Method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization and application of modified phosphorus-nitrogen flame retardant

Abstract

The invention discloses a method for preparing a modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization and application of the modified phosphorus-nitrogen flame retardant. The preparation method comprises the following steps: respectively preparing a phosphorus-containing solution, a piperazine-containing solution, melamine and a cross-linking agent dispersion liquid; the preparation method comprises the following steps: slowly adding a piperazine-containing solution into a phosphorus-containing solution at a certain temperature under a stirring condition, then adding melamine and a cross-linking agent dispersion liquid, and adjusting the pH value of a system to carry out a primary reaction; after the primary reaction is finished, adding a hydrophobic modifier into a reaction system, and carrying out secondary reaction; after the secondary reaction is finished, cooling to room temperature, filtering reaction liquid, washing a filter cake, drying, crushing and sieving to obtain the modified phosphorus-nitrogen flame retardant. The cross-linking agent and the hydrophobic modifier are introduced into a reaction system in situ, so that the generated PAPP and MPP are interwoven to form a stable hybrid network, a hydrophobic layer is synchronously constructed on the surface of the flame retardant, and the prepared modified phosphorus-nitrogen flame retardant has excellent flame retardant synergy and excellent water precipitation resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame retardant preparation, in particular to a method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization and application thereof. BACKGROUND

[0002] Piperazine pyrophosphate (PAPP) and melamine polyphosphate (MPP) are both excellent phosphorus-nitrogen intumescent flame retardants. PAPP has the characteristics of good char forming and outstanding gas phase flame retardant effect; MPP has high thermal stability and significant condensed phase flame retardant effect. The combination of the two can produce good synergistic effect. However, both of them are small molecule or oligomer salts with high molecular polarity, and there are a large number of hydrophilic groups such as P-OH and N-H on the crystal surface, resulting in strong inherent hygroscopicity and solubility in water. When applied to polymers, especially in high temperature and high humidity environment, they are prone to migration and precipitation, causing surface powdering of the product, permanent attenuation of flame retardant performance and environmental pollution.

[0003] To solve the above problems, the existing improved methods are mostly to compound the flame retardant with a larger molecule charring agent. The above method has the following disadvantages: 1. For the compound system of PAPP and MPP, simple physical mixing cannot solve the problems of interface compatibility and synergistic precipitation; 2. Single component coating may destroy the ideal synergistic effect between the two; 3. The process is complex and the cost is high.

[0004] Therefore, it is of great importance to develop a new synthesis method that can firmly combine PAPP and MPP and at the same time endow them with overall hydrophobic properties, for promoting the development of high-performance long-acting flame retardants. SUMMARY

[0005] Therefore, the present application provides a method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization. The method introduces crosslinking agent and hydrophobic modifier in-situ in the reaction system, so that the generated PAPP and MPP interweave to form a stable hybrid network, and a hydrophobic layer is simultaneously constructed on the surface of the flame retardant. The prepared modified phosphorus-nitrogen flame retardant has excellent flame retardant synergistic effect and excellent water precipitation resistance.

[0006] To better solve the above technical problems, the present application provides the following technical solutions:

[0007] A method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization, comprising the following steps:

[0008] (1) preparing a phosphorus-containing solution, a piperazine-containing solution, a melamine dispersion and a crosslinking agent dispersion, respectively;

[0009] (2) Under certain temperature and stirring conditions, the piperazine-containing solution is slowly added to the phosphorus-containing solution, and then melamine and crosslinking agent dispersion are added, and the pH of the system is adjusted for the first reaction;

[0010] (3) After the first reaction, a hydrophobic modifier is added to the reaction system for the second reaction;

[0011] (4) After the second reaction, the reaction solution is cooled to room temperature, filtered, and the filter cake is washed with deionized water and ethanol, dried, crushed, sieved, and the modified phosphorus-nitrogen flame retardant is obtained.

[0012] Preferably, in step (1), the preparation of the phosphorus-containing solution includes the following process: dissolving a phosphoric acid source in deionized water to obtain a phosphorus-containing solution with a concentration of 30-60wt% in terms of P2O5 mass fraction; the phosphoric acid source is selected from at least one of orthophosphoric acid and polyphosphoric acid.

