Modified ammonium polyphosphate, high flash point fire retardant coating and preparation method thereof

Abstract

The application discloses a modified ammonium polyphosphate, a high-flash-point fireproof paint and a preparation method thereof, and belongs to the technical field of protective fireproof paint. The high-flash-point fireproof paint comprises the following components in mass fraction: 20-45 parts of modified ammonium polyphosphate, 13-19 parts of a flame-retardant aid, 80-110 parts of an epoxy resin, 60-80 parts of a curing agent and 5-15 parts of other aids, wherein the modified ammonium polyphosphate is prepared by introducing a halogen-containing group into ammonium polyphosphate. In the application, 3-amino-1,2-propanediol is used to introduce a hydroxyl group on the surface of the ammonium polyphosphate, so as to prepare hydroxyl-containing ammonium polyphosphate, and meanwhile, the element Cl or Br is introduced, so as to enhance the flame-retardant effect, improve the carbon content, improve the carbonization rate of the flame-retardant aid in cooperation with the modified ammonium polyphosphate, further improve the thickness of the carbon layer, improve the flame-retardant effect of the fireproof paint in cooperation with the element Cl or Br, and finally prepare the high-flash-point fireproof paint with better flame-retardant effect.

Description

Technical Field

[0001] This invention belongs to the field of protective flame-retardant coating technology, and more specifically, relates to a modified ammonium polyphosphate, a high flash point fire-retardant coating, and their preparation methods. Background Technology

[0002] Steel structures are widely used in the construction industry due to their advantages such as light weight, high strength, ease of installation, and recyclability. However, a fatal flaw of steel structure buildings is their poor fire resistance. Studies show that the critical temperature at which structural steel loses stability is 540℃, while fire temperatures typically reach 800-1200℃. At such high temperatures, exposed steel structures quickly deform and collapse within 15 minutes. Therefore, necessary fire protection for steel structures is essential.

[0003] Epoxy fire-retardant coatings are made by grinding and dispersing epoxy resin as a base material, organic solvent as a dispersion medium, and adding flame retardants, pigments, fillers, and additives. However, epoxy resins suffer from poor brittleness and flammability. Most flame retardants used are physically additive, with ammonium polyphosphate being a commonly used one. However, ammonium polyphosphate has low flame-retardant efficiency, requiring a relatively large amount to be added. As an inorganic substance with a hydrophilic surface, ammonium polyphosphate exhibits poor compatibility with the matrix in organic polymer systems such as epoxy resin systems, reducing the mechanical properties of the epoxy fire-retardant coating and significantly limiting its practical application. Therefore, a more efficient flame retardant is needed that can meet the requirements of fire-retardant coatings while reducing the amount of flame retardant required.

[0004] Existing modification methods include microencapsulation, coupling agent blocking of polar sites, and organic amine ion exchange. However, microencapsulation has low coating efficiency, coupling agents blocking polar sites are prone to volatility, and organic amine ion exchange involves complex processes. A common method is to modify the surface of ammonium polyphosphate with alcohols, using water or lower alcohols as solvents and adding organic amines or alkanolamines, as seen in patents CN107163292A and CN103756013A. While these patents improve the compatibility of ammonium polyphosphate with the system, their flame retardant properties are relatively low. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the problem of poor flame retardant properties of existing modified ammonium polyphosphate, this invention provides a modified ammonium polyphosphate and its preparation method, resulting in modified ammonium polyphosphate with high flame retardant properties.

[0007] Another object of the present invention is to provide a fire-retardant coating containing the above-mentioned modified ammonium polyphosphate and a method for preparing the same, wherein the fire-retardant coating has high flame retardant properties and a high flash point.

[0008] 2. Technical Solution

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] This invention discloses a modified ammonium polyphosphate, which is prepared by introducing halogen-containing groups into ammonium polyphosphate, and its structural formula is as follows: Figure 1 As shown,

[0011] Where X = Cl, Br. The ammonium polyphosphate is composed of particles with a size of 40-100 μm. If the particles are too small, they are prone to deliquescence; if they are too large, they will be unevenly dispersed.

