Flame retardant for fireproof paint and preparation method thereof

Abstract

The invention relates to the technical field of fireproof materials, and discloses a flame retardant for fireproof paint and a preparation method of the flame retardant. The flame retardant is prepared from modified aluminum polyphosphate, a borate-phosphate composite acid source, a silica modified carbon forming agent, chitosan modified nano carbon, melamine cyanurate, bicarbonate, graphene oxide, nano titanium dioxide and an interface reinforcing agent. Through the multi-stage catalysis of the composite acid source, the efficient charring of the modified charring agent, the multi-stage gas source release and the synergistic effect of the nano additive, a compact and uniform expansion layer is formed, and the high-temperature stability, the heat insulation performance and the thickness retention rate in a dynamic environment of the expansion layer are remarkably improved. According to the preparation method, by optimizing the steps of mixing, dispersing, drying and curing the components, the high-efficiency exertion of the performance of the flame retardant is ensured. The flame retardant is widely applicable to fireproof coatings for buildings, steel structures, wood and the like, has the characteristics of high expansion efficiency, lasting heat insulation and excellent mechanical properties, and effectively overcomes the defects in the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of fireproof materials, in particular to a flame retardant for fireproof paint and a preparation method thereof. Background Art

[0002] Fire retardant paint is a kind of coating widely used in buildings, industrial equipment and other high-temperature environments. Its main function is to expand in a fire to form an insulating layer, delay the temperature rise of the substrate and block the spread of flames. The core of intumescent fire retardant paint lies in its flame retardant formula, which usually generates a dense expansion layer through the synergistic effect of acid source, gas source and carbon forming agent to achieve fireproof effect. With the improvement of building safety requirements and the increase of complex fire environments, flame retardants need to maintain excellent expansion effect under dynamic high-temperature impact, and further improve the thermal insulation performance and mechanical strength of the expansion layer.

[0003] In the prior art, an acid source formula based on ammonium polyphosphate or phosphate is often used, and the carbonizing agent is catalyzed by a single acid source, and an expansion layer is generated by combining a gas source such as melamine cyanurate. However, the performance of these expansion layers has certain limitations in a high-temperature dynamic environment. Specifically, the thermal stability of traditional acid sources is poor, and the catalytic efficiency drops rapidly at high temperatures, making it difficult to continuously provide sufficient acidic substances for the carbonization reaction. At the same time, due to the lack of efficient barrier and stable structure in the expansion layer, its thermal insulation performance and antioxidant capacity are often insufficient, resulting in the expansion layer being prone to collapse and peeling under the impact of dynamic flames or high-temperature airflows, thereby reducing the overall protective effect.

[0004] However, the low thermal stability and catalytic efficiency of the acid source in the prior art are one of the main reasons for the failure of the expansion layer. At high temperatures, the traditional acid source cannot provide continuous chemical reaction support for the expansion layer due to its fast decomposition rate or incomplete decomposition, which will cause the mechanical strength of the expansion layer to decrease or even collapse, thereby significantly reducing the flame retardant performance of the fire retardant paint. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a flame retardant for fire retardant paint and a preparation method thereof, which solves the problems of insufficient structural stability, thermal insulation performance and mechanical properties of intumescent fire retardant coating flame retardants in high temperature dynamic environments.

[0006] To achieve the above object, the present invention is implemented by the following technical scheme: a flame retardant for fire retardant paint, the flame retardant comprising the following components in mass percentage: Modified aluminum polyphosphate: 20%-30%; Borate-phosphate composite acid source: 5%-15%; Silicon oxygen modified into carbon agent: 15%-25%; Chitosan modified nanocarbon: 5%-15%; Melamine cyanurate: 5%-10%; Bicarbonate: 5%-10%; Graphene oxide: 3%-7%; Nano titanium dioxide: 2%-5%; Interface enhancer: 1%-3%.

[0007] Preferably, the modified aluminum polyphosphate is modified by adding a rare earth element, and the rare earth element is titanium or yttrium.

[0008] Preferably, the borate-phosphate composite acid source is a mixture of borate and diammonium phosphate in a mass ratio of 1:1 to 1:3.

[0009] Preferably, the silicon-oxygen modified carbon-forming agent is a composite product of pentaerythritol and a siloxane compound.

[0010] Preferably, the chitosan-modified nanocarbon is prepared by carbonizing chitosan and combining it with a nanocarbon material to form a composite.

[0011] Preferably, the graphene oxide is flaky graphene oxide with a particle size less than 50 nanometers.

[0012] A method for preparing a flame retardant for fire retardant paint comprises the following steps: (1) mixing modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon agent, and subjecting them to high-speed shear stirring; (2) dispersing graphene oxide and nano-titanium dioxide in deionized water, and ultrasonically dispersing to form a nano-dispersion liquid; (3) adding the nano-dispersion to the mixture obtained in step (1), and simultaneously adding melamine cyanurate, bicarbonate and an interface enhancer, and stirring evenly; (4) drying the mixture of step (3) and then curing it at high temperature; (5) The solidified material is crushed to obtain flame retardant powder with a particle size of 20-50 μm.

