Fireproof core material with sandwich structure as well as preparation method and application of fireproof core material

Abstract

The invention discloses a fireproof core material with a sandwich structure and a preparation method and application thereof, the fireproof core material is of a sandwich layered structure, the inner surface and the outer surface are organic / inorganic composite base layers, and the middle is a core material layer. The core material disclosed by the invention is simple and feasible in preparation method, controllable in thickness and high in firmness, shows remarkable advantages in strength, toughness and stability, and is a fireproof material with good comprehensiveness and high reliability.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and specifically relates to a sandwich structure fireproof core material and its preparation method, as well as the application of the sandwich structure fireproof core material in Class A fireproof aluminum composite panels. Background Technology

[0002] With the rapid urbanization in my country, the number of high-rise and super high-rise buildings continues to grow, and their architectural forms are becoming increasingly complex and large-scale. These buildings have expansive facades and diverse structural forms, resulting in significantly higher fire loads than ordinary buildings. Furthermore, fires spread rapidly and through multiple pathways, making firefighting extremely difficult. Therefore, extremely high requirements are placed on the fire safety performance of their exterior wall decoration materials. Currently, the widely used traditional aluminum-core-aluminum composite panels hold a large market share in the building exterior decoration field due to their good formability, weather resistance, durability, and ease of construction. However, these panels typically use polyethylene (PE) as the core material, which has a low limiting oxygen index and a fire rating generally only Class B, posing significant safety hazards in practical use.

[0003] Traditional aluminum-core-aluminum Class B fire-resistant aluminum composite panels have many inherent defects, especially in building exterior wall applications. The PE core material is highly flammable under high temperatures or open flames, producing a large amount of molten drippings. These drippings, carrying flames, can ignite combustibles below or nearby, causing the fire to spread rapidly vertically or horizontally along the facade, significantly increasing the fire's area. Furthermore, the dense smoke and toxic gases (such as CO and hydrocarbons) released when PE burns severely hinder escape and firefighting efforts, threatening public health. Under heat, the PE core material softens, shrinks, and may even decompose, causing the entire composite panel structure to lose its integrity, leading to panel detachment or overall collapse, further exacerbating the fire's hazard and increasing the difficulty of rescue operations.

[0004] Although some existing technologies have developed Class B fire-resistant PE core materials modified with flame retardants, which can delay the combustion process to some extent, their matrix is ​​still a thermoplastic organic polymer, and their flammability cannot be fundamentally changed. Under sufficient ignition conditions, they will continue to burn and release heat, failing to achieve a non-combustible or flame-retardant rating. Therefore, these modified materials still cannot meet the mandatory requirement of Class A fire performance for building exterior wall decoration materials in the national standard "Code for Fire Protection Design of Buildings" (GB 50016). Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a sandwich-structure fire-resistant core material for aluminum composite panels. This fire-resistant core material has a sandwich structure consisting of an organic / inorganic composite base layer, a core material layer, and another organic / inorganic composite base layer. This structural system significantly improves overall performance by introducing a dual protection mechanism: the inner and outer organic / inorganic composite base layers are non-combustible and high-temperature resistant, easily enabling the material to meet Class A fire resistance standards and effectively blocking heat transfer to the inner core material layer in the early stages of a fire; the central dedicated core material layer provides the composite panel with both extremely high fire resistance and reliable structural stability. This fire-resistant core material structure combines excellent fire safety performance, smokeless and non-toxic environmental characteristics, and stable physical properties, providing a safer and more reliable solution for building exterior walls.

[0006] The specific technical solution of this invention is as follows: A sandwich-structured fire-resistant core material, wherein the inner and outer surfaces of the fire-resistant core material are organic / inorganic composite base layers, and the core material layer is located between the two organic / inorganic composite base layers. This fire-resistant core material has a layered structure.

[0007] Furthermore, the organic / inorganic composite base layer is made from the following raw materials: 10-30 parts white cement, 20-30 parts vinyl acetate-ethylene copolymer emulsion, 5-10 parts calcium carbonate whiskers, 2-10 parts calcium powder (400 mesh), 2-10 parts calcium powder (1000 mesh), 10-20 parts quartz powder (400 mesh), 0.5-1.0 parts polyvinyl alcohol fiber, 0.5-2.0 parts alkali-resistant glass fiber, 0.05-0.4 parts polycarboxylate superplasticizer (PCE), and 20-25 parts water.

