An intumescent fire-retardant coating for steel structures

Abstract

The application belongs to the technical field of paint, and particularly relates to an intumescent fire-retardant coating for steel structure. The fire-retardant coating for steel structure comprises the following components: emulsion 10-12%, flame retardant 18-20%, carbon agent 18-20%, foaming agent 18-20%, pretreated calcium sulfate whisker and calcium silicate whisker 2-3%, other auxiliary agent 5-6%, and the balance is deionized water; the flame retardant is high-poly ammonium phosphate, and the polymerization degree of the high-poly ammonium phosphate is greater than 1200. The bonding strength of the fire-retardant coating for steel structure can be as high as 0.3 MPa, the deviation of heat insulation efficiency is as low as 7%, the fireproof time is as high as 140 min, and the shelf life is 26 months.

Description

Technical Field

[0001] This application belongs to the field of coating technology, specifically relating to an intumescent fireproof coating for steel structures. Background Technology

[0002] With economic and social development, steel structure buildings are becoming increasingly common. When a fire occurs in a building, the temperature at the fire scene is mostly between 800 and 1200°C. At such temperatures, the temperature of exposed steel components can rise to 500°C within minutes. Although the steel structure itself does not burn, when a fire occurs, the steel structure of the building will lose its supporting capacity because it reaches its critical temperature (more than 500 degrees Celsius). Therefore, fire-retardant coatings are needed to protect the safety of steel structure buildings at this time.

[0003] Fire-retardant coatings for steel structures are specialized coatings applied to building steel structures. They work by insulating and slowing down the temperature rise of steel in a fire, maintaining its load-bearing capacity, and comply with the national standard GB14907-2018. Based on their fire-retardant mechanism, they are divided into two categories: intumescent and non-intumescent. Intumescent coatings include ultra-thin (≤3mm) and thin (3-7mm) types, which foam upon contact with fire to form a heat-insulating char layer with a fire resistance limit of ≤2 hours. They are suitable for exposed steel components indoors, such as those in airports and commercial complexes.

[0004] Intumescent fire-retardant coatings for steel structures expand and thicken when exposed to high temperatures. These coatings are typically made with suitable water-based polymers as a base (such as polyacrylates, water-based polyurethane resins, etc.), combined with a flame retardant composite system, fire-retardant additives, and refractory fibers. In existing technologies, intumescent fire-retardant coatings for steel structures exhibit sedimentation of denser fillers and flame retardants during storage, resulting in a shelf life ranging from 6 to 12 months. Within this shelf life, only easily stirred, soft sedimentation occurs; beyond this time, clumping occurs, preventing uniform dispersion through stirring. Inadequate mixing before application leads to poor adhesion, easy cracking, peeling, and even complete detachment of the coating. In particular, the absence or uneven distribution of fire-retardant additives can cause inconsistent shrinkage during drying or heating, resulting in cracks. In severe cases, structural cracks exceeding 0.5 mm in width may appear, directly impacting fire resistance.

[0005] Taking a project with a total steel structure area of ​​10,000 square meters as an example, the design fire resistance limit requirement is 2.0 hours, corresponding to a coating thickness of approximately 5.0 mm. The total coating requirement is 60,000 kg. If the coating is packaged in 25 kg / barrel containers, 2,400 barrels are needed. If the equipment allows for mixing before use in barrel units, the existing thin-film intumescent fireproof coatings for steel structures generally require mixing for 3-5 minutes before use. Therefore, 2,400 barrels × 5 minutes / barrel (mixing) ÷ 60 minutes / hour equals 200 hours. This does not include the 10-15 minutes of settling and defoaming time required after mixing. Therefore, the time cost brought to construction by the settlement process is also enormous. Summary of the Invention

[0006] Based on the above technical problems, this application provides a fire-retardant coating for anti-settlement steel structures. Specifically, the fire-retardant coating for steel structures in this application comprises the following components: 10-12% emulsion, 18-20% flame retardant, 18-20% charring agent, 18-20% foaming agent, 2-3% calcium sulfate whiskers and / or calcium silicate whiskers, 5-6% other additives, and the balance being deionized water; the emulsion is a polyacrylate or vinyl acetate emulsion; the flame retardant is ammonium polyphosphate, and the degree of polymerization of the ammonium polyphosphate is greater than 1200; the charring agent is pentaerythritol, and the foaming agent is melamine; the other additives include 0.3-0.5% acrylate defoamer, 4-5% dispersant ammonium polyacrylate, and 0.3-0.5% thickener fumed silica.

