Fire-extinguishing and fireproof steel structure coating as well as preparation method and application thereof

Abstract

The invention provides a fire-extinguishing and fireproof steel structure coating as well as a preparation method and application thereof, and belongs to the technical field of fire-fighting materials. In the steel structure coating provided by the invention, the temperature-sensitive fire extinguishing functional unit and the composite expansion system stably coexist and are uniformly distributed in the coating, and respective functional completeness is kept, so that an advanced protective material which is reliable in performance and simple and convenient to construct is obtained. The coating has dual functions of active fire extinguishing and passive fire prevention, can start corresponding protection mechanisms at different time points when a fire disaster occurs, can play an effective protection role in different stages of the fire disaster, realizes rapid inhibition in the germination period of the fire disaster and long-acting heat insulation in the development period of the fire disaster, and provides whole-process and multi-layer intelligent protection for a steel structure.

Description

Technical Field

[0001] This invention relates to the field of fire protection materials technology, and in particular to a steel structure coating that combines fire extinguishing and fire prevention, its preparation method, and its application. Background Technology

[0002] Steel structures are the main load-bearing structures in modern large-scale buildings, industrial facilities, and transportation hubs, but their fire resistance limit is relatively low. When the temperature exceeds 538℃, the mechanical properties of steel will drop sharply, seriously threatening the safety of the overall structure. Therefore, providing efficient fire protection for steel structures is a key issue in the field of building engineering.

[0003] Currently, the most widely used fire protection method for steel structures is intumescent fire-retardant coatings. The basic principle of these coatings is that under high temperatures, the coating foams and expands to form a porous char layer, utilizing the low thermal conductivity of the char layer to slow down the temperature rise of the steel components. Traditional intumescent coatings typically consist of components such as a base resin (e.g., epoxy resin, acrylic emulsion), an acid source (e.g., ammonium polyphosphate), a carbon source (e.g., pentaerythritol), and a gas source (e.g., melamine). However, this traditional technology has significant limitations.

[0004] The protective mechanism of traditional intumescent coatings is entirely passive and delayed. Their expansion reaction only initiates when the ambient temperature reaches 250 to 300°C, by which time a fire has often already occurred and may have begun to spread. This means that in the most critical initial stage of a fire, traditional coatings are effectively "ineffective" and cannot provide any protection. Furthermore, the sole function of these coatings is heat insulation; they lack any ability to suppress or extinguish flames. Once flammable materials within their protected area are ignited, the fire will spread uncontrollably.

[0005] To compensate for the lack of proactive fire extinguishing properties in traditional coatings, researchers have attempted to incorporate fire extinguishing agents into coating systems. Existing technology (publication number: CN120733312A) discloses coatings containing heat-sensitive fire extinguishing microcapsules, which rupture upon heating to release fire extinguishing agents (such as perfluorohexanone). However, these approaches typically focus on fire extinguishing functionality, often at the expense of the coating's own expansion and insulation properties, resulting in insufficient long-term high-temperature protection for steel structures. Another technology (publication number: CN121371570A) focuses on preparing high-performance fire extinguishing microcapsules, but has failed to address the issues of stable compounding, uniform dispersion, and functional synergy with the expansion system in intumescent fire-retardant coating systems.

[0006] Therefore, developing a new type of coating that can break through the bottlenecks of traditional technology and achieve an organic combination of "early proactive intervention" and "later robust protection" is of great significance for significantly improving the fire safety level of steel structures. Summary of the Invention

[0007] The purpose of this invention is to provide a steel structure coating that combines fire extinguishing and fire prevention, as well as its preparation method and application. This coating has the dual functions of early active release of fire extinguishing agent for fire extinguishing and long-term passive fire prevention, and can provide dynamic and phased intelligent protection for the entire process of fire development.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a steel structure coating that combines fire extinguishing and fireproofing properties, comprising the following components by weight percentage: The composition includes: 20-30% waterborne epoxy resin emulsion, 15-22% ammonium polyphosphate, 8-11% pentaerythritol, 6-9% melamine, 6-9% titanium dioxide, 2-5% expandable graphite, 2-5% silica, 2-5% aluminum hydroxide, 8-15% thermosensitive perfluorohexanone microcapsules, 3-6% composite synergistic flame retardant, 0.4-1% wetting and dispersing agent, 0.15-1% defoamer, 0.25-1% leveling agent, 0.2-1% thickener, and 4.7-27% water. The preparation method of the thermosensitive perfluorohexanone microcapsules includes the following steps: Poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide were heated and mixed with water to obtain a polymer solution; The polymer solution is mixed with perfluorohexanone and an emulsifier, and then emulsified to obtain an oil-in-water emulsion. The oil-in-water emulsion was heated to undergo a conformational phase change, a photoinitiator was added, and ultraviolet light was used for curing to obtain thermosensitive perfluorohexanone microcapsules. The preparation method of the composite synergistic flame retardant includes the following steps: Zinc borate, ammonium polyphosphate, melamine, and water were mixed, and the pH was adjusted to 4.0-5.0 for coating to obtain a composite synergistic flame retardant.

[0009] Preferably, the mass ratio of poly(N-isopropylacrylamide) to N,N'-methylenebisacrylamide is 30-100:1; The heating and mixing temperature is 40~60℃, and the time is 1~3h.

