Preparation method of light-weight fire-retardant sound-absorbing fiberboard

Abstract

The application discloses a preparation method of light fireproof sound-absorbing fiberboard and relates to the technical field of fiberboard materials.The method comprises the following steps: washing, cooking, hot grinding, adding black dye, adding a fire retardant, adding azodicarbonamide as an additive, spraying, hot pressing, and sawing.The temperature of the spraying is controlled within 100-110 DEG C, and the spraying amount is controlled within 30-50 kg / h.The fiberboard prepared by the method has a single-layer structure, has good sound-absorbing effect, does not need to be matched with sound-absorbing materials, can be thinnest to 9 mm, reaches the national fireproof B1-B level standard, and can reduce the density of the board to 600-700 kg / m 3 , so as to achieve the purpose of lightening.

Description

Technical Field

[0001] This invention relates to the field of fiberboard technology, and in particular to a method for preparing a lightweight flame-retardant sound-absorbing fiberboard. Background Technology

[0002] Fiberboard, as one of the three major types of engineered wood products, is an important raw material for the furniture manufacturing industry. With the increasing demands of the furniture industry for materials with sound absorption, sound insulation, lightweighting, and flame retardancy, the performance requirements for fiberboard are becoming increasingly stringent.

[0003] Currently, there are many sound-absorbing panels on the home decoration market, but the manufacturing process is basically a composite of fiberboard and sound-absorbing materials. The sound absorption effect mainly relies on the sound-absorbing materials, as the fiberboard itself has no sound absorption effect. Therefore, the finished panels are generally quite thick (over 30mm), making it difficult to achieve lightweight design. Moreover, as fiberboard is a combustible material, whether it can meet the national flame-retardant B1 standard is also a concern.

[0004] Chinese patent CN218857866U provides a perforated sound-absorbing fiberboard, comprising a first microporous fiberboard, a wood-based sound-absorbing material, a second microporous fiberboard, a sound-absorbing felt, and a multi-layered edge-sealing material. The preparation method of this patent is complex, the fiberboard thickness can reach 300mm, making it impossible to achieve lightweighting, and the sound absorption function depends on additional sound-absorbing materials, while the sound absorption function of the fiberboard itself is very limited.

[0005] To solve the above problems, it is necessary to develop a lightweight fiberboard that can be used independently without the need for sound-absorbing materials, or it can be combined with sound-absorbing materials to achieve better sound absorption. It meets the national flame retardant B1-B standard and can be used in public places, entertainment venues and other places with high fire protection requirements. Summary of the Invention

[0006] To address the above shortcomings, this invention provides a method for preparing lightweight flame-retardant sound-absorbing fiberboard. The fiberboard itself has excellent sound absorption properties, eliminating the need for additional sound-absorbing materials. It can be as thin as 9mm and meets the national flame-retardant B1-B standard. The board density can be reduced to 600-700 kg / m³. 3 This achieves the goal of lightweight design. The specific technical solution is as follows:

[0007] A method for preparing a lightweight flame-retardant sound-absorbing fiberboard includes:

[0008] S1. Washing, steaming, and hot grinding: Take miscellaneous wood as raw material, peel it with a peeling machine and then chip it to obtain wood chips. Wash the wood chips with water and place them in a steaming tank for steaming. Then, heat grind the cooked fibers to obtain heat-ground fibers.

[0009] S2. Adding black dye: Mix urea-formaldehyde resin and black dye powder in a mass ratio of 10 to 20:1. Then, apply the mixture evenly to the thermo-milled fiber obtained in step S1 using a sizing device to obtain sizing fiber.

[0010] The applicant of this invention adds black dye to the production process to achieve two purposes: First, the traditional mainstream method is to use fiberboard and sound-absorbing cotton together, and the colors of the two cannot be too different. Sound-absorbing cotton is generally black, so making the board black can reduce the pressing and wrapping process and save costs; Second, the subsequent addition of additives to the board may cause water spots on the board surface. Adding black dye can reduce appearance defects and improve the yield.

[0011] S3. Add flame retardant: Dry the fiber after sizing in step S2 to a moisture content of 6-10%, cool the temperature to 50-70°C in the drying pipe, and after screening for impurities by air classification, add flame retardant to obtain fiber with added flame retardant.

