Fire-resistant magnesium oxide boards

Abstract

A fireproof magnesium oxide board is made from the following raw materials, the names and weight parts of which are as follows: 80-100 parts of magnesium oxide; 20-30 parts of anhydrous magnesium chloride; 10-20 parts of modified expanded vermiculite foaming agent; 20-30 parts of aluminum silicate fiber; 5-10 parts of sawdust; 10-15 parts of fly ash; 8-12 parts of glass magnesium board powder; 1.5-5 parts of non-woven fabric; 10-20 parts of water; wherein, the modified expanded vermiculite is prepared by the following steps: (1) the vermiculite is subjected to non-woven fabric foaming agent. (2) Take acrylic acid monomer, sodium hydroxide, acrylamide monomer, initiator potassium persulfate, crosslinking aid pentaerythritol polyglycidyl ether, incompletely expanded vermiculite, and water, stir evenly and disperse ultrasonically to obtain the first reaction solution, and place it in a reaction vessel to react and obtain a gel substance; (3) Perform preliminary crushing and drying on the gel substance, then further pulverize it in a ball mill, and then perform surface crosslinking modification to obtain fireproof expanded vermiculite with water absorption properties.

Description

Technical Field

[0001] This invention relates to a sheet material, and more particularly to a magnesium oxide sheet material and its manufacturing process. Background Technology

[0002] Magnesium oxide board is a new type of multifunctional building material. It combines the lightweight, flexibility, and reprocessing properties of wood-based organic boards with the fire resistance and water resistance of inorganic boards, making it suitable for use in wall construction, ceiling installation, floor lining, and other areas requiring fire protection. Currently, the main components of magnesium oxide boards are fiberglass mesh (the primary source of strength), magnesium oxide, magnesium chloride, perlite, filler fibers, and modifying additives. However, existing magnesium oxide boards suffer from moisture absorption and efflorescence, as well as embrittlement, affecting product quality and resulting in poor fire resistance and insulation, thus limiting their widespread application. Chinese patent application CN201310232377 attempted to use an expanded foam material composed of melamine, pentaerythritol, and ammonium polyphosphate, achieving a certain degree of flame retardancy. However, the flame retardant performance fails to meet the stringent requirements of the high-end market, such as a fire resistance rating of ≥4 hours.

[0003] Vermiculite is a complex hydrous iron-magnesium silicate mineral, a regenerated mineral formed by hydrothermal alteration or weathering of mica-like minerals. The chemical composition of vermiculite is [(Mg,Fe,Al)3(Si,Al)4O10(OH)2]·4H2O, but this composition often varies. It belongs to the monoclinic crystal system, occurs in platy forms, has a hardness of 1–1.5, and a density of 2400–2700 kg / m³. Thin flakes are flexible. Its most important property is its expansion upon heating, with maximum expansion at 800–1000℃, and an expansion ratio of 8–15 times, sometimes reaching 30 times. Expanded vermiculite typically has a density of 80–200 kg / m³, a thermal conductivity of 0.047–0.07 W / (m·K), a sound absorption coefficient of 0.50–0.63 (frequency 512 Hz), and a refractoriness of 1300–1350℃. Furthermore, expanded vermiculite, when in a dry state, exhibits excellent frost resistance; at -20℃, its particle size distribution remains unchanged after 15 freeze-thaw cycles. Simultaneously, being inorganic, it is unaffected by fungal erosion, rot, or deterioration, and is also resistant to insect and rodent damage. Due to these superior properties, its applications are quite extensive. Current Applications of Vermiculite: Vermiculite is primarily used in the construction industry, but it also has unique applications in other fields. The production process of expanded vermiculite is as follows: After removing impurities, the vermiculite is crushed into 1-2mm particles and sieved to remove fine powder. After drying (preheating) the raw material, it is placed in a rotary kiln or vertical kiln for expansion heat treatment. The thermal regime of the expansion heat treatment has a significant impact on the expansion rate of the vermiculite. Generally, the vermiculite is first slowly heated to 100℃, and then quickly placed into a heating furnace preheated to 1000℃, with an expansion time of 0.5-1.0 minutes. After being expanded and heat-treated, vermiculite is annealed and cooled to become expanded vermiculite. The expanded vermiculite coming out of the furnace needs to be screened to remove unexpanded impurity particles.

