Self-repairing type steel structure fireproof coating and preparation method thereof

Abstract

The invention discloses a self-repairing type steel structure fireproof coating and a preparation method thereof, and belongs to the technical field of fireproof coatings, the self-repairing type steel structure fireproof coating comprises the following raw materials: water-borne epoxy resin, a microencapsulated flame retardant, a self-repairing blocking agent, expanded perlite, nano titanium dioxide, kaolin, a water-borne epoxy resin curing agent, a dispersing agent, a flatting agent, a defoaming agent and deionized water; the preparation method comprises the following steps: adding expanded perlite, nano titanium dioxide and kaolin into deionized water, dispersing at a first rotating speed, then adding water-borne epoxy resin, a microencapsulated flame retardant, a self-repairing blocking agent, a dispersing agent, a flatting agent and a defoaming agent, continuously stirring, finally adding a water-borne epoxy resin curing agent, and stirring at a second rotating speed, the self-repairing type steel structure fireproof coating is obtained; through cooperative addition of the microencapsulated flame retardant and the self-repairing blocking agent, collaborative optimization of fireproof, flame-retardant and self-repairing functions is realized, so that the prepared fireproof coating has excellent flame-retardant performance and self-repairing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of fireproof coatings, and particularly relates to a self-healing type steel structure fireproof coating and a preparation method thereof. Background Art

[0002] As a new type of building material, steel structures have the advantages of high strength, light self-weight, strong seismic resistance, short construction period, and environmental friendliness compared with traditional masonry and concrete structures. They are widely used in commercial buildings, stadiums, industrial workshops, airports, railway stations, etc. Although steel structures themselves are incombustible, their fireproof performance is poor, their thermal conductivity is high, and their mechanical properties will rapidly decrease as the temperature rises. Generally, when the temperature reaches 250°C, the mechanical properties of the steel structure begin to decline; when the temperature reaches 500°C, its mechanical properties will rapidly decline; when the temperature reaches above 600°C, the steel will lose its load-bearing capacity, resulting in the collapse of the building and causing huge losses to people's lives and property. Among the many methods to improve the fireproof performance of steel structures, the most economical and effective method is to brush fireproof coatings on the surface of steel structures.

[0003] The invention patent with the publication number of CN106221346B discloses a self-healing type steel structure fireproof coating, which is prepared from epoxy-modified waterborne polyurethane emulsion, melamine formaldehyde resin microencapsulated ammonium polyphosphate, polyurethane microencapsulated inorganic particles, self-healing microcapsules, hydroxyethyl cellulose, dispersant, defoamer, mildew-proof agent, n-octanol and water, and has the advantages of large adhesion to the substrate, excellent fireproof performance, excellent surface decoration and corrosion resistance, and good self-healing function; however, the preparation of its raw materials is too complex, involving multiple raw materials microencapsulated in different ways. During the process of synthesizing melamine formaldehyde resin microencapsulated ammonium polyphosphate by in-situ polymerization method, polluting gases such as formaldehyde will be generated, which is harmful to the human body and the environment; the self-healing microcapsules need to coat epoxy resin and curing agent separately, increasing the production cost and difficulty, and the self-healing microcapsules use urea-formaldehyde resin with easy aging as the wall material, which is easy to cause the premature leakage of the content of the self-healing microcapsules in the long term, not only losing the self-healing function, but also the flammable content will affect the fireproof and flame-retardant performance of the fireproof coating.

[0004] Therefore, developing a steel structure fireproof coating that can self-heal coating cracks and synergistically improve the flame retardant and fireproof performance is a technical problem that needs to be solved currently. Summary of the Invention

[0005] The purpose of the present invention is to provide a self-healing type steel structure fireproof coating and a preparation method thereof to solve the problems in the background art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A self-healing steel structure fireproof coating, comprising the following raw materials in parts by weight:

[0008] 30 - 40 parts of waterborne epoxy resin, 15 - 22 parts of microencapsulated flame retardant, 5 - 9 parts of self-healing barrier agent, 6 - 8 parts of expanded perlite, 5 - 7 parts of nano-titanium dioxide, 4 - 6 parts of kaolin, 2 - 4 parts of waterborne epoxy resin curing agent, 2 - 5 parts of dispersant, 3 - 5 parts of leveling agent, 4 - 7 parts of defoaming agent, 25 - 32 parts of deionized water.

