Recycling method of biodegradable polyester poly (butylene adipate-co-butylene adipate) (PBAT) and biodegradable copolyester prepared from biodegradable polyester poly (butylene adipate-co-butylene adipate) (PBAT)
By using terephthalic acid and/or adipic acid catalysts in an aqueous system to carry out the hydrolysis reaction of PBAT, the problems of thermal degradation and catalyst separation in the PBAT recycling process are solved, realizing efficient and environmentally friendly PBAT recycling and utilization, and producing high-performance biodegradable copolyesters.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2026-03-10
AI Technical Summary
Existing PBAT recovery methods suffer from problems such as thermal degradation and thermal oxidation reactions leading to a decline in product quality, and the chemical recovery process is complex and environmentally unfriendly, with difficulties in catalyst separation.
Using terephthalic acid and/or adipic acid as catalysts, PBAT hydrolysis was carried out in an aqueous system. The hydrolysis products were directly used for repolymerization, avoiding the catalyst separation step, to prepare biodegradable copolyesters.
The operation process was simplified, energy consumption was reduced, the hydrolysis rate and product yield of PBAT were improved, and a biodegradable copolyester with excellent mechanical properties was obtained.
Smart Images
Figure CN121628064A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of recycling technology. More specifically, it relates to a method for recycling biodegradable polyester polybutylene terephthalate (PBAT) and the biodegradable copolyester prepared therefrom. Background Technology
[0002] Polybutylene terephthalate (PBAT) is a biodegradable polyester copolymerized from terephthalic acid (PTA), adipic acid (AA), and 1,4-butanediol (BDO). Due to its significant advantages in stretchability, processability, and cost-effectiveness, it is gradually replacing traditional recalcitrant polyethylene and is widely used in single-use packaging and agricultural films. According to the latest market data from European Bioplastics, global biodegradable plastic production reached 1.14 million tons in 2023, of which PBAT production reached 100,000 tons. In China, PBAT production capacity has exceeded 500,000 tons. With its expanding application prospects, focusing on the recycling and sustainable utilization of PBAT is essential for the effective management of plastic resources and environmental protection.
[0003] Generally, waste PBAT can be recycled using physical or chemical methods. During the melting and regranulation processes of physical recycling, PBAT is prone to thermal degradation and oxidation, leading to problems such as a decrease in the average molecular weight of the product and increased color difference, affecting the quality of the final product and ultimately requiring downgrading. Furthermore, PBAT slowly degrades during use; once the degradation is excessive, it cannot be recycled using physical methods. Chemical recycling, on the other hand, decomposes waste PBAT into monomers or low-molecular-weight compounds through chemical reactions. These monomers or low-molecular-weight compounds can then be used to synthesize new plastics or other high-value-added products. It can handle low-value, mixed, and contaminated waste plastics, solving the problem that traditional physical recycling cannot effectively handle such waste. In recent years, the chemical recycling of polyethylene terephthalate (PET) has received widespread attention, with methods such as hydrolysis, methanololysis, and glycolysis already being applied. However, research on PBAT, which is also a semi-aromatic polyester, is relatively limited.
[0004] Chemical recovery of PBAT mostly utilizes homogeneous metal catalysts, which typically exhibit high activity and selectivity. However, this also presents challenges in separation, recovery, and regeneration. Furthermore, existing recovery systems often require complex product separation steps, increasing operational complexity and potentially leading to energy and environmental costs. Therefore, developing a simpler and more environmentally friendly PBAT recovery process is essential. Summary of the Invention
[0005] Based on this, the first objective of this invention is to provide a method for recycling biodegradable polyester polybutylene terephthalate (PBAT). This recycling method uses terephthalic acid (TPA) and / or adipic acid (AA) as catalysts, and the hydrolysis reaction of PBAT can be completed in an aqueous system. The compounds terephthalic acid and adipic acid are both catalysts and major components in the reaction products, thus avoiding the need for catalyst separation. Furthermore, after the hydrolysis reaction is complete, no separation step is required; the product can be directly used in the next repolymerization reaction to prepare different types of biodegradable copolyesters, achieving closed-loop recycling of PBAT polyester.
[0006] A second objective of this invention is to provide a biodegradable copolyester prepared using the recycling method described above.