[0004] In the prior art, vermiculite has been modified to obtain higher performance, and a series of attempts have been made. For example, CN115304344A discloses a fireproof and heat-insulating filler for steel fire doors. The fireproof and heat-insulating filler for steel fire doors includes component A and component B. Component A includes the following components in parts by weight: 55-65 parts of lightweight heat-insulating material, 8-14 parts of expandable graphite, 9-13 parts of bentonite, 7-14 parts of anhydrous gypsum, and 9-14 parts of additives; component B is water, the lightweight heat-insulating material is expanded vermiculite, and the additives include 5-6 parts of a polymer water-retaining agent. For example, Chinese invention patent CN100404612A discloses a "preparation method of expanded vermiculite / potassium polyacrylate-acrylamide super absorbent composite material". This method directly uses expanded vermiculite as raw material and prepares super absorbent composite material through graft copolymerization reaction of potassium acrylate and acrylamide monomers. This method uses expanded vermiculite at room temperature as raw material to combine with organic matter, and uses expanded vermiculite to improve the network structure and water-absorbing groups of potassium polyacrylate-acrylamide, thereby improving the performance of the material and reducing production costs.

[0005] As is well known, fire-resistant materials such as magnesium oxide boards use expanded vermiculite, primarily due to its heat resistance and hollow structure, which provides excellent fire resistance and heat insulation. The addition of water-retaining agents utilizes the fact that during a fire, the large amount of water lost from the water-retaining material causes evaporation, leading to heat dissipation and a decrease in temperature. However, the amount of water-retaining agent used in the material is limited; the key issue is that excessive use will severely affect the initial strength of the fire-resistant material. Furthermore, during a fire, the large-scale evaporation of moisture creates numerous voids within the material, resulting in a lack of internal strength support and a sharp decline in the fire-resistant material's strength, making it prone to collapse. It is evident that in CN115304344A, expanded vermiculite and water-retaining agent are only used in combination, and the amount of water-retaining agent used is limited, resulting in limited fire resistance and strength of the fire-retardant material. While CN100404612A prepares expanded vermiculite-modified potassium polyacrylate-acrylamide composite water-absorbing material, which significantly improves the water absorption performance, this technology uses potassium polyacrylate-acrylamide polymer water-absorbing material as the main water-absorbing material, with expanded vermiculite merely serving as an aggregate to improve its network structure strength and water absorption. The high molecular weight of the water-absorbing material as the main component limits its use in fire-retardant materials. As observed in actual use, excessive use can lead to a sharp decrease in strength, causing the fire-retardant material to collapse.

[0006] In the patent application CN202310795005.7 filed by the inventor on June 30, 2023, the inventor discovered that a composite structure formed by incompletely expanded vermiculite and water-absorbing resin can better improve fire resistance. However, in practical applications, our company has found that after the above-mentioned type of fire-resistant material is stored in a dry space for a long time, especially in the dry autumn and winter seasons, the fire resistance of the fire-resistant board material decreases to a certain extent compared with the initial laboratory test results, indicating an unstable fire resistance performance. Summary of the Invention

[0007] This invention provides a fire-resistant magnesium oxide board with long-term stable fire resistance. It is composed of the following raw materials in parts by weight: 80-100 parts magnesium oxide; 20-30 parts anhydrous magnesium chloride; 10-20 parts modified expanded vermiculite foaming agent; 20-30 parts aluminum silicate fiber; 5-10 parts sawdust; 10-15 parts fly ash; 8-12 parts pulverized magnesium oxide board powder; 1.5-5 parts non-woven fabric; and 10-20 parts water.

