Production process of moisture-proof flame-retardant thin high-density fiberboard

Abstract

The invention provides a production process of a moisture-proof flame-retardant thin high-density fiberboard. The production process comprises the following steps: S1, chipping; s2, screening is carried out; s3, carrying out pre-cooking; s4, performing cooking; s5, hot grinding; s6, drying; s7, sizing is conducted; s8, winnowing is conducted; s9, adding a moisture-proof flame retardant; s10, paving is carried out; s11, prepressing is carried out; s12, hot pressing; s13, cooling the plate; and S14, post-treatment is carried out. S15, carrying out health maintenance; s16, saw cutting is conducted; and S17, grading and packaging. According to the production process of the damp-proof flame-retardant thin high-density fiberboard, the stability of the board in a humid environment and the flame-retardant performance of the board in a fire disaster condition are achieved, synchronous sizing is adopted in the drying process, a non-corrosive damp-proof flame-retardant agent is accurately added, and multi-section temperature control hot pressing and sufficient curing treatment are combined, so that the quality of the board is improved. The internal bonding strength and the dimensional stability of the thin plate are effectively improved, and the requirements of high-end decoration and functional application scenes are met.

Description

Technical Field

[0001] This invention belongs to the field of fiberboard production technology, and specifically relates to a production process for moisture-proof and flame-retardant thin high-density fiberboard. Background Technology

[0002] With the rapid development of the building decoration, furniture manufacturing, and interior decoration industries, the market's performance requirements for engineered wood products are increasing, especially in terms of moisture resistance, flame retardancy, and environmental friendliness. Traditional engineered wood products, such as medium-density fiberboard (MDF), while exhibiting good strength and processing performance, are prone to absorbing water and swelling in humid environments and are easily flammable under fire conditions, posing significant safety hazards. Furthermore, conventional production processes often struggle to balance product thinness with high performance.

[0003] Current thin fiberboard production processes largely focus on basic physical forming techniques, lacking systematic functional modification methods. For example, the adhesive application stage typically only considers bonding performance without integrating moisture resistance and flame retardancy into the overall design; hot-pressing process parameters are relatively simple, failing to effectively guarantee the uniformity and density of the board's internal structure; curing and post-treatment processes are often neglected, resulting in insufficient release of internal stress and affecting the final dimensional stability. Furthermore, some companies use post-production spraying or impregnation to achieve moisture resistance and flame retardancy, which not only increases process complexity but may also introduce corrosive substances, affecting the long-term performance of the material.

[0004] Therefore, there is an urgent need to develop a production process for thin fiberboard that integrates moisture resistance, flame retardancy, and high density. This process can comprehensively improve the functional characteristics and environmental adaptability of the board by optimizing key steps such as raw material processing, fiber preparation, precise control of additives, hot pressing curve regulation, and subsequent curing, while ensuring the mechanical properties of the product. Summary of the Invention

[0005] In view of this, the present invention addresses the shortcomings of the prior art by providing a production process for moisture-proof and flame-retardant thin high-density fiberboard. This process not only achieves the stability of the board in humid environments and its flame-retardant properties under fire conditions, but also effectively improves the internal bonding strength and dimensional stability of the thin board by simultaneously applying adhesive during the drying process, precisely adding non-corrosive moisture-proof and flame-retardant agents, and combining multi-stage temperature-controlled hot pressing with thorough curing treatment, thus meeting the needs of high-end decorative and functional applications.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a production process for moisture-proof and flame-retardant thin high-density fiberboard, comprising the following steps: S1, chipping; S2, Filter; S3, pre-steaming; S4, steaming / boiling; S5, hot grinding; S6, drying; S7, applying adhesive; S8, Wind Select; S9, moisture-proof and flame-retardant agent added, the amount of moisture-proof and flame-retardant agent added is dynamically adjusted according to the fiber flow rate, and a metering device is provided to ensure the accuracy of addition. The moisture-proof and flame-retardant agent used is a non-corrosive material. S10, paved; S11, pre-compression; S12, hot pressing, uses a multi-stage temperature-controlled hot press. The first frame temperature at the press inlet is 210℃, serving as the high-pressure zone; the second frame temperature is 210℃, serving as the pressure-holding zone; the third frame temperature is 190℃, serving as the first pressure-holding zone; the fourth frame temperature is 180℃, serving as the pressure-holding and thickness-fixing zone; and the fifth frame temperature is 170℃, serving as the second pressure-holding zone. S13, Cool board; S14, post-processing: After cooling, the products are trimmed, then automatically stacked and labeled. S15, Health Preservation: Transfer the products that have just come off the production line to the health preservation area, keep them neatly and flat, and let them stand for no less than 48 hours before proceeding to the next process. S16, sawing, cutting the cured board into 4 sheets, including the edges; S17, graded packaging, health-promoting products are sorted manually one by one, or infrared detection and analysis can be used to remove unqualified products and separate them into superior, qualified and unqualified products.

