Lightweight formaldehyde-free fire-retardant board and preparation method thereof

Abstract

The application discloses a light formaldehyde-free flame-retardant board and a preparation method thereof, and relates to the technical field of boards. The flame-retardant board is prepared from formaldehyde-free components such as magnesium-based inorganic substances, plant fibers, hollow glass microbeads and modified expanded perlite. The modified expanded perlite is prepared by loading inorganic fillers on a carrier and combining with a flame retardant. The preparation process of the flame-retardant board comprises the following steps: step-by-step stirring and pulping, laying of reinforcing cloth, vacuum suction filtration forming, pre-solidification, maintenance and waterproof coating, and the like. The application effectively improves the brittleness of inorganic substrates, realizes the synergistic optimization of formaldehyde-free, light weight, flame-retardant performance and mechanical performance, is suitable for various scenes such as building decoration, and has good practical value.

Description

Technical Field

[0001] This application relates to the technical field of sheet materials, and in particular to a lightweight formaldehyde-free flame-retardant sheet and its preparation method. Background Technology

[0002] In various fields such as building decoration and furniture manufacturing, flame-retardant boards have become indispensable basic materials due to their fire safety performance, and market demand continues to rise. However, the mainstream flame-retardant boards currently on the market generally have many technical shortcomings, making it difficult to meet the comprehensive requirements of modern production and life for materials in terms of environmental protection, safety, and practicality. This situation has also promoted the research and development and application of formaldehyde-free flame-retardant boards. Existing wood-based flame-retardant boards mostly use particleboard and MDF as base materials, and formaldehyde-containing adhesives are often used for bonding during the production process, resulting in significant formaldehyde release problems. Long-term use can pose potential hazards to human health. At the same time, their flame-retardant performance is limited, making them unsuitable for places with high fire protection requirements. Moreover, these boards have a high density, causing many inconveniences in handling and installation during construction. In contrast, inorganic fireproof boards, although having certain advantages in flame-retardant performance, also have many fatal flaws. Some products also suffer from quality problems such as efflorescence and warping, seriously affecting construction quality and service life.

[0003] From a technical perspective, existing flame-retardant boards still face a performance bottleneck that is difficult to overcome. The pursuit of environmentally friendly, formaldehyde-free boards can easily lead to a decline in the mechanical properties of the boards, compromising their strength. Conversely, reducing the density of the boards to achieve lightweighting significantly impacts their structural strength, failing to meet basic usage requirements. These prevalent problems have created an increasingly urgent market demand for new flame-retardant boards that combine formaldehyde-free environmental friendliness, excellent flame-retardant properties, and good mechanical properties. Formaldehyde-free flame-retardant boards have emerged in this context, becoming an important direction for overcoming the current industry predicament.

[0004] Formaldehyde-free flame-retardant boards are suitable for use in duplex apartment attic renovations. With rising living standards, many families are converting their duplex attics into spaces that combine storage, relaxation, or office functions. Attic spaces typically have limited ceiling height, narrow stairwells, and numerous corners. Furthermore, construction often involves on-site work, requiring workers to frequently move various boards into the attic for cutting and installation. In such cases, the boards used must be formaldehyde-free and environmentally friendly to prevent formaldehyde accumulation and health risks due to the relatively enclosed attic space. Lightweight boards are also crucial due to limited access in the attic, facilitating manual handling, reducing damage to walls and stair railings, and lowering construction difficulty and labor costs. In addition, the renovation of the attic requires the installation of custom-made storage cabinets, shelves, partition walls, etc. This requires the boards to be easy to fix the hardware connectors, screws and other fasteners, to ensure the assembly stability of the storage cabinets, shelves and other furniture, and to avoid safety hazards such as furniture loosening or falling off due to insufficient nail holding power. Summary of the Invention

[0005] The purpose of this application is to provide a lightweight, formaldehyde-free flame-retardant board that not only has good flame-retardant properties, but also is lightweight, easy to handle, and has good nail-holding power.

