Waste TLCP circuit board recycling method based on catalytic depolymerization and controllable remodeling

Abstract

The invention relates to the technical field of electronic waste resourceful treatment and macromolecule cyclic utilization, and particularly discloses a waste TLCP circuit board resourceful method based on catalytic depolymerization and controllable remodeling, and the method comprises the following steps: S1, intelligent identification and enrichment; s2, catalytic depolymerization; s3, controllable remodeling, namely performing closed-loop regeneration on the path A; s4, performing controllable remodeling, namely performing open-loop conversion on the path B; and S5, full-life-cycle carbon benefit accounting is carried out. According to the method, a'catalytic depolymerization-double-path remodeling 'special process chain is designed for TLCP for the first time, the problem that TLCP is difficult to recycle due to chemical inertness is solved, molecular-level closed-loop circulation from waste circuit boards to high-performance raw materials and degradable materials is achieved, and resource consumption and greenhouse gas emission are remarkably reduced through full-life-cycle carbon management.

Description

Technical Field

[0001] This invention relates to the field of electronic waste resource utilization and polymer recycling technology, specifically a method for the resource utilization of waste TLCP circuit boards based on catalytic depolymerization and controllable remodeling. Background Technology

[0002] Thermotropic liquid crystalline polymers (TLCPs) are a class of high-performance engineering plastics with rigid backbones and highly ordered liquid crystal structures. Their typical characteristics include the ability to form anisotropic liquid crystal phases in the molten state, exhibiting low melt viscosity, high crystallinity, and excellent dimensional stability. TLCPs also possess high heat resistance, low dielectric constant and low dielectric loss, good flowability and processability, making them widely used in high-end electronic fields such as 5G communication base stations, high-speed servers, automotive radar, precision connectors, and high-density interconnect circuit boards.

[0003] With the rapid iteration of new-generation information technology and electronic products, a large number of circuit boards and connectors containing TLCPs enter the scrapping stage after their service life, forming representative high-end electronic waste. Compared with traditional epoxy resins or polyimides, TLCPs are more chemically inert, have higher chain segment rigidity, and higher glass transition temperature and melting point. They are also often deeply compounded with inorganic fillers, glass fibers, and metal components, posing greater challenges to traditional recycling technologies.

[0004] Existing technologies for processing waste circuit boards mainly include physical crushing and sorting, incineration / pyrolysis, acid and alkali leaching, and use as low-value fillers. However, these methods have significant shortcomings for TLCP substrates or components. 1. Physical crushing + mixed packing utilization After being crushed, the non-metallic parts of discarded circuit boards are often simply ground into powder and mixed into cement, rubber, or plastic as fillers. This method does not preserve or reconstruct the chemical structure of TLCPs at any level, completely destroys the original high performance of the material, results in low overall added value, and makes no substantial contribution to high-end applications.

[0005] 2. High-temperature incineration or pyrolysis Incinerating or pyrolyzing circuit boards containing TLCP at temperatures above 500°C yields pyrolysis oil, pyrolysis gas, and solid residue. However: (1) The high aromaticity and high stability of TLCP result in higher pyrolysis temperature and greater energy consumption; (2) Circuit boards often contain bromine-based flame retardants, and the pyrolysis process can easily generate bromine-containing polycyclic aromatic hydrocarbons or dioxins, which pose a risk to the environment and health. (3) Pyrolysis oil has a complex composition and contains many impurities, resulting in high refining costs and making it difficult to convert into high-value monomers or high-performance materials.

[0006] 3. Chemical treatment of strong acid / strong oxidizing systems Some studies have attempted to use strong oxidizing systems such as concentrated sulfuric acid and nitric acid to attack engineering plastics, thereby achieving partial degradation. However, for TLCP, although such processes can destroy some chain segments under harsh conditions, they are often accompanied by serious side reactions, corrosion problems, and secondary pollution. The decomposition products generated are complex and difficult to use for repolymerization or precise remodeling.

[0007] 4. Forward-looking design of biodegradable circuit substrates In recent years, new biodegradable circuit substrates (such as circuit boards based on glass-like polymers) have begun to attract attention. However, these materials are mainly aimed at the green design of future products and are not suitable for traditional TLCP-based circuit boards that have been put into use on a large scale and are entering the scrap stage, thus failing to solve the problem of existing stock.

[0008] Against the backdrop of rapid growth in global e-waste production, the development of efficient, high-value closed-loop resource recovery technologies specifically targeting TLCPs is particularly urgent. On the one hand, it is necessary to achieve molecular-level depolymerization of TLCPs under mild and controllable conditions, reconstructing the recalcitrant polymer structure into reusable oligomers or monomers. On the other hand, it is necessary to construct diversified remodeling pathways so that recycled products can be used for closed-loop regeneration of high-performance TLCPs, or copolymerized with bio-based monomers to transform into biodegradable materials with good environmental adaptability. Simultaneously, to meet policy and market requirements for green manufacturing and transparent product environmental information, it is necessary to introduce Life Cycle Assessment (LCA) and carbon footprint accounting into resource recovery processes to achieve quantifiable and traceable management of the environmental performance of the resource recovery process.

