Phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and preparation method of phosphorus-boron-nitrogen multi-element synergistic flame retardant

Abstract

The invention relates to the technical field of chemical synthesis, and discloses a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and a preparation method thereof.The preparation method comprises the steps that 2, 4-dinitrophenol is dissolved in a reaction solvent containing aniline, a reaction is conducted in the hydrogen atmosphere under the action of a catalyst, and 2-aminobiphenyl is obtained; the preparation method comprises the following steps: dissolving 2-aminobiphenyl in an organic solvent to form a reaction base solution, adding a phosphoryl chloride compound into the reaction base solution, and condensing to obtain a phosphamide product; and dissolving the phosphamide product in an organic solvent system, adding a boron compound, and reacting to obtain the flame retardant. The flame retardant takes aminobiphenyl as a framework, and a phosphorus-containing unit and a boron-containing unit are introduced to the framework, so that molecules contain flame-retardant elements of phosphorus, boron and nitrogen, the synergistic effect of gas-phase flame retardance and condensed-phase charring is realized, the limit oxygen index and the vertical combustion performance are improved under the condition of relatively low addition amount, and the peak heat release rate and the smoke density are reduced; and after being subjected to damp-heat aging, the flame-retardant plastic still has a relatively high flame-retardant property retention rate.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, specifically to a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl and its preparation method. Background Technology

[0002] The industrial production of aromatic chemicals such as nitrobenzene and aniline generates large amounts of high-concentration wastewater containing substances like dinitrophenol and aniline. These pollutants are highly toxic and difficult to degrade, typically treated as hazardous waste in biological treatment systems. This process places a heavy burden on equipment and microbial systems, incurs high treatment costs, and has long lacked high-value-added resource utilization pathways, leading to potential resource waste and increased environmental pressure. The dinitrophenol and aniline compounds in this wastewater are essentially reactive aromatic compounds; efficient conversion and utilization could provide new raw material sources for green chemistry.

[0003] In the field of flame retardant materials, biphenyl flame retardants have attracted attention due to their high carbon content and good thermal stability, but they still have many shortcomings in practical applications. On the one hand, their processing window is narrow, and they are prone to migration and precipitation in resin or rubber systems, affecting the appearance and mechanical properties of the products. On the other hand, their flame retardant efficiency is relatively low compared to traditional halogen or phosphorus-based flame retardants, requiring high addition amounts to achieve the same level of flame retardant effect, which further weakens the mechanical properties of the material and increases processing difficulty. In addition, some modified biphenyl flame retardants usually rely on complex functionalization reactions or multi-step synthesis routes, resulting in high production costs and hindering large-scale promotion.

[0004] Some existing solutions improve flame retardancy ratings by compounding multiple flame retardants or introducing multihalogen structures into the biphenyl framework. However, the synergistic effect of such flame retardant systems is limited, and the flame retardant mechanism remains relatively simple. Furthermore, multihalogen structures may generate corrosive or toxic byproducts during combustion, posing potential risks to the environment and health. While some modified flame retardants containing biphenyl structures can improve flame retardant performance to some extent, they generally suffer from insufficient high-temperature stability, high risk of migration and precipitation, poor system compatibility, and decreased mechanical properties, making it difficult to simultaneously meet the requirements of high flame retardant efficiency, good durability, and environmental friendliness.

[0005] In summary, high-concentration wastewater containing aromatic compounds such as dinitrophenol and aniline generated during industrial production processes is typically treated only as hazardous waste, lacking mature and stable resource utilization technologies. This results in high treatment costs and underutilization of raw material value. In the field of flame retardant materials, existing biphenyl-based flame retardants generally suffer from low flame retardant efficiency, require high addition levels to meet flame retardant grade requirements, have poor processing adaptability, and are prone to migration and precipitation. While introducing multihalogen structures into the biphenyl framework or using a combination of multiple flame retardants can be effective in balancing structural stability, environmental safety, and overall performance requirements, related technical solutions still have room for improvement in terms of raw material utilization and product application performance. Summary of the Invention

[0006] This invention provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, in order to solve the problems of insufficient thermal stability, easy migration and precipitation during processing, low flame retardant efficiency, decreased mechanical properties of products, and complex synthesis routes and high costs of existing biphenyl flame retardants.

[0007] In a first aspect, the present invention provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl, wherein the flame retardant is shown in formula (I):

[0008] Wherein, R is a C1 to C3 straight-chain or branched alkyl group; for example, R can be methyl, ethyl, n-propyl or isopropyl.

