Process for the synthesis of a tensile elongation branched PBAT degradable copolymer

Abstract

This invention discloses a method for synthesizing a tensile-strength, long-branched PBAT biodegradable copolymer, belonging to the field of biodegradable material processing technology. This invention addresses the technical problems of insufficient tensile properties and high initial biodegradation rates in agricultural films prepared from existing biodegradable copolymers. The method for synthesizing the tensile-strength, long-branched PBAT biodegradable copolymer includes the following steps: adding (E)-octyl-4-ene-1,8-diacid, 1-octadecene, and toluene to a three-necked flask and stirring; raising the temperature of the three-necked flask to 70-80°C; adding an initiator to the three-necked flask; maintaining the reaction temperature for 6-8 hours; and then post-processing to obtain intermediate I. The biodegradable copolymer of this invention, when used to prepare agricultural films, not only effectively improves the tensile properties of the agricultural film but also exhibits good degradation performance. Furthermore, the film has a low initial degradation rate, providing good environmental protection for agricultural seedlings.

Description

Technical Field

[0001] This invention relates to the field of biodegradable material processing technology, specifically to a method for synthesizing a tensile-strength, long-branched, biodegradable PBAT copolymer. Background Technology

[0002] With the rapid growth of the national economy, the plastics industry has developed rapidly, and its applications have permeated all sectors of the national economy, becoming extremely widespread. The main materials of plastics are polypropylene, polyethylene, and polystyrene, which cannot decompose naturally. Random disposal will cause serious white pollution due to their non-degradable nature, accumulating on the land. Moreover, this potential pollution will intensify with increased usage and over time. With the increasing environmental awareness of the public, traditional petrochemical-based plastics are gradually being replaced by biodegradable and reusable bio-based materials, often referred to as "green materials." Currently, the most important and widely used biodegradable polymers are aliphatic polyesters and proteins, such as polylactic acid, polybutylene adipate / terephthalate, and polybutylene succinate.

[0003] Most biodegradable copolymers in existing technologies have long, straight-chain structures containing numerous ester bonds. Through redox reactions, these ester bonds break, causing the long polymer chains to split into shorter segments. This decomposes the macromolecular polymer into smaller molecular structures, leading to degradation. Taking agricultural mulch films as an example, agricultural mulch films made from existing biodegradable copolymers generally have lower performance than PE films under the same conditions, with the most significant differences being in tensile and tear strength. To improve the tensile and tear strength of agricultural films, it is common practice to increase film thickness, use more expensive raw materials, and employ more complex processing techniques. Furthermore, the degradation rate of existing biodegradable materials in soil is initially high, but gradually slows down over time. This means that the protective performance of agricultural films for seedlings in the early stages of seedling growth needs further improvement, making it difficult to promote the application of biodegradable copolymers in agricultural films.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing tensile-strength, branched, biodegradable PBAT copolymers, which addresses the technical problems in the prior art where the tensile strength and tear strength of agricultural films prepared from biodegradable copolymers need further improvement, and the high initial biodegradation rate of biodegradable copolymers makes them prone to rapid degradation in a short period of time, thus failing to provide good protection for agricultural seedlings in the early growth stage.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for synthesizing tensile-strength, long-branched, biodegradable PBAT copolymers includes the following steps:

[0008] S1. Add (E)-octyl-4-en-1,8-dicarboxylic acid, 1-octadecene, and toluene to a three-necked flask and stir. Raise the temperature of the three-necked flask to 70-80℃, add an initiator to the three-necked flask, and keep the reaction at this temperature for 6-8 hours. After post-treatment, obtain intermediate I.

[0009] The principle of the synthesis reaction of intermediate I is as follows:

[0010]

[0011] S2. Add terephthalic acid, 1,4-butanediol and catalyst one into a three-necked flask under nitrogen protection and stir. Raise the temperature of the three-necked flask to 210-220℃ and react for 3-5 hours. After post-treatment, obtain intermediate II.

