Flame-retardant heat-conducting polyacrylic acid fireproof coating and preparation method thereof

Abstract

The invention provides a flame-retardant heat-conducting polyacrylic acid fireproof coating and a preparation method thereof. The flame-retardant heat-conducting polyacrylic acid fireproof coating is prepared from the following raw materials in parts by mass: 3-24 parts of methyl methacrylate, 3-30 parts of butyl acrylate, 0.5-9 parts of acrylic acid, 2-15 parts of an intumescent monomer, 0.6-10 parts of a modified ceramic material, 0.6-3 parts of a compound emulsifier, 0.8-1.8 parts of a buffering agent and 0.2-1.5 parts of an initiator. The intumescent monomer is obtained by reaction of a bio-based material, methacrylic acid phosphate and melamine; the modified ceramic material is a ceramic material modified by a silane coupling agent. The flame-retardant heat-conducting polyacrylic acid fireproof coating disclosed by the invention is simple in formula, and has the advantages of no environmental pollution, low toxicity, relatively low VOC content, no pungent smell and the like; the flame-retardant efficiency is high, and a high-quality expanded carbon layer can be quickly generated after the fire occurs.

Description

Technical Field

[0001] The present invention relates to the technical field of cable fire retardant coatings, and in particular to a flame retardant and heat-conductive polyacrylic acid fire retardant coating and a preparation method thereof. Background Art

[0002] With the continued growth of electricity demand and advancements in transmission technology, the voltage levels of power cables are constantly increasing. However, the heat accumulation and temperature rise associated with high-voltage transmission pose serious challenges to power safety. Cable fires have become a particularly pressing and significant threat. Cable fires can not only cause severe damage to power systems but also result in casualties and substantial property losses, with potentially devastating consequences.

[0003] Fire retardant coatings are an important part of cable fire prevention measures and are usually made up of film-forming resins, flame retardant components and other additives. Intumescent fire retardant coatings have become a widely used choice in the industry because of their thin coating and their ability to flexibly adapt to the extension requirements of cables when bent. Currently, this type of coating mostly uses physical blending technology to add intumescent flame retardants and other additives to the film-forming resin. Intumescent flame retardants are a compound mixture of three components: acid source, carbon source and gas source. Therefore, the ratio between them is extremely complex and it is difficult to control the ratio between the three. In addition, the compounded mixed system has the disadvantages of large total addition amount, easy precipitation, easy moisture absorption, poor thermal stability, poor compatibility with polymers and uneven phase distribution.

[0004] To address the above-mentioned difficulties, researchers have developed a series of single-component intumescent flame retardants that combine three sources into one molecule, namely "three-source-in-one" intumescent flame retardants. These can not only effectively reduce the amount of additives and reduce moisture absorption, but also have good thermal stability. Despite this, most three-source-in-one intumescent flame retardants are still added in the form of physical blending, which has poor compatibility with film-forming resins and can easily have an adverse effect on the mechanical properties and film-forming properties of the film-forming resin. More critically, intumescent fire retardant coatings are usually unable to improve the thermal conductivity and insulation properties of resin materials, making it difficult for the heat generated by the cable during operation to be effectively dissipated. Local high temperatures may trigger pyrolysis and combustion of the material, increasing the risk of fire; and in the case of cable leakage, fire accidents are more likely to occur. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the thermal conductivity and insulation of fire retardant coatings.

[0006] The present invention solves the above technical problems through the following technical means: The first aspect of the present invention provides a flame-retardant, thermally conductive polyacrylic fire-retardant coating, which comprises the following raw materials in parts by mass: 3-24 parts of methyl methacrylate, 3-30 parts of butyl acrylate, 0.5-9 parts of acrylic acid, 2-15 parts of an expandable monomer, 0.6-10 parts of a modified ceramic material, 0.6-3 parts of a composite emulsifier, 0.8-1.8 parts of a buffer, and 0.2-1.5 parts of an initiator; the expandable monomer is obtained by reacting a bio-based material, methacrylate phosphate, and melamine; and the modified ceramic material is obtained by modification with a silane coupling agent.