[0007] To achieve the first objective mentioned above, the present invention adopts the following technical solution:
[0008] This invention discloses a method for recycling biodegradable polyester polybutylene terephthalate (PBAT), using terephthalic acid and / or adipic acid as catalysts to carry out the hydrolysis reaction of PBAT.
[0009] The PBAT in this invention is selected from recycled materials of various molecular weights obtained through different methods.
[0010] Furthermore, the amount of catalyst used, by weight percentage, is 10-200 wt% of PBAT. For example, the amount of catalyst used can be 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 100 wt%, 110 wt%, 120 wt%, 130 wt%, 140 wt%, 150 wt%, 160 wt%, 170 wt%, 180 wt%, 190 wt%, 200 wt% of PBAT, etc., preferably in the range of 10-100 wt%, more preferably 10-50 wt%.
[0011] Furthermore, the solvent used in the hydrolysis reaction is water. Using water as the sole solvent improves environmental friendliness.
[0012] Furthermore, the amount of water used, by mass percentage, is 10-1000 wt% of PBAT. For example, the amount of water used is 10 wt%, 50 wt%, 100 wt%, 150 wt%, 200 wt%, 250 wt%, 300 wt%, 350 wt%, 400 wt%, 450 wt%, 500 wt%, 550 wt%, 600 wt%, 650 wt%, 700 wt%, 750 wt%, 800 wt%, 850 wt%, 900 wt%, 950 wt%, 1000 wt% of PBAT, etc., preferably 100-1000 wt%, more preferably 100-500 wt%.
[0013] Furthermore, the hydrolysis reaction temperature is 50-250℃, preferably 140-180℃; the hydrolysis reaction time is 0.5-12h, so that the hydrolysis rate of PBAT in the hydrolysis reaction is 0-100%. When the hydrolysis rate of PBAT is 0%, the mass of the solid does not change, but the molecular weight decreases significantly, forming oligomers.
[0014] Furthermore, the hydrolysis reaction temperature is 50-250℃, the hydrolysis reaction time is 1-8h, that is, the hydrolysis rate of PBAT in the hydrolysis reaction is 0.6-83.5%.
[0015] Furthermore, the hydrolysis reaction is carried out under closed conditions, such as in a closed reaction vessel.
[0016] Furthermore, the recycling method also includes repolymerizing the hydrolysis reaction products with additionally added monomers and polymerization catalysts to prepare biodegradable copolyesters.
[0017] In this invention, the hydrolysis reaction product used for repolymerization can be either a monomer compound obtained after complete hydrolysis, an unreacted oligomer, or a mixture of oligomer and monomer. Regardless of whether it is a monomer, oligomer, or a mixture of the two, it has little impact on the properties of the biodegradable copolyester obtained in the subsequent repolymerization reaction. Therefore, this invention can obtain biodegradable copolyester with relatively lower energy consumption and in a shorter time.
[0018] Furthermore, the hydrolysis reaction products include oligomers and / or monomers of PBAT (e.g., terephthalic acid, adipic acid, 1,4-butanediol, etc.).
[0019] Furthermore, the additional monomers are selected from one or more of diols, diacids, hydroxy acids, and lactones; the polymerization catalyst is selected from one or more of antimony catalysts (e.g., antimony trioxide, antimony glycolate, and antimony acetate), germanium catalysts (e.g., germanium oxide), rare earth catalysts, and titanium catalysts (e.g., titanates, titanate esters, and titanium oxides), preferably titanate ester catalysts, such as tetrabutyl titanate (TBT).
[0020] Furthermore, the additional monomers are selected from one or more of terephthalic acid, adipic acid, 1,4-butanediol, lactic acid, glycolic acid, ε-caprolactone, glycolide, and lactide.
[0021] Furthermore, the repolymerization includes an esterification reaction and a polycondensation reaction performed sequentially.
[0022] Furthermore, the re-aggregation includes the following steps:
[0023] The hydrolysis product is subjected to an esterification reaction with additional monomers and a polymerization catalyst, wherein the esterification reaction is carried out under the following conditions: atmospheric pressure and reaction temperature of 180-240℃.
