Synergistic reinforced composite board based on multi-source waste and preparation method thereof

Abstract

The invention relates to the field of environment-friendly composite materials, in particular to a synergistically reinforced composite board based on multi-source waste and a preparation method of the synergistically reinforced composite board. The composite board comprises the following raw materials in parts by weight: 10-30 parts of modified waste paper fibers, 15-30 parts of chopped waste textile fibers, 20-40 parts of waste plastic fragments, 30-60 parts of matrix resin, 2-8 parts of a compatibilizer and 1-5 parts of a functional additive. According to the invention, waste paper fibers in waste plastics and waste textile fibers are utilized to form a'short-long fiber synergetic enhanced network ', unmodified PE / PP is added as a matrix modifier, and a dynamic compatibilization technology is adopted to improve interface bonding, so that the mechanical properties of the composite material are remarkably improved, the tensile strength can reach more than 35 MPa, the impact strength can reach more than 15 kJ / m < 2 >, and the mechanical properties of the composite material are improved. The problems that the utilization rate of single waste is low, and the mechanical property is insufficient due to poor interfacial compatibility of waste plastics and waste fibers are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of environmentally friendly composite materials, and in particular to a synergistically reinforced composite plate based on multi-source waste and a preparation method thereof. Background Art

[0002] In recent years, as environmental protection has become increasingly popular, the use of waste to prepare environmentally friendly composite materials has become an important resource recycling method. However, existing technologies have some shortcomings, such as low utilization rates of single waste materials and poor interfacial compatibility between waste plastics and waste fibers, resulting in suboptimal mechanical properties of composite materials. Traditional fiber reinforcement processes rely heavily on high-purity raw materials, resulting in high levels of impurities and poor fiber dispersion in recycled materials. Multi-component composite materials are difficult to recycle, making it difficult to balance mechanical properties with environmental performance.

[0003] There are currently some invention patents that address the issues of low utilization of single waste materials and poor interfacial compatibility between waste plastics and waste fibers, which lead to insufficient mechanical properties. For example, patent CN107298868A discloses a lignin-reinforced wood-plastic composite material, which is composed of one or more of plant fibers, lignin, recycled thermoplastics, mineral powder, and processing aids. This patent improves the mechanical properties, thermal stability, and anti-aging properties of wood-plastic materials by adding lignin to them. However, this patent still has the problem of further research on the modification of lignin to improve its compatibility and dispersibility with recycled thermoplastics. Patent CN114806108A discloses a method for manufacturing outdoor panels from waste textiles, which composites waste textiles with PE powder or PP powder to prepare outdoor panels. This patent enables textile products to be used outdoors, and the prepared outdoor panels do not rot and are not prone to deformation or cracking. However, this patent still has the problem that during the pretreatment process of waste textiles, the dosage and activation conditions of the maleic anhydride activator need to be further optimized to improve the compatibility and performance of the waste textiles.

[0004] In summary, the existing technology has the following shortcomings: 1. The utilization rate of single waste is low, and the interface compatibility between waste plastics and waste fibers in composite materials is poor, resulting in unsatisfactory mechanical properties of the composite materials; 2. The traditional fiber reinforcement process is highly dependent on high-purity raw materials, and the recycled materials contain many impurities and poor fiber dispersion, which affects the performance of the composite materials; 3. The recycling and reuse of multi-component composite materials is difficult, and it is difficult to take into account both the mechanical properties and environmental protection of the composite materials; 4. The compatibility and dispersibility of lignin and recycled thermoplastics need to be further improved; 5. During the pretreatment of waste textiles, the dosage and activation conditions of maleic anhydride activator need to be optimized to improve the compatibility and performance of waste textiles. Summary of the Invention

[0005] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide a synergistically reinforced composite board based on multi-source waste and a preparation method thereof, which is used to solve the problems existing in the prior art such as low utilization rate of single waste, poor interface compatibility between waste plastics and waste fibers resulting in insufficient mechanical properties, strong dependence of traditional fiber reinforcement processes on high-purity raw materials, poor polydispersity of impurities in recycled materials, and difficulty in recycling multi-component composite materials.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention is achieved through the following technical solutions.

[0007] The first aspect of the present invention provides a synergistically reinforced composite board based on multi-source waste, which includes the following raw materials in parts by weight: 50-100 parts of modified waste paper fiber, 10-30 parts of short-cut waste textile fiber, 30-60 parts of waste plastic fragments, 60-120 parts of matrix resin, 5-15 parts of compatibilizer, and 5-15 parts of functional additives.

[0008] In some embodiments of the present invention, the modified waste paper fiber is obtained by surface-modifying waste paper fiber by adding a coupling agent, wherein the coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent, or a phosphate coupling agent.

[0009] In some embodiments of the present invention, the chopped waste textile fibers are obtained by depolymerizing waste textile fibers by adding a chemical depolymerization agent, wherein the chemical depolymerization agent is ethylene glycol or an ionic liquid.

[0010] In some embodiments of the present invention, the length of the chopped textile waste fibers is 2-10 mm.

[0011] In some embodiments of the present invention, the base resin is selected from one or more of unmodified PE, unmodified PP, recycled PE or recycled PP; the weight ratio of the unmodified PE, unmodified PP, recycled PE or recycled PP is (1.33-8): (1-6): (0.67-5.00): 1.

[0012] In some embodiments of the present invention, the compatibilizer is selected from one or more of maleic anhydride grafted PE, maleic anhydride grafted PP or a dynamic crosslinker; the dynamic crosslinker is selected from one or more of hyperbranched epoxy resin, maleic anhydride grafted polypropylene or ethylene-acrylate copolymer.

[0013] In some embodiments of the present invention, the functional additive is calcium carbonate and / or a flame retardant. The flame retardant is selected from one or more of aluminum hydroxide, magnesium hydroxide, or a phosphorus-based flame retardant; and the mass ratio of the calcium carbonate to the flame retardant is (2-6):1.

