Highly flame-retardant board and production process thereof

Abstract

This invention discloses a high flame-retardant sheet material and its manufacturing process, relating to the field of flame-retardant materials technology. The high flame-retardant sheet material comprises the following raw materials in parts by weight: 90-110 parts magnesium oxide, 15-20 parts magnesium chloride, 30-35 parts magnesium sulfate, 1.5-3 parts modified polyvinyl alcohol, 1-2 parts starch, 0.3-0.8 parts modified borax, 0.2-0.5 parts silane coupling agent KH-550, 1-2 parts anhydrous ethanol, 2.5-3.5 parts nano zinc borate, 2-4 parts chlorinated paraffin-70, 0.5-1 part nano titanium dioxide, 5-10 parts basalt fiber, 0.2-0.5 parts calcium stearate, and 90-110 parts deionized water. The raw materials of this high flame-retardant sheet material undergo modified polyvinyl alcohol condensation crosslinking and nano-reinforcement, and modified borax esterification chelation treatment to improve flame-retardant compatibility. During production, silane coupling agent pre-dispersion and starch paste synergistic mixing, combined with precise viscosity control and stepped sanding, ensure uniform slurry consistency. Optimized hot-pressing parameters result in high board density, excellent flame retardancy, and superior surface finish.

Description

Technical Field

[0001] This invention relates to the field of flame retardant materials technology, specifically to a high flame retardant sheet material and its production process. Background Technology

[0002] In fields such as construction, furniture, and rail transportation, the flame-retardant performance of wood-based panels is one of the core indicators for ensuring safety. Traditional wood-based panels mostly rely on wood, plastics, and other base materials, which have poor flame retardancy, are easily ignited when exposed to fire, and release toxic fumes, posing serious safety hazards. Although existing flame-retardant panels improve performance by adding flame retardants, they generally suffer from low flame-retardant efficiency, poor mechanical properties, and insufficient processing stability.

[0003] Currently used flame retardants such as zinc borate and chlorinated paraffin are unevenly dispersed in the substrate, which can easily lead to fluctuations in the flame retardant performance of the board. Moreover, excessive addition can reduce the strength and toughness of the material. When additives such as polyvinyl alcohol and borax are not modified, they have poor compatibility with inorganic substrates and are prone to delamination and cracking, affecting the service life of the board.

[0004] In terms of production processes, traditional mixing methods struggle to achieve uniform dispersion of raw materials, and improper control of slurry viscosity can lead to uneven coating. During hot pressing, a single-step temperature increase can easily cause internal stress concentration, resulting in board deformation or insufficient density. Furthermore, if the length and diameter of reinforcing materials such as basalt fiber are not properly controlled, they not only fail to provide reinforcement but may also become weak points in stress, reducing the mechanical properties of the board.

[0005] In existing technologies, magnesium chloride and magnesium sulfate are often directly dry-mixed and then added to the system, and a ratio of high magnesium chloride and low magnesium sulfate is often used. Although this can quickly build up strength, excessive magnesium chloride content can easily cause the board to absorb moisture and become efflorescent. In high humidity environments, salt frost and water droplets are likely to appear on the surface, affecting service life and aesthetics. At the same time, the concentration of the salt solution is not controlled, which further exacerbates performance fluctuations. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a high flame-retardant board and its production process, solving the problems of uneven flame retardant dispersion, poor substrate compatibility, and insufficient mechanical properties in traditional flame-retardant boards.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A high flame-retardant board comprises the following raw materials in parts by weight: 90-110 parts magnesium oxide, 15-20 parts magnesium chloride, 30-35 parts magnesium sulfate, 1.5-3 parts modified polyvinyl alcohol, 1-2 parts starch, 0.3-0.8 parts modified borax, 0.2-0.5 parts silane coupling agent KH-550, 1-2 parts anhydrous ethanol, 2.5-3.5 parts nano zinc borate, 2-4 parts chlorinated paraffin-70, 0.5-1 part nano titanium dioxide, 5-10 parts basalt fiber, 0.2-0.5 parts calcium stearate, and 90-110 parts deionized water.