[0009] The phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl provided by this invention uses the biphenyl structure as the molecular backbone. While maintaining a high carbon content and structural stability, it introduces multiple flame-retardant active elements such as phosphorus, boron, and nitrogen, giving the flame retardant molecule a multi-element synergistic characteristic in its structure, which is beneficial to improving the overall stability of the flame retardant system in practical applications. This invention, through the reasonable limitation of the substituent R, enables the flame retardant molecule structure to have a certain degree of tunability. While meeting the requirements for flame retardant performance, it helps to improve its compatibility with different polymer matrices and reduce the risk of migration and precipitation. Compared with flame retardant systems with single structures or those dependent on halogen elements, the flame retardant of this invention has a simpler and more reasonable structural design, enabling stable application under low addition conditions. It is suitable for polymer material systems that require both flame retardant performance and long-term stability of the material.

[0010] Secondly, the present invention provides a method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl, comprising the following steps: (1) Dissolve 2,4-dinitrophenol in a reaction solvent containing aniline and react it under a hydrogen atmosphere and a catalyst to obtain 2-aminobiphenyl; (2) Dissolve 2-aminobiphenyl in an organic solvent to form a reaction base liquid, add chlorophosphoryl compound to the reaction base liquid, and condense to obtain phosphoramide product; (3) In an organic solvent system, the phosphoramide product is dissolved and then reacted with boron compounds to obtain a flame retardant.

[0011] The preparation method provided by this invention uses 2,4-dinitrophenol and a reaction solvent containing aniline as starting materials. The target flame retardant molecular structure is constructed sequentially through hydrogenation, condensation, and the introduction of boron-based units. The reaction steps are clearly connected, and the process route is simple, enabling the efficient preparation of the target product with fewer reaction steps. The reaction conditions used in this method are relatively mild, the equipment requirements are low, and the solvents and reagents used are all conventional chemical raw materials, exhibiting good operability and repeatability.

[0012] This invention first constructs a 2-aminobiphenyl intermediate, then introduces phosphoryl and boron-based structural units, enabling the stable introduction of functional units in a predetermined order. This improves reaction controllability and product structure consistency, avoiding side reaction problems caused by the simultaneous reaction of multiple functional groups. Compared to synthetic routes requiring multi-step protection-deprotection or complex functionalization operations, the method of this invention is more direct and suitable for continuous or scale-up production.

[0013] In one alternative embodiment, in step (1), the catalyst comprises a supported metal catalyst; In an optional embodiment, in step (2), the chlorophosphoryl compound includes one or both of diethyl chlorophosphate and diisopropyl chlorophosphate; In an optional embodiment, in step (3), the boron compound includes one or both of boric acid and boron trichloride; Preferably, the support for the supported metal catalyst is activated carbon, and the supported metal includes one or more of Fe, Zn, Pd, Pt, or Ru; Preferably, the amount of the supported metal catalyst is 2.5% to 3.5% of the mass of 2,4-dinitrophenol; for example, the amount of the supported metal catalyst is 2.5%, 2.8%, 3.0%, 3.2% or 3.5% of the mass of 2,4-dinitrophenol.

[0014] Preferably, the chlorophosphoryl compound and / or the boron compound are added to the reaction system dropwise.

[0015] In an optional embodiment, in step (2), the molar ratio of the chlorophosphoryl compound to 2-aminobiphenyl is (1.01~1.1):1; for example, the molar ratio of the chlorophosphoryl compound to 2-aminobiphenyl is 1.01:1, 1.05:1, 1.09:1, or 1.1:1.

[0016] By controlling the chlorophosphoryl compound in a slightly excess relative to 2-aminobiphenyl, the full condensation of the amino group and the chlorophosphoryl group can be promoted, the residue of unreacted raw materials can be reduced, and the side reactions or post-processing burden caused by the excess of chlorophosphoryl compound can be avoided.

[0017] In an optional embodiment, in step (3), the molar ratio of the boron compound to the phosphoramide product is (1~1.1):3; for example, the molar ratio of the boron compound to the phosphoramide product is 1:3, 1.02:3, 1.05:3, 1.08:3, or 1.1:3.

[0018] Limiting the molar ratio of boron compounds to phosphoramide products to a range close to the stoichiometry facilitates the full reaction of boron units with phosphoramide products, promotes the efficient construction of boron-nitrogen or boron-oxygen structures, and improves the consistency and stability of product structures. Through the synergistic control of the molar ratio, the risk of by-product formation can be reduced while ensuring complete reaction, thereby improving the synthesis efficiency and product quality stability of flame retardants.

[0019] In one optional embodiment, in step (1), the hydrogenation reaction is carried out in a hydrogen atmosphere, and the pressure inside the reaction system is 1.5 MPa to 2 MPa; for example, the pressure inside the reaction system is 1.5 MPa, 1.6 MPa, 1.8 MPa, 1.9 MPa or 2 MPa.