[0009] Furthermore, the microencapsulated flame retardant is prepared by the following steps:

[0010] Step A1: Add ammonium polyphosphate and piperazine into deionized water and mix evenly, then add the dichloromethane solution of emulsifier, and stir and disperse at high speed for 20 - 30 min to obtain a water-in-oil emulsion;

[0011] Step A2: Add trimellitic acid chloride and phenyl dichlorophosphate into dichloromethane and stir to dissolve, then add them into the water-in-oil emulsion, and slowly dropwise add triethylamine, stir and react at room temperature for 2 - 3 h, filter by suction, wash, and vacuum dry at 40 °C to obtain the microencapsulated flame retardant.

[0012] Piperazine and deionized water are dispersed on the surface of ammonium polyphosphate in a physical adsorption manner to form an aqueous phase, then the dichloromethane solution of emulsifier is added as an oil phase into the aqueous phase, and stirred at high speed to form a uniformly dispersed and stable water-in-oil emulsion; then add trimellitic acid chloride and phenyl dichlorophosphate, and dropwise add triethylamine. Under the catalysis of triethylamine, trimellitic acid chloride and phenyl dichlorophosphate react with piperazine aggregated on the surface of ammonium polyphosphate to rapidly generate a poly(piperazine amide) wall material doped with phosphorus. When drying, the wall material allows the water molecules inside it to pass through, but the larger polyphosphate is coated inside the wall material and cannot flow out, thus obtaining the microencapsulated flame retardant, which has the advantages of fast reaction process and easy control, and there is no emulsifier impurity inside the capsule.

[0013] Furthermore, the dosage ratio of ammonium polyphosphate, piperazine, deionized water and the dichloromethane solution of emulsifier is 18 - 20 g : 1.8 - 2 g : 100 mL : 150 mL; the ammonium polyphosphate is sufficiently ground before use to avoid the agglomeration of ammonium polyphosphate.

[0014] Furthermore, the dichloromethane solution of emulsifier is composed of Span 80 and dichloromethane mixed according to 0.8 - 1 g : 150 mL. Selecting Span 80 with good compatibility with dichloromethane as the emulsifier can, on the one hand, improve the stability of the water-in-oil emulsion, and on the other hand, Span 80 is insoluble in the aqueous phase and will not or rarely remain in the ammonium polyphosphate core material when preparing the microencapsulated flame retardant, avoiding negative impacts on the flame retardant performance.

[0015] Further, the rotation speed of the stirring and dispersion in step A1 is 3000 - 5000 r / min; under high-speed stirring and dispersion, ammonium polyphosphate can be uniformly and stably dispersed in the water-in-oil emulsion.

[0016] Further, the dosage ratio of trimellitic acid chloride, phenyl dichlorophosphate, dichloromethane and triethylamine is 4 - 4.5 g : 1.8 - 2 g : 50 mL : 4 - 5 mL.

[0017] Further, the self-healing barrier agent is prepared by the following steps:

