Carbon fiber composite for waste polyester glycolysis, method for manufacturing the same, and method for waste polyester glycolysis

Abstract

The present application relates to the technical field of waste polyester recycling, and provides a carbon fiber composite material for waste polyester alcoholysis, a preparation method thereof and a waste polyester alcoholysis method; wherein the preparation method of the carbon fiber composite material is to use carbon fibers with good chemical stability as carriers, deposit catechol-based polymers and polylysine, and load zinc oxide onto the surface of the carbon fibers by using self-polymerization, thereby preparing a heterogeneous carbon fiber composite material. The carbon fiber composite material prepared by the present application has the advantages of high catalytic efficiency, easy separation and recovery, good stability, small pollution and the like as a catalyst for waste polyester alcoholysis, provides a new idea for the exploration of waste polyester glycol alcoholysis catalysts, and has great practical application prospect.

Description

Technical Field

[0001] This invention relates to the field of waste polyester recycling technology, and in particular to a carbon fiber composite material for the alcoholysis of waste polyester, its preparation method, and a method for the alcoholysis of waste polyester. Background Technology

[0002] Polyethylene terephthalate (PET) possesses excellent mechanical strength and chemical stability, and is widely used in the plastic packaging, textile, construction, and medical and health industries. The recycling of waste polyester is a problem that needs to be addressed.

[0003] Waste polyester recycling mainly involves physical and chemical methods. Physical recycling has many advantages, such as simple recycling processes and low processing costs. However, the mechanical properties of the recycled polyester are prone to decline, and there are difficulties in recycling copolymerized or composite modified PET products. Chemical recycling can not only produce high-quality recycled polyester through depolymerization and polycondensation, but also process waste polyester into products with higher added value, thereby achieving upgraded recycling of waste polyester. Therefore, chemical recycling has received widespread research and application.

[0004] Chemical methods mainly include methanol hydrolysis, hydrolysis, ethylene glycol alcoholysis, and ammonolysis. Among them, ethylene glycol alcoholysis has attracted much attention from researchers due to its advantages such as mild reaction conditions, high boiling point and low volatility of solvents, and easy separation and purification of products. The ethylene glycol alcoholysis reaction of PET utilizes ethylene glycol to attack the ester bonds of PET, causing the long-chain polymer chains to break into oligomers, thereby forming bis(2-hydroxyethyl) terephthalate (BHET). BHET can then be used in a polycondensation reaction to obtain high-quality PET material again, thus achieving PET recycling. Ethylene glycol alcoholysis has become an ideal way to achieve efficient utilization of renewable resources, and the key to the ethylene glycol alcoholysis of waste PET is the development of efficient alcoholysis catalysts. Researchers have also conducted numerous studies, such as:

[0005] Patent application CN202310815652.X discloses a method for preparing a boron nitride-doped metal atom catalyst. By anchoring metal atoms to boron nitride vacancies through metal atom doping, a transition metal-doped boron nitride catalyst for the alcoholysis of polyester glycol is obtained. This catalyst has advantages such as high catalytic efficiency, good cycle performance, and low cost. Patent application CN202110332669.0 discloses a method for catalyzing the depolymerization of waste polyester materials using a zinc catalyst. This method employs a simple zinc catalyst for the alcoholysis of polyester glycol. Zinc is non-toxic, colorless, inexpensive, and readily available. As a trace element in the human body, it has good biocompatibility, making the production process more environmentally friendly. The catalyst structure is simple, the synthesis steps are few, and the production cost is economical. Patent application CN202311391474.9 discloses a method for preparing a supported mesoporous molecular sieve catalyst. This involves reacting a metal salt and a mesoporous molecular sieve in deionized water, followed by evaporation, drying, and calcination. This catalyst is used for the alcoholysis of waste polyester materials from ethylene glycol, enabling separation, recycling, and reuse.

