A core-shell structure flame retardant with anti-thermal oxidative aging function and application thereof in preparing flame-retardant materials

Abstract

The application discloses a kind of core-shell structure flame retardant with anti-thermal oxidative aging function and application thereof in preparing flame retardant material, belong to flame retardant technical field.The core-shell structure flame retardant with anti-thermal oxidative aging function is composed of core and shell structure, wherein the core is flame retardant, and the shell structure is polymer containing hindered phenol and low-valence phosphorus, which can improve the hydrophobicity of flame retardant on one hand, and also improve the compatibility and dispersibility of flame retardant in polymeric material, thereby improving the flame retardant and mechanical properties of polymeric material.In addition, the hindered phenol and low-valence phosphorus in the shell polymer can not only capture RO· and ROO· free radicals to inhibit the thermal oxidative aging process of polymer, but also play a role in free radical capture during combustion, further improving the flame retardant properties of polymeric material.The flame retardant has excellent flame retardant properties and heat aging resistance, and can be applied in the fields of building, transportation, chemical industry, machinery, communication and energy.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology, specifically relating to a core-shell structured flame retardant with anti-thermal-oxidative aging function and its application in the preparation of flame retardant materials. Background Technology

[0002] Polymer resins possess excellent toughness, strength, wear resistance, impact resistance, and low-temperature resistance, making them widely used in construction, transportation, chemical, machinery, and communications industries. However, most polymer materials are flammable and easily ignited during use, potentially causing fires. Furthermore, polymer materials are susceptible to thermal oxidative degradation during long-term service, resulting in surface defects such as spots, streaks, cracks, blooming, chalking, and changes in gloss and color, leading to a comprehensive decline in the mechanical, electrical, and service properties of the polymer. Therefore, flame retardants and antioxidants are needed to improve the flame retardant and anti-aging properties of polymer materials to meet market demands.

[0003] Currently, existing technologies involve directly adding flame retardants and commercially available small-molecule antioxidants to polymer materials to achieve flame retardancy and anti-aging properties. Antioxidants are mostly small-molecule compounds, which are prone to volatilization and migration during processing and use, losing their antioxidant properties. Furthermore, when added in high amounts, they can cause blooming, polluting the environment in which the polymer material is used. Research by Hu et al. (Journal of Hazardous Materials 352 (2018) 92-100) shows that during long-term service, flame-retardant elements and agents migrate to the material surface, leading to the precipitation of flame retardants and a decrease in the flame-retardant performance of the polymer material. Therefore, directly adding flame retardants and antioxidants to polymer materials will result in the migration and precipitation of antioxidants and flame retardants during long-term use, leading to a deterioration in the anti-aging and flame-retardant properties of the polymer material.

[0004] Increasing research indicates that microencapsulation technology can improve the compatibility of flame retardants in polymers and the durability of flame-retardant materials, significantly enhancing the flame-retardant performance of microencapsulated flame retardant materials. Free radical polymerization is a commonly used method for preparing microencapsulated polymer shells. It uses olefin monomers containing unsaturated double bonds as raw materials, breaking the double bonds in the monomer molecules and repeatedly incorporating them through addition reactions to link many monomers together to form macromolecules. This invention prepares the polymer shell through free radical copolymerization containing double bonds. The molecular weight of condensation polymerization initially increases slowly, then accelerates; in free radical copolymerization, the molecular weight is independent of time, increasing rapidly after initiation. Encapsulating the flame retardant surface with a polymer layer through free radical polymerization gives it hydrophobic, oleophilic, and polymer-affinity interfacial properties, resulting in better compatibility within the matrix and reducing damage to the material's mechanical properties caused by the addition of the flame retardant.

[0005] Phosphorus compounds are excellent flame retardants, and substances containing low-valent phosphorus act as hydroperoxide decomposers, reducing hydroperoxides released from polymers to alcohols while being oxidized to phosphate esters, such as phosphites, which are commonly used as halogen-free flame retardants and antioxidants. 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO, phosphorus in +1 valence) and diphenylphosphine chloride (DC, phosphorus in +1 valence) are novel flame retardant intermediates. Low-valent phosphorus flame retardants primarily improve flame retardant performance through a gas-phase flame retardant mechanism. Furthermore, hindered phenols not only effectively scavenge free radicals within substances, acting as antioxidants, but also possess certain gas-phase flame retardant properties. However, there are no research reports on +1 valence phosphorus-containing flame retardants and hindered phenols being coated onto the flame retardant surface via double bond polymerization. Therefore, it is of great significance to prepare core-shell structured flame retardants with anti-thermal-oxidative aging function by free radical polymerization of compounds containing low-valent phosphorus or hindered phenols, and to apply them to the research on flame retardancy and anti-oxidation of polymer composites. Summary of the Invention