[0010] Preferably, the volume ratio of the perfluorohexanone to the mass ratio of the poly(N-isopropylacrylamide) is 7-10 mL: 1 g. The emulsifier includes Tween 80 or sodium dodecyl sulfate (SDS); The volume ratio of perfluorohexanone to Tween 80 is 20:1 to 80:1; the volume ratio of perfluorohexanone to sodium dodecyl sulfate is 30:1 to 90:1. The emulsification speed is 1000~2000 rpm, and the time is 10~20 min.

[0011] Preferably, the conformational phase transition temperature is 50~60℃ and the time is 1~3h.

[0012] Preferably, the photoinitiator includes Irgacure 2959 or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO); the volume ratio of the oil-in-water emulsion to the photoinitiator is 50:1 to 100:1; The wavelength of the ultraviolet curing is 200~380 nm, and the time is 10~30 min.

[0013] Preferably, the mass ratio of ammonium polyphosphate to melamine is 2:1 to 3:1; the mass ratio of zinc borate to melamine is 1:1 to 3:2. The coating temperature is 80~90℃, and the time is 1~3h.

[0014] Preferably, the wetting and dispersing agent includes one or more of sodium dodecyl sulfate and ammonium polyacrylate; the defoamer includes one or more of polyoxypropylene glycerol ether (GP type) and polydimethylsiloxane.

[0015] Preferably, the leveling agent comprises one or more of octyl polymethylsiloxane and polyacrylate copolymer, and the thickener comprises one or more of hydroxyethyl cellulose and sodium polyacrylate.

[0016] This invention provides a method for preparing the steel structure coating that combines fire extinguishing and fireproofing properties as described in the above technical solution, comprising the following steps: The water, wetting and dispersing agent, defoamer, titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide are mixed in the first step to obtain the basic slurry; The base slurry is mixed with an aqueous epoxy resin emulsion for a second time to obtain a coating matrix; The coating matrix is ​​mixed with a composite synergistic flame retardant, thermosensitive perfluorohexanone microcapsules and silica to obtain a composite coating. After the composite coating is mixed with leveling agent and thickener in a fourth step, it is then cured and filtered in sequence to obtain a steel structure coating that combines fire extinguishing and fire prevention.

[0017] This invention provides the application of the steel structure coating with both fire extinguishing and fireproof properties described in the above technical solution, or the steel structure coating with both fire extinguishing and fireproof properties prepared by the preparation method described in the above technical solution, in the field of steel structure protection.

[0018] This invention provides a steel structure coating that combines fire extinguishing and fire protection. In this protective coating, a temperature-sensitive fire extinguishing functional unit (temperature-sensitive perfluorohexanone microcapsules) and a composite expansion system (zinc borate, ammonium polyphosphate, and melamine) coexist stably and are uniformly distributed, maintaining their respective functional integrity, thus obtaining a reliable and advanced protective coating. Specifically, the temperature-sensitive perfluorohexanone microcapsules release perfluorohexanone extinguishing agent at around 100°C, extinguishing early flames and achieving an early-stage active release protective function. If the fire is large and the combustion temperature is high, the composite expansion system forms a char layer at high temperatures, protecting the steel structure and achieving long-term fire protection through later expansion. Therefore, this coating has both active fire extinguishing and passive fire protection functions, activating corresponding protective mechanisms at different times during a fire, and providing effective protection at different stages of a fire. It achieves rapid suppression of the fire in its early stages and long-term heat insulation during the fire's development, providing intelligent protection for the steel structure throughout the entire process and at multiple levels.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention constructs a three-stage dynamic protection system that consists of “early active suppression, mid-term expansion flame retardancy, and late-stage stable heat insulation.” Thermosensitive perfluorohexanone microcapsules enable rapid response and physical extinguishing during the fire initiation stage, a composite expansion system enables chemical and physical synergistic flame retardancy during the fire development stage, and a high-strength composite char layer enables long-term heat insulation during the intense fire stage, overcoming the inherent defects of traditional coatings such as delayed response and single function.

[0020] (2) This invention achieves uniform composite and functional synergy of different flame-retardant elements (phosphorus-nitrogen-boron-zinc) at the microscale by introducing a core-shell structured composite synergistic flame retardant. This design not only improves the efficiency and quality of char formation but also enhances the thermal stability and mechanical strength of the char layer, making the fire-retardant performance of the coating more reliable and durable.

[0021] (3) The formulation design and preparation process of this invention fully consider the integrity protection of functional materials. Through optimized feeding sequence and precise shear force control, the temperature-sensitive microcapsules are ensured not to be damaged during dispersion, thus guaranteeing the reliability of their active fire extinguishing function. At the same time, the good compatibility and dispersion stability among the components result in a long shelf life and excellent application performance of the coating product.

[0022] (4) The protective coating provided by this invention has both excellent fire resistance and good environmental adaptability. The water-based system is environmentally friendly and safe, perfluorohexanone is a clean fire extinguishing agent, and the composite flame retardant system is highly efficient and produces low smoke. This protective coating has strong adhesion to the substrate and good weather resistance. It can be adapted to different application scenarios by adjusting the microcapsule trigger temperature and the expansion system ratio, demonstrating high design flexibility and broad engineering application prospects. Attached Figure Description

[0023] Figure 1 Thermogravimetric curve of perfluorohexanone microcapsules prepared in Example 1; Figure 2 Infrared spectra of zinc borate and the composite synergistic flame retardant prepared in Preparation Example 4. Detailed Implementation

[0024] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0025] This invention provides a steel structure coating that combines fire extinguishing and fireproofing properties, comprising the following components by weight percentage: The composition includes: 20-30% waterborne epoxy resin emulsion, 15-22% ammonium polyphosphate, 8-11% pentaerythritol, 6-9% melamine, 6-9% titanium dioxide, 2-5% expandable graphite, 2-5% silica, 2-5% aluminum hydroxide, 8-15% thermosensitive perfluorohexanone microcapsules, 3-6% composite synergistic flame retardant, 0.4-1% wetting and dispersing agent, 0.15-1% defoamer, 0.25-1% leveling agent, 0.2-1% thickener, and 4.7-27% water.

