Cement-based polyphenyl thermal insulation board and preparation method thereof

Abstract

This invention discloses a cement-based polystyrene insulation board and its preparation method, belonging to the field of building energy conservation technology. The insulation board comprises, along its thickness direction, a base bonding layer, an insulation core layer, and a weather-resistant finishing layer. These three layers form an integrated, continuous gradient structure without rigid interfaces, with thickness proportions of 18-23%, 55-65%, and 18-23%, respectively. The dry powder raw materials for each layer include silicate cement, desulfurized gypsum, slag powder, graphene polystyrene particles, latex powder, nano-silica, lignin fiber, composite flame retardant, hydroxypropyl methylcellulose ether, and a chlorine-free composite early-strength agent. This invention, through its functionally graded formulation and continuous gradient structure, eliminates interlayer interfaces, achieving low thermal conductivity, Class A fire resistance, high bonding strength, and rapid demolding. Furthermore, it makes extensive use of industrial solid waste, making it environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of building energy conservation technology, specifically to a cement-based polystyrene insulation material and its preparation method. Background Technology

[0002] Cement-based polystyrene insulation board is a lightweight insulation board made of cement as cementitious material and polystyrene foam particles as lightweight aggregate, with the addition of various admixtures. It combines the durability of inorganic materials with the excellent thermal insulation performance of organic materials and is widely used in external wall insulation systems.

[0003] Polystyrene particles exhibit significant hydrophobicity, which can lead to poor fluidity when used as aggregate in lightweight concrete preparation, or aggregate floating when the water-cement ratio is high. Existing technologies using a "constant volume-cold pressing" process to prepare cement-based polystyrene particle composite insulation materials have shown poor homogeneity and significant fluctuations in physical and mechanical properties in specimens cut from different parts of the green body, according to mass, thermal conductivity, and strength tests. Key factors affecting homogeneity include paste properties, mixture properties, uniform distribution, and green body thickness. Furthermore, existing cement-based polystyrene particle insulation boards exhibit compressive strength no higher than 0.35 MPa when the thermal conductivity is below 0.06 W / (m·K). Excessive polystyrene particle content results in insufficient strength, while insufficient content leads to insufficient thermal conductivity, highlighting a significant contradiction between strength and insulation performance. Therefore, achieving uniform dispersion of organic aggregates in an inorganic matrix and improving board strength while maintaining low thermal conductivity remain long-standing technical challenges in this field.

[0004] In terms of structural design, existing composite insulation boards mostly adopt a multi-layered, physically bonded "sandwich" structure, where the insulation core layer is bonded to two cement-based protective layers on both sides using adhesives. This structure has a significant weak interface layer. Due to inconsistencies in shrinkage rates and elastic moduli between different material layers, peeling, hollowing, and even detachment can easily occur at the interface during long-term use. Existing research indicates that the reasons for insulation layer detachment in external wall insulation systems are complex. The insulation board is mainly bonded to the base wall using adhesives. If the adhesive quality is poor, the tensile bond strength between the adhesive and the base wall or the insulation board is low, or if the insulation board itself has low strength, detachment of the insulation layer is likely to occur. Some patent literature describes solutions to the problems of easy delamination and poor integrity of composite insulation boards by setting grooves between the inner cement-based polymer mortar layer and the core insulation board, or by adding connectors. However, these solutions often require the introduction of additional connecting components or secondary processing of the core material, increasing the complexity of the production process and manufacturing costs.

[0005] Regarding functionally graded structures, existing technologies have introduced the design principles of functionally graded materials into the field of thermal insulation materials. For example, one patent discloses a geopolymer exterior wall insulation board with controllable porosity gradient, which achieves a balance between insulation and strength by distributing air bubbles in a gradient with thickness within the insulation board. Another patent discloses a functionally graded foamed concrete insulation material, which achieves a gradual increase in mechanical strength and a gradual decrease in thermal conductivity from the outside to the inside by continuously varying the pore size and porosity from the core surface to the outside. However, these solutions mainly achieve performance gradients by controlling the amount of foaming agent and the pore distribution. The foaming process itself has problems such as uncontrollable pore structure, large strength loss, and large dimensional changes after carbonization leading to cracking of the decorative layer. Furthermore, it is difficult to achieve low thermal conductivity while maintaining Class A fire resistance.

[0006] In summary, developing a cement-based polystyrene insulation board and its preparation method that can combine low thermal conductivity and high mechanical strength, form a continuous gradient transition between functional layers to eliminate weak interfacial layers, and have synergistic matching properties of the slurry in each layer, is of great practical significance for improving the safety and durability of building exterior wall insulation systems. Summary of the Invention

[0007] To address the aforementioned technical problems in the prior art, this invention aims to provide a cement-based polystyrene insulation board and its preparation method that combines low thermal conductivity with high mechanical strength, forms a continuous gradient transition between functional layers to eliminate weak interfacial layers, and has synergistically matched slurry properties in each layer.

[0008] One objective of this invention is to provide a cement-based polystyrene insulation board, wherein the insulation board comprises, along its thickness direction, a base bonding layer, an insulation core layer, and a weather-resistant finishing layer, the three layers forming an integrated continuous gradient structure without rigid interfaces, and the thickness ratios of the base bonding layer, the insulation core layer, and the weather-resistant finishing layer being 18-23%, 55-65%, and 18-23%, respectively. The raw material composition of each layer of dry powder, by weight, is as follows: The base bonding layer comprises: 43-47 parts silicate cement, 10-12.5 parts desulfurized gypsum, 8-10 parts slag powder, 10-14 parts graphene polystyrene particles, 3.0-3.5 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.1-1.4 parts hydroxypropyl methylcellulose ether, and 4.0-4.5 parts chlorine-free composite early strength agent; The thermal insulation core layer comprises: 34-38 parts silicate cement, 12-15 parts desulfurized gypsum, 8-10 parts slag powder, 22-26 parts graphene polystyrene particles, 3.8-4.2 parts latex powder, 0.9-1.1 parts nano silica, 0.4-0.6 parts lignin fiber, 1.1-1.3 parts composite flame retardant, 1.4-1.6 parts hydroxypropyl methylcellulose ether, and 1.5-2.0 parts chlorine-free composite early strength agent; The weather-resistant finishing layer comprises: 39-42 parts silicate cement, 8-10 parts desulfurized gypsum, 8-10 parts slag powder, 12-16 parts graphene polystyrene particles, 3.3-3.7 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.2-1.4 parts hydroxypropyl methylcellulose ether, and 2.0-2.5 parts chlorine-free composite early strength agent.

[0009] Preferably, the insulation board has a thickness of 50-120mm, and there is a continuous transition area with a thickness of 1-3mm between two adjacent layers.

[0010] Preferably, the lignin fiber is alkali-resistant lignin fiber, the length of the alkali-resistant lignin fiber in the base bonding layer is 0.4~0.6mm, the length of the alkali-resistant lignin fiber in the heat insulation core layer is 0.7~0.85mm, and the length of the alkali-resistant lignin fiber in the weather-resistant finishing layer is 0.9~1.1mm.

[0011] Preferably, the alkali-resistant lignin fiber has an aspect ratio of 20~30:1, a fracture strength retention rate of ≥90% after soaking in cement alkali solution for 28 days, and a moisture content of ≤5%; the fiber length difference between adjacent layers is ≤0.4mm.

[0012] Preferably, the graphene polystyrene particles are internally dispersed foamed polystyrene particles, prepared by secondary surface modification with silane coupling agent-nano silica; the particle size of the graphene polystyrene particles is 1.0~3.0 mm, and the bulk density is 20~25 kg / m³. 3 The closed-pore rate is ≥99%, and the graphene content is 0.10~0.15%.

[0013] Preferably, the composite flame retardant is a mixture of aluminum hydroxide and montmorillonite in a mass ratio of 4:1, with a fineness ≥100 mesh; the chlorine-free composite early strength agent is a mixture of aluminum sulfate, lithium carbonate, and nano-calcium carbonate in a mass ratio of 6:1:3.

[0014] Preferably, the silicate cement is grade 42.5 silicate cement.

[0015] Preferably, the desulfurized gypsum is an industrial solid waste byproduct of flue gas desulfurization in power plants, with calcium sulfate dihydrate as its main component, a fineness ≥80 mesh, and a moisture content ≤10%.

[0016] Preferably, the slag powder is S95 grade slag powder with a fineness ≥400 mesh and a 28-day activity index ≥95%.

[0017] Preferably, the latex powder is an ethylene-vinyl acetate type redispersible latex powder.

[0018] Preferably, the hydroxypropyl methylcellulose ether has a viscosity of 100,000 mPa·s and a water retention rate of ≥90%; the lignin fiber is an alkali-resistant lignin fiber with a length of 0.5~1.0 mm.

[0019] Preferably, the particle size of the nano-silica is 50~100nm.

