Steel structure intumescent fireproof coating and preparation method thereof

Abstract

The invention relates to the field of fireproof coatings, in particular to an intumescent fireproof coating for a steel structure and a preparation method of the intumescent fireproof coating. The raw materials comprise matrix resin, a flame retardant, graphene oxide, chlorinated paraffin, a rheological additive, a defoaming agent, fumed silica and titanium dioxide. The flame retardant is a flame retardant of an ammonium polyphosphate-pentaerythritol-melamine system, and the mass ratio of ammonium polyphosphate to pentaerythritol to melamine is (2 to 2.5): (1 to 1.5): (1 to 1.5); the thickness of the sheet layer of the graphene oxide is 0.8 to 1.5 nm. The self-made graphene oxide (GO) and the flame-retardant system form a good synergistic effect, so that the strength and density of a carbon layer can be effectively improved, and the fire endurance of the coating is further improved.

Description

Technical Field

[0001] This application relates to the field of fire-retardant coatings, and more specifically, to an intumescent fire-retardant coating for steel structures and a method for preparing the same. Background Technology

[0002] Steel structures are characterized by high strength and good toughness, and are therefore widely used in building structures such as high-speed railway stations, heavy workshops, and airports. While steel itself is not flammable, its fire resistance is poor. In the event of a fire, bare steel rapidly heats up to a critical temperature, causing its load-bearing capacity to drop quickly, leading to building collapse and safety accidents.

[0003] Intumescent fire-retardant coatings protect and insulate steel structures. In the event of a fire, they can slow down and prevent the spread of flames, thus reducing economic losses and preventing casualties.

[0004] Solvent-based fire-retardant coating systems are relatively well-established, offering advantages such as excellent fire resistance and ease of application. Intumescent fire-retardant coatings, under high temperatures, react with the acidic substances decomposed from the charring agent (carbon source) and dehydration charring catalyst (acid source) to undergo dehydration and carbonization. During this process, the non-flammable gas generated by the decomposition of the foaming agent (gas source) causes the fire-retardant coating system to expand and foam. The components interact to form a closed, expanded char layer with heat-insulating properties. This layer prevents heat conduction between the heat source and the steel structure substrate, and prevents oxygen from gradually diffusing to the substrate surface, significantly slowing down the heating rate of the substrate to achieve protective effects. The strength of the char layer is a crucial factor affecting the fire-retardant performance of intumescent fire-retardant coatings.

[0005] Currently, the main intumescent fire-retardant coatings for steel structures are PC-N intumescent systems, with a fire resistance limit of at least 60 minutes. After a fire occurs, the strength of the intumescent char layer of the fire-retardant coating decreases significantly. In addition, intumescent fire-retardant coatings are thin or ultra-thin fire-retardant coatings, and after combustion, they have a high degree of expansion, with the char layer thickness reaching several times or even dozens of times the original thickness. This increases the heat conduction distance and reduces the heat conductivity. The unit density of the high-expansion char layer will inevitably decrease, which also leads to a weaker char layer strength that needs to be further improved to enhance the stability of the intumescent char layer in the flame and improve the fire resistance limit of the coating. Summary of the Invention

[0006] This application provides an intumescent fire-retardant coating for steel structures and its preparation method. The self-made graphene oxide (GO) and the flame-retardant system of this application form a good synergistic effect, which can effectively improve the strength and density of the char layer, thereby improving the fire resistance limit of the coating.

[0007] In a first aspect, this application provides an intumescent fire-retardant coating for steel structures, employing the following technical solution: An intumescent fireproof coating for steel structures is composed of raw materials including a base resin, flame retardant, graphene oxide, chlorinated paraffin, rheology modifier, defoamer, fumed silica, and titanium dioxide. The flame retardant is a flame retardant system of ammonium polyphosphate-pentaerythritol-melamine, wherein the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is (2-2.5):(1-1.5):(1-1.5). The thickness of the graphene oxide sheets is 0.8-1.5 nm.

