Fireproof coating material for color-coated aluminum plate strip and preparation method thereof

Abstract

This invention belongs to the field of coating technology, and specifically relates to a fire-retardant coating material for color-coated aluminum sheets and strips and its preparation method, comprising the following raw materials in parts by weight: 35-40 parts epoxy resin base, 25-30 parts composite modified flame retardant, 5-10 parts modified reinforcing filler, 3-6 parts char-forming accelerator, 1-2 parts dispersant, 0.5-1 part defoamer, 15-20 parts solvent, and 2-4 parts wear-resistant additive; wherein, the composite modified flame retardant is prepared by first modifying melamine cyanurate, then reacting it with a prepolymer synthesized from diethanolamine and adipic acid, and adding ammonium polyphosphate and expandable graphite; the modified reinforcing filler is prepared by treating silica with a silane coupling agent, and then reacting it with chitosan and zinc nitrate. This coating material, through the synergistic effect of its components, exhibits excellent fire resistance, adhesion, corrosion resistance, and bending resistance, and is suitable for surface protection of color-coated aluminum sheets and strips, effectively improving the fire resistance rating and service life of aluminum sheets and strips.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a fire-retardant coating material for color-coated aluminum sheets and strips and its preparation method. Background Technology

[0002] Color-coated aluminum sheets and strips are widely used in numerous fields such as construction, home appliances, and transportation. Their surface coating plays a crucial role in enhancing the performance of the aluminum sheets and strips. Especially in scenarios with stringent fire protection requirements, such as building exteriors, interior decoration, and appliance casings, the performance of fire-retardant coating materials directly affects the safety of people and property and the lifespan of products. Currently, commonly available fire-retardant coating materials for color-coated aluminum sheets and strips have many shortcomings. Some fire-retardant coating materials have poor fire resistance; when exposed to high temperatures or open flames, they cannot effectively prevent the spread of fire, failing to meet relevant fire safety standards and easily causing severe losses in the event of a fire. Simultaneously, some coating materials have poor durability. During long-term use, environmental factors (such as ultraviolet radiation, humidity, and temperature changes) can cause the coating to peel, powder, and crack, leading to a decline in fire resistance and requiring frequent maintenance or replacement, increasing usage costs and inconvenience.

[0003] Chinese Patent Application No. CN202211376708.8 discloses a powder coating for coil aluminum sheets and its preparation method. The powder coating comprises the following components in parts by weight: 55-90 parts carboxyl-terminated polyester resin, 5-15 parts curing agent, 1-25 parts surface-modified barium sulfate, 0-40 parts filler, 0-12 parts pigment, and 0-10 parts additives. The powder coating provided by this invention not only meets the coating process requirements for coil materials but also satisfies the thick coating requirements for coil aluminum sheets, while possessing advantages such as excellent thick coating flexibility, T-bending performance, impact resistance, solvent resistance, powder application performance, and scratch resistance. However, the coating's salt spray resistance and fire resistance are relatively weak, failing to provide long-term effective flame retardant, fireproof, and corrosion protection for aluminum sheets. Chinese Patent Application No. CN202111637750.6 discloses an anti-corrosion coating and its preparation method. The coating's raw materials, by weight, include the following components: 32-41 parts epoxy resin, 7-11 parts citric acid, 3-7 parts aluminum chloride hexahydrate, 10-16 parts polyacrylamide, 3-5 parts hydroxysulfonate betaine, 11-15 parts silica, 13-18 parts chitosan, 10-16 parts ethanol, 6-13 parts penetrant, 1-3 parts curing aid, and 55-71 parts solvent. The penetrant, by weight, includes the following components: 12-22 parts lignin fiber and 20-36 parts nano-silica sol. This invention can improve the adhesion between the coating and the aluminum plate, exhibiting excellent anti-corrosion effects. However, chitosan, polyacrylamide, and hydroxysulfobetaine in the formula are all highly hydrophilic substances. Therefore, moisture or other corrosive media can easily penetrate through the coating and reach the surface of the metal substrate, thereby causing the coating to blister or even peel off, greatly shortening its anti-corrosion life.

[0004] To address the aforementioned issues, developing a fire-retardant coating material for color-coated aluminum sheets and strips that exhibits excellent fire resistance and corrosion resistance, good durability, and stable overall performance is of significant practical importance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a fire-retardant coating material for color-coated aluminum sheets and strips and its preparation method. Through the synergistic effect of various components such as composite modified flame retardants, modified reinforcing fillers, and epoxy resin base materials, the fire-retardant coating material for color-coated aluminum sheets and strips exhibits excellent fire resistance, adhesion, corrosion resistance, and bending resistance. It is suitable for surface protection of color-coated aluminum sheets and strips and can effectively improve the fire resistance rating and service life of aluminum sheets and strips.

