A2-grade fireproof core material and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to an A2-grade fireproof core material and a preparation method thereof. Glass fibers are purely adopted as reinforcing fibers of an A2-level fireproof core material, and the core material is insufficient in toughness and difficult to roll and form. In order to solve the problems, the A2-grade fireproof core material is provided, hard glass fibers and flexible modacrylic are compounded to form a framework structure of the A2-grade fireproof core material, the glass fibers and the modacrylic can be evenly distributed in the core material under the dispersion effect of water-based emulsion, a three-dimensional reinforced network is formed, balance of the rigidity and the flexibility of the core material is considered, and the fireproof performance of the A2-grade fireproof core material is improved. And due to the addition of the flexible modacrylic, the processing requirements of high toughness and rolling of the core material are met. The core material skeleton structure cooperates with the activated slag, the quartz sand and other inorganic mineral powder, so that the A2-level flame retardance of the obtained fireproof core material is effectively ensured.

Description

A Class A2 fire-resistant core material and its preparation method Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an A2-grade fire-resistant core material and its preparation method. Background Technology

[0002] Fire-resistant core materials are widely used in building insulation, composite panels, and other fields. With the upgrading of fire protection standards, the demand for A2-grade fire-resistant core materials is becoming increasingly urgent. These materials need to simultaneously meet the requirements of wide-temperature-range fire resistance, reliable mechanical properties, and convenient processing and transportation. Currently, existing fire-resistant core materials face many technical bottlenecks. The core problem lies in the difficulty of balancing mechanical properties and rollability, as well as insufficient flame-retardant and fire-resistant performance, making them unsuitable for large-scale production and practical application needs, thus limiting their widespread use.

[0003] To improve the mechanical properties of core materials, existing technologies mostly employ glass fiber as a single reinforcement method, utilizing its rigidity to construct a reinforcing network and suppress curing shrinkage cracking. However, this method has significant drawbacks. The high rigidity of glass fiber easily leads to embrittlement of the core material, resulting in insufficient toughness. It is also difficult to wind and shape during processing, and the resulting core materials are mostly sheets, which occupy a lot of space during transportation, have a high loss rate, and significantly increase transportation costs. On the other hand, reducing the amount of glass fiber to improve toughness will lead to a decrease in core material strength, making it prone to breakage and unable to meet the requirements of subsequent composite board processing and long-term service. It is difficult to balance rigidity and toughness.

[0004] The existing core material bonding and flame retardant design has obvious defects. The bonding process mostly uses ordinary water-based emulsions, which can only achieve basic bonding functions. At the same time, the combustion of organic components aggravates the fire and increases the release of smoke. In terms of flame retardancy, it mostly relies on a single inorganic flame retardant, which is difficult to cover a wide temperature range and cannot meet the requirements of A2 fire rating.

[0005] In summary, existing solutions suffer from insufficient targeting and poor synergy, failing to simultaneously resolve the core contradictions of rollability, mechanical properties, and flame retardant properties. There is an urgent need to develop a multi-component synergistically optimized A2-grade fire-resistant core material. Summary of the Invention

[0006] The problem with existing technologies is that using glass fiber as the reinforcing fiber for A2-grade fire-resistant core materials results in insufficient core material toughness, making it difficult to wind and form. To address this problem, this invention provides an A2-grade fire-resistant core material comprising the following raw materials in parts by weight: 25-40 parts quartz sand; 35-55 parts calcium powder; 12-20 parts silica powder; 5-8 parts modified zeolite; 30-45 parts aluminum hydroxide; 15-25 parts magnesium hydroxide; 8-12 parts magnesium carbonate; 6-12 parts glass fiber; 3-5 parts acrylonitrile chlorofiber; 4-8 parts activated slag; 25-35 parts aqueous emulsion; and 1-2 parts polycarboxylate superplasticizer. The aqueous emulsion is a blended emulsion system formed by vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion at a mass ratio of (6.5-7.5):(2.5-3.5). Preferably, the solid content of the vinyl acetate-ethylene copolymer emulsion is 55-60%. The solid content of the vinyl chloride copolymer emulsion is 45-50%; and the chlorine content is >50%.

[0007] Preferably, the vinyl chloride copolymer emulsion is a mixture of vinyl chloride-vinyl acetate copolymer emulsion and vinyl chloride-acrylate copolymer emulsion in a mass ratio of 1:(1-2).

[0008] The above-mentioned A2-grade fireproof core material, according to the formula, is prepared by the following steps: S1, premixing: Quartz sand, calcium powder, silica powder, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, activated slag, and modified zeolite are added to a vacuum mixer and stirred to obtain a uniform inorganic mixed powder (vacuum degree ≤ -0.08MPa, 1300-1600r / min). S1, Stir for 15-20 min); S2, Pulping: Add glass fiber, acrylonitrile, water-based emulsion, and water-reducing agent to the uniform inorganic mixed powder, and stir evenly to obtain slurry (vacuum stirring at 1600-1900 r / min for 22-32 min); S3, Molding: Simultaneously feed the slurry and upper and lower nonwoven fabrics into an extrusion molding equipment, so that the slurry is extruded into a sheet between the upper and lower nonwoven fabrics; S4, High-temperature baking and curing: Send the sheet sandwiched between the upper and lower nonwoven fabrics into an oven for segmented curing; S5, Nonwoven fabric recycling: After that, separate the upper and lower nonwoven fabrics from the fireproof core material sheet, and rewind them separately; S6, Precision rolling and post-treatment: Precision roll and trim the fireproof core material sheet, and rewind it to obtain a fireproof core material roll of the required thickness (3-8 mm).

