Corrosion-resistant fireproof plate

Abstract

The invention relates to the technical field of plates, and provides a corrosion-resistant fireproof plate. The corrosion-resistant fireproof plate comprises a base material layer and a composite protective layer from bottom to top, wherein the base material layer comprises the following raw materials in parts by weight: 55-65 parts of straw short fibers, 10-12 parts of nano magnesium oxide particles, 22-26 parts of calcium silicate powder and 3-5 parts of a polyvinyl alcohol adhesive; the composite protective layer is prepared from the following raw materials in parts by weight: 60 to 65 parts of epoxy resin, 25 to 30 parts of methyl tetrahydrophthalic anhydride, 10 to 15 parts of CaAl-LDH loaded zinc borate, 8 to 10 parts of nitrile rubber, 5 to 7 parts of silane coupling agent, 4 to 6 parts of ammonium polyphosphate, 10 to 12 parts of acetone, 10 to 12 parts of ethanol and 1 to 2 parts of accelerant. According to the corrosion-resistant fireproof plate prepared in the invention, the corrosion resistance of the plate is enhanced, and the fireproof and flame-retardant properties are also improved.

Description

Technical Field

[0001] The present invention relates to the technical field of panels, and in particular to a corrosion-resistant fireproof panel. Background Art

[0002] In modern industry and construction, material performance requirements are becoming increasingly stringent. Especially in specialized environments such as chemical plants, marine facilities, and underground structures, materials must not only possess excellent fire resistance to protect life and property, but also possess excellent corrosion resistance to withstand the erosion of various chemicals and extend service life. Corrosion-resistant fireproof panels, a new material that combines these two key properties, are gaining widespread attention.

[0003] Corrosion-resistant fireproof panels are specially treated to resist chemical attack and prevent the spread of flames. They typically consist of a base material and a fire-resistant and corrosion-resistant layer. The base material is typically made of a material with a certain strength and stability, such as calcium silicate board or fiber cement board, to provide the basic mechanical support for the panel. The fire-resistant and corrosion-resistant layer, through the addition of special corrosion-resistant additives or the use of specialized surface treatment techniques, enables the panel to withstand corrosion from chemicals such as acids, alkalis, and salts. Flame-retardant materials, such as aluminum hydroxide and zinc borate, also react chemically at high temperatures, absorbing heat and releasing non-combustible gases such as water, thereby preventing the spread of flames.

[0004] While existing corrosion-resistant fireproof panels can resist chemical attack to a certain extent, their corrosion resistance remains insufficient when exposed to some highly corrosive media. For example, in some chemical production processes, they come into contact with high-concentration acid and alkali solutions. Long-term exposure to these media can cause corrosion and peeling on the surface of existing corrosion-resistant fireproof panels, resulting in a decrease in performance and a shortened service life. To address this technical problem, the present invention proposes a new corrosion-resistant fireproof panel. Summary of the Invention

[0005] The present invention provides a corrosion-resistant fireproof board, which enhances the corrosion resistance of the board and improves the fire retardancy.

[0006] The technical solutions of the present invention are as follows: In a first aspect, the present invention provides a corrosion-resistant fireproof board comprising a substrate layer and a composite protective layer; The substrate layer comprises the following raw materials in parts by weight: 55-65 parts of straw short fibers, 10-12 parts of nano magnesium oxide particles, 22-26 parts of calcium silicate powder, and 3-5 parts of polyvinyl alcohol adhesive; The composite protective layer comprises the following raw materials in parts by weight: 60-65 parts of epoxy resin, 25-30 parts of methyltetrahydrophthalic anhydride, 10-15 parts of CaAl-LDH-loaded zinc borate, 8-10 parts of nitrile rubber, 5-7 parts of silane coupling agent, 4-6 parts of ammonium polyphosphate, 10-12 parts of acetone, 10-12 parts of ethanol, and 1-2 parts of accelerator.

[0007] As a further technical solution, the preparation method of the substrate layer includes: mixing straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive in proportion, adding deionized water to adjust the solid content to 40%-45%, and continuously stirring at a speed of ≥1000 rpm for 30-40 minutes to form a slurry. After injecting into the mold, it is maintained at a pressure of 10-12 MPa and a temperature of 75-85°C for 30-40 minutes, and after demolding, it is transferred to a 55-65°C oven for drying for 22-26 hours.

