Phosphate ester complex flame retardant and preparation method thereof

Abstract

The application discloses a phosphate ester composite flame retardant and a preparation method thereof, and relates to the technical field of flame retardants.The phosphate ester composite flame retardant is composed of phosphorus-nitrogen grafted coated network-like silicon dioxide powder, Co-MOF composite graphene oxide catalytic carrier and pentaerythritol phosphate ester.The phosphorus-nitrogen grafted coated network-like silicon dioxide powder is composed of network-like dispersing modifier, silicon dioxide, dopamine hydrochloride, phosphorus oxychloride and 4,4-diamino diphenyl methane.The phosphorus-nitrogen grafted coated network-like silicon dioxide powder and the pentaerythritol phosphate ester are filled on the Co-MOF composite graphene oxide catalytic carrier, the migration of components is effectively reduced, the thermal stability of the flame retardant system is enhanced, meanwhile, the compatibility and dispersibility in the epoxy resin matrix are improved, the three components synergistically act, the carbon residue layer after combustion is more dense and continuous, the isolation and protection effects can be better, and the flame retardant performance is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of flame retardants, and particularly relates to a phosphate ester composite flame retardant and a preparation method thereof. BACKGROUND

[0002] Epoxy resin has become one of important matrix materials for coating, electronic material and fiber reinforced composite material due to its excellent mechanical property, high adhesion strength, good heat resistance and high resistance, but epoxy resin is flammable when exposed to open flame, and releases a large amount of toxic gas in the combustion process, which seriously endangers human life and health; halogen-based flame retardants release toxic smoke and gas in the process of epoxy resin flame retardation, which poses a great threat to the environment, therefore, halogen-free flame retardants are gradually replacing halogen-containing flame retardants and becoming a new trend of epoxy resin flame retardants.

[0003] Adding phosphorus-based flame retardants has become one of the main ways to improve the flame retardant property of epoxy resin, and the advantages of the flame retardant lie in that the flame retardant effect is remarkable, the smoke emission is less, and the influence on the ecological environment is also small; the phosphorus-based flame retardant can also be used in the lubricating oil industry, and it can effectively enhance the fire resistance of lubricating oil, especially in harsh environments such as high temperature, high pressure, flammable and explosive, the use of lubricating oil containing the flame retardant can ensure the safe operation of the equipment and reduce the risk of fire; compared with the traditional halogen flame retardant, the application prospect of the phosphorus-based flame retardant is more broad, it can play a flame-retardant role in gas phase and condensed phase, in the gas phase process, the phosphorus-based compound generates PO· to quench H· and HO· and other free radicals, reduces the concentration of combustible gas generated during combustion to terminate the combustion chain reaction, in the condensed phase, the phosphorus-containing compound starts to decompose at a lower temperature to generate phosphoric acid and polyphosphoric acid and other substances, and the generated phosphoric acid substances cover the surface of the material, which not only can prevent the release of combustible gas, but also has the functions of heat insulation and oxygen insulation.

[0004] The existing technology mainly has the following problems:

[0005] The commonly used compound flame retardant system has poor compatibility with epoxy resin and other matrixes, is not conducive to uniform dispersion in the resin matrix, and the thermal stability of the organic components in the flame retardant system is generally easy to migrate in the resin matrix, thereby greatly limiting the play of the flame retardant property. SUMMARY

[0006] In view of the above situation, in order to overcome the defects of the prior art, the application provides a phosphate ester composite flame retardant, which comprises the following components in parts by weight: phosphorus-nitrogen grafted coated network silica powder 30-40 parts, Co-MOF composite graphene oxide catalyst carrier 10-20 parts, and pentaerythritol phosphate 10-20 parts.

[0007] The phosphorus-nitrogen grafting coated network silica powder comprises the following components in parts by weight: network dispersing modifier 20-25 parts, silica 60-75 parts, dopamine hydrochloride 10-15 parts, phosphorus oxychloride 3-6 parts, and 4,4-diaminodiphenyl methane 6-8 parts.

[0008] The Co-MOF composite graphene oxide catalytic carrier comprises the following components in parts by weight: Co-MOF 30-40 parts and graphene oxide 10-15 parts.

[0009] The preparation method of the phosphorus-nitrogen grafting coated network silica powder specifically comprises the following steps:

[0010] (1) 1 mol of KH550 and 1 mol of KH560 are added into a three-necked flask in a nitrogen atmosphere, and heated to 120-130 DEG C under magnetic stirring for 3-5 h, and then cooled to room temperature; the primary amine groups of KH550 and the epoxy groups of KH560 are subjected to an epoxy ring-opening reaction, and a network material with three alkoxy groups at two ends is synthesized, thereby obtaining a network dispersing modifier;

[0011] (2) 90 mL of anhydrous ethanol and 10 mL of water are added into a beaker, and then a hydrochloric acid solution is used to adjust the pH to 4.0; then the network dispersing modifier in step (1) is added, and stirred at 40-50 DEG C for 4-5 h; 6.0-7.5 g of silica powder is added into the modified solution, and the silica can form a dense barrier layer on the surface of the material under high temperature, thereby isolating oxygen and heat and preventing the spread of combustion; the temperature is raised to 60 DEG C, and the mixture is fully stirred for 4-5 h at a stirring speed of 500-600 rpm; after drying and crushing, the alkoxy groups at two ends of the network dispersing modifier are simultaneously grafted on different silica particles, a large number of silica particles are connected, and a network silica structure with a large overall particle size is formed; meanwhile, there is a certain gap between the silica particles, thereby reducing the adsorption and aggregation between the particles, effectively increasing the exchange interface of the flame-retardant system, and improving the flame-retardant performance of the silica, thereby obtaining network silica.

[0012] (3) Take 0.6-1.0 g of the network-like silica in step (2) and add it into 100 mL of Tris-HCl buffer solution, and ultrasonic treatment for 10-20 min. Then, add hydrochloric acid dopamine into 200 mL of Tris-HCl buffer solution and dissolve completely. Then, pour the network-like silica dispersion liquid into it, and ultrasonic treatment for 10-15 min. Put it into a water bath environment at 25℃, and magnetic stirring at a speed of 160-180 rpm for 6-12 h. Then, centrifugal treatment for 2 times, centrifugal speed of 7000-8000 rpm, the first centrifugal time of 15 min, and the second centrifugal time of 10 min. The precipitate is freeze-dried, ground, and the polydopamine is wrapped with a layer of "nanosuit" with rich o-diphenol groups on the surface of the silica particles, which has excellent adhesion and film-forming property, can be used for further modification and functionalization, can improve the compatibility and dispersibility in the epoxy resin matrix, and significantly improves the thermal stability. The polydopamine coating forms a protective layer in the combustion process, which can isolate oxygen and heat, thereby interrupting the combustion process and reducing the generation of smoke, and polydopamine@network-like silica is obtained.

[0013] (4) Take 0.5-1.0 g of the polydopamine@network-like silica in step (3) and add it into a 250 mL three-necked flask with 0.3-0.6 g of phosphorus oxychloride liquid, 50 mL of THF and 0.3 g of triethylamine liquid. Ultrasonic treatment for 0.5-1 h at 25℃. Then, dissolve 0.6-0.8 g of 4,4-diaminodiphenyl methane solid in 20 mL of THF, and slowly drop it into the three-necked flask within 1 h. Put it into room temperature for 24 h. The product is washed with THF and deionized water in sequence, and dried. By grafting phosphorus and nitrogen elements on the surface of the polydopamine@network-like silica, the thermal stability and flame retardant property of the composite are improved. The polydopamine@network-like silica is effectively attached to the surface of the epoxy resin matrix, which isolates the combustible gas and heat from the outside into the matrix. The phosphorus and nitrogen small molecules will degrade first when heated, which effectively promotes the dehydration of the epoxy resin matrix to carbon. The protective layer formed by the combustion of the silica particles cooperates with the protective layer to block the release of heat and smoke, and the phosphorus and nitrogen grafted network-like silica powder is obtained.

