Expandable polystyrene with low flash fire risk and preparation method thereof

Abstract

The present application relates to the technical field of foaming materials, and in particular to an expandable polystyrene with low flash fire risk and a preparation method thereof. An expandable polystyrene with low flash fire risk, the raw materials of which include styrene, a nucleating agent, an initiator, a suspending agent, sodium dodecylbenzene sulfonate, sodium phosphate, a brominated flame retardant, hydroxyethyl cellulose, a foaming agent, a plasticizer, zinc stearate, glyceryl stearate, an antistatic agent, and pure water. The obtained expandable polystyrene is matured in a 25°C environment for 24 hours and then molded. After molding, in a 25°C environment, no flash fire will occur for 18-24 hours, which greatly reduces the risk of fire.

Description

Technical Field

[0001] The present application relates to the technical field of foaming materials, and in particular to an expandable polystyrene with low flash fire risk and a preparation method thereof. Background Art

[0002] Expandable polystyrene is a polystyrene product with a foaming agent added, abbreviated as "EPS". It appears as colorless and transparent beads.

[0003] Expandable polystyrene has been widely used in daily life, agriculture, transportation, military industry, aerospace industry, etc. due to its excellent and long-lasting thermal insulation, unique cushioning and shock resistance, anti-aging and waterproof properties, especially in the fields of construction, packaging, electronic and electrical products, ships, vehicles and aircraft manufacturing. For example, household appliances such as televisions, refrigerators, washing machines, air conditioners, refrigeration systems, civilian light industrial products such as electronic instruments, precision instruments, glassware, ceramic products, art crafts, fish fillets for marine aquaculture, seafood freezing, vegetable preservation, incubators, cold storage, refrigerated trucks, railways, municipal construction, etc., all of which are inseparable from EPS sheets and packaging products.

[0004] Flash fire refers to the phenomenon that the vapor of flammable liquids, when mixed with air to a certain concentration, will flash and burn when exposed to open flames. Or when flammable solids are heated to a certain temperature, they will flash and burn when exposed to open flames. For expandable polystyrene, the low-boiling hydrocarbon foaming agent contained in it may evaporate when heated and mix with oxygen in the air to form flammable gas. When this gas reaches a certain concentration range and encounters open flames or high temperatures, flash fire may occur.

[0005] Existing expandable polystyrene raw materials are pre-expanded, aged for 8-24 hours in an environment above 20°C, and then molded. 24 hours after molding, flash fire is still very likely to occur, posing a huge safety hazard. Summary of the invention

[0006] In order to reduce the flash fire risk of expandable polystyrene, the present application provides an expandable polystyrene with low flash fire risk and a preparation method thereof.

[0007] In a first aspect, the present application provides an expandable polystyrene with low flash fire risk, which adopts the following technical solution.

[0008] The invention discloses an expandable polystyrene with low flash fire risk. The raw materials of the expandable polystyrene include styrene and the following raw materials in weight percentage: 0.1-0.3% of a nucleating agent, 0.51-1.05% of an initiator, 0.1-0.4% of a suspending agent, 0.001-0.003% of sodium dodecylbenzene sulfonate, 0.05-0.07% of sodium phosphate, 0.8-1.5% of a brominated flame retardant, 0.001-0.002% of hydroxyethyl cellulose, 5.5-8% of a foaming agent, 0.1-0.5% of a plasticizer, 0.25-0.33% of zinc stearate, 0.15-0.30% of glyceryl stearate, 0.01-0.02% of an antistatic agent and 90-120% of pure water.

[0009] By adopting the above technical scheme, the present application adds brominated flame retardants and adjusts the ratio of various functional additives to styrene. After the raw materials are pre-expanded, the expandable polystyrene is aged for 24 hours in an environment above 20°C and then molded. After molding, there is no flash fire phenomenon within 18-24 hours.

[0010] Furthermore, the brominated flame retardant is one or more of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether.

[0011] In some specific embodiments, the brominated flame retardant is any one of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether.

