Inorganic composite environment-friendly flame-retardant plate and preparation method thereof

Abstract

The invention discloses an inorganic composite environment-friendly flame-retardant board and a preparation method thereof, and belongs to the technical field of building materials and artificial boards. The inorganic composite environment-friendly flame-retardant plate is of a sandwich structure and sequentially comprises a flame-retardant layer, a plate core layer and a flame-retardant layer from top to bottom, and the two sides of the plate core layer are coated with adhesion agents. The flame-retardant layer is prepared from a magnesium cementing material, and the material comprises magnesium sulfate, magnesium chloride, citric acid, trisodium phosphate, lithopone, wood fiber, magnesium oxide and water. The preparation method comprises the following steps: preparing a loose flame-retardant layer material, sequentially paving a bottom-layer flame-retardant layer material, placing a core plate coated with an interface agent, paving an upper-layer flame-retardant layer material, and then carrying out cold pressing, drying and curing to obtain a finished product. The technical problems that an existing flame-retardant board is complex in process, high in cost and poor in environment-friendly performance are solved, and the prepared composite board has the advantages of being light in weight, good in flame-retardant performance, simple in process, low in cost, environmentally friendly, healthy and the like and is suitable for the field of building fire prevention.

Description

Technical Field

[0001] This invention relates to the field of building materials and artificial board technology, specifically to an inorganic composite environmentally friendly flame-retardant board and its preparation method. Background Technology

[0002] With the continuous improvement of building safety standards, the demand for building materials with excellent fire resistance is increasing. Wood is widely used in building decoration and structural materials due to its good mechanical properties and decorative effects; however, its flammable nature limits its use in locations with high fire protection requirements. Currently, the market mainly uses various flame-retardant treatment technologies to improve the fire resistance of wood.

[0003] Finger-jointed solid wood panels are solid wood side panels that are widened laterally perpendicular to the wood fiber direction or lengthened longitudinally along the wood fiber direction. The surface wood is directly exposed, making it susceptible to moisture and fire, leading to dimensional changes, rot, and mold. Even with subsequent finishing processes to improve fire resistance, wear resistance, and smoothness, the lifespan remains limited due to loose bonding and insufficient adhesive strength, and the cost is relatively high.

[0004] Currently, the mainstream methods for fire retardant treatment of wood include: wood impregnation, wood coating, and surface application of non-combustible materials. Wood impregnation is an important method for improving the fire retardant properties of wood. The inherent vascular structure of wood provides suitable conditions for impregnating its interior with flame retardants. Wood impregnation typically involves using a vacuum and pressure to allow the flame retardant in the solvent to penetrate the wood. After impregnation, the wood is removed and dried. Wood coating involves constructing a flame retardant coating on the wood surface. When flames strike, this coating can temporarily interrupt the ignition source, isolate the heat and oxygen exchange, and protect the wood matrix from the spread of fire into the wood. Surface application of non-combustible materials involves applying non-combustible materials such as gypsum board or thin metal sheets to the wood surface to improve its fire resistance. However, these treatment methods have the following disadvantages: (1) The flame retardant effects of wood impregnation and coating are not obvious. There are problems such as uneven and incomplete impregnation of flame retardant and poor coating adhesion, resulting in an insignificant flame retardant effect. Moreover, after use, it is very easy to return to efflorescence, absorb moisture and precipitate, and corrode the structural light steel keel; (2) The flame retardant effects of wood impregnation and coating have the problems of complex process flow, high cost and poor economy; (3) The interface bonding strength of non-combustible materials on the wood surface is poor, and the structure is easy to delaminate and be damaged.

[0005] Calcium silicate board is an inorganic building material with high strength and stable performance, made primarily from calcareous and siliceous materials and reinforcing fibers. It is produced through a process of slurry forming, board compaction, and autoclaving. The main siliceous raw materials for producing calcium silicate board include quartz sand, fly ash, and diatomaceous earth. The main sources of calcium are quicklime and hydrated lime. A small amount of cement is usually added to facilitate forming. The reinforcing fibers are wood fibers such as paper fibers. Calcium silicate board has high flexural strength, low moisture expansion rate, and low thermal conductivity. It is fireproof, heat-insulating, non-deformable, moisture-proof, corrosion-proof, mildew-proof, lightweight, high-strength, and impact-resistant. It is also easy to drill, saw, and process. Currently, low-quality calcium silicate boards have low flexural strength, while high-quality boards have high flexural strength, but the production cost and difficulty are correspondingly higher. Low-density calcium silicate boards have high porosity and high water absorption, making them prone to significant deformation, leading to problems such as water seepage and brick falling off walls.