[0014] Preferably, in step (2), the amount of network-like dispersion modifier added is 2.0-2.5 g. The alkoxyl groups at both ends can react with the active hydroxyl groups on the surface of the silica to achieve graft modification of the silica.

[0015] Preferably, in step (3), the amount of hydrochloric acid dopamine added is 1.0-1.5 g. The hydrochloric acid dopamine self-polymerizes to form a polydopamine protective layer, and the outer layer is arranged with uniformly distributed hydroxyl groups.

[0016] The application further provides a preparation method of the phosphate ester composite flame retardant, and specifically comprises the following steps:

[0017] S1, 70mL of concentrated sulfuric acid with a mass fraction of 98% is added into a 1000mL beaker under ice bath, 3.0g of graphite powder and 1.5g of sodium nitrate are added after stirring, the temperature is controlled to be 0-4℃, fully stirred, 9.0g of potassium permanganate is slowly added, then the temperature is increased to 40℃, the reaction time is 10-30min, then the above solution is slowly added into 140mL of deionized water, the temperature is quickly increased to 98℃, the reaction is stopped after 15min, cooling, then 15mL of hydrogen peroxide solution and 420mL of deionized water are added, filtration, centrifugation, washing, drying, and the graphene oxide can be used as a flame retardant additive, and the unique two-dimensional sheet structure can promote the formation of a dense and continuous carbon layer in the combustion process, so as to isolate heat transfer and gas exchange with the outside, and obtain the graphene oxide;

[0018] S2, the cobalt acetate tetrahydrate powder, 94.0mg of Fbtx and 60.0mg of H2dcpa are added into 7mL of deionized water, stirred for 0.5-1h, then transferred into a reaction kettle lined with polytetrafluoroethylene, the temperature is controlled to be 160-170℃, the reaction time is 48-72h, a new cobalt-based MOF material is synthesized by using the mixed ligand of cobalt salt, Fbtx and H2dcpa through a hydrothermal method, which has good thermal stability and adsorption, can maintain structural stability at high temperature, adsorb harmful gases and smoke generated in combustion, reduce the release of toxic gases in the fire, the transition metal cobalt has catalytic performance, can promote the carbonization reaction in the combustion process, form a more stable carbon layer, so as to isolate oxygen and heat, slow down the combustion speed, and obtain the Co-MOF;

[0019] S3, the graphene oxide in step S1 and the Co-MOF in step S2 are poured into 100-200mL of methanol solution, ultrasonic dispersion treatment is performed for 30-50min, then stirring is performed for 1-2h, static precipitation is performed, filtration and washing are performed, drying is performed, the Co-MOF is uniformly distributed on the surface of the graphene oxide and is combined tightly, the carbon layer formed by combustion of the composite carrier is dense and maintains a certain geometric shape and is not easy to fall off, and the carbon layer covering degree is more dense and more wide, meanwhile, in the composite carrier, the graphene oxide can also promote the rapid carbonization of the polymer and produce a plurality of non-combustible gases when the polymer is decomposed under heat, the gases can isolate oxygen and combustible gases from contacting, and block the continuous combustion condition, so as to play a flame retardant role, and obtain the Co-MOF composite graphene oxide catalytic carrier;

[0020] S4, the phosphorus-nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalytic carrier in step S3 and pentaerythritol phosphate are mixed uniformly, the molecular structure of pentaerythritol phosphate presents a highly symmetrical cage shape, has excellent thermal stability and carbon formation, and simultaneously provides abundant acid source and carbon source, melt blending in a banbury mixer, the mixing temperature is 160-180 DEG C, the rotating speed is 40-50 rpm, then extruding and granulating, the phosphorus-nitrogen grafted coated network silica powder and pentaerythritol phosphate further fill the Co-MOF composite graphene oxide catalytic carrier, the fixation of the carrier effectively reduces the migration and movement of organic components, the synergistic effect of the three increases the compatibility and dispersibility in the epoxy resin, enhances the thermal stability of the flame retardant system, so that the residual carbon layer after combustion presents a continuous and more dense form, almost no gap and hole appear, can better play the isolation and protection effect, effectively prevent the diffusion of smoke and heat, significantly improve the flame retardant performance, obtain a phosphate composite flame retardant;

[0021] Preferably, in step S2, the amount of cobalt acetate tetrahydrate added is 40.0-50.0 mg, and cobalt elements can be used in combination with other flame-retardant elements such as phosphorus, silicon, etc. to play a synergistic flame-retardant effect.

[0022] The beneficial effects obtained by the present application are as follows:

[0023] The application effectively reduces the migration of components, enhances the thermal stability of the flame-retardant system, and also improves the compatibility and dispersibility in the epoxy resin matrix, and the synergistic effect of the three makes the carbon residue layer after combustion more dense and continuous, which can better play the isolation and protection effect, and significantly improve the flame-retardant performance; in the phosphorus-nitrogen grafted coated network silica powder, the network dispersion modifier is used to modify the silica first, forming a special network structure in which the silica particles are connected to each other but there are small gaps between the particles, reducing the aggregation and migration of the particles, then the polydopamine coats the silica particles, enhancing the compatibility in the epoxy resin, and also facilitating the introduction of phosphorus and nitrogen elements on the surface of the polydopamine network silica, the thermal degradation of the phosphorus and nitrogen small molecules effectively promotes the dehydration of the epoxy resin matrix to form carbon, and the protective layer formed during the combustion of the polydopamine network silica particles synergistically blocks the release of heat and smoke, effectively enhancing the flame-retardant performance; in the Co-MOF composite graphene oxide catalytic carrier, Co-MOF is uniformly distributed on the surface of graphene oxide, forming a composite carrier with a tight and large surface area lamellar structure, which can better carry the phosphorus-nitrogen grafted coated network silica powder and pentaerythritol phosphate, further enhancing the thermal stability and reducing the migration of components, also enhancing the compatibility and dispersion effect in the epoxy resin, and also having a catalytic performance of promoting the carbonization reaction, so that each component can fully play the flame-retardant effect, and under the filling effect of the phosphorus-nitrogen grafted coated network silica powder and pentaerythritol phosphate, the carbon layer generated after combustion is more dense and continuous, maintains a certain geometric shape and is not easy to fall off, and the carbon layer covering degree is more dense and wide, which can fully play the isolation and protection effect, effectively prevent the diffusion of smoke and heat, and significantly improve the flame-retardant performance; the application uses the phosphorus-nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalytic carrier and the pentaerythritol phosphate to prepare a phosphate composite flame retardant, which effectively reduces the migration of components, enhances the thermal stability of the flame-retardant system, and also improves the compatibility in the epoxy resin matrix, thereby significantly improving the flame-retardant performance. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The scanning electron microscope image of the phosphorus-nitrogen grafted coated network silica powder prepared in Example 1 of the application;

[0025] Figure 2 The cross-sectional scanning electron microscope image of the phosphate composite flame retardant prepared in Example 1 of the application and the epoxy resin;

[0026] Figure 3 The scanning electron microscope image of the carbon residue of the phosphate composite flame retardant prepared in Example 1 of the application.

[0027] Figure 4 Limiting oxygen index results chart for examples 1-4 and comparative examples 1-3 of the present application;

[0028] Figure 5 Heat release rate peak, total heat release and total smoke production results chart for examples 1-4 and comparative examples 1-3 of the present application;

[0029] Figure 6 Ignition time results chart for examples 1-4 and comparative examples 1-3 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art. In addition, any method and material similar or equivalent to those described herein can be used in the present application. The preferred methods and materials described herein are only for demonstration, but cannot limit the content of the present application.

[0032] The experimental methods in the following examples are all conventional methods unless otherwise specified. The experimental materials used in the following examples are all purchased from commercial channels unless otherwise specified.

[0033] Example 1

[0034] The present embodiment proposes a phosphate ester composite flame retardant, which comprises the following components in parts by weight: phosphorus-nitrogen grafted coated network silica powder 40 parts, Co-MOF composite graphene oxide catalytic carrier 20 parts, pentaerythritol phosphate 20 parts.

