A composite board based on synergistic enhancement of waste biochar and tailings and a preparation method thereof

Abstract

This invention discloses a composite board based on the synergistic enhancement of waste biochar and tailings, and its preparation method, belonging to the technical field of solid waste resource utilization and polymer composite materials. The composite board comprises a core layer and a skin layer. The core layer raw materials include 40-60 parts PVC resin, 20-50 parts tailings, 5-40 parts waste biochar, 0.8-4 parts ACR impact modifier, 1.8-3 parts titanate coupling agent, and 3-10 parts composite processing aid A. The skin layer raw materials include 25 parts ABS resin, 10-20 parts tailings, 0.9 parts titanate coupling agent, 1.35 parts color masterbatch, and 1.25-2.75 parts composite processing aid B. In the preparation process, the tailings are first modified with titanate coupling agent, then the core layer and skin layer premixes are prepared separately, and finally co-extruded. This invention utilizes the synergistic effect of waste biochar and tailings to significantly improve the mechanical and thermal conductivity properties of the composite board, while realizing the high-value utilization of bulk solid waste and reducing production costs and carbon emissions.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and polymer composite material technology, and particularly relates to a composite board based on the synergistic reinforcement of waste biochar and tailings and its preparation method. Background Technology

[0002] With the acceleration of industrialization and the continuous advancement of infrastructure construction, the scale of mining resources such as steel and graphite is constantly expanding, resulting in a year-on-year increase in the stockpiles of bulk industrial solid waste such as iron tailings and graphite tailings. The long-term stockpiling of tailings not only occupies a large amount of valuable land resources (approximately one acre of land is needed for every 10,000 tons of tailings stockpiled), but may also cause a series of ecological and environmental problems such as soil, water, and air pollution through rainwater leaching, surface runoff, and dust dispersion. Furthermore, tailings dam failures can trigger major geological disasters, seriously threatening the lives and property of surrounding residents.

[0003] At the same time, market demand for green, environmentally friendly, and low-carbon building materials is growing rapidly. Traditional building materials generally suffer from prominent problems such as high energy consumption, high carbon emissions, and high resource dependence. Therefore, developing green and low-carbon composite materials based on bulk solid waste has become a dual key path to solving the tailings storage problem and meeting the market demand for green building materials.

[0004] Polyvinyl chloride (PVC), as a general-purpose thermoplastic, boasts excellent comprehensive mechanical properties, outstanding corrosion resistance, good processability, and controllable cost, making it widely used in building materials, automotive parts, and daily consumer goods. Traditional PVC composites often use calcium carbonate and wood flour as fillers, but these fillers have drawbacks such as limited performance improvement, high resource consumption, and high carbon emissions. While calcium carbonate can reduce costs, it offers limited improvement to the material's thermal conductivity and thermal stability; wood flour, although possessing certain environmental properties, is highly hygroscopic, prone to mold growth, has poor weather resistance, and consumes large amounts of timber resources. Using tailings as an inorganic filler in PVC composites can achieve large-scale disposal of solid waste. However, the highly polar surface of tailings has poor compatibility with the non-polar PVC matrix, and direct filling can easily lead to stress concentration and filler agglomeration within the composite material, resulting in a decline in mechanical properties. Furthermore, using tailings alone makes it difficult to synergistically balance the material's strength, toughness, and thermal conductivity, limiting its engineering applications in high-end building materials.

[0005] Waste biochar is a solid product obtained by high-temperature pyrolysis of biomass (such as straw, sawdust, and livestock manure) under anaerobic or hypoxic conditions. It features a porous structure, large specific surface area, and abundant surface functional groups. With its wide availability and low cost, it is a potential filler for polymer materials. Currently, the application of waste biochar in composite materials is mostly focused on single-filler modification, primarily used to improve adsorption performance or reduce carbon emissions. A synergistic reinforcement technology system with tailings has not yet been established, and its potential in improving interfacial bonding and synergistically enhancing mechanical and thermal properties of composite materials has not been fully realized. Furthermore, existing technologies suffer from insufficient tailings modification, unreasonable composite system formulations, and mismatched preparation process parameters, resulting in the overall performance of solid waste-based PVC composites failing to meet engineering application requirements and limiting their industrial-scale promotion. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a composite board based on the synergistic reinforcement of waste biochar and tailings, and its preparation method. This addresses issues such as the limited performance of fillers in traditional PVC composite materials, poor compatibility between tailings and the matrix, low solid waste utilization rate, and unsatisfactory overall performance. The invention achieves synergistic optimization of the mechanical properties, thermal conductivity, thermal stability, and processing performance of the composite board, while simultaneously reducing production costs and carbon emissions. This provides technical support for the industrial production of bulk solid waste resources and green, low-carbon building materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A composite panel based on the synergistic reinforcement of waste biochar and tailings includes a core layer and a skin layer; wherein, The core layer raw material composition, by mass, includes: 40-60 parts PVC resin, 20-50 parts tailings, 5-40 parts waste biochar, 0.8-4 parts ACR impact modifier, 1.8-3 parts titanate coupling agent, and 3-10 parts composite processing aid A. The skin material composition, by mass, includes: 25 parts ABS resin, 10-20 parts tailings, 0.9 parts titanate coupling agent, 1.35 parts color masterbatch, and 1.25-2.75 parts composite processing aid B.

[0008] This invention optimizes the compatibility between tailings and the matrix through surface modification technology, enhances the overall performance of materials by utilizing the synergistic effect of waste biochar and tailings, and simultaneously optimizes the formulation system and preparation process. It has important practical significance and application value for realizing the high-value resource utilization of iron tailings, graphite tailings and waste biochar, reducing the production cost and carbon emissions of green building materials, and promoting the transformation of the building materials industry towards green and low-carbon directions.

[0009] Furthermore, the PVC resin is SG-8 type polyvinyl chloride, with a viscosity range of 73~86 mL / g, an average degree of polymerization between 700 and 740, a particle size distribution of 63~250 μm, a volatile matter mass fraction ≤0.40%, an apparent density ≥0.500 g / mL, and a whiteness value ≥75% after heating at 160℃ for 10 min; The tailings are iron tailings or graphite tailings; The titanate coupling agent is isopropyltris(dioctylpyrophosphoryloxy) titanate; The particle size of the waste biochar is 1~100μm; The ACR impact modifier is a core-shell structure acrylate elastomer; The raw material composition of the composite processing aid A, by mass parts, includes: 1-3 parts calcium-zinc stabilizer, 0.5-2 parts lubricant, 1-3 parts plasticizer, and 0.5-3 parts impact-resistant agent; The raw material composition of the composite processing aid B, by mass, includes: 0.75 parts of calcium-zinc stabilizer and 0.5 to 2 parts of lubricant.