[0007] In some preferred embodiments of this application, the calcium sulfate whiskers and / or calcium silicate whiskers are pretreated calcium sulfate whiskers and / or pretreated calcium silicate whiskers.

[0008] The method for preparing the pretreated calcium sulfate whiskers includes treatment with a silane coupling agent followed by treatment with bisphenol A type epoxy resin; the mass ratio of bisphenol A type epoxy resin E-51 to calcium sulfate whiskers is 1:1-1.5:1. In a specific embodiment, the method for preparing the pretreated calcium sulfate whiskers is as follows: a 20% (w / w) methanol solution of silane coupling agent KH550 is prepared, dry calcium sulfate whiskers are added under stirring, and after stirring for 10 min, bisphenol A type epoxy resin E-51 is added dropwise. The temperature is raised to 75-80℃, and the reaction is stirred for 2 h to obtain the pretreated calcium sulfate whiskers, wherein the mass ratio of bisphenol A type epoxy resin E-51 to calcium sulfate whiskers is 1:1-1.5:1.

[0009] The pretreated calcium silicate whiskers are prepared by pretreating calcium silicate whiskers with a silane coupling agent; or by pretreating calcium silicate whiskers with a silane coupling agent and an aluminum-titanium composite coupling agent; or by pretreating calcium silicate whiskers with a silane coupling agent and then encapsulating them with GMA in situ polymerization.

[0010] Calcium silicate whiskers pretreated with silane coupling agent, with an amount of 2-3% silane coupling agent.

[0011] The calcium silicate whiskers pretreated with silane coupling agent and aluminum-titanium composite coupling agent have a mass ratio of 0.8:1 to 1.2:1; the total amount of silane coupling agent and aluminum-titanium composite coupling agent is 2-3% of the mass of the calcium silicate whiskers. In some preferred embodiments of this application, the mass ratio of silane coupling agent to aluminum-titanium composite coupling agent is 1:1, and the amount of silane coupling agent and aluminum-titanium composite coupling agent is 2% of the calcium silicate whiskers. The specific method for modifying calcium silicate whiskers with silane coupling agent and aluminum-titanium composite coupling agent is as follows: 1% KH550 (by mass) of calcium silicate whiskers is prepared into a 20% methanol / water solution with a methanol / water volume ratio of 4 / 1. The pH value is adjusted to 5 with glacial acetic acid and allowed to stand for 8 minutes. 1% aluminum-titanium composite coupling agent (by mass) of calcium silicate whiskers is prepared into a 20% isopropanol solution and allowed to stand for 8 minutes. The two prepared coupling agent solutions are simultaneously sprayed onto the surface of calcium silicate whiskers under high-speed mixing. After spraying, the mixture is stirred for 5 minutes and then dried at 90-100℃ for 1 hour to obtain calcium silicate whiskers with surface modification by the composite coupling agent, i.e., pretreated calcium silicate whiskers.

[0012] The method for preparing GMA-pretreated calcium silicate whiskers includes silane coupling agent pretreatment and in-situ GMA polymerization to encapsulate the calcium silicate whiskers. Specifically, the method for preparing GMA-pretreated calcium silicate whiskers includes: preparing a 20% methanol / water solution (methanol / water volume ratio of 4 / 1) with 2% (by mass) of silane coupling agent KH570 on the calcium silicate whiskers; adjusting the pH to 5 with glacial acetic acid and allowing it to stand for 8 minutes; spraying the prepared silane coupling agent solution onto the surface of the calcium silicate whiskers under high-speed mixing; stirring for 5 minutes after spraying; and then drying at 90-100℃ for 1 hour to obtain silane coupling agent-pretreated calcium silicate whiskers; then mixing the silane coupling agent-pretreated calcium silicate whiskers, GMA, dispersant, and deionized water; adding an initiator; polymerizing under nitrogen protection at 45-50℃; centrifuging; washing; and drying to obtain GMA-encapsulated calcium silicate whiskers. The mass ratio of calcium silicate whiskers modified with GMA and silane coupling agent is 1:1 to 3:1.

