Preparation method of nitrogen-phosphorus intumescent flame retardant of specific size

Abstract

This invention discloses a method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size, comprising the following steps: mixing a piperazine solution and a phosphoric acid solution in stages under low temperature and ultrasonic conditions; filtering the reaction solution after mixing, washing the filter cake with a composite treatment agent composed of silicone oil, silane coupling agent, and PEG-400, and drying it; and then dehydrating the dried material at high temperature to obtain the nitrogen-phosphorus intumescent flame retardant of a specific size. This invention controls the particle size of piperazine diphosphate from the source by optimizing the production process, and then prepares a piperazine pyrophosphate flame retardant that can be directly applied to a plastic matrix through a high-temperature dehydration process. The process is simple, the prepared flame retardant does not require grinding, and it exhibits excellent flame retardant properties.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, and specifically to a method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size. Background Technology

[0002] Halogen-free flame retardants are popular due to their relatively low price, low corrosiveness, non-toxicity, and environmental friendliness. With continuous technological innovation, new halogen-free flame retardant products such as phosphorus-nitrogen, silicon-based, and boron-based halogen-free flame retardants are constantly emerging. Furthermore, increasingly stringent environmental regulations worldwide are further restricting the application of halogen-containing flame retardants, enabling the halogen-free flame retardant industry to develop rapidly. Among them, nitrogen-phosphorus intumescent flame retardants have attracted widespread attention due to their halogen-free nature and advantages such as low smoke and high flame-retardant efficiency.

[0003] Piperazine pyrophosphate flame retardant, as a powder-based flame retardant, faces challenges such as poor compatibility with polymer materials when added in large quantities to plastic matrices, severely impacting its production and application. In practical applications, poor dispersion of piperazine pyrophosphate flame retardant can significantly reduce its flame retardant and mechanical properties, and may also cause defects such as white spots on the surface of plastic products.

[0004] To better disperse flame retardants in polymer matrix materials, commonly used piperazine pyrophosphate flame retardants undergo particle size reduction. Common methods include mechanical grinding and air jet milling, where the prepared piperazine pyrophosphate is pulverized before being applied to the matrix material. For example, CN120098480A discloses a halogen-free flame retardant for acrylic inks and its preparation method. Metal nitrides and silica are added to an organic solvent, followed by vapor deposition modification of nanomaterials and organic phosphate esters. Finally, the particle size of the flame retardant is controlled to ≤3μm by air jet milling and sieving. CN114410128A discloses a method for ultrafine magnesium hydroxide and surface modification and its application. Magnesium hydroxide is prepared by chemical modification of brucite powder, followed by ball milling and finally, ultrafine magnesium hydroxide flame retardant is prepared by staged air jet milling.

[0005] Reducing the particle size of piperazine pyrophosphate flame retardants through a mechanical or air-jet milling process to improve their compatibility with matrix materials is a common method to enhance flame retardant dispersion. However, this milling process disrupts the original crystal morphology of the flame retardant, altering its surface properties, increasing the surface energy of the powder, and making it prone to agglomeration. This results in larger flame retardant particles that are more likely to precipitate in the finished product. Furthermore, this method is costly and involves a complex process. Therefore, it is essential to adjust process parameters and control crystal particle size during preparation, directly preparing piperazine pyrophosphate flame retardants with a D90 ≤ 20 μm through high-temperature dehydration for direct application in plastic matrices. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size. This method controls the particle size of piperazine diphosphate from the source by optimizing the production process, and then prepares a piperazine pyrophosphate flame retardant that can be directly applied to a plastic matrix through a high-temperature dehydration process. The process is simple, the prepared flame retardant does not require a grinding process, and has excellent flame retardant properties.

[0007] To better solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0009] Under low temperature and ultrasonic and stirring conditions, the piperazine solution and phosphoric acid solution were mixed in stages;

[0010] After mixing, the reaction solution was filtered, and the filter cake was washed with a composite treatment agent consisting of silicone oil, silane coupling agent, and PEG-400 and a solvent, and then dried.

[0011] The dried material is dehydrated at high temperature to obtain a large-size nitrogen-phosphorus intumescent flame retardant.

