A modified graphene oxide waterborne intumescent fire-retardant coating and its preparation method

Abstract

This invention relates to the field of fire-retardant coating technology, specifically to a modified graphene oxide water-based intumescent fire-retardant coating and its preparation method. The coating formulation includes deionized water, ammonium polyphosphate, melamine, pentaerythritol, titanium dioxide, graphene oxide-modified aerogel, wetting and dispersing agent, defoamer, film-forming aid, and emulsion. This invention uses magnesium zirconium aerogel and graphene oxide to prepare graphene oxide-modified aerogel via organosilane. This aerogel can be more uniformly dispersed in the fire-retardant coating and synergistically enhances the barrier effect with titanium dioxide; simultaneously, the coating has a foaming ratio as high as 30-45 times, and can continuously expand and foam from low to high temperatures in a fire, thereby continuously and effectively isolating the temperature conduction between the flame and the protective components, thus improving the fire-retardant performance of the coating and increasing the safety and service life of the substrate.

Description

Technical Field

[0001] This invention relates to the field of fire-retardant coating technology, and in particular to a modified graphene oxide water-based intumescent fire-retardant coating and its preparation method. Background Technology

[0002] Fire-retardant coatings are primarily applied to the surfaces of steel structures. They effectively slow the spread of flames, improve the fire resistance of steel, and reduce fire hazards such as the collapse of industrial components and buildings due to the loss of strength in high-temperature environments. Intumescent fire-retardant coatings are widely used in industrial and engineering fire protection systems due to their decorative properties and cost-effectiveness.

[0003] Nanomaterials possess many superior properties, enabling them to fill internal defects in coatings and enhance overall adhesion. Graphene is composed of carbon atoms and sp atoms. 2 Two-dimensional carbon nanomaterials composed of a hexagonal honeycomb lattice with hybrid orbitals maintain a near-perfect crystal structure and excellent crystallographic properties, exhibiting superior mechanical properties and thermal stability. Aerogels are solid materials with excellent thermal insulation properties, possessing a unique microstructure including high specific surface area, nanoscale pores, and low density. Based on these structural characteristics, they can exhibit excellent thermal performance.

[0004] Currently, water-based intumescent fire-retardant coatings in practical applications suffer from many problems, such as poor coating expansion and foaming performance, weak char layer strength, and inability to continuously and effectively isolate the temperature conduction between the flame and the substrate. The addition of graphene oxide and aerogel can effectively improve the overall adhesion strength of the coating, increase the expansion coefficient, enhance the char layer strength, form a dense, sponge-like porous structure, reduce the thermal conductivity of the char layer, effectively delay the temperature rise of the protective substrate, and thus improve the fire resistance of the fire-retardant coating. Patent CN201611241904.9 discloses a water-based graphene intumescent fire-retardant coating. The components and contents of this fire-retardant coating are as follows: 80 parts of water-based film-forming matrix, 0.2-0.8 parts of graphene oxide, 150-180 parts of melamine pyrophosphate, 10-15 parts of titanium dioxide, 10-20 parts of porous material, 1-2 parts of additives, and 200-250 parts of water. Microwave technology is used to graft and modify graphene oxide, which then reacts with melamine pyrophosphate as an acid and gas source to generate a "skeleton" structure to reinforce the carbon layer, thereby enhancing the flame retardancy of the coating. However, this method has limited flame retardant protection, and the adhesion strength of the coating is unknown. If the adhesion of the fire-retardant coating is not high, it is easy to lose its fire-retardant effect due to peeling.

[0005] Patent CN202210483653.4 discloses a multi-layer fire-retardant coating for steel structures of high-rise buildings. It includes a base layer and a top layer; the base layer is a non-intumescent fire-retardant coating using EVA redispersible polymer powder as an additive; the top layer is an intumescent fire-retardant coating formed by introducing nano-graphene into a nitrogen-carbon-phosphorus system. This method requires designing two coating layers, making the process relatively complex, and the bonding strength between the two layers is difficult to guarantee.

[0006] Therefore, it is necessary to provide a modified graphene oxide waterborne intumescent fire-retardant coating to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to provide a modified graphene oxide waterborne intumescent fire-retardant coating and its preparation method. The modified graphene oxide aerogel is prepared by using magnesium zirconium aerogel and graphene oxide through organosilane. It can be more uniformly dispersed in the coating to effectively reduce the thermal conductivity of the coating. At the same time, it can also synergistically enhance the barrier effect with titanium dioxide, thereby improving the fire-retardant performance of the coating and improving the safety and service life of the substrate.