[0012] S4. Adding additives: Prepare an azodicarbonamide suspension by mixing water and azodicarbonamide in a ratio of 18-22:1. Control the stirring speed at 500-800 rpm. Apply the suspension evenly to the vacuum laying box through three nozzles at a pressure of 2-4 kg. Then, after being divided by a material distribution laying device (the material distribution laying device is a patent applied for by the applicant, application number 202421493136.6), lay the fiber with added flame retardant obtained in step S3 to obtain the fiber with added additives.

[0013] S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-pressed and formed by a pre-pressing machine. After pre-pressing, it is steamed by a steam spraying machine. The temperature of the steam spraying plate is controlled at 100-110℃, and the steam spraying volume of saturated steam is controlled at 30-50kg / h to obtain the steam-prepared board.

[0014] S6. Hot pressing: The pre-shaped board obtained from the steam spraying in step S5 is hot pressed, and the board is sawn after hot pressing.

[0015] Further, in step S1, among the fibers, fibers with a diameter ≤ 0.06 mm account for 1 to 10% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 50 to 80% of the total weight, fibers with a diameter between 0.125 and 1 mm account for 20 to 30% of the total weight, and fibers with a diameter > 1 mm account for 0.1 to 1% of the total weight.

[0016] Furthermore, the water washing process in step S1 specifically involves washing with a phosphate solution, wherein the concentration of the phosphate solution is controlled at 5-30%, and the washing time is 10-20 seconds.

[0017] Furthermore, in step S1, the cooking temperature is 160–180°C, the steam pressure is 8–9 bar, and the cooking time is 2–5 min.

[0018] Furthermore, in step S3, the flame retardant is one or a combination of several of the following: ammonium polyphosphate, magnesium hydroxide, aluminum hydroxide, and organosilicon flame retardants.

[0019] Furthermore, in step S3, the amount of flame retardant added is 80–100 kg / m³. 3 .

[0020] Further, in step S4, the ratio of water to azodicarbonamide in the azodicarbonamide suspension is 18–22:1, and the total amount of azodicarbonamide suspension applied is 2–15 g suspension / m³. 3 Board material.

[0021] Furthermore, in step S6, the hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section; the high-pressure section has a temperature of 210–230°C and a pressure of 0.5–2.0 N / mm. 2 The temperature of the pressure holding section is 180–185℃, and the pressure is 0.2–1.2 N / mm². 2 The temperature of the thickness-fixed section is 150–170℃, and the pressure is 1.2–3.0 N / mm. 2 The total speed of the pressure plate is 6.0 to 6.7 m / min.

[0022] Further, the additive comprises the following components in parts by weight: 1-2 parts azodicarbonamide, 0.5-1 parts terephthalic anhydride or isophthalic anhydride, phthalic anhydride, 1-2 parts polylactic acid-glycolic acid copolymer, 20-25 parts water, with a total application amount of 2-15 g suspension / m 3 Board material.

[0023] Furthermore, the lightweight flame-retardant sound-absorbing fiberboard has a thickness of 9–18 mm and an average density of 600–700 kg / m³. 3 .

[0024] Furthermore, the lightweight flame-retardant sound-absorbing fiberboard of the present invention has a single-layer structure, which can be used independently without the need for sound-absorbing materials, or it can be combined with sound-absorbing materials to achieve better sound absorption effect.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. This invention provides a method for preparing a lightweight flame-retardant sound-absorbing fiberboard. The prepared fiberboard has a single-layer structure and inherently possesses excellent sound absorption properties, eliminating the need for additional sound-absorbing materials. It can be as thin as 9mm and meets the national flame-retardant B1-B standard. The board density can be reduced to 600-700 kg / m³. 3 This achieves the goal of lightweight design.