[0020] In one optional embodiment, the reaction temperature in step (1) is 90°C to 120°C. For example, the reaction temperature is 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C.

[0021] In one optional embodiment, in step (1), the mass ratio of aniline to 2,4-dinitrophenol is (0.8~3):1; for example, the mass ratio of aniline to 2,4-dinitrophenol is 0.8:1, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1.

[0022] In step (1), the reaction solvent containing aniline is a mixed solution of nitrobenzene and aniline; Preferably, the mass fraction of aniline in the mixed solution is 8 wt% to 15 wt%; for example, the mass fraction of aniline is 8 wt%, 9 wt%, 10 wt%, 12 wt%, 13 wt%, 14 wt% or 15 wt%.

[0023] In step (1), the mixed solution of 2,4-dinitrophenol and nitrobenzene and aniline is derived from industrial wastewater from the production process of nitrobenzene and aniline; The 2,4-dinitrophenol and aniline contained in the wastewater from the nitrobenzene and aniline plants are preliminarily purified and used directly as reaction raw materials. This approach not only replaces some high-purity chemical raw materials, significantly reducing raw material procurement costs and production expenses, but also reduces the treatment load and environmental costs associated with disposing of high-concentration organic wastewater as hazardous waste. Furthermore, by utilizing the reactive aromatic compounds in the wastewater, a synergistic effect of pollutant reduction and high-value-added chemical preparation is achieved, improving the overall economic efficiency and environmental friendliness of the process. This method provides a feasible technical path for the resource utilization of chemical wastewater while ensuring reaction feasibility and product quality, enhancing the practical value of the preparation method in industrial scale-up and engineering applications.

[0024] In an optional embodiment, in step (2), the organic solvent includes one or more of toluene, xylene, ethylbenzene, and cumene; preferably, the amount of organic solvent used is 8.2 to 10.6 mL of organic solvent per gram of 2-aminobiphenyl; for example, 8.2 mL, 9 mL, or 10.6 mL of organic solvent per gram of 2-aminobiphenyl.

[0025] In an optional embodiment, in step (2), an organic base catalyst is also added to the reaction substrate; Preferably, the molar ratio of 2-aminobiphenyl to the organic base catalyst is (50~76):1; for example, the molar ratio of 2-aminobiphenyl to the organic base catalyst is 50:1, 60:1, 70:1 or 76:1. Preferably, the organic base catalyst includes one or more of triethylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, and N,N-diisopropylethylamine.

[0026] In one optional embodiment, in step (2), 2-aminobiphenyl is dissolved in an organic solvent to form a reaction base liquid, and a chlorophosphoryl compound is added dropwise to the reaction base liquid. Then, the temperature is raised to 65-75°C and reacted for 2-6 hours to obtain a phosphoramide product through a condensation reaction. For example, the reaction temperature is 65°C, 68°C, 70°C, 72°C or 75°C, and the reaction time is 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0027] In one optional embodiment, in step (2), after the reaction is completed, the reaction system is concentrated by vacuum distillation and recrystallized to obtain the phosphoramide product.

[0028] In an optional embodiment, in step (3), the organic solvent includes one or two of xylene and ethylbenzene; preferably, the amount of organic solvent used is 3.9 to 5.4 mL of organic solvent per gram of phosphoramide product; for example, 3.9 mL, 4.1 mL, 5 mL or 5.4 mL of organic solvent per gram of phosphoramide product.

[0029] In an optional embodiment, in step (3), an acidic catalyst is further added to the organic solvent system; preferably, the acidic catalyst includes one or more of p-toluenesulfonic acid, sulfuric acid, and phosphoric acid. In one optional embodiment, the amount of acidic catalyst used is 0.78 wt% to 1.64 wt% of the mass of phosphoramide product A; for example: In an optional embodiment, in step (3), the phosphoramide product is dissolved in an organic solvent at 105°C to 120°C, and after the boron compound is added dropwise, the temperature is raised to 130°C to 150°C for reaction; for example, the dissolution temperature is 105°C, 110°C, 115°C or 120°C, and the reaction temperature is 130°C, 135°C, 140°C, 145°C or 150°C.

[0030] In an optional embodiment, in step (3), an antioxidant is added before the reaction; preferably, the antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol, tert-butylhydroquinone, or 1076 antioxidant.

[0031] The technical solution of this invention has the following advantages: The raw materials 2,4-dinitrophenol and aniline used in this invention are derived from high-concentration wastewater generated during industrial production. Compared with the traditional method of directly sending this type of wastewater into a biochemical treatment system, this invention utilizes the organic components as reaction raw materials, avoiding the cost pressure and resource waste caused by high-load treatment processes, and providing a new technical approach for the resource utilization of related wastewater.

