under stirring, add SiO2-ZrO2-coated expandable graphite to the silicon source solution at a ratio of 1:35, add ammonia water, adjust the pH to 9, stir for 3 hours, centrifuge, wash and dry, and heat treat at 400℃ to obtain the final product.

[0026] Preparation Example 1.4 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 30 mL of tetraethyl orthosilicate in 60 mL of anhydrous ethanol, add 5 mL of deionized water and 2 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze and obtain silicon source solution; 10g of zirconium oxychloride was dissolved in a mixture of 40mL of anhydrous ethanol and 3mL of acetylacetone, and stirred at 60℃ for 1h to obtain zirconium source solution. Under stirring conditions, zirconium source liquid was added dropwise to silicon source liquid, 2g of hexadecyltrimethylammonium bromide was added, and stirring was continued for 2h to form SiO2-ZrO2 composite sol; S3: Heat the suspension to 50℃, add SiO2-ZrO2 composite sol dropwise to the suspension under ultrasonic conditions at a drop rate of 2mL / min, heat to 60℃ and stir in a water bath for 6h, let stand and age for 12h, wash and dry, then heat to 500℃ at 2℃ / min and keep warm for 3h to obtain the final product.

[0027] Preparation Example 1.5 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 30 mL of tetraethyl orthosilicate in 60 mL of anhydrous ethanol, add 5 mL of deionized water and 2 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze and obtain silicon source solution; 10g of zirconium oxychloride was dissolved in a mixture of 40mL of anhydrous ethanol and 3mL of acetylacetone, and stirred at 60℃ for 1h to obtain zirconium source solution. Under stirring conditions, zirconium source liquid was added dropwise to silicon source liquid, and stirring was continued for 2 hours to form SiO2-ZrO2 composite sol; S3: The suspension was heated to 50℃, and SiO2-ZrO2 composite sol was added to the suspension under ultrasonic conditions at a dropping rate of 2mL / min. The mixture was heated to 60℃ and stirred in a water bath for 6 hours. After standing and aging for 12 hours, the mixture was washed and dried to obtain SiO2-ZrO2-coated expandable graphite. S4: Dissolve aluminum nitrate in water to form a 0.3 mol / L aluminum source solution. Under stirring, add SiO2-ZrO2-coated expandable graphite to the silicon source solution at a ratio of 1:30, add ammonia water, adjust the pH to 8.5, stir for 3 hours, centrifuge, wash and dry, and heat treat at 400℃ to obtain the final product.

[0028] Preparation Example 1.6 A method for preparing modified expandable graphite includes the following steps: S1: Disperse 10g of expandable graphite in 200mL of anhydrous ethanol and sonicate for 15min to form a suspension; S2: Dissolve 50 mL of tetraethyl orthosilicate in 100 mL of anhydrous ethanol, add 8 mL of deionized water and 3 mL of 0.1 M hydrochloric acid, stir at room temperature for 30 min to pre-hydrolyze to obtain silicon source solution, add 2 g of hexadecyltrimethylammonium bromide under stirring, and continue stirring for 2 h to form SiO2 sol; S3: The suspension was heated to 50℃, and SiO2 sol was added to the suspension under ultrasonic conditions at a dropping rate of 2mL / min. The mixture was heated to 60℃ and stirred in a water bath for 6h. After standing and aging for 12h, the mixture was washed and dried. The temperature was then increased to 500℃ at 2℃ / min and kept at that temperature for 3h to obtain SiO2-ZrO2-coated expandable graphite. S4: Dissolve aluminum nitrate in water to form a 0.3 mol / L aluminum source solution. Under stirring, add SiO2-ZrO2-coated expandable graphite to the silicon source solution at a ratio of 1:30, add ammonia water, adjust the pH to 8.5, stir for 3 hours, centrifuge, wash and dry, and heat treat at 400℃ to obtain the final product. Examples of preparation of hydroxyalkyl phosphonates of methacrylate 2.1-2.3