[0006] However, the aforementioned catalysts for PET depolymerization still have some problems, such as low catalytic efficiency, poor stability, and difficulty in complete separation, recovery, and reuse. Therefore, to address the related issues in the catalytic PET alcoholysis process, it is necessary to develop novel alcoholysis catalysts that can efficiently catalyze PET alcoholysis while being easy to separate, recover, and reuse, causing minimal environmental pollution, and exhibiting good stability. Summary of the Invention

[0007] The technical problem solved by this invention is to provide a method for preparing carbon fiber composite material for waste polyester alcoholysis. The carbon fiber composite material prepared in this application has good catalytic efficiency and stability as a catalyst for waste polyester alcoholysis, and is easy to recycle.

[0008] In view of this, this application provides a method for preparing carbon fiber composite materials from waste polyester alcoholysis, comprising the following steps:

[0009] S1. Prepare a buffer solution containing zinc hydroxide, catechol derivatives and polylysine;

[0010] S2. The carbon fiber is immersed in a solvent and then immersed in the buffer solution. After the reaction, a precursor of catechol-based polymer / polylysine-loaded Zn(OH)2 is deposited on the surface of the carbon fiber.

[0011] S3. The precursor is subjected to high-temperature treatment to obtain carbon fiber composite material.

[0012] In some specific embodiments, the method further includes the following step before step S1:

[0013] The carbon fiber is treated in a potassium permanganate solution, then the potassium permanganate solution and the carbon fiber are separated by filtration, and then the carbon fiber is washed and dried.

[0014] The concentration of the potassium permanganate solution is 2~10 mol / L, the treatment temperature is 30~60℃, and the treatment time is 10~24h.

[0015] In some specific embodiments, the catechol derivatives include one or more of dopamine, levodopa, catechol, adrenaline, and noradrenaline.

[0016] In some specific embodiments, in step S1, the buffer solution is a Tris buffer solution with a concentration of 0.01~0.10 mol / L and a pH of 8.0~9.0; and / or, the concentration of zinc hydroxide in the Tris buffer solution is 1~5 mg / L, the concentration of catechol derivatives is 1~5 mg / L, and the mass ratio of polylysine to catechol derivatives is (0.25~1):1.

[0017] In some specific embodiments, in step S2, the solvent is anhydrous ethanol, the amount of carbon fiber immersed in the buffer solution is 10~40 g / L, the immersion time in the buffer solution is 30~60 min, and the reaction time is 10~24 h.

[0018] In some specific embodiments, in step S3, the temperature of the high-temperature treatment is 100~200℃, and the time of the high-temperature treatment is 1~5h.

[0019] This application also provides a carbon fiber composite material for waste polyester alcoholysis prepared by the preparation method described above, comprising a carbon fiber matrix and a polymer film formed on the surface of the carbon fiber matrix, wherein the polymer film is prepared from polylysine and catechol-based polymers, and the polymer film is composited with ZnO.

[0020] This application also provides a method for the alcoholysis of waste polyester, comprising:

[0021] Waste polyethylene terephthalate, ethylene glycol, and catalyst are mixed and reacted.

[0022] The catalyst is prepared by the preparation method described in the above scheme or is the carbon fiber composite material described in the above scheme.

[0023] In some specific embodiments, the ratio of ethylene glycol to waste polyethylene terephthalate is (10~20) ml: 1 g, and the catalyst is 1~20 wt% of the waste polyethylene terephthalate.

[0024] In some specific embodiments, the reaction temperature is 150~250°C and the time is 30~200 min.

