Efficient and recoverable carbon fiber plastic resin material depolymerization recovery process

Abstract

The invention discloses an efficient and recoverable carbon fiber plastic resin material depolymerization recovery process which is characterized in that microwave-assisted supercritical fluid is coupled with a heterogeneous photo-thermal catalysis technology to realize efficient separation (llt of resin and carbon fibers; 2 hours) and monomer selective recovery. According to the process, resin is depolymerized in a 520 kW microwave field by adopting an acetic acid / ethanol supercritical fluid (the volume ratio is 3: 7), mixed polyester is selectively depolymerized through photo-thermal catalysis in combination with a GB-rich CeO2 catalyst (GaCl3 is loaded with 0.5 mol%), and the carbon fiber recovery rate is gt; and the 3D printing resolution ratio of the regenerated resin reaches 100 microns. Compared with a traditional method, the technology has the advantages that the energy consumption is reduced by 40%, secondary pollution is avoided, the product value is high, and the technology is suitable for closed-loop resource utilization of wind power blades, aerospace waste and consumed plastics.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of carbon fiber recycling, in particular to a high-efficiency recyclable carbon fiber plastic grease material depolymerization recycling process. BACKGROUND

[0002] Carbon fiber reinforced resin matrix composite materials are widely used in wind power blades, aerospace, automobile lightweight (new energy automobile battery box weight reduction of 30%) and high-end sports equipment due to their high strength, lightweight and corrosion resistance. With the global carbon fiber production capacity breaking through 200,000 tons / year (2025 data), it is expected that the retired CFRP will reach 800,000 tons / year in 2030. The existing recycling technologies are mainly divided into three categories, all of which have significant limitations:

[0003] Pyrolysis method: the resin is cracked under high temperature (400-600 DEG C) in an inert atmosphere to recover carbon fiber. The disadvantages are: high energy consumption (> 15 kWh / kg), easy to produce tar to block the equipment, and cannot recover the resin component.

[0004] Chemical depolymerization method: strong acid (such as concentrated sulfuric acid), strong base (such as NaOH) or organic solvent (such as acetone) are used to destroy the cross-linked structure of the resin at high temperature (200-300 DEG C). The disadvantages are: solvent toxicity, poor reaction selectivity (easy to corrode the surface of carbon fiber), and the purity of resin monomer is only 85-90%.

[0005] Physical conversion method: the resin is rapidly graphitized by Joule heating (such as lightning Joule heating, LJH) to convert into graphene coated carbon fiber. The disadvantages are: only suitable for laboratory scale, and cannot separate different resin components in mixed plastics.

[0006] Therefore, in view of the above problems, an efficient recyclable carbon fiber plastic grease material depolymerization recycling process needs to be improved. SUMMARY

[0007] The purpose of the present application is to provide an efficient recyclable carbon fiber plastic grease material depolymerization recycling process to solve the problems raised in the background art.

[0008] To achieve the above purpose, the present application provides the following technical scheme: an efficient recyclable carbon fiber plastic grease material depolymerization recycling process, comprising the following steps: first step, pretreatment stage: stripping the release paper on the surface of the carbon fiber prepreg, cutting into a length of 10±2 cm; preparing a supercritical fluid: using acetic acid and alcohol (ethanol or methanol) as solvent, the volume ratio is 1:1 to 4:6, the solid-liquid ratio is 1:4 to 1:10; mixing the pretreated material with the supercritical fluid according to the solid-liquid ratio, and transferring to a microwave reaction kettle;

[0009] The second step, a microwave-assisted supercritical depolymerization stage: the pretreated material in the first step is heated to 150-280°C, and maintained in a supercritical state for 1-15 minutes under a microwave power of 500-800 kW; the resin component is quickly dissolved in the supercritical fluid, and the carbon fiber realizes interface peeling due to selective heating by the microwave, and the solid residue rate after depolymerization is ≤0.1%;

[0010] The third step, a photo-thermal catalytic deep depolymerization stage: an inhomogeneous photo-thermal catalyst is introduced into the depolymerization system, the catalyst is GaCl3-loaded GB-rich CeO2 nanoparticles, and the loading amount is 0.1-1 mol%; the photo-thermal catalytic reaction is carried out at 140-190°C for 10-30 minutes, and the polyester component in the residual resin is selectively depolymerized to generate bisphenol A (BPA) and terephthalic acid (BHET) monomers; the catalyst can be recycled for ≥5 times, and the activity maintenance rate is ≥90%

[0011] The fourth step, a product separation and regeneration stage: the solid carbon fiber is separated, washed to neutral with ethanol, and dried at 120°C to a water content of ≤0.5%; the depolymerized monomers are collected, purified by rectification, and blended with a dynamic disulfide resin in a mass ratio of 7:3 to 9:1 to prepare a regenerated resin for photo-curable 3D printing; preferably, in the first step, the alcohol solvent is ethanol, the volume ratio of acetic acid to ethanol is 3:7, and the solid-liquid ratio is 1:410.