[0013] Preferably, the high-speed shear stirring rate in step (1) is 500-800 rpm, and the time is 20-30 minutes.

[0014] Preferably, the high temperature curing temperature in step (4) is 150-180° C. and the curing time is 2-3 hours.

[0015] The present invention provides a flame retardant for fire retardant paint and a preparation method thereof. The invention has the following beneficial effects: 1. The present invention adopts an acid source system with modified aluminum polyphosphate as the core, and achieves the technical effect of continuously providing an acid catalyst at high temperature through the modification design of rare earth elements and the synergistic effect of borate-phosphate composite acid source. Compared with the problem that the acid source in the prior art only relies on a single phosphate material, has poor thermal stability and insufficient catalytic efficiency, the present invention solves the problem of the collapse of the expansion layer caused by the failure of the acid source catalysis in the high temperature stage in the prior art through the design of rare earth modification and composite acid source.

[0016] 2. The present invention adopts a nano-auxiliary system combining nano-graphene oxide and nano-titanium dioxide, constructs a nano-porous barrier network in the expansion layer, and forms a thermal barrier layer, achieving the technical effect of significantly reducing heat conduction and oxygen diffusion rate. Compared with the existing technology that only relies on the thickness of the macro expansion layer to improve the thermal insulation performance and lacks the problem of effective heat and gas barrier of the nano-scale structure, the present invention solves the shortcomings of the existing technology that the expansion layer has limited thermal insulation effect and insufficient protection ability in high-temperature dynamic environment by introducing nanomaterials.

[0017] 3. The present invention adopts a multifunctional carbon-forming system combining a silicon-oxygen modified carbon-forming agent and chitosan modified nanocarbon, which generates a dense silicon-oxygen-carbon composite structure during the expansion process. At the same time, the interface enhancer improves the bonding force between the expansion layer and the coating, thereby achieving the technical effect of improving the mechanical strength and anti-peeling ability of the expansion layer. Compared with the problem of uneven carbon layer generation and poor mechanical properties in the prior art, the present invention solves the problem of the expansion layer being easy to break and peel off, resulting in protection failure in the prior art through the optimization design of multi-level carbon-forming technology and interface enhancer.

[0018] 4. The present invention adopts a composite gas source design of melamine cyanurate and bicarbonate, and releases non-flammable gas through multi-stage decomposition during the expansion process, thereby achieving multi-stage optimization of expansion efficiency and significantly improving the structural integrity and volume retention rate of the expansion layer under a dynamic heat flow environment. Compared with the problem of a single gas source and easy rupture or collapse of the expansion layer under strong heat flow impact in the prior art, the present invention solves the problems of insufficient expansion efficiency and protection failure under high temperature impact environment in the prior art through the design of a composite gas source. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in 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 creative work are within the scope of protection of the present invention.

[0021] Please see attached Figure 1 The embodiment of the present invention provides a flame retardant for fire retardant paint, comprising the following components (in percentage by mass): Modified aluminum polyphosphate: 20%-30%; Modified aluminum polyphosphate is the core acid source of the intumescent flame retardant. It releases phosphoric acid when it is thermally decomposed, and forms an intumescent carbon layer by catalyzing the carbonization reaction of the carbonizing agent. The modification improves its high temperature stability by introducing rare earth elements (such as titanium or yttrium). The high thermal stability of rare earth elements enables it to maintain catalytic activity at higher temperatures, thereby extending the protection time of the intumescent layer.

[0022] Borate-phosphate composite acid source: 5%-15%; The borate and phosphate compound form a multifunctional acid source, which decomposes at high temperature to generate a boron-oxygen network and phosphate glassy substances. These substances can fill the pores of the expansion layer, significantly improving the mechanical strength and anti-stripping performance of the expansion layer. At the same time, the boron-oxygen bonds generated by the decomposition of the borate further enhance the heat resistance in the expansion layer.

[0023] Silicon oxygen modified into carbon agent: 15%-25%; The silicon-oxygen modified carbon agent generates a dense silicon-oxygen-carbon composite structure during the carbonization process by introducing silicon-oxygen bonds. At high temperatures, the silicon-oxygen bonds can combine with other inorganic substances in the expansion layer to form a silicon-oxygen cross-linked network, further improving the oxidation resistance and mechanical strength of the expansion layer. At the same time, the carbon layer generated by the silicon-oxygen bonds has stronger oxidation resistance in oxidizing flames.

[0024] Chitosan modified nanocarbon: 5%-15%; Chitosan is a natural polymer material with excellent carbonization performance. After carbonization, chitosan is combined with nano-carbon materials to form a composite carbonizing agent, which can generate more carbon layers at high temperatures and improve the uniformity and density of the carbon layer. The generated carbon layer is further strengthened under the catalytic action of the acid source, significantly improving the protective ability of the expansion layer.