[0007] As a further improvement of the present invention, in step S1, the moisture content of the raw material is higher than 40%, and after being cut into wood chips with a length of 20–40 mm, it enters the next process.

[0008] As a further improvement of the present invention, in step S2, the shaved wood chips are screened by adjusting the mesh size to remove impurities such as bark, mud, sand, and dust.

[0009] As a further improvement of the present invention, in step S3, the screened wood chips are preheated in advance to improve the efficiency of subsequent cooking.

[0010] As a further improvement of the present invention, in step S4, the preheated wood chips are steamed for 3–5 minutes under high temperature and high pressure conditions.

[0011] As a further improvement of the present invention, in step S6, the wet fibers are subjected to high-temperature drying treatment at about 70°C in the drying pipe.

[0012] As a further improvement of the present invention, in step S7, the process is carried out simultaneously in the drying pipeline, and uniform glue application is achieved through the glue spraying pipe.

[0013] As a further improvement of the present invention, in step S10, the fibers with added moisture-proof and flame-retardant agents are mixed and then laid on the board.

[0014] As a further improvement of the present invention, in step S11, the formed slab is pre-pressed to enhance its structural stability.

[0015] As a further improvement of the present invention, in step S13, the sheet material output from the hot press at a temperature of about 160°C is placed on a cooling rack for natural cooling; the post-processing steps include trimming, automatic stacking and labeling.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Firstly, by precisely adding non-corrosive moisture-proof and flame-retardant agents during the production process and dynamically adjusting the amount added according to the fiber flow rate, the moisture-proof agent is evenly distributed, significantly improving the dimensional stability and resistance to moisture absorption and expansion of the board in humid environments, and effectively preventing problems such as deformation and warping caused by changes in humidity.

[0017] Secondly, the non-corrosive flame retardant used can play a flame-retardant role under high temperature or fire conditions, improve the fire resistance rating of the board, prolong the combustion ignition time, reduce smoke release, and meet the high standards of fire safety requirements for building and decoration materials.

[0018] Third, the simultaneous application of adhesive in the drying pipeline not only improves the uniformity of adhesive dispersion, but also makes full use of drying heat energy, improves reaction efficiency, reduces energy consumption, and achieves energy-saving and environmentally friendly green production.

[0019] Fourth, a five-stage temperature gradient controlled hot pressing process (210℃→210℃→190℃→180℃→170℃) is adopted, which gradually cools down and holds pressure to fix the thickness, effectively avoiding internal stress concentration and delamination defects caused by excessive temperature difference in thin plates, and significantly enhancing the internal bonding strength and surface flatness of the plates.

[0020] Fifth, through a static curing process of no less than 48 hours, the internal stress of the board is fully released, the moisture content is further balanced, and the physical performance stability and subsequent processing adaptability of the product are greatly improved.

[0021] Sixth, it is equipped with metering equipment to achieve precise addition and feedback adjustment of moisture-proof and flame-retardant agents, ensuring the consistency of product quality between batches, and is suitable for high-end decoration, furniture manufacturing and functional application scenarios.

[0022] Seventh, the entire process from chipping to grading and packaging has been optimized, especially the S2 screening to remove impurities and the S16 sawing to cut into four sheets including the edges, which not only ensures the quality of raw materials but also improves the yield and resource utilization efficiency. Attached Figure Description

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0025] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0026] like Figure 1 As shown, a manufacturing process for moisture-proof and flame-retardant thin high-density fiberboard includes the following steps: S1, chipping: Fresh wood (such as fast-growing timber like pine and poplar) or forestry residues with a moisture content ≥40% are selected and chipped into uniform wood chips of 20–40 mm in length using a disc chipper. High moisture content raw materials can reduce subsequent cooking energy consumption and improve fiber separation efficiency.

[0027] S2, Screening: Using a vibrating screen with adjustable mesh size (recommended range 5–10 mm), bark, sand, metal shavings, and excessively small particles are removed from the wood chips to ensure the purity of the raw material. Impurities that pass through the screen can be recycled for fuel or scrap reuse.

[0028] S3, pre-cooking: The screened wood chips are placed in a cooking vessel for preheating at 100–120°C (for about 10–15 minutes) to soften the fiber cell walls, reduce energy consumption in subsequent cooking, and improve the uniformity of fiber separation.