[0008] Furthermore, the fire-retardant coating comprises the following components by weight percentage: The composition consists of 15-25% matrix resin, 40-50% flame retardant, 0.5-1.5% graphene oxide, 5-10% chlorinated paraffin, 2-4% rheology modifier, 0.5-1% defoamer, 0.5-1.5% fumed silica, 0.2-1% titanium dioxide, and the remainder is solvent.

[0009] Furthermore, the matrix resin is a mixture of amino resin and acrylic resin, wherein the mass ratio of amino resin to acrylic resin is (3-6):(2-4).

[0010] By adopting the above technical solution, this application selects a mixture of amino resin and acrylic resin with specified content as the base resin. On the one hand, the amino resin provides a nitrogen source and crosslinking points, while the acrylic resin provides a carbon skeleton and toughness, together forming a dense and strong expanded char layer, effectively insulating heat and oxygen, and playing a synergistic role in char formation. On the other hand, the acrylic resin can reduce the excessive crosslinking of the amino resin, improve flexibility and weather resistance, and prevent char layer cracking at high temperatures, playing a role in crosslinking regulation. Finally, the nitrogen element of the amino resin and the phosphorus element of the IFR system work synergistically to promote dehydration, char formation, and expansion, thereby improving flame retardant efficiency. Furthermore, the method for preparing the graphene oxide includes the following steps: Oxidation: Graphite powder, phosphoric acid, and concentrated sulfuric acid are stirred in an ice-water bath at a mass ratio of (1-1.2):(45-50):(5-10) for 1-1.5 hours. Potassium permanganate is added in portions over 1.5-2 hours. The temperature is raised to 40-45℃ and held for 1.5-2 hours. Then the temperature is raised to 50-55℃ and the reaction is continued for 2-2.5 hours. The temperature is then raised again, and high-purity water is slowly added during the heating process. The ratio of high-purity water (ml) to graphite powder (g) is (100-120):1. The temperature is then raised to 70-85℃, and the heating is stopped. The temperature is then continuously stirred and lowered to below 45℃. Hydrogen peroxide is added. The ratio of hydrogen peroxide (ml) to graphite powder (g) is (4-6):1. The reaction is continued for 1.5-2 hours. At this time, the solution changes from reddish-brown to golden yellow. Washing: Centrifuge to remove supernatant, wash with hydrochloric acid solution, let stand to separate into layers, remove supernatant, acid wash and then wash with deionized water until neutral; Preparation: The washed product is dispersed in high-purity water, stirred and sonicated, centrifuged to remove unoxidized graphite, and the supernatant is obtained. The supernatant is then freeze-dried to obtain the final graphene oxide.

[0011] Furthermore, the mass ratio of potassium permanganate to graphite powder is (25-30):(3-5).

[0012] Furthermore, the temperature is increased to 70-85℃ within 60±5 minutes.

[0013] Further, the washed product is dispersed in high-purity water, stirred, and then subjected to strong ultrasonication for 1-2 hours at 600-800W power in an ice-water bath. After centrifugation to remove unoxidized graphite, the supernatant is obtained and freeze-dried for 48-72 hours to obtain the final graphene oxide.

[0014] Furthermore, the titanium dioxide has a mesh size of 325-600 mesh, and the fumed silica has a particle size of 7-40 nm.

[0015] Secondly, this application provides a method for preparing an intumescent fire-retardant coating for steel structures, which adopts the following technical solution: A method for preparing an intumescent fire-retardant coating for steel structures includes the following steps: S1. Mix and disperse the amino resin and acrylic resin; S2. Add chlorinated paraffin and rheology modifier to the mixture from step S1 and stir. S3. Add defoamer to the mixture from step S2 and stir. S4. Add flame retardant, fumed silica and graphene oxide to the mixture in step S3, stir, and obtain an intumescent fireproof coating for steel structures.