[0026] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 20-30% water-based epoxy resin emulsion, preferably 22-25%.

[0027] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 15-22% ammonium polyphosphate, preferably 16-20%, and more preferably 18-19%.

[0028] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 8-11% pentaerythritol, preferably 8.5-10%, and more preferably 9.0-9.5%.

[0029] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 6-9% melamine, preferably 6.5-8.5%, and more preferably 7-8%.

[0030] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 6-9% titanium dioxide, preferably 6.5-8%, and more preferably 7-7.5%.

[0031] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 2-5% expandable graphite, preferably 3-4.5%, and more preferably 3.5-4.0%.

[0032] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 2-5% silica, preferably 3-4%, and more preferably 3.5%.

[0033] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 2-5% aluminum hydroxide, preferably 3-4%.

[0034] Based on 100% of the total mass of the coating, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 8-15% of temperature-sensitive perfluorohexanone microcapsules, preferably 10-12%.

[0035] In this invention, the preparation method of the thermosensitive perfluorohexanone microcapsules includes the following steps: Poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide were heated and mixed with water to obtain a polymer solution; The polymer solution is mixed with perfluorohexanone and an emulsifier, and then emulsified to obtain an oil-in-water emulsion. The oil-in-water emulsion was heated to undergo a conformational phase change, a photoinitiator was added, and ultraviolet light was used for curing to obtain thermosensitive perfluorohexanone microcapsules.

[0036] In this invention, the mass ratio of poly(N-isopropylacrylamide) to N,N'-methylenebisacrylamide is preferably 30-100:1, more preferably 40-90:1, and even more preferably 50-60:1. This invention does not have a specific limitation on the amount of water used, as long as the materials are completely dissolved. This invention uses poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide as temperature-sensitive materials, achieving a rapid response of 85°C and good durability.

[0037] In this invention, the preferred heating and mixing temperature is 40-60°C, more preferably 50-55°C, and the preferred time is 1-3 hours, more preferably 2 hours; the heating and mixing is preferably carried out under stirring conditions. This invention does not limit the stirring speed, as long as poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide are completely dissolved in water.

[0038] In this invention, perfluorohexanone is preferably mixed with an emulsifier and then added to the polymer solution for emulsification.

[0039] In this invention, the volume ratio of perfluorohexanone to the mass ratio of poly(N-isopropylacrylamide) is preferably 7-10 mL:1 g, more preferably 7-8 mL:1 g.

[0040] In this invention, the emulsifier preferably includes Tween 80 or sodium dodecyl sulfate (SDS); the volume ratio of perfluorohexanone to Tween 80 is preferably 20:1 to 80:1, more preferably 30:1 to 60:1, and even more preferably 50:1; the volume ratio of perfluorohexanone to sodium dodecyl sulfate is preferably 30:1 to 90:1, more preferably 50:1 to 80:1.

[0041] In this invention, the emulsification speed is preferably 1000~2000 rpm, more preferably 1500 rpm, and the time is preferably 10~20 min, more preferably 15 min.

[0042] In this invention, the temperature of the conformational phase transition is preferably 50~60℃, more preferably 55~60℃, and the time is 1~3h, more preferably 1~2h. During the phase transition, the thermosensitive polymer (poly-N-isopropylacrylamide) undergoes a conformational phase transition, forming a dense shell on the surface of the oil droplet. This phase transition is a transformation of the polymer chains from an extended and dissolved state to a collapsed and aggregated state. Macroscopically, it manifests as a viscoelastic polymer-rich layer coating the surface of the oil droplet, not a "solid hard shell," but a high-viscosity gel-like solid.

[0043] In this invention, the photoinitiator preferably includes Irgacure 2959 or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO); the volume ratio of the oil-in-water emulsion to the photoinitiator is preferably 50:1 to 100:1, more preferably 60:1 to 80:1, and even more preferably 70:1.

[0044] In this invention, the wavelength of the ultraviolet curing is preferably 200-380 nm, more preferably 350-380 nm, and the time is preferably 10-30 min, more preferably 20-30 min. This invention achieves cross-linking and fixation of the shell layer through curing under ultraviolet light irradiation.

[0045] After UV curing, the product is preferably cooled to 25°C, centrifuged, washed 2-3 times with deionized water, and dried under low-temperature vacuum to obtain thermosensitive perfluorohexanone microcapsules. In this invention, the centrifugation speed is preferably 600-6000 rpm, more preferably 3000-5000 rpm; the low-temperature vacuum drying temperature is preferably 5-10°C, more preferably 5-8°C, and the drying time is preferably 4-6 hours, more preferably 4-5 hours.

[0046] By weight percentage, the steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, includes 3-6% composite synergistic flame retardant, preferably 4-5%.

[0047] In this invention, the preparation method of the composite synergistic flame retardant includes the following steps: Zinc borate, ammonium polyphosphate, melamine, and water were mixed, and the pH was adjusted to 4.0-5.0 for coating to obtain a composite synergistic flame retardant.