[0008] Preferably, the organic / inorganic composite base layer is made from the following raw materials: 20 parts white cement, 25 parts vinyl acetate-ethylene copolymer emulsion, 5 parts calcium carbonate whiskers, 5 parts calcium powder (400 mesh), 7 parts calcium powder (1000 mesh), 15 parts quartz powder (400 mesh), 0.5 parts polyvinyl alcohol fiber, 0.8 parts alkali-resistant glass fiber, 0.2 parts polycarboxylate superplasticizer (PCE), and 25 parts water.

[0009] Furthermore, the core material layer is made from the following raw materials: 5-15 parts aluminum hydroxide, 15-35 parts magnesium hydroxide, 60-90 parts calcium powder (400 mesh), 3-10 parts calcium powder (1000 mesh), 5-20 parts wollastonite powder (400 mesh), 5-20 parts fly ash, 30-60 parts dolomite powder (400 mesh), 2-20 parts alkali-resistant glass short fibers, 30-60 parts vinyl acetate-ethylene copolymer emulsion, 20-50 parts water, 30-70 parts quartz powder (400 mesh), 5-30 parts white cement, and 0.01-0.1 parts sodium gluconate retarder.

[0010] Preferably, the core material layer is made of the following raw materials: 11 parts aluminum hydroxide, 27 parts magnesium hydroxide, 73 parts calcium powder (400 mesh), 7 parts calcium powder (1000 mesh), 13 parts wollastonite powder (400 mesh), 11 parts fly ash, 39 parts dolomite powder (400 mesh), 10 parts alkali-resistant glass short fibers, 40 parts vinyl acetate-ethylene copolymer emulsion, 38 parts water, 50 parts quartz powder (400 mesh), 15 parts white cement, and 0.045 parts sodium gluconate retarder.

[0011] Furthermore, in the organic / inorganic composite base layer, the length of the polyvinyl alcohol fiber is 6-12 mm, and the length of the alkali-resistant glass fiber is 3-6 mm.

[0012] Furthermore, in the core material layer, the length of the alkali-resistant glass short fibers is less than or equal to 20 mm.

[0013] Furthermore, in the organic / inorganic composite base layer and core layer, the vinyl acetate-ethylene copolymer emulsion, also known as VEA emulsion, has a solid content of 57-59 wt%, a viscosity of 1000-2500 mPa•s, a pH of 3.5-4.5, and a main particle size of 0.5-1.0 micrometers. This vinyl acetate-ethylene copolymer emulsion has good compatibility with flame retardants such as aluminum hydroxide and magnesium hydroxide, produces few toxic gases during combustion, and does not affect the flame retardant effect of the board.

[0014] Preferably, the vinyl acetate-ethylene copolymer emulsion is PRIMIS®EP 1700, which has good fluidity, stable chemical properties, and good compatibility with various resins, solvents, plasticizers, flame retardants, etc.

[0015] Furthermore, the thickness of the core material layer is 2.5-3.5mm, and the total thickness of the sandwich structure fireproof core material is 5-8mm.

[0016] Furthermore, the width of the sandwich structure fireproof core material is greater than or equal to 1 meter.

[0017] Based on long-term research and repeated experimental verification, the inventors finally determined the above-mentioned raw material system and its proportions. This proportion design is mainly based on the following considerations: First, the organic / inorganic composite base layer designed in this scheme uses an organic / inorganic composite system of white cement and vinyl acetate-ethylene copolymer emulsion as the cementitious base. This not only ensures the decorative properties of the base layer but also achieves seamless strength development and continuous optimization of the microstructure through the hydration and cementing characteristics of white cement and the bonding characteristics of vinyl acetate-ethylene copolymer emulsion. The incorporation of calcium powder of different particle sizes, through its micro-aggregate filling effect, significantly improves the density of the base layer and enhances high-temperature stability and chemical resistance. The calcium powder and quartz powder of different particle sizes, through optimized particle size distribution, effectively reduce shrinkage and improve wear resistance. The composite short fiber system (polyvinyl alcohol fiber, alkali-resistant glass fiber, and calcium carbonate whiskers) forms a multi-scale three-dimensional network structure in the matrix, inhibiting the initiation and propagation of microcracks through an efficient bridging mechanism, fundamentally changing the material's failure mode and endowing it with excellent toughness and impact resistance. Crucially, after curing, the vinyl acetate-ethylene copolymer emulsion forms a continuous polymer film in the matrix pores and fiber-substrate interface region. This flexible phase not only enhances the overall toughness of the substrate but also ensures effective stress transfer among components by significantly strengthening interfacial bonding strength, allowing the toughening effect of the fibers to be fully realized. Through the synergistic effect of multiple mechanisms, including physical filling, chemical reinforcement, and interfacial modification, the components jointly construct a high-strength, high-toughness, dense, and durable organic / inorganic composite material layer, providing crucial mechanical support and high-temperature protection for the overall composite structure.

