Method and device for modifying and recycling waste plastics

Abstract

The invention discloses a method and a device for modifying and recycling waste plastics. The method comprises the following steps: carrying out multi-band electromagnetic resonance sorting on plastic fragments, distinguishing plastic types through an intelligent recognition algorithm, and synchronously adopting high-frequency eddy current sorting to remove metal impurities, so as to obtain classified plastic fragments; then supercritical fluid treatment is conducted, impurities are removed through a pressure oscillation system, obtained purified plastic fragments, a chain extender and nanofiller are jointly fed into solid-state shearing equipment, a molecular chain repairing reaction is triggered through a temperature control system, then the purified plastic fragments are injected into an intelligent forming system, and technological parameters are dynamically adjusted based on real-time monitoring data; forming a microstructure self-repairing replica through gradient cooling to obtain a regenerated plastic product, and embedding a traceable chip into the regenerated plastic product; impurity separation efficiency is improved through electromagnetic-vortex synergistic separation, microporous pollutants are deeply removed through supercritical fluid treatment, aged molecular chains are effectively repaired through a solid-state shearing chain extension technology, the microstructure of a product is optimized, and the strength and quality of the regenerated plastic product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling, and particularly to a method and device for modifying and recycling waste plastics. Background Art

[0002] In fields such as aerospace and precision medical devices, carbon fiber reinforced thermoplastic composites (CFRTP) are widely used to manufacture high-value structural components (such as satellite brackets and artificial joint housings). Such materials are composed of special engineering plastics such as polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) compounded with carbon fibers, and the monomer cost is as high as 50 - 100 times that of ordinary polyethylene. After being discarded during service, due to long-term exposure to extreme environments (external radiation, body fluid corrosion), microcracks and chemical cross-linking layers are formed on the surface of CFRTP, and the interface between the internal carbon fibers and the matrix is peeled off, resulting in the fact that although it has recycling value, the mechanical properties cannot be restored by traditional methods, and there is an urgent need to develop a directional regeneration technology to achieve closed-loop application.

[0003] Existing recycling technologies mostly focus on the melt regeneration of single-component plastics. Usually, carbon fibers are recycled through pyrolysis-reforming processes, but the regeneration problem of the matrix resin is not solved. Its core defect lies in that although high-temperature treatment (>380 °C) can separate carbon fibers, it causes irreversible degradation of matrix resins such as PEEK / PPS, and the molecular weight of the regenerated resin decreases by more than 60%, making it impossible to be reused for injection molding; and the remaining radiation cross-linking layer and microcracks will cause stress cracking of the regenerated products (impact strength < 15 kJ / m²). This makes high-value CFRTP can only be downgraded to filler use, unable to achieve "same-level regeneration", resulting in huge waste of resources.

[0004] In view of this, it is necessary to improve the waste plastic recycling technology in the prior art to solve the technical problem of performance deterioration during the regeneration of aged plastics. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and device for modifying and recycling waste plastics to solve the above technical problems.

[0006] To achieve this purpose, the present invention adopts the following technical solutions: A method for modifying and recycling waste plastics, comprising: Performing multi-band electromagnetic resonance sorting on plastic fragments, distinguishing plastic types through an intelligent recognition algorithm, and simultaneously removing metal impurities by high-frequency eddy current sorting to obtain classified plastic fragments; Performing supercritical fluid treatment on the classified plastic fragments, adding an amphiphilic ionic liquid to the supercritical system, and removing salts and biofilm pollutants in micropores through a pressure oscillation system to obtain purified plastic fragments; Feed the purified plastic fragments, chain extender, and nano-fillers into a solid-state shearing device, trigger the molecular chain repair reaction through the temperature control system, and obtain high-molecular-weight plastic masterbatch; Inject the high-molecular-weight plastic masterbatch into an intelligent molding system, dynamically adjust the process parameters based on real-time monitoring data, and form a micro-structure self-healing product through gradient cooling to obtain recycled plastic products; Embed a traceable chip in the recycled plastic products, compare the material spectral fingerprints in combination with blockchain technology and generate a verification report, and output recycled plastic finished products with traceable quality.

[0007] Optionally, perform multi-band electromagnetic resonance sorting on the plastic fragments, distinguish the plastic types through an intelligent recognition algorithm, and simultaneously use high-frequency eddy current sorting to remove metal impurities to obtain classified plastic fragments, specifically including: Transport the crushed plastic fragments to an electromagnetic resonance pretreatment unit, stimulate the dielectric response of the fragments through a multi-band alternating magnetic field, and obtain dielectric loss spectrum data; Input the dielectric loss spectrum data into the intelligent recognition algorithm module, compare the characteristic peak positions and intensity distributions, and dynamically generate classification instructions for plastic types; Control the multi-stage pneumatic sorting valves according to the classification instructions, sort plastic fragments of different materials into independent transmission channels, and obtain primary classified fragments.

[0008] Optionally, after controlling the multi-stage pneumatic sorting valves according to the classification instructions, sorting plastic fragments of different materials into independent transmission channels to obtain primary classified fragments, it further includes: Perform dielectric spectroscopy-infrared spectroscopy combined verification on the primary classified fragments, collect the chemical bond vibration spectrum on the surface of the fragments through an infrared probe, correct the classification error and generate optimized sorting parameters; Feed the optimized sorting parameters back to the high-frequency eddy current separator, and remove metal impurities based on the conductivity difference of the fragments to complete the sorting of the plastic fragments; Perform particle size screening on the sorted fragments, adjust the cutter distance of the crusher through a closed-loop control system, and output classified plastic fragments with uniform particle size.