[0006] The technical solution of the present invention to solve the above problems is as follows:

[0007] A fire-retardant coating material for color-coated aluminum sheets and strips comprises the following raw materials in parts by weight: 35-40 parts epoxy resin base, 25-30 parts composite modified flame retardant, 5-10 parts modified reinforcing filler, 3-6 parts char-forming accelerator, 1-2 parts dispersant, 0.5-1 part defoamer, 15-20 parts solvent, and 2-4 parts wear-resistant additive;

[0008] The preparation method of the composite modified flame retardant is as follows:

[0009] Step S1: Add melamine cyanurate to deionized water, ultrasonically disperse for 30-40 min, add silane coupling agent KH-550, stir at 80-85℃ for 4-5 h, and obtain modified melamine cyanurate after post-treatment.

[0010] Step S2: Under an inert atmosphere, diethanolamine and adipic acid are reacted at 160-170℃ for 1.5-2.5h, and then the temperature is raised to 190-200℃ for 2.5-3.5h to obtain the prepolymer.

[0011] Step S3: Add the modified melamine cyanurate to N,N-dimethylformamide, stir to dissolve, then add the prepolymer and p-toluenesulfonic acid, stir at 120-130℃ for 6-8 hours, then add ammonium polyphosphate and expandable graphite and continue stirring for 2-2.5 hours. After post-treatment, the composite modified flame retardant is obtained.

[0012] Further, in step S1, the mass ratio of melamine cyanurate, silane coupling agent KH-550, and deionized water is 10:1-1.5:50-60.

[0013] Furthermore, the mass ratio of diethanolamine to adipic acid in step S2 is 5:8-10.

[0014] Further, in step S3, the mass ratio of modified melamine cyanurate, prepolymer, p-toluenesulfonic acid, ammonium polyphosphate, expandable graphite, and N,N-dimethylformamide is 11:10-14:0.2-0.3:4.5-5.5:1.5-2.5:30-40.

[0015] Furthermore, the preparation method of the modified reinforcing filler is as follows:

[0016] Step a: Add silica to deionized water, ultrasonically disperse for 50-60 min, add silane coupling agent KH-560, stir at 70-75℃ for 3-4 h, and obtain product 1 after post-treatment;

[0017] Step b: Add chitosan to an aqueous acetic acid solution, stir to dissolve, add product 1, stir at 65-70℃ for 5-6 hours, then add zinc nitrate, continue stirring for 2-3 hours, and obtain the modified reinforced filler after post-treatment.

[0018] Further, in step a, the mass ratio of silicon dioxide, silane coupling agent KH-560, and deionized water is 5:0.4-0.6:35-40.

[0019] Further, in step b, the mass ratio of chitosan, zinc nitrate, product 1, and acetic acid aqueous solution is 2-2.5:0.5-0.8:10:50-60.

[0020] Furthermore, the char-forming accelerator is pentaerythritol or dipentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene, and the wear-resistant additive is polytetrafluoroethylene micro powder.

[0021] This invention also provides a method for preparing a fire-retardant coating material for color-coated aluminum sheets and strips, comprising the following steps:

[0022] (1) Add epoxy resin base to part of the solvent, stir at 60-70℃ for 30-40 min, then add modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 75-85℃ and stir for 90-110 min, then add composite modified flame retardant in batches, stirring for 20-25 min after each addition to obtain a mixture;

[0023] (2) Ball mill the mixture for 2.5-3.5 hours, then add the remaining solvent, stir for 15-20 minutes, adjust the viscosity to 25-30 seconds, and filter to obtain the fireproof coating material for color-coated aluminum sheet and strip.

[0024] The present invention has the following beneficial effects:

[0025] The fire-retardant coating material for color-coated aluminum sheets and strips of this invention achieves significantly improved overall performance through the synergistic effect of multiple components, including a composite modified flame retardant, modified reinforcing filler, and epoxy resin matrix. The composite modified flame retardant constructs a multi-component, synergistic, and highly efficient flame-retardant system, achieving excellent flame-retardant effects through the synergistic action of both gas-phase and condensed-phase mechanisms: In terms of gas-phase flame retardancy, the composite modified flame retardant decomposes and releases inert gases such as nitrogen and carbon dioxide, diluting the concentration of oxygen and combustible gases and capturing free radicals to terminate chain reactions; in terms of condensed-phase flame retardancy, the composite modified flame retardant catalyzes the dehydration and cross-linking of epoxy resin and char-forming promoter to form a dense char layer, while simultaneously utilizing the thermal expansion of expandable graphite to further thicken the char layer. The synergistic effect of these two mechanisms rapidly inhibits flame spread, reduces combustion intensity, and effectively reduces burning drips to avoid the risk of secondary ignition, thereby endowing the coating with excellent fire resistance and overall fire safety. Modified reinforcing fillers not only enhance coating adhesion and corrosion resistance by acting as a rigid skeleton, but their excellent interfacial bonding with the resin matrix also prevents filler agglomeration, ensuring superior coating durability and flexural strength. At high temperatures, modified reinforcing fillers can synergistically enhance the density, thermal stability, and mechanical strength of the char layer through the flame-retardant system, forming a robust protective barrier and significantly delaying heat transfer to the aluminum substrate.