[0025] Melamine cyanurate: 5%-10%; Melamine cyanurate is a highly efficient gas source, which decomposes and releases a large amount of nitrogen in the temperature range of 200℃-300℃. The nitrogen expands in the expansion layer to form a foam structure, while diluting the oxygen concentration in the flame, thereby playing the role of expansion insulation and combustion inhibition.

[0026] Bicarbonate: 5%-10%; Bicarbonate has a low decomposition temperature and releases carbon dioxide at 150℃-250℃, further increasing the volume of the expansion layer and enhancing the thermal insulation performance. Carbon dioxide, as an inert gas, further reduces the oxygen concentration in the expansion layer and enhances the flame retardant effect.

[0027] Graphene oxide: 3%-7%; Graphene oxide forms a nanoporous network structure in the expansion layer, which can significantly reduce the oxygen diffusion rate and heat conduction rate in the expansion layer. According to the Knudsen diffusion principle, the nanoporous structure has a significant barrier effect on the diffusion and transfer of molecules, thereby improving the thermal insulation and fire resistance of the expansion layer.

[0028] Nano titanium dioxide: 2%-5%; Nano-titanium dioxide has high infrared reflection performance and thermal stability. At high temperatures, nano-titanium dioxide is distributed in the expansion layer, which can reflect thermal radiation and reduce the efficiency of heat conduction to the substrate, thereby further enhancing the protective effect. At the same time, the addition of titanium dioxide makes the expansion layer structure more compact and improves the overall mechanical strength.

[0029] Interface enhancer: 1%-3%.

[0030] Interface enhancers (such as γ-aminopropyltriethoxysilane) significantly improve the adhesion between the expansion layer and the substrate by forming a chemical bond at the interface between the expansion layer and the coating. This interfacial bonding can prevent the expansion layer from delamination or peeling in a high-temperature dynamic environment, thereby maintaining the integrity of the expansion layer.

[0031] Based on the components of the flame retardant disclosed in this embodiment, a method for preparing a flame retardant for fire retardant paint is also disclosed, comprising the following steps: Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon forming agent are mixed in proportion and stirred using a high-speed shear stirring device at a stirring rate of 500-800rpm for 20-30 minutes. Mechanism analysis: High-speed shear stirring can promote the uniform mixing of the acid source and the carbon forming agent, ensure the consistency of the reaction efficiency and carbon forming efficiency of the expansion layer, and avoid the poor local carbonization effect caused by uneven distribution of components.

[0032] Nano additive dispersion Graphene oxide and nano-titanium dioxide are dispersed in deionized water, and the frequency of the ultrasonic dispersion equipment is set to 20-40kHz for 30-60 minutes to form a stable nano-dispersion liquid. Mechanism analysis: Ultrasonic dispersion can effectively destroy the agglomeration of graphene oxide and make nano-titanium dioxide evenly distributed in the dispersion liquid, thereby ensuring that the nano-additive forms a uniform porous network and thermal barrier structure in the expansion layer.

[0033] Mixing and homogenization of components The nano-dispersion is gradually added to the acid source and carbon forming agent premix, and melamine cyanurate, bicarbonate and interface enhancer are added at the same time, and homogenized using a medium-speed stirrer at a stirring rate of 200-500rpm for 30-60 minutes. Mechanism analysis: In this process, the components gradually form a uniform distribution through mechanical stirring, ensuring that they can work together in the subsequent thermal expansion process to avoid stratification and unevenness in the formation of the carbon layer.

[0034] Drying and curing The mixed slurry is placed in a vacuum drying oven at 60-80°C for 6-8 hours, and then cured at 150-180°C for 2-3 hours. Mechanism analysis: The drying process removes the dispersion medium in the slurry, and the curing process further promotes the chemical bonding between the components, improves the thermal stability and dispersibility of the particles, and provides a guarantee for the final performance of the flame retardant.

[0035] Powder preparation The solidified material is ground into fine powder with a particle size of 20-50 μm by a jet mill, and unqualified particles are removed by screening.

[0036] The uniformity of powder particle size directly affects the dispersibility of flame retardant in fire retardant paint substrate. Reasonable particle size range can ensure that flame retardant is evenly distributed in coating and guarantee flame retardant performance.

[0037] Example 1: Flame retardant for indoor steel structure fire retardant paint 1. Group distribution ratio By mass percentage: Modified aluminum polyphosphate: 25%; Borate-phosphate composite acid source: 10%; Silicon oxygen modified into carbon agent: 20%; Chitosan modified nanocarbon: 10%; Melamine cyanurate: 8%; Bicarbonate: 7%; Graphene oxide: 5%; Nano titanium dioxide: 3%; Interface enhancer (γ-APTES): 2%.

[0038] 2. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon agent were mixed in proportion; and stirred using a high-speed shear stirring device at a rate of 600 rpm for 25 minutes.

[0039] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, the ultrasonic frequency was set to 30 kHz, and the ultrasonic time was 40 minutes to form a uniform dispersion.

[0040] Main mixing and homogenization The dispersion was added to the premix, followed by melamine cyanurate, bicarbonate and interfacial enhancer, with the stirring rate set at 400 rpm for 40 minutes.