[0012] In some specific embodiments, the brominated flame retardant is a combination of any two of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether, such as decabromodiphenyl ethane and octabromoether in a weight ratio of 1:1, octabromoether and decabromodiphenyl ether in a weight ratio of 2:3, etc.

[0013] In some specific embodiments, the brominated flame retardant is a combination of any three of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether, such as octabromoether, methyl octabromoether, and brominated styrene-butadiene-styrene block copolymer in a weight ratio of 1:1:1.

[0014] In some specific embodiments, the brominated flame retardant is a combination of any four of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether, such as octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether in a weight ratio of 1:2:1:1.

[0015] In some specific embodiments, the brominated flame retardant is a combination of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether, such as decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether in a weight ratio of 1:1:3:1:2.

[0016] Furthermore, the brominated flame retardant is subjected to microencapsulation modification treatment, and the treatment method is as follows:

[0017] 1) Dissolve starch in water, heat and stir to form a uniform starch solution;

[0018] 2) Dispersing the brominated flame retardant in water to form an aqueous phase;

[0019] 3) Add the polyurethane prepolymer and starch solution into the aqueous phase containing the flame retardant and disperse them by shearing to form a stable emulsion;

[0020] 4) Add curing agent to the emulsion to react and form polyurethane-starch composite wall material, which is wrapped around the brominated flame retardant particles to complete the microencapsulation process;

[0021] 5) After the microencapsulation reaction is completed, the unreacted raw materials and solvent are removed by centrifugation, washing and drying to obtain dry microencapsulated brominated flame retardant.

[0022] By adopting the above technical scheme, starch and polyurethane are compounded as wall materials, brominated flame retardants are used as core materials, NCO groups in polyurethane prepolymers react with curing agents, and at the same time, hydroxyl groups in starch molecules react with curing agents and active groups in prepolymers to form polyurethane-starch composite wall materials, which are wrapped around flame retardant particles to prepare microencapsulated brominated flame retardants.

[0023] Among them, starch molecules can be degraded into carbonized products at high temperatures, and the carbonized products can form an insulating film at high temperatures, thereby achieving a flame retardant effect. Polyurethane can firmly adhere to the surface of expandable polystyrene to form an effective flame retardant layer. The combination of the two can improve the processability of encapsulated brominated flame retardants and their binding force with polystyrene, and improve the uniformity of the distribution of flame retardants in the styrene matrix, thereby improving the anti-flash effect of expandable polystyrene. In addition, microencapsulation treatment can also improve the durability of flame retardants, allowing flame retardants to effectively act on expandable polystyrene for a long time.

[0024] Furthermore, the weight ratio of the starch to the polyurethane prepolymer is 3:(5-7).

[0025] By adopting the above technical scheme, the ratio of starch to polyurethane prepolymer in the wall material is regulated. Within the ratio range specified in the present application, the composite effect of the two is better, that is, the combination of the microencapsulated flame retardant and polystyrene can be guaranteed, and the mechanical properties of the microcapsule wall can be guaranteed, so that the microencapsulated flame retardant can be suitable for high and low temperature environments and is not easy to break during processing.

[0026] Furthermore, the concentration of the starch solution may be 8-12% w / v.

[0027] By adopting the above technical solution, the mechanical properties of the wall material are improved without causing processing difficulties due to excessive concentration.

[0028] Furthermore, the polyurethane prepolymer is a polyurethane terminated prepolymer having a double bond at the end group.

[0029] By adopting the above technical scheme, the prepolymer containing double bonds at the end group has better binding property with styrene, which can significantly improve the binding property between the polyurethane prepolymer and styrene, thereby preparing expandable polystyrene with better performance.

[0030] Furthermore, based on the total weight of the initiator, the initiator includes 2-4 parts of benzoyl peroxide, 0.5-1.5 parts of tert-butyl perbenzoate, 0.1-1 parts of tert-amyl peroxide-2-ethylhexyl carbonate, and 2.4-4 parts of diisopropylbenzene peroxide.

[0031] Furthermore, the suspending agent is calcium phosphate.

[0032] In a second aspect, the present application provides a method for preparing expandable polystyrene with low flash fire risk, using the following technical solution.