[0009] In summary, existing technologies lack an integrated solution for the catalytic depolymerization and controlled remodeling of waste TLCP circuit boards, and cannot achieve both high-value utilization and full life-cycle carbon management while achieving efficient recycling. Summary of the Invention

[0010] The purpose of this invention is to address the problems of inefficient recycling of waste TLCP circuit boards, difficulty in releasing the value of their polymer structure, and significant environmental and carbon emission pressures in existing technologies. It provides a resource recovery method for waste TLCP circuit boards based on catalytic depolymerization and controllable remodeling. Through a holistic approach of "precise identification and enrichment—selective depolymerization with a composite catalyst—dual-path remodeling via closed-loop regeneration and open-loop conversion—full life-cycle carbon benefit accounting," the invention achieves molecular-level targeted degradation and reconstruction of TLCP, realizing the dual goals of resource value enhancement and carbon emission reduction.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a method for resource recovery of waste TLCP circuit boards based on catalytic depolymerization and controllable remodeling, comprising the following steps: S1. Intelligent identification and enrichment: Non-destructive testing and intelligent identification of waste circuit boards containing thermotropic liquid crystal polymer (TLCP) are performed to locate TLCP substrates or components, and TLCP enriched materials are obtained through physical separation and disassembly. S2. Catalytic depolymerization: Under an inert atmosphere, the TLCP-enriched material obtained in step S1 is mixed with the composite catalyst in a solvent, and a catalytic depolymerization reaction is carried out at 240–320°C for 2–6 hours to obtain a depolymerization product containing TLCP oligomers; the composite catalyst is composed of Lewis acid metal salts and nitrogen-containing ligands. S3, Controlled Remodeling - Path A is Closed-Loop Regeneration: The depolymerization product containing TLCP oligomers obtained in step S2 is purified and then subjected to a repolymerization reaction in the presence of vacuum and a polycondensation catalyst to obtain regenerated TLCP resin. S4. Controlled remodeling – Path B is ring-opening conversion: The depolymerization product containing TLCP oligomers obtained in step S2 is mixed with bio-based monomers at a predetermined mass ratio and copolymerized under the action of an ester exchange catalyst to prepare a biodegradable copolyester material. S5. Life Cycle Carbon Benefit Calculation: Track the material and energy flows throughout the entire process from steps S1 to S4, and calculate and compare the carbon footprint and carbon reduction benefits of path A and path B based on the life cycle assessment method.

[0012] As a preferred technical solution of the present invention, in step S1, the non-destructive testing and intelligent identification adopts terahertz imaging technology or near-infrared spectroscopy combined with artificial intelligence algorithm to perform non-contact scanning on the circuit board to distinguish TLCP from epoxy resin, polyimide and thermoplastic polymer materials, and the accuracy of TLCP identification and positioning is not less than 95%.

[0013] As a preferred technical solution of the present invention, in step S1, the acquisition of the TLCP-enriched material includes: heating the TLCP-containing area to 180-220°C on a controllable hot air disassembly table to melt the solder and remove the electronic components and metal parts without damage, and then obtaining a substrate or fragment mainly composed of TLCP by mechanical cutting or punching.

[0014] As a preferred embodiment of the present invention, in step S2, the Lewis acid metal salt is one or more of zinc acetate, stannous chloride or antimony trioxide, the nitrogen-containing ligand is 1,10-phenanthroline or 2,2′-bipyridine, and the solvent is a mixed solvent of phenol and tetrachloroethane or γ-valerolactone.

[0015] As a preferred embodiment of the present invention, in step S2, a bromine scavenger is further added to the catalytic depolymerization reaction system. The bromine scavenger is at least one of zinc oxide or iron oxide nanoparticles, used to fix bromine species produced by the decomposition of bromine-based flame retardants that may be contained in TLCP in situ, and to inhibit the generation of bromine-containing harmful gases. The amount of bromine scavenger added is 0.5% to 5% of the mass of the TLCP enriched material. The amount of the composite catalyst is 0.5% to 3.0% of the mass of the TLCP enriched material, wherein the molar ratio of Lewis acid metal salt to nitrogen-containing ligand is 1:(0.5 to 2.0).

[0016] As a preferred embodiment of the present invention, in step S3, the re-condensation reaction is carried out at 260-300°C and a vacuum degree of less than 100 Pa. The condensation catalyst used is tetrabutyl titanate or tetraisopropyl titanate, and the amount of catalyst used is 0.01%-0.2% of the TLCP oligomer mass. The intrinsic viscosity of the resulting recycled TLCP resin is not less than 0.6 dL / g, and it can be re-injected or extruded into high-performance connectors, fine-pitch sockets or circuit board substrates.