[0009] Furthermore, the basalt fibers have a length of 3-5 mm and a diameter of 10-15 μm. Basalt fibers of this size can be uniformly dispersed in the substrate to construct a three-dimensional reinforcing skeleton. This avoids uneven dispersion caused by excessively long fibers, while also preventing ineffective stress transfer due to excessively short fibers. It synergistically enhances the flexural strength and toughness of the board by modifying polyvinyl alcohol, reducing stress-prone areas.

[0010] Furthermore, the modified polyvinyl alcohol is prepared using the following specific steps:

[0011] A1. Add polyvinyl alcohol powder to a three-necked flask, then add deionized water, and place in a 70℃ constant temperature water bath. Stir at 300 rpm for 40 minutes until the polyvinyl alcohol is completely swollen. Heating weakens the intermolecular forces of polyvinyl alcohol, allowing water molecules to penetrate between the chains and achieve full swelling, providing a homogeneous system for subsequent reactions. Then add sodium dodecyl sulfate and continue stirring at 300 rpm for 20 minutes to improve the dispersibility of polyvinyl alcohol. Next, slowly add glacial acetic acid dropwise with a dropper while stirring, adjusting the pH of the system to 5.5 to provide suitable catalytic conditions for the subsequent hydroxyl condensation crosslinking reaction of glutaraldehyde and polyvinyl alcohol. After stirring for 15 minutes, a pretreated polyvinyl alcohol solution is obtained.

[0012] A2. While stirring at 300 rpm, add ethylene glycol to the pretreated polyvinyl alcohol solution and stir for 10 min. Ethylene glycol acts as a chain extender, and its hydroxyl groups interact with the hydroxyl groups on the polyvinyl alcohol molecular chain, providing more active sites for the cross-linking reaction. Then, add glutaraldehyde in three portions, with a 5-min interval between each addition. Adjust the water bath temperature to 50℃ and maintain a stirring speed of 250 rpm for 40 min. The aldehyde group of glutaraldehyde and the hydroxyl group of polyvinyl alcohol undergo a condensation reaction at 50℃ to form a stable ether bond or hemiacetal structure, constructing a three-dimensional cross-linking network. Turn off the water bath heating and allow the solution to cool naturally to room temperature.

[0013] A3. Under stirring at 300 rpm, a titanate coupling agent was added to the reaction system after the second modification. The mixture was stirred for 15 min. The titanate coupling agent reacted with the hydroxyl groups on the surface of the nano-calcium carbonate through the alkoxy groups in its molecules to form chemical bonds. The organic groups at the other end interacted with the hydroxyl groups of the polyvinyl alcohol molecular chain, thereby improving the interfacial compatibility between the nano-calcium carbonate and polyvinyl alcohol. Subsequently, nano-calcium carbonate was added, and the stirring speed was increased to 400 rpm. The mixture was stirred continuously at room temperature for 30 min to obtain modified polyvinyl alcohol. The mechanical properties of polyvinyl alcohol and its compatibility with inorganic substrates were further improved through the nano-reinforcement effect.

[0014] Furthermore, the ratio of polyvinyl alcohol powder, deionized water, sodium dodecyl sulfate, and glacial acetic acid in A1 is 15g:150mL:0.5g:3mL; wherein the polyvinyl alcohol is of type 1788, which has suitable degree of polymerization and degree of alcoholysis to ensure swelling and reactivity.

[0015] Furthermore, the ratio of ethylene glycol to glutaraldehyde in A2 is 5 mL: 2 mL.

[0016] Furthermore, the ratio of titanate coupling agent to nano-calcium carbonate in A3 is 1 mL: 2 g.