[0027] 2. Due to its good gas uniformity and easy activation, azodicarbonamide is usually used as an additive in paperboard or foam board in the existing technology. Additives can be added arbitrarily in paperboard and foam board. However, due to the hot pressing process of fiberboard, azodicarbonamide is difficult to apply to fiberboard, and ammonia gas can easily escape through the decomposition of ammonium ions at high temperature. This invention uses a steam spraying process, controlling the temperature at 100-110℃ and the steam spraying rate of saturated steam at 30-50 kg / h, both lower than the steam spraying temperature and rate of traditional processes. This allows for the early curing of urea-formaldehyde resin on the board surface, preventing premature activation of additives. The terephthalic anhydride or isophthalic anhydride and phthalic anhydride in the additives of this invention can make the foaming process more stable and uniform by adjusting the foaming rate. Polylactic acid-glycolic acid copolymer provides stability, enabling the fiberboard to maintain structural stability during the foaming process, preventing excessive expansion or rupture of pores, improving pore uniformity, and thus optimizing sound absorption and board strength. At the same time, it also avoids the large amount of gas released by azodicarbonamide activation during the next hot pressing process from collapsing the board surface and affecting the surface bonding strength of the board, thereby increasing the porosity of the fiberboard from 45-50% to 55-65%.

[0028] 3. To avoid explosions and ensure practical safety, the present invention prepares azodicarbonamide as a suspension. To avoid adhesion to equipment, the present invention also employs a vacuum dispensing and laying device for laying (the mainstream method is mechanical laying). This dispensing and laying device is a patent applied for by the applicant of the present invention, application number 202421493136.6. Using this dispensing and laying device can improve the fiber arrangement structure and enhance the mixing uniformity of the additives, thereby avoiding a significant decrease in board strength caused by lightweighting and foaming, and improving the board strength.

[0029] 4. Adding a phosphate solution to the water washing process of this invention can further increase the flame retardant properties. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a cross-sectional view of the lightweight flame-retardant sound-absorbing fiberboard of the present invention;

[0032] Figure 2 This is a front view of the lightweight flame-retardant sound-absorbing fiberboard of the present invention. Detailed Implementation

[0033] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0034] The flame retardant used in this embodiment of the invention was purchased from Guangdong Jushi Chemical Co., Ltd.

[0035] Example 1

[0036] A method for preparing a lightweight flame-retardant sound-absorbing fiberboard includes:

[0037] S1. Washing, Steaming, and Hot Milling: Mixed hardwood is used as the raw material. After peeling with a debarker, the wood chips are obtained. The wood chips are washed with water, followed by washing with a phosphate solution at a concentration of 15% for 10 seconds. After washing, the fibers are placed in a steaming tank for steaming at 170°C and 8.5 bar for 3 minutes. The steamed fibers are then hot-milled to obtain hot-milled fibers. Of these fibers, fibers with a diameter ≤0.06 mm account for 5.5% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 65%, fibers with a diameter between 0.125 and 1 mm account for 29%, and fibers with a diameter >1 mm account for 0.5%.

[0038] S2. Adding black dye: Mix urea-formaldehyde resin and black dye powder in a mass ratio of 15:1, and then apply the mixture evenly to the thermo-milled fibers obtained in step S1 using a sizing device to obtain sizing fibers.

[0039] S3. Add flame retardant: Dry the fibers after sizing in step S2 to a moisture content of 8%, cool the temperature to 60°C in the drying pipe, and after air classification to remove impurities, add ammonium polyphosphate flame retardant at a dosage of 90 kg / m². 3 The resulting fiber has been treated with flame retardant.

[0040] S4. Addition of additives: Prepare an azodicarbonamide suspension by mixing water and azodicarbonamide in a ratio of 20:1, controlling the stirring speed at 650 rpm. The total amount of azodicarbonamide suspension applied is 10 g suspension / m³. 3 The board material is prepared by applying the suspension evenly to the vacuum laying box through three nozzles at a pressure of 3 kg. Then, the fiber obtained in step S3 with added flame retardant is laid after being divided by the material distribution laying equipment (application number 202421493136.6) to obtain the fiber with added additives.

[0041] S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-pressed and formed by a pre-pressing machine. After pre-pressing, it is steamed by a steam spraying machine. The temperature of the steam spraying plate is controlled at 110℃ and the steam spraying amount of saturated steam is controlled at 45kg / h to obtain the steam-prepared board.

[0042] S6. Hot pressing: The pre-shaped sheet material obtained from steam spraying in step S5 is hot-pressed. The hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section. The high-pressure section has a temperature of 210–230℃ and a pressure of 1.2 N / mm. 2 The temperature of the pressure holding section is 180–185℃, and the pressure is 0.7 N / mm². 2 The temperature of the thickness-fixed section is 150–170℃, and the pressure is 2.0 N / mm. 2 The total speed of the pressing plate is 6.0 m / min. After hot pressing, the plate is sawn to obtain a thickness of 18 mm and an average density of 634 kg / m³. 3 Lightweight flame-retardant sound-absorbing fiberboard.