[0026] Furthermore, the char-forming accelerator, in conjunction with the flame-retardant system, accelerates the charring process and improves the quality of the char layer; the wear-resistant additive imparts excellent wear resistance and surface smoothness to the coating, extending its service life; and the dispersant and defoamer ensure the uniformity and defect-free film formation of the coating. In summary, the fire-retardant coating material for color-coated aluminum sheets and strips prepared by this invention possesses excellent fire safety, long-lasting durability, and good process adaptability, making it suitable for various application scenarios of color-coated aluminum sheets and strips. Attached Figure Description

[0027] Figure 1 The figures show the flame retardant performance results of the fire-retardant coating materials for color-coated aluminum sheets and strips prepared in Examples 1-4 and Comparative Examples 1-4 of this invention;

[0028] Figure 2 The figures show the fire resistance performance results of the fire-retardant coating materials for color-coated aluminum sheets and strips prepared in Examples 1-4 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] All raw materials used in the following examples are commercially available products. The color-coated aluminum sheet / strip has an aluminum content of 99.6%, is 1060 aluminum sheet / strip, and has a thickness of 0.3-2.0 mm; it is manufactured by Shandong Yanrun Metal Products Co., Ltd.; the epoxy resin base has an effective component content of 99% and a density of 1.2. Brand E-44, Shandong Luxing Chemical Co., Ltd.; Ammonium polyphosphate, effective ingredient content 99%, density 10. Average particle size <50μm, P content 31.5wt%, N content 14.5wt%, Nanjing Xinyi Synthetic Technology Co., Ltd.; Expandable graphite with fixed carbon content of 95%, expansion degree 300, particle size 50-200 mesh, Qingdao Mingrun Chenyue Graphite Co., Ltd.; Silica type CY-SP3OH, effective component content 99.8%, particle size 30nm, specific surface area 150-300 Hangzhou Jiupeng New Materials Co., Ltd.; Chitosan, effective ingredient content 98%, degree of deacetylation 90%, Shandong Pingju Biotechnology Co., Ltd.; Polycarboxylate dispersant, water-based wetting and dispersing agent 9673, effective ingredient content 25%, viscosity 1600 mPa·s, Guangzhou Huidigao Chemical Co., Ltd.; Organosilicon defoamer, effective ingredient content 40%, pH value 6.5-7.5, Shandong Wanhua Tianhe New Materials Co., Ltd.; Polytetrafluoroethylene micro powder, effective ingredient content 99%, density 2.2. Dongguan Hongyu Plastics Co., Ltd.

[0031] Example 1

[0032] A fire-retardant coating material for color-coated aluminum sheets and strips comprises the following raw materials in parts by weight: 35 parts epoxy resin base, 25 parts composite modified flame retardant, 5 parts modified reinforcing filler, 3 parts char-forming accelerator, 1 part dispersant, 0.5 parts defoamer, 15 parts solvent, and 2 parts wear-resistant additive.

[0033] The preparation method of the composite modified flame retardant is as follows:

[0034] Step S1: Melamine cyanurate was added to deionized water and ultrasonically dispersed for 35 min at a power of 400 W and a frequency of 40 kHz. Silane coupling agent KH-550 was added, and the mixture was stirred at 400 r / min for 4.5 h at 83 °C. After naturally cooling to room temperature, the mixture was filtered, washed three times with deionized water, and vacuum dried at 105 °C for 6 h to obtain modified melamine cyanurate. The mass ratio of melamine cyanurate, silane coupling agent KH-550, and deionized water was 10:1.3:55.

[0035] Step S2: Under a nitrogen atmosphere, diethanolamine and adipic acid are reacted at 165°C for 2 hours, then the temperature is raised to 195°C, the pressure is reduced to -0.09~-0.08 MPa and the reaction is carried out for 3 hours. After naturally cooling to room temperature, a prepolymer is obtained, wherein the mass ratio of diethanolamine to adipic acid is 5:9.

[0036] Step S3: Add modified melamine cyanurate to N,N-dimethylformamide, stir to dissolve, then add prepolymer and p-toluenesulfonic acid, stir at 125℃ and 500 r / min for 7 h, then add ammonium polyphosphate and expandable graphite and continue stirring for 2.2 h. Pour the reaction solution into acetone with a volume of 3 times the reaction solution to precipitate, filter, and vacuum dry the precipitate at 80℃ for 5 h, then pulverize to a particle size of 3-8 μm to obtain a composite modified flame retardant. The mass ratio of modified melamine cyanurate, prepolymer, p-toluenesulfonic acid, ammonium polyphosphate, expandable graphite, and N,N-dimethylformamide is 11:12:0.25:5:2:35.

