Preparation method of sepiolite synergistic flame retardant and application thereof in rubber

Abstract

The application relates to the technical field of flame retardants, and discloses a preparation method of a sepiolite synergistic flame retardant and application of the sepiolite synergistic flame retardant in rubber, wherein sepiolite itself contains non-halogen flame-retardant elements such as magnesium and silicon, has a fibrous structure, can inhibit the diffusion of oxygen, forms a protective layer to block the transmission of heat, the silicon-oxy group of a nitrogen-phosphorus-silicon flame retardant side chain is grafted with the hydroxyl group on the surface of sepiolite, so that the flame retardant forms intercalation or delamination structure between the silicate layers of sepiolite, the interfacial force between the flame retardant and sepiolite is enhanced, the two have good compatibility, the sepiolite synergistic flame retardant acts as a bridge and plays a reinforcing role in the crosslinking network structure between fillers and rubber matrix during the vulcanization of rubber, has a great reinforcing effect on rubber, effectively inhibits the penetration of oxygen molecules, and has good thermal stability and flame retardation in the combustion process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame retardants, in particular to a preparation method of sepiolite synergistic flame retardant and its application in rubber. BACKGROUND

[0002] Ethylene propylene diene rubber (EPDM) belongs to high-saturation non-crystalline rubber, has a main chain structure of saturated carbon chain, and unsaturated double bonds only exist in side chains, so that it has excellent heat aging performance, ozone resistance and insulation performance and other characteristics, and is widely used in automobile parts, aerospace components, heat-resistant and weather-resistant rubber pipes and other fields. However, the flame retardance of EPDM material products is poor, the oxygen index of pure rubber is only 19%, and almost no residual carbon is formed after burning, so it is difficult to meet the flame retardant requirements in many cases. In order to expand the application range of EPDM, it is necessary to improve the flame retardance of EPDM.

[0003] In recent years, many scholars have paid attention to the flame-retardant modification of EPDM. Patent No. CN115160575B discloses a flame-retardant ethylene propylene diene rubber and a preparation method thereof. A small molecule compound with a hydroxyl group is introduced into the molecular chain of EPDM, and is esterified and crosslinked with octavinylsilsesquioxane grafted with mercaptopropionic acid. At the same time, magnesium hydroxide, aluminum oxide, boron nitride and other materials are added to avoid the deterioration of the mechanical properties of the rubber material. The silicon dioxide generated by octavinylsilsesquioxane under high-temperature combustion can form a thermal stable condensation barrier with boron nitride sheet, which is used for heat and mass transfer to protect the rubber matrix from further burning and improve the flame retardant effect of the product. However, the number of hydroxyl groups on EPDM is limited, which affects the crosslinking of the rubber matrix. The flame-retardant efficiency of metal oxides such as magnesium hydroxide is low, and a large amount of addition is required to achieve the flame-retardant effect, which limits the dispersion effect in the rubber matrix, and then the agglomeration becomes the stress concentration point of the rubber matrix, affecting the mechanical properties of the product and limiting its application field.

[0004] The present application introduces a small molecule of nitrogen-phosphorus-silicon flame retardant, the siloxyl group of which is grafted with a large number of hydroxyl active groups on the surface of sepiolite to form a delamination structure, and then vulcanized with EPDM to obtain a sepiolite synergistic nitrogen-phosphorus-silicon flame-retardant rubber. The mechanical properties are enhanced, and the flame-retardant performance is also improved. SUMMARY

[0005] The technical problem solved by the present application is to provide a preparation method of sepiolite synergistic flame retardant and its application in rubber, which solves the problem of poor rubber flame retardance.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A preparation method of sepiolite synergistic flame retardant, the preparation method comprising the following steps: adding a mixed solvent of ethanol and water into a reaction flask, adding a small molecule compound with a structure formula of nitrogen phosphorus silicon flame retardant, stirring hydrolysis, ultrasonic vibration 20-40 min, adding acidified sepiolite, stirring reaction, after the reaction, cooling, deionized water washing, sepiolite synergistic flame retardant is obtained.

[0008] Further, the mass of the nitrogen phosphorus silicon flame retardant is 500-800% of the mass of the acidified sepiolite.

[0009] Further, the reaction temperature is 70-90℃, and the reflux time is 4-8h.