[0009] Optionally, perform supercritical fluid treatment on the classified plastic fragments, add an amphiphilic ionic liquid to the supercritical system, and remove salts and biofilm pollutants in the micropores through a pressure oscillation system to obtain purified plastic fragments, specifically including the following steps: Place the classified plastic fragments in a preheating chamber, heat them to the initial temperature of the supercritical system through microwave radiation, and simultaneously evacuate to remove surface adsorbed gas; Inject the preheated plastic fragments and amphiphilic ionic liquid with a concentration of 0.3 - 1.5 wt% NTf2 into a supercritical reactor, fill it with CO2 to the critical pressure, and start the pressure oscillation system; Control the pressure oscillation system to cyclically adjust the pressure in the range of 7.4 - 35 MPa in a triangular wave mode, and utilize the sudden change effect of the interfacial tension of the ionic liquid to peel off the pollutants in the micropores; By on-line real-time monitoring of the gas composition at the reactor outlet, when the intensity of the biofilm characteristic peak is detected to drop to the baseline value, trigger the cleaning termination signal; Dynamically switch to the constant pressure mode according to the cleaning termination signal, and maintain the supercritical fluid flow rate to continuously rinse the residual ionic liquid on the surface of the fragments; Remove the residual supercritical fluid in the pores of the fragments through a centrifugal separation device to obtain purified plastic fragments with the salt content and biofilm coverage rate within the qualified range.

[0010] Optionally, send the purified plastic fragments, chain extender, and nano filler into a solid-state shear device, and trigger the molecular chain repair reaction through a temperature control system to obtain high molecular weight plastic masterbatch, specifically including: Input the purified plastic fragments, chain extender, and nano-hydrotalcite into the premixing bin in proportion, and form a uniform premix through ultrasonic vibration dispersion; Send the premix into a co-rotating twin-screw solid-state shear device, adopt a segmented screw structure, and increase the temperature in stages from 135 °C → 148 °C → 155 °C in the shear zone through an intelligent temperature control system to trigger the activity of the chain extender and bind it to the ends of the broken molecular chains; Real-time monitor the melt rheological properties through an on-line viscosity sensor, and dynamically adjust the screw speed according to the melt rheological properties; After rapid shaping at a cooling rate of 50 °C / s through a water-cooled die head, pelletize to obtain high molecular weight plastic masterbatch.

[0011] Optionally, inject the high molecular weight plastic masterbatch into an intelligent forming system, dynamically adjust the process parameters based on real-time monitoring data, and form a microstructural self-repairing product through gradient cooling to obtain recycled plastic products, specifically including: Send the high molecular weight plastic masterbatch into a vacuum drying bin, and preheat it to 20 - 30 °C above the glass transition temperature of the masterbatch through far-infrared heating to obtain a masterbatch with optimized fluidity; Inject the masterbatch with optimized fluidity into the plasticizing mold of the intelligent forming system, and generate an initial process parameter set by real-time collecting melt rheological data through a multi-sensor module; Based on the multi-sensor module embedded in the mold to monitor the melt flow front, dynamically adjust the injection speed and holding pressure, and start the gradient cooling program after filling; Implement three-stage cooling of the mold through a zone temperature controller; After ejecting the plastic product, a microstructure is formed on the surface of the plastic product by laser micro-etching, triggering the self-healing behavior induced by residual stress to obtain a recycled plastic product.

[0012] Optionally, the process of three-stage cooling specifically includes: In the first stage, surface hardening is achieved by nitrogen jet at a cooling rate of 200 °C / s. In the second stage, it is switched to a liquid cooling channel to control the crystallinity in the middle at a cooling rate of 50 °C / s. In the third stage, isothermal annealing is used to release the interfacial stress.

[0013] Optionally, the multi-sensor module includes a pressure sensor, a temperature sensor, and a viscosity detector.

[0014] Optionally, a traceable chip is embedded in the recycled plastic product. Combining blockchain technology to compare the material spectral fingerprints and generate a verification report, and output a recycled plastic product with traceable quality, specifically including: A micro-groove is opened in the non-stressed area of the recycled plastic product, and a high-temperature resistant NFC chip is embedded using microwave-induced encapsulation technology to form a recycled product with a chip; The surface of the product is scanned by a laser scanner to collect the carbon / oxygen element distribution spectrum and polymer characteristic peaks, and generate material spectral fingerprint data; The spectral fingerprint data is dynamically compared with the original plastic database pre-stored in the blockchain. Based on the convolutional neural network to optimize the matching algorithm, the material consistency is verified; When the verification passes, a credible report including recycling process parameters, performance indicators, and environmental benefits is automatically generated, encrypted and written into the chip, and a traceable recycled plastic product with a unique digital identity is output.