[0035] The phosphorus-nitrogen grafted coated network silica powder comprises the following components in parts by weight: network dispersion modifier 25 parts, silica 75 parts, dopamine hydrochloride 15 parts, phosphorus oxychloride 6 parts, 4,4-diaminodiphenyl methane 8 parts.

[0036] The Co-MOF composite graphene oxide catalytic carrier comprises the following components in parts by weight: Co-MOF 40 parts, graphene oxide 15 parts.

[0037] The preparation method of the phosphorus-nitrogen grafted coated network silica powder specifically comprises the following steps:

[0038] (1) 1 mol of KH550 and 1 mol of KH560 were added to a three-necked flask under a nitrogen atmosphere, heated to 130°C under magnetic stirring for 5 h, and cooled to room temperature. The primary amine groups of KH550 reacted with the epoxy groups of KH560 to synthesize a network-like substance with three alkoxy groups at both ends, thereby obtaining a network-like dispersion modifier;

[0039] (2) 90 mL of anhydrous ethanol and 10 mL of water were added to a beaker, the pH was adjusted to 4.0 using a hydrochloric acid solution, and then the network-like dispersion modifier of step (1) was added in an amount of 2.5 g. The alkoxy groups at both ends can react with the active hydroxyl groups on the surface of the silica to achieve graft modification of the silica. The mixture was stirred at 50°C for 5 h, 7.5 g of silica powder was added to the modified solution, and the silica can form a dense barrier layer on the surface of the material at high temperature to isolate oxygen and heat, thereby preventing the spread of combustion. The temperature was raised to 60°C, and the mixture was fully stirred for 5 h at a stirring speed of 600 rpm. The alkoxy groups at both ends of the network-like dispersion modifier were simultaneously grafted onto different silica particles, connecting a large number of silica particles to form a network-like silica structure with a larger overall particle size. At the same time, there is a certain gap between the silica particles, which reduces the adsorption and aggregation between the particles and effectively increases the exchange interface of the flame retardant system, thereby improving the flame retardant performance of the silica. The network-like silica was obtained;

[0040] (3) 1.0 g of the network-like silica of step (2) was added to 100 mL of Tris-HCl buffer, and ultrasonic treatment was performed for 20 min. Hydrochloric acid dopamine was added to 200 mL of Tris-HCl buffer and dissolved completely, and then the network-like silica dispersion was poured into it and ultrasonic treatment was performed for 15 min. The amount of hydrochloric acid dopamine added was 1.5 g. The hydrochloric acid dopamine self-polymerized to form a polydopamine protective layer, and the outer layer was arranged with uniformly distributed hydroxyl groups. The mixture was placed in a water bath at 25°C and magnetically stirred at a speed of 180 rpm for 12 h. Then, centrifugal treatment was performed twice at a centrifugal speed of 8000 rpm, with the first centrifugal time being 15 min and the second centrifugal time being 10 min. The precipitate was freeze-dried and ground. The polydopamine formed a "nanosuit" with a layer of polydopamine on the surface of the silica particles, which had excellent adhesion and film-forming properties and could be used for further modification and functionalization. The compatibility and dispersibility of the silica in the epoxy resin matrix were improved, and the thermal stability was also significantly improved. The polydopamine coating formed a protective layer during combustion, which could isolate oxygen and heat, thereby interrupting the combustion process and reducing the generation of smoke. Polydopamine@network-like silica was obtained;

[0041] (4) 1.0 g of the polydopamine@network-like silicon dioxide obtained in step (3) is added into a 250 mL three-necked flask with 0.6 g of phosphorus oxychloride liquid, 50 mL of THF and 0.3 g of triethylamine liquid, respectively, and then ultrasonic treatment is performed at 25°C for 1 h; 0.8 g of 4,4-diaminodiphenyl methane solid is dissolved in 20 mL of THF, and then slowly dripped into the three-necked flask within 1 h; the reaction is performed at room temperature for 24 h; the product is sequentially washed with THF and deionized water, and then dried; phosphorus and nitrogen elements are introduced by grafting on the surface of the polydopamine@network-like silicon dioxide, so that the thermal stability and flame retardant performance of the composite are improved; the polydopamine@network-like silicon dioxide is effectively attached to the surface of an epoxy resin matrix and the like, so as to isolate the combustible gas and heat from the outside into the matrix; the phosphorus and nitrogen small molecules are degraded first when heated, so as to effectively promote the dehydration of the epoxy resin matrix into carbon, and the protective layer formed by the combustion of the silicon dioxide particles cooperates with the carbon to jointly block the release of heat and smoke, so that a phosphorus and nitrogen grafted and coated network-like silicon dioxide powder is obtained.

[0042] The embodiment provides a preparation method of a phosphate ester composite flame retardant, and specifically includes the following steps.

[0043] S1, 70 mL of concentrated sulfuric acid with a mass fraction of 98% is added into a 1000 mL beaker under ice bath, 3.0 g of graphite powder and 1.5 g of sodium nitrate are added after stirring, the temperature is controlled to be 4°C, and stirring is fully performed; 9.0 g of potassium permanganate is slowly added, then the temperature is increased to 40°C, and the reaction time is 30 min; then the above solution is slowly added into 140 mL of deionized water, the temperature is quickly increased to 98°C, the reaction is stopped after 15 min, and then 15 mL of hydrogen peroxide solution and 420 mL of deionized water are added; after cooling, filtration, centrifugation, washing and drying, graphene oxide is obtained, which can be used as a flame retardant additive; the unique two-dimensional sheet structure of the graphene oxide can promote the formation of a dense and continuous carbon layer in the combustion process, so as to isolate the heat transfer and gas exchange with the outside world.

[0044] S2, cobalt acetate tetrahydrate powder, 94.0 mg of Fbtx and 60.0 mg of H2dcpa are added into 7 mL of deionized water, the addition amount of the cobalt acetate tetrahydrate is 50.0 mg, and the cobalt element can be combined with other flame-retardant elements such as phosphorus and silicon to play a synergistic flame-retardant effect; stirring is performed for 1 h, and then the reaction kettle lined with polytetrafluoroethylene is transferred; the temperature is controlled to be 170°C, and the reaction time is 72 h; a new cobalt-based MOF material is synthesized by using the mixed ligand of cobalt salt, Fbtx and H2dcpa through a hydrothermal method, the material has good thermal stability and adsorption, can maintain structural stability at high temperature, and can adsorb harmful gas and smoke generated in combustion, so as to reduce the release of toxic gas in the fire; the transition metal cobalt has catalytic performance, can promote the carbonization reaction in the combustion process, form a more stable carbon layer, so as to isolate oxygen and heat, slow down the combustion speed, and obtain Co-MOF.

[0045] S3, the graphene oxide of step S1 and the Co-MOF of step S2 are poured into 200 mL of methanol solution, ultrasonic dispersion treatment is performed for 50 min, stirring is performed for 2 h, precipitation is performed, and filtration, washing and drying are performed. The Co-MOF is uniformly distributed on the surface of the graphene oxide and is combined closely. The carbon layer formed by combustion of the composite carrier is dense and maintains a certain geometric shape, is not easy to fall off, and the carbon layer is covered more densely and widely. Meanwhile, in the composite carrier, the graphene oxide can also promote the rapid carbonization of the polymer and produce various non-combustible gases when the polymer is decomposed by heat. These gases can isolate oxygen and combustible gases from contact, block the continuous combustion condition, and thus play a flame-retardant role. A Co-MOF composite graphene oxide catalytic carrier is obtained;

[0046] S4, the phosphorus-nitrogen grafted coated network-like silica powder, the Co-MOF composite graphene oxide catalytic carrier of step S3 and the pentaerythritol phosphate are uniformly mixed. The molecular structure of the pentaerythritol phosphate presents a highly symmetrical cage shape, has excellent thermal stability and carbonization property, and provides abundant acid source and carbon source. Melt blending is performed in a banbury mixer, the banbury mixing temperature is 180°C, the rotating speed is 50 rpm, and then extrusion granulation is performed. The phosphorus-nitrogen grafted coated network-like silica powder and the pentaerythritol phosphate further fill the Co-MOF composite graphene oxide catalytic carrier. The fixation of the carrier effectively reduces the migration and movement of the organic components. The three components synergistically increase the compatibility and dispersibility in the epoxy resin, enhance the thermal stability of the flame-retardant system, make the carbon residue layers after combustion present a continuous and more dense form, and almost no gaps and holes appear, which can better play the isolation and protection role, effectively prevent the diffusion of smoke and heat, significantly improve the flame-retardant property, and obtain a phosphate ester composite flame retardant.