[0010] Further, the preparation method of the nitrogen phosphorus silicon flame retardant comprises the following steps:

[0011] (1) adding diethanolamine and 37% formaldehyde aqueous solution into a flask equipped with a thermometer and a reflux condenser, stirring uniformly, reacting at 35-50℃ for 1-3h, then increasing the temperature to 70-90℃, removing the water generated in the reaction under reduced pressure, cooling to 55-65℃, slowly adding diphenyl phosphite, and continuing to react for 2-5h, concentrating, distilling, and obtaining bis-hydroxyethyl diphenyl phosphate. The preparation process is as follows:

[0012]

[0013] (2) adding bis-hydroxyethyl diphenyl phosphate and chloroform into a flask equipped with a thermometer and a reflux condenser, stirring and dispersing, adding dichlorosulfoxide and chloroform dropwise at 0-10℃, reacting at 20-35℃ for 1-2h, then increasing the temperature to 50-70℃ for 4-6h, filtering, adding ethanol, refluxing and dissolving, cooling and crystallizing, and obtaining bis-chloroethyl diphenyl phosphate. The preparation process is as follows:

[0014]

[0015] (3) under ice water bath, adding KH550, triethylamine and tetrahydrofuran into a flask equipped with a thermometer and a reflux condenser, stirring and dissolving, adding bis-chloroethyl diphenyl phosphate, stirring and reacting, after the reaction, filtering, concentrating the filtrate, and purifying by column to obtain the nitrogen phosphorus silicon flame retardant. The preparation process is as follows:

[0016]

[0017] Further, the mass of diethanolamine and formaldehyde in step (1) is 39-51% and 31-38% of the mass of diphenyl phosphite, respectively.

[0018] Further, the mass of dichlorosulfoxide in step (2) is 82-98% of the mass of bis-hydroxyethyl diphenyl phosphate.

[0019] Further, the mass of KH550 and triethylamine in the step (3) is 135%-155% and 48%-60% of the mass of the bis (chloroethyl) phosphate, respectively.

[0020] Further, the reaction temperature in the step (3) is 35-50 DEG C, and the reaction time is 5-10h.

[0021] An application of sepiolite synergistic flame retardant in rubber, adding EPDM, zinc oxide, stearic acid, sepiolite synergistic flame retardant, antioxidant, accelerator and auxiliary crosslinking agent into an open mill, and finally adding sulfur, mixing at a roll temperature of 40-50 DEG C to obtain a mixed rubber, vulcanizing on a flat vulcanizing machine at a vulcanizing temperature of 160-180 DEG C, a vulcanizing pressure of 12-16 MPa and a vulcanizing time of 10-20 min to obtain sepiolite flame-retardant rubber.

[0022] Further, the mass of the sepiolite synergistic flame retardant is 5-25% of the mass of the EPDM.

[0023] The application has the beneficial technical effects that:

[0024] Diphenyl phosphite, diethanolamine and aqueous formaldehyde solution are reacted to obtain bis (hydroxyethyl) diphenyl phosphate, which is chlorinated by dichlorosulfoxide to obtain bis (chloroethyl) diphenyl phosphate, which is then reacted with KH550 in the presence of triethylamine to obtain a nitrogen-phosphorus-silicon flame retardant, which is grafted with the hydroxyl groups on the surface of acidified sepiolite through the siloxyl groups on the surface of the nitrogen-phosphorus-silicon flame retardant to obtain a sepiolite synergistic flame retardant, which is finally mixed and vulcanized with EPDM to obtain sepiolite flame-retardant rubber.

[0025] Sepiolite itself contains non-halogen flame-retardant elements such as magnesium and silicon, has a fibrous structure, can inhibit the diffusion of oxygen, reduce thermal decomposition and volatilization, form a protective layer to block the transmission of heat; the phosphorus-based flame retardant generates dehydrated phosphoric acid when heated, which reacts with nitrogen-containing molecules to form P-O-P, P-N-P and other chemical bonds, which is conducive to the formation of coking carbon structure, thereby insulating the contact between the burning material and air, interrupting the chain reaction of combustion, and the nitrogen-containing compound generates inert gas when decomposed under heat, which dilutes the combustible gas and combustion-supporting gas, thereby forming an insulating protective film on the surface of the material and better playing the flame-retardant role; the siloxane of the silicon-based flame retardant forms a layered SiO2 when degraded, which has low heat release, thereby preventing the oxidation of the carbon layer, and the nitrogen-phosphorus-silicon flame retardant improves the stability of the carbon layer of the material and enhances the flame-retardant performance.