[0006] Firstly, this application provides a lightweight, formaldehyde-free, flame-retardant board and its preparation method, which adopts the following technical solution: A lightweight formaldehyde-free flame-retardant board comprises the following raw materials in parts by weight: 130-150 parts magnesium-based inorganic material, 1-2 parts composite additive, 15-20 parts plant fiber, 4-8 parts vinyl acetate-ethylene copolymer emulsion, 2-6 parts hollow glass microspheres, 13-20 parts modified expanded perlite, 0.1-0.4 parts foaming agent, and 0.05-0.1 parts antibacterial agent; wherein the modified expanded perlite comprises inorganic filler, carrier supporting inorganic filler, silane coupling agent, expanded perlite, binder, phosphorus-based flame retardant, and inorganic flame retardant; the mass ratio of the inorganic filler, carrier supporting inorganic filler, silane coupling agent, expanded perlite, binder, phosphorus-based flame retardant, and inorganic flame retardant is (10-20):(5-15):(5-10):100:(5-15):(4-6):(8-12).

[0007] By adopting the above technical solution, in this formulation for preparing flame-retardant boards, magnesium-based inorganic materials, treated with composite additives, serve as the main substrate to construct a rigid framework. Plant fibers enhance the toughness of the board through fiber interweaving. The two are firmly bonded by the adhesive effect of vinyl acetate-ethylene copolymer emulsion. Hollow glass microspheres and foaming agents synergistically construct a closed porous structure, which not only reduces the density of the board to achieve lightweighting but also improves thermal insulation performance by blocking heat transfer through pores. Antibacterial agents inhibit mold growth by disrupting the metabolic processes of microorganisms. The preparation of modified expanded perlite involves loading inorganic fillers onto a carrier and using silane coupling agents to improve interfacial compatibility with the matrix, making the porous structure of expanded perlite more stable. At the same time, phosphorus-based and inorganic flame retardants form a synergistic flame-retardant system, which can promote the formation of a char layer and block heat and oxygen transfer at high temperatures, inhibiting the release of toxic gases. Adding it to the substrate of the board can, on the one hand, further enhance the lightweight heat insulation effect by relying on the porous structure, and on the other hand, the flame retardant components it carries complement the magnesium-based inorganic materials, improving the flame retardant performance through the dual mechanism of physical barrier and chemical flame retardancy. At the same time, it improves the brittleness of the inorganic substrate and enhances the structural stability of the board, ultimately achieving synergistic optimization of formaldehyde-free, lightweight, high flame retardancy and excellent mechanical properties.

[0008] Optionally, the mass ratio of the inorganic filler, the carrier supporting the inorganic filler, the expanded perlite, and the binder is (13-17):(8-12):100:(6-10).

[0009] By adopting the above technical solution, this mass ratio optimizes the performance of the flame-retardant board through the synergistic effect between the components. The carrier can fully load the inorganic filler, avoiding filler agglomeration and ensuring its uniform dispersion and effectiveness. The appropriate ratio of carrier to expanded perlite allows the carrier carrying the filler to adhere evenly to the surface and pores of the expanded perlite, without damaging its porous structure, and by leveraging the porosity of the expanded perlite to enhance the bonding force between the components. An appropriate amount of binder can achieve a tight bond between the three components, ensuring the structural stability of the board, while avoiding clogging the pores or covering the active components due to excessive use, and preventing weak bonding due to insufficient use.

[0010] Optionally, the carrier for the loaded inorganic filler is any one of β-cyclodextrin, chitosan, or tara gum.

[0011] By adopting the above technical solutions, β-cyclodextrin, chitosan, and tara gum, as carriers for inorganic fillers, all meet the requirements for formaldehyde-free and environmentally friendly products, and can achieve efficient loading and uniform dispersion of inorganic fillers through their own structural characteristics. β-cyclodextrin, with its unique cavity structure, can encapsulate inorganic fillers, effectively inhibiting filler agglomeration. Simultaneously, its molecular structure can form mild interactions with other components, improving interfacial compatibility. Chitosan, rich in amino and hydroxyl groups, possesses both strong adsorption and adhesive properties. It can firmly load inorganic fillers through intermolecular forces and enhance the bonding strength between the carrier and expanded perlite and binders, simultaneously improving the structural stability of the board. Tara gum, as a natural polysaccharide, has viscosity characteristics suitable for loading requirements. When dispersing inorganic fillers, it can reduce damage to the porous structure of expanded perlite and has excellent compatibility with other components, reducing interfacial resistance of the system.