[0024] The product of the esterification reaction is then subjected to a further polycondensation reaction to obtain a biodegradable copolyester. The conditions for the polycondensation reaction are: a vacuum degree of 10-100 Pa and a reaction temperature of 220-270 °C.
[0025] Furthermore, the repolymerization is carried out in a glass bottle or a reaction vessel.
[0026] To achieve the second objective mentioned above, the present invention adopts the following technical solution:
[0027] This invention discloses a biodegradable copolyester prepared using the recycling method described above, wherein the biodegradable copolyester is selected from one of the following structures:
[0028]
[0029] Where x is 1-10, y is 1-10, and z is 1-33.
[0030] The beneficial effects of this invention are as follows:
[0031] 1. The recycling method provided by this invention uses terephthalic acid (TPA) and / or adipic acid (AA) as catalysts to complete the hydrolysis reaction of PBAT in an aqueous system. Terephthalic acid and adipic acid are both catalysts and major components of the reaction products, thus avoiding the catalyst separation step, simplifying the operation, and reducing energy efficiency. Furthermore, when using adipic acid (AA) as a catalyst, the hydrolysis rate of PBAT is high, and the yields of hydrolysis products AA and TPA are also high.
[0032] 2. Based on the hydrolysis reaction, this invention further carries out a repolymerization reaction without adding monomers and polymerization catalysts, achieving a closed-loop recycling of biodegradable polyester-raw materials-biodegradable polyester. Furthermore, the thermal properties of the biodegradable polyester obtained from the repolymerization reaction are basically unaffected by the degree of hydrolysis in the previous step. Therefore, technicians do not need to strictly control the degree of hydrolysis reaction, i.e., they do not need to react and separate various monomers. Repolymerization can also be carried out in the form of a mixture of oligomers and monomers to obtain biodegradable polyester with good mechanical properties and excellent thermal properties. Attached Figure Description
[0033] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0034] Figure 1 The image shows the chromatogram of filtrate 1 determined by ultra-high performance liquid chromatography in Example 1 when the hydrolysis conditions were: temperature 170°C, reaction time 8 h, AA dosage 50 wt%, and water dosage 300 wt%.
[0035] Figure 2 The repolymerized product PBAT obtained in Examples 4-6 is shown. 1 H NMR spectrum.
[0036] Figure 3 The mechanical properties of the repolymerized product PBAT obtained in Examples 4-6 are shown in the diagram.
[0037] Figure 4 The DSC spectra of the repolymerized product PBAT obtained in Examples 4-6 are shown.
[0038] Figure 5 The TGA spectra of the repolymerized product PBAT obtained in Examples 4-6 are shown. Detailed Implementation
[0039] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.
[0040] The content of AA in PBAT hydrolysis products was determined using UPLC (Vanquish, Thermo Scientific, USA). The UPLC was equipped with a CNW Athena C18-WP 250×4.6 mm, 5 μm column, and the UV detector was set to 210 nm. The mobile phase was 0.02 mol / L NaH2PO4 aqueous solution at pH 2.7, the flow rate was 0.7 mL / min, and the injection volume was 10 μL.
[0041] The molecular weight of the products in the liquid phase after hydrolysis was determined using ESI-MS (Q Exactive, Thermo Scientific, USA).
[0042] use 1 Hydrolysis products and polymer structures were analyzed by 1H NMR (Avance 400, Bruker, Germany) using heavy water (D2O) or tritium-chloroform (CDCl3) as solvents.
[0043] The molecular weight and distribution of the polymer were tested using GPC (e2695, Waters, USA), with chloroform as the solvent and mobile phase, and PMMA as the reference material.
[0044] The thermal properties of the polymer were tested using a DSC (DSC 1, Mettler Toledo, Switzerland) with a test temperature range of 0-200℃ and a heating / cooling rate of 10℃ / min.
[0045] The thermal stability of the polymer was tested using TGA (Q50, TA Instruments, USA) in a temperature range of room temperature to 600°C.
[0046] Polymer blends of different proportions were prepared using an extruder (Process 11, Thermo Scientific, USA) at a processing temperature of 180°C.