[0026] The siloxyl of the nitrogen-phosphorus-silicon flame retardant side chain is grafted with the hydroxyl on the surface of the sepiolite, so that the flame retardant forms an intercalation or delamination structure between the silicate layers of the sepiolite, the interfacial force between the flame retardant and the sepiolite is enhanced, and the two have good compatibility. The sepiolite cooperates with the flame retardant as a bridge to strengthen the crosslinked network structure between the filler and the rubber matrix during the rubber vulcanization process, effectively inhibits the penetration of oxygen molecules, and exhibits good thermal stability and flame retardant effect during the combustion process. DETAILED DESCRIPTION

[0027] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the properties. The endpoints of the ranges and the individual values are not to be understood as limited to the precise values recited as the exact dimensions are not critical unless expressly stated otherwise. The ranges, endpoints and individual values are understood to be approximate such that slight variations are to be expected. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. For compositions, percentages can be expressed as a weight / weight percent (wt / wt %) or a weight / volume percent (wt / vol %) unless otherwise specified. The percentages disclosed herein are understood to be approximate such that slight variations are to be expected.

[0028] Preparation of acidified sepiolite: mix sepiolite ore powder with 1 mol / L dilute hydrochloric acid at a solid-liquid mass ratio of 1 / 20, ultrasonically oscillate at 70°C for 2 h for acidification, take the suspension, wash with deionized water for 3-5 times, and obtain acidified sepiolite.

[0029] Example 1

[0030] (1) A flask equipped with a thermometer and a reflux condenser was added with 2.25 g of diethanolamine, 5.05 g of 37% concentration formaldehyde aqueous solution, and stirred uniformly, reacted at 45°C for 2 h, then warmed to 85°C, vacuumized to remove water generated in the reaction, cooled to 60°C, and slowly added with 5 g of diphenyl phosphite, and continuously reacted for 3 h, concentrated, and distilled to obtain bis-hydroxyethyl phosphoric acid diphenyl ester.

[0031] (2) A flask equipped with a thermometer and a reflux condenser was added with 4 g of bis-hydroxyethyl phosphoric acid diphenyl ester and chloroform, and stirred and dispersed, and 3.8 g of dichlorosulfoxide and chloroform was added dropwise at 5°C, reacted at 30°C for 2 h, then warmed to 65°C and reacted for 5 h, filtered, added with ethanol, dissolved by reflux, and cooled to crystallize to obtain bis-chloroethyl phosphoric acid diphenyl ester.

[0032] (3) Under ice water bath, a flask equipped with a thermometer and a reflux condenser was added with 4.3 g of KH550, 1.6 g of triethylamine and tetrahydrofuran, stirred and dissolved, added with 3 g of bis-chloroethyl phosphoric acid diphenyl ester, stirred and reacted, reacted at 35°C for 70 h, then filtered, concentrated the filtrate, and purified by column to obtain the nitrogen-phosphorus-silicon flame retardant.

[0033] (4) A mixed solvent of ethanol and water was added to a reaction flask, 2.5 g of nitrogen-phosphorus-silicon flame retardant was added, hydrolysis was stirred, ultrasonic oscillation was performed for 30 min, 0.4 g of acidified sepiolite was added, stirring reaction was performed, reflux was performed at 90°C for 8 h, cooling was performed, deionized water washing was performed, and sepiolite synergistic flame retardant was obtained.

[0034] (5) 100 g of EPDM rubber, 0.9 g of zinc oxide, 0.7 g of stearic acid, 5 g of sepiolite synergistic flame retardant, 1.1 g of antioxidant MB, 0.6 g of accelerator DCP, and 4 g of auxiliary crosslinking agent TAIC-70 were added to an open mill, and finally 1.5 g of sulfur was added, mixing was performed at a roll temperature of 50°C, a rubber mixture was obtained, vulcanization was performed on a flat vulcanization machine, the vulcanization temperature was 170°C, the vulcanization pressure was 13 MPa, the vulcanization time was 15 min, and a sepiolite flame-retardant rubber was obtained.