[0013] Preferably, in step (1), the preparation of the piperazine-containing solution includes the following process: dissolving piperazine or a piperazine salt in deionized water to obtain a solution with a concentration of 20-40wt%; the piperazine salt is selected from at least one of piperazine phosphate and piperazine hydrochloride.

[0014] Preferably, in step (1), the preparation of the melamine and crosslinking agent solution includes the following process: forming a suspension of melamine in water and adding a crosslinking agent; the crosslinking agent is a compound containing at least two active groups that can react with amino or phosphoric acid groups; further, the crosslinking agent is selected from one of a polyaldehyde compound, a polyepoxy compound, and cyanuric acid chloride; further, the polyaldehyde compound is selected from one of glyoxal and glutaraldehyde, and the polyepoxy compound is polyethylene glycol diglycidyl ether.

[0015] Preferably, in step (2), the molar ratio of piperazine or its salt to the phosphoric acid source is 1:(1.0-1.2) in terms of piperazine and P2O5; the molar ratio of melamine to the phosphoric acid source is (0.2-0.6):1 in terms of melamine and P2O5, and the addition amount of the crosslinking agent accounts for 0.5%-3% of the total solid content in the reaction system.

[0016] Preferably, in step (2), the conditions for adjusting the pH of the system for the first reaction are: pH 2.0-4.5, temperature 60-85°C, and time 2-5h.

[0017] Preferably, in step (3), the hydrophobic modifier is selected from at least one of long-chain alkyl siloxane and silicone resin emulsion. Further, the hydrophobic modifier is a mixture of amino silicone oil and alkyl siloxane with a mass ratio of 0.5:10~4:6, and its amount is 1%-5% of the theoretical mass of the phosphorus-nitrogen flame retardant in the system after the first reaction.

[0018] Preferably, in step (3), the temperature of the secondary reaction is 70-80℃ and the time is 1-2h.

[0019] The present invention also discloses the application of modified flame retardants in polyolefins or engineering plastics, wherein the amount of flame retardant added is 15%-30% of the polymer matrix mass.

[0020] Compared with the prior art, the present invention has at least the following advantages:

[0021] 1. This invention provides a method for preparing modified phosphorus-nitrogen flame retardants based on in-situ hybridization and functionalization. PAPP and MPP are locked in a hybrid network through chemical crosslinking, and water molecules are isolated by physical hydrophobic coating, achieving dual protection and improving the stability of the flame retardant. The product prepared by adding the modified phosphorus-nitrogen flame retardant of this invention to polyolefins, after immersion in water at 85°C for 168 hours, shows a phosphorus and nitrogen element dissolution rate of less than 1%, far superior to any physically compounded or single-modified product.

[0022] 2. The PAPP generated in situ in this invention is in close contact with MPP through cross-linking points, which can more efficiently exert the "gas-condensation" synergistic flame retardant effect during combustion, and promote the formation of a denser and more stable expanded char layer. Adding 18% to PP can achieve the UL-94V-0 rating.

[0023] 3. The hydrophobic shell of the modified phosphorus-nitrogen flame retardant of the present invention improves the compatibility of the flame retardant with non-polar matrices such as polyolefins and reduces the performance degradation caused by filler agglomeration.

[0024] 4. The method of the present invention can be completed in a single reaction vessel, avoiding the complexity and high energy consumption of multi-step separation and processing. The raw materials used are inexpensive and suitable for industrial production. Detailed Implementation

[0025] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with embodiments, is provided below.

[0026] Example 1

[0027] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0028] (1) Dissolve 110g of 85wt% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of glutaraldehyde aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0029] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir. Slowly add the above piperazine solution (dropping rate is 2.6 ml / min). During the dropping process, control the temperature to <80°C. After the dropping is completed, slowly add the above melamine and crosslinking agent dispersion to the reaction system (dropping rate is 2.6 ml / min). Adjust the pH of the system to 3.0 with phosphoric acid and keep the reaction at the temperature for 4 h.

[0030] (3) Add 5g of a mixture of amino silicone oil and octyltriethoxysilane (mass ratio 1:1) to the above slurry and continue the reaction at 78°C for 1.5h;

[0031] (4) After the reaction is completed, the reaction solution is cooled, filtered, washed with water and ethanol, dried under vacuum at 110°C, and pulverized to obtain the modified flame retardant, which is denoted as HFR-1.

