Nitrogen-series halogen-free flame-retardant melamine cyanurate and synthesis method thereof

Abstract

The invention discloses nitrogen-based halogen-free flame-retardant melamine cyanurate and a synthesis method thereof. The nitrogen-based halogen-free flame-retardant melamine cyanurate is prepared from the following components: melamine; cyanuric acid; a melamine polyphosphate; ammonia water; and water; wherein the water is composed of a first part of water and a second part of water, the molar ratio of melamine to cyanuric acid is (1: 0.9)-(1: 1.1) by taking the molar number of melamine as a metering basis, the amount of melamine polyphosphate is 0.02-2% of the sum of the mass of melamine and cyanuric acid, the amount of the first part of water is 70-110% of the sum of the mass of melamine and cyanuric acid, and the amount of the second part of water is 70-110% of the sum of the mass of melamine and cyanuric acid. The second part of water accounts for 5-25% of the sum of the mass of the melamine and the mass of the cyanuric acid, and the amount of the ammonia water accounts for 0.2-12% of the first part of water. The melamine cyanurate product disclosed by the invention is small in particle size, uniform in distribution and high in thermal stability.

Description

Technical Field

[0001] The present invention particularly relates to a nitrogen-based halogen-free flame-retardant melamine cyanurate and a synthesis method thereof. Background Art

[0002] Melamine cyanurate, referred to as MCA, is a nitrogen-based halogen-free flame retardant with excellent performance. MCA is a non-toxic, harmless, environmentally friendly green product with high temperature resistance and good thermal stability. After melamine cyanurate is added to synthetic resin, a product with no fading, no blooming, and excellent electrical and mechanical properties can be obtained; melamine cyanurate is particularly suitable for the flame retardancy of polyamide 6 and 66 without fillers, and the flame retardancy can reach UL 94V-0 level.

[0003] The higher the MCA purity and the higher the GA temperature, the smaller the particle size and the more uniform the particle size distribution, and the better the flame retardant properties.

[0004] Currently, the methods for preparing MCA from melamine and cyanuric acid mainly include the cyanuric acid method and the urea method, and each method has its own advantages and disadvantages.

[0005] In the cyanuric acid method, although the synthesis method using organic solvent as the medium can obtain better MCA, it uses organic solvents, which has great limitations on safe production and environmental protection.

[0006] CN201611036353.2 discloses a method for synthesizing melamine cyanurate flame retardant by solid phase synthesis, wherein melamine and cyanuric acid are ground, solid phase reacted in a reactor for about 8-10 hours, washed with water, filtered and crushed to obtain the product. This method has the following defects: (1) Washing the product generates a large amount of wastewater. (2) The filtration process will produce filteration, and the purity of the solid phase reaction product is not high.

[0007] CN202110663760.0 discloses a method for preparing melamine cyanurate and its application, which adopts a semi-solid thermal method combining a solid phase slurry method and an aqueous phase hydrothermal method. In the first step, a small amount of water and a catalyst are added to react, and in the second step, a large amount of water is added to react in an aqueous phase, and the MCA product is obtained by filtration and drying. The product particle size obtained by the reaction is 0.5 microns (D50). This method has the following defects: (1) The solid content is about 20% during the final aqueous phase reaction, and the water consumption is high; (2) When the particle size is low, the penetration phenomenon is serious and it is difficult to reduce the moisture content of the filter cake.

[0008] CN201710478170.4 discloses a high-performance melamine cyanurate and a preparation method thereof, wherein, under the action of modifiers such as diatomaceous earth, ammeline, ammeline and silane coupling agent, melamine and cyanuric acid are reacted in an ammonia system at a temperature of 90-110°C and a pressure of 0.1-1Mpa to obtain an MCA slurry with a D50 of about 1 micron. The disadvantages thereof are: (1) the maximum solid content after the reaction is only about 35%, and the drying energy consumption is relatively high. (2) the reaction needs to be carried out under a pressure of 0.1-1Mpa, which places high requirements on production equipment.