[0006] Magnesium-based cementitious materials are characterized by their lightweight, high strength, low alkali content, high temperature resistance, and low carbon dioxide emissions, and have been widely used in precast construction, road repair, and nuclear waste fixation. Magnesium-based cementitious materials primarily consist of MgO and can be classified into magnesium phosphate cement, magnesium oxychloride cement, magnesium sulfide cement, and hydrated magnesium silicate cement, depending on the salt solution used. In this invention, the magnesium-based cementitious material refers to magnesium oxychloride cement, which is prepared by mixing magnesium oxide and a certain concentration of magnesium chloride aqueous solution. The hydration process of the magnesium-based cementitious system includes three steps: sol, gel, and crystallization. Under normal temperature and pressure, the main hydration products in the system are 5Mg(OH)₂·MgCl₂·8H₂O (referred to as the 518 phase) and 3Mg(OH)₂·MgCl₂·8H₂O (referred to as the 318 phase). The 518 phase is more beneficial to the development of the mechanical properties of MOC cement. This is because the 518 phase is a needle-like hydration product that can grow alternately within the MOC matrix, forming a spatial network structure.

[0007] Although some related patents, such as CN119874322A, CN119954490A, CN119263768A, and CN119874321A, involve the application of magnesium cementitious materials in composite panels, these technical solutions still have many problems. For example, in CN119874322A, the manufacturing process of the glued core board is much more complex than that of the toothed joint board, requiring multiple laying, molding, and curing processes to obtain the final product. Furthermore, the silane coupling agents, crosslinking agents such as cationic polyacrylamide, modifiers such as aluminum tripolyphosphate, and carbon dot modified hydrosols used in these patents are expensive, significantly increasing production costs.

[0008] Therefore, there is an urgent need to develop a composite environmentally friendly flame-retardant board with simple process, moderate cost, environmental protection and health, and excellent flame-retardant properties, as well as its preparation method. Summary of the Invention

[0009] Based on the problems existing in the background technology, the present invention provides an inorganic composite environmentally friendly flame retardant board and its preparation method to solve the technical problems of the prior art, such as the flame retardant effect being not obvious, the process being complex, the cost being high, and the environmental performance being poor.

[0010] This invention is implemented through the following technical solutions:

[0011] The first aspect of this invention discloses an inorganic composite environmentally friendly flame-retardant board, which has a sandwich structure, consisting of a flame-retardant layer, a core layer, and a flame-retardant layer from top to bottom; the core layer is coated with an interface agent on both sides, and the flame-retardant layer is made of magnesium cementitious material.

[0012] Furthermore, the magnesium cementitious material comprises, by weight, 30-50 parts magnesium sulfate, 100-120 parts magnesium chloride, 3-5 parts citric acid, 1-3 parts trisodium phosphate, 10-30 parts lithopone, 50-80 parts wood fiber, 300 parts magnesium oxide, and 350 parts water.

[0013] Furthermore, the magnesium cementitious material comprises, by weight, 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, 20 parts lithopone, 65 parts wood fiber, 300 parts magnesium oxide, and 350 parts water.

[0014] Furthermore, the wood fiber has a mesh size of 40-60 mesh.

[0015] Furthermore, the preparation method of the magnesium-based cementitious material specifically includes the following steps:

[0016] Step 1. Mix magnesium sulfate, magnesium chloride, citric acid, trisodium phosphate, and lithopone evenly and set aside for later use;

[0017] Step 2. Add water to the mixture prepared in Step 1 in batches and stir well to obtain brine;

[0018] Step 3. Mix the wood fiber and magnesium oxide evenly and set aside for later use;

[0019] Step 4. Gradually add the mixture from Step 3 to the brine from Step 2, mix evenly, and then stir at high speed to obtain magnesium-based cementitious material, i.e., loose flame-retardant layer material.

[0020] Furthermore, step 1 involves mixing the brine raw materials and fillers evenly without adding water. If water is added first to make magnesium chloride and water brine, and then citric acid, trisodium phosphate, and lithopone are added later, uneven mixing is likely to affect the coagulation process of the gelling material.