[0025] This application provides a method for preparing carbon fiber composite materials from waste polyester alcoholysis. First, a buffer solution containing zinc hydroxide, catechol derivatives, and polylysine is prepared. Then, carbon fibers are immersed in a solvent to displace the air layer on the carbon fiber surface, followed by immersion in the aforementioned buffer solution. After reaction, a precursor with catechol polymer / polylysine-loaded zinc hydroxide deposited on the carbon fiber surface is obtained. Finally, the precursor is subjected to high-temperature treatment to obtain a composite material with a polymer film of catechol polymer and polylysine loaded on the carbon fiber surface, and ZnO is incorporated into the film. During the preparation of the composite material, zinc hydroxide is mixed with the buffer solution containing catechol derivatives and polylysine. Zinc hydroxide is loaded onto the surface of carbon fibers via self-polymerization, and then converted into zinc oxide at high temperature. The zinc oxide is more firmly loaded on the carbon fiber surface and is less prone to loss, resulting in higher stability of the composite material. At the same time, the composite material contains amino groups and zinc oxide, which play a synergistic catalytic role in the catalytic alcoholysis of waste polyester. Furthermore, the zinc oxide loaded on the carbon fibers can improve the dispersibility of zinc oxide, which is beneficial to improving catalytic efficiency. In addition, polylysine can improve the adhesion between the catechol polymer and the carbon fiber interface and can also provide amino groups, further improving the catalytic efficiency and stability of the composite material. The carbon fiber as a carrier makes the composite material easy to recycle, separate, and reuse. Attached Figure Description

[0026] Figure 1 This is a SEM image of the carbon fiber composite material prepared in Example 1 of the present invention. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] In view of the requirements for catalytic efficiency, stability, and ease of separation and recycling of waste polyester alcoholysis catalysts in the prior art, this application provides a carbon fiber composite material for waste polyester alcoholysis and its preparation method. The method involves depositing catechol-based polymers and polylysine on the surface of carbon fibers and loading zinc oxide to obtain a carbon fiber composite material rich in amino groups and zinc oxide. The synergistic catalysis of these two groups improves the catalytic efficiency and stability of the composite material as a catalyst for waste polyester alcoholysis. Simultaneously, this composite material is easy to separate and recycle, exhibits high reproducibility, and low pollution. Specifically, this invention discloses a method for preparing a carbon fiber composite material for waste polyester alcoholysis, including the following steps:

[0029] S1. Prepare a buffer solution containing zinc hydroxide, catechol derivatives and polylysine;

[0030] S2. The carbon fiber is immersed in a solvent and then immersed in the buffer solution. After the reaction, a precursor of catechol-based polymer / polylysine-loaded Zn(OH)2 is deposited on the surface of the carbon fiber.

[0031] S3. The precursor is subjected to high-temperature treatment to obtain carbon fiber composite material.

[0032] In the preparation of carbon fiber composite materials for waste polyester alcoholysis, it is preferable to pretreat the carbon fibers and prepare zinc hydroxide; wherein, the pretreatment of the carbon fibers specifically includes:

[0033] Carbon fibers (CFs) are treated in a potassium permanganate solution, then the potassium permanganate solution and the carbon fibers are separated by filtration, and then the carbon fibers are washed and dried.

[0034] The concentration of the potassium permanganate solution is 2~10 mol / L, the treatment temperature is 30~60℃, and the treatment time is 10~24h; specifically, the concentration of the potassium permanganate solution is 4~8 mol / L, the treatment temperature is 40~50℃, and the treatment time is 12~18h.

[0035] The carbon fibers (CFs) mentioned above have good chemical stability, are inexpensive and easy to recycle, making them a relatively ideal multiphase catalyst support.

[0036] The zinc hydroxide is prepared as follows:

[0037] Prepare a zinc acetate aqueous solution and a sodium hydroxide aqueous solution of a certain concentration. Add the sodium hydroxide aqueous solution dropwise to the zinc acetate aqueous solution to adjust the pH of the solution. A white precipitate appears in the solution. After heating and stirring for a period of time, separate the zinc hydroxide (Zn(OH)2) precipitate and dry it in an oven to constant weight for later use.

[0038] In the above process, the concentration of the zinc acetate aqueous solution is 0.5~1.0 mol / L, specifically 0.6~0.8 mol / L, and the sodium hydroxide aqueous solution contains 2~8 wt% sodium hydroxide, specifically 4~5 wt%. The pH is 9~13, specifically 10~11. The heating and stirring temperature is 50~100℃, and the time is 1~5 h, specifically 60~80℃, and the time is 2~3 h.