[0012] The principle of the synthesis reaction of intermediate II is as follows:

[0013]

[0014] S3. Intermediate I, Intermediate II, 1,5-Butanediol, glutaric acid, DMF and catalyst II are added to a three-necked flask under nitrogen protection and stirred. The oil bath temperature is set to 150-160℃, the pressure of the three-necked flask is reduced to 0.3-0.5kPa, and the reaction is carried out for 6-8 hours. The modified PBAT is obtained after post-treatment.

[0015] The synthesis reaction principle of modified PBAT is as follows:

[0016]

[0017] S5. Polybutylene succinate, polylactic acid, modified PBAT, and additives are added to a twin-screw extruder for melt extrusion granulation to obtain a biodegradable copolymer.

[0018] Furthermore, in step S1, the molar ratio of (E)-oct-4-en-1,8-diacid to 1-octadecene is 1:3, the amount of toluene used is 9 times the weight of (E)-oct-4-en-1,8-diacid, and the amount of initiator used is 0.1 times the weight of (E)-oct-4-en-1,8-diacid, wherein the initiator is azobisisobutyronitrile.

[0019] Further, the post-processing operation in step S1 includes: after the reaction is complete, the temperature of the three-necked flask is lowered to room temperature, drinking water is added to the three-necked flask and stirred for 10-20 minutes, allowed to stand, separated, the organic phase is transferred to a rotary evaporator, the water bath temperature is set to 85-95℃, the solvent is removed by vacuum evaporation to obtain intermediate I.

[0020] Furthermore, in step S2, the molar ratio of terephthalic acid and 1,4-butanediol is 1:4, the first catalyst is 0.02 times the weight of terephthalic acid, and the first catalyst is potassium titanium oxalate.

[0021] Further, the post-processing operation in step S2 includes: after the reaction is complete, the temperature of the three-necked flask is reduced by 150-160°C, purified water is slowly added to the three-necked flask, solid precipitates out, and the mixture is allowed to cool naturally to room temperature while stirring. The mixture is then filtered, the filter cake is washed with purified water and transferred to a drying oven at 70-80°C for vacuum drying to constant weight to obtain intermediate II.

[0022] Furthermore, in step S3, the weight ratio of intermediate I, intermediate II, 1,5-butanediol, glutaric acid, DMF and catalyst II is 1:1.5:3:3:8:0.1, and catalyst II is stannous chloride.

[0023] Further, the post-processing operation in step S3 includes: after the reaction is complete, the oil bath temperature is reduced to 95-105℃, and the mixture is distilled under reduced pressure until no liquid is collected. The oil bath temperature is then reduced to 55-65℃, and acetone is added to a three-necked flask under stirring. The mixture is stirred for 5-10 minutes, and the same volume of purified water is slowly added to the three-necked flask. A solid precipitates out. The three-necked flask is then transferred to a water bath and cooled to room temperature under stirring. The mixture is then filtered, and the filter cake is washed with 50wt% ethanol solution. The filter cake is then transferred to a drying oven at 65-75℃ and dried under vacuum to constant weight to obtain modified PBAT.

[0024] Furthermore, in step S5, the weight ratio of polybutylene succinate, polylactic acid, modified PBAT, and additives is 5:2:0.6-1:0.025. The twin-screw extruder barrel has multiple temperature zones from the feed end to the discharge end with temperatures of 190℃, 200℃, 200℃, 200℃, and 200℃ respectively, and the screw speed is 20 r / min. After extrusion by the twin-screw extruder, the sample is water-cooled and then cut into wet copolymer PBAT by a pelletizer at a speed of 260 r / min. The wet copolymer PBAT is transferred to a drying oven at a temperature of 85-95℃ and vacuum-dried to constant weight to obtain a biodegradable copolymer.

