A bionic graphene / sulfur-containing copolymer-based flame retardant coating and its preparation method

Abstract

The present invention belongs to the technical field of flame-retardant coatings, and specifically relates to a bionic graphene / sulfur-containing copolymer-based flame-retardant coating and a preparation method thereof. The bionic graphene / sulfur-containing copolymer-based flame-retardant coating is composed of modified graphite / low-temperature glass bead composite particles, a sulfur-containing copolymer and other additives. First, the present invention uses the solution polymerization method to synthesize and prepare an aqueous solution of sodium vinyl sulfonate copolymer. Secondly, using the sulfur-containing copolymer as a dispersion stabilizer, the modified graphene / low-temperature glass bead composite particles are prepared by an acidification-in-situ mechanical shearing method. Finally, the modified graphene / low-temperature glass bead composite particles and other additives are added to the aqueous solution of sodium vinyl sulfonate copolymer to obtain the bionic graphene / sulfur-containing copolymer-based flame-retardant coating. Compared with traditional flame-retardant coatings, it is not only environmentally friendly and green, but also has higher flame-retardant performance and mechanical stability, and has wide applications in the flame-retardant fields of plastics, wood, metals, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant coatings, and particularly relates to a bionic graphene / sulfur-containing copolymer-based flame retardant coating and a preparation method thereof. Background Art

[0002] Polymer materials have excellent properties and many characteristics that other materials do not have, such as light weight, good processing performance, high fluidity and easy molding, insulation, wear resistance, etc. However, most polymer materials are hydrocarbon organic structures and belong to flammable and combustible materials. When burning, they have a large heat release rate, high calorific value, fast flame propagation speed, and are not easy to extinguish; some materials also produce thick smoke and toxic gases when burning, posing a potential threat to human life safety and environmental protection. In recent years, the output value of the global flame retardant material industry has been increasing year by year. At the same time, countries have successively upgraded the regulations on material flame retardancy, putting forward higher requirements for the flame retardancy of polymer materials.

[0003] At present, there are mainly three ways to achieve the flame retardancy of polymer materials: 1) Adding flame retardants to the polymer matrix by physical blending, but this method will significantly reduce the mechanical properties and elasticity of polymer materials, especially rubber materials, thus limiting their scope of use. 2) Adopting the method of bulk flame retardancy, that is, introducing flame retardant structural units into the main chain or side chain structure of polymer materials by chemical reaction, but this method has a high cost. 3) Coating a flame retardant coating on the surface so that the substrate can not only obtain good fire protection performance but also avoid the decline of the mechanical properties and elasticity of the substrate; this method is inexpensive, the implementation scheme is simple, and the practicability is strong. It not only effectively protects the excellent mechanical properties of the polymer substrate itself but also realizes flame retardancy, thus fully reflecting the significance of the flame retardant coating on the surface of polymer substrates.

[0004] The flame retardant path of flame retardant coatings mainly adds flame retardants to the polymer matrix coating by physical blending. In order to obtain a highly flame retardant coating, a large amount of flame retardants must be added, but this method will significantly reduce the adhesion and mechanical properties of the polymer-based coating, so the flame retardant performance of traditional flame retardant coatings is limited, restricting their scope of use. Therefore, considering the structure and performance of the flame retardant and matrix materials of flame retardant coatings, further optimize and improve the comprehensive performance of flame retardant coatings. For example, graphene is a two-dimensional nanomaterial formed by a hexagonal honeycomb network of sp 2 hybridized carbon atoms, with high mechanical strength and specific surface area (2600 m 2) Lamellar graphene can be dispersed in a polymer matrix to form a "detour" structure, and the "path" effect slows down the thermal diffusion rate and the matrix decomposition rate. Therefore, it is often used as a carrier flame retardant for information. However, the flame retardant performance of single graphene is still not satisfactory and difficult to meet the requirements of practical applications. The thin nanocoating (50 mm) based on MXene will exhibit self-extinguishing phenomenon and has excellent flame retardant effect. However, its high price and difficult preparation also limit its application.

[0005] In nature, the lava erupted from volcanoes is incombustible but shows good fluidity at high temperatures. In addition, ceramic lava is characterized by a thermal conductivity less than 1.29 W / m·K because of its internal porous structure generated by gas release. Recent studies have shown that lava consists of various inorganic oxides (such as SiO 2 、Al 2 O 3 、CaO、Na 2 O), which can melt at high temperatures to produce flow and fill the pores of the burning carbon, and cooperate with the immobile incombustible carbon layer with low thermal conductivity to retard the penetration of combustible O 2 gas and heat, forming a strong fire barrier.