[0014] A second aspect of the present invention provides a method for preparing a synergistically reinforced composite plate based on multi-source waste, comprising the following steps:

[0015] S1. Collecting waste plastic packaging and obtaining waste paper fibers and waste plastic fragments through dry separation. Placing the waste paper fibers in an alkaline solution for alkaline treatment, and then adding a coupling agent and anhydrous ethanol for surface modification to obtain modified waste paper fibers.

[0016] S2. collecting waste textile fibers, pre-treating them, and then chemically depolymerizing them using a chemical depolymerization system to obtain chopped waste textile fibers;

[0017] S3, uniformly mixing the modified waste paper fibers and waste plastic fragments obtained in step S1, the chopped waste textile fibers obtained in step S2, a matrix resin, a compatibilizer, and a functional additive to obtain a mixed material;

[0018] S4. Melt and blend the mixed materials obtained in step S3, and after forming, obtain a synergistically reinforced composite plate based on multi-source waste through post-processing.

[0019] In some embodiments of the present invention, in step S1, the alkaline solution is a NaOH solution with a mass fraction of 1.5-5%.

[0020] In some embodiments of the present invention, in step S1, the mass volume ratio of the waste paper fibers to the alkaline solution is 1 g: (10-30) mL.

[0021] In some embodiments of the present invention, in step S1, the temperature of the alkali treatment is 40-80° C. and the time is 15-60 min.

[0022] In some embodiments of the present invention, in step S1, the mass ratio of the waste paper fibers, the coupling agent and anhydrous ethanol is (5-20):(1-5):1.

[0023] In some embodiments of the present invention, in step S2, the pretreatment includes mechanical opening, air flow sorting, and electrostatic sorting to remove impurities.

[0024] In some embodiments of the present invention, in step S2, the mass ratio of the waste textile fibers to the chemical depolymerizing agent is 1:(5-15).

[0025] In some embodiments of the present invention, in step S2, the temperature of the chemical depolymerization is 120-220° C. and the time is 1-4 h.

[0026] In some embodiments of the present invention, in step S3, the weight ratio of the modified waste paper fiber, waste plastic fragments, short-cut waste textile fiber, matrix resin, compatibilizer and functional additive is (5-15): (20-40): (5-15): (40-70): (3-8): 1.

[0027] In some embodiments of the present invention, in step S4, the melt blending temperature is 180-220° C. and the time is 2-8 minutes.

[0028] In some embodiments of the present invention, the molding is volume pulsation injection molding or gradient hot pressing molding.

[0029] In some embodiments of the present invention, in step S4, the post-processing includes UV curing and water cooling.

[0030] As mentioned above, the present invention provides a synergistically reinforced composite plate based on multi-source waste and a preparation method thereof, which has the following characteristics:

[0031] Beneficial effects:

[0032] 1) The present invention utilizes waste paper fibers from waste plastics and waste textile fibers to form a "short-long fiber synergistic reinforcement network", adds matrix resin as a matrix modifier, and adds a compatibilizer to improve interface bonding, thereby significantly improving the mechanical properties of the composite material, with a tensile strength of more than 35MPa and an impact strength of 15kJ / m 2 The above effectively solves the problem of low utilization rate of single waste and poor interface compatibility between waste plastics and waste fibers, which leads to insufficient mechanical properties;

[0033] 2) The composite board material cost of the present invention is relatively low, reducing the cost of conventional composite boards on the market by approximately 40%, and the proportion of recycled materials can reach over 70%, reducing carbon emissions by approximately 50%. Furthermore, the mechanical property retention rate of the present invention can still reach over 80% after three recycling cycles, enabling multiple material recycling and reusing, solving the problems of difficult recycling of multi-component composite materials and the difficulty in balancing mechanical properties and environmental performance. This meets the needs of the circular economy and has broad application prospects. DETAILED DESCRIPTION

[0034] The following describes in detail a synergistically reinforced composite plate based on multi-source waste and a preparation method thereof of the present invention.

[0035] The present invention proposes a synergistically reinforced composite board based on multi-source waste and a preparation method thereof. This method utilizes waste paper fibers and waste textile fibers from waste plastics to form a "short-long fiber synergistic reinforcement network," adds unmodified PE / PP as a matrix modifier, and improves interfacial bonding through dynamic volume expansion technology; combines dry processing with solvent methods to reduce water consumption and pollution, and adopts volume pulsation injection molding or gradient hot pressing molding processes to improve fiber dispersion and interfacial bonding; introduces dynamic covalent bonds or hyperbranched polymer networks to achieve multiple recycling of materials. This method not only reduces raw material costs and carbon emissions through the integrated innovation of synergistic enhancement of multi-source waste, interface modification technology, and green molding processes, but also significantly improves the mechanical properties of composite materials, realizes the recyclable reuse of materials, meets the needs of a circular economy, and has broad application prospects. On this basis, the present invention was completed.

[0036]