[0025] Furthermore, the additive mentioned in step S5 is composed of antioxidant, light stabilizer, antistatic agent and dispersant in a ratio of 1:1:1:2, wherein the antioxidant is one or more of tea polyphenols, butylated hydroxyanisole, butylated hydroxytoluene, and tert-butylhydroquinone; the light stabilizer is one or more of zinc oxide, titanium dioxide, benzophenone, benzotriazole and salicylate; the antistatic agent is one or more of antistatic agent SN, antistatic agent TM and antistatic agent SP; and the dispersant is polyethylene wax.

[0026] The present invention has the following beneficial effects:

[0027] This invention utilizes (E)-octyl-4-en-1,8-diacid and 1-octadecene in the presence of an initiator to generate intermediate I with an octadecene long-branched structure via free radical polymerization. Under catalytic conditions, terephthalic acid and 1,4-butanediol undergo a reaction where the carboxyl groups of terephthalic acid and the hydroxyl groups of 1,4-butanediol crosslink through ester bonds, generating intermediate II. Intermediate I, intermediate II, 1,5-butanediol, and glutaric acid react under catalysis. During the reaction, 1,5-butanediol acts as a chain extender, and the carboxyl and hydroxyl groups of the raw materials react to generate a long, straight-chain structure crosslinked by ester bonds, containing numerous long tentacle structures composed of octadecene long-branched chains. Modified PBAT is then melt-extruded and granulated with polybutylene succinate and polylactic acid, resulting in modified PBAT... BAT is melt-blended with polybutylene succinate and polylactic acid. The long straight chains and branches of modified PBAT are physically cross-linked and entangled with polybutylene succinate and polylactic acid, thereby effectively improving the tear strength and tensile strength of agricultural films made from biodegradable copolymers. Experiments show that when the amount of modified PBAT is around 12.8%, the mechanical properties of agricultural films made from biodegradable copolymers are optimal. Decreasing or increasing the amount of modified PBAT will lead to a decrease in the mechanical properties of agricultural films made from biodegradable copolymers. Furthermore, the addition of modified PBAT to biodegradable copolymers can effectively slow down their early degradation rate, providing protection during the early growth stage of agricultural seedlings and improving the protective effect of biodegradable films on agricultural seedlings in the early growth stage. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] The method for synthesizing the tensile-resistant, branched, biodegradable PBAT copolymer provided in this embodiment includes the following steps:

[0031] S1. Weigh out 34.4g of (E)-octyl-4-ene-1,8-dioctanoic acid, 151.5g of 1-octadecene, and 309.6g of toluene by weight and add them to a three-necked flask. Stir the mixture and raise the temperature of the three-necked flask to 70°C. Add 3.44g of azobisisobutyronitrile to the three-necked flask and keep it at this temperature for 6 hours. Lower the temperature of the three-necked flask to room temperature and add 200g of drinking water to the three-necked flask. Stir for 10 minutes, let it stand, separate the liquids, and transfer the organic phase to a rotary evaporator. Set the water bath temperature to 85°C and remove the solvent under reduced pressure to obtain intermediate I.

[0032] S2. Weigh out 33.2g of terephthalic acid, 72.1g of 1,4-butanediol and 0.66g of potassium titanium oxalate by weight and add them to a three-necked flask under nitrogen protection. Stir the mixture and raise the temperature of the three-necked flask to 210℃. React for 3 hours and then lower the temperature of the three-necked flask by 150℃. Slowly add 166g of purified water to the three-necked flask. A solid precipitates out. Allow the mixture to cool naturally to room temperature while stirring. Filter the mixture and wash the filter cake with purified water. Transfer the cake to a drying oven at 70℃ and vacuum dry it to constant weight to obtain intermediate II.