[0008] The modified expanded vermiculite is prepared by the following steps:

[0009] (1) Incomplete expansion calcination of vermiculite: take vermiculite raw material, remove impurities, and put it into a rotary furnace at a temperature of 700-1000℃, heat and expand for 10-20 seconds, and after discharge, incompletely expanded vermiculite is obtained with a bulk density of 1000-1200kg / m3.

[0010] (2) Take acrylic acid monomer, sodium hydroxide, acrylamide monomer, potassium persulfate initiator, pentaerythritol polyglycidyl ether crosslinking aid, incompletely expanded vermiculite, and water, stir evenly and ultrasonically disperse for 20-40 minutes to obtain the first reaction solution, and place it in a reaction vessel for reaction at a temperature of 80-100℃ for 0.5-2 hours to obtain a gel substance; wherein, the mass ratio of acrylic acid monomer, acrylamide monomer, and incompletely expanded vermiculite is (2-4):(0.4-0.6):6;

[0011] (3) The gel material is initially crushed, dried at 150-200℃, and then further pulverized in a ball mill until a fire-resistant expanded vermiculite with water absorption properties and a particle size of 0.6-1.0mm is obtained.

[0012] (4) Surface modification of fire-resistant expanded vermiculite

[0013] A surface crosslinking solution was prepared by mixing 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A in a specific ratio. The mass ratio of the surface crosslinking solution to fire-retardant expanded vermiculite with water absorption properties was (0.5-4):100. A measured amount of fire-retardant expanded vermiculite with water absorption properties was placed in a high-speed stirrer, and the surface crosslinking solution was evenly sprayed onto the surface. After stirring for 8-15 minutes, the expanded vermiculite was placed in an oven and subjected to surface crosslinking at 60-150℃ for 0.5-1.5 hours to obtain the final product, fire-retardant expanded vermiculite.

[0014] The manufacturing process of fire-resistant magnesium oxide boards includes the following steps:

[0015] (1) Put magnesium oxide, anhydrous magnesium chloride, foaming agent and glass magnesium board powder into a mixer according to the weight of the magnesium oxide board and stir. At the same time, gas is introduced into the mixer to form bubbles and stir for 15 minutes.

[0016] (2) Add the aluminum silicate fiber, fly ash, sawdust and the magnesium oxide board in the weight proportions to the mixer, continue to mix and stir evenly for 30 minutes to make a slurry;

[0017] (3) Then introduce the prepared template into the press and lay the non-woven fabric.

[0018] (4) Take out the slurry from step (2) and add it to the press feed hopper. Then fill the slurry into the seamless fabric of the template and press it to the required size. After drying for 8-10 hours, it can be demolded.

[0019] (5) Place the cured board and template upside down, gently lift one corner of the mold with your hand, press the cured board with your hand and it will fall off. Then, starting from this corner, remove one side and lift the mold.

[0020] (6) Stack the molded boards together and cure them in the curing room for 3 days. Then put the products in a dry room for 10 days.

[0021] (7) Then cut off the four sides of the dried board according to the specifications.

[0022] The mass ratio of 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol and tetrabromobisphenol A is 1:1:2:1.

[0023] The mass ratio of the surface crosslinking solution to fire-retardant expanded vermiculite with water absorption properties is 1:100. The stirring time is 10 minutes, the surface temperature is 80℃, and the crosslinking time is 1 hour.

[0024] The rotary kiln operates at a temperature of 850-950℃ and has a heating expansion time of 12-15 seconds.

[0025] The heating expansion time is 13 seconds.

[0026] The bulk density of incompletely expanded vermiculite is 1000-1100 kg / m3.

[0027] In step (2), the stirring speed in the reactor is 1200-1800 rpm.

[0028] In step (2), the mass ratio of acrylic monomer to incompletely expanded vermiculite is 1:2.

[0029] In step (2), the mass ratio of water to incompletely expanded vermiculite is (15-25):6.

