High-strength moisture-proof medium-density fiber artificial board and preparation method thereof
By combining modified fibers with isocyanate adhesives and nano-silica, the problems of strength reduction and flammability of medium-density fiberboard in humid environments have been solved, achieving a comprehensive improvement in high strength, moisture resistance and flame retardancy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-16
- Publication Date
- 2026-04-14
AI Technical Summary
Traditional medium-density fiberboard (MDF) has shortcomings in mechanical properties, moisture resistance, and flame retardancy. In particular, its strength decreases, it is prone to deformation and flammability in humid environments, and the addition of flame retardants or waterproofing agents can affect other properties.
By using surface-modified reinforcing fibers, isocyanate adhesives, nano-silica, and interface-compatible flame retardants, a strong interfacial bonding structure is formed through stepwise sizing and a two-stage hot-pressing process, which reduces moisture absorption and improves flame retardancy.
It significantly improves the static bending strength, elastic modulus and impact toughness of the board, reduces the water absorption swelling rate, has an extremely low water absorption thickness swelling rate and good flame retardant properties, and is suitable for high humidity environments.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of engineered wood products manufacturing and composite materials technology, and in particular to a high-strength, moisture-resistant medium-density fiberboard and its preparation method. Background Technology
[0002] Medium-density fiberboard (MDF) is widely used in furniture manufacturing, interior decoration, and construction due to its uniform material and excellent processing performance. It is used for making cabinets, doors, partitions, and decorative moldings. However, traditional MDF, primarily made by hot-pressing wood fibers with adhesives such as urea-formaldehyde resin, generally suffers from the following technical defects: 1) Mechanical properties need improvement: The static bending strength, elastic modulus, and internal bond strength of ordinary MDF are limited, mainly due to uneven fiber length distribution, brittleness of the cured adhesive, and weak interfacial bonding. Especially in humid environments, moisture penetration causes the wood fibers to absorb moisture and swell, and the adhesive to degrade, resulting in a significant decrease in strength. The static bending strength may decrease by more than 30%, thus limiting its application in load-bearing structures or applications requiring high strength, such as flooring, stair treads, or structural supports. 2) Poor moisture resistance and water resistance: The wood fibers in the board have natural hydrophilicity, and commonly used adhesives such as urea-formaldehyde resin are also prone to absorbing water, resulting in a high thickness expansion rate after water absorption, reaching 10%-20%. In humid environments, deformation, warping, and delamination are likely to occur, making the board dimension unstable and significantly shortening its service life. In addition, it is highly flammable: Wood fibers and organic adhesives are flammable materials. When exposed to fire, they burn rapidly and release toxic gases such as formaldehyde, posing a significant fire hazard. Therefore, MDF that has not been flame-retardant treated cannot meet the requirements of places with fire safety requirements, such as schools, hospitals, shopping malls and other public places. 3) To improve a particular property, such as adding flame retardants to enhance fire resistance, other properties, such as mechanical strength, are often compromised. This is because flame retardants can fill fiber gaps, weaken the adhesive interface, or cause chemical degradation. Similarly, adding waterproofing agents may affect the curing reaction of the adhesive. Poor interfacial compatibility between components creates a bottleneck in performance improvement, making it difficult to achieve synergistic optimization of multiple properties through simple additives.
[0003] Therefore, it is of great significance to provide a high-performance medium-density fiberboard that can simultaneously achieve high strength, excellent moisture resistance, good flame retardancy, and synergistic effects of its components. Summary of the Invention
[0004] To address the aforementioned technical problems, the present invention aims to provide a high-strength, moisture-resistant medium-density fiberboard and its preparation method.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a high-strength, moisture-resistant medium-density fiberboard (MDF) prepared from raw materials comprising the following parts by weight: 70-90 parts wood fiber 3-8 parts of surface-modified reinforcing fibers, 10-15 parts isocyanate adhesive, 2-5 parts of desiccant 1-4 parts of nano-silica 1-4 parts of interface-compatible flame retardant 1-3 parts of curing agent.
[0006] Furthermore, the wood fiber is a mixture of pine fiber and eucalyptus fiber, with a mass ratio of pine fiber to eucalyptus fiber of 1~3:1; The isocyanate adhesive includes diphenylmethane diisocyanate; The desiccant includes a paraffin emulsion; The curing agent includes triethylenediamine.