[0033] S3. Weigh out the following by weight: 20g of intermediate I, 30g of intermediate II, 60g of 1,5-butanediol, 60g of glutaric acid, 160g of DMF, and 2g of stannous chloride. Add them to a three-necked flask under nitrogen protection and stir. Set the oil bath temperature to 150℃ and reduce the pressure of the three-necked flask to 0.3kPa. React for 6 hours, then reduce the oil bath temperature to 95℃. Distill under reduced pressure until no liquid is collected. Reduce the oil bath temperature to 55℃ and add 100mL of acetone to the three-necked flask while stirring. Stir for 5 minutes, then slowly add 100mL of purified water to the three-necked flask. A solid precipitates out. Transfer the three-necked flask to a water bath and cool it to room temperature while stirring. Filter the mixture. Wash the filter cake with 50wt% ethanol solution and transfer it to a drying oven at 65℃. Dry the filter cake under vacuum to constant weight to obtain modified PBAT.

[0034] S5. Weigh out the following by weight: 100g polybutylene succinate, 40g polylactic acid, 12g modified PBAT, 0.1g tea polyphenols, 0.1g zinc oxide, 0.1g antistatic agent SN, and 0.2g polyethylene wax. Add these to a twin-screw extruder. Set the temperatures of the multiple temperature zones from the feed end to the discharge end of the twin-screw extruder barrel to 190℃, 200℃, 200℃, 200℃, and 200℃ respectively. Set the screw speed to 20r / min. After extrusion by the twin-screw extruder, the sample is water-cooled and then cut into wet copolymer PBAT by a pelletizer at a speed of 260r / min. Transfer the wet copolymer PBAT to a drying oven at 85℃ and vacuum dry to constant weight to obtain a biodegradable copolymer. Melt extrusion granulation yields the biodegradable copolymer.

[0035] Example 2

[0036] The method for synthesizing the tensile-resistant, branched, biodegradable PBAT copolymer provided in this embodiment includes the following steps:

[0037] S1. Weigh out 34.4g of (E)-octyl-4-ene-1,8-dioctanoic acid, 151.5g of 1-octadecene, and 309.6g of toluene by weight and add them to a three-necked flask. Stir the mixture and raise the temperature of the three-necked flask to 75°C. Add 3.44g of azobisisobutyronitrile to the three-necked flask and keep it at this temperature for 7 hours. Lower the temperature of the three-necked flask to room temperature and add 200g of drinking water to the three-necked flask. Stir for 15 minutes, let it stand, separate the liquids, and transfer the organic phase to a rotary evaporator. Set the water bath temperature to 90°C and remove the solvent under reduced pressure to obtain intermediate I.

[0038] S2. Weigh out 33.2g of terephthalic acid, 72.1g of 1,4-butanediol and 0.66g of potassium titanium oxalate by weight and add them to a three-necked flask under nitrogen protection. Stir the mixture and raise the temperature of the three-necked flask to 215℃. React for 4 hours and then lower the temperature of the three-necked flask by 155℃. Slowly add 166g of purified water to the three-necked flask. A solid precipitates out. Allow the mixture to cool naturally to room temperature while stirring. Filter the mixture and wash the filter cake with purified water. Transfer the cake to a drying oven at 75℃ and vacuum dry it to constant weight to obtain intermediate II.

[0039] S3. Weigh out the following by weight: 20g of intermediate I, 30g of intermediate II, 60g of 1,5-butanediol, 60g of glutaric acid, 160g of DMF, and 2g of stannous chloride. Add them to a three-necked flask under nitrogen protection and stir. Set the oil bath temperature to 155℃ and reduce the pressure of the three-necked flask to 0.4kPa. React for 7 hours, then reduce the oil bath temperature to 100℃. Distill under reduced pressure until no liquid is collected. Reduce the oil bath temperature to 60℃ and add 100mL of acetone to the three-necked flask while stirring. Stir for 8 minutes, then slowly add 100mL of purified water to the three-necked flask. A solid precipitates out. Transfer the three-necked flask to a water bath and cool it to room temperature while stirring. Filter the mixture. Wash the filter cake with 50wt% ethanol solution and transfer it to a drying oven at 70℃. Vacuum dry the filter cake to constant weight to obtain modified PBAT.