[0006] The highly viscous sulfur-containing ionic liquid polymer coatings poly(VS-co-HEA) or PVH have developed rapidly and show good flame retardant performance even without adding flame retardants. However, to obtain good flame retardant performance, the coating thickness is large, it is easy to absorb water, and the structural stability is poor, which also limits its industrial application. Therefore, how to efficiently design cheap and scalable flame retardant coatings remains a huge challenge. Summary of the Invention

[0007] The purpose of the present invention is to overcome the contradictory problem that it is difficult to optimize the flame retardant performance and mechanical properties of existing flame retardant coatings at the same time, and to provide a biomimetic graphene / sulfur-containing copolymer-based flame retardant coating and its preparation method. Based on the flame retardant characteristics and mechanisms of lava erupted from volcanoes, innovations are made from two aspects: the polymer coating matrix and the flame retardant system. Compared with traditional flame retardant coatings, it not only shows excellent comprehensive performance, but also has a simple preparation process, and at the same time has characteristics such as high wear resistance and high water resistance, and has a broader application scenario.

[0008] To achieve the above technical purposes and reach the above technical effects, the present invention is realized through the following technical solutions:

[0009] The present invention provides a preparation method of a biomimetic graphene / sulfur-containing copolymer-based flame retardant coating, which includes the following steps:

[0010] 1) Synthesis of sulfur-containing copolymer dispersant

[0011] Add 25 wt % sodium vinyl sulfonate aqueous solution and deionized water a into a mixing container according to a ratio, and slowly add an appropriate amount of hydroxy ester monomer while stirring to obtain a blended solution;

[0012] The obtained blended solution and the mixing container are placed in a water bath, and the temperature is raised to 60-75° C. while stirring. After the blended solution is evenly stirred, a 1 wt % potassium persulfate aqueous solution is uniformly added dropwise to the blended solution using a constant pressure funnel;

[0013] After the potassium persulfate solution is added dropwise, the reaction is continued for 4 to 6 hours to obtain a sulfur-containing copolymer dispersant;

[0014] 2) Synthesis of sulfur-containing copolymer matrix emulsion

[0015] A 25 wt% aqueous solution of sodium vinyl sulfonate and deionized water b are added to a four-necked flask a and placed in a constant temperature water bath, and stirred uniformly at 35-45° C. to obtain a reaction solution A;

[0016] After premixing 25 wt% sodium vinyl sulfonate aqueous solution and deionized water c, add them together with styrene monomer and acrylate into a four-necked flask b and place it in a constant temperature water bath, stir evenly at 35-45° C. to obtain a reaction solution B;

[0017] When the reaction solution A is heated to 70° C., the reaction solution B and a 2-3 wt% potassium persulfate aqueous solution are uniformly added dropwise to the reaction solution A within 3-5 hours, and the solution is kept warm for 0.5-2 hours, then cooled to room temperature, and neutralized with ammonia water to a pH value of 8-9 to obtain a sulfur-containing copolymer matrix emulsion;

[0018] 3) Preparation of graphene / glass microsphere composite particles

[0019] Gradually add potassium permanganate to concentrated sulfuric acid, stir to dissolve at room temperature, then slowly add graphite and stir to obtain a paste;

[0020] Weigh anhydrous sodium carbonate and paste, add them gradually into a clean beaker and mix thoroughly. After sufficient heat is released during the stirring process, add anhydrous sodium carbonate and paste gradually and sequentially. After the addition is complete, continue mixing and stirring until the paste becomes a solid powder.

[0021] Add concentrated phosphoric acid to the solid powder, mechanically stir for 6-7 hours at room temperature, filter and wash with water until the pH value of the solution is 5-6, and then filter and remove water to obtain expanded acidified graphite;

[0022] Prepare an appropriate amount of deionized water d, and sequentially add expanded acidified graphite, low-melting-point glass microspheres, and the sulfur-containing copolymer dispersant obtained in step 1) to the deionized water d to obtain solution C; among them, the addition amount of the expanded acidified graphite is 5-10 wt% of the mass of the deionized water d, the addition amount of the low-melting-point glass microspheres is 20-25 wt% of the mass of the deionized water d, and the addition amount of the sulfur-containing copolymer dispersant is 1-10 wt% of the sum of the masses of the expanded acidified graphite and the low-melting-point glass microspheres;