[0012] Preferably, the phosphoric acid solution is selected from at least one of 85wt% phosphoric acid, 80wt% phosphoric acid, and 75wt% phosphoric acid.

[0013] Preferably, the preparation of the piperazine solution includes: mixing 68 piperazine with a solvent and stirring until the solid dissolves, thus obtaining the solution.

[0014] Preferably, the solvent is selected from at least one of methanol, ethanol, ethylene glycol, and n-propanol.

[0015] Preferably, in the system after the piperazine solution and phosphoric acid solution are completely mixed, the solvent accounts for 40-70% by mass, and the stirring speed during the entire preparation process is 250-500 r / min.

[0016] Preferably, the process of mixing the piperazine solution and the phosphoric acid solution in stages includes the process of adding the phosphoric acid solution dropwise to the piperazine solution in stages.

[0017] Preferably, the process of adding phosphoric acid solution in stages includes: first, adding 25-30% of the total amount of phosphoric acid solution at 10-15℃, 250W, and a stirring speed of 250-500r / min, with a dropping rate of 1 drop / 4 seconds; then cooling to -5 to 0℃ at a cooling rate of 1-3℃, and continuing to add 40-70% of the total amount of phosphoric acid solution at 450W and a stirring speed of 250-500r / min, with a dropping rate of 1 drop / 2 seconds; finally, continuing to add the remaining phosphoric acid solution at -10 to -2℃, 450W, and a stirring speed of 250-500r / min, with a dropping rate of 1 drop / 3 seconds.

[0018] Preferably, the molar ratio of phosphoric acid to piperazine is (1.9-2.1):1.

[0019] Preferably, the process of mixing the piperazine solution and the phosphoric acid solution in stages includes the process of adding the piperazine solution dropwise to the phosphoric acid solution in stages.

[0020] Preferably, the silicone oil is selected from at least one of hydroxypropyl silicone oil, hydrogen-containing silicone oil, methyl silicone oil, and phenyl silicone oil.

[0021] Preferably, the mass ratio of the silicone oil, silane coupling agent, and PEG-400 is (13-15):(4-5):1.

[0022] Preferably, the mass ratio of the composite treatment agent, solvent and filter cake is 1:(100-250):(100-250).

[0023] Preferably, the drying is vacuum negative pressure drying, with a vacuum pressure of -0.06 to -0.1 MPa, a drying temperature of 105-150℃, and a drying time of 1-3 hours.

[0024] Preferably, the high-temperature dehydration temperature is 250-300℃, and the reaction time is 3-6h.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] 1. This invention provides a method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size. This method optimizes process conditions, using phosphoric acid and piperazine as raw materials and alcohols as solvents when preparing the semi-finished piperazine diphosphate. By controlling the temperature, ultrasound, and composite treatment agents, the crystal particle size is controlled. Then, the flame retardant is dehydrated at high temperature. The obtained flame retardant does not require grinding and has a particle size D90≤20μm. The process is simple, cost-effective, and easy to scale up.

[0027] 2. The solvent in this invention is environmentally friendly, recyclable, and can be reused, saving production costs and improving efficiency.

[0028] 3. The flame retardant prepared by this invention is not pulverized, thus preserving its original crystal morphology to the greatest extent possible and not changing the surface properties of the flame retardant powder.

[0029] 4. In the washing of filter cake, the present invention uses solvent and composite treatment agent as washing agent, which can not only keep the flame retardant powder loose and reduce material agglomeration, but also effectively improve the compatibility between the flame retardant and the plastic matrix. The flame retardant of the present invention can be directly applied to the plastic matrix to improve its flame retardant performance. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0031] Example 1

[0032] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0033] (1) Dissolve 68.00g of 68piperazine and 456.47g of ethanol at 30℃ for 1h by stirring to obtain a piperazine solution; cool the piperazine solution to 10℃, add 85wt% phosphoric acid (38.29g) dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min, then cool to -5℃ at a rate of 2℃ / min, add 85% phosphoric acid (51.05g) dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min, and finally add 85% phosphoric acid (38.29g) dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -4℃.

[0034] (2) After the phosphoric acid addition is completed, the reaction solution is filtered, and the filter cake is washed with a mixture of 250g ethanol, 0.72g methyl silicone oil, 0.22g KH550 and 0.06g PEG-400, and then dried at -0.05MPa and 110℃ for 3h.

