Dense flame-retardant board of wood micro-powder fibers having multi-dimensional cross-linked structure, and forming method therefor

Abstract

A dense flame-retardant board of wood micro-powder fibers having a multi-dimensional cross-linked structure, and a forming method therefor. The board consists of wood micro-powder fibers and a multi-dimensional cross-linking agent, the multi-dimensional cross-linking agent comprising polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate. The multi-dimensional cross-linking agent and the wood micro-powder fibers are mixed according to a certain proportion, and the multi-dimensional cross-linking agent forms a multi-dimensional cross-linked network structure in the board. The board has high density, high strength and high flame retardance, and the manufacturing process is simple and environment-friendly. The forming method comprises four steps extrusion, pre-pressing, hot pressing and cooling, and does not need high-temperature and high-pressure or special devices, thus facilitating mass production and energy conservation and emission reduction.

Description

Dense flame-retardant board with multi-dimensional cross-linked structure of wood micropowder fiber and forming method thereof Technical Field

[0001] The invention relates to a dense flame-retardant plate with a multi-dimensional cross-linked structure of wood micropowder fibers and a forming method thereof, and belongs to the field of wood processing. Background Art

[0002] Wood is a widely used natural material with advantages such as being renewable, biodegradable, lightweight, high-strength, and aesthetically pleasing. However, wood also has some disadvantages, such as susceptibility to moisture, deformation, and flammability. To improve the properties of wood, various wood modification methods have been developed, including chemical modification, physical modification, and biological modification.

[0003] Wood micronized fiber is a micron-sized fiber obtained by mechanical or chemical treatment of wood. It has high specific surface area, high water absorbency, and high strength. It can be used as a new bio-based material for the preparation of various composite materials, nanopaper, and films. However, wood micronized fiber also has some disadvantages, such as susceptibility to moisture, deformation, and flammability.

[0004] To improve the density, strength, and flame retardancy of wood powder fibers, researchers have experimented with various crosslinking agents, such as polyvinyl alcohol (PVA), boric acid (H3BO3), potassium dihydrogen phosphate (KH2PO4), and aluminum sulfate (Al2(SO4)3). These crosslinking agents can form chemical or physical bonds between wood powder fibers, increasing the interaction between them and thereby improving their density and strength.

[0005] However, there are still some problems with the existing wood micropowder fiber cross-linking method, such as:

[0006] A single cross-linking agent often cannot meet the requirements of density, strength and flame retardancy at the same time, and multiple cross-linking agents need to be used for compounding;

[0007] The combination of multiple cross-linkers often increases cost and complexity, and may cause incompatibility or instability between cross-linkers;

[0008] Some cross-linking agents, such as formaldehyde (HCHO), are toxic or environmentally polluting and do not meet environmental protection requirements;

[0009] Traditional molding methods such as pressing and injection molding require the use of high temperature and high pressure or special equipment, which is not conducive to large-scale production and energy conservation and emission reduction. Summary of the Invention

[0010] The purpose of the present invention is to provide a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers and a forming method thereof. The board has high density, high strength and high flame retardancy, and the preparation process is simple and environmentally friendly.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers, the board being prepared by the following steps:

[0013] Mixing wood micropowder fiber with water to obtain wood micropowder fiber slurry with a water content of 50%-80%;

[0014] The wood powder fiber slurry is mixed with polyvinyl alcohol (PVA), boric acid , potassium dihydrogen phosphate and aluminum sulfate Mixing the wood micropowder fiber slurry containing a multidimensional crosslinking agent in a mass ratio of 100:5-15:1-5:1-5:0.5-5 to obtain a wood micropowder fiber slurry containing a multidimensional crosslinking agent; extruding, pre-pressing, hot-pressing and cooling the wood micropowder fiber slurry containing a multidimensional crosslinking agent to obtain the board;

[0015] Wherein, the multi-dimensional cross-linking agent forms the following chemical reaction in the sheet: PVA and Reaction to generate polyvinyl alcohol borate (PVA-B) and water, the reaction equation is: PVA and Reaction to generate polyvinyl alcohol phosphate (PVA-P) and potassium hydroxide , the reaction equation is: Reacts with KOH to generate aluminum hydroxide and potassium sulfate , the reaction equation is:

[0016] The PVAB, PVAP and A multi-dimensional cross-linked network structure is formed in the board material, thereby improving the density, strength and flame retardancy of the board material.