[0008] As a further technical solution, the alkaline solution pretreatment step includes: soaking the straw short fibers in a NaOH aqueous solution with a mass concentration of 9%-11% for 2-3 hours, then rinsing with clean water until neutral, centrifugally dehydrating, and then drying in an oven at 70-80°C to a moisture content of ≤5%.

[0009] As a further technical solution, the preparation method of the CaAl-LDH loaded with zinc borate includes: dispersing CaAl-LDH in deionized water, adding H3BO3 and Zn(NO3)2·6H2O, ultrasonically dispersing, adjusting the solution pH to 8.0±0.5, heating to 55-65°C and stirring for 4-5 hours, centrifugally separating the precipitation, washing, and drying.

[0010] As a further technical solution, the weight ratio of the CaAl-LDH, deionized water, H3BO3 and Zn(NO3)2·6H2O is 20-24:500-550:120-130:85-95.

[0011] As a further technical solution, the preparation method of the CaAl-LDH includes: dissolving 230-240 parts of Ca(NO3)2·4H2O and 155-167 parts of Al(NO3)3·6H2O in 500-540 parts of deionized water, stirring until completely dissolved to obtain a mixed salt solution; dissolving 100-120 parts of NaOH in 200-240 parts of deionized water, slowly adding it dropwise to the mixed salt solution, controlling the pH to 10.0±0.2, and continuously stirring for 2-3 hours; reacting at 95-105°C for 10-12 hours, centrifuging, washing with water, and drying to obtain CaAl-LDH.

[0012] As a further technical solution, the preparation method of the composite protective layer includes: mixing CaAl-LDH-loaded zinc borate, silane coupling agent, ammonium polyphosphate, acetone and ethanol, ultrasonically treating at 300-350W for 30-40 minutes, adding epoxy resin and nitrile rubber, stirring at 200-250rpm for 30-40 minutes, then increasing the stirring speed to 400-500rpm, and sequentially adding methyltetrahydrophthalic anhydride and accelerator, and continuing to stir for 20-25 minutes.

[0013] As a further technical solution, the preparation method of the fireproof board includes: applying the prepared composite protective layer to the substrate layer by spraying twice and curing it, wherein the thickness of the single layer film is 100-150μm and the interval time between the two spraying is 25-35min.

[0014] As a further technical solution, the spraying pressure is 18-20 MPa, the spray gun caliber is 1.3-1.5 mm, and the spray distance is 25-30 cm.

[0015] As a further technical solution, the curing conditions include: pre-curing at room temperature for 24-26 hours, followed by post-curing in an oven at 100-120°C for 2-4 hours.

[0016] The working principle and beneficial effects of the present invention are: In the present invention, the nano-magnesium oxide in the substrate layer exhibits excellent adsorption and reaction activity due to its high specific surface area. When interacting with calcium silicate, this high specific surface area property enables the nano-magnesium oxide to fully contact the calcium silicate and form a tighter bond, thereby constructing a dense network structure. In contrast, aluminum hydroxide only occupies space through physical filling, while the dense network formed by nano-magnesium oxide and calcium silicate not only achieves space filling, but also significantly enhances the internal bonding force and integrity of the material, improving the physical properties and stability of the material. This structure effectively resists the erosion of external factors and provides a more reliable structural support for the material.

[0017] In the present invention, the zinc borate loaded on the CaAl-LDH plays a key role in the composite protective layer. After the zinc borate is loaded between the LDH layers, it is gradually released during the material's use, influenced by the external environment (such as temperature and humidity). In contrast, when zinc borate is added directly, the zinc borate particles tend to agglomerate, resulting in uneven distribution within the material and hindering its full performance. The interlayer loading method effectively avoids zinc borate agglomeration, ensuring uniform dispersion throughout the material and timely release when necessary, thereby more efficiently performing its function and improving the overall performance of the material.