[0029] Preparation Example 2.1 The preparation method of hydroxyalkyl phosphonate methacrylate includes the following steps: S1: In a 500mL four-necked flask, N2 was continuously introduced to replace the air in the flask at a flow rate of 30m / min to maintain the N2 gas atmosphere. 0.1mol of hydroxyethylphosphonic acid (CAS: 22987-21-9) and 0.11mol of methacrylic acid were added as reactants, and 200mL of toluene was added as solvent. After stirring and mixing until completely dissolved, 0.1wt% hydroquinone and 0.5wt% p-toluenesulfonic acid were added. The temperature was raised to 110℃ and the reaction was stirred at a constant temperature for 8h to obtain the reaction solution. S2: After cooling the reaction solution, add 5wt% sodium bicarbonate solution, stir to neutralize, adjust the pH to 6.5-7, let it stand to separate the layers, dry the organic phase with anhydrous magnesium sulfate, filter, and then evaporate under reduced pressure to obtain the final product.

[0030] Preparation Example 2.2 The preparation method of hydroxyalkyl phosphonate methacrylate includes the following steps: S1: In a 500mL four-necked flask, N2 is continuously introduced to replace the air in the flask at a flow rate of 30m / min to maintain the N2 gas atmosphere. 0.1mol of hydroxyethylphosphonic acid and 0.13mol of methacrylic acid are added as reactants, and 200mL of toluene is added as a solvent. After stirring and mixing until completely dissolved, 0.3wt% of hydroquinone and 0.8wt% of p-toluenesulfonic acid are added. The temperature is raised to 100℃ and the reaction is stirred at a constant temperature for 12h to obtain the reaction solution. S2: After cooling the reaction solution, add 5wt% sodium bicarbonate solution, stir to neutralize, adjust the pH to 6.5-7, let it stand to separate the layers, dry the organic phase with anhydrous magnesium sulfate, filter, and then evaporate under reduced pressure to obtain the final product.

[0031] Preparation Example 2.3 The preparation method of hydroxyalkyl phosphonate methacrylate includes the following steps: S1: In a 500mL four-necked flask, N2 is continuously introduced to replace the air in the flask at a flow rate of 30m / min to maintain the N2 gas atmosphere. 0.1mol of hydroxyethylphosphonic acid and 0.15mol of methacrylic acid are added as reactants, and 200mL of toluene is added as a solvent. After stirring and mixing until completely dissolved, 0.4wt% of hydroquinone and 1wt% of p-toluenesulfonic acid are added. The temperature is raised to 110℃ and the reaction is stirred at a constant temperature for 6h to obtain the reaction solution. S2: After cooling the reaction solution, add 5wt% sodium bicarbonate solution, stir to neutralize, adjust the pH to 6.5-7, let it stand to separate the layers, dry the organic phase with anhydrous magnesium sulfate, filter, and then evaporate under reduced pressure to obtain the final product. Example Example 1

[0032] A highly flame-retardant expandable polystyrene, comprising, by weight, 90 parts styrene, 0.1 parts BR-SBS, 0.0014 parts polyvinyl alcohol, 0.001 parts potassium metabisulfite, 5 parts modified expandable graphite prepared in Preparation Example 1.1, 0.1 parts bis(tert-butylperoxyisopropyl)benzene, 1 part isopentane, 0.1 parts hydroxyalkylphosphonate methacrylate prepared in Preparation Example 2.1, 0.0002 parts hydroxyethyl cellulose, 0.05 parts activated calcium phosphate, 0.002 parts magnesium phosphate, 0.1 parts polyethylene wax, and 120 parts water, wherein the BR-SBS is selected from Shandong Dongxin New Material Technology Co., Ltd., and the brominated SBS masterbatch is used. The above-mentioned method for preparing highly flame-retardant expandable polystyrene includes the following steps: (1) According to the raw material ratio, the modified expandable graphite and hydroxyalkyl phosphonate methacrylate are mixed and stirred evenly to form a mixture; (2) Add water to the reactor, then add hydroxyethyl cellulose, active calcium phosphate and the mixture, stir evenly and then add styrene, BR-SBS, polyvinyl alcohol, potassium metabisulfite, bis(tert-butylperoxyisopropyl)benzene, magnesium phosphate and polyethylene wax to obtain a suspension. (3) The suspension was heated to 88°C and kept at that temperature for 6 hours to obtain the blend; (4) Add isopentane to the blend, heat to 118°C, react for 5 hours, cool down and discharge to obtain the product. Example 2