[0012] Preferably, the preparation method of the inhomogeneous photo-thermal catalyst in the third step includes the following procedures: taking cerium nitrate as a precursor, synthesizing CeO2 nanoparticles with a particle size of 20-50 nm by a hydrothermal method; increasing the grain boundary defect density to ≥15% by using plasma etching technology; loading GaCl3 by an immersion method, and the loading amount is 0.5 mol%, and activated by calcining at 500°C for 2 hours.

[0013] Preferably, in the second step, the reaction conditions of the microwave-assisted supercritical depolymerization stage are: a temperature of 280°C, a microwave power of 520 kW, and a depolymerization time of 90 minutes; the carbon fiber recovery rate is ≥63%, and the tensile strength retention rate is ≥98%.

[0014] Preferably, in the third step, the selective depolymerization conditions of the photo-thermal catalytic stage for mixed polyester (PET / PC mass ratio 7:3) are: the catalyst is 0.5 mol% GaCl3-loaded GB-rich CeO; the reaction temperature is 190°C, and the time is 15 minutes; the BPA yield is ≥97.8%, and the BHET yield is ≥93.4%.

[0015] Preferably, the formulation of the regenerated resin is: the mass ratio of depolymerization monomers (BPA and BHET) to dynamic disulfide resin is 8:2; 0.1-1wt% of a photoinitiator (such as phenyl bis (2, 4, 6-trimethyl benzoyl) phenylphosphine oxide) is added; the regenerated resin can be repeatedly photocured for ≥5 times, and the heat distortion temperature is ≥120℃.

[0016] Preferably, the process is suitable for recycling at least one of the following waste materials: epoxy resin-based composite materials with a carbon fiber mass fraction of ≥50%; wind power blades, aerospace components, or automobile lightweight structural parts;

[0017] Post-consumer mixed plastics (PET / PC / ABS blend).

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. The wave-assisted supercritical depolymerization of the present application: through the microwave-assisted supercritical fluid technology, the depolymerization can be completed at 280℃ in only 90 minutes (the traditional thermal decomposition method requires 400-600℃ and 6-8 hours), and the energy consumption is reduced by more than 50%. The selective heating of microwaves makes the heating speed of carbon fibers reach 50℃ / second (the traditional heat conduction is only 2℃ / second), and the solubility of supercritical fluid in resin is increased by 3 times.

[0020] After depolymerization, the residual resin rate on the surface of carbon fibers is <0.05% (the residual rate of the thermal decomposition method is 5-10%), the tensile strength retention rate is ≥98% (the traditional chemical method is only 70-85%), and it can be directly used for high-end manufacturing (such as aerospace-grade prepreg). Using a grain boundary defect type CeO2 catalyst, the ester bond of PET / PC is broken at 190℃, and the yield of bisphenol A (BPA) is 97.8%, and the yield of terephthalic acid (BHET) is 93.4% (the yield of the traditional method is <85%), achieving "one process recycling two high-purity monomers".

[0021] 2. The heterogeneous photo-thermal catalytic system of the present application: using a GB-rich CeO2 nano-catalyst, the mixed polyester (such as PET / PC) is selectively depolymerized under photo-thermal conditions, and the yield of BPA is 97.8%. At the same time, the activity of the GB-rich CeO2 catalyst is maintained at 92% after 5 cycles (the activity of the traditional homogeneous catalyst is reduced by 50% after 3 cycles), and the catalyst cost can be saved by about 1200 yuan per ton of waste. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The step block diagram of the high-efficiency recyclable carbon fiber plastic material depolymerization and recycling process of the present application. DETAILED DESCRIPTION

[0023] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0024] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application. Figure 1 The present application provides a technical solution: a high-efficiency recyclable carbon fiber plastic grease material depolymerization recycling process, comprising the following steps,

[0025] First step, pretreatment stage: composite material pretreatment

[0026] For carbon fiber prepreg (containing epoxy resin matrix mass fraction 45-65%), first, a mechanical stripping device is used to remove the surface silicone oil-based release paper, and the stripping speed needs to be controlled ≤5 m / min to avoid fiber damage. The stripped prepreg is processed into a standardized section of 10±2 cm by a laser cutting system, with a cutting accuracy of ±0.1 mm and a flatness of the cutout Ra≤0.8 μm. The cut material is removed by a pneumatic sorting device to remove micro powder (particle size <50 μm) to ensure the purity of the subsequent reaction system.