[0018] In the present invention, the zinc borate slowly released between the CaAl-LDH-loaded zinc borate layers forms a phosphorus-nitrogen synergistic flame retardant system with ammonium polyphosphate, which plays a key role in the flame retardant process. During combustion, ammonium polyphosphate decomposes at high temperatures to produce acidic substances such as phosphoric acid, and the organic components in the catalytic material are dehydrated and carbonized to form carbonized products rich in carbon elements and accumulate and expand into an expanded carbon layer, which is heat-insulating and oxygen-isolating, and suppresses combustion. At the same time, zinc borate decomposes under heat to release water vapor and boric acid, and the water vapor dilutes the concentration of combustible gases, and the boric acid catalyzes the formation and stabilization of the carbon layer. In addition, the LDH system changes its structure at high temperatures to release substances such as metal oxides, which work in conjunction with the decomposition products of ammonium polyphosphate and zinc borate to promote the formation and improvement of the expanded carbon layer, effectively blocking heat and oxygen transfer, protecting the material matrix, and improving fire resistance and thermal stability. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] It should be noted that the polyvinyl alcohol in the present invention, CAS: 9002-89-5, was purchased from Wuhan Jixin Yibang Biotechnology Co., Ltd.; the nitrile rubber was purchased from Shanghai Youdian Industrial Co., Ltd., with the product number NBR2865; and the ammonium polyphosphate was purchased from Jinan Xinquan Chemical Technology Co., Ltd., with the CAS number 68333-79-9.

[0021] Example 1 This embodiment provides a corrosion-resistant fireproof board, comprising a substrate layer and a composite protective layer; The substrate layer includes the following raw materials in parts by weight: 60 parts of straw short fibers, 11 parts of nano magnesium oxide particles, 24 parts of calcium silicate powder, and 4 parts of polyvinyl alcohol adhesive; The composite protective layer includes the following raw materials in parts by weight: 62 parts of epoxy resin E-51, 28 parts of methyltetrahydrophthalic anhydride, 12 parts of CaAl-LDH loaded zinc borate, 9 parts of nitrile rubber, 6 parts of silane coupling agent KH-550, 5 parts of ammonium polyphosphate, 11 parts of acetone, 11 parts of ethanol, and 1.5 parts of accelerator DMP-30.

[0022] The preparation method of the fireproof board comprises: Preparation of the substrate layer: soak straw short fibers with an average length of 25 mm in a 10% mass concentration NaOH aqueous solution for 2.5 h, then rinse with clean water until neutral, centrifuge and dehydrate, and then dry in a 75°C oven to a moisture content of 5%; mix the straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive in proportion, add deionized water to adjust the solid content to 42%, and stir continuously at a speed of 1000 rpm for 35 min to form a slurry. After injection into the mold, keep it at a pressure of 11 MPa and a temperature of 80°C for 35 min, demold and transfer it to a 60°C oven for drying for 24 h.

[0023] Preparation of CaAl-LDH: Dissolve 235 parts of Ca(NO3)2·4H2O and 161 parts of Al(NO3)3·6H2O in 520 parts of deionized water and stir until completely dissolved to obtain a mixed salt solution; dissolve 110 parts of NaOH in 220 parts of deionized water and slowly add it dropwise to the mixed salt solution, control the pH to 10.0, and continue stirring for 2.5 hours; react at 100°C for 11 hours, centrifuge, wash with water, and dry to obtain CaAl-LDH; Preparation of CaAl-LDH loaded with zinc borate: 22 parts of CaAl-LDH were dispersed in 520 parts of deionized water, 125 parts of H3BO3 and 90 parts of Zn(NO3)2·6H2O were added, and ultrasonic dispersion was performed. The pH of the solution was adjusted to 8.0, and the temperature was raised to 60°C and stirred for 4.5 hours. The precipitate was separated by centrifugation, washed with ethanol three times, and dried in a vacuum at 80°C for 6 hours. Preparation of the composite protective layer: CaAl-LDH-loaded zinc borate, silane coupling agent, ammonium polyphosphate, acetone, and ethanol were mixed and ultrasonicated at 320W for 35 minutes. Epoxy resin and nitrile rubber were added and stirred at 220 rpm for 35 minutes. The stirring speed was then increased to 450 rpm, and methyltetrahydrophthalic anhydride and accelerator were added in sequence. Stirring was continued for 22 minutes to obtain the composite protective layer. Preparation of fireproof board: The prepared composite protective layer is applied to the substrate layer by spraying twice, pre-cured at room temperature for 25 hours, and then post-cured in a 110°C oven for 3 hours. The spraying pressure is 19 MPa, the spray gun diameter is 1.4 mm, and the spray distance is 28 cm; the thickness of the single layer film is 120 μm, and the interval between the two sprayings is 30 minutes.