[0007] Beneficial Effects: The intumescent monomer of the present invention utilizes readily available, environmentally friendly raw materials. It can be directly introduced into acrylic acid under polymerization conditions to achieve intrinsic flame retardancy and achieve excellent flame retardant charring. It also avoids the drawbacks of traditional intumescent flame retardants, such as complex formulations, difficulty in achieving uniform dispersion, and migration and precipitation. The functional groups in the bio-based material can enhance the adhesion of flame-retardant, thermally conductive polyacrylic acid fire-retardant coatings. The present invention utilizes modified ceramic materials as fillers, optimizing the method for adding functional fillers. The silane coupling agent acts as a bridge between the ceramic material and the acrylic emulsion, enhancing their bonding and overcoming the difficulty of dispersing the ceramic material in the emulsion.

[0008] The flame-retardant and heat-conductive polyacrylic acid fire-retardant coating of the present invention has the advantages of simple formula, no environmental pollution, low toxicity, low VOC content, and no irritating odor; it has high flame retardancy efficiency and can quickly generate a high-quality expanded carbon layer when exposed to fire.

[0009] Preferably, the bio-based material is one or more of lignin, starch, cellulose, chitosan, β-cyclodextrin, and sodium alginate.

[0010] Preferably, the ceramic material is one or two of boron nitride, silicon carbide, aluminum nitride, silicon nitride and aluminum oxide.

[0011] Preferably, the silane coupling agent is one or more of KH570, A151, A171, A172, and A174.

[0012] Preferably, the composite emulsifier is nonylphenol polyoxyethylene ether and sodium dodecyl sulfonate, and the mass ratio of nonylphenol polyoxyethylene ether to sodium dodecyl sulfonate is 1:1-1:2.

[0013] Preferably, the initiator is one or more of potassium persulfate, sodium persulfate and ammonium persulfate.

[0014] Preferably, the buffer is one or more of sodium bicarbonate, sodium dihydrogen phosphate, and sodium acetate.

[0015] Preferably, the mass ratio of the bio-based material, methacrylate phosphate and melamine is 8-15:18-25:5-18.

[0016] The second aspect of the present invention provides a method for preparing the flame-retardant and thermally conductive polyacrylic acid fire retardant coating, comprising the following steps: S1 Pre-emulsion: 0.4-2 parts of a composite emulsifier, 0.1-0.8 parts of an initiator, and 20-100 parts of water are mixed, and 2-16 parts of methyl methacrylate, 2-20 parts of butyl acrylate, 0.3-6 parts of acrylic acid, 2-15 parts of an expandable monomer, and 0.6-10 parts of a modified ceramic material are added thereto and stirred to obtain a pre-emulsion; S2 Seed emulsion: 0.8-1.8 parts of the buffer and the remaining composite emulsifier are mixed, and the remaining methyl methacrylate, butyl acrylate, and acrylic acid are added thereto for emulsification. The remaining initiator is then added to carry out polymerization reaction until the solution begins to turn blue to obtain a seed emulsion; S3: slowly dropwise adding the pre-emulsion into the seed emulsion to react, adjusting the pH of the solution with a neutralizer, and then cooling and sieving to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

[0017] Beneficial effects: The preparation method of the present invention utilizes the core-shell emulsion polymerization reaction between methyl methacrylate, butyl acrylate, acrylic acid, expandable monomer, and modified ceramic material to prepare a flame-retardant and thermally conductive polyacrylic acid fire-retardant coating, which can improve the flame retardancy, thermal conductivity, insulation, weather resistance and coating performance of the cable fire-retardant coating.

[0018] Intumescent monomers are introduced into acrylic acid through copolymerization to produce an intumescent, inherently flame-retardant and thermally conductive polyacrylic acid fire-retardant coating. After combustion, this coating exhibits a high expansion height and a dense foam layer. The phosphate groups and functional groups on the bio-based material enhance the latex's adhesion to cables.

[0019] The modified ceramic material has good thermal conductivity and excellent electrical insulation properties. The silane coupling agent can serve as a bridge connecting the thermally conductive insulating ceramic material and the acrylic emulsion, thereby improving the interfacial bonding strength and the dispersion of the ceramic material, thereby improving the coating properties of the emulsion; the ceramic material can enhance the water resistance and mechanical properties of the cable coating and play a synergistic flame retardant role.