[0020] A second objective of this invention is to provide a method for preparing the insulation board as described above, the method comprising the following steps: (1) Slurry preparation The dry powders of the base bonding layer, the thermal insulation core layer, and the weather-resistant finishing layer are mixed with water to prepare the base bonding layer slurry, the thermal insulation core layer slurry, and the weather-resistant finishing layer slurry, respectively. The amount of water is 30-35% of the weight of the dry powder of each layer. The slump deviation of the three-layer slurry should be controlled to be ≤20mm, the plastic viscosity deviation to be ≤15%, and the initial setting time deviation to be ≤30min. (2) Fabric and molding The three-layer slurry is distributed through three feeding ports. All three feeding ports are flat, continuous openings with the same width as the inner cavity of the mold. The three-layer slurry is distributed using a single-stroke progressive and closely following feeding process. During the feeding process, the distance between any two adjacent feeding ports is 30-50mm, and the travel speed of the three feeding ports is 1.5-2m / min. Throughout the process, the fabric is subjected to low-frequency micro-vibration of 30~50Hz and amplitude of 0.3~0.5mm on the mold, which allows the adjacent layers of slurry to penetrate and fuse in both directions, forming a continuous transition area with a thickness of 1~3mm. (3) Maintenance After molding, the mold is allowed to stand for 24 hours at room temperature (20±5℃) before demolding. After demolding, the blank is cured with low-temperature steam at 40℃ for 24 hours, and then cured for 3 days at room temperature and humidity (60~70%).

[0021] Preferably, in step (1), the feeding sequence of the slurry preparation is as follows: first, silicate cement, desulfurized gypsum, slag powder and lignin fiber are dry mixed at 300 r / min for 3 min, then other components except graphene polystyrene particles are added and dry mixed for 1 min, water is added and wet mixed at 200 r / min for 3 min, and finally graphene polystyrene particles are added and stirred at 100 r / min at low speed for 2 min.

[0022] Preferably, the viscosity of the three-layer slurry is matched by adjusting the amount of hydroxypropyl methylcellulose ether and the amount of water added during mixing, with a slump of 180±10mm as the viscosity benchmark.

[0023] The beneficial effects of this invention include: 1. Through continuous gradient structural design, weak interlayer layers are eliminated, significantly improving the integrity and durability of the board. The insulation board of this invention comprises, along its thickness direction, a base bonding layer, an insulation core layer, and a weather-resistant finishing layer, with the thickness proportions of the three layers being 18-23%, 55-65%, and 18-23%, respectively. It employs an integrated, continuous gradient structure without rigid interfaces. Unlike the sandwich structure of existing technologies that physically bond multiple layers with adhesives, the three layers of this invention do not have distinct interfaces, avoiding peeling, hollowing, or detachment problems caused by inconsistent shrinkage rates and elastic moduli between different layers. Simultaneously, the reasonable thickness distribution (the core layer accounting for 55-65% ensures the insulation effect, while the other two layers each accounting for 18-23% ensure bonding strength and surface protection) ensures symmetrical shrinkage and deformation of the entire board under temperature and humidity changes, reducing the risk of warping and significantly improving the safety and durability of the insulation board during long-term use.

[0024] 2. Through functionally graded formulation design, a synergistic optimization of low thermal conductivity and high mechanical strength is achieved. Based on the functional requirements of each layer, this invention employs a gradient design for key components such as the cementitious material system, the amount of polystyrene particles, and the amount of early-strength agent. The thermal insulation core layer has the highest content of graphene polystyrene particles (22-26 parts) and the content of silicate cement is relatively low (34-38 parts), thereby maximizing the reduction of thermal conductivity and achieving high-efficiency thermal insulation. The base bonding layer has the highest content of silicate cement (43~47 parts) and the highest content of chloride-free composite early strength agent (4.0~4.5 parts), which ensures high bonding strength with the wall and early anchoring ability; The formulation of the weather-resistant finishing layer is between the two (39-42 parts silicate cement and 12-16 parts polystyrene particles), which takes into account both surface crack resistance and durability.

[0025] In the three-layer formulation, the mass ratio of silicate cement, desulfurized gypsum, and slag powder is maintained within the range of (3.8~7.0):(0.8~2.0):1, forming a consistent gradient variation. This functional gradient design allows for a smooth transition between mechanical and thermal insulation properties along the thickness direction, overcoming the contradiction between strength and thermal insulation that is difficult to balance in existing technologies. This enables the insulation board to achieve a dry density of 220~240 kg / m³. 3 Under these conditions, it can also achieve a low thermal conductivity while possessing sufficient bonding strength and impact resistance.

[0026] 3. Through the ternary solid waste coagulation system, high-value utilization of industrial by-products was achieved and the heat of hydration was reduced. This invention incorporates desulfurized gypsum and slag powder into each layer, which, together with silicate cement, form a ternary synergistic cementitious system. The desulfurized gypsum provides Ca... 2+ and SO4 2- Ions activate the pozzolanic activity of slag; slag powder fills the capillary pores of cement stone, improving density and later-stage strength. The total content of desulfurized gypsum and slag powder in this system reaches a high level in each layer, not only significantly reducing industrial solid waste and meeting the requirements of green and low-carbon development, but also significantly reducing the heat of cement hydration, decreasing the risk of cracking in thick plates due to internal and external temperature differences, and improving the long-term volume stability and durability of the plates.

[0027] 4. Through the synergistic effect of chlorine-free composite early-strength agent and flame retardant, a balance between rapid demolding and Class A fire resistance is achieved. This invention employs a chloride-free composite early-strength agent, which does not introduce chloride ions, thus avoiding the risk of steel reinforcement corrosion. This allows the boards to be demolded after 24 hours of curing at room temperature, significantly improving production efficiency. Furthermore, composite flame retardants are added to each layer, achieving a Class A fire resistance rating for the insulation board. Unlike existing technologies that rely on foaming agents or large amounts of organic flame retardants, this invention achieves both low thermal conductivity and Class A fire resistance entirely through the closed-cell structure of graphene polystyrene particles and the flame retardant system, without adding any foaming agents. This avoids problems such as uncontrollable pore structure and significant strength loss associated with foaming processes.

[0028] 5. Excellent overall performance, with comprehensive indicators significantly superior to existing similar products. Through the combined effect of the above-mentioned technical features, the insulation board of the present invention can achieve the following performance indicators: dry density 220~240kg / m³ 3 It has a low thermal conductivity and achieves a Class A fire rating. Compared to existing cement-based polystyrene insulation boards, this invention significantly reduces thermal conductivity while maintaining Class A fire resistance, and also possesses higher bonding strength and crack resistance, providing a safe, efficient, and durable solution for external wall insulation systems in high-rise buildings. Detailed Implementation

[0029] The following description includes certain specific details to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented without employing one or more of these specific details, but using other methods, components, materials, etc.

[0030] Unless otherwise required by the present invention, throughout the specification and the following claims, the words “comprising” and “including” shall be interpreted in an open-ended, inclusive sense, meaning “including but not limited to”.

[0031] Throughout this specification, the terms "an embodiment," "an embodiment," "a preferred embodiment," or "some embodiments" refer to including, in at least one embodiment, a specific reference element, structure, or feature associated with that embodiment. Therefore, the phrases "in an embodiment," "in a preferred embodiment," or "in some embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. Furthermore, specific elements, structures, or features may be combined in one or more embodiments in any suitable manner.

[0032] According to a first aspect of the present invention, a cement-based polystyrene insulation board is provided, wherein the insulation board comprises, in sequence along the thickness direction, a base bonding layer, an insulation core layer and a weather-resistant finishing layer, the three layers being an integrated continuous gradient structure without rigid interfaces, and the thickness ratios of the base bonding layer, the insulation core layer and the weather-resistant finishing layer being 18~23%, 55~65% and 18~23%, respectively.

[0033] In this invention, the thickness percentage of the base bonding layer is, for example, 18%, 19%, 20%, 21%, 22%, or 23%. The thickness percentage of the thermal insulation core layer is, for example, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, or 65%. The thickness percentage of the weather-resistant finishing layer is, for example, 18%, 19%, 20%, 21%, 22%, or 23%.

[0034] Preferably, the thickness ratios of the base bonding layer, the thermal insulation core layer, and the weather-resistant finishing layer are 20%, 60%, and 20%, respectively.

[0035] The raw material composition of each layer of dry powder, by weight, is as follows: The base bonding layer comprises: 43-47 parts silicate cement, 10-12.5 parts desulfurized gypsum, 8-10 parts slag powder, 10-14 parts graphene polystyrene particles, 3.0-3.5 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.1-1.4 parts hydroxypropyl methylcellulose ether, and 4.0-4.5 parts chlorine-free composite early strength agent; The thermal insulation core layer comprises: 34-38 parts silicate cement, 12-15 parts desulfurized gypsum, 8-10 parts slag powder, 22-26 parts graphene polystyrene particles, 3.8-4.2 parts latex powder, 0.9-1.1 parts nano silica, 0.4-0.6 parts lignin fiber, 1.1-1.3 parts composite flame retardant, 1.4-1.6 parts hydroxypropyl methylcellulose ether, and 1.5-2.0 parts chlorine-free composite early strength agent; The weather-resistant finishing layer comprises: 39-42 parts silicate cement, 8-10 parts desulfurized gypsum, 8-10 parts slag powder, 12-16 parts graphene polystyrene particles, 3.3-3.7 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.2-1.4 parts hydroxypropyl methylcellulose ether, and 2.0-2.5 parts chlorine-free composite early strength agent.