[0032] Example 2

[0033] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0034] (1) Dissolve 110g of 85% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of glutaraldehyde aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0035] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir. Slowly add the above piperazine solution (dropping rate is 2.6 ml / min). During the dropping process, control the temperature to <80°C. After the dropping is complete, slowly add the above melamine and crosslinking agent dispersion (dropping rate is 2.6 ml / min). Adjust the pH to 3.0 with phosphoric acid and keep the reaction at the temperature for 4 hours.

[0036] (3) Add 5g of octyltriethoxysilane to the reaction system and continue the reaction at 78℃ for 1.5h;

[0037] (4) After the reaction is completed, cool to room temperature, filter, wash the precipitate with water and ethanol, dry it under vacuum at 110°C, and pulverize it to obtain the modified phosphorus-nitrogen flame retardant, which is denoted as HFR-2.

[0038] Example 3

[0039] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0040] (1) Dissolve 110g of 85% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of glutaraldehyde aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0041] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir. Slowly add the above piperazine solution (dropping rate is 2.6 ml / min). During the dropping process, control the temperature to <80°C. After the dropping is complete, slowly add the melamine and crosslinking agent dispersion (dropping rate is 2.6 ml / min). Adjust the pH to 3.0 with phosphoric acid and keep the reaction at the temperature for 4 hours.

[0042] (3) Add 5g of amino silicone oil to the reaction system and continue the reaction at 78℃ for 1.5h;

[0043] (4) After the reaction is completed, the mixture is cooled to room temperature and filtered. The precipitate is washed with water and ethanol and then dried under vacuum at 110°C. The precipitate is then pulverized to obtain the modified phosphorus-nitrogen flame retardant, which is designated as HFR-3.

[0044] Example 4

[0045] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0046] (1) Dissolve 110g of 85% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of glutaraldehyde aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0047] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir. Slowly add the above piperazine solution (dropping rate is 2.6 ml / min). During the dropping process, control the temperature to <80°C. After the dropping is complete, slowly add the above melamine and crosslinking agent dispersion (dropping rate is 2.6 ml / min). Adjust the pH to 3.0 with phosphoric acid and keep the reaction at the temperature for 4 hours.

[0048] (3) Add 5g of a mixture of amino silicone oil and octadecyltrimethoxysilane (mass ratio 1:1) to the above reaction system and continue the reaction at 78°C for 1.5h;

[0049] (4) After the reaction is completed, cool to room temperature, filter, wash the precipitate with water and ethanol, dry it under vacuum at 110°C, and pulverize it to obtain the modified phosphorus-nitrogen flame retardant, which is designated as HFR-4.

[0050] Example 5

[0051] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0052] (1) Dissolve 110g of 85% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of polyethylene glycol diglycidyl ether aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0053] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir. Slowly add the above piperazine solution (dropping rate is 2.6 ml / min). During the dropping process, control the temperature to <80°C. After the dropping is complete, slowly add the above melamine and crosslinking agent solution (dropping rate is 2.6 ml / min). Adjust the pH to 3.0 with phosphoric acid and keep the reaction at the temperature for 4 hours.

[0054] (3) Add 5g of a mixture of amino silicone oil and octadecyltrimethoxysilane (mass ratio 1:1) to the above reaction system and continue the reaction at 78°C for 1.5h.

[0055] (4) After the reaction is completed, cool to room temperature, filter, wash the precipitate with water and ethanol, dry it under vacuum at 110°C, and pulverize it to obtain the modified phosphorus and nitrogen flame retardant, which is designated as HFR-5.

[0056] Example 6

[0057] A method for preparing modified flame retardants based on hybridization and functionalization includes the following steps:

[0058] (1) Dissolve 110g of 85% phosphoric acid (containing 80g of P2O5, 0.56mol) in 150mL of water to obtain a phosphoric acid solution; dissolve 43g of piperazine hexahydrate (containing 0.25mol of piperazine) in 100mL of water to obtain a piperazine solution; disperse 25g of melamine (0.2mol) in 100mL of water, and add 1.5g of cyanuric acid chloride aqueous solution (concentration of 50wt%) to obtain a melamine and crosslinking agent dispersion;

[0059] (2) Place the phosphoric acid solution in the reactor, heat it to 75°C and stir, slowly add the above piperazine solution (dropping time 2.5h), control the temperature <80°C during the dropping process, after the dropping is completed, slowly add the above melamine and crosslinking agent solution (dropping time 2.5h), adjust the pH to 3.0 with phosphoric acid, and keep the reaction at the temperature for 4h;

[0060] (3) Add 5g of a mixture of amino silicone oil and octadecyltrimethoxysilane (mass ratio 1:1) to the above reaction system and continue the reaction at 78°C for 1.5h;

[0061] (4) After the reaction is completed, cool to room temperature, filter, wash the precipitate with water and ethanol, dry it under vacuum at 110°C, and pulverize it to obtain the modified phosphorus-nitrogen flame retardant, which is designated as HFR-6.