[0013] When both the calcium sulfate whiskers and the calcium silicate whiskers are untreated whiskers, the bonding strength is 0.22, the thermal insulation efficiency deviation is 11%, the fire resistance time is 127 min, and the shelf life is 14 months.

[0014] When 2-3% of the calcium sulfate whiskers and / or calcium silicate whiskers are calcium sulfate whiskers, the coating has a bonding strength of up to 0.21 MPa, a fireproof time of 121 min, and a shelf life of 13 months.

[0015] When 2-3% of the calcium sulfate whiskers and / or calcium silicate whiskers are calcium silicate whiskers, the coating has a bonding strength of up to 0.20 MPa, a fireproof time of 131 min, and a shelf life of 15 months.

[0016] When 2-3% of the calcium sulfate whiskers and / or calcium silicate whiskers are pretreated calcium sulfate whiskers, and the calcium silicate whiskers are calcium silicate whiskers pretreated with silane coupling agent and aluminum-titanium composite coupling agent in a 1:1 ratio, the coating has a bonding strength of up to 0.32 MPa, a fireproof time of 135 min, and a shelf life of 24 months.

[0017] When 2-3% of the calcium sulfate whiskers and / or calcium silicate whiskers are pretreated calcium sulfate whiskers, and the calcium silicate whiskers are GMA pretreated calcium silicate whiskers at a ratio of 1:1, the coating has a bonding strength of up to 0.33 MPa, a fireproof time of 141 min, and a shelf life of 26 months. Detailed Implementation

[0018] The ammonium polyphosphate used in this application has a degree of polymerization greater than 1200; calcium silicate whiskers: Senard, diameter 10 μm; whiteness 96%; calcium sulfate whiskers: length 40-190 μm, average aspect ratio 55; aluminum-titanium composite coupling agent: Lida Chemical; polyacrylate or vinyl acetate emulsion effective ingredient content 99%; acrylate defoamer ASK-307; dispersant ammonium polyacrylate, CAS No. 9003-03-6; KPS, potassium persulfate.

[0019] The shelf life mentioned in this application refers to the time required for the density to not differ significantly within a 3 cm thickness above the bottom layer (compared to a coating with a shelf life of 12 months).

[0020] The various indicators of the intumescent fire-retardant coating applied for in this application were tested according to GB / T14907-2018. To clearly and concisely illustrate the embodiments of this application, the operations performed using existing technologies are not described in excessive detail. For example, the purpose of modifying with silane coupling agents and / or aluminum-titanium composite coupling agents is to enhance the compatibility and bonding strength between inorganic materials and emulsions, and whether this can effectively prevent sedimentation. However, calcium silicate itself is a superior inorganic fire-retardant material. Therefore, the focus is only on whether the pretreatment can significantly improve the anti-settling effect. Based on this, the embodiments of this application are only for illustrating the technical solutions and do not represent the entirety of this application.

[0021] The pretreated calcium sulfate whiskers are prepared by the following method: silane coupling agent KH550 is prepared into a 20% methanol / water solution with a methanol / water volume ratio of 4 / 1. Dry calcium sulfate whiskers are added while stirring. After stirring for 10 minutes, bisphenol A epoxy resin E-51 is added dropwise. The temperature is raised to 80°C and the reaction is stirred for 2 hours to obtain pretreated calcium sulfate whiskers. The mass ratio of bisphenol A epoxy resin E-51 to calcium sulfate whiskers is 1:1-1.5:1.

[0022] In the actual research and development process, the inventors of this application tested multiple ratios of bisphenol A type epoxy resin E-51 to calcium sulfate whiskers, such as 0.8:1, 1:1, 1.2:1, 1.4:1, 1.5:1, and 1.7:1; and multiple reaction temperatures, such as 70℃, 75℃, 80℃, and 85℃. The experimental results showed that when the ratio was within the range of 1:1-1.5:1, not only could the shelf life be maintained for up to 18 months, but the bond strength also reached over 0.2 MPa. The above test temperatures had no significant effect on the anti-settling properties and bond strength of the final coating.