[0043] Example 2

[0044] A method for preparing a lightweight flame-retardant sound-absorbing fiberboard includes:

[0045] S1. Washing, Steaming, and Hot Milling: Mixed-grain wood is used as the raw material. After peeling with a debarker, the wood chips are obtained. The wood chips are washed with water, followed by washing with a phosphate solution at a concentration of 5% for 20 seconds. After washing, the fibers are placed in a steaming tank for steaming at 160°C and 8 bar for 5 minutes. The steamed fibers are then hot-milled to obtain hot-milled fibers. Of these fibers, fibers with a diameter ≤0.06 mm account for 9% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 70%, fibers with a diameter between 0.125 and 1 mm account for 20%, and fibers with a diameter >1 mm account for 1%.

[0046] S2. Adding black dye: Mix urea-formaldehyde resin and black dye powder in a mass ratio of 10:1. Then, apply the mixture evenly to the thermo-milled fibers obtained in step S1 using a sizing device to obtain sizing fibers.

[0047] S3. Add flame retardant: Dry the fibers after sizing in step S2 to a moisture content of 6%, cool the temperature to 50°C in the drying pipe, and after air classification to remove impurities, add aluminum hydroxide flame retardant at a dosage of 80 kg / m². 3 The resulting fiber has been treated with flame retardant.

[0048] S4. Adding additives: Prepare an azodicarbonamide suspension by mixing water and azodicarbonamide in a ratio of 20:1, controlling the stirring speed at 600 rpm. The total amount of azodicarbonamide suspension applied is 2 g suspension / m³. 3 The board material is prepared by applying the suspension at a pressure of 2 kg through three nozzles into a vacuum laying box. Then, the fiber obtained in step S3 with added flame retardant is laid after being divided by a material distribution laying device (application number 202421493136.6) to obtain a fiberboard with added additives.

[0049] S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-pressed and formed by a pre-pressing machine. After pre-pressing, it is steamed by a steam spraying machine. The temperature of the steam spraying plate is controlled at 100℃, and the steam spraying amount of saturated steam is controlled at 30kg / h to obtain the steam-prepared board.

[0050] S6. Hot pressing: The pre-shaped sheet material obtained from steam spraying in step S5 is hot-pressed. The hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section. The high-pressure section has a temperature of 210–230℃ and a pressure of 0.5 N / mm. 2 The pressure holding section temperature is 180–185℃, and the pressure is 0.2 N / mm². 2 The temperature of the thickness-fixed section is 150–170℃, and the pressure is 1.2 N / mm. 2 The total speed of the pressing plate is 6.7 m / min. After hot pressing, the plate is sawn to obtain a thickness of 14 mm and an average density of 640 kg / m³. 3 Lightweight flame-retardant sound-absorbing fiberboard.

[0051] Example 3

[0052] A method for preparing a lightweight flame-retardant sound-absorbing fiberboard includes:

[0053] S1. Washing, Steaming, and Hot Milling: Mixed-grain wood is used as the raw material. After peeling with a debarker, the wood chips are obtained. The wood chips are washed with water, followed by washing with a phosphate solution at a concentration of 30% for 10 seconds. After washing, the fibers are placed in a steaming tank for steaming at 180°C and 9 bar for 2 minutes. The steamed fibers are then hot-milled to obtain hot-milled fibers. Of these fibers, fibers with a diameter ≤ 0.06 mm account for 2% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 75.5% of the total weight, fibers with a diameter between 0.125 and 1 mm account for 22% of the total weight, and fibers with a diameter > 1 mm account for 0.5% of the total weight.

[0054] S2. Adding black dye: Mix urea-formaldehyde resin and black dye powder in a mass ratio of 20:1. Then, apply the mixture evenly to the thermo-milled fibers obtained in step S1 using a sizing device to obtain sizing fibers.