[0035] Example 2

[0036] (1) A flask equipped with a thermometer and a reflux condenser was charged with 7.5 g of diethanolamine, 4.5 g of a 37% formaldehyde aqueous solution, and stirring was performed, reaction was performed at 35°C for 3 h, then the temperature was increased to 75°C, water generated in the reaction was removed by vacuum pumping, the temperature was decreased to 60°C, 15 g of diphenyl phosphite was slowly added, and reaction was continued for 4 h, concentration was performed, and distillation was performed, and diphenyl bis-hydroxyethyl phosphate was obtained.

[0037] (2) A flask equipped with a thermometer and a reflux condenser was charged with 12 g of diphenyl bis-hydroxyethyl phosphate and chloroform, stirring was performed, 10.8 g of dichlorosulfoxide and chloroform were added dropwise at 0°C, reaction was performed at 30°C for 1.5 h, then the temperature was increased to 55°C, and reaction was continued for 4 h, filtration was performed, ethanol was added, reflux dissolution was performed, cooling crystallization was performed, and diphenyl bis-chloroethyl phosphate was obtained.

[0038] (3) Under an ice water bath, a flask equipped with a thermometer and a reflux condenser was charged with 11.6 g of KH550, 4.8 g of triethylamine, and tetrahydrofuran, stirring was performed, 8 g of diphenyl bis-chloroethyl phosphate was added, stirring reaction was performed, reaction was continued at 40°C for 9 h, filtration was performed, the filtrate was concentrated, column purification was performed, and a nitrogen-phosphorus-silicon flame retardant was obtained.

[0039] (4) A mixed solvent of ethanol and water was added to a reaction flask, 7 g of a nitrogen-phosphorus-silicon flame retardant was added, hydrolysis was stirred, ultrasonic oscillation was performed for 25 min, 0.9 g of acidified sepiolite was added, stirring reaction was performed, reflux was performed at 90°C for 5 h, cooling was performed, deionized water washing was performed, and sepiolite synergistic flame retardant was obtained.

[0040] (5) Into an open mill, 100 g of EPDM rubber, 1.2 g of zinc oxide, 0.7 g of stearic acid, 10 g of sepiolite synergistic flame retardant, 1.3 g of antioxidant MB, 0.6 g of accelerator DCP and 3.5 g of auxiliary crosslinking agent TAIC-70 were added, and finally 2.1 g of sulfur was added, and mixing was performed at a roll temperature of 45°C to obtain a rubber compound, which was vulcanized on a flat vulcanization machine at a vulcanization temperature of 165°C, a vulcanization pressure of 14 MPa and a vulcanization time of 12 min to obtain a sepiolite flame-retardant rubber.

[0041] Example 3

[0042] (1) Into a flask equipped with a thermometer and a reflux condenser, 9.5 g of diethanolamine, 23.5 g of a 37% formaldehyde aqueous solution were added, and stirred uniformly, and then reacted at 45°C for 3 h, and then the temperature was raised to 85°C, and water generated in the reaction was removed by vacuum pumping, and then the temperature was lowered to 60°C, and 24 g of diphenyl phosphite was slowly added, and then the reaction was continued for 5 h, and then concentrated and distilled to obtain bis-hydroxyethyl diphenyl phosphate.

[0043] (2) Into a flask equipped with a thermometer and a reflux condenser, 18 g of bis-hydroxyethyl diphenyl phosphate and chloroform were added, and stirred and dispersed, and then 16.2 g of dichloro sulfoxide and chloroform were added dropwise at 2°C, and then the reaction was continued at 25°C for 1.2 h, and then the temperature was raised to 65°C, and the reaction was continued for 6 h, and then filtered, and then ethanol was added, and then dissolved by reflux, and then cooled and crystallized to obtain bis-chloroethyl diphenyl phosphate.

[0044] (3) Under ice water bath, into a flask equipped with a thermometer and a reflux condenser, 20.1 g of KH550, 6.6 g of triethylamine and tetrahydrofuran were added, and stirred and dissolved, and then 13 g of bis-chloroethyl diphenyl phosphate was added, and then stirred and reacted at 50°C for 9 h, and then filtered, and then the filtrate was concentrated and purified by column to obtain a nitrogen-phosphorus-silicon flame retardant.