[0023] The method for preparing the pretreated calcium silicate whiskers includes: preparing a 20% methanol / water solution with 1% KH570 of calcium silicate whiskers by mass, the volume ratio of methanol to water being 4 / 1; adjusting the pH value to 5 with glacial acetic acid; and letting it stand for 8 minutes; preparing a 20% isopropanol solution with 1% aluminum-titanium composite coupling agent of calcium silicate whiskers by mass, and letting it stand for 8 minutes; simultaneously spraying the prepared two coupling agent solutions onto the surface of calcium silicate whiskers under high-speed mixing; stirring for 5 minutes after spraying; and then drying at 90-100℃ for 1 hour to obtain calcium silicate whiskers with surface modification by composite coupling agent, i.e., pretreated calcium silicate whiskers.

[0024] The preparation method of the pretreated calcium silicate whiskers includes: preparing a 20% methanol / water solution by dissolving 2% KH570 (by mass) of calcium silicate whiskers in glacial acetic acid, with a methanol / water volume ratio of 4 / 1; adjusting the pH value to 5 with glacial acetic acid and allowing it to stand for 8 minutes; spraying the prepared KH570 coupling agent solution onto the surface of the calcium silicate whiskers under high-speed mixing; stirring for 5 minutes after spraying; and then drying at 90-100℃ for 1 hour to obtain calcium silicate whiskers with surface modification by multiple coupling agents, i.e., pretreated calcium silicate whiskers.

[0025] The preparation method of the pretreated calcium silicate whiskers includes: preparing a 20% isopropanol solution by dissolving 2% (by mass) of aluminum-titanium composite coupling agent in calcium silicate whiskers and letting it stand for 8 minutes; spraying the prepared aluminum-titanium composite coupling agent solution onto the surface of calcium silicate whiskers under high-speed mixing; stirring for 5 minutes after spraying; and then drying at 90-100℃ for 1 hour to obtain calcium silicate whiskers with surface modification by composite coupling agent, i.e., pretreated calcium silicate whiskers.

[0026] During the research and development process, the effects of modifying coatings with silane coupling agents and aluminum-titanium composite coupling agents separately were not as good as the anti-settling effect of their 1:1 synergistic combination. The inventors of this application speculate that although silane coupling agents are a better match for calcium silicate modification, calcium sulfate also settles in the coating, and calcium sulfate has a higher specific gravity than calcium silicate. Therefore, the long-term anti-settling effect of the two silane coupling agents is better. Their optimal 1:1 synergistic anti-settling effect can reach 26 months, while the anti-settling effect of a single silane coupling agent can reach about 18 months, and the aluminum-titanium composite coupling agent alone can only reach about 16 months.

[0027] The preparation method of the pretreated calcium silicate whiskers includes: preparing a 20% methanol / water solution by dissolving 2% KH570 (by mass) of calcium silicate whiskers in a 4 / 1 volume ratio of methanol to water; adjusting the pH to 5 with glacial acetic acid and allowing it to stand for 8 minutes; spraying the prepared silane coupling agent solution onto the surface of the calcium silicate whiskers under high-speed mixing; stirring for 5 minutes after spraying; and then drying at 90-100℃ for 1 hour to obtain silane coupling agent pretreated calcium silicate whiskers; then mixing the silane coupling agent pretreated calcium silicate whiskers, GMA, sodium dodecylbenzenesulfonate, and the remaining deionized water; adding 0.3%~0.5% KPS and 0.15%~0.25% NaHSO3; purging with nitrogen for 30 minutes; heating to 45~50℃ and stirring for 2~3 hours; centrifuging, washing, and drying below 50℃ to obtain GMA-coated calcium silicate whiskers. The mass ratio of calcium silicate whiskers modified with GMA and silane coupling agent is 1:1 to 3:1.

[0028] The mass ratio of GMA to silane coupling agent-modified calcium silicate whiskers was obtained through multiple experiments. Within the above range, this ratio ensures good adhesion of the coating while also providing excellent thermal insulation and fire resistance. While the adhesion strength increases with increasing GMA content, the fire resistance test shows a slightly higher level followed by a slow decrease. Furthermore, compared to Preparation Example 2, further modification with silane coupling agent followed by GMA further enhances the adhesion strength and anti-settling effect.

[0029] Example 1.1 100 kg of polyacrylate emulsion, 180 kg of ammonium polyphosphate flame retardant, 180 kg of pentaerythritol charring agent, 180 kg of melamine foaming agent, 20 kg of pretreated calcium sulfate whiskers and calcium silicate whiskers (10 kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers), 3 kg of acrylate defoamer, 44 kg of ammonium polyacrylate dispersant, 3 kg of fumed silica thickener, and 290 kg of deionized water.