[0027] Ethanol is used as an alcohol solvent, and a binary solvent system is prepared with acetic acid in a volume ratio of 3:7. The ratio is determined by orthogonal experiment optimization, which can achieve the best balance between resin swelling rate and fiber protection. The solid-liquid ratio is set to 1:4.1 (mass-volume ratio), which is determined by rheological test, which can ensure that the fluid fully infiltrates the material and control the viscosity of the reaction system ≤50 mPa·s. The pretreated material and supercritical fluid are transferred to a hastelloy microwave reaction kettle (design pressure 35 MPa, temperature resistance 400℃) under nitrogen protection, and a tetrafluoroethylene stirring paddle (speed 50-200 rpm) is provided in the kettle to ensure uniform mass transfer;

[0028] Second step, microwave-assisted supercritical depolymerization stage: the pretreated material in the first step is pre-swelled at a rate of 10℃ / min to 150℃ for 10 minutes, and then increased to the target temperature of 280℃ at a rate of 5℃ / min. The microwave power is set to 520 kW (frequency 2.45 GHz), which is optimized by electromagnetic field simulation to form a uniform 10 6 -10 7 W / m 3Power density field. The supercritical state was maintained for 90 min, during which the fluid pressure (8-12 MPa) and dielectric constant changes were monitored in real time. The resin matrix undergoes three-stage degradation in the supercritical fluid: first, acid-catalyzed hydrolysis of ester bonds occurs to generate carboxylic acid and alcohol intermediates; then, under the action of the microwave field, the dielectric heating effect of polar groups (the heating rate can reach 50℃ / min) accelerates the chain scission reaction; finally, the van der Waals force at the interface between the carbon fiber and the resin is destroyed, achieving non-destructive peeling. Experiments show that under this condition, the solid residue rate is ≤0.1%, the carbon fiber recovery rate is ≥63%, and the tensile strength retention rate is ≥98% (compared to the original fiber strength of 4.9 GPa);

[0029] Third step, photo-thermal catalytic deep depolymerization stage: hydrothermal method was used to synthesize grain boundary defect type CeO2 nanoparticles: cerium nitrate precursor was dissolved in deionized water (concentration 0.1 mol / L), transferred to a polytetrafluoroethylene-lined autoclave, and reacted at 180℃ for 12 hours to obtain cubic fluorite structure CeO2 with a particle size of 20-50 nm. The grain boundary defect density was increased to ≥15% by plasma etching technology (Ar / O2 mixed gas, power 300W, time 30 minutes), and the defect structure was verified by TEM-EDS to provide more active sites. 0.5mol% GaCl3 was loaded by impregnation method, and Ga-O-Ce bond structure was formed by calcination at 500℃ for 2 hours, and the specific surface area of the catalyst reached 85m 2 / g.

[0030] The catalyst (amounting to 2wt% of the mass of the resin) was added to the depolymerization system, and the photo-thermal catalytic reaction was carried out at 190℃ for 15 minutes. During the reaction, Ga 3+ acted as Lewis acid sites to activate ester bonds, while grain boundary defects promoted the separation of photo-generated carriers, achieving high selective depolymerization of PET / PC (mass ratio 7:3) mixed polyesters. HPLC analysis of the products showed that the yield of bisphenol A (BPA) was ≥97.8%, the yield of bis-hydroxyethyl terephthalate (BHET) was ≥93.4%, and the activity of the catalyst was maintained at ≥90% after 5 cycles (XRD characterization showed that the crystal structure did not change significantly).

[0031] Fourth step, product separation and regeneration stage: the depolymerized carbon fiber bundle was separated by multiple stages: first, large particle impurities were removed by an 80-mesh screen, then ultrasonic cleaning (power 200 W, time 30 min) was performed in an ethanol-water mixed solvent (volume ratio 1:1), and finally, deionized water was used to rinse to neutral. The drying process used a two-stage process: vacuum drying at 60°C for 2 hours to remove surface moisture, followed by constant temperature drying at 120°C until the water content was ≤0.5% (determined by Karl Fischer method). The surface morphology of the regenerated fiber remained intact, and the single fiber tensile strength was ≥4.8 GPa. The collected depolymerized monomers (BPA and BHET) were blended with dynamic disulfide resin at a mass ratio of 8:2, and 0.5wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (TPO-Li) was added as a photoinitiator. The mixed system was melt blended by a twin-screw extruder (temperature 160-180°C, screw rotation speed 200 rpm) to prepare a special resin for light-cured 3D printing. The resin has the following properties: tensile strength ≥80 MPa (ASTM D638 standard test), flexural modulus ≥3.2 GPa, heat distortion temperature ≥120°C (1.8 MPa load), and repeatable light-curing times ≥5 times (wavelength 365 nm, light intensity 50 mW / cm 2 ). The 3D printing resolution reached 50-200 μm, meeting the needs of aerospace precision component manufacturing.