[0045] (4) Into a reaction flask, a mixed solvent of ethanol and water was added, and then 12 g of the nitrogen-phosphorus-silicon flame retardant was added, and then stirred and hydrolyzed, and then ultrasonic oscillation was performed for 40 min, and then 1.8 g of acidified sepiolite was added, and then stirred and reacted at 75°C for 6 h, and then cooled, and then washed with deionized water to obtain a sepiolite synergistic flame retardant.

[0046] (5) Into an open mill, 100 g of EPDM rubber, 1.5 g of zinc oxide, 0.82 g of stearic acid, 15 g of sepiolite synergistic flame retardant, 2 g of antioxidant MB, 0.7 g of accelerator DCP and 3 g of auxiliary crosslinking agent TAIC-70 were added, and finally 2.5 g of sulfur was added, and mixing was performed at a roll temperature of 40°C to obtain a rubber compound, which was vulcanized on a flat vulcanization machine at a vulcanization temperature of 175°C, a vulcanization pressure of 15 MPa and a vulcanization time of 20 min to obtain a sepiolite flame-retardant rubber.

[0047] Example 4

[0048] (1) A flask equipped with a thermometer and a reflux condenser was charged with 17.7 g of diethanolamine, 29.3 g of a 37% concentration formaldehyde aqueous solution, and stirred uniformly, and reacted at 45°C for 3 h, then warmed to 90°C, and vacuumed to remove water generated in the reaction, and cooled to 65°C, and slowly added with 35 g of diphenyl phosphite, and continued to react for 5 h, concentrated, and distilled to obtain bis-hydroxyethyl phosphoric acid diphenyl ester.

[0049] (2) A flask equipped with a thermometer and a reflux condenser was charged with 30 g of bis-hydroxyethyl phosphoric acid diphenyl ester and chloroform, and stirred to disperse, and added with 25.5 g of dichlorosulfoxide and chloroform dropwise at 10°C, and reacted at 30°C for 1 h, then warmed to 55°C to react for 5 h, filtered, added with ethanol, dissolved by reflux, and cooled to crystallize to obtain bis-chloroethyl phosphoric acid diphenyl ester.

[0050] (3) A flask equipped with a thermometer and a reflux condenser was charged with 35 g of KH550, 16.5 g of triethylamine, and tetrahydrofuran under ice water bath, and stirred to dissolve, and added with 25 g of bis-chloroethyl phosphoric acid diphenyl ester, and stirred to react, and reacted at 40°C for 8 h, then filtered, concentrated the filtrate, and purified by column to obtain a nitrogen-phosphorus-silicon flame retardant.

[0051] (4) A reaction flask was charged with a mixed solvent of ethanol and water, and added with 23 g of the nitrogen-phosphorus-silicon flame retardant, and stirred to hydrolyze, and ultrasonically vibrated for 40 min, and added with 3.1 g of acidified sepiolite, and stirred to react, and refluxed at 85°C for 8 h, then cooled, and washed with deionized water to obtain a sepiolite synergistic flame retardant.

[0052] (5) An open mill was charged with 100 g of ethylene propylene diene rubber, 1.4 g of zinc oxide, 0.8 g of stearic acid, 20 g of the sepiolite synergistic flame retardant, 3 g of antioxidant MB, 0.7 g of accelerator DCP, and 3.5 g of auxiliary crosslinking agent TAIC-70, and finally added with 1.5 g of sulfur, and mixed at a roll temperature of 45°C to obtain a rubber compound, and vulcanized on a flat vulcanizing machine at a vulcanization temperature of 180°C, a vulcanization pressure of 13 MPa, and a vulcanization time of 12 min to obtain a sepiolite flame-retardant rubber.

[0053] Example 5

[0054] (1) A flask equipped with a thermometer and a reflux condenser was charged with 4 g of diethanolamine, 7.6 g of a 37% concentration formaldehyde aqueous solution, and stirred uniformly, and reacted at 50°C for 2 h, then warmed to 80°C, and vacuumed to remove water generated in the reaction, and cooled to 65°C, and slowly added with 8 g of diphenyl phosphite, and continued to react for 3 h, concentrated, and distilled to obtain bis-hydroxyethyl phosphoric acid diphenyl ester.

[0055] (2) Add 6 g of bis-hydroxyethyl phosphoric acid diphenyl ester and chloroform into a flask equipped with a thermometer and a reflux condenser, stir and disperse, add 5.6 g of dichloro sulfoxide and chloroform dropwise at 6℃, react for 2 h at 25℃, then heat to 60℃ and react for 4 h, filter, add ethanol, dissolve by reflux, cool and crystallize to obtain bis-chloroethyl phosphoric acid diphenyl ester.