[0020] The present invention uses a seed emulsion polymerization reaction, which is different from general copolymers or blends. Under the condition of the same raw material composition, the core-shell structure of the latex particles can significantly improve the wear resistance, waterproofness, weather resistance, anti-fouling properties, as well as the mechanical strength and bonding strength of the polymer emulsion, reduce the minimum film-forming temperature and improve the processing performance.

[0021] Preferably, the expandable monomer is obtained by the following method: a bio-based material is mixed with methacrylic acid phosphate for reaction, and then a melamine solution is added thereto for reaction to finally obtain the expandable monomer.

[0022] Preferably, the modified ceramic material is obtained by the following method: dispersing the ceramic material in a solvent, adding a silane coupling agent thereto, adjusting the pH, and heating the reaction to finally obtain the modified ceramic material.

[0023] Preferably, in S2, the emulsification temperature is 80-85°C, and the emulsification time is 0.5-2h.

[0024] Preferably, the polymerization temperature is 80-90°C.

[0025] Preferably, in S3, the reaction temperature is 85-90°C, and the reaction time is 1-3 hours.

[0026] Preferably, the neutralizing agent is one or more of triethylamine, dimethylethanolamine, triethanolamine, and aqueous ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the structural formula of the expandable monomer PCSM of Example 1; Figure 2 is the infrared spectra of melamine, chitosan, methacrylate phosphate and expandable monomer PCSM in Example 1; Figure 3 This is a performance test table of the flame retardant and thermally conductive polyacrylic acid fire retardant coatings of Examples 1-4 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0029] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0030] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0031] Example 1 This embodiment provides a flame retardant and thermally conductive polyacrylic acid fire retardant coating and a preparation method thereof, as follows: A flame-retardant, heat-conductive polyacrylic fire-retardant coating comprises the following raw materials, in parts by mass: 8.2 parts of methyl methacrylate, 10 parts of butyl acrylate, 1 part of acrylic acid, 4.8 parts of an expandable monomer, 2.8 parts of modified boron nitride, 0.6 parts of a composite emulsifier, 0.8 parts of sodium bicarbonate, and 0.2 parts of potassium persulfate; the composite emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium dodecyl sulfonate in a mass ratio of 1:1.5; the expandable monomer is obtained by reacting chitosan, methacrylic acid phosphate, and melamine; and the modified boron nitride is obtained by modification with a silane coupling agent KH570.

[0032] The preparation of the flame-retardant and heat-conductive polyacrylic acid fire-retardant coating specifically comprises the following steps: S1 Preparation of Expandable Monomer 9.6 parts of chitosan and 21 parts of methacrylate phosphate were esterified at 120°C to produce bio-based phosphate. Subsequently, the temperature was adjusted to 100°C, and a melamine solution was added dropwise. The melamine solution was obtained by dissolving 12.6 parts of melamine in 30 parts of ethanol. The reaction was continued for 1 hour to ensure that the melamine and bio-based phosphate fully reacted to form the expected salt product. After the reaction was completed, the solution was gradually cooled to room temperature, and the solid product was separated by centrifugation. The product was then washed several times with ethanol and deionized water, respectively, and finally dried to obtain an expandable monomer PCSM, whose structural formula is as follows: Figure 1 shown.

[0033] The infrared spectra of the melamine, chitosan, methacrylate phosphate and expandable monomer PCSM are as follows: Figure 2 As shown in the figure, it can be seen that due to the esterification reaction between chitosan and methacrylate phosphate and the salt reaction between melamine and methacrylate phosphate, the expandable monomer PCSM is located at 1058 cm -1 The P–OH stretching vibration peak at 1085 cm -1 The C–O stretching vibration signal in the C–OH structure at 3470 cm -1 and 3420 cm -1 The NH2 stretching vibration signal is significantly weakened, and a peak at 1330 cm -1 The stretching vibration peak of P=O at 3140 cm -1 NH3 + The stretching vibration peak fully proves the successful synthesis of the expanded monomer PCSM.

[0034] Preparation of S2 modified boron nitride 3 parts of boron nitride were added to 200 parts of anhydrous ethanol solution (with a volume ratio of 3:1) and ultrasonically dispersed for 1 hour. Next, 20 parts of silane coupling agent KH570 were added, and the pH was adjusted to approximately 4 with acetic acid. The mixture was then placed in an oil bath at 100°C and heated with stirring for 4 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged, washed alternately with ethanol and deionized water, and dried to obtain the modified boron nitride.