[0029] S4, Cooking: Wood chips are cooked in a high-temperature, high-pressure cooker (temperature 160–180℃, pressure 0.8–1.2MPa) for 3–5 minutes to soften the lignin, break the hydrogen bonds between cellulose fibers, and release long fibers. The cooking liquor can be recycled to reduce production costs.

[0030] S5, Hot Milling: The cooked wood chips are separated into fibers using a hot mill (milling disc speed 800–1000 rpm) to prepare fiber bundles with a fiber length ≤3 mm and a width of approximately 20–50 μm. The hot milling temperature is controlled at 120–140℃ to avoid excessive thermal degradation of the fibers.

[0031] S6, Drying: The wet fibers after thermal grinding are conveyed to the drying pipeline by a screw conveyor and dried by high-temperature hot air (70±5℃) to reduce the fiber moisture content to 5–8% to ensure uniformity of subsequent sizing.

[0032] S7, Glue application: The glue application process is carried out simultaneously at the end of the drying pipeline. Phenolic resin or melamine-formaldehyde resin (solid content 50-60%) is evenly sprayed onto the fiber surface through a pneumatic spraying system. The glue application amount is controlled at a glue weight ratio of 8-12%.

[0033] S8, air separation: After drying and sizing, the fibers are separated by an air separator to separate short fibers (≤1 mm) and dust, which are then recycled and put back into the system. The long fibers are then put into the next process to improve the strength of the finished product.

[0034] S9, moisture-proof and flame-retardant agent addition: The amount of moisture-proof and flame-retardant agent added is dynamically adjusted according to the fiber flow rate, and a metering device is equipped to ensure the accuracy of addition. The moisture-proof and flame-retardant agent used is a non-corrosive material. A dynamic metering pump is used to accurately add the moisture-proof and flame-retardant agent (such as ammonium phosphate, aluminum hydroxide composite material, non-corrosive) according to the real-time fiber flow rate (monitored by a flow sensor). The addition amount is controlled at 1.5-3.0% of the fiber mass to ensure that the moisture-proof (water absorption rate ≤0.5%) and flame-retardant (oxygen index ≥32) performance meets the standards.

[0035] S10, paving: The mixed fibers are fed into the paving machine and formed into a uniform slab with a thickness deviation of ≤0.5 mm through multi-layer staggered paving. The paving density is controlled at 550–650 kg / m³.

[0036] S11, Pre-compression: The slab is pre-compressed on one or both sides by a pre-compressor (pressure 0.2–0.4 MPa) to eliminate fiber voids and enhance the strength of the slab. After pre-compression, the thickness is reduced to 1.2–1.3 times the target value.

[0037] S12, hot pressing, uses a multi-stage temperature-controlled hot press. The first frame temperature at the press inlet is 210℃, serving as the high-pressure zone; the second frame temperature is 210℃, serving as the pressure-holding zone; the third frame temperature is 190℃, serving as the first pressure-holding zone; the fourth frame temperature is 180℃, serving as the pressure-holding and thickness-fixing zone; and the fifth frame temperature is 170℃, serving as the second pressure-holding zone. A five-zone gradient hot press is used, with the following specific parameters: Zone 1 (High Pressure Zone): Temperature 210℃, Pressure 2.5–3.0 MPa, hold for 50–60 seconds; Zone 2 (Pressure Holding Zone): Temperature 210℃, Pressure 2.0–2.5 MPa, hold for 40 seconds; Zone 3 (Pressure Holding Zone): Temperature 190℃, Pressure 1.8–2.2 MPa, hold for 30 seconds; Zone 4 (Pressure Holding and Thickness Setting Zone): Temperature 180℃, Pressure 1.5–1.8 MPa, hold for 25 seconds; Zone 5 (Pressure Holding Zone): Temperature 170℃, Pressure 1.2–1.5 MPa, held for 20 seconds. Each zone uses an independent PID temperature control system to ensure temperature fluctuation ≤ ±2℃.

[0038] S13, Cooled Board: After hot pressing, the board (outlet temperature approximately 160℃) is transferred to a forced air cooling rack. It is then naturally cooled to room temperature by circulating cooling air (temperature ≤30℃). The cooling time is controlled within 15–20 minutes to avoid sudden cooling that could cause internal stress.

[0039] S14, Post-processing: After cooling, the products undergo edge trimming, then are automatically stacked and labeled. Trimming: Use a high-speed band saw or milling cutter to remove irregular parts of the board edge, ensuring dimensional tolerance ≤1mm; Stacking identification: Stacked in batches by an automated stacker and accompanied by a QR code label (containing information such as production batch number, specifications, and performance parameters).