[0056] (3) Under ice water bath, add 4.5 g of KH550, 1.7 g of triethylamine and tetrahydrofuran into a flask equipped with a thermometer and a reflux condenser, stir and dissolve, add 3 g of bis-chloroethyl phosphoric acid diphenyl ester, stir and react, react for 9 h at 50℃, then filter, concentrate the filtrate, purify by column to obtain a nitrogen-phosphorus-silicon flame retardant.

[0057] (4) Add a mixed solvent of ethanol and water into a reaction flask, add 2.5 g of the nitrogen-phosphorus-silicon flame retardant, stir and hydrolyze, ultrasonic oscillation for 40 min, add 0.41 g of acidified sepiolite, stir and react, reflux at 85℃ for 8 h, then cool and wash with deionized water to obtain a sepiolite synergistic flame retardant.

[0058] (5) Add 100 g of ethylene propylene diene monomer rubber, 1.3 g of zinc oxide, 0.6 g of stearic acid, 25 g of the sepiolite synergistic flame retardant, 1 g of antioxidant MB, 0.6 g of accelerator DCP and 3.5 g of auxiliary crosslinking agent TAIC-70 into an open mill, finally add 2.5 g of sulfur, mix at a roll temperature of 50℃ to obtain a rubber compound, vulcanize on a flat plate vulcanizer, the vulcanization temperature is 160℃, the vulcanization pressure is 12 MPa, and the vulcanization time is 20 min to obtain a sepiolite flame-retardant rubber.

[0059] Comparative Example 1

[0060] The difference between this comparative example and Example 1 is that no sepiolite synergistic flame retardant is added in step (5), only 4.29 g of bis-hydroxyethyl phosphoric acid diphenyl ester and 0.71 g of acidified sepiolite are added, and other conditions are unchanged.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that only 5 g of the nitrogen-phosphorus-silicon flame retardant is added in step (5), no sepiolite synergistic flame retardant is added, and other conditions are unchanged.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that only 5 g of acidified sepiolite is added in step (5), no sepiolite synergistic flame retardant is added, and other conditions are unchanged.

[0065] Limiting oxygen index test: tested by an oxygen index tester. Cone calorimeter test: the thermal performance and smoke performance of the rubber are tested by a cone calorimeter, the irradiation power is 50 kW / m 2.

[0066]

[0067] The limiting oxygen index of pure ethylene-propylene-diene rubber is about 19%, which belongs to flammable material; it can be seen from the test data in the above table that the limiting oxygen index gradually increases with the increase of the amount of sepiolite synergistic flame retardant, and when the amount of sepiolite synergistic flame retardant is 25 parts, the limiting oxygen index reaches 30.2%, which belongs to the range of difficult-to-burn materials, indicating that the addition of sepiolite synergistic flame retardant in rubber plays an excellent flame retardant performance, because sepiolite itself contains magnesium, silicon and other non-halogen flame-retardant elements, has a fibrous structure, inhibits the diffusion of oxygen, reduces thermal decomposition and volatilization, forms a protective layer to block the transfer of heat, at the same time, nitrogen and phosphorus silicon flame retardants can form inert gas to dilute combustible gas when heated, which is beneficial to the formation of coking carbon structure, thereby improving the stability of the carbon layer of the material and enhancing the flame retardant performance.

[0068] The ignition time indicates the fire resistance of the material to some extent, and the ignition time of the composite material increases from 9.3s of the comparative example 3 to 21.7s of the example 5 with the increase of the amount of sepiolite synergistic flame retardant, indicating that the fire resistance of the material is greatly improved; the total smoke emission decreases from 7.5m 2 to 3.2m 2 of the example 5, indicating that the fire hazard of the material is reduced, and a better flame retardant effect is achieved.

[0069] Mechanical property test: the hardness of the sample was tested by using a Shore hardness tester.