[0017] The average particle size of the wood powder fiber is 10-100 microns. In a preferred embodiment, this technical solution can make the wood powder fiber easier to mix with the multi-dimensional cross-linking agent, and can make the surface of the board smoother and more uniform.

[0018] The molecular weight of the polyvinyl alcohol is 5000-50000 Daltons. In a preferred embodiment, this technical solution can make the polyvinyl alcohol have appropriate solubility and viscosity, and can make the polyvinyl alcohol react more effectively with the boric acid and the potassium dihydrogen phosphate to form a more stable cross-linked structure.

[0019] The thickness of the plate is 0.5-10 mm. In a preferred embodiment, the technical solution can make the plate have appropriate rigidity and flexibility, and can make the plate suitable for different uses, such as furniture, construction, decoration, etc.

[0020] The density of the board is 0.8-1.5 g / cm3. In a preferred embodiment, this technical solution can make the board have a higher density, thereby improving the strength and flame retardancy of the board, and can make the board have a lower weight, thereby reducing the cost and transportation difficulty of the board.

[0021] The bending strength of the plate is 10-50 MPa. In a preferred embodiment, this technical solution can make the plate have a higher bending strength, thereby improving the durability and deformation resistance of the plate, and can enable the plate to withstand greater external forces, thereby increasing the safety and reliability of the plate.

[0022] The flame retardant grade of the board is B1 or B2. In a preferred embodiment, this technical solution can make the board have a higher flame retardant grade, thereby improving the fire resistance of the board, and making the board less likely to burn or delaying combustion in the event of a fire, thereby reducing the loss and damage of the board.

[0023] A method for forming a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers comprises the following steps:

[0024] Mixing wood micropowder fiber with water to obtain wood micropowder fiber slurry with a water content of 50%-80%;

[0025] The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:5-15:1-5:1-5:0.5-5 to obtain a wood powder fiber slurry containing a multidimensional crosslinking agent;

[0026] The wood micropowder fiber slurry containing a multi-dimensional cross-linking agent is subjected to extrusion, pre-pressing, hot pressing and cooling to obtain the board;

[0027] The extrusion step comprises extruding the wood micropowder fiber slurry containing a multi-dimensional cross-linking agent through a die having a certain shape and size to obtain a board blank of a desired shape and size;

[0028] The pre-pressing step is to place the sheet blank in a mold of a certain shape and size, apply a certain pressure, reduce the moisture content of the sheet blank to 30%-50%, and make the sheet blank fit tightly with the mold;

[0029] The hot pressing step is to place the pre-pressed sheet material in a heating device and apply a certain temperature and pressure to cause the multi-dimensional cross-linking agent to chemically react in the sheet material and reduce the water content of the sheet material to below 10%;

[0030] The cooling step is to place the hot-pressed plate blank in a cooling device, apply a certain temperature and pressure, and cool and solidify the plate blank to obtain the plate.

[0031] During the extrusion step, the mold can be shaped and sized to be circular, square, rectangular, trapezoidal, or any other arbitrary shape, and the mold size is the same as or slightly larger than the size of the desired sheet material. In preferred embodiments, this technical solution can produce sheets of various shapes and sizes to meet diverse needs and preferences, improve sheet material forming efficiency, and reduce sheet material cutting and processing.

[0032] In the pre-pressing step, the pressure applied is 0.5-5 MPa. In a preferred embodiment, this technical solution can reduce the moisture content of the sheet material to an appropriate range and reduce the gap between the sheet material and the mold, thereby improving the density and strength of the sheet material.