Synergistically reinforced composite panels based on multi-source waste

[0037] The present invention provides a synergistically reinforced composite board based on multi-source waste, comprising the following raw materials in parts by weight: 10-30 parts of modified waste paper fibers, which may be 10-15 parts, 15-20 parts, 20-25 parts or 25-30 parts, 15-30 parts of chopped waste textile fibers, which may be 15-20 parts, 20-25 parts or 25-30 parts, 20-40 parts of waste plastic fragments, which may be 20-25 parts, 25-30 parts, 30-35 parts or 35-40 parts, 30-60 parts of matrix resin, which may be 30-40 parts, 40-50 parts or 50-60 parts, 2-8 parts of a compatibilizer, which may be 2-4 parts, 4-6 parts or 6-8 parts, and 1-5 parts of a functional additive, which may be 1-2 parts, 2-3 parts, 3-4 parts or 4-5 parts. The formula design achieves a balance between performance, cost and environmental benefits by precisely controlling the weight range of each component. Among them, the composite board contains 10-30 parts of modified waste paper fibers, which can significantly improve the bending modulus and dimensional stability of the material as a rigid reinforcement. If the content is less than 10 parts, the reinforcement effect is insufficient, and if it is higher than 30 parts, it is easy to cause fiber agglomeration and increased brittleness; 15-30 parts of short-cut waste textile fibers form a long fiber network, giving the material excellent impact resistance and elongation at break. When the content is less than 15 parts, the impact resistance is limited, and when it exceeds 30 parts, the processing fluidity may be reduced due to excessive fiber length; 20-40 parts of waste plastic fragments are used as a continuous phase matrix to wrap the reinforcing fibers. If it is less than 20 parts, the material structure will be loose, and if it is higher than 40 parts, it may Fluctuations in the molecular weight of recycled materials affect performance stability; 30-60 parts of matrix resin (unmodified PE / PP or recycled PE / PP) provide support for the main structure. When it is less than 30 parts, insufficient matrix easily leads to delamination. When it is more than 60 parts, the utilization rate of recycled materials is insufficient and the cost increases; 2-8 parts of compatibilizer improve the overall performance of composite materials by improving interface compatibility. When it is less than 2 parts, the compatibilization effect is insufficient. When it is more than 8 parts, it may cause excessive cross-linking and make the material brittle; 1-5 parts of functional additives (such as calcium carbonate and flame retardants) are used to adjust the rigidity and fire rating of the material respectively. When it is less than 1 part, the functional effect is not significant. When it is more than 5 parts, the toughness may be reduced due to the aggregation of additives. Through the above-mentioned ratio design, the composite board of the present invention has excellent tensile strength (≥35MPa), impact strength (≥15kJ / m 2 ) and other key performance indicators, while achieving the technical effects of recycled materials accounting for ≥ 70%, raw material costs reduced by more than 40%, and carbon emissions reduced by 50%, which perfectly meets the needs of the circular economy.

[0038] In the synergistically reinforced composite sheet based on multi-source waste provided by the present invention, waste paper fibers and waste plastic fragments are obtained after dry process treatment such as bulk packaging, magnetic separation, crushing, wire drawing dissociation and screening of waste plastic packaging, and waste plastic packaging includes waste printing paper, waste copy paper, waste plastic film, waste plastic bottles, waste agricultural plastic film, waste plastic boxes, etc. Modified waste paper fibers are obtained by surface modification of waste paper fibers by adding a coupling agent. The coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent or a phosphate coupling agent. In a preferred embodiment, the collected waste paper fibers are pretreated with NaOH to destroy the keratinization of the fibers, and then surface modified with a silane coupling agent to improve compatibility with a hydrophobic resin. Wherein, the silane coupling agent is a silane coupling agent KH550 (CAS No.: 919-30-2) produced by Wuhan Huaxiang Kejie Biotechnology Co., Ltd.

[0039] In the multi-source waste-based synergistically reinforced composite board provided by the present invention, the chopped textile waste fibers are produced by depolymerizing textile waste fibers by adding a chemical depolymerization agent. The textile waste fibers may be, for example, waste cotton textile fibers, waste polyester textile fibers, waste wool textile fibers, waste nylon textile fibers, waste acrylic textile fibers, or waste blended fibers. The chemical depolymerization agent is ethylene glycol or an ionic liquid, such as an imidazole ionic liquid, a sulfonate ionic liquid, an acetate ionic liquid, or a fluorosulfonyl ionic liquid.

[0040] In the synergistically reinforced composite board based on multi-source waste provided by the present invention, the length of the chopped waste textile fibers is 3-12mm, which can be selected as 3-5mm, 5-7mm, 7-9mm, 9-12mm, 3-9mm or 6-12mm. This design is based on a comprehensive consideration of cost, performance, processability and environmental protection. First of all, from the perspective of cost and process compatibility, chopped fibers can be obtained directly from waste textiles by mechanical shearing, without the need for complex pretreatment, which significantly reduces the utilization cost of recycled raw materials. At the same time, its length is highly matched with the screw size of conventional injection molding machines, avoiding the equipment entanglement or mold blocking problems that may be caused by long fibers, and there is no need to modify the existing production line, ensuring the versatility of the process. Secondly, in terms of performance balance, the fiber length of 3-12mm can form an effective three-dimensional randomly distributed network in the matrix, which not only ensures the impact resistance (impact strength ≥15kJ / m 2) and flexural modulus (≥2.5GPa), and the toughness of the material is retained through the fiber pull-out mechanism (elongation at break > 8%). In addition, this length range has a high tolerance for trace impurities in waste textile raw materials, which improves the recycling rate and the qualified rate of finished products. In terms of processing fluidity and molding cycle optimization, 3-12mm fibers have the best compatibility with the matrix resin, and the melt viscosity is controlled in the range of 500-1500Pa·s, which is suitable for a variety of molding processes, and the filling time and holding time are significantly shortened, and the overall production efficiency is improved by more than 30%. Finally, from the perspective of environmental protection and performance synergy, short-cut fiber processing has low energy consumption, and can reduce carbon emissions by 80-120kg CO2eq per ton of material. It also has a high degree of matching with the particle size of waste plastic fragments, which is conducive to the formation of a "fiber-wrapped plastic" microstructure, further improving material performance. If the fiber length exceeds the range of 3-12mm, it will lead to problems such as reduced reinforcement effect, processing difficulties or performance fluctuations. For example, fibers that are too short (<3mm) can reduce impact resistance due to insufficient interfacial bonding area; fibers that are too long (>12mm) can easily form agglomerates, leading to localized stress concentration and prolonged molding cycles. Therefore, by strictly controlling the length range of chopped textile waste fibers, this invention achieves high-value utilization of multi-source waste, providing a technical solution for the composite material field that combines economic efficiency, environmental friendliness, and high performance.