[0016] Further, in step S1, the dispersion is carried out at a speed of 800-1000 r / min for 10-15 minutes; in step S2, the dispersion is carried out at a speed of 600-800 r / min for 0.5-1 hour; in step S3, the dispersion is carried out at a speed of 800-900 r / min for 20-30 minutes; and in step S4, the dispersion is carried out at a speed of 600-800 r / min for 10 minutes.

[0017] In summary, this application has the following beneficial effects: 1. This application uses self-made graphene oxide (GO), which, upon addition, forms a good synergistic effect with the flame retardant system of this application. When the temperature rises, the chemical substances between the GO layers generate gas upon heating, causing the graphite to expand along the axial direction. This can isolate heat and oxygen contact, delay or even interrupt the spread of flame. During combustion, the "worm-shaped" GO expands and bonds with the inorganic layer to form a protective layer. After adding GO, the fire resistance limit increases, which can effectively improve the strength and density of the char layer.

[0018] 2. In the formulation system of this application, chlorinated paraffin, as a chlorine-based flame retardant, has flame retardant and plasticizing effects, which can improve the flexibility and processing performance of the coating.

[0019] 3. The flame retardant system of this application contains NP cage-type macromolecules, which are the core components of the intumescent flame retardant system. It is not only an environmentally friendly flame retardant (halogen-free), but also facilitates the expansion and charring of fire-retardant coatings. Detailed Implementation

[0020] The present application will be further described in detail below with reference to the embodiments.

[0021] Example The sources of raw materials involved in the embodiments of this application are shown in Table 1.

[0022] Table 1. Sources of raw materials used in the embodiments and comparative examples of the present invention. The following explanation is provided through specific examples.

[0023] Example 1 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1:46:7 to a beaker. Stir for 1.5 hours under ice-water bath conditions. Then, add potassium permanganate in multiple portions over 2 hours, with a mass ratio of potassium permanganate to graphite powder of 25:3. Continue stirring, raise the temperature to 45°C and hold for 2 hours. Then, raise the temperature to 55°C and continue the reaction for 2 hours. Continue heating to 80°C within 1 hour, slowly adding high-purity water during the heating process. The ratio of high-purity water (ml) to graphite powder (g) is 110:1. Stop heating after reaching 80°C, and continue stirring to cool down to below 45°C. Add hydrogen peroxide, with a hydrogen peroxide (ml) to graphite powder (g) ratio of 5:1. Continue the reaction for 1.5 hours, at which point the solution changes from reddish-brown to golden yellow.

[0024] Washing: Centrifuge to remove supernatant, wash with 1.5 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0025] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0026] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 15g of amino resin and 9g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 6g of 52° chlorinated paraffin and 2g of rheology modifier. After dispersion, add 0.2g of titanium dioxide, 7g of xylene, and 0.5g of defoamer. Then adjust the reactor speed to 2000 rpm and add 48g of flame retardant, 0.5g of fumed silica, 0.5g of graphene oxide, and 11.3g of 200# solvent. Disperse and stir evenly for 30 minutes, then filter to obtain an intumescent fireproof coating for steel structures. The mass ratio of ammonium polyphosphate, pentaerythritol, and melamine in the flame retardant is 2.2:1.2:1.4.

[0027] Example 2 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1.1:48:7 to a beaker. Stir for 1.5 hours under ice-water bath conditions. Then, add potassium permanganate in multiple portions over 2 hours, with a mass ratio of potassium permanganate to graphite powder of 25:3. Continue stirring, raise the temperature to 55°C and hold for 2 hours. Then, raise the temperature to 65°C and continue the reaction for 2 hours. Continue heating for 1 hour to 85°C, slowly adding high-purity water during the heating process. The ratio of high-purity water (ml) to graphite powder (g) is 110:1. Stop heating after reaching 85°C, and continue stirring to cool down to below 50°C. Add hydrogen peroxide, with a hydrogen peroxide (ml) to graphite powder (g) ratio of 5:1. Continue the reaction for 1.5 hours. At this point, the solution changes from reddish-brown to golden yellow.