[0006] This invention addresses the problem in existing flame-retardant polymer materials where the migration and precipitation of antioxidants and flame retardants during long-term use leads to a decline in the anti-aging and flame-retardant properties of the polymer materials. It provides a core-shell structured flame retardant with anti-thermal-oxidative aging capabilities and its application in the preparation of flame-retardant materials. This flame retardant not only imparts excellent flame-retardant and mechanical properties to polymer composites but also solves the problem of long-term heat aging resistance in flame-retardant polymer composites.

[0007] The flame retardant of this invention has a core-shell structure. The shell layer is formed by free radical copolymerization of phosphorus-containing flame retardant monomers with double bonds or hindered phenolic monomers with double bonds on the surface of the core flame retardant. The shell layer not only alters the surface and interfacial properties and water resistance of the flame retardant, but also possesses flame retardant properties, working synergistically with the core flame retardant. Furthermore, the low-valence phosphorus or hindered phenol in the shell layer imparts antioxidant properties to the core-shell flame retardant, improving the material's aging resistance.

[0008] This invention relates to a core-shell structured flame retardant with resistance to thermo-oxidative aging, comprising a core and a shell structure. The core is a flame retardant, and the shell structure is a polymer containing hindered phenols and low-valence phosphorus. The mass ratio of the core to the shell structure is 100:5–25.

[0009] The flame retardant is selected from one or more of the following: magnesium hydroxide, aluminum hydroxide, metal double hydroxides, basic magnesium carbonate, basic lanthanum carbonate, basic cerium carbonate, melamine phosphate, melamine polyphosphate, melamine cyanurate, pentaerythritol, ammonium polyphosphate, piperazine pyrophosphate, aluminum hypophosphite, aluminum phosphonate, charring agent, expandable graphite, zinc borate, graphene, transition metal disulfides, carbon nanotubes, halloysite, sepiolite, and kaolin, mixed in any proportion.

[0010] The present invention discloses a method for preparing a core-shell structured flame retardant with anti-thermal-oxidative aging function, comprising the following steps:

[0011] The flame retardant (FR) was added to the solvent and stirred and dispersed evenly under a nitrogen atmosphere. Antioxidant double bond monomers and free radical initiators were added, and the temperature was raised to 60-80℃ for 4-12 hours. After the reaction was completed, the temperature was lowered to room temperature, filtered and washed, and the resulting product was dried in an oven at 60-80℃ to constant weight to obtain a solid product.

[0012] The free radical initiator is selected from one or more of cyclohexanone peroxide, benzoyl peroxide, tert-butyl hydroperoxide, azobisisobutyronitrile, and azobisisoheptanenitrile. The amount of free radical initiator added is 0.5%-5% of the antioxidant double bond monomer.

[0013] The solvent is selected from one or more solvents such as tetrahydrofuran, dimethyl sulfoxide, cyclohexane, cyclohexanone, chloroform, toluene, xylene, benzene, dioxane, ethyl acetate, acetone, and butanone.

[0014] The antioxidant double bond monomer is selected from one or more of DHA, DCHA, HHA, and HDPP, and its structure is shown below:

[0015] .

[0016] Different monomers can be combined and copolymerized to exert flame-retardant effects with different structures. The synergistic effect makes the flame retardant more efficient than the shell prepared by polymerization of a single monomer.

[0017] The synthetic route for the antioxidant double bond monomer includes:

[0018] Route 1: Add DOPO to the solvent and stir, then heat to 40-60℃. After the DOPO is completely dissolved, add hydroxyethyl acrylate and triethylamine, and stir at this temperature for 30 minutes. Then add carbon tetrachloride dropwise and react for 4-8 hours. After the reaction is complete, cool to room temperature, wash with hydrochloric acid, saturated saline solution and sodium bicarbonate solution, remove water with anhydrous magnesium sulfate, filter and rotary evaporate to recover the solvent, and obtain the product DHA (DOPO grafted hydroxyethyl acrylate).