[0039] After preparing the above-mentioned raw materials, a buffer solution containing zinc hydroxide, catechol derivatives, and polylysine is prepared. In this process, zinc hydroxide, catechol derivatives, and polylysine are mixed in the buffer solution and then subjected to sonication. Specifically, the buffer solution is a Tris buffer solution with a concentration of 0.01–0.10 mol / L and a pH of 8.0–9.0. Specifically, the concentration of the Tris buffer solution is 0.02–0.08 mol / L, and the pH is 8.5. The catechol derivatives include one or more of dopamine, levodopa, catechol, adrenaline, and noradrenaline. Specifically, the catechol derivatives are selected from dopamine, levodopa, catechol, adrenaline, or noradrenaline. The concentration of zinc hydroxide in the Tris buffer is 1-5 mg / L, specifically 2-4 mg / L; the concentration of the catechol derivative is 1-5 mg / L, specifically 2-4 mg / L; the mass ratio of polylysine to the catechol derivative is (0.25-1):1, specifically (0.5-0.75):1. The sonication time is 10-30 min.

[0040] The aforementioned catechol derivatives are a class of compounds and their modified products with catechol as the core structure. They possess adhesiveness and biocompatibility, contain abundant amino groups, and can be conformally coated on substrates of almost any material and size. The aforementioned polylysine (PLL) exhibits good thermal stability and acid and alkali resistance. PLL is rich in cationic amino groups, which can prevent the peroxidation of catechol derivatives on the CFs surface and improve the adhesion of the two-phase interface.

[0041] This application then immerses the carbon fiber in a solvent, specifically anhydrous ethanol, to displace the air layer on the surface of the carbon fiber. The carbon fiber is then immersed in the aforementioned buffer solution. After the reaction, a precursor of catechol-based polymer / polylysine-loaded Zn(OH)₂ is deposited on the carbon fiber surface. The reaction is preferably carried out in a constant-temperature shaking water bath. The immersion time of the carbon fiber in the buffer solution is 30-60 min, specifically 40-50 min, and the reaction time is 10-24 h, specifically 12-18 h. The concentration of the carbon fiber in the buffer solution is 10-40 g / L, specifically 20-30 g / L. In the above process, catechol derivatives and polylysine self-polymerize to form a catechol-based polymer / polylysine polymer, which is co-deposited onto the carbon fiber surface, and zinc hydroxide is loaded in the catechol-based polymer / polylysine polymer film.

[0042] According to the present invention, the precursor is finally subjected to high-temperature treatment to convert zinc hydroxide into zinc oxide, thereby obtaining carbon fiber composite material. The high-temperature treatment temperature is 100-200°C, and the high-temperature treatment time is 1-5 hours, specifically, the high-temperature treatment temperature is 120-160°C, and the high-temperature treatment time is 3-4 hours. Loading zinc oxide onto CFs improves the dispersibility of zinc oxide, and the resulting composite material is macroscopically blocky and recyclable. Therefore, by loading zinc oxide onto carbon fibers and adding amino groups, the alcoholysis efficiency of PET is improved, and environmental pollution is reduced.

[0043] This application also provides a carbon fiber composite material for waste polyester alcoholysis prepared by the above preparation method, comprising a carbon fiber matrix and a polymer film formed on the surface of the carbon fiber matrix, wherein the polymer film is prepared from polylysine and catechol-based polymers, and the polymer film is composited with ZnO.

[0044] Furthermore, this application also provides a method for the alcoholysis of waste polyester, comprising:

[0045] Waste polyethylene terephthalate, ethylene glycol, and catalyst are mixed and reacted.

[0046] The catalyst is prepared by the preparation method described in the above scheme or is the carbon fiber composite material described in the above scheme.