[0023] Adjust the pH value of solution C to 10-12 with NaOH, and after stirring and sanding, filter to remove slag to obtain a mixed solution of graphene / glass microsphere composite particles, denoted as Graphene@GP dispersion;

[0024] 4) Preparation of flame retardant coating

[0025] Use the sulfur-containing copolymer matrix emulsion obtained in step 2) as the coating matrix, add the Graphene@GP dispersion obtained in step 3), and after stirring and sanding, filter to remove slag to obtain a mixed solution of Graphene@GP / sulfur-containing copolymer;

[0026] Add an appropriate amount of defoamer and leveling agent to the above mixed solution, stir evenly to obtain a bionic graphene / sulfur-containing copolymer-based flame retardant coating.

[0027] Furthermore, in step 1), the mass ratio of the sodium vinyl sulfonate aqueous solution, deionized water a, hydroxy ester monomer, and 1 wt% potassium persulfate aqueous solution is 130:20-50:15-30:40-80.

[0028] Furthermore, in step 1), the hydroxy ester monomer is at least one of vinyl acetate, vinyl methacrylate, vinyl acrylate, and 2-hydroxyethyl acrylate.

[0029] Furthermore, in step 2), during the preparation of reaction solution A, the mass ratio of the 25 wt% sodium vinyl sulfonate aqueous solution to deionized water b is 2-10:1.

[0030] Furthermore, in step 2), during the preparation of reaction solution B, the mass ratio of the 25 wt% sodium vinyl sulfonate aqueous solution, deionized water c, styrene monomer, and acrylate is 400:40-60:50-80:30-70.

[0031] Furthermore, in step 2), the acrylate is at least one of ethyl acrylate, butyl acrylate, and isobutyl acrylate.

[0032] Further, in step 3), the concentration of the concentrated sulfuric acid is 98 wt%, the mass ratio of potassium permanganate to graphite is 1:1, and the mass ratio of potassium permanganate to the volume of concentrated sulfuric acid is 0.2 g / ml; the anhydrous sodium carbonate weighed each time is in excess relative to the paste; the concentration of the concentrated phosphoric acid is 85 wt%, and the volume ratio of concentrated phosphoric acid to concentrated sulfuric acid is 6 - 8:1.

[0033] Further, in step 4), the mass ratio of the sulfur-containing copolymer matrix emulsion to the Graphene@GP dispersion is 1.5 - 2:1 by volume.

[0034] Further, in step 4), the addition amount of the defoamer is 0.4 - 1.5 wt% of the mass of the mixed solution, and the addition amount of the leveling agent is 0.2 - 1.5 wt% of the mass of the mixed solution.

[0035] The present invention also provides a bionic graphene / sulfur-containing copolymer-based flame retardant coating, which is prepared by the above preparation method.

[0036] The beneficial effects of the present invention are as follows:

[0037] 1. The present invention synthesizes a surface active dispersant with flame retardant properties and uses it for surface modification of inorganic particles in coatings. It can not only improve the stability and dispersibility of inorganic particles, endow the particles with good flame retardancy, but also avoid introducing flammable organic surfactants.

[0038] 2. The present invention synthesizes a new type of sulfur-containing copolymer. Compared with traditional self-flame-retardant polymers, it not only has excellent water resistance, weather resistance and film-forming properties, but also a large number of sulfonic acid groups endow it with excellent flame retardant properties, providing the possibility for the development of multifunctional coatings such as flame retardant and anticorrosion.

[0039] 3. The present invention adopts a new type of green and environmentally friendly flame retardant system, namely the graphene / glass microsphere system. By using the "detour" structure "path" effect of graphene to slow down the heat diffusion rate and the matrix decomposition rate mechanism, combined with the melting flow characteristics of glass microspheres, it can more effectively shield the transfer and penetration of combustible gases and heat, solve the problem that the flame retardant system of the traditional condensed-phase flame retardant mechanism cannot form a continuous-phase shielding layer, and effectively improve the flame retardant effect.

[0040] 4. The present invention uses a new type of acidification-in-situ mechanical glass method to prepare graphene / glass microsphere composite particles. Compared with the traditional solution blending method, it can not only effectively improve the dispersion uniformity between glass microspheres and graphene, but also use the load of glass microspheres to avoid the formation of irrecoverable superposition of graphene and improve its dispersion and stability in coatings.