[0009] The aforementioned A2-grade fire-resistant core material can be used as a flame-retardant composite board in the building materials field. Specifically, the fire-resistant core material board, inorganic adhesive, and panel can be double-sided laminated to obtain a flame-retardant composite board with a layered structure of panel / inorganic adhesive film / fire-resistant core material / inorganic adhesive film / panel. The panel is one or more of the following materials: aluminum alloy plate, copper alloy plate, stainless steel plate, or galvanized plate.

[0010] Beneficial effects: (1) This invention provides an A2 grade fireproof core material. Through the formulation and particle size design of each component, the fireproof performance of multiple temperature ranges is improved, and the fireproof effect covers a wider temperature range.

[0011] (2) This invention provides an A2-grade fire-resistant core material, the material skeleton system of which is formed by a composite of rigid glass fiber and flexible acrylonitrile chlorofiber. First, the rigid glass fiber can construct a macroscopic rigid reinforcing network, synergistically activating inorganic fillers such as slag and quartz sand, effectively improving the strength of the core material, while inhibiting shrinkage cracking during the curing process of the core material; second, the flexible acrylonitrile chlorofiber can meet the processing requirements of high toughness and rollability of the core material, while also having flame-retardant properties; third, the glass fiber and acrylonitrile chlorofiber can be uniformly distributed inside the core material to form a three-dimensional reinforcing network, taking into account the balance between the rigidity and flexibility of the core material; in addition, the copolymer emulsion of acrylonitrile chlorofiber and vinyl chloride has excellent compatibility, promoting dispersion and improving adhesion between phases.

[0012] (3) This invention provides an A2-grade fire-resistant core material. The aqueous emulsion in the formula is a composite system formed by vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion. First, the vinyl acetate-ethylene copolymer emulsion provides basic adhesion, adapts to the core material winding requirements, and avoids cracking when the core material is bent. Second, the high chlorine content in the vinyl chloride copolymer emulsion causes it to decompose at high temperature and release HCl to form a flame-retardant barrier. In synergy with the aluminum hydroxide / magnesium hydroxide flame-retardant system, it can significantly reduce the total calorific value of the core material and enhance the A2-grade fire resistance. Third, the strong polarity of the vinyl chloride copolymer emulsion has a strong binding force with inorganic active components such as silane coupling agent-modified zeolite, acrylonitrile chlorofiber, and acid-activated slag, further improving the interfacial bonding between the emulsion phase and the inorganic phase. Fourth, the flexibility and adhesion of the vinyl acetate-ethylene copolymer emulsion, together with the flame retardancy and high adhesion of the vinyl chloride copolymer emulsion, synergistically improve the mechanical strength of the core material, achieving a balance between fire resistance and mechanical properties, thereby improving the processing adaptability and long-term service reliability of the composite board.

[0013] (4) This invention provides an A2-grade fireproof core material, in which modified zeolite is added to the raw material formula. First, the modified zeolite has a unique porous structure, which can effectively adsorb chloride ions generated by the decomposition of vinyl chloride copolymer emulsion and improve the thermal stability of vinyl chloride copolymer emulsion; second, the porous structure of the modified zeolite can block heat transfer and has heat insulation and flame retardant properties.

[0014] (5) This invention provides an A2-grade fire-resistant core material. The activated slag added to its raw material formulation is formed by dissolving soluble components (such as CaO and Al2O3) in industrial slag with sulfuric acid. The sulfuric acid dissolution destroys the original structure of the slag, forming micropores on the slag surface and exposing more active sites. At the same time, sulfates (such as CaSO4) generated by the sulfuric acid dissolution may adhere to the slag surface, also forming a microporous structure and increasing the specific surface area. During the curing process, it is easier to form a stable inorganic cement / dense skeleton, thereby improving the internal densification and structural stability of the core material, and helping to reduce pore defects and improve strength, thus supporting the core material to achieve stable molding and rewinding in continuous production. Detailed Implementation

[0015] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0016] This invention addresses the problems of high brittleness and inability to be wound up in conventional A2-grade fire-resistant core materials using single glass fiber as reinforcement. A new A2-grade fire-resistant core material is designed and developed. The main inventive concepts are as follows: Regarding flame retardancy, this invention uses a graded compound of inorganic flame retardants (aluminum hydroxide, magnesium hydroxide, magnesium carbonate, and calcium powder) that decompose at multiple temperature ranges, combined with a high-chlorine-content vinyl chloride copolymer emulsion and flame-retardant acrylonitrile fiber. Simultaneous optimization of particle size distribution achieves flame retardancy relay, supplemented by modified zeolite to adsorb HCl and inhibit yellowing. Addressing the contradiction between mechanical properties and winding processability, this invention uses rigid glass fiber to construct a reinforcing network, synergistically enhancing strength with inorganic fillers. Flexible acrylonitrile fiber balances toughness and windingability, forming a three-dimensional reinforcement system. Regarding interface issues, silane coupling agents modify zeolite, and sulfuric acid activates slag to enhance activity, strengthening the bonding force between the organic emulsion and the inorganic phase. The compounding of vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion balances adhesion and flame retardancy.