[0024] Example 2 This embodiment provides a corrosion-resistant fireproof board, comprising a substrate layer and a composite protective layer; The substrate layer includes the following raw materials in parts by weight: 55 parts of straw short fibers, 10 parts of nano magnesium oxide particles, 22 parts of calcium silicate powder, and 3 parts of polyvinyl alcohol adhesive; The composite protective layer includes the following raw materials in parts by weight: 60 parts of epoxy resin E-51, 25 parts of methyltetrahydrophthalic anhydride, 10 parts of CaAl-LDH loaded zinc borate, 8 parts of nitrile rubber, 5 parts of silane coupling agent KH-550, 4 parts of ammonium polyphosphate, 10 parts of acetone, 10 parts of ethanol, and 1 part of accelerator DMP-30.

[0025] The preparation method of the fireproof board comprises: Preparation of the substrate layer: soak 20mm straw short fibers in a 9% mass concentration NaOH aqueous solution for 2 hours, then rinse with clean water until neutral, centrifuge and dehydrate, and then dry in a 70°C oven to a moisture content of 5%; mix the straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive in proportion, add deionized water to adjust the solid content to 40%, and stir continuously at a speed of 1000 rpm for 30 minutes to form a slurry. After injection into the mold, keep it at a pressure of 10 MPa and a temperature of 75°C for 30 minutes. After demolding, transfer it to a 55°C oven and dry it for 22 hours.

[0026] Preparation of CaAl-LDH: Dissolve 230 parts of Ca(NO3)2·4H2O and 155 parts of Al(NO3)3·6H2O in 500 parts of deionized water and stir until completely dissolved to obtain a mixed salt solution; dissolve 100 parts of NaOH in 200 parts of deionized water and slowly add it dropwise to the mixed salt solution, control the pH to 10.0, and continue stirring for 2 hours; react at 95°C for 10 hours, centrifuge, wash with water, and dry to obtain CaAl-LDH; Preparation of CaAl-LDH loaded with zinc borate: 20 parts of CaAl-LDH were dispersed in 500 parts of deionized water, 120 parts of H3BO3 and 85 parts of Zn(NO3)2·6H2O were added, and ultrasonic dispersion was performed. The pH of the solution was adjusted to 8.0, and the temperature was raised to 55°C and stirred for 4 hours. The precipitate was separated by centrifugation, washed with ethanol three times, and dried in a vacuum at 80°C for 6 hours. Preparation of the composite protective layer: CaAl-LDH-loaded zinc borate, silane coupling agent, ammonium polyphosphate, acetone, and ethanol were mixed and ultrasonicated at 300W for 30 minutes. Epoxy resin and nitrile rubber were added and stirred at 200 rpm for 30 minutes. The stirring speed was then increased to 400 rpm, and methyltetrahydrophthalic anhydride and accelerator were added in sequence. Stirring was continued for 20 minutes to obtain the composite protective layer. Preparation of fireproof board: The prepared composite protective layer is applied to the substrate layer by two spraying processes, pre-cured at room temperature for 24 hours, and then post-cured in a 100°C oven for 2 hours. The spraying pressure is 18 MPa, the spray gun diameter is 1.3 mm, and the spray distance is 25 cm. The thickness of the single layer film is 120 μm, and the interval between the two spraying processes is 25 minutes.

[0027] Example 3 This embodiment provides a corrosion-resistant fireproof board, comprising a substrate layer and a composite protective layer; The substrate layer includes the following raw materials in parts by weight: 65 parts of straw short fibers, 12 parts of nano magnesium oxide particles, 26 parts of calcium silicate powder, and 5 parts of polyvinyl alcohol adhesive; The composite protective layer includes the following raw materials in parts by weight: 65 parts of epoxy resin E-51, 30 parts of methyltetrahydrophthalic anhydride, 15 parts of CaAl-LDH loaded zinc borate, 10 parts of nitrile rubber, 7 parts of silane coupling agent KH-550, 6 parts of ammonium polyphosphate, 12 parts of acetone, 12 parts of ethanol, and 2 parts of accelerator DMP-30.