[0012] The preparation process specifically includes the following steps:

[0013] Step S1: Preparation of hydroxyl-containing ammonium polyphosphate: 3-amino-1,2-propanediol and ammonium polyphosphate are dispersed in a solvent and reacted under nitrogen or an inert atmosphere with heating and stirring; wherein, the mass ratio of 3-amino-1,2-propanediol to ammonium polyphosphate is (10-13):(40-50), the solvent is water, the atmosphere can be a nitrogen atmosphere or an inert atmosphere, such as helium or neon, the reaction temperature is 70-80℃, and the reaction time is 3-4h. 3-amino-1,2-propanediol is used to introduce hydroxyl groups on the surface of ammonium polyphosphate, and its reaction formula is as follows: Figure 2 As shown, 3-amino-1,2-propanediol is coupled with nitrogen on ammonium polyphosphate, and hydroxyl groups are used to graft halogen sources.

[0014] Step S2: filtration, washing, and drying to obtain hydroxyl-containing ammonium polyphosphate; wherein the drying temperature is 60-70℃ and the drying time is 24-36h.

[0015] Step S3: Preparation of modified ammonium polyphosphate: Disperse hydroxyl-containing ammonium polyphosphate and a halogen source in a solvent and stir to react; wherein, the halogen source can be 3-chloro-5-hydroxybenzoic acid or 3-bromo-5-hydroxybenzoic acid, and the reaction formula is as follows. Figure 3 As shown.

[0016] The mass ratio of the halogen source to hydroxyl-containing ammonium polyphosphate is (3-5):(5-8), the solvent is water, the stirring speed is 600-1000 rpm, and the stirring time is 30-50 min.

[0017] Step S4: filtration, washing, and vacuum drying to obtain modified ammonium polyphosphate, wherein the drying temperature is 60-70℃ and the drying time is 24-36h.

[0018] The modified ammonium polyphosphate is added to a fire-retardant coating to prepare a high flash point fire-retardant coating. The high flash point fire-retardant coating comprises the following components in parts by weight: 20-45 parts of modified ammonium polyphosphate, 13-19 parts of flame retardant additive, 80-110 parts of epoxy resin, 60-80 parts of curing agent, and 5-15 parts of other additives.

[0019] Preferably, the flame retardant is a mixture of pentaerythritol, dipentaerythritol and starch in a mass ratio of 1:4:5.

[0020] The curing agent is a mixture of diethylenetriamine and diethylaminopropylamine in a mass ratio of 1:1.

[0021] Other additives are a mixture of asbestos fiber, glass fiber and quartz powder in a mass ratio of 1:1:1, which are used to improve the mechanical properties of the fire-retardant coating.

[0022] This invention also discloses a preparation process for the above-mentioned high flash point fire-retardant coating containing modified ammonium polyphosphate, comprising the following steps:

[0023] Step a: Add the modified ammonium polyphosphate to the epoxy resin, then stir vigorously in a high-speed homogenizer, add the flame retardant additive, and mix evenly; the stirring time is 30-50 minutes, and the mixture is ultrasonically treated at 150-170W for 15-25 minutes.

[0024] Step b: Add other additives and stir the mixture; the stirring time is 20-30 minutes.

[0025] Step c: Add curing agent and mix evenly to obtain a high flash point fireproof coating containing modified ammonium polyphosphate.

[0026] In practical applications, ammonium polyphosphate is prone to absorbing moisture and agglomerating, and cannot be evenly dispersed in the resin, thus affecting its flame retardant properties. It has poor resistance to damp heat, and under high temperature conditions, it is dehydrated to form polyphosphoric acid or metaphosphoric acid, which can easily migrate from the inside of the resin to the surface of the resin and seep out, and may even fail to play a flame retardant role. To improve its compatibility with organic polymers, ammonium polyphosphate typically requires surface modification to reduce its surface polarity and water solubility. Modification methods include microencapsulation, coupling agent blocking of polar sites, and organic amine ion exchange. However, microencapsulation suffers from low encapsulation efficiency, coupling agent blocking of polar sites is prone to volatility, and organic amine ion exchange involves complex processes. Therefore, this invention first introduces hydroxyl groups onto the surface of ammonium polyphosphate using 3-amino-1,2-propanediol to obtain hydroxyl-containing ammonium polyphosphate. Compared to lower alcohols such as ethanol, 3-amino-1,2-propanediol has the advantage of high binding rate, thereby introducing more hydroxyl groups onto the surface of ammonium polyphosphate, improving its compatibility with resins, and contributing to improved dispersion uniformity and mechanical properties of the modified ammonium polyphosphate coating. However, hydroxyl-containing ammonium polyphosphate has low flame retardant properties. Therefore, 3-chloro-5-hydroxybenzoic acid or 3-bromo-5-hydroxybenzoic acid is grafted onto the surface of hydroxyl-containing ammonium polyphosphate to obtain modified ammonium polyphosphate with stronger flame retardant properties. By introducing highly efficient flame retardant elements Cl or Br onto the surface of hydroxyl-containing ammonium polyphosphate with 3-chloro-5-hydroxybenzoic acid or 3-bromo-5-hydroxybenzoic acid, and applying them as flame retardants in epoxy resin systems, the flame retardant properties of fireproof coatings can be effectively improved. Furthermore, this invention uses 3-chloro-5-hydroxybenzoic acid as a chlorine source or 3-bromo-5-hydroxybenzoic acid as a bromine source. On the one hand, the introduction of highly efficient flame-retardant elements Cl or Br has a synergistic effect with the intumescent flame-retardant system materials (ammonium polyphosphate, flame-retardant additives) in the fire-retardant coating, enhancing the flame-retardant effect. On the other hand, by increasing the char content through 3-chloro-5-hydroxybenzoic acid or 3-bromo-5-hydroxybenzoic acid, it works synergistically with modified ammonium polyphosphate to increase the char formation rate of the flame-retardant additives, further increasing the char layer thickness, and synergistically with Cl or Br elements to improve the flame-retardant effect of the fire-retardant coating.