[0007] Furthermore, the surface-modified reinforcing fiber is glass fiber and / or carbon fiber coated with silane coupling agent. The preparation method of the surface-modified reinforcing fiber includes: immersing the reinforcing fiber in an ethanol solution of silane coupling agent and performing ultrasonic treatment for 10-30 minutes, and then removing it and drying and curing it at 80-120°C. The silane coupling agent is γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane; The amount of the silane coupling agent used is 0.5 to 2.0% of the weight of the reinforcing fiber.
[0008] Furthermore, the interface-compatible flame retardant is an inorganic flame-retardant microparticle or a phosphorus-nitrogen intumescent flame retardant.
[0009] Furthermore, the inorganic flame-retardant microparticles are aluminum hydroxide, zinc borate, or silicon dioxide that have been surface-treated with a silane coupling agent; The phosphorus-nitrogen intumescent flame retardant is a mixture of ammonium polyphosphate, melamine, and pentaerythritol, wherein the mass ratio of ammonium polyphosphate, melamine, and pentaerythritol is 1~10:0.5~8:0.5~5.
[0010] The present invention also provides a method for preparing the high-strength, moisture-resistant medium-density fiberboard, comprising the following steps: 1) Wood fibers, surface-modified reinforcing fibers, a portion of isocyanate adhesive and a portion of curing agent are premixed to obtain pretreated fiber bundles; 2) Mix the pretreated fiber bundles, remaining isocyanate adhesive, moisture-proofing agent, nano-silica, interface-compatible flame retardant and remaining curing agent to obtain a mixture; 3) The mixture is laid out and molded, and then pressed using a hot-pressing process to obtain a high-strength, moisture-proof medium-density fiberboard.
[0011] Furthermore, the mass ratio of the partial isocyanate adhesive to the remaining isocyanate adhesive is 2~4:6~8; The mass ratio of the partially cured agent to the remaining cured agent is 1~3:7~9.
[0012] Furthermore, the premixing speed is 200~500 r / min, and the premixing time is 5~15 min; The mixing time is 20-40 minutes.
[0013] Furthermore, a pre-pressing process is performed before the hot pressing process. The pre-pressing pressure is 1~2MPa and the pre-pressing time is 30~60s.
[0014] Furthermore, the hot pressing process is divided into two stages. In the first stage, hot pressing is carried out at 5~6MPa and 170~185℃ until the center temperature of the slab reaches 100~110℃. In the second stage, hot pressing continues at 2~3MPa and 170~185℃ until the total time reaches 30~60 seconds / mm thickness.
[0015] The beneficial effects of this invention are: 1) This invention introduces glass fibers or carbon fibers that have been surface modified with silane coupling agents as a reinforcing phase, so that they form a strong interfacial bond structure with wood fibers, which significantly improves the static bending strength, elastic modulus and impact toughness of the board. 2) This invention uses hydrophobic isocyanate adhesive and paraffin emulsion moisture-proofing agent to fundamentally reduce the moisture absorption of the board; the filling effect of nano silica can block some capillary channels, and the components work together to give the board an extremely low water absorption thickness expansion rate, which is suitable for high humidity environments. 3) This invention solves the problem of mechanical property degradation caused by the addition of traditional flame retardants by adding an interface-compatible flame retardant; the flame retardant is well compatible with MDI adhesive system and can be evenly dispersed, and can effectively play a flame retardant and smoke-suppressing role during combustion, and improve the oxygen index of the board. 4) This invention employs a stepwise sizing and mixing process, combined with a two-stage hot pressing process, to ensure the uniform dispersion and full curing of various heterogeneous components such as fibers, powdered flame retardants, and liquid adhesives. This ensures the uniformity and stability of product performance and overcomes common problems such as agglomeration and uneven dispersion in multi-component composite systems. The stepwise sizing process ensures that the reinforcing fibers are fully impregnated by the adhesive, further optimizing stress transfer. Detailed Implementation
[0016] This invention provides a high-strength, moisture-resistant medium-density fiberboard (MDF) prepared from raw materials comprising the following parts by weight: 70-90 parts wood fiber 3-8 parts of surface-modified reinforcing fibers, 10-15 parts isocyanate adhesive, 2-5 parts of desiccant 1-4 parts of nano-silica 1-4 parts of interface-compatible flame retardant 1-3 parts of curing agent.
[0017] In this invention, the content of wood fiber is preferably 72 to 87 parts by weight, and more preferably 75 to 85 parts by weight.