[0048] In this invention, the mass ratio of ammonium polyphosphate to melamine is preferably 2:1 to 3:1, more preferably 2:1 to 2.5:1; the mass ratio of zinc borate to melamine is preferably 1:1 to 3:2, more preferably 1.2:1 to 1.5:1.

[0049] In this invention, zinc borate powder is preferably dispersed in water at a rotation speed of 500-800 rpm for 30-60 minutes to obtain a zinc borate dispersion. Ammonium polyphosphate is mixed with melamine and water to obtain an ammonium polyphosphate-melamine dispersion. This ammonium polyphosphate-melamine dispersion is then added to the zinc borate dispersion under stirring, followed by heating and pH adjustment for coating. The preferred mass ratio of zinc borate to water in the zinc borate dispersion is 1:8 to 1:15; the mass ratio of the total mass of ammonium polyphosphate and melamine to the mass of the ammonium polyphosphate-melamine dispersion is 1:10.

[0050] In this invention, a 1% (v / v) hydrochloric acid solution is preferably used to adjust the pH value to 4.0-5.0; the coating temperature is preferably 80-90℃, more preferably 80-85℃, and the coating time is preferably 1-3 hours, more preferably 2 hours. During the coating process, ammonium polyphosphate and melamine co-precipitate on the surface of zinc borate particles to form a coating layer.

[0051] After the coating is completed, the present invention preferably filters the obtained product sequentially, washes it with deionized water, and vacuum dries it at 85°C for 6 hours to obtain a core-shell structured composite synergistic flame retardant.

[0052] The steel structure coating with both fire extinguishing and fireproofing properties provided by this invention, by weight percentage, comprises 0.4-1% wetting and dispersing agent, preferably 0.5-0.8%, and more preferably 0.6-0.7%; the wetting and dispersing agent preferably includes one or more of sodium dodecyl sulfate and ammonium polyacrylate. When the wetting and dispersing agent is two or more of the above-mentioned types, this invention does not have a special limitation on the ratio of different types of wetting and dispersing agents, and can be adjusted according to requirements.

[0053] By weight percentage, the fire-extinguishing and fire-resistant steel structure coating provided by this invention comprises 0.15-1% defoamer, preferably 0.2-0.8%, and more preferably 0.5-0.6%; the defoamer preferably includes one or more of polyoxypropylene glycerol ether (GP type) and polydimethylsiloxane. When the defoamer is two or more of the above-mentioned types, this invention does not have a special limitation on the proportion of different types of defoamers, and can be adjusted according to requirements.

[0054] By weight percentage, the fire-extinguishing and fire-resistant steel structure coating provided by this invention comprises 0.25-1% leveling agent, preferably 0.4-0.8%, more preferably 0.5-0.6%; the leveling agent preferably includes one or more of octyl polymethylsiloxane and polyacrylate copolymer. When the leveling agent is two or more of the above-mentioned types, this invention does not have a special limitation on the proportion of different types of leveling agents, and can be adjusted according to requirements.

[0055] The fire-extinguishing and fire-resistant steel structure coating provided by this invention, by weight percentage, comprises 0.2-1% thickener, preferably 0.5-0.9%, more preferably 0.6-0.8%, and the thickener preferably includes one or more of hydroxyethyl cellulose and sodium polyacrylate. When the thickener is two or more of the above-mentioned types, this invention does not have a special limitation on the ratio of different types of thickeners, and can be adjusted according to requirements.

[0056] The steel structure coating provided by the present invention, which combines fire extinguishing and fire prevention, comprises 4.7-27% water, preferably 4.7-9%, and more preferably 5-7%, by weight percentage.

[0057] This invention provides a method for preparing the steel structure coating that combines fire extinguishing and fireproofing properties as described in the above technical solution, comprising the following steps: The water, wetting and dispersing agent, defoamer, titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide are mixed in the first step to obtain the basic slurry; The base slurry is mixed with an aqueous epoxy resin emulsion for a second time to obtain a coating matrix; The coating matrix is ​​mixed with a composite synergistic flame retardant, thermosensitive perfluorohexanone microcapsules and silica to obtain a composite coating. After the composite coating is mixed with leveling agent and thickener in a fourth step, it is then cured and filtered in sequence to obtain a steel structure coating that combines fire extinguishing and fire prevention.

[0058] In this invention, water, a wetting and dispersing agent, and a defoamer are added to a dispersion tank, and stirring is started. Titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite, and aluminum hydroxide are added sequentially at a low speed of 300-700 r / min. The stirring speed is gradually increased to 1300-1600 r / min, and dispersion is continued for 35-55 min, more preferably 40 min, to obtain a basic slurry. The stirring speed is then reduced to 300-700 r / min, and an aqueous epoxy resin emulsion is added. Stirring is continued for 12-18 min, more preferably 15 min, so that the resin and the slurry are fused to form a uniform coating matrix.

[0059] The present invention preferably involves adding a composite synergistic flame retardant to the coating matrix, stirring for 5-25 minutes, adding thermosensitive perfluorohexanone microcapsules, stirring at 100-200 r / min for 5-25 minutes, adding silica, and stirring at 100-200 r / min for 5-25 minutes to obtain a composite coating.

[0060] The present invention preferably adds a leveling agent and a thickener to the composite coating, stirs and matures it at 50~100 r / min for 25~45 min, more preferably 30~35 min, and filters the matured coating with a 100~150 mesh filter to obtain a steel structure coating that has both fire extinguishing and fireproof properties.

[0061] This invention provides the application of the steel structure coating with both fire extinguishing and fireproof properties described in the above technical solution, or the steel structure coating with both fire extinguishing and fireproof properties prepared by the preparation method described in the above technical solution, in the field of steel structure protection.