[0017] Furthermore, the modified borax is prepared using the following specific steps:

[0018] B1. Dissolve borax in distilled water and place it in a 50°C constant temperature water bath. Stir at 200 rpm until the borax is completely dissolved. After dissolution, maintain this temperature and speed and continue stirring for 30 minutes. Borax hydrolyzes in the 50°C water bath to generate boric acid and borate ions. Then, slowly add glycerol and adjust the stirring speed to 250 rpm. Continue stirring in the 50°C water bath for 50 minutes to complete the esterification reaction. Allow it to cool naturally to room temperature. Glycerol undergoes an esterification reaction with boric acid. The hydroxyl groups of boric acid and glycerol dehydrate to form borate ester bonds. This introduces organic groups to improve the organic compatibility of borax, while the ester bond structure enhances its thermal stability.

[0019] B2. Tartaric acid was added to the reaction system after the first modification, and the mixture was stirred at 250 rpm for 15 min. Citric acid was then added in two portions, with a 10 min interval between each addition. After all the citric acid was added, the mixture was stirred at 250 rpm for 30 min to form a chelate structure. The chelate structure fixes boron through strong coordination bonds, preventing boron loss at high temperatures, and also enhances the synergistic effect with flame retardants such as nano zinc borate and chlorinated paraffin-70.

[0020] B3. Under stirring at 300 rpm, polyethylene glycol was added to the second modified system and stirred for 20 min. Then, hydroxypropyl methylcellulose was added and stirred at 300 rpm at room temperature for 40 min to obtain modified borax. Polyethylene glycol reduced the interfacial tension by interacting with the active groups on the surface of the borax chelate through its hydroxyl groups. Hydroxypropyl methylcellulose, as a polymeric dispersant, prevented the agglomeration of borax chelate particles through the steric hindrance effect of the molecular chain. The synergistic effect of the two made the modified borax uniformly dispersed in the subsequent slurry, avoiding fluctuations in flame retardant performance caused by local aggregation, while improving compatibility with the substrate.

[0021] Furthermore, the ratio of borax, distilled water, and glycerol in B1 is 8g:80mL:6mL.

[0022] Furthermore, the ratio of tartaric acid to citric acid in B2 is 1.5g:1g.

[0023] Furthermore, the ratio of polyethylene glycol to hydroxypropyl methylcellulose in B3 is 3 mL: 0.5 g.

[0024] Furthermore, citric acid is added to B2 in stages and combines with tartaric acid to form a chelate structure, ensuring the thermal stability and flame-retardant synergistic effect of borax.

[0025] A production process for a high flame-retardant board specifically includes the following steps:

[0026] S1. Add silane coupling agent KH-550 and anhydrous ethanol to a container, stir at 1300 rpm for 15 min, and let stand for 30 min. Separately, add modified borax to deionized water at 80-90℃ and stir until dissolved. Pour in the above diluted silane coupling agent solution, stir at 300 rpm for 15-20 min in a water bath at 60-70℃, and cool for later use. Add deionized water to a mixing tank, stir at 150 rpm and heat to 30-40℃. First, add magnesium sulfate and stir for 5 min, then add magnesium chloride. After adding all the magnesium chloride, adjust the stirring speed to 200 rpm and stir for 25-35 min until the salts are completely dissolved. Ensure that the magnesium chloride and magnesium sulfate compound aqueous solution has a magnesium content of 22-28 Be°. Let stand for 15 min to remove bubbles, seal the mixing tank, and set aside for later use. Prepare an aqueous solution of magnesium chloride and magnesium sulfate with a magnesium content of 22-28 Be° in advance to ensure that the two salts are evenly dispersed, avoid dissolution differences during dry mixing, and accurately control the salt concentration to provide a stable environment for the full reaction of magnesium cement.

[0027] S2. Pour deionized water into the reactor and heat it to 60-70°C while stirring at 200 rpm. Slowly add modified polyvinyl alcohol and continue stirring until completely dissolved. Mix starch with deionized water and stir at 400 rpm for 10-15 minutes to make starch paste. Pour the paste into the above solution and stir at 250 rpm for 30 minutes to obtain organic modified adhesive.