[0010] Furthermore, the calcium-zinc stabilizer is an R502 type composite calcium-zinc stabilizer; The lubricant comprises, by weight, 0.2-0.8 parts polyethylene wax, 0.2-0.64 parts stearic acid, and 0.1-0.6 parts oxidized polyethylene wax; The plasticizer is epoxidized soybean oil; The impact-resistant additive is chlorinated polyethylene.

[0011] This invention also provides a method for preparing a composite board based on the synergistic reinforcement of waste biochar and tailings, comprising the following steps: S1. Preparation of modified tailings: The dried tailings and titanate coupling agent were mixed according to the ratio of tailings to titanate coupling agent in the core layer premix and the skin layer premix, respectively. The bonding reaction was carried out under stirring, cooled to room temperature, sieved, and the sieved product was dried again to obtain core layer premix modified tailings and skin layer premix modified tailings. S2. Preparation of core layer premix: Weigh the raw materials according to the formula ratio, and add PVC resin, core layer premix modified tailings, waste biochar, ACR impact modifier and composite processing aid A into the mixer in sequence, stir, and obtain core layer premix. S3. Preparation of leather premix: Weigh the raw materials according to the formula ratio, and add ABS resin, leather premix modified tailings, color masterbatch and composite processing aid B into the mixer in sequence, stir, and obtain leather premix. S4. Preparation of composite board: The core layer premix and the skin layer premix are processed into shape to obtain a composite board based on the synergistic reinforcement of waste biochar and tailings.

[0012] Further, in step S1, the specific operation steps of the bonding reaction are as follows: first, premix by manual stirring for 3-5 minutes, then carry out high-speed dispersion reaction at a speed of 1000-1500 r / min for 15-25 minutes, and the system temperature naturally rises to 75-85℃. When the temperature exceeds 85℃, reduce the speed to 50-100 r / min.

[0013] Furthermore, in steps S2 and S3, the specific operation steps of stirring are as follows: first, stir at a low speed of 500~800 r / min for 4~6 min, then increase the speed to 1000~1200 r / min and stir at a high speed for 4~6 min, and control the system temperature to not exceed 90℃ during the mixing process.

[0014] Further, in step S4, the specific operation steps of the processing and molding are as follows: the core layer premix is ​​placed into the main twin-screw extruder, and the skin layer premix is ​​placed into the co-extruder. The temperatures of zones 1 to 4 of the main extruder barrel are controlled to be 198℃, 202℃, 202℃, and 200℃, respectively, and the flange zone temperature is 205℃. The temperature of the co-extruder barrel is 5℃ lower than that of the main extruder. The main extruder speed is adjusted to 18.5 r / min, and the feeding speed is 8 r / min. The core layer premix and the skin layer premix are extruded synchronously through a hollow floor die. The skin layer thickness is controlled to be 0.8 mm, and the core layer thickness is controlled to be 23.5 mm. After cooling, embossing and cutting are performed, followed by static curing to complete the processing.

[0015] Furthermore, the embossing pressure is 0.3~0.5MPa, the embossing roller temperature is controlled at 165~170℃, and the pattern depth is 0.3~0.5mm.

[0016] Furthermore, the static curing is carried out by leaving the plant at room temperature and relative humidity of 40-60% for 24 hours.

[0017] This invention also provides an application of composite panels based on the synergistic enhancement of waste biochar and tailings in the preparation of green and low-carbon building materials, such as for building decoration, outdoor paving, municipal landscaping or rail transit.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention constructs a multi-component synergistic reinforcement system of "PVC matrix-modified tailings-waste biochar-composite additive". The tailings are surface modified by titanate coupling agent, so that the coupling agent and the hydroxyl groups on the tailings surface are chemically bonded, realizing the organic functionalization modification of the tailings surface. This significantly reduces the polarity of the tailings surface and improves its compatibility with the PVC matrix, effectively solving the problems of agglomeration and poor interfacial bonding caused by traditional tailings filling. The layered structure and porous characteristics of waste biochar can provide sufficient anchoring sites for PVC molecular chains, forming a mechanical interlocking effect. At the same time, it overlaps with the tailings particles to build a continuous reinforcement network and thermal conductivity network, realizing the simultaneous improvement of mechanical properties and thermal conductivity. The final composite plate has a tensile strength of up to 43.81 MPa, a flexural strength of up to 76.66 MPa, a thermal conductivity of up to 0.3476 W / (m·K), and a notched impact strength of up to 8.2 kJ / m. 2 This achieves synergistic optimization of strength, toughness, and thermal conductivity.

[0019] (2) This invention uses solid waste such as iron tailings, graphite tailings and waste biochar as the main fillers. The amount of tailings can reach 20~50wt% and the amount of waste biochar can reach 5~40wt%, which greatly reduces the dependence on traditional fillers such as calcium carbonate and wood powder. It not only realizes the large-scale disposal of bulk solid waste (each ton of composite board can dispose of 0.4~0.8 tons of tailings and 0.1~0.4 tons of waste biochar), but also significantly reduces production costs and carbon emissions, achieving the dual goals of "treating waste with waste and low-carbon environmental protection", with significant environmental and economic benefits.

[0020] (3) The preparation process of this invention is mature and feasible. The high-speed mixing, melt blending, and co-extrusion molding processes used are all conventional processes in the field of polymer material processing. The equipment is highly compatible and does not require special equipment, making it easy to promote industrialization. By precisely optimizing the process parameters of key links such as tailings pretreatment, surface modification, raw material mixing, melt blending, and molding, the stability and consistency of product quality are ensured. The pilot-scale test and demonstration project application have verified the reliability of the technology. All physical and chemical properties of the product meet the requirements of the national standard GB / T 24508-2020 "Wood-Plastic Flooring". It has been applied in a demonstration project covering more than 200 square meters in the Xiong'an New Area University Town project. Actual verification shows that the boards are tightly laid, have good weather resistance, and do not deform, crack, or arch after being soaked in rainwater. The locking / splitting joints are tightly fitted without loosening, abnormal noise, or gaps. It can be widely used in building decoration, outdoor paving, municipal landscaping, rail transit, and other fields, with broad application prospects.