[0021] The reason for adding magnesium sulfate to the magnesium cementitious material of this invention is that in the magnesium cementitious system, magnesium chloride dominates the formation of the 518 phase, but Cl...- Easily soluble, reducing water resistance and causing efflorescence; replacing 20-30% magnesium chloride with magnesium sulfate reduces the total amount of soluble ions and reduces moisture absorption and efflorescence; excessive addition of magnesium sulfate will form an unstable 318 phase, affecting the performance of the hydration reaction products.

[0022] The reason for adding citric acid is that citric acid acts as a retarder, and its carboxyl groups complex with Mg. 2+ It slows down the hydration rate, preventing crystal coarsening caused by localized supersaturation; it protects the five-phase crystalline structure and prevents its hydrolysis, ultimately achieving a dual improvement in the strength and water resistance of magnesium oxychloride cement. Adding too much will excessively inhibit the reaction.

[0023] The reason for adding trisodium phosphate is that phosphoric acid is also a type of retarder, and its... With Mg 2+ An insoluble magnesium phosphate coating is formed, blocking water molecule penetration; the porosity of the cementitious material structure is reduced, decreasing the diffusion effect of capillaries on water and Cl-. - The dissolution channels of Cl are thus inhibited. - The dissolution of the substance improves the water resistance of the system and enhances phase stability.

[0024] The reason for adding lithopone (mainly composed of BaSO4 / ZnS) is that lithopone is an inert particle that can fill 10-100nm capillaries, reducing the average pore size; Zn 2+ It inhibits fungal growth and is suitable for humid environments; it also functions as a white pigment.

[0025] Furthermore, in step 2, slow stirring is used at a speed of 30 r / min for a duration of more than 30 min. The purpose of slow stirring is to ensure that the material is fully dissolved, and to accelerate the dissolution while minimizing air bubbles and voids in the solution.

[0026] Furthermore, in step 3, magnesium oxide and wood fiber filler are mixed evenly without adding brine; if magnesium oxide is added to the brine first and then wood fiber is added, it is easy to clump together and not mix evenly.

[0027] The reason for adding wood fiber to the magnesium cementitious material of this invention is that adding wood fiber to the cementitious material can disperse stress, improve flexural strength, and adsorb free ions to reduce efflorescence. Excessive addition will cause the viscosity of the slurry to increase sharply, affecting the cementing process.

[0028] The reason for adding magnesium oxide is that magnesium-based cementitious materials have magnesium oxide as their main component, and magnesium oxide provides Mg. 2+ With the Cl provided by magnesium chloride -The hydration reaction produces phase 518 (5Mg(OH)2·MgCl2·8H2O); the molar ratio of MgO to total magnesium salt is approximately 6-12:1. If the ratio is too low, the reaction will be incomplete and prone to efflorescence; if the ratio is too high, it will lead to cracking.

[0029] Furthermore, in step 4, the high-speed stirring speed is 240 r / min, the stirring time is 5-10 min, and the mixing and stirring process time does not exceed 20 min.

[0030] The initial setting time of the magnesium-based cementitious system of this invention is approximately within 90 minutes. After high-speed stirring, a loose, paste-like magnesium oxychloride cement can be obtained. The initial setting time, also known as the pot life, is the appropriate time for paving. If the initial setting time is too short, the flame-retardant layer material will not bond sufficiently with the core board, and effective wetting and adsorption will not be achieved. Conversely, if the initial setting time is too long, the flame-retardant layer material will not be able to begin the hydration reaction in time, which will affect the strength of the finished board.

[0031] The second aspect of this invention discloses a method for preparing the inorganic composite flame-retardant board, comprising the following steps:

[0032] S1. The prepared loose flame-retardant layer material is evenly spread on the pad using a special laying equipment;

[0033] To achieve the "sandwich" structure, it is necessary to lay the layers, and this step is to first lay the flame-retardant layer material on the bottom layer.

[0034] S2. Apply inorganic interface agent evenly to both sides of the toothed plate or calcium silicate core plate using a roller coating machine.