[0015] The present invention also provides a modified recycling device for waste plastics to implement the modified recycling method of waste plastics as described above. The modified recycling device includes: A multi-modal sorting module, including an electromagnetic resonance detector and a high-frequency eddy current separator, integrating pneumatic sorting valves and particle size screening units, for realizing plastic type sorting and removing metal impurities; A supercritical reaction kettle, equipped with a microwave preheating chamber, an amphiphilic ionic liquid injection pump, and a pressure oscillation system; A solid-state shearing device, used to trigger the molecular chain repair reaction through a temperature control system to obtain high molecular weight plastic masterbatch; An intelligent forming module, composed of an injection molding machine equipped with a multi-sensor module, and combined with a laser micro-etching device, for preparing a microstructure self-healing product; A packaging mechanism, used to package the traceable chip and output a recycled plastic product with traceable quality.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Firstly, by combining multi-band electromagnetic resonance separation and high-frequency eddy current separation, high-precision classification of plastic fragments and removal of metal impurities are achieved; then, treatment with a supercritical fluid containing an amphiphilic ionic liquid is used, combined with pressure oscillation to remove microporous pollutants; the purified fragments are combined with a chain extender and nano-fillers in a solid-state shearing device to trigger a molecular chain repair reaction to generate high-molecular-weight masterbatch; then, through dynamic parameter adjustment and gradient cooling of an intelligent forming system, a micro-structure self-repairing product is formed; finally, a traceable chip is embedded and quality verification is completed based on blockchain technology to form a traceable recycled plastic product; this method improves the impurity separation efficiency through electromagnetic-eddy current synergistic separation, deeply removes microporous pollutants through supercritical fluid treatment, effectively repairs aged molecular chains with solid-state shearing chain extension technology, optimizes the microstructure of the product, and combines blockchain traceability to ensure the traceability of materials, improving the strength and quality of recycled plastic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for description in the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] The structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limited conditions under which the present invention can be implemented. Therefore, they do not have technical essential significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention.

[0019] Figure 1 It is one of the flow diagrams of the modified recycling method for waste plastics in the first embodiment; Figure 2 It is another flow diagram of the modified recycling method for waste plastics in the first embodiment; Figure 3 It is the system layout diagram of the modified recycling device for waste plastics in the second embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the objectives, features, and advantages of the present invention more obvious and understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be intermediate components present at the same time.

[0022] The following further illustrates the technical solutions of the present invention with reference to the accompanying drawings and through specific embodiments.

[0023] Embodiment 1: Combined with Figure 1 and Figure 2 As shown, the embodiment of the present invention provides a method for modified recycling of waste plastics, including: S1. Perform multi-band electromagnetic resonance sorting on plastic fragments, distinguish plastic types through an intelligent recognition algorithm, and synchronously remove metal impurities by high-frequency eddy current sorting to obtain classified plastic fragments; Adopt multi-band electromagnetic resonance sorting technology. Based on the dielectric constant differences of different polymers (such as PEEK, PPS, etc.), by adjusting the resonance frequency of the 0.5 - 5 GHz electromagnetic wave band, the dipole resonance effect of specific types of plastics is excited. The intelligent recognition system analyzes the dielectric spectrum characteristics of each fragment in real time through Fourier transform to achieve high-precision sorting. Synchronously apply a 50 kHz high-frequency alternating magnetic field to induce eddy currents with an amplitude of up to 2.3 kA / m on the surface of the fragments, and separate metal inclusions through the Lorentz force to avoid the problem of metal-catalyzed resin degradation in subsequent processes.

[0024] S2. Perform supercritical fluid treatment on the classified plastic fragments, add amphiphilic ionic liquids to the supercritical system, and remove salts and biofilm pollutants in the micropores through a pressure oscillation system to obtain purified plastic fragments; Supercritical CO2 (scCO2, 31.1 °C / 7.38 MPa) is used as the mass transfer medium. Its diffusion coefficient is two orders of magnitude higher than that of liquid solvents and can penetrate into the interior of microcracks. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]) amphiphilic ionic liquid is added (addition amount 0.5 wt%). Its lipophilic group (-CF3) can dissolve the free radical chain-breaking products in the crosslinked layer, while the polar group (SO2) strips the biofilm proteins through hydrogen bonding. The pressure oscillation system generates microjets to achieve the mechanical stripping of inorganic salts such as NaCl in the micropores.

[0025] S3, Feed the purified plastic fragments, chain extender, and nano-fillers into a solid-state shear device together, trigger the molecular chain repair reaction through the temperature control system, and obtain high-molecular-weight plastic masterbatch; By combining an on-line viscosity sensor and an infrared thermal imager, dynamically adjust the screw speed to maintain the grafting reaction degree. After rapid shaping with a water-cooled die head, a masterbatch with a molecular weight distribution index <2.1 is obtained, and its tensile strength is restored to more than 85% of the virgin material.

[0026] S4, Inject the high-molecular-weight plastic masterbatch into an intelligent molding system, dynamically adjust the process parameters based on real-time monitoring data, and form a micro-structural self-repairing product through gradient cooling to obtain recycled plastic products.

[0027] S5, Embed a traceable chip in the recycled plastic products, compare the material spectral fingerprints in combination with blockchain technology and generate a verification report, and output recycled plastic finished products with traceable quality.

[0028] The working principle of the present invention is as follows: First, through the combined use of multi-band electromagnetic resonance sorting and high-frequency eddy current sorting, high-precision classification of plastic fragments and removal of metal impurities are achieved; then, treatment with supercritical fluids containing amphiphilic ionic liquids is used, combined with pressure oscillation to remove micropore pollutants; the purified fragments, chain extender, and nano-fillers trigger a molecular chain repair reaction in a solid-state shear device to generate high-molecular-weight masterbatch; then, through dynamic parameter adjustment and gradient cooling of an intelligent molding system, a micro-structural self-repairing product is formed; finally, a traceable chip is embedded and quality verification is completed based on blockchain technology to form traceable recycled plastic finished products; this method improves the impurity separation efficiency through electromagnetic-eddy current collaborative sorting, deeply removes micropore pollutants through supercritical fluid treatment, effectively repairs aging molecular chains through solid-state shear chain extension technology, and optimizes the microstructure of the products, and combines blockchain traceability to ensure the traceability of materials, and improves the strength and quality of recycled plastic products.