[0028] The preparation method of the fireproof board comprises: Preparation of the substrate layer: soak 30mm straw short fibers in an 11% mass concentration NaOH aqueous solution for 3 hours, then rinse with clean water until neutral, centrifuge and dehydrate, and then dry in an 80°C oven to a moisture content of 5%; mix the straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive in proportion, add deionized water to adjust the solid content to 45%, and stir continuously at a speed of 1000 rpm for 40 minutes to form a slurry. After injection into the mold, keep it at a pressure of 12 MPa and a temperature of 85°C for 40 minutes. After demolding, transfer it to a 65°C oven and dry it for 26 hours.

[0029] Preparation of CaAl-LDH: Dissolve 240 parts of Ca(NO3)2·4H2O and 167 parts of Al(NO3)3·6H2O in 540 parts of deionized water and stir until completely dissolved to obtain a mixed salt solution; dissolve 120 parts of NaOH in 240 parts of deionized water and slowly add it dropwise to the mixed salt solution, control the pH to 10.0, and continue stirring for 3 hours; react at 105°C for 12 hours, centrifuge, wash with water, and dry to obtain CaAl-LDH; Preparation of CaAl-LDH loaded with zinc borate: 24 parts of CaAl-LDH were dispersed in 550 parts of deionized water, 130 parts of H3BO3 and 95 parts of Zn(NO3)2·6H2O were added, and ultrasonic dispersion was performed. The pH of the solution was adjusted to 8.0, and the temperature was raised to 65°C and stirred for 5 hours. The precipitate was separated by centrifugation, washed with ethanol three times, and dried in a vacuum at 80°C for 6 hours. Preparation of the composite protective layer: CaAl-LDH-loaded zinc borate, silane coupling agent, ammonium polyphosphate, acetone, and ethanol were mixed and ultrasonicated at 350W for 40 minutes. Epoxy resin and nitrile rubber were added and stirred at 250 rpm for 40 minutes. The stirring speed was then increased to 500 rpm, and methyltetrahydrophthalic anhydride and accelerator were added in sequence. Stirring was continued for 25 minutes to obtain the composite protective layer. Preparation of fireproof board: The prepared composite protective layer is sprayed on the substrate layer twice, pre-cured at room temperature for 26 hours, and then post-cured in a 120°C oven for 4 hours. The spraying pressure is 20 MPa, the spray gun diameter is 1.5 mm, and the spray distance is 30 cm; the thickness of the single layer film is 120 μm, and the interval between the two sprayings is 35 minutes.

[0030] Example 4 This embodiment provides a corrosion-resistant fireproof board, comprising a substrate layer and a composite protective layer; The substrate layer includes the following raw materials in parts by weight: 55 parts of straw short fibers, 12 parts of nano magnesium oxide particles, 22 parts of calcium silicate powder, and 5 parts of polyvinyl alcohol adhesive; The composite protective layer includes the following raw materials in parts by weight: 60 parts of epoxy resin E-51, 30 parts of methyltetrahydrophthalic anhydride, 10 parts of CaAl-LDH loaded zinc borate, 10 parts of nitrile rubber, 5 parts of silane coupling agent KH-550, 6 parts of ammonium polyphosphate, 10 parts of acetone, 12 parts of ethanol, and 1 part of accelerator DMP-30.

[0031] The preparation method of the fireproof board comprises: Preparation of the substrate layer: 30mm straw short fibers were soaked in a 9% NaOH aqueous solution for 3 hours, then rinsed with clean water until neutral, centrifuged and dried in a 70°C oven to a moisture content of 5%; the straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive were mixed in proportion, deionized water was added to adjust the solid content to 40%, and the slurry was continuously stirred at a speed of 1000 rpm for 40 minutes to form a slurry. After injection into the mold, the slurry was maintained at a pressure of 10 MPa and a temperature of 85°C for 30 minutes. After demolding, the slurry was transferred to a 65°C oven and dried for 22 hours.