[0033] A highly flame-retardant expandable polystyrene, comprising, by weight, 95 parts styrene, 0.1 parts BR-SBS, 0.0014 parts polyvinyl alcohol, 0.001 parts potassium metabisulfite, 7 parts modified expandable graphite prepared in Preparation Example 1.1, 0.2 parts bis(tert-butylperoxyisopropyl)benzene, 1.5 parts isopentane, 0.15 parts hydroxyalkylphosphonate methacrylate prepared in Preparation Example 2.1, 0.0003 parts hydroxyethyl cellulose, 0.1 parts activated calcium phosphate, 0.003 parts magnesium phosphate, 0.15 parts polyethylene wax, and 130 parts water, wherein the BR-SBS is selected from Shandong Dongxin New Material Technology Co., Ltd., and the brominated SBS masterbatch is used. The above-mentioned method for preparing highly flame-retardant expandable polystyrene includes the following steps: (1) According to the raw material ratio, the modified expandable graphite and hydroxyalkyl phosphonate methacrylate are mixed and stirred evenly to form a mixture; (2) Add water to the reactor, then add hydroxyethyl cellulose, active calcium phosphate and the mixture, stir evenly and then add styrene, BR-SBS, polyvinyl alcohol, potassium metabisulfite, bis(tert-butylperoxyisopropyl)benzene, magnesium phosphate and polyethylene wax to obtain a suspension. (3) The suspension was heated to 90°C and kept at that temperature for 5 hours to obtain the blend. (4) Add isopentane to the blend, heat to 130°C, react for 3 hours, cool down and discharge to obtain the product. Example 3

[0034] A highly flame-retardant expandable polystyrene, comprising, by weight, 100 parts styrene, 0.2 parts BR-SBS, 0.0014 parts polyvinyl alcohol, 0.001 parts potassium metabisulfite, 10 parts modified expandable graphite prepared in Preparation Example 1.1, 0.3 parts bis(tert-butylperoxyisopropyl)benzene, 2 parts isopentane, 0.2 parts hydroxyalkylphosphonate methacrylate prepared in Preparation Example 2.1, 0.0004 parts hydroxyethyl cellulose, 0.15 parts activated calcium phosphate, 0.004 parts magnesium phosphate, 0.2 parts polyethylene wax, and 140 parts water, wherein the BR-SBS is selected from Shandong Dongxin New Material Technology Co., Ltd., and the brominated SBS masterbatch is used. The above-mentioned method for preparing highly flame-retardant expandable polystyrene includes the following steps: (1) According to the raw material ratio, the modified expandable graphite and hydroxyalkyl phosphonate methacrylate are mixed and stirred evenly to form a mixture; (2) Add water to the reactor, then add hydroxyethyl cellulose, active calcium phosphate and the mixture, stir evenly and then add styrene, BR-SBS, polyvinyl alcohol, potassium metabisulfite, bis(tert-butylperoxyisopropyl)benzene, magnesium phosphate and polyethylene wax to obtain a suspension. (3) The suspension was heated to 89°C and kept at that temperature for 6 hours to obtain the blend; (4) Add isopentane to the blend, heat to 125°C, react for 4 hours, cool down and discharge to obtain the product. Example 4

[0035] A highly flame-retardant expandable polystyrene differs from Example 1 only in that the modified expandable graphite in the raw materials is prepared by Preparation Example 1.2, and the hydroxyalkyl phosphonate methacrylate is prepared by Preparation Example 2.2. Example 5

[0036] A highly flame-retardant expandable polystyrene differs from Example 1 only in that the modified expandable graphite in the raw materials is prepared by Preparation Example 1.3, and the hydroxyalkyl phosphonate methacrylate is prepared by Preparation Example 2.3. Example 6

[0037] A highly flame-retardant expandable polystyrene, differing from Example 1 only in that the modified expandable graphite in the raw material is obtained from Preparation Example 1.5. Comparative Example

[0038] Comparative Example 1 A highly flame-retardant expandable polystyrene, differing from Example 1 only in that the modified expandable graphite in the raw material is prepared as in Preparation Example 1.4.