[0033] A method for preparing expandable polystyrene with low flash fire risk, characterized in that it comprises the following steps:

[0034] S1. According to the raw material ratio, styrene, a low nucleating agent, an initiator, and a plasticizer are mixed to obtain a mixture;

[0035] S2. Add pure water to mixture 1 to obtain mixture 2;

[0036] S3. Add part of the suspending agent, emulsifier, sodium phosphate, hydroxyethyl cellulose to the mixture and mix well to obtain a mixture of three;

[0037] S4. The mixture was heated to 85-90°C and kept at this temperature for 3.5-4h, and the particles were allowed to sink;

[0038] S5. Continue to maintain constant temperature for 5-6 hours, add suspending agent to the system to stabilize the suspension system;

[0039] S6. A protective gas is introduced into the suspension system and a foaming agent is added;

[0040] S7. The reaction system is heated to 115-130°C, the system pressure is 0.8-0.9MPa, and the temperature is kept for 2-4h;

[0041] S8. Lowering the temperature of the reaction system to 30-40°C;

[0042] S9. Dehydrating and drying the reaction product beads;

[0043] S10. The dried beads are surface treated with zinc stearate, glyceryl stearate and an antistatic agent to obtain expandable polystyrene with low flash fire risk.

[0044] Furthermore, the weight ratio of the suspending agent added to S3 and S5 is (2-4):1.

[0045] By adopting the above technical solution and combining a specific production process with a raw material ratio, expandable polystyrene with a low flash fire risk can be obtained.

[0046] In summary, this application has the following beneficial effects:

[0047] 1. In this application, the expandable polystyrene obtained by adding brominated flame retardants and adjusting the ratio of various functional additives to styrene is aged in an environment of 25°C for 24 hours and then formed. After forming, it is placed in an environment of 25°C for 18-24 hours without flash fire, which greatly reduces the risk of fire;

[0048] 2. The present application uses a compound of starch and polyurethane as the wall material to microencapsulate the flame retardant. The obtained expandable polystyrene is matured in an environment of 25°C for 24 hours and then formed. After forming, it is placed in an environment of 25°C and will not flash over for 18-20 hours, further reducing the risk of flash over. DETAILED DESCRIPTION

[0049] The present application is further described in detail below in conjunction with embodiments.

[0050] Raw materials and intermediate preparation examples

[0051] raw material

[0052] The raw materials in the examples of this application can be obtained from the market:

[0053] Styrene, analytical grade;

[0054] Nucleating agent, low molecular weight PE wax, Thailand SCG Chemical LP1020P;

[0055] Blowing agent, pentane;

[0056] Suspension agent, calcium phosphate;

[0057] Plasticizer, xylene and white oil in a weight ratio of 1:2;

[0058] Curing agent, amine compound curing agent;

[0059] Polyether polyol, N-210, technical grade.

[0060] Preparation Example

[0061] Preparation Example 1

[0062] A polyurethane prepolymer, the preparation method of which is:

[0063] 8 kg of polyether polyol was vacuum dehydrated at 120 ° C for 2 hours, then cooled to 50 ° C, 22 kg of 2,4-toluene diisocyanate was added, and the temperature was raised to 80 ° C for reaction for 2 hours. When the free -NCO was controlled to 4%, 13 kg of hydroxyethyl methacrylate was added dropwise, and the temperature was kept at 80 ° C for reaction for 3 hours to obtain a polyurethane prepolymer.

[0064] Preparation Example 2

[0065] A microencapsulated brominated flame retardant, the preparation method of which is as follows:

[0066] 1) Dissolve 3 kg of starch in water, heat and stir to form a uniform starch solution with a concentration of 10% w / v;

[0067] 2) Disperse 10 kg of brominated flame retardant in water to form an aqueous phase;

[0068] 3) 6 kg of the polyurethane prepolymer obtained in Preparation Example 1 and the starch solution obtained in step 1) are added to the aqueous phase containing the flame retardant obtained in step 2) and dispersed by shearing to form a stable emulsion;

[0069] 4) Add 0.7 kg of curing agent to the emulsion obtained in step 3) to react and form a polyurethane-starch composite wall material, which is wrapped around the brominated flame retardant particles to complete the microencapsulation process;

[0070] 5) After the microencapsulation reaction is completed, the unreacted raw materials and solvent are removed through the steps of centrifugation, washing and drying to obtain dry microencapsulated brominated flame retardant.