[0047] In this embodiment, the fracture surface of the prepared phosphorus-nitrogen grafted coated network-like silica powder, the phosphate ester composite flame retardant and the epoxy resin, and the combustion residue carbon of the phosphate ester composite flame retardant are observed by scanning electron microscopy, Figure 1 The SEM image of the phosphorus-nitrogen grafted coated network-like silica powder prepared in Example 1 is magnified by 100,000 times, Figure 2 The SEM image of the fracture surface of the phosphate ester composite flame retardant and the epoxy resin prepared in Example 1 is magnified by 500 times, Figure 3 The SEM image of the combustion residue carbon of the phosphate ester composite flame retardant prepared in Example 1 is magnified by 200 times, as Figure 1 The phosphorus-nitrogen grafted coated network-like silica powder prepared in this embodiment presents a network structure in which coarse silica particles are connected but have voids, as Figure 2 The fracture surface of the phosphate ester composite flame retardant and the epoxy resin prepared in this embodiment has good compatibility and dispersibility, as Figure 3The carbon residue of the phosphate ester composite flame retardant prepared in the embodiment presents a continuous and dense structure.

[0048] Embodiment 2

[0049] The embodiment provides a phosphate ester composite flame retardant, which comprises the following components in parts by weight: phosphorus-nitrogen grafted coated network-like silicon dioxide powder 30 parts, Co-MOF composite graphene oxide catalytic carrier 10 parts, and pentaerythritol phosphate 10 parts.

[0050] The phosphorus-nitrogen grafted coated network-like silicon dioxide powder comprises the following components in parts by weight: network-like dispersion modifier 20 parts, silicon dioxide 60 parts, dopamine hydrochloride 10 parts, phosphorus oxychloride 3 parts, and 4,4-diaminodiphenyl methane 6 parts.

[0051] The Co-MOF composite graphene oxide catalytic carrier comprises the following components in parts by weight: Co-MOF 30 parts and graphene oxide 10 parts.

[0052] The preparation method of the phosphorus-nitrogen grafted coated network-like silicon dioxide powder specifically comprises the following steps:

[0053] (1) 1 mol of KH550 and 1 mol of KH560 are added to a three-necked flask in a nitrogen atmosphere, and heated to 120 DEG C under magnetic stirring for 3 h, and then cooled to room temperature; the primary amine groups of the KH550 and the epoxy groups of the KH560 are subjected to an epoxy ring-opening reaction, a network-like substance with three alkoxy groups at two ends is synthesized, and a network-like dispersion modifier is obtained;

[0054] (2) 90 mL of anhydrous ethanol and 10 mL of water are added to a beaker, and then a hydrochloric acid solution is used to adjust the pH to 4.0; then the network-like dispersion modifier in step (1) is added, the network-like dispersion modifier is added in an amount of 2.0 g, the alkoxy groups at two ends can be combined with the active hydroxyl groups on the surface of the silicon dioxide to realize the grafting modification of the silicon dioxide, and the modified solution is stirred at 40 DEG C for 4 h; 6.0 g of silicon dioxide powder is added to the modified solution, the silicon dioxide can form a dense barrier layer on the surface of the material at high temperature to isolate oxygen and heat and prevent the spread of combustion, and the temperature is increased to 60 DEG C, and the mixture is fully stirred for 4 h at a stirring speed of 500 rpm; drying, crushing, and network-like dispersion modifier alkoxy groups at two ends are grafted on different silicon dioxide particles, a large number of silicon dioxide particles are connected to form a network-like silicon dioxide structure with a large overall particle size, and there is a certain gap between the silicon dioxide particles to reduce the adsorption and aggregation between the particles, effectively increase the exchange interface of the flame retardant system, and thus the flame retardant performance of the silicon dioxide is improved, and the network-like silicon dioxide is obtained.

[0055] (3) 0.6 g of the network-like silicon dioxide described in step (2) is weighed and added into 100 mL of Tris-HCl buffer solution, and ultrasonic treatment is performed for 10 min. Then, dopamine hydrochloride is added into 200 mL of Tris-HCl buffer solution and dissolved completely, and then the network-like silicon dioxide dispersion liquid is poured into it, and ultrasonic treatment is performed for 10 min. The amount of dopamine hydrochloride added is 1.0 g. The dopamine hydrochloride is self-polymerized to form a polydopamine protective layer, and the outer layer is arranged with uniformly distributed hydroxyl groups. It is placed in a water bath environment at 25°C, and magnetic stirring is performed at a speed of 160 rpm for 6 h. Then, centrifugal treatment is performed twice at a speed of 7000 rpm, and the first centrifugal time is 15 min and the second centrifugal time is 10 min. The precipitate is freeze-dried and ground. The polydopamine is wrapped with a "nanosuit" with rich o-diphenol groups on the surface of the silicon dioxide particles, has excellent adhesion and film-forming properties, can be used for further modification and functionalization, can improve the compatibility and dispersibility in the epoxy resin matrix, and significantly improves the thermal stability. The polydopamine coating forms a protective layer during the combustion process, can isolate oxygen and heat, thereby interrupting the combustion process, reducing the generation of smoke, and obtaining polydopamine@network-like silicon dioxide.

[0056] (4) 0.5 g of the polydopamine@network-like silicon dioxide described in step (3) is weighed and sequentially added into a 250 mL three-necked flask with 0.3 g of phosphorus oxychloride liquid, 50 mL of THF and 0.3 g of triethylamine liquid. Ultrasonic treatment is performed at 25°C for 0.5 h. Then, 0.6 g of 4,4-diaminodiphenyl methane solid is dissolved in 20 mL of THF and slowly dropped into the three-necked flask within 1 h. The reaction is performed at room temperature for 24 h. The product is sequentially washed with THF and deionized water, and dried. Phosphorus and nitrogen elements are introduced on the surface of the polydopamine@network-like silicon dioxide by grafting, which improves the thermal stability and flame retardant performance of the composite. The polydopamine@network-like silicon dioxide is effectively attached to the surface of the epoxy resin matrix, which isolates the combustible gas and heat from the outside into the matrix. The phosphorus and nitrogen small molecules are degraded first when heated, which effectively promotes the dehydration of the epoxy resin matrix to carbon. The protective layer formed by the combustion of the silicon dioxide particles cooperates with the protective layer to block the release of heat and smoke, and a phosphorus and nitrogen grafted and coated network-like silicon dioxide powder is obtained.

[0057] The embodiment provides a preparation method of a phosphate ester composite flame retardant, and specifically includes the following steps.