[0009] Therefore, how to synthesize MCA with high purity, small particle size and uniform particle size distribution has become the goal of technological improvement in the industry. How to find a simple process, easy operation and reduced production in the synthesis has also become the key point of technological improvement in the industry. Summary of the invention

[0010] In view of the above-mentioned defects, the present invention provides a nitrogen-based halogen-free flame-retardant melamine cyanurate, aiming to improve at least one of the problems mentioned in the background technology.

[0011] The technical solution is: a nitrogen-based halogen-free flame-retardant melamine cyanurate, which is made of the following ingredients:

[0012] Melamine;

[0013] Cyanuric acid;

[0014] Melamine polyphosphate;

[0015] Ammonia; and

[0016] water;

[0017] The water consists of a first part of water and a second part of water, with the molar number of melamine as the measurement basis, the molar ratio of melamine to cyanuric acid is 1:0.9-1:1.1, the amount of melamine polyphosphate is 0.02-2% of the sum of the masses of melamine and cyanuric acid, the amount of the first part of water is 70-110% of the sum of the masses of melamine and cyanuric acid, the amount of the second part of water is 5-25% of the sum of the masses of melamine and cyanuric acid, and the amount of ammonia water is 0.2-12% of the amount of the first part of water.

[0018] Optionally, the molar ratio of melamine to cyanuric acid is 1:1 to 1:1.05, the amount of melamine polyphosphate is 0.04 to 1% of the sum of the mass of melamine and cyanuric acid, the amount of the first part of water is 80 to 100% of the sum of the mass of melamine and cyanuric acid, the amount of the second part of water is 10 to 20% of the sum of the mass of melamine and cyanuric acid, and the amount of ammonia water is 0.5% to 10% of the first part of water.

[0019] Optionally, the ammonia mass content in the ammonia water is 20-28%.

[0020] Optionally, the particle size of the nitrogen-based halogen-free flame-retardant melamine cyanurate is D50=0.2-8 μm, D98=1.0-13.6 μm, and the 1% weight loss temperature by thermogravimetric analysis is greater than 280°C.

[0021] Optionally, the particle size of the nitrogen-based halogen-free flame-retardant melamine cyanurate is D50=0.2-0.5 μm, D98=1.0-2.0 μm, and the 1% weight loss temperature by thermogravimetric analysis is greater than 300°C.

[0022] Optionally, the nitrogen-based halogen-free flame retardant melamine cyanurate is prepared by the following steps:

[0023] S1, taking the first part of water and melamine polyphosphate and adding them into the reactor, stirring evenly;

[0024] S2, taking melamine and cyanuric acid and mixing them evenly, slowly adding the mixture into the reactor, stirring while adding, mixing evenly, then adding ammonia water into the reactor, stirring and reacting at room temperature for 0.5 to 4 hours;

[0025] S3, adding the second portion of water to the reactor, stirring, and transforming the mixture from a sludge state to a slurry state;

[0026] S4, heating to 80-95°C and reacting for 0.3-1 hour under stirring to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate slurry;

[0027] S5, adding a surfactant to the nitrogen-based halogen-free flame-retardant melamine cyanurate slurry and spray drying to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate, wherein the surfactant is preferably fatty alcohol polyoxyethylene ether, and the amount of fatty alcohol polyoxyethylene ether is 0.001-0.1% of the mass of melamine.

[0028] The present invention also provides a method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate, aiming to improve at least one problem mentioned in the background technology.