[0035] (3) The dried material was dehydrated at 270℃ and -0.1MPa for 5 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0036] Example 2

[0037] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0038] (1) 68.00 g of 68 piperazine and 189.40 g of ethanol were stirred and dissolved at 40 °C for 1.5 h to obtain a piperazine solution; then the solution was cooled to 10 °C and 85 wt% phosphoric acid (36.42 g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250 W and stirring speed of 300 r / min. Then the solution was cooled to -5 °C at a rate of 2 °C / min and 85 wt% phosphoric acid (48.56 g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450 W and stirring speed of 300 r / min. Finally, 85% phosphoric acid (36.42 g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450 W and stirring speed of 300 r / min at -7 °C.

[0039] (2) After the phosphoric acid addition is completed, the reaction solution is filtered, and the filter cake is washed with a mixture of 210g ethanol, 1.44g methyl silicone oil, 0.44g KH550 and 0.12g PEG-400, and then dried at -0.07MPa and 130℃ for 2h.

[0040] (3) The dried material was dehydrated at 280℃ and -0.1MPa for 4 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0041] Example 3

[0042] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0043] (1) 68.00g of 68piperazine was added to 124.19g of ethanol and stirred at 50℃ for 1h to obtain a piperazine solution. The 85wt% phosphoric acid solution was cooled to 10℃, and the piperazine solution (57.66g) was added dropwise at a rate of 1 drop / 4 seconds under the conditions of ultrasonic power of 250W and stirring speed of 300r / min. Then, it was cooled to -5℃ at a rate of 2℃ / min, and the piperazine solution (76.88g) was added dropwise at a rate of 1 drop / 2 seconds under the conditions of ultrasonic power of 450W and stirring speed of 300r / min. Finally, the piperazine solution (57.66g) was added dropwise at a rate of 1 drop / 3 seconds under the conditions of -6℃, ultrasonic power of 450W and stirring speed of 300r / min.

[0044] (2) After the piperazine solution was added dropwise, the filter cake was washed with a mixture of 200g ethanol, 1.44g methyl silicone oil, 0.44g KH550 and 0.12g PEG-400, and then dried at -0.09MPa and 150℃ for 1h.

[0045] (3) The dried material was dehydrated at 285℃ and -0.1MPa for 3 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0046] Example 4

[0047] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0048] (1) 68.00g of 68piperazine was added to 189.40g of ethanol and stirred at 40℃ for 1.5h to obtain a piperazine solution; 85wt% phosphoric acid solution was cooled to 10℃, and piperazine solution (77.22g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min. Then, it was cooled to -5℃ at a rate of 2℃ / min, and piperazine solution (128.7g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min. Finally, piperazine solution (51.48g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -6℃.

[0049] (2) After the piperazine was added, the filter cake was washed with a mixture of 250g ethanol, 0.72g methyl silicone oil, 0.22g KH550 and 0.06g PEG-400, and then dried at -0.07MPa and 130℃ for 2h.

[0050] (3) The dried material was dehydrated at 280℃ and -0.1MPa for 4 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0051] Example 5

[0052] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0053] (1) 68.00g of 68piperazine was added to 189.40g of ethanol and stirred at 40℃ for 1.5h to obtain a piperazine solution; 85wt% phosphoric acid solution was cooled to 10℃, and piperazine solution (77.22g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min. Then, it was cooled to -5℃ at a rate of 2℃ / min, and piperazine solution (128.7g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min. Finally, piperazine solution (51.48g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -7℃.

[0054] (2) After the piperazine solution was added dropwise, the filter cake was washed with a mixture of 250g ethanol, 0.72g methyl silicone oil, 0.22g KH550 and 0.06g PEG-400, and then dried at -0.07MPa and 130℃ for 2h.

[0055] (3) The dried material was dehydrated at 280℃ and -0.1MPa for 4 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0056] Example 6

[0057] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0058] (1) 68.00g of 68piperazine was added to 288.78g of ethanol and stirred at 45℃ for 1.5h to obtain a piperazine solution; 85wt% phosphoric acid solution was cooled to 10℃, and piperazine solution (107.03g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min. Then, it was cooled to -5℃ at a rate of 2℃ / min, and piperazine solution (178.39g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min. Finally, piperazine solution (71.36g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -5℃.