[0012] Optionally, the adhesive is any one of shellac, vinyl acetate-ethylene copolymer emulsion, or yarrow gum.

[0013] By adopting the above technical solutions, shellac, vinyl acetate-ethylene copolymer emulsion, and tragacanth gum, as binders, all meet the formaldehyde-free and environmentally friendly requirements. Shellac, as a natural resin binder, exhibits stable bonding strength and excellent weather resistance, forming a strong adhesive layer between components. It also has good compatibility with natural substrates, reducing interface defects. Vinyl acetate-ethylene copolymer emulsion provides strong adhesion and a degree of flexibility, enhancing the bonding tightness between components and alleviating the brittleness of inorganic substrates, thus improving the flexural strength of the board. Tragacanth gum, a natural polysaccharide binder, has excellent viscosity compatibility, causes minimal damage to the porous structure of expanded perlite during bonding, and exhibits excellent compatibility with other components, reducing mixing resistance and promoting uniform dispersion of components.

[0014] Optionally, the inorganic filler is a mixture of niobium hydroxide and lanthanum nitrate; the mass ratio of niobium hydroxide to lanthanum nitrate is (1-2):1.

[0015] By adopting the above technical solution, a mixture of niobium hydroxide and lanthanum nitrate is used as an inorganic filler, and the performance of the flame-retardant board is optimized through functional synergy and proportional adaptation. Niobium hydroxide forms a physical barrier layer due to its high-temperature resistance, while lanthanum nitrate, as a rare earth compound, can catalyze the formation of a char layer at high temperatures. The combination of the two achieves a dual flame-retardant mechanism of physical barrier and chemical catalysis.

[0016] Optionally, the preparation method of the modified expanded perlite includes the following steps: S1. Disperse the inorganic filler in a solvent, add the carrier loaded with the inorganic filler, let stand, dry, sinter, add silane coupling agent solution, stir, filter, dry, shear, add water, stir, and obtain an intermediate for later use. S2. Mix the intermediate, binder, phosphorus flame retardant, inorganic flame retardant and water prepared in step S1, stir, coat the mixture on the surface of expanded perlite, let it stand and dry to obtain modified expanded perlite.

[0017] By adopting the above technical solution, the first step involves fully compounding the inorganic filler with the carrier and then performing sintering and coupling treatment. This ensures that the inorganic filler is uniformly loaded onto the carrier and firmly bonded. The silane coupling agent can pre-modify the carrier surface, improving its compatibility with other components, while shear dispersion further prevents agglomeration and ensures the stability of the intermediate's performance. The second step involves mixing the intermediate with various flame retardants and binders and then coating it onto the surface of expanded perlite. This allows the modified components to uniformly cover the surface and pores, while the binder ensures a firm bond between the modified layer and the expanded perlite, forming a continuous and stable modified film.

[0018] Optionally, the sintering temperature in step S1 is 850-1050℃.

[0019] By adopting the above technical solution, this sintering temperature range can achieve a stable bond between the support and the inorganic filler. Mechanistically, it avoids the problems of loose component bonding and weak loading caused by excessively low temperatures, while preventing damage to the structure of the support or inorganic filler at high temperatures, thus preserving its original functional properties. A suitable temperature can promote the exposure of active sites on the support surface, enhance the interaction with the inorganic filler, form a stable loading structure, and simultaneously remove residual impurities or solvents from the system, improving the purity of the intermediates. Furthermore, this temperature condition can optimize the surface morphology of the support, creating favorable conditions for the subsequent adsorption and action of silane coupling agents, helping to improve the interfacial compatibility between the modified components and the matrix, and ensuring the stable performance of the final modified expanded perlite.

[0020] Optionally, the stirring speed in step S1 is 300-700 rpm; the stirring time in step S1 is 6-8 h; and the stirring time in step S2 is 20-60 min.