[0041] Of course, it is not necessary for any product implementing the present invention to achieve all the above advantages simultaneously. Description of the Drawings

[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0043] Figure 1 Scanning electron micrograph of the GPs@G@PVH composite flame retardant prepared for Example 1;

[0044] Figure 2 AFM image of graphene in the GP@G@PVH composite flame retardant in Example 1;

[0045] Figure 3 Optical photograph of the dispersion of the GPs@G@PVH composite flame retardant prepared for Example 1 in water;

[0046] Figure 4 Scanning electron micrograph of the bio-inspired graphene / sulfur-containing copolymer-based flame retardant coating prepared for Example 1;

[0047] Figure 5 Raman spectrum of the bio-inspired graphene / sulfur-containing copolymer-based flame retardant coating prepared for Example 1;

[0048] Figure 6 Schematic diagram of the flame retardant effect of different flame retardant coatings on plastic films. Detailed implementation manners

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, rather than all, embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0050] The relevant specific embodiments of the present invention are as follows:

[0051] Example 1

[0052] A bio-inspired graphene / sulfur-containing copolymer-based flame retardant coating and its preparation method, characterized by comprising the following steps:

[0053] 1) Synthesis of sulfur-containing copolymer dispersant

[0054] Take out 130 g of a 25 wt% aqueous solution of sodium vinyl sulfonate and additionally add 25 g of deionized water. Slowly add 20 g of vinyl acetate under mechanical stirring. Place the blend solution in a water bath and heat it to 65 °C while stirring, with a stirring speed of 500 rpm. After stirring the blend solution for 3 min to mix it evenly, slowly add a 1.0 wt% aqueous solution of potassium persulfate dissolved in 60 g dropwise into the blend solution at a constant rate using a constant pressure funnel, and finish dropping in 40 min. After the dropping of the potassium persulfate solution is completed, continue the reaction for 5 h to obtain an aqueous solution of a sodium vinyl sulfonate-based copolymer.

[0055] 2) Synthesis of sulfur-containing copolymer matrix emulsion

[0056] At room temperature, add 400 g of a 25 wt% aqueous solution of sodium vinyl sulfonate and 50 g of deionized water to a 1000 mL four-necked flask and place it in a constant temperature water bath. Stir at a speed of 200 r / min for 20 min at 40 °C to obtain reaction solution A.

[0057] In another 1000 mL four-necked flask, at 30 °C, disperse 400 g of a 25 wt% aqueous solution of sodium vinyl sulfonate and 50 g of deionized water evenly with a high-speed disperser at a speed of 300 r / min. Subsequently, add 60 g of styrene monomer and 50 g of ethyl acrylate, and stir at a speed of 1500 r / min for 2 h at 40 °C to obtain reaction solution B.

[0058] When the temperature of reaction solution A reaches 70 °C, add reaction solution B and 100 g of a 2.5 wt% aqueous solution of potassium persulfate dropwise into reaction solution A at a constant rate, finish dropping in 4 h, keep the temperature for 1 h, then cool down to room temperature, and neutralize with ammonia water to a pH value of 8.5 to obtain the flame retardant coating base material.

[0059] 3) Preparation of graphene / glass microsphere composite particles

[0060] 15 g of graphite, 15 g of potassium permanganate, 90 ml of concentrated sulfuric acid; first add concentrated sulfuric acid, and gradually add potassium permanganate while stabilizing. After adding, stabilize for 10 min; then slowly add graphite, and after adding, stir mechanically until it becomes a paste; weigh 70 g of anhydrous sodium carbonate, ensure an excess of sodium carbonate and a relatively small amount of paste each time, add it to a clean beaker and stir well. After sufficient heat release during the stirring process, perform repeated addition again, and finally stir until the graphite becomes powdery again; add 210 ml of concentrated phosphoric acid, stir mechanically for 6 h, and adjust the pH of the solution to 5 by washing with water to prepare expanded acidified graphite.

[0061] First, prepare a certain amount of water. Pour expanded acidified graphite accounting for 7 wt% of the water mass into the water, and pour GP (low-melting glass microspheres with a melting point below 550 °C) accounting for 23 wt% of the water mass into the water. Add a sulfur-containing copolymer dispersant solution accounting for 5 wt% of the sum of the masses of Graphene and GP to the water. Adjust the aqueous solution to pH 11 with NaOH. First, stir with a high-speed stirrer for 10 min, and then grind with a sand mill at a rotational speed of 2000 r / min for 10 h. The obtained solution is filtered to obtain a Graphene@GP mixed solution.