[0028] S3. Add dried magnesium oxide, nano zinc borate, chlorinated paraffin-70, nano titanium dioxide, basalt fiber and calcium stearate to a twin-shaft mixer and dry mix at 300 rpm for 3-5 min. Add the organic modified adhesive prepared in S2, the salt compound water agent prepared in S1 and the pretreatment solution in S1, and stir at 200-300 rpm for 30-40 min until the slurry is uniform and free of particles. Adjust the slurry viscosity to 2000-3000 cP with the remaining deionized water.

[0029] S4. Place the slurry onto the coating machine conveyor belt and adjust the gap to achieve the desired coating amount. The blank is formed by placing it into a hot press and hot pressing it at 110-120℃ and 1.2-1.5MPa for 1.2 min per millimeter of plate thickness.

[0030] S5. The board blank is naturally cooled to room temperature for 2-3 hours, and then sanded with 120 and 240 mesh stepped sanding until the surface roughness Ra≤1.6μm to obtain a high flame retardant board.

[0031] Furthermore, in the S4 hot pressing process, a temperature of 110-120℃ and a pressure of 1.2-1.5MPa are used, and the hot pressing time is controlled to be 1.2min per millimeter of plate thickness, so that a dense structure is formed inside the plate, while ensuring the uniform distribution of flame retardant components, thereby obtaining excellent flame retardant performance and dimensional stability.

[0032] This invention provides a high flame-retardant sheet material and its manufacturing process, which has the following beneficial effects:

[0033] 1. By combining the condensation-crosslinking structure of modified polyvinyl alcohol with a nano-calcium carbonate reinforcement system, along with the esterification-chelation synergistic structure of modified borax, a highly efficient flame-retardant synergistic network is formed with nano-zinc borate and chlorinated paraffin-70. This combination ensures uniform dispersion of flame-retardant components in the substrate, avoiding performance fluctuations caused by localized aggregation of traditional flame retardants. Simultaneously, chemical bonding enhances the adhesion between the flame-retardant components and the substrate, ensuring the board continues to exert its flame-retardant effect at high temperatures, effectively slowing down the combustion rate and reducing the release of toxic fumes.

[0034] 2. Basalt fiber and modified polyvinyl alcohol form a three-dimensional reinforcing skeleton. The cross-linking structure of the modified polyvinyl alcohol improves the bonding strength of the substrate, and the addition of calcium stearate improves the interfacial bonding state of the material. The synergistic effect of these three elements solves the problem of strength reduction caused by the addition of flame retardants in traditional flame-retardant boards, giving the boards both high flexural strength and toughness, reducing the risk of cracking and damage due to stress during use.

[0035] 3. Pre-dilution treatment with silane coupling agents enhances the compatibility of inorganic raw materials and organic additives. Precise control of process parameters such as stepwise stirring and gradient heating ensures that the slurry is uniform and free of particles during mixing and coating, with viscosity stably controlled within the range of 2000-3000 cP. Optimization of temperature, pressure, and time in the hot pressing process avoids internal air bubbles and stress concentration in the board. Combined with 120 and 240 mesh stepped sanding treatment, the finished board has high density and a surface roughness Ra≤1.6μm, significantly reducing quality fluctuations during production.

[0036] 4. The modified polyvinyl alcohol and borax form a stable chemical bond with inorganic substrates such as magnesium oxide and magnesium chloride, improving the water resistance and anti-aging properties of the board. The corrosion resistance of basalt fiber and the photocatalytic activity of nano-titanium dioxide work synergistically to reduce damage to the board structure caused by humid environments or long-term use, enabling the board to maintain stable performance and extend its service life in various scenarios such as construction and furniture.