[0028] Washing: Centrifuge to remove supernatant, wash with 1.5 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0029] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0030] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 12g of amino resin and 9g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 8g of 52° chlorinated paraffin and 3g of rheology modifier. After dispersion, add 0.6g of titanium dioxide, 5g of xylene, and 0.5g of defoamer. Then adjust the reactor speed to 2000 rpm and add 45g of flame retardant, 1.5g of fumed silica, 1g of graphene oxide, and 14.1g of 200# solvent sequentially. Disperse and stir evenly for 30 minutes, filter, and package to obtain an intumescent fireproof coating for steel structures. In the flame retardant, the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is 1.2:1.3:1.2.

[0031] Example 3 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1.2:5:10 to a beaker. Stir for 1.5 hours under ice-water bath conditions. Then, add potassium permanganate in multiple portions over 2 hours, with a mass ratio of potassium permanganate to graphite powder of 30:5. Continue stirring, raise the temperature to 50°C and hold for 2 hours. Then, raise the temperature to 60°C and continue the reaction for 2 hours. Continue heating to 70°C. During the heating process, slowly add high-purity water, with a high-purity water volume (ml) to graphite powder volume (g) ratio of 120:1. Stop heating after reaching 70°C, and continue stirring to cool down to below 35°C. Add hydrogen peroxide, with a hydrogen peroxide volume (ml) to graphite powder volume (g) ratio of 6:1, and continue the reaction for 1.5 hours. At this point, the solution changes from reddish-brown to golden yellow.

[0032] Washing: Centrifuge to remove supernatant, wash with 2.0 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0033] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0034] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 15g of amino resin and 10g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 10g of 52° chlorinated paraffin and 4g of rheology modifier. After dispersion, add 1g of titanium dioxide, 5g of xylene, and 1g of defoamer. Then adjust the reactor speed to 2000 rpm and add 40g of flame retardant, 1g of fumed silica, 1.5g of graphene oxide, and 11.5g of 200# solvent. Disperse and stir evenly for 30 minutes, filter, and package to obtain an intumescent fire-retardant coating for steel structures. In the flame retardant, the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is 2.5:1.5:1.5.

[0035] Example 4 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1:45:10 to a beaker. Stir for 1.5 hours under ice-water bath conditions. Then, add potassium permanganate in multiple portions over 2 hours, with a mass ratio of potassium permanganate to graphite powder of 25:3. Continue stirring, raise the temperature to 45°C and hold for 2 hours. Then, raise the temperature to 55°C and continue the reaction for 2 hours. Continue heating to 80°C within 1 hour, slowly adding high-purity water during the heating process. The ratio of high-purity water (ml) to graphite powder (g) is 100:1. Stop heating after reaching 80°C, and continue stirring to cool down to below 45°C. Add hydrogen peroxide, with a hydrogen peroxide (ml) to graphite powder (g) ratio of 4:1. Continue the reaction for 1.5 hours, at which point the solution changes from reddish-brown to golden yellow.

[0036] Washing: Centrifuge to remove supernatant, wash with 1.5 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0037] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0038] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 9g of amino resin and 6g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 7g of 52° chlorinated paraffin and 3g of rheology modifier. After dispersion, add 0.4g of titanium dioxide, 8g of xylene, and 1g of defoamer. Then adjust the reactor speed to 2000 rpm and add 50g of flame retardant, 1g of fumed silica, 1g of graphene oxide, and 13.6g of 200# solvent. Disperse and stir evenly for 30 minutes, then filter to obtain an intumescent fireproof coating for steel structures. The mass ratio of ammonium polyphosphate, pentaerythritol, and melamine in the flame retardant is 2:1:1.