[0047] The polymer was processed into standard tensile specimens using an injection molding machine (HAAKE MiniJet Pro, Thermo Scientific, USA) at a processing temperature of 190°C and a mold temperature of 35°C. The specimens were 25.0±1.0 mm long, 6.0±0.4 mm wide, and 2.0±0.2 mm thick, with a mass of 1.0 to 2.0 g.
[0048] The mechanical properties of the polymer were tested using a general-purpose material testing machine (WDW-10, Songdun, China). The specimens were stretched at 50 mm / min at 25°C, and the average value of at least three specimens was used as the reference value.
[0049] Example 1
[0050] Adipic acid (AA) catalyzes the hydrolysis of PBAT
[0051] 1.0 g of PBAT granules, a certain amount of AA, and water were added to a 50 mL reaction vessel. The mixture was heated and stirred at a certain temperature for a certain time at a stirring speed of 25 rpm. After the reaction was completed, the reaction vessel was allowed to cool naturally to 60 °C. The mixture was filtered, and the remaining solid 1 and filtrate 1 were collected separately. The content of AA in filtrate 1 was determined by ultra-high performance liquid chromatography. The remaining solid 1 was placed in NaOH solution and reacted for a period of time. Then, it was filtered again, and the remaining solid 2 (i.e., unreacted PBAT) and filtrate 2 were collected. The remaining solid 2 was washed three times with deionized water and dried in a vacuum oven at 60 °C for 12 h until constant weight was reached. Dilute H2SO4 was added to filtrate 2, and the precipitated remaining solid 3 (i.e., product TPA) was collected by filtration and dried in a vacuum oven at 60 °C for 12 h until constant weight was reached.
[0052] The hydrolysis rate of PBAT was calculated using formula (1), and the yields of products AA and TPA were calculated using formulas (2) and (3).
[0053] PBAT hydrolysis rate (%) = (m0-m1)×100 / m0 (1)
[0054] Where m0 is the initial mass of PBAT and m1 is the mass of the remaining solid 2.
[0055] AA yield (%) = (m a -m b )×100 / m c (2)
[0056] TPA yield (%) = m d ×100 / m e (3)
[0057] Where, m a The mass of AA in filtrate 1, determined by UPLC, is m. b It is the mass of AA used as a catalyst, m c This is the theoretical mass of AA obtainable from the complete hydrolysis of PBAT; m d The mass of the remaining solid 3, m e It is the theoretical mass of TPA that can be obtained from the complete hydrolysis of PBAT.
[0058] The specific product results under different conditions are shown in Table 1.
[0059] Table 1. Product results under different reaction conditions
[0060]
[0061] Note: The dosage of AA and water in Table 1 are calculated as a percentage by mass, representing the dosage of AA or water relative to PBAT.
[0062] As shown in Table 1, the addition of an appropriate amount of AA significantly increased the hydrolysis rate and product yield of PBAT. This may be because the H+ produced by AA in water... + The hydrolysis of PBAT was accelerated. Furthermore, the degree of PBAT hydrolysis can be controlled by adjusting catalyst dosage, reaction time, and other conditions to obtain oligomers and monomers. The optimal hydrolysis conditions were determined to be a temperature of 170℃, a reaction time of 8 h, an AA dosage of 50 wt%, and a water dosage of 300 wt%. Under these conditions, the PBAT hydrolysis conversion rate was 83.5%, and the AA yield was 61.0%. It is worth noting that this does not mean that PBAT cannot react completely under this catalytic system. With prolonged reaction time, the PBAT hydrolysis rate and monomer yield will still gradually increase, but the rate of increase will be slower. Moreover, since the product under these conditions can be used for subsequent polymerization reactions, more stringent conditions are not necessary to increase the monomer yield.
[0063] Figure 1 The chromatogram of filtrate 1 is shown when the hydrolysis conditions are: temperature 170℃, reaction time 8h, AA dosage 50wt%, and water dosage 300wt%.
[0064] Example 2
[0065] PBAT film or PBAT bag (20.0 g), AA (10.0 g), and water (60.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the product was determined to be mainly monomers AA and BDO, with some oligomers and a small amount of byproduct tetrahydrofuran (THF), according to the detection method and yield calculation method in Example 1. The hydrolysis rates of the above PBAT-based products were 75.5% and 80.2%, respectively, which were basically consistent with the results obtained under the same process conditions in Example 1.