[0037] 5. By adopting an optimized ratio of low magnesium chloride and high magnesium sulfate, it ensures that most of the magnesium chloride can effectively participate in the reaction, forming an effective cementitious structure, thereby achieving better strength development and higher final mechanical properties. The pre-preparation of a salt solution with precise Baume degrees fundamentally inhibits the transformation of the 518 phase to the 318 phase, greatly reducing the content of free chloride ions. This not only completely solves the problem of moisture absorption and efflorescence in the boards but also significantly improves the water resistance and dimensional stability of the boards under long-term use, overcoming the biggest obstacle to the application of magnesium oxychloride cement materials. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1: Preparation of highly flame-retardant sheet material. The specific preparation steps are as follows:

[0040] S1. Add 0.2 parts of silane coupling agent KH-550 and 1 part of anhydrous ethanol to a container, stir at 1300 rpm for 15 min, and let stand for 30 min. Separately, add 0.3 parts of modified borax to 12 parts of 80℃ deionized water and stir until dissolved. Pour the above silane coupling agent dilution into the solution, stir at 300 rpm for 15 min in a 60℃ water bath, and cool. Add 48 parts of deionized water to a mixing tank, stir at 150 rpm and heat to 30℃. First, add 30 parts of magnesium sulfate and stir for 5 min, then add 15 parts of magnesium chloride. After the addition is complete, adjust the stirring speed to 200 rpm and stir for 25 min until the salts are completely dissolved. Then let stand for 15 min to remove bubbles, seal the mixing tank, and set aside.

[0041] S2. Pour 18 parts of deionized water into the reactor, heat to 60°C with stirring at 200 rpm, slowly add 1.5 parts of modified polyvinyl alcohol, and continue stirring until completely dissolved; mix 1 part of starch with 6 parts of deionized water, stir at 400 rpm for 10 min to make starch paste, pour into the above solution, stir at 250 rpm for 30 min to obtain organic modified adhesive solution.

[0042] S3. Add 90 parts of dried magnesium oxide, 2.5 parts of nano zinc borate, 2 parts of chlorinated paraffin-70, 0.5 parts of nano titanium dioxide, 5 parts of basalt fiber and 0.2 parts of calcium stearate to a twin-shaft mixer and dry mix at 300 rpm for 3 min. Add the organic modified adhesive prepared in S2, the salt compound water agent prepared in S1 and the pretreatment solution in S1, and stir at 200 rpm for 30 min until the slurry is uniform and free of particles. Adjust the slurry viscosity to 2000 cP with the remaining 6 parts of deionized water.

[0043] S4. Place the slurry onto the coating machine conveyor belt and adjust the gap to achieve a coating amount of 165g / m². 2 The blank is formed by placing it into a hot press and hot pressing it at 110℃ and 1.2MPa for 1.2 minutes per millimeter of plate thickness.

[0044] S5. The board blank is naturally cooled to room temperature for 2 hours, and then sanded with 120 and 240 mesh stepped sanding until the surface roughness Ra≤1.6μm to obtain a high flame retardant board.

[0045] Example 2: Preparation of highly flame-retardant boards. The specific preparation steps are as follows:

[0046] S1. Add 0.5 parts of silane coupling agent KH-550 and 2 parts of anhydrous ethanol to a container, stir at 1300 rpm for 15 min, and let stand for 30 min. Separately, add 0.8 parts of modified borax to 14 parts of 90℃ deionized water and stir until dissolved. Pour the above silane coupling agent dilution into the solution, stir at 300 rpm for 20 min in a 70℃ water bath, and cool. Add 56 parts of deionized water to a mixing tank, stir at 150 rpm and heat to 40℃. First, add 35 parts of magnesium sulfate and stir for 5 min, then add 20 parts of magnesium chloride. After the addition is complete, adjust the stirring speed to 200 rpm and stir for 35 min until the salts are completely dissolved. Then let stand for 15 min to remove bubbles, seal the mixing tank, and set aside.