[0032] The flame retardant preparation process of the present invention adopts conventional chemical reaction steps and mature reaction equipment. The reaction conditions involved are mild, the process route is clear, and the reagents and solvents used are all readily available conventional chemical raw materials. The overall preparation process does not rely on complex or special equipment and has good process operability and a good basis for scale-up applications.

[0033] The flame retardant obtained by this invention does not contain halogen elements in its molecular structure design, which can avoid the environmental and safety hazards that traditional halogen flame retardants may bring during use or combustion. It is in line with the current technical trend of flame retardant materials developing towards low-halogen and halogen-free directions, and is conducive to improving the environmental adaptability of the material system.

[0034] This invention constructs a flame retardant molecular skeleton with biphenyl structure as the core and introduces a variety of flame retardant functional units on this basis. This makes the resulting flame retardant easier to use in practical applications, reducing the amount required and mitigating the adverse effects on the processing and mechanical properties of the matrix material. As a result, a better balance is achieved between flame retardant performance and overall material performance.

[0035] Based on the above structural characteristics and preparation method, the flame retardant of the present invention has good applicability in different polymer material systems, can meet the application requirements of high material thermal stability and flame retardant performance, and has good engineering application potential. Detailed Implementation

[0036] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0037] The sources of raw materials in the embodiments and comparative examples of this invention are as follows: 2,4-Dinitrophenol, as well as nitrobenzene and aniline, all originate from wastewater containing relevant components generated during the production process of the nitrobenzene-aniline unit of Wanhua Chemical Co., Ltd.

[0038] Melamine polyphosphate (MPP) and decabromodiphenyl ether were both purchased from Beijing Innocare Technology Co., Ltd.

[0039] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0040] Example 1 This embodiment provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, specifically including the following steps: (1) Weigh 18.4 g of 2,4-dinitrophenol and dissolve it completely in 200 g of nitrobenzene-aniline solution to obtain a homogeneous reaction raw material solution; wherein the nitrobenzene-aniline solution is a mixed solution composed of nitrobenzene and aniline, and the mass fraction of aniline in the mixed solution is 10 wt%; The above-mentioned reactant solution was added to a reaction vessel, followed by the addition of 0.6 g of catalyst. The catalyst was a supported metal catalyst with activated carbon as the support, on which Fe, Pd, and Pt were loaded, and the total mass fraction of Fe, Pd, and Pt in the catalyst was 10 wt%. The system was then heated to 90 °C and hydrogenated at a hydrogen pressure of 1.5 MPa for 1 h. After the reaction was completed, the catalyst was recovered by filtration. The filtrate was subjected to vacuum distillation to recover unreacted aniline, and the remaining material was further distilled to obtain the product 2-aminobiphenyl.

[0041] (2) Weigh 16.9 g of 2-aminobiphenyl and 0.2 g of 1,8-diazabicyclo[5.4.0]undec-7-ene, add them to 150 mL of toluene, and stir under ice-water bath conditions to dissolve them completely, obtaining the reaction base solution. Place 18.0 g of diethyl chlorophosphate in a constant pressure dropping funnel and slowly add it dropwise to the above reaction base solution under nitrogen protection. After the addition is complete, remove the ice-water bath, raise the temperature to 70 ℃ and continue the reaction for 4 h. Monitor the reaction by thin-layer chromatography (TLC) to confirm the end of the reaction. After the reaction is complete, concentrate the reaction solution to near dryness by vacuum distillation, add 100 mL of anhydrous ethanol to the residue for recrystallization, and obtain phosphoramide product A.

[0042] (3) Weigh 30.5 g of phosphoramide product A and 0.15 g of 2,6-di-tert-butyl-p-cresol, add them to 100 mL of xylene, and stir to dissolve them under nitrogen protection at 110 °C to form a homogeneous reaction system. Dissolve 2.1 g of boric acid and 0.5 g of p-toluenesulfonic acid in 20 mL of xylene, and add them dropwise to the above reaction system under nitrogen atmosphere. After the addition is complete, maintain the reaction for 2 h. Then raise the system to 145 °C and continue the reaction for 3 h, during which time a water separator is connected to continuously remove the water generated in the reaction. After the reaction is completed, cool the system to room temperature to precipitate solid, and filter to obtain crude product; add 1 L of toluene to the filter cake for recrystallization purification to obtain the target product, aminobiphenyl, phosphorus-boron-nitrogen multi-component synergistic flame retardant; the nuclear magnetic resonance characterization data of the target product are as follows: 1 H NMR (500 MHz, Chloroform-d) δ 7.60 - 7.55 (m, 3H), 7.52 - 7.46 (m,6H), 7.39 (dt, 3H), 7.24 - 7.18 (m, 3H), 7.13 - 7.07 (m, 6H), 6.95 – 6.90 (m,3H), 6.88 – 6.83 (m, 3H), 4.49 (q, 12H), 1.30 (t, 18H).