[0037] The method for preparing the modified reinforced filler is as follows:

[0038] Step a: Add silica to deionized water and ultrasonically disperse for 55 min at a power of 400 W and a frequency of 40 kHz. Add silane coupling agent KH-560 and stir at 400 r / min for 3.5 h at 73 °C. After naturally cooling to room temperature, centrifuge at 8000 r / min for 20 min. Then wash three times with deionized water and vacuum dry at 80 °C for 3 h to obtain product 1. The mass ratio of silica, silane coupling agent KH-560 and deionized water is 5:0.5:38.

[0039] Step b: Add chitosan to a 1% acetic acid aqueous solution, stir to dissolve, add product 1, stir at 450 r / min for 5.5 h at 67℃, then add zinc nitrate, continue stirring for 2.5 h, adjust the pH of the reaction solution to 7-8 with 10% sodium hydroxide solution, centrifuge at 9000 r / min for 25 min, then wash with deionized water until neutral, vacuum dry at 100℃ and vacuum degree -0.08~-0.07 MPa for 5 h, pulverize and pass through a 300 mesh sieve to obtain the modified reinforcing filler, wherein the mass ratio of chitosan, zinc nitrate, product 1 and acetic acid aqueous solution is 2.3:0.6:10:55.

[0040] The char-forming accelerator is pentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene in a weight ratio of 3:2, and the wear-resistant additive is polytetrafluoroethylene micro powder.

[0041] The preparation method of the above-mentioned fire-retardant coating material for color-coated aluminum sheets and strips includes the following steps:

[0042] (1) Add epoxy resin base to two-thirds of the solvent, stir at 300 r / min for 30 min at 60℃, then add modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 75℃, increase the speed to 600 r / min and stir for 90 min, then add composite modified flame retardant in 4 parts, stirring for 20 min after each addition to obtain a mixture;

[0043] (2) The mixture was ball-milled at 2200 r / min for 2.5 h with a ball-to-material ratio of 2:1. Zirconia balls were selected with large, medium and small ball diameters of 1.2 mm, 1.0 mm and 0.8 mm respectively, and a weight ratio of 3:5:2. Then the remaining solvent was added and stirred for 15 min. The viscosity was adjusted to 25-30 s at 25 °C using a Forecast-4 cup. The mixture was then filtered through a 300 mesh screen to obtain the fireproof coating material for color-coated aluminum sheet and strip.

[0044] Example 2

[0045] A fire-retardant coating material for color-coated aluminum sheets and strips comprises the following raw materials in parts by weight: 40 parts epoxy resin base, 30 parts composite modified flame retardant, 10 parts modified reinforcing filler, 6 parts char-forming accelerator, 2 parts dispersant, 1 part defoamer, 20 parts solvent, and 4 parts wear-resistant additive.

[0046] The preparation methods of the composite modified flame retardant and the modified reinforcing filler are the same as in Example 1;

[0047] The char-forming accelerator is dipentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene in a weight ratio of 3:2, and the wear-resistant additive is polytetrafluoroethylene micro powder.

[0048] The preparation method of the above-mentioned fire-retardant coating material for color-coated aluminum sheets and strips includes the following steps:

[0049] (1) Add the epoxy resin base to two-thirds of the solvent, stir at 300 r / min at 70℃ for 40 min, then add the modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 85℃, increase the speed to 600 r / min and stir for 110 min, then add the composite modified flame retardant in 4 parts, stirring for 25 min after each addition to obtain the mixture;

[0050] (2) The mixture was ball-milled at 2200 r / min for 3.5 h with a ball-to-material ratio of 2:1. Zirconia balls were selected with large, medium and small ball diameters of 1.2 mm, 1.0 mm and 0.8 mm respectively, and a weight ratio of 3:5:2. Then the remaining solvent was added and stirred for 20 min. The viscosity was adjusted to 25-30 s at 25 °C using a Forecast-4 cup. The mixture was then filtered through a 300 mesh screen to obtain the fireproof coating material for color-coated aluminum sheet and strip.

[0051] Example 3

[0052] A fire-retardant coating material for color-coated aluminum sheets and strips comprises the following raw materials in parts by weight: 38 parts epoxy resin base, 27 parts composite modified flame retardant, 8 parts modified reinforcing filler, 4 parts char-forming accelerator, 1.5 parts dispersant, 0.8 parts defoamer, 18 parts solvent, and 3 parts wear-resistant additive.

[0053] The preparation methods of the composite modified flame retardant and the modified reinforcing filler are the same as in Example 1;

[0054] The char-forming accelerator is dipentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene in a weight ratio of 3:2, and the wear-resistant additive is polytetrafluoroethylene micro powder.

[0055] The preparation method of the above-mentioned fire-retardant coating material for color-coated aluminum sheets and strips includes the following steps:

[0056] (1) Add epoxy resin base to two-thirds of the solvent, stir at 300 r / min for 35 min at 65℃, then add modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 80℃, increase the speed to 600 r / min and stir for 100 min, then add composite modified flame retardant in 4 parts, stirring for 22 min after each addition to obtain a mixture;

[0057] (2) The mixture was ball-milled at 2200 r / min for 3 h with a ball-to-material ratio of 2:1. Zirconia balls were selected with large, medium and small ball diameters of 1.2 mm, 1.0 mm and 0.8 mm respectively, and a weight ratio of 3:5:2. Then the remaining solvent was added and stirred for 18 min. The viscosity was adjusted to 25-30 s at 25 °C using a Forecast-4 cup. The mixture was then filtered through a 300 mesh screen to obtain the fireproof coating material for color-coated aluminum sheet and strip.