[0021] (4) The raw materials of the present invention are widely available and inexpensive. Iron tailings and graphite tailings can be obtained directly from mining enterprises, waste biochar can be prepared by pyrolysis of agricultural and forestry waste, and PVC resin and various additives are all commercially available conventional products that are easy to purchase. At the same time, the formulation system of the present invention has good flexibility. The tailings type, filling amount, waste biochar filling amount and additive ratio can be adjusted according to the characteristics of solid waste resources in different regions and the performance requirements of different application scenarios. It has strong adaptability and scalability. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The images are FT-IR spectra of iron tailings before and after modification in Example 1 (where IOT represents unmodified iron tailings and T-IOT represents modified iron tailings). Figure 2 The images show the SEM microstructure of the waste biochar from Examples 1 and 2. Figure 3 The images show SEM images (magnifications of 500× and 5000×) of the tensile cross-sections of the composite plates prepared in Example 1. (A) shows the tensile cross-section morphology of the 10 wt% iron tailings / PVC composite material at 500x magnification; (B) shows the tensile cross-section morphology of the 10 wt% iron tailings / PVC composite material at 5000x magnification; (C) shows the tensile cross-section morphology of the 30 wt% iron tailings / PVC composite material at 500x magnification; (D) shows the tensile cross-section morphology of the 30 wt% iron tailings / PVC composite material at 5000x magnification; (E) shows the tensile cross-section morphology of the 50 wt% iron tailings / PVC composite material at 5000x magnification; and (F) shows the tensile cross-section morphology of the 50 wt% iron tailings / PVC composite material at 5000x magnification. Figure 4 The images shown are SEM images (magnifications of 500× and 5000×) of the tensile cross-sections of the composite plates prepared in Example 2. (A) shows the tensile cross-section morphology of the 10 wt% graphite tailings / PVC composite material at 500x magnification; (B) shows the tensile cross-section morphology of the 10 wt% graphite tailings / PVC composite material at 5000x magnification; (C) shows the tensile cross-section morphology of the 30 wt% graphite tailings / PVC composite material at 500x magnification; (D) shows the tensile cross-section morphology of the 30 wt% graphite tailings / PVC composite material at 5000x magnification; (E) shows the tensile cross-section morphology of the 50 wt% graphite tailings / PVC composite material at 5000x magnification; and (F) shows the tensile cross-section morphology of the 50 wt% graphite tailings / PVC composite material at 5000x magnification. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] This invention provides a composite panel based on the synergistic reinforcement of waste biochar and tailings, comprising a core layer and a skin layer; wherein, By weight, the core layer raw material composition includes: 40-60 parts (e.g., 50 parts) of PVC resin, 20-50 parts (e.g., 40 parts) of tailings, 5-40 parts (e.g., 20 parts) of waste biochar, 0.8-4 parts (e.g., 2.4 parts) of ACR impact modifier, 1.8-3 parts (e.g., 1.83 parts) of titanate coupling agent, and 3-10 parts (e.g., 9.2 parts or 9.36 parts) of composite processing aid A; The mass ratio of tailings to waste biochar is 1 to 4:1 (e.g., 2:1). This ratio ensures that the core material has both good mechanical strength and thermal conductivity. By weight, the raw material composition of the skin layer includes: 25 parts ABS resin, 10-20 parts tailings (e.g., 15 parts), 0.9 parts titanate coupling agent, 1.35 parts color masterbatch, and 1.25-2.75 parts (e.g., 1.35 parts) composite processing aid B; the color masterbatch is selected according to the product appearance requirements (e.g., light gray, dark gray, etc.). The skin layer mainly plays the role of protecting the core layer and improving the product's appearance quality and surface performance.

[0029] In some optional embodiments of the present invention, the PVC resin is SG-8 type polyvinyl chloride. This type of resin has a suitable degree of polymerization and viscosity, which can balance the processing performance and mechanical strength of the composite material. Its specific performance parameters are: viscosity range of 73~86mL / g, average degree of polymerization between 700~740, particle size distribution of 63~250μm, volatile matter mass fraction ≤0.40%, apparent density ≥0.500g / mL, and whiteness value ≥75% after heating at 160℃ for 10min. This ensures that it can be fully combined with fillers such as modified tailings and waste biochar in the subsequent melt blending process to form a composite material matrix with a uniform structure.

[0030] In some optional embodiments of the present invention, the tailings are iron tailings or graphite tailings; wherein the iron tailings originate from surrounding mining areas (such as Laiyuan County Frontier Mining Co., Ltd.), and their main chemical composition is SiO2: 50~58%, Al2O3: 25~30%, Fe2O3: 4~8%, CaO2: 2~4%, MgO2: 2~3%, K2O: 2~3%, with the remainder being trace metal oxides. The mineral composition is mainly quartz, hematite, and magnetite. These minerals have high hardness and thermal stability, which can provide good rigid support and thermal stability for composite materials. The particle size range is concentrated in 1~80μm, D 50 =7~10μm, with a volume average particle size of 9~12μm. This suitable particle size distribution helps improve the uniformity of filler dispersion in the PVC matrix and reduces agglomeration. The graphite tailings originate from the Pingdu mining area in Qingdao (e.g., Qingdao Guyu Graphite Co., Ltd.), and their chemical composition is: SiO2: 52~58%, Al2O3: 10~15%, CaO: 10~14%, MgO: 6~10%, Fe2O3: 4~7%, K2O: 2~4%, with the remainder being trace metal oxides. The mineral composition includes quartz, sericite, and calcite. Sericite has a layered structure and can form a reinforcing fiber-like effect in composite materials, improving the mechanical and thermal properties of the material. The particle size range of the graphite tailings is concentrated between 1~90μm, D... 50 =10~13μm, with a volume average particle size of 13~16μm, which complements the particle size distribution of iron tailings, making it easy to construct a continuous packing network in the composite system.

[0031] In some optional embodiments of the present invention, the titanate coupling agent is isopropyltris(dioctylpyrophosphate) titanate (model TCA-K38S). The coupling agent molecule contains an inorganic functional group (-Ti(OR)3) and an organic functional group (long-chain alkyl). The inorganic functional group can undergo an efficient dehydration condensation reaction with the active hydroxyl groups on the tailings surface to achieve chemical bonding, while the organic functional group can entangle with the PVC molecular chain, thereby effectively reducing the polarity of the tailings surface, improving its compatibility with the PVC matrix, and enhancing the dispersibility and interfacial bonding strength of the filler.

[0032] In some optional embodiments of the present invention, the waste biochar is a solid waste obtained by mechanical crushing after biomass pyrolysis (such as waste biochar produced by Shandong Ruiyi High-speed Railway Technology Co., Ltd.), with a particle size of 1~100μm, exhibiting a typical irregular thin sheet shape, with distinct edges and corners, irregular geometric contours, and a porous carbon structure on the surface. This structural feature enables it to not only form a good mechanical interlocking effect with the PVC matrix and tailings particles, but also to construct a continuous thermal conduction path. At the same time, the carbon structure on its surface has good compatibility with the PVC matrix, which helps to improve the interfacial bonding strength of the composite system.

[0033] In some optional embodiments of the present invention, the ACR impact modifier is a core-shell structured acrylate elastomer. The core phase is a cross-linked acrylate elastomer latex particle with a low glass transition temperature (Tg < -20℃), which can undergo elastic deformation under impact load and absorb impact energy. The shell phase is an acrylate polymer with a high glass transition temperature (Tg > 80℃) and excellent compatibility with PVC, which can ensure good bonding between the impact modifier and the PVC matrix and avoid phase separation, thereby significantly improving the impact toughness and elongation at break of the composite material and alleviating the brittleness problem caused by inorganic fillers. The ACR impact modifier was purchased from Wuxi Zhengsheng Plastic Products Manufacturing Co., Ltd.