[0071] Preparation Example 3

[0072] Different from Preparation Example 2, the amount of polyurethane prepolymer used in Preparation Example 3 is 5 kg.

[0073] Preparation Example 4

[0074] Different from Preparation Example 2, the amount of polyurethane prepolymer used in Preparation Example 4 is 7 kg.

[0075] Preparation Example 5

[0076] Different from Preparation Example 2, the amount of polyurethane prepolymer used in Preparation Example 5 is 4 kg.

[0077] Preparation Example 6

[0078] Different from Preparation Example 2, the amount of polyurethane prepolymer used in Preparation Example 6 is 8 kg.

[0079] Preparation Example 7

[0080] Different from Preparation Example 2, the concentration of the starch solution in Preparation Example 7 is 8% w / v.

[0081] Preparation Example 8

[0082] Different from Preparation Example 2, the concentration of the starch solution in Preparation Example 8 is 12% w / v.

[0083] Preparation Example 9

[0084] Different from Preparation Example 2, the concentration of the starch solution in Preparation Example 9 is 14% w / v.

[0085] Preparation Example 10

[0086] A microencapsulated brominated flame retardant, the preparation method of which is as follows:

[0087] 1) Dissolve 9 kg of starch in water, heat and stir to form a uniform starch solution with a concentration of 10% w / v;

[0088] 2) Disperse 10 kg of brominated flame retardant in water to form an aqueous phase;

[0089] 3) adding the starch solution obtained in step 1) to the aqueous phase containing the flame retardant obtained in step 2) and dispersing by shearing to form a stable emulsion;

[0090] 4) Add 0.7 kg of cross-linking agent formaldehyde to the emulsion obtained in step 3) to react and form starch wall material, which is wrapped around the brominated flame retardant particles to complete the microencapsulation process;

[0091] 5) After the microencapsulation reaction is completed, the starch wall material is further cross-linked and stabilized by heating and curing, and then the unreacted raw materials and solvents are removed through steps such as centrifugation, washing and drying to obtain dry microencapsulated brominated flame retardants.

[0092] Preparation Example 11

[0093] A microencapsulated brominated flame retardant, the preparation method of which is as follows:

[0094] 1) Disperse 10 kg of brominated flame retardant in water to form an aqueous phase;

[0095] 2) adding 9 kg of the polyurethane prepolymer obtained in Preparation Example 1 to the aqueous phase containing the flame retardant obtained in step 1), and dispersing by shearing to form a stable emulsion;

[0096] 3) Add 0.7 kg of curing agent to the emulsion obtained in step 3) to react and form a polyurethane-starch composite wall material, which is wrapped around the brominated flame retardant particles to complete the microencapsulation process;

[0097] 4) After the microencapsulation reaction is completed, the unreacted raw materials and solvent are removed through the steps of centrifugation, washing and drying to obtain dry microencapsulated brominated flame retardant.

[0098] Example

[0099] Examples 1-3

[0100] A low flash fire risk expandable polystyrene, the preparation method of which is:

[0101] S1. According to the raw material ratio, styrene was added to the reactor, and then a low nucleating agent, an initiator, and a plasticizer were added, and stirred at room temperature for 30 minutes to obtain a mixture;

[0102] S2. Pure water was added to the reactor to obtain a mixture of two;

[0103] S3. Add 1 / 4 of the suspending agent, emulsifier, sodium phosphate, hydroxyethyl cellulose to the reactor and stir for 30 minutes to obtain a mixture of three;

[0104] S4. The suspension system in the reactor was heated to 90 ° C with steam and kept at a constant temperature for 3.5 h, and the particles sank;

[0105] S5. Continue to maintain constant temperature for 5 hours and 20 minutes, add the remaining suspending agent to the system to stabilize the suspension system;