[0018] Secondly, in the intermediate core layer designed in this scheme, magnesium hydroxide is selected as the key flame-retardant component. It not only possesses excellent environmental compatibility but also integrates flame retardancy, smoke suppression, and filling functions. Due to its high decomposition temperature, it can adapt to high-temperature processing conditions. When exposed to fire, magnesium hydroxide releases water molecules through an endothermic decomposition reaction, effectively reducing the temperature of the combustion zone and diluting combustible gases. The generated metal oxides cover the matrix surface, forming a dense barrier layer that inhibits oxygen and heat transfer, thereby significantly delaying flame spread, reducing smoke release, and achieving a self-extinguishing effect. Fly ash, derived from industrial waste, realizes the resource utilization of industrial by-products, further reducing costs. Sodium gluconate, as a cement retarder, has significant retarding effects with a good linear relationship with dosage, effectively improving the early fluidity of cement, increasing later strength, and reducing heat of hydration. It also features good compatibility with cement and is environmentally friendly and economical. White cement, through synergistic action with the retarder, adjusts the setting time, improving process operability and the convenience of transporting the boards. The particle size distribution of calcium powder, wollastonite powder, fly ash, dolomite powder, and quartz powder effectively reduces shrinkage and improves strength and wear resistance.

[0019] The sandwich-structure fire-resistant core material of this invention is a Class A fire-resistant core material, which can be used to prepare Class A aluminum composite panels. The determination of the raw material types and proportions for this sandwich-structure fire-resistant core material underwent extensive experimental screening and performance verification. All quantities are designed to meet the comprehensive requirements of Class A fire-resistant aluminum composite panels for high performance, low cost, and environmental friendliness of the core material. This proportion achieves a high fire resistance rating, excellent physical properties, and environmental friendliness while minimizing production costs. Any deviation from this design in raw material selection or proportions may lead to increased product costs or failure to meet key performance standards.

[0020] The present invention also provides a method for preparing the above-mentioned sandwich structure fireproof core material. This method, through precise material formulation and lamination process control, can stably produce continuous core material with a total thickness of 5-8 mm and a width of 1 meter or more. It solves the problems of easy deformation and low strength of traditional core materials in ultra-thin cases, and can stably prepare high-performance fireproof core material with completely non-combustible properties and environmental friendliness.

[0021] Furthermore, the preparation method of the present invention includes the following steps: (1) Dry mix all raw materials except water and polycarboxylate superplasticizer evenly, and then add water and polycarboxylate superplasticizer and mix evenly to obtain organic / inorganic composite base layer mixture; (2) Mix white cement and sodium gluconate retarder evenly, then add aluminum hydroxide, magnesium hydroxide, 400 mesh calcium powder, 1000 mesh calcium powder, 400 mesh wollastonite powder, fly ash, 400 mesh dolomite powder, and 400 mesh quartz powder, mix evenly, and finally add alkali-resistant glass short fiber, vinyl acetate-ethylene copolymer emulsion and water, mix evenly to obtain the core material layer mixture; (3) Apply an organic / inorganic composite base layer mixture to the release film, pre-cur it, apply a core material layer mixture to the surface of the organic / inorganic composite base layer mixture, pre-cur it, apply an organic / inorganic composite base layer mixture to the surface of the core material layer mixture, and then cover the surface with a release film to form a composite structure of release film-lower organic / inorganic composite base layer-core material layer-upper organic / inorganic composite base layer-release film; (4) The above composite structure is compacted using a pressure roller to obtain a sandwich structure of the desired thickness; (5) Curing the compacted sandwich structure to obtain the sandwich structure fireproof core material.

[0022] Furthermore, in step (1), after adding water and polycarboxylate superplasticizer, the mixture is stirred at a speed of 45-60 rpm for 10-15 minutes. The resulting organic / inorganic composite base mixture has good fluidity, is free of particles, and has a viscosity between 5000-6000 mPa·s.

[0023] Further, in step (2), white cement and sodium gluconate retarder are stirred at 45–60 rpm for 5–6 minutes. Then, aluminum hydroxide, magnesium hydroxide, 400-mesh calcium powder, 1000-mesh calcium powder, 400-mesh wollastonite powder, fly ash, 400-mesh dolomite powder, and 400-mesh quartz powder are added, and stirred at 60–70 rpm for 1–2 minutes. Finally, the remaining raw materials are added, and stirring is continued at 55–65 rpm for a total stirring time of 15–17 minutes. The resulting core material mixture is viscous, paste-like, and without sedimentation. The viscosity of the core material mixture should be significantly higher than that of the organic / inorganic composite base layer mixture to prevent interpenetration during lamination, which could lead to interface blurring. The viscosity of the core material mixture is between 20,000 and 22,000 mPa·s.