[0062] 4) Preparation of flame-retardant coating

[0063] Weigh 1000 ml of 32 wt% sulfur-containing copolymer matrix emulsion as the coating matrix, add 500 ml of 30 wt% Graphene@GP dispersion liquid. At room temperature, stir at 500 prm for 10 min, and then grind with a sand mill at a rotational speed of 1000 r / min for 20 min. The obtained solution is filtered to obtain a Graphene@GP / sulfur-containing copolymer mixed solution. Then, add 0.6% defoamer and 0.5% leveling agent to the above solution, and stir at 1500 rpm at high speed for 10 min to obtain a bionic graphene / sulfur-containing copolymer-based flame-retardant coating.

[0064] Example 2

[0065] A bionic graphene / sulfur-containing copolymer-based flame-retardant coating and its preparation method, characterized by including the following steps:

[0066] 1) Synthesis of sulfur-containing copolymer dispersant

[0067] Take out 130 g of 25 wt% sodium vinyl sulfonate aqueous solution and add another 25 g of deionized water. Slowly add 20 g of vinyl acetate under mechanical stirring. Place the blend solution in a water bath and heat it to 65 °C while stirring, with a stirring speed of 500 rpm. After stirring the blend solution for 3 min to make it uniform, use a constant-pressure funnel to slowly drop 60 g of 1.0 wt% potassium persulfate aqueous solution into the blend solution, and finish dropping in 40 min. After the dropping of the potassium persulfate solution is completed, continue the reaction for 5 h to obtain a sodium vinyl sulfonate-based copolymer aqueous solution.

[0068] 2) Synthesis of sulfur-containing copolymer matrix emulsion

[0069] At room temperature, add 400 g of 25 wt% sodium vinyl sulfonate aqueous solution and 50 g of deionized water to a 1000 mL four-necked flask and place it in a constant-temperature water bath. Under the condition of 40 °C, stir at a rotational speed of 200 r / min for 20 min to obtain reaction solution A;

[0070] In another 1000 mL four-necked flask, at 30 °C, 400 g of a 25 wt% aqueous solution of sodium vinyl sulfonate and 50 g of deionized water were dispersed evenly with a high-speed disperser at a speed of 300 r / min. Subsequently, 50 g of styrene monomer and 70 g of ethyl acrylate were added, and at 40 °C, the mixture was stirred at a speed of 1500 r / min for 2 h to obtain reaction solution B.

[0071] When the temperature of reaction solution A reached 70 °C, reaction solution B and 100 g of a 2.5 wt% aqueous solution of potassium persulfate were added dropwise to reaction solution A at a constant rate and completed within 4 h. After holding the temperature for 1 h, it was cooled to room temperature and neutralized with ammonia water to a pH value of 8.5 to obtain the flame-retardant coating base material.

[0072] 3) Preparation of graphene / glass microsphere composite particles

[0073] 15 g of graphite, 15 g of potassium permanganate, and 90 ml of concentrated sulfuric acid; first add concentrated sulfuric acid, and gradually add potassium permanganate while stirring steadily. After adding, stir steadily for 10 min; then slowly add graphite, and after adding, stir mechanically until it becomes a paste; weigh 70 g of anhydrous sodium carbonate, ensure an excess of sodium carbonate and a relatively small amount of paste each time, add them to a clean beaker and stir well. After sufficient heat release during the stirring process, repeat the addition again. Finally, stir until the graphite becomes powdery again; add 210 ml of concentrated phosphoric acid, stir mechanically for 6 h, and adjust the pH of the solution to 5 by washing with water to obtain expanded acidified graphite.

[0074] First, prepare a certain amount of water. Pour 5 wt% of the expanded acidified graphite based on the mass of water into the water, and pour 25 wt% of GP (low-melting glass microspheres with a melting point below 550 °C) based on the mass of water into the water. Add a sulfur-containing copolymer dispersant solution of 2 wt% based on the sum of the masses of graphene and GP to the water. Adjust the pH of the aqueous solution to 10 with NaOH. First, stir with a high-speed stirrer for 10 min, and then grind with a sand mill at a speed of 2000 r / min for 10 h. The resulting solution was filtered to obtain a graphene@GP mixed solution.