[0008] To achieve the above objectives, the present invention first provides a method for preparing graphene oxide modified aerogel, comprising the following steps:

[0009] S1. Add inorganic magnesium salt and inorganic zirconium salt to organic solvent and deionized water, add catalyst to react, then dry, crush and calcine to obtain magnesium zirconium aerogel;

[0010] S2. After the magnesium zirconium aerogel is mixed and dispersed evenly with graphene oxide, a silane coupling agent is added to react and obtain graphene oxide modified magnesium zirconium aerogel.

[0011] This aerogel can be more evenly dispersed inside the coating to effectively reduce the thermal conductivity of the coating. At the same time, it can also synergistically enhance the barrier effect with titanium dioxide, thereby improving the fire resistance of the coating. Therefore, the graphene oxide modified aerogel prepared by this invention is a good fire-retardant additive.

[0012] Furthermore, the inorganic magnesium salt and inorganic zirconium salt satisfy the requirement that zirconium accounts for 1-20% of the total amount of zirconium and magnesium, preferably 5-15%. The composite aerogel formed by the two has a good synergistic flame retardant effect with graphene oxide.

[0013] Furthermore, the mass ratio of the magnesium zirconium aerogel to graphene oxide is 1:(0.1~0.5).

[0014] The ratio of the amount of catalyst added to the sum of the masses of the inorganic magnesium salt and the inorganic zirconium salt is (0.9 to 1.3):1.

[0015] Furthermore, the calcination temperature is 500–700℃, and the time is 1–5 hours. Calcination promotes the formation of a porous aerogel structure. After crushing, the aerogel powder is passed through a 100–200 mesh sieve and then calcined to facilitate the formation of the porous structure and its subsequent application in coatings.

[0016] Furthermore, after adding a silane coupling agent, the reaction was carried out at 70–90 °C for 1–5 h, followed by filtration, washing, and drying to obtain graphene oxide-modified magnesium zirconium aerogel. The silane coupling agent facilitates the grafting reaction between graphene oxide and magnesium zirconium aerogel, while also improving their compatibility and dispersibility.

[0017] Furthermore, the silane coupling agent comprises one or more of γ-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyltriethoxysilane, acryloyloxypropyltrimethoxysilane, vinyltriisopropoxysilane, γ-methacryloyloxypropyltriisopropoxysilane, and propenyltrimethoxysilane;

[0018] Furthermore, the inorganic magnesium salt includes one or more of magnesium sulfate, magnesium nitrate, and magnesium chloride;

[0019] The inorganic zirconium salt includes one or more of zirconium chloride, zirconium nitrate, and zirconium sulfate;

[0020] The catalyst includes one of oxalic acid, glacial acetic acid, and formic acid;

[0021] The organic solvent includes one or more of methanol, ethanol, propanol, and isopropanol. The volume ratio of the organic solvent to deionized water is (3-6):1.

[0022] The present invention also provides a modified graphene oxide waterborne intumescent fire retardant coating, comprising graphene oxide modified aerogel obtained by any of the preparation methods described above.

[0023] Furthermore, the fire-retardant coating also includes flame retardants and titanium dioxide, wherein the flame retardants are phosphorus-based and / or nitrogen-based flame retardants. The flame retardants form a barrier carbon layer, which plays a major role in fire prevention and flame retardancy. At the same time, the graphene oxide-modified aerogel and titanium dioxide synergistically enhance the barrier effect, and the foaming rate is as high as 30-45 times. In the fire scene, it can continuously expand and foam from low temperature to high temperature, thereby continuously and effectively isolating the temperature conduction between the flame and the protective components, thereby improving the fire resistance performance of the coating and improving the safety and service life of the substrate.

[0024] Preferably, the amount of graphene oxide modified aerogel added is 0.001%-2% of the mass of the fire-retardant coating, the amount of titanium dioxide added is 8%-10% of the mass of the fire-retardant coating, and the amount of flame retardant added is 30%-75% of the mass of the fire-retardant coating.

[0025] Furthermore, fire-retardant coatings include deionized water, ammonium polyphosphate, melamine, pentaerythritol, titanium dioxide, graphene oxide modified aerogel, wetting and dispersing agents, defoamers, film-forming aids, and emulsions.

[0026] Furthermore, by mass percentage, it includes:

[0027]

[0028] Furthermore, the wetting and dispersing agent is one or more of block polymers, nonionic surfactants, and polyunsaturated hydrochloric acid.