[0058] Example 4

[0059] The preparation methods of the composite modified flame retardant and the modified reinforcing filler in this embodiment are different from those in Example 1, but all other aspects are the same as in Example 1.

[0060] The preparation method of the composite modified flame retardant is as follows:

[0061] Step S1: Melamine cyanurate was added to deionized water and ultrasonically dispersed for 40 min at a power of 400 W and a frequency of 40 kHz. Silane coupling agent KH-550 was added, and the mixture was stirred at 85 °C and 400 r / min for 5 h. After naturally cooling to room temperature, the mixture was filtered, washed three times with deionized water, and vacuum dried at 105 °C for 6 h to obtain modified melamine cyanurate. The mass ratio of melamine cyanurate, silane coupling agent KH-550, and deionized water was 10:1.5:60.

[0062] Step S2: Under a nitrogen atmosphere, diethanolamine and adipic acid are reacted at 170°C for 2.5 h, then the temperature is raised to 200°C, the pressure is reduced to -0.09~-0.08 MPa and the reaction is carried out for 3.5 h. After naturally cooling to room temperature, a prepolymer is obtained, wherein the mass ratio of diethanolamine to adipic acid is 5:10.

[0063] Step S3: Add modified melamine cyanurate to N,N-dimethylformamide, stir to dissolve, then add prepolymer and p-toluenesulfonic acid, stir at 130℃ and 500 r / min for 8 h, then add ammonium polyphosphate and expandable graphite and continue stirring for 2.5 h. Pour the reaction solution into acetone with a volume of 3 times the reaction solution to precipitate, filter, and vacuum dry the precipitate at 80℃ for 5 h, then pulverize to a particle size of 3-8 μm to obtain a composite modified flame retardant. The mass ratio of modified melamine cyanurate, prepolymer, p-toluenesulfonic acid, ammonium polyphosphate, expandable graphite, and N,N-dimethylformamide is 11:14:0.3:5.5:2.5:40.

[0064] The method for preparing the modified reinforced filler is as follows:

[0065] Step a: Add silica to deionized water and ultrasonically disperse for 60 min at a power of 400 W and a frequency of 40 kHz. Add silane coupling agent KH-560 and stir at 400 r / min for 4 h at 75 °C. After naturally cooling to room temperature, centrifuge at 8000 r / min for 20 min. Then wash three times with deionized water and vacuum dry at 80 °C for 3 h to obtain product 1. The mass ratio of silica, silane coupling agent KH-560 and deionized water is 5:0.6:40.

[0066] Step b: Add chitosan to a 1% acetic acid aqueous solution, stir to dissolve, add product 1, stir at 70℃ and 450 r / min for 6 h, then add zinc nitrate, continue stirring for 3 h, adjust the pH of the reaction solution to 7-8 with 10% sodium hydroxide solution, centrifuge at 9000 r / min for 25 min, then wash with deionized water until neutral, vacuum dry at 100℃ and vacuum degree -0.08~-0.07 MPa for 5 h, pulverize and pass through a 300 mesh sieve to obtain the modified reinforcing filler, wherein the mass ratio of chitosan, zinc nitrate, product 1 and acetic acid aqueous solution is 2.5:0.8:10:60.

[0067] Comparative Example 1

[0068] A fire-retardant coating material for color-coated aluminum sheets and strips comprises the following raw materials in parts by weight: 30 parts epoxy resin base, 20 parts composite modified flame retardant, 1 part modified reinforcing filler, 4 parts char-forming accelerator, 1.5 parts dispersant, 0.8 parts defoamer, 18 parts solvent, and 3 parts wear-resistant additive.

[0069] The preparation method of the composite modified flame retardant is as follows:

[0070] Step S1: Melamine cyanurate was added to deionized water and ultrasonically dispersed for 35 min at a power of 400 W and a frequency of 40 kHz. Silane coupling agent KH-550 was added, and the mixture was stirred at 400 r / min for 4.5 h at 50 °C. After naturally cooling to room temperature, the mixture was filtered, washed three times with deionized water, and vacuum dried at 105 °C for 6 h to obtain modified melamine cyanurate. The mass ratio of melamine cyanurate, silane coupling agent KH-550, and deionized water was 10:0.1:55.

[0071] Step S2: Under a nitrogen atmosphere, diethanolamine and adipic acid are reacted at 165°C for 1 hour, then the temperature is raised to 195°C, the pressure is reduced to -0.09~-0.08 MPa and the reaction is carried out for 3 hours. After naturally cooling to room temperature, a prepolymer is obtained, wherein the mass ratio of diethanolamine to adipic acid is 1:1.