[0030] Vinyl acetate emulsion 100kg, flame retardant ammonium polyphosphate 180kg, charring agent pentaerythritol 180kg, foaming agent melamine 180kg, pretreated calcium sulfate whiskers and calcium silicate whiskers 20kg (10kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers), acrylate defoamer 3kg, dispersant ammonium polyacrylate 44kg, thickener fumed silica 3kg, deionized water 290kg.

[0031] 100 kg of polyacrylate and vinyl acetate emulsion (50 kg each of polyacrylate and vinyl acetate emulsion), 180 kg of ammonium polyphosphate flame retardant, 180 kg of pentaerythritol charring agent, 180 kg of melamine foaming agent, 20 kg of pretreated calcium sulfate whiskers and calcium silicate whiskers (10 kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers), 3 kg of acrylate defoamer, 44 kg of ammonium polyacrylate dispersant, 3 kg of fumed silica thickener, and 290 kg of deionized water.

[0032] 120 kg of polyacrylate, 200 kg of ammonium polyphosphate flame retardant, 200 kg of pentaerythritol charring agent, 200 kg of melamine foaming agent, 30 kg of pretreated calcium sulfate whiskers and calcium silicate whiskers (15 kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers), 5 kg of acrylate defoamer, 50 kg of ammonium polyacrylate dispersant, 5 kg of fumed silica thickener, and 190 kg of deionized water.

[0033] Vinyl acetate emulsion 120kg, flame retardant ammonium polyphosphate 200kg, charring agent pentaerythritol 200kg, foaming agent melamine 200kg, pretreated calcium sulfate whiskers and calcium silicate whiskers 30kg (pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers 15kg each), acrylate defoamer 5kg, dispersant ammonium polyacrylate 50kg, thickener fumed silica 5kg, deionized water 190kg.

[0034] Example 2.3 120 kg of polyacrylate and vinyl acetate emulsion (60 kg each of polyacrylate and vinyl acetate emulsion), 200 kg of ammonium polyphosphate flame retardant, 200 kg of pentaerythritol charring agent, 200 kg of melamine foaming agent, 30 kg of pretreated calcium sulfate whiskers and calcium silicate whiskers (15 kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers), 5 kg of acrylate defoamer, 50 kg of ammonium polyacrylate dispersant, 5 kg of fumed silica thickener, and 190 kg of deionized water.

[0035] The preparation method of Examples 1-2 is as follows: after thoroughly stirring deionized water and dispersant, pretreated calcium silicate whiskers and pretreated calcium sulfate whiskers, expansion foaming system (ammonium polyphosphate, pentaerythritol, melamine) and additives are added in sequence and mixed evenly. The mixture is then ground in a ball mill for 1 hour, and emulsion base material is added and grinding is continued for 3 hours to obtain a fireproof coating for steel structure.

[0036] The pretreated calcium sulfate whiskers used in the above examples are the calcium sulfate whiskers prepared in Preparation Example 1, and the pretreated calcium silicate whiskers are the calcium silicate whiskers prepared in Preparation Example 2.

[0037] The test results of the fire-retardant coatings obtained in Examples 1.1-1.3 and 2.1-2.3 are shown in Table 1.

[0038] Table 1.1 Test results of fire-retardant coatings obtained in Examples 1.1-1.3

[0039]

[0040] Table 1.2 Test results of fire-retardant coatings obtained in Examples 2.1-2.3

[0041]

[0042] 120 kg of polyacrylate and vinyl acetate emulsion (60 kg each of polyacrylate and vinyl acetate emulsion), 200 kg of ammonium polyphosphate flame retardant, 200 kg of pentaerythritol charring agent, 200 kg of melamine foaming agent, 30 kg of pretreated calcium sulfate whiskers and calcium silicate whiskers (15 kg each of pretreated calcium sulfate whiskers and pretreated calcium silicate whiskers, the pretreated calcium silicate whiskers used were prepared in Preparation Example 3), 5 kg of acrylate defoamer, 50 kg of ammonium polyacrylate dispersant, 5 kg of fumed silica thickener, and 190 kg of deionized water.