[0040] S5. Weigh out the following by weight: 100g polybutylene succinate, 40g polylactic acid, 16g modified PBAT, 0.1g butylated hydroxyanisole, 0.1g titanium dioxide, 0.1g antistatic agent TM, and 0.2g polyethylene wax. Add these to a twin-screw extruder. Set the temperatures of the multiple temperature zones from the feed end to the discharge end of the twin-screw extruder barrel to 190℃, 200℃, 200℃, 200℃, and 200℃ respectively. Set the screw speed to 20r / min. After extrusion by the twin-screw extruder, the sample is water-cooled and then cut into wet PBAT copolymer by a pelletizer at a speed of 260r / min. Transfer the wet PBAT copolymer to a drying oven at a temperature of 85-95℃ and vacuum dry to constant weight to obtain a biodegradable copolymer. Melt extrusion granulation yields the biodegradable copolymer.

[0041] Example 3

[0042] The method for synthesizing the tensile-resistant, branched, biodegradable PBAT copolymer provided in this embodiment includes the following steps:

[0043] S1. Weigh out 34.4g of (E)-octyl-4-ene-1,8-dicarboxylic acid, 151.5g of 1-octadecene, and 309.6g of toluene by weight and add them to a three-necked flask. Stir the mixture and raise the temperature of the three-necked flask to 80°C. Add 3.44g of azobisisobutyronitrile to the three-necked flask and keep it at this temperature for 8 hours. Then, lower the temperature of the three-necked flask to room temperature and add 200g of drinking water to the three-necked flask. Stir for 20 minutes, let it stand, separate the liquids, and transfer the organic phase to a rotary evaporator. Set the water bath temperature to 95°C and remove the solvent under reduced pressure to obtain intermediate I.

[0044] S2. Weigh out 33.2g of terephthalic acid, 72.1g of 1,4-butanediol and 0.66g of potassium titanium oxalate by weight and add them to a three-necked flask under nitrogen protection. Stir the mixture and raise the temperature of the three-necked flask to 220℃. React for 5 hours and then lower the temperature of the three-necked flask by 160℃. Slowly add 166g of purified water to the three-necked flask. A solid precipitates out. Allow the mixture to cool naturally to room temperature while stirring. Filter the mixture and wash the filter cake with purified water. Transfer the cake to a drying oven at 80℃ and vacuum dry it to constant weight to obtain intermediate II.

[0045] S3. Weigh out the following by weight: 20g of intermediate I, 30g of intermediate II, 60g of 1,5-butanediol, 60g of glutaric acid, 160g of DMF, and 2g of stannous chloride. Add them to a three-necked flask under nitrogen protection and stir. Set the oil bath temperature to 160℃ and reduce the pressure of the three-necked flask to 0.5kPa. React for 8 hours, then reduce the oil bath temperature to 105℃. Distill under reduced pressure until no liquid is collected. Reduce the oil bath temperature to 65℃ and add 100mL of acetone to the three-necked flask while stirring. Stir for 10 minutes, then slowly add 100mL of purified water to the three-necked flask. A solid precipitates out. Transfer the three-necked flask to a water bath and cool it to room temperature while stirring. Filter the mixture. Wash the filter cake with 50wt% ethanol solution and transfer it to a drying oven at 75℃. Dry the filter cake under vacuum to constant weight to obtain modified PBAT.

[0046] S5. Weigh out the following by weight: 100g polybutylene succinate, 40g polylactic acid, 20g modified PBAT, 0.1g tert-butylhydroquinone, 0.1g benzotriazole, 0.1g antistatic agent SP, and 0.2g polyethylene wax. Add these to a twin-screw extruder. Set the temperatures of the multiple temperature zones from the feed end to the discharge end of the twin-screw extruder barrel to 190℃, 200℃, 200℃, 200℃, and 200℃ respectively. Set the screw speed to 20r / min. After extrusion by the twin-screw extruder, the sample is water-cooled and then cut into wet copolymer PBAT by a pelletizer at a speed of 260r / min. Transfer the wet copolymer PBAT to a drying oven at a temperature of 85-95℃ and vacuum dry to constant weight to obtain a biodegradable copolymer. Melt extrusion granulation yields the biodegradable copolymer.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 3 is that modified PBAT was not added in step S5.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 3 is that the weight of the modified PBAT in step S5 is 30g.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 3 is that the weight of the modified PBAT in step S5 is 40g.