[0021] By adopting the above technical solution, appropriate stirring speed and time can ensure that all components are fully contacted and uniformly dispersed. Stirring in step S1 promotes the stable composite of inorganic filler and carrier, allows silane coupling agent to uniformly modify the carrier surface, avoids component agglomeration, and helps impurities to detach, improving the purity and compatibility of intermediates. Stirring in step S2 allows intermediates to form a uniform mixed system with flame retardant and binder, ensuring that it is completely and firmly coated on the surface and pores of expanded perlite without damaging the porous structure, ensuring the continuity and stability of the modified layer, and laying the foundation for subsequent improvement of interfacial compatibility with the matrix and the overall performance of the board.

[0022] Optionally, the magnesium-based inorganic material is a mixture of magnesium oxide and magnesium chloride; the mass ratio of magnesium oxide to magnesium chloride is (2-3):1.

[0023] By employing the above technical solution, a composite of magnesium oxide and magnesium chloride can construct a rigid framework for the board. An appropriate mass ratio ensures a thorough gelation reaction, improving the density and structural stability of the matrix. The synergistic effect of the two components leverages the high strength of magnesium oxide while magnesium chloride regulates the reaction process, enhancing interfacial bonding with other components.

[0024] Secondly, the lightweight formaldehyde-free flame-retardant board provided in this application adopts the following technical solution: A method for preparing a lightweight formaldehyde-free flame-retardant board includes the following steps: Step 1: Mix magnesium-based inorganic materials with composite additives, stir, add plant fiber, vinyl acetate-ethylene copolymer emulsion, hollow glass microspheres, and modified expanded perlite, stir, add foaming agent and antibacterial agent, stir, and obtain mixed slurry; Step 2: Lay the mixed slurry onto the reinforcing cloth, use vacuum filtration to form, pre-cur, demold, cure, grind, apply a waterproof coating, and dry to obtain a lightweight formaldehyde-free flame-retardant board.

[0025] By employing the above technical solution, this preparation method, through step-by-step feeding and stirring, allows the components to fuse and disperse evenly, preventing the agglomeration of functional components and ensuring the full reaction of magnesium-based inorganic materials and composite additives to form a stable basic system. Simultaneously, it allows the binder to function efficiently, strengthening the interfacial bonding between components. Vacuum filtration molding quickly removes excess water from the slurry, resulting in a denser board structure. Combined with reinforcing fabric laying, this further enhances mechanical properties without damaging the porous, lightweight structure. Pre-curing and maintenance ensure a full gelation reaction, improving structural stability. Subsequent thickness sanding and waterproof coating ensure dimensional accuracy and water resistance, ultimately achieving a synergistic improvement in the board's lightweight, flame-retardant, environmentally friendly properties, and excellent mechanical performance.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with existing technologies, modified expanded perlite is prepared through a specific combination of raw materials. The carrier supporting inorganic fillers achieves efficient loading and uniform dispersion of the fillers, preventing agglomeration. Silane coupling agents modify the carrier surface, improving interfacial compatibility with other components. Phosphorus-based and inorganic flame retardants form a synergistic flame retardant system, enhancing flame retardant performance. The raw materials exhibit good compatibility, and the modified layer formed through stepwise preparation is firmly bonded to the expanded perlite, ensuring the structural stability and functional effectiveness of the modified expanded perlite itself, laying the foundation for subsequent improvements in the overall performance of the board. 2. Compared with existing technologies, incorporating modified expanded perlite into the formaldehyde-free flame-retardant board preparation system allows for synergistic effects with magnesium-based inorganic materials, plant fibers, and other components. This not only enhances the lightweight properties of the board through its porous structure but also improves flame-retardant performance by creating a complementary flame-retardant mechanism between the loaded flame-retardant components and the matrix. Simultaneously, it reduces the brittleness of the inorganic substrate, enhances the structural stability and mechanical properties of the board, and achieves synergistic optimization of formaldehyde-free environmental friendliness, lightweight and easy handling, high nail-holding power, and excellent flame-retardant effect, effectively resolving the performance contradictions of existing technologies. Detailed Implementation