[0047] S2. Pour 28 parts of deionized water into the reactor, heat to 70°C with stirring at 200 rpm, slowly add 3 parts of modified polyvinyl alcohol, and continue stirring until completely dissolved; mix 2 parts of starch with 7 parts of deionized water, stir at 400 rpm for 15 min to make starch paste, pour into the above solution, stir at 250 rpm for 30 min to obtain organic modified adhesive solution.

[0048] S3. Add 110 parts of dried magnesium oxide, 3.5 parts of nano zinc borate, 4 parts of chlorinated paraffin-70, 1 part of nano titanium dioxide, 10 parts of basalt fiber and 0.5 parts of calcium stearate to a twin-shaft mixer and dry mix at 300 rpm for 5 min. Add the organic modified adhesive prepared in S2, the salt compound water agent prepared in S1 and the pretreatment solution in S1, and stir at 300 rpm for 40 min until the slurry is uniform and free of particles. Adjust the slurry viscosity to 3000 cP with the remaining 5 parts of deionized water.

[0049] S4. Place the slurry onto the coating machine conveyor belt and adjust the gap to achieve a coating amount of 175g / m². 2 The blank is formed by placing it into a hot press and hot pressing it at 120℃ and 1.5MPa for 1.2 minutes per millimeter of plate thickness.

[0050] S5. The board blank is naturally cooled to room temperature for 3 hours, and then sanded with 120 and 240 mesh stepped sanding until the surface roughness Ra≤1.6μm to obtain a high flame retardant board.

[0051] Example 3: Preparation of highly flame-retardant boards. The specific preparation steps are as follows:

[0052] S1. Add 0.3 parts of silane coupling agent KH-550 and 1 part of anhydrous ethanol to a container, stir at 1300 rpm for 15 min, and let stand for 30 min. Separately, add 0.5 parts of modified borax to 13 parts of 85℃ deionized water and stir until dissolved. Pour the above silane coupling agent dilution into the solution, stir at 300 rpm for 17 min in a 65℃ water bath, and cool. Add 52 parts of deionized water to a mixing tank, stir at 150 rpm and heat to 35℃. First, add 32 parts of magnesium sulfate and stir for 5 min, then add 18 parts of magnesium chloride. After the addition is complete, adjust the stirring speed to 200 rpm and stir for 25-35 min until the salts are completely dissolved. Then let stand for 15 min to remove bubbles, seal the mixing tank, and set aside.

[0053] S2. Pour 23 parts of deionized water into the reactor, heat to 65°C with stirring at 200 rpm, slowly add 2 parts of modified polyvinyl alcohol, and continue stirring until completely dissolved; mix 1 part of starch with 6 parts of deionized water, stir at 400 rpm for 12 min to make starch paste, pour into the above solution, stir at 250 rpm for 30 min to obtain organic modified adhesive solution.

[0054] S3. Add 100 parts of dried magnesium oxide, 3 parts of nano zinc borate, 3 parts of chlorinated paraffin-70, 0.7 parts of nano titanium dioxide, 7 parts of basalt fiber and 0.3 parts of calcium stearate to a twin-shaft mixer and dry mix at 300 rpm for 4 min. Add the organic modified adhesive prepared in S2, the salt compound water agent prepared in S1 and the pretreatment solution in S1, and stir at 250 rpm for 35 min until the slurry is uniform and free of particles. Adjust the slurry viscosity to 2500 cP with the remaining 6 parts of deionized water.

[0055] S4. Place the slurry onto the coating machine conveyor belt and adjust the gap to achieve a coating amount of 170g / m². 2 The blank is formed by placing it into a hot press and hot pressing it at 115℃ and 1.3MPa for 1.2 minutes per millimeter of plate thickness.

[0056] S5. The board blank is naturally cooled to room temperature for 2.5 hours, and then sanded with 120 and 240 mesh stepped sanding until the surface roughness Ra≤1.6μm to obtain a high flame retardant board.