[0035] Preparation of S3 flame retardant thermal conductive polyacrylic acid fire retardant coating (1) Pre-emulsion: 0.4 parts of composite emulsifier, 0.1 parts of potassium persulfate and 50 parts of deionized water were mixed and stirred evenly, and 5.6 parts of methyl methacrylate, 6.7 parts of butyl acrylate, 0.7 parts of acrylic acid, 4.8 parts of expandable monomer PCSM and 2.8 parts of modified boron nitride were slowly added thereto while stirring continuously. After the addition was completed, the mixture was stirred rapidly at room temperature for 1.5 hours to obtain a pre-emulsion.

[0036] (2) Seed emulsion: 0.8 parts of sodium bicarbonate, 0.2 parts of composite emulsifier and 25 parts of deionized water were mixed and heated to 80°C. 2.6 parts of methyl methacrylate, 3.3 parts of butyl acrylate and 0.3 parts of acrylic acid were slowly added dropwise and stirred continuously. After the addition was completed, the mixture was emulsified for 0.5 hours. Then 0.1 parts of potassium persulfate were slowly added dropwise and the temperature was raised to 88°C for polymerization reaction. The reaction was continued until the emulsion began to turn blue to obtain a seed emulsion.

[0037] (3) At 85°C, the pre-emulsion was added dropwise to the bluish seed emulsion. The addition was completed within 1.5 hours. The reaction was continued for 1.5 hours and then the temperature was lowered to 50°C. The pH was adjusted to 7.0 using triethylamine. The mixture was then cooled and sieved to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

[0038] Example 2 This embodiment provides a flame retardant and thermally conductive polyacrylic acid fire retardant coating and a preparation method thereof, as follows: A flame-retardant, thermally conductive polyacrylic fire-retardant coating comprises the following raw materials, in parts by mass: 7 parts of methyl methacrylate, 12 parts of butyl acrylate, 5 parts of acrylic acid, 8 parts of an expandable monomer, 6.1 parts of modified boron nitride / aluminum nitride, 1 part of a composite emulsifier, 1.4 parts of sodium bicarbonate, and 0.6 part of potassium persulfate; the composite emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium dodecylsulfonate in a mass ratio of 1:1.2; the expandable monomer is obtained by reacting starch, methacrylic acid phosphate, and melamine; and the modified boron nitride / aluminum nitride is modified with a silane coupling agent A171.

[0039] The preparation of the flame-retardant and heat-conductive polyacrylic acid fire-retardant coating specifically comprises the following steps: S1 Preparation of Expandable Monomer 9.0 parts of starch were esterified with 21 parts of methacrylate phosphate at 110°C to produce a bio-based phosphate. Subsequently, the temperature was adjusted to 100°C, and a melamine solution (12.6 parts of melamine dissolved in 35 parts of ethanol) was added dropwise. The reaction was allowed to proceed for 2 hours to ensure sufficient reaction between the melamine and the bio-based phosphate, forming the desired salt product. After the reaction was complete, the solution was gradually cooled to room temperature, and the solid product was separated by centrifugation. The product was then washed several times with ethanol and deionized water, respectively, and finally dried to obtain the expandable monomer PSTM, whose structural formula is shown below.

[0040]

[0041] Expandable monomer PSTM Preparation of S2 modified boron nitride / aluminum nitride 7 parts of boron nitride and aluminum nitride (a 1:1 mass ratio mixture) were added to 350 parts of anhydrous ethanol (3:1 volume ratio of anhydrous ethanol to water) and ultrasonically dispersed for 3 hours. Next, 20 parts of silane coupling agent A171 were added, and the pH was adjusted to approximately 4 with acetic acid. The mixture was then placed in an oil bath at 110°C and heated with stirring for 6 hours. After completion of the reaction, the mixture was cooled to room temperature, centrifuged, washed alternately with ethanol and deionized water, and dried to obtain the modified boron nitride / aluminum nitride.

[0042] Preparation of S3 flame retardant thermal conductive polyacrylic acid fire retardant coating (1) Pre-emulsion: 0.5 parts of composite emulsifier, 0.3 parts of sodium persulfate and 43.7 parts of deionized water were mixed and stirred evenly, and 4.7 parts of methyl methacrylate, 8 parts of butyl acrylate, 3.3 parts of acrylic acid, 8 parts of expandable monomer PSTM and 6.1 parts of modified boron nitride / aluminum nitride were slowly added thereto while stirring continuously. After the addition was completed, the mixture was stirred rapidly at room temperature for 2 hours to obtain a pre-emulsion.