[0027] Furthermore, the modified ammonium polyphosphate incorporates C, N, and Cl (Br) elements into its molecular formula, ensuring uniform distribution of these elements within the flame retardant. By controlling the proportions of C, N, and Cl (Br) in the modified ammonium polyphosphate, the modified ammonium polyphosphate increases the char formation rate, while N increases the char layer thickness. Simultaneously, Cl (Br) plays a role in capturing free radicals and blocking the combustion chain in the expanded char layer, achieving a synergistic effect of gas-phase flame retardancy and condensed-phase flame retardancy.

[0028] Furthermore, the modified ammonium polyphosphate of the present invention contains a benzene ring structure, which improves the rigidity of the material. At the same time, the conjugation between the electron cloud on the benzene ring and the ammonium polyphosphate improves the thermal stability of the ammonium polyphosphate and prevents it from decomposing under heat to form polyphosphoric acid or metaphosphoric acid, thus affecting the flame retardant performance of the fireproof coating.

[0029] 3. Beneficial effects

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) In this invention, 3-amino-1,2-propanediol and 3-chloro(bromo)-5-hydroxybenzoic acid are used to modify ammonium polyphosphate. The modified ammonium polyphosphate has better compatibility with resin and good flame retardant effect.

[0032] (2) In this invention, 3-chloro(bromo)-5-hydroxybenzoic acid is used to modify hydroxyl-containing ammonium polyphosphate. By introducing elements Cl or Br, the flame retardant effect is enhanced, and the char content is increased. The modified ammonium polyphosphate works synergistically to increase the char formation rate of the flame retardant additive, further increase the char layer thickness, and work synergistically with Cl or Br to improve the flame retardant effect of the fireproof coating.

[0033] (3) In this invention, 3-amino-1,2-propanediol is used to introduce hydroxyl groups on the surface of ammonium polyphosphate to obtain hydroxyl-containing ammonium polyphosphate, which has a higher binding rate, thereby introducing more hydroxyl groups on the surface of ammonium polyphosphate and improving its compatibility with resin.

[0034] (4) The modified ammonium polyphosphate obtained by the present invention contains a benzene ring structure, which improves the rigidity of the material and the thermal stability of the ammonium polyphosphate.

[0035] (5) The fire-retardant coating prepared by the present invention can effectively improve the flame retardant performance of the fire-retardant coating by adding modified ammonium polyphosphate and applying it as a flame retardant in the epoxy resin system. The modified ammonium polyphosphate introduces a large number of hydroxyl groups on its surface, which has excellent compatibility with the epoxy resin substrate, which is beneficial to improving the dispersion uniformity of the modified ammonium polyphosphate and the mechanical properties of the coating. Attached Figure Description

[0036] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0037] Figure 1 This is a schematic diagram of the modified ammonium polyphosphate structure of the present invention;

[0038] Figure 2 The reaction formula for preparing hydroxyl-containing ammonium polyphosphate according to the present invention;

[0039] Figure 3 The reaction formula for preparing the modified ammonium polyphosphate of the present invention is as follows;

[0040] Figure 4 The infrared spectrum of the modified ammonium polyphosphate in Example 1 of this invention;

[0041] Figure 5 This is a product image of the high flash point fire retardant coating of Embodiment 1 of the present invention. Detailed Implementation