[0036] In this invention, the base bonding layer is mainly used for anchoring to the wall and bearing loads, requiring high strength, rapid hardening, and reliable bonding. The thermal insulation core layer is the core insulation and stress buffer layer, requiring low thermal conductivity, lightweight, and high toughness. The weather-resistant finishing layer is mainly used to resist environmental erosion and cracking, requiring high density, crack resistance, and aging resistance. This invention decomposes multiple performance requirements that a single homogeneous material cannot simultaneously meet into three functional layers, each focusing on achieving its core function, avoiding the trade-offs in performance optimization of a single material. A transition zone with gradual compositional changes and no clear interface is formed between adjacent layers. The material properties change continuously within the transition zone, eliminating stress concentration points and preventing interfacial stress caused by differences in shrinkage rate and elastic modulus during temperature and humidity changes, thus preventing peeling during long-term service.

[0037] A core layer thickness of 55-65% ensures sufficient insulation path length, providing structural support for achieving low thermal conductivity. The remaining two layers, each 15-25%, guarantee bonding strength and surface protection. Simultaneously, the symmetrical design ensures symmetrical deformation of the entire board during drying and thermal shrinkage, reducing the risk of warping and significantly improving the safety and durability of the insulation board during long-term use.

[0038] In this invention, the base bonding layer, the thermal insulation core layer, and the weather-resistant finishing layer all use a ternary cementitious system of silicate cement + desulfurized gypsum + slag powder. Silicate cement provides early strength and hydration products (CSH gel, Ca(OH)2), while desulfurized gypsum provides Ca... 2+ and SO4 2- It regulates setting time, inhibits shrinkage, and slag powder fills capillary pores, participates in secondary hydration, and improves later strength.

[0039] Desulfurized gypsum can activate slag activity; the dissolution of desulfurized gypsum produces Ca. 2+ and SO4 2- It reacts with active Al2O3 and SiO2 in the slag to form ettringite (AFt) and CSH gel. The ettringite crystals fill the pores and increase the density; the CSH gel is the main source of strength.

[0040] Slag powder can be used for both physical filling and chemical reinforcement. With a fineness ≥400 mesh, slag powder has a particle size smaller than cement particles, allowing it to fill the capillary pores (approximately 0.1~10μm in diameter) in cement stone, thus densifying the structure. The active SiO2 in the slag undergoes a secondary pozzolanic reaction with Ca(OH)2 produced during cement hydration: Ca(OH)2 + SiO2 + H2O → CSH. This reaction consumes the weaker Ca(OH)2 crystals in the cement stone, generating a stronger CSH gel.

[0041] Replacing part of the cement with slag powder and desulfurized gypsum (total replacement amount ≥35%) reduces cement usage, lowers heat of hydration, and prevents thick plates from cracking due to internal and external temperature differences.

[0042] Desulfurized gypsum is a byproduct of flue gas desulfurization in power plants, and slag powder is a byproduct of blast furnace ironmaking, thus realizing the high-value utilization of industrial solid waste.

[0043] The mass ratio of silicate cement, desulfurized gypsum, and slag powder in the three layers all meet the requirement of (3.8~7.0):(0.8~2.0):1. The cement, gypsum, and slag in each layer utilize a cementitious system with the same proportion range, ensuring the continuity of the chemical composition of the materials in each layer. When the three layers of slurry interpenetrate in a wet state, the similar chemical composition prevents adverse reactions (such as incompatible precipitation) in the penetration area, facilitating the formation of a defect-free gradient transition zone. Simultaneously, by adjusting the absolute dosage (rather than the proportion) of the three components, the performance differences between the layers are achieved, ensuring the stable formation of the gradient structure.

[0044] Graphene polystyrene particles are the core functional aggregate for achieving lightweight insulation in this invention. In the three layers, their content exhibits a gradient distribution: highest in the insulation core layer (22-26 parts), moderate in the weather-resistant finishing layer (12-16 parts), and lowest in the base bonding layer (10-14 parts). As the most important insulation layer of the entire panel, the insulation core layer needs to have its thermal conductivity minimized.

[0045] The higher the graphene-polystyrene particle content, the lower the dry density of the board, the higher the gas phase porosity, and the lower the thermal conductivity. A content of 22-26 parts per unit area in the insulation core layer is the upper limit while ensuring the wet-state molding stability and basic strength of the core layer. The insulation core layer does not directly bear external shear and pull-out forces, so the absolute strength requirement is relatively low, allowing for a sacrifice of some cement matrix strength in exchange for higher insulation performance. Simultaneously, the lowest cement content (34-38 parts per unit area) in the insulation core layer forms a combination of low-cementing material and high-lightweight aggregate with the high-content particles, further reducing density and thermal conductivity. Meanwhile, the highest cellulose ether content (1.4-1.6 parts per unit area) in the insulation core layer provides sufficient slurry viscosity and water retention, preventing the high-content polystyrene particles from floating in a wet state. The lowest early-strength agent content (1.5-2.0 parts per unit area) in the insulation core layer avoids shrinkage cracking caused by premature hardening, while also providing a longer process window for uniform particle distribution.

[0046] As the anchoring layer in direct contact with the wall, the base bonding layer needs to provide high bond strength, high shear capacity, and dimensional stability. Polystyrene particles are low-modulus, low-strength organic materials; excessive dosage will significantly reduce the overall strength and elastic modulus of the cement paste, weakening the anchoring ability between the bonding layer and the wall. A dosage of 10-14 parts is the minimum particle content to ensure that the bonding layer has a sufficiently continuous cementitious phase, ensuring that the cement paste forms a complete three-dimensional skeleton capable of effectively transferring and bearing loads. Lower particle content also means higher dry density and lower porosity, which is beneficial for increasing the contact area and bond strength with the bonding mortar. Meanwhile, the base bonding layer has the highest cement content (43~47 parts), which, together with the low particle content, forms a combination of high cementitious material and low lightweight aggregate to maximize mechanical properties; the early strength agent content is the highest (4.0~4.5 parts), ensuring that the board quickly establishes anchoring strength after being installed on the wall, preventing displacement or detachment due to its own weight or wind pressure; the nano silica content is relatively high (1.0~1.2 parts), further filling the capillary pores of cement stone and improving the interface density and bonding strength.

[0047] As a protective layer directly exposed to the external environment, the weather-resistant finishing layer needs to possess crack resistance, impact resistance, and a certain degree of thermal insulation contribution. The finishing layer needs to resist temperature stress, drying shrinkage stress, and external impact. Excessive polystyrene particle content will reduce the tensile strength and elastic modulus of the cementitious material, increasing the risk of cracking. A moderate content of 12-16 parts ensures sufficient continuous cementitious phase to guarantee surface strength and impact resistance, while maintaining a certain degree of flexibility to allow the finishing layer to adapt to the temperature and humidity deformation of the substrate. This moderate content also ensures that the finishing layer contributes to thermal insulation, avoiding becoming a thermal bridge channel for the entire slab, while maintaining performance continuity with adjacent core layers. In the weather-resistant finishing layer, a moderate cement content (39-42 parts) falls between the bonding layer and the core layer, forming a smooth strength gradient transition; a moderate latex powder content (3.3-3.7 parts) provides sufficient flexibility and adhesion to prevent surface cracking. The appropriate amount of cellulose ether (1.2~1.4 parts) ensures the water retention and workability of the surface slurry and avoids plastic cracking caused by excessive water loss.

[0048] The gradient variation in particle content across the three layers, along with the gradient variations in cement, early-strength agent, and cellulose ether content, creates a multi-dimensional synergy, resulting in a continuous, rather than abrupt, change in the physical properties (strength, modulus, density, and thermal conductivity) of the entire panel along its thickness. When the three layers of slurry interpenetrate in a wet state to form a continuous gradient transition zone, a smooth transition of performance is achieved, eliminating the interfacial stress concentration problem common in traditional composite panels. The gradient in graphene-polystyrene particle content is one of the core carriers of the panel's "functional gradient structure." By differentially distributing this key functional aggregate along the thickness direction, each layer can achieve excellent performance under its specific service environment. Simultaneously, through the synergistic effect of the multi-dimensional gradient, a smooth transition and overall optimization of the panel's performance are achieved.

[0049] This invention does not add any foaming agent; the heat insulation and lightweight effect are entirely provided by graphene polystyrene particles, completely avoiding the problems of uncontrollable pore structure, large strength loss, and high water absorption caused by the foaming process.

[0050] In a preferred embodiment of the present invention, the insulation board has a thickness of 50-120 mm, and there is a continuous transition region with a thickness of 1-3 mm between two adjacent layers.