[0062] The steel structure coating described in this invention combines fire extinguishing and fire prevention functions, possessing both active fire extinguishing and passive fire prevention capabilities. This coating is suitable for various steel structure buildings and facilities requiring high-level fire protection, such as commercial complexes, transportation hubs, power facilities, data centers, historical buildings, and petrochemical plants.

[0063] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0064] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the reagents and raw materials described below are all commercially available.

[0065] Poly(N-isopropylacrylamide), N,N'-methylenebisacrylamide, emulsifier Tween 80, sodium dodecyl sulfate (SDS), photoinitiator Irgacure 2959 and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) were purchased from Shanghai Aladdin Reagent Co., Ltd. (purity ≥99%), perfluorohexanone (3F-5112) was purchased from Wuhan Sanfu New Material Technology Co., Ltd., zinc borate was provided by Jinan Shengfeng Industry and Trade Co., Ltd. (purity ≥99%), high degree of polymerization ammonium polyphosphate (polymerization degree ≥1000), melamine (purity 99.8%), pentaerythritol (purity ≥99%) were produced by Shandong Jinyingtai Chemical Co., Ltd., waterborne epoxy resin emulsion (3510-W-60A) was produced by Henson Chemical Co., Ltd., USA, expandable graphite (80 mesh) was produced by Qingdao Nanshu Hongda Graphite Co., Ltd., titanium dioxide (rutile type CR-300) was produced by CITIC Titanium Industry Co., Ltd., and silicon dioxide (purity ≥99%) and aluminum hydroxide (purity ≥99.5%) were produced by Jiangyin Guangyuan Ultrafine Powder Co., Ltd. The auxiliary products selected are: sodium dodecyl sulfate and ammonium polyacrylate wetting and dispersing agent produced by Beijing Bio-Laibo Technology Co., Ltd.; polyoxypropylene glycerol ether (GP type) and polydimethylsiloxane defoamer produced by Wuhan Jiyesheng Chemical Co., Ltd.; octyl polymethylsiloxane and polyacrylate copolymer leveling agent produced by Guangdong Leibang High-tech Materials Co., Ltd.; and hydroxyethyl cellulose and sodium polyacrylate thickener produced by Hubei Shiteng Chemical Technology Co., Ltd.

[0066] Preparation Example 1

[0067] The preparation steps of thermosensitive perfluorohexanone microcapsules are as follows: (1) Dissolve poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide in 500 mL of deionized water at a mass ratio of 60:1, wherein 12 g of poly(N-isopropylacrylamide) is heated to 50 °C and stirred for 2 h to dissolve evenly to obtain a polymer solution. (2) Mix perfluorohexanone at a volume ratio of 50:1 with emulsifier Tween 80, wherein 84 mL of perfluorohexanone is added to the above polymer solution and emulsified at 1500 rpm for 15 min to form a uniform oil-in-water emulsion. (3) Heat the emulsion system to 60°C and react for 1 hour. Then add the photoinitiator Irgacure 2959. The volume ratio of the emulsion to the photoinitiator is 70:1. Cure the emulsion under ultraviolet light with a wavelength of 380 nm for 30 minutes to crosslink and fix the shell layer. (4) Cool the system obtained in (3) to 25°C, centrifuge at 3000 rpm, wash with deionized water 3 times, and vacuum dry at 5°C for 4 hours to obtain perfluorohexanone microcapsules.

[0068] Preparation Example 2

[0069] The preparation steps of thermosensitive perfluorohexanone microcapsules are as follows: (1) Dissolve poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide in 600 mL of deionized water at a mass ratio of 30:1, wherein 12 g of poly(N-isopropylacrylamide) is heated to 40 °C and stirred for 1 h to dissolve evenly, so as to obtain a homogeneous and transparent solution. (2) Mix perfluorohexanone at a volume ratio of 90:1 with sodium dodecyl sulfate (SDS) as an emulsifier, wherein 120 mL of perfluorohexanone is added to the above polymer solution and emulsified at 2000 rpm for 20 min to form a uniform oil-in-water emulsion. (3) Heat the emulsion system to 50°C and react for 2 hours. Then add the photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). The volume ratio of the emulsion to the photoinitiator is 100:1. Cure the emulsion under ultraviolet light with a wavelength of 200 nm for 30 minutes to crosslink and fix the shell layer. (4) Cool the system obtained in (3) to 25°C, centrifuge at 6000 rpm, wash with deionized water 3 times, and vacuum dry at 10°C for 6 hours to obtain perfluorohexanone microcapsules.

[0070] Preparation Example 3

[0071] The preparation steps of thermosensitive perfluorohexanone microcapsules are as follows: (1) Dissolve poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide in 1000 mL of deionized water at a mass ratio of 100:1, wherein 10 g of poly(N-isopropylacrylamide) is heated to 60 °C and stirred for 3 h to dissolve evenly, to obtain a homogeneous and transparent solution. (2) Mix perfluorohexanone at a volume ratio of 20:1 with emulsifier Tween 80 and add it to the above polymer solution, wherein the volume of perfluorohexanone is 80 mL. Emulsify at 1000 rpm for 10 min to form a uniform oil-in-water emulsion. (3) Heat the emulsion system to 50°C and react for 3 hours. Then add the photoinitiator 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO). The volume ratio of the emulsion to the photoinitiator is 50:1. Cure the emulsion under ultraviolet light with a wavelength of 380 nm for 10 minutes to crosslink and fix the shell layer. (4) Cool the system obtained in (3) to 25°C, centrifuge at 600 rpm, wash with deionized water three times, and vacuum dry at 5°C for 6 hours to obtain perfluorohexanone microcapsules.