[0059] (2) After the piperazine solution was added dropwise, the filter cake was washed with a mixture of 230g ethanol, 1.08g methyl silicone oil, 0.33g KH550 and 0.09g PEG-400, and then dried at -0.06MPa and 120℃ for 2.5h.

[0060] (3) The dried material was dehydrated at 275℃ and -0.1MPa for 4 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0061] Example 7

[0062] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0063] (1) 68.00g of 68piperazine was added to 236.82g of ethanol and stirred at 40℃ for 2h to obtain a piperazine solution. Then the solution was cooled to 10℃ and 85wt% phosphoric acid (35.63g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min. Then the solution was cooled to -5℃ at a rate of 2℃ / min and 85% phosphoric acid (78.39g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min. Finally, 85% phosphoric acid (28.51g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -10℃.

[0064] (2) After the phosphoric acid solution was added dropwise, the filter cake was filtered. The filter cake was washed with a mixture of 200g ethanol, 1.08g methyl silicone oil, 0.33g KH550 and 0.09g PEG-400, and then dried at -0.1MPa and 140℃ for 1.5 hours.

[0065] (3) The dried material was dehydrated at 280℃ and -0.1MPa for 4 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0066] Example 8

[0067] A method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size includes the following steps:

[0068] (1) 68.00g of 68piperazine was added to 361.01g of ethanol and stirred at 35℃ for 2h to obtain a piperazine solution. Then the solution was cooled to 12℃ and 85wt% phosphoric acid (37.92g) was added dropwise at a rate of 1 drop / 4 seconds under ultrasonic power of 250W and stirring speed of 300r / min. Then the solution was cooled to -5℃ at a rate of 2℃ / min and 85% phosphoric acid (50.56g) was added dropwise at a rate of 1 drop / 2 seconds under ultrasonic power of 450W and stirring speed of 300r / min. Finally, 85% phosphoric acid (37.92g) was added dropwise at a rate of 1 drop / 3 seconds under ultrasonic power of 450W and stirring speed of 300r / min at -5℃.

[0069] (2) After the phosphoric acid solution was added dropwise, the filter cake was filtered and washed with a mixture of 200g ethanol, 0.864g methyl silicone oil, 0.264g KH550 and 0.072g PEG-400. Then it was dried at -0.1MPa and 130℃ for 2h.

[0070] (3) The dried material was dehydrated at 270℃ and -0.1MPa for 5 hours to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

[0071] Comparative Example 1

[0072] The difference between this example and Example 8 is that in step (3), only ethanol is used for washing, and the other operations are the same as in Example 8.

[0073] Comparative Example 2

[0074] The difference between this example and Example 8 is that in step (3), 200g of ethanol is washed with a mixture of 7.2g of methyl silicone oil, 2.2g of KH550 and 0.6g of PEG-400, and the other operations are the same as in Example 8.

[0075] Comparative Example 3

[0076] The preparation method of flame retardant includes the following steps:

[0077] 68.00 g of 68-piperazine was added to 361.01 g of ethanol and stirred at 35 °C for 2 h to dissolve. Then, 85 wt% phosphoric acid (126.39 g) was added dropwise at 35 °C at a rate of 1 drop / 1 s. After the phosphoric acid was added, the mixture was filtered and the filter cake was washed with 200 g of ethanol. Other conditions were the same as in Example 8.

[0078] Test case

[0079] I. Particle size test:

[0080] The particle sizes of the flame retardants and intermediates in the above embodiments and comparative examples are shown in Tables 1 and 2.

[0081] Table 1

[0082]

[0083] Table 2

[0084]

[0085] As can be seen from the test results in Tables 1 and 2, this invention controls the particle size of the flame retardant from the source by using ultrasonic dispersion, temperature and raw material dripping speed control, and washing the filter cake with composite treatment agents and solvents. It does not require a crushing process and is simple to operate.

[0086] Compared to Example 8, in Comparative Example 1, no composite treatment agent was added to wash the prepared filter cake, and the prepared flame retardant exhibited agglomeration. In Comparative Example 2, too much composite treatment agent was added, which was detrimental to the fluffiness of the material, and the flame retardant powder also agglomerated.