[0017] In summary: This invention first prepares modified zeolite and activated slag to optimize the particle size distribution of inorganic fillers; secondly, it premixes inorganic flame retardants with skeleton fillers to ensure uniform dispersion; then, it adds two types of reinforcing fibers, a compounded aqueous emulsion, and a water-reducing agent, and prepares a uniform slurry by vacuum stirring; finally, it obtains A2-grade fireproof core material through extrusion molding, segmented high-temperature curing, and fine rolling post-treatment, which is suitable for the preparation of composite panels.

[0018] The modified zeolite used in the following embodiments of the present invention was prepared as follows: 1 g of zeolite (1250 mesh, purchased from Shanghai Hengye Chemical Co., Ltd.) was added to a mixed solution of 20 mL of deionized water and anhydrous ethanol at a volume ratio of 1:9. After ultrasonic dispersion for 1 h, the pH was adjusted to 5.0, 0.02 g of silane coupling agent (KH550 or KH560) was added and ultrasonicated for 0.5 h. The mixture was then heated to 60 °C and refluxed for 10 h. After the reaction was completed, the mixture was filtered, washed three times with deionized water, and dried to obtain the target product.

[0019] The activated slag used in the following embodiments of the present invention was obtained by soaking industrial slag in sulfuric acid solution, washing it with water until the pH of the filtrate was 6-7, and then drying it. The preparation method of the activated slag used in the following embodiments of the present invention is as follows: 1g of industrial slag was ball-milled to a particle size of 20-80μm, added to 5mL of dilute sulfuric acid (mass concentration of 4wt%), and completely soaked at 45℃ for 30min. After filtration, the insoluble matter was collected, washed with deionized water until the pH of the filtrate was 7, and then dried at 100℃ for 3h to obtain the target product.

[0020] In the following embodiments of the present invention, the quartz sand used has a particle size of 80-150 μm; the calcium powder (heavy calcium carbonate) used has a D50 particle size of 30-50 μm; the silica powder used has a particle size of 3-5 μm; the modified zeolite used has a particle size of 5-15 μm; the aluminum hydroxide used has a D50 particle size of 10-20 μm; the magnesium hydroxide used has a D50 particle size of 15-25 μm; the magnesium carbonate used has a particle size of 400-600 mesh; and the activated slag used has a particle size of 20-80 μm. All particle sizes were measured by laser particle size analysis after ball milling.

[0021] In this invention, the glass fiber has a length of 6-12 mm and a diameter of 10-15 μm; the glass fiber used in the following embodiments of this invention is type 558 (6 mm in length and 13 μm in diameter), purchased from China Jushi Group.

[0022] The acrylonitrile cellulose used in this invention has a length of 3-5 mm and a diameter of 10-50 μm; the acrylonitrile cellulose used in the following examples of this invention (3.3 dtex (equivalent diameter of about 18 μm) / 4.00 mm) was purchased from Goonvean Fibres in the UK.

[0023] The water-based emulsion used in this invention is a mixed emulsion system formed by vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion at a mass ratio of (6.5-7.5):(2.5-3.5).

[0024] In this invention, the vinyl chloride copolymer emulsion has a solid content of 45-50% and a chlorine content >50%. The vinyl chloride copolymer emulsion is a mixed emulsion formed by vinyl chloride-vinyl acetate copolymer emulsion and vinyl chloride-acrylate copolymer emulsion at a mass ratio of 1:(1-2). In the following examples of this invention, the vinyl chloride-vinyl acetate copolymer emulsion used is model VINNASI 2658 (solid content 50%, pH=6); the vinyl chloride-acrylate copolymer emulsion is model VINNASI 2715 (solid content 47%, pH=4), purchased from Wuxi Honghui New Material Technology Co., Ltd.

[0025] The vinyl acetate-ethylene copolymer emulsion in this invention has a solid content of 55-60%; the vinyl acetate-ethylene copolymer emulsion in the following examples of this invention is model PRIMIS EP 1700 (solid content of 58%, pH=4), purchased from Wacker Chemie AG, Germany.

[0026] The aqueous emulsion preparation process in the following embodiments of the present invention is as follows: Step A: VINNASI 2715 and VINNASI 2658 are added to a mixing vessel at a mass ratio of 1:(1-2) and stirred at 25±2℃ (300-800 r / min) until homogeneous to obtain a homogeneous mother liquor; Step B: The actual pH value of the mother liquor is measured, and dimethylethanolamine aqueous solution (mass concentration of 15wt%) is slowly added dropwise to the mother liquor under stirring conditions as needed to adjust the pH to 6; Step C: The mother liquor obtained in Step B is added to PRIMIS EP 1700 emulsion in a thin stream and stirred at 25±2℃ (300-800 r / min) until homogeneous to obtain an aqueous emulsion.

[0027] The polycarboxylate superplasticizer used in the following examples of the present invention is model PCA®-V, purchased from Jiangsu Subote New Material Co., Ltd.