[0039] Comparative Example 2 A highly flame-retardant expandable polystyrene, differing from Example 1 only in that the modified expandable graphite in the raw material is prepared as in Preparation Example 1.6.

[0040] Comparative Example 3 A highly flame-retardant expandable polystyrene differs from Example 1 only in that the expandable graphite is not modified, and the modified expandable graphite in the raw material is replaced with an equal mass of unmodified expandable graphite.

[0041] Comparative Example 4 A highly flame-retardant expandable polystyrene, differing from Example 1 only in that hydroxyalkyl methacrylate is not added to the raw materials. Performance testing

[0042] The high flame-retardant expandable polystyrene obtained in Examples 1-6 and Comparative Examples 1-4 were subjected to the following related performance tests. Each test was conducted 3 times, and the average value of the 3 test results was taken as the final result and recorded in Table 1.

[0043] 1. Thermal conductivity: In accordance with the provisions of GB / T 10294-2008 "Determination of steady-state thermal resistance and related properties of thermal insulation materials - protective hot plate method", each group of samples was made into a standard specimen with a specification of 300mm×300mm×50mm and the thermal conductivity was tested. 2. Combustion performance: In accordance with GB / T 2406.2-2009 "Determination of combustion behavior of plastics by oxygen index method - Part 2: Room temperature test", each group of samples was made into a 250mm×90mm×60mm polystyrene foam sample, and the limiting oxygen index was determined. The flame retardant rating was determined in accordance with the requirements of GB 8624-2012 "Classification of Burning Performance of Building Materials and Products"; 3. Tensile strength: In accordance with the provisions of GB 9641-1988 "Test Method for Tensile Properties of Rigid Foamed Plastics", each group of samples was made into dumbbell-shaped polystyrene foam templates and tensile properties were tested using a testing machine at 25℃, with the clamp moving speed being 5±1mm / min.

[0044] Table 1

[0045] According to the performance test results of Examples 1-5 in Table 1, the expandable polystyrene material prepared by adding expandable graphite as the core, SiO2-ZrO2 composite porous layer as the intermediate buffer, and aluminum hydroxide as the shell has a thermal conductivity ≤0.036W / m·K, a limiting oxygen index ≥32.1%, which meets the requirements of GB / T8624 B1 grade, and a tensile strength of 0.32-0.41MPa. This shows that the expandable polystyrene material of this application has excellent flame retardant and heat insulation properties, as well as excellent mechanical strength.

[0046] In Example 6, no cetyltrimethylammonium bromide template agent was added, and the resulting SiO2-ZrO2 composite layer lacked a porous structure. It can be seen that the thermal insulation performance and limiting oxygen index of the material both decreased. This is because the SiO2-ZrO2 composite porous layer with a mesoporous structure can provide more anchoring points for the aluminum hydroxide load, improving the flame retardant performance and mechanical strength of the modified expandable graphite. On the other hand, it can regulate heat transfer in the early stage of combustion. The porous structure can effectively delay the transfer of heat to the core, effectively regulate the heat, and improve the thermal insulation performance of the material.

[0047] In Comparative Example 2, the intermediate layer only contains a porous SiO2 layer without the addition of ZrO2. It can be seen that the thermal insulation performance and limiting oxygen index of the material are both deteriorated. This also proves that the ceramic phase formed by the high-temperature resistant ZrO2 and SiO2 composite can more effectively improve the heat resistance and combustion performance of the material when it works in synergy with metal oxides.

[0048] In Comparative Example 1, the lack of an aluminum hydroxide shell layer shows a significant decrease in the flame retardant properties of the material. This demonstrates that the mixed protective layer of flame-retardant metal oxide and ceramic, along with the carbonization barrier effect of graphite, forms a continuous and dense carbon-ceramic composite flame-retardant layer throughout the styrene matrix, which can significantly improve the limiting oxygen index and flame retardant stability of the material.

[0049] According to the performance test results of Example 1 and Comparative Examples 3-4, the introduction of the SiO2-ZrO2 composite porous layer and aluminum hydroxide shell layer effectively improves the surface polarity of expandable graphite. When hydroxyethylphosphonic acid and methacrylic acid are used as raw materials to prepare hydroxyalkylphosphonate methacrylate as a dispersant, the modified expandable graphite can be uniformly and stably dispersed in the polystyrene matrix, effectively improving the problem of easy agglomeration of carbon-based materials, improving the combustion performance of expandable polystyrene materials, and improving the mechanical strength of the materials.