[0043] (2) Seed emulsion: 1.4 parts of sodium bicarbonate, 0.5 parts of composite emulsifier and 21.8 parts of deionized water were mixed and heated to 80°C. 2.3 parts of methyl methacrylate, 4 parts of butyl acrylate and 1.7 parts of acrylic acid were slowly added dropwise and stirred continuously. After the addition was completed, the mixture was emulsified for 0.5 hours. Then 0.3 parts of sodium persulfate was slowly added dropwise and the temperature was raised to 85°C for polymerization reaction. The reaction was continued until the emulsion began to turn blue to obtain a seed emulsion.

[0044] (3) At 85°C, the pre-emulsion was added dropwise to the bluish seed emulsion. The addition was completed over 1.5 hours. The reaction was continued for 1.5 hours and then the temperature was lowered to 50°C. Ammonia water was used to adjust the pH of the system to 8.0. The system was then cooled and sieved to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

[0045] Example 3 This embodiment provides a flame retardant and thermally conductive polyacrylic acid fire retardant coating and a preparation method thereof, as follows: A flame-retardant, thermally conductive polyacrylic fire-retardant coating comprises the following raw materials, in parts by mass: 5.4 parts of methyl methacrylate, 20 parts of butyl acrylate, 1 part of acrylic acid, 4.8 parts of an expandable monomer, 4.7 parts of modified silicon carbide, 1.5 parts of a composite emulsifier, 1.8 parts of sodium acetate, and 0.5 part of ammonium persulfate; the composite emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium dodecyl sulfonate in a mass ratio of 1:1.5; the expandable monomer is obtained by reacting β-cyclodextrin, methacrylic acid phosphate, and melamine; and the modified silicon carbide is obtained by modification with a silane coupling agent A151.

[0046] The preparation of the flame-retardant and heat-conductive polyacrylic acid fire-retardant coating specifically comprises the following steps: S1 Preparation of Expandable Monomer 5.6 parts of β-cyclodextrin and 21 parts of methacrylate phosphate were esterified at 150°C to produce a bio-based phosphate. Subsequently, the temperature was adjusted to 90°C, and a melamine solution (12.6 parts of melamine dissolved in 30 parts of ethanol) was added dropwise. The reaction was continued for 2 hours to ensure sufficient reaction between the melamine and the bio-based phosphate, forming the desired salt product. After the reaction was completed, the solution was gradually cooled to room temperature, and the solid product was separated by centrifugation. The product was then washed several times with ethanol and deionized water, respectively, and finally dried to obtain the expandable monomer PCDM, the structural formula of which is shown below.

[0047]

[0048] Expandable monomer PCDM Preparation of S2 modified silicon carbide 5 parts of silicon carbide nanomaterial were added to 250 parts of anhydrous ethanol aqueous solution (with a volume ratio of 3:1), and ultrasonically dispersed for 1 hour. Next, 20 parts of silane coupling agent A151 were added, and the pH was adjusted to approximately 4 with acetic acid. The mixture was then placed in a 100°C oil bath and heated with stirring for 4 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged, washed alternately with ethanol and deionized water, and dried to obtain the modified silicon carbide.

[0049] Preparation of S3 flame retardant thermal conductive polyacrylic acid fire retardant coating (1) Pre-emulsion: 0.9 parts of composite emulsifier, 0.3 parts of ammonium persulfate and 45.5 parts of deionized water were mixed and stirred evenly, and 3.6 parts of methyl methacrylate, 16.7 parts of butyl acrylate, 0.7 parts of acrylic acid, 4.8 parts of expandable monomer PCDM and 4.7 parts of modified silicon carbide were slowly added thereto and stirred continuously. After the addition was completed, the mixture was stirred rapidly at room temperature for 1.5 hours to obtain a pre-emulsion.