[0029] In this embodiment, specifically, step S1 specifically includes: S11, Transport the crushed plastic fragments to an electromagnetic resonance pretreatment unit, and obtain dielectric loss spectrum data by exciting the dielectric response of the fragments through a multi-band alternating magnetic field; A multi - band alternating magnetic field generator is adopted to apply non - thermal electromagnetic excitation to the crushed plastic fragments. By collecting the dielectric loss spectra of the fragments in real - time, the dielectric response characteristics are analyzed based on the Debye relaxation model. PEEK presents a characteristic loss peak at 2.4 GHz, while PPS shows polarization loss at 1.8 GHz. An initial classification benchmark is established through the spectral differences.

[0030] S12, input the dielectric loss spectrum data into the intelligent recognition algorithm module, compare the positions and intensity distributions of the characteristic peaks, and dynamically generate classification instructions for the plastic types; the intelligent recognition algorithm module can be a pre - trained deep residual network.

[0031] Based on the pre - trained deep residual network (ResNet - 34), input the joint training dataset of dielectric spectra and infrared spectra. The model is optimized by the cross - entropy loss function to improve the classification accuracy. The characteristic peak localization is processed by Savitzky - Golay filtering for smoothing, and the intensity distribution is used to extract the peak area ratio through Gaussian fitting (such as the ratio of the C = O vibration peak at 1600 cm⁻¹ of PEEK ≥ 18%). Classification instructions are dynamically generated and mapped to the pneumatic valve control matrix.

[0032] S13, control the multi - stage pneumatic sorting valve according to the classification instructions, sort the plastic fragments of different materials into independent transmission channels, and obtain the primary classified fragments.

[0033] The multi - stage pneumatic sorting valve adopts a high - speed solenoid valve array, and drives the compressed air to jet the fragments directionally according to the classification instructions. The sorting channel is designed as a five - stage fluidized bed structure, and secondary sorting is realized by using the density difference of the fragments (PEEK 1.32 g / cm3, PPS 1.35 g / cm3) to output the primary classified fragments with high purity.

[0034] S14, conduct a combined verification of dielectric spectra - infrared spectra on the primary classified fragments, collect the chemical bond vibration spectra on the surface of the fragments through an infrared probe, correct the classification errors and generate optimized sorting parameters; Integrate the attenuated total reflection Fourier transform infrared spectroscopy and the dielectric probe to conduct on - line spectral review on the primary classified fragments. By comparing with the standard spectral library (NIST reference database) through partial least squares discriminant analysis, correct the classification errors. The optimization algorithm adopts Bayesian optimization to adjust the sorting frequency weight and the valve opening duration, and generate parameter iteration instructions.

[0035] S15, feedback the optimized sorting parameters to the high - frequency eddy current separator, and remove metal impurities based on the conductivity difference of the fragments to complete the sorting of the plastic fragments. The optimized sorting parameters are loaded into the high-frequency eddy current separator. Based on the difference in the conductivity of the fragments (the conductivity of metal impurities > 106 S / m, and that of plastics < 10-12 S / m), a reverse eddy current repulsive force is generated to improve the separation efficiency of metal impurities. The metal residue on the surface of the sorted plastic fragments is low, meeting the purity requirements for subsequent supercritical treatment.

[0036] S16, perform particle size screening on the sorted fragments, adjust the cutter distance of the crusher through a closed-loop control system, and output classified plastic fragments with uniform particle size.

[0037] Use a vibrating screen to classify the sorted fragments by particle size. The laser particle size analyzer real-time feeds back the particle size distribution to the PLC control system to dynamically adjust the cutter distance of the crusher. Through the PID algorithm (proportional coefficient Kp = 0.8, integral time Ti = 2 s), the particle size is controlled to be uniform, and classified plastic fragments with a qualification rate ≥ 99.5% are output.

[0038] In this embodiment, specifically, step S2 specifically includes the following steps: S21, place the classified plastic fragments into the preheating bin, heat them to the initial temperature of the supercritical system by microwave radiation, and simultaneously evacuate to remove the surface adsorbed gas; Use microwave radiation to uniformly preheat the classified plastic fragments to raise their temperature to 45 ± 3 °C (the initial temperature of the supercritical CO 2 system), and at the same time remove the gas adsorbed on the surface of the fragments by high-vacuum suction to avoid the influence of gas residue on the cleaning effect during subsequent supercritical treatment. Compared with traditional hot air heating, microwave heating can reduce energy consumption and ensure the temperature difference between the core and the surface of the fragments, preventing plastic deformation caused by local overheating.