[0019] Route 2: Hydroxyethyl acrylate and triethylamine were added to a solvent and stirred, and the temperature was raised to 40-60℃. After uniform dispersion, diphenylphosphine chloride was added dropwise to the above solution and reacted for 4-8 hours. After the reaction was completed, the solution was cooled to room temperature, washed with hydrochloric acid, saturated saline solution and sodium bicarbonate solution, and dehydrated with anhydrous magnesium sulfate. The solvent was recovered by rotary evaporation after filtration to obtain the product DCHA (diphenylphosphine chloride grafted hydroxyethyl acrylate).

[0020] Route 3: 3,5-Di-tert-butyl-4-hydroxyphenylpropionic acid was added to the reaction system of thionyl chloride and solvent, and the mixture was heated to 40-60℃ under a nitrogen atmosphere for 4-8 h. After the reaction was completed, the mixture was cooled to room temperature, and the solvent was recovered by rotary evaporation to obtain a viscous liquid product (3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride). Hydroxyethyl acrylate and triethylamine were added to the solvent and stirred, and the mixture was heated to 40-60℃. After uniform dispersion, 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride was added dropwise to the above solution, and the mixture was reacted for 4-8 h. After the reaction was completed, the mixture was cooled to room temperature, washed with hydrochloric acid, saturated brine and sodium bicarbonate solution, dehydrated with anhydrous magnesium sulfate, filtered and the solvent was recovered by rotary evaporation to obtain the product HHA (3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride grafted with hydroxyethyl acrylate).

[0021] Route 4: Hydroxyethyl acrylate and triethylamine are added to a solvent and stirred, and the temperature is raised to 40-60℃. After they are evenly dispersed, diphenyl chlorophosphate is added dropwise to the above solution and reacted for 4-8 hours. After the reaction is completed, the solution is cooled to room temperature, washed with hydrochloric acid, saturated saline solution and sodium bicarbonate solution, dehydrated with anhydrous magnesium sulfate, filtered and rotary evaporated to recover the solvent, and the product HDPP (diphenyl phosphate grafted with hydroxyethyl methacrylate) is obtained.

[0022] This invention relates to the application of a core-shell structured flame retardant with anti-thermal-oxidative aging properties in the preparation of flame-retardant materials.

[0023] Specifically, the core-shell structure flame retardant is added to the polymer matrix and mixed uniformly in a mixer or extruder at 120-250°C. Then, a crosslinking agent and a lubricant are added, and after mixing uniformly, the mixture is vulcanized for different times in a flat vulcanizing machine to prepare a flame-retardant polymer composite material.

[0024] The components, by mass, include: 40-90 parts polymer, 10-60 parts core-shell flame retardant, 0-1.5 parts crosslinking agent, and 0-1 part lubricant.

[0025] The polymer matrix is ​​selected from one or more of the following polymers: polyethylene, ethylene propylene diene monomer (EPDM) rubber, polypropylene, ethylene-vinyl acetate copolymer, ethylene-octene copolymer, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, natural rubber, chloroprene rubber, silicone rubber, polyurethane, polyurea, polyamide, polyester, polycarbonate, polylactic acid, polystyrene, thermoplastic elastomers, epoxy resin, and unsaturated polyester.

[0026] The crosslinking agent is selected from one or more of dicumyl peroxide, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate, mixed in any proportion.

[0027] The lubricant is selected from one or more of silicone powder, zinc stearate, paraffin wax, and PE wax, mixed in any proportion.

[0028] The core-shell structured flame retardant of this invention, which has anti-thermal and oxidative aging function, has excellent flame retardant and anti-oxidative functions when used in polymer materials, thus meeting the requirements of long-term flame retardancy and anti-thermal and oxidative aging performance of polymer materials.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The core-shell structured microencapsulated flame retardant for polymers with anti-thermal-oxidative aging function proposed in this invention abandons the traditional small-molecule antioxidants. It adopts interface control technology to polymerize hindered phenols or low-valence phosphorus compounds containing double bonds on the surface of the core-shell structured flame retardant through free radical polymerization, forming a polymer shell layer with anti-thermal-oxidative aging function, thus obtaining a high molecular weight antioxidant. This makes the antioxidant resistant to migration and precipitation, and it can exert anti-thermal-oxidative aging effect for a long time during the service life of polymer materials. When used to prepare antioxidant polymer composite materials, it has excellent long-term anti-thermal-oxidative aging function.