[0043] The preparation method of Example 3 is as follows: After thoroughly stirring deionized water and a dispersant, pretreated calcium silicate whiskers and pretreated calcium sulfate whiskers, an expansion foaming system (ammonium polyphosphate, pentaerythritol, melamine), and additives are added sequentially and mixed evenly. The mixture is then ground in a ball mill for 1 hour, followed by the addition of an emulsion base and further grinding for 3 hours to obtain a fire-retardant coating for steel structures. The test results of the coating obtained in Example 3 are shown in Table 2. Table 2 Test results of the coating obtained in Example 3

[0044] Comparative Example 1.1 120 kg of polyacrylate and vinyl acetate emulsion (60 kg each of polyacrylate and vinyl acetate emulsion), 200 kg of ammonium polyphosphate flame retardant, 200 kg of pentaerythritol charring agent, 200 kg of melamine foaming agent, 30 kg of pretreated calcium sulfate whiskers (Preparation Example 1), 5 kg of acrylate defoamer, 50 kg of ammonium polyacrylate dispersant, 5 kg of fumed silica thickener, and 190 kg of deionized water.

[0045] The preparation method of Comparative Example 1 is as follows: after thoroughly stirring deionized water and dispersant, pretreated calcium sulfate whiskers, expansion foaming system (ammonium polyphosphate, pentaerythritol, melamine) and additives are added in sequence and mixed evenly. The mixture is then ground in a ball mill for 1 hour, and emulsion base is added and the mixture is ground for another 3 hours to obtain a fireproof coating for steel structures.

[0046] Unlike Comparative Example 1.1, the calcium sulfate whiskers are untreated calcium sulfate whiskers. Comparative Example 2.1 120 kg of polyacrylate and vinyl acetate emulsion (60 kg each of polyacrylate and vinyl acetate emulsion), 200 kg of ammonium polyphosphate flame retardant, 200 kg of pentaerythritol charring agent, 200 kg of melamine foaming agent, 30 kg of pretreated calcium silicate whiskers (Preparation Example 2), 5 kg of acrylate defoamer, 50 kg of ammonium polyacrylate dispersant, 5 kg of fumed silica thickener, and 190 kg of deionized water.

[0047] The preparation method of Comparative Example 2.1 is as follows: after thoroughly stirring deionized water and dispersant, pretreated calcium silicate whiskers, expanded foaming system (ammonium polyphosphate, pentaerythritol, melamine) and additives are added in sequence and mixed evenly. The mixture is then ground in a ball mill for 1 hour, and emulsion base material is added and the mixture is ground for another 3 hours to obtain a fireproof coating for steel structures.

[0048] Unlike Comparative Example 2.1, the calcium silicate whiskers are untreated calcium silicate whiskers.

[0049] Unlike Comparative Example 2.1, the calcium silicate whiskers are the calcium silicate whiskers of Preparation Example 3.

[0050] Unlike Example 2.3, the calcium sulfate whiskers and calcium silicate whiskers described herein were not pretreated.

[0051] The comparison results of Examples 2.3, 3 and Comparative Examples 1-3 are shown in Table 3.

[0052] Table 3 Comparison results of Examples 2.3, 3 and Comparative Examples 1-3

[0053] Comparative Example 4 has a bonding strength of 0.22, a thermal insulation efficiency deviation of 11%, a fire resistance time of 127 minutes, and a shelf life of 14 months.

[0054] Compared to Example 1.1, Example 2.3 uses only calcium sulfate whiskers as the inorganic insulating filler, resulting in a relatively large deviation in insulating efficiency. This is consistent with the fact that the thermal conductivity of calcium sulfate is greater than that of calcium silicate. Compared to Example 1.2, Example 2.3 shows a decrease in both insulating efficiency and fire resistance and shelf life, in addition to the larger deviation in insulating efficiency. Therefore, pretreatment of calcium sulfate whiskers with bisphenol A resin can significantly improve the compatibility and adhesion between calcium sulfate whiskers and other components. Compared to Examples 2.1-2.2, Example 2.3 shows a lower deviation in insulating efficiency due to the lower thermal conductivity of calcium silicate whiskers compared to calcium sulfate, but its bonding strength is inferior to that of bisphenol A-modified calcium sulfate whiskers compared to Comparative Example 1.1. Compared with Examples 2 and 3 and Comparative Example 3, bisphenol A modified calcium sulfate whiskers and GMA modified calcium silicate whiskers have better bonding strength, anti-settling effect and better fire resistance. This may be related to the fact that the phosphate ester formed by the ring opening of the epoxy groups of bisphenol A epoxy resin and GMA at high temperature and the decomposition of phosphoric acid produced by the flame retardant ammonium polyphosphate has both flame retardant and plasticizing effects.