[0042] The following detailed description of exemplary embodiments of the invention is taken with reference to the accompanying drawings, which form part of the description and illustrate exemplary embodiments in which the invention may be practiced. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from the spirit and scope thereof. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not restrictive of the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0043] According to national standard GB / T13690 According to the "Classification and Marking of Commonly Used Hazardous Chemicals" (No. 92), liquids with a flash point below 60°C are classified as hazardous materials, posing safety hazards during transportation and storage, thus limiting the application of paint thinners as a marketable commodity. Therefore, this invention refers to a flash point (closed cup) > 60°C as a high flash point. The epoxy resin used in this invention is epoxy resin 828 (molecular formula C...). 54 H 60 O9 (flash point 78ºC) or epoxy resin 815 (molecular formula C) 25 H 35 ClO5, flash point 192.4ºC), epoxy resin (C 14 H 20 In addition to O4 (flash point 118.3℃), other types of epoxy resins with flash points higher than 60℃ can also be used in the fire-retardant coatings of this invention. The addition of diethylaminopropylamine is relatively small and has almost no effect on the flash point of the fire-retardant coating. The fire-retardant coatings prepared with pentaerythritol (flash point 200.1℃), dipentaerythritol (flash point 282.1℃), and diethylenetriamine (flash point 94℃) all have flash points above 60℃, and are high flash point fire-retardant coatings.

[0044] Example 1

[0045] A high flash point fire-retardant coating comprises the following components in parts by weight: 20 parts modified ammonium polyphosphate, 13 parts flame retardant additive, 80 parts epoxy resin, 60 parts curing agent, and 5 parts other additives.

[0046] The preparation process of the modified ammonium polyphosphate includes the following steps:

[0047] Step S1: Preparation of hydroxyl-containing ammonium polyphosphate: 10g of 3-amino-1,2-propanediol and 40g of ammonium polyphosphate were placed in a three-necked flask containing 500ml of distilled water and heated to 70℃ under a nitrogen atmosphere with magnetic stirring for 3h.

[0048] Step S2, filtration, washing, and drying: The sample was vacuum filtered and washed, and then dried at 60°C for 24 hours to obtain ammonium polyphosphate containing hydroxyl groups.

[0049] Step S3: Preparation of modified ammonium polyphosphate: Place 5g of hydroxyl-containing ammonium polyphosphate and 3g of 3-chloro-5-hydroxybenzoic acid into a three-necked flask containing 300ml of distilled water, and stir at 600rpm for 30min at room temperature;

[0050] Step S4, filtration, washing, and drying: The sample is vacuum filtered and washed 5 times, then dried at 60°C for 24 hours to obtain modified ammonium polyphosphate.

[0051] The flame retardant is a mixture of pentaerythritol, dipentaerythritol and starch in a mass ratio of 1:4:5.

[0052] The curing agent is a mixture of diethylenetriamine and diethylaminopropylamine in a mass ratio of 1:1.

[0053] The other additives are a mixture of asbestos fiber, glass fiber and quartz powder in a mass ratio of 1:1:1.

[0054] The preparation process of the high flash point fire retardant coating includes the following steps:

[0055] Step a: Add the modified ammonium polyphosphate to the epoxy resin, then stir vigorously in a high-speed homogenizer for 30 minutes, then add the flame retardant additive and perform ultrasonic treatment at 150W for 15 minutes.

[0056] Step b: Add other additives and stir for 20 minutes;

[0057] Step c: Add the curing agent and mix thoroughly to obtain a high flash point fire-retardant coating, the infrared spectrum of which is shown below. Figure 4 As shown, 3190 cm -1 The peak is the -NH4 asymmetric stretching vibration peak, at 1248 cm⁻¹. -1 This is the peak of the P=O stretching vibration, at 1080 cm⁻¹. -1 and 890 cm -1 These are the symmetric and asymmetric stretching vibration peaks of P–O, respectively, at 740 cm⁻¹. -1 This represents the C-Cl stretching vibration peak. A product image of the fire-retardant coating after use is shown below. Figure 5As shown.

[0058] Example 2

[0059] A high flash point fire-retardant coating comprises the following components in parts by weight: 40 parts modified ammonium polyphosphate, 19 parts flame retardant additive, 100 parts epoxy resin, 70 parts curing agent, and 12 parts other additives.