[0034] In some optional embodiments of the present invention, the raw material composition of composite processing aid A, by mass parts, includes: ① Calcium-zinc stabilizer (R502 type composite calcium-zinc stabilizer): Dosage 1~3 parts (e.g. 2.88 parts), which has both heat stabilization and lubrication functions, can inhibit the thermal degradation reaction of PVC during processing, extend the processing cycle, and improve the flowability of materials; ② Lubricant: 0.5~2 parts (e.g., 1.6 parts), composed of polyethylene wax (L102), stearic acid (ZY-60s), and oxidized polyethylene wax (OS-25); wherein, polyethylene wax is 0.2~0.8 parts (e.g., 0.64 parts), stearic acid is 0.2~0.64 parts (e.g., 0.64 parts), and oxidized polyethylene wax is 0.1~0.6 parts (e.g., 0.32 parts); polyethylene wax and oxidized polyethylene wax are external lubricants, which can reduce the friction between materials and processing equipment, while stearic acid is an internal lubricant, which can improve the flowability between PVC molecular chains. The synergistic effect of the three can optimize the plasticizing rate and balanced torque of the material, ensuring the stability of the processing process; ③ Plasticizer (epoxidized soybean oil ESO): Dosage 1-3 parts (e.g., 1.92 parts), environmentally friendly and non-toxic, can reduce the interaction force between PVC molecular chains and improve the flexibility and processing fluidity of the material; ④ Impact-resistant additive (chlorinated polyethylene CPE-135A): Dosage is 0.5~3 parts (e.g., 2.8 parts). Its chlorine content is about 35%. It has good compatibility with PVC matrix and can further improve the impact resistance and processing stability of composite materials.

[0035] In some optional embodiments of the present invention, the raw material composition of the composite processing aid B, by mass parts, includes: ① Calcium-zinc stabilizer (R502 type compound calcium-zinc stabilizer): dosage 0.75 parts; ② Lubricant: 0.5~2 parts (e.g. 0.6 parts) is a compound of polyethylene wax (L102), stearic acid (ZY-60s) and oxidized polyethylene wax (OS-25); wherein, polyethylene wax is 0.2~0.8 parts (e.g. 0.3 parts), stearic acid is 0.2~0.6 parts (e.g. 0.2 parts) and oxidized polyethylene wax is 0.1~0.6 parts (e.g. 0.1 parts).

[0036] The above-mentioned method for preparing composite panels based on the synergistic reinforcement of waste biochar and tailings includes the following steps: S1. Preparation of modified tailings: (1) The iron tailings or graphite tailings raw ore is sent to the crushing and grinding equipment produced by Zhengzhou Jiemeilong Mining Machinery Co., Ltd. for processing. Large particles with a particle size greater than 100μm are removed by classification and screening to obtain finely ground tailings powder. The powder is placed in a forced-air drying oven at 60~80℃ and dried at a constant temperature for 20~28h to remove free moisture from the material. The moisture content of the dried tailings is controlled to be ≤0.5% to avoid moisture causing defects such as bubbles and pinholes in subsequent processing. After pretreatment, the tailings are sealed for later use. (2) Place the dried tailings and titanate coupling agent in a dry mixing container and premix by manual stirring for 3-5 minutes to ensure that the coupling agent initially and evenly adheres to the surface of the tailings powder, thus preventing local aggregation of the coupling agent during subsequent batch feeding. Add the premixed material as a whole into the main chamber of the SRL-Z500 / 1000A high-speed mixer produced by Jiangsu Lianguan Machinery Co., Ltd. Seal the feed inlet to maintain a closed system environment, start the high-speed mixer, and perform a high-speed dispersion reaction at a speed of 1000-1500 r / min for 15-25 minutes. The heat generated by the intense friction between the materials will naturally raise the system temperature to 75-85℃, driving the coupling agent to react with the surface of the tailings. The coupling reaction is fully carried out. When the temperature exceeds 85℃, the rotation speed is reduced to 50~100r / min to avoid the coupling agent decomposition due to excessive temperature. After the reaction is completed, the high-speed mixer is turned off. After the material inside the chamber cools down to room temperature naturally, the feed port is opened and the mixture is taken out. It is then subjected to vibration screening using a 200-mesh standard sieve to remove insufficiently dispersed agglomerate particles, resulting in a preliminarily purified modified tailings intermediate product. The screened product is placed in a forced-air drying oven at 100~110℃ for constant temperature drying for 2~3 hours to further remove residual trace moisture and small molecules of coupling agent that have not participated in the reaction. After drying, it is taken out and cooled to room temperature to finally obtain the modified tailings product. S2. Preparation of core layer premix: Weigh the raw materials according to the formula ratio, and add PVC resin, the modified tailings prepared above, waste biochar, ACR impact modifier, and composite processing aid A into a high-speed mixer in sequence. First, stir at a low speed of 500~800 r / min for 4~6 min to make the various raw materials initially mixed evenly and avoid the flying of light raw materials (such as stearic acid and ACR impact modifier); then increase the speed to 1000~1200 r / min and stir at high speed for 4~6 min to achieve deep mixing of each component by utilizing the shearing action between materials. During the mixing process, control the system temperature not to exceed 90℃ to prevent premature plasticization of PVC resin; after the mixing is completed, take out the mixture and place it in a sealed container for later use to avoid moisture absorption, and obtain the core layer premix. S3. Preparation of the skin premix: Weigh the raw materials according to the formula ratio, and add ABS resin, the modified tailings, color masterbatch and composite processing aid B into a high-speed mixer in sequence. First, stir at a low speed of 500~800 r / min for 4~6 min to make the various raw materials initially mixed evenly and avoid the light raw materials flying away; then increase the speed to 1000~1200 r / min and stir at high speed for 4~6 min to achieve deep mixing of each component by utilizing the shearing action between materials to obtain the skin premix. S4. Preparation of composite panels: (1) Extrusion molding: The core layer premix is ​​added to the SJ55 / 120 main twin-screw extruder produced by Suzhou Jinwei Machinery Manufacturing Co., Ltd., and the skin layer premix is ​​placed into the SJ45 co-extruder produced by Suzhou Jinwei Machinery Manufacturing Co., Ltd. The temperatures of zones 1 to 4 of the main extruder barrel are controlled as follows: 190~198℃ (e.g., 195℃ or 198℃), 195~202℃ (e.g., 200℃ or 202℃), and 195~202℃ (e.g., 200℃ or 202℃). Temperatures should be set at 190~200℃ (e.g., 198℃ or 200℃), flange area temperature at 200~205℃ (e.g., 203℃ or 205℃), and co-extruder barrel temperature 5~10℃ lower than main extruder temperature (e.g., 5℃ or 10℃). Adjust the main extruder speed to 17~19 r / min and the feed speed to 7.5~8.5 r / min to ensure that the material is fully melted and plasticized under the shearing, compression and conveying action of the screw, while ensuring a stable extrusion rate. (2) Co-extrusion composite and cooling and shaping: The core layer molten material is extruded through the core layer flow channel of the hollow floor mold produced by Jinan Feixiang Mold Machinery Co., Ltd., and the skin layer molten material is extruded synchronously with the core layer through the skin layer flow channel of the mold to achieve co-extrusion composite of the skin layer and the core layer. The skin layer fully wraps the core layer. During the composite process, the skin layer thickness is controlled to be 0.5~1.0mm, the core layer thickness is 23~24mm, and the total thickness is 24~25mm. The extruded composite slab is introduced into the cooling and shaping table. Through the coordinated action of the circulating water cooling system, the closed cavity structure and the air cooling system, rapid cooling and shape fixation are achieved. The temperature of the cooled slab is controlled to be ≤40℃, the cooling time is 3~5min, and the flatness error of the cooled slab is ≤0.5mm / m to avoid warping and deformation of the slab due to uneven cooling. (3) Embossing and cutting: After cooling and shaping, the board is kept at a residual temperature (30~40℃) and embossed by a KY60 embossing roller produced by Changzhou Keyi Steel Printing Roller Factory. The temperature of the embossing roller is controlled at 165~170℃ and the embossing pressure is 0.3~0.5MPa. Stable patterns are formed on the upper and lower surfaces of the board through the squeezing action of the upper and lower rollers. The pattern depth is 0.3~0.5mm, which improves the anti-slip performance and appearance of the product. The traction speed is linked by the built-in program behind the traction device. A high-precision cutting device is used to achieve precise fixed-length cutting of the composite floor. The length is set according to the engineering application requirements (such as 2000mm, 3000mm, etc.). The cutting length error is ≤±2mm. (4) Finished product curing: Transfer the cut composite board finished product to the finished product warehouse and let it stand for 24 hours in an environment with room temperature and relative humidity of 40~60% to complete the release of internal stress and performance stabilization, and obtain the final composite board product; during the curing process, avoid the board from being squeezed, collided or other external forces to prevent deformation or damage. (5) Post-processing and inspection: A comprehensive quality inspection is carried out on the molded composite board, including: Appearance quality inspection: Visual and tactile methods are used to check whether there are cracks, wrinkles, bulges, pits, embossing defects, etc. on the surface of the board. Check whether the skin and core layers are in close contact and without delamination. Check whether the shape and diameter of the round holes in the hollow cylindrical area in the middle of the core layer are relatively uniform and without obvious defects such as pinholes and cracks. Dimensional deviation measurement: The thickness and width of the sheet metal are measured using a vernier caliper with an accuracy of 0.01mm, and the length is measured using a steel tape measure to ensure that the dimensional deviations meet the design requirements; Physical and chemical performance testing: Testing is conducted in accordance with the national standard GB / T 24508-2020 "Wood-Plastic Flooring", including density, hardness, warpage, static bending strength, modulus of elasticity, water absorption rate, water absorption dimensional change rate, surface abrasion resistance, linear thermal expansion coefficient, and room temperature drop ball impact test, to ensure that all performance indicators meet the standard requirements. Products that pass the test are packaged and stored, while unqualified products are recycled, crushed, and reprocessed.