[0028] The flame-retardant principle of this invention is as follows: Aluminum hydroxide (particle size D50 of 10-20 μm) decomposes at 180-220℃, generating aluminum oxide (Al2O3) and water vapor; magnesium hydroxide (particle size D50 of 15-25 μm) decomposes at 300-350℃, generating magnesium oxide (MgO) and water vapor; magnesium carbonate (particle size of 400-600 mesh) decomposes at 400-550℃, generating magnesium oxide (MgO) and carbon dioxide (CO2); calcium powder (heavy calcium carbonate, particle size D50 of 30-50 μm) decomposes at 890-1000℃, generating calcium oxide (CaO) and carbon dioxide (CO2); vinyl chloride copolymer emulsion... Liquid (chlorine content >50%, solid content 45-50%) releases hydrogen chloride (HCl) at high temperatures, forming a flame-retardant barrier; acrylonitrile chlorofiber (length 3-5mm, equivalent diameter approximately 18μm) chars at high temperatures, with chlorine and acrylonitrile groups working synergistically to suppress flames and smoke; modified zeolite (particle size 5-15μm, modified with KH550 / KH560) has a porous structure, which can insulate heat and adsorb HCl, improving thermal stability; silica powder (particle size ≤5μm) fills the voids, making the structure more compact; activated slag (particle size 20-80μm) forms an inorganic cementitious skeleton; quartz sand (particle size 80-150μm) constructs a rigid skeleton and optimizes particle size distribution.

[0029] This invention uses non-combustible inorganic materials as its core, combined with flame-retardant water-based emulsions and reinforcing fibers. Through the synergistic effect of multiple components, it achieves flame retardancy across multiple temperature ranges and enhances the flame-retardant effect through multi-dimensional coupling: First, temperature coupling, with multiple components relaying flame retardancy across low, medium, and high temperature ranges; second, time coupling, achieving rapid initiation and sustained flame retardancy based on particle size and decomposition temperature matching; third, gas coupling, with water vapor, carbon dioxide, and hydrogen chloride working synergistically to isolate oxygen and inhibit flame chain reactions; fourth, oxide and char coupling, generating multi-layered heat insulation barriers and suppressing smoke; fifth, structural coupling, ensuring system stability through particle gradation and interface reinforcement; and sixth, organic-inorganic coupling, with emulsion compounding and reinforcing fiber dispersion, improving flame retardancy, mechanical and processing properties, reducing total calorific value, and meeting A2 fire resistance requirements.

[0030] In this invention, the mechanical strength mechanism and the winding flexibility mechanism of each component are as follows: Glass fiber (6mm in length, 13μm in diameter) constructs a macroscopic rigid reinforcement network, which, together with inorganic fillers, inhibits shrinkage cracking and improves the tensile strength of the core material; Acrylic fiber (3-5mm in length, approximately 18μm in equivalent diameter) combines flame retardancy and flexibility, adapts to winding requirements, alleviates bending stress, and prevents crack formation; Activated slag (20-80μm in particle size) forms a stable inorganic cementitious skeleton, improving the densification degree and dimensional stability of the core material; Quartz sand (80-150μm in particle size) constructs a rigid skeleton and optimizes the particle size distribution. The formula enhances the continuity of the system; silica powder (particle size ≤ 5μm) fills the micro-voids in the core material, densifies the structure, and reduces mechanical defects; modified zeolite improves the bonding force at the organic-inorganic interface and strengthens the overall integrity of the skeleton; vinyl acetate-ethylene copolymer emulsion provides basic adhesion and flexibility, adapts to winding, and avoids bending cracks; vinyl chloride copolymer emulsion enhances polar bonding force and improves the interfacial adhesion between the emulsion and the inorganic phase; calcium powder (particle size D50 of 30-50μm) optimizes the particle size distribution and assists in building a dense skeleton; polycarboxylate superplasticizer improves the fluidity of the slurry, enhances the uniformity of component dispersion, and ensures more uniform mechanical properties of the core material.

[0031] This invention achieves a balance between mechanical strength and rollability through the synergistic effect of multiple components: First, the rigidity enhancement of glass fiber complements the flexibility of acrylonitrile and vinyl acetate-ethylene copolymer emulsion, balancing tensile strength and rollability; second, quartz sand and activated slag construct a rigid skeleton, while silica powder and calcium powder filler make the core material denser, reducing mechanical defects and improving structural stability; third, modified zeolite and silane coupling agent optimize the organic-inorganic interface bonding, and vinyl chloride copolymer emulsion strengthens polar bonding (vinyl chloride copolymer emulsion has excellent wettability for acrylonitrile, and the strongly polar chlorine groups in the components have excellent adsorption effects on the inorganic interface). The vinyl acetate structure in the vinyl chloride copolymer emulsion has excellent compatibility with the vinyl acetate-ethylene copolymer emulsion; the acrylate structure provides excellent toughness, and it forms a highly compatible bonding system with the vinyl acetate-ethylene copolymer emulsion, acrylonitrile, and other inorganic components, avoiding core material delamination; the addition of water-reducing agent improves component dispersibility, and the emulsion ensures slurry formability, making it more suitable for extrusion and multi-pass precision rolling processes; through segmented curing and hot pressing, the flatness and flexibility of the core material are taken into account, achieving stable winding of rolls with a thickness of ≤8mm, while improving the processing adaptability and long-term service reliability of the composite board.