[0060] The preparation process of the modified ammonium polyphosphate includes the following steps:

[0061] Step S1: Preparation of hydroxyl-containing ammonium polyphosphate: 12g of 3-amino-1,2-propanediol and 45g of ammonium polyphosphate were placed in a three-necked flask containing 500ml of distilled water and heated to 75℃ under a nitrogen atmosphere with magnetic stirring for 3.5h.

[0062] Step S2, filtration, washing, and drying: The sample was vacuum filtered and washed, and then dried at 65°C for 30 hours to obtain ammonium polyphosphate containing hydroxyl groups;

[0063] Step S3: Preparation of modified ammonium polyphosphate: Place 6g of hydroxyl-containing ammonium polyphosphate and 4g of 3-chloro-5-hydroxybenzoic acid into a three-necked flask containing 300ml of distilled water and stir at 800rpm for 40min at room temperature.

[0064] Step S4, filtration, washing, and drying: The sample is vacuum filtered and washed 5 times, then dried at 65°C for 30 hours to obtain modified ammonium polyphosphate.

[0065] The flame retardant is a mixture of pentaerythritol, dipentaerythritol and starch in a mass ratio of 1:4:5.

[0066] The curing agent is a mixture of diethylenetriamine and diethylaminopropylamine in a mass ratio of 1:1.

[0067] The other additives are a mixture of asbestos fiber, glass fiber and quartz powder in a mass ratio of 1:1:1.

[0068] The preparation process of the high flash point fire retardant coating includes the following steps:

[0069] Step a: Add the modified ammonium polyphosphate to the epoxy resin, then stir vigorously in a high-speed homogenizer for 50 minutes, then add the flame retardant additive and perform ultrasonic treatment at 170W for 20 minutes.

[0070] Step b: Add other additives and stir for 25 minutes;

[0071] Step c: Add curing agent and mix evenly to obtain high flash point fireproof coating.

[0072] Example 3

[0073] A high flash point fire-retardant coating comprises the following components in parts by weight: 45 parts modified ammonium polyphosphate, 19 parts flame retardant additive, 110 parts epoxy resin, 80 parts curing agent, and 15 parts other additives.

[0074] The preparation process of the modified ammonium polyphosphate includes the following steps:

[0075] Step S1: Preparation of hydroxyl-containing ammonium polyphosphate: 13g of 3-amino-1,2-propanediol and 50g of ammonium polyphosphate were placed in a three-necked flask containing 500ml of distilled water and heated to 80℃ under a nitrogen atmosphere with magnetic stirring for 4h.

[0076] Step S2, filtration, washing, and drying: The sample was vacuum filtered and washed, and then dried at 70°C for 36 hours to obtain ammonium polyphosphate containing hydroxyl groups;

[0077] Step S3: Preparation of modified ammonium polyphosphate: Place 8g of hydroxyl-containing ammonium polyphosphate and 5g of 3-chloro-5-hydroxybenzoic acid into a three-necked flask containing 300ml of distilled water, and stir at 1000rpm for 50min at room temperature;

[0078] Step S4, filtration, washing, and drying: The sample is vacuum filtered and washed 5 times, then dried at 70°C for 36 hours to obtain modified ammonium polyphosphate.

[0079] The flame retardant additive is a mixture of pentaerythritol, dipentaerythritol and starch in a ratio of 1:4:5.

[0080] The curing agent is a mixture of diethylenetriamine and diethylaminopropylamine in a mass ratio of 1:1.

[0081] The other additives are a mixture of asbestos fiber, glass fiber and quartz powder in a mass ratio of 1:1:1.

[0082] The preparation process of the high flash point fire retardant coating includes the following steps:

[0083] Step a: Add the modified ammonium polyphosphate to the epoxy resin, then stir vigorously in a high-speed homogenizer for 50 minutes, then add the flame retardant additive and perform ultrasonic treatment at 170W for 25 minutes.

[0084] Step b: Add other additives and stir for 30 minutes;

[0085] Step c: Add curing agent and mix evenly to obtain high flash point fireproof coating.

[0086] Comparative Example

[0087] The product comprises the following components in parts by weight: 40 parts ammonium polyphosphate, 15 parts pentaerythritol, 80 parts epoxy resin, 60 parts curing agent, and 5 parts other additives.

[0088] The preparation process of the fire-retardant coating includes the following steps:

[0089] Step a: Add ammonium polyphosphate to epoxy resin, then stir vigorously in a high-speed homogenizer for 30 minutes, then add pentaerythritol, and sonicate the mixture at 150W for 15 minutes.

[0090] Step b: Add other additives and stir for 30 minutes;

[0091] Step c: Add the curing agent and mix well to obtain the fire-retardant coating.