[0072] Step S3: Add modified melamine cyanurate to N,N-dimethylformamide, stir to dissolve, then add prepolymer and p-toluenesulfonic acid, stir at 500 r / min for 1 h at 50℃, then add ammonium polyphosphate and expandable graphite and continue stirring for 2.2 h. Pour the reaction solution into acetone with a volume of 3 times the reaction solution to precipitate, filter, and vacuum dry the precipitate at 80℃ for 5 h, then pulverize to a particle size of 3-8 μm to obtain a composite modified flame retardant. The mass ratio of modified melamine cyanurate, prepolymer, p-toluenesulfonic acid, ammonium polyphosphate, expandable graphite, and N,N-dimethylformamide is 11:5:0.25:5:2:35.

[0073] The method for preparing the modified reinforced filler is as follows:

[0074] Step a: Add silica to deionized water and ultrasonically disperse for 20 min at a power of 400 W and a frequency of 40 kHz. Add silane coupling agent KH-560 and stir at 400 r / min for 1 h at 73 °C. After naturally cooling to room temperature, centrifuge at 8000 r / min for 20 min. Then wash three times with deionized water and vacuum dry at 80 °C for 3 h to obtain product 1. The mass ratio of silica, silane coupling agent KH-560 and deionized water is 5:0.1:38.

[0075] Step b: Add chitosan to a 1% acetic acid aqueous solution, stir to dissolve, add product 1, stir at 450 r / min for 5.5 h at 40℃, then add zinc nitrate, continue stirring for 2.5 h, adjust the pH of the reaction solution to 7-8 with 10% sodium hydroxide solution, centrifuge at 9000 r / min for 25 min, then wash with deionized water until neutral, vacuum dry at 100℃ and vacuum degree -0.08~-0.07 MPa for 5 h, pulverize and pass through a 300 mesh sieve to obtain the modified reinforcing filler, wherein the mass ratio of chitosan, zinc nitrate, product 1 and acetic acid aqueous solution is 1:0.6:10:55.

[0076] The char-forming accelerator is dipentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene in a weight ratio of 3:2, and the wear-resistant additive is polytetrafluoroethylene micro powder.

[0077] The preparation method of the above-mentioned fire-retardant coating material for color-coated aluminum sheets and strips includes the following steps:

[0078] (1) Add epoxy resin base to two-thirds of the solvent, stir at 300 r / min for 35 min at 40℃, then add modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 80℃, increase the speed to 600 r / min and stir for 20 min, then add composite modified flame retardant and stir for 22 min to obtain the mixture;

[0079] (2) The mixture was ball-milled at 2200 r / min for 1 h with a ball-to-material ratio of 2:1. Zirconia balls were selected with large, medium and small ball diameters of 1.2 mm, 1.0 mm and 0.8 mm respectively, and a weight ratio of 3:5:2. Then the remaining solvent was added and stirred for 18 min. The viscosity was adjusted to 25-30 s at 25 °C using a Forecast-4 cup. The mixture was then filtered through a 300 mesh screen to obtain the fireproof coating material for color-coated aluminum sheet and strip.

[0080] Comparative Example 2

[0081] In this comparative example, commercially available melamine cyanurate was used instead of the composite modified flame retardant, and all other aspects were the same as in Example 1.

[0082] Comparative Example 3

[0083] In this comparative example, commercially available silica was used instead of the modified reinforcing filler, and all other aspects were the same as in Example 1.

[0084] Comparative Example 4

[0085] In this comparative example, commercially available melamine cyanurate was used instead of the composite modified flame retardant, and commercially available silica was used instead of the modified reinforcing filler. All other aspects were the same as in Example 1.

[0086] The fire-retardant coating materials for color-coated aluminum sheets and strips prepared in Examples 1-4 and Comparative Examples 1-4 were applied to the surface of the color-coated aluminum sheets and strips using a roller coating method. The linear speed was 20-30 m / min, the roller temperature was 25-35℃, the roller speed ratio was upper roller / lower roller = 1.05-1.1, and the wet film thickness was 20-25 μm. Then, the sheets were baked at a low temperature of 80-90℃ for 2-3 min, cured at a high temperature of 180-200℃ for 15-20 min, and allowed to cool naturally to room temperature to obtain the fire-retardant color-coated aluminum sheets and strips.

[0087] The performance of the fire-retardant coating materials for color-coated aluminum sheets and strips prepared in Examples 1-4 and Comparative Examples 1-4, and the fire-retardant color-coated aluminum sheets and strips treated with the coating materials prepared in the four examples and four comparative examples were tested. The results are recorded in Table 1. Figure 1-2 .

[0088] Fire resistance: The burning drip test shall be conducted in accordance with the requirements of GB / T 20284-2006 "Burn test of building materials or products", and the fire resistance limit test shall be conducted in accordance with the requirements of GB / T 9978.1-2008 "Fire resistance test method for building components - Part 1: General requirements" (the requirement is to meet the requirements of thermal insulation and integrity, with no penetrating cracks or continuous burning).