[0029] The technical solution is: a method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate, comprising the following steps:

[0030] S1, taking the first part of water and melamine polyphosphate and adding them into the reactor, stirring evenly;

[0031] S2, taking melamine and cyanuric acid and mixing them evenly, slowly adding the mixture into the reactor, stirring while adding, mixing evenly, then adding ammonia water into the reactor, and reacting for 0.5 to 4 hours under stirring;

[0032] S3, adding the second portion of water to the reactor, stirring, and transforming the mixture from a sludge state to a slurry state;

[0033] S4, continue the reaction for 0.3-1 hour to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate slurry;

[0034] S5, adding a surfactant to the nitrogen-based halogen-free flame-retardant melamine cyanurate slurry and spray drying to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate;

[0035] The molar ratio of melamine to cyanuric acid is 1:0.9 to 1:1.1, the amount of melamine polyphosphate is 0.05 to 2% of the sum of the masses of melamine and cyanuric acid, the amount of the first part of water is 70 to 110% of the sum of the masses of melamine and cyanuric acid, the amount of the second part of water is 5 to 25% of the sum of the masses of melamine and cyanuric acid, and the amount of ammonia water is 0.2 to 12% of the amount of the first part of water.

[0036] Optionally, in S2, the reaction is a room temperature reaction; in S4, the reaction is a room temperature reaction.

[0037] Optionally, in S2, the reaction is carried out at room temperature; in S4, the reaction is carried out at 80-95°C.

[0038] Optionally, the surfactant is fatty alcohol polyoxyethylene ether, and the amount of fatty alcohol polyoxyethylene ether used is 0.001 to 0.1% of the mass of melamine.

[0039] Invention principle and beneficial effects:

[0040] In the synthesis method of the present invention, first: at room temperature, the reaction system completes the salt reaction, and its reaction rate is slow, and a large piece of network structure cannot be quickly formed. At the same time, MPP (melamine polyphosphate) is first dispersed in the water system, hydrogen bonds with MCA molecules, and its network structure is terminated to extend around to form a stable fine-particle product; after the salt-forming reaction of the fine-particle product is completed, in the subsequent water-adding slurrying process, MPP can block the continued hydrogen bond reaction between MCA molecules, and the system only needs to add a small amount of water to adjust to a slurry material, so that the product solid content can still maintain a slurry state when it is 45-52%; due to the high solid content, it can be directly dried without filtering; the temperature is subsequently raised to 80-95°C for reaction, ensuring that a very small amount of unreacted raw materials are fully reacted, thereby ensuring the purity of the product. Adding a surfactant for spray drying can ensure the integrity of the crystallization, and is more conducive to the uniform dispersion of the product in the polymer material, and avoids product agglomeration. DETAILED DESCRIPTION

[0041] The present invention will be further described below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0042] In the following Examples 1 to 6 and Comparative Examples 1 to 3, the materials involved were all purchased from the market, wherein the ammonia content in the ammonia water was 25 wt%.

[0043] Example 1

[0044] S1, weigh 2.85kg water and add it into the kneader, add 15g MPP and stir evenly.

[0045] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, and stir to react for 3 hours.

[0046] S3, add 600g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0047] S4, raising the temperature to 90°C and stirring for reaction for 45 minutes to obtain MCA slurry, and detecting the reaction degree.

[0048] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0049] The test results are shown in Table 1.

[0050] Example 2

[0051] S1, weigh 2.4 kg of water and add it into a kneader, add 15 g of MPP and stir evenly.

[0052] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, and stir to react for 3 hours.

[0053] S3, add 300g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0054] S4, raising the temperature to 90°C and stirring for reaction for 45 minutes to obtain MCA slurry, and detecting the reaction degree.

[0055] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0056] The test results are shown in Table 1.

[0057] Example 3

[0058] S1, weigh 2.85kg water and add it into the kneader, add 15g MPP and stir evenly.

[0059] S2, weigh 1.5 kg of melamine and 1.63 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 300 g of ammonia water into the kneader, and stir to react for 3 hours.

[0060] S3, add 600g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0061] S4, raising the temperature to 90°C and stirring for reaction for 45 minutes to obtain MCA slurry, and detecting the reaction degree.