[0031] 2. This invention proposes a core-shell structured flame retardant for polymers with anti-thermal and oxidative aging properties. The shell layer of the flame retardant incorporates low-valent phosphorus or hindered phenolic compounds. The shell layer contains a benzene ring structure with char-forming function and phosphorus elements. This not only allows for synergistic flame retardancy with the core flame retardant, but also the +5 and +1 / 3 valent phosphorus composite shell layer and the hindered phenol and low-valent phosphorus composite shell layer themselves can achieve synergistic flame retardancy in both the gas phase and condensed phase. Applying core-shell structured flame retardants to polymers can improve the flame retardant performance and flame retardant rating of flame-retardant materials. During combustion, the low-valent phosphorus flame retardant and hindered phenol capture free radicals, interrupting the combustion chain reaction and thus exerting a gas-phase flame retardant effect, while the high-valent phosphorus exerts a condensed-phase flame retardant effect, further improving the flame retardant performance of the flame-retardant polymer material.

[0032] 3. The present invention proposes a core-shell structured flame retardant for polymers with anti-thermal and oxidative aging function. The microencapsulated shell is an organic macromolecular polymer, which can improve the interfacial compatibility between the flame retardant and the polymer, thereby improving the compatibility of the flame retardant in the polymer and thus improving the mechanical properties of the polymer material. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the synthesis route of the present invention.

[0034] Figure 2 The corresponding proton spectrum (a) and phosphorus spectrum (b) for DHA.

[0035] Figure 3 The corresponding proton spectrum (a) and phosphorus spectrum (b) of DCHA.

[0036] Figure 4 The corresponding proton spectrum of HHA.

[0037] Figure 5 The corresponding 1H NMR spectrum (a) and 1H NMR spectrum (b) for HDPP.

[0038] Figure 6 Contact angle test images for the corresponding APP and DHA@APP.

[0039] Figure 7 Contact angle test images corresponding to MH and HHA@MH.

[0040] Figure 8 The changes in oxidation induction time for each sample after 5 days of extraction in acetone.

[0041] Figure 9 Contact angle test images corresponding to PAPP and DCHA@PAPP.

[0042] Figure 10 Contact angle test images corresponding to MPP and DCHA@MPP. Detailed Implementation

[0043] To further illustrate the technical solution of the present invention, preferred embodiments are described below in conjunction with examples. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Example 1:

[0044] 1. Add 2.16 g DOPO to 300 mL of chloroform and stir. Heat to 40°C until DOPO is completely dissolved. Then add 1.16 g hydroxyethyl acrylate and 2.02 g triethylamine and stir at this temperature for 1 h. Next, add 2.31 g carbon tetrachloride dropwise and react for 6 h. After the reaction is complete, cool to room temperature and wash with 1 mol / L hydrochloric acid, saturated saline solution, and 1 mol / L sodium bicarbonate solution. Remove water with anhydrous magnesium sulfate. Recover the solvent by rotary evaporation to obtain the product DHA (DOPO-grafted hydroxyethyl acrylate).

[0045] 2. Add 1.16 g of hydroxyethyl acrylate and 2.02 g of triethylamine to 300 mL of tetrahydrofuran and stir, then heat to 50 °C. After uniform dispersion, add 3.56 g of diphenylphosphine chloride dropwise to the above solution and react for 5 h. After the reaction is complete, cool to room temperature and wash with 1 mol / L hydrochloric acid, saturated saline solution, and 1 mol / L sodium bicarbonate solution, then remove water with anhydrous magnesium sulfate. Recover the solvent by rotary evaporation to obtain the product DCHA (diphenylphosphine chloride grafted hydroxyethyl acrylate).

[0046] 3. Dissolve 5.56 g (0.02 mol) of 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid in 100 mL of chloroform in a 250 mL three-necked flask. Under nitrogen protection, slowly add 4 mL of thionyl chloride and react at 50 °C for 5 h. After the reaction is complete, remove the solvent and unreacted thionyl chloride by vacuum distillation to obtain 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride. Add 2.3 g of hydroxyethyl acrylate and 4 g of triethylamine to chloroform and stir, then heat to 60 °C. After uniform dispersion, add 5.56 g of 3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride dropwise to the above solution and react for 7 h. After the reaction is complete, cool to room temperature and wash with 1 mol / L hydrochloric acid, saturated saline solution, and 1 mol / L sodium bicarbonate solution, then remove water with anhydrous magnesium sulfate. The solvent was recovered by rotary evaporation to obtain the product HHA (3,5-di-tert-butyl-4-hydroxyphenylpropionyl chloride grafted hydroxyethyl acrylate).