[0030] This invention, developed through extensive research by researchers in actual production, utilizes in-situ polymerization to allow most of the water-absorbing resin to enter the interlayer of the incompletely expanded vermiculite. This significantly reduces the negative impact of the strong water absorption of the water-absorbing resin on the durability and strength of the refractory material, thereby greatly improving its refractory properties while maintaining its strength.

[0031] The amount of water used is not excessive. Due to the water-absorbing properties of vermiculite, a large amount of water will enter the interlayer of the expanded vermiculite, and a large number of reactive monomers will be dispersed within it. During the reaction, superabsorbent polymers will polymerize in situ within the interlayer of the expanded vermiculite to form a superabsorbent polymer resin. Ultimately, a fire-retardant material will be formed with the superabsorbent polymer resin embedded inside the expanded vermiculite and the expanded vermiculite forming the outer shell. Of course, it is unavoidable that a small amount of superabsorbent resin will remain on the surface of the expanded vermiculite. If too much water is used, a large amount of water will also remain on the outside of the vermiculite, causing a large amount of acrylic acid to react on the surface of the expanded vermiculite, resulting in a large amount of superabsorbent resin being exposed on the outside of the expanded vermiculite, thus reducing the fire resistance of the material. Therefore, in step 2 of this application, the mass ratio of water to incompletely expanded vermiculite is (15-25):6.

[0032] In preparing the first reaction solution, the inventors discovered that conventional dispersion and stirring could not achieve the technical objective of this invention. Extensive research revealed that ultrasonic dispersion facilitates the rapid penetration of water and reactive monomers such as acrylic acid and acrylamide into the interlayer of expanded vermiculite. Conventional dispersion, on the other hand, results in the formation of a large amount of water-absorbing resin on the surface of the expanded vermiculite.

[0033] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0034] (1) By adjusting the amount of water, water-absorbing polymer monomers and expanded vermiculite, and by using an ultrasonic dispersion process, most of the monomers are polymerized in situ in the interlayer of the expanded vermiculite, thus forming a composite particle with expanded vermiculite as the shell and water-absorbing polymer material coated on it, which is an expanded vermiculite that has both water absorption and fire resistance properties.

[0035] (2) In the modified expanded vermiculite, the expanded vermiculite and the water-absorbing polymer have strong water absorption properties. The two work together to fill the internal interlayer of the expanded vermiculite with water-absorbing and expanding polyacrylic acid water-absorbing resin. The expanded water-absorbing resin can also increase the interlayer distance of the expanded vermiculite. At the same time, the external surface can maintain the strength of the expanded vermiculite as an inorganic mineral filler. In this way, the water absorption performance of the modified expanded vermiculite can be significantly improved, and it can also play a reinforcing role in fireproof materials, avoiding the negative impact of poor strength of water-absorbing resin on the strength of fireproof materials.

[0036] (3) When the fire-retardant material containing the above-mentioned modified expanded vermiculite is burned, a large amount of water evaporates first, taking away a large amount of heat. Although the water-absorbing resin inside the expanded vermiculite will shrink, it does not significantly affect the strength of the fire-retardant material. At the same time, further heating causes the incompletely expanded vermiculite to expand further, thus forming a huge heat-insulating void inside the expanded vermiculite. It can be seen that the modified expanded vermiculite produces a dual fire-retardant effect of water evaporation heat absorption and hollow heat insulation, which greatly improves the fire-retardant performance of the fire-retardant material and avoids the problems of insufficient strength of water-absorbing polymer materials and local collapse of fire-retardant materials caused by water evaporation.

[0037] (4) In actual production, we found that there is also a small amount of water-absorbing resin on the surface of vermiculite. At high temperature, it will shrink, resulting in material layout defects. We chose uncommon incompletely expanded vermiculite, which will expand further at high temperature. This can effectively make up for the space reduced by the shrinkage of the external water-absorbing resin, effectively maintain the strength of the fireproof material at high temperature, and delay its high temperature deformation time.