[0037] Unless otherwise specified, "room temperature" in this invention refers to 20~25℃.

[0038] Unless otherwise specified, the term "parts" in this invention refers to parts by weight.

[0039] All raw materials used in this invention were purchased from the market.

[0040] The technical solution of the present invention will be further illustrated by the following embodiments.

[0041] Example 1 A composite board based on the synergistic reinforcement of waste biochar and tailings, raw material preparation: (1) The core layer raw material composition includes: 50 parts PVC resin, 40 parts iron tailings, 20 parts waste biochar, 2.4 parts ACR impact modifier, 1.83 parts titanate coupling agent and 9.2 parts composite processing aid A; wherein, the mass ratio of tailings to waste biochar is 2:1; composite processing aid A includes: 2.88 parts calcium zinc stabilizer R502, 0.64 parts polyethylene wax L102, 0.64 parts stearic acid ZY-60s, 0.32 parts oxidized polyethylene wax OS-25, 1.92 parts epoxidized soybean oil ESO, and 2.8 parts chlorinated polyethylene CPE-135A; (2) The raw material composition of the skin layer includes: 25 parts ABS resin, 15 parts iron tailings, 0.9 parts titanate coupling agent, 1.35 parts light gray masterbatch and 1.35 parts composite processing aid B; wherein, composite processing aid B includes: 0.75 parts calcium zinc stabilizer R502, 0.3 parts polyethylene wax L102, 0.2 parts stearic acid ZY-60s and 0.1 parts oxidized polyethylene wax OS-25; (3) The iron tailings originated from Bianjiang Mining Co., Ltd. in Laiyuan County, Baoding City, Hebei Province. The main chemical components are SiO2 54.77%, Al2O3 27.16%, Fe2O3 5.80%, CaO 2.68%, MgO 2.42%, K2O 2.14%, with the remainder being 2.45% trace metal oxides. The particle size D 50 The particle size is 7.794 μm, and the volume average particle size is 10.56 μm; (4) The waste biochar comes from Shandong Ruiyi High-speed Railway Technology Co., Ltd., with a particle size range of 1~100μm and an irregular thin sheet shape.