[0051] In this invention, a 50mm thickness of the insulation board corresponds to a 10mm base bonding layer, a 30mm insulation core layer, and a 10mm weather-resistant finishing layer, ensuring the core function of each layer. Below this thickness, it is difficult to achieve uniform material distribution and stable interlayer permeability between the upper and lower functional layers, resulting in poor gradient structure design. A 120mm thickness of the insulation board corresponds to a 24mm base bonding layer, a 72mm insulation core layer, and a 24mm weather-resistant finishing layer, which is beneficial for balancing insulation performance, structural safety, and crack resistance. Exceeding this thickness significantly increases the board's weight, raising the safety risks of the external wall bonding and anchoring system. Simultaneously, the internal stress from hydration shrinkage and temperature deformation of the board surges, potentially leading to overall cracking.

[0052] Insulation board thickness of 50-80mm is suitable for exterior wall insulation systems in hot-summer and cold-winter regions or those meeting general energy-saving standards. 80-100mm thickness is suitable for cold regions or buildings with higher energy-saving standards (such as 65% energy saving rate). 100-120mm thickness is suitable for extremely cold regions or passive ultra-low energy consumption buildings, meeting even higher insulation performance requirements.

[0053] In this invention, the continuous transition zone with a thickness of 1-3 mm is formed during the fabric forming process through the interpenetration between two adjacent layers. Within this transition zone, the composition and properties of the materials gradually change. When temperature changes or shrinkage occurs, the transition zone acts as a "buffer zone," absorbing and dissipating interlayer stress instead of concentrating stress on a fragile adhesive line. This significantly improves the insulation board's peel resistance and long-term service safety. If the transition zone is too thin (<1 mm), the gradient effect is not obvious, and stress concentration may still exist; if the transition zone is too thick (>3 mm), it will encroach on the effective thickness of the insulation core layer, potentially reducing the overall insulation efficiency of the board and also affecting the independent performance of each functional layer.

[0054] In a preferred embodiment of the present invention, the lignin fiber is an alkali-resistant lignin fiber, the length of the alkali-resistant lignin fiber in the base bonding layer is 0.4~0.6mm, the length of the alkali-resistant lignin fiber in the heat insulation core layer is 0.7~0.85mm, and the length of the alkali-resistant lignin fiber in the weather-resistant finishing layer is 0.9~1.1mm.

[0055] In this invention, alkali-resistant lignin fiber refers to fiber that has undergone alkali-resistant modification treatment (such as acetylation, graft copolymerization, surface coating with alkali-resistant resin, etc.). After cement hydration, the interior of the matrix is ​​a strongly alkaline environment with a pH of 12-14. Ordinary lignin fibers will be degraded and brittle by alkali solutions within 3-5 years. The alkali-resistant lignin fiber selected in this invention can maintain stable performance in the highly alkaline environment of cement, which is a fundamental prerequisite for the long-term effectiveness of cross-layer fiber bridging networks.

[0056] In this invention, the lignin fibers in the base bonding layer are 0.4~0.6mm in length. The short fiber length allows for more uniform dispersion in the high cementitious matrix, making it less prone to agglomeration and preventing damage to the density of the cementitious matrix. This ensures the bonding strength and impermeability of the wall, avoiding the problems of increased porosity and decreased bonding strength on the base surface caused by long fibers. It can also evenly disperse the concentrated stress during anchor fixing, preventing localized cracking of the board, while effectively inhibiting early hydration shrinkage microcracks in the base layer, ensuring the integrity of the bonding surface.

[0057] The lignin fibers in the insulation core layer are 0.7~0.85mm in length. This length helps to suppress the shrinkage of the large-volume matrix, restrain the floating of polystyrene particles, and support the bridging of the upper and lower fiber layers. The fiber length is matched with the maximum thickness of the core layer (60%), which can form a uniform three-dimensional randomized crack-resistant network inside the core layer. This effectively suppresses the hydration shrinkage cracks of the large-volume cementitious matrix, while restraining the high-dosage graphene polystyrene particles, preventing particle floating and delamination during the fabric application process, and ensuring the uniformity of the core layer's insulation performance.

[0058] The weather-resistant alkali-resistant lignin fiber in the surface layer is 0.9~1.1mm in length. As a protective barrier against the external environment, the surface layer's core functions are crack resistance, impact resistance, weather resistance, aging resistance, and resistance to temperature changes and freeze-thaw cycles. The surface layer is directly exposed to external ultraviolet radiation, alternating wet and dry conditions, and freeze-thaw cycles, making it a high-risk area for cracking. Long fibers can form a denser, higher-strength crack-resistant network in the surface layer, significantly improving its flexural strength and impact resistance, effectively inhibiting surface shrinkage cracks and temperature-induced cracks, and preventing chipping and damage during transportation and installation.

[0059] In the transition region between the base layer and the core layer, the short fibers (0.4~0.6mm) of the base layer and the medium-length fibers (0.7~0.85mm) of the core layer complement each other due to their length difference. The ends of the short fibers are embedded in the core layer, and the ends of the medium-length fibers are embedded in the base layer, interweaving with each other. In the transition region between the core layer and the surface layer, the medium-length fibers (0.7~0.85mm) of the core layer and the long fibers (0.9~1.1mm) of the surface layer also overlap, with the ends of the long fibers embedded in the core layer and the ends of the medium-length fibers embedded in the surface layer. Thus, the three layers of fibers construct a continuous interlayer bridging network in the transition region, further optimizing the three-layer structure into an inseparable integrated whole.

[0060] Meanwhile, the synergistic effect of the fiber length gradient and the viscosity matching design of the three-layer slurry further stabilizes the flowability of the three-layer slurry, preventing sagging and mixing during the fabric application process. Small-scale production verification shows that the synergistic effect of the fiber length gradient design and slurry viscosity matching in this scheme allows for layer thickness deviation to be controlled within ±0.5mm, achieving a whole-board yield of over 98%. This is a significant improvement over the conventional uniform fiber blending process (yield of approximately 85-90%), effectively reducing the cost of waste products during mass production.

[0061] Furthermore, the three specifications of 0.4~0.6mm, 0.7~0.85mm, and 0.9~1.1mm can cover the core general-purpose models of 0.5mm, 0.8mm, and 1.0mm that are commonly produced in the market. They can be purchased directly from stock without the need for customized production, and the cost is controllable.

[0062] In a preferred embodiment of the present invention, the aspect ratio of the lignin fiber is 20~30:1, the fracture strength retention rate is ≥90% after soaking in cement alkali solution for 28 days, the moisture content is ≤5%, and the fiber length difference between adjacent layers is ≤0.4mm.

[0063] In this invention, the aspect ratio of the lignin fiber is 20-30:1, meaning the ratio of fiber length to diameter (L / D) is controlled between 20 and 30. If the aspect ratio is too small (<20), the contact area between the fiber and the matrix is ​​insufficient, resulting in poor stress transfer and weak reinforcement. If the aspect ratio is too large (>30), the fiber is prone to entanglement and agglomeration in the slurry, affecting dispersion uniformity and potentially significantly increasing slurry viscosity and reducing workability. A lignin fiber with an aspect ratio of 20-30:1 provides sufficient anchoring length while maintaining good dispersion during mixing and spreading.

[0064] After immersing the fibers in a simulated cement pore solution (a saturated calcium hydroxide solution with a pH of ≈12~13 or actual cement slurry filtrate) for 28 days, the ratio of their tensile strength to their original strength before immersion is no less than 90%. The matrix interior after cement hydration is a strongly alkaline environment (pH 12~14). In this environment, the hemicellulose and lignin of ordinary plant fibers (such as untreated wood pulp fibers) gradually undergo alkaline degradation, leading to fiber embrittlement, a significant decrease in strength, and typically the loss of reinforcing function within 3~5 years. A ≥90% 28-day strength retention rate means that the fibers are almost undamaged during the most intense 28 days of cement hydration, enabling them to participate in the early reinforcement of the matrix throughout the process. Furthermore, based on aging kinetics calculations, long-term stability is expected to be maintained in an alkaline environment, with an expected service life matching that of the main building structure.

[0065] The moisture content of lignin fiber ≤5% means that the moisture content (by mass) of the fiber before it is added to the dry powder does not exceed 5%. This is because lignin fiber is hydrophilic and easily absorbs moisture from the air. Excessive moisture content can lead to the following problems: during the dry powder premixing stage, high moisture content fibers can cause powder clumping and uneven dispersion; high moisture content fibers can absorb a large amount of free water, affecting the precise control of the water-cement ratio, and consequently affecting the fluidity and hydration reaction of the slurry; fluctuations in moisture content can lead to unstable performance in each batch of slurry.

[0066] The fiber length difference between two adjacent layers is ≤0.4mm, which means that the fiber length difference between the base bonding layer and the insulation core layer, and the fiber length difference between the insulation core layer and the weather-resistant finishing layer are both no more than 0.4mm. The fiber lengths of adjacent layers will not differ too much, which is conducive to the interpenetration, overlapping and entanglement of fibers in the interlayer transition area, forming a continuous cross-layer bridging network.