[0055] S3. Add flame retardant: Dry the fibers after sizing in step S2 to a moisture content of 10%, cool the temperature to 70°C in the drying pipe, and after air classification to remove impurities, add magnesium hydroxide flame retardant at a dosage of 100 kg / m². 3 The resulting fiber has been treated with flame retardant.

[0056] S4. Adding additives: Prepare an azodicarbonamide suspension by mixing water and azodicarbonamide in a ratio of 20:1, controlling the stirring speed at 700 rpm. The total amount of azodicarbonamide suspension applied is 15 g suspension / m³. 3 The suspension is applied evenly to the vacuum laying box at a pressure of 4 kg through 3 nozzles. Then, the fiber obtained in step S3 with added flame retardant is laid after being divided by the material distribution laying equipment (application number 202421493136.6) to obtain the fiberboard with added additives.

[0057] S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-pressed and formed by a pre-pressing machine. After pre-pressing, it is steamed by a steam spraying machine. The temperature of the steam spraying plate is controlled at 110℃, and the steam spraying amount of saturated steam is controlled at 50kg / h to obtain the steam-prepared board.

[0058] S6. Hot pressing: The pre-shaped sheet material obtained from steam spraying in step S5 is hot-pressed. The hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section. The high-pressure section has a temperature of 210–230℃ and a pressure of 2.0 N / mm. 2 The temperature of the pressure holding section is 180–185℃, and the pressure is 1.2 N / mm². 2 The temperature of the thickness-fixed section is 150–170℃, and the pressure is 3.0 N / mm. 2The total speed of the pressing plate is 6.4 m / min. After hot pressing, the plate is sawn to obtain a thickness of 9 mm and an average density of 636 kg / m³. 3 Lightweight flame-retardant sound-absorbing fiberboard.

[0059] Example 4

[0060] A method for preparing a lightweight flame-retardant sound-absorbing fiberboard includes:

[0061] S1. Washing, Steaming, and Hot Milling: Mixed hardwood is used as the raw material. After peeling with a debarker, the wood chips are obtained. The wood chips are washed with water, followed by washing with a phosphate solution at a concentration of 15% for 10 seconds. After washing, the fibers are placed in a steaming tank for steaming at 170°C and 8.5 bar for 3 minutes. The steamed fibers are then hot-milled to obtain hot-milled fibers. Of these fibers, fibers with a diameter ≤0.06 mm account for 5.5% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 65%, fibers with a diameter between 0.125 and 1 mm account for 29%, and fibers with a diameter >1 mm account for 0.5%.

[0062] S2. Adding black dye: Mix urea-formaldehyde resin and black dye powder in a mass ratio of 15:1, and then apply the mixture evenly to the thermo-milled fibers obtained in step S1 using a sizing device to obtain sizing fibers.

[0063] S3. Add flame retardant: Dry the fibers after sizing in step S2 to a moisture content of 8%, cool the temperature to 60°C in the drying pipe, and after air classification to remove impurities, add ammonium polyphosphate flame retardant at a dosage of 90 kg / m². 3 The resulting fiber has been treated with flame retardant.

[0064] S4. Addition of additives: The additives include the following components in parts by weight: 1-2 parts azodicarbonamide, 0.5-1 parts terephthalic anhydride or isophthalic anhydride, phthalic anhydride, 1-2 parts polylactic acid-glycolic acid copolymer, and 20-25 parts water. The additive raw materials are mixed to form an additive suspension, with the stirring speed controlled at 650 rpm. The total amount of additive suspension applied is 10 g suspension / m³. 3 The board material is prepared by applying the suspension evenly to the vacuum laying box through three nozzles at a pressure of 3 kg. Then, the fiber obtained in step S3 with added flame retardant is laid after being divided by the material distribution laying equipment (application number 202421493136.6) to obtain the fiber with added additives.

[0065] S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-pressed and formed by a pre-pressing machine. After pre-pressing, it is steamed by a steam spraying machine. The temperature of the steam spraying plate is controlled at 110℃ and the steam spraying amount of saturated steam is controlled at 45kg / h to obtain the steam-prepared board.