[0029] And / or, the film-forming aid is one or more of propylene glycol methyl ether, ethylene glycol ethyl ether, and hexanediol;

[0030] The defoamer's main components are one or more of mineral oil containing hydrophobic particles, emulsified polysiloxane, and polysiloxane containing hydrophobic particles.

[0031] The emulsion is an aqueous vinyl acetate-ethylene emulsion. Optionally, the vinyl acetate-ethylene emulsion is a low-VOCs vinyl acetate-ethylene emulsion EZ3112.

[0032] The present invention also provides a method for preparing the modified graphene oxide waterborne intumescent fire-retardant coating as described in any one of the above claims, comprising the following steps:

[0033] Graphene oxide-modified aerogel and wetting and dispersing agent are mixed evenly in water; then ammonium polyphosphate, pentaerythritol, melamine and titanium dioxide are added and stirred until evenly dispersed; then emulsion, film-forming aid and defoamer are added and stirred evenly to obtain fire-retardant coating.

[0034] Furthermore, this includes the following steps:

[0035] The graphene oxide-modified aerogel and wetting and dispersing agent are dispersed and stirred in water at a speed of 700-900 r / min for 8-15 min to ensure uniform mixing. Then, ammonium polyphosphate, pentaerythritol, melamine and titanium dioxide are added and stirred at a speed of 1300-1700 r / min for 20-40 min to ensure uniform dispersion. Finally, emulsion, film-forming aid and defoamer are added and stirred at a speed of 500-800 r / min for 8-15 min to obtain the fire-retardant coating.

[0036] Graphene oxide possesses excellent mechanical properties and thermal stability, among which the sp bonds of C and C are particularly valuable. 2 Hybrid properties are the reason for its excellent mechanical properties. Aerogel is a solid material with excellent thermal insulation properties, possessing a unique microstructure such as high specific surface area, nanoscale pores, and low density. Based on these structures, graphene oxide-modified aerogel exhibits excellent thermal properties. Furthermore, graphene oxide-modified magnesium zirconium aerogel can synergistically enhance the thermal stability and strength of the char layer with titanium dioxide, thereby strengthening the fire resistance and protective capabilities of water-based intumescent fire-retardant coatings, providing important protection for industrial and engineering development.

[0037] The beneficial effects of this invention are as follows:

[0038] The modified graphene oxide waterborne intumescent fire-retardant coating provided by this invention utilizes magnesium zirconium oxide aerogel and graphene oxide prepared via organosilane to create a graphene oxide-modified aerogel. This aerogel can be more uniformly dispersed within the coating, exhibiting a nano-filling effect, improving the overall adhesion of the coating, and effectively reducing the thermal conductivity of the coating. Simultaneously, it can synergistically enhance the barrier effect with titanium dioxide. The resulting coating has a foaming ratio as high as 30-45 times, and can continuously expand and foam from low to high temperatures in a fire, thereby continuously and effectively isolating the temperature conduction between the flame and the protective components, thus improving the fire-retardant performance of the coating, as well as the safety and service life of the substrate. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] Example 1

[0041] Step 1: Preparation of graphene oxide modified aerogel

[0042] First, magnesium nitrate hexahydrate and zirconium nitrate pentahydrate were dissolved in ethanol and deionized water in a 4:1 ratio, with zirconium atoms accounting for 0.1% of the total number of zirconium and magnesium atoms, to obtain a mixture. Oxalic acid of the same mass as magnesium nitrate and zirconium nitrate was slowly added dropwise to the mixture while stirring continuously to obtain a viscous gel. After standing for 12 hours, the gel was dried at 100°C for 24 hours.

[0043] The dried solid was ground and passed through a 120-mesh sieve to obtain gel powder, which was then decomposed at 600℃ for 3 hours to obtain magnesium zirconium aerogel.

[0044] Magnesium zirconium aerogel and graphene oxide were mixed in an ethanol solution at a mass ratio of 1:0.1 and ultrasonically dispersed at 15°C for 30 min to obtain a mixture. Then, 0.1 parts of γ-aminopropyltriethoxysilane were added, and the mixture was reacted at 80°C for 3 hours. After the reaction was completed, the reaction solution was cooled to room temperature and filtered. It was washed three times with a 1:1 ethanol-water solution and then dried at 50°C for 10 hours to obtain graphene oxide modified aerogel.