[0017] As a preferred embodiment of the present invention, in step S4, the bio-based monomer is selected from any one or a combination of lactic acid, lactide, succinic anhydride, succinic acid, and 2,5-furandicarboxylic acid; the mass ratio of the bio-based monomer to the TLCP oligomer is 1:5 to 1:1; the transesterification catalyst is stannous octoate or an organotitanium catalyst; the reaction temperature is 180 to 220°C; the reaction time is 3 to 8 hours; and the number average molecular weight of the obtained biodegradable copolyester material is not less than 30,000. The biodegradable copolyester material has a biodegradability of no less than 80% under standard aerobic composting conditions for 180 days, and is suitable for preparing disposable electronic device shells, electronic product packaging materials or electronic tag substrates.

[0018] As a preferred technical solution of the present invention, in step S5, the baseline scenario for calculating the carbon emission reduction benefits includes: the production process of virgin TLCP resin with equivalent performance, and the treatment scenario of landfilling or incinerating waste circuit boards containing TLCP after simple dismantling; the calculation results show that the carbon footprint of recycled TLCP in path A is reduced by no less than 40% compared with virgin TLCP, and the carbon footprint of biodegradable copolyester material in path B is reduced by no less than 50% compared with traditional petroleum-based plastics.

[0019] A waste TLCP circuit board resource recovery system for implementing the above-described method includes: The intelligent identification and fine disassembly unit includes a terahertz imager and / or a near-infrared spectroscopy detection device, a robotic arm and a controllable hot air disassembly table, used to identify and separate TLCP substrates or components and obtain TLCP-enriched materials. The catalytic depolymerization reaction unit includes a high-pressure reactor with stirring, temperature control and reflux condensation devices, and an built-in automatic catalyst and bromine capture agent addition system for catalytic depolymerization of TLCP-enriched materials. The product separation and purification unit includes a centrifuge, a filtration device, a thin-film evaporator, and a washing tower, used to separate solid residues, purify TLCP oligomers, and recover solvents; The dual-path remodeling unit includes a vacuum polycondensation reactor and an atmospheric or slightly positive pressure copolymerization reactor arranged in parallel, corresponding to path A, the regeneration of TLCP resin, and path B, the preparation of biodegradable copolyester, respectively. The lifecycle data management unit includes sensors, data acquisition devices, databases, and lifecycle assessment accounting software modules connected to each unit, used to collect energy consumption and material consumption data in real time and generate carbon footprint reports.

[0020] As a preferred embodiment of the present invention, the temperature of the hot air disassembly table in the intelligent identification and fine disassembly unit can be precisely controlled between 180 and 220°C. This temperature is higher than the melting point of solder but lower than the heat distortion temperature of the TLCP substrate, so as to achieve non-destructive removal of electronic components and metal parts. The carbon footprint report generated by the life cycle data management unit conforms to ISO 14040 and ISO 14044 standards, and assigns a unique digital identifier to each batch of processed materials for tracing its environmental performance throughout its entire life cycle. As a preferred embodiment of the present invention, the two-dimensional sheet-like insulating high thermal conductivity filler in step 1.3 is one or more of boron nitride nanosheets and alumina nanosheets; the modifier used in the amination modification is an amino-containing silane coupling agent.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1. Dedicated recycling route for TLCP This invention addresses the unique liquid crystal structure and high chemical stability of TLCP by designing a dedicated technical route of "selective depolymerization of composite catalysts - controllable reshaping at the molecular level." This overcomes the bottlenecks of low depolymerization efficiency and low product value of TLCP by traditional physical crushing and pyrolysis methods, thereby fully releasing the value of the polymer structure.

[0022] 2. Dual-path reshaping to achieve high-value utilization By using path A (closed-loop recycling), TLCP oligomers are re-condensed into recycled TLCP resins with high intrinsic viscosity, which can be reused in high-value fields such as high-end connectors and circuit board substrates. By using path B (open-loop conversion), TLCP oligomers are copolymerized with bio-based monomers to achieve the functional transformation from recalcitrant engineering plastics to biodegradable copolyester materials, expanding the application scenarios of materials and realizing multi-level high-value utilization.

[0023] 3. The composite catalyst system is highly efficient and controllable. The Lewis acid metal salt / nitrogen-containing ligand composite catalytic system can effectively act on the ester bonds in the TLCP molecular chain under relatively mild medium and high temperature conditions, achieving directional cleavage and oligomer generation with controllable molecular weight distribution. At the same time, by adjusting the catalyst ratio and reaction conditions, it can balance depolymerization efficiency and oligomer structure reconfigurability, providing a good precursor for subsequent remodeling.

[0024] 4. Synergistic bromine capture and pollution control By adding bromine scavengers such as zinc oxide or iron oxide nanoparticles to the depolymerization reaction, the bromine produced by the decomposition of bromine-based flame retardants can be fixed in situ in the solid phase. Combined with a closed reaction system and solvent recovery device, the emissions of bromine-containing organic matter and acidic gases are significantly reduced, improving the overall environmental friendliness of the process.