[0040] S15, Curing: Transfer the newly produced products to the curing area, keep them neatly and flat, and let them stand for no less than 48 hours before proceeding to the next process. Move the boards to a closed curing area (humidity ≤60%, temperature 20–25℃) and let them stand for more than 48 hours to allow the internal stress to be fully released and reduce the risk of cracking later.

[0041] S16, sawing, cuts the cured board into 4 sheets, including the edges. The cured board is longitudinally cut into 4 sheets of equal thickness (including the edges) by a four-blade sawing system. The sawing accuracy is controlled within ±0.2 mm to reduce the waste rate.

[0042] S17, graded packaging, health-promoting products are sorted manually one by one, or infrared detection and analysis can be used to remove unqualified products and separate them into superior, qualified and unqualified products.

[0043] Quality inspection is conducted using the following two methods: 1. Manual sorting: Inspect each sheet for surface defects (such as delamination, cracks, color difference); 2. Infrared scanning: Using a thermal imager to detect internal density uniformity and defects, rejecting defective products.

[0044] Finally, the products are graded and packaged according to quality: Superior grade: density deviation ≤ ±2%, thickness deviation ≤ ±0.5 mm, and no surface defects; Qualified product: Minor defects but meets strength, moisture-proof and flame-retardant standards; Defective products: scrap or rework directly.

[0045] The production process for moisture-proof and flame-retardant thin high-density fiberboard is as follows: 1. Raw material processing stage S1 chippers use fresh wood (such as fast-growing timber like pine and poplar) or forestry residues with a moisture content ≥40%, which are then chipped into uniform wood chips 20-40mm long using a disc chipper. High moisture content raw materials can reduce subsequent cooking energy consumption and improve fiber separation efficiency.

[0046] The S2 screening process uses a vibrating screen with an adjustable mesh size (5-10mm) to remove bark, silt, metal debris, and excessively small particles. The undersized impurities can be recycled for use as biomass fuel or as scraps, ensuring the purity of the raw materials.

[0047] 2. Fiber pretreatment stage S3 pre-cooking involves placing the screened wood chips in a cooking vessel and preheating them at 100-120℃ for 10-15 minutes to initially soften the fiber cell walls and improve the efficiency of subsequent cooking.

[0048] S4 cooking involves cooking in a high-temperature, high-pressure digester (160-180℃, 0.8-1.2MPa) for 3-5 minutes, during which lignin softens, hydrogen bonds between cellulose fibers break, and long fibers are released. The cooking liquor is recycled to reduce costs.

[0049] S5 Hot-milled wood chips that have been cooked are processed into fiber bundles (length ≤3mm, width 20-50μm) using a hot mill (milling disc speed 800-1000rpm, temperature 120-140℃) to avoid excessive thermal degradation.

[0050] 3. Fiber forming stage S6 Drying: The fibers are dried in a drying pipe at 70±5℃ with hot air, reducing the moisture content to 5-8% to ensure uniform sizing.

[0051] S7 sizing: Sizing is performed simultaneously at the end of the drying pipeline using a pneumatic spraying system. Phenolic resin or melamine-formaldehyde resin (solid content 50-60%) is used, and the amount of sizing is controlled at 8-12% of the fiber weight.

[0052] S8 air separation: Dry fibers are separated into short fibers and dust by an air separator, which are then recycled and put back into the system, while the long fibers are retained to enhance the strength of the board.

[0053] S9 moisture-proof and flame-retardant agent addition: Based on real-time fiber flow (monitored by flow sensor), the amount of non-corrosive moisture-proof and flame-retardant agent (such as ammonium phosphate, aluminum hydroxide composite material) added is dynamically adjusted and controlled at 1.5-3.0% of fiber mass to ensure moisture-proof (water absorption rate ≤0.5%) and flame-retardant (oxygen index ≥32) performance.

[0054] 4. Sheet metal forming and processing S10 paving involves laying multiple layers of mixed fibers in an interlaced manner using a paving machine to form a uniform slab with a thickness deviation of ≤0.5mm and a density of 550-650 kg / m³.

[0055] S11 pre-compression: The slab is pre-compressed on one or both sides by a pre-compressor (pressure 0.2-0.4MPa) to eliminate voids and enhance the strength of the slab. After pre-compression, the thickness is reduced to 1.2-1.3 times the target value.