[0062] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0063] The test results are shown in Table 1.

[0064] Example 4

[0065] S1, weigh 2.85kg water and add it into the kneader, add 15g MPP and stir evenly.

[0066] S2, weigh 1.5 kg of melamine and 1.53 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 30 g of ammonia water into the kneader, and stir to react for 3 hours.

[0067] S3, add 600g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0068] S4, raising the temperature to 90°C and stirring for reaction for 45 minutes to obtain MCA slurry, and detecting the reaction degree.

[0069] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0070] The test results are shown in Table 1.

[0071] Example 5

[0072] S1, weigh 2.85kg water and add it into the kneader, add 15g MPP and stir evenly.

[0073] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, heat to 90 degrees for reaction, and stir for reaction for 3 hours.

[0074] S3, add 600g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0075] S4, continue stirring for 45 minutes to obtain MCA slurry, obtain MCA slurry, and detect the degree of reaction.

[0076] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0077] The test results are shown in Table 1.

[0078] Example 6

[0079] S1, weigh 2.85kg water and add it into the kneader, add 15g MPP and stir evenly.

[0080] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, and stir to react for 5 hours.

[0081] S3, add 600g of water to the kneader, stir for 1 hour, the mixture becomes slurry, and the solid content is detected.

[0082] S4, continue stirring for 45 minutes to obtain MCA slurry and detect the degree of reaction.

[0083] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether into the MCA slurry, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0084] The test results are shown in Table 1.

[0085] Comparative Example 1

[0086] S1, weigh 3kg water and add it into the kneader.

[0087] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, then slowly add them into a kneader while stirring, mix evenly, and stir to react for 3 hours.

[0088] S3, add 600g of water to the kneader, stir for 1 hour, the mixture is still in a sludge state, and the solid content is detected.

[0089] S4, heating to 90°C and stirring for reaction for 45 minutes to obtain MCA sludge, and detecting the reaction degree.

[0090] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether to the MCA sludge, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0091] The test results are shown in Table 1.

[0092] Comparative Example 2

[0093] S1, weigh 2.85 kg of water and add it into the kneader.

[0094] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, and stir to react for 3 hours.

[0095] S3, add 600g of water to the kneader, stir for 1 hour, the mixture is still in a sludge state, and the solid content is detected.

[0096] S4, heating to 90°C and stirring for reaction for 45 minutes to obtain MCA sludge, and detecting the reaction degree.

[0097] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether to the MCA sludge, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0098] The test results are shown in Table 1.

[0099] Comparative Example 3

[0100] S1, weigh 2.85kg of water and add it to the kneader, then add 192g of modifier (modifier composition: 44.5wt% diatomaceous earth, 10wt% of ammeline, 45wt% of ammeline, 0.5wt% of 3-aminopropylmethyldiethoxysilane) into the kneader and stir evenly.

[0101] S2, weigh 1.5 kg of melamine and 1.58 kg of cyanuric acid, mix them evenly, and then slowly add them into a kneader while stirring to mix evenly, then add 150 g of ammonia water into the kneader, and stir to react for 3 hours.

[0102] S3, add 600g of water to the kneader, stir for 1 hour, the mixture is still in a sludge state, and the solid content is detected.

[0103] S4, heating to 90°C and stirring for reaction for 45 minutes to obtain MCA sludge, and detecting the reaction degree.

[0104] S5, after adding 0.5 g of fatty alcohol polyoxyethylene ether to the MCA sludge, spray drying is performed to obtain the MCA product, and the particle size and TGA (1% weight loss temperature) of the MCA are detected.

[0105] The test results are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] In Table 1, TGA is the 1% weight loss temperature.