[0038] (5) In practical applications, our company has found that after prolonged storage in dry spaces, especially during the dry autumn and winter seasons, the fire resistance of fireproof boards using unmodified expanded vermiculite decreases compared to laboratory test results. Analysis by our R&D engineers indicates that although expanded vermiculite has strong water absorption, the surface of the vermiculite also contains directly exposed water-absorbing resin, and the porous structure of vermiculite cannot completely cover the core water-absorbing resin. Therefore, prolonged dry storage, especially in autumn and winter, leads to a significant loss of moisture from the water-absorbing resin, resulting in a certain degree of decrease in actual fire resistance.

[0039] Based on the company's existing innovative technology, this invention utilizes a surface crosslinking solution prepared with 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A to perform crosslinking modification, thereby increasing the crosslinking density of the water-absorbing resin on the surface of expanded vermiculite. This results in a high-density crosslinked interpenetrating network structure, making it difficult for moisture in the water-absorbing and fire-retardant expanded vermiculite to evaporate, thus exhibiting good water retention. Even after long-term storage in a dry environment, it still maintains good fire-retardant performance.

[0040] (6) In the modification of expanded vermiculite, tetrabromobisphenol A was added in the form of chemical crosslinking. Through chemical crosslinking with expanded vermiculite, the dispersibility of tetrabromobisphenol A was improved by utilizing the dispersibility of expanded vermiculite in inorganic fireproof materials. At the same time, the three different fireproofing mechanisms of chemical fireproofing of tetrabromobisphenol A, heat insulation fireproofing of expanded vermiculite and water evaporation fireproofing of water-absorbing resin were organically combined and complemented each other, so that the modified expanded vermiculite exhibited better fireproofing performance. Detailed Implementation

[0041] The technical solution of the invention will be described in detail below with reference to specific embodiments.

[0042] Example 1

[0043] (1) The preparation method of fireproof expanded vermiculite A includes the following steps: (1) Incomplete expansion and calcination of vermiculite: take vermiculite raw material to remove impurities and put it into a rotary furnace at a temperature of 850℃, heat and expand for 13 seconds, and after discharge, incomplete expanded vermiculite is obtained with a bulk density of 1050kg / m3.

[0044] (2) 300g of acrylic acid monomer, 120g of sodium hydroxide, 50g of acrylamide monomer, 1g of potassium persulfate initiator, 0.1g of pentaerythritol polyglycidyl ether crosslinking aid, 600g of incompletely expanded vermiculite, and 2000g of water were stirred evenly to obtain the first reaction solution, and the reaction was carried out in a reaction vessel at a reaction temperature of 85℃ for 1 hour to obtain a gel substance;

[0045] (3) The gel material is initially crushed, dried at 170°C, and then further pulverized in a ball mill until a fire-resistant expanded vermiculite with water absorption properties and a particle size of 0.6-1.0 mm is obtained.

[0046] (4) Surface modification of fire-resistant expanded vermiculite

[0047] A surface crosslinking solution was prepared by mixing 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A in a specific ratio. The mass ratio of the surface crosslinking solution to fire-retardant expanded vermiculite with water absorption properties was 1:100. A measured amount of fire-retardant expanded vermiculite with water absorption properties was placed in a high-speed stirrer, and the surface crosslinking solution was evenly sprayed onto the surface. After stirring for 10 minutes, the expanded vermiculite was placed in an oven and subjected to surface crosslinking at 80°C for 1 hour to obtain the final product, fire-retardant expanded vermiculite A with water absorption properties.

[0048] The mass ratio of 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol and tetrabromobisphenol A is 1:1:2:1.

[0049] Example 2

[0050] (1) The preparation method of fireproof expanded vermiculite A includes the following steps: (1) Incomplete expansion and calcination of vermiculite: take vermiculite raw material to remove impurities and put it into a rotary furnace at a temperature of 850℃, heat and expand for 13 seconds, and after discharge, incomplete expanded vermiculite is obtained with a bulk density of 1050kg / m3.