[0047] 4. Add 1.16 g of hydroxyethyl acrylate and 2.02 g of triethylamine to 300 mL of tetrahydrofuran and stir, then heat to 50 °C. After uniform dispersion, add 2.69 g of diphenylphosphine chloride dropwise to the above solution and react for 7 h. After the reaction is complete, cool to room temperature and wash with 1 mol / L hydrochloric acid, saturated saline solution, and 1 mol / L sodium bicarbonate solution, then remove water with anhydrous magnesium sulfate. Recover the solvent by rotary evaporation to obtain the product HDPP (diphenyl phosphate grafted with hydroxyethyl acrylate). Example 2:

[0048] 1. Add 100 g of ammonium polyphosphate (APP) to a 500 mL three-necked flask and stir while purging with nitrogen. After the mixture is evenly dispersed, add 10 g of DHA and 0.2 g of cyclohexanone peroxide. After dissolution, heat to 80 °C and react for 6 h. After the reaction is complete, cool to room temperature, filter, wash and dry. Dry the obtained product in an oven at 60 °C to constant weight to obtain a solid product (DHA@APP).

[0049] 2. Add 12 parts of aging-resistant core-shell structure flame retardant (DHA@APP) and 4 parts of triazine macromolecular charring agent (CFA) to 84 parts of ethylene propylene diene monomer (EPDM) by mass ratio, then add 0.6 parts of triallyl cyanurate (TAIC) and 0.6 parts of dicumyl peroxide (DCP). Then mix in an internal mixer or extruder at 90-100℃ until uniformly extruded and granulated, and vulcanize at 160℃ for 15 minutes in a flat vulcanizing machine to produce sheets.

[0050] To further verify the performance of the aging-resistant core-shell flame retardant DHA@APP, we designed the following methods for flame retardant applications in EPDM: equal replacement with uncoated APP and a mixture of APP and DHA. These methods are shown in Tables 1, 2, 3, and 4. Figure 5 The comparative formulations shown are compared to the comprehensive physical property test results of the two. Table 1 is the formulation table of the durable antioxidant flame retardant polymer composite material and the vertical burning and oxygen index test results; Table 2 is the mechanical property change data table of the durable antioxidant flame retardant polymer composite material before and after being placed in a 125℃ heat aging oven for 100h; Table 3 is the mechanical property test table of each sample of the durable antioxidant flame retardant polymer composite material with refrigerant R134a / R1234yf and refrigeration oil POE / PAG (10:1), after pre-aging at 90℃×96h and then aging at 150℃×168h; Table 4 is the test table of compression set of the durable antioxidant flame retardant polymer composite material at 130℃×96h×40%; Figure 5 These are contact angle test images of APP and DHA@APP.

[0051]

[0052]

[0053]

[0054] Example 3:

[0055] 1. Add 100 g of magnesium hydroxide (MH) to a 500 mL three-necked flask and stir while purging with nitrogen. After the mixture is evenly dispersed, add 2 g of HHA, 8 g of DHA, and 0.8 g of azobisisobutyronitrile (AIO). After the HHA dissolves, heat to 70 °C and react for 8 h. After the reaction is complete, cool to room temperature, filter, wash, and dry. The resulting product is then dried in an oven at 60 °C to constant weight to obtain a solid product (DH@MH).

[0056] 2. Add 60 parts of aging-resistant core-shell flame retardant (DH@MH) to 40 parts of ethylene propylene diene monomer (EPDM) by mass ratio, then add 0.5 parts of trimethylolpropane trimethacrylate (TPT) and 0.4 parts of dicumyl peroxide (DCP), add 1 part of silicone powder, and then mix in an internal mixer or extruder at 100-120℃ until uniform, then extrude and granulate, and vulcanize at 165℃ for 15 minutes in a flat vulcanizing machine to make sheets.