[0043] The preparation route in this embodiment is as follows:

[0044] Example 2 This embodiment provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, specifically including the following steps: (1) Weigh 36.8 g of 2,4-dinitrophenol and dissolve it completely in 500 g of nitrobenzene-aniline solution to obtain a homogeneous reaction raw material solution; wherein the nitrobenzene-aniline solution is a mixed solution composed of nitrobenzene and aniline, and the mass fraction of aniline in the mixed solution is 15 wt%; The above-mentioned reactant solution was added to the reactor through a feed bottle, and then 1.0 g of catalyst was added to the reactor. The catalyst was a supported metal catalyst with activated carbon as the support, on which Fe, Pd, and Pt were loaded, and the total mass fraction of Fe, Pd, and Pt in the catalyst was 10 wt%. The system was then heated to 120 °C and hydrogenated at a hydrogen pressure of 2 MPa for 1 h. After the reaction was completed, the catalyst was recovered by filtration. The filtrate was subjected to vacuum distillation to recover unreacted aniline, and the remaining material was further purified by distillation to obtain the product 2-aminobiphenyl.

[0045] (2) Weigh 33.8 g of 2-aminobiphenyl and 0.5 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), add them to 300 mL of toluene, and stir under ice-water bath conditions to dissolve them completely, obtaining the reaction base solution. Place 35.0 g of diethyl chlorophosphate in a constant pressure dropping funnel and slowly add it dropwise to the above reaction base solution under nitrogen protection. After the addition is complete, remove the ice-water bath, raise the temperature to 70 ℃ and continue the reaction for 5 h. Monitor the reaction by thin-layer chromatography (TLC) to confirm the end of the reaction. After the reaction is complete, concentrate the reaction solution to near dryness by vacuum distillation, add 200 mL of anhydrous ethanol to the residue for recrystallization, and obtain phosphoramide product A.

[0046] (3) Weigh 61.5 g of phosphoramide product A and 0.3 g of 2,6-di-tert-butyl-p-cresol, add them to 200 mL of xylene, and stir to dissolve under nitrogen protection at 110 °C to form a homogeneous reaction system. Dissolve 4.3 g of boric acid and 0.8 g of p-toluenesulfonic acid in 50 mL of xylene, and add them dropwise to the above reaction system under nitrogen atmosphere. After the addition is complete, maintain the reaction for 2 h. Then raise the system to 135 °C and continue the reaction for 4 h, during which time a water separator is connected to continuously remove the water generated in the reaction. After the reaction is completed, cool the system to room temperature to precipitate solid, filter to obtain crude product; add 2 L of toluene to the filter cake for recrystallization purification to obtain the target product, aminobiphenyl, as a phosphorus-boron-nitrogen multi-component synergistic flame retardant.

[0047] Example 3 This embodiment provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, specifically including the following steps: (1) Weigh 92g of 2,4-dinitrophenol and dissolve it completely in 920g of nitrobenzene-aniline solution to obtain a homogeneous reaction raw material solution; wherein the nitrobenzene-aniline solution is a mixed solution composed of nitrobenzene and aniline, and the mass fraction of aniline in the mixed solution is 8 wt%; The above-mentioned reactant solution was added to the reactor through a feed bottle, followed by the addition of 3.2 g of catalyst. The catalyst was a supported metal catalyst with activated carbon as the support, on which Fe, Pd, and Pt were loaded, and the total mass fraction of Fe, Pd, and Pt in the catalyst was 10 wt%. The system was then heated to 100 °C and subjected to hydrogenation reaction at a hydrogen pressure of 1.6 MPa for 1.5 h. After the reaction was completed, the catalyst was recovered by filtration. The filtrate was subjected to vacuum distillation to recover unreacted aniline, and the remaining material was further purified by distillation to obtain the product 2-aminobiphenyl.

[0048] (2) Weigh 85g of 2-aminobiphenyl and 0.70g of triethylamine, add them to 700 mL of ethylbenzene, and stir under ice-water bath conditions to dissolve them completely, obtaining the reaction base solution. Place 87.5g of diethyl chlorophosphate in a constant pressure dropping funnel and slowly add it dropwise to the above reaction base solution under nitrogen protection. After the addition is complete, remove the ice-water bath, raise the temperature to 65℃ and continue the reaction for 6h. Monitor the reaction by thin-layer chromatography (TLC) to confirm the end of the reaction. After the reaction is complete, concentrate the reaction solution to near dryness by vacuum distillation, add 500 mL of anhydrous ethanol to the residue for recrystallization, and obtain phosphoramide product A.