[0047] In a specific embodiment, the method for alcoholysis of waste polyester is as follows:

[0048] A certain amount of PET, ethylene glycol, and catalyst are placed in a reactor, and the temperature is slowly raised to a suitable temperature. After reacting for a period of time, the solution is cooled to 130~160℃ and filtered while hot. The solid is washed with deionized water, dried, and weighed to obtain the mass of undepolymerized PET. The PET conversion rate is then calculated.

[0049] Then, a large amount of deionized water was added to the filtrate, stirred and heated to 70~110℃, filtered while hot, and after the filtrate was cooled to room temperature, it was placed at a low temperature of 2~14℃ for 15~24h, filtered and dried to obtain BHET, weighed and the BHET yield was calculated.

[0050] In the above process, the ratio of ethylene glycol to waste polyethylene terephthalate is (10~20) ml: 1 g, and the catalyst is 1~20 wt% of the waste polyethylene terephthalate; specifically, the ratio of ethylene glycol to waste polyethylene terephthalate is (12~15) ml: 1 g, and the catalyst is 5~15 wt% of the waste polyethylene terephthalate. The reaction temperature is 150~250℃, and the time is 30~200 min; specifically, the reaction temperature is 180~200℃, and the time is 90~150 min.

[0051] This application provides a method for preparing carbon fiber composite materials for waste polyester alcoholysis. The method involves mixing zinc hydroxide with a buffer solution containing catechol derivatives and polylysine, and then loading the zinc hydroxide onto the carbon fiber surface via self-polymerization. The zinc hydroxide is then converted to zinc oxide at high temperature, resulting in a more robust zinc oxide loading and thus higher stability of the carbon fiber composite material. Simultaneously, the carbon fiber composite material contains amino groups and zinc oxide, which work synergistically in the catalytic process of polyester alcoholysis. Loading zinc oxide onto the carbon fiber improves its dispersibility, facilitates recovery, provides high catalytic efficiency, and minimizes zinc contamination. The carbon fiber composite material employs a co-deposition method using polylysine and catechol-based polymers. Polylysine improves the adhesion between the catechol-based polymer and the carbon fiber interface and provides amino groups, further enhancing the catalytic efficiency and stability of the carbon fiber composite material.

[0052] To further understand the present invention, the carbon fiber composite material for alcoholysis waste polyester, its preparation method and its application are described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0053] Example 1

[0054] S1: Place 0.6 g CFs in an 8 mol / L potassium permanganate solution for 12 h. After treatment, filter the potassium permanganate solution and CFs to separate them. Rinse the CFs repeatedly with deionized water until neutral and dry them in an oven until constant weight for later use.

[0055] S2: Prepare 40 ml of 0.6 mol / L zinc acetate aqueous solution and 30 ml of 5 wt% sodium hydroxide solution. Add the sodium hydroxide aqueous solution dropwise to the zinc acetate aqueous solution and adjust the pH of the solution to 11. A white precipitate will appear in the solution. After heating and stirring at 80 ℃ for 1 h, separate the zinc hydroxide (Zn(OH)2) precipitate and dry it in an oven to constant weight for later use.

[0056] S3: Prepare a Tris buffer containing 2 mg / L zinc hydroxide, 2 mg / L dopamine and 1 mg / L polylysine (PLL), with a mass ratio of polylysine to dopamine of 0.5:1, and sonicate for 20 min.

[0057] S4: 0.6 g of CFs treated in S1 were first soaked in anhydrous ethanol for 40 min to replace the air layer on the surface, and then immersed in Tris buffer containing zinc hydroxide, dopamine and polylysine. The modification reaction was carried out in a constant temperature shaking water bath at room temperature for 18 h to form CFs deposited polydopamine / PLL loaded Zn(OH)2 precursor. After separation, it was repeatedly washed with deionized water until neutral and then placed in an oven to dry to constant weight for later use.

[0058] S5: The dried precursor was placed in a high-temperature test chamber and treated at 160 °C for 3 h. After cooling to room temperature, CFs-deposited polydopamine / PLL-supported ZnO composite material was obtained.