[0032] The A2-grade fireproof core material in the following embodiments of the present invention is prepared according to the following formula: S1, Premixing: Quartz sand, calcium powder, silicon powder, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, activated slag, and modified zeolite are mixed uniformly under vacuum (vacuum mixer, vacuum degree ≤ -0.08MPa, 1300-1600r / min) to obtain a uniform inorganic mixed powder; S2, Slurrying: Glass fiber, acrylonitrile, aqueous emulsion, and water-reducing agent are added to the obtained inorganic mixed powder and stirred uniformly (vacuum stirring at 1600-1900r / min for 22-32min) to obtain a uniform slurry; S3, Molding: The slurry and upper and lower nonwoven fabrics are simultaneously fed into an extrusion molding device, so that the slurry is extruded into a sheet between the upper and lower nonwoven fabrics. S4, High-temperature baking and curing: The sheet sandwiched between the upper and lower nonwoven fabrics is sent into an oven for segmented curing; First curing stage: 88-108℃ for 20-30 minutes; Second curing stage: 128-148℃ for 15-25 minutes; S5, Nonwoven fabric recycling: After nonwoven fabric recycling, the upper and lower nonwoven fabrics are separated from the fireproof core material sheet and wound up separately; S6, Precision rolling and post-processing: The fireproof core material sheet is precision rolled, trimmed, and wound up to obtain a 3-8mm thick fireproof core material roll; The hot pressing precision rolling is carried out at 150℃ and 2-5MPa pressure for 10-20 minutes for shaping and densification; then it is continuously pressed at about 100-130℃ for 8-10 passes to obtain the target thickness and flatness.

[0033] Example 1: A Class A2 fireproof core material, by weight, has the following raw material composition: 32 parts quartz sand; 45 parts calcium powder; 16 parts silica powder; 6.5 parts modified zeolite; 38 parts aluminum hydroxide; 20 parts magnesium hydroxide; 10 parts magnesium carbonate; 9 parts glass fiber; 4 parts acrylonitrile chlorofiber; 6 parts activated slag; 30 parts water-based emulsion; and 1.5 parts polycarboxylate superplasticizer.

[0034] The modified zeolite is KH550 modified zeolite.

[0035] The mass ratio of vinyl acetate-ethylene copolymer emulsion to vinyl chloride copolymer emulsion in the aqueous emulsion is 7:3.

[0036] The vinyl chloride copolymer emulsion is made by adding vinyl chloride-vinyl acetate copolymer emulsion and vinyl chloride-acrylate copolymer emulsion at a mass ratio of 1:1.5.

[0037] The preparation process of the aqueous emulsion is as follows: Step A: Add VINNASI 2715 and VINNASI 2658 to a mixing vessel at a mass ratio of 1:1.5, and stir evenly at 25±2℃ to obtain a homogeneous mother liquor; Step B: Measure the actual pH value of the mother liquor, and slowly add dimethylethanolamine aqueous solution (mass concentration of 15%) to the mother liquor under stirring conditions as needed to adjust the pH of the solution to 6; Step C: Add the mother liquor obtained in Step B to the PRIMIS EP 1700 emulsion in a thin stream, and stir evenly at 25±2℃ to obtain an aqueous emulsion.

[0038] The A2-grade fireproof core material is prepared according to the following formula: S1, Premixing: Quartz sand, calcium powder, silicon powder, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, activated slag, and modified zeolite are added to a vacuum mixer and stirred (vacuum degree ≤ -0.08MPa, 1450r / min) until uniform, resulting in an inorganic mixed powder; S2, Slurry preparation: Glass fiber, acrylonitrile, aqueous emulsion, and water-reducing agent are added to the inorganic mixed powder and stirred until uniform (1750r / min), resulting in a uniform slurry; S3, Molding: The slurry and upper and lower nonwoven fabrics are simultaneously fed into an extrusion molding device, allowing the slurry to be extruded between the upper and lower nonwoven fabrics. S4, High-temperature baking and curing: The sheet sandwiched between the upper and lower nonwoven fabrics is sent into an oven for segmented curing; Curing stage 1: 100℃ for 25 minutes; Curing stage 2: 138℃ for 20 minutes; S5, Nonwoven fabric recycling: The upper and lower nonwoven fabrics are separated from the fireproof core material sheet and wound up and recycled separately; S6, Precision rolling and post-treatment: The fireproof core material sheet is precision rolled, trimmed, and wound up to obtain a 3.5mm thick fireproof core material roll; The hot pressing precision rolling is to hold at 150℃ and 3MPa pressure for 17 minutes for shaping and densification; then it is continuously pressed 9 times at about 120℃.

[0039] The preparation method of the flame-retardant composite board is as follows: A fire-resistant core material board and a metal panel are hot-pressed together on both sides using an inorganic binder (liquid water glass, modulus 3.2) (150℃, pressure 1.0MPa, time 20min), resulting in a flame-retardant composite board with a layered structure of metal panel / inorganic binder film / fire-resistant core material / inorganic binder film / metal panel. The metal panel is an aluminum alloy plate (model 3003-H24). The thicknesses of the metal panel and the inorganic binder film are 0.3mm and 0.12mm, respectively.