[0072] Preparation Example 4

[0073] The preparation method of the composite synergistic flame retardant includes the following steps: Zinc borate powder (2ZnO·3B2O3·3.5H2O) was dispersed in deionized water at a mass ratio of 1:8 at 800 rpm for 30 min to obtain a zinc borate dispersion. Ammonium polyphosphate was mixed with melamine and water to obtain an ammonium polyphosphate-melamine dispersion. The ammonium polyphosphate-melamine dispersion was then added to the zinc borate dispersion under stirring, with a mass ratio of ammonium polyphosphate to melamine of 2:1, a mass ratio of zinc borate to melamine of 1:1, and a mass ratio of the total mass of ammonium polyphosphate and melamine to the mass of the ammonium polyphosphate-melamine dispersion of 1:10. The resulting mixture was heated to 80°C, and the pH was adjusted to 4.0 using a 1% hydrochloric acid solution for 2 h for coating. The resulting product was filtered, washed with deionized water, and dried under vacuum at 85°C for 6 h to obtain a core-shell structured composite synergistic flame retardant.

[0074] Preparation Example 5

[0075] The preparation method of the composite synergistic flame retardant includes the following steps: Zinc borate powder was dispersed in deionized water at 800 rpm for 60 min at a mass ratio of 1:15 to 1:15 to obtain a zinc borate dispersion. Ammonium polyphosphate was mixed with melamine and water to obtain an ammonium polyphosphate-melamine dispersion. The ammonium polyphosphate-melamine dispersion was then added to the zinc borate dispersion under stirring, with a mass ratio of 3:1 for ammonium polyphosphate and melamine, a mass ratio of 3:2 for zinc borate and melamine, and a mass ratio of 1:10 between the total mass of ammonium polyphosphate and melamine and the mass of the ammonium polyphosphate-melamine dispersion. The resulting mixture was heated to 80°C, and the pH was adjusted to 4.0 using a 1% (v / v) hydrochloric acid solution. After coating for 3 h, the mixture was filtered, washed with deionized water, and dried under vacuum at 85°C for 6 h to obtain a core-shell structured composite synergistic flame retardant.

[0076] Thermogravimetric analysis was performed on the perfluorohexanone microcapsules prepared in Example 1, and the results are as follows: Figure 1 As shown, the weight of the microcapsules began to decrease from 117°C, indicating that the microcapsules broke down at this temperature, and perfluorohexanone changed from a liquid to a gaseous state and began to volatilize. By 130°C, it had almost completely volatilized, leaving 13% of the weight, indicating that the perfluorohexanone core accounted for as much as 87% of the prepared perfluorohexanone microcapsules. These thermogravimetric data show that the perfluorohexanone microcapsules have been successfully prepared.

[0077] Infrared spectroscopy was performed on zinc borate and the composite synergistic flame retardant of Preparation Example 4, and the results are as follows: Figure 2 As shown, the composite synergistic flame retardant has four more characteristic peaks compared to zinc borate, namely 3418 and 3131 cm⁻¹. -1 1653cm -1 1275cm-1 The corresponding functional groups are NH, C=N, and P=O bonds. Among them, NH and C=N are functional groups unique to melamine, while P=O is a functional group unique to ammonium polyphosphate, indicating that the composite synergistic flame retardant has been successfully prepared.

[0078] Example 1

[0079] The protective coating provided in this embodiment, with the total mass of the coating as 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 25.0% Ammonium polyphosphate 18.0% Pentaerythritol 9.0% melamine 7.0% Titanium dioxide 7.0% Expandable graphite 5.0% 2.0% silicon dioxide Aluminum hydroxide 2.0% Thermosensitive perfluorohexanone microcapsules (Preparation Example 1) 10.0% Composite synergistic flame retardant (Preparation Example 4) 4.0% Wetting and dispersing agent: Sodium dodecyl sulfate 0.5% Defoamer: Polydimethylsiloxane 0.2% Leveling agent: 0.4% octyl polymethylsiloxane Thickener: Sodium polyacrylate 0.9% Deionized water 9.0%.

[0080] The preparation method of the protective coating is as follows: 1) In a dispersion tank, add deionized water, wetting and dispersing agent and defoamer, start stirring, and add titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide in sequence at a speed of 300 r / min. Gradually increase the stirring speed to 1600 r / min and continue high-speed dispersion for 55 min to obtain the basic slurry. Reduce the stirring speed to 300 r / min, add the water-based epoxy resin emulsion, and continue stirring at this speed for 18 min to form a uniform coating matrix.

[0081] 2) Add a composite synergistic flame retardant to the coating matrix, stir for 25 min, add thermosensitive perfluorohexanone microcapsules, stir at 100 r / min for 25 min, add silica, and continue stirring for 25 min to obtain the composite coating. 3) Add leveling agent and thickener, adjust the speed to 50 r / min, stir and mature for 45 min, filter the matured coating with a 100 mesh filter, and fill it into a sealed container to obtain the protective coating.