[0110] The results in Table 1 show that since no MPP was added to Comparative Example 2, the particle control of the product was not effectively controlled, so the particle size became higher. After the salt-forming reaction was completed, it was muddy and lacked fluidity under the same amount of water, resulting in a low degree of reaction completion. Although it also had a high solid content, the particle size was large, the distribution was uneven, and the thermal stability was poor. Compared with Comparative Example 1, Comparative Example 2 also did not add MPP, and even did not add ammonia water. Although the amount of water was increased and the solid content was the same as that of Comparative Example 1, the particle size and distribution were improved compared with Comparative Example 2, but the thermal stability was poor and the reaction was incomplete.

[0111] In Examples 1 to 6, due to the addition of MPP, the reaction degree of MCA is effectively controlled, and a stable fine-particle product is obtained; after the salt-forming reaction is mostly completed, a small amount of water is continued to be added, and no hydrogen bonding reaction occurs between MCA molecules, causing the system viscosity to be too high and become solid (or paste-like). Only a small amount of water is added to the system to adjust it to a slurry product, so that the product can still maintain a slurry when the solid content is 45-52%.

[0112] In Comparative Example 3, the modifier is used to replace the MPP. Although an MCA product with a lower particle size can be obtained, after the salt-forming reaction is completed, when water is added, hydrogen bonding reactions will continue to occur between the MCA molecules, making the system viscosity higher. Under the condition of the same amount of water, the reaction material is sludge-like and lacks fluidity, and the reaction completion degree is not high. Although the D50 particle size can reach 1.92 μm, the D98 is as high as 18.42 μm, and the thermal stability is much lower than that of Examples 1 to 6.

[0113] Compared with Example 5 and Example 6, Example 1 adopts a mode of first normal temperature and then temperature reaction. In Example 1, at room temperature, the reaction system completes the salt reaction, and its reaction rate is slow, which is more conducive to the formation of fine-particle products. At the same time, MPP (melamine polyphosphate) is first dispersed in the water system, hydrogen bonds with MCA molecules, and terminates its network structure to extend around, controls the degree of MCA reaction, and forms a stable fine-particle product; after the salt formation reaction of this fine-particle product is completed, in the subsequent process of adding water to adjust the slurry, MPP can block the continued hydrogen bond reaction between MCA molecules; during the temperature reaction, the unreacted raw materials are fully reacted to ensure the purity of the product. Example 5 adopts a temperature-only mode, because its reaction rate is fast, which is not conducive to the formation of fine-particle products, and ultimately leads to the particle size, particle size distribution and thermal stability being worse than Example 1. Example 6 adopts only the room temperature mode. Although fine particle size products are formed, the slow reaction time results in that even if the reaction time is extended, the unreacted content is greater than that of Example 1. Ultimately, although D50 is slightly better than that of Example 1, D98 is far worse than that of Example 1, and the thermal stability is also far worse than that of Example 1 (TGA is reduced from 355°C to 282°C).

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nitrogen-based halogen-free flame-retardant melamine cyanurate, characterized in that: Made with ingredients including: Melamine; Cyanuric acid; Melamine polyphosphate; ammonia; as well as water; The water consists of a first part of water and a second part of water, with the molar number of melamine as the measurement basis, the molar ratio of melamine to cyanuric acid is 1:0.9-1:1.1, the amount of melamine polyphosphate is 0.02-2% of the sum of the masses of melamine and cyanuric acid, the amount of the first part of water is 70-110% of the sum of the masses of melamine and cyanuric acid, the amount of the second part of water is 5-25% of the sum of the masses of melamine and cyanuric acid, and the amount of ammonia water is 0.2-12% of the amount of the first part of water.

2. The nitrogen-based halogen-free flame-retardant melamine cyanurate according to claim 1, characterized in that: The molar ratio of melamine to cyanuric acid is 1:1 to 1:1.05, the amount of melamine polyphosphate is 0.04 to 1% of the sum of the mass of melamine and cyanuric acid, the amount of the first part of water is 80 to 100% of the sum of the mass of melamine and cyanuric acid, the amount of the second part of water is 10 to 20% of the sum of the mass of melamine and cyanuric acid, and the amount of ammonia water is 0.5% to 10% of the first part of water.