[0042] A method for preparing a composite board based on the synergistic reinforcement of waste biochar and tailings, comprising the following steps: S1. Preparation of core layer premix: (1) The iron tailings are fed into a crushing and grinding equipment for processing. Large particles with a particle size greater than 100μm are removed by grading and screening to obtain finely ground tailings powder. The powder is placed in a 70℃ forced-air drying oven for constant temperature drying for 24h. The moisture content of the dried tailings is controlled to be ≤0.5%. The powder is then sealed for later use. (2) According to the core layer formula, the dried iron tailings and titanate coupling agent were placed in a dry mixing container and premixed by manual stirring for 3 minutes. The premixed material was added to the main chamber of the SRL-Z500 / 1000A high-speed mixer and dispersed at a speed of 1200 r / min for 20 minutes. The system temperature was naturally raised to 80℃ by the heat generated by the intense friction between the materials. After the reaction was completed, the mixture was cooled to room temperature and sieved using a 200 mesh standard sieve. The sieved product was placed in a 105℃ forced-air drying oven and dried at a constant temperature for 2 hours to obtain modified iron tailings. (3) Weigh the raw materials according to the formula ratio, and add PVC resin, modified iron tailings, waste biochar, ACR impact modifier and composite processing aid A into a high-speed mixer in sequence. First, stir at a low speed of 600 r / min for 5 min, and then increase the speed to 1100 r / min and stir at a high speed for 5 min. After the mixing is completed, take out the mixture and place it in a sealed container for later use to obtain the core layer premix. S2. Preparation of the cortex premix: (1) The iron tailings are fed into a crushing and grinding equipment for processing. Large particles with a particle size greater than 100μm are removed by grading and screening to obtain finely ground tailings powder. The powder is placed in a 70℃ forced-air drying oven for constant temperature drying for 24h. The moisture content of the dried tailings is controlled to be ≤0.5%. The powder is then sealed for later use. (2) According to the formulation of the skin layer, the dried iron tailings and titanate coupling agent were placed in a dry mixing container and premixed by manual stirring for 3 minutes. The premixed material was added to the main chamber of the SRL-Z500 / 1000A high-speed mixer and dispersed at a speed of 120 r / min for 20 minutes. The system temperature was naturally raised to 80℃ by the heat generated by the intense friction between the materials. After the reaction was completed, the mixture was cooled to room temperature and sieved using a 200-mesh standard sieve. The sieved product was placed in a 105℃ forced-air drying oven and dried at a constant temperature for 2 hours to obtain modified iron tailings. (3) Weigh the raw materials according to the formula ratio, and add ABS resin, the modified tailings, color masterbatch and composite processing aid B into the high-speed mixer in sequence. First, stir at a low speed of 600 r / min for 5 min to make the various raw materials initially mixed evenly and avoid the light raw materials flying away; then increase the speed to 1100 r / min and stir at high speed for 5 min to obtain the skin premix. S3. Preparation of composite panels: (1) Extrusion molding: Add the core layer premix to the SJ55 / 120 main twin-screw extruder, and put the skin layer premix into the SJ45 co-extruder. Control the temperature of the barrel 1~4 of the main extruder to be 198℃, 202℃, 202℃ and 200℃ respectively, and the temperature of the flange area to be 205℃. The barrel temperature of the co-extruder is 5℃ lower than that of the main extruder. Adjust the main machine speed to 18.5r / min and the feeding speed to 8r / min. (2) Co-extrusion and cooling: The core and skin materials are extruded simultaneously through a hollow floor mold; during the compounding process, the skin thickness is controlled to be 0.8 mm, the core thickness to be 23.5 mm, and the total thickness to be 24.3 mm; the extruded composite board is introduced into the cooling and shaping table, and the temperature of the board after cooling is controlled to be 35℃, the cooling time to be 4 min, and the flatness error of the board after cooling to be 0.3 mm / m; (3) Embossing and cutting: After cooling and shaping, the board is kept at a residual temperature (30~40℃) and passed through an embossing roller. The temperature of the embossing roller is controlled at 170℃, the embossing pressure is 0.4MPa, the pattern depth is 0.4mm, and it is cut to a fixed length of 3000mm with a cutting length error of ±1mm. (4) Finished product curing: Transfer the cut composite board finished product to the finished product warehouse and let it stand for 24 hours in an environment of room temperature and relative humidity of 50% to complete the release of internal stress and performance stabilization, and obtain the final composite board product. S4. Post-processing and inspection: The finished boards are subjected to appearance quality inspection, dimensional deviation measurement and physical and chemical property testing. The test results are shown in Table 1.

[0043] Example 2 A composite board based on the synergistic reinforcement of waste biochar and tailings, raw material preparation: (1) The core layer raw material composition includes: 50 parts PVC resin, 40 parts graphite tailings, 20 parts waste biochar, 2.4 parts ACR impact modifier, 1.83 parts titanate coupling agent and 9.36 parts composite processing aid A; wherein, the mass ratio of tailings to waste biochar is 2:1; composite processing aid A includes: 2.88 parts calcium zinc stabilizer R502, 0.64 parts polyethylene wax L102, 0.64 parts stearic acid ZY-60s, 0.48 parts oxidized polyethylene wax OS-25, 1.92 parts epoxidized soybean oil ESO and 2.8 parts chlorinated polyethylene CPE-135A; (2) The raw material composition of the skin layer includes: 5 parts ABS resin, 15 parts graphite tailings, 0.9 parts titanate coupling agent, 1.35 parts light gray masterbatch and 1.35 parts composite processing aid B; wherein, composite processing aid B includes: 0.75 parts calcium zinc stabilizer R502, 0.3 parts polyethylene wax L102, 0.2 parts stearic acid ZY-60s and 0.1 parts oxidized polyethylene wax OS-25; (3) The graphite tailings originated from Qingdao Guyu Graphite Co., Ltd. in Pingdu City, Qingdao, Shandong Province. The main chemical components are SiO2 55.51%, Al2O3 12.87%, CaO 11.84%, MgO 8.09%, Fe2O3 5.06%, K2O 2.69%, with the remainder being 2.08% trace metal oxides. The particle size D 50 The particle size is 11.91 μm, and the volume average particle size is 14.61 μm; (4) The source of waste biochar is the same as in Example 1.

[0044] A method for preparing a composite board based on the synergistic reinforcement of waste biochar and tailings, comprising the following steps: S1. Preparation of core layer premix: Same as step S1 in Example 1; S2. Preparation of the cortex premix: Same as step S2 in Example 1; S3. Preparation of composite panels: (1) Extrusion molding: Add the core layer premix to the SJ55 / 120 main twin-screw extruder, and put the skin layer premix into the SJ45 co-extruder. Control the temperature of the barrel 1~4 of the main extruder to be 195℃, 200℃, 200℃ and 198℃ respectively, and the temperature of the flange area to be 203℃. The barrel temperature of the co-extruder is 5℃ lower than that of the main extruder. Adjust the main machine speed to 18.5r / min and the feeding speed to 8r / min. (2) Co-extrusion and cooling: The core and skin materials are extruded simultaneously through a hollow floor mold; during the compounding process, the skin thickness is controlled to be 0.8 mm, the core thickness to be 23.5 mm, and the total thickness to be 24.3 mm; the extruded composite board is introduced into the cooling and shaping table, and the temperature of the board after cooling is controlled to be 35℃, the cooling time to be 4 min, and the flatness error of the board after cooling to be 0.3 mm / m; (3) Embossing and cutting: After cooling and shaping, the board is kept at a residual temperature (30~40℃) and passed through an embossing roller. The temperature of the embossing roller is controlled at 168℃, the embossing pressure is 0.4MPa, the pattern depth is 0.4mm, and it is cut to a fixed length of 3000mm with a cutting length error of ±1mm. (4) Finished product curing: Transfer the cut composite board finished product to the finished product warehouse and let it stand for 24 hours in an environment of room temperature and relative humidity of 50% to complete the release of internal stress and performance stabilization, and obtain the final composite board product. S4. Post-processing and inspection: The finished boards are subjected to appearance quality inspection, dimensional deviation measurement and physical and chemical property testing. The test results are shown in Table 1.