[0027] Unless otherwise specified, the parameters and sources of the specific chemical substances used in the embodiments and comparative examples of this application are all commercially available products. Silica solution, product number: S-1430, Huihe Yongsheng; Retarder, model: XSG2-16, Shengyu; Early strength agent, product number: A00254, Jiyesheng; Foaming agent, brand: MasterFoam 30S, BASF; Antibacterial agent, model: AJ10D, brand: Zeomic; Silane coupling agent, model: KH171, Xinlantian; Plant fiber, brand name: I501, Jinshixiang; Expanded perlite, product number: T21400-25g, source: Yuan Ye; Hollow glass microspheres, 30μm; Reinforcing fabric, made of carbon fiber, from Forsmann; Shellac, product number: S33183-30g, source leaves; Achillea gum, product number: S30512-100, source leaf; Tara gum, CAS: 39300-88-4; Duoyang Biotechnology. Example 1

[0028] A method for preparing a lightweight formaldehyde-free flame-retardant board includes the following steps: 6.5 kg of niobium hydroxide and 6.5 kg of lanthanum nitrate were added to 96 kg of 90 wt% ethanol solution and stirred at 500 rpm for 30 min to obtain the first mixture. 8 kg of chitosan was immersed in the first mixture, allowed to stand for 10 min, dried at 80 °C for 10 h, and sintered at 900 °C for 1 h to obtain the second mixture. 7 kg of silane coupling agent was mixed with 70 kg of 90 wt% ethanol solution to obtain a silane coupling agent solution. The silane coupling agent solution was added to the second mixture and stirred at 500 rpm for 8 h. The mixture was filtered to obtain a filter cake, which was dried at 80 °C for 24 h. The filter cake was sheared into particles with a diameter of 0.5 mm, then dispersed in 44 L of water and stirred at 500 rpm for 3 min to obtain an intermediate for later use. The above intermediate, 6 kg of vinyl acetate-ethylene copolymer, 5 kg of potassium dihydrogen phosphate, 10 kg of magnesium oxide, and 54 L of water were mixed and stirred at 500 rpm for 30 h to obtain a third mixture. 100 kg of expanded perlite was kept rotating at 100 r / min, and the third mixture was sprayed onto the surface of the rotating expanded perlite. The mixture was then allowed to stand at 25 °C for 24 h and dried at 40 °C for 24 h to obtain modified expanded perlite.

[0029] 90 kg of magnesium oxide and 45 kg of magnesium chloride were mixed to obtain a fourth mixture.

[0030] Mix 0.7 kg of retarder, 0.5 kg of early-strength agent, and 0.5 kg of silane coupling agent to obtain a composite additive.

[0031] The fourth mixture above is mixed with the composite additive above and stirred at 500 rpm for 10 min. Then, 17 kg of plant fiber, 6 kg of vinyl acetate-ethylene copolymer emulsion, 4 kg of hollow glass microspheres, and 20 kg of modified expanded perlite are added and stirred at 500 rpm for 30 min. Finally, 0.2 kg of foaming agent and 0.1 kg of antibacterial agent are added and stirred at 200 rpm for 3 min to obtain a mixed slurry. Step 2: Lay the mixed slurry into the mold, spread a layer of reinforcing fabric evenly on the surface of the base slurry layer, and then cover the reinforcing fabric with an appropriate amount of mixed slurry, so that the reinforcing fabric is completely embedded in the slurry to form a sandwich structure of slurry and reinforcing fabric. Perform a vacuum filtration molding operation on the sandwich structure at a vacuum degree of 0.08 MPa to obtain the initial sandwich. Pre-cur the initial sandwich at 25℃ for 5 hours, demold, and cure at 25℃ and 90% relative humidity for 24 hours; cure at 40℃ and 90% relative humidity for 48 hours; and cure at 25℃ and 70% relative humidity for 14 days to obtain the final sandwich. Grind the final sandwich, coat the surface with 15 kg of silica solution, and dry at 60℃ for 24 hours to obtain a lightweight, formaldehyde-free, flame-retardant board. Example 2