3. The nitrogen-based halogen-free flame-retardant melamine cyanurate according to any one of claims 1 to 2, characterized in that: It is characterized in that The ammonia content in the ammonia water is 20-28% by mass.

4. The nitrogen-based halogen-free flame-retardant melamine cyanurate according to any one of claims 1 to 3, characterized in that: The particle size of the nitrogen-based halogen-free flame-retardant melamine cyanurate is D50=0.2-8 μm, D98=1.0-13.6 μm, and the 1% weight loss temperature according to the thermogravimetric analysis method is greater than 280°C.

5. The nitrogen-based halogen-free flame-retardant melamine cyanurate according to claim 4, characterized in that: The particle size of the nitrogen-based halogen-free flame-retardant melamine cyanurate is D50=0.2-0.5 μm, D98=1.0-2.0 μm, and the 1% weight loss temperature of the thermogravimetric analysis method is greater than 300°C.

6. The nitrogen-based halogen-free flame-retardant melamine cyanurate according to any one of claims 1 to 5, characterized in that: The nitrogen-based halogen-free flame-retardant melamine cyanurate is prepared by the following steps: S1, taking the first part of water and melamine polyphosphate and adding them into the reactor, stirring evenly; S2, taking melamine and cyanuric acid and mixing them evenly, slowly adding the mixture into the reactor, stirring while adding, mixing evenly, then adding ammonia water into the reactor, stirring and reacting at room temperature for 0.5 to 4 hours; S3, adding the second portion of water to the reactor, stirring, and transforming the mixture from a sludge state to a slurry state; S4, heating to 80-95°C and reacting for 0.3-1 hour under stirring to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate slurry; S5, adding a surfactant to the nitrogen-based halogen-free flame-retardant melamine cyanurate slurry and spray drying to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate, wherein the surfactant is preferably fatty alcohol polyoxyethylene ether, and the amount of fatty alcohol polyoxyethylene ether is 0.001-0.1% of the mass of melamine.

7. A method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate, characterized in that: The following steps are involved: S1, taking the first part of water and melamine polyphosphate and adding them into the reactor, stirring evenly; S2, taking melamine and cyanuric acid and mixing them evenly, slowly adding the mixture into the reactor, stirring while adding, mixing evenly, then adding ammonia water into the reactor, and reacting for 0.5 to 4 hours under stirring; S3, adding the second portion of water to the reactor, stirring, and transforming the mixture from a sludge state to a slurry state; S4, continue the reaction for 0.3-1 hour to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate slurry; S5, adding a surfactant to the nitrogen-based halogen-free flame-retardant melamine cyanurate slurry and spray drying to obtain nitrogen-based halogen-free flame-retardant melamine cyanurate; The molar ratio of melamine to cyanuric acid is 1:0.9 to 1:1.1, the amount of melamine polyphosphate is 0.05 to 2% of the sum of the masses of melamine and cyanuric acid, the amount of the first part of water is 70 to 110% of the sum of the masses of melamine and cyanuric acid, the amount of the second part of water is 5 to 25% of the sum of the masses of melamine and cyanuric acid, and the amount of ammonia water is 0.2 to 12% of the amount of the first part of water.

8. The method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate according to claim 7, characterized in that: In S2, the reaction is a room temperature reaction; in S4, the reaction is a room temperature reaction.

9. The method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate according to claim 7, characterized in that: In S2, the reaction is carried out at room temperature; in S4, the reaction is carried out at 80 to 95°C.

10. The method for synthesizing nitrogen-based halogen-free flame-retardant melamine cyanurate according to claim 7, characterized in that: The surfactant is fatty alcohol polyoxyethylene ether, and the amount of fatty alcohol polyoxyethylene ether is 0.001-0.1% of the mass of melamine.

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