[0051] (2) 300g of acrylic acid monomer, 120g of sodium hydroxide, 50g of acrylamide monomer, 1g of potassium persulfate initiator, 0.1g of pentaerythritol polyglycidyl ether crosslinking aid, 600g of incompletely expanded vermiculite, and 2000g of water were stirred evenly to obtain the first reaction solution, and the reaction was carried out in a reaction vessel at a reaction temperature of 85℃ for 1 hour to obtain a gel substance;

[0052] (3) The gel material is initially crushed, dried at 170°C, and then further pulverized in a ball mill until a fire-resistant expanded vermiculite B with water absorption properties and a particle size of 0.6-1.0 mm is obtained.

[0053] Example 3

[0054] Based on Example 1, the incompletely expanded vermiculite was replaced with ordinary expanded vermiculite available in the market, with a bulk density of 2500 kg / m3. The other preparation steps were the same, resulting in modified expanded vermiculite C.

[0055] Example 4

[0056] (1) The preparation method of fireproof expanded vermiculite A includes the following steps: (1) Incomplete expansion and calcination of vermiculite: take vermiculite raw material to remove impurities and put it into a rotary furnace at a temperature of 850℃, heat and expand for 13 seconds, and after discharge, incomplete expanded vermiculite is obtained with a bulk density of 1050kg / m3.

[0057] (2) 300g of acrylic acid monomer, 120g of sodium hydroxide, 50g of acrylamide monomer, 1g of potassium persulfate initiator, 0.1g of pentaerythritol polyglycidyl ether crosslinking aid, and 2000g of water were stirred evenly to obtain the first reaction solution, and the reaction was carried out in a reaction vessel at a reaction temperature of 85℃ for 1 hour to obtain a gel substance.

[0058] (3) The gel material is initially crushed, dried at 170°C, and then further pulverized in a ball mill. 600g of incompletely expanded vermiculite is added for blending to obtain blended modified expanded vermiculite D.

[0059] Example 5

[0060] Based on Example 1, the amount of acrylic monomer was adjusted from 300g to 600g, while the other preparation steps remained the same, to obtain modified expanded vermiculite E.

[0061] Example 6

[0062] Based on Example 1, the amount of water was adjusted from 2000g to 3000g, while the other preparation steps remained the same, to obtain modified expanded vermiculite F.

[0063] Example 7 (Tetrabromobisphenol A blend modification)

[0064] Fire-resistant expanded vermiculite with water absorption properties and a particle size of 0.6-1.0 mm was obtained by using steps (1)-(3) in Example 1.

[0065] (4) Surface modification of fire-resistant expanded vermiculite

[0066] A surface crosslinking solution was prepared by mixing 1,3-propanediol and trimethylolpropane triglycidyl ether in a specific ratio. The mass ratio of the surface crosslinking solution to fire-retardant expanded vermiculite with water-absorbing properties was 0.4:100. A measured amount of fire-retardant expanded vermiculite with water-absorbing properties was placed in a high-speed stirrer, and the surface crosslinking solution was evenly sprayed onto its surface. After stirring for 10 minutes, the expanded vermiculite was placed in an oven and subjected to surface crosslinking at 80°C for 1 hour to obtain fire-retardant expanded vermiculite with water-absorbing properties. The mass ratio of 1,3-propanediol to trimethylolpropane triglycidyl ether was 1:1.

[0067] Ethanol and tetrabromobisphenol A are mixed in a mass ratio of 2:1 to obtain a tetrabromobisphenol A alcohol solution, which is then sprayed onto the surface of fire-retardant expanded vermiculite obtained by the aforementioned process under high-speed stirring, thereby obtaining fire-retardant expanded vermiculite G.