[0018] Add graphene oxide and cobalt acetate anhydrous into methanol and stir and mix well to obtain a suspension. Then add 2-mercaptobenzimidazole and sodium formate into methanol and stir until completely dissolved to obtain a mixed solution. Then drop the mixed solution into the suspension, stir and mix at room temperature for 30 min, then add 2-methylimidazole and stir and react at 90 - 95 °C for 5 h. After centrifugal separation, washing with methanol and drying, the self-healing barrier agent is obtained. First, the mixed solution and the suspension are mixed to enable 2-mercaptobenzimidazole to be adsorbed on the surface of graphene oxide through electrostatic or chemical reactions. Then, ZIF-67 is in-situ grown on the surface of graphene oxide adsorbed with 2-mercaptobenzimidazole, thereby encapsulating 2-mercaptobenzimidazole into ZIF-67, and a self-healing barrier agent with multiple functions is prepared. ZIF-67 coated with 2-mercaptobenzimidazole can improve the dispersion of graphene oxide in the fireproof coating, and the synergistic effect of using ZIF-67 with a slow-release effect to coat 2-mercaptobenzimidazole can achieve better anti-corrosion and self-healing effects.

[0019] Further, the dosage ratio of graphene oxide, cobalt acetate anhydrous, 2-mercaptobenzimidazole, sodium formate, 2-methylimidazole and methanol is 0.15 g : 1 - 1.1 g : 0.8 - 1 g : 0.5 g : 2.2 g : 70 mL; the dosage ratio of methanol in the suspension and the mixed solution is 2 : 5. In the present invention, environmentally friendly 2-mercaptobenzimidazole is used as a corrosion inhibitor, which can not only chelate with iron ions to form a complex on the surface of the steel structure, but also adsorb on the steel surface to form a protective film to resist the attack of corrosive media.

[0020] A preparation method of a self-healing steel structure fireproof coating, comprising the following steps:

[0021] Add expanded perlite, nano-titanium dioxide and kaolin into deionized water and stir and disperse at a first rotation speed for 30 min, then add waterborne epoxy resin, microencapsulated flame retardant, self-healing barrier agent, dispersant, leveling agent and defoaming agent and continue to stir and mix at the first rotation speed for 30 min. Finally, add a waterborne epoxy resin curing agent and stir and mix at a second rotation speed for 20 min to obtain a self-healing steel structure fireproof coating.

[0022] Furthermore, the first rotation speed is 1500 - 2000 r / min, and the second rotation speed is 500 - 1000 r / min. Stirring at a stepped rotation speed makes the dispersion of each component more uniform, effectively avoiding the rupture of microcapsules, and at the same time ensuring the full cross-linking of the curing agent to form a dense coating.

[0023] Beneficial effects:

[0024] In the present invention, ammonium polyphosphate is used as the core material, and piperazine is polymerized with trimesoyl chloride and phenyl dichlorophosphate by an interfacial polymerization method to generate a wall material on the surface of ammonium polyphosphate, and the ammonium polyphosphate is encapsulated and modified to obtain a microencapsulated flame retardant; by copolymerizing phenyl dichlorophosphate and trimesoyl chloride with piperazine together, phosphorus elements are effectively incorporated into the main chain of the molecular structure of the wall material, and combined with the piperazine ring structure, the obtained wall material has excellent thermal stability and char-forming performance at the same time; on the one hand, the wall material with excellent performance can firmly coat the ammonium polyphosphate core material inside it, prevent the migration of ammonium polyphosphate from contacting and corroding the steel structure, and improve the compatibility between ammonium polyphosphate and the coating substrate; on the other hand, the excellent char-forming property of the wall material can cooperate with the flame retardancy of ammonium polyphosphate, significantly improving the flame retardant performance of the microencapsulated flame retardant;

[0025] The self-healing barrier agent prepared by the present invention exhibits multiple functions in the fireproof coating: First, as a two-dimensional nano-filler, the self-healing barrier agent can improve the barrier performance of the fireproof coating to corrosive media and delay the diffusion of corrosive media from the fireproof coating to the surface of the steel structure; second, when cracks appear in the fireproof coating and corrosive media enter the cracks to corrode the surface of the steel structure, the self-healing barrier agent can release 2-mercaptobenzimidazole according to the change of the pH value in the local corrosion area, and form a new protective layer after chelating with iron ions. This self-healing behavior can effectively prevent further damage to the steel structure and exhibit excellent active anti-corrosion performance; finally, the self-healing barrier agent can also act synergistically with the microencapsulated flame retardant to promote the formation of a denser and more stable carbon layer during the combustion process, jointly improving the fireproof performance of the steel structure fireproof coating;