[0059] like Figure 1 As shown, Figure 1 The image shows a SEM image of the CFs-deposited polydopamine / PLL-supported ZnO composite material prepared in this embodiment. As can be seen from the image, ZnO particles are uniformly loaded on the carbon fiber surface.

[0060] The above-prepared composite material was used as a catalyst in the alcoholysis method for recycling waste polyester: 10 g PET, 150 ml ethylene glycol, and 0.5 g catalyst were placed in a reactor, the temperature was slowly raised to 200 ℃ and stirred for 90 min. After the reaction, the solution was cooled to 160 ℃ and filtered while hot. The solid was washed with deionized water, dried, and weighed to obtain the mass of undepolymerized PET. The PET conversion rate was calculated to be 100%.

[0061] Then, a large amount of deionized water was added to the filtrate, stirred and heated to 95 °C, filtered while hot, cooled to room temperature and placed at 3 °C for 24 h, filtered and dried to obtain BHET, weighed and the BHET yield was calculated to be 81%.

[0062] Example 2

[0063] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the catechol derivative is levodopa.

[0064] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The PET conversion rate was calculated to be 100% and the BHET yield was 81%.

[0065] Example 3

[0066] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the catechol derivative is catechol.

[0067] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 100% and the BHET yield was 80%.

[0068] Example 4

[0069] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the catechol derivative is adrenaline.

[0070] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 100% and the BHET yield was 79%.

[0071] Example 5

[0072] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the catechol derivative is norepinephrine.

[0073] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 100% and the BHET yield was 78%.

[0074] Example 6

[0075] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the mass ratio of polylysine to dopamine is 0.25:1.

[0076] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 99% and the BHET yield was 68%.

[0077] Example 7

[0078] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the mass ratio of polylysine to dopamine is 0.75:1.

[0079] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 100% and the BHET yield was 74%.

[0080] Example 8

[0081] The preparation method of CFs-deposited polydopamine / PLL-supported ZnO composite material is basically the same as that in Example 1, except that the mass ratio of polylysine to dopamine is 1.

[0082] The composite material prepared above was used as a catalyst to recycle waste polyester. The method was the same as in Example 1. The calculated PET conversion rate was 99% and the BHET yield was 70%.

[0083] Comparative Example 1

[0084] S1: Place 0.6 g CFs in an 8 mol / L potassium permanganate solution for 12 h. After treatment, filter the potassium permanganate solution and CFs to separate them. Rinse the CFs repeatedly with deionized water until neutral and dry them in an oven until constant weight for later use.

[0085] S2: Prepare 40 ml of 0.6 mol / L zinc acetate aqueous solution and 30 ml of 5 wt% sodium hydroxide solution. Add the sodium hydroxide aqueous solution dropwise to the zinc acetate aqueous solution and adjust the pH of the solution to 11. A white precipitate will appear in the solution. After heating and stirring at 80 ℃ for 1 h, separate the zinc hydroxide (Zn(OH)2) precipitate and dry it in an oven to constant weight for later use.

[0086] S3: Prepare a 2 mg / L zinc hydroxide solution and ultrasonically disperse it for 20 min;

[0087] S4: 0.6 g of CFs treated in S1 were first soaked in anhydrous ethanol for 40 min to replace the air layer on the surface, and then immersed in zinc hydroxide solution. The modification reaction was carried out in a constant temperature shaking water bath at room temperature for 18 h to form CFs-supported Zn(OH)2 precursor. After separation, it was repeatedly rinsed with deionized water until neutral and then placed in an oven to dry to constant weight for later use.

[0088] S5: The dried precursor was placed in a high-temperature test chamber and treated at 160 °C for 3 h. After cooling to room temperature, CF-supported ZnO composite material was obtained.