[0018] In this invention, the wood fiber is a mixture of pine fiber and eucalyptus fiber, and the mass ratio of pine fiber to eucalyptus fiber is 1~3:1, preferably 1.2~2.8:1, and more preferably 1.5~2.5:1.
[0019] In this invention, the content of the surface-modified reinforcing fiber is preferably 3.5 to 7.5 parts by weight, and more preferably 4 to 7 parts by weight.
[0020] In this invention, the surface-modified reinforcing fiber is glass fiber and / or carbon fiber coated with a silane coupling agent. The preparation method of the surface-modified reinforcing fiber includes: immersing the reinforcing fiber in an ethanol solution of a silane coupling agent and performing ultrasonic treatment for 10-30 minutes, and then removing it and drying and curing it at 80-120°C. The ultrasonic treatment time is preferably 15-25 min, and more preferably 20 min; Preferably, the product is dried and cured at 85~115℃; more preferably, it is dried and cured at 90~110℃.
[0021] In this invention, the silane coupling agent is γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane, preferably γ-aminopropyltriethoxysilane; The amount of the silane coupling agent is 0.5-2.0% of the weight of the reinforcing fiber, preferably 0.8-1.7%, and more preferably 1-1.5%.
[0022] In this invention, the content of the isocyanate adhesive is preferably 11 to 14 parts by weight, and more preferably 12 to 13 parts by weight.
[0023] In this invention, the isocyanate adhesive is preferably diphenylmethane diisocyanate.
[0024] In this invention, the content of the desiccant is preferably 2.5 to 4.5 parts by weight, and more preferably 3 to 4 parts by weight.
[0025] In this invention, the desiccant is preferably a paraffin emulsion.
[0026] In this invention, the content of the nano-silica is preferably 1.5 to 3.5 parts by weight, and more preferably 2 to 3 parts by weight.
[0027] In this invention, the content of the interface-compatible flame retardant is preferably 1.5 to 3.5 parts by weight, and more preferably 2 to 3 parts by weight.
[0028] In this invention, the interface-compatible flame retardant is an inorganic flame retardant microparticle or a phosphorus-nitrogen intumescent flame retardant, preferably a phosphorus-nitrogen intumescent flame retardant.
[0029] In this invention, the inorganic flame-retardant microparticles are aluminum hydroxide, zinc borate, or silicon dioxide that have been surface-treated with a silane coupling agent, preferably aluminum hydroxide or silicon dioxide that have been surface-treated with a silane coupling agent. The phosphorus-nitrogen intumescent flame retardant is a mixture of ammonium polyphosphate, melamine, and pentaerythritol, wherein the mass ratio of ammonium polyphosphate, melamine, and pentaerythritol is 1~10:0.5~8:0.5~5, preferably 2~8:1~7:0.7~4.5, and more preferably 3~6:2~6:1~4.
[0030] In this invention, the content of the curing agent is preferably 1.2 to 2.7 parts by weight, and more preferably 1.5 to 2.5 parts by weight.
[0031] In this invention, the curing agent is preferably triethylenediamine.
[0032] The present invention also provides a method for preparing the high-strength, moisture-resistant medium-density fiberboard, comprising the following steps: 1) Wood fibers, surface-modified reinforcing fibers, a portion of isocyanate adhesive and a portion of curing agent are premixed to obtain pretreated fiber bundles; 2) Mix the pretreated fiber bundles, remaining isocyanate adhesive, moisture-proofing agent, nano-silica, interface-compatible flame retardant and remaining curing agent to obtain a mixture; 3) The mixture is laid out and molded, and then pressed using a hot-pressing process to obtain a high-strength, moisture-proof medium-density fiberboard.
[0033] In this invention, the mass ratio of the partial isocyanate adhesive to the remaining isocyanate adhesive is 2~4:6~8, preferably 2.5~3.5:6.5~7.5, and more preferably 3:7; The mass ratio of the partial curing agent to the remaining curing agent is 1~3:7~9, preferably 1.5~2.5:7.5~8.5, and more preferably 2:8.
[0034] In this invention, the premixing speed is 200~500 r / min, preferably 250~450 r / min, more preferably 300~400 r / min; the premixing time is 5~15 min, preferably 7~12 min, more preferably 10 min; The mixing time is 20-40 min, preferably 25-35 min, and more preferably 30 min.
[0035] In this invention, a pre-pressing process is performed before the hot pressing process. The pre-pressing pressure is 1~2MPa, preferably 1.2~1.8MPa, and more preferably 1.4~1.6MPa. The pre-pressing time is 30~60s, preferably 35~55s, and more preferably 40~50s.