[0026] Based on waterborne epoxy resin as the base material, through the combined addition of the microencapsulated flame retardant and the self-healing barrier agent, the present invention realizes the synergistic optimization of fireproof and self-healing functions, making the prepared fireproof coating have both excellent flame retardant performance and self-healing performance; the combined filling of expanded perlite, nano-titanium dioxide and kaolin in the raw materials can enhance the adhesion, impact resistance and heat insulation performance of the coating; moreover, the preparation method of the fireproof coating of the present invention is simple, and the dispersion of each component is made uniform through the setting of stepped rotation speed stirring, improving the stability of the fireproof coating. Specific embodiments

[0027] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a microencapsulated flame retardant, which is prepared by the following steps:

[0030] Step A1: Add 18 g of well-ground ammonium polyphosphate and 1.8 g of piperazine to 100 mL of deionized water and mix evenly. Then add the dichloromethane solution of the emulsifier composed of 0.8 g of Span 80 and 150 mL of dichloromethane, and stir and disperse at a speed of 3000 r / min for 30 min to obtain a water-in-oil emulsion.

[0031] Step A2: Add 4 g of trimellitic acid chloride and 1.8 g of phenyl dichlorophosphate to 50 mL of dichloromethane and stir to dissolve. Then add it to the water-in-oil emulsion, and slowly dropwise add 4 mL of triethylamine. Stir and react at room temperature for 2 h, filter by suction, wash, and vacuum dry at 40 °C to obtain the microencapsulated flame retardant.

[0032] Example 2

[0033] This embodiment provides a microencapsulated flame retardant, which is prepared by the following steps:

[0034] Step A1: Add 19 g of well-ground ammonium polyphosphate and 1.9 g of piperazine to 100 mL of deionized water and mix evenly. Then add the dichloromethane solution of the emulsifier composed of 0.9 g of Span 80 and 150 mL of dichloromethane, and stir and disperse at a speed of 4000 r / min for 25 min to obtain a water-in-oil emulsion.

[0035] Step A2: Add 4.2 g of trimellitic acid chloride and 1.9 g of phenyl dichlorophosphate to 50 mL of dichloromethane and stir to dissolve. Then add it to the water-in-oil emulsion, and slowly dropwise add 4.5 mL of triethylamine. Stir and react at room temperature for 3 h, filter by suction, wash, and vacuum dry at 40 °C to obtain the microencapsulated flame retardant.

[0036] Example 3

[0037] This embodiment provides a microencapsulated flame retardant, which is prepared by the following steps:

[0038] Step A1: Add 20 g of well-ground ammonium polyphosphate and 2 g of piperazine into 100 mL of deionized water and mix evenly. Then add the dichloromethane solution of the emulsifier composed of 1 g of Span 80 and 150 mL of dichloromethane, and stir and disperse at a speed of 5000 r / min for 20 min to obtain a water-in-oil emulsion.

[0039] Step A2: Dissolve 4.5 g of trimellitic acid chloride and 2 g of phenyl dichlorophosphate in 50 mL of dichloromethane by stirring. Then add it to the water-in-oil emulsion, and slowly dropwise add 5 mL of triethylamine. Stir and react at room temperature for 3 h, filter by suction, wash, and vacuum dry at 40 °C to obtain the microencapsulated flame retardant.

[0040] Comparative Example 1

[0041] This comparative example is different from Example 3 in that phenyl dichlorophosphate is not added in Step A2, and the other raw materials and steps are the same.