[0040] Example 2 is the same as Example 1, except that the A2 fireproof core material in Example 2, by weight, has the following raw material composition: 25 parts quartz sand; 35 parts calcium powder; 12 parts silica powder; 5 parts modified zeolite; 30 parts aluminum hydroxide; 15 parts magnesium hydroxide; 8 parts magnesium carbonate; 6 parts glass fiber; 3 parts acrylonitrile chlorofiber; 4 parts activated slag; 25 parts water-based emulsion; and 1 part polycarboxylate superplasticizer.

[0041] The modified zeolite is KH550 modified zeolite.

[0042] The mass ratio of vinyl acetate-ethylene copolymer emulsion to vinyl chloride copolymer emulsion in the aqueous emulsion is 7:3.

[0043] The vinyl chloride copolymer emulsion is composed of vinyl chloride-vinyl acetate and vinyl chloride-acrylate copolymer emulsions added at a mass ratio of 1:1.5.

[0044] Example 3 is the same as Example 1, except that the A2 fireproof core material in Example 3, by weight, has the following raw material composition: 40 parts quartz sand; 55 parts calcium powder; 20 parts silica powder; 8 parts modified zeolite; 45 parts aluminum hydroxide; 25 parts magnesium hydroxide; 12 parts magnesium carbonate; 12 parts glass fiber; 5 parts acrylonitrile chlorofiber; 8 parts activated slag; 35 parts water-based emulsion; and 2 parts polycarboxylate superplasticizer.

[0045] The modified zeolite is KH550 modified zeolite.

[0046] The mass ratio of vinyl acetate-ethylene copolymer emulsion to vinyl chloride copolymer emulsion in the aqueous emulsion is 7:3.

[0047] The vinyl chloride copolymer emulsion is composed of vinyl chloride-vinyl acetate and vinyl chloride-acrylate copolymer emulsions added at a mass ratio of 1:1.5.

[0048] Example 4 is the same as Example 1, except that in Example 4, the same amount of KH560 modified zeolite is added to replace the KH550 modified zeolite in Example 1.

[0049] Example 5 is the same as Example 1, except that the mass ratio of vinyl acetate-ethylene copolymer emulsion to vinyl chloride copolymer emulsion in the aqueous emulsion in Example 5 is 6.5:3.5.

[0050] Example 6 is the same as Example 1, except that the mass ratio of vinyl acetate-ethylene copolymer emulsion to vinyl chloride copolymer emulsion in the aqueous emulsion in Example 6 is 7.5:2.5.

[0051] Example 7 is the same as Example 1, except that in Example 7, the vinyl chloride copolymer emulsion is a vinyl chloride-vinyl acetate and vinyl chloride-acrylate copolymer emulsion added at a mass ratio of 1:1.

[0052] Example 8 is the same as Example 1, except that in Example 7, the vinyl chloride copolymer emulsion is a vinyl chloride-vinyl acetate and vinyl chloride-acrylate copolymer emulsion added at a mass ratio of 1:2.

[0053] Comparative Example 1 is the same as Example 1, except that the quartz sand particle size in Comparative Example 1 is 10-50 μm.

[0054] Comparative Example 2 is the same as Example 1, except that the particle size of the quartz sand in Comparative Example 2 is 10-50 μm; the particle size range of the calcium powder D50 is 30-50 μm; the particle size range of the aluminum hydroxide D50 is 80-150 μm; and the particle size range of the magnesium hydroxide D50 is 80-150 μm.

[0055] Comparative Example 3 is the same as Example 1, except that no silicon powder was added to the core material of Comparative Example 3.

[0056] Comparative Example 4 is the same as Example 1, except that no acrylic fiber was added to the core material of Comparative Example 4.

[0057] Comparative Example 5 is the same as Example 1, except that the core material of Comparative Example 5 contains 8 parts by weight of acrylonitrile and 5 parts by weight of glass fiber.

[0058] Comparative Example 6 is the same as Example 1, except that Comparative Example 6 uses the same weight parts of aramid (1313) to replace the acrylonitrile fiber in Example 1. Aramid (1313) has better toughness and flame retardancy, but poor compatibility with the aqueous emulsion of the present invention.

[0059] Comparative Example 7 is the same as Example 1, except that no modified zeolite was added in Comparative Example 7.

[0060] Comparative Example 8 is the same as Example 1, except that the same weight proportions of unmodified zeolite are used in Comparative Example 8 to replace the modified zeolite in Example 1.

[0061] Comparative Example 9 is the same as Example 1, except that no activated slag was added in Comparative Example 9.

[0062] Comparative Example 10 is the same as Example 1, except that the same weight proportions of unmodified industrial slag are used in Comparative Example 10 to replace the activated slag in Example 1.

[0063] Comparative Example 11 is the same as Example 1, except that the aqueous emulsion in Comparative Example 11 is a vinyl acetate-ethylene copolymer emulsion.

[0064] Comparative Example 12 is the same as Example 1, except that the vinyl chloride copolymer emulsion in Comparative Example 12 is a vinyl chloride-vinyl acetate copolymer emulsion.

[0065] Comparative Example 13 is the same as Example 1, except that the vinyl chloride copolymer emulsion in Comparative Example 13 is a vinyl chloride-acrylate copolymer emulsion.

[0066] Performance test (1) Appearance: Visually check whether there are tiny cracks in the winding; whether it is yellowed.