[0045] Step 2: Preparation of modified graphene oxide waterborne intumescent fire-retardant coating

[0046] 1g of graphene oxide modified aerogel was transferred to a dispersion tank containing 100ml of deionized water and a wetting and dispersing agent was added. The mixture was stirred at 800r / min for 10min to ensure uniform mixing. Then, 30g of ammonium polyphosphate, 15g of pentaerythritol, 15g of melamine, and 8g of titanium dioxide were added to the dispersion tank in sequence. The speed of the dispersion tank was adjusted to 1500r / min and stirred for 30min to ensure complete dispersion of the powder materials. The speed of the dispersion tank was then adjusted to 700r / min, and 15g of emulsion, 2g of film-forming aid, and 1g of defoamer were added to the tank in sequence. The mixture was stirred for 10min to ensure complete mixing, thus obtaining the fire-retardant coating.

[0047] Example 2

[0048] Step 1: Preparation of graphene oxide modified aerogel

[0049] First, magnesium nitrate hexahydrate and zirconium nitrate pentahydrate were dissolved in ethanol and deionized water in a 4:1 ratio, with zirconium atoms accounting for 0.01% of the total number of zirconium and magnesium atoms, to obtain a mixture. Oxalic acid of the same mass as magnesium nitrate and zirconium nitrate was slowly added dropwise to the mixture while stirring continuously to obtain a viscous gel. After standing for 12 hours, the gel was dried at 100°C for 24 hours.

[0050] The dried solid was ground and passed through a 120-mesh sieve to obtain gel powder, which was then decomposed at 600℃ for 3 hours to obtain magnesium zirconium aerogel.

[0051] Magnesium zirconium aerogel and graphene oxide were mixed in an ethanol solution at a mass ratio of 1:0.5 and ultrasonically dispersed at 15°C for 30 min to obtain a mixture. Then, 0.1 parts of vinyltriethoxysilane were added and reacted at 80°C for 3 hours. After the reaction was completed, the reaction solution was cooled to room temperature and filtered. It was washed three times with a 1:1 ethanol-water solution and then dried at 50°C for 10 hours to obtain graphene oxide modified aerogel.

[0052] Step 2: Preparation of modified graphene oxide waterborne intumescent fire-retardant coating

[0053] 0.5g of graphene oxide modified aerogel was transferred to a dispersion tank containing 100ml of deionized water and a wetting and dispersing agent was added. The mixture was stirred at 800r / min for 10min to ensure uniform mixing. Then, 30g of ammonium polyphosphate, 15g of pentaerythritol, 15g of melamine, and 8g of titanium dioxide were added to the dispersion tank in sequence. The speed of the dispersion tank was adjusted to 1500r / min and stirred for 30min to ensure complete dispersion and dissolution of the powder materials. The speed of the dispersion tank was then adjusted to 700r / min, and 15g of emulsion, 2g of film-forming aid, and 1g of defoamer were added to the tank in sequence. The mixture was stirred for 10min to ensure complete mixing, thus obtaining the coating.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that the magnesium zirconium aerogel and graphene oxide were not reacted and were directly added to the coating. 0.91g of magnesium zirconium aerogel and 0.09g of graphene oxide were transferred to a dispersion tank containing 100ml of deionized water, and a wetting and dispersing agent was added. The mixture was stirred at 800 rpm for 10 minutes to ensure uniform mixing. Then, 30g of ammonium polyphosphate, 15g of pentaerythritol, 15g of melamine, and 8g of titanium dioxide were added sequentially to the dispersion tank. The stirring speed was adjusted to 1500 rpm for 30 minutes to ensure complete dispersion of the powder materials. The stirring speed was then adjusted to 700 rpm, and 15g of emulsion, 2g of film-forming aid, and 1g of defoamer were added sequentially. The mixture was stirred for 10 minutes to ensure complete mixing, resulting in a fire-retardant coating.

[0056] Comparative Example 2

[0057] The difference from Example 1 is that 0.91g of silica aerogel and 0.09g of graphene oxide were transferred to a dispersion tank containing 100ml of deionized water and a wetting and dispersing agent was added. The mixture was stirred at 800r / min for 10min to ensure uniform mixing. Then, 30g of ammonium polyphosphate, 15g of pentaerythritol, 15g of melamine, and 8g of titanium dioxide were added to the dispersion tank in sequence. The speed of the dispersion tank was adjusted to 1500r / min and stirred for 30min to ensure complete dispersion of the powder materials. The speed of the dispersion tank was then adjusted to 700r / min, and 15g of emulsion, 2g of film-forming aid, and 1g of defoamer were added to the tank in sequence. The mixture was stirred for 10min to ensure complete mixing, thus obtaining the fire-retardant coating.

[0058] Table 1. Physicochemical properties of the coatings in the examples and comparative examples.

[0059]

[0060]

[0061] Note: F p The time required for the steel structure to withstand ordinary cellulose fires.