[0035] The role of the interface agent is to enhance the interfacial bonding strength between the flame-retardant layer material and the core board;

[0036] S3. Place the core board coated with double-sided interface agent on the pad that has been laid with the bottom flame retardant layer material;

[0037] S4. Evenly lay loose flame-retardant layer material on the top layer of the core board;

[0038] At this point, the "sandwich" structure is roughly formed, consisting of flame-retardant layer - core board - flame-retardant layer from top to bottom;

[0039] S5. Repeat steps S1-S4 to complete the production of multiple slabs, stack them, and then send them into a cold press for cold pressing;

[0040] S6. After drying, sawing, and sanding the cold-pressed slab, the finished product can be obtained by curing it at room temperature for 7 days.

[0041] The reason for curing for 7 days is that, generally speaking, the longer the curing time, the more complete the hydration reaction, the higher the crystal content, and the stronger the mechanical properties of the resulting board. Considering factors such as time cost and the quality of boards obtained with different curing times, the optimal curing time is 7 days.

[0042] Furthermore, the inorganic interface agent in S2 is specifically: magnesium cementitious material or silicate cement cementitious material.

[0043] Furthermore, the parameters for cold pressing in S5 are: unit pressure 2.5MPa, pressurization time 12h.

[0044] The beneficial effects of this invention are:

[0045] 1. The composite flame-retardant board prepared by this invention has excellent quality and flame-retardant properties. The finished board is lightweight, and using finger-jointed board or calcium silicate board as the core board results in a lighter weight than core boards made of other materials or pure magnesium cementitious boards. Calcium silicate is an inorganic board material, and the finished product using calcium silicate as the core board can meet the A2 standard for flat building materials in GB 8624-2012 "Classification of Burning Performance of Building Materials and Products", significantly improving fire resistance.

[0046] 2. Unlike the multiple molding and curing processes of other patents, the interface agent of this invention is uniformly coated on both sides of the core board using a roller coating method. The pressing process only needs to be completed in one step, without the need for complicated curing procedures, which reduces the number of processes and the construction period, and significantly improves production efficiency.

[0047] 3. The formulation of this invention does not use expensive chemical reagents such as silane coupling agents, crosslinking agents such as cationic polyacrylamide, modifiers such as aluminum tripolyphosphate, and carbon dot modified hydrosols. Instead, it uses relatively inexpensive materials such as citric acid, trisodium phosphate, and lithopone, which greatly reduces the cost of raw materials.

[0048] 4. This invention's formula does not contain red mud or other potentially harmful industrial waste that could be harmful if not properly treated; the finger-jointed board uses white latex instead of aldehyde adhesives, thus not producing free formaldehyde and ensuring a healthy and safe working environment. Through reasonable formula design and process control, this invention achieves a balance of environmental protection, economy, and efficiency while ensuring product performance. Attached Figure Description

[0049] The accompanying drawings are provided to further explain the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0050] In the attached diagram:

[0051] Figure 1 This is a schematic diagram of the structure of the inorganic composite flame-retardant board of the present invention;

[0052] Figure 2This is a process flow diagram for preparing the flame-retardant layer material (magnesium cementitious material) of the present invention;

[0053] Figure 3 This is a process flow diagram for preparing the inorganic composite flame-retardant board of the present invention. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0055] Examples 1-12

[0056] Examples 1-12 determined the optimal ratio for the hydration reaction of the magnesium cementitious system.

[0057] The experimental sample preparation process is as follows: According to the proportions in Table 1, a certain amount of magnesium chloride and magnesium sulfate were thoroughly mixed. Then, 350 parts of water were added in batches and stirred at 30 r / min for 30 min. Next, 300 parts of magnesium oxide were added in batches and stirred at 240 r / min for 10 min. The mixture was then laid out to a thickness of 18 mm and placed in a press. It was then cold-pressed at a pressure of 2.5 MPa for 12 h. After drying, edge trimming, sanding, and curing for 7 days, the samples were obtained. The samples were tested according to the following standards: WB / T 1023-2005 "Magnesium Oxide Cementitious Material Modifier"; GB / T17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels". The test results are shown in Tables 1 and 2.

[0058] Table 1. Effect of the ratio of magnesium chloride to magnesium sulfate in magnesium cementitious materials in Examples 1-12 on the flame retardant layer performance.