[0039] S22, inject the preheated plastic fragments and the amphiphilic ionic liquid with a concentration of 0.3 - 1.5 wt% NTf2 into the supercritical reaction kettle, fill it with CO2 to the critical pressure, and start the pressure oscillation system; The preheated plastic fragments and the amphiphilic ionic liquid [BMIM]NTf2 (0.3 - 1.5 wt%) are jointly injected into the supercritical reaction kettle, and CO 2 is filled to the critical pressure (7.4 MPa) to form a supercritical fluid environment. The addition of the ionic liquid can significantly enhance the dissolution ability of the supercritical fluid, especially for the salt crystallization and biofilm residues in the micropores. The pressure oscillation system is started synchronously to provide a dynamic environment for subsequent pollutant stripping.

[0040] S23, control the pressure oscillation system to cyclically adjust the pressure in the range of 7.4 - 35 MPa in a triangular wave mode, and use the sudden change effect of the interfacial tension of the ionic liquid to strip the pollutants in the micropores; The pressure is cyclically adjusted in a triangular wave mode. By utilizing the sudden change in pressure to trigger the periodic change of the interfacial tension of the ionic liquid, a micro-scale turbulent effect is generated, effectively stripping the pollutants infiltrated into the plastic micropores. Compared with traditional constant-pressure cleaning, this mode can improve the pollutant removal rate and avoid the swelling of the plastic matrix caused by excessive pressure.

[0041] S24. By online real-time monitoring of the gas composition at the outlet of the reaction kettle, when the intensity of the biofilm characteristic peak is detected to drop to the baseline value, a cleaning termination signal is triggered. By online mass spectrometer to real-time monitor the gas composition at the outlet of the reaction kettle. When the intensities of the biofilm characteristic peaks (m / z = 115, 213) are detected to drop to the baseline value, the intelligent system automatically triggers a cleaning termination signal. This technology can avoid the problems of over-cleaning or under-cleaning in traditional timed cleaning, ensure the optimal cleaning efficiency, and reduce the biofilm residue.

[0042] S25. According to the cleaning termination signal, dynamically switch to the constant-pressure mode to maintain the supercritical fluid flow rate and continuously rinse the residual ionic liquid on the surface of the debris. After the cleaning is terminated, the system automatically switches to the constant-pressure mode (32 MPa) to maintain the supercritical fluid flow rate and continuously rinse the plastic debris to thoroughly remove the residual ionic liquid on the surface, prevent its corrosive effect on the subsequent solid-state shear equipment, reduce the amount of ionic liquid residue, and meet the higher-grade material standards.

[0043] S26. Use a centrifugal separation device to remove the residual supercritical fluid in the pores of the debris, and obtain purified plastic debris with the salt content and biofilm coverage rate within the qualified range.

[0044] Use high-speed centrifugal separation to remove the residual supercritical fluid in the pores of the plastic debris. Finally, purified plastic debris with a salt content < 20 ppm and a biofilm coverage rate < 0.1% is obtained. The centrifuged debris can directly enter the subsequent chain extension and repair process without secondary drying treatment, significantly shortening the process flow.

[0045] In this embodiment, specifically, step S3 specifically includes: S31. Input the purified plastic debris, chain extender, and nano-hydrotalcite into the premixing bin in proportion, and form a uniform premix through ultrasonic vibration dispersion. Input the purified plastic debris, chain extender, and nano-hydrotalcite into the premixing bin according to the precise ratio, and perform physical dispersion by ultrasonic vibration. The ultrasonic cavitation effect can effectively break the agglomerated structure of the nano-fillers, make them evenly distributed in the plastic matrix, and at the same time promote the preliminary contact between the chain extender and the plastic debris, improving the uniformity of the subsequent reaction. Compared with mechanical stirring, ultrasonic dispersion can reduce energy consumption and avoid the problem of uneven performance caused by local aggregation of the fillers.

[0046] S32. Feed the premix into a co-rotating twin-screw solid-state shearing device. Adopt a segmented screw structure and increase the temperature in stages from 135°C to 148°C to 155°C in the shearing zone through an intelligent temperature control system, trigger the activity of the chain extender and bind it to the ends of the broken molecular chains. The premix enters a co-rotating twin-screw solid-state shearing device (length-diameter ratio 48:1) and is shear plasticized under segmented temperature control (135°C → 148°C → 155°C). This temperature control strategy optimizes the reaction environment in three stages: 135°C: Soften the plastic fragments to facilitate further dispersion of the nano-fillers. 148°C: Activate the chain extender (ADR-4468) to react with the end functional groups (such as carboxyl groups and hydroxyl groups) of the broken molecular chains. 155°C (below the melting point of PE / PEEK): Ensure the full progress of the chain extension reaction and avoid high-temperature degradation at the same time.

[0047] Through the synergistic action of shear force and temperature, the broken molecular chains are reconnected, the molecular weight recovery rate is increased, and the mechanical properties of the recycled plastic are significantly improved.

[0048] S33. Real-time monitor the melt rheological properties through an on-line viscosity sensor and dynamically adjust the screw speed according to the melt rheological properties. Adopt an on-line viscosity sensor to real-time monitor the melt rheological properties, and combine an infrared thermal imager to detect the temperature distribution. The intelligent system dynamically adjusts the screw speed according to the change of the melt viscosity to ensure the uniform progress of the chain extension reaction and avoid material degradation caused by local overheating. This closed-loop control technology can make the performance volatility of the recycled plastic tend to be stable, which is better than the production method with traditional fixed process parameters.

[0049] S34. After rapid shaping at a cooling rate of 50°C / s through a water-cooled die head, pelletize to obtain high-molecular-weight plastic masterbatch.