[0041] In the synergistically reinforced composite sheet based on multi-source waste provided by the present invention, the matrix resin is selected from one or more of unmodified PE, unmodified PP, recycled PE, or recycled PP. Unmodified PE and unmodified PP are purchased from Sinopec, while recycled PE and recycled PP are purchased from Kingfa Science & Technology. The recycled PE is preferably Kingfa Science & Technology's recycled HDPE, and the recycled PP is preferably Kingfa Science & Technology's recycled HDPP. The weight ratio of unmodified PE, unmodified PP, recycled PE and recycled PP is: (1-5): (1-5): (0.5-3): (0.5-3): 1, which can be (1-3): (1-5): (0.5-3): (0.5-3): 1, (3-5): (1-5): (0.5-3): (0.5-3): 1, (1-5): (1-3): (0.5-3): (0.5-3): 1, (1-5): (3-5): (0.5-3): (0.5-3): 1, (1-5): (1-5): (0 .5-1.5):(0.5-3):1, (1-5):(1-5):(1.5-3):(0.5-3):1, (1-5):(1-5):(0.5-3):(0.5-1.5):1, (1-5):(1-5):(0.5-3):(1.5-3):1, and the total weight proportions of the four satisfy (unmodified PE+unmodified PP):(recycled PE+recycled PP)=(1-7):1, and the synergistic proportion relationship can be selected as (1-3):1, (3-5):1, (5-7):1 or (3-7):1.

[0042] In the synergistically reinforced composite board based on multi-source waste provided by the present invention, the compatibilizer is one or more of maleic anhydride grafted PE, maleic anhydride grafted PP or a dynamic cross-linking agent, and the dynamic cross-linking agent is a hyperbranched epoxy resin, a diene peroxide cross-linking agent (such as diisopropylbenzene peroxide DCP) or a silicon hydrogen addition type cross-linking agent (such as hydrogenated silicone oil and platinum catalyst system). The role of the compatibilizer in the composite board is mainly to improve the compatibility between different materials so that they can be evenly dispersed and form a stable structure. Maleic anhydride grafted PE and maleic anhydride grafted PP enhance the binding force between polyolefins and polar fillers by introducing polar groups, thereby improving mechanical properties and heat resistance; dynamic cross-linking agents (such as hyperbranched epoxy resins) form hyperbranched polymer networks during processing, which can improve the toughness, strength and durability of the material, while optimizing processing fluidity and making the board easier to form. In a preferred embodiment, maleic anhydride-grafted PE can be selected from DowDuPont products represented by Dongguan Kangjin New Materials Technology Co., Ltd. or Ningbo Shunou Plastics Co., Ltd., while maleic anhydride-grafted PP can be selected from the DuPont Fusabond series represented by Dongguan Jinshixiang Plastic Materials Co., Ltd. Both maleic anhydride-grafted polyethylene (PE-g-MAH) and maleic anhydride-grafted polypropylene (PP-g-MAH) are produced by chemically grafting maleic anhydride groups onto polyolefin molecular chains, imparting enhanced polarity and reactivity. The dynamic crosslinker can be a TAIC product (purity ≥98%) produced by Hefei Anbang Chemical Co., Ltd., a hyperbranched epoxy resin (such as the HyperPoX series, functionality ≥12) supplied by CVC Thermoset Specialty Materials (USA), or a dynamically vulcanized compatibilizer (such as the Kraton D series, containing controlled crosslinking points) supplied by BASF (Germany).

[0043] In the synergistically reinforced composite board based on multi-source waste provided by the present invention, the functional additives are calcium carbonate and / or a flame retardant. As a filler, calcium carbonate can improve the rigidity and dimensional stability of the composite board. It also absorbs heat during decomposition at high temperatures, helping to reduce the surface temperature of the material and delay combustion. Furthermore, as an inexpensive filler, it can reduce the use of polymer materials, lowering production costs. It also decomposes to produce calcium oxide, forming a protective layer that blocks oxygen supply, thereby assisting in flame retardancy. The flame retardant is one or more of aluminum hydroxide, magnesium hydroxide, or a phosphorus-based flame retardant (e.g., red phosphorus, ammonium polyphosphate (APP), or melamine polyphosphate (MPP)). The mass ratio of calcium carbonate to flame retardant is (2-6):1, optionally (2-4):1 or (4-6):1. When the calcium carbonate to flame retardant ratio is within the range of (2-6):1, the calcium oxide (CaO) produced by the high-temperature decomposition of calcium carbonate can form a dense ceramic layer with the flame retardant (e.g., Al2O3 produced by the decomposition of aluminum hydroxide), effectively blocking thermal radiation and oxygen penetration.

[0044] Preparation method of synergistically reinforced composite panels based on multi-source waste

[0045] The present invention also provides a method for preparing the above-mentioned synergistically reinforced composite board based on multi-source waste, comprising the following steps:

[0046] S1. Collecting waste plastic packaging and obtaining waste paper fibers and waste plastic fragments through dry separation. Placing the waste paper fibers in an alkaline solution for alkaline treatment, and then adding a coupling agent and anhydrous ethanol for surface modification to obtain modified waste paper fibers.

[0047] S2. collecting waste textile fibers, pre-treating them, and then chemically depolymerizing them using a chemical depolymerization system to obtain chopped waste textile fibers;

[0048] S3, uniformly mixing the modified waste paper fibers and waste plastic fragments obtained in step S1, the chopped waste textile fibers obtained in step S2, a matrix resin, a compatibilizer, and a functional additive to obtain a mixed material;

[0049] S4. Melt and blend the mixed materials obtained in step S3, and after forming, obtain a synergistically reinforced composite plate based on multi-source waste through post-processing.

[0050] In the preparation method of the synergistically reinforced composite board based on multi-source waste provided by the present invention, step S1 is to collect waste plastic packaging, separate waste paper fibers and waste plastic fragments through a dry process, place the waste paper fibers in an alkaline solution for alkaline treatment, and then use a coupling agent and anhydrous ethanol to perform surface modification to obtain modified waste paper fibers. Specifically: through the steps of unpacking, magnetic separation, crushing, wire drawing dissociation, screening, etc., the waste paper fibers and waste plastic fragments in the waste plastic packaging are dry-separated, and then NaOH pretreatment is used to destroy the keratinization of the waste paper fibers. Then, a coupling agent and anhydrous ethanol are used for surface modification to improve compatibility with the hydrophobic resin.

[0051] In step S1 of the present invention, the waste plastic packaging includes waste printing paper, waste copy paper, waste plastic film, waste plastic bottles, waste agricultural plastic film, waste plastic boxes, etc.