[0050] (2) Preparation of seed emulsion: 1.8 parts of sodium acetate, 0.6 parts of composite emulsifier and 22.8 parts of deionized water were mixed and heated to 80°C. 1.8 parts of methyl methacrylate, 3.3 parts of butyl acrylate and 0.3 parts of acrylic acid were slowly added dropwise and stirred continuously. After the addition was completed, the mixture was emulsified for 0.5 hours. Then 0.2 parts of ammonium persulfate were slowly added dropwise and the temperature was raised to 88°C for polymerization reaction. The reaction was continued until the emulsion began to turn blue to obtain the seed emulsion.

[0051] (3) At 85°C, the pre-emulsion was added dropwise to the bluish seed emulsion. The addition was completed within 1.5 hours. The reaction was continued for 1.5 hours and then cooled to 50°C. The pH was adjusted to 7.0 using dimethylethanolamine. The mixture was then cooled and sieved to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

[0052] Example 4 This embodiment provides a flame retardant and thermally conductive polyacrylic acid fire retardant coating and a preparation method thereof, as follows: A flame-retardant, thermally conductive polyacrylic fire-retardant coating comprises the following raw materials, in parts by mass: 4.4 parts of methyl methacrylate, 15 parts of butyl acrylate, 3 parts of acrylic acid, 5.6 parts of an expandable monomer, 1.6 parts of modified silicon nitride / aluminum oxide, 0.7 parts of a composite emulsifier, 0.9 parts of triethanolamine, and 0.3 parts of potassium persulfate; the composite emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium dodecylsulfonate in a mass ratio of 1:1.8; the expandable monomer is obtained by reacting lignin, methacrylic acid phosphate, and melamine; and the modified silicon nitride / aluminum oxide is obtained by modification with a silane coupling agent A174.

[0053] The preparation of the flame-retardant and heat-conductive polyacrylic acid fire-retardant coating specifically comprises the following steps: S1 Preparation of Expandable Monomer 9.8g of lignin was esterified with 21 parts of methacrylate phosphate at 160°C to produce a bio-based phosphate. Subsequently, the temperature was adjusted to 90°C, and a melamine solution (12.6 parts of melamine dissolved in 50 parts of ethanol) was added dropwise. The reaction was continued for 4 hours to ensure sufficient reaction between the melamine and the bio-based phosphate, forming the desired salt product. After the reaction was completed, the mixture was gradually cooled to room temperature, and the solid product was separated by centrifugation. The product was then washed several times with ethanol and deionized water, respectively, and finally dried to obtain the expandable monomer PLiM, whose structural formula is shown below.

[0054]

[0055] Expandable Monomer PLiM Preparation of S2 modified silicon nitride / alumina 5 parts of silicon nitride and aluminum oxide (a mixture with a mass ratio of 1:1) were added to 550 parts of anhydrous ethanol aqueous solution (with a volume ratio of 3:1 for anhydrous ethanol to water). The mixture was ultrasonically dispersed for 2 hours. Next, 20 parts of silane coupling agent A174 were added, and the pH was adjusted to approximately 4 with acetic acid. The mixture was then placed in an oil bath at 100°C and heated with stirring for 4 hours. After the reaction was complete, the mixture was cooled to room temperature, centrifuged, washed alternately with ethanol and deionized water, and dried to obtain a modified silicon nitride / aluminum oxide product.

[0056] Preparation of S3 flame retardant thermal conductive polyacrylic acid fire retardant coating (1) Preparation of pre-emulsion: 0.5 parts of composite emulsifier, 0.2 parts of potassium persulfate and 46.9 parts of deionized water were mixed and stirred evenly, and 2.9 parts of methyl methacrylate, 10 parts of butyl acrylate, 2 parts of acrylic acid, 5.6 parts of expandable monomer PLiM and 1.6 parts of modified silicon nitride / aluminum oxide were slowly added thereto while stirring continuously. After the addition was completed, the mixture was stirred rapidly at room temperature for 1.5 hours to obtain a pre-emulsion.

[0057] (2) Preparation of seed emulsion: 0.2 parts of triethanolamine, 0.2 parts of composite emulsifier and 23.4 parts of deionized water were mixed and heated to 80°C. 1.5 parts of methyl methacrylate, 5 parts of butyl acrylate and 1 part of acrylic acid were slowly added dropwise and stirred continuously. After the addition was completed, the mixture was emulsified for 0.5 hours. Then 0.1 parts of potassium persulfate were slowly added dropwise. After the addition was completed, the mixture was heated to 85°C for polymerization reaction. The reaction was continued until the emulsion began to turn blue to obtain the seed emulsion.