[0050] The melt after shear repair is rapidly shaped through a water-cooled die head (cooling rate 50°C / s) to inhibit the decrease in crystallinity caused by molecular chain relaxation and retain the oriented structure. Subsequently, it is processed by a pelletizer into plastic masterbatch with a particle size of 3 - 5 mm, whose molecular weight distribution index PDI < 2.1 and tensile strength ≥ 140 MPa, meeting the application requirements of high added value.

[0051] In this embodiment, specifically, step S4 specifically includes: S41. Feed the high-molecular-weight plastic masterbatch into a vacuum drying bin and preheat it to 20 - 30°C above the glass transition temperature of the masterbatch through far-infrared heating to obtain a masterbatch with optimized fluidity. The high molecular weight plastic masterbatch is pretreated in a vacuum drying chamber and uniformly heated to 20 - 30 °C above the glass transition temperature Tg by combining far - infrared heating. This heating method has the characteristics of strong penetrability and low energy consumption, and can avoid the surface overheating problem caused by traditional hot - air drying. The pre - heated masterbatch melt improves its fluidity, and at the same time controls the moisture content, effectively preventing the generation of bubbles and silver streaks during the subsequent injection molding process.

[0052] S42, Inject the fluidity - optimized masterbatch into the plasticizing mold of the intelligent forming system, and collect melt rheological data in real - time through a multi - sensor module to generate an initial process parameter set. After the fluidity is optimized, the masterbatch enters the plasticizing unit of the intelligent forming system, and melt rheological data is collected in real - time through an integrated multi - sensor module (pressure / temperature / viscosity). Based on digital twin technology, the system automatically generates an optimized initial process parameter set, including key parameters such as injection pressure and melt temperature.

[0053] S43, Based on the multi - sensor module embedded in the mold, monitor the melt flow front, dynamically adjust the injection speed and holding pressure, and start the gradient cooling program after filling is completed. The sensor array embedded in the mold monitors the morphology of the melt flow front in real - time, and the intelligent control system dynamically adjusts the injection speed and holding pressure accordingly. Through the adaptive PID algorithm, ensure the complete filling of complex cavities, and at the same time avoid flash and short - shot defects. After filling is completed, the system automatically triggers the gradient cooling program, laying a foundation for subsequent microstructure control.

[0054] S44, Implement three - stage cooling of the mold through a zone - temperature controller. The process of three - stage cooling specifically includes: In the first stage, surface quenching is achieved by nitrogen jet at a cooling rate of 200 °C / s to form an amorphous surface layer (thickness 50 - 100 μm), improving the surface hardness. In the second stage, switch to the liquid - cooling channel to control the middle crystallinity at a cooling rate of 50 °C / s to obtain an ideal crystallinity and balance the mechanical properties. In the third stage, use isothermal annealing to release the interfacial stress and make the product size stable.

[0055] S45, After ejecting the plastic product, form microstructures on the surface of the plastic product by laser micro - etching, trigger the self - repair behavior induced by residual stress, and obtain a regenerated plastic product.

[0056] The ejected product constructs topological microstructures with a depth of 10 - 50 μm on the surface by laser micro - etching. These microstructures can induce the redistribution of residual stress inside the product, activate the unreacted chain extender in the matrix, and achieve self - repair of micro - cracks. The treated regenerated plastic product improves its fatigue life and meets the usage requirements of engineering structural parts.

[0057] In this embodiment, it is further illustrated that the multi-sensor module includes a pressure sensor, a temperature sensor, and a viscosity detector. After the pressure-temperature-viscosity data is fused, the shrinkage rate of the product is predicted through a digital twin model, providing real-time input parameters for the dynamic adjustment of the injection speed and improving the filling integrity of complex structures.

[0058] In this embodiment, specifically, step S5 specifically includes: S51, opening micro-grooves in the non-loaded area of the recycled plastic product, and embedding a high-temperature resistant NFC chip using microwave-induced encapsulation technology to form a recycled product with a chip. In the non-loaded area of the recycled plastic product (such as the inside of the rib and the assembly interface), micro-grooves with a depth of 0.5 - 1.2 mm are machined by precision milling. Using microwave-induced encapsulation technology, while locally heating and softening the matrix material (the softening range is precisely controlled within ±0.3 mm), a high-temperature resistant NFC chip (operating temperature -40~250 °C) is embedded. Compared with traditional hot pressing encapsulation, this technology can avoid the deformation of the product caused by overall heating. The chip has a built-in encrypted memory, providing a physical carrier for subsequent data writing.

[0059] S52, scanning the surface of the product with a laser scanner to collect the carbon / oxygen element distribution spectrum and polymer characteristic peaks, and generating material spectral fingerprint data. Use a laser-induced breakdown spectrometer to scan the surface of the product, excite the material to generate plasma, and collect the carbon / oxygen element distribution spectrum and polymer characteristic peaks (such as the C=O bond at 1720 cm-1). Through multi-spectral fusion technology, three-dimensional fingerprint data including element composition, molecular structure, and filler distribution is generated, and its information density is 8 times that of traditional infrared spectroscopy, which can uniquely identify the material batch.

[0060] S53, dynamically comparing the spectral fingerprint data with the original plastic database pre-stored in the blockchain, and verifying the material consistency based on a convolutional neural network optimized matching algorithm. Upload the spectral fingerprint data to the blockchain platform and compare it with the pre-stored original plastic database. Using a convolutional neural network, through the feature extraction layer and the similarity calculation layer, high-precision verification of material consistency is achieved. This algorithm is optimized for the spectral shift characteristics of recycled plastics, with a misjudgment rate lower than 0.3%, and supports automatic compensation for fluctuations in the carbon fiber content (15 - 60 wt%).