[0036] In this invention, the hot pressing process is divided into two stages. The first stage involves hot pressing at 5-6 MPa and 170-185°C until the center temperature of the slab reaches 100-110°C. The second stage involves continuing hot pressing at 2-3 MPa and 170-185°C until the total time reaches 30-60 seconds per millimeter of slab thickness.
[0037] Preferably, the first stage involves hot pressing at 5.2~5.8MPa and 173~182℃ until the center temperature of the slab reaches 102~108℃; the second stage involves continuing hot pressing at 2.2~2.8MPa and 173~182℃ until the total time reaches 35~55 seconds per millimeter of slab thickness.
[0038] Further preferred, the first stage involves hot pressing at 5.5 MPa and 175~180℃ until the center temperature of the slab reaches 105℃; the second stage involves continuing hot pressing at 2.4~2.6 MPa and 175~180℃ until the total time reaches 40~50 seconds per millimeter of slab thickness.
[0039] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.
[0040] Example 1
[0041] Carbon fibers were impregnated in an ethanol solution of γ-aminopropyltriethoxysilane and ultrasonically treated for 20 minutes. After ultrasonic treatment, the fibers were removed and dried and cured at 100°C to obtain surface-modified reinforcing fibers. 80 parts of a mixture of pine and eucalyptus fibers (the mass ratio of pine to eucalyptus fibers was 5:3), 6 parts of surface-modified reinforcing fibers, 3.9 parts of diphenylmethane diisocyanate and 0.4 parts of triethylenediamine were added to a high-speed mixer and premixed at a speed of 350 r / min for 10 min to obtain pretreated fiber bundles. The pretreated fiber bundle, 9.1 parts of diphenylmethane diisocyanate, 3.5 parts of paraffin emulsion, 2.5 parts of nano silica, 2.5 parts of a mixture of ammonium polyphosphate, melamine and pentaerythritol in a mass ratio of 5:3:2, and 1.6 parts of triethylenediamine were mixed at a speed of 300 r / min for 30 min to obtain the mixture. The mixture is laid out and pre-pressed at 1.5 MPa for 45 seconds, followed by hot pressing. In the first stage, the board is hot-pressed at 5.5 MPa and 180°C until the center temperature reaches 105°C. In the second stage, the board is hot-pressed at 2.5 MPa and 180°C until the total time reaches 45 seconds per millimeter of board thickness. After cooling, cutting, and inspection, a high-strength, moisture-proof medium-density fiberboard is obtained.
[0042] Example 2
[0043] Carbon fibers were impregnated in an ethanol solution of γ-glycidyl oxypropyltrimethoxysilane and ultrasonically treated for 20 minutes. After ultrasonic treatment, the fibers were removed and dried and cured at 100°C to obtain surface-modified reinforcing fibers. 80 parts of a mixture of pine and eucalyptus fibers (the mass ratio of pine to eucalyptus fibers was 3:1), 4 parts of surface-modified reinforcing fibers, 3.6 parts of diphenylmethane diisocyanate and 0.36 parts of triethylenediamine were added to a high-speed mixer and premixed at a speed of 350 r / min for 10 min to obtain pretreated fiber bundles. The pretreated fiber bundle, 8.4 parts of diphenylmethane diisocyanate, 3 parts of paraffin emulsion, 2 parts of nano silica, 2 parts of aluminum hydroxide surface-treated with silane coupling agent and 1.44 parts of triethylenediamine were mixed at a speed of 300 r / min for 30 min to obtain the mixture. The mixture is laid out and pre-pressed at 1.5 MPa for 45 seconds, followed by hot pressing. In the first stage, the board is hot-pressed at 5.5 MPa and 180°C until the center temperature of the board reaches 105°C. In the second stage, the board is hot-pressed at 2.5 MPa and 180°C until the total time reaches 40 seconds per millimeter of board thickness. After cooling, cutting, and inspection, a high-strength, moisture-proof medium-density fiberboard is obtained.