[0032] The difference between Example 2 and Example 1 is that 6.5 kg of niobium hydroxide, 6.5 kg of lanthanum nitrate, 8 kg of chitosan, and 6 kg of vinyl acetate-ethylene copolymer are replaced with 7 kg of niobium hydroxide, 7 kg of lanthanum nitrate, 9 kg of chitosan, and 7 kg of vinyl acetate-ethylene copolymer. Example 3

[0033] The difference between Example 3 and Example 1 is that 6.5 kg of niobium hydroxide, 6.5 kg of lanthanum nitrate, 8 kg of chitosan, and 6 kg of vinyl acetate-ethylene copolymer are replaced with 7.5 kg of niobium hydroxide, 7.5 kg of lanthanum nitrate, 10 kg of chitosan, and 8 kg of vinyl acetate-ethylene copolymer. Example 4

[0034] The difference between Example 4 and Example 1 is that 6.5 kg of niobium hydroxide, 6.5 kg of lanthanum nitrate, 8 kg of chitosan, and 6 kg of vinyl acetate-ethylene copolymer are replaced with 8.5 kg of niobium hydroxide, 8.5 kg of lanthanum nitrate, 12 kg of chitosan, and 10 kg of vinyl acetate-ethylene copolymer. Example 5

[0035] The difference between Example 5 and Example 3 is that 10 kg of chitosan is replaced with 10 kg of β-cyclodextrin. Example 6

[0036] The difference between Example 6 and Example 3 is that 10 kg of chitosan is replaced with 10 kg of tara gum. Example 7

[0037] The difference between Example 7 and Example 6 is that 8 kg of vinyl acetate-ethylene copolymer is replaced with 8 kg of shellac. Example 8

[0038] The difference between Example 8 and Example 6 is that 8 kg of vinyl acetate-ethylene copolymer is replaced with 8 kg of yarrow gum. Comparative Example 1

[0039] The difference between Comparative Example 1 and Example 1 is that 6.5 kg of niobium hydroxide, 6.5 kg of lanthanum nitrate, 8 kg of chitosan, and 6 kg of vinyl acetate-ethylene copolymer were replaced with 5 kg of niobium hydroxide, 5 kg of lanthanum nitrate, 7 kg of chitosan, and 12 kg of vinyl acetate-ethylene copolymer. Comparative Example 2

[0040] The difference between Comparative Example 2 and Example 3 is that 10 kg of chitosan was replaced with 10 kg of kapok fiber. Comparative Example 3

[0041] The difference between Comparative Example 3 and Example 6 is that 8 kg of vinyl acetate-ethylene copolymer was replaced with 8 kg of styrene-acrylic emulsion. Test case

[0042] Density was tested according to GB / T6343-2009 "Determination of apparent density of foamed plastics and rubber"; The bending strength was tested according to GB / T1936.1-2009 "Test Method for Bending Strength of Timber"; Nail holding force test: After driving a round steel nail of the same specification into the sample at a certain length, hold the nail head tightly with a nail holder and pull the nail out at a uniform loading speed until the pointer of the testing machine turns back obviously. Record the maximum load. Flame retardant performance was tested according to GB / T5454-1997 "Test for Burning Performance of Textiles - Oxygen Index Method", and the test results are shown in Table 1.

[0043]

[0044] A comparative analysis of Examples 1-4 and Comparative Example 1 revealed that the flame-retardant board prepared in Example 3 exhibited the best density, flexural strength, and nail-holding power. The difference in these properties may be due to variations in the mass ratios of niobium hydroxide, lanthanum nitrate, chitosan, and vinyl acetate-ethylene copolymer, or fundamentally, differences in the raw material formulations used to prepare the modified expanded perlite. Niobium hydroxide and lanthanum nitrate, as modifying components, are effectively dispersed in the chitosan matrix in a suitable ratio, forming a dense and stable coating layer on the expanded perlite surface after sintering. Appropriate chitosan addition provides good skeletal support for the coating layer, enhancing its structural integrity. The matching ratio of vinyl acetate-ethylene copolymer strengthens the interfacial bonding between the coating layer and the expanded perlite surface, while also optimizing the compatibility between the modified particles and the board matrix. The modified expanded perlite formed in Example 3 can effectively regulate the internal pore structure of the board, reduce ineffective pores, and improve the uniformity of pore distribution, thereby making the board density tend to be within a reasonable range. Good interfacial compatibility and dense coating can enhance the bonding strength between modified particles and components such as matrix and plant fibers. Under stress, the components can work together to bear the load, avoiding stress concentration, thereby improving bending strength. At the same time, it can enhance the mechanical interlocking effect when nails are embedded to improve nail holding force. In addition, the uniformly dispersed flame retardant components can form a continuous and dense flame retardant barrier during combustion to ensure flame retardant performance. However, an imbalance in the ratio will destroy the above-mentioned synergistic effect and lead to performance degradation.