[0032] Preparation of CaAl-LDH: Dissolve 240 parts of Ca(NO3)2·4H2O and 155 parts of Al(NO3)3·6H2O in 540 parts of deionized water and stir until completely dissolved to obtain a mixed salt solution; dissolve 100 parts of NaOH in 240 parts of deionized water and slowly add it dropwise to the mixed salt solution, control the pH to 10.0, and continue stirring for 3 hours; react at 95°C for 12 hours, centrifuge, wash with water, and dry to obtain CaAl-LDH; Preparation of CaAl-LDH loaded with zinc borate: 20 parts of CaAl-LDH were dispersed in 550 parts of deionized water, 120 parts of H3BO3 and 95 parts of Zn(NO3)2·6H2O were added, and ultrasonic dispersion was performed. The pH of the solution was adjusted to 8.0, and the temperature was raised to 55°C and stirred for 5 hours. The precipitate was separated by centrifugation, washed with ethanol three times, and dried in a vacuum at 80°C for 6 hours. Preparation of the composite protective layer: CaAl-LDH-loaded zinc borate, silane coupling agent, ammonium polyphosphate, acetone, and ethanol were mixed and ultrasonicated at 300W for 40 minutes. Epoxy resin and nitrile rubber were added and stirred at 200 rpm for 40 minutes. The stirring speed was then increased to 400 rpm, and methyltetrahydrophthalic anhydride and accelerator were added in sequence. Stirring was continued for 25 minutes to obtain the composite protective layer. Preparation of fireproof board: The prepared composite protective layer is applied to the substrate layer by spraying twice, pre-cured at room temperature for 24 hours, and then post-cured in a 120°C oven for 2 hours. The spraying pressure is 20 MPa, the spray gun diameter is 1.3 mm, and the spray distance is 30 cm; the thickness of the single layer film is 120 μm, and the interval between the two sprayings is 35 minutes.

[0033] Comparative Example 1 Adjustments were made based on Example 1, except that nano magnesium oxide was replaced with an equal amount of nano aluminum hydroxide.

[0034] Comparative Example 2 Adjustments were made based on Example 1, except that ammonium polyphosphate was removed and the CaAl-LDH loading of zinc borate was increased to 17 parts.

[0035] Comparative Example 3 Adjustments were made based on Example 1, except that the CaAl-LDH-loaded zinc borate was replaced with an equal mass of CaAl-LDH.

[0036] Comparative Example 4 Adjustments were made based on Example 1, except that the CaAl-LDH-loaded zinc borate was replaced with an equal mass of zinc borate.

[0037] Comparative Example 5 Adjustments were made on the basis of Example 1, except that CaAl-LDH-loaded zinc borate was replaced by CaAlZn-LDH, and the preparation method included: dissolving 240 parts of Ca(NO3)2·4H2O, 155 parts of Al(NO3)3·6H2O, and 95 parts of Zn(NO3)2·6H2O in 540 parts of deionized water, and stirring until completely dissolved to obtain a mixed salt solution; dissolving 100 parts of NaOH in 240 parts of deionized water, and slowly adding the solution dropwise to the mixed salt solution, controlling the pH to 10.0, and continuously stirring for 3 hours; reacting at 95°C for 12 hours, centrifuging, washing with water, and drying to obtain the result.

[0038] Comparative Example 6 Adjustments were made based on Example 1. The difference from Example 1 was that the composite protective layer was eliminated and only the base material layer was retained.

[0039] Comparative Example 7 Adjustments were made based on Example 1, except that the post-curing temperature was increased from 110° C. to 130° C., and the curing time was shortened to 2 hours.

[0040] Test Example 1: The corrosion-resistant fireproof panels prepared in Examples 1-4 and Comparative Examples 1-6 were tested as follows: Adhesion test: Refer to the GB / T 9286-2021 cross-hatch method to evaluate the bonding strength between the coating and the substrate. Use a knife to scratch a 1mm x 1mm grid (6 x 6) on the coating surface. Apply 3M tape and quickly peel it off. The coating is rated based on the percentage of the peeled area (Grade 1: ≤5% peeled); Impact resistance test: Refer to GB / T 1732-2020 drop weight impact method to determine the material's ability to resist dynamic impact. A 1 kg drop weight is dropped freely from a height of 50 cm to impact the surface of the sample to observe whether cracks or perforations are generated. Corrosion resistance test: Refer to ASTM B117 neutral salt spray test (NSS). Place the sample in a salt spray chamber and spray 5% NaCl solution (pH=6.5-7.2) at 35°C to simulate a high salt spray environment for 500 hours. Observe surface blistering, peeling, and corrosion depth, and record the mass loss rate. Flame retardancy test: refer to GB / T 2408-2021 (UL94 vertical burning method) and limiting oxygen index (LOI) test; The test results are shown in Table 1 below: Table 1