[0050] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A highly flame-retardant expandable polystyrene, characterized in that, By weight, the raw materials include 90-100 parts styrene, 0.1-0.2 parts flame retardant, 5-10 parts modified expandable graphite, 0.1-0.3 parts initiator, 1-2 parts foaming agent, 0.1-0.2 parts dispersant, 0.0002-0.0004 parts organic suspending agent, 0.05-0.15 parts inorganic suspending agent, 0.002-0.004 parts stabilizer, 0.1-0.2 parts nucleating agent, and 120-140 parts water; the modified expandable graphite is a core-shell structure particle with expandable graphite as the core, and the shell material includes silicon dioxide, zirconium dioxide, and aluminum hydroxide.

2. The high flame-retardant expandable polystyrene according to claim 1, characterized in that, The method for preparing the modified expandable graphite includes the following steps: S1: Disperse expandable graphite in ethanol to form a suspension; S2: Tetraethyl orthosilicate is dissolved in anhydrous ethanol, water and catalyst are added, and the mixture is stirred to pre-hydrolyze to obtain a silicon source solution; Zirconium oxychloride is dissolved in a mixture of anhydrous ethanol and acetylacetone to obtain a zirconium source solution; the zirconium source solution is added dropwise to the silicon source solution under stirring, a surfactant template agent is added, and the mixture is stirred to form a SiO2-ZrO2 composite sol. S3: Under ultrasonic conditions, SiO2-ZrO2 composite sol was added dropwise to a suspension, heated and stirred in a water bath, aged, washed and dried, and then calcined at high temperature to obtain SiO2-ZrO2 coated expandable graphite. S4: Dissolve aluminum nitrate in water to form an aluminum source solution. Then add the SiO2-ZrO2-coated expandable graphite to the silicon source solution, add ammonia water, adjust the pH to 8.5-9.5, stir the reaction, centrifuge, wash and dry, and then heat treat to obtain the final product.

3. The high flame-retardant expandable polystyrene according to claim 2, characterized in that, The surfactant template agent in step S2 is selected from hexadecyltrimethylammonium bromide. The high-temperature calcination conditions in step S3 are: heating to 500-600℃ at a rate of 2-5℃ / min and holding at that temperature for 2-3 hours.

4. The high flame-retardant expandable polystyrene according to claim 1, characterized in that, The dispersant is hydroxyalkylphosphonate methacrylate.

5. The high flame-retardant expandable polystyrene according to claim 4, characterized in that, The preparation method of the hydroxyalkyl phosphonate methacrylate includes the following steps: Hydroxyethylphosphonic acid and methacrylic acid were mixed in a molar ratio of 1:(1.1-1.5) and added to toluene as reactants. Then, 0.1-0.4 wt% hydroquinone and 0.5-1 wt% p-toluenesulfonic acid were added. The mixture was heated to 100-110℃ under an inert gas atmosphere and stirred for 6-12 h to obtain a reaction solution. After the reaction solution is cooled, sodium bicarbonate solution is added, stirred to neutralize, allowed to stand and separate into layers, and the organic phase is dried with anhydrous magnesium sulfate. After filtration, it is evaporated under reduced pressure to obtain the final product.

6. The high flame-retardant expandable polystyrene according to claim 1, characterized in that, The organic suspending agent is hydroxyethyl cellulose, and the inorganic suspending agent is active calcium phosphate.

7. The method for preparing high flame-retardant expandable polystyrene according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Mix the modified expandable graphite with the dispersant until a uniform mixture is formed; (2) Add water to the reactor, then add organic suspending agent, inorganic suspending agent and mixture, stir evenly and then add styrene, flame retardant, initiator, stabilizer and nucleating agent to obtain suspension; (3) The suspension is heated to 88-90℃ and kept at that temperature for 5-6 hours to obtain a blend; (4) Add foaming agent to the blend, heat to 118-130℃, react for 3-5 hours, cool down and discharge to obtain the product.

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