[0056] S12 hot pressing adopts a five-stage gradient hot pressing process: Zone 1 (High Voltage Zone): 210℃, 2.5-3.0MPa, hold for 50-60 seconds; Zone 2 (Pressure Holding Zone): 210℃, 2.0-2.5MPa, hold for 40 seconds; Zone 3 (Pressure Holding Zone): 190℃, 1.8-2.2MPa, hold for 30 seconds; Zone 4 (Pressure Holding and Thickness Setting Zone): 180℃, 1.5-1.8MPa, hold for 25 seconds; Zone 5 (Pressure Holding Zone): 170℃, 10 seconds, with independent PID temperature control for each zone (fluctuation ≤ ±2℃) to avoid internal stress concentration and stratification.

[0057] S13 cold board: After hot pressing, the board (160℃) is transferred to a forced air cooling rack and cooled to room temperature (15-20 minutes) by circulating cooling air below 30℃ to avoid sudden cooling and cracking.

[0058] 5. Post-processing and quality inspection S14 post-processing, Trimming: Use a high-speed band saw or milling cutter to remove irregular edges, with a dimensional tolerance of ≤1mm; Stacking identification: Automatic stacker cranes stack items in batches, each with a QR code label (containing production batch number, specifications, and performance parameters).

[0059] S15 Health Preservation The boards should be moved to a closed curing area (humidity ≤60%, temperature 20-25℃) and left to stand for more than 48 hours to release internal stress and reduce the risk of cracking.

[0060] S16 sawing: After curing, the board is longitudinally cut into 4 equal-thickness thin boards (including the edges) by a four-blade saw with an accuracy of ±0.2mm, reducing the waste rate.

[0061] S17 graded packaging, Manual sorting: Inspect each sheet for surface defects (delamination, cracks, color difference); Infrared scanning: Thermal imagers detect internal density uniformity and defects; Grading standards: Superior grade: density deviation ≤ ±2%, thickness deviation ≤ ±0.5mm, no defects; Qualified product: Minor defects but meets strength and flame retardancy standards; Defective products: scrap or rework directly.

[0062] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 manufacturing process for moisture-proof and flame-retardant thin high-density fiberboard, characterized in that: Includes the following steps: S1, chipping; S2, Filter; S3, pre-steaming; S4, steaming / boiling; S5, hot grinding; S6, drying; S7, applying adhesive; S8, Wind Select; S9, moisture-proof and flame-retardant agent added, the amount of moisture-proof and flame-retardant agent added is dynamically adjusted according to the fiber flow rate, and a metering device is provided to ensure the accuracy of addition. The moisture-proof and flame-retardant agent used is a non-corrosive material. S10, paved; S11, pre-compression; S12, hot pressing, uses a multi-stage temperature-controlled hot press. The first frame temperature at the press inlet is 210℃, serving as the high-pressure zone; the second frame temperature is 210℃, serving as the pressure-holding zone; the third frame temperature is 190℃, serving as the first pressure-holding zone; the fourth frame temperature is 180℃, serving as the pressure-holding and thickness-fixing zone; and the fifth frame temperature is 170℃, serving as the second pressure-holding zone. S13, Cool board; S14, post-processing: After cooling, the products are trimmed, then automatically stacked and labeled. S15, Health Preservation: Transfer the products that have just come off the production line to the health preservation area, keep them neatly and flat, and let them stand for no less than 48 hours before proceeding to the next process. S16, sawing, cutting the cured board into 4 sheets, including the edges; S17, graded packaging, health-promoting products are sorted manually one by one, or infrared detection and analysis can be used to remove unqualified products and separate them into superior, qualified and unqualified products.

2. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S1, the raw material has a moisture content of more than 40%, and after being shaved into wood chips with a length of 20–40 mm, it enters the next process.

3. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S2, the shaved wood chips are screened by adjusting the mesh size to remove impurities such as bark, mud, sand, and dust.

4. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S3, the screened wood chips are preheated to improve the efficiency of subsequent cooking.

5. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S4, the preheated wood chips are steamed for 3–5 minutes under high temperature and high pressure.

6. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S6, the wet fibers undergo high-temperature drying at approximately 70°C in a drying pipe.

7. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S7, the process is carried out simultaneously in the drying pipeline, and uniform glue application is achieved through the glue spraying pipe.

8. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S10, the fibers with added moisture-proof and flame-retardant agents are mixed and then laid on the slab.

9. The production process of moisture-proof and flame-retardant thin high-density fiberboard as described in claim 1, characterized in that: In step S11, the formed slab is pre-pressed to enhance its structural stability.

10. The production process for moisture-proof and flame-retardant thin high-density fiberboard as described in any one of claims 1-9, characterized in that: In step S13, the sheet material output from the hot press at a temperature of approximately 160°C is placed on a cooling rack for natural cooling. The post-processing steps include trimming, automatic stacking, and labeling.

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