[0089] The method of using the above-prepared composite material as a catalyst to recover waste polyester via alcoholysis:

[0090] 10 g PET, 150 ml ethylene glycol, and 0.5 g catalyst were placed in a reactor, and the temperature was slowly raised to 200 °C while stirring. The reaction time was 90 min. After the reaction was completed, the solution was cooled to 160 °C and filtered while hot. The solid was washed with deionized water, dried, and weighed to obtain the mass of undepolymerized PET. The PET conversion rate was calculated to be 95%.

[0091] Then, a large amount of deionized water was added to the filtrate, stirred and heated to 95 °C, filtered while hot, cooled to room temperature and placed at 3 °C for 24 h, filtered and dried to obtain BHET, weighed and the BHET yield was calculated to be 60%.

[0092] Comparative Example 2

[0093] S1: Place 0.6 g CFs in an 8 mol / L potassium permanganate solution for 12 h. After treatment, filter the potassium permanganate solution and CFs to separate them. Rinse the CFs repeatedly with deionized water until neutral and dry them in an oven until constant weight for later use.

[0094] S2: Prepare a Tris buffer containing 2 mg / L dopamine and 1 mg / L polylysine (PLL), with a mass ratio of polylysine to dopamine of 0.5:1;

[0095] S3: 0.6 g of CFs treated in S1 were first soaked in anhydrous ethanol for 40 min to replace the air layer on the surface, and then immersed in Tris buffer containing dopamine and polylysine. The modification reaction was carried out in a constant temperature shaking water bath at room temperature for 18 h to form CFs deposited polydopamine / PLL composite material. After separation, the material was repeatedly rinsed with deionized water until neutral and then dried in an oven to constant weight for later use.

[0096] The method of using the above-prepared composite material as a catalyst to recover waste polyester via alcoholysis:

[0097] 10 g PET, 150 ml ethylene glycol, and 0.5 g catalyst were placed in a reactor, and the temperature was slowly raised to 200 °C while stirring. The reaction time was 90 min. After the reaction was completed, the solution was cooled to 160 °C and filtered while hot. The solid was washed with deionized water, dried, and weighed to obtain the mass of undepolymerized PET. The PET conversion rate was calculated to be 75%.

[0098] Then, a large amount of deionized water was added to the filtrate, stirred and heated to 95 °C, filtered while hot, cooled to room temperature and placed at 3 °C for 24 h, filtered and dried to obtain BHET, weighed and the BHET yield was calculated to be 25%.

[0099] Comparative Example 3

[0100] S1: Place 0.6 g CFs in an 8 mol / L potassium permanganate solution for 12 h. After treatment, filter the potassium permanganate solution and CFs to separate them. Rinse the CFs repeatedly with deionized water until neutral and dry them in an oven until constant weight for later use.

[0101] S2: Prepare 40 ml of 0.6 mol / L zinc acetate aqueous solution and 30 ml of 5 wt% sodium hydroxide solution. Add the sodium hydroxide aqueous solution dropwise to the zinc acetate aqueous solution and adjust the pH of the solution to 11. A white precipitate will appear in the solution. After heating and stirring at 80 ℃ for 1 h, separate the zinc hydroxide (Zn(OH)2) precipitate and dry it in an oven to constant weight for later use.

[0102] S3: Prepare a Tris buffer solution containing 2 mg / L zinc hydroxide and 2 mg / L dopamine, and sonicate for 20 min.

[0103] S4: 0.6 g of CFs treated in S1 were first soaked in anhydrous ethanol for 40 min to replace the air layer on the surface, and then immersed in Tris buffer containing zinc hydroxide and dopamine. The modification reaction was carried out in a constant temperature shaking water bath at room temperature for 18 h to form CFs deposited polydopamine-loaded Zn(OH)2 precursor. After separation, it was repeatedly rinsed with deionized water until neutral and then placed in an oven to dry to constant weight for later use.

[0104] S5: The dried precursor was placed in a high-temperature test chamber and treated at 160 °C for 3 h. After cooling to room temperature, CFs-deposited polydopamine-supported ZnO composite material was obtained.