[0057] To further verify the performance of the aging-resistant core-shell flame retardant DH@MH, we designed equal-volume replacements of it with uncoated MH and MH and HHA in EPDM flame retardant systems, as shown in Tables 5 and 6. Figure 6 , 7 The comparative formulations shown are compared to the comprehensive physical property test results of the two. Table 7 is the formulation table of the durable antioxidant flame retardant polymer composite material and the results of vertical burning and oxygen index tests; Table 8 is the data table of mechanical property changes of the durable antioxidant flame retardant polymer composite material before and after 14 days in a 180 ℃ heat aging oven; Table 9 is the data table of mechanical property changes of the durable antioxidant flame retardant polymer composite material before and after 14 days in a 180 ℃ heat aging oven. Figure 6 These are contact angle test images for MH and DH@MH. Figure 7 This is a graph showing the changes in oxidation induction time of each sample after 5 days of extraction in acetone.

[0058]

[0059] Example 4:

[0060] 1. Add 100 g of piperazine pyrophosphate (PAPP) to a 500 mL three-necked flask and stir while purging with nitrogen. After the mixture is evenly dispersed, add 15 g of DCHA and 1 g of benzoyl peroxide. After the mixture dissolves, heat to 75 °C and react for 7 h. After the reaction is complete, cool to room temperature, filter, wash and dry. The resulting product is then dried in an oven at 60 °C to constant weight to obtain the solid product (DCHA@APP).

[0061] 2. Add 28 parts of aging-resistant core-shell structure flame retardant (DCHA@PAPP) to 72 parts of polyethylene (PE) by mass ratio, then add 0.8 parts of triallyl triisocyanurate (TAIC) and 0.4 parts of dicumyl peroxide (DCP). Then mix them in an internal mixer or extruder at 110-115℃ until uniform, then extrude and granulate. Finally, vulcanize in a flat vulcanizing machine at 165℃ for 12 minutes to make sheets.

[0062] To further verify the performance of the aging-resistant core-shell flame retardant DCHA@PAPP, we designed comparative formulations as shown in Tables 7 and 8, and compared the comprehensive physical property test results of the two formulations, using equal amounts of DCHA@PAPP@PAPP and uncoated PAPP@PAPP, as well as blends of DCHA@PAPP ... Figure 8 These are contact angle test images of PAPP and DCHA@PAPP.

[0063]

[0064] Example 5:

[0065] 1. Add 100 g of melamine polyphosphate (MPP) to a 500 mL three-necked flask and stir while purging with nitrogen. After the mixture is evenly dispersed, add 20 g of DCHA and 1 g of azobisisobutyronitrile. After the mixture dissolves, heat to 75 °C and react for 7 h. After the reaction is complete, cool to room temperature, filter, wash, and dry. The resulting product is then dried in an oven at 60 °C to constant weight to obtain a solid product (DCHA@MPP).

[0066] 2. Add 16 parts of aging-resistant core-shell structure flame retardant (DCHA@PAPP) to 84 parts of thermoplastic polyurethane (TPU) by mass ratio, then mix them in an internal mixer or extruder at 180°C until uniform. After uniform mixing, extrude and granulate at 190°C, and press them into sheets in a flat vulcanizing machine.

[0067] To further verify the performance of the aging-resistant core-shell flame retardant DCHA@MPP, we designed comparative formulations as shown in Tables 9 and 10, and compared the comprehensive physical property test results of the two formulations, using equal amounts of DCHA@MPP, uncoated MPP, and blends of MPP and DCHA in TPU flame retardant systems. Table 9 shows the formulation table of the durable antioxidant flame retardant polymer composite material and the results of vertical burning and oxygen index tests; Table 10 shows the changes in mechanical properties of the durable antioxidant flame retardant polymer composite material before and after 125 days in a 150℃ heat aging oven. Figure 9These are contact angle test images of MPP and DCHA@MPP.

[0068]

[0069] Example 6:

[0070] 1. Add 100 g of aluminum hypophosphite (AHP) to a 500 mL three-necked flask and stir while purging with nitrogen. After the mixture is evenly dispersed, add 10 g of DCHA, 10 g of HDPP, and 1 g of azobisisobutyronitrile. After the mixture dissolves, heat to 80 °C and react for 6 h. After the reaction is complete, cool to room temperature, filter, wash, and dry. The resulting product is then dried in an oven at 60 °C to constant weight to obtain the solid product (DP@AHP).

[0071] 2. Add 52 parts of aging-resistant core-shell structure flame retardant (DP@AHP) to 48 parts of thermoplastic elastomer (TPE) by mass ratio, and then mix them in an internal mixer or extruder at 185°C until uniform. After uniform mixing, extrude and granulate at 195°C, and press them into sheets in a flat vulcanizing machine.