[0058] S1, 70 mL of 98% concentrated sulfuric acid was added to a 1000 mL beaker under ice bath, after stirring, 3.0 g of graphite powder, 1.5 g of sodium nitrate was added, the temperature was controlled at 0℃, fully stirred, 9.0 g of potassium permanganate was slowly added, then the temperature was raised to 40℃, the reaction time was 10 min, then the above solution was slowly added to 140 mL of deionized water, quickly heated to 98℃, reacted for 15 min, then stopped heating, cooled, then added 15 mL of hydrogen peroxide solution and 420 mL of deionized water, filtered, centrifuged, washed and dried, the graphene oxide can be used as a flame retardant additive, its unique two-dimensional sheet structure can promote the formation of a dense and continuous carbon layer during combustion, which can isolate heat transfer and gas exchange with the outside world, and obtain graphene oxide;

[0059] S2, 94.0 mg of Fbtx, 60.0 mg of H2dcpa and 40.0 mg of cobalt acetate tetrahydrate powder were added to 7 mL of deionized water, the amount of cobalt acetate tetrahydrate added was 40.0 mg, and cobalt elements can be used in combination with other flame-retardant elements such as phosphorus and silicon to play a synergistic flame-retardant effect, stirred for 0.5 h, then transferred to a reaction kettle lined with polytetrafluoroethylene, the temperature was controlled at 160℃, and the reaction time was 48 h, a new cobalt-based MOF material was synthesized by hydrothermal method using the mixed ligand of cobalt salt, Fbtx and H2dcpa, which has good thermal stability and adsorption, can maintain structural stability at high temperature, and can adsorb harmful gases and smoke generated during combustion, reduce the release of toxic gases during fire, the transition metal cobalt has catalytic properties, can promote the carbonization reaction during combustion, form a more stable carbon layer, thereby isolating oxygen and heat, slowing down the combustion speed, and obtain Co-MOF;

[0060] S3, the graphene oxide of step S1 and the Co-MOF of step S2 were poured into 100 mL of methanol solution, ultrasonic dispersion treatment was performed for 30 min, then stirred for 1 h, and then precipitated, filtered, washed and dried, the Co-MOF was uniformly distributed on the surface of the graphene oxide and tightly combined, the carbon layer formed by the composite carrier during combustion was dense and maintained a certain geometric shape, and was not easy to fall off, and the carbon layer covered a wider area, at the same time, the graphene oxide in the composite carrier can also promote the rapid carbonization of polymers and produce a variety of non-combustible gases during thermal decomposition, which can isolate oxygen and combustible gas contact, block the continuous combustion condition, thereby playing a flame-retardant effect, and obtain Co-MOF composite graphene oxide catalyst carrier;

[0061] S4, the phosphorus-nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalytic carrier of step S3 and the pentaerythritol phosphate are mixed uniformly, the molecular structure of the pentaerythritol phosphate presents a highly symmetrical cage shape, has excellent thermal stability and carbon formation, and simultaneously provides abundant acid and carbon sources, melt blending is carried out in a banbury mixer, the banbury mixing temperature is 160℃, the rotating speed is 40rpm, then extrusion granulation is carried out, the phosphorus-nitrogen grafted coated network silica powder and the pentaerythritol phosphate further fill the Co-MOF composite graphene oxide catalytic carrier, the fixing effect of the carrier effectively reduces the migration and movement of organic components, the three components synergistically increase the compatibility and dispersibility in the epoxy resin, enhance the thermal stability of the flame retardant system, so that the residual carbon layers after combustion present a continuous and more dense morphology, almost no gaps and holes appear, which can better play the isolation and protection role, effectively prevent the diffusion of smoke and heat, significantly improve the flame retardant performance, and obtain a phosphate ester composite flame retardant.

[0062] Example 3

[0063] The embodiment provides a phosphate ester composite flame retardant, which comprises the following components in parts by weight: 35 parts of phosphorus-nitrogen grafted coated network silica powder, 15 parts of a Co-MOF composite graphene oxide catalytic carrier and 15 parts of pentaerythritol phosphate.

[0064] The phosphorus-nitrogen grafted coated network silica powder comprises the following components in parts by weight: 22.5 parts of a network dispersion modifier, 67.5 parts of silica, 12.5 parts of dopamine hydrochloride and 4.5 parts of phosphorus oxychloride and 7 parts of 4,4-diaminodiphenyl methane.

[0065] The Co-MOF composite graphene oxide catalytic carrier comprises the following components in parts by weight: 35 parts of Co-MOF and 12.5 parts of graphene oxide.

[0066] The preparation method of the phosphorus-nitrogen grafted coated network silica powder specifically comprises the following steps:

[0067] (1) 1 mol of KH550 and 1 mol of KH560 are added to a three-necked flask in a nitrogen atmosphere, under magnetic stirring, heating to 125℃, and stirring for 4h, and then cooling to room temperature; the primary amine groups of the KH550 and the epoxy groups of the KH560 undergo an epoxy ring-opening reaction, a network substance with three alkoxy groups at both ends is synthesized, and a network dispersion modifier is obtained;

[0068] (2) 90 mL of anhydrous ethanol and 10 mL of water were added to a beaker, and the pH was adjusted to 4.0 using a hydrochloric acid solution, then the network dispersion modifier described in step (1) was added, the amount of network dispersion modifier added was 2.25 g, the alkoxy groups at both ends could react with the active hydroxyl groups on the surface of the silica to achieve graft modification of the silica, and the mixture was stirred at 45°C for 4.5 h. 6.75 g of silica powder was added to the modified solution, and at high temperature, the silica could form a dense barrier layer on the surface of the material, isolating oxygen and heat, preventing the spread of combustion, and the temperature was raised to 60°C, and the mixture was thoroughly stirred for 4.5 h at a stirring speed of 550 rpm. After drying and crushing, the alkoxy groups at both ends of the network dispersion modifier were grafted onto different silica particles, connecting a large number of silica particles to form a network-like silica structure with a larger overall particle size, and there was a certain gap between the silica particles, reducing the adsorption and aggregation between the particles, effectively increasing the exchange interface of the flame retardant system, thereby improving the flame retardant performance of the silica, and obtaining a network-like silica;

[0069] (3) 0.8 g of the network-like silica described in step (2) was added to 100 mL of Tris-HCl buffer, and ultrasonic treatment was performed for 15 min. Hydrochloric acid dopamine was added to 200 mL of Tris-HCl buffer and dissolved completely, then the network-like silica dispersion was poured into it, and ultrasonic treatment was performed for 12.5 min. The amount of hydrochloric acid dopamine added was 1.25 g. The hydrochloric acid dopamine self-polymerized to form a polydopamine protective layer, with uniformly distributed hydroxyl groups on the outer layer. It was placed in a water bath environment at 25°C and magnetically stirred at a speed of 170 rpm for 9 h. Then it was centrifuged twice at a speed of 7500 rpm, with the first centrifugation time being 15 min and the second centrifugation time being 10 min. The precipitate was freeze-dried and ground. The polydopamine was wrapped in a "nanosuit" with a rich o-diphenol group, which had excellent adhesion and film-forming properties, could be used for further modification and functionalization, could improve its compatibility and dispersibility in the epoxy resin matrix, and also significantly improved the thermal stability. The polydopamine coating formed a protective layer during combustion, which could isolate oxygen and heat, thereby interrupting the combustion process and reducing the generation of smoke, obtaining polydopamine@network-like silica;

[0070] (4) 0.75 g of the polydopamine@network-like silica obtained in step (3) is weighed and sequentially added into a 250 mL three-necked flask with 0.45 g of phosphorus oxychloride liquid, 50 mL of THF and 0.3 g of triethylamine liquid, and then ultrasonic treatment is performed at 25°C for 0.75 h; 0.7 g of 4,4-diaminodiphenyl methane solid is dissolved in 20 mL of THF, and then slowly dripped into the three-necked flask within 1 h; the reaction is performed at room temperature for 24 h; the product is sequentially washed with THF and deionized water, and then dried; phosphorus and nitrogen elements are introduced by grafting on the surface of the polydopamine@network-like silica, so that the thermal stability and flame retardant performance of the composite are improved; the polydopamine@network-like silica is effectively attached to the surface of an epoxy resin matrix and the like, so that the combustible gas and heat from the outside are isolated from the inside of the matrix; the phosphorus and nitrogen small molecules are degraded first when heated, so that the epoxy resin matrix is effectively dehydrated to form carbon, and cooperates with the protective layer formed by the combustion of the silica particles, so that the release of heat and smoke is blocked, and a phosphorus-nitrogen grafted and coated network-like silica powder is obtained.

[0071] The embodiment provides a preparation method of a phosphate ester composite flame retardant, and specifically includes the following steps.