[0052] In step S1 of the present invention, the alkaline solution is a NaOH solution with a mass fraction of 1.5-5%, and can be optionally 1.5-3% or 3-5%.

[0053] In step S1 of the present invention, the mass volume ratio of waste paper fiber to alkaline solution is 1g:(10-30)mL, which can be optionally 1g:(10-15)mL, 1g:(15-30)mL or 1g:(20-30)mL.

[0054] In step S1 of the present invention, the temperature of the alkali treatment is 40-80° C., optionally 40-60° C. or 60-80° C.; the time is 15-60 min, optionally 15-30 min, 30-45 min or 45-60 min.

[0055] In step S1 of the present invention, the mass ratio of waste paper fiber, coupling agent, and anhydrous ethanol is (5-20):(1-5):1, and can be optionally (5-10):(1-5):1, (10-15):(1-5):1, (15-20):(1-5):1, (5-20):(1-3):1, and (5-20):(3-5):1. A coupling agent dosage of 1-5 parts can effectively introduce amino reactive groups on the fiber surface, forming chemical bonds with the polyolefin matrix, and significantly improving interfacial compatibility (interfacial bonding strength is increased by more than 30%). If the amount of KH550 is less than 1 part, the modification effect is insufficient; if it is greater than 5 parts, the dispersibility may deteriorate due to self-polymerization.

[0056] In the method for preparing a synergistically reinforced composite board based on multi-source waste provided by the present invention, step S2 involves collecting waste textile fibers, pre-treating them, and then chemically depolymerizing them using a chemical depolymerization system to produce chopped waste textile fibers. Specifically, the waste textile fibers are collected, mechanically opened, airflow-sorted, and electrostatically separated to remove impurities, and a chemical depolymerization agent is added to the pre-treated waste textile fibers for chemical depolymerization to produce chopped waste textile fibers.

[0057] In step S2 of the present invention, the mass ratio of the waste textile fibers to the chemical depolymerizing agent is 1:(5-15), which can be optionally 1:(5-10) or 1:(10-15).

[0058] In step S2 of the present invention, the temperature of chemical depolymerization is 120-220°C, which can be 120-140°C, 140-160°C, 160-180°C, 180-200°C or 200-220°C; and the time is 1-4h, which can be 1-2h, 2-3h or 3-4h.

[0059] In the method for preparing a synergistically reinforced composite board based on multi-source waste provided by the present invention, step S3 involves uniformly mixing the modified waste paper fibers and waste plastic fragments obtained in step S1, the chopped waste textile fibers obtained in step S2, a matrix resin, a compatibilizer, and functional additives to obtain a mixed material. In actual operation, when the materials are fed into a twin-screw extruder for mixing, the modified waste paper fibers, waste plastic fragments, matrix resin, compatibilizer, and functional additives obtained in step S1 are premixed, and then the chopped waste textile fibers obtained in step S2 are added via a side feed from the twin-screw extruder for mixing. This process design aims to optimize the performance of composite materials through staged dispersion control: after the modified waste paper fiber is treated with alkali and modified with silane coupling agent, the surface polarity is significantly enhanced and the compatibility with the matrix resin is high. Therefore, it can be fully melt-blended with waste plastic fragments, compatibilizers, etc. in the main feeding section to form a homogeneous dispersion system; while short-cut waste textile fibers (such as depolymerized PET / PA6 oligomer modified fibers) have strong molecular chain rigidity and large surface energy differences. If directly blended with the main material, it is easy to cause agglomeration. Therefore, they are added independently through side feeding, and the high shear field (shear rate ≥500s) in the middle and rear sections of the twin-screw extruder can be utilized. -1 ) to achieve directional dispersion and orientation of fibers, thereby increasing the tensile strength of the composite material by more than 15%, while avoiding excessive fiber breakage (length retention rate > 70%), and ultimately achieving a synergistic enhancement of rigidity and toughness.

[0060] In step S3 of the present invention, the weight ratio of the modified waste paper fiber, waste plastic fragments, short-cut waste textile fiber, matrix resin, compatibilizer and functional additive is (5-15): (20-40): (5-15): (40-70): (3-8): 1, and can be optionally (5-10): (20-40): (5-15): (40-70): (3-8): 1, (10-15): (20-40): (5-15): (40-70): (3-8): 1, (5-15): (20-30): (5-15): (40-70): (3-8): 1, (5-15): (30-40): (5-15): (40-70): (3-8): 1. (5-15): (20-40): (5-10): (40-70): (3-8): 1. (5-15): (20-40): (10-15): (40-70): (3-8): 1. (5-15): (20-40): (5-15): (40-55): (3-8): 1. (5-15): (20-40): (5-15): (55-70): (3-8): 1. (5-15): (20-40): (5-15): (40-70): (3-5): 1. (5-15): (20-40): (5-15): (40-70): (5-8): 1.

[0061] In the preparation method of the synergistically reinforced composite board based on multi-source waste provided by the present invention, step S4 is to put the mixed material obtained in step S3 into a twin-screw extruder, control the temperature in sections for melt blending, and after the melted material is formed by volume pulse injection molding or gradient hot pressing, the synergistically reinforced composite board based on multi-source waste is obtained by post-processing. Specifically: after the mixed material is put into the twin-screw extruder, the temperature is controlled in sections at 180-220°C for melt blending, and the melt-blended material is formed by volume pulse injection molding or gradient hot pressing. The formed product is cured by ultraviolet light and water-cooled to obtain a synergistically reinforced composite board based on multi-source waste.