[0044] Example 3
[0045] Glass fibers were impregnated in an ethanol solution of γ-aminopropyltriethoxysilane and ultrasonically treated for 20 minutes. After ultrasonic treatment, the fibers were removed and dried and cured at 100°C to obtain surface-modified reinforcing fibers. 80 parts of a mixture of pine and eucalyptus fibers (the mass ratio of pine to eucalyptus fibers was 1.3:1), 7 parts of surface-modified reinforcing fibers, 4.2 parts of diphenylmethane diisocyanate and 0.44 parts of triethylenediamine were added to a high-speed mixer and premixed at a speed of 350 r / min for 10 min to obtain pretreated fiber bundles. The pretreated fiber bundle, 9.8 parts of diphenylmethane diisocyanate, 4 parts of paraffin emulsion, 3 parts of nano silica, 3 parts of a mixture of ammonium polyphosphate, melamine and pentaerythritol in a mass ratio of 6:4:3, and 1.76 parts of triethylenediamine were mixed at a speed of 300 r / min for 30 min to obtain the mixture. The mixture is laid out and pre-pressed at 1.5 MPa for 45 seconds, followed by hot pressing. In the first stage, the board is hot-pressed at 5.5 MPa and 180°C until the center temperature of the board reaches 105°C. In the second stage, the board is hot-pressed at 2.5 MPa and 180°C until the total time reaches 50 seconds per millimeter of board thickness. After cooling, cutting, and inspection, a high-strength, moisture-proof medium-density fiberboard is obtained.
[0046] Example 4
[0047] Glass fibers were impregnated in an ethanol solution of γ-aminopropyltriethoxysilane and ultrasonically treated for 20 minutes. After ultrasonic treatment, the fibers were removed and dried and cured at 100°C to obtain surface-modified reinforcing fibers. 80 parts of a mixture of pine and eucalyptus fibers (the mass ratio of pine to eucalyptus fibers was 2.2:1), 5 parts of surface-modified reinforcing fibers, 3.3 parts of diphenylmethane diisocyanate and 0.3 parts of triethylenediamine were added to a high-speed mixer and premixed at a speed of 350 r / min for 10 min to obtain pretreated fiber bundles. The pretreated fiber bundle, 7.7 parts of diphenylmethane diisocyanate, 2.5 parts of paraffin emulsion, 1.5 parts of nano silica, 1.5 parts of zinc borate surface-treated with silane coupling agent, and 1.2 parts of triethylenediamine were mixed at a speed of 300 r / min for 30 min to obtain the mixture. The mixture is laid out and pre-pressed at 1.5 MPa for 45 seconds, followed by hot pressing. In the first stage, the board is hot-pressed at 5.5 MPa and 180°C until the center temperature reaches 105°C. In the second stage, the board is hot-pressed at 2.5 MPa and 180°C until the total time reaches 35 seconds per millimeter of board thickness. After cooling, cutting, and inspection, a high-strength, moisture-proof medium-density fiberboard is obtained.
[0048] Comparative Example 1
[0049] Compared with Example 1, the difference is that ordinary glass fiber was used in Comparative Example 1, and no surface-modified reinforcing fiber was used.
[0050] Comparative Example 2
[0051] The difference between Comparative Example 2 and Example 1 is that no nano-silica was added.
[0052] Comparative Example 3
[0053] Compared with Example 1, the difference is that in Comparative Example 3, urea-formaldehyde resin adhesive was used instead of isocyanate adhesive, and no interfacial compatible flame retardant was added.
[0054] The performance of the high-strength, moisture-resistant medium-density fiberboard prepared in Examples 1-4 and Comparative Examples 1-3 was tested according to GB-T 11718-2021 standard. The test results are shown in Table 1.
[0055] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-3
[0056] As shown in Table 1, the performance of the embodiments of the present invention is superior to that of the comparative examples. In comparative example 1, there is no surface-modified reinforcing fiber, and the weak interfacial bonding leads to a decrease in elastic modulus and an increase in water absorption swelling rate. In comparative example 2, there is no nano-silica, and the lack of pore filling effect results in a significant increase in water absorption thickness swelling rate. In comparative example 3, urea-formaldehyde resin is used and there is no interfacial compatible flame retardant. Due to the hydrophilicity of the adhesive and the poor dispersion of the flame retardant, the performance of the embodiments of the present invention is significantly reduced.
[0057] As can be seen from the above embodiments, the present invention provides a high-strength, moisture-resistant medium-density fiberboard and its preparation method. The high-strength, moisture-resistant medium-density fiberboard is prepared from raw materials comprising the following parts by weight: 70-90 parts wood fiber, 3-8 parts surface-modified reinforcing fiber, 10-15 parts isocyanate adhesive, 2-5 parts moisture-proofing agent, 1-4 parts nano-silica, 1-4 parts interface-compatible flame retardant, and 1-3 parts curing agent. The present invention, through the synergistic effect of its components, endows the board with extremely low water absorption thickness swelling rate, high strength, excellent moisture resistance, and good flame retardancy. It is suitable for high-humidity environments. The step-by-step gluing and mixing process, combined with a two-stage hot-pressing process, ensures uniform dispersion and full curing of the components, guaranteeing the uniformity and stability of product performance, and overcoming the common problems of agglomeration and uneven dispersion in multi-component composite systems.