[0049] (3) Weigh 153 g of phosphoramide product A and 0.8 g of 2,6-di-tert-butyl-p-cresol, add them to 500 mL of xylene, and stir to dissolve under nitrogen protection at 120 °C to form a homogeneous reaction system. Dissolve 10.3 g of boric acid and 1.2 g of sulfuric acid in 100 mL of xylene, and add them dropwise to the above reaction system under nitrogen atmosphere. After the addition is complete, maintain the reaction for 3 h. Then raise the system to 150 °C and continue the reaction for 4 h, during which time a water separator is connected to continuously remove the water generated in the reaction. After the reaction is completed, cool the system to room temperature to precipitate solid, filter to obtain crude product; add 4 L of toluene to the filter cake for recrystallization purification to obtain the target product, aminobiphenyl, as a phosphorus-boron-nitrogen multi-component synergistic flame retardant.

[0050] Example 4 This embodiment provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, specifically including the following steps: (1) Weigh 92g of 2,4-dinitrophenol and dissolve it completely in 1840g of nitrobenzene-aniline solution to obtain a homogeneous reaction raw material solution; wherein the nitrobenzene-aniline solution is a mixed solution composed of nitrobenzene and aniline, and the mass fraction of aniline in the mixed solution is 15wt%; The above-mentioned reactant solution was added to the reactor through a feed bottle, followed by the addition of 2.3 g of catalyst. The catalyst was a supported metal catalyst with activated carbon as the support, on which Fe, Pd, and Pt were loaded, and the total mass fraction of Fe, Pd, and Pt in the catalyst was 10 wt%. The system was then heated to 120 °C and hydrogenated at a hydrogen pressure of 2 MPa for 1 h. After the reaction was completed, the catalyst was recovered by filtration. The filtrate was subjected to vacuum distillation to recover unreacted aniline, and the remaining material was further purified by distillation to obtain the product 2-aminobiphenyl.

[0051] (2) Weigh 85g of 2-aminobiphenyl and 0.9g of N,N-diisopropylethylamine, add them to 800 mL of xylene, and stir under ice-water bath conditions to dissolve them completely, obtaining the reaction base solution. Place 95.3g of diethyl chlorophosphate in a constant pressure dropping funnel and slowly add it dropwise to the above reaction base solution under nitrogen protection. After the addition is complete, remove the ice-water bath, raise the temperature to 75℃ and continue the reaction for 2 hours. Monitor the reaction by thin-layer chromatography (TLC) to confirm the end of the reaction. After the reaction is complete, concentrate the reaction solution to near dryness by vacuum distillation, add 600 mL of anhydrous ethanol to the residue for recrystallization, and obtain phosphoramide product A.

[0052] (3) Weigh 153g of phosphoramide product A and 0.7g of 2,6-di-tert-butyl-p-cresol, add them to 600 mL of ethylbenzene, and stir to dissolve under nitrogen protection at 105℃ to form a homogeneous reaction system. Dissolve 21.5g of boron trichloride and 1.2g of phosphoric acid in 100 mL of ethylbenzene, and add them dropwise to the above reaction system under nitrogen atmosphere. After the addition is complete, maintain the reaction for 2h. Then raise the system to 130℃ and continue the reaction for 4h, during which time a water separator is connected to continuously remove the water generated in the reaction. After the reaction is completed, cool the system to room temperature to precipitate solid, filter to obtain crude product; add 4L of toluene to the filter cake for recrystallization purification to obtain the target product aminobiphenyl phosphorus-boron-nitrogen multi-component synergistic flame retardant.

[0053] Example 5 This embodiment provides a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl and its preparation method, specifically including the following steps: (1) Weigh 9.2g of 2,4-dinitrophenol and dissolve it completely in 92g of nitrobenzene-aniline solution to obtain a homogeneous reaction raw material solution; wherein the nitrobenzene-aniline solution is a mixed solution composed of nitrobenzene and aniline, and the mass fraction of aniline in the mixed solution is 8wt%; The above-mentioned reactant solution was added to the reactor through a feed bottle, and then 0.3 g of catalyst was added to the reactor. The catalyst was a supported metal catalyst with activated carbon as the support, on which Fe and Pd were loaded, and the total mass fraction of Fe and Pd in ​​the catalyst was 10 wt%. The system was then heated to 90 °C and hydrogenated at a hydrogen pressure of 1.5 MPa for 2 h. After the reaction was completed, the catalyst was recovered by filtration. The filtrate was subjected to vacuum distillation to recover unreacted aniline, and the remaining material was further purified to obtain the product 2-aminobiphenyl.