[0062] In step S4 of the present invention, the temperature of the segmented temperature control is 180-220° C., which can be optionally 180-200° C. or 200-220° C.; the temperature control time is 2-8 min, which can be optionally 2-4 min, 4-6 min or 6-8 min. In step S4 of the present invention, the segmented temperature control is specifically divided into three stages: the first stage (180-190 ° C) is temperature controlled for 2-3 minutes to make the matrix resin (such as recycled PE / PP) initially melt and infiltrate the fiber surface, reduce the viscosity of the system (melt viscosity is reduced to 3000-5000 Pa·s), and promote the uniform dispersion of modified waste paper fibers and short-cut waste textile fibers; the second stage (200-210 ° C) is temperature controlled for 3-5 minutes to accelerate the chemical reaction between the compatibilizer (such as PE-g-MAH) and the polar group of the fiber (the interface shear strength is increased to 8-12 MPa), and at the same time promote the dynamic crosslinking agent (such as DCP) to induce moderate crosslinking of the matrix to form a three-dimensional network structure to improve the toughness of the material (impact strength ≥15 kJ / m 2 ); the third stage (210-220°C) is temperature-controlled for 0-2 minutes (enabled only when the formula contains a high-melting-point matrix resin or requires deep cross-linking), further optimizing melt fluidity and completing cross-linking and curing (gel content ≥ 60%), but the time must be strictly controlled to avoid thermal degradation of the fiber (length retention rate > 75%). The synergistic effect of temperature and time at each stage ensures processing efficiency (total temperature control time ≤ 8 minutes) while achieving a balance between the rigidity and toughness of the composite material (flexural modulus ≥ 1.8 GPa, elongation at break ≥ 8%) and meeting the dispersion requirements of different functional additives (such as flame retardants and calcium carbonate).

[0063] In step S4 of the present invention, volume pulsation injection molding is an improved injection molding process, which applies a pulsating force field during the injection process to cause the molten polymer to produce periodic volume changes in the mold cavity. This technology can optimize material flow, improve filling uniformity, and reduce internal stress, thereby improving the mechanical properties and dimensional stability of the product. Gradient hot pressing molding is a hot pressing process that heats by partitioning. The present invention adopts volume pulsation injection molding or gradient hot pressing molding technology to improve fiber dispersion and interfacial bonding strength, and overcomes the defects of traditional fiber reinforcement technology that is highly dependent on high-purity raw materials, has many impurities in recycled materials, and has poor fiber dispersion. In a specific embodiment, volume pulsation injection molding is adopted (DPII-90 electromagnetic dynamic injection molding machine can be selected), the pulsation frequency is controlled at 10-20Hz, and the pressure fluctuation range is ±5MPa. In another specific embodiment, a gradient hot pressing process is used to first lay the material in layers into a structure of alternating waste paper fiber layers and waste prevention fiber layers, the outer layer temperature is controlled at 200-220°C, the inner layer temperature is controlled at 180-200°C, and the overall pressure is 8-15MPa.

[0064] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is described in detail below with reference to the embodiments.

[0065] In the following examples, unless otherwise specified, all reaction raw materials are commercially available products.

[0066] Unless otherwise specified, the purity of each product in each embodiment of the present invention exceeds 98%.

[0067] Example 1

[0068] 100 kg of waste plastic packaging, including 50 kg of waste printing paper and 50 kg of waste copy paper, was weighed. The waste plastic packaging was subjected to a dry process involving unbundling, magnetic separation, crushing, spinning, and screening, separating 20 kg of waste paper fiber. The waste paper fiber was pretreated with a 2% NaOH solution at 60°C for 30 minutes to degrade keratinization. The fiber was then surface-modified with 8 kg of silane coupling agent KH550 and 144 kg of anhydrous ethanol to improve compatibility with the hydrophobic resin.

[0069] In addition, 15 kg of waste textile fibers were weighed, and after mechanical opening, air flow separation and electrostatic separation to remove impurities, 10 kg of chopped fibers were prepared by glycol hydrolysis.

[0070] The modified 20 kg waste paper fibers and 10 kg short-cut waste textile fibers were mixed evenly with 40 kg waste plastic fragments, 30 kg unmodified PP particles, 30 kg recycled PP particles, 5 kg maleic anhydride grafted PP (PP-g-MAH) and 5 kg calcium carbonate according to the proportions.

[0071] The mixed material is put into a twin-screw extruder and melt-blended at a temperature of 180-220°C in sections, wherein the waste paper fiber and PP-g-MAH are pre-mixed first, and the short-cut waste textile fiber is fed into the side.

[0072] The melt-blended materials are then molded using volumetric pulsation injection molding, with a controlled pulsation frequency of 12Hz and a pressure fluctuation range of ±5MPa, to induce in-situ fiber formation. The molded product is UV-cured to enhance surface cross-linking and water-cooled to reduce thermal stress.

[0073] The mechanical properties of the obtained composite board were tested according to relevant national standards: the tensile properties were tested according to GB / T1447-2005 "Test method for tensile properties of fiber reinforced plastics", using a standard dumbbell-shaped specimen and a universal material testing machine at a constant speed. The tensile strength was measured to be 38 MPa; the impact properties were tested according to GB / T 1451-2005 "Test method for simply supported beam impact toughness of fiber reinforced plastics", using a pendulum impact on the specimen in a simply supported state. The impact strength was measured to be 18 kJ / m 2 The proportion of recycled materials was assessed using the Mass Balance Method, which calculates the proportion of recycled resources at 85%, based on the mass composition of raw materials before and after input and the precise tracking of the sources of recycled materials.

[0074] Example 2

[0075] 100 kg of waste plastic packaging, including 40 kg of waste plastic film and 60 kg of waste plastic bottles, was weighed. The waste plastic packaging was subjected to a dry process to separate 15 kg of waste paper fiber. After pre-treating the waste paper fiber with NaOH, it was surface-modified using 6 kg of silane coupling agent KH550 and 108 kg of anhydrous ethanol.

[0076] In addition, 20 kg of waste cotton textile fibers were weighed and prepared into 15 kg of nanofibers using an ionic liquid dissolution method.

[0077] The modified 15 kg waste paper fibers and 15 kg nano waste cotton fibers were mixed evenly with 40 kg waste plastic fragments, 30 kg pure HDPE particles, 30 kg recycled HDPE particles and 3 kg hyperbranched epoxy resin according to a proportion.

[0078] The mixed material is put into a twin-screw extruder for melt blending, and the temperature is controlled in stages at 190-230°C.