[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A high-strength, moisture-resistant medium-density fiberboard, characterized in that, It is prepared from raw materials comprising the following parts by weight: 70-90 parts wood fiber 3-8 parts of surface-modified reinforcing fibers, 10-15 parts isocyanate adhesive, 2-5 parts of desiccant 1-4 parts of nano-silica 1-4 parts of interface-compatible flame retardant 1-3 parts of curing agent.
2. The high-strength, moisture-proof medium-density fiberboard according to claim 1, characterized in that, The wood fiber is a mixture of pine fiber and eucalyptus fiber, with a mass ratio of pine fiber to eucalyptus fiber of 1~3:1; The isocyanate adhesive includes diphenylmethane diisocyanate; The desiccant includes a paraffin emulsion; The curing agent includes triethylenediamine.
3. The high-strength, moisture-proof medium-density fiberboard according to claim 1 or 2, characterized in that, The surface-modified reinforcing fiber is glass fiber and / or carbon fiber coated with silane coupling agent. The preparation method of the surface-modified reinforcing fiber includes: immersing the reinforcing fiber in an ethanol solution of silane coupling agent and performing ultrasonic treatment for 10-30 minutes, and then removing it and drying and curing it at 80-120°C. The silane coupling agent is γ-aminopropyltriethoxysilane and / or γ-glycidoxypropyltrimethoxysilane; The amount of the silane coupling agent used is 0.5 to 2.0% of the weight of the reinforcing fiber.
4. The high-strength, moisture-proof medium-density fiberboard according to claim 3, characterized in that, The interface-compatible flame retardant is an inorganic flame retardant microparticle or a phosphorus-nitrogen intumescent flame retardant.
5. The high-strength, moisture-proof medium-density fiberboard according to claim 4, characterized in that, The inorganic flame-retardant microparticles are aluminum hydroxide, zinc borate, or silicon dioxide that have been surface-treated with a silane coupling agent. The phosphorus-nitrogen intumescent flame retardant is a mixture of ammonium polyphosphate, melamine, and pentaerythritol, wherein the mass ratio of ammonium polyphosphate, melamine, and pentaerythritol is 1~10:0.5~8:0.5~5.
6. A method for preparing a high-strength, moisture-proof medium-density fiberboard according to any one of claims 1 to 5, characterized in that, Includes the following steps: 1) Wood fibers, surface-modified reinforcing fibers, a portion of isocyanate adhesive and a portion of curing agent are premixed to obtain pretreated fiber bundles; 2) Mix the pretreated fiber bundles, remaining isocyanate adhesive, moisture-proofing agent, nano-silica, interface-compatible flame retardant and remaining curing agent to obtain a mixture; 3) The mixture is laid out and molded, and then pressed using a hot-pressing process to obtain a high-strength, moisture-proof medium-density fiberboard.
7. The method for preparing high-strength, moisture-proof medium-density fiberboard according to claim 6, characterized in that, The mass ratio of the partial isocyanate adhesive to the remaining isocyanate adhesive is 2~4:6~8; The mass ratio of the partially cured agent to the remaining cured agent is 1~3:7~9.
8. The method for preparing high-strength, moisture-proof medium-density fiberboard according to claim 7, characterized in that, The premixing speed is 200~500 r / min, and the premixing time is 5~15 min; The mixing time is 20-40 minutes.
9. The method for preparing high-strength, moisture-proof medium-density fiberboard according to claim 8, characterized in that, Before the hot pressing process, a pre-pressing process is performed. The pre-pressing pressure is 1~2MPa and the pre-pressing time is 30~60s.
10. The method for preparing high-strength, moisture-proof medium-density fiberboard according to claim 9, characterized in that, The hot pressing process is divided into two stages. In the first stage, hot pressing is carried out at 5~6MPa and 170~185℃ until the center temperature of the slab reaches 100~110℃. In the second stage, hot pressing continues at 2~3MPa and 170~185℃ until the total time reaches 30~60 seconds per millimeter of slab thickness.