[0045] Comparative analysis of Examples 5-6 and Comparative Example 2 revealed that the flame-retardant board prepared in Example 6 exhibited the best overall performance. The difference in performance might be attributed to the use of different carriers for loading inorganic fillers. The optimal overall performance of Example 6 is likely due to the superior compatibility between the structure and performance of Tara gum, while β-cyclodextrin and kapok fiber have significant limitations due to their inherent structural characteristics, ultimately leading to differences in flame-retardant board performance. Tara gum molecules are rich in active groups such as hydroxyl and carboxyl groups, and possess a loose, porous three-dimensional network structure. This structure not only provides ample loading sites for inorganic fillers, achieving uniform dispersion, but also allows for strong chemical bonding between the active groups and components such as magnesium oxide, magnesium chloride, and plant fibers in the board matrix. Furthermore, its porous structure can regulate the pore morphology of modified expanded perlite while ensuring sufficient loading, preventing the formation of ineffective pores. Although β-cyclodextrin possesses a unique cavity structure capable of accommodating some inorganic fillers, its molecular chain has fewer active groups, resulting in weaker bonding with the matrix. This makes it difficult to achieve efficient loading and uniform dispersion of fillers, and also hinders the effective optimization of the internal bonding state of the board. Kapok fiber has a linear fiber structure with a smooth surface and a lack of active sites. This results in poor loading capacity for inorganic fillers and poor interfacial compatibility with matrix components, easily leading to defects at the interface. Tara resin, due to its efficient and uniform loading effect, allows the flame-retardant components to form a continuous and dense flame-retardant barrier. Simultaneously, its strong interfacial bonding enhances the synergistic load-bearing capacity between components, optimizing the internal pore distribution for a more reasonable density and strengthening mechanical interlocking to improve nail-holding force and bending strength. In contrast, the limited loading capacity of β-cyclodextrin and the interfacial defects of kapok fiber both compromise the internal structural integrity and component synergy of the board, leading to poor performance across various aspects.

[0046] Analysis of Examples 7-8 and Comparative Example 3 revealed that the flame-retardant board prepared in Example 8 exhibited the best overall performance. The difference in performance was likely due to the use of an adhesive. The core reason for the superior overall performance of Example 8 lies in the optimal compatibility of the structure and properties of the tragacanth resin used. In contrast, shellac, vinyl acetate-ethylene copolymer, and the styrene-acrylic emulsion of Comparative Example 3 had inherent structural limitations, ultimately leading to differences in overall performance. Tragacanth resin molecules are rich in active groups such as hydroxyl and carboxyl groups, and possess excellent viscosity adjustment and film-forming properties. Its molecular chains can form strong chemical bonds and physical entanglement with the surface of inorganic fillers and the substrate components of the board through active groups. Simultaneously, after film formation, it can form a dense and flexible film, effectively encapsulating inorganic fillers and enhancing the interfacial bonding strength between components. Furthermore, its suitable viscosity can control the uniformity of the coating of modified expanded perlite, preventing coating layer detachment or local accumulation. While shellac can form a film, its molecular chains have a relatively small number of active groups, resulting in weak bonding with the matrix and significant brittleness after film formation, making it difficult to buffer stress transmission in the board under load. Vinyl acetate-ethylene copolymers generally have limited polarity and compatibility with inorganic fillers and matrices, leading to limited interfacial bonding. Styrene-acrylic emulsions, on the other hand, have highly hydrophobic molecular chains, resulting in poor compatibility with hydrophilic matrix components and a tendency to form voids and defects at the interface. In contrast, tragacanth resin, due to its excellent interfacial bonding and coating effect, can enhance the synergistic load-bearing capacity of modified expanded perlite with the matrix, plant fibers, and other components, reducing internal defects and ineffective pores, thus bringing the board density closer to a reasonable range. The dense coating and strong interfacial bonding enhance stress dispersion under load, improving flexural strength, while also strengthening the mechanical interlocking action when nails are embedded, thus increasing nail-holding power. The uniformly coated flame-retardant components also form a continuous and stable flame-retardant barrier during combustion, ensuring flame-retardant performance. However, the brittleness of shellac, the insufficient compatibility of vinyl acetate-ethylene copolymer, and the compatibility defects of styrene-acrylic emulsion can all damage the internal structural integrity of the board, resulting in poor performance.