[0062] Comparative Example 1

[0063] Commercial PAPP and MPP were physically mixed according to the theoretical P / N ratio of the final product of Example 1.

[0064] Comparative Example 2

[0065] The physical mixture of Comparative Example 1 was surface-treated with the same amount of silane mixture as in Example 1 under the same conditions.

[0066] Application Example 1

[0067] By weight, 20 parts of flame retardant HFR-1 (Example 1), 0.2 parts of polytetrafluoroethylene (FA-500H, Daikin Fluorochemicals (China) Co., Ltd.), 0.1 parts of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 0.1 parts of phosphite antioxidant (tris(2,4-di-tert-butylphenyl)phosphite), 0.1 parts of calcium stearate, 0.5 parts of black masterbatch (Cabot Plasblack series), and 1 part of zinc oxide were added to 88 parts of polypropylene (melt flow index MFR = 8 g / 10 min 230℃ / 2.16 kg) to prepare polypropylene resin composition particles. These particles were injection molded at 190℃ to obtain a sample with a size of 1.6 mm × 12.7 mm × 127 mm, denoted as A1.

[0068] Application Example 2

[0069] The difference between this example and Application Example 1 is that HFR-2 from Example 2 is used instead of HFR-1, while other operations are the same as in Application Example 1, denoted as A2.

[0070] Application Example 3

[0071] The difference between this example and Application Example 1 is that HFR-3 of Example 3 is used in place of HFR-1, while the other operations are the same as in Application Example 1, and it is referred to as A3.

[0072] Application Example 4

[0073] The difference between this example and Application Example 1 is that HFR-4 from Example 4 is used instead of HFR-1, while the other operations are the same as in Application Example 1, denoted as A4.

[0074] Application Example 5

[0075] The difference between this example and Application Example 1 is that HFR-5 of Example 5 is used instead of HFR-1, while other operations are the same as in Application Example 1, and it is denoted as A5.

[0076] Application Example 6

[0077] The difference between this example and Application Example 1 is that HFR-6 of Example 6 is used instead of HFR-1, while the other operations are the same as in Application Example 1, denoted as A6.

[0078] Application Comparative Example 1

[0079] The difference between this example and Application Example 1 is that an equal amount of flame retardant from Comparative Example 1 is used to replace HFR-1, while the other operations are the same as in Application Example 1, denoted as D1.

[0080] Application Comparative Example 2

[0081] The difference between this example and Application Example 1 is that an equal amount of flame retardant from Comparative Example 2 is used to replace HFR-1, while the other operations are the same as in Application Example 1, denoted as D2.

[0082] Performance testing

[0083] 1. Water resistance test:

[0084] A certain amount of the test sample was placed in a 500mL beaker, and 400mL of distilled water was added to the beaker. The mouth of the beaker was sealed with plastic wrap and placed in a constant temperature water bath at 85±2℃. The surface of the sample was observed to see if flame retardant was precipitated. The observation was recorded for 7 consecutive days. The surface of the sample without precipitation was smooth, without white frost or powdering. The surface of the sample with flame retardant precipitation showed obvious white precipitate and frost.

[0085] On the seventh day, the sample was removed, dried, and its weight was measured. The amount of flame retardant dissolved in the sample was calculated by comparing the weight before and after immersion. The amount dissolved is expressed as a percentage of the amount dissolved from the sample.

[0086] 2. Flame retardant properties:

[0087] The samples prepared above were subjected to UL-94 (1.6mm) flame retardancy tests, with flame retardancy performance tested before immersion and after immersion at 85℃ for 168h. The limiting oxygen index was tested according to ASTM D2863 standard before immersion and after immersion at 85℃ for 168h. The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] As can be seen from the test results in Table 1, the phosphate-piperazine-melamine system in Examples 1-6 of this invention forms a three-dimensional network structure under the action of the crosslinking agent, which enhances the thermal stability of the flame retardant. Then, a hydrophobic modifier is added to the reaction system of the phosphorus-nitrogen flame retardant to further introduce hydrophobic groups, reduce surface energy, and improve the compatibility between the flame retardant and the polypropylene matrix.