[0092] The parameters of fire-retardant coatings prepared in Examples 1-3 were compared with the requirements of national and industry standards for various parameters. Maximum heat release rate: ASTM D7309-2007a; decomposition residue ratio; peak degradation temperature: GBT27761-2011; flash point: GB / T 261-2008, determination of flash point using the Binsky-Martin closed-cup method. The test results are shown in Table 1.

[0093] Table 1. Test results of various parameters of the fire-retardant coatings in comparative examples and experimental examples 1-3.

[0094]

[0095] As shown in Table 1, the peak degradation temperature of the coatings prepared in Examples 1-3 is higher than that of the comparative example; the maximum heat release rate of the coatings prepared in Examples 1-3 is lower than that of the comparative example; and the proportion of decomposition residue of the coatings prepared in Examples 1-3 is higher than that of the comparative example. Therefore, the fire-retardant coatings prepared in this invention have superior flame-retardant properties. The flash points of the fire-retardant coatings in Examples 1-3 are all >60℃, which meets the requirements for non-hazardous chemical identification in the "Regulations on the Safety Management of Hazardous Chemicals," classifying them as non-hazardous chemicals, which is beneficial for the storage and transportation of fire-retardant coatings.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high flash point fire-retardant coating, characterized in that, The composition comprises the following parts by weight: 20-45 parts modified ammonium polyphosphate, 13-19 parts flame retardant, 80-110 parts epoxy resin, 60-80 parts curing agent, and 5-15 parts other additives. The modified ammonium polyphosphate is characterized by being prepared by introducing halogen-containing groups into ammonium polyphosphate, and its structural formula is as follows: , where X = Cl, Br.

2. The high flash point fire-retardant coating according to claim 1, characterized in that, The epoxy resin is epoxy resin 828, with the molecular formula C. 54 H 60 O9, or epoxy resin 815, with the molecular formula C 25 H 35 ClO5, or epoxy resin C 14 H 20 O4.

3. The high flash point fire-retardant coating according to claim 1, characterized in that, The flame retardant is a mixture of pentaerythritol, dipentaerythritol and starch in a mass ratio of 1:4:

5. The curing agent is a mixture of diethylenetriamine and diethylaminopropylamine in a mass ratio of 1:1; Other additives are a mixture of asbestos fiber, glass fiber and quartz powder in a mass ratio of 1:1:

1.

4. A method for preparing the high flash point fire-retardant coating according to any one of claims 1-3, characterized in that, Specifically, the following steps are included: Step a: Add the modified ammonium polyphosphate to the epoxy resin, stir until uniform, then add the flame retardant additive and mix until uniform; Step b: Add other additives and mix well; Step c: Add curing agent and mix evenly to obtain a high flash point fireproof coating containing modified ammonium polyphosphate; The preparation method of the modified ammonium polyphosphate includes the following steps: Step S1: Preparation of hydroxyl-containing ammonium polyphosphate: 3-amino-1,2-propanediol and ammonium polyphosphate are dispersed in a solvent and reacted by heating and stirring under nitrogen or an inert atmosphere; Step S2: Filtration, washing, and drying to obtain ammonium polyphosphate containing hydroxyl groups; Step S3: Preparation of modified ammonium polyphosphate: Disperse hydroxyl-containing ammonium polyphosphate and a halogen source in a solvent and stir to react. The halogen source is 3-chloro-5-hydroxybenzoic acid or 3-bromo-5-hydroxybenzoic acid. Step S4: filtration, washing, and vacuum drying to obtain modified ammonium polyphosphate.

5. The method for preparing the high flash point fire-retardant coating according to claim 4, characterized in that, The mass ratio of 3-amino-1,2-propanediol to ammonium polyphosphate is (10-13):(40-50), and the mass ratio of the halogen source to hydroxyl-containing ammonium polyphosphate is (3-5):(5-8).

6. The method for preparing the high flash point fire-retardant coating according to claim 4, characterized in that, The solvent in step S1 is water, the reaction temperature is 70-80℃, and the reaction time is 3-4h; the stirring time in step S3 is 30-50min; the drying temperature in steps S2 and S4 is 60-70℃, and the drying time is 24-36h.

7. The method for preparing a high flash point fire-retardant coating according to claim 4, characterized in that, In step a, the stirring time is 30-50 minutes, and after adding the flame retardant additive, the mixture is ultrasonically treated at 150-170W for 15-25 minutes; in step b, the mixing time is 20-30 minutes.

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