[0042] Example 4

[0043] This example provides a self-healing barrier agent, which is prepared through the following steps:

[0044] Add 0.15 g of graphene oxide and 1 g of anhydrous cobalt acetate into 20 mL of methanol and stir and mix well to obtain a suspension. Then add 0.8 g of 2-mercaptobenzimidazole and 0.5 g of sodium formate into 50 mL of methanol and stir until completely dissolved to obtain a mixed solution. Then drop the mixed solution into the suspension, stir and mix at room temperature for 30 min, then add 2.2 g of 2-methylimidazole and stir and react at 90 °C for 5 h. Centrifuge at 8000 r / min for 10 min, separate, wash with methanol, and vacuum dry for 24 h to obtain the self-healing barrier agent.

[0045] Example 5

[0046] This example provides a self-healing barrier agent, which is prepared through the following steps:

[0047] Add 0.15 g of graphene oxide and 1.05 g of anhydrous cobalt acetate into 20 mL of methanol and stir and mix well to obtain a suspension. Then add 0.9 g of 2-mercaptobenzimidazole and 0.5 g of sodium formate into 50 mL of methanol and stir until completely dissolved to obtain a mixed solution. Then drop the mixed solution into the suspension, stir and mix at room temperature for 30 min, then add 2.2 g of 2-methylimidazole and stir and react at 93 °C for 5 h. Centrifuge at 8000 r / min for 10 min, separate, wash with methanol, and vacuum dry for 24 h to obtain the self-healing barrier agent.

[0048] Example 6

[0049] This embodiment provides a self-healing barrier agent, which is prepared by the following steps:

[0050] Add 0.15 g of graphene oxide and 1.1 g of anhydrous cobalt acetate to 20 mL of methanol, stir and mix well to obtain a suspension. Then add 1 g of 2-mercaptobenzimidazole and 0.5 g of sodium formate to 50 mL of methanol, stir until completely dissolved to obtain a mixed solution. Then drop the mixed solution into the suspension, stir and mix at room temperature for 30 min, then add 2.2 g of 2-methylimidazole, stir and react at 95 °C for 5 h. After centrifuging at 8000 r / min for 10 min and separating, wash with methanol and then dry in vacuum for 24 h to obtain the self-healing barrier agent.

[0051] Comparative Example 2

[0052] Compared with Example 6, the difference in this comparative example is that 2-mercaptobenzimidazole is not added and used, and the other raw materials and steps are the same.

[0053] Comparative Example 3

[0054] Compared with Example 6, the difference in this comparative example is that 2-methylimidazole is not added and used, and the other raw materials and steps are the same.

[0055] Example 7

[0056] This embodiment provides a self-healing type steel structure fireproof coating, which is prepared by the following steps:

[0057] Add 6 parts by weight of expanded perlite, 5 parts by weight of nano-titanium dioxide and 4 parts by weight of kaolin to 25 parts by weight of deionized water, stir and disperse at a speed of 1500 r / min for 30 min. Then add 30 parts by weight of waterborne epoxy resin (ERE2581), 15 parts by weight of the microencapsulated flame retardant prepared in Example 1, 5 parts by weight of the self-healing barrier agent prepared in Example 4, 2 parts by weight of a dispersant, 3 parts by weight of a leveling agent and 4 parts by weight of an antifoaming agent, and continue to stir and mix for 30 min. Finally, add 2 parts by weight of a waterborne epoxy resin curing agent (ERC 2610) and stir and mix at a speed of 500 r / min for 20 min to obtain the self-healing type steel structure fireproof coating.

[0058] Example 8

[0059] This embodiment provides a self-healing type steel structure fireproof coating, which is prepared by the following steps:

[0060] 7 parts by weight of expanded perlite, 6.5 parts by weight of nano-titanium dioxide, and 5 parts by weight of kaolin were added to 30 parts by weight of deionized water and stirred and dispersed at a speed of 1800 r / min for 30 min. Then, 35 parts by weight of waterborne epoxy resin (ERE2581), 19 parts by weight of the microencapsulated flame retardant prepared in Example 2, 7.5 parts by weight of the self-healing barrier agent prepared in Example 5, 4 parts by weight of a dispersant, 4 parts by weight of a leveling agent, and 6 parts by weight of an antifoaming agent were added and stirred and mixed for another 30 min. Finally, 3 parts by weight of a waterborne epoxy resin curing agent (ERC 2610) was added and stirred and mixed at a speed of 800 r / min for 20 min to obtain a self-healing type steel structure fireproof coating.