[0072] To further verify the performance of the aging-resistant core-shell flame retardant DP@MPP, we designed comparative formulations as shown in Tables 11 and 12, and compared the comprehensive physical property test results of the two formulations, using DP@MPP as an equal substitute for uncoated AHP and blends of AHP, DCHA, and HDPP in TPE flame retardant systems. Table 11 shows the formulation table of the durable antioxidant flame retardant polymer composite and the results of vertical burning and oxygen index tests; Table 12 shows the changes in mechanical properties of the durable antioxidant flame retardant polymer composite before and after 125 days in a 150℃ heat aging oven.

[0073]

[0074]

[0075] Based on the above experimental results, the following conclusions can be drawn:

[0076] (1) The hydrophobicity of the synthesized core-shell structure flame retardant with anti-thermal and oxygen aging function is improved. On the other hand, the compatibility and dispersibility of the aging-resistant core-shell structure flame retardant in organic polymer materials are also improved.

[0077] (2) Composite materials with added core-shell structure flame retardants with anti-thermal and oxygen aging functions have better physical and mechanical properties and flame retardant properties than flame retardant composite materials with added small molecule antioxidants.

[0078] (3) The composite material with added core-shell structure flame retardant with anti-thermal and oxygen aging function showed better mechanical property degradation than other composite materials after long-term heat aging test.

Claims

1. A method for preparing a flame retardant with a core-shell structure having a function of resisting thermal oxidative aging, characterized by It comprises the following steps: The flame retardant is added into the solvent, stirred and dispersed uniformly under the nitrogen atmosphere, the antioxidant functional double bond monomer and the free radical initiator are added, the temperature is raised to 60-80℃, and the reaction is carried out for 4-12h; after the reaction is completed, the temperature is lowered to room temperature, filtered and washed, and dried to constant weight to obtain a solid product; The core-shell structure flame retardant with the anti-thermal oxidation aging function is composed of a core and a shell structure, wherein the core is a flame retardant, the shell structure is a polymer containing a hindered phenol and a low-valence phosphorus, and the mass ratio of the core layer to the shell structure is 100:5-25; The flame retardant is selected from one or more of magnesium hydroxide, aluminum hydroxide, metal double hydroxide, basic magnesium carbonate, basic lanthanum carbonate, basic cerium carbonate, melamine phosphate, melamine polyphosphate, melamine cyanurate, ammonium polyphosphate, piperazine pyrophosphate, aluminum hypophosphite, aluminum hypophosphite, expandable graphite, zinc borate in any proportion; The antioxidant functional double bond monomer is selected from one or more of DHA, DCHA, HHA, HDPP, and the structure is as shown below: 。 2. The preparation method according to claim 1, characterized in that: The free radical initiator is selected from one or more of cyclohexanone peroxide, dibenzoyl peroxide, tert-butyl hydroperoxide, azobis isobutyronitrile, and azobis isohexyl nitrile.

3. The preparation method according to claim 1, characterized in that: The solvent is selected from one or more of tetrahydrofuran, dimethyl sulfoxide, cyclohexane, cyclohexanone, chloroform, toluene, xylene, benzene, dioxane, ethyl acetate, acetone, and butanone.

4. The application of the core-shell structure flame retardant with the anti-thermal oxidation aging function prepared by the preparation method of any one of claims 1-3 in the preparation of a flame-retardant material.

5. The application according to claim 4, characterized in that: The core-shell structure flame retardant is added to a polymer matrix, mixed in a banbury mixer or an extruder at 120-250℃ until uniform, and then a crosslinking agent and a lubricant are added, mixed uniformly, and vulcanized to prepare a flame-retardant polymer composite material.

6. The application according to claim 5, characterized in that: The components include, by mass fraction, 40-90 parts of a polymer, 10-60 parts of the core-shell structure flame retardant, 0-1.5 parts of a crosslinking agent, and 0-1 part of a lubricant.

7. The application according to claim 5, characterized in that: The polymer matrix is selected from one or more of polyethylene, ethylene-propylene-diene rubber, polypropylene, ethylene-vinyl acetate copolymer, ethylene-octene copolymer, styrene-butadiene-styrene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, natural rubber, chloroprene rubber, silicone rubber, polyurethane, polyurea, polyamide, polyester, polycarbonate, polylactic acid, and epoxy resin.

8. The application according to claim 5, characterized in that: The crosslinking agent is selected from one or more of dicumyl peroxide, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate in any proportion.

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