[0041] Combining the above, it can be seen that Examples 1-4 demonstrate significant advantages in corrosion resistance, flame retardancy, and mechanical properties through the coordinated design of the substrate layer and the composite protective layer. The substrate layer utilizes alkali-treated short straw fibers as a reinforcing framework, while nano-magnesium oxide and calcium silicate form an inorganic-organic composite network, effectively enhancing the material's thermal stability and mechanical strength. In the composite protective layer, CaAl-LDH-loaded zinc borate forms a phosphorus-nitrogen synergistic flame retardant system with ammonium polyphosphate through interlayer sustained-release zinc borate. Simultaneously, a silane coupling agent and nitrile rubber enhance the interfacial bonding between the coating and the substrate, ultimately achieving comprehensive performance: Grade 1 adhesion, UL94 V-0 flame retardancy (LOI ≥ 42%), and salt spray resistance with a mass loss rate of ≤1.2% after 500 hours. Example 1 exhibits optimal performance due to the optimized component ratios and process parameters.

[0042] In Comparative Example 1, nanomagnesium oxide was replaced with aluminum hydroxide. Due to aluminum hydroxide's lower thermal stability and insufficient fiber bonding, the substrate layer structure became loose, resulting in adhesion dropping to Level 2, LOI dropping to 38%, and mass loss in the salt spray test increasing to 3.2%. This demonstrates that nanomagnesium oxide is irreplaceable in improving substrate thermal stability and interfacial bonding.

[0043] In Comparative Example 2, ammonium polyphosphate was removed and zinc borate was added to the CaAl-LDH system. Without the phosphorus-nitrogen synergistic effect of ammonium polyphosphate, the flame-retardant carbon layer failed to effectively expand and block heat, causing the LOI to drop to 36% and the UL94 rating to drop to V-2. Furthermore, slight concavity was observed after impact. This demonstrates that the synergistic effect of ammonium polyphosphate and the LDH system is crucial to flame retardancy.

[0044] In Comparative Example 3, CaAl-LDH loaded with zinc borate was replaced with pure LDH. Due to the lack of zinc borate's vapor-phase flame retardancy (release of water vapor and boric acid) and smoke suppression properties, the LOI dropped to 40%, and corrosion resistance declined. This validated the dual synergistic effects of loaded zinc borate on flame retardancy and corrosion protection.

[0045] In Comparative Example 4, LDH-loaded zinc borate was replaced with pure zinc borate. Direct addition of zinc borate resulted in poor dispersibility, weak interfacial bonding with the epoxy resin, and adhesion collapsed to level 3. The coating peeled off, with a mass loss rate as high as 5.8%. This highlights the necessity of LDH loading to improve zinc borate dispersibility and interfacial bonding.

[0046] In Comparative Example 5, the LDH loading was replaced with a CaAlZn-LDH co-precipitation. After zinc ion embedding into the LDH laminate, laminate rigidity increased, zinc borate slow-release efficiency decreased, and LOI dropped to 37%. However, cracking occurred after impact, and edge corrosion worsened. This demonstrates that the loading process is superior to the co-precipitation method in retaining structural flexibility.

[0047] In Comparative Example 6, the composite protective layer was omitted. Direct exposure of the substrate resulted in fracture after impact and severe degradation of flame retardancy, with a mass loss rate as high as 12.3% in the salt spray test. This demonstrates that the composite protective layer is the core carrier of flame retardancy and corrosion resistance.

[0048] In Comparative Example 7, the post-curing temperature was raised to 130°C. This excessively high temperature caused thermal stress in the coating, leading to surface cracking and a drop in adhesion to level 3, but the flame retardancy was not affected. This suggests that the curing process needs to balance the degree of crosslinking and internal stress, and avoid excessively high temperatures.