[0039] Example 5 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1:45:10 to a beaker. Stir for 1.5 hours under ice-water bath conditions. Then, add 10g of potassium permanganate in several portions over 2 hours, stirring continuously. Raise the temperature to 45℃ and hold for 2 hours. Then, raise the temperature to 55℃ and continue the reaction for 2 hours. Continue to raise the temperature to 70℃ over 1 hour, slowly adding high-purity water in a ratio of 110:1 (ml to g of graphite powder). Stop heating once 70℃ is reached, and continue stirring while cooling to below 50℃. Add hydrogen peroxide in a ratio of 5:1 (ml to g of graphite powder) and continue the reaction for 1.5 hours. At this point, the solution changes from reddish-brown to golden yellow.

[0040] Washing: Centrifuge to remove supernatant, wash with 1.5 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0041] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0042] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 16g of amino resin and 8g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 7g of 52° chlorinated paraffin and 3g of rheology modifier. After dispersion, add 0.5g of titanium dioxide, 5g of xylene, and 1g of defoamer. Then adjust the reactor speed to 2000 rpm and add 40g of flame retardant, 1.5g of fumed silica, 1g of graphene oxide, and 12g of 200# solvent sequentially. Disperse and stir evenly for 30 minutes, filter, and package to obtain an intumescent fire-retardant coating for steel structures. In the flame retardant, the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is 1.2:1.3:1.2.

[0043] Example 6 This application first provides a method for preparing graphene oxide, including the following steps: Oxidation: Add graphite powder, phosphoric acid, and concentrated sulfuric acid in a ratio of 1:46:8 to a beaker. Stir for 1.5 hours in an ice-water bath. Then, add 25g of potassium permanganate in several portions over 2 hours, stirring continuously. Raise the temperature to 45℃ and hold for 2 hours. Then, raise the temperature to 55℃ and continue the reaction for 2 hours. Continue heating to 80℃, slowly adding 400mL of high-purity water during the heating process. Stop heating after reaching 80℃, continue stirring, and cool down to below 45℃. Add 18mL of hydrogen peroxide and continue the reaction for 1.5 hours. At this point, the solution changes from reddish-brown to golden yellow.

[0044] Washing: Centrifuge to remove supernatant, wash with 1.5 mol / L hydrochloric acid solution, allow to stand for separation, remove supernatant, acid wash three times, and then wash with deionized water until neutral.

[0045] Preparation: The washed product was dispersed in high-purity water, stirred, and then subjected to ultrasonic cell disruption at 600W power in an ice-water bath for 1 hour. Unoxidized graphite was removed by centrifugation, and the supernatant was freeze-dried for 48 hours to obtain the final product, graphene oxide. The thickness of the graphene oxide sheets was 0.8–1.5 nm.

[0046] This application also provides a method for preparing a fire-retardant coating, comprising the following steps: Weigh 9g of amino resin and 12g of acrylic resin and add them to a dispersion tank. While stirring at 1200 rpm, add 7g of 52° chlorinated paraffin and 3g of rheology modifier. After dispersion, add 0.4g of titanium dioxide, 5g of xylene, and 1g of defoamer. Then adjust the reactor speed to 2000 rpm and add 47g of flame retardant, 1g of fumed silica, 1g of graphene oxide, and 13.6g of 200# solvent. Disperse and stir evenly for 30 minutes, filter, and package to obtain an intumescent fireproof coating for steel structures. The mass ratio of ammonium polyphosphate, pentaerythritol, and melamine in the flame retardant is 2.2:1.2:1.4.

[0047] Comparative Example The difference between Comparative Example 1 and Example 1 is that no graphene oxide is added to the coating.

[0048] The difference between Comparative Example 2 and Example 1 is that expandable graphite with a particle size of 45-150 micrometers is used to replace graphene oxide in an equal amount to obtain an expandable fireproof coating for steel structures.

[0049] The difference between Comparative Example 3 and Example 1 is that 200-325 mesh coal gangue is used in an equal amount to replace graphene oxide, thus obtaining an intumescent fireproof coating for steel structures. The difference between Comparative Example 4 and Example 1 is that the thickness of graphene oxide in the coating is 5-10 nm.