[0075] 4) Preparation of flame-retardant coating

[0076] Weigh 1000 ml of 35 wt% sulfur-containing copolymer matrix emulsion as the coating matrix, add 500 ml of 25 wt% Graphene@GP dispersion liquid, stir at 500 prm for 10 min at room temperature, and then grind with a sand mill at a rotation speed of 1000 r / min for 20 min. The obtained solution is filtered to obtain a mixed solution of Graphene@GP / sulfur-containing copolymer, and then 0.6% defoamer and 0.5% leveling agent are added to the above solution, and stirred at a high speed of 1500 rpm for 10 min to obtain a bionic graphene / sulfur-containing copolymer-based flame retardant coating.

[0077] Example 3

[0078] A bionic graphene / sulfur-containing copolymer-based flame retardant coating and its preparation method, characterized in that it comprises the following steps:

[0079] 1) Synthesis of sulfur-containing copolymer dispersant

[0080] Take out 130 g of 25 wt% sodium vinyl sulfonate aqueous solution and add 25 g of deionized water additionally. Slowly add 20 g of vinyl acetate under mechanical stirring. Place the blend solution in a water bath and heat it to 65 °C while stirring, with a stirring speed of 500 rpm. After stirring the blend solution for 3 min to make it uniform, use a constant pressure funnel to slowly drop 60 g of 1.0 wt% potassium persulfate aqueous solution into the blend solution at a constant speed, and finish dropping in 40 min. After the dropping of the potassium persulfate solution is completed, continue the reaction for 5 h to obtain an aqueous solution of sodium vinyl sulfonate-based copolymer.

[0081] 2) Synthesis of sulfur-containing copolymer matrix emulsion

[0082] At room temperature, add 400 g of 25 wt% sodium vinyl sulfonate aqueous solution and 50 g of deionized water to a 1000 mL four-necked flask and place it in a constant temperature water bath. Stir at a rotation speed of 200 r / min for 20 min at 40 °C as reaction solution A;

[0083] In another 1000 mL four-necked flask, at 30 °C, disperse 400 g of 25 wt% sodium vinyl sulfonate aqueous solution and 50 g of deionized water evenly with a high-speed disperser at a rotation speed of 300 r / min, then add 80 g of styrene monomer and 30 ethyl acrylate, and stir at a rotation speed of 1500 r / min for 2 h at 40 °C as reaction solution B.

[0084] When the temperature of reaction solution A reaches 70 °C, add reaction solution B and 100 g of 2.5 wt% potassium persulfate aqueous solution dropwise into reaction solution A at a constant speed, finish dropping in 4 h, keep the temperature for 1 h, then cool down to room temperature, and neutralize with ammonia water to a pH value of 8.5 as the flame retardant coating base material.

[0085] 3) Preparation of Graphene / Glass Microsphere Composite Particles

[0086] 15 g of graphite, 15 g of potassium permanganate, and 90 ml of concentrated sulfuric acid; first add concentrated sulfuric acid, and gradually add potassium permanganate while stabilizing. After adding, stabilize for 10 min; then slowly add graphite. After adding, stir mechanically until it becomes a paste; weigh 70 g of anhydrous sodium carbonate. Each time, ensure an excess of sodium carbonate and a relatively small amount of paste, add it to a clean beaker and stir well. After sufficient heat release during the stirring process, perform repeated addition again. Finally, stir until the graphite becomes powdery again; add 210 ml of concentrated phosphoric acid, stir mechanically for 6 h, and adjust the pH of the solution to 5 by washing with water to obtain expanded acidified graphite.

[0087] First, prepare a certain amount of water. Pour 10 wt% of the expanded acidified graphite based on the mass of water into the water, and pour 20 wt% of GP (low-melting glass microspheres with a melting point below 550 °C) based on the mass of water into the water. Add a sulfur-containing copolymer dispersant solution accounting for 9 wt% of the sum of the masses of Graphene and GP to the water. Adjust the pH of the aqueous solution to 12 with NaOH. First, stir with a high-speed stirrer for 10 min, and then grind with a sand mill at a rotational speed of 2000 r / min for 10 h. The obtained solution is filtered to obtain a mixed solution of Graphene@GP.

[0088] 4) Preparation of Flame Retardant Coating

[0089] Weigh 1000 ml of 30 wt% sulfur-containing copolymer matrix emulsion as the coating matrix, add 500 ml of 35 wt% Graphene@GP dispersion liquid. At room temperature, stir at 500 prm for 10 min, and then grind with a sand mill at a rotational speed of 1000 r / min for 20 min. The obtained solution is filtered to obtain a mixed solution of Graphene@GP / sulfur-containing copolymer. Then, add 0.6% defoamer and 0.5% leveling agent to the above solution, and stir at 1500 rpm at high speed for 10 min to obtain a bionic graphene / sulfur-containing copolymer-based flame retardant coating.