[0066] S6. Hot pressing: The pre-shaped sheet material obtained from steam spraying in step S5 is hot-pressed. The hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section. The high-pressure section has a temperature of 210–230℃ and a pressure of 1.2 N / mm. 2 The temperature of the pressure holding section is 180–185℃, and the pressure is 0.7 N / mm². 2 The temperature of the thickness-fixed section is 150–170℃, and the pressure is 2.0 N / mm. 2 The total speed of the pressing plate is 6.0 m / min. After hot pressing, the plate is sawn to obtain a thickness of 18 mm and an average density of 653 kg / m³. 3 Lightweight flame-retardant sound-absorbing fiberboard.

[0067] Example 5

[0068] In this embodiment, the phosphate solution concentration is controlled at 5%, and the washing time is 10 seconds. The remaining methods are the same as in Example 1.

[0069] Example 6

[0070] In this embodiment, the phosphate solution concentration is controlled at 30%, and the washing time is 10 seconds. The remaining methods are the same as in Example 1.

[0071] Example 7

[0072] In this embodiment, the phosphate solution concentration is controlled at 15%, and the washing time is 20 seconds. The remaining methods are the same as in Example 1.

[0073] Example 8

[0074] In this embodiment, the washing process uses clean water and the washing time is 10 seconds. The remaining methods are the same as in Embodiment 1.

[0075] The finished fiberboard products obtained in Examples 1 and 5-8 were tested for oxygen index using an oxygen index tester (refer to the testing method disclosed in patent number CN107014948A). Ten fiberboard strips with a length of 10cm and a width of 10cm were cut into the flame-retardant fiberboard to be tested.

[0076] After turning on and preheating the oxygen index tester, introduce nitrogen to zero the pressure and introduce oxygen to full pressure. Open the nitrogen valve to allow nitrogen to flow. At this point, the oxygen pressure gauge and nitrogen pressure gauge should both read 0.1 MPa, and the pressure gauge reading for the nitrogen + oxygen mixture should not exceed 0.2 MPa. Adjust the nitrogen and oxygen flow valves to achieve the required oxygen percentage after mixing, allowing the nitrogen and oxygen mixture to flow from bottom to top. Vertically clamp the cut fiber strip onto the support, cover it with the combustion chamber glass cover, and ignite the fiber strip using the top ignition method after 5-10 seconds. Start timing from the moment the flame contacts the top of the fiber strip. After 20-30 seconds of ignition, remove the flame, observe the burning of the fiber strip, and record the oxygen index value on the oxygen index tester.

[0077] The method for determining the oxygen index value is as follows: when the observation time is 20-30 seconds and the fiber strip just extinguishes its combustion, the oxygen percentage displayed by the oxygen index meter at this time is the oxygen index value of the tested fiber strip. The results are shown in Table 1 below.

[0078] Table 1 shows the oxygen index test results of the fiberboard products obtained in Examples 1 and 5-8.

[0079]

[0080]

[0081] Table 1 shows that washing with phosphate solution can further improve flame retardant properties.

[0082] Comparative Example 1

[0083] In this comparative example, the steam spraying process was carried out at a temperature of 150°C and a steam spraying rate of 45 kg / h. The remaining methods were the same as in Example 1.

[0084] Comparative Example 2

[0085] In this comparative example, the steam spraying process was carried out at a temperature of 150°C and a steam spraying rate of 200 kg / h. The remaining methods were the same as in Example 1.

[0086] Comparative Example 3

[0087] In this comparative example, the steam spraying process was carried out at a temperature of 110°C and a steam spraying rate of 100 kg / h. The remaining methods were the same as in Example 1.

[0088] Comparative Example 4

[0089] In this comparative example, the steam spraying process was carried out at a temperature of 70°C and a steam spraying rate of 45 kg / h. The remaining methods were the same as in Example 1.

[0090] Comparative Example 5

[0091] The hot pressing process parameters of this invention are: platen temperature 175–185°C, pressure 2.5–5 MPa, and time 140–160 s. The remaining methods are the same as in Example 1.

[0092] Comparative Example 6

[0093] The additive in this comparative example is calcium carbonate, and the rest of the methods are the same as in Example 1.

[0094] Comparative Example 7

[0095] This comparative example uses ordinary fiberboard purchased from a furniture market, with a thickness of 18mm and an average density of 760kg / m³. 3 .

[0096] The internal bond strength and surface bond strength of the finished product were determined according to GB / T17657-2022.

[0097] The formula for calculating porosity is P = (1 - ρ0 / ρ) × 100%.