[0025] 5. Full life-cycle carbon management and digital tracking This invention embeds life cycle assessment methods into process design, and uses a life cycle data management unit to collect and analyze the material and energy flows of each step in real time, quantifying the carbon footprint of path A and path B, and comparing it with native TLCP production and traditional waste disposal scenarios. The results show that this invention can significantly reduce carbon emissions per unit product, achieving quantitative, visual, and traceable management of the resource recovery process of waste TLCP circuit boards, which is beneficial for the electronics industry to achieve "dual carbon" goals and green supply chain management. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0027] This invention provides a method for the resource recovery of waste TLCP circuit boards based on catalytic depolymerization and controllable remodeling, comprising the following steps: S1. Intelligent identification and enrichment: Non-destructive testing and intelligent identification of waste circuit boards containing thermotropic liquid crystal polymer (TLCP) are performed to locate TLCP substrates or components, and TLCP enriched materials are obtained through physical separation and disassembly. The non-destructive testing and intelligent identification employs terahertz imaging technology or near-infrared spectroscopy combined with artificial intelligence algorithms to perform non-contact scanning of the circuit board to distinguish TLCP from epoxy resin, polyimide, and thermoplastic polymer materials. The accuracy rate of TLCP identification and positioning is no less than 95%. The TLCP-enriched material is obtained by heating the TLCP-containing area to 180-220°C on a controllable hot air disassembly table, so that the solder melts, electronic components and metal parts are detached without damage, and then mechanically cutting or punching to obtain a substrate or fragments mainly composed of TLCP. The Lewis acid metal salt is one or more of zinc acetate, stannous chloride or antimony trioxide, the nitrogen-containing ligand is 1,10-phenanthroline or 2,2′-bipyridine, and the solvent is a mixed solvent of phenol and tetrachloroethane or γ-valerol. S2. Catalytic depolymerization: Under an inert atmosphere, the TLCP-enriched material obtained in step S1 is mixed with the composite catalyst in a solvent, and a catalytic depolymerization reaction is carried out at 240–320°C for 2–6 hours to obtain a depolymerization product containing TLCP oligomers; the composite catalyst is composed of Lewis acid metal salts and nitrogen-containing ligands. A bromine scavenger is also added to the catalytic depolymerization reaction system. The bromine scavenger is at least one of zinc oxide or iron oxide nanoparticles, used to immobilize bromine species produced by the decomposition of bromine-based flame retardants that may be present in TLCP in situ, and to inhibit the generation of bromine-containing harmful gases. The amount of bromine scavenger added is 0.5% to 5% of the mass of the TLCP enriched material. The amount of the composite catalyst is 0.5% to 3.0% of the mass of the TLCP enriched material, wherein the molar ratio of Lewis acid metal salt to nitrogen-containing ligand is 1:(0.5 to 2.0). S3, Controlled Remodeling - Path A is Closed-Loop Regeneration: The depolymerization product containing TLCP oligomers obtained in step S2 is purified and then subjected to a repolymerization reaction in the presence of vacuum and a polycondensation catalyst to obtain regenerated TLCP resin. The repolymerization reaction is carried out at 260–300°C and a vacuum of less than 100 Pa. The catalyst used is tetrabutyl titanate or tetraisopropyl titanate, and the amount of catalyst is 0.01%–0.2% of the TLCP oligomer mass. The resulting recycled TLCP resin has an intrinsic viscosity of not less than 0.6 dL / g and can be re-injected or extruded into high-performance connectors, fine-pitch sockets, or circuit board substrates. S4. Controlled remodeling – Path B is ring-opening conversion: The depolymerization product containing TLCP oligomers obtained in step S2 is mixed with bio-based monomers at a predetermined mass ratio and copolymerized under the action of an ester exchange catalyst to prepare a biodegradable copolyester material. The bio-based monomer is selected from any one or a combination of lactic acid, lactide, succinic anhydride, succinic acid, and 2,5-furandicarboxylic acid. The mass ratio of the bio-based monomer to the TLCP oligomer is 1:5 to 1:1. The transesterification catalyst is stannous octoate or an organotitanium catalyst. The reaction temperature is 180 to 220°C, the reaction time is 3 to 8 hours, and the number average molecular weight of the obtained biodegradable copolyester material is not less than 30,000. The biodegradable copolyester material has a biodegradability of no less than 80% under standard aerobic composting conditions for 180 days, and is suitable for preparing disposable electronic device shells, electronic product packaging materials or electronic tag substrates; S5. Life cycle carbon benefit accounting: Track the material and energy flows throughout the entire process from step S1 to step S4, and calculate and compare the carbon footprint and carbon reduction benefits of path A and path B based on the life cycle assessment method. The baseline scenario for calculating the carbon emission reduction benefits includes: the production process of virgin TLCP resin with equivalent performance, and the treatment scenario of landfilling or incineration after simple dismantling of waste circuit boards containing TLCP; the calculation results show that the carbon footprint per unit product of recycled TLCP in Path A is reduced by no less than 40% compared with virgin TLCP, and the carbon footprint per unit product of biodegradable copolyester materials in Path B is reduced by no less than 50% compared with traditional petroleum-based plastics.