[0106] S6. Seal the sampling port of the reactor, fill the reactor with nitrogen, check the sealing of the system, and start adding the foaming agent after there is no leakage;

[0107] S7. The reaction system was heated to 120°C, the system pressure was 0.8MPa, and the temperature was kept for 3h;

[0108] S8. The temperature of the reaction system is lowered to 25°C;

[0109] S9. Dehydrating and drying the reaction product beads;

[0110] S10. The dried expandable polystyrene beads are added with zinc stearate and stearic acid monoglyceride in a ribbon mixer, sprayed with an antistatic agent, and coated for 10 minutes to obtain an expandable polystyrene raw material with a low flash fire risk.

[0111] S11. Expandable polystyrene raw materials are packed in multi-layer nylon composite polyethylene bags and stored in a cool and ventilated place.

[0112] Table 1 Raw material ratio table of Example 1-3 (g)

[0113]

[0114] Among them, the nucleating agent is low molecular weight PE wax; the initiator is benzoyl peroxide, tert-butyl perbenzoate, tert-amyl peroxide-2-ethylhexyl carbonate, and diisopropylbenzene peroxide in a weight ratio of 3:1:0.5:3; the suspending agent is calcium phosphate; the plasticizer is xylene and white oil in a weight ratio of 1:2; the brominated flame retardant is decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether in a weight ratio of 1:1:3:1:2.

[0115] Embodiment 4-13

[0116] Different from Example 2, the brominated flame retardants in Examples 4-13 were treated by the methods in Preparation Examples 2-11 to obtain microencapsulated brominated flame retardants.

[0117] Comparative Example

[0118] Comparative Example 1

[0119] Different from Example 1, the amount of initiator used in Comparative Example 1 is 230 g.

[0120] Comparative Example 2

[0121] Different from Example 1, the amount of initiator used in Comparative Example 2 is 600 g.

[0122] Comparative Example 3

[0123] Different from Example 1, in Comparative Example 3, an equal amount of hydroxyethyl cellulose was used to replace sodium dodecylbenzene sulfonate.

[0124] Comparative Example 4

[0125] Different from Example 1, in Comparative Example 4, an equal amount of sodium dodecylbenzene sulfonate replaces hydroxyethyl cellulose.

[0126] Performance Testing

[0127] The raw materials obtained in the examples and comparative examples were pre-fermented, aged for 24 hours in an environment of 25°C, and then molded. After molding, they were placed in an environment of 25°C, and the density was 30kg / m 3 , record the occurrence of flash fire, and the results are shown in Table 2.

[0128] Table 2 Performance test results

[0129]

[0130] Combining the embodiments and comparative examples, and in combination with Table 2, it can be seen that the expandable polystyrene obtained in the embodiments has no flash fire for 24 hours at 25°C after ripening and molding, while the comparative example has flash fire for 24 hours but no flash fire for 48 hours. This indicates that the expandable polystyrene obtained in the present application can be kept at 25°C for 24 hours without flash fire, thereby greatly reducing the risk of fire.

[0131] Combining Example 2 with Example 4-13 and Table 2, it can be seen that the expandable polystyrene obtained in Example 4-13 has no flash fire for 20 hours at 25°C after ripening and molding, which indicates that microencapsulation of the flame retardant can further reduce the flash fire risk of the expandable polystyrene. This may be because the microencapsulated flame retardant can be more evenly distributed in the polystyrene matrix and well combined with the polystyrene matrix, which greatly improves the effect of the flame retardant. In addition, the capsule wall material also has a certain effect of reducing the risk of flash fire. The combined effect further delays the time for the expandable polystyrene to flash.