[0072] S1, 70 mL of concentrated sulfuric acid with a mass fraction of 98% is added into a 1000 mL beaker under ice bath, and then 3.0 g of graphite powder and 1.5 g of sodium nitrate are added after stirring; the temperature is controlled to be 2°C, and the mixture is fully stirred and slowly added with 9.0 g of potassium permanganate; then the temperature is increased to 40°C, and the reaction is performed for 20 min; then the above solution is slowly added into 140 mL of deionized water, and the temperature is quickly increased to 98°C; the reaction is performed for 15 min, and then the heating is stopped; after cooling, 15 mL of hydrogen peroxide solution and 420 mL of deionized water are added; the mixture is filtered, centrifuged, washed and dried; the graphene oxide can be used as a flame retardant additive; the unique two-dimensional sheet structure of the graphene oxide can promote the formation of a dense and continuous carbon layer during the combustion process, so that the heat transfer and gas exchange with the outside are isolated, and the graphene oxide is obtained.

[0073] S2, add cobalt acetate tetrahydrate powder, 94.0 mg Fbtx, 60.0 mg H2dcpa into 7 mL of deionized water, the amount of cobalt acetate tetrahydrate added is 45.0 mg, and cobalt elements can be combined with other flame-retardant elements such as phosphorus and silicon to play a synergistic flame-retardant effect, stir for 0.75 h, then transfer to a reaction kettle lined with polytetrafluoroethylene, control the temperature at 165°C, and react for 60 h, a new cobalt-based MOF material is synthesized by hydrothermal method using a mixed ligand of cobalt salt, Fbtx and H2dcpa, which has good thermal stability and adsorption, can maintain structural stability at high temperature, and can adsorb harmful gases and smoke generated during combustion, reduce the release of toxic gases in the fire, the transition metal cobalt has catalytic properties, can promote the charring reaction during combustion, form a more stable carbon layer, thereby isolating oxygen and heat, slowing down the combustion speed, and obtain Co-MOF;

[0074] S3, pour the graphene oxide of step S1 and the Co-MOF of step S2 into 150 mL of methanol solution, ultrasonic dispersion treatment for 40 min, then stir for 1.5 h, let it stand and precipitate, filter and wash, and dry, the Co-MOF is uniformly distributed on the surface of the graphene oxide and is tightly combined, the carbon layer formed by the composite carrier during combustion is dense and maintains a certain geometric shape and is not easy to fall off, and the carbon layer covers a wider and denser area, at the same time, in the composite carrier, the graphene oxide can also promote the rapid carbonization of the polymer and produce a variety of non-combustible gases during thermal decomposition, which can isolate oxygen and combustible gases from contact, thereby blocking the continuous combustion condition and playing a flame-retardant effect, and obtain a Co-MOF composite graphene oxide catalytic carrier;

[0075] S4, mix the phosphorus-nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalytic carrier of step S3, and pentaerythritol phosphate uniformly, the molecular structure of pentaerythritol phosphate presents a highly symmetrical cage shape, has excellent thermal stability and carbonation, and provides abundant acid and carbon sources, melt blend in an internal mixer, the melt blending temperature is 170°C, and the rotating speed is 45 rpm, then extrude and granulate, the phosphorus-nitrogen grafted coated network silica powder and pentaerythritol phosphate further fill the Co-MOF composite graphene oxide catalytic carrier, the fixation of the carrier effectively reduces the migration and movement of organic components, the three components synergistically increase the compatibility and dispersibility in the epoxy resin, enhance the thermal stability of the flame-retardant system, make the carbon layers after combustion present a continuous and more dense morphology, and almost no gaps and holes appear, which can better play the isolation and protection role, effectively prevent the diffusion of smoke and heat, and significantly improve the flame-retardant performance, and obtain a phosphate composite flame retardant.

[0076] Example 4

[0077] The embodiment provides a phosphate ester composite flame retardant, which comprises the following components in parts by weight: phosphorus-nitrogen grafting coated network-like silicon dioxide powder 30 parts, Co-MOF composite graphene oxide catalytic carrier 10 parts, and pentaerythritol phosphate 20 parts.

[0078] The phosphorus-nitrogen grafting coated network-like silicon dioxide powder comprises the following components in parts by weight: network-like dispersion modifier 20 parts, silicon dioxide 75 parts, dopamine hydrochloride 15 parts, phosphorus oxychloride 3 parts, and 4,4-diaminodiphenyl methane 6 parts.

[0079] The Co-MOF composite graphene oxide catalytic carrier comprises the following components in parts by weight: Co-MOF 30 parts and graphene oxide 15 parts.

[0080] The preparation method of the phosphorus-nitrogen grafting coated network-like silicon dioxide powder specifically comprises the following steps:

[0081] (1) 1 mol of KH550 and 1 mol of KH560 are added into a three-necked flask in a nitrogen atmosphere, under magnetic stirring, heated to 130 DEG C, the stirring time is 3 h, and the temperature is cooled to room temperature; the primary amine groups of KH550 and the epoxy groups of KH560 are subjected to an epoxy ring-opening reaction, a network-like substance with three alkoxy groups at two ends is synthesized, and a network-like dispersion modifier is obtained;

[0082] (2) 90 mL of anhydrous ethanol and 10 mL of water are added into a beaker, hydrochloric acid solution is used to adjust the pH to 4.0, then the network-like dispersion modifier in step (1) is added, the addition amount of the network-like dispersion modifier is 2.0 g, the alkoxy groups at two ends can be combined with the active hydroxyl groups on the surface of the silicon dioxide to realize the grafting modification of the silicon dioxide, 7.5 g of silicon dioxide powder is added into the modified solution under stirring at 50 DEG C for 4 h, the silicon dioxide can form a dense barrier layer on the surface of the material under high temperature, so as to isolate oxygen and heat and prevent the spread of combustion, the temperature is increased to 60 DEG C, and the mixture is fully stirred for 4 h at a stirring speed of 600 rpm; after drying and crushing, the alkoxy groups at two ends of the network-like dispersion modifier are grafted on different silicon dioxide particles, a large number of silicon dioxide particles are connected, a network-like silicon dioxide structure with a large overall particle size is formed, and a certain gap exists between the silicon dioxide particles, so that the adsorption and aggregation between the particles are reduced, the exchange interface of the flame retardant system is effectively increased, the flame retardant performance of the silicon dioxide is improved, and the network-like silicon dioxide is obtained.

[0083] (3) 1.0 g of the network-like silicon dioxide described in step (2) is weighed and added into 100 mL of Tris-HCl buffer solution, and ultrasonic treatment is performed for 10 min. Then, dopamine hydrochloride is added into 200 mL of Tris-HCl buffer solution and dissolved completely, and then the network-like silicon dioxide dispersion liquid is poured into it, and ultrasonic treatment is performed for 10 min. The amount of dopamine hydrochloride added is 1.5 g. The dopamine hydrochloride is self-polymerized to form a polydopamine protective layer, and the outer layer is arranged with uniformly distributed hydroxyl groups. It is placed in a water bath environment at 25°C, and magnetic stirring is performed at a speed of 180 rpm for 6 h. Then, centrifugal treatment is performed twice at a speed of 8000 rpm, and the first centrifugal time is 15 min and the second centrifugal time is 10 min. The precipitate is freeze-dried and ground. The polydopamine is wrapped with a "nanosuit" with rich o-diphenol groups on the surface of the silicon dioxide particles, has excellent adhesion and film-forming properties, can be used for further modification and functionalization, can improve the compatibility and dispersibility in the epoxy resin matrix, and significantly improves the thermal stability. The polydopamine coating forms a protective layer during the combustion process, can isolate oxygen and heat, thereby interrupting the combustion process, reducing the generation of smoke, and obtaining polydopamine@network-like silicon dioxide;

[0084] (4) 1.0 g of the polydopamine@network-like silicon dioxide described in step (3) is weighed and sequentially added into a 250 mL three-necked flask with 0.3 g of phosphorus oxychloride liquid, 50 mL of THF and 0.3 g of triethylamine liquid. Ultrasonic treatment is performed for 0.5 h at 25°C. Then, 0.6 g of 4,4-diaminodiphenyl methane solid is dissolved in 20 mL of THF and slowly dropped into the three-necked flask within 1 h. The reaction is performed at room temperature for 24 h. The product is sequentially washed with THF and deionized water, and dried. Phosphorus and nitrogen elements are introduced on the surface of the polydopamine@network-like silicon dioxide by grafting, which improves the thermal stability and flame retardant performance of the composite. The polydopamine@network-like silicon dioxide is effectively attached to the surface of the epoxy resin matrix, which isolates the combustible gas and heat from the outside into the matrix. The phosphorus and nitrogen small molecules are degraded first when heated, which effectively promotes the dehydration of the epoxy resin matrix to carbon. The protective layer formed by the combustion of the silicon dioxide particles cooperates with the protective layer to block the release of heat and smoke, and a phosphorus and nitrogen grafted and coated network-like silicon dioxide powder is obtained.