[0028] A waste TLCP circuit board resource recovery system for implementing the above-described method includes: The intelligent identification and fine disassembly unit includes a terahertz imager and / or a near-infrared spectroscopy detection device, a robotic arm and a controllable hot air disassembly table, used to identify and separate TLCP substrates or components and obtain TLCP-enriched materials. The catalytic depolymerization reaction unit includes a high-pressure reactor with stirring, temperature control and reflux condensation devices, and an built-in automatic catalyst and bromine capture agent addition system for catalytic depolymerization of TLCP-enriched materials. The product separation and purification unit includes a centrifuge, a filtration device, a thin-film evaporator, and a washing tower, used to separate solid residues, purify TLCP oligomers, and recover solvents; The dual-path remodeling unit includes a vacuum polycondensation reactor and an atmospheric or slightly positive pressure copolymerization reactor arranged in parallel, corresponding to path A, the regeneration of TLCP resin, and path B, the preparation of biodegradable copolyester, respectively. The lifecycle data management unit includes sensors, data acquisition devices, databases, and lifecycle assessment accounting software modules connected to each unit, used to collect energy consumption and material consumption data in real time and generate carbon footprint reports.

[0029] The temperature of the hot air disassembly station in the intelligent identification and fine disassembly unit can be precisely controlled between 180 and 220°C. This temperature is higher than the melting point of solder but lower than the heat distortion temperature of the TLCP substrate, so as to achieve non-destructive removal of electronic components and metal parts. The carbon footprint report generated by the life cycle data management unit complies with ISO 14040 and ISO 14044 standards, and assigns a unique digital identifier to each batch of processed materials for tracing its environmental performance throughout its entire life cycle.

[0030] Example 1: Recycling the TLCP substrate from a 5G base station filter circuit board Raw materials: The circuit board of the cavity filter of the scrapped 5G base station is selected. Its core substrate is TLCP material filled with inorganic mineral particles, and electronic components such as metal resonant pillars and shielding covers are installed on the surface.

[0031] S1: Intelligent Recognition and Enrichment The circuit board is placed in the intelligent identification and fine disassembly unit. A terahertz imager scans the entire board, and based on the differences in absorption characteristics of TLCP material and other resins in the terahertz band, combined with a neural network classification model, the TLCP substrate area is accurately identified. A robotic arm cuts out the TLCP substrate area based on the identification results and places it on a hot air disassembly table. Heating at 210℃ melts the solder, causing the metal resonant pillars and small components to detach without damage, allowing for the recovery of relatively pure TLCP substrate fragments. Statistics show that the TLCP purity is greater than 90 wt%.

[0032] S2: Catalytic depolymerization Weigh 5 kg of TLCP substrate fragments, cut them into pieces approximately 5–10 mm in size, and place them into a high-pressure reactor equipped with a stirrer. Add 20 kg of a phenol / tetrachloroethane (mass ratio 7:3) mixed solvent, 0.8 wt% zinc acetate (relative to the mass of TLCP), 0.4 wt% 1,10-phenanthroline, and 1.0 wt% iron oxide nanoparticles as a bromine scavenging agent. After purging the air three times with nitrogen, raise the temperature to 280°C, control the pressure inside the reactor within a safe range, and stir the reaction for 4 hours.

[0033] After the reaction is complete, the temperature is lowered to 150°C, and the mixture is discharged through the bottom discharge valve and sent to a centrifuge to separate the solid and liquid phases. The solid phase mainly consists of inorganic filler, iron oxide particles, and a small amount of undepolymerized residue; the liquid phase consists of solvent and TLCP depolymerization products.

[0034] The liquid phase was fed to a thin-film evaporator, where most of the solvent was evaporated under reduced pressure. The recovered phenol / tetrachloroethane mixed solvent was returned to the depolymerization step for recycling. The remaining dark brown viscous substance was a TLCP oligomer, with a number-average molecular weight (Mn) of approximately 2500 determined by GPC, and a calculated depolymerization rate of approximately 88%.

[0035] S3: Path A: Closed-loop regeneration TLCP Take 2.5 kg of the above TLCP oligomer, dilute it with a small amount of solvent, and wash it with an appropriate amount of alcohol solvent in a washing tower to remove residual low molecular weight byproducts and inorganic salts. After drying, 2.2 kg of purified TLCP oligomer is obtained.

[0036] The purified oligomers were added to a vacuum polycondensation reactor, and 0.05 wt% tetrabutyl titanate was added as a polycondensation catalyst. The reaction was carried out at 285°C and a vacuum degree below 50 Pa for 3 hours. Vacuum was continuously pumped during the reaction to remove the small molecule byproducts generated.