[0041] Drying and curing Dry in a vacuum oven at 60°C for 6 hours; High temperature curing at 160℃ for 3 hours.

[0042] Powder preparation The solidified material was ground to a particle size of 30 μm using a jet mill; The flame retardant was obtained after screening.

[0043] 3. Experimental results The expansion ratio is 45 times of the original volume; The high temperature expansion layer thickness retention rate is 96%; Heat flux reduction efficiency 65%.

[0044] 4. Summary of Examples This example optimizes the ratio of acid source to carbon forming agent and combines the introduction of nano additives to achieve significant application of flame retardant in indoor steel structure fire retardant paint. Experiments show that the expansion ratio is high, the thickness retention rate of the expansion layer is excellent, and the thermal insulation performance is outstanding, meeting the fire protection requirements of indoor steel structures.

[0045] Example 2: Flame retardant for tunnel fire retardant coating 1. Group distribution ratio By mass percentage: Modified aluminum polyphosphate: 30%; Borate-phosphate composite acid source: 12%; Silicon oxygen modified into carbon agent: 18%; Chitosan modified nanocarbon: 12%; Melamine cyanurate: 7%; Bicarbonate: 6%; Graphene oxide: 5%; Nano titanium dioxide: 5%; Interface enhancer (γ-APTES): 3%.

[0046] 2. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon agent are mixed in proportion; the high-speed shear stirring rate is 800 rpm, and the time is 20 minutes.

[0047] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, with an ultrasonic frequency of 25 kHz and an ultrasonic time of 50 minutes to form a stable dispersion.

[0048] Main mixing and homogenization adding the nanodispersion to the premix; Melamine cyanurate, bicarbonate and interfacial enhancer were added with stirring at a rate of 300 rpm for 50 minutes.

[0049] Drying and curing Dry in a vacuum oven at 70°C for 8 hours; High temperature curing at 150℃ for 2 hours.

[0050] Powder preparation The solidified material is ground to a particle size of 20-50 μm and then screened to obtain a flame retardant.

[0051] 3. Experimental results The expansion ratio is 40 times of the original volume; The expansion layer thickness retention rate in the dynamic heat flow shock test is 97%; Heat flux reduction efficiency 60%.

[0052] 4. Summary of Examples In a tunnel environment, the dynamic heat flow shock is more significant, so this example increases the acid source ratio and increases the amount of nano-additives added. The experimental results show that the expansion layer thickness retention rate is increased to 97%, and the stability in a high temperature dynamic environment is better than that of Example 1, but the expansion ratio is slightly lower, because the density of the expansion layer is required to be higher in the tunnel environment, and the structural integrity is given priority.

[0053] Example 3: Flame retardant for outdoor wood fire retardant coating 1. Group distribution ratio By mass percentage: Modified aluminum polyphosphate: 22%; Borate-phosphate composite acid source: 10%; Silicon oxygen modified into carbon agent: 18%; Chitosan modified nanocarbon: 8%; Melamine cyanurate: 10%; Bicarbonate: 8%; Graphene oxide: 7%; Nano titanium dioxide: 4%; Interface enhancer (γ-APTES): 3%.

[0054] 2. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon agent were mixed in proportion; the stirring rate was 500 rpm and the time was 30 minutes.

[0055] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, with an ultrasonic frequency of 35 kHz and an ultrasonic time of 45 minutes.

[0056] Main mixing and homogenization The dispersion was added to the premix, along with melamine cyanurate, bicarbonate and interfacial enhancer, at a stirring rate of 400 rpm for 30 minutes.

[0057] Drying and curing Dry in a drying oven at 80°C for 6 hours; Curing at 180℃ for 3 hours.

[0058] Powder preparation The solidified material was ground to a particle size of 25 μm and then screened to obtain a flame retardant.

[0059] 3. Experimental results The expansion ratio is 50 times of the original volume; After 500 hours of UV aging test, the adhesion retention rate is 92%; Heat flux reduction efficiency 70%.

[0060] 4. Summary of Examples In view of the outdoor wood fire protection requirements, this example increases the proportion of the gas source, which significantly improves the expansion ratio. At the same time, the synergistic effect of the interface enhancer and the nano-additive enhances the adhesion and weather resistance of the coating. Compared with Example 1 and Example 2, this example gives priority to improving the thermal insulation and anti-aging ability of the expansion layer, and is suitable for outdoor protection.

[0061] Analysis of the differences in results between the examples Expansion ratio difference The expansion ratio is the highest in Example 3 because the wood fire retardant coating requires stronger thermal insulation performance, so the air source ratio is higher; while the expansion ratio is the lowest in Example 2 because the tunnel fire retardant coating pays more attention to the high-density expansion layer to cope with the dynamic heat flow impact.

[0062] Difference in Expansion Layer Thickness Retention Rate: The expansion layer thickness retention rate of Example 2 is the highest (97%), which is due to the increase in the acid source ratio and the strengthening of the nano-additive; while the thickness retention rate of Example 1 is slightly lower than that of Example 2 due to the relatively low density of the expansion layer.