[0085] The embodiment provides a preparation method of a phosphate ester composite flame retardant, and specifically includes the following steps:

[0086] S1, 70 mL of 98% mass fraction concentrated sulfuric acid is added to a 1000 mL beaker under ice bath, after stirring, 3.0 g of graphite powder, 1.5 g of sodium nitrate is added, the temperature is controlled at 4 ℃, and the stirring is fully stirred, 9.0 g of potassium permanganate is slowly added, then the temperature is raised to 40 ℃, the reaction time is 10 min, then the above solution is slowly added to 140 mL of deionized water, quickly heated to 98 ℃, and the heating is stopped after 15 min of reaction, then 15 mL of hydrogen peroxide solution and 420 mL of deionized water are added, and the filtration, centrifugation, washing and drying are carried out, and the graphene oxide can be used as a flame retardant additive, which has a unique two-dimensional sheet structure, which can promote the formation of a dense and continuous carbon layer during combustion, and can isolate heat transfer and gas exchange with the outside, and obtain graphene oxide;

[0087] S2, the cobalt acetate tetrahydrate powder, 94.0 mg of Fbtx, and 60.0 mg of H2dcpa are added to 7 mL of deionized water, the amount of cobalt acetate tetrahydrate added is 40.0 mg, and the cobalt element can be combined with other flame-retardant elements such as phosphorus and silicon to play a synergistic flame-retardant effect, and the stirring is carried out for 0.5 h, then it is transferred to a reaction kettle lined with polytetrafluoroethylene, the temperature is controlled at 170 ℃, and the reaction time is 48 h, a new cobalt-based MOF material is synthesized by using the mixed ligand of cobalt salt, Fbtx and H2dcpa by hydrothermal method, which has good thermal stability and adsorption, can maintain structural stability at high temperature, and can adsorb harmful gases and smoke generated during combustion, reduce the release of toxic gases in the fire, the transition metal cobalt has catalytic performance, can promote the carbonization reaction during combustion, form a more stable carbon layer, and isolate oxygen and heat, slow down the combustion speed, and obtain Co-MOF;

[0088] S3, the graphene oxide in step S1 and the Co-MOF in step S2 are poured into 200 mL of methanol solution, ultrasonic dispersion treatment is carried out for 30 min, then stirring is carried out for 1 h, and the mixture is left to settle, and then filtration, washing and drying are carried out, the Co-MOF is uniformly distributed on the surface of the graphene oxide and is combined tightly, the carbon layer formed by combustion is dense and maintains a certain geometric shape and is not easy to fall off, and the carbon layer is covered more densely and widely, at the same time, the graphene oxide in the composite carrier can also promote the rapid carbonization of polymers and produce a variety of non-combustible gases during thermal decomposition, which can isolate oxygen and combustible gas contact, block the continuous combustion condition, and thus play a flame-retardant effect, and obtain a Co-MOF composite graphene oxide catalyst carrier;

[0089] S4, mixing the phosphorus-nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalytic carrier of step S3, and the pentaerythritol phosphate uniformly, the molecular structure of the pentaerythritol phosphate presents a highly symmetrical cage shape, has excellent thermal stability and carbon formation property, and provides abundant acid source and carbon source, melt blending in an internal mixer, the mixing temperature is 180°C, the rotating speed is 50 rpm, and then extruding and granulating, the phosphorus-nitrogen grafted coated network silica powder and the pentaerythritol phosphate further fill the Co-MOF composite graphene oxide catalytic carrier, the fixation of the carrier effectively reduces the migration and movement of organic components, the synergistic effect of the three increases the compatibility and dispersibility in the epoxy resin, enhances the thermal stability of the flame-retardant system, makes the residual carbon layers after combustion present a continuous and more dense form, and almost no gaps and holes appear, which can better play the isolation and protection role, effectively prevent the diffusion of smoke and heat, significantly improve the flame-retardant performance, and obtain a phosphate ester composite flame retardant.

[0090] Comparative Example 1

[0091] The present comparative example provides a phosphate ester composite flame retardant, which is different from example 1 in that the phosphorus-nitrogen grafted coated network silica powder does not contain a network dispersion modifier; the preparation method of the phosphorus-nitrogen grafted coated network silica powder does not include step (1); and the preparation method of the phosphate ester composite flame retardant is the same as that of example 1.

[0092] Comparative Example 2

[0093] The present comparative example provides a phosphate ester composite flame retardant, which is different from example 1 in that the phosphorus-nitrogen grafted coated network silica powder does not contain dopamine hydrochloride; the preparation method of the phosphorus-nitrogen grafted coated network silica powder does not include step (3); and the preparation method of the phosphate ester composite flame retardant is the same as that of example 1.

[0094] Comparative Example 3

[0095] The present comparative example provides a phosphate ester composite flame retardant, which is different from example 1 in that the Co-MOF composite graphene oxide catalytic carrier does not contain Co-MOF; the preparation method of the phosphorus-nitrogen grafted coated network silica powder is the same as that of example 1; and the preparation method of the phosphate ester composite flame retardant does not include step S2.

[0096] Experimental Example 1

[0097] Flame-retardant performance experiment

[0098] Test sample: the phosphate ester composite flame retardants prepared in examples 1-4 and comparative examples 1-3.

[0099] Test method: the test sample was prepared by high temperature curing method with epoxy resin according to the addition amount of 15%, and then the sample was tested as follows: the limiting oxygen index test (LOI) was tested according to GB / T2406-2009, and the sample size was 100mmx6.5mmx3mm; the cone calorimeter test was tested according to ISO5660-1 to obtain the peak heat release rate (kW / m 2 ), total heat release (MJ / m 2 ), total smoke (m 2 / m 2 ) and ignition time (s), wherein the heat radiation flow during the test was 50kW / m 2 , and the sample size was 100mmx100mmx3mm.

[0100] Figure 4 the limiting oxygen index result graph of examples 1-4 and comparative examples 1-3; Figure 5 the peak heat release rate, total heat release and total smoke result graph of examples 1-4 and comparative examples 1-3; Figure 6 the ignition time result graph of examples 1-4 and comparative examples 1-3; as Figure 4 , the limiting oxygen index of examples 1-4 was 34.0-35.8%, as Figure 5 , the peak heat release rate, total heat release and total smoke of examples 1-4 were 153-186kW / m 2 , 46-56MJ / m 2 , 165-182m 2 / m 2 , as Figure 6 , the ignition time of examples 1-4 was 112-120s, the limiting oxygen index was higher, the peak heat release rate, total heat release and total smoke were lower, and the ignition time was longer, indicating that the flame retardant performance was better; as Figure 4 , the limiting oxygen index of comparative examples 1-3 was 22.3-30.8%, as Figure 5 , the peak heat release rate, total heat release and total smoke of comparative examples 1-3 were 227-298kW / m 2 , 69-87MJ / m 2 , 209-246m 2 / m 2 , as Figure 6The ignition time of Comparative Example 1-3 is 89-102 s, indicating that the flame retardant performance is general; Comparative Example 1 does not contain a network-like dispersion modifier in the phosphorus-nitrogen grafted coated network-like silica powder, and cannot form a network structure between particles, increasing the aggregation and migration of silica, thereby being not conducive to the isolation and protection of the protective layer, resulting in general flame retardant performance; Comparative Example 2 does not contain dopamine hydrochloride in the phosphorus-nitrogen grafted coated network-like silica powder, which cannot coat the silica particles to enhance the compatibility in the epoxy resin, and is also not conducive to the grafting of phosphorus and nitrogen elements on the particle surface to play a synergistic flame retardant effect, thereby failing to effectively block oxygen, heat and smoke, resulting in general flame retardant performance; Comparative Example 3 does not contain Co-MOF in the Co-MOF composite graphene oxide catalyst carrier, which is not conducive to reducing the aggregation of graphene oxide, and also cannot form a more compact and larger surface area of the sheet structure, which cannot better load the phosphorus-nitrogen grafted coated network-like silica powder and pentaerythritol phosphate, and is not conducive to the densification and continuity of the combustion char layer and the coverage range, which cannot fully play the isolation and protection effect, and also cannot play the catalytic performance of promoting the carbonation reaction, resulting in general flame retardant performance.