[0037] After the reaction, the melt was extruded, water-cooled, and pelletized to obtain light brown recycled TLCP particles. Tests showed that the intrinsic viscosity was 0.68 dL / g, the heat distortion temperature was 210℃, and the tensile strength and modulus were comparable to commercial injection-grade TLCP resin. These recycled TLCP particles were used to injection mold high-density connector housings, and the samples exhibited good dimensional stability under continuous reflow soldering conditions at 260℃.

[0038] S4: Pathway B: Ring-opening conversion to biodegradable copolyester Take 2.2 kg of the remaining TLCP oligomer and mix it with 1.1 kg of lactide (prepared from bio-based fermented lactic acid) at a mass ratio of 2:1. Add 0.1 wt% stannous octoate and send it into an atmospheric pressure copolymerization reactor. Under nitrogen protection, heat the mixture to 190°C and react for 5 hours.

[0039] After the reaction, the material was cooled and discharged, yielding a pale yellow, blocky copolyester. GPC analysis showed a Mn content of approximately 35,000. Biodegradation testing under standard aerobic composting conditions showed a biodegradation rate exceeding 90% after 180 days. This copolyester was extruded into sheets and stamped into disposable electronic device housing samples. Mechanical and heat resistance tests confirmed that it meets the requirements for medium-strength applications such as disposable sensor housings.

[0040] S5: Life Cycle Carbon Benefit Accounting The lifecycle data management unit collects data such as electricity consumption, steam consumption, and solvent loss during the batch processing in real time, and combines this data with background database information such as equipment manufacturing and raw material production to calculate the carbon footprint in accordance with ISO 14040 / 14044 standards.

[0041] The calculation results show that producing 1 kg of recycled TLCP particles from Path A can reduce CO2 equivalent emissions by about 4.2 kg compared to producing 1 kg of virgin TLCP resin, a reduction of about 46%; producing 1 kg of copolyester material from Path B can reduce CO2 equivalent emissions by about 1.8 kg compared to producing 1 kg of virgin polylactic acid, a reduction of about 52%.

[0042] Example 2: Recycling TLCP injection molded parts from high-speed connectors Raw materials: High-speed connector components are selected from scrapped switches and high-speed routers. The outer shell and part of the skeleton are made by TLCP injection molding, and the interior contains fine metal contacts and local potting compound.

[0043] S1: Intelligent Identification and Disassembly The disassembled connector assemblies are fed into an intelligent identification unit, where near-infrared spectroscopy is used to rapidly scan the connector surface. Combined with the characteristic spectral maps of TLCP and other engineering plastics in the database, a support vector machine or convolutional neural network model is employed for identification, distinguishing TLCP injection molded parts from those made of other materials such as PBT and PA. A robotic arm collects the TLCP injection molded parts in batches according to the identification results and disassembles them under 190℃ hot air conditions to separate the metal contacts, obtaining relatively pure TLCP injection molded waste parts.

[0044] S2: Catalytic depolymerization Weigh 3 kg of TLCP waste parts, cut them into pieces, and send them into a high-pressure reactor. Add 12 kg of γ-valerol solvent, 1.0 wt% stannous chloride, 0.5 wt% 2,2′-bipyridine, and 1.5 wt% zinc oxide nanoparticles. After nitrogen purging, heat to 260℃ and hold for 3 hours.

[0045] After centrifugation and solvent recovery, 2.7 kg of viscous TLCP oligomers were obtained. GPC analysis showed that the Mn content was approximately 2200 and the depolymerization rate was approximately 85%.

[0046] S3: Path A Regenerates TLCP 1.5 kg of TLCP oligomer was washed with alcohol and dried, then 0.08 wt% tetraisopropyl titanate was added to a vacuum polycondensation reactor. The reaction was carried out at 275 °C and a vacuum of 80 Pa for 2.5 hours. Regenerated TLCP particles with an intrinsic viscosity of approximately 0.64 dL / g were obtained and used for injection molding of small high-speed connector housings. After electrical performance and dimensional stability tests, they met the requirements for 56 Gbps high-frequency signal transmission.

[0047] S4: Pathway B copolymerization modification The remaining 1.2 kg of TLCP oligomer was mixed with 0.6 kg of succinic anhydride and 0.4 kg of 1,4-butanediol, and 0.1 wt% of an organotitanium catalyst was added. The mixture was reacted at 200 °C for 4 hours to obtain an aromatic-aliphatic copolyester with a Mn content of approximately 32,000. This material exhibits good molding properties and a moderate balance of stiffness and toughness below 60 °C, and can be used to prepare biodegradable electronic accessories, cable winding clips, and other products.

[0048] S5: Carbon benefits: Compared with the direct production of the same connector housing using virgin TLCP, the carbon emissions per unit product of the recycled TLCP particles in this embodiment are reduced by approximately 42%; the carbon emissions of the copolymerized modified material in Path B are reduced by approximately 50% compared with the same petroleum-based PBT material.