[0058] (3) At 85°C, the pre-emulsion was added dropwise to the bluish seed emulsion. The addition was completed within 1.5 hours. The reaction was continued for 1.5 hours and then the temperature was lowered to 50°C. The pH was adjusted to 8.0 using triethanolamine. The mixture was then cooled and sieved to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

[0059] Comparative Example 1 The difference between this comparative example and Example 1 is that no expandable monomer PCSM is added in this comparative example, and the other aspects are the same as those in Example 1.

[0060] Comparative Example 2 The difference between this comparative example and Example 1 is that no modified boron nitride is added in this comparative example, and the other aspects are the same as Example 1.

[0061] Comparative Example 3 Compared with Example 1, the difference between this comparative example and Example 1 is that the expandable monomer of this comparative example is obtained by physically mixing chitosan, methacrylate phosphate and melamine in the same mass parts as Example 1, and the boron nitride is not modified by a silane coupling agent. Other aspects are the same as Example 1.

[0062] Experimental example The flame retardant and thermal conductive polyacrylic acid fire retardant coatings of Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests. Clean steel plates were selected as substrates. The flame retardant and thermal conductive polyacrylic acid fire retardant coatings of Examples 1-4 and Comparative Examples 1-3 were brushed on the substrates respectively, left at room temperature for 12 hours, and then placed in a blast drying oven and baked at 80°C for 1 hour. The thickness was controlled according to different test items. The thickness standard was referenced to GB / T 1727-2021. Three substrates were brushed on each group of samples as samples. According to relevant standards, test standards and performance indicators are as follows: Figure 3 shown.

[0063] from Figure 3 It can be seen from the data that the flame retardant and thermally conductive polyacrylic acid fire retardant coatings of Examples 1-4 have excellent comprehensive performance, which is significantly better than that of Comparative Examples 1-3, fully verifying the synergistic effect of the "three-source-in-one" intumescent monomer and modified ceramic material.

[0064] The adhesion and hardness of Examples 1-4 are both higher than those of Comparative Examples 1-3, indicating that the dense network formed by chemical cross-linking of the "three-source-in-one" expandable monomer works synergistically with the strong interfacial bonding force of the ceramic material modified by the silane coupling agent to jointly construct a highly stable coating skeleton structure, thereby effectively inhibiting crack propagation and improving mechanical strength.

[0065] The flame-retardant and thermally conductive polyacrylic fire-retardant coatings of Examples 1-4 remained intact in the corrosion and boiling water tests, while the comparative examples 1-3 showed wrinkling and blistering, which was attributed to the density of the fire-retardant coatings and the uniform dispersion of the modified ceramic material, which effectively blocked the penetration of the medium.

[0066] The limiting oxygen index of the flame retardant and thermally conductive polyacrylic acid fire retardant coatings of Examples 1-4 is much higher than that of Comparative Examples 1-3, among which the flame retardant and thermally conductive polyacrylic acid fire retardant coating of Comparative Example 1 has the lowest oxygen index, proving that the intumescent monomer PCSM is an effective component that exerts a flame retardant effect.

[0067] The oxygen index of the flame-retardant thermally conductive polyacrylic fire-retardant coating of Comparative Example 3 is lower than that of all the examples but higher than that of Comparative Examples 1-2, indicating that the physically mixed methacrylate phosphate / melamine / chitosan still has a certain flame retardant effect, but the efficiency is lower than that of the "three-in-one" expandable monomer PCSM.

[0068] The flame-retardant, thermally conductive polyacrylic acid fire-retardant coatings of Examples 1-4 exhibit significantly longer flame retardancy than Comparative Examples 1-3, with smaller carbonized volumes, demonstrating the effective thermal insulation and flame retardancy of the intumescent PCSM carbon layer. Comparative Example 2 exhibits the lowest thermal conductivity, demonstrating the dominant role of modified boron nitride in thermal conductivity. However, Comparative Example 3 exhibits limited thermal conductivity due to the poor dispersibility of unmodified boron nitride. Due to the insulating properties of modified boron nitride, the volume resistivity of Example 1 is significantly higher than that of Comparative Example 2. Comparative Example 3 exhibits reduced insulation due to leakage caused by interface defects in the unmodified filler.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A flame retardant and thermally conductive polyacrylic acid fire retardant coating, characterized in that: The following raw materials are included in parts by mass: 3-24 parts of methyl methacrylate, 3-30 parts of butyl acrylate, 0.5-9 parts of acrylic acid, 2-15 parts of expandable monomer, 0.6-10 parts of modified ceramic material, 0.6-3 parts of composite emulsifier, 0.8-1.8 parts of buffer and 0.2-1.5 parts of initiator; The expandable monomer is obtained by reacting bio-based materials, methacrylate phosphate and melamine; the modified ceramic material is obtained by modifying with a silane coupling agent.