[0090] Example 4

[0091] Perform relevant performance tests on the bionic graphene / sulfur-containing copolymer-based flame retardant coating prepared in Example 1 and its internal flame retardant (GPs@G@PVH):

[0092] The scanning electron micrograph of the sulfur-containing polymer modified graphene@glass microsphere composite particles (GPs@G@PVH) is as Figure 1 shown. According to Figure 1 , it can be seen that the glass microspheres (GPs) show a typical flaky shape with an average size of 2.5 μm. As Figure 2As shown, some graphene nanosheets were observed on the surface of GPs from high-magnification SEM, indicating that the surface of GPs was wrapped by dense graphene nanosheets.

[0093] The dispersion results of the bionic graphene / sulfur-containing copolymer-based flame retardant coating in water are as Figure 3 shown. According to Figure 3 , it can be seen that the sulfur-containing polymer-modified graphene@glass microsphere composite particles (GPs@G@PVH) did not precipitate within more than 24 hours, indicating excellent stability and dispersibility in water.

[0094] The SEM results of the bionic graphene / sulfur-containing copolymer-based flame retardant coating are as Figure 4 shown. According to Figure 4 , it can be seen that there are obvious large aggregates on the surface and no pore defects, indicating that the G@GPs@PV composite particles are not only uniformly dispersed in the resin matrix but also have good compatibility and interfacial interaction.

[0095] The Raman spectroscopy results of the bionic graphene / sulfur-containing copolymer-based flame retardant coating are as Figure 5 shown. According to Figure 5 , two obvious graphene Raman peaks appear at positions near 1360 cm -1 and 1587 cm -1 for both the G@GPs@PV composite particles and their coatings. This result further indicates that the graphene-based flame retardant system and the coating have been successfully prepared.

[0096] The flame retardant effects of different flame retardant coatings are as Figure 6 shown. The first group is a pure PMMA film, which is ignited within 3 seconds and burns within 120 seconds, indicating that PMMA is a flammable material; the second group is a commercially available ball shield fireproof black paint coated on the surface of PMMA for flame retardant protection of the PMMA film. Because of the coated flame retardant paint, although it is ignited, the flame is smaller and it does not burn completely. It remains basically intact within 90 seconds, indicating that this flame retardant paint has certain flame retardant properties; the third group is the flame retardant paint prepared in this embodiment coated on the surface of the PMMA film for flame retardant protection of the PMMA film. It is difficult to be ignited under the flame, and the material stops burning automatically after the flame is removed, showing excellent flame retardant properties.