[0061] Example 9

[0062] This example provides a self-healing type steel structure fireproof coating, which is prepared by the following steps:

[0063] 8 parts by weight of expanded perlite, 7 parts by weight of nano-titanium dioxide, and 6 parts by weight of kaolin were added to 32 parts by weight of deionized water and stirred and dispersed at a speed of 2000 r / min for 30 min. Then, 40 parts by weight of waterborne epoxy resin (ERE2581), 22 parts by weight of the microencapsulated flame retardant prepared in Example 3, 9 parts by weight of the self-healing barrier agent prepared in Example 6, 5 parts by weight of a dispersant, 5 parts by weight of a leveling agent, and 7 parts by weight of an antifoaming agent were added and stirred and mixed for another 30 min. Finally, 4 parts by weight of a waterborne epoxy resin curing agent (ERC 2610) was added and stirred and mixed at a speed of 1000 r / min for 20 min to obtain a self-healing type steel structure fireproof coating.

[0064] Comparative Example 4

[0065] Compared with Example 9, the difference in this comparative example is that the microencapsulated flame retardant prepared in Example 3 was replaced with the microencapsulated flame retardant prepared in Comparative Example 1 in equal amounts, and the other raw materials and steps were the same.

[0066] Comparative Example 5

[0067] Compared with Example 9, the difference in this comparative example is that the microencapsulated flame retardant prepared in Example 3 was replaced with melamine formaldehyde resin microencapsulated ammonium polyphosphate in the prior art in equal amounts, and the other raw materials and steps were the same.

[0068] Comparative Example 6

[0069] Compared with Example 9, the difference in this comparative example is that the self-healing barrier agent prepared in Example 6 was replaced with the self-healing barrier agent prepared in Comparative Example 2 in equal amounts, and the other raw materials and steps were the same.

[0070] Comparative Example 7

[0071] This comparative example is different from Example 9 in that the self-healing barrier agent prepared in Example 6 is replaced in equal amount with the self-healing barrier agent prepared in Comparative Example 3, and the remaining raw materials and steps are the same.

[0072] Performance tests were carried out on the fireproof coatings for steel structures prepared in Examples 7 - 9 and Comparative Examples 4 - 7. The fire resistance limit of the fireproof coatings was tested according to the standard of GB 14907 - 2002, and the corrosion resistance of the fireproof coatings was tested according to the standard of GB / T 1771 - 2007. Cross scratches were engraved on the surface of the fireproof coatings and left to self-heal for 30 days under natural indoor conditions, and then the fire resistance limit and corrosion resistance were tested again. The results are shown in Table 1:

[0073] Table 1

[0074]

[0075]

[0076] It can be seen from the data in Table 1 that the fireproof coatings of Examples 7 - 9 of the present invention show excellent performance in fire resistance limit and corrosion resistance, and the performance degradation after self-healing is small (the reduction of fire resistance limit is less than 15%, and the corrosion resistance remains stable). Among them, dichlorophenyl phosphate was not added in Comparative Example 4, and the carbonization performance of the microcapsule wall material became poor, resulting in a reduction of the fire resistance limit; 2-mercaptobenzimidazole and 2-methylimidazole were missing in Comparative Examples 6 - 7 respectively, resulting in the lack of corrosion inhibitor and ZIF-67, and the function of the self-healing barrier agent was limited. Generally speaking, by optimizing the formulations of the microencapsulated flame retardant and the self-healing barrier agent, the present invention realizes the synergistic improvement of fire prevention and self-healing performance, which is significantly better than the prior art.