[0070]

[0071] It can be seen from the test data in the above table that the Shore A hardness of the composite material increases with the increase of the amount of sepiolite synergistic flame retardant, and when the amount of sepiolite synergistic flame retardant is 25 parts, the Shore A hardness reaches 85.9, which is 12.9 units higher than that of the comparative example 2, and the mechanical property is significantly improved; this is because with the increase of the amount of sepiolite, the combined rubber around the sepiolite particles increases, which can fill the ethylene-propylene-diene rubber and has a great reinforcing effect on the rubber; the modified sepiolite synergistic flame retardant plays a bridging role between sepiolite and the rubber matrix, increases the crosslinking density of the composite rubber, and enhances the hardness of the rubber.

[0072] The above describes the preferred embodiments of the present application, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application, and all fall within the protection scope of the present application.

Claims

1. A process for the preparation of a synergistic sepiolite flame retardant, characterized by, The preparation method comprises the following steps: adding a mixed solvent of ethanol and water into a reaction flask, adding a nitrogen-phosphorus-silicon flame retardant with a structural formula of , stirring hydrolysis, ultrasonic oscillation for 20-40 min, adding acidified sepiolite, stirring reaction, cooling after reaction, deionized water washing, and obtaining sepiolite synergistic flame retardant; the reaction temperature is 70-90 DEG C, and the reflux time is 4-8 h. The preparation method of the nitrogen-phosphorus-silicon flame retardant comprises the following steps: (1) adding diethanolamine and 37% formaldehyde aqueous solution into a flask equipped with a thermometer and a reflux condenser, stirring uniformly, reacting at 35-50 DEG C for 1-3 h, then increasing the temperature to 70-90 DEG C, removing water generated in the reaction under reduced pressure, decreasing the temperature to 55-65 DEG C, and slowly adding diphenyl phosphite, continuing to react for 2-5 h, concentrating, and distilling to obtain dihydroxyethyl diphenyl phosphate; (2) adding dihydroxyethyl diphenyl phosphate and chloroform into a flask equipped with a thermometer and a reflux condenser, stirring and dispersing, adding dichloro sulfoxide and chloroform dropwise at 0-10 DEG C, reacting at 20-35 DEG C for 1-2 h, then increasing the temperature to 50-70 DEG C to react for 4-6 h, filtering, adding ethanol, refluxing and dissolving, cooling and crystallizing to obtain dichloroethyl diphenyl phosphate; (3) under ice water bath, adding KH550, triethylamine and tetrahydrofuran into a flask equipped with a thermometer and a reflux condenser, stirring and dissolving, adding dichloroethyl diphenyl phosphate, stirring and reacting, after the reaction, filtering, concentrating the filtrate, and purifying through a column to obtain the nitrogen-phosphorus-silicon flame retardant; The mass of the nitrogen-phosphorus-silicon flame retardant is 500-800% of the mass of the acidified sepiolite.

2. The method of claim 1, wherein the sepiolite synergistic flame retardant is prepared by the steps of: In the step (1), the mass of diethanolamine and formaldehyde is 39-51% and 31-38% of the mass of diphenyl phosphite respectively.

3. The method of claim 1, wherein the sepiolite synergistic flame retardant is prepared by the steps of: In the step (2), the mass of dichloro sulfoxide is 82-98% of the mass of dihydroxyethyl diphenyl phosphate.

4. The method of claim 1, wherein the sepiolite synergistic flame retardant is prepared by the steps of: In the step (3), the mass of KH550 and triethylamine is 135%-155% and 48%-60% of the mass of dichloroethyl diphenyl phosphate respectively.

5. The method for preparing the sepiolite synergistic flame retardant according to claim 1, characterized in that, In the step (3), the reaction temperature is 35-50 DEG C, and the reaction time is 5-10 h.

6. Use of the sepiolite synergistic flame retardant obtained by the process according to any one of claims 1 to 5 in rubber, characterized in that, Adding the ternary ethylene-propylene rubber, zinc oxide, stearic acid, sepiolite synergistic flame retardant, antioxidant, accelerator and auxiliary crosslinking agent into an open mill, and finally adding sulfur, mixing at 40-50 DEG C roll temperature to obtain a mixed rubber, and vulcanizing on a flat vulcanizing machine, wherein the vulcanizing temperature is 160-180 DEG C, the vulcanizing pressure is 12-16 MPa, and the vulcanizing time is 10-20 min to obtain the sepiolite flame-retardant rubber.

7. Use of the sepiolite synergistic flame retardant according to claim 6 in rubber, characterized in that, The mass of the sepiolite synergistic flame retardant is 5-25% of the mass of the ternary ethylene-propylene rubber.

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