[0079] The melt-blended materials are then formed using a gradient hot pressing process. The materials are first layered into alternating layers of waste paper fiber and nano-waste cotton fiber. The outer layer temperature is controlled at 210°C, the inner layer temperature at 190°C, and the overall pressure is 12 MPa. The formed product is then water-cooled to set the shape.

[0080] The tensile strength of the obtained composite board is 42 MPa, and the strength retention rate after three recycling is 85%.

[0081] Example 3

[0082] 120 kg of waste plastic packaging, including 60 kg of waste agricultural plastic film and 60 kg of waste plastic boxes, was weighed. The waste plastic packaging was subjected to a dry process to separate 25 kg of waste paper fiber. After pre-treating the waste paper fiber with NaOH, it was surface-modified using 10 kg of silane coupling agent KH550 and 180 kg of anhydrous ethanol.

[0083] In addition, 20 kg of waste polyester textile fibers were weighed and prepared into 15 kg of chopped fibers using ethylene glycol alcoholysis method.

[0084] The above-mentioned modified 25 kg of waste paper fiber and 15 kg of short-cut waste polyester fiber were mixed evenly with 40 kg of waste plastic fragments, 30 kg of unmodified PP particles, 30 kg of recycled PP particles, 8 kg of maleic anhydride grafted PP (PP-g-MAH), 5 kg of calcium carbonate and 3 kg of aluminum hydroxide flame retardant according to the proportion.

[0085] The mixed material is put into a twin-screw extruder and melt-blended at a temperature of 180-220°C in sections, wherein the waste paper fiber and PP-g-MAH are pre-mixed first, and the short-cut waste polyester fiber is added as a side feed.

[0086] The melt-blended materials are then molded using volumetric pulsation injection molding, with a pulsation frequency controlled at 15Hz and a pressure fluctuation range of ±5MPa. The molded product is then cured with UV light and water-cooled to set its shape.

[0087] The tensile strength of the composite plate is 40MPa and the impact strength is 20kJ / m 2 , recycled materials account for 80%, and it has certain flame retardant properties.

[0088] Comparative Example 1

[0089] Comparative Example 1 prepared a composite board according to CN201910876543.2 "A composite board of waste textiles and waste plastics and its preparation method". The waste textile fibers were mainly physically crushed without chemical depolymerization. They were directly mixed with waste plastics and then hot-pressed to prepare the composite board. Under this treatment method, the length distribution of the textile fibers is relatively wide, but it is difficult to form an ordered fiber network structure, resulting in limited improvement in the mechanical properties of the composite board. In addition, the weight ratio of waste textile fibers to waste plastics in Comparative Example 1 is relatively narrow, and the specific amount of compatibilizer and functional additive cannot be accurately added. This can easily lead to poor interfacial compatibility between the fibers and the matrix resin under certain ratios, resulting in insufficient mechanical properties.

[0090] The present invention retains the original length advantage of waste paper fibers and short-cut waste textile fibers through specific modification treatments, and utilizes a compatibilizer to promote the interfacial bonding between the fibers and the matrix resin, thereby forming a network structure with synergistic reinforcement of short and long fibers. This structure significantly improves the mechanical properties (such as tensile strength, flexural modulus, etc.) of the composite board while maintaining good toughness. In addition, this patent has determined the optimized weight ratio range of modified waste paper fibers, waste plastic fragments, short-cut waste textile fibers, matrix resin, compatibilizer and functional additives through a large number of experiments. These ranges not only take into account the mechanical properties of the materials, but also take into account processing costs and environmental protection requirements. For example, by adjusting the amount of compatibilizer, the interfacial bonding strength between the fibers and the matrix resin can be significantly improved, thereby improving the overall performance of the composite board.

[0091] The cost, performance and recovery data of Comparative Example 1 and the present invention are compared in Table 1.

[0092] Table 1 Comparison of cost, performance and recovery data

[0093]

[0094] Comparative Example 2

[0095] Conventional composite panels: Using traditional physical mixing and hot pressing processes, the utilization rate of textile waste is low, and uneven fiber distribution can lead to unstable mechanical properties. Furthermore, conventional composite panels have a low recycling rate and may cause secondary pollution.

[0096] By optimizing the weight ratio of components and the processing technology, this invention achieves high-value utilization of waste textile and waste paper fibers. The patented composite board not only exhibits excellent mechanical properties, but is also environmentally friendly and has a high recycling rate. Furthermore, due to the one-step molding process, the processing cost is relatively low.

[0097] In summary, this patent demonstrates significant advantages in terms of short-long fiber synergistic reinforcement network, optimized component weight ratio range, cost, performance, and recycling data. These advantages give this patent broad application prospects in the field of composite utilization of waste textile and waste paper fibers.

[0098] Cost and carbon reduction benefit verification

[0099] To verify the cost advantages and environmental benefits of the present invention, a life cycle cost (LCC) and carbon emission (LCA) analysis was conducted using the preparation of 1 ton of synergistically reinforced composite board as an example, compared with traditional virgin plastic board (unmodified PE / PP matrix + glass fiber reinforcement). The results are as follows:

[0100] Table 2 Comparison of raw material costs

[0101]

[0102]

[0103] Key data description:

[0104] The procurement cost of recycled PE / PP is 60-70% of that of virgin materials (refer to the "China Renewable Resources Recycling Industry Development Report");

[0105] The cost of waste paper fiber (0.2 yuan / kg) and waste textile fiber (0.5 yuan / kg) is only 10-15% of that of glass fiber (4.5 yuan / kg) (data source: China Chemical Fiber Association);

[0106] Although the cost of the dynamic crosslinker (HBP-EP) is higher than that of the traditional compatibilizer, the added amount is only 3-8wt%, which has limited impact on the total cost.

[0107] Table 3 Comparison of carbon emissions

[0108]

[0109] The life cycle assessment (LCA) model is used to calculate the carbon emissions of the entire process from raw material acquisition to sheet forming:

[0110] Key data description:

[0111] The carbon emissions of recycled PE / PP are 30-40% of those of virgin materials (refer to the White Paper on Plastic Circular Economy);

[0112] The energy consumption of dry processing of waste fiber is 85% lower than that of glass fiber melt drawing (data source: China Paper Association);

[0113] Gradient temperature control technology (B13) reduces molding energy consumption by 15-20%, achieved through infrared heating and waste heat recovery.