[0063] Difference in Thermal Insulation Performance The heat flux reduction efficiency of Example 3 is the highest (70%). This is because stronger thermal insulation performance is required in outdoor wood fire protection scenarios, so the optimization of the air source and nano-additive ratio significantly improves the thermal insulation effect.

[0064] The optimized design and result analysis of the above embodiments further verify the adaptability and technical advantages of the technical solution of the present invention in different application scenarios.

[0065] Comparative Example 1: Designed for Example 1 1. Comparative design This comparative example is an improvement on the acid source in Example 1, where only a single ammonium phosphate (such as diammonium phosphate) is used as the acid source, and modified polyaluminum phosphate and borate-phosphate composite acid source are not used. The remaining components and process parameters are the same as those in Example 1.

[0066] 2. Group distribution ratio By mass percentage: Ammonium dihydrogen phosphate: 25%; Silicon oxygen modified into carbon agent: 20%; Chitosan modified nanocarbon: 10%; Melamine cyanurate: 8%; Bicarbonate: 7%; Graphene oxide: 5%; Nano titanium dioxide: 3%; Interface enhancer (γ-APTES): 2%.

[0067] 3. Preparation method Premixing of acid source and carbon forming agent The ammonium dihydrogen phosphate, the silicon-oxygen modified carbon agent and the chitosan modified nanocarbon are mixed in proportion; High-speed stirring equipment, stirring rate 600 rpm, time 25 minutes.

[0068] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, with an ultrasonic frequency of 30 kHz and an ultrasonic time of 40 minutes to form a dispersion.

[0069] Main mixing and homogenization Add the dispersion, and at the same time add melamine cyanurate, bicarbonate and interface enhancer; Homogenize and stir for 40 minutes at a speed of 400 rpm.

[0070] Drying and curing Dry under vacuum at 60°C for 6 hours; Curing at 160℃ for 3 hours.

[0071] Powder preparation The mixture was ground using a jet mill to a particle size of 30 μm.

[0072] Comparative Example 2: Designed for Example 2 1. Comparative Example Design This comparative example is designed for the application of nano-additives in Example 2, without adding graphene oxide and nano-titanium dioxide, and the remaining components and process parameters are consistent with Example 2.

[0073] 2. The composition ratio is calculated by mass percentage: Modified aluminum polyphosphate: 30%; Borate-phosphate composite acid source: 12%; Silicon oxygen modified into carbon agent: 18%; Chitosan modified nanocarbon: 12%; Melamine cyanurate: 7%; Bicarbonate: 6%; Interface enhancer (γ-APTES): 3%.

[0074] 3. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and carbon forming agent were mixed, and the high-speed shear stirring rate was 800 rpm for 20 minutes.

[0075] Main mixing and homogenization adding melamine cyanurate, bicarbonate and an interfacial enhancer; The homogenization stirring rate was 300 rpm and the time was 50 minutes.

[0076] Drying and curing: vacuum drying at 70°C for 8 hours; high temperature curing at 150°C for 2 hours.

[0077] Powder preparation The solidified material is ground to a particle size of 20-50 μm.

[0078] Comparative Example 3: Design for Example 3 1. Comparative design This comparative example is an improvement on the composite gas source in Example 3, where only melamine cyanurate is used as the gas source without adding bicarbonate. The remaining components and process parameters are the same as those in Example 3.

[0079] 2. Group distribution ratio By mass percentage: Modified aluminum polyphosphate: 22%; Borate-phosphate composite acid source: 10%; Silicon oxygen modified into carbon agent: 18%; Chitosan modified nanocarbon: 8%; Melamine cyanurate: 15%; Graphene oxide: 7%; Nano titanium dioxide: 4%; Interface enhancer (γ-APTES): 3%.

[0080] 3. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, borate-phosphate composite acid source and carbon forming agent were mixed in proportion, and stirred at a high speed of 500 rpm for 30 minutes.

[0081] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, with an ultrasonic frequency of 35 kHz and a time of 45 minutes.

[0082] Main mixing and homogenization Add the dispersion, melamine cyanurate and interface enhancer at the same time, stirring at 400 rpm for 30 minutes.

[0083] Drying and curing: vacuum drying at 80°C for 6 hours; high temperature curing at 180°C for 3 hours.

[0084] Powder preparation: Grind to a particle size of 25 μm.

[0085] Comparative Example 4: 1. Comparative design This comparative example is based on Example 1, the carbon forming agent is not modified, and unmodified pentaerythritol and ordinary carbon black are used instead of silicon-oxygen modified carbon forming agent and chitosan modified nanocarbon. The remaining components and process parameters are consistent with Example 1.

[0086] 2. Group distribution ratio By mass percentage: Modified aluminum polyphosphate: 25%; Borate-phosphate composite acid source: 10%; Unmodified pentaerythritol: 20%; Ordinary carbon black: 10%; Melamine cyanurate: 8%; Bicarbonate: 7%; Graphene oxide: 5%; Nano titanium dioxide: 3%; Interface enhancer (γ-APTES): 2%.