[0067] In a preferred embodiment of the present invention, the graphene polystyrene particles are internally dispersed foamed polystyrene particles, prepared by secondary surface modification with a silane coupling agent-nano silica; the graphene polystyrene particles have a particle size of 1.0~3.0 mm and a bulk density of 20~25 kg / m³. 3 The closed-pore rate is ≥99%, and the graphene content is 0.10~0.15%.

[0068] In this invention, within the graphene-dispersed foamed polystyrene particles, graphene forms a three-dimensional thermally conductive network within the PS matrix, while its sheet structure creates a randomly oriented thermal reflective barrier within the cell walls. This internally dispersed structure causes heat to be repeatedly reflected, scattered, and blocked by the graphene sheets as it propagates within the cell walls, significantly reducing heat conduction efficiency.

[0069] Methods for modifying graphene polystyrene particles using a secondary process involving silane coupling agents and nano-silica include: By weight; First, weigh 100 parts of graphene polystyrene particles and dry them in an oven at 45°C for 2 hours for later use. Then, weigh out nano-silica (particle size 50~100nm, specific surface area ≥600m²). 2 3 parts of (g) were dispersed in 50 parts of anhydrous ethanol and ultrasonically dispersed for 30 min to obtain a uniform nano-silica alcohol dispersion. Then, 5 parts of vinyltriethoxysilane (VTES) were dissolved in a mixed solvent of 30 parts anhydrous ethanol and 13.8 parts deionized water. The pH was adjusted to 4.0 with glacial acetic acid, and the mixture was stirred at room temperature for 30 min to allow for complete hydrolysis. Subsequently, the nano-silica alcohol dispersion was slowly added to the above hydrolysate, and stirring was continued for 30 min to allow the silanol groups on the surface of the nano-silica to undergo a pre-condensation reaction with the hydrolyzed silane coupling agent. Finally, 0.2 parts of benzoyl peroxide (BPO) and 1 part of dibutyltin dilaurate were added, and the mixture was stirred evenly to obtain the modified treatment solution. Then, the dried graphene polystyrene particles were added to the modification solution and stirred at low speed at room temperature for 40 minutes to allow the modification solution to fully wet the particle surface and cause a grafting reaction. Finally, the reacted particles were removed, washed twice with anhydrous ethanol, and dried at a low temperature of 55℃ for 3 hours to obtain graphene polystyrene particles with surface grafted and modified by nano-silica-silane coupling agent.

[0070] By grafting nano-silica onto the surface of graphene polystyrene particles through the "molecular bridging" effect of silane coupling agents, the particle surface changes from hydrophobic to hydrophilic, and Si-O-Si or Si-O-Ca chemical bonds can be formed at the particle-cement interface. This significantly improves the dispersibility and interfacial compatibility of nanoparticles in the polymer matrix, and further prevents polystyrene particles from floating and stratifying in cement paste.

[0071] In this invention, the diameter of the graphene polystyrene particles is distributed in the range of 1.0~3.0 mm. Particles with excessively small diameters (<1.0 mm) have an excessively large specific surface area, requiring more cement paste to coat them, which significantly increases the paste viscosity and water consumption, while reducing the particle packing efficiency in the paste. Particles with excessively large diameters (>3.0 mm) tend to have uneven distribution in boards with a thickness of 50~120 mm, especially in thinner base bonding layers and weather-resistant finishing layers. Particles with a diameter of 1.0~3.0 mm form appropriately sized cells after molding, which helps ensure sufficient porosity to reduce thermal conductivity while avoiding increased heat convection due to excessively large cells. 20~25 kg / m³ 3 A slightly higher bulk density also helps stabilize the suspension of particles in cement slurry, reducing stratification. A high closed-cell rate of ≥99% means that the cell walls are intact and undamaged, and the particles themselves have high compressive strength and elastic recovery ability, which helps the board maintain structural integrity when bearing loads.

[0072] In a preferred embodiment of the present invention, the composite flame retardant is a mixture of aluminum hydroxide and montmorillonite in a mass ratio of 4:1, with a fineness ≥100 mesh.

[0073] In this invention, aluminum hydroxide (ATH) accounts for 80% of the composite flame retardant. Upon heating, it undergoes a decomposition reaction: 2Al(OH)3 → Al2O3 + 3H2O↑. This reaction is strongly endothermic (absorbing approximately 1.97 kJ / g of heat), effectively reducing the surface temperature of the material. Simultaneously, the released water vapor dilutes the concentration of combustible gases, and the generated alumina (Al2O3) forms a heat-insulating protective layer. Montmorillonite (MMT) accounts for 20% of the composite flame retardant. Upon heating, the interlayer structure of montmorillonite collapses, forming a dense silicate carbon layer. This carbon layer possesses excellent heat insulation and oxygen barrier properties, effectively blocking heat transfer and oxygen diffusion. Aluminum hydroxide is the primary flame retardant, providing the main endothermic cooling and dilution / flame-suppressing effects; montmorillonite is the auxiliary flame retardant, providing charring enhancement and melt stabilization. In the initial stage of combustion (200~400℃): Aluminum hydroxide decomposes endothermally, releasing water vapor, which inhibits the pyrolysis of polystyrene particles and slows the spread of fire. In the middle and later stages of combustion (>400℃): After the aluminum hydroxide decomposes completely, the silicate carbon layer formed by montmorillonite continues to play an isolating role, preventing the flame from spreading into the interior of the board. A 4:1 ratio controls the total amount of flame retardant to 1.1~1.4 parts (slightly different for each layer), which helps to minimize the impact on the density and thermal conductivity of the board while ensuring Class A fire resistance.

[0074] The insulation board of this invention does not contain any foaming agent; its insulation performance relies entirely on the closed-cell structure of the graphene-polystyrene particles. This technical approach requires that the flame retardant not damage the closed-cell structure of the particles, nor introduce additional bubble defects. Aluminum hydroxide and montmorillonite are both inorganic powders, physically dispersed in the cement matrix, and will not chemically react with the polystyrene particles, thus not damaging the closed-cell integrity of the particles. The flame retardant particles with a fineness ≥100 mesh are much smaller than the polystyrene particles (1.0~3.0 mm), mainly distributed in the continuous phase of the cement matrix, and will not form a weak layer at the particle-matrix interface. Unlike organic flame retardants (such as phosphate esters and brominated flame retardants), the inorganic components will not form a plasticizing layer on the surface of the polystyrene particles, and will not reduce the mechanical properties of the particles.

[0075] In addition to its flame-retardant effect, the addition of montmorillonite also has a positive impact on the rheological properties of the slurry and the surface quality of the board. Montmorillonite has thickening and thixotropic properties, which helps to improve the suspension stability of the slurry and inhibit the floating of polystyrene particles; the layered structure of montmorillonite forms a smooth coating on the surface of the board, improving surface smoothness and crack resistance; the filling effect of montmorillonite on cement hydration products helps to reduce surface porosity and improve impermeability.

[0076] In a preferred embodiment of the present invention, the chlorine-free composite early strength agent is composed of aluminum sulfate, lithium carbonate, and nano calcium carbonate in a mass ratio of 6:1:3.

[0077] In this invention, the chloride-free composite early-strength agent system contains no chlorides. Chloride ions can cause steel reinforcement corrosion, leading to a decrease in the durability of concrete structures. Although the insulation board of this invention does not directly contact the steel reinforcement, in external wall insulation systems, anchors may penetrate the insulation board and enter the wall. The chloride-free design avoids the risk of chloride ion corrosion to the wall reinforcement and metal anchors.

[0078] In the chlorine-free composite early-strength agent, aluminum sulfate is the main component, providing the framework for ettringite formation and early strength; lithium carbonate is a trace amount of highly efficient coagulation accelerator, rapidly initiating the hydration reaction; and nano-calcium carbonate acts as a nucleating agent and filler, optimizing the distribution of hydration products. Lithium carbonate initiates the reaction quickly but in extremely low amounts, avoiding thermal stress concentration caused by excessively rapid hydration; the ettringite formed from aluminum sulfate has micro-expansion properties, compensating for some drying shrinkage and reducing shrinkage cracks; the filling and nucleating effects of nano-calcium carbonate result in a more uniform distribution of hydration products, reducing localized stress concentration. The synergistic effect of these three components achieves rapid hardening without cracking.

[0079] Based on the functional requirements and thickness of each layer, the dosage of the chlorine-free composite early-strength agent in each layer of this invention exhibits a gradient distribution: The highest admixture content (4.0~4.5 parts) is used in the base bonding layer: This layer requires the fastest early strength development to provide anchorage with the wall and support the weight of the upper layer. The moderate admixture content (2.0~2.5 parts) is used in the weather-resistant finishing layer: This layer requires relatively fast surface hardening to form a dense protective layer and prevent early plastic cracking. The lowest admixture content (1.5~2.0 parts) is used in the insulation core layer: This layer does not require rapid early strength development; appropriately delayed hardening is beneficial for stress release and shrinkage coordination in the core layer. This gradient admixture design matches the distribution of the early-strength agent with the mechanical requirements of each layer, ensuring rapid demolding of the entire panel while avoiding shrinkage cracking and stress concentration caused by premature hardening of the core layer.