[0114] Synergy between economic and environmental benefits

[0115] Cost leverage effect: Recycled materials account for 72% (including 40% waste plastic fragments, 15% waste paper fibers, and 17% waste textile fibers). Every 1 yuan / ton reduction in raw material costs can lead to a 0.72 yuan reduction in total costs;

[0116] Carbon tax deduction potential: According to the EU Carbon Border Tax (CBAM) standard (100 euros / ton CO2eq), each ton of panel can be exempted from carbon tax of 172 euros, and export competitiveness will be improved by 12%.

[0117] In summary, through high-proportion recycled material substitution, low-energy consumption process optimization and dynamic cross-linking technology, the present invention reduces costs by 41% while reducing carbon emissions by 60%, which is significantly better than the industry average (traditional recycled board costs are usually reduced by 20-30%, and carbon emissions are reduced by 30-40%), providing a quantifiable solution for the upgrading of the materials industry.

[0118] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A synergistically reinforced composite panel based on multi-source waste, characterized in that: The composite board comprises the following raw materials in parts by weight: 10-30 parts of modified waste paper fibers, 15-30 parts of chopped waste textile fibers, 20-40 parts of waste plastic fragments, 30-60 parts of base resin, 2-8 parts of compatibilizer, and 1-5 parts of functional additives.

2. The synergistically reinforced composite panel based on multi-source waste according to claim 1, characterized in that: Includes any one or more of the following characteristics: A1) the modified waste paper fiber is prepared by surface-modifying waste paper fiber by adding a coupling agent; A2) the chopped textile waste fibers are obtained by depolymerizing textile waste fibers by adding a chemical depolymerizing agent; A3) the length of the chopped textile waste fibers is 3-12 mm; A4) the matrix resin is selected from one or more of unmodified PE, unmodified PP, recycled PE or recycled PP; A5) the compatibilizer is selected from one or more of maleic anhydride grafted PE, maleic anhydride grafted PP or a dynamic crosslinking agent; A6) The functional additive is calcium carbonate and / or a flame retardant.

3. The synergistically reinforced composite panel based on multi-source waste according to claim 2, characterized in that: Includes any one or more of the following characteristics: A11) the coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent or a phosphate coupling agent; A21) The chemical depolymerization agent is ethylene glycol or an ionic liquid.

4. The synergistically reinforced composite panel based on multi-source waste according to claim 2, characterized in that: Includes any one or more of the following characteristics: A41) The weight ratio of the unmodified PE, unmodified PP, recycled PE and recycled PP is (1-5): (1-5): (0.5-3): (0.5-3): 1; A51) the dynamic crosslinking agent is selected from one or more of a hyperbranched epoxy resin, maleic anhydride grafted polypropylene, or an ethylene-acrylate copolymer; A61 The flame retardant is selected from one or more of aluminum hydroxide, magnesium hydroxide or phosphorus-based flame retardants; A62) The mass ratio of the calcium carbonate to the flame retardant is (2-6):

1.

5. The method for preparing a synergistically reinforced composite board based on multi-source waste according to any one of claims 1 to 4, characterized in that: The steps include: S1. Collecting waste plastic packaging and obtaining waste paper fibers and waste plastic fragments through dry separation. Placing the waste paper fibers in an alkaline solution for alkaline treatment, and then adding a coupling agent and anhydrous ethanol for surface modification to obtain modified waste paper fibers. S2. collecting waste textile fibers, pre-treating them, and then chemically depolymerizing them using a chemical depolymerization system to obtain chopped waste textile fibers; S3, uniformly mixing the modified waste paper fibers and waste plastic fragments obtained in step S1, the chopped waste textile fibers obtained in step S2, a matrix resin, a compatibilizer, and a functional additive to obtain a mixed material; S4. Melt and blend the mixed materials obtained in step S3, and after forming, obtain a synergistically reinforced composite plate based on multi-source waste through post-processing.

6. The method for preparing a synergistically reinforced composite board based on multi-source waste according to claim 5, characterized in that: Includes any one or more of the following characteristics: B1) In step S1, the alkaline solution is a NaOH solution with a mass fraction of 1.5-5%; B2) in step S1, the mass volume ratio of the waste paper fiber and the alkaline solution is 1 g: (10-30) mL; B3) In step S1, the alkali treatment temperature is 40-80°C and the time is 15-60 minutes; B4) In step S1, the mass ratio of the waste paper fibers, the coupling agent and the anhydrous ethanol is (5-20):(1-5):

1.

7. The method for preparing a synergistically reinforced composite board based on multi-source waste according to claim 6, characterized in that: Includes any one or more of the following characteristics: B5) in step S2, the pretreatment includes mechanical opening, air flow sorting, and electrostatic sorting to remove impurities; B7) in step S2, the mass ratio of the waste textile fibers to the chemical depolymerizing agent is 1:(5-15); B8) In step S2, the temperature of the chemical depolymerization is 120-220° C. and the time is 1-4 hours.

8. The method for preparing a synergistically reinforced composite board based on multi-source waste according to claim 6, characterized in that: In step S3, the weight ratio of the modified waste paper fiber, waste plastic fragments, short-cut waste textile fiber, matrix resin, compatibilizer and functional additive is (5-15): (20-40): (5-15): (40-70): (3-8):

1.

9. The method for preparing a synergistically reinforced composite board based on multi-source waste according to claim 6, characterized in that: In step S4, the melt blending temperature is 180-220° C. and the time is 2-8 minutes.

10. The method for preparing a synergistically reinforced composite board based on multi-source waste according to claim 6, characterized in that: Includes any one or more of the following characteristics: B9) in step S4, the molding is volume pulsation injection molding or gradient hot pressing molding; B10) In step S4, the post-processing includes ultraviolet light curing and water cooling for shaping.

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