[0087] 3. Preparation method Premixing of acid source and carbon forming agent The modified aluminum polyphosphate, the phosphate-borate composite acid source, the unmodified pentaerythritol and the common carbon black are mixed; The high-speed stirring rate was 600 rpm for 25 minutes.

[0088] Nano additive dispersion Graphene oxide and nano-titanium dioxide were dispersed in deionized water, with an ultrasonic frequency of 30 kHz and an ultrasonic time of 40 minutes.

[0089] Main mixing and homogenization Add the dispersion, and at the same time add melamine cyanurate, bicarbonate and interface enhancer; Homogenize and stir for 40 minutes at a speed of 400 rpm.

[0090] Drying and curing Dry under vacuum at 60°C for 6 hours; Curing at 160℃ for 3 hours.

[0091] Powder preparation The mixture was ground using a jet mill to a particle size of 30 μm.

[0092] Experiment 1: Expansion ratio test Experimental Description Purpose: The expansion capacity of different flame retardants under high temperature conditions is tested to verify the influence of key components such as acid source, carbon former, gas source on the generation effect of the expansion layer, and the technical advantages of the flame retardant of the present invention are highlighted through data comparison.

[0093] Experimental Materials: The flame retardants of Example 1, Example 3, Comparative Example 1 and Comparative Example 3.

[0094] Experimental equipment: Box-type high temperature furnace (temperature control accuracy ±5°C); Vernier caliper (measurement accuracy 0.01mm); Standard steel plate sample (size 50mm×50mm×1mm).

[0095] Experimental methods: Sample coating: After each flame retardant is formulated into a fire retardant coating, it is evenly coated on the surface of the steel plate with a coating thickness of 2 mm. After coating, it is placed in a 60°C environment to dry naturally for 24 hours to ensure that the coating is completely cured.

[0096] Expansion test: Place the coated steel plate sample into a box-type high-temperature furnace; Set the heating rate to 10℃ / min, and keep the temperature constant at 500℃ for 30 minutes; Take out the sample, cool it to room temperature, and measure the thickness of the expanded coating with a vernier caliper.

[0097] Data calculation: Record the initial coating thickness (h0) and the thickness after expansion (h1); Calculate the expansion ratio: Table 1 Expansion ratio test results of different flame retardants under high temperature conditions Sample No. Initial thickness(mm) Thickness after expansion (mm) Expansion ratio Example 1 2 9.56 4.78 Comparative Example 1 2 6.43 3.22 Example 3 2 10.35 5.18 Comparative Example 3 2 7.22 3.61 This experiment tested the expansion ratio of different flame retardants and verified that the ability of the present invention to generate an expansion layer under high temperature conditions is better than that of the comparative design. The expansion ratio of Example 1 is 4.78, which is significantly higher than 3.22 of Comparative Example 1; the expansion ratio of Example 3 reaches 5.18, while that of Comparative Example 3 is only 3.61. This shows that under the conditions of optimized compounding of acid source and gas source, the generation of the expansion layer is more efficient and uniform.

[0098] The experimental results show that the modified aluminum polyphosphate and borate-phosphate composite acid source used in Examples 1 and 3 can release phosphoric acid and boron oxide in multiple temperature zones, synergistically catalyze the carbon forming agent to quickly form carbon, and generate a dense expanded carbon layer. However, in Comparative Example 1, only a single ammonium phosphate was used, which had a narrow decomposition temperature zone and a low reaction rate, resulting in insufficient thickness of the expanded layer and an uneven carbon layer. At the same time, the multi-stage gas source release mechanism in Example 3 further enhanced the expansion ratio, showing a significant advantage over the single gas source design in Comparative Example 3.

[0099] From the perspective of the mechanism of expansion layer generation, the silicon-oxygen modified carbonizing agent used in the embodiment improves the compactness and mechanical strength of the carbon layer through silicon-oxygen cross-linking, and promotes a more uniform expansion process. The carbon layer generated by the unmodified carbonizing agent in the comparative example has a loose structure, resulting in a weakened expansion effect. In addition, the introduction of nano-additives (graphene oxide and nano-titanium dioxide) in the embodiment plays a role in enhancing the uniformity and stability of the expansion layer, and the comparative experiment further verifies its positive effect on the expansion ratio.

[0100] Experiment 2: Thermal insulation performance test Experimental Description Purpose: The thermal insulation performance of different flame retardant coatings under high temperature radiation conditions is tested, and the thermal insulation protection ability of the flame retardant to the substrate is verified by the temperature change on the back side, reflecting the role of acid source, gas source, carbon forming agent and nano additives.

[0101] Experimental Materials: The flame retardants of Example 2, Example 3, Comparative Example 2 and Comparative Example 3.

[0102] Experimental equipment: Thermal radiation meter (radiation temperature 700℃); Thermocouple (K type, accuracy 0.5℃); Temperature recorder; Steel plate sample (size 50mm×50mm×2mm).