[0057] Example 4: Preparation of modified polyvinyl alcohol. The specific preparation steps are as follows:

[0058] A1. Take 15g of polyvinyl alcohol powder and add it to a three-necked flask. Then add 150mL of deionized water and place it in a 70℃ constant temperature water bath. Stir at 300rpm for 40min until the polyvinyl alcohol is completely swollen. Then add 0.5g of sodium dodecyl sulfate and continue stirring at 300rpm for 20min. Next, slowly add 3mL of glacial acetic acid dropwise with a dropper while stirring. Adjust the pH of the system to 5.5 and stir for 15min to obtain the pretreated polyvinyl alcohol solution.

[0059] A2. While stirring at 300 rpm, add 5 mL of ethylene glycol to the pretreated polyvinyl alcohol solution and stir for 10 min. Then add 2 mL of glutaraldehyde in 3 portions, with a 5 min interval between each addition. Adjust the water bath temperature to 50℃ and stir continuously at 250 rpm for 40 min to complete the condensation crosslinking reaction. Turn off the water bath heating and allow the solution to cool naturally to room temperature.

[0060] A3. Under stirring at 300 rpm, add 1 mL of titanate coupling agent to the reaction system after the second modification and stir for 15 min; then add 2 g of nano calcium carbonate, increase the stirring speed to 400 rpm, and continue stirring at room temperature for 30 min to obtain modified polyvinyl alcohol.

[0061] Example 5: Preparation of modified borax. The specific preparation steps are as follows:

[0062] B1. Dissolve 8g of borax in 80mL of distilled water and place it in a 50℃ constant temperature water bath. Stir at 200rpm until the borax is completely dissolved. After dissolution, maintain the temperature and speed and continue stirring for 30min to allow the borax to fully hydrolyze. Then slowly add 6mL of glycerol and adjust the stirring speed to 250rpm. Continue stirring in a 50℃ water bath for 50min to complete the esterification reaction. Allow to cool naturally to room temperature.

[0063] B2. Add 1.5g of tartaric acid to the reaction system after the first modification and stir at 250rpm for 15min. Then add 1g of citric acid in two portions, with a 10min interval between each addition. After all the citric acid has been added, continue stirring at 250rpm for 30min to form a chelate structure.

[0064] B3. While stirring at 300 rpm, add 3 mL of polyethylene glycol to the system after the second modification and stir for 20 min; then add 0.5 g of hydroxypropyl methylcellulose and stir at 300 rpm at room temperature for 40 min to obtain modified borax.

[0065] Comparative Example 1: High flame retardant sheet material was prepared. The specific preparation steps are as follows:

[0066] The remaining steps remain the same, except that the modified polyvinyl alcohol in Example 3 is replaced with untreated polyvinyl alcohol to prepare a highly flame-retardant board.

[0067] Comparative Example 2: High flame retardant board was prepared. The specific preparation steps are as follows:

[0068] The remaining steps remain the same, except that the modified borax in Example 3 is replaced with untreated borax to prepare a highly flame-retardant board.

[0069]

[0070] According to the performance test results, the high flame-retardant boards of Examples 1-3 are superior to those of Comparative Example 1 (using unmodified polyvinyl alcohol) and Comparative Example 2 (using unmodified borax) in terms of limiting oxygen index (32.5-33.8), vertical burning rating (both reaching V-0), flexural strength (18.6-19.8MPa), flexural modulus of elasticity (3.2-3.5GPa), and heat distortion temperature (135-142℃). They also have a lower water absorption thickness swelling rate (1.7-2.1%), exhibiting superior flame retardancy, mechanical properties, heat resistance, and water resistance.