[0087] Compared with Example 8, Comparative Example 3 did not undergo ultrasonic treatment, low-temperature treatment, or composite treatment agent treatment, and the prepared piperazine diphosphate particles were coarser.

[0088] II. Flame retardant properties

[0089] By weight, the flame retardant, melamine polyphosphate, and zinc borate prepared in the above examples and comparative examples were added to 79.5 parts of PP resin (grade EP300M, MI: 9 g / 10 min (test method: ASTM D-1238)) at proportions of 12 parts, 7.6 parts, and 0.4 parts, respectively. Additionally, 0.1 parts of calcium stearate (99% purity) and 0.4 parts of fluorinated anti-dripping agent (prepared using the method described in Example 1 of our patent 202210767187.2) were added. After thorough mixing, the mixture was granulated using a twin-screw extruder, and flame-retardant test strips (meeting UL94 testing standards) with a thickness of 1.6 mm were prepared using an injection molding machine. Flame retardancy tests were then conducted using a horizontal and vertical flame retardant tester. The test results are shown in Table 3.

[0090] Table 3

[0091]

[0092] As can be seen from the test results in Table 3, the addition of the flame retardant of the present invention to the PP resin matrix can effectively improve the flame retardant properties of the material.

[0093] 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 a nitrogen-phosphorus intumescent flame retardant of a specific size, characterized in that, Includes the following steps: 68 piperazine was mixed with a solvent and stirred until the solid dissolved to obtain a piperazine solution; The piperazine solution and phosphoric acid solution were mixed in stages under low temperature, stirring and ultrasonic conditions; After mixing, the reaction solution was filtered, and the filter cake was washed with a composite treatment agent consisting of silicone oil, silane coupling agent, and PEG-400 and a solvent, and then dried. The dried material is dehydrated at high temperature to obtain a nitrogen-phosphorus intumescent flame retardant of a specific size.

2. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The phosphoric acid solution is selected from at least one of 85wt% phosphoric acid, 80wt% phosphoric acid, and 75wt% phosphoric acid.

3. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The solvent is selected from at least one of methanol, ethanol, ethylene glycol, and n-propanol; in the system after the piperazine solution and phosphoric acid solution are completely mixed, the solvent accounts for 40-70% by mass, and the stirring speed during the entire preparation process is 250-500 r / min.

4. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The process of mixing piperazine solution and phosphoric acid solution in stages includes either adding phosphoric acid solution dropwise to piperazine solution in stages or adding piperazine solution dropwise to phosphoric acid solution in stages.

5. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 4, characterized in that, The process of adding phosphoric acid solution in stages includes: first, adding 25-30% of the total amount of phosphoric acid solution at 10-15℃, 250W, and a stirring speed of 250-500r / min, at a dropping rate of 1 drop / 4 seconds; then cooling to -5 to 0℃ at a cooling rate of 1-3℃, and continuing to add 40-70% of the total amount of phosphoric acid solution at 450W and a stirring speed of 250-500r / min, at a dropping rate of 1 drop / 2 seconds; finally, continuing to add the remaining phosphoric acid solution at -10 to -2℃, 450W, and a stirring speed of 250-500r / min, at a dropping rate of 1 drop / 3 seconds.

6. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The molar ratio of phosphoric acid to piperazine is (1.9-2.1):

1.

7. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The silicone oil is selected from at least one of hydroxypropyl silicone oil, hydrogen-containing silicone oil, methyl silicone oil, and phenyl silicone oil.

8. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The mass ratio of the silicone oil, silane coupling agent, and PEG-400 is (13-15):(4-5):

1.

9. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, During washing, the mass ratio of the composite treatment agent, solvent and filter cake is 1:(100-250):(100-250).

10. The method for preparing a nitrogen-phosphorus intumescent flame retardant of a specific size according to claim 1, characterized in that, The drying process is vacuum negative pressure drying, with a vacuum pressure of -0.06 to -0.1 MPa, a drying temperature of 105-150℃, and a drying time of 1-3 hours; the high-temperature dehydration temperature is 250-300℃, and the reaction time is 3-6 hours.

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