[0066] Example 3
[0067] terephthalic acid (TPA) catalyzes the hydrolysis of PBAT
[0068] 1.0 g of PBAT granules, a certain amount of TPA, and water were added to a 50 mL reaction vessel. The mixture was heated and stirred at a certain temperature for a certain time at a stirring speed of 25 rpm. After the reaction was completed, the reaction vessel was allowed to cool naturally to 60 °C. The mixture was filtered, and the remaining solid 1 and filtrate 1 were collected separately. The content of AA in filtrate 1 was determined by ultra-high performance liquid chromatography. The remaining solid 1 was placed in NaOH solution and reacted for a period of time. Then, it was filtered again, and the remaining solid 2 (i.e., unreacted PBAT) and filtrate 2 were collected. The remaining solid 2 was washed three times with deionized water and dried in a vacuum oven at 60 °C for 12 h until constant weight was reached. Dilute H2SO4 was added to filtrate 2, and the precipitated solid 3 (i.e., product TPA) was collected by filtration and dried in a vacuum oven at 60 °C for 12 h until constant weight was reached.
[0069] The hydrolysis rate of PBAT was calculated using formula (1), and the yields of products AA and TPA were calculated using formulas (2) and (3). The specific product results under different conditions are shown in Table 2.
[0070] PBAT hydrolysis rate (%) = (m0-m1)×100 / m0 (1)
[0071] Where m0 is the initial mass of PBAT and m1 is the mass of the remaining solid 2.
[0072] AA yield (%) = m a ×100 / m b (2)
[0073] TPA yield (%) = (m c -m d )×100 / m e (3)
[0074] Where, m a The mass of AA in filtrate 1, determined by UPLC, is m. b This is the theoretical mass of AA obtainable from the complete hydrolysis of PBAT, m c The mass of the remaining solid 3; m d It is the mass of TPA used as a catalyst, m e It is the theoretical mass of TPA that can be obtained from the complete hydrolysis of PBAT.
[0075] The specific product results under different conditions are shown in Table 2.
[0076] Table 2. Product results under different reaction conditions
[0077]
[0078] Note: The TPA and water dosages in Table 2 are calculated as TPA or water relative to PBAT by mass percentage.
[0079] As shown in Table 2, TPA has a relatively small promoting effect on the hydrolysis of PBAT. This may be because TPA has low solubility in water, making it difficult to generate H+. + Accelerate PBAT hydrolysis.
[0080] Example 4
[0081] The recycling of PBAT polyester involves the following steps:
[0082] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 1 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the remaining materials (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA, and BDO, as well as water) were added to a 500 mL three-necked flask. At this point, the hydrolysis rate of PBAT was 0.6%, and the yields of products AA and TPA were both 0.
[0083] Repolymerization: TPA (28.4 g), BDO (83.1 g), and tetrabutyl titanate (TBT, 0.45 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at 450 rpm. The reaction was then carried out at 200-240°C for approximately 5 hours, until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250°C to initiate the polycondensation reaction. The polycondensation reaction continued for 3-4 hours. The reaction was considered complete when the polymer viscosity significantly increased and the stirring torque reached 30 N·cm. The repolymerized product PBAT... 1 See the H NMR spectrum. Figure 2 The performance is shown in Tables 3 and 4. Figures 3 to 5 As shown.
[0084] Example 5
[0085] The preparation method is the same as in Example 4, except that the hydrolysis reaction time is adjusted to 5 hours. The specific steps are as follows:
[0086] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 5 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the residues (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA, BDO, and water) were added to a 500 mL three-necked flask. At this point, the hydrolysis rate of PBAT was 45.3%, the yield of product AA was 30.2%, and the yield of TPA was 21.0%.
[0087] Repolymerization: TPA (28.4 g), BDO (83.1 g), and tetrabutyl titanate (TBT, 0.45 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at 450 rpm. The reaction was then carried out at 200-240°C for approximately 5 hours, until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250°C to initiate the polycondensation reaction. The polycondensation reaction continued for 3-4 hours. When the viscosity of the polymer significantly increased and the torque of the stirrer reached 30 N·cm, the reaction was considered to have reached its endpoint. The repolymerized product PBAT... 1 See the H NMR spectrum. Figure 2 The performance is shown in Tables 3 and 4. Figures 3 to 5 As shown.