[0068] The mass ratio of the tetrabromobisphenol A modified solution to fire-retardant expanded vermiculite (based on unmodified vermiculite) is 0.6:100. The mass ratio of 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A is 1:1:2:1.

[0069] Example 8

[0070] Fire-resistant expanded vermiculite with water absorption properties and a particle size of 0.6-1.0 mm was obtained by using steps (1)-(3) in Example 1.

[0071] (4) Surface modification of fire-resistant expanded vermiculite

[0072] A surface crosslinking solution was prepared by mixing 1,3-propanediol, trimethylolpropane triglycidyl ether, and ethanol in a specific ratio. The mass ratio of the surface crosslinking solution to the water-absorbing, fire-retardant expanded vermiculite was 1:100. A measured amount of the water-absorbing, fire-retardant expanded vermiculite was placed in a high-speed stirrer, and the surface crosslinking solution was evenly sprayed onto its surface. After stirring for 10 minutes, the expanded vermiculite was placed in an oven and subjected to surface crosslinking at 80°C for 1 hour to obtain the final product, which is the water-absorbing, fire-retardant expanded vermiculite H.

[0073] The mass ratio of 1,3-propanediol, trimethylolpropane triglycidyl ether, and ethanol is 1:2:2.

[0074] Example 9

[0075] Fire-retardant magnesium oxide boards are prepared from the following raw materials: 90 kg of magnesium oxide; 25 kg of anhydrous magnesium chloride; 15 kg of modified expanded vermiculite foaming agent; 25 kg of aluminum silicate fiber; 8 kg of sawdust; 12 kg of fly ash; 10 parts of glass magnesium board powder; 5 kg of non-woven fabric; and 15 kg of water. The specific preparation process is as follows:

[0076] (1) Put magnesium oxide, anhydrous magnesium chloride, foaming agent, and glass magnesium board powder into a mixer according to the above-mentioned parts by weight of magnesium oxide board, and stir while filling the mixer with gas to form bubbles. Stir for 15 minutes.

[0077] (2) Add aluminum silicate fiber, fly ash and sawdust into the mixer according to the weight of the magnesium oxide board, continue to mix and stir evenly for 30 minutes to make a slurry;

[0078] (3) Then introduce the prepared template into the press and lay the non-woven fabric.

[0079] (4) Take out the slurry from step (2) and add it to the press feed hopper. Then fill the slurry into the seamless fabric of the template and press it to the required size. After drying for 8-10 hours, it can be demolded.

[0080] (5) Place the cured board and template upside down, gently lift one corner of the mold with your hand, press the cured board with your hand and it will fall off. Then, starting from this corner, remove one side and lift the mold.

[0081] (6) Stack the molded boards together and cure them in the curing room for 3 days. Then put the products in a dry room for 10 days.

[0082] (7) Then cut off the four sides of the dried board according to the specifications. Among them, fireproof magnesium oxide boards A, B, C, D, E, F, G, and H are obtained by using the modified expanded vermiculite A, B, C, D, E, F, G, and H prepared in Examples 1-6.

[0083] Fire resistance performance test

[0084] According to GB50045-95, the fire resistance limit (hours) is tested. A specimen reaches its fire resistance limit if any of the following conditions occur: Loss of stability: Axial deformation of the column member exceeds h / 100 (mm) or the axial deformation rate exceeds 3h / 1000 (mm / min). h is the initial fire-exposed height of the column member after loading and before the fire resistance test, in mm.

[0085] The fire resistance test was divided into two groups. The first group was tested 3 days after the fire-resistant boards were manufactured, and the second group was tested 3 months after the fire-resistant boards were manufactured and stored in a dry environment.

[0086]

[0087] It is evident that the flame retardant properties of fire-retardant magnesium oxide boards with specially modified expanded vermiculite are significantly improved compared to those with directly blended or other conventionally modified expanded vermiculite.