[0049] Example 3: Co-recycling of mixed circuit boards containing TLCP and other resins Raw materials: A certain type of high-density interconnect (HDI) board is selected, which is composed of TLCP-based dielectric layer and epoxy / glass fiber layer between different layers. After disposal, the TLCP content in the overall board is about 30 wt%.

[0050] S1: Hierarchical Identification and Enrichment Terahertz imaging is used to scan the entire plate, identifying the location and thickness of each TLCP dielectric layer. This, combined with mechanical milling or laser cutting, allows for the preferential stripping and enrichment of the TLCP dielectric layers. During the stripping process, a small amount of TLCP laminate containing epoxy resin fragments is generated. This is further purified through density difference and solvent pre-swelling, ultimately yielding enriched material with a TLCP content exceeding 85 wt%.

[0051] S2: Catalytic depolymerization Four kilograms of TLCP-enriched material and 16 kilograms of phenol / tetrachloroethane solvent were added to a reactor, along with 0.8 wt% antimony trioxide, 0.6 wt% 1,10-phenanthroline, and 2 wt% iron oxide. The mixture was heated to 290°C under argon protection and reacted for 3.5 hours. After separation and concentration, 3.6 kilograms of TLCP oligomers with approximately 2400 Mn were obtained.

[0052] S3: Dual-path combination utilization Based on market demand, approximately 60% of the TLCP oligomers are used for the recycled TLCP resin in pathway A, and approximately 40% are used for the preparation of biodegradable copolyesters in pathway B. By adjusting the ratio of the two pathways, it is possible to flexibly switch between high-performance recycled materials and biodegradable materials, achieving a dynamic balance between economic and environmental benefits.

[0053] Example 4: Expansion of Bio-based Monomers – Copolymerization with 2,5-furandicarboxylic Acid Based on Examples 1-3, TLCP oligomers and bio-based dimethyl 2,5-furandicarboxylate were mixed at a mass ratio of 3:1, and 0.12 wt% stannous octoate was added. The mixture was reacted at 210°C for 5 hours to prepare a copolyester containing dual rigid units of aromatic and furan rings. This material still exhibits high energy storage modulus and low dielectric loss at 100°C, making it suitable for use in disposable or short-life electronic device housings for mid-to-high frequency signal transmission scenarios. After use, it can degrade under composting conditions, further enhancing the environmental performance of the material system.

[0054] Comparative Example: Traditional pyrolysis method for treating circuit boards containing TLCP The same batch of 5G base station filter circuit boards from Example 1 were directly crushed and fed into a fluidized bed pyrolysis furnace for pyrolysis at 500°C under a nitrogen atmosphere for 2 hours. The resulting pyrolysis oil has a complex composition, containing a large amount of aromatic hydrocarbons and some bromine-containing organic compounds. The pyrolysis gas has a low calorific value, and the carbon residue is a mixture of porous carbon and inorganic fillers, which can only be used as low-value filler or fuel. According to life cycle assessment, this traditional pyrolysis route has significantly higher carbon emissions per unit product than the routes A and B of this invention due to high energy consumption and low-value products, resulting in a negative overall environmental benefit.

[0055] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for resource recovery of waste TLCP circuit boards based on catalytic depolymerization and controllable remodeling, characterized in that, Includes the following steps: S1. Intelligent identification and enrichment: Non-destructive testing and intelligent identification of waste circuit boards containing thermotropic liquid crystal polymer (TLCP) are performed to locate TLCP substrates or components, and TLCP enriched materials are obtained through physical separation and disassembly. S2. Catalytic depolymerization: Under an inert atmosphere, the TLCP-enriched material obtained in step S1 is mixed with the composite catalyst in a solvent, and a catalytic depolymerization reaction is carried out at 240–320°C for 2–6 hours to obtain a depolymerization product containing TLCP oligomers; the composite catalyst is composed of Lewis acid metal salts and nitrogen-containing ligands. S3, Controlled Remodeling - Path A is Closed-Loop Regeneration: The depolymerization product containing TLCP oligomers obtained in step S2 is purified and then subjected to a repolymerization reaction in the presence of vacuum and a polycondensation catalyst to obtain regenerated TLCP resin. S4. Controlled remodeling – Path B is ring-opening conversion: The depolymerization product containing TLCP oligomers obtained in step S2 is mixed with bio-based monomers at a predetermined mass ratio and copolymerized under the action of an ester exchange catalyst to prepare a biodegradable copolyester material. S5. Life Cycle Carbon Benefit Calculation: Track the material and energy flows throughout the entire process from steps S1 to S4, and calculate and compare the carbon footprint and carbon reduction benefits of path A and path B based on the life cycle assessment method.

2. The method according to claim 1, characterized in that, In step S1, the non-destructive testing and intelligent identification uses terahertz imaging technology or near-infrared spectroscopy combined with artificial intelligence algorithms to perform non-contact scanning on the circuit board to distinguish TLCP from epoxy resin, polyimide and thermoplastic polymer materials. The accuracy of TLCP identification and positioning is not less than 95%.