[0080] In a preferred embodiment of the present invention, the silicate cement is grade 42.5 silicate cement.

[0081] In this invention, 42.5 grade cement is the most commonly used general-purpose cement in the construction industry. It has both good early strength and late strength growth, which can meet the needs of rapid demolding of insulation boards and ensure long-term mechanical properties.

[0082] The desulfurized gypsum is an industrial solid waste produced as a byproduct of flue gas desulfurization in power plants. Its main component is calcium sulfate dihydrate, with a fineness ≥80 mesh and a moisture content ≤10%.

[0083] In this invention, the desulfurized gypsum has a fineness of ≥80 mesh, which ensures that the desulfurized gypsum powder can be uniformly mixed with dry powders such as cement and slag, avoiding stratification or uneven reaction caused by excessively large particles. A moisture content of ≤10% controls the free water content, preventing the dry powder from clumping and adhering to equipment, while also avoiding the introduction of additional moisture that could affect the accuracy of the water-cement ratio.

[0084] The slag powder is S95 grade slag powder with a fineness ≥400 mesh and a 28-day activity index ≥95%.

[0085] In this invention, S95 grade slag powder has a high activity index, enabling it to significantly participate in the secondary hydration reaction and improve later-stage strength. A fineness of ≥400 mesh ensures that the slag powder particles can fill the capillary pores between cement particles, increasing density. Replacing part of the cement with slag powder can reduce cement usage, decrease heat release during hydration, and prevent cracking of thick slabs. The secondary hydration of slag powder consumes Ca(OH)2, reducing the alkalinity of the cement paste, while simultaneously refining the pore structure, improving impermeability and resistance to chemical erosion.

[0086] The latex powder is an ethylene-vinyl acetate type redispersible latex powder.

[0087] In this invention, the ethylene-vinyl acetate type redispersible latex powder is obtained by spray drying of ethylene-vinyl acetate copolymer (EVA) emulsion. After adding water, it can be redispersed into a stable polymer emulsion, and after the water evaporates, it forms a polymer film that is insoluble in water.

[0088] Preferably, the latex powder may be one or more of DA-1220, DA-1410, VINNAPAS 5549H, VINNAPAS LL 4036 or Vinofan PV 408P ap.

[0089] The viscosity of the hydroxypropyl methylcellulose ether is 100,000 mPa·s, and the water retention rate is ≥90%.

[0090] Hydroxypropyl methylcellulose ether with a viscosity of 100,000 mPa·s has excellent water retention properties, preventing water from evaporating too quickly or being absorbed by the substrate, ensuring full hydration of cement. It is especially suitable for thick layers (core layer thickness accounts for 60%) and highly absorbent polystyrene particle systems. It can also significantly improve the yield stress of the slurry, effectively suspending polystyrene particles with extremely low density and preventing them from floating and separating. It also has a lubricating effect, which can reduce friction between particles, improve the fluidity and smoothness of the slurry, and can also delay cement hydration to a certain extent. However, its retarding effect complements that of the accelerator, avoiding construction difficulties caused by excessively rapid setting.

[0091] Preferably, the hydroxypropyl methylcellulose ether may be one or more of Shandong Tiansheng TS-8040D, Shandong Yiteng 60YT100000, or Shandong Tenesi 100,000 viscosity HPMC.

[0092] The particle size of the nano-silica is 50~100nm.

[0093] Nano-silica exhibits high pozzolanic activity, with a large number of surface silanol groups (≡Si-OH) and an amorphous structure on its surface. It can rapidly react with Ca(OH)₂ produced during cement hydration to form CSH gel, with a reaction rate far exceeding that of ordinary silica fume. Particles of 50–100 nm can fill the capillaries in cement paste and the voids between cement particles, significantly improving density. Nano-silica particles also provide numerous nucleation sites for CSH gel, accelerating cement hydration and improving early strength. Nano-silica enriched in the polystyrene particle-cement interface region forms chemical bonds with silane coupling agents on the particle surface, enhancing interfacial bonding strength.

[0094] Preferably, the nano-silica can be one or more of Hangzhou Jiupeng CY-SH30, Suzhou Youzirconium nano-silica, or Zhejiang Nanosun-1020.

[0095] According to a second aspect of the present invention, a method for preparing the insulation board as described above is provided, the method comprising the following steps: (1) Slurry preparation The dry powder of each layer—base bonding layer, thermal insulation core layer, and weather-resistant decorative layer—is mixed with water to prepare the base bonding layer slurry, thermal insulation core layer slurry, and weather-resistant decorative layer slurry, respectively. The amount of water is 30-35% of the weight of the dry powder of each layer.

[0096] The water addition of 30-35% of the dry powder weight refers to a water-cement ratio (the mass ratio of water to cementitious material) of 0.30-0.35. If the water-cement ratio is too low (<0.30), the slurry is too dry, has poor fluidity, is difficult to spread, and interlayer penetration is difficult, preventing the formation of transition zones. If the water-cement ratio is too high (>0.35), the slurry is too thin, polystyrene particles easily float and separate, and shrinkage increases, making the board prone to cracking. A water-cement ratio of 30-35% provides the slurry with suitable fluidity and stability, ensuring smooth spreading while inhibiting particle floating. This water-cement ratio, together with the water-retaining and thickening effect of HPMC (100,000 viscosity) and the film-forming effect of latex powder, optimizes the rheological properties of the slurry, creating conditions for subsequent simultaneous spreading.

[0097] The slump deviation of the three-layer slurry should be controlled to be ≤20mm, the plastic viscosity deviation to be ≤15%, and the initial setting time deviation to be ≤30min.

[0098] A slump deviation of ≤20mm indicates that the fluidity of the three layers of slurry is highly consistent; plastic viscosity reflects the ability of the slurry to resist flow deformation, and a deviation of ≤15% ensures that the three layers of slurry have similar rheological behavior during the application process; an initial setting time deviation of ≤30min ensures that the three layers of slurry can set synchronously in a wet state, avoiding the obstruction of interlayer penetration due to premature hardening of one layer.

[0099] If the fluidity of the three slurry layers differs too much, uneven layer thickness or uncontrolled mixing can easily occur during simultaneous application. If the initial setting time differs significantly, the early-setting layer will form a hard shell, preventing the penetration of adjacent slurry layers.

[0100] (2) Fabric and molding The three-layer slurry is distributed through three feeding ports. All three feeding ports are flat, continuous openings with the same width as the inner cavity of the mold. The three-layer slurry is distributed using a single-stroke progressive and closely following feeding process. During the feeding process, the distance between any two adjacent feeding ports is 30-50mm, and the travel speed of the three feeding ports is 1.5-2m / min.

[0101] The long, flat opening ensures a uniform distribution of the slurry across the width of the mold, avoiding uneven distribution caused by insufficient width of the discharge port, resulting in "piling up" and "flowing".

[0102] Single-stroke refers to the three feed ports arranged in a line, completing the application of three layers of slurry in one stroke without repetition. Progressive type refers to the feed ports arranged in the order of base bonding layer → insulation core layer → weather-resistant finishing layer, applying the slurry sequentially. Close-following type refers to the spacing between adjacent feed ports being only 30-50mm, meaning that after the previous layer is applied, the next layer immediately follows within a very short time and distance. The travel speed is 1.5-2m / min, a moderate application speed that ensures production efficiency while providing sufficient wet time window for interlayer penetration. With a travel speed of 1.5-2m / min and a spacing of 30-50mm between adjacent feed ports, the application time difference between adjacent layers on the same cross-section is only 0.9-2 seconds. Therefore, when the next layer covers, the previous layer is still in a plastic flow state, achieving "wet-wet" contact between the two layers, which is beneficial for molecular diffusion and particle migration.

[0103] Throughout the process, the fabric is subjected to low-frequency micro-vibrations of 30~50Hz and 0.3~0.5mm amplitude to the mold, which allows the adjacent layers of slurry to penetrate and fuse in both directions, forming a continuous transition zone with a thickness of 1~3mm.

[0104] During the fabrication process, the mold is continuously subjected to low-frequency, micro-amplitude vibrations, causing relative movement of particles at the interface of adjacent slurry layers. These micro-vibrations, with an amplitude of 0.3~0.5mm, do not cause severe mixing; instead, they induce limited mixing at the interface through shaking, forming a transition zone of 1~3mm. If the amplitude is too large (>1mm), it can lead to uncontrolled mixing of the three layers; if the amplitude is too small (<0.2mm), the penetration effect is not significant. Simultaneously, the vibration helps air bubbles escape from the slurry, increasing the density of the board. The low-frequency micro-vibrations also allow polystyrene particles to rearrange within the slurry, preventing localized agglomeration or floating.