2. The flame retardant and thermally conductive polyacrylic acid fire retardant coating according to claim 1, characterized in that: The bio-based material is one or more of lignin, starch, cellulose, chitosan, β-cyclodextrin, and sodium alginate; the ceramic material is one or two of boron nitride, silicon carbide, aluminum nitride, silicon nitride, and aluminum oxide; and the silane coupling agent is one or more of KH570, A151, A171, A172, and A174.

3. The flame retardant and thermally conductive polyacrylic acid fire retardant coating according to claim 1, characterized in that: The composite emulsifier is obtained by mixing nonylphenol polyoxyethylene ether and sodium lauryl sulfonate, and the mass ratio of the nonylphenol polyoxyethylene ether to the sodium lauryl sulfonate is 1:1-1:

2.

4. The flame retardant and thermally conductive polyacrylic acid fire retardant coating according to claim 1, characterized in that: The initiator is one or more of potassium persulfate, sodium persulfate or ammonium persulfate; the buffer is one or more of sodium bicarbonate, sodium dihydrogen phosphate or sodium acetate.

5. The flame retardant and thermally conductive polyacrylic acid fire retardant coating according to claim 1, characterized in that: The mass ratio of the bio-based material, methacrylate phosphate and melamine is 8-15:18-25:5-18.

6. The method for preparing the flame retardant and heat conductive polyacrylic acid fire retardant coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1 Pre-emulsion: 0.4-2 parts of a composite emulsifier, 0.1-0.8 parts of an initiator, and 20-100 parts of water are mixed, and 2-16 parts of methyl methacrylate, 2-20 parts of butyl acrylate, 0.3-6 parts of acrylic acid, 2-15 parts of an expandable monomer, and 0.6-10 parts of a modified ceramic material are added thereto and stirred to obtain a pre-emulsion; S2 Seed emulsion: 0.8-1.8 parts of the buffer and the remaining composite emulsifier are mixed, and the remaining methyl methacrylate, butyl acrylate, and acrylic acid are added thereto for emulsification, and the remaining initiator is added thereto for polymerization reaction. The reaction is carried out until the emulsion begins to turn blue to obtain a seed emulsion; S3: slowly dropwise adding the pre-emulsion into the seed emulsion to react, adjusting the pH of the solution with a neutralizer, and then cooling and sieving to obtain a flame-retardant and thermally conductive polyacrylic acid fire retardant coating.

7. The method for preparing the flame retardant and heat conductive polyacrylic acid fire retardant coating according to claim 6, characterized in that: The expandable monomer is obtained by the following method: a bio-based material is mixed with methacrylic acid phosphate for reaction, and then a melamine solution is added thereto for reaction, thereby finally obtaining the expandable monomer.

8. The method for preparing the flame retardant and heat conductive polyacrylic acid fire retardant coating according to claim 6, wherein: The modified ceramic material is obtained by the following method: dispersing the ceramic material in a solvent, adding a silane coupling agent thereto, adjusting the pH, and heating the reaction to finally obtain the modified ceramic material.

9. The method for preparing the flame retardant and heat conductive polyacrylic acid fire retardant coating according to claim 6, wherein: In S2, the emulsification temperature is 80-85°C, the emulsification time is 0.5-2h; the polymerization temperature is 80-90°C.

10. The method for preparing the flame retardant and heat conductive polyacrylic acid fire retardant coating according to claim 6, characterized in that: In S3, the reaction temperature is 85-90° C., and the reaction time is 1-3 hours; the neutralizing agent is one or more of triethylamine, dimethylethanolamine, triethanolamine, and ammonia water.

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