[0061] S54, when the verification is passed, a credible report including recycling process parameters, performance indicators, and environmental benefits is automatically generated, encrypted and written into the chip, and a traceable recycled plastic finished product with a unique digital identity is output.

[0062] After the verification is passed, the system automatically generates a structured credible report, including: Process traceability data: Supercritical cleaning parameters (pressure 32 MPa), solid-state shear temperature, etc.; Performance indicators: Tensile strength (≥140 MPa), self-healing efficiency; Environmental benefits: Carbon emission reduction, energy consumption saving rate.

[0063] The report is encrypted with AES-256 and written into the chip, and at the same time, a blockchain hash value is generated and stored on the chain. The finished product obtains a unique digital identity, supports full-life cycle query, and is tamper-proof.

[0064] This technical system enables the recycled plastic finished products to meet strict traceability standards such as aerospace AS9100D and medical device ISO 13485, and realizes the value improvement from "recycled materials" to "certified materials".

[0065] Example 2: Combined with Figure 3 As shown, the present invention also provides a modified recycling device for waste plastics to implement the modified recycling method for waste plastics as described in Example 1. The modified recycling device includes: A multi-modal sorting module, including an electromagnetic resonance detector and a high-frequency eddy current sorter, integrating a pneumatic sorting valve and a particle size screening unit, for realizing plastic type sorting and metal impurity removal.

[0066] A supercritical reactor, equipped with a microwave preheating chamber, an amphiphilic ionic liquid injection pump, and a pressure oscillation system.

[0067] A solid-state shear device, for triggering a molecular chain repair reaction through a temperature control system to obtain a high molecular weight plastic masterbatch.

[0068] An intelligent molding module, composed of an injection molding machine equipped with a multi-sensor module, and combined with a laser micro-etching device, for preparing micro-structured self-healing products.

[0069] A packaging mechanism, for packaging a traceable chip and outputting a recycled plastic finished product with traceable quality.

[0070] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for modifying and recycling waste plastics, characterized in that: include: Plastic fragments are sorted by multi-band electromagnetic resonance, and the types of plastics are distinguished by intelligent recognition algorithms. High-frequency eddy current sorting is used to remove metal impurities to obtain classified plastic fragments. The classified plastic fragments are subjected to supercritical fluid treatment, an amphiphilic ionic liquid is added to the supercritical system, and salt and biofilm pollutants in the micropores are removed by a pressure oscillation system to obtain purified plastic fragments; The purified plastic fragments, chain extender and nanofiller are fed into a solid-state shearing device, and a molecular chain repair reaction is triggered by a temperature control system to obtain a high molecular weight plastic masterbatch; The high molecular weight plastic masterbatch is injected into the intelligent molding system, the process parameters are dynamically adjusted based on the real-time monitoring data, and a microstructure self-repairing product is formed by gradient cooling to obtain a recycled plastic product; A traceable chip is embedded in the recycled plastic product, and blockchain technology is used to compare the material spectral fingerprint and generate a verification report, thereby outputting a recycled plastic finished product with traceable quality.

2. The method for modifying and recycling waste plastics according to claim 1, characterized in that: The plastic fragments are subjected to multi-band electromagnetic resonance sorting, the types of plastics are distinguished by an intelligent recognition algorithm, and metal impurities are removed by high-frequency eddy current sorting to obtain classified plastic fragments, specifically including: The crushed plastic fragments are transported to the electromagnetic resonance pre-processing unit, and the dielectric response of the fragments is stimulated by a multi-band alternating magnetic field to obtain dielectric loss spectrum data; Input the dielectric loss spectrum data into the intelligent recognition algorithm module, compare the characteristic peak position and intensity distribution, and dynamically generate classification instructions for plastic types; The multi-stage pneumatic sorting valve is controlled according to the classification instruction to sort the plastic fragments of different materials into independent transmission channels to obtain primary classified fragments.

3. The method for modifying and recycling waste plastics according to claim 2, characterized in that: According to the classification instruction, the multi-stage pneumatic sorting valve is controlled to sort the plastic fragments of different materials into independent transmission channels to obtain primary classified fragments, and then it also includes: The primary classification fragments are verified by dielectric spectroscopy-infrared spectroscopy, and the chemical bond vibration spectrum of the fragment surface is collected by infrared probe to correct the classification error and generate optimized sorting parameters; Feedback the optimized sorting parameters to the high-frequency eddy current separator to remove metal impurities based on the difference in conductivity of the fragments to complete the sorting of plastic fragments; The sorted fragments are screened according to particle size, and the crusher blade distance is adjusted through a closed-loop control system to output classified plastic fragments with uniform particle size.