[0082] Example 2

[0083] The protective coating provided in this embodiment, with the total mass of the coating as 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 22.0% Ammonium polyphosphate 20.0% Pentaerythritol 10.0% melamine 8.0% Titanium dioxide 6.5% Expandable graphite 4.5% 3.0% silicon dioxide Aluminum hydroxide 2.0% Thermosensitive perfluorohexanone microcapsules (Preparation Example 2) 12.0% Composite synergistic flame retardant (Preparation Example 5) 5.0% Wetting and dispersing agent: Ammonium polyacrylate 0.6% Defoamer: Polyoxypropylene glycerol ether (GP type) 0.5% Leveling agent: 0.4% octyl polymethylsiloxane Thickener: 0.8% hydroxyethyl cellulose Deionized water 4.7%.

[0084] The method steps are as follows: S1) In a dispersion tank, add deionized water, wetting and dispersing agent and defoamer, start stirring, and add titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide in sequence at a low speed of 700 r / min. Gradually increase the stirring speed to 1300 r / min and continue high-speed dispersion for 35 min to obtain the basic slurry. Reduce the stirring speed to 700 r / min, add the water-based epoxy resin emulsion, and continue stirring at this speed for 12 min to form a uniform coating matrix.

[0085] 2) Add composite synergistic flame retardant powder to the coating matrix, stir for 5 minutes to disperse it evenly, then add thermosensitive perfluorohexanone microcapsules, stir at 200 r / min for 5 minutes, add silica, and continue stirring for 5 minutes to obtain the composite coating; 3) Add leveling agent and thickener to the composite coating, reduce the rotation speed to 100 r / min, mature for 25 min, filter the matured coating with a 150 mesh filter, and fill it into a sealed container to obtain the protective coating.

[0086] Example 3

[0087] The protective coating provided in this embodiment, with the total mass of the coating as 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 25.0% Ammonium polyphosphate 16.0% Pentaerythritol 8.5% 6.5% melamine Titanium dioxide 8.0% Expandable graphite 4.0% 3.5% silicon dioxide Aluminum hydroxide 5.0% Thermosensitive perfluorohexanone microcapsules (Preparation Example 3) 8.0% Composite synergistic flame retardant (Preparation Example 4) 6.0% Wetting and dispersing agent: Sodium dodecyl sulfate 1.0% Defoamer: Polydimethylsiloxane 0.5% Leveling agent: 0.5% octyl polymethylsiloxane Thickener: Sodium polyacrylate 0.5% Deionized water 7.0%.

[0088] The only difference between this embodiment and Embodiment 1 is that: 3) Add leveling agent and thickener, reduce the speed to 100 r / min, mature for 35 min, and filter the matured coating using a 150 mesh filter.

[0089] The remaining steps are exactly the same as in Example 1.

[0090] Example 4

[0091] The protective coating provided in this embodiment, with the total mass of the coating as 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 20.0% Ammonium polyphosphate 15.0% Pentaerythritol 8.0% 6.0% melamine Titanium dioxide 6.0% Expandable graphite 2.0% 2.0% silicon dioxide Aluminum hydroxide 2.0% Thermosensitive perfluorohexanone microcapsules (Preparation Example 1) 8.0% Composite synergistic flame retardant (Preparation Example 5) 3.0% Wetting and dispersing agent: Ammonium polyacrylate 0.4% Defoamer: 0.15% polydimethylsiloxane Leveling agent: 0.25% octyl polymethylsiloxane Thickener: 0.2% hydroxyethyl cellulose Deionized water 27%.

[0092] The only difference between this embodiment and Embodiment 1 is that: 2) Add composite synergistic flame retardant powder to the coating matrix, stir for 5 minutes, add temperature-sensitive perfluorohexanone microcapsules, stir at 200 r / min for 5 minutes, add silica, and continue stirring for 5 minutes.

[0093] The remaining steps are exactly the same as in Example 1.

[0094] Example 5

[0095] The protective coating provided in this embodiment, with the total mass of the coating as 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 30.0% Ammonium polyphosphate 15.0% Pentaerythritol 8.0% 6.0% melamine Titanium dioxide 6.0% Expandable graphite 2.0% 2.0% silicon dioxide Aluminum hydroxide 2.0% Thermosensitive perfluorohexanone microcapsules (Preparation Example 2) 15.0% Composite synergistic flame retardant (Preparation Example 5) 5.0% Wetting and dispersing agent: Sodium dodecyl sulfate 1.0% Defoamer: Polyoxypropylene glycerol ether (GP type) 1.0% Leveling agent: 1.0% polyacrylate copolymer Thickener: 1.0% hydroxyethyl cellulose 5% deionized water.

[0096] The only difference between this embodiment and Embodiment 1 is that: 1) In a dispersion tank, add deionized water, wetting and dispersing agent and defoamer, start stirring, and add titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide in sequence at 700 r / min. Gradually increase the stirring speed to 1300 r / min and continue high-speed dispersion for 40 min to obtain the basic slurry. Reduce the stirring speed to 700 r / min, add the water-based epoxy resin emulsion, and continue stirring at this speed for 15 min to form a uniform coating matrix.

[0097] The remaining steps are exactly the same as in Example 1.

[0098] Comparative Example 1

[0099] The protective coating provided in this comparative example, based on a total coating mass of 100%, has the following components and their mass fractions: Waterborne epoxy resin emulsion 30.0% Ammonium polyphosphate 21.0% Pentaerythritol 7.0% melamine 7.0% Composite synergistic flame retardant (Preparation Example 4) 5.0% Titanium dioxide 6.0% Expandable graphite 2.0% 6.0% silicon dioxide Aluminum hydroxide 4.0% Sodium dodecyl sulfate 1.0% Polydimethylsiloxane 1.0% Octyl polymethylsiloxane 1.0% Sodium polyacrylate 1.0% Deionized water 8.0%; The only difference between this comparative example and Example 1 is that: No thermosensitive perfluorohexanone microcapsules were added; otherwise, it was the same as in Example 1.