[0047] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A lightweight, formaldehyde-free, flame-retardant board, characterized in that, The raw materials include the following parts by weight: 130-150 parts magnesium-based inorganic material, 1-2 parts composite additive, 15-20 parts plant fiber, 4-8 parts vinyl acetate-ethylene copolymer emulsion, 2-6 parts hollow glass microspheres, 13-20 parts modified expanded perlite, 0.1-0.4 parts foaming agent, and 0.05-0.1 parts antibacterial agent; the modified expanded perlite includes inorganic filler, carrier supporting inorganic filler, silane coupling agent, expanded perlite, binder, phosphorus flame retardant, and inorganic flame retardant; the mass ratio of the inorganic filler, carrier supporting inorganic filler, silane coupling agent, expanded perlite, binder, phosphorus flame retardant, and inorganic flame retardant is (10-20):(5-15):(5-10):100:(5-15):(4-6):(8-12).

2. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The mass ratio of the inorganic filler, the carrier supporting the inorganic filler, the expanded perlite, and the binder is (13-17):(8-12):100:(6-10).

3. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The carrier for the inorganic filler is any one of β-cyclodextrin, chitosan, or tara gum.

4. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The adhesive is any one of shellac, vinyl acetate-ethylene copolymer emulsion, or yarrow gum.

5. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The inorganic filler is a mixture of niobium hydroxide and lanthanum nitrate; the mass ratio of niobium hydroxide to lanthanum nitrate is (1-2):

1.

6. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The preparation method of the modified expanded perlite includes the following steps: S1. Disperse the inorganic filler in a solvent, add the carrier loaded with the inorganic filler, let stand, dry, sinter, add silane coupling agent solution, stir, filter, dry, shear, add water, stir, and obtain an intermediate for later use. S2. Mix the intermediate, binder, phosphorus flame retardant, inorganic flame retardant and water prepared in step S1, stir, coat the mixture on the surface of expanded perlite, let it stand and dry to obtain modified expanded perlite.

7. The lightweight formaldehyde-free flame-retardant board according to claim 6, characterized in that, The sintering temperature in step S1 is 850-1050℃.

8. The lightweight formaldehyde-free flame-retardant board according to claim 6, characterized in that, The stirring speed in step S1 is 300-700 rpm; the stirring time in step S1 is 6-8 h; and the stirring time in step S2 is 20-60 min.

9. The lightweight formaldehyde-free flame-retardant board according to claim 1, characterized in that, The magnesium-based inorganic compound is a mixture of magnesium oxide and magnesium chloride; the mass ratio of magnesium oxide to magnesium chloride is (2-3):

1.

10. A method for preparing a lightweight, formaldehyde-free, flame-retardant board, characterized in that, Includes the following steps: Step 1: Mix magnesium-based inorganic materials with composite additives, stir, add plant fiber, vinyl acetate-ethylene copolymer emulsion, hollow glass microspheres, and modified expanded perlite, stir, add foaming agent and antibacterial agent, stir, and obtain mixed slurry; Step 2: Lay the mixed slurry onto the reinforcing cloth, use vacuum filtration to form, pre-cur, demold, cure, grind, apply a waterproof coating, and dry to obtain a lightweight formaldehyde-free flame-retardant board.

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