[0103] Experimental methods: Sample coating: The coatings prepared with each flame retardant were evenly coated on the surface of the steel plate, and the coating thickness was 3 mm.

[0104] After coating, dry at 60℃ for 24 hours to ensure the coating is cured.

[0105] Test equipment construction: Fix the coated sample on the sample holder of the thermal radiation instrument, with the coating side facing the radiation source, and install a K-type thermocouple on the back side. Use a temperature recorder to record the temperature change on the back side in real time. The radiation source temperature was set to 700°C and the heating time was 30 minutes.

[0106] Experimental process: Turn on the thermal radiation instrument to radiate high temperature to the sample; Record the back temperature change curve during heating; After heating, the maximum back surface temperature and temperature rise rate of each sample were analyzed.

[0107] Table 2: Thermal insulation performance test results of different flame retardant coatings Sample No. Maximum back temperature (℃) Temperature rise rate (℃ / min) Example 2 125 4.2 Comparative Example 2 174 6.1 Example 3 117 3.8 Comparative Example 3 162 5.5 The results of the thermal insulation performance test show that the back temperature of the coating of Example 2 and Example 3 is relatively low, with the highest temperatures being 125°C and 117°C, respectively, and the temperature rise rates being 4.2°C / min and 3.8°C / min, respectively, while the back maximum temperatures of Comparative Examples 2 and 3 are significantly higher, at 174°C and 162°C, respectively, and the temperature rise rates being 6.1°C / min and 5.5°C / min, respectively. This shows that the flame retardant of the present invention can form an effective thermal insulation protective layer under high temperature conditions, greatly reduce the temperature of heat conduction to the substrate, and show thermal insulation performance that is significantly better than that of the prior art solution.

[0108] The experimental results can be attributed to the synergistic effect of the nano-additives (graphene oxide and nano-titanium dioxide) in the embodiment. Graphene oxide forms a uniform nanoporous network structure, which effectively inhibits the conduction of heat and oxygen in the expansion layer through the Knudsen diffusion effect. Nano-titanium dioxide further reduces the transfer of radiant heat by reflecting high-temperature radiation. However, no nano-additives were added in Comparative Examples 2 and 3, resulting in a shorter and faster heat conduction path in the thermal insulation layer, and a significant decrease in thermal insulation performance.

[0109] At the same time, the composite acid source and the modified carbon-forming agent used in the embodiment work together to generate a dense and uniform carbon layer, further enhancing the thermal insulation performance. The modified aluminum polyphosphate releases phosphoric acid to catalyze the carbonization of the carbon-forming agent in multiple stages, and the glassy substance generated by the borate fills the pores of the expansion layer, making the expansion layer denser and enhancing the heat barrier effect. The single acid source and the unmodified carbon-forming agent in the comparative example result in a loose carbon layer structure and a weakened thermal insulation effect.

[0110] In addition, the multi-stage release of the gas source is also the key to the thermal insulation performance. In the embodiment, melamine cyanurate and bicarbonate release gas by decomposing at different temperatures, so that the expansion layer forms a uniform honeycomb pore structure, thereby further reducing the heat transfer efficiency. The single gas source design in the comparative example leads to concentrated gas release, uneven pores, and a significant difference in thermal insulation performance. It can be seen that the optimized design of the present invention significantly improves the thermal insulation performance of the flame retardant.

[0111] Experiment 3: Expansion layer thickness retention test (high temperature dynamic heat flow test) Experimental Description Purpose: By simulating a dynamic heat flow environment, the thickness retention rate of the flame retardant expansion layer under high temperature impact is tested, the high temperature dynamic stability of the expansion layer and its ability to protect the substrate are verified, and the role of the acid source, carbon former and nano-additive in the mechanical properties of the expansion layer is reflected.

[0112] Experimental Materials: The flame retardants of Example 2, Example 3, Comparative Example 2 and Comparative Example 3.

[0113] Experimental equipment: High temperature combustion wind tunnel test device (wind speed range 5–20m / s); Digital thickness gauge (accuracy 0.01mm); Standard steel plate sample (50mm×50mm×2mm).

[0114] Experimental methods: Sample coating: Each flame retardant is formulated into a fire retardant coating, which is evenly coated on the surface of the steel plate with a coating thickness of 2 mm; After coating, place in a 60°C drying oven for 24 hours to ensure that the coating is fully cured.

[0115] Test equipment construction: The coated sample is fixed in a high temperature combustion wind tunnel device; Set the flame temperature to 800°C, the wind speed to 10m / s, and the burning time to 10 minutes.