[0033] During the hot pressing step, the applied temperature is 150-250 degrees Celsius and the applied pressure is 5-15 MPa. In preferred implementations, this technical solution allows the multi-dimensional crosslinking agent to fully chemically react within the sheet material and minimizes the moisture content of the sheet material, thereby improving the flame retardancy and stability of the sheet material.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention uses wood micropowder fiber as raw material to prepare a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fiber. The board has high density, high strength and high flame retardancy, and the preparation process is simple and environmentally friendly.

[0036] The present invention uses polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate as multidimensional cross-linking agents to form a multidimensional cross-linked network structure in the board, thereby improving the density, strength and flame retardancy of the board;

[0037] The present invention provides a forming method for preparing a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers. The method includes four steps of extrusion, pre-pressing, hot pressing and cooling. The moisture content, temperature and pressure of the board can be effectively controlled, and boards of different shapes and sizes can be prepared as needed.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a SEM image of the material of the present invention.

[0040] FIG2 is a process flow chart of the present invention. DETAILED DESCRIPTION

[0041] The following embodiments are merely examples of the present invention and do not limit the scope of the present invention. Implementation method 1:

[0042] This embodiment provides a specific embodiment of a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers and a molding method thereof, and the specific steps are as follows:

[0043] In the first step, wood micro-powder fiber is mixed with water to obtain a wood micro-powder fiber slurry with a water content of 60%. The wood micro-powder fiber is pine wood micro-powder fiber with an average particle size of 50 microns.

[0044] In the second step, the wood powder fiber slurry is mixed with polyvinyl alcohol (PVA), boric acid (H3BO3), potassium dihydrogen phosphate (KH2PO4), and aluminum sulfate (Al2(SO4)3) in a mass ratio of 100:10:3:3:2 to obtain a wood powder fiber slurry containing a multi-dimensional crosslinker. The polyvinyl alcohol has a molecular weight of 10,000 Daltons.

[0045] In the third step, the wood micropowder fiber slurry containing the multi-dimensional crosslinking agent is extruded through a circular die to obtain a board blank with a diameter of 10 cm. The size of the die is slightly larger than the size of the board to be prepared.

[0046] The fourth step is to place the sheet blank in a circular mold and apply a pressure of 2 MPa to reduce the water content of the sheet blank to 40%, and to make the sheet blank fit tightly with the mold.

[0047] The fifth step is to place the pre-pressed sheet blank in a heating device, apply a temperature of 200 degrees Celsius and a pressure of 10 MPa, so that the multi-dimensional cross-linking agent reacts chemically in the sheet blank and reduces the water content of the sheet blank to below 5%.

[0048] The sixth step is to place the hot-pressed board blank in a cooling device, apply a temperature of 20 degrees Celsius and a pressure of 5 MPa, and cool and solidify the board blank to obtain a dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers with a thickness of 1 mm.

[0049] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0050] Density is 1.2 g / cm3;

[0051] Flexural strength is 30 MPa;

[0052] The flame retardant grade is B1. Implementation 2:

[0053] This embodiment is similar to Embodiment 1, except that:

[0054] The wood powder fiber is birch powder fiber, and its average particle size is 20 microns;

[0055] The polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate are mixed in a mass ratio of 100:15:5:5:5;

[0056] The shape and size of the mold are rectangular, 20 cm long and 10 cm wide;

[0057] In the pre-pressing step, the applied pressure is 5 MPa;

[0058] During the hot pressing step, the applied temperature was 250 degrees Celsius and the applied pressure was 15 MPa;

[0059] The thickness of the plate is 5 mm.

[0060] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0061] Density is 1.5 g / cm3;

[0062] Flexural strength is 50 MPa;

[0063] The flame retardant grade is B2. Implementation 3:

[0064] This embodiment is similar to Embodiment 1, except that:

[0065] The wood micro-powder fiber is willow wood micro-powder fiber, and its average particle size is 10 microns;

[0066] The polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate are mixed in a mass ratio of 100:5:1:1:0.5;

[0067] The shape and size of the mold are trapezoidal, with an upper base of 15 cm, a lower base of 10 cm, and a height of 20 cm;

[0068] In the pre-pressing step, the applied pressure is 0.5 MPa;

[0069] During the hot pressing step, the applied temperature was 150 degrees Celsius and the applied pressure was 5 MPa;

[0070] The thickness of the plate is 10 mm.