[0097] The preferred embodiments of the present invention disclosed above are only helpful for explaining the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only the specific implementation manners. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the relevant technical fields can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing a bionic graphene / sulfur-containing copolymer-based flame retardant coating, It is characterized in that The steps include: 1) Synthesis of sulfur-containing copolymer dispersant Add 25 wt % sodium vinyl sulfonate aqueous solution and deionized water a into a mixing container according to a ratio, and slowly add an appropriate amount of hydroxy ester monomer while stirring to obtain a blended solution; The obtained blended solution and the mixing container are placed in a water bath, and the temperature is raised to 60-75° C. while stirring. After the blended solution is evenly stirred, a 1 wt % potassium persulfate aqueous solution is uniformly added dropwise to the blended solution using a constant pressure funnel; After the potassium persulfate solution is added dropwise, the reaction is continued for 4 to 6 hours to obtain a sulfur-containing copolymer dispersant; 2) Synthesis of sulfur-containing copolymer matrix emulsion Add 25 wt% sodium vinyl sulfonate aqueous solution and deionized water b into a four-necked flask a and place it in a constant temperature water bath, and stir evenly at 35-45° C. to obtain a reaction solution A; After premixing 25 wt% sodium vinyl sulfonate aqueous solution and deionized water c, add them together with styrene monomer and acrylate into a four-necked flask b and place it in a constant temperature water bath, stir evenly at 35-45° C. to obtain a reaction solution B; When the reaction solution A is heated to 70° C., the reaction solution B and a 2-3 wt% potassium persulfate aqueous solution are uniformly added dropwise to the reaction solution A within 3-5 hours, and the solution is kept warm for 0.5-2 hours, then cooled to room temperature, and neutralized with ammonia water to a pH value of 8-9 to obtain a sulfur-containing copolymer matrix emulsion; 3) Preparation of graphene / glass microsphere composite particles Gradually add potassium permanganate to concentrated sulfuric acid, stir to dissolve at room temperature, then slowly add graphite and stir to obtain a paste; Weigh anhydrous sodium carbonate and paste, add them gradually into a clean beaker and mix thoroughly. After sufficient heat is released during the stirring process, add anhydrous sodium carbonate and paste gradually and sequentially. After the addition is complete, continue mixing and stirring until the paste becomes a solid powder. Add concentrated phosphoric acid to the solid powder, mechanically stir at room temperature for 6 to 7 hours, filter and wash with water until the pH value of the solution is 5 to 6, and then filter and remove water to obtain expanded acidified graphite; Prepare an appropriate amount of deionized water d, add expanded acidified graphite, low-melting point glass microspheres, and the sulfur-containing copolymer dispersant obtained in step 1) to the deionized water d in sequence to obtain a solution C; wherein the amount of expanded acidified graphite added is 5-10wt% of the mass of the deionized water d, the amount of low-melting point glass microspheres added is 20-25wt% of the mass of the deionized water d, and the amount of sulfur-containing copolymer dispersant added is 1-10wt% of the sum of the mass of expanded acidified graphite and low-melting point glass microspheres; The pH value of solution C was adjusted to 10-12 with NaOH, and after stirring and sand grinding, the solution was filtered to remove residues, thereby obtaining a mixed solution of graphene / glass microbead composite particles, which was recorded as Graphene@GP dispersion. 4) Preparation of flame retardant coatings The sulfur-containing copolymer matrix emulsion obtained in step 2) is used as the coating matrix, and the Graphene@GP dispersion obtained in step 3) is added, and after stirring and sand milling, the dispersion is filtered to remove residues to obtain a mixed solution of Graphene@GP / sulfur-containing copolymer; An appropriate amount of defoamer and leveling agent are added to the above-mentioned mixed solution and stirred evenly to obtain a bionic graphene / sulfur-containing copolymer-based flame retardant coating.

2. The preparation method according to claim 1, characterized in that: in step 1), the mass ratio of the sodium vinyl sulfonate aqueous solution, deionized water a, hydroxy ester monomer, and 1 wt% potassium persulfate aqueous solution is 130:20 - 50:15 - 30:40 - 80.

3. The preparation method according to claim 1, characterized in that: in step 1), the hydroxy ester monomer is at least one of vinyl acetate, vinyl methacrylate, vinyl acrylate, and 2-hydroxyethyl acrylate.

4. The preparation method according to claim 1, characterized in that: in the process of preparing reaction solution A in step 2), the mass ratio of the 25 wt% sodium vinyl sulfonate aqueous solution to deionized water b is 2 - 10:

1.

5. The preparation method according to claim 1, characterized in that: in the process of preparing reaction solution B in step 2), the mass ratio of the 25 wt% sodium vinyl sulfonate aqueous solution, deionized water c, styrene monomer, and acrylate is 400:40 - 60:50 - 80:30 - 70.

6. The preparation method according to claim 1, characterized in that: in step 2), the acrylate is at least one of ethyl acrylate, butyl acrylate, and isobutyl acrylate.

7. The preparation method according to claim 1, characterized in that: in step 3), the concentration of the concentrated sulfuric acid is 98 wt%, the mass ratio of potassium permanganate to graphite is 1:1, the mass of potassium permanganate to the volume of concentrated sulfuric acid is 0.2 g / ml; each time the anhydrous sodium carbonate weighed is in excess relative to the paste; the concentration of the concentrated phosphoric acid is 85 wt%, and the volume ratio of the concentrated phosphoric acid to the concentrated sulfuric acid is 6 - 8:

1.

8. The preparation method according to claim 1, characterized in that: in step 4), the volume ratio of the sulfur-containing copolymer matrix emulsion to the Graphene@GP dispersion is 1.5 - 2:

1.

9. The preparation method according to claim 1, characterized in that: in step 4), the addition amount of the defoamer is 0.4 - 1.5 wt% of the mass of the mixed solution, and the addition amount of the leveling agent is 0.2 - 1.5 wt% of the mass of the mixed solution.

10. A bionic graphene / sulfur-containing copolymer-based flame retardant coating prepared by the preparation method according to any one of claims 1 - 9.

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