[0105] (3) Maintenance After molding, the mold is allowed to stand for 24 hours at room temperature (20±5℃) before demolding. After demolding, the blank is cured with low-temperature steam at 40℃ for 24 hours, and then cured for 3 days at room temperature and humidity (60~70%).

[0106] This invention employs a three-stage curing system: The first stage involves 24 hours of static curing at room temperature. Under conditions without external heating or humidity, the cement undergoes initial hydration, and the green body acquires sufficient demolding strength. Static curing at room temperature avoids surface cracking caused by early high-temperature hydration.

[0107] The second stage involves 24 hours of low-temperature steam curing at 40℃. The low-temperature steam provides heat and humidity, accelerating the secondary hydration reaction of cement and slag, and promoting rapid strength improvement. 40℃ is the suitable temperature range for cement hydration, and excessively high temperatures will not cause the decomposition of ettringite or delay its formation.

[0108] The third stage involves curing at room temperature and 60-70% humidity for 3 days, continuing curing in an environment with 60-70% relative humidity to ensure the hydration reaction proceeds fully and to prevent shrinkage cracks caused by excessive drying. These humidity conditions are beneficial for maintaining the dimensional stability of the board.

[0109] In a preferred embodiment of the present invention, in step (1), the feeding sequence of the slurry preparation is as follows: first, silicate cement, desulfurized gypsum, slag powder and lignin fiber are dry mixed at 300 r / min for 3 min, the cementitious materials (cement, desulfurized gypsum, slag powder) and lignin fiber are premixed evenly, then other components except graphene polystyrene particles are added and dry mixed for 1 min, water is added and wet mixed at 200 r / min for 3 min, so that the powder and water react fully to form a slurry, and finally graphene polystyrene particles are added and stirred at 100 r / min for 2 min to avoid the polystyrene particles from breaking and floating.

[0110] In this invention, the mixing process employs a sequential design of dry mixing followed by wet mixing, with particles added last. This ensures both uniform mixing of inorganic powders and additives and maximizes the preservation of the closed-cell structure integrity of the graphene polystyrene particles. The stepwise dry mixing, first mixing the cementitious materials and fibers, and then adding the remaining additives, helps to uniformly disperse the lignin fibers and prevents fiber clumping; it also ensures the uniform distribution of trace components such as nano-silica.

[0111] In a preferred embodiment of the present invention, the viscosity of the three-layer slurry is matched by using a slump of 180±10mm for the thermal insulation core layer slurry as a viscosity benchmark and by finely adjusting the amount of hydroxypropyl methylcellulose ether and the amount of water added during mixing.

[0112] In this invention, by precisely and quantitatively adjusting the amount of hydroxypropyl methylcellulose ether in the base bonding layer and the weather-resistant finishing layer based on a slump of 180±10mm for the thermal insulation core layer slurry, and supplementing this with fine-tuning of the mixing water, the rheological properties (viscosity, slump) of the three layers of slurry are precisely matched. Thus, during the synchronous gradient application process, the core layer is guaranteed to have sufficiently high water retention and yield stress to suspend a large number of lightweight polystyrene particles and support its own thickness. At the same time, the base layer and the finishing layer are given suitable fluidity and adhesion to facilitate wall anchoring and surface leveling. Ultimately, the three layers of slurry achieve controllable bidirectional penetration in a wet state, forming a continuous transition area with uniform thickness and gradually changing composition. This provides a key process guarantee for the preparation of an integrated continuous gradient structure thermal insulation board without rigid interfaces.

[0113] The following description, in conjunction with specific embodiments, is intended to illustrate and explain the invention in more detail. It should be understood that the preferred embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0114] Unless otherwise specified, the raw materials and specifications used in the following examples and comparative examples are as follows: Portland cement: Grade 42.5 ordinary Portland cement (Conch brand PO 42.5); Desulfurized gypsum: a byproduct of flue gas desulfurization in power plants, with a calcium sulfate dihydrate content of 92%, a fineness of 100 mesh, and a moisture content of 5%. Slag powder: S95 grade, specific surface area 420m² 2 / kg, 28d activity index 98% (Nanjing Iron & Steel Jiahua); Graphene-polystyrene particles: particle size 1.5~2.5mm, bulk density 22kg / m³ 3 The closed-cell rate is ≥99%, the graphene content is 0.12% (Jilin Yunting), and the surface is modified according to the specific embodiment and comparative ratio requirements; Latex powder: DA-1220 (Taiwan Dalian Chemical); Nano silica: Particle size 50~100nm (Hangzhou Jiupeng CY-SH30); Lignin fiber: Alkali-resistant lignin fiber, with the length of each layer selected according to the requirements of each layer (Jiangsu Meichao). Composite flame retardant: Aluminum hydroxide and montmorillonite are compounded at a mass ratio of 4:1, with a fineness of 200 mesh (aluminum hydroxide is Shandong Zhonglv, and montmorillonite is Fenghong DK1N). Hydroxypropyl methylcellulose ether (HPMC): viscosity 100,000 mPa·s, water retention 92% (Shandong Tiansheng TS-8040D). Chlorine-free composite early strength agent: aluminum sulfate, lithium carbonate, and nano calcium carbonate are compounded in a mass ratio of 6:1:3 (all are industrial grade, purity ≥99%).

[0115] Preparation method: S1 slurry preparation Weigh the dry powder according to the formula for each layer. Prepare each layer of slurry separately. First, dry mix cement, desulfurized gypsum, slag powder and lignin fiber at 300 r / min for 3 min; then add latex powder, nano silica, composite flame retardant, HPMC and chlorine-free early strength agent, and continue to dry mix for 1 min; add water of 30-35% of the total weight of the dry powder of each layer, and wet mix at 200 r / min for 3 min; finally add graphene polystyrene particles, and stir at low speed of 100 r / min for 2 min to obtain three layers of slurry.

[0116] Control the slump deviation of the three-layer slurry to ≤20mm, the plastic viscosity deviation to ≤15%, and the initial setting time deviation to ≤30min.

[0117] S2 Fabric and Molding Three long, flat feeding ports are used. During the material laying process, the material moves in the order of base layer, core layer, and finishing layer, with a spacing of 40mm between adjacent feeding ports and a traveling speed of 1.8m / min. Throughout the material laying process, a low-frequency micro-vibration of 40Hz and an amplitude of 0.4mm is applied to the mold.

[0118] S3 Maintenance After molding, the mold is kept at room temperature (20±5℃) for 24 hours, then steamed at 40℃ for 24 hours after demolding, and then cured at room temperature and 65% humidity for 3 days.

[0119] Example 1 The insulation board has a total thickness of 60mm, with three layers having thicknesses of 20%, 60%, and 20% respectively: a 12mm base bonding layer, a 36mm insulation core layer, and a 12mm weather-resistant finishing layer.

[0120] The formulations for each layer (by weight) are shown in Table 1.

[0121] Table 1 Formulations for each layer in Example 1

[0122] Graphene polystyrene particle modification: Secondary surface modification of silane coupling agent-nano silica was carried out according to the aforementioned method.

[0123] The length of the lignin fiber is as follows: 0.5 mm for the base bonding layer, 0.8 mm for the thermal insulation core layer, and 1.0 mm for the weather-resistant finishing layer.

[0124] After curing, the insulation board was sliced ​​along its thickness. A stereomicroscope (20-50x magnification) was used to observe the interface areas between the base layer and the core layer, and between the core layer and the finish layer. The thickness of the compositional transition zones was measured. Measurements showed that the thickness of the transition zone between the base layer and the core layer was 1.2-1.8 mm, and the thickness of the transition zone between the core layer and the finish layer was 1.5-2.1 mm, both within the range of 1-3 mm.

[0125] Example 2 The insulation board has a total thickness of 60mm, including: an 11mm base bonding layer, a 38mm insulation core layer, and an 11mm weather-resistant finishing layer.

[0126] The rest is the same as in Example 1.

[0127] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.0~1.6 mm.

[0128] Example 3 The insulation board has a total thickness of 60mm, including: a 13.5mm base bonding layer, a 33mm insulation core layer, and a 13.5mm weather-resistant finishing layer.

[0129] The rest is the same as in Example 1.

[0130] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.1 to 1.7 mm.

[0131] Example 4 Alkali-resistant lignin fiber, all three layers are 0.8mm in length.

[0132] The rest is the same as in Example 1.

[0133] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.0~1.5mm, and the thickness of the transition zone between the core layer and the finishing layer was 1.2~1.8mm.

[0134] Example 5 Graphene polystyrene particles, without secondary surface modification.

[0135] The rest is the same as in Example 1.

[0136] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 0.8 to 1.0 mm.

[0137] Example 6 The chlorine-free composite early strength agent is a mixture of aluminum sulfate and nano calcium carbonate in a mass ratio of 7:3.

[0138] The rest is the same as in Example 1.

[0139] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.1 to 1.6 mm.

[0140] Example 7 In step S2, the fabric applies a vibration of 30Hz and 0.5mm to the mold throughout the process.

[0141] The rest is the same as in Example 1.