[0071] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high flame-retardant board material, characterized in that: This high flame-retardant board contains the following raw materials in parts by weight: 90-110 parts magnesium oxide, 15-20 parts magnesium chloride, 30-35 parts magnesium sulfate, 1.5-3 parts modified polyvinyl alcohol, 1-2 parts starch, 0.3-0.8 parts modified borax, 0.2-0.5 parts silane coupling agent KH-550, 1-2 parts anhydrous ethanol, 2.5-3.5 parts nano zinc borate, 2-4 parts chlorinated paraffin-70, 0.5-1 part nano titanium dioxide, 5-10 parts basalt fiber, 0.2-0.5 parts calcium stearate, and 90-110 parts deionized water; The modified polyvinyl alcohol is prepared using the following specific steps: A1. Add polyvinyl alcohol powder to a three-necked flask, then add deionized water, place in a 70℃ constant temperature water bath, and stir at 300 rpm for 40 minutes until the polyvinyl alcohol is completely swollen; then add sodium dodecyl sulfate, and continue stirring at 300 rpm for 20 minutes; then slowly add glacial acetic acid dropwise with a dropper while stirring, adjust the pH of the system to 5.5, and stir for 15 minutes to obtain a pretreated polyvinyl alcohol solution; A2. While stirring at 300 rpm, add ethylene glycol to the pretreated polyvinyl alcohol solution and stir for 10 min. Then add glutaraldehyde in 3 portions, with a 5 min interval between each addition. Adjust the water bath temperature to 50℃ and keep stirring at 250 rpm for 40 min to complete the condensation crosslinking reaction. Turn off the water bath heating and allow the solution to cool naturally to room temperature. A3. Under stirring at 300 rpm, add titanate coupling agent to the reaction system after the second modification and stir for 15 min; then add nano calcium carbonate, increase the stirring speed to 400 rpm, and continue stirring at room temperature for 30 min to obtain modified polyvinyl alcohol. The modified borax is prepared using the following specific steps: B1. Dissolve borax in distilled water and place it in a 50°C constant temperature water bath. Stir at 200 rpm until the borax is completely dissolved. After dissolution, maintain the temperature and speed and continue stirring for 30 minutes to allow the borax to fully hydrolyze. Then slowly add glycerol and adjust the stirring speed to 250 rpm. Continue stirring in a 50°C water bath for 50 minutes to complete the esterification reaction. Allow it to cool naturally to room temperature. B2. Add tartaric acid to the reaction system after the first modification and stir at 250 rpm for 15 min; then add citric acid in two portions, with a 10 min interval between each addition. After all the citric acid has been added, continue stirring at 250 rpm for 30 min to form a chelate structure. B3. While stirring at 300 rpm, add polyethylene glycol to the second modified system and stir for 20 min; then add hydroxypropyl methylcellulose and stir at 300 rpm at room temperature for 40 min to obtain modified borax.

2. The high flame-retardant sheet material according to claim 1, characterized in that: The basalt fibers are 3-5 mm in length and 10-15 μm in diameter.

3. The high flame-retardant sheet material according to claim 1, characterized in that: The ratio of polyvinyl alcohol powder, deionized water, sodium dodecyl sulfate, and glacial acetic acid in A1 is 15g:150mL:0.5g:3mL; wherein the polyvinyl alcohol is type 1788. The ratio of ethylene glycol to glutaraldehyde in A2 is 5 mL: 2 mL; The ratio of titanate coupling agent to nano-calcium carbonate in A3 is 1 mL: 2 g.

4. The high flame-retardant sheet material according to claim 1, characterized in that: The ratio of borax, distilled water, and glycerol in B1 is 8g:80mL:6mL; The ratio of tartaric acid to citric acid in B2 is 1.5g:1g; The ratio of polyethylene glycol to hydroxypropyl methylcellulose in B3 is 3 mL: 0.5 g.

5. The high flame-retardant sheet material according to claim 1, characterized in that: Citric acid is added to B2 in stages and combines with tartaric acid to form a chelate structure, ensuring the thermal stability and flame-retardant synergistic effect of borax.

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