[0045] Table 1. Performance test results of the composite panels prepared in Examples 1-2 According to the calculation, the composite panels prepared in Examples 1 and 2 all meet the requirements of the national standard GB / T24508-2020.

[0046] Figure 1 The following are FT-IR spectra of iron tailings before and after modification in Example 1 (where IOT represents unmodified iron tailings and T-IOT represents modified iron tailings); from Figure 1 As can be seen from this, unmodified IOT has a peak thickness of 3687 cm⁻¹. -1 The T-IOT exhibits a significant absorption peak characteristic of hydroxyl (-OH) stretching vibration at this wavenumber. This peak corresponds to the large number of naturally occurring polar hydroxyl groups on the IOT surface, which is the main structural source of its surface hydrophilicity. However, after modification with a titanate coupling agent, the absorption peak intensity of T-IOT at this wavenumber significantly decreases and the peak shape becomes flatter. This indicates that the inorganic functional group (-Ti(OR)3) in the coupling agent molecule undergoes an efficient dehydration condensation reaction with the active -OH on the IOT surface, achieving chemical consumption and structural reconstruction of the surface polar hydroxyl groups. Meanwhile, T-IOT exhibits a significant absorption peak at 2960 cm⁻¹. -1 (-CH3 asymmetric stretching vibration), 2868cm -1 (-CH2- symmetric stretching vibration) and 1432cm -1The characteristic absorption peak of the alkyl chain in the titanate coupling agent molecule appeared in the (CH bending vibration) region, while the unmodified IOT showed no obvious absorption signal in the above wavenumber range, directly confirming that the coupling agent has been stably grafted onto the IOT surface through chemical bonding, achieving organic functionalization modification of the inorganic powder surface. Furthermore, IOT showed an absorption peak at 740 cm⁻¹. -1 (Fe-O bond or Si-O-Si bending vibration), 446 cm -1 (Lattice framework vibration) and 1088cm -1 The characteristic absorption peak at the (Si-O stretching vibration) remains intact in the T-IOT, with only slight modulation of peak intensity. This indicates that the modification process only acts on the active sites on the IOT surface, without damaging its internal crystal structure and core inorganic mineral composition, thus ensuring the physicochemical properties of the powder itself. The titanate coupling agent achieves surface modification of IOT, effectively reducing its surface polarity, and the modification effect is stable and significant.

[0047] Figure 2 Here are SEM microstructure images of the waste biochar from Examples 1 and 2; from Figure 2 As can be seen, the waste biochar particles exhibit a typical irregular flake-like morphology, with distinct edges and corners and an irregular geometric outline, which is a typical morphological feature formed by mechanical crushing after biomass pyrolysis.

[0048] Figure 3 The images shown are SEM images (magnifications of 500× and 5000×) of the tensile cross-section of the composite plate prepared in Example 1. Figure 3 From (A) and (B), it can be seen that when the IOT filler content is 10wt%, the tensile fracture surface of the composite material is smooth, and the continuity of the PVC matrix is ​​good. At this time, the material mainly exhibits ductile fracture, and the PVC matrix can effectively bear load and undergo plastic deformation. However, the lower filler content has limited room for improvement in the overall performance of the composite material. Figure 3 (C) and (D) show that as the IOT filling amount increases to 30wt%, the cross-section exhibits more optimized characteristics. The IOT particles are relatively uniformly dispersed in the PVC matrix, with only a very small amount of slight agglomeration, good interfacial bonding, and high stress transfer efficiency. Although a certain number of micropores and microcracks exist in the cross-section, these defects effectively terminate crack propagation, significantly improving the strength and rigidity of the material while maintaining a certain degree of plastic deformation capacity. Figure 3 As shown in (E) and (F), when the IOT filling content is further increased to 50 wt%, the cross-section of the composite material is extremely rough, with a large number of IOT particles exposed on the cross-section. The PVC matrix is ​​fragmented, with dense and interconnected pores. The IOT particles undergo severe agglomeration, and the debonding phenomenon at the interface with the PVC matrix is ​​significant, becoming the main source of stress concentration and failure initiation point, resulting in a significant decrease in the mechanical properties of the composite material.

[0049] Figure 4 The images shown are SEM images (magnifications of 500× and 5000×) of the tensile cross-section of the composite plate prepared in Example 2. Figure 4 As shown in (A) and (B), when the GOT filling content is 10wt%, the tensile fracture surface of the composite material is generally smooth and dense, and the continuity of the PVC matrix is ​​well maintained, with only a small amount of distributed graphite tailings inorganic particles observed. At this point, the material fracture mode is mainly ductile fracture, and the PVC matrix can effectively bear external forces through plastic deformation. However, due to the low filler content, the enhancement effect on the core properties of the composite material, such as strength and rigidity, is limited, and the potential for performance improvement has not been fully realized. Figure 4 As shown in (C) and (D), with the GOT filling amount increasing to 30 wt%, the cross-sectional morphology exhibits the optimal structural characteristics. The GOT particles are uniformly dispersed in the PVC matrix, with no obvious agglomeration; only a very small number of particles show slight aggregation. The matrix tightly encapsulates the filler particles, and the two-phase interface is well-bonded, providing microscopic protection for the efficient transfer of stress between the filler and the matrix. The small number of micropores and fine textures distributed in the cross-section can play a role in terminating crack propagation during stress, enabling the composite material to achieve a synergistic improvement in strength and rigidity while retaining a certain degree of plastic deformation capacity. Figure 4 As shown in (E) and (F), when the GOT filler content is further increased to 50 wt%, the tensile fracture surface of the composite material becomes extremely rough. A large number of GOT particles are directly exposed on the fracture surface, and the originally continuous PVC matrix is ​​divided into fragments by the dense filler particles, forming dense and interconnected pores and gaps between the particles. At this time, the GOT particles undergo severe agglomeration, and the debonding phenomenon at the interface with the PVC matrix is ​​very significant. The agglomerates and the interfacial gaps become the main stress concentration sources and fracture failure initiation points under stress, ultimately leading to a significant deterioration in the overall mechanical properties of the composite material.

[0050] Comparative Example 1 Similar to Example 1, except that the core layer raw material composition includes 50 parts PVC resin, 10 parts iron tailings, 50 parts waste biochar, 2.4 parts ACR impact modifier, 1.83 parts titanate coupling agent and 7.36 parts composite processing aid A; that is, the mass ratio of tailings to waste biochar is 1:5.