[0088] Example 6
[0089] The preparation method is the same as in Example 4, except that the hydrolysis reaction time is adjusted to 8 hours. The specific steps are as follows:
[0090] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the residues (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA, BDO, and water) were added to a 500 mL three-necked flask. At this point, the hydrolysis rate of PBAT was 80.2%, the yield of product AA was 57.8%, and the yield of TPA was 53.1%.
[0091] Repolymerization: TPA (28.4 g), BDO (83.1 g), and tetrabutyl titanate (TBT, 0.45 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at 450 rpm. The reaction was then carried out at 200-230°C for 4-12 hours until esterification was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 240°C to initiate polycondensation. The polycondensation reaction continued for 6-8 hours. The reaction was considered complete when the polymer viscosity significantly increased and the stirring torque reached 30 N·cm. The repolymerized product PBAT... 1 See the H NMR spectrum. Figure 2 The performance is shown in Tables 3 and 4. Figures 3 to 5 As shown.
[0092] Figure 2 The repolymerized product PBAT obtained in Examples 4-6 is shown. 11H NMR spectrum. As can be seen from the figure, PBAT was obtained in Examples 4-6 after the repolymerization process.
[0093] Table 3 Mechanical properties and molecular weight of the repolymerized products
[0094]
[0095] Note: In Table 3, T:A refers to the molar ratio of terephthalic acid units (T) and adipic acid units (A) in the repolymerized PBAT.
[0096] Table 4 Thermal properties of the repolymerization products
[0097]
[0098] From Table 3, Table 4 and Figures 3 to 5 It can be seen that although three products with different degrees of hydrolysis were obtained by changing the hydrolysis time of PBAT, the thermal properties of the repolymerized products obtained when directly used in the next step of repolymerization were not significantly different. For the system with a higher degree of hydrolysis, the mechanical properties of the repolymerized products were relatively better.
[0099] Example 7
[0100] x is 1-10, y is 1-10, and z is 1-3.
[0101] The recycling of PBAT polyester involves the following steps:
[0102] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the remaining materials (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA and BDO, and water) were added to a 500 mL three-necked flask.
[0103] Repolymerization: TPA (28.4 g), lactic acid (LA, 26.1 g), BDO (83.1 g), and tetrabutyl titanate (TBT, 0.58 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at 450 rpm. The reaction was then carried out at 200-240°C for approximately 5 hours until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250°C to initiate the polycondensation reaction. The polycondensation reaction continued for 3-4 hours. The reaction was considered complete when the polymer viscosity significantly increased and the stirring torque reached 30 N·cm. The molecular weight of the repolymerized product PBATL is shown in Table 5.
[0104] Example 8
[0105] x is 1-10, y is 1-10, and z is 1-3.
[0106] The recycling of PBAT polyester involves the following steps:
[0107] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the remaining materials (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA and BDO, and water) were added to a 500 mL three-necked flask.
[0108] Repolymerization: TPA (28.4 g), glycolic acid (GA, 22.0 g), BDO (83.1 g), and tetrabutyl titanate (TBT, 0.56 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at a stirring rate of 450 rpm. The reaction was then carried out at 200-240 °C for approximately 5 hours until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250 °C to initiate the polycondensation reaction. The polycondensation reaction continued for 3-4 hours. The reaction was considered complete when the viscosity of the polymer significantly increased and the torque of the stirrer reached 30 N·cm. The molecular weight of the repolymerized product PBATG is shown in Table 5.
[0109] Example 9
[0110] x is 1-10, y is 1-10, and z is 1-3.
[0111] The recycling of PBAT polyester involves the following steps:
[0112] Hydrolysis: PBAT granules (50.0 g), AA (25.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the remaining materials (including unreacted oligomers, added catalyst AA, hydrolysis products AA, TPA, and BDO, and water) were added to a 500 mL three-necked flask.