[0071] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0072] Density is 0.8 g / cm3;

[0073] Flexural strength is 10 MPa;

[0074] The flame retardant grade is B2.

[0075] Implementation 4:

[0076] This embodiment is similar to Embodiment 1, except that:

[0077] The wood micro-powder fiber is beech micro-powder fiber, and its average particle size is 100 microns;

[0078] The polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate are mixed in a mass ratio of 100:20:10:10:10;

[0079] The shape and size of the mold is square, with a side length of 15 cm;

[0080] In the pre-pressing step, the applied pressure is 10 MPa;

[0081] During the hot pressing step, the applied temperature was 250 degrees Celsius and the applied pressure was 20 MPa;

[0082] The thickness of the plate is 0.5 mm.

[0083] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0084] Density is 1.5 g / cm3;

[0085] Flexural strength is 50 MPa;

[0086] The flame retardant grade is B1.

[0087] Implementation 5:

[0088] This embodiment is similar to Embodiment 1, except that:

[0089] The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:8:2:2:1;

[0090] The shape and size of the mold is hexagonal with a side length of 10 cm;

[0091] In the pre-pressing step, the applied pressure is 3 MPa;

[0092] During the hot pressing step, the applied temperature was 200 degrees Celsius and the applied pressure was 10 MPa;

[0093] The thickness of the plate is 2 mm.

[0094] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0095] Density is 1.0 g / cm3;

[0096] Flexural strength is 20 MPa;

[0097] The flame retardant grade is B1.

[0098] Implementation 6:

[0099] This embodiment is similar to Embodiment 1, except that:

[0100] The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:12:4:4:3;

[0101] The shape and size of the mold are circular, with an outer diameter of 15 cm and an inner diameter of 10 cm;

[0102] In the pre-pressing step, the applied pressure is 4 MPa;

[0103] During the hot pressing step, the applied temperature was 220 degrees Celsius and the applied pressure was 12 MPa;

[0104] The thickness of the plate is 3 mm.

[0105] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0106] Density is 1.3 g / cm3;

[0107] Flexural strength is 40 MPa;

[0108] The flame retardant grade is B1.

[0109] Implementation 7:

[0110] This embodiment is similar to Embodiment 1, except that:

[0111] The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:6:2:2:1;

[0112] The shape and size of the mold is a five-pointed star with a side length of 10 cm;

[0113] In the pre-pressing step, the applied pressure is 1 MPa;

[0114] During the hot pressing step, the applied temperature was 180 degrees Celsius and the applied pressure was 8 MPa;

[0115] The thickness of the plate is 4 mm.

[0116] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0117] Density is 0.9 g / cm3;

[0118] Flexural strength is 15 MPa;

[0119] The flame retardant grade is B2.

[0120] Implementation 8:

[0121] This embodiment is similar to Embodiment 1, except that:

[0122] The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:18:6:6:4;

[0123] The shape and size of the mold are heart-shaped, 15 cm long and 10 cm wide;

[0124] In the pre-pressing step, the applied pressure is 6 MPa;

[0125] During the hot pressing step, the applied temperature was 230 degrees Celsius and the applied pressure was 18 MPa;

[0126] The thickness of the plate is 0.5 mm.

[0127] The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers prepared in this embodiment has the following properties:

[0128] Density is 1.4 g / cm3;

[0129] Flexural strength is 45 MPa;

[0130] The flame retardant grade is B1.

[0131] Comparative Example 1:

[0132] This comparative example is similar to embodiment 1, except that:

[0133] The wood micro-powder fiber slurry is not mixed with any multi-dimensional cross-linking agent, and is directly subjected to extrusion, pre-pressing, hot pressing and cooling to obtain the wood micro-powder fiber board.