[0050] The difference between Comparative Example 5 and Example 1 is that the flame retardant in the coating is a mixture of hexabromocyclododecane and antimony trioxide in a mass ratio of 4:1, while the total amount of flame retardant remains unchanged.

[0051] The difference between Comparative Example 6 and Example 1 is that the mass ratio of the flame retardant in the ammonium polyphosphate-pentaerythritol-melamine system in the coating is 3:1:3.

[0052] Performance testing The coatings obtained in the examples and comparative examples were tested for properties such as fire resistance limit, foaming ratio, bond strength, and char layer state. The specific procedures are as follows: (1) The fire resistance limit of intumescent steel structure fireproof coating is determined by the following method: After the prepared sample is cured for 7 days, it is fixed on an iron frame with the side coated with fireproof coating facing down. It is burned with a spray gun and the temperature on the back of the steel plate is checked with an infrared thermometer. The time taken for the temperature to reach 580℃ is the fire resistance limit of the coating.

[0053] (2) The foaming ratio of intumescent fireproof coating for steel structures is determined by the following method: the ratio of the height of the fireproof coating after it expands after combustion to the thickness before combustion.

[0054] (3) The bonding strength of the intumescent fireproof coating for steel structures shall be determined by the following method: Apply adhesive evenly in a 40mm x 40mm area in the center of the sample, then attach the steel connector and press it with a 1 kg weight. Carefully remove the adhesive around the connector. After 3 days, apply a tensile force in the vertical direction of the specimen base plate at a speed of 1500 N / min to 2000 N / min. Measure the maximum tensile load. The bonding strength of each specimen shall be calculated according to formula (1).

[0055] f=F / A…………………… (1) In the formula: f—bonding strength, in megapascals (MPa). F — Maximum load, in Newtons (N). A—Bonded area, in square millimeters (mm2). (4) The char layer state of intumescent fireproof coating for steel structures shall be determined by the following method: After the fireproof coating is burned, observe whether the char layer is cracked and the density of the structure.

[0056] (5) The initial drying crack resistance of intumescent fireproof coatings for steel structures shall be determined by the following method: The test shall be conducted in accordance with 6.10 of GB / T 9779-2015. Visual inspection shall be performed to check for cracks or the crack width shall be measured using appropriate tools.

[0057] (6) The drying time (surface dry) of intumescent fireproof coating for steel structures shall be determined by the following method: the test shall be conducted according to the finger test method specified in GB / T 1728-1979.

[0058] The test results are shown in Table 2. Table 2 Example 1 6 and Comparative Example 1 3. Performance Test Results As shown in Table 2, Embodiment 1 of the present invention 6. Intumescent fire-retardant coatings for steel structures were prepared. Among them, the state of Examples 1-6 was uniform after stirring without hard lumps. The fire resistance time was more than 60 minutes, the foaming ratio was more than 15 times, the char layer was dense and without cracks, and all other properties met the requirements of GB-14907-2018 "Fire-retardant Coatings for Steel Structures".

[0059] Compared with Example 1 Compared to Comparative Example 1, which uses a commercially available intumescent fire-retardant coating formulation for steel structures without added reinforcing materials, its fire resistance time is only 23 minutes, and its char layer shows cracks, failing to meet performance standards. Comparative Examples 2-6, using different reinforcing materials or different flame retardant systems, also showed significantly worse performance than the present application. This is because the present application uses self-made graphene oxide (GO), and its flame retardant system is specific. The addition of these two substances creates a synergistic effect. When the temperature rises, the chemical substances between the GO layers are heated to produce gas, causing the graphite to expand along its axis. This isolates heat and oxygen, delaying or even interrupting flame spread. Furthermore, during combustion, the "worm-shaped" GO expands and bonds with the inorganic layer to form a protective layer, effectively improving the strength and density of the char layer.