3. The method according to claim 2, characterized in that, In step S1, obtaining the TLCP-enriched material includes: heating the TLCP-containing area to 180-220°C on a controllable hot air disassembly table to melt the solder and remove the electronic components and metal parts without damage, and then obtaining a substrate or fragments mainly composed of TLCP through mechanical cutting or punching.

4. The method according to claim 3, characterized in that, In step S2, the Lewis acid metal salt is one or more of zinc acetate, stannous chloride, or antimony trioxide; the nitrogen-containing ligand is 1,10-phenanthroline or 2,2′-bipyridine; and the solvent is a mixed solvent of phenol and tetrachloroethane or γ-valerolactone.

5. The method according to claim 1 or 4, characterized in that, In step S2, a bromine scavenger is also added to the catalytic depolymerization reaction system. The bromine scavenger is at least one of zinc oxide or iron oxide nanoparticles, used to immobilize bromine species produced by the decomposition of bromine-based flame retardants that may be contained in TLCP in situ, and to inhibit the generation of bromine-containing harmful gases. The amount of bromine scavenger added is 0.5% to 5% of the mass of the TLCP enriched material. The amount of the composite catalyst is 0.5% to 3.0% of the mass of the TLCP enriched material, wherein the molar ratio of Lewis acid metal salt to nitrogen-containing ligand is 1:(0.5 to 2.0).

6. The method according to claim 1, characterized in that, In step S3, the re-condensation reaction is carried out at 260-300°C and a vacuum of less than 100 Pa. The condensation catalyst used is tetrabutyl titanate or tetraisopropyl titanate, and the amount of catalyst used is 0.01%-0.2% of the TLCP oligomer mass. The intrinsic viscosity of the resulting recycled TLCP resin is not less than 0.6 dL / g, and it can be re-injected or extruded into high-performance connectors, fine-pitch sockets or circuit board substrates.

7. The method according to claim 1, characterized in that, In step S4, the bio-based monomer is selected from any one or a combination of lactic acid, lactide, succinic anhydride, succinic acid, and 2,5-furandicarboxylic acid. The mass ratio of the bio-based monomer to the TLCP oligomer is 1:5 to 1:

1. The transesterification catalyst is stannous octoate or an organotitanium catalyst. The reaction temperature is 180 to 220°C, the reaction time is 3 to 8 hours, and the number average molecular weight of the obtained biodegradable copolyester material is not less than 30,000. The biodegradable copolyester material has a biodegradability of no less than 80% under standard aerobic composting conditions for 180 days, and is suitable for preparing disposable electronic device shells, electronic product packaging materials or electronic tag substrates.

8. The method according to claim 1, characterized in that, In step S5, the baseline scenario for calculating the carbon emission reduction benefits includes: the production process of virgin TLCP resin with equivalent performance, and the treatment scenario of landfilling or incinerating waste circuit boards containing TLCP after simple dismantling; the calculation results show that the carbon footprint per unit product of recycled TLCP in path A is reduced by no less than 40% compared with virgin TLCP, and the carbon footprint per unit product of biodegradable copolyester material in path B is reduced by no less than 50% compared with traditional petroleum-based plastics.

9. A waste TLCP circuit board resource recovery system for implementing the method according to any one of claims 1 to 8, characterized in that, include: The intelligent identification and fine disassembly unit includes a terahertz imager and / or a near-infrared spectroscopy detection device, a robotic arm and a controllable hot air disassembly table, used to identify and separate TLCP substrates or components and obtain TLCP-enriched materials. The catalytic depolymerization reaction unit includes a high-pressure reactor with stirring, temperature control and reflux condensation devices, and an automatic catalyst and bromine capture agent addition system, which is used to catalytically depolymerize TLCP-enriched materials. The product separation and purification unit includes a centrifuge, a filtration device, a thin-film evaporator, and a washing tower, used to separate solid residues, purify TLCP oligomers, and recover solvents; The dual-path remodeling unit includes a vacuum polycondensation reactor and an atmospheric or slightly positive pressure copolymerization reactor arranged in parallel, corresponding to path A, the regeneration of TLCP resin, and path B, the preparation of biodegradable copolyester, respectively. The lifecycle data management unit includes sensors, data acquisition devices, databases, and lifecycle assessment accounting software modules connected to each unit, used to collect energy consumption and material consumption data in real time and generate carbon footprint reports.

10. The system according to claim 9, characterized in that, The temperature of the hot air disassembly station in the intelligent identification and fine disassembly unit can be precisely controlled between 180 and 220°C. This temperature is higher than the melting point of solder but lower than the heat distortion temperature of the TLCP substrate, so as to achieve non-destructive removal of electronic components and metal parts. The carbon footprint report generated by the life cycle data management unit complies with ISO 14040 and ISO 14044 standards, and assigns a unique digital identifier to each batch of processed materials for tracing its environmental performance throughout its entire life cycle.