[0032] It should be noted that the relational terms herein such as first and second, and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0033] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A highly efficient and recyclable carbon fiber plastic material depolymerization and recycling process, comprising the following steps, characterized in that: Step 1, Pretreatment stage: Peel off the release paper from the surface of the carbon fiber prepreg and cut it into segments with a length of 10±2cm; Prepare supercritical fluid: use acetic acid and alcohol (ethanol or methanol) as solvents, with a volume ratio of 1:1 to 4:6 and a solid-liquid ratio of 1:4 to 1:10; Mix the pretreated material with the supercritical fluid according to the solid-liquid ratio and transfer it to a microwave reactor. Step 2, Microwave-assisted supercritical depolymerization stage: The pretreated material from the first step is heated to 150-280℃ and maintained in a supercritical state for 1-15 minutes at a microwave power of 500-800kW. The resin component dissolves rapidly in the supercritical fluid, and the carbon fiber achieves interfacial exfoliation due to selective microwave heating, resulting in a solid residue rate of ≤0.1% after depolymerization. Step 3, Photothermal Catalytic Deep Depolymerization Stage: A heterogeneous photothermal catalyst is introduced into the depolymerization system. The catalyst is GaCl3-supported grain boundary defect type CeO2 nanoparticles (GB-rich CeO2), with a loading of 0.1-1 mol%. A photothermal catalytic reaction is carried out at 140-190℃ for 10-30 minutes to selectively depolymerize the polyester component in the residual resin, generating bisphenol A (BPA) and terephthalic acid (BHET) monomers. The catalyst can be recycled ≥5 times, with an activity retention rate ≥90%. Step 4, Product Separation and Regeneration Stage: Separate solid carbon fibers, wash them with ethanol until neutral, and dry them at 120℃ until the moisture content is ≤0.5%; collect depolymerized monomers, purify them by distillation, and then blend them with dynamic disulfide resin at a mass ratio of 7:3 to 9:1 to prepare a photocurable 3D printing regenerated resin; the tensile strength of the regenerated resin is ≥80MPa, and the 3D printing resolution reaches 50-200μm.

2. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: In the first step, the alcohol solvent is ethanol, the volume ratio of acetic acid to ethanol is 3:7, and the solid-liquid ratio is 1:

410.

3. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: The preparation method of the heterogeneous photothermal catalyst in the third step includes the following steps: using cerium nitrate as a precursor, CeO2 nanoparticles with a particle size of 20-50 nm are synthesized by hydrothermal method; plasma etching technology is used to increase the grain boundary defect density to ≥15%; GaCl3 is loaded by impregnation method with a loading of 0.5 mol%, and activated by calcination at 500℃ for 2 hours.

4. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: In the second step, the reaction conditions for the microwave-assisted supercritical depolymerization stage are: temperature 280℃, microwave power 520kW, depolymerization time 90 minutes; carbon fiber recovery rate ≥63%, tensile strength retention rate ≥98%.

5. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: The selective depolymerization conditions for the mixed polyester (PET / PC mass ratio 7:3) in the photothermal catalysis stage of the third step are as follows: the catalyst is 0.5 mol% GaCl3 supported GB-rich CeO; the reaction temperature is 190℃ and the time is 15 minutes; the BPA yield is ≥97.8% and the BHET yield is ≥93.4%.

6. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: The formulation of the regenerated resin is as follows: the mass ratio of depolymerized monomers (BPA and BHET) to dynamic disulfide resin is 8:2; 0.1-1wt% of photoinitiator (such as phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide) is added; the regenerated resin can be photocured ≥5 times and has a heat distortion temperature ≥120℃.

7. The efficient recyclable carbon fiber plastic material depolymerization and recycling process according to claim 1, characterized in that: The process is applicable to the recycling of at least one of the following wastes: epoxy resin-based composites with a carbon fiber mass fraction of ≥50%; wind turbine blades, aerospace components or lightweight automotive structural parts; post-consumer blended plastics (PET / PC / ABS blends).

Images