[0098] ρ0 is the density of the fiberboard in its natural state, which is obtained by the ratio of mass to apparent volume (including pores);

[0099] ρ is the density of the fiberboard in its compacted state, which needs to be measured by grinding the material to eliminate pore volume.

[0100] ρ0 is the density of the fiberboard in its natural state: the mass (m) and volume (v0) of the fiberboard in its natural state are measured, and ρ0 = m / v0 is calculated. The volume is obtained through geometric measurement.

[0101] ρ is the density of the fiberboard in its compacted state: after grinding the fiberboard into fine powder and removing the internal pores, the compacted volume (v) is measured using a Leigh bottle apparatus, and ρ = m / v is calculated.

[0102] The performance test results of the fiberboard products obtained in Examples 1 and Comparative Examples 1-4 are shown in Table 2 below. The purpose is to explore the influence of the steam spraying process parameters. The performance test results of the fiberboard products obtained in Examples 1 and Comparative Examples 5-6 are shown in Table 3 below. The purpose is to explore the influence of the hot pressing process and additives.

[0103] Table 2. Performance test results of fiberboard products obtained in Examples 1 and Comparative Examples 1-4

[0104]

[0105] Table 3. Performance test results of fiberboard products obtained in Example 1 and Comparative Examples 5-6

[0106]

[0107] The sound absorption performance of the fiberboards from Examples 1-4 and Comparative Examples 5-7 was tested: the sound absorption performance of the samples was tested using a JTZB standing wave tube sound absorption coefficient measuring instrument, and the measurement process was carried out in accordance with GBJ88-85 "Measurement of Sound Absorption Coefficient and Acoustic Impedance by Standing Wave Tube Method".

[0108] The standard specifies that standing waves are a characteristic of sound wave propagation. The principle is that a standing wave is generated when a normally incident sinusoidal plane wave and a plane wave reflected from the specimen are superimposed. The standard test block has a diameter of 10 cm. In the experiment, the sound absorption coefficients of the specimens were tested at frequencies of 125 Hz, 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz. The weighted average of the sound absorption coefficients at these five frequencies was selected as the material's sound absorption coefficient NRC (250 Hz weighted at 35%, 500 Hz at 35%, 1000 Hz at 20%, 2000 Hz at 10%, and 125 Hz excluded), reflecting the overall sound absorption performance of the material. The results are shown in Table 4 below.

[0109] Table 4. Test results of sound absorption performance of fiberboards in Examples 1-4 and Comparative Examples 5-7

[0110]

[0111] In summary, this invention provides a method for preparing a lightweight flame-retardant sound-absorbing fiberboard. The prepared fiberboard has a single-layer structure and inherently possesses excellent sound absorption properties, eliminating the need for additional sound-absorbing materials. It can be as thin as 9mm and meets the national flame-retardant B1-B standard. The board density can be reduced to 600-700 kg / m³. 3 This achieves the goal of lightweight design.

[0112] Azodicarbonamide, due to its good gas uniformity and easy activation, is commonly used as an additive in existing technologies for paperboard or foam board. While additives can be added arbitrarily in paperboard and foam board, the hot-pressing process of fiberboard makes it difficult to apply azodicarbonamide there. This invention, however, optimizes the steam spraying process, controlling the temperature at 100–110°C and the saturated steam spraying rate at 30–50 kg / h, both lower than the traditional spraying temperature and rate. This allows for the premature curing of the urea-formaldehyde resin on the board surface, preventing premature activation of the azodicarbonamide additive. The terephthalic anhydride in this invention's additive... The use of isophthalic anhydride or phthalic anhydride can make the foaming process more stable and uniform by adjusting the foaming rate. Polylactic acid-glycolic acid copolymer provides stability as an additive, enabling the fiberboard to maintain structural stability during the foaming process, preventing excessive expansion or rupture of pores, improving pore uniformity, and thus optimizing sound absorption and board strength. At the same time, it also avoids the large amount of gas released by azodicarbonamide activation during the next hot pressing process from collapsing the surface of the board blank and affecting the surface bonding strength of the board. This increases the porosity of the fiberboard to 55-65%, allowing the fiberboard to maintain good mechanical properties while having good sound absorption.