[0024] Furthermore, in step (3), the coating is applied by roller coating; preferably, the temperature of the roller is 50-90℃.

[0025] Furthermore, in step (3), pre-curing is carried out by hot air at 60-80℃ to achieve a "touch-dry" state and prevent material from spreading between layers.

[0026] Furthermore, in step (4), compaction is carried out at room temperature and under a pressure of 5-10 MPa. Compaction is performed using a roller press, preferably by alternating longitudinal and transverse pressure.

[0027] Furthermore, in step (4), the operation mode of the roller press is as follows: the roller press first performs longitudinal rolling compaction, that is, it runs along the machine running direction. The reinforcing fibers such as calcium carbonate whiskers, alkali-resistant glass fibers, polyvinyl alcohol fibers, and alkali-resistant glass short fibers in the composite structure will begin to align longitudinally in the shear flow field. Through the strong shear flow field generated during longitudinal rolling, the fibers will rotate and migrate in the flow field, and eventually their long axis direction tends to be parallel to the flow direction (i.e., the machine direction / MD). This can significantly improve the tensile strength and bending strength of the final sandwich structure fireproof core material in the longitudinal direction (machine direction). After the longitudinal rolling is completed, the fireproof core material blank is immediately guided into the second set of transverse rolling devices. The pressure rollers rotate from both sides of the blank towards the center line to apply pressure, thereby achieving transverse rolling of the blank. The pressure and shear force applied by the transverse rolling, which are perpendicular to the initial fiber orientation, can effectively disrupt, break, or redistribute the oriented fiber bundles formed in the longitudinal rolling, making them present a more random and isotropic network structure in the plane of the plate. The roller press applies pressure alternately in the longitudinal and transverse directions. This ultimately results in a more random and uniform two-dimensional distribution of fibers within the board plane (XY plane).

[0028] Furthermore, in step (4), during the precision lamination process, a linear pressure of 5-10 MPa is applied. The pressure will remove large air bubbles in the slurry, compact each layer, and ultimately precisely define the total thickness of the board. By adjusting the gap of the pressure rollers, the final thickness of the board can be precisely controlled between 5.0-8.0 mm.

[0029] Furthermore, in step (5), the laminated board is cured. First, it is cured for 2-4 hours in an environment of 40-60℃ and relative humidity >90%. After curing, the upper and lower release films are removed to complete demolding. The demolded board is then naturally cured for at least 24 hours in an environment of 20-35℃.

[0030] The present invention has the following beneficial effects: 1. Precision thickness control: This invention adopts a combination process of "roller coating + alternating longitudinal and transverse rolling of the press roller". The final thickness is limited by mechanical means rather than simply by the slurry flow rate or its own weight, which has high control precision and good repeatability.

[0031] 2. Interface bonding technology: By adjusting the viscosity matching and pre-curing degree of the organic / inorganic composite base layer and core material slurry, a clear interface and firm bonding are achieved in the ultra-thin structure, which not only prevents interlayer penetration but also avoids delamination.

[0032] 3. Ultra-thin and wide-format molding: It solves the process problem of continuous coating of ultra-thin (<5mm layer thickness) and wide (>1m) organic / inorganic composite base materials. The thickness can be controlled during the preparation process and it is not easy to deform.

[0033] 4. Low-temperature hot pressing: Applying pressure at room temperature not only allows for precise control of thickness at low temperatures, but also promotes early hydration, improves initial strength and production efficiency, and avoids damage to the inorganic hydration process and fireproof filler caused by high temperature and high pressure.

[0034] 5. The preparation method of this invention is simple and easy to implement, the product thickness is controllable, and the repeatability is strong. The resulting sandwich structure fireproof core material is thin, not easily deformed, has high strength, good toughness, good durability, good flame retardancy, and good environmental protection. It is a comprehensive and highly reliable Class A fireproof core material. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the sandwich structure fireproof core material of the present invention.

[0036] The structure consists of: 1. Upper organic / inorganic composite base layer; 2. Middle core material layer; 3. Lower organic / inorganic composite base layer. Detailed Implementation

[0037] The following description illustrates exemplary embodiments of the present invention, including various details to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions, operations, and structures are omitted in the following description.

[0038] Unless otherwise defined, the technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, the present invention describes materials and methods hereinafter. In case of conflict, the definitions included herein shall prevail.