[0089] Adhesion: Tested according to the requirements of GB / T 9286-2021 "Paints and Varnishes - Cross-cut Test", where the cut spacing is 1 mm, adhesion grade 0 means the cut edges are completely smooth and there is no peeling within the grid; adhesion grade 1 means there is a small amount of coating peeling at the cut intersections, but the affected cross-cut area is no more than 5%; adhesion grade 2 means there is coating peeling at the cut intersections and / or along the cut edges, and the affected cross-cut area is greater than 5% but not more than 15%.

[0090] Bending performance: The test shall be conducted in accordance with the requirements of GB / T 6742-2007 "Bending test of paints and varnishes (cylindrical shaft)" using a Type II bending tester.

[0091] Corrosion resistance: Tested according to the requirements of GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes", with a salt spray treatment time of 1000h.

[0092] Table 1 Performance Tests

[0093]

[0094] From Table 1 and Figure 1-2 It can be seen that the fire-retardant coating materials for color-coated aluminum sheets and strips prepared in Examples 1-4 have strong adhesion, excellent fire resistance, and perform well in bending and salt spray tests, all of which are superior to Comparative Example 1. This indicates that the formulation and test parameters proposed in this invention for preparing fire-retardant coating materials are optimal.

[0095] From Table 1 and Figure 1-2 It can be seen that the flame retardancy and fire resistance of the coating material prepared in Comparative Example 2 decreased, that is, the combustion dripping situation worsened and the fire resistance limit was shortened. This is because commercially available melamine cyanurate replaced the composite modified flame retardant. The composite modified flame retardant is a multi-component synergistic flame retardant system. Its main functions are to inhibit flame spread, reduce combustion intensity, inhibit the generation of combustion dripping, avoid the risk of secondary ignition, and work synergistically with resin base material and reinforcing filler to maintain the structural stability of the coating at high temperature. In the composite modified flame retardant, melamine cyanurate decomposes upon heating, releasing inert gases such as nitrogen and carbon dioxide, which dilute the concentration of oxygen and combustible gases in the combustion zone. The cyanuric acid derivatives produced during decomposition can capture free radicals, terminate the combustion chain reaction, and inhibit flame spread. After surface modification with silane coupling agent KH-550, its compatibility with epoxy resin is improved, effectively preventing agglomeration. The prepolymer generated by the reaction of diethanolamine and adipic acid anchors the flame retardant components in the resin system through chemical bonding, improving flame retardant durability and coating integrity. In the composite modified flame retardant, ammonium polyphosphate decomposes upon heating to produce phosphoric acid, which catalyzes the dehydration and carbonization of epoxy resin and char-forming accelerator to form a dense and porous carbon layer. Expandable graphite expands upon heating to thicken the carbon layer, forming a physical barrier layer that blocks heat transfer and gas-phase mass transfer. Melamine derivatives from the decomposition of modified melamine cyanurate crosslink with the carbon layer, enhancing the density and high-temperature resistance of the coating. Therefore, the composite modified flame retardant, through the synergistic effect of multiple mechanisms such as gas phase and condensed phase char formation, constructs an efficient and stable fire protection system. It not only achieves excellent flame retardant and fireproof performance, but also improves the interfacial bonding force with the resin matrix, thereby enhancing the coating adhesion, durability and toughness, and ensuring that the color-coated aluminum sheet and strip have fireproof, corrosion-resistant and stable mechanical properties and durability.

[0096] From Table 1 and Figure 1-2It can be seen that the adhesion, corrosion resistance and bending resistance of the coating material prepared in Comparative Example 3 all decreased. This is because commercially available silica replaced the modified reinforcing filler. The modified reinforcing filler enhances the mechanical properties of the coating, improves adhesion, improves the dispersibility of the filler in the system, avoids agglomeration affecting the uniformity of the coating, and can also synergistically retard flame, optimize char quality, and improve the fire resistance stability of the coating. The silica in the modified reinforcing filler acts as a rigid skeleton, enhancing the adhesion and heat resistance of the coating and forming a stable silicate network at high temperatures, effectively supporting the char layer. After modification with silane coupling agent KH-560, organic functional groups are introduced onto its surface, significantly improving its compatibility with epoxy resin and preventing the agglomeration of inorganic fillers. The amino and hydroxyl groups in the chitosan in the modified reinforcing filler combine with the surface functional groups of product 1 to form a three-dimensional network structure. Zinc nitrate acts as a crosslinking point to further strengthen this network, thereby blocking the penetration of water vapor, oxygen, and corrosive ions and improving corrosion resistance. Furthermore, as a nitrogen-containing organic compound, chitosan promotes char formation and forms a nitrogen-containing flame-retardant layer at high temperatures. Silica fills the pores of the char layer, making it more compact and effectively hindering heat conduction and the volatilization of combustibles. Zinc ions can also catalyze the crosslinking of epoxy resin, improving the thermal stability and bending resistance of the coating.