[0054] (2) Weigh 8.5 g of 2-aminobiphenyl and 0.1 g of triethylamine, add them to 90 mL of cumene, and stir under ice-water bath conditions to dissolve them completely, obtaining the reaction base solution. Place 10.2 g of diisopropyl chlorophosphate in a constant pressure dropping funnel and slowly add it dropwise to the above reaction base solution under nitrogen protection. After the addition is complete, remove the ice-water bath, raise the temperature to 65℃ and continue the reaction for 6 h. Monitor the reaction by thin-layer chromatography (TLC) to confirm the end of the reaction. After the reaction is complete, concentrate the reaction solution to near dryness by vacuum distillation, add 80 mL of anhydrous ethanol to the residue for recrystallization, and obtain phosphoramide product A.

[0055] (3) Weigh 16.6 g of phosphoramide product A and 0.06 g of tert-butylhydroquinone, add them to 80 mL of ethylbenzene, and stir to dissolve under nitrogen protection at 120 °C to form a homogeneous reaction system. Dissolve 1.13 g of boric acid and 0.2 g of sulfuric acid in 10 mL of ethylbenzene, and add them dropwise to the above reaction system under nitrogen atmosphere. After the addition is complete, maintain the reaction for 2 h. Then raise the system to 150 °C and continue the reaction for 4 h, during which time connect a water separator to continuously remove the water generated in the reaction. After the reaction is completed, cool the system to room temperature to precipitate solid, filter to obtain crude product; add 2 L of toluene to the filter cake for recrystallization purification to obtain the target product aminobiphenyl phosphorus-boron-nitrogen multi-component synergistic flame retardant.

[0056] Comparative Example 1 This comparative example uses melamine polyphosphate (MPP) as a flame retardant.

[0057] Comparative Example 2 This comparative example uses decabromodiphenyl ether as a flame retardant.

[0058] Test Example 1 The flame retardants prepared in the embodiments and comparative examples of this invention were added to polyurethane flexible foam systems at a mass fraction of 18 wt%, and flame-retardant samples were prepared under the same preparation conditions. The flame-retardant properties, combustion behavior, and durability of the obtained flame-retardant samples were tested and evaluated.

[0059] The limiting oxygen index (LOI) was determined according to GB / T 2406.2-2009; the UL-94 vertical flammability rating was determined according to GB / T 5169.16-2017; the peak heat release rate (pHRR) in the cone calorimetry test was determined according to GB / T 16172-2007; the smoke density was determined according to GB / T 8323.2-2008; and the samples were subjected to damp heat aging treatment according to GB / T 12000-2017, the oxygen index after aging was measured, and the oxygen index retention rate was calculated.

[0060] Table 1: Flame retardant performance test results:

[0061] As shown in Table 1, under the same addition conditions, the flame-retardant samples prepared in the embodiments of the present invention are generally superior to the comparative samples in terms of flame-retardant performance. Compared with the comparative samples, the samples of the embodiments of the present invention exhibit a higher flame-retardant rating in the oxygen index test, indicating that the flame retardant of the present invention can effectively improve the flame resistance of polyurethane flexible foam materials under combustion conditions.

[0062] In the vertical combustion performance test, the samples of the present invention all achieved a high level, while the combustion level of the comparative sample was relatively low, indicating that under the same conditions, the flame retardant of the present invention has a more stable performance in inhibiting flame spread and promoting material self-extinguishing.

[0063] The results of the cone calorimetry test show that the heat released by the sample in the embodiment of the present invention during combustion is significantly lower than that of the comparative sample, indicating that the flame retardant of the present invention can effectively reduce the heat release intensity during combustion, which is beneficial to slowing down the combustion development rate and improving the safety of the material.

[0064] In the smoke density test, the smoke produced by the sample of the present invention during combustion was significantly less than that of the comparative sample, indicating that the flame retardant of the present invention has a significant advantage in smoke suppression performance and helps to reduce the impact of smoke on personnel evacuation and the environment in the event of a fire.

[0065] Furthermore, after damp heat aging treatment, the samples of the present invention can still maintain relatively stable flame retardant properties, while the performance of the comparative samples is significantly degraded, indicating that the flame retardant of the present invention has good durability and stability under long-term use or damp heat environment conditions.

[0066] The flame retardant prepared by this invention exhibits good flame retardant stability and comprehensive application performance in polyurethane flexible foam systems. Compared with comparative flame retardants, it has significant advantages in flame retardant rating, combustion behavior control, smoke generation inhibition, and performance retention under humid and hot environments. It can improve the overall reliability and durability of the flame retardant system while ensuring material processing and performance.