[0039] Unless otherwise specified, all materials used in the following examples and comparative examples are commercially available products. The vinyl acetate-ethylene copolymer emulsion used was PRIMIS® EP 1700, with a solids content of 57-59%, a viscosity of 1000-2500 mPa•s, a pH of 3.5-4.5, and a density of 1.09 g / cm³. 3 The main particle size is 0.5-1.0 micrometers. The polycarboxylate superplasticizer used is Grace's ADVA series high-efficiency superplasticizer. The length of the polyvinyl alcohol fiber used is 6-12mm, the length of the alkali-resistant glass fiber is 3-6mm, and the length of the alkali-resistant short glass fiber is less than or equal to 20mm.

[0040] Example 1 A sandwich-structured fireproof core material, the structure of which is as follows: Figure 1 As shown, the structure is layered, comprising an upper organic / inorganic composite base layer 1, an intermediate core layer 2, and a lower organic / inorganic composite base layer 3. The intermediate core layer 2 is firmly bonded between the upper organic / inorganic composite base layer 1 and the lower organic / inorganic composite base layer 3 through a one-time compression molding process. The organic / inorganic composite base layer and the intermediate core layer work together to bear the structural load and provide fireproof and heat insulation functions, achieving the integration of decoration and function.

[0041] The raw material composition (parts by weight) of the upper and lower organic / inorganic composite base layers of the sandwich structure fireproof core material is as follows: 20 parts white cement, 25 parts vinyl acetate-ethylene copolymer emulsion, 5 parts calcium carbonate whiskers, 5 parts calcium powder (400 mesh), 7 parts calcium powder (1000 mesh), 15 parts quartz powder (400 mesh), 0.5 parts polyvinyl alcohol fiber, 0.8 parts alkali-resistant glass fiber, 0.2 parts polycarboxylate superplasticizer (PCE), and 25 parts water.

[0042] The intermediate core layer of this sandwich structure fireproof core material is composed of the following raw materials (parts by weight): 11 parts aluminum hydroxide, 27 parts magnesium hydroxide, 73 parts calcium powder (400 mesh), 7 parts calcium powder (1000 mesh), 13 parts wollastonite powder (400 mesh), 11 parts fly ash, 39 parts dolomite powder (400 mesh), 10 parts alkali-resistant glass short fiber, 40 parts vinyl acetate-ethylene copolymer emulsion, 38 parts water, 50 parts quartz powder (400 mesh), 15 parts white cement, and 0.045 parts sodium gluconate retarder.

[0043] The preparation method of this sandwich structure fireproof core material includes the following steps: 1. First, dry mix all raw materials except water and polycarboxylate superplasticizer evenly, then add water and polycarboxylate superplasticizer, and stir at 55 rpm for 15 minutes to obtain a free-flowing, particle-free organic / inorganic composite base mixture (viscosity at 6000 mPa·s).

[0044] 2. Add white cement and sodium gluconate retarder to the mixer. Set the mixer speed to 50 rpm. After mixing for 5-6 minutes, add the powder mixture formed by aluminum hydroxide, magnesium hydroxide, calcium powder, wollastonite powder, fly ash, dolomite powder, and quartz powder. Adjust the mixer speed to 65 rpm and continue mixing for 1-2 minutes. Finally, pour alkali-resistant glass short fibers, vinyl acetate-ethylene copolymer emulsion, and water into the mixer. At the same time, adjust the mixer speed to 60 rpm and mix for a total mixing time of 15-17 minutes to obtain a viscous, paste-like, non-settling, uniform slurry (viscosity at 21000 mPa·s).

[0045] 3. The coating is applied using a roller coating method with the roller temperature set at 70℃. The PET film is laid on a continuously running conveyor belt, and an organic / inorganic composite base layer mixture is applied to the PET film as the conveyor belt moves. After coating, it is pre-cured with 70℃ hot air to achieve a "touch-dry" state, preventing material transfer between layers. After pre-curing, a core material layer mixture is applied to the surface of the organic / inorganic composite base layer, and pre-cured again with 70℃ hot air. After pre-curing, another organic / inorganic composite base layer mixture is applied to the surface of the core material layer. Finally, a release film is applied to the surface, forming a composite structure of release film - lower organic / inorganic composite base layer - core material layer - upper organic / inorganic composite base layer - release film.