[0049] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A corrosion-resistant fireproof board, characterized in that: From bottom to top, it includes a base material layer and a composite protective layer; The substrate layer comprises the following raw materials in parts by weight: 55-65 parts of straw short fibers, 10-12 parts of nano magnesium oxide particles, 22-26 parts of calcium silicate powder, and 3-5 parts of polyvinyl alcohol adhesive; The composite protective layer comprises the following raw materials in parts by weight: 60-65 parts of epoxy resin, 25-30 parts of methyltetrahydrophthalic anhydride, 10-15 parts of CaAl-LDH-loaded zinc borate, 8-10 parts of nitrile rubber, 5-7 parts of silane coupling agent, 4-6 parts of ammonium polyphosphate, 10-12 parts of acetone, 10-12 parts of ethanol, and 1-2 parts of accelerator.

2. A corrosion-resistant fireproof board according to claim 1, characterized in that: The preparation method of the substrate layer includes: mixing straw short fibers pretreated with alkali solution, nano-magnesium oxide particles, calcium silicate powder and polyvinyl alcohol adhesive in proportion, adding deionized water to adjust the solid content to 40%-45%, continuously stirring at a speed of 1000 rpm or higher for 30-40 minutes to form a slurry, injecting the slurry into a mold, maintaining the slurry at a pressure of 10-12 MPa and a temperature of 75-85°C for 30-40 minutes, and transferring the slurry to a 55-65°C oven for drying for 22-26 hours after demolding.

3. A corrosion-resistant fireproof board according to claim 2, characterized in that: The alkali solution pretreatment step comprises: soaking the straw short fibers in a NaOH aqueous solution for 2-3 hours, then washing with clean water until neutral, centrifugally dehydrating, and then drying in an oven at 70-80° C. to a moisture content of ≤5%.

4. The corrosion-resistant fireproof board according to claim 1, characterized in that: The preparation method of the CaAl-LDH loaded with zinc borate comprises the following steps: dispersing the CaAl-LDH in deionized water, adding H3BO3 and Zn(NO3)2·6H2O, performing ultrasonic dispersion, adjusting the solution pH to 8.0±0.5, heating the solution to 55-65°C and stirring for 4-5 hours, centrifugally separating the precipitation, washing, and drying the solution.

5. The corrosion-resistant fireproof board according to claim 5, characterized in that: The weight ratio of the CaAl-LDH, deionized water, H3BO3 and Zn(NO3)2·6H2O is 20-24:500-550:120-130:85-95.

6. The corrosion-resistant fireproof board according to claim 5, characterized in that: The preparation method of the CaAl-LDH includes: dissolving 230-240 parts of Ca(NO3)2·4H2O and 155-167 parts of Al(NO3)3·6H2O in 500-540 parts of deionized water, stirring until completely dissolved to obtain a mixed salt solution; dissolving 100-120 parts of NaOH in 200-240 parts of deionized water, slowly adding the solution dropwise to the mixed salt solution, controlling the pH to 10.0±0.2, and continuously stirring for 2-3 hours; reacting at 95-105°C for 10-12 hours, centrifuging, washing with water, and drying to obtain CaAl-LDH.

7. The corrosion-resistant fireproof board according to claim 1, characterized in that: The preparation method of the composite protective layer includes: mixing CaAl-LDH-loaded zinc borate, a silane coupling agent, ammonium polyphosphate, acetone and ethanol, ultrasonically treating the mixture at 300-350W for 30-40 minutes, adding epoxy resin and nitrile rubber, stirring the mixture at 200-250rpm for 30-40 minutes, then increasing the stirring speed to 400-500rpm, and sequentially adding methyltetrahydrophthalic anhydride and a accelerator, and continuing stirring for 20-25 minutes to obtain the composite protective layer.

8. The method for preparing a corrosion-resistant fireproof board according to any one of claims 1 to 7, characterized in that: The following steps are involved: The composite protective layer is coated on the substrate layer by spraying twice and then solidified to obtain the composite protective layer, wherein the thickness of a single layer is 100-150 μm, and the interval between the two sprayings is 25-35 minutes.

9. The method for preparing a corrosion-resistant fireproof board according to claim 8, characterized in that: The spraying pressure is 18-20 MPa, the spray gun caliber is 1.3-1.5 mm, and the spray distance is 25-30 cm.

10. The method for preparing a corrosion-resistant fireproof board according to claim 8, characterized in that: The curing conditions include: pre-curing at room temperature for 24-26 hours, followed by post-curing in an oven at 100-120°C for 2-4 hours.

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