[0067] (2) Tensile strength: The test shall be conducted in accordance with GB / T 228.1 2021.

[0068] (3) Calorific value of core material and total calorific value of composite board: determined according to GB / T 14402-2007 standard. The qualified index is ≤3.0.

[0069] (4) Combustion growth rate index: Refer to GB / T20284-2006. The qualified index is ≤120.

[0070] (5) Total heat release within 600s: GB / T 20284-2006. Qualified index ≤7.5.

[0071] (6) Flame transverse spread length: GB / T 20284-2006. Acceptable index < sample edge.

[0072] The core material and flame-retardant composite board obtained in the embodiments and comparative examples of the present invention were subjected to performance tests. The specific test results are shown in Table 1, Table 1 (continued), and Table 2. The A2 flame retardant level is determined by simultaneously meeting the following criteria: calorific value, combustion growth rate index, total heat release within 600s, and flame lateral spread length. If any criterion is not met, it is determined that the A2 flame retardant level has not been achieved.

[0073] Table 1 Continued from Table 1 Table 2 The test results above show that, firstly, as can be seen from Table 1 (Examples 1-8), the A2-grade fire-resistant core material of the present invention exhibits high mechanical properties (tensile strength 6.6-7.6 MPa), excellent flame retardancy (calorific value of core material and total calorific value of composite board both ≤3.0), and its appearance is rewound without cracks and basically without yellowing; at the same time, Table 2 shows that the combustion growth rate index, total heat release within 600s, and flame lateral spread length of Examples 1-8 are all qualified, indicating that the core material and its composite board of the present invention meet the A2 grade requirements.

[0074] Secondly, as can be observed from Example 1 and Comparative Examples 1-2, the particle size distribution design of each inorganic filler in this invention is key to achieving both high mechanical properties and qualified flame retardancy in the core material: In Comparative Example 1, the tensile strength decreased after only changing the quartz sand particle size, and the flame retardancy index was unqualified, resulting in failure to reach A2; In Comparative Example 2, after coarsening the overall particle size of various fillers, the core material showed microcracks, a significant decrease in tensile strength, and the flame retardancy index was unqualified, resulting in failure to reach A2. This indicates that the particle size matching and gradation principles followed in this invention can effectively improve the density and structural uniformity of the system, avoid the increase in porosity, increased heat release, and intensified flame spread caused by disordered particle size matching, thereby ensuring that the flame retardancy index and mechanical properties meet the standards simultaneously.

[0075] Third, it can be observed from Example 1 and Comparative Example 3 that the addition of silicon powder significantly contributes to the mechanical properties and flame retardant performance of the core material: Comparative Example 3 showed a significant decrease in tensile strength without the addition of silicon powder, and also failed to meet the flame retardant index, resulting in the overall material not reaching A2. This indicates that silicon powder can improve strength and reduce the risk of heat release by filling micropores, promoting the densification of the inorganic framework and interfacial bonding.

[0076] Fourth, from Examples 1 and Comparative Examples 4-6, it can be observed that the introduction of acrylonitrile chlorofiber and its synergistic reinforcement with glass fiber are the key fiber systems for achieving rollable, crack-free, and high-strength core materials: Comparative Example 4, without the addition of acrylonitrile chlorofiber, showed obvious cracks and a decrease in strength, while the composite board's calorific value exceeded the standard and did not reach A2; Comparative Example 5, although increasing acrylonitrile chlorofiber to 8 parts and reducing glass fiber to 5 parts could maintain the A2 flame retardancy standard, showed a significant decrease in strength and obvious yellowing, indicating that the amount of acrylonitrile chlorofiber and the ratio of glass fiber need to be synergistically optimized between "toughness / rollability, strength, and appearance stability"; Comparative Example 6, after replacing acrylonitrile chlorofiber with aramid 1313, could still meet the A2 flame retardancy index, but microcracks appeared and the strength decreased, further indicating that the acrylonitrile chlorofiber selected in this invention has better interfacial compatibility and comprehensive molding stability in this system, and can form a more stable three-dimensional reinforcing network with glass fiber, taking into account both rigidity and flexibility.

[0077] Fifth, as observed from Example 1 and Comparative Examples 7-8, the silane coupling agent-modified zeolite is crucial to the appearance and structural stability of the core material: Comparative Example 7, without the addition of modified zeolite, still meets the A2 flame retardancy index, but exhibits significant yellowing; Comparative Example 8, when replaced with unmodified zeolite, shows microcracks and significant yellowing. These results indicate that the porous structure and surface modification of zeolite work together to improve the system's thermal stability and interfacial bonding, reducing the risk of yellowing and cracking due to interfacial defects during curing, thereby ensuring continuous production and the appearance requirements of the winding process.

[0078] Sixth, it can be observed from Example 1 and Comparative Examples 9-10 that activated slag and its activation treatment make a significant contribution to achieving flame retardancy standards: in Comparative Example 9, the core material failed to meet flame retardancy standards and ultimately did not reach A2 when no activated slag was added; in Comparative Example 10, even after replacing it with unmodified industrial slag, the core material still failed to meet standards and did not reach A2. This indicates that activated slag forms a stable inorganic cementitious / dense skeleton, improves densification and structural continuity during the solidification process, and is an important factor in reducing total heat release and inhibiting flame spread.