[0077] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0078] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made therein without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A self-healing steel structure fireproof coating, characterized in that, It comprises the following raw materials in parts by weight: 30-40 parts of waterborne epoxy resin, 15-22 parts of microencapsulated flame retardant, 5-9 parts of self-healing barrier agent, 6-8 parts of expanded perlite, 5-7 parts of nano-titanium dioxide, 4-6 parts of kaolin, 2-4 parts of waterborne epoxy resin curing agent, 2-5 parts of dispersant, 3-5 parts of leveling agent, 4-7 parts of defoaming agent, and 25-32 parts of deionized water.

2. The self-healing type steel structure fireproof coating according to claim 1, characterized in that, The microencapsulated flame retardant is prepared by the following steps: Step A1: Add ammonium polyphosphate and piperazine into deionized water and mix evenly, then add the dichloromethane solution of emulsifier, and stir rapidly to disperse evenly to obtain a water-in-oil emulsion; Step A2: Add trimellitic acid chloride and phenyl dichlorophosphate into dichloromethane and stir to dissolve, then add it into the water-in-oil emulsion, and slowly dropwise add triethylamine, stir and react at room temperature for 2-3 h, filter by suction, wash and dry to obtain the microencapsulated flame retardant.

3. The self-healing type steel structure fireproof coating according to claim 2, characterized in that, The dosage ratio of ammonium polyphosphate, piperazine, deionized water and the dichloromethane solution of emulsifier is 18-20 g: 1.8-2 g: 100 mL: 150 mL.

4. The self-healing type steel structure fireproof coating according to claim 2, characterized in that, The dichloromethane solution of emulsifier is composed of Span 80 and dichloromethane mixed according to 0.8-1 g: 150 mL.

5. The self-repairing steel structure fireproof coating according to claim 2, wherein, The rotation speed of the stirring and dispersion is 3000-5000 r / min.

6. The self-healing type steel structure fireproof coating according to claim 2, characterized in that, The dosage ratio of trimellitic acid chloride, phenyl dichlorophosphate, dichloromethane and triethylamine is 4-4.5 g: 1.8-2 g: 50 mL: 4-5 mL.

7. The self-healing type steel structure fireproof coating according to claim 1, wherein The self-healing barrier agent is prepared by the following steps: Add graphene oxide and anhydrous cobalt acetate into methanol and stir well to mix to obtain a suspension, then add 2-mercaptobenzimidazole and sodium formate into methanol and stir until completely dissolved to obtain a mixed solution, then drop the mixed solution into the suspension, stir and mix evenly at room temperature, then add 2-methylimidazole and stir and react at 90-95 °C for 5 h, centrifuge, wash with methanol and dry to obtain the self-healing barrier agent.

8. A self-healing type steel structure fireproof coating according to claim 7, characterized in that, The dosage ratio of graphene oxide, anhydrous cobalt acetate, 2-mercaptobenzimidazole, sodium formate, 2-methylimidazole and methanol is 0.15 g: 1-1.1 g: 0.8-1 g: 0.5 g: 2.2 g: 70 mL; the dosage ratio of methanol in the suspension and the mixed solution is 2:

5.

9. The preparation method of a self-healing type steel structure fireproof coating according to claim 1, characterized in that, It comprises the following steps: Add expanded perlite, nano-titanium dioxide and kaolin into deionized water and stir and disperse evenly at the first rotation speed, then add waterborne epoxy resin, microencapsulated flame retardant, self-healing barrier agent, dispersant, leveling agent and defoaming agent and continue to stir and mix evenly at the first rotation speed, and finally add the waterborne epoxy resin curing agent and stir and mix fully at the second rotation speed to obtain the self-healing type steel structure fireproof coating.

10. The preparation method of a self-healing steel structure fireproof coating according to claim 9, characterized in that, The first rotation speed is 1500-2000 r / min, and the second rotation speed is 500-1000 r / min.

Images