[0116] Testing process: Turn on the wind tunnel device to perform dynamic heat flow heating on the sample; After heating, the sample was cooled to room temperature, and the thickness of the expansion layer was measured using a digital thickness gauge; Calculate the expansion layer thickness retention rate: Table 3: Test results of thickness retention of different flame retardant expansion layers under high temperature dynamic heat flow conditions The experimental results show that the thickness retention rates of the expansion layer of Example 2 and Example 3 under a high temperature dynamic heat flow environment are 95.9% and 96.9% respectively, while the retention rates of Comparative Example 2 and Comparative Example 3 are 80.6% and 81.3% respectively, which are significantly lower than those of the Examples. This shows that the flame retardant of the present invention can maintain the structural integrity of the expansion layer under a dynamic heat flow environment and provide more durable protective performance.

[0117] The superior performance of the embodiment is attributed to the synergistic effect of the acid source and the carbon forming agent. The modified aluminum polyphosphate used in the embodiment improves the high-temperature catalytic efficiency through rare earth modification, and the phosphoric acid and polyphosphoric acid produced by decomposition continuously promote the carbonization reaction of the carbon forming agent, generating a dense and high-strength expanded carbon layer. The glassy substance generated by the decomposition of the borate fills the micropores of the expansion layer at high temperature, further enhancing the mechanical strength and thermal shock resistance of the expansion layer. In contrast, the single acid source design in the comparative example lacks multi-stage catalysis, resulting in a loose expansion layer structure and a significantly reduced thickness retention rate.

[0118] In addition, the modified design of the carbonizing agent is also a key factor in improving the dynamic stability of the expansion layer. The silicon-oxygen modified carbonizing agent in the embodiment significantly enhances the compression resistance and spalling resistance of the expansion layer by forming a silicon-oxygen cross-linked structure. The chitosan-modified nanocarbon generates a uniform carbon layer during the carbonization process, which gives the expansion layer higher mechanical properties. The carbon layer generated by the unmodified carbonizing agent in the comparative example is relatively fragile, and is prone to cracking and falling off under the impact of dynamic heat flow, resulting in a low thickness retention rate.

[0119] The introduction of nano-additives (graphene oxide and nano-titanium dioxide) also plays an important role in enhancing the stability of the expansion layer. Graphene oxide forms a nanoscale support network in the expansion layer, which effectively inhibits the collapse of the expansion layer under high temperature impact; nano-titanium dioxide further reduces the destructive power of the high temperature dynamic environment on the expansion layer by improving the thermal barrier performance of the expansion layer. The lack of nano-additives in the comparative example leads to poor structural stability of the expansion layer and a significant decrease in thickness retention rate. The experiment verified the technical advantages of the flame retardant of the present invention in the stability of the expansion layer.

[0120] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A flame retardant for fire retardant paint, characterized in that: The flame retardant comprises the following components in percentage by mass: Modified aluminum polyphosphate: 20%-30%; Borate-phosphate composite acid source: 5%-15%; Silicon oxygen modified carbon agent: 15%-25%; Chitosan modified nanocarbon: 5%-15%; Melamine cyanurate: 5%-10%; Bicarbonate: 5%-10%; Graphene oxide: 3%-7%; Nano titanium dioxide: 2%-5%; Interface enhancer: 1%-3%.

2. A flame retardant for fire retardant paint according to claim 1, characterized in that: The modified aluminum polyphosphate is modified by adding rare earth elements, and the rare earth elements are titanium or yttrium.

3. A flame retardant for fire retardant paint according to claim 1, characterized in that: The borate-phosphate composite acid source is a mixture of borate and diammonium phosphate in a mass ratio of 1:1 to 1:

3.

4. The flame retardant for fire retardant paint according to claim 1, characterized in that: The silicon-oxygen modified carbon-forming agent is a composite product of pentaerythritol and a siloxane compound.

5. The flame retardant for fire retardant paint according to claim 1, characterized in that: The chitosan-modified nano-carbon is prepared by carbonizing chitosan and combining chitosan with nano-carbon materials to form a composite.

6. The flame retardant for fire retardant paint according to claim 1, characterized in that: The graphene oxide is flaky graphene oxide with a particle size less than 50 nanometers.

7. The flame retardant for fire retardant paint according to claim 1, characterized in that: The interface enhancer is γ-aminopropyltriethoxysilane.

8. A method for preparing a flame retardant for fire retardant paint, according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) mixing modified aluminum polyphosphate, borate-phosphate composite acid source and silicon-oxygen modified carbon agent, and subjecting the mixture to high-speed shear stirring; (2) dispersing graphene oxide and nano-titanium dioxide in deionized water, and ultrasonically dispersing to form a nano-dispersion liquid; (3) adding the nano-dispersion to the mixture obtained in step (1), and simultaneously adding melamine cyanurate, bicarbonate and an interface enhancer, and stirring evenly; (4) drying the mixture of step (3) and then curing it at high temperature; (5) The solidified material is crushed to obtain flame retardant powder with a particle size of 20-50 μm.

9. The method for preparing a flame retardant for fire retardant paint according to claim 8, characterized in that: The high-speed shear stirring in step (1) is carried out at a rate of 500-800 rpm for 20-30 minutes.

10. The method for preparing a flame retardant for fire retardant paint according to claim 8, characterized in that: The high temperature curing temperature in step (4) is 150-180° C. and the time is 2-3 hours.

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