[0101] The above experimental results show that the flame retardant performance of Examples 1-4 of the present application is obviously better than that of Comparative Examples 1-3, wherein the flame retardant performance of Example 1 using phosphorus-nitrogen grafted coated network-like silica powder and Co-MOF composite graphene oxide catalyst carrier is better, in the phosphorus-nitrogen grafted coated network-like silica powder, the network-like dispersion modifier is used to modify the silica first, forming a special network structure in which the silica particles are connected to each other but there are small gaps between the particles, reducing the aggregation and migration of the particles, then the polydopamine coats the silica particles, enhancing the compatibility in the epoxy resin, and also being conducive to the grafting of phosphorus and nitrogen elements on the surface of the polydopamine@network-like silica, effectively enhancing the flame retardant performance, the Co-MOF is uniformly distributed on the surface of the graphene oxide, forming a composite carrier with a compact and larger surface area of the sheet structure, which can better load the phosphorus-nitrogen grafted coated network-like silica powder and pentaerythritol phosphate, further enhancing the thermal stability and reducing the migration of the components, also enhancing the compatibility and dispersibility in the epoxy resin, and also having the catalytic performance of promoting the carbonation reaction, so that each component can fully play the flame retardant effect, and under the filling effect of the phosphorus-nitrogen grafted coated network-like silica powder and pentaerythritol phosphate, the carbon layer generated after combustion is more dense and continuous, and maintains a certain geometric shape and is not easy to fall off, and the carbon layer has a more dense and wide coverage, which can fully play the isolation and protection effect, effectively preventing the diffusion of smoke and heat, and significantly improving the flame retardant performance.

[0102] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary and that changes can be made in the embodiments without departing from the spirit and scope of the application.

[0103] The above description of the application and its embodiments is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual application is not limited thereto. In general, if a person skilled in the art is inspired by it, without departing from the purpose of the application, without creative design, similar ways and embodiments of the technical solution should belong to the protection scope of the application.

Claims

1. A phosphate ester composite flame retardant, characterized in that: The phosphate ester composite flame retardant comprises the following components in parts by weight: 30-40 parts of phosphorus-nitrogen grafted and coated network silica powder, 10-20 parts of Co-MOF composite graphene oxide catalyst carrier, and 10-20 parts of pentaerythritol phosphate; the phosphorus-nitrogen grafted and coated network silica powder comprises the following components in parts by weight: 20-25 parts of network dispersion modifier, 60-75 parts of silica, 10-15 parts of dopamine hydrochloride, 3-6 parts of phosphorus oxychloride, and 6-8 parts of 4,4-diaminodiphenylmethane; the Co-MOF composite graphene oxide catalyst carrier comprises the following components in parts by weight: 30-40 parts of Co-MOF and 10-15 parts of graphene oxide. The preparation method of the network-like dispersion modifier specifically includes the following steps: 1 mol of KH550 and 1 mol of KH560 were added to a three-necked flask under a nitrogen atmosphere. The mixture was heated to 120-130℃ with magnetic stirring for 3-5 hours and then cooled to room temperature to obtain a network-like dispersion modifier.

2. A method for preparing the phosphate ester composite flame retardant according to claim 1, characterized in that: Specifically, the following steps are included: S1. Add 70 mL of 98% concentrated sulfuric acid to a 1000 mL beaker under ice bath conditions. After stirring, add 3.0 g of graphite powder and 1.5 g of sodium nitrate. Control the temperature at 0-4℃ and stir thoroughly. Slowly add 9.0 g of potassium permanganate, then raise the temperature to 40℃ and react for 10-30 min. Slowly add the resulting solution to 140 mL of deionized water, rapidly raise the temperature to 98℃, and react for 15 min. Stop heating, cool, and then add 15 mL of hydrogen peroxide solution and 420 mL of deionized water. Filter, centrifuge, wash, and dry to obtain graphene oxide. S2. Add cobalt acetate tetrahydrate powder, 94.0 mg Fbtx, and 60.0 mg H2dcpa to 7 mL of deionized water, stir for 0.5-1 h, and then transfer to a reaction vessel lined with polytetrafluoroethylene. Control the temperature at 160-170 °C and the reaction time at 48-72 h to obtain Co-MOF. S3. Pour the graphene oxide described in step S1 and the Co-MOF described in step S2 into 100-200 mL of methanol solution, ultrasonically disperse for 30-50 min, stir for 1-2 h, let stand to precipitate, filter, wash, and dry to obtain Co-MOF composite graphene oxide catalyst support. S4. The phosphorus and nitrogen grafted coated network silica powder, the Co-MOF composite graphene oxide catalyst carrier mentioned in step S3, and pentaerythritol phosphate are mixed evenly and melt-blended in a mixer at a mixing temperature of 160-180℃ and a speed of 40-50rpm. Then, the mixture is extruded and granulated to obtain the phosphate ester composite flame retardant.

3. The method for preparing the phosphate ester composite flame retardant according to claim 2, characterized in that: In step S2, the amount of cobalt acetate tetrahydrate added is 40.0-50.0 mg.

4. The method for preparing the phosphate ester composite flame retardant according to claim 3, characterized in that: The preparation method of the phosphorus-nitrogen grafted coated network silica powder specifically includes the following steps: (1) Add 1 mol of KH550 and 1 mol of KH560 to a three-necked flask under a nitrogen atmosphere, heat to 120-130℃ under magnetic stirring, stir for 3-5 hours, cool to room temperature, and obtain a network dispersion modifier. (2) Add 90 mL of anhydrous ethanol and 10 mL of water to a beaker, then adjust the pH to 4.0 with hydrochloric acid solution, then add the network dispersion modifier described in step (1), stir at 40-50℃ for 4-5 h, add 6.0-7.5 g of silica powder to the modified solution, heat to 60℃, stir and mix thoroughly for 4-5 h at a stirring speed of 500-600 rpm, dry, and pulverize to obtain network silica; (3) Weigh 0.6-1.0g of the network silica described in step (2) and add it to 100mL of Tris-HCl buffer. Sonicate for 10-20min. Then add dopamine hydrochloride to 200mL of Tris-HCl buffer and dissolve it completely. Next, pour the network silica dispersion into it and sonicate for 10-15min. Place it in a water bath at 25℃ and magnetically stir at 160-180rpm for 6-12h. Then centrifuge twice at 7000-8000rpm. The first centrifugation time is 15min and the second centrifugation time is 10min. Freeze-dry the precipitate and grind it to obtain polydopamine@network silica. (4) Weigh 0.5-1.0g of the polydopamine@network silica mentioned in step (3), add 0.3-0.6g of phosphorus oxychloride liquid, 50mL of THF and 0.3g of triethylamine liquid to a 250mL three-necked flask, sonicate at 25℃ for 0.5-1h, then dissolve 0.6-0.8g of 4,4-diaminodiphenylmethane solid in 20mL of THF and slowly drop it into the three-necked flask over 1h, and react at room temperature for 24h. Wash the product with THF and deionized water in sequence, and dry to obtain phosphorus-nitrogen grafted network silica powder.

5. The method for preparing the phosphate ester composite flame retardant according to claim 4, characterized in that: In step (2), the amount of network dispersion modifier added is 2.0-2.5g.

6. The method for preparing the phosphate ester composite flame retardant according to claim 5, characterized in that: In step (3), the amount of dopamine hydrochloride added is 1.0-1.5g.

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