[0097] From Table 1 and Figure 1-2 It is evident that the coating material prepared in Comparative Example 4 exhibited the worst performance across all aspects. This is because commercially available melamine cyanurate replaced the composite modified flame retardant, and commercially available silica replaced the modified reinforcing filler. The modified reinforcing filler and the composite modified flame retardant worked synergistically to construct an efficient and robust fire protection system. The composite modified flame retardant primarily functions as a flame retardant, rapidly forming a porous, expanding initial char layer through gas-phase and condensed-phase mechanisms, thus acting as a basic barrier for heat and oxygen insulation. The modified reinforcing filler, on the other hand, serves as a crucial structural reinforcement. The rigid silica framework supports the char layer at high temperatures, preventing collapse, while the cross-linked network formed by chitosan and zinc nitrate further enhances the density and integrity of the char layer. This allows the coating to effectively block heat and combustible gases, significantly improving its adhesion, corrosion resistance, and durability. Therefore, the simultaneous introduction of both the composite modified flame retardant and the modified reinforcing filler not only endows the color-coated aluminum strip with excellent fire resistance but also ensures the coating's superior mechanical strength, durability, and corrosion resistance.

[0098] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fire-retardant coating material for color-coated aluminum sheets and strips, characterized in that, The raw materials include the following parts by weight: 35-40 parts epoxy resin base, 25-30 parts composite modified flame retardant, 5-10 parts modified reinforcing filler, 3-6 parts char formation accelerator, 1-2 parts dispersant, 0.5-1 part defoamer, 15-20 parts solvent, and 2-4 parts wear-resistant additive. The preparation method of the composite modified flame retardant is as follows: Step S1: Melamine cyanurate is added to deionized water and ultrasonically dispersed for 30-40 min. Silane coupling agent KH-550 is added and stirred at 80-85℃ for 4-5 h. After post-treatment, modified melamine cyanurate is obtained. The mass ratio of melamine cyanurate, silane coupling agent KH-550, and deionized water is 10:1-1.5:50-60. Step S2: Under an inert atmosphere, diethanolamine and adipic acid are reacted at 160-170℃ for 1.5-2.5h, and then the temperature is raised to 190-200℃ for 2.5-3.5h to obtain a prepolymer. The mass ratio of diethanolamine to adipic acid is 5:8-10. Step S3: Add modified melamine cyanurate to N,N-dimethylformamide, stir to dissolve, then add prepolymer and p-toluenesulfonic acid, stir at 120-130℃ for 6-8 hours, then add ammonium polyphosphate and expandable graphite and continue stirring for 2-2.5 hours. After post-treatment, a composite modified flame retardant is obtained. The mass ratio of modified melamine cyanurate, prepolymer, p-toluenesulfonic acid, ammonium polyphosphate, expandable graphite, and N,N-dimethylformamide is 11:10-14:0.2-0.3:4.5-5.5:1.5-2.5:30-40. The method for preparing the modified reinforced filler is as follows: Step a: Add silica to deionized water, ultrasonically disperse for 50-60 min, add silane coupling agent KH-560, stir at 70-75℃ for 3-4 h, and obtain product 1 after post-treatment; Step b: Add chitosan to an aqueous acetic acid solution, stir to dissolve, add product 1, stir at 65-70℃ for 5-6 hours, then add zinc nitrate, continue stirring for 2-3 hours, and obtain the modified reinforced filler after post-treatment.

2. The fire-retardant coating material for color-coated aluminum sheets and strips according to claim 1, characterized in that, The mass ratio of silica, silane coupling agent KH-560, and deionized water in step a is 5:0.4-0.6:35-40.

3. The fire-retardant coating material for color-coated aluminum sheets and strips according to claim 1, characterized in that, The mass ratio of chitosan, zinc nitrate, product 1, and acetic acid aqueous solution in step b is 2-2.5:0.5-0.8:10:50-60.

4. The fire-retardant coating material for color-coated aluminum sheets and strips according to claim 1, characterized in that, The char-forming accelerator is pentaerythritol or dipentaerythritol, the dispersant is a polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the solvent is a mixture of ethylene glycol ethyl ether and xylene, and the wear-resistant additive is polytetrafluoroethylene micro powder.

5. The method for preparing the fire-retardant coating material for color-coated aluminum sheets and strips according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Add epoxy resin base to part of the solvent, stir at 60-70℃ for 30-40 min, then add modified reinforcing filler, char accelerator, wear resistant agent, dispersant and defoamer, heat to 75-85℃ and stir for 90-110 min, then add composite modified flame retardant in batches, stirring for 20-25 min after each addition to obtain a mixture; (2) Ball mill the mixture for 2.5-3.5 hours, then add the remaining solvent, stir for 15-20 minutes, adjust the viscosity to 25-30 seconds, and filter to obtain the fireproof coating material for color-coated aluminum sheet and strip.

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