[0046] 4. The composite structure is compacted at room temperature using a roller press with a pressure of 8 MPa. The specific compaction operation is as follows: the roller press first performs longitudinal rolling compaction, i.e., it runs along the machine's direction of travel. After longitudinal rolling, the fireproof core material blank is immediately guided into the second set of transverse rolling devices. The rollers rotate from both sides of the blank towards the center line to apply pressure, achieving transverse rolling of the blank. The roller press alternates between longitudinal and transverse pressing, ultimately obtaining a sandwich structure with a thickness of 5 mm and a width of 1.2 m.

[0047] 5. Curing the laminated slab: First, cure it at 50℃ and relative humidity >90% for 3 hours. After curing, remove the upper and lower release films to demold. Then, naturally cure the demolded slab at 25℃ for 24 hours to obtain a sandwich-structured fireproof core material with a thickness of 5mm and a width of 1.2m. This fireproof core material has no obvious cracks, a smooth surface, and no warping or deformation.

[0048] Example 2 The sandwich structure fireproof core material was prepared according to the method of Example 1, except that the raw material composition of the organic / inorganic composite base layer was as follows (parts by weight): 10 parts white cement, 20 parts vinyl acetate-ethylene copolymer emulsion, 5 parts calcium carbonate whiskers, 2 parts calcium powder (400 mesh), 2 parts calcium powder (1000 mesh), 10 parts quartz powder (400 mesh), 0.5 parts polyvinyl alcohol fiber, 0.5 parts alkali-resistant glass fiber, 0.05 parts polycarboxylate superplasticizer (PCE), and 20 parts water.

[0049] Example 3 The sandwich structure fireproof core material was prepared according to the method of Example 1, except that the raw material composition of the organic / inorganic composite base layer was as follows (parts by weight): 30 parts white cement, 30 parts vinyl acetate-ethylene copolymer emulsion, 10 parts calcium carbonate whiskers, 10 parts calcium powder (400 mesh), 10 parts calcium powder (1000 mesh), 20 parts quartz powder (400 mesh), 1.0 part polyvinyl alcohol fiber, 2.0 parts alkali-resistant glass fiber, 0.4 parts polycarboxylate superplasticizer (PCE), and 25 parts water.

[0050] Example 4 The sandwich structure fireproof core material was prepared according to the method of Example 1, except that the raw material composition of the middle core layer was as follows (parts by weight): 5 parts aluminum hydroxide, 15 parts magnesium hydroxide, 60 parts calcium powder (400 mesh), 3 parts calcium powder (1000 mesh), 5 parts wollastonite powder (400 mesh), 5 parts fly ash, 30 parts dolomite powder (400 mesh), 2 parts alkali-resistant glass short fiber, 30 parts vinyl acetate-ethylene copolymer emulsion, 20 parts water, 30 parts quartz powder (400 mesh), 5 parts white cement, and 0.01 parts sodium gluconate retarder.

[0051] Example 5 The sandwich structure fireproof core material was prepared according to the method of Example 1, except that the raw material composition of the middle core layer was as follows (parts by weight): 15 parts aluminum hydroxide, 35 parts magnesium hydroxide, 90 parts calcium powder (400 mesh), 10 parts calcium powder (1000 mesh), 20 parts wollastonite powder (400 mesh), 20 parts fly ash, 60 parts dolomite powder (400 mesh), 20 parts alkali-resistant glass short fiber, 60 parts vinyl acetate-ethylene copolymer emulsion, 50 parts water, 70 parts quartz powder (400 mesh), 30 parts white cement, and 0.1 parts sodium gluconate retarder.

[0052] Comparative Example 1 The sandwich-structured fireproof core material was prepared according to the method in Example 1, with the following differences: vinyl acetate-ethylene copolymer emulsion was not added to the raw material formulation of the organic / inorganic composite base layer; the amount of white cement was adjusted to 40 parts; and the mesh size of the calcium powder was changed to 1000 mesh. The results showed that the absence of vinyl acetate-ethylene copolymer emulsion and the lack of proper gradation of the calcium powder mesh size led to deterioration of the slurry's rheological properties, resulting in a loss of flexibility and toughness. During the roller coating process, the slurry lacked the cohesiveness and lubricity provided by the polymer, making it difficult to achieve an ultra-thin and uniform structure through roller coating. The surface was rough and prone to defects, resulting in a significant reduction in toughness, a significant increase in brittleness, and easy breakage. The final resulting board had numerous cracks.

[0053] Comparative Example 2 The sandwich-structured fireproof core material was prepared according to the method in Example 1, except that white cement was replaced with ordinary silicate cement in the raw material formulation of the organic / inorganic composite base layer. The final board had a small number of cracks.