[0055] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An intumescent fire-retardant coating for steel structures, characterized in that, The fireproof coating for steel structures comprises the following components: 10-12% emulsion, 18-20% flame retardant, 18-20% charring agent, 18-20% foaming agent, 2-3% calcium sulfate whiskers and / or calcium silicate whiskers, 5-6% other additives, and the balance being deionized water; the emulsion is a polyacrylate or vinyl acetate emulsion; the flame retardant is ammonium polyphosphate with a degree of polymerization greater than 1200; the charring agent is pentaerythritol, and the foaming agent is melamine; the other additives include 0.3-0.5% acrylate defoamer, 4-5% ammonium polyacrylate dispersant, and 0.3-0.5% fumed silica thickener.

2. The intumescent fireproof coating for steel structures according to claim 1, characterized in that, The calcium sulfate whiskers and / or calcium silicate whiskers comprise 2-3% of the total calcium sulfate whiskers and calcium silicate whiskers, and their mass ratio is 1:

1.

3. The intumescent fireproof coating for steel structures according to claim 1, characterized in that, The calcium sulfate whiskers are pretreated calcium sulfate whiskers. The preparation method of the pretreated calcium sulfate whiskers includes treatment with a silane coupling agent followed by treatment with bisphenol A type epoxy resin. The mass ratio of the bisphenol A type epoxy resin to the calcium sulfate whiskers is 1:1-1.5:

1.

4. The intumescent fireproof coating for steel structures according to claim 3, characterized in that, The silane coupling agent used in the pretreated calcium sulfate whiskers is KH550; the bisphenol A type epoxy resin is E-51.

5. The intumescent fireproof coating for steel structures according to claim 1, characterized in that, The calcium silicate whiskers are pretreated calcium silicate whiskers, which are calcium silicate whiskers pretreated with a silane coupling agent; or calcium silicate whiskers pretreated with a silane coupling agent and an aluminum-titanium composite coupling agent; or calcium silicate whiskers pretreated with GMA.

6. The intumescent fire-retardant coating for steel structures according to claim 5, characterized in that, The calcium silicate whiskers pretreated with silane coupling agent and aluminum-titanium composite coupling agent have a mass ratio of 0.8:1 to 1.2:1; the total amount of silane coupling agent and aluminum-titanium composite coupling agent is 2-3% of the mass of calcium silicate whiskers.

7. The intumescent fire-retardant coating for steel structures according to claim 5, characterized in that, The method for preparing the GMA-pretreated calcium silicate whiskers includes first pretreating with a silane coupling agent, and then encapsulating the calcium silicate whiskers with GMA in situ polymerization.

8. The intumescent fire-retardant coating for steel structures according to claim 7, characterized in that, The mass ratio of GMA to calcium silicate whiskers in the GMA pretreated calcium silicate whiskers is 1:1 to 3:

1.

9. The intumescent fire-retardant coating for steel structures according to claim 8, characterized in that, The specific steps for the GMA pretreatment of calcium silicate whiskers are as follows: 2% by mass of silane coupling agent is prepared into a 20% methanol / water solution with a methanol / water volume ratio of 4 / 1. The pH value is adjusted to 5 with glacial acetic acid and allowed to stand for 8 minutes. The prepared silane coupling agent solution is sprayed onto the surface of the calcium silicate whiskers under high-speed mixing. After spraying, the mixture is stirred for another 5 minutes and then dried at 90-100℃ for 1 hour to obtain silane coupling agent pretreated calcium silicate whiskers. Then, the silane coupling agent pretreated calcium silicate whiskers, GMA, dispersant, and deionized water are stirred and mixed. An initiator is added, and the mixture is polymerized under nitrogen protection at 45-50℃. After centrifugation, washing, and drying, GMA-coated calcium silicate whiskers are obtained.

10. The intumescent fire-retardant coating for steel structures according to any one of claims 3-9, characterized in that, The amount of pretreated calcium sulfate whiskers or pretreated calcium silicate whiskers added is based on the mass of the calcium sulfate whiskers and calcium silicate whiskers, respectively.

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