[0067] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl, characterized in that: The flame retardant is as shown in formula (Ⅰ): Equation (Ⅰ); In this context, R is independently selected from C1 to C3 straight-chain or branched alkyl groups.

2. A method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl, characterized in that: Includes the following steps: (1) Dissolve 2,4-dinitrophenol in a reaction solvent containing aniline and react it under a hydrogen atmosphere and a catalyst to obtain 2-aminobiphenyl; (2) Dissolve 2-aminobiphenyl in an organic solvent to form a reaction base liquid, add chlorophosphoryl compound to the reaction base liquid, and condense to obtain phosphoramide product; (3) In an organic solvent system, the phosphoramide product is dissolved and then reacted with boron compounds to obtain a flame retardant.

3. The method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl according to claim 2, characterized in that: In step (1), the catalyst includes a supported metal catalyst; And / or, in step (2), the chlorophosphoryl compound includes one or both of diethyl chlorophosphate and diisopropyl chlorophosphate; And / or, in step (3), the boron compound includes one or both of boric acid and boron trichloride; Preferably, the support for the supported metal catalyst is activated carbon, and the supported metal includes one or more of Fe, Zn, Pd, Pt, or Ru; Preferably, the amount of the supported metal catalyst is 2.5% to 3.5% of the mass of 2,4-dinitrophenol; Preferably, the chlorophosphoryl compound and / or the boron compound are added to the reaction system dropwise.

4. A method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl according to claim 2 or 3, characterized in that: In step (2), the molar ratio of the chlorophosphoryl compound to 2-aminobiphenyl is (1.01~1.1):1; And / or, in step (3), the molar ratio of the boron compound to the phosphoramide product is (1~1.1):

3.

5. A method for preparing a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl according to any one of claims 2-4, characterized in that: In step (1), the hydrogenation reaction is carried out in a hydrogen atmosphere, and the pressure in the reaction system is 1.5 MPa to 2 MPa. And / or, in step (1), the reaction temperature is 90℃~120℃.

6. A method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl according to any one of claims 2-5, characterized in that: In step (1), the mass ratio of aniline to 2,4-dinitrophenol is (0.8~3):1; And / or, in step (1), the reaction solvent containing aniline is a mixed solution of nitrobenzene and aniline; Preferably, the mass fraction of aniline in the mixed solution is 8 wt% to 15 wt%.

7. A method for preparing a phosphorus-boron-nitrogen multi-component synergistic flame retardant based on aminobiphenyl according to any one of claims 2-6, characterized in that: In step (2), the organic solvent includes one or more of toluene, xylene, ethylbenzene, and cumene; And / or, in step (2), an organic base catalyst is also added to the reaction substrate; Preferably, the molar ratio of 2-aminobiphenyl to the organic base catalyst is (50~76):1; Preferably, the organic base catalyst comprises one or more of triethylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, and N,N-diisopropylethylamine; Preferably, in step (2), the amount of organic solvent used is 8.2 to 10.6 mL of organic solvent per gram of 2-aminobiphenyl.

8. A method for preparing a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl according to any one of claims 2-7, characterized in that: In step (2), 2-aminobiphenyl is dissolved in an organic solvent to form a reaction base liquid. Chlorphosphoyl compound is added dropwise to the reaction base liquid, and then the temperature is raised to 65-75°C and reacted for 2-6 hours to obtain the phosphoramide product through a condensation reaction.

9. A method for preparing a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl according to any one of claims 2-7, characterized in that: In step (2), after the reaction is completed, the reaction system is concentrated by vacuum distillation and recrystallized to obtain the phosphoramide product.

10. A method for preparing a phosphorus-boron-nitrogen multi-element synergistic flame retardant based on aminobiphenyl according to any one of claims 2-9, characterized in that: In step (3), the organic solvent includes one or both of xylene and ethylbenzene; And / or, in step (3), an acidic catalyst is also added to the organic solvent system; preferably, the acidic catalyst includes one or more of p-toluenesulfonic acid, sulfuric acid, and phosphoric acid; And / or, in step (3), the phosphoramide product is dissolved in an organic solvent at 105℃~120℃, and after the boron compound is added dropwise, the temperature is raised to 130℃~150℃ for reaction; And / or, in step (3), an antioxidant is added before the reaction; preferably, the antioxidant includes one or more of 2,6-di-tert-butyl-p-cresol, tert-butylhydroquinone, or 1076 antioxidant; Preferably, in step (3), the amount of organic solvent used is 3.9 to 5.4 mL of organic solvent per gram of phosphoramide product.

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