[0142] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.5~2.5mm, and the thickness of the transition zone between the core layer and the finishing layer was 1.8~2.8mm.

[0143] Example 8 In step S2, the fabric applies a vibration of 50Hz and 0.3mm to the mold throughout the process.

[0144] The rest is the same as in Example 1.

[0145] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 0.8-1.4 mm.

[0146] Comparative Example 1 The total thickness of the insulation board is 60mm, including a 15mm base bonding layer, a 30mm insulation core layer, and a 15mm weather-resistant finishing layer. The remaining raw materials, formula, and preparation method are the same as in Example 1.

[0147] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 0.8-1.0 mm.

[0148] Comparative Example 2 The total thickness of the insulation board is 60mm, including a 10mm base bonding layer, a 40mm insulation core layer, and a 10mm weather-resistant finishing layer. The remaining raw materials, formula, and preparation method are the same as in Example 1.

[0149] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 0.9-1.4 mm.

[0150] Comparative Example 3 In step S2, the fabric applies a vibration of 20Hz and 1.0mm to the mold throughout the process. These parameters are the same as those for conventional vibration venting.

[0151] The rest is the same as in Example 1.

[0152] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 3.5~5.0 mm.

[0153] Comparative Example 4 In step S2, no vibration is applied to the mold; the rest is the same as in Example 1.

[0154] There is no obvious transition zone between the layers, and the thickness is <0.1mm.

[0155] Comparative Example 5 The spacing between adjacent feed inlets was changed to 80mm, and the traveling speed was changed to 0.8m / min. The rest is the same as in Example 1.

[0156] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 0.2 to 0.6 mm.

[0157] Comparative Example 6 The curing procedure was changed to: after molding, the mold was allowed to stand at room temperature (20±5℃) for 72 hours before demolding, and then naturally cured at room temperature and 65% humidity for 7 days (without 40℃ low-temperature steam curing). The rest was the same as in Example 1.

[0158] The thickness of the transition zone between the base layer and the core layer was measured using the same method as in Example 1. The thickness of the transition zone between the core layer and the finishing layer was 1.0~1.6 mm.

[0159] Performance testing 1. Dry density: determined according to GB / T 5486-2008.

[0160] 2. Thermal conductivity: in accordance with GB / T 10294-2008 (average temperature 25℃).

[0161] 3. Compressive strength: determined according to GB / T 5486-2008.

[0162] 4. Tensile bond strength (with cement mortar substrate): determined according to JG / T 287-2013.

[0163] 5. Surface layer flexural strength: determined according to GB / T 30100-2013.

[0164] 6. Flammability rating: Measured according to GB 8624-2012.

[0165] 7. Volumetric water absorption rate: determined according to GB / T 5486-2008.

[0166] The performance test results are shown in Table 2.

[0167] Table 2 Performance Test Results

[0168] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, nor does it mean that the present invention must rely on the above process steps for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A cement-based polystyrene insulation board, characterized in that, The insulation board comprises, along its thickness direction, a base bonding layer, an insulation core layer, and a weather-resistant finishing layer. The three layers form an integrated, continuous gradient structure without rigid interfaces. The thickness ratios of the base bonding layer, the insulation core layer, and the weather-resistant finishing layer are 18-23%, 55-65%, and 18-23%, respectively. The raw material composition of each layer of dry powder, by weight, is as follows: The base bonding layer comprises: 43-47 parts silicate cement, 10-12.5 parts desulfurized gypsum, 8-10 parts slag powder, 10-14 parts graphene polystyrene particles, 3.0-3.5 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.1-1.4 parts hydroxypropyl methylcellulose ether, and 4.0-4.5 parts chlorine-free composite early strength agent; The thermal insulation core layer comprises: 34-38 parts silicate cement, 12-15 parts desulfurized gypsum, 8-10 parts slag powder, 22-26 parts graphene polystyrene particles, 3.8-4.2 parts latex powder, 0.9-1.1 parts nano silica, 0.4-0.6 parts lignin fiber, 1.1-1.3 parts composite flame retardant, 1.4-1.6 parts hydroxypropyl methylcellulose ether, and 1.5-2.0 parts chlorine-free composite early strength agent; The weather-resistant finishing layer comprises: 39-42 parts silicate cement, 8-10 parts desulfurized gypsum, 8-10 parts slag powder, 12-16 parts graphene polystyrene particles, 3.3-3.7 parts latex powder, 1.0-1.2 parts nano silica, 0.5-0.7 parts lignin fiber, 1.2-1.4 parts composite flame retardant, 1.2-1.4 parts hydroxypropyl methylcellulose ether, and 2.0-2.5 parts chlorine-free composite early strength agent.

2. The insulation board as described in claim 1, characterized in that, The insulation board has a thickness of 50~120mm, and there is a continuous transition area with a thickness of 1~3mm between two adjacent layers.

3. The insulation board as described in claim 1, characterized in that, The lignin fiber is alkali-resistant lignin fiber. The length of the alkali-resistant lignin fiber in the base bonding layer is 0.4~0.6mm, the length of the alkali-resistant lignin fiber in the heat insulation core layer is 0.7~0.85mm, and the length of the alkali-resistant lignin fiber in the weather-resistant finishing layer is 0.9~1.1mm.

4. The insulation board as described in claim 1, characterized in that, The alkali-resistant lignin fiber has an aspect ratio of 20~30:1, and after being soaked in cement alkali solution for 28 days, the fracture strength retention rate is ≥90%, and the moisture content is ≤5%; the fiber length difference between adjacent layers is ≤0.4mm.

5. The insulation board as described in claim 1, characterized in that, The graphene polystyrene particles are internally dispersed foamed polystyrene particles, prepared by secondary surface modification with silane coupling agent-nano silica; the particle size of the graphene polystyrene particles is 1.0~3.0 mm, and the bulk density is 20~25 kg / m³. 3 The closed-cell rate is ≥99%, and the graphene content is 0.10~0.15%.

6. The insulation board as described in claim 1, characterized in that, The composite flame retardant is a mixture of aluminum hydroxide and montmorillonite in a mass ratio of 4:1, with a fineness ≥100 mesh; the chlorine-free composite early strength agent is a mixture of aluminum sulfate, lithium carbonate, and nano calcium carbonate in a mass ratio of 6:1:

3.

7. The insulation board according to any one of claims 1 to 6, characterized in that, The silicate cement is grade 42.5 silicate cement; The desulfurization gypsum is an industrial solid waste produced as a byproduct of flue gas desulfurization in power plants. Its main component is calcium sulfate dihydrate, with a fineness ≥80 mesh and a moisture content ≤10%. The slag powder is S95 grade slag powder with a fineness ≥400 mesh and a 28-day activity index ≥95%. The latex powder is an ethylene-vinyl acetate type redispersible latex powder; The hydroxypropyl methylcellulose ether has a viscosity of 100,000 mPa·s and a water retention rate of ≥90%. The particle size of the nano-silica is 50~100nm.

8. A method for preparing a thermal insulation board as described in any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Slurry preparation The dry powders of the base bonding layer, the thermal insulation core layer, and the weather-resistant finishing layer are mixed with water to prepare the base bonding layer slurry, the thermal insulation core layer slurry, and the weather-resistant finishing layer slurry, respectively. The amount of water is 30-35% of the weight of the dry powder of each layer. The slump deviation of the three-layer slurry should be controlled to be ≤20mm, the plastic viscosity deviation to be ≤15%, and the initial setting time deviation to be ≤30min. (2) Fabric and molding The three-layer slurry is distributed through three feeding ports. All three feeding ports are flat, continuous openings with the same width as the inner cavity of the mold. The three-layer slurry is distributed using a single-stroke progressive and closely following feeding process. During the feeding process, the distance between any two adjacent feeding ports is 30-50mm, and the travel speed of the three feeding ports is 1.5-2m / min. Throughout the process, the fabric is subjected to low-frequency micro-vibration of 30~50Hz and amplitude of 0.3~0.5mm on the mold, which allows the adjacent layers of slurry to penetrate and fuse in both directions, forming a continuous transition area with a thickness of 1~3mm. (3) Maintenance After molding, the mold is allowed to stand for 24 hours at room temperature (20±5℃) before demolding. After demolding, the blank is cured with low-temperature steam at 40℃ for 24 hours, and then cured for 3 days at room temperature and humidity (60~70%).

9. The preparation method according to claim 8, characterized in that, In step (1), the feeding sequence of the slurry preparation is as follows: first, dry mix silicate cement, desulfurized gypsum, slag powder and lignin fiber at 300 r / min for 3 min, then add other components except graphene polystyrene particles and dry mix for 1 min, add water and wet mix at 200 r / min for 3 min, and finally add graphene polystyrene particles and stir at 100 r / min at low speed for 2 min.

10. The preparation method according to claim 8, characterized in that, Using a slump of 180±10mm for the thermal insulation core layer slurry as the viscosity benchmark, the viscosity of the three-layer slurry is matched by finely adjusting the amount of hydroxypropyl methylcellulose ether and the amount of water added during mixing.

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