[0051] The results showed that excessive use of waste biochar and a low proportion of iron tailings completely eliminated the synergistic enhancement effect. The excessively porous structure of the waste biochar severely disrupted the matrix continuity, significantly increasing internal porosity and decreasing interfacial bonding strength; tensile strength, flexural strength, and notched impact strength all decreased dramatically, dropping to 28.5 MPa, 49.2 MPa, and 4.1 kJ / m², respectively. 2The thermal conductivity is only 0.21 W / (m·K), which cannot form a continuous heat conduction network; the material brittleness increases significantly, the water absorption dimensional change rate rises to more than 0.5%, the water resistance and dimensional stability deteriorate significantly, and the overall performance is far lower than that of Example 1, which cannot meet the requirements of GB / T 24508-2020 standard.

[0052] Comparative Example 2 Same as Example 1, except that the core layer raw material composition includes 50 parts PVC resin, 0 parts iron tailings, 60 parts waste biochar, 2.4 parts ACR impact modifier, 1.83 parts titanate coupling agent and 7.36 parts composite processing aid A; that is, the mass ratio of tailings to waste biochar is 0:6.

[0053] The results showed that the complete lack of rigid support and synergistic framework provided by iron tailings, coupled with a high proportion of waste biochar, led to a comprehensive deterioration in the material's overall performance. Tensile strength was only 25.3 MPa, flexural strength was 43.7 MPa, indicating insufficient strength; and notched impact strength dropped to 3.5 kJ / m. 2 It is extremely brittle; its thermal conductivity is as low as 0.18 W / (m・K), resulting in poor thermal conductivity; its processing fluidity is significantly reduced, making extrusion molding difficult; the surface of the sheet is rough and has many internal pores; its water absorption rate reaches 1.2%, and its water absorption dimensional change rate exceeds the standard. Its mechanical, thermal, processing, and performance characteristics are all substandard, and it has no engineering application value.

[0054] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite board based on synergistic reinforcement of waste biochar with tailings, characterized by, Includes the core layer and the skin layer; among which, The core layer raw material composition, by mass, includes: 40-60 parts PVC resin, 20-50 parts tailings, 5-40 parts waste biochar, 0.8-4 parts ACR impact modifier, 1.8-3 parts titanate coupling agent, and 3-10 parts composite processing aid A. The skin material composition, by mass, includes: 25 parts ABS resin, 10-20 parts tailings, 0.9 parts titanate coupling agent, 1.35 parts color masterbatch, and 1.25-2.75 parts composite processing aid B.

2. The composite board based on synergistic reinforcement of waste biochar and tailings according to claim 1, characterized in that, The PVC resin is SG-8 type polyvinyl chloride, with a viscosity of 73~86 mL / g, an average degree of polymerization of 700~740, a particle size distribution of 63~250 μm, a volatile matter mass fraction of ≤0.40%, an apparent density of ≥0.500 g / mL, and a whiteness value of ≥75% after heating at 160℃ for 10 min. The tailings are iron tailings or graphite tailings; The titanate coupling agent is isopropyltris(dioctylpyrophosphoryloxy) titanate; The particle size of the waste biochar is 1~100μm; The ACR impact modifier is a core-shell structure acrylate elastomer; The raw material composition of the composite processing aid A, by mass parts, includes: 1-3 parts calcium-zinc stabilizer, 0.5-2 parts lubricant, 1-3 parts plasticizer, and 0.5-3 parts impact-resistant agent; The raw material composition of the composite processing aid B, by mass, includes: 0.75 parts of calcium-zinc stabilizer and 0.5 to 2 parts of lubricant.

3. The composite board based on synergistic reinforcement of waste biochar with tailings according to claim 2, characterized in that, The calcium-zinc stabilizer is an R502 type composite calcium-zinc stabilizer. The lubricant comprises, by weight, 0.2-0.8 parts polyethylene wax, 0.2-0.64 parts stearic acid, and 0.1-0.6 parts oxidized polyethylene wax; The plasticizer is epoxidized soybean oil; The impact-resistant additive is chlorinated polyethylene.

4. A method of manufacturing a composite board based on synergistic reinforcement of waste biochar and tailings according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Preparation of modified tailings: The dried tailings and titanate coupling agent were mixed according to the ratio of tailings to titanate coupling agent in the core layer premix and the skin layer premix, respectively. The bonding reaction was carried out under stirring, cooled to room temperature, sieved, and the sieved product was dried again to obtain core layer premix modified tailings and skin layer premix modified tailings. S2. Preparation of core layer premix: Weigh the raw materials according to the formula ratio, and add PVC resin, core layer premix modified tailings, waste biochar, ACR impact modifier and composite processing aid A into the mixer in sequence, stir, and obtain core layer premix. S3. Preparation of leather premix: Weigh the raw materials according to the formula ratio, and add ABS resin, leather premix modified tailings, color masterbatch and composite processing aid B into the mixer in sequence, stir, and obtain leather premix. S4. Preparation of composite board: The core layer premix and the skin layer premix are processed into shape to obtain a composite board based on the synergistic reinforcement of waste biochar and tailings.

5. The preparation method according to claim 4, characterized in that, In step S1, the specific operation steps of the bonding reaction are as follows: first, premix by manual stirring for 3-5 minutes, then carry out high-speed dispersion reaction at a speed of 1000-1500 r / min for 15-25 minutes, and the system temperature naturally rises to 75-85℃.

6. The preparation method according to claim 4, characterized in that, In steps S2 and S3, the specific stirring operation steps are as follows: first, stir at a low speed of 500~800 r / min for 4~6 min, then increase the speed to 1000~1200 r / min and stir at a high speed for 4~6 min, and control the system temperature to not exceed 90℃ during the mixing process.

7. The preparation method according to claim 4, characterized in that, In step S4, the specific processing steps are as follows: the core layer premix is ​​placed into the main extruder, and the skin layer premix is ​​placed into the co-extruder. The temperatures of zones 1-4 of the main extruder barrel are controlled to be 190-198℃, 195-202℃, 195-202℃, and 190-200℃, respectively, and the flange zone temperature is 200-205℃. The co-extruder barrel temperature is 5-10℃ lower than the main extruder barrel temperature. The main extruder speed is adjusted to 17-19 r / min, and the feeding speed is 7.5-8.5 r / min. The core layer premix and the skin layer premix are extruded synchronously through a hollow floor die. The skin layer thickness is controlled to be 0.8 mm, and the core layer thickness is controlled to be 23.5 mm. After cooling, embossing and cutting are performed, followed by static curing to complete the processing.

8. The preparation method according to claim 7, characterized in that, The embossing pressure is 0.3~0.5MPa, the embossing roller temperature is 165~170℃, and the pattern depth is 0.3~0.5mm.

9. The preparation method according to claim 7, characterized in that, The static curing process involves placing the object at room temperature and relative humidity of 40-60% for 24 hours.

10. The application of a composite panel based on the synergistic reinforcement of waste biochar and tailings as described in any one of claims 1 to 3 in the preparation of green and low-carbon building materials.

Images