[0088] The fire retardant performance of expanded vermiculite without added tetrabromobisphenol A (TBBPA) was slightly reduced, while the performance of expanded vermiculite modified with TCBPA blends was lower than that of expanded vermiculite modified with chemical crosslinking. This is presumably due to the slightly poor compatibility and dispersibility of TCBPA in inorganic material systems. However, chemical modification with TCBPA improves the crosslinking density and hydrophobicity of the vermiculite surface, enhancing the long-term stability of its fire retardant performance. Furthermore, the well-dispersed TCBPA itself acts as a fire retardant, significantly improving the fire retardant performance of expanded vermiculite.

Claims

1. A fireproof magnesium oxide board, characterized by, The following raw materials are mixed to form the product, and the raw material names and weight parts are as follows: magnesium oxide 80-100 parts; anhydrous magnesium chloride 20-30 parts; modified expanded vermiculite 10-20 parts; aluminum silicate fiber 20-30 parts; sawdust 5-10 parts; fly ash 10-15 parts; glass magnesium plate crushed powder 8-12 parts; non-woven fabric 1.5-5; water 10-20 parts, wherein the modified expanded vermiculite is prepared by the following steps: (1) Incomplete expansion calcination of vermiculite: The vermiculite raw material is removed and put into a rotary furnace with a temperature of 700-1000℃. Heat and expand for 10-20 seconds. After discharging, the incomplete expansion vermiculite with a bulk density of 1000-1200 kg / m3 is obtained. (2) Take acrylic monomer, sodium hydroxide, acrylamide monomer, initiator, crosslinking aid, incomplete expansion vermiculite, and water, stir evenly and ultrasonic dispersion for 20-40 minutes to obtain a first reaction solution, and place it in a reaction kettle for reaction. The reaction temperature is 80-100℃, and the reaction time is 0.5-2 hours to obtain a gel material. The mass ratio of acrylic monomer, acrylamide monomer, and incomplete expansion vermiculite is (2-4):(0.4-0.6):

6. (3) The gel material is preliminarily broken, dried at 150-200℃, and then further crushed in a ball mill until the fireproof expanded vermiculite with water absorption performance with a particle size of 0.6-1.0 mm is obtained. (4) Surface modification of fireproof expanded vermiculite 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A are prepared into a surface crosslinking solution according to a certain proportion. The mass ratio of the surface crosslinking solution and the expanded vermiculite is (0.5-4):

100. A certain amount of fireproof expanded vermiculite with water absorption performance is placed in a high-speed stirrer, and the surface crosslinking solution is uniformly sprayed onto its surface. After stirring for 8-15 minutes, the above-mentioned expanded vermiculite is placed in an oven for surface crosslinking at 60-150℃ for 0.5-1.5 hours to obtain the final product, modified expanded vermiculite.

2. The fireproof magnesium oxide board according to claim 1, characterized in that, The working temperature of the rotary furnace is 850-950℃, and the heating expansion time is 12-15 seconds.

3. The fireproof magnesium oxide board according to claim 1, characterized in that, The heating expansion time is 13 seconds.

4. The fireproof magnesium oxide board according to claim 1, characterized in that, The bulk density of the incomplete expansion vermiculite is 1000-1100 kg / m3.

5. The fireproof magnesium oxide board according to claim 1, characterized in that, The stirring speed in the reaction kettle in step (2) is 1200-1800 revolutions per minute.

6. The fireproof magnesium oxide board according to claim 1, wherein In step (2), the mass ratio of acrylic monomer to incomplete expansion vermiculite is 1:

2.

7. The fireproof magnesium oxide board according to claim 1, wherein In step (2), the mass ratio of water to incomplete expansion vermiculite is (15-25):

6.

8. The fireproof magnesium oxide board according to claim 1, wherein, In step (2), the crosslinking aid is pentaerythritol polyglycidol ether.

9. The fireproof magnesium oxide board according to claim 1, wherein In step (4), the mass ratio of 1,3-propanediol, trimethylolpropane triglycidyl ether, ethanol, and tetrabromobisphenol A is 1:1:2:1.

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