[0113] To avoid explosions and ensure practical safety, this invention prepares azodicarbonamide as a suspension. To prevent adhesion to equipment, this invention also employs a vacuum dispensing and laying device for laying. This dispensing and laying device is a patent previously applied for by the applicant of this invention, application number 202421493136.6. Using this dispensing and laying device can improve the fiber arrangement structure and enhance the mixing uniformity of the additives, thereby avoiding a significant decrease in board strength caused by lightweighting and foaming, and improving the board strength.

[0114] The addition of phosphate solution to the water washing process of this invention can further enhance the flame retardant properties.

[0115] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a lightweight flame-retardant sound-absorbing fiberboard, characterized in that, include: S1. Washing, steaming, and hot grinding: Take miscellaneous wood as the raw material, peel and chip it to obtain wood chips, wash the wood chips with water, steam them, and then heat grind the cooked fibers to obtain heat-ground fibers. The water washing process specifically involves washing with a phosphate solution, wherein the concentration of the phosphate solution is controlled at 5-30%, and the washing time is 10-20 seconds. S2. Add black dye: Mix urea-formaldehyde resin and black dye powder, and then apply it evenly to the thermo-milled fiber obtained in step S1 through a sizing device to obtain sizing fiber. S3. Add flame retardant: Dry the fibers after sizing in step S2, cool the temperature in the drying pipe, remove impurities by air separation, and add flame retardant to obtain fibers with added flame retardant. S4. Adding additives: Prepare the additives, apply them evenly to the vacuum laying box through the nozzle, and then lay the fibers with added flame retardant obtained in step S3 after being divided by the material distribution laying equipment to obtain the fibers with added additives. The auxiliary agent includes the following components by mass parts: azodicarbonamide 1~2 parts, terephthalic anhydride or isophthalic anhydride 0.5~1 part, polylactic acid-glycolic acid copolymer 1~2 parts, water 20~25 parts, and the total amount of application is 2~15 g of suspension / m 3 Sheet material; S5. Steam spraying: First, the fiber with added additives obtained in step S4 is pre-compressed. After pre-compression, it is steamed through a steam spraying machine. The temperature of the steam spraying plate is controlled at 100~110℃, and the steam spraying amount of saturated steam is controlled at 30~50kg / h to obtain the steam-prepared board. S6. Hot pressing: The pre-shaped board obtained from the steam spraying in step S5 is hot pressed, and the board is sawn after hot pressing.

2. The method for preparing a lightweight flame-retardant sound-absorbing fiberboard according to claim 1, characterized in that, In step S1, among the fibers, fibers with a diameter ≤ 0.06 mm account for 1 to 10% of the total weight, fibers with a diameter between 0.06 and 0.125 mm account for 50 to 80% of the total weight, fibers with a diameter between 0.125 and 1 mm account for 20 to 30% of the total weight, and fibers with a diameter > 1 mm account for 0.1 to 1% of the total weight.

3. The method for preparing a lightweight flame-retardant sound-absorbing fiberboard according to claim 1, characterized in that, In step S1, the cooking temperature is 160~180℃, the steam pressure is 8~9 bar, and the cooking time is 2~5 min.

4. The method for preparing a lightweight flame-retardant sound-absorbing fiberboard according to claim 1, characterized in that, In step S3, the flame retardant is one or a combination of several of the following: ammonium polyphosphate, magnesium hydroxide, aluminum hydroxide, and organosilicon flame retardants, and the amount of flame retardant added is 80~100 kg / m³. 3 .

5. The method for preparing a lightweight flame-retardant sound-absorbing fiberboard according to claim 1, characterized in that, In step S6, the hot pressing process is divided into a high-pressure section, a pressure-holding section, and a thickness-fixing section; the high-pressure section has a temperature of 210~230℃ and a pressure of 0.5~2.0 N / mm. 2 The pressure holding section temperature is 180~185℃, and the pressure is 0.2~1.2N / mm. 2 The temperature of the thickness-fixed section is 150~170℃, and the pressure is 1.2~3.0 N / mm. 2 .

6. The method for preparing a lightweight flame-retardant sound-absorbing fiberboard according to claim 1, characterized in that, The lightweight flame-retardant sound-absorbing fiberboard has a thickness of 9-18 mm and an average density of 600-700 kg / m³. 3 .

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