[0105] The method of using the above-prepared composite material as a catalyst to recover waste polyester via alcoholysis:

[0106] 10 g PET, 150 ml ethylene glycol, and 0.5 g catalyst were placed in a reactor, and the temperature was slowly raised to 200 °C while stirring. The reaction time was 90 min. After the reaction was completed, the solution was cooled to 160 °C and filtered while hot. The solid was washed with deionized water, dried, and weighed to obtain the mass of undepolymerized PET. The PET conversion rate was calculated to be 98%.

[0107] Then, a large amount of deionized water was added to the filtrate, stirred and heated to 95 °C, filtered while hot, cooled to room temperature and placed at a low temperature of 3 °C for 24 h, filtered and dried to obtain BHET, weighed and the BHET yield was calculated to be 65%.

[0108] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0109] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing carbon fiber composite materials from waste polyester alcoholysis, characterized in that, Includes the following steps: S1. Prepare a buffer solution containing zinc hydroxide, catechol derivatives and polylysine; S2. The carbon fiber is immersed in a solvent and then immersed in the buffer solution. After the reaction, a precursor of catechol-based polymer / polylysine-loaded Zn(OH)2 is deposited on the surface of the carbon fiber. S3. The precursor of catechol-based polymer / polylysine-loaded Zn(OH)2 deposited on the carbon fiber surface is subjected to high temperature treatment to obtain carbon fiber composite material. The carbon fiber composite material includes a carbon fiber matrix and a polymer film formed on the surface of the carbon fiber matrix. The polymer film is prepared by polylysine and catechol-based polymer and is composited with ZnO. The temperature of the high temperature treatment is 100~200℃.

2. The preparation method according to claim 1, characterized in that, Step S1 is preceded by: The carbon fiber is treated in a potassium permanganate solution, then the potassium permanganate solution and the carbon fiber are separated by filtration, and then the carbon fiber is washed and dried. The concentration of the potassium permanganate solution is 2~10 mol / L, the treatment temperature is 30~60℃, and the treatment time is 10~24h.

3. The preparation method according to claim 1, characterized in that, The catechol derivatives include one or more of dopamine, levodopa, catechol, adrenaline, and noradrenaline.

4. The preparation method according to claim 1, characterized in that, In step S1, the buffer solution is a Tris buffer solution with a concentration of 0.01~0.10 mol / L and a pH of 8.0~9.0; and / or, the concentration of zinc hydroxide in the Tris buffer solution is 1~5 mg / L, the concentration of catechol derivatives is 1~5 mg / L, and the mass ratio of polylysine to catechol derivatives is (0.25~1):

1.

5. The preparation method according to claim 4, characterized in that, In step S2, the solvent is anhydrous ethanol, the amount of carbon fiber immersed in the buffer solution is 10~40g / L, the immersion time in the buffer solution is 30~60min, and the reaction time is 10~24h.

6. The preparation method according to claim 1, characterized in that, In step S3, the high-temperature treatment time is 1 to 5 hours.

7. The carbon fiber composite material for waste polyester alcoholysis prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It includes a carbon fiber matrix and a polymer film formed on the surface of the carbon fiber matrix, the polymer film being prepared from polylysine and catechol-based polymers, and the polymer film being composited with ZnO.

8. A method for the alcoholysis of waste polyester, characterized in that, include: Waste polyethylene terephthalate, ethylene glycol, and catalyst are mixed and reacted. The catalyst is prepared by the preparation method according to any one of claims 1 to 6 or the carbon fiber composite material according to claim 7.

9. The method according to claim 8, characterized in that, The ratio of ethylene glycol to waste polyethylene terephthalate is (10~20) ml: 1 g, and the catalyst is 1~20 wt% of the waste polyethylene terephthalate.

10. The method according to claim 8, characterized in that, The reaction is carried out at a temperature of 150~250℃ for a time of 30~200min.

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