4. The method for modifying and recycling waste plastics according to claim 1, characterized in that: The classified plastic fragments are subjected to supercritical fluid treatment, an amphiphilic ionic liquid is added to the supercritical system, and salt and biofilm pollutants in the micropores are removed by a pressure oscillation system to obtain purified plastic fragments, which specifically includes the following steps: The classified plastic fragments are placed in a preheating chamber, heated to the initial temperature of the supercritical system by microwave radiation, and vacuumed simultaneously to remove the surface adsorbed gas; The preheated plastic fragments and the amphiphilic ionic liquid NTf2 with a concentration of 0.3-1.5wt% are co-injected into a supercritical reactor, CO2 is charged to the critical pressure, and the pressure oscillation system is started; The pressure oscillation system is controlled to cyclically adjust the pressure in the range of 7.4-35MPa in a triangular wave mode, and the pollutants in the micropores are stripped by using the sudden change effect of the interfacial tension of the ionic liquid; By monitoring the gas composition at the reactor outlet in real time online, when the intensity of the biofilm characteristic peak is detected to drop to the baseline value, the cleaning termination signal is triggered; Dynamically switching to a constant pressure mode according to the cleaning termination signal, maintaining the supercritical fluid flow rate to continuously flush the residual ionic liquid on the surface of the fragments; The residual supercritical fluid in the pores of the fragments is removed by a centrifugal separation device to obtain purified plastic fragments with salt content and biofilm coverage within the acceptable range.

5. The method for modifying and recycling waste plastics according to claim 1, characterized in that: The purified plastic fragments, chain extender and nanofiller are fed into a solid shearing device, and a molecular chain repair reaction is triggered by a temperature control system to obtain a high molecular weight plastic masterbatch, specifically comprising: The purified plastic fragments, chain extender and nano-hydrotalcite are introduced into a premixing bin in proportion, and dispersed by ultrasonic vibration to form a uniform premix; The premix is ​​fed into a co-rotating twin-screw solid-state shearing device, which adopts a segmented screw structure, and the temperature is raised in stages from 135°C → 148°C → 155°C in the shearing zone through an intelligent temperature control system to trigger the activity of the chain extender and combine with the ends of the broken molecular chains; The online viscosity sensor monitors the rheological properties of the melt in real time and dynamically adjusts the screw speed according to the rheological properties of the melt; After being quickly shaped by a water-cooled die at a cooling rate of 50°C / s, the pellets are cut to obtain high molecular weight plastic masterbatch.

6. The method for modifying and recycling waste plastics according to claim 1, characterized in that: The high molecular weight plastic masterbatch is injected into the intelligent molding system, the process parameters are dynamically adjusted based on real-time monitoring data, and a microstructure self-repairing product is formed by gradient cooling to obtain a recycled plastic product, specifically including: The high molecular weight plastic masterbatch is sent into a vacuum drying chamber and preheated to 20-30° C. above the glass transition temperature of the masterbatch by far infrared heating to obtain a fluidity optimized masterbatch; Injecting the fluidity-optimized masterbatch into a plasticizing mold of an intelligent molding system, collecting melt rheology data in real time through a multi-sensor module, and generating an initial process parameter set; Based on the multi-sensor module embedded in the mold, the melt flow front is monitored, the injection speed and holding pressure are dynamically adjusted, and the gradient cooling program is started after the filling is completed; Implement three-stage cooling of the mold through zone temperature controllers; After ejecting the plastic product, a microstructure is formed on the surface of the plastic product by laser micro-etching, triggering the residual stress-induced self-repairing behavior to obtain a recycled plastic product.

7. The method for modifying and recycling waste plastics according to claim 6, characterized in that: The three-stage cooling process specifically includes: In the first stage, nitrogen jet was used to achieve surface quenching at a cooling rate of 200°C / s. In the second stage, the liquid cooling channel was switched to control the crystallinity in the middle at a cooling rate of 50°C / s. In the third stage, constant temperature annealing was used to release interface stress.

8. The method for modifying and recycling waste plastics according to claim 6, characterized in that: The multi-sensor module includes a pressure sensor, a temperature sensor and a viscosity detector.

9. The method for modifying and recycling waste plastics according to claim 1, characterized in that: Embed a traceable chip in the recycled plastic product, combine blockchain technology to compare the material spectral fingerprint and generate a verification report, and output a recycled plastic finished product with traceable quality, specifically including: A micro-groove is provided in the non-stress-bearing area of ​​the recycled plastic product, and a high-temperature-resistant NFC chip is embedded by microwave-induced packaging technology to form a recycled product with a chip; Scan the surface of the product with a laser scanner to collect carbon / oxygen element distribution spectrum and polymer characteristic peaks to generate material spectrum fingerprint data; Dynamically compare the spectral fingerprint data with the original plastic database pre-stored in the blockchain, and optimize the matching algorithm based on the convolutional neural network to verify the consistency of the material; When the verification is passed, a credible report containing recycling process parameters, performance indicators and environmental benefits is automatically generated and encrypted into the chip, outputting a traceable recycled plastic product with a unique digital identity.

10. A waste plastic modification and recovery device, characterized in that: Used to implement the modification and recycling method of waste plastics as claimed in any one of claims 1 to 9, the modification and recycling device comprises: Multi-modal sorting module, including electromagnetic resonance detector and high-frequency eddy current sorting machine, integrated pneumatic sorting valve and particle size screening unit, used to sort plastic types and remove metal impurities; Supercritical reactor, equipped with microwave preheating chamber, amphiphilic ionic liquid injection pump and pressure oscillation system; Solid-state shearing equipment, used to trigger the molecular chain repair reaction through the temperature control system to obtain high molecular weight plastic masterbatch; The intelligent molding module consists of an injection molding machine equipped with a multi-sensor module, which is combined with a laser micro-etching device to prepare micro-structure self-repairing products; The packaging mechanism is used to package traceable chips and output recycled plastic finished products with traceable quality.

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