[0059]

[0060] Table 2. Analysis of variance of test data from Examples 1-12

[0061]

[0062] As shown in Tables 1 and 2, magnesium chloride and magnesium sulfate have significant effects on static bending strength and modulus of elasticity. The optimal ratio is 40 parts magnesium sulfate, 110 parts magnesium chloride, 300 parts magnesium oxide, and 350 parts water. The initial setting time can be adjusted according to the actual production process requirements; a setting time of 40 minutes is suitable under the optimal ratio. Replacing magnesium chloride with an appropriate amount of magnesium sulfate can significantly improve the material's resistance to moisture absorption and efflorescence. However, adding excessive amounts of magnesium sulfate does not further improve the resistance to moisture absorption and efflorescence. Magnesium oxychloride cement cannot completely solve the problem of moisture absorption and efflorescence; therefore, further research on its water resistance will be conducted.

[0063] Examples 13-21

[0064] Examples 13-21 determine the optimal ratio of citric acid, trisodium phosphate, and lithopone in magnesium cementitious materials.

[0065] An optimal formula was selected, consisting of 40 parts magnesium sulfate, 110 parts magnesium chloride, 300 parts magnesium oxide, and 350 parts water, to explore the best ratio of citric acid, trisodium phosphate, and lithopone.

[0066] The experimental sample preparation process is as follows: 40 parts magnesium sulfate, 110 parts magnesium chloride, a certain amount (data in Table 3) of citric acid, trisodium phosphate, and lithopone were thoroughly mixed. Then, 350 parts water were added in batches and stirred at 30 rpm for 30 minutes. Next, 300 parts magnesium oxide were added in batches and stirred at 240 rpm for 10 minutes. The mixture was then laid out to a thickness of 18 mm and cold-pressed at 2.5 MPa for 12 hours. After drying, edge trimming, sanding, and curing for 7 days, the samples were obtained. The samples were tested according to the relevant standard: GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; the test results are shown in Tables 3 and 4.

[0067] Table 3. Effect of the ratio of citric acid, trisodium phosphate, and lithopone on the flame retardant layer performance in Examples 13-21

[0068]

[0069] Table 4. Analysis of variance of test data from Examples 13-21

[0070]

[0071]

[0072] As shown in Tables 3 and 4, the three factors significantly affect the mechanical properties. Citric acid and trisodium phosphate significantly affect the retarding time. The optimal ratio was determined to be 4 parts citric acid, 2 parts trisodium phosphate, and 20 parts lithopone. At this ratio, the initial setting time is 89 minutes, which is moderate and meets actual production requirements. When the optimal dosages are not reached (citric acid < 4 parts / trisodium phosphate < 2 parts / lithopone < 20 parts), each component significantly improves the mechanical and water resistance properties. However, exceeding the optimal dosages leads to a loose structure due to excess citric acid and trisodium phosphate, and excessive lithopone can cause uneven filling and stress concentration. The optimal ratio represents the performance inflection point.

[0073] Examples 22-31

[0074] Examples 22-31 determine the optimal ratio of wood fiber content and wood fiber mesh size in magnesium cementitious materials.

[0075] An optimal formula was selected, consisting of 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, 20 parts lithopone, 300 parts magnesium oxide, and 350 parts water, to explore the best ratio of wood fiber.

[0076] The sample preparation process is as follows: 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, and 20 parts lithopone were thoroughly mixed. Then, 350 parts water were added in batches and stirred at 30 rpm for 30 minutes to obtain brine. 300 parts magnesium oxide were mixed with a certain amount of wood fiber and added in batches to the brine. The mixture was stirred at 240 rpm for 10 minutes and then laid out to a thickness of 18 mm. The mixture was then cold-pressed at 2.5 MPa for 12 hours, dried, sanded, and cured for 7 days to obtain the sample. The sample was tested according to the relevant standard: GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; the test results are shown in Tables 5 and 6.

[0077] Table 5. Effects of wood fiber content and mesh size on flame retardant layer performance in Examples 22-31

[0078]

[0079]

[0080] Table 6. Analysis of variance of test data for groups 22-31 in Examples 22-31

[0081]

[0082] As shown in Tables 5 and 6, the mechanical strength of the magnesium cementitious material is significantly improved after the addition of wood fiber. Both the amount and mesh size of the wood fiber significantly affect the mechanical strength of the material. Stress concentration points are easily generated when the wood fiber mesh size is approximately 10 mesh, while the optimal aspect ratio is achieved when the mesh size is 40-60 mesh, with the experimental results showing a difference of less than 2%. Excessive mesh size can easily lead to agglomeration, resulting in a decrease in strength. Therefore, considering all factors, the optimal mesh size is 40 mesh. Excessive wood fiber content can cause a sharp increase in slurry viscosity, affecting the cementation process. Furthermore, excessive wood fiber absorption can lead to incomplete hydration. Therefore, the optimal ratio is 65 parts wood fiber and 40 mesh.