[0054] Comparative Example 3 The sandwich-structured fireproof core material was prepared according to the method in Example 1, except that the composition of the intermediate core layer raw materials (parts by weight) was as follows: 11 parts aluminum hydroxide, 27 parts magnesium hydroxide, 80 parts calcium powder (400 mesh), 13 parts wollastonite powder (400 mesh), 11 parts fly ash, 39 parts dolomite powder (400 mesh), 40 parts vinyl acetate-ethylene copolymer emulsion, 38 parts water, 50 parts quartz powder (400 mesh), 15 parts white cement, and 0.045 parts sodium gluconate retarder. The results showed that due to the lack of calcium powder gradation and alkali-resistant glass short fibers, the core layer strength was reduced, and multiple visible cracks appeared on the slab during the rolling process.

[0055] Comparative Example 4 The sandwich-structured fireproof core material was prepared according to the method in Example 1, except that the composition of the middle core layer was as follows (parts by weight): 11 parts aluminum hydroxide, 27 parts magnesium hydroxide, 73 parts calcium powder (400 mesh), 7 parts calcium powder (1000 mesh), 53 parts wollastonite powder (400 mesh), 18 parts fly ash, 72 parts dolomite powder (400 mesh), 10 parts alkali-resistant glass short fibers, 40 parts vinyl acetate-ethylene copolymer emulsion, 38 parts water, 50 parts quartz powder (400 mesh), 15 parts white cement, and 0.045 parts sodium gluconate retarder. The results showed that due to the lack of calcium powder for gradation, the core layer underwent uneven shrinkage during drying and curing, resulting in overall warping and deformation of the final board, with a small number of cracks.

[0056] Comparative Example 5 The sandwich structure fireproof core material was prepared according to the formulation and method of Example 1, with the following differences: in step 3, no pre-curing was performed during roller coating; in step 4, only longitudinal rolling was performed during rolling. The final obtained board had a small number of cracks.

[0057] Experimental Example 1. The density, water absorption rate, 28-day drying shrinkage value, and coefficient of thermal expansion of the sandwich structure fireproof core materials prepared in Examples 1-5 above were tested. Specifically, the water absorption rate was tested according to standard JC / T 2561-2020, the 28-day drying shrinkage value was tested according to standard GB / T 8811-2008, and the coefficient of thermal expansion was tested according to standard ASTM E831. Density test: Fireproof core materials of the same volume (10cm × 10cm × 3mm) were cut and weighed. Density = weight / volume.

[0058] The test results are shown in Table 1 below.

[0059] Table 1 The comparison of Examples 1-5 shows that the fireproof core material of Example 1 has low water absorption, low drying yield, and low coefficient of thermal expansion, and has better durability and impermeability. This indicates that the fireproof core material of Example 1 has better dimensional stability in long-term use, which is crucial for large-area exterior wall applications.

[0060] 2. Molding tests, crack sensitivity tests, three-point bending tests, and fire resistance tests were conducted on Example 1 and Comparative Examples 2, 4, and 5. The molding tests were performed according to standard GB / T 30100-2013, the crack sensitivity tests according to standard ASTM D7857-24, the three-point bending tests according to standard GB / T 11546.2-2022, and the fire resistance tests according to T / CECS 10407-2024.

[0061] The test results are shown in Table 2 below: Table 2 As can be seen from Table 2, the fire-resistant core material of Example 1 has significantly better performance than the comparative examples, exhibiting excellent toughness, strength and fire resistance, and the board shows no cracks even with a large width.

Claims

1. A sandwich-structured fireproof core material, characterized in that: Its inner and outer surfaces are organic / inorganic composite base layers, with a core material layer between the two organic / inorganic composite base layers; the organic / inorganic composite base layer is made of the following raw materials: 10-30 parts white cement, 20-30 parts vinyl acetate-ethylene copolymer emulsion, 5-10 parts calcium carbonate whiskers, 2-10 parts 400 mesh calcium powder, 2-10 parts 1000 mesh calcium powder, 10-20 parts 400 mesh quartz powder, 0.5-1.0 parts polyvinyl alcohol fiber, 0.5-2.0 parts alkali-resistant glass fiber, 0.05-0.4 parts polycarboxylate superplasticizer, and 20-25 parts water; The core material layer is made of the following raw materials: 5-15 parts aluminum hydroxide, 15-35 parts magnesium hydroxide, 60-90 parts 400-mesh calcium powder, 3-10 parts 1000-mesh calcium powder, 5-20 parts 400-mesh wollastonite powder, 5-20 parts fly ash, 30-60 parts 400-mesh dolomite powder, 2-20 parts alkali-resistant glass short fibers, 30-60 parts vinyl acetate-ethylene copolymer emulsion, 20-50 parts water, 30-70 parts 400-mesh quartz powder, 5-30 parts white cement, and 0.01-0.1 parts sodium gluconate retarder.