[0091] Compared to the examples, the flame retardant in Comparative Example 1 was a physical mixture of PAPP and MPP without hydrophobic modification; while the flame retardant in the comparative example was hydrophobically modified after physical mixing, which prevented the formation of a stable hybrid structure, resulting in a significant decrease in its water resistance.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization, characterized in that, The method comprises the following steps: (1) preparing phosphorus-containing solution, piperazine-containing solution, melamine and crosslinking agent dispersion solution respectively; (2) under certain temperature and stirring conditions, slowly adding the piperazine-containing solution into the phosphorus-containing solution, then adding the melamine and crosslinking agent dispersion solution, adjusting the pH of the system to carry out the first reaction; (3) after the first reaction, adding a hydrophobic modifier into the reaction system to carry out the second reaction; (4) after the second reaction, cooling to room temperature, filtering the reaction solution, washing the filter cake with deionized water and ethanol, drying, crushing and sieving to obtain the modified phosphorus-nitrogen flame retardant.

2. A process for the in situ hybridization and functionalization based preparation of modified phosphorus-nitrogen flame retardants as claimed in claim 1, wherein, In step (1), the preparation of the phosphorus-containing solution comprises the following process: dissolving a phosphoric acid source in deionized water to obtain a phosphorus-containing solution with a concentration of 30-60wt% in terms of P2O5 mass fraction; the phosphoric acid source is selected from at least one of orthophosphoric acid and polyphosphoric acid.

3. The method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization according to claim 1, characterized in that, In step (1), the preparation of the piperazine-containing solution comprises the following process: dissolving piperazine or a piperazine salt in deionized water to obtain a solution with a concentration of 20-40wt%; the piperazine salt is selected from at least one of piperazine phosphate and piperazine hydrochloride.

4. The method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization according to claim 1, characterized in that, In step (1), the preparation of the melamine and crosslinking agent solution comprises the following process: forming a suspension of melamine in water and adding a crosslinking agent; the crosslinking agent is selected from one of polyaldehyde compounds, polyepoxy compounds and cyanuric acid chloride.

5. The method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization according to claim 1, characterized in that, In step (2), the molar ratio of the piperazine or its salt to the phosphoric acid source is 1:(1.0-1.2) in terms of piperazine and P2O5; the molar ratio of the melamine to the phosphoric acid source is (0.2-0.6):1 in terms of melamine and P2O5; and the addition amount of the crosslinking agent accounts for 0.5%-3% of the total solid content in the reaction system.

6. The method for preparing modified phosphorus-nitrogen flame retardant based on in-situ hybridization and functionalization according to claim 1, characterized in that, In step (2), the conditions for adjusting the pH of the system to carry out the first reaction are as follows: the pH is 2.0-4.5, the temperature is 60-85℃, and the time is 2-5h.

7. The method of claim 1, wherein the modified phosphorus-nitrogen flame retardant is prepared in situ by hybridization and functionalization. In step (3), the hydrophobic modifier is selected from at least one of long-chain alkyl siloxane and silicone resin emulsion; and the amount of the hydrophobic modifier is 1%-5% of the theoretical mass of the phosphorus-nitrogen flame retardant in the system after the first reaction.

8. The method for in-situ hybridization and functionalization based preparation of modified phosphorus-nitrogen flame retardant according to claim 7, characterized in that, The hydrophobic modifier is a mixture of amino silicone oil and alkyl siloxane, and the mass ratio of the two is 0.5:10-4:

6.

9. The method of claim 1, wherein the modified phosphorus-nitrogen flame retardant is prepared in situ by hybridization and functionalization, characterized in that, In step (3), the temperature of the second reaction is 70-80℃, and the time is 1-2h.

10. Use of in-situ hybridization and functionalization for the preparation of modified phosphorus-nitrogen flame retardants, characterized by the fact that, The modified phosphorus-nitrogen flame retardant prepared by the method of any one of claims 1-7 is applied in polyolefins or engineering plastics.

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