[0134] The wood powder fiber board prepared in this comparative example has the following properties:

[0135] Density is 0.6 g / cm3;

[0136] flexural strength is 5 MPa;

[0137] The flame retardant grade is C.

[0138] This comparative example shows that the density, strength and flame retardancy of the wood powder fiber board without the multi-dimensional cross-linking agent are relatively low, and cannot meet the purpose of the present invention.

[0139] Comparative Example 2:

[0140] This comparative example is similar to embodiment 1, except that:

[0141] The multidimensional cross-linking agent only includes polyvinyl alcohol and boric acid, which are mixed in a mass ratio of 100:10.

[0142] The dense flame-retardant board with multi-dimensional cross-linked structure of wood micropowder fiber prepared in this comparative example has the following properties:

[0143] Density is 0.8 g / cm3;

[0144] Flexural strength is 10 MPa;

[0145] The flame retardant grade is B2.

[0146] This comparative example shows that the density, strength and flame retardant properties of the dense flame retardant board with a multidimensional cross-linked structure of wood micropowder fibers using only polyvinyl alcohol and boric acid as multidimensional cross-linking agents are low and cannot meet the purpose of the present invention.

[0147] Comparative Example 3:

[0148] This comparative example is similar to embodiment 1, except that:

[0149] The multidimensional cross-linking agent only includes polyvinyl alcohol and potassium dihydrogen phosphate, which are mixed in a mass ratio of 100:10.

[0150] The dense flame-retardant board with multi-dimensional cross-linked structure of wood micropowder fiber prepared in this comparative example has the following properties:

[0151] Density is 0.9 g / cm3;

[0152] Flexural strength is 15 MPa;

[0153] The flame retardant grade is B2.

[0154] This comparative example shows that the density, strength and flame retardant properties of the dense flame retardant board with a multidimensional cross-linked structure of wood micropowder fibers using only polyvinyl alcohol and potassium dihydrogen phosphate as multidimensional cross-linking agents are low and cannot meet the purpose of the present invention.

[0155] Comparative Example 4:

[0156] This comparative example is similar to embodiment 1, except that:

[0157] The multidimensional cross-linking agent only includes polyvinyl alcohol and aluminum sulfate, which are mixed in a mass ratio of 100:10.

[0158] The dense flame-retardant board with multi-dimensional cross-linked structure of wood micropowder fiber prepared in this comparative example has the following properties:

[0159] Density is 1.0 g / cm3;

[0160] Flexural strength is 20 MPa;

[0161] The flame retardant grade is B2.

[0162] This comparative example shows that the density, strength and flame retardant properties of the dense flame retardant board with a multidimensional cross-linked structure of wood micropowder fibers using only polyvinyl alcohol and aluminum sulfate as multidimensional cross-linking agents are low and cannot meet the purpose of the present invention.

[0163] Comparative Example 5:

[0164] This comparative example is similar to embodiment 1, except that:

[0165] The multidimensional cross-linking agent includes polyvinyl alcohol, boric acid, potassium dihydrogen phosphate, aluminum sulfate and formaldehyde (HCHO), which are mixed in a mass ratio of 100:10:3:3:2:5.

[0166] The dense flame-retardant board with multi-dimensional cross-linked structure of wood micropowder fiber prepared in this comparative example has the following properties:

[0167] Density is 1.2 g / cm3;

[0168] Flexural strength is 30 MPa;

[0169] The flame retardant grade is B1.

[0170] This comparative example shows that although the dense flame-retardant board with a multidimensional cross-linked structure of wood micropowder fibers using formaldehyde as a multidimensional cross-linking agent has high density, strength and flame retardant properties, formaldehyde is a toxic and harmful substance that can cause harm to the human body and the environment, and does not meet the environmental protection purpose of the present invention.

[0171] Summary analysis table:

[0172] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. This article uses specific examples to illustrate the principles and implementation methods of the technical solution of this patent. The above examples are only used to help understand the method of this patent and its core ideas. The above is only a preferred implementation method of this patent. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of this patent, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the patent concept and technical solution to other occasions without improvement, should be regarded as the scope of protection of this patent.