[0053] Performance testing:

[0054] The biodegradable copolymers prepared in Examples 1-3 and Comparative Examples 1-3 were added to a blown film machine to prepare film samples with a thickness of 60±5μm. The tear strength (kN / m) of the samples was determined according to standard GB / T 16578.1-2008 "Determination of tear resistance of plastic films and sheets - Part 1: Pants tear method". The tensile properties of the samples were determined according to standard GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". For the biodegradability test, the samples were cut into 5cm×5cm pieces, dried, and the original weight m0 of the samples was measured. Then, all samples were placed in a container filled with soil, maintaining the same burial depth and burial interval. Under natural conditions, water was applied regularly and quantitatively. After 30 and 150 days, the samples were removed, repeatedly washed with distilled water, dried, and the weight m0 used was measured. t According to the formula The degradation rate of the samples was obtained, and the specific test results are shown in the table below:

[0055]

[0056]

[0057] Data Analysis:

[0058] By comparing and analyzing the data recorded in the table above, the tensile strength and tear strength of Examples 1-3 are better than those of Examples 1-3. Furthermore, the average degradation rate of the samples prepared in Examples 1-3 was only 12.8% in 30 days, indicating that they can provide good protection for seedlings in the first 30 days. The average degradation rate reached 78.9% in 150 days. In the subsequent degradation process, the samples can degrade rapidly, which is more in line with the actual application of agricultural films.

[0059] Comparing the test data of Comparative Example 1 with those of Examples 1-3, without adding modified PBAT, the tensile strength and tear strength of the specimens prepared in Examples 1-3 need to be further improved. However, the degradation rate in the first 30 days is higher, and the protective performance of the specimens for seedlings in the first 30 days needs to be improved compared with Examples 1-3.

[0060] In Comparative Examples 2-3, the amount of modified PBAT was increased. However, as the amount of modified PBAT increased, the tensile strength and tear strength of the samples decreased, and the degradation rate of the samples was not improved. This indicates that the mechanical properties and degradation properties of the agricultural film prepared by the biodegradable copolymer with a modified PBAT content of around 12.8% are most suitable for the actual application of agricultural films.

[0061] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for the synthesis of a tensile elongation branched PBAT degradable copolymer characterized in that, Includes the following steps: S1. Add (E)-octyl-4-en-1,8-dicarboxylic acid, 1-octadecene, and toluene to a three-necked flask and stir. Raise the temperature of the three-necked flask to 70-80℃, add an initiator to the three-necked flask, and keep the reaction at this temperature for 6-8 hours. After post-treatment, obtain intermediate I. S2. Add terephthalic acid, 1,4-butanediol and catalyst one into a three-necked flask under nitrogen protection and stir. Raise the temperature of the three-necked flask to 210-220℃ and react for 3-5 hours. After post-treatment, obtain intermediate II. S3. Intermediate I, Intermediate II, 1,5-pentanediol, glutaric acid, DMF and catalyst II are added to a three-necked flask under nitrogen protection and stirred. The oil bath temperature is set to 150-160℃, the pressure of the three-necked flask is reduced to 0.3-0.5kPa, and the reaction is carried out for 6-8 hours. The modified PBAT is obtained after post-treatment. S5. Polybutylene succinate, polylactic acid, modified PBAT and additives are added to a twin-screw extruder for melt extrusion granulation to obtain a biodegradable copolymer.

2. The process for synthesis of tensile long chain branched PBAT degradable copolymer as claimed in claim 1 wherein, In step S1, the molar ratio of (E)-oct-4-en-1,8-diacid to 1-octadecene is 1:3, the amount of toluene used is 9 times the weight of (E)-oct-4-en-1,8-diacid, and the amount of initiator used is 0.1 times the weight of (E)-oct-4-en-1,8-diacid. The initiator is azobisisobutyronitrile.