[0083] Examples 32-33

[0084] Examples 32 and 33 investigate the effects of different stirring methods on the performance of magnesium cementitious materials.

[0085] The preferred formula is: 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, 20 parts lithopone, 65 parts wood fiber (40 mesh), 300 parts magnesium oxide, and 350 parts water.

[0086] The sample preparation process is as follows:

[0087] Example 32: As Figure 2 As shown in the preparation process flow chart, 40 parts of magnesium sulfate, 110 parts of magnesium chloride, 4 parts of citric acid, 2 parts of trisodium phosphate, and 20 parts of lithopone are thoroughly mixed. Then, 350 parts of water are added in batches and stirred at 30 r / min for 30 min to obtain brine. 300 parts of magnesium oxide and 65 parts of 40-mesh wood fiber are mixed evenly and added in batches to the brine. The mixture is stirred at 240 r / min for 10 min to obtain a soft, loose flame-retardant layer material. The material is then laid with a thickness of 18 mm and fed into a press. It is cold-pressed at a pressure of 2.5 MPa for 12 h, dried, sawn, sanded, and cured for 7 days to obtain the sample.

[0088] Example 33: 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, and 20 parts lithopone were thoroughly mixed. Then, 350 parts water were added in batches and stirred at 30 rpm for 30 minutes to obtain brine. 300 parts magnesium oxide and 65 parts 40-mesh wood fiber were mixed thoroughly and added in batches to the brine, stirring slowly at 30 rpm for 10 minutes to obtain a thick paste-like flame-retardant layer material. This material was laid to a thickness of 18 mm and then cold-pressed at 2.5 MPa for 12 hours. After drying, edge trimming, sanding, and curing for 7 days, a sample was obtained. The sample was tested according to GB / T 17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; the test results are shown in Table 7.

[0089] Table 7. Effect of stirring method on flame retardant layer performance in Examples 32-33

[0090]

[0091] As can be seen from the data in Table 7, high-speed stirring helps to uniformly disperse fibers, eliminate agglomerates of powdered raw materials, and improve the mechanical strength of materials; it also helps to improve stability, reduce standard deviation, and ensure consistency in batch production.

[0092] Example 34

[0093] The flame-retardant layer material of this invention is directly pressed into a board: 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, and 20 parts lithopone are thoroughly mixed evenly. Then, 350 parts water are added in batches and stirred at 30 r / min for 30 min to obtain brine. 300 parts magnesium oxide and 65 parts 40-mesh wood fiber are mixed evenly and added in batches to the brine. The mixture is stirred at 240 r / min for 10 min to obtain a soft, loose flame-retardant layer material. The material is laid with a thickness of 18 mm and then fed into a press. It is cold-pressed at a pressure of 2.5 MPa for 12 h. After drying, sawing, sanding, and curing for 7 days, a sample is obtained.

[0094] Example 35

[0095] The inorganic composite flame-retardant board is prepared with calcium silicate board as the core board. The specific preparation method is as follows: Figure 3 As shown, it includes the following steps:

[0096] S1. Preparation of loose flame retardant layer material: After thoroughly mixing 40 parts of magnesium sulfate, 110 parts of magnesium chloride, 4 parts of citric acid, 2 parts of trisodium phosphate, and 20 parts of lithopone, 350 parts of water are added in batches and stirred at 30 r / min for 30 min to obtain brine. After thoroughly mixing 300 parts of magnesium oxide and 65 parts of 40 mesh wood fiber, the mixture is added in batches to the brine and stirred at 240 r / min for 10 min to obtain a paste-like loose flame retardant layer material.

[0097] S2. The prepared loose flame-retardant layer material is evenly spread on the mat using a special laying equipment;

[0098] S3. Apply inorganic interface agent magnesium oxychloride cementitious material evenly to both sides of the toothed plate or calcium silicate core plate using a roller coating machine.

[0099] S4. Place the core board coated with double-sided interface agent on the pad that has been laid with the bottom flame retardant layer material;

[0100] S5. Evenly lay loose flame-retardant layer material on the top layer of the core board;

[0101] S6. Repeat steps S2-S5 to complete the production of multiple slabs, stack them, and then send them into a cold press for cold pressing at a pressure of 2.5MPa for 12 hours.