Claims

1. A dense flame-retardant board with a multi-dimensional cross-linked structure of wood micropowder fibers, characterized in that: The plate is prepared by the following steps: Mixing wood micro-powder fiber with water to obtain wood micro-powder fiber slurry with a water content of 50%-80%; The wood powder fiber slurry is mixed with polyvinyl alcohol (PVA), boric acid , potassium dihydrogen phosphate and aluminum sulfate The mixture is mixed in a mass ratio of 100:5-15:1-5:1-5:0.5-5 to obtain a wood micropowder fiber slurry containing a multi-dimensional cross-linking agent; The wood micro-powder fiber slurry containing the multi-dimensional cross-linking agent is subjected to extrusion, pre-pressing, hot pressing and cooling to obtain the board; wherein the multi-dimensional cross-linking agent forms the following chemical reaction in the board: PVA and Reaction to generate polyvinyl alcohol borate (PVA-B) and water, the reaction equation is: PVA and Reaction to generate polyvinyl alcohol phosphate (PVA-P) and potassium hydroxide , the reaction equation is: Reacts with KOH to generate aluminum hydroxide and potassium sulfate , the reaction equation is: The PVAB, PVAP and A multi-dimensional cross-linked network structure is formed in the board material, thereby improving the density, strength and flame retardancy of the board material.

2. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to claim 1, characterized in that: The average particle size of the wood micro-powder fiber is 10-100 microns.

3. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to claim 1 or 2, characterized in that: The molecular weight of the polyvinyl alcohol is 5000-50000 Daltons.

4. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to any one of claims, characterized in that: The thickness of the plate is 0.5-10 mm.

5. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to any one of claims, characterized in that: The density of the board is 0.8-1.5 g / cm3.

6. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to any one of claims, characterized in that: The bending strength of the plate is 10-50 MPa.

7. The dense flame-retardant board with a multi-dimensional cross-linked structure of wood micro-powder fibers according to any one of claims, characterized in that: The flame retardant grade of the board is B1 or B2.

8. A method for preparing a dense flame-retardant board having a multi-dimensional cross-linked structure of wood micropowder fibers according to any one of claims 1 to 7, characterized in that: The following steps are involved: Mixing wood micro-powder fiber with water to obtain wood micro-powder fiber slurry with a water content of 50%-80%; The wood powder fiber slurry is mixed with polyvinyl alcohol, boric acid, potassium dihydrogen phosphate and aluminum sulfate in a mass ratio of 100:5-15:1-5:1-5:0.5-5 to obtain a wood powder fiber slurry containing a multi-dimensional cross-linking agent; The wood micro-powder fiber slurry containing a multi-dimensional cross-linking agent is subjected to extrusion, pre-pressing, hot pressing and cooling to obtain the board; The extrusion step is to extrude the wood micropowder fiber slurry containing a multi-dimensional cross-linking agent through a die having a certain shape and size to obtain a board blank of a desired shape and size; The pre-pressing step is to place the sheet blank in a mold with a certain shape and size, apply a certain pressure, reduce the water content of the sheet blank to 30%-50%, and make the sheet blank fit closely with the mold; The hot pressing step is to place the pre-pressed sheet blank in a heating device, apply a certain temperature and pressure, so that the multi-dimensional cross-linking agent reacts chemically in the sheet blank and reduces the water content of the sheet blank to less than 10%; The cooling step is to place the hot-pressed sheet blank in a cooling device, apply a certain temperature and pressure, and cool and solidify the sheet blank to obtain the sheet.

9. The molding method according to claim 8, characterized in that: In the extrusion step, the shape and size of the mold are circular, square, rectangular, trapezoidal or other arbitrary shapes, and the size of the mold is the same as or slightly larger than the size of the plate to be prepared.

10. The molding method according to claim 8 or 9, characterized in that: In the pre-pressing step, the applied pressure is 0.5-5 MPa, and in the hot pressing step, the applied temperature is 150-250 degrees Celsius and the applied pressure is 5-15 MPa.

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