[0079] Seventh, from Examples 1 and Comparative Examples 11-13, it can be observed that the compound system of vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion is the key to balancing flame retardancy and processing appearance: When only vinyl acetate-ethylene copolymer emulsion was used in Comparative Example 11, the calorific value of the core material and composite board significantly exceeded the standard, directly resulting in failure to meet A2; when only vinyl chloride-vinyl acetate copolymer emulsion was used in Comparative Example 12, although it could meet the A2 flame retardancy index, microcracks and slight yellowing appeared; when only vinyl chloride-acrylate copolymer emulsion was used in Comparative Example 13, the flame retardancy index was unqualified, and A2 was not met. The above results show that the compound emulsion can achieve synergy between adhesion, flexibility and flame retardancy contribution, ensuring both film formation and interfacial bonding of the system, and suppressing the risk of heat release and spread in the early stage of combustion, thereby enabling the core material and composite board to simultaneously meet the comprehensive criteria for A2 level.

[0080] In summary, the A2-grade fire-resistant core material of this invention, through precise inorganic filler particle size distribution and densification design, functionalized fiber reinforcement system, interface / skeleton reinforcement of silane-modified zeolite and activated slag, and synergistic compounding of vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion, not only meets the calorific value limit but also ensures that key indicators such as combustion growth rate index, total heat release within 600s, and flame lateral spread length simultaneously meet the standards. It also possesses high tensile strength, continuous extrusion molding capability, and rollable appearance stability, fully meeting the A2-grade fire resistance standard requirements. It is suitable for the industrial production of flame-retardant composite panels and has broad application prospects.

[0081] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A Class A2 fire-resistant core material, characterized in that... The raw materials include inorganic mineral powder, reinforcing fibers, aqueous emulsion and water-reducing agent. The reinforcing fibers include at least glass fiber and acrylonitrile. The aqueous emulsion is a blended emulsion system formed by vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion.

2. The A2-grade fire-resistant core material according to claim 1, characterized in that... By weight, the raw materials include 134-213 parts inorganic mineral powder, 9-17 parts reinforcing fiber, 25-35 parts water-based emulsion, and 1-2 parts water-reducing agent.

3. The A2-grade fire-resistant core material according to claim 2, characterized in that... The inorganic mineral powder, by weight, comprises the following components: 25-40 parts of quartz sand, 35-55 parts of calcium powder, 12-20 parts of silica powder, 5-8 parts of modified zeolite, 30-45 parts of aluminum hydroxide, 15-25 parts of magnesium hydroxide, 8-12 parts of magnesium carbonate, and 4-8 parts of activated slag.

4. The A2-grade fire-resistant core material according to claim 3, characterized in that... The modified zeolite is a silane coupling agent modified zeolite. The silane coupling agent is an aminosilane coupling agent or an epoxysilane coupling agent. The silanol formed by the hydrolysis of the silane coupling agent reacts with the hydroxyl groups on the surface of the zeolite to form Si-O-Si chemical bonds.

5. The A2-grade fire-resistant core material according to claim 3, characterized in that... The activated slag is produced by dissolving the soluble components in industrial slag with sulfuric acid, thereby destroying the original structure of the slag and forming a microporous structure on the slag surface.

6. The A2-grade fire-resistant core material according to claim 2, characterized in that... The reinforcing fibers, by weight, comprise 6-12 parts glass fiber and 3-5 parts acrylonitrile.

7. The A2-grade fire-resistant core material according to claim 2, characterized in that... The water-reducing agent is a polycarboxylate-based water-reducing agent.

8. The A2-grade fire-resistant core material according to claim 2, characterized in that... Aqueous emulsions are blended emulsion systems formed by vinyl acetate-ethylene copolymer emulsion and vinyl chloride copolymer emulsion at a mass ratio of (6.5-7.5):(2.5-3.5).

9. A Class A2 fire-resistant core material according to any one of claims 1-8, characterized in that... According to the formula, the preparation method includes the following steps: S1, premixing: Quartz sand, calcium powder, silicon powder, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, activated slag, and modified zeolite are mixed evenly to obtain a uniform inorganic powder; S2, pulping: Glass fiber, acrylonitrile chlorofiber, water-based emulsion, and water-reducing agent are added to the uniform inorganic powder and stirred evenly to obtain a slurry; S3, molding: The slurry and upper and lower nonwoven fabrics are simultaneously fed into an extrusion molding equipment, so that the slurry is extruded into a sheet between the upper and lower nonwoven fabrics; S4, high-temperature baking and curing: The sheet sandwiched between the upper and lower nonwoven fabrics is sent into an oven for segmented curing; S5, nonwoven fabric recycling: After recycling, the upper and lower nonwoven fabrics are separated from the fireproof core material sheet and wound up and recycled separately; S6, fine rolling and post-treatment: The fireproof core material sheet is finely rolled, trimmed, and wound up to the required thickness of fireproof core material roll.

10. A flame-retardant building composite panel, characterized in that... The fireproof core material of any one of claims 1-8 is used as the fireproof core material. The fireproof core material is bonded and fixed together with the panel on both sides. The panel is one or two of the following materials: aluminum alloy plate, copper alloy plate, stainless steel plate or galvanized plate.

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