[0102] S7. After drying, sawing, and sanding the cold-pressed slab, the finished product can be obtained by curing it at room temperature for 7 days.

[0103] Example 36

[0104] The difference between this embodiment and embodiment 35 is that the core board is a toothed plate, while the rest of the preparation steps are the same as in embodiment 35.

[0105] Test example

[0106] The performance of the plates prepared in Examples 34-36 was tested, and the test results are shown in Tables 8 and 9.

[0107] Table 8. Performance Comparison Results of Different Board Materials

[0108]

[0109] As can be seen from the results in Table 8, compared with the non-composite toothed board and calcium silicate board, the composite board has lower density and higher toughness, while also having better water resistance and flame retardancy, making it a high-performance lightweight flame-retardant board.

[0110] Table 9. Physicochemical property test data of the inorganic composite environmentally friendly flame-retardant boards prepared in Examples 35 and 36.

[0111]

[0112] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An inorganic composite environmentally friendly flame-retardant board, characterized in that, The inorganic composite environmentally friendly flame-retardant board has a sandwich structure, consisting of a flame-retardant layer, a core layer, and another flame-retardant layer from top to bottom. The core layer is coated with an interface agent on both sides, and the flame-retardant layer is made of magnesium cementitious material.

2. The inorganic composite environmentally friendly flame-retardant board according to claim 1, characterized in that, The magnesium-based cementitious material comprises, by weight, 30-50 parts magnesium sulfate, 100-120 parts magnesium chloride, 3-5 parts citric acid, 1-3 parts trisodium phosphate, 10-30 parts lithopone, 50-80 parts wood fiber, 300 parts magnesium oxide, and 350 parts water.

3. The inorganic composite environmentally friendly flame-retardant board according to claim 2, characterized in that, The magnesium-based cementitious material comprises, by weight, 40 parts magnesium sulfate, 110 parts magnesium chloride, 4 parts citric acid, 2 parts trisodium phosphate, 20 parts lithopone, 65 parts wood fiber, 300 parts magnesium oxide, and 350 parts water.

4. The inorganic composite environmentally friendly flame-retardant board according to claim 2 or 3, characterized in that, The wood fibers have a mesh size of 40-60.

5. The inorganic composite environmentally friendly flame-retardant board according to claim 2 or 3, characterized in that, The preparation method of the magnesium cementitious material specifically includes the following steps: Step 1. Mix magnesium sulfate, magnesium chloride, citric acid, trisodium phosphate, and lithopone evenly and set aside for later use; Step 2. Add water to the mixture prepared in Step 1 in batches and stir well to obtain brine; Step 3. Mix the wood fiber and magnesium oxide evenly and set aside for later use; Step 4. Gradually add the mixture from Step 3 to the brine from Step 2, mix evenly, and then stir at high speed to obtain magnesium-based cementitious material, i.e., loose flame-retardant layer material.

6. The inorganic composite environmentally friendly flame-retardant board according to claim 5, characterized in that, In step 2, slow stirring is used, with a stirring speed of 30 r / min and a stirring time of more than 30 minutes.

7. The inorganic composite environmentally friendly flame-retardant board according to claim 5, characterized in that, In step 4, the high-speed stirring speed is 240 r / min, the stirring time is 5-10 min, and the mixing and stirring process time does not exceed 20 min.

8. A method for preparing an inorganic composite flame-retardant board as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. The prepared loose flame-retardant layer material is evenly spread on the pad using a special laying equipment; S2. Apply inorganic interface agent evenly to both sides of the toothed plate or calcium silicate core plate using a roller coating machine. S3. Place the core board coated with double-sided interface agent on the pad that has been laid with the bottom flame retardant layer material; S4. Evenly lay loose flame-retardant layer material on the top layer of the core board; S5. Repeat steps S1-S4 to complete the production of multiple slabs, stack them, and then send them into a cold press for cold pressing; S6. After drying, sawing, and sanding the cold-pressed slab, the finished product can be obtained by curing it at room temperature for 7 days.

9. The preparation method according to claim 8, characterized in that, The inorganic interface agent in S2 is specifically: magnesium cementitious material or silicate cement cementitious material.

10. The preparation method according to claim 8, characterized in that, The parameters for cold pressing in S5 are: unit pressure 2.5MPa, pressurization time 12h.

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