[0132] In combination with Examples 4-13 and Table 2, it can be seen that the expandable polystyrene obtained in Example 4-11 has no flash fire for 18 hours after ripening and molding at 25°C, which shows that the use of starch and polyurethane compounded as wall materials to prepare microencapsulated flame retardants can further reduce the risk of flash fire. This may be because starch molecules can be degraded into carbonized products at high temperatures, and the carbonized products can form an insulating film at high temperatures, thereby achieving a flame retardant effect. Polyurethane can firmly adhere to the surface of expandable polystyrene to form an effective flame retardant layer. After the two are compounded, the processability of the encapsulated bromine flame retardant and the binding force with polystyrene can be improved, and the uniformity of the distribution of the flame retardant in the styrene matrix can be improved, thereby improving the anti-flash effect of expandable polystyrene. In addition, microencapsulation treatment can also improve the durability of the flame retardant, so that the flame retardant can effectively act on the expandable polystyrene for a long time.

[0133] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. An expandable polystyrene with low flash fire risk, the raw material of which includes styrene, characterized in that: According to the weight percentage of styrene, the following raw materials are also included in weight percentage: nucleating agent 0.1-0.3%, initiator 0.51-1.05%, suspending agent 0.1-0.4%, sodium dodecylbenzene sulfonate 0.001-0.003%, sodium phosphate 0.05-0.07%, brominated flame retardant 0.8-1.5%, hydroxyethyl cellulose 0.001-0.002%, foaming agent 5.5-8%, plasticizer 0.1-0.5%, zinc stearate 0.25-0.33%, stearic acid glyceryl 0.15-0.30%, antistatic agent 0.01-0.02%, pure water 90-120%; The brominated flame retardant is subjected to microencapsulation modification treatment, and the treatment method is as follows: 1) Dissolve starch in water, heat and stir to form a uniform starch solution; 2) Dispersing the brominated flame retardant in water to form an aqueous phase; 3) Add the polyurethane prepolymer and starch solution into the aqueous phase containing the flame retardant and disperse them by shearing to form a stable emulsion; 4) Add curing agent to the emulsion to react and form polyurethane-starch composite wall material, which is wrapped around the brominated flame retardant particles to complete the microencapsulation process; 5) After the microencapsulation reaction is completed, the unreacted raw materials and solvent are removed by centrifugation, washing and drying to obtain dry microencapsulated brominated flame retardant.

2. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: The brominated flame retardant is one or more of decabromodiphenyl ethane, octabromoether, methyl octabromoether, brominated styrene-butadiene-styrene block copolymer, and decabromodiphenyl ether.

3. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: The weight ratio of the starch to the polyurethane prepolymer is 3:(5-7).

4. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: The concentration of the starch solution is 8-12% w / v.

5. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: The polyurethane prepolymer is a polyurethane terminated prepolymer with a double bond at the end group.

6. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: Based on the total weight of the initiator, the initiator includes 2-4 parts of benzoyl peroxide, 0.5-1.5 parts of tert-butyl perbenzoate, 0.1-1 parts of tert-amyl peroxide-2-ethylhexyl carbonate, and 2.4-4 parts of diisopropylbenzene peroxide.

7. The expandable polystyrene with low flash fire risk according to claim 1, characterized in that: The suspending agent is calcium phosphate.

8. A method for preparing expandable polystyrene with low flash fire risk according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. According to the raw material ratio, styrene, a nucleating agent, an initiator and a plasticizer are mixed to obtain a mixture; S2. Add pure water to mixture 1 to obtain mixture 2; S3. Add part of the suspending agent, emulsifier, sodium phosphate, hydroxyethyl cellulose to the mixture II and mix well to obtain a mixture III; S4. The mixture was heated to 85-90°C and kept at this temperature for 3.5-4h, and the particles were allowed to sink; S5. Continue to maintain constant temperature for 5-6 hours, add suspending agent to the system to stabilize the suspension system; S6. A protective gas is introduced into the suspension system and a foaming agent is added; S7. The reaction system is heated to 115-130°C, the system pressure is 0.8-0.9MPa, and the temperature is kept for 2-4h; S8. Lowering the temperature of the reaction system to 30-40°C; S9. Dehydrating and drying the reaction product beads; S10. The dried beads are surface treated with zinc stearate, glyceryl stearate and an antistatic agent to obtain expandable polystyrene with low flash fire risk.

9. The method for preparing expandable polystyrene with low flash fire risk according to claim 8, characterized in that: The weight ratio of the suspending agent added to S3 and S5 is (2-4):1.

Images