3. The process for synthesis of draw elongation resistant branched PBAT degradable copolymer as claimed in claim 1 wherein, The post-processing steps of step S1 include: after the reaction is complete, the temperature of the three-necked flask is lowered to room temperature, drinking water is added to the three-necked flask and stirred for 10-20 minutes, allowed to stand, separated, and the organic phase is transferred to a rotary evaporator. The water bath temperature is set to 85-95℃, and the solvent is removed by vacuum evaporation to obtain intermediate I.

4. The process for synthesis of draw elongation resistant branched PBAT degradable copolymer as claimed in claim 1 wherein, In step S2, the molar ratio of terephthalic acid and 1,4-butanediol is 1:4, the first catalyst is 0.02 times the weight of terephthalic acid, and the first catalyst is potassium titanium oxalate.

5. The process for synthesis of draw elongation resistant branched PBAT degradable copolymer as claimed in claim 1 wherein, The post-processing steps in step S2 include: after the reaction is complete, the temperature of the three-necked flask is reduced by 150-160°C, purified water is slowly added to the three-necked flask, solids are precipitated, the mixture is allowed to cool naturally to room temperature while stirring, filtered, the filter cake is washed with purified water and then transferred to a drying oven at 70-80°C for vacuum drying to constant weight, to obtain intermediate II.

6. The process for synthesis of draw elongation resistant branched PBAT degradable copolymer as claimed in claim 1 wherein, In step S3, the weight ratio of intermediate I, intermediate II, 1,5-pentanediol, glutaric acid, DMF and catalyst II is 1:1.5:3:3:8:0.1, and catalyst II is stannous chloride.

7. The process for synthesis of draw elongation resistant branched PBAT degradable copolymer as claimed in claim 1 wherein, The post-processing steps in step S3 include: after the reaction is complete, the oil bath temperature is lowered to 95-105℃, and the mixture is distilled under reduced pressure until no liquid is collected. The oil bath temperature is then lowered to 55-65℃, and acetone is added to a three-necked flask while stirring. The mixture is stirred for 5-10 minutes, and the same volume of purified water is slowly added to the three-necked flask. A solid precipitates out. The three-necked flask is then transferred to a water bath and cooled to room temperature while stirring. The mixture is then filtered, and the filter cake is washed with 50wt% ethanol solution. The filter cake is then transferred to a drying oven at 65-75℃ and dried under vacuum to constant weight to obtain modified PBAT.

8. The method for synthesizing the tensile-strength, long-branched, biodegradable PBAT copolymer according to claim 1, characterized in that, In step S5, the weight ratio of polybutylene succinate, polylactic acid, modified PBAT, and additives is 5:2:0.6-1:0.

025. The twin-screw extruder barrel has multiple temperature zones from the feed end to the discharge end with temperatures of 190℃, 200℃, 200℃, 200℃, and 200℃ respectively, and the screw speed is 20 r / min. After extrusion by the twin-screw extruder, the sample is water-cooled and then cut into wet copolymer PBAT by a pelletizer at a speed of 260 r / min. The wet copolymer PBAT is transferred to a drying oven at a temperature of 85-95℃ and vacuum-dried to constant weight to obtain a biodegradable copolymer.

9. The method for synthesizing the tensile-strength, long-branched, biodegradable PBAT copolymer according to claim 1, characterized in that, The additive described in step S5 consists of an antioxidant, a light stabilizer, an antistatic agent, and a dispersant in a ratio of 1:1:1:

2. The antioxidant is one or more of tea polyphenols, butylated hydroxyanisole, butylated hydroxytoluene, and tert-butylhydroquinone. The light stabilizer is one or more of zinc oxide, titanium dioxide, benzophenone, benzotriazole, and salicylate. The antistatic agent is one or more of antistatic agent SN, antistatic agent TM, and antistatic agent SP. The dispersant is polyethylene wax.

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