[0060] 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 raw materials consist of matrix resin, flame retardant, graphene oxide, chlorinated paraffin, rheology modifier, defoamer, fumed silica, and titanium dioxide. The flame retardant is a flame retardant system of ammonium polyphosphate-pentaerythritol-melamine, wherein the mass ratio of ammonium polyphosphate, pentaerythritol, and melamine is (2-2.5):(1-1.5):(1-1.5). The thickness of the graphene oxide sheets is 0.8-1.5 nm.

2. The intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The fire-retardant coating comprises the following components by mass percentage: The composition consists of 15-25% matrix resin, 40-50% flame retardant, 0.5-1.5% graphene oxide, 5-10% chlorinated paraffin, 2-4% rheology modifier, 0.5-1% defoamer, 0.5-1.5% fumed silica, 0.2-1% titanium dioxide, and the remainder is solvent.

3. The intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The matrix resin is a mixture of amino resin and acrylic resin, and the mass ratio of the amino resin to the acrylic resin is (3-6):(2-4).

4. The intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The method for preparing the graphene oxide includes the following steps: Oxidation: Graphite powder, phosphoric acid, and concentrated sulfuric acid are stirred in an ice-water bath at a mass ratio of (1-1.2):(45-50):(5-10) for 1-1.5 hours. Potassium permanganate is added in portions over 1.5-2 hours. The temperature is raised to 40-45℃ and held for 1.5-2 hours. Then the temperature is raised to 50-55℃ and the reaction is continued for 2-2.5 hours. The temperature is then raised again, and high-purity water is slowly added during the heating process. The ratio of high-purity water (ml) to graphite powder (g) is (100-120):

1. The temperature is then raised to 70-85℃, and the heating is stopped. The temperature is then continuously stirred and lowered to below 45℃. Hydrogen peroxide is added. The ratio of hydrogen peroxide (ml) to graphite powder (g) is (4-6):

1. The reaction is continued for 1.5-2 hours. At this time, the solution changes from reddish-brown to golden yellow. Washing: Centrifuge to remove supernatant, wash with hydrochloric acid solution, let stand to separate into layers, remove supernatant, acid wash and then wash with deionized water until neutral; Preparation: The washed product is dispersed in high-purity water, stirred and sonicated, centrifuged to remove unoxidized graphite, and the supernatant is obtained. The supernatant is then freeze-dried to obtain the final graphene oxide.

5. The intumescent fire-retardant coating for steel structures according to claim 5, characterized in that, The mass ratio of potassium permanganate to graphite powder is (25-30):(3-5).

6. The intumescent fire-retardant coating for steel structures according to claim 5, characterized in that, The temperature rises to 70-85℃ within 60±5 minutes.

7. The intumescent fire-retardant coating for steel structures according to claim 5, characterized in that, The washed product is dispersed in high-purity water, stirred, and then subjected to strong ultrasonication for 1-2 hours at 600-800W power in an ice-water bath. After centrifugation to remove unoxidized graphite, the supernatant is obtained and freeze-dried for 48-72 hours to obtain the final graphene oxide.

8. The intumescent fire-retardant coating for steel structures according to claim 1, characterized in that, The titanium dioxide has a particle size of 325-600 mesh, and the fumed silica has a particle size of 7-40 nm.

9. A method for preparing an intumescent fire-retardant coating for steel structures as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Mix and disperse the amino resin and acrylic resin; S2. Add chlorinated paraffin and rheology modifier to the mixture from step S1 and stir. S3. Add defoamer to the mixture from step S2 and stir. S4. Add flame retardant, fumed silica and graphene oxide to the mixture in step S3, stir, and obtain an intumescent fireproof coating for steel structures.

10. The method for preparing an intumescent fire-retardant coating for steel structures according to claim 9, characterized in that, In step S1, disperse at a speed of 800-1000 r / min for 10-15 minutes; in step S2, disperse at a speed of 600-800 r / min for 0.5-1 hour; in step S3, disperse at a speed of 800-900 r / min for 20-30 minutes; and in step S4, disperse at a speed of 600-800 r / min for 10 minutes.

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