[0113] Repolymerization: TPA (28.4 g), ε-caprolactone (CL, 33.1 g), BDO (83.1 g), tetrabutyl titanate catalyst (TBT, 0.62 g), and stannous octoate ring-opening agent (0.17 g) were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at a stirring rate of 450 rpm. The reaction was then carried out at 200-240 °C for approximately 5 hours until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250 °C to initiate the polycondensation reaction. The polycondensation reaction continued for 3-4 hours. The reaction was considered complete when the viscosity of the polymer significantly increased and the torque of the stirrer reached 30 N·cm. The molecular weight of the repolymerized product PBATCL is shown in Table 5.
[0114] Example 10
[0115] x is 1-10, y is 1-10.
[0116] The recycling of PBAT polyester involves the following steps:
[0117] Hydrolysis: PBAT granules (50.0 g), TPA (15.0 g), and water (150.0 g) were added to a 1.2 L reactor and heated and stirred at 170 °C for 8 h at a stirring speed of 25 rpm. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. All the remaining materials (including unreacted oligomers, added catalyst TPA, hydrolysis products AA, TPA and BDO, and water) were added to a 500 mL three-necked flask.
[0118] Repolymerization: AA (13.2 g), BDO (54.0 g), and tetrabutyl titanate (TBT, 0.33 g) catalyst were added to a three-necked flask. The flask was placed in an oil bath equipped with a top stirrer at 450 rpm. The reaction was then carried out at 200-240 °C for approximately 5 hours, until the esterification reaction was complete. The pressure of the reaction system was reduced to below 100 Pa, and the oil bath temperature was increased to 250 °C to initiate a polycondensation reaction. The polycondensation reaction continued for 3-4 hours. The reaction was considered complete when the polymer viscosity significantly increased and the stirring torque reached 30 N·cm. The molecular weight of the repolymerized product PBAT is shown in Table 5.
[0119] Table 5 Mechanical properties and molecular weight of the repolymerized products
[0120]
[0121] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A recycling method of a biodegradable polyester polybutylene adipate terephthalate (PBAT), characterized by, The hydrolysis reaction of PBAT is carried out with terephthalic acid and / or adipic acid as a hydrolysis catalyst.
2. The recycling method according to claim 1, characterized in that, The amount of the hydrolysis catalyst is 10-200wt% of PBAT, preferably 10-100wt% of PBAT, in terms of mass percentage.
3. The recycling method according to claim 1, characterized in that, The solvent used in the hydrolysis reaction is water; The amount of the water is 10-1000wt% of PBAT, preferably 100-1000wt% of PBAT, in terms of mass percentage.
4. The recycling method according to claim 1, characterized in that, The temperature of the hydrolysis reaction is 50-250℃, and the time of the hydrolysis reaction is 0.5-12h, so that the hydrolysis rate of PBAT in the hydrolysis reaction is 0-100%.
5. The recycling method according to claim 1, characterized in that, The recycling method further comprises re-polymerizing the hydrolysis reaction product with additional monomers and a polymerization catalyst to prepare a biodegradable copolyester.
6. The recycling method according to claim 5, characterized in that, The hydrolysis reaction product comprises oligomers and / or monomers of PBAT. Preferably, the monomers are selected from one or more of terephthalic acid, adipic acid, and 1,4-butanediol.
7. The recycling method according to claim 5, characterized in that, The additional monomers are selected from one or more of diols, diacids, hydroxy acids, and lactones. The polymerization catalyst is selected from one or more of antimony-based catalysts, germanium-based catalysts, rare earth catalysts, and titanium-based catalysts, preferably titanium ester-based catalysts.
8. The recycling method according to claim 5, characterized in that, The additional monomers are selected from one or more of terephthalic acid, adipic acid, 1,4-butanediol, lactic acid, glycolic acid, ε-caprolactone, glycolide, and lactide.
9. The recycling method according to claim 5, characterized in that, The re-polymerization comprises an esterification reaction and a polycondensation reaction performed in sequence. Preferably, the esterification reaction is performed under normal pressure at a temperature of 180-240℃, and the polycondensation reaction is performed under a vacuum degree of 10-100Pa at a temperature of 220-270℃.
10. A biodegradable copolyester characterized in that, The biodegradable copolyester is selected from one of the following structures: wherein x is 1-10, y is 1-10, and z is 1-33.