[0062] As shown in Table 1, when magnesium zirconium oxide aerogel and graphene oxide are added directly without modification, the adhesion strength of the coating decreases and the fire resistance time is reduced. This indicates that the graphene oxide-modified aerogel prepared by the present invention using magnesium zirconium oxide aerogel and graphene oxide via organosilane is more beneficial to the adhesion strength and fire resistance of the coating.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified graphene oxide water-based intumescent fire-retardant coating, characterized in that, Included by mass percentage: Deionized water 10%-20%; Ammonium polyphosphate 20%-35%; Melamine 5%-20%; Pentaerythritol 5%-20%; Titanium dioxide 8%-10%; Graphene oxide modified aerogel 0.001%-2%; Wetting and dispersing agent 0.5%-2%; Defoamer 1%-5%; Film-forming aids: 0.5%-2%; Emulsion 15%-25%; The preparation method of the graphene oxide modified aerogel includes the following steps: S1. Inorganic magnesium salt and inorganic zirconium salt are mixed with organic solvent and deionized water, a catalyst is added to react, and then dried, crushed and calcined to obtain magnesium zirconium aerogel. S2. After the magnesium zirconium aerogel is mixed and dispersed evenly with graphene oxide, a silane coupling agent is added to react and obtain graphene oxide modified magnesium zirconium aerogel. The inorganic magnesium salt and inorganic zirconium salt satisfy the condition that zirconium accounts for 1 to 20% of the total amount of zirconium and magnesium. The mass ratio of the magnesium zirconium aerogel to graphene oxide is 1:(0.1~0.5).

2. The modified graphene oxide waterborne intumescent fire-retardant coating according to claim 1, characterized in that, The ratio of the amount of catalyst added to the sum of the masses of the inorganic magnesium salt and the inorganic zirconium salt is (0.9~1.3):1; the catalyst includes one of oxalic acid, glacial acetic acid, and formic acid.

3. The modified graphene oxide waterborne intumescent fire-retardant coating according to claim 1, characterized in that, The calcination temperature is 500~700℃, and the time is 1~5h; And / or, after adding a silane coupling agent, react at 70~90℃ for 1~5h, then filter, wash and dry to obtain graphene oxide modified magnesium zirconium aerogel.

4. The modified graphene oxide water-based intumescent fire-retardant coating according to claim 1, characterized in that, The silane coupling agent includes one or more of γ-aminopropyltriethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-methacryloyloxypropyltriethoxysilane, acryloyloxypropyltrimethoxysilane, vinyltriisopropoxysilane, γ-methacryloyloxypropyltriisopropoxysilane, and propenyltrimethoxysilane; And / or, the inorganic magnesium salt includes one or more of magnesium sulfate, magnesium nitrate and magnesium chloride; The inorganic zirconium salt includes one or more of zirconium chloride, zirconium nitrate, and zirconium sulfate; The organic solvent includes one or more of methanol, ethanol, and propanol.

5. The modified graphene oxide waterborne intumescent fire-retardant coating according to claim 1, characterized in that, The wetting and dispersing agent is one or more of block polymers and nonionic surfactants; And / or, the film-forming aid is one or more of propylene glycol methyl ether, ethylene glycol ethyl ether, and hexanediol; The defoamer's main components are one or more of mineral oil containing hydrophobic particles, emulsified polysiloxane, and polysiloxane containing hydrophobic particles. The emulsion is an aqueous vinyl acetate-ethylene emulsion.

6. A method for preparing a modified graphene oxide waterborne intumescent fire-retardant coating according to any one of claims 1-5, characterized in that, Includes the following steps: Graphene oxide-modified aerogel and wetting and dispersing agent are mixed evenly in water; then ammonium polyphosphate, pentaerythritol, melamine and titanium dioxide are added and stirred until evenly dispersed; then emulsion, film-forming aid and defoamer are added and stirred evenly to obtain fire-retardant coating.

7. The preparation method of the modified graphene oxide waterborne intumescent fire-retardant coating according to claim 6, characterized in that, Includes the following steps: The graphene oxide-modified aerogel and wetting and dispersing agent are dispersed and stirred in water at a speed of 700-900 r / min for 8-15 min to ensure uniform mixing. Then, ammonium polyphosphate, pentaerythritol, melamine and titanium dioxide are added and stirred at a speed of 1300-1700 r / min for 20-40 min to ensure uniform dispersion. Finally, emulsion, film-forming aid and defoamer are added and stirred at a speed of 500-800 r / min for 8-15 min to obtain the fire-retardant coating.

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