2. The sandwich structure fireproof core material according to claim 1, characterized in that: The organic / inorganic composite base layer is made from the following raw materials: 20 parts white cement, 25 parts vinyl acetate-ethylene copolymer emulsion, 5 parts calcium carbonate whiskers, 5 parts 400 mesh calcium powder, 7 parts 1000 mesh calcium powder, 15 parts 400 mesh quartz powder, 0.5 parts polyvinyl alcohol fiber, 0.8 parts alkali-resistant glass fiber, 0.2 parts polycarboxylate superplasticizer, and 25 parts water. Preferably, the core material layer is made of the following raw materials: 11 parts aluminum hydroxide, 27 parts magnesium hydroxide, 73 parts 400-mesh calcium powder, 7 parts 1000-mesh calcium powder, 13 parts 400-mesh wollastonite powder, 11 parts fly ash, 39 parts 400-mesh dolomite powder, 10 parts alkali-resistant glass short fibers, 40 parts vinyl acetate-ethylene copolymer emulsion, 38 parts water, 50 parts 400-mesh quartz powder, 15 parts white cement, and 0.045 parts sodium gluconate retarder.

3. The sandwich structure fireproof core material according to claim 1 or 2, characterized in that: In the organic / inorganic composite base layer, the length of polyvinyl alcohol fiber is 6-12mm, and the length of alkali-resistant glass fiber is 3-6mm; in the core layer, the length of alkali-resistant glass short fiber is less than or equal to 20mm.

4. The sandwich-structured fireproof core material according to any one of claims 1-3, characterized in that: The core layer thickness is 2.5-3.5mm, and the total thickness of the sandwich structure fireproof core material is 5-8mm.

5. A method for preparing the sandwich structure fireproof core material according to claim 1, characterized in that: Includes the following steps: (1) Dry mix all raw materials except water and polycarboxylate superplasticizer evenly, and then add water and polycarboxylate superplasticizer and mix evenly to obtain organic / inorganic composite base layer mixture; (2) Mix white cement and sodium gluconate retarder evenly, then add aluminum hydroxide, magnesium hydroxide, 400 mesh calcium powder, 1000 mesh calcium powder, 400 mesh wollastonite powder, fly ash, 400 mesh dolomite powder, and 400 mesh quartz powder, mix evenly, and finally add alkali-resistant glass short fiber, vinyl acetate-ethylene copolymer emulsion and water, mix evenly to obtain the core material layer mixture; (3) Apply an organic / inorganic composite base layer mixture to the release film, pre-cur it, apply a core material layer mixture to the surface of the organic / inorganic composite base layer mixture, pre-cur it, apply an organic / inorganic composite base layer mixture to the surface of the core material layer mixture, and then cover the surface with a release film to form a composite structure of release film-lower organic / inorganic composite base layer-core material layer-upper organic / inorganic composite base layer-release film; (4) The above composite structure is compacted using a pressure roller to obtain a sandwich structure of the desired thickness; (5) Curing the compacted sandwich structure to obtain the sandwich structure fireproof core material.

6. The preparation method according to claim 5, characterized in that: In step (1), stir at a speed of 45-60 rpm.

7. The preparation method according to claim 5, characterized in that: In step (2), white cement and sodium gluconate retarder are stirred at a speed of 45–60 rpm for 5–6 minutes. After adding aluminum hydroxide, magnesium hydroxide, 400-mesh calcium powder, 1000-mesh calcium powder, 400-mesh wollastonite powder, fly ash, 400-mesh dolomite powder and 400-mesh quartz powder, the mixture is stirred at a speed of 60–70 rpm for 1–2 minutes. After adding alkali-resistant glass short fibers, vinyl acetate-ethylene copolymer emulsion and water, the mixture is stirred at a speed of 55–65 rpm. The total stirring time is 15–17 minutes.

8. The preparation method according to claim 5, characterized in that: In step (3), the coating is applied by roller coating, with the roller temperature being 50-90℃; and pre-curing is performed by hot air at 60-80℃.

9. The preparation method according to claim 5, characterized in that: In step (4), compaction is carried out at room temperature and 5-10 MPa pressure; preferably, the compaction is carried out by alternating longitudinal and transverse pressure of the roller press.

10. The preparation method according to claim 5, characterized in that: In step (5), the board is first cured at 40-60℃ and relative humidity >90% for 2-4 hours, then the upper and lower release films are removed to complete the demolding, and the demolded board is naturally cured at 20-35℃ for at least 24 hours.

Images