[0100] Performance testing

[0101] The protective coatings prepared in Examples 1-5 and Comparative Example 1 were tested according to the method specified in the national standard GB / T 14907-2018 "Fireproof Coatings for Steel Structures". The protective coatings were applied to a standard steel beam with a dry film thickness of 2.0 mm.

[0102] The fire resistance limit test (standard temperature rise curve) results show that the steel beams protected by the protective coatings of Examples 1-5 have fire resistance limits of 135 minutes, 124 minutes, 121 minutes, 158 minutes, and 140 minutes, respectively, with Example 4 reaching 158 minutes. The fire resistance limit of Comparative Example 1 is 120 minutes, slightly lower than that of Examples 1-5, indicating that the fire-retardant coating prepared by this invention has superior fire resistance.

[0103] Small-chamber fire extinguishing tests showed that the substrate coated with the coating of this invention was actively suppressed and extinguished within 5-8 seconds after contact with a small open flame, indicating that its early active fire extinguishing function was effective. However, the substrate coated with the coating of Comparative Example 1 did not release extinguishing gas after contact with a small open flame, and could not perform early active fire extinguishing, indicating that the perfluorohexanone microcapsules played a crucial role in active fire extinguishing.

[0104] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A steel structure coating that combines fire extinguishing and fireproofing properties, characterized in that, It comprises the following components by weight percentage: The composition includes: 20-30% waterborne epoxy resin emulsion, 15-22% ammonium polyphosphate, 8-11% pentaerythritol, 6-9% melamine, 6-9% titanium dioxide, 2-5% expandable graphite, 2-5% silica, 2-5% aluminum hydroxide, 8-15% thermosensitive perfluorohexanone microcapsules, 3-6% composite synergistic flame retardant, 0.4-1% wetting and dispersing agent, 0.15-1% defoamer, 0.25-1% leveling agent, 0.2-1% thickener, and 4.7-27% water. The preparation method of the thermosensitive perfluorohexanone microcapsules includes the following steps: Poly(N-isopropylacrylamide) and N,N'-methylenebisacrylamide were heated and mixed with water to obtain a polymer solution; The polymer solution is mixed with perfluorohexanone and an emulsifier, and then emulsified to obtain an oil-in-water emulsion. The oil-in-water emulsion was heated to undergo a conformational phase change, a photoinitiator was added, and ultraviolet light was used for curing to obtain thermosensitive perfluorohexanone microcapsules. The preparation method of the composite synergistic flame retardant includes the following steps: Zinc borate, ammonium polyphosphate, melamine, and water were mixed, and the pH was adjusted to 4.0-5.0 for coating to obtain a composite synergistic flame retardant.

2. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The mass ratio of poly(N-isopropylacrylamide) to N,N'-methylenebisacrylamide is 30~100:1; The heating and mixing temperature is 40~60℃, and the time is 1~3h.

3. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The volume ratio of perfluorohexanone to the mass ratio of poly(N-isopropylacrylamide) is 7-10 mL: 1 g. The emulsifier includes Tween 80 or sodium dodecyl sulfate; The volume ratio of perfluorohexanone to Tween 80 is 20:1 to 80:1; the volume ratio of perfluorohexanone to sodium dodecyl sulfate is 30:1 to 90:

1. The emulsification speed is 1000~2000 rpm, and the time is 10~20 min.

4. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The conformational phase transition occurs at a temperature of 50-60°C for 1-3 hours.

5. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The photoinitiator includes Irgacure 2959 or 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; the volume ratio of the oil-in-water emulsion to the photoinitiator is 50:1 to 100:1; The wavelength of the ultraviolet curing is 200~380 nm, and the time is 10~30 min.

6. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The mass ratio of ammonium polyphosphate to melamine is 2:1 to 3:1; the mass ratio of zinc borate to melamine is 1:1 to 3:

2. The coating temperature is 80~90℃, and the time is 1~3h.

7. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The wetting and dispersing agent includes one or more of sodium dodecyl sulfate and ammonium polyacrylate; the defoamer includes one or more of polyoxypropylene glycerol ether and polydimethylsiloxane.

8. The steel structure coating with both fire extinguishing and fireproofing properties according to claim 1, characterized in that, The leveling agent includes one or more of octyl polymethylsiloxane and polyacrylate copolymer, and the thickener includes one or more of hydroxyethyl cellulose and sodium polyacrylate.

9. The method for preparing the steel structure coating with both fire extinguishing and fireproofing properties as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The water, wetting and dispersing agent, defoamer, titanium dioxide, ammonium polyphosphate, pentaerythritol, melamine, expandable graphite and aluminum hydroxide are mixed in the first step to obtain the basic slurry; The base slurry is mixed with an aqueous epoxy resin emulsion for a second time to obtain a coating matrix; The coating matrix is ​​mixed with a composite synergistic flame retardant, thermosensitive perfluorohexanone microcapsules and silica to obtain a composite coating. After the composite coating is mixed with leveling agent and thickener in a fourth step, it is then cured and filtered in sequence to obtain a steel structure coating that combines fire extinguishing and fire prevention.

10. The application of the steel structure coating with both fire extinguishing and fire protection properties as described in any one of claims 1 to 8, or the steel structure coating with both fire extinguishing and fire protection properties prepared by the preparation method described in claim 9, in the field of steel structure protection.

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