A PBAT / PLA composite biodegradable plastic and its preparation process

Abstract

This invention belongs to the field of polyester biodegradable plastics technology, specifically relating to a PBAT / PLA composite biodegradable plastic and its preparation process. This invention aims to solve the problems of poor weather resistance and insufficient mechanical properties in existing PBAT / PLA composite materials. The invention involves preheating PBAT resin particles and then performing melt grafting to obtain modified PBAT; obtaining hydroxyl-terminated PBS through transesterification polycondensation, and further obtaining a triblock compatibilizer through bulk polymerization; acetylifying nanocellulose to obtain a dispersing reinforcing agent, and then melt-blending it with PLA resin particles to obtain a reinforcing masterbatch; reactively blending the modified PBAT, reinforcing masterbatch, and triblock compatibilizer, followed by vacuum drying, to obtain the biodegradable plastic. The biodegradable plastic provided by this invention maintains excellent biodegradability while possessing good mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of polyester biodegradable plastics technology, specifically relating to a PBAT / PLA composite biodegradable plastic and its preparation process. Background Technology

[0002] Polybutylene terephthalate (PBAT) is a novel biodegradable polymer that can be completely decomposed by microorganisms under specific conditions. PBAT possesses excellent flexibility and good processability, exhibiting unique advantages, particularly in the film industry. It can meet the requirements for material ductility and tear resistance in applications such as packaging and tableware. However, its relatively low mechanical strength and rigidity limit its use in applications requiring higher load-bearing capacity. On the other hand, polylactic acid (PLA) is also a biodegradable plastic known for its high strength, high modulus, and good rigidity, with wide applications in injection molding, fibers, and films. However, its inherent brittleness and low elongation at break limit its application in situations requiring good toughness.

[0003] To overcome the shortcomings of PBAT and PLA respectively and fully utilize their advantages, blending modification of the two has become an important research direction. Blending modification can effectively combine the flexibility of PBAT and the strength of PLA, resulting in composite materials with superior overall performance. Such composites typically exhibit better impact strength, tensile properties, and processability, expanding their application range. However, existing PBAT / PLA composites still face some technical challenges. Due to differences in polarity and melt viscosity, PBAT and PLA have poor compatibility and are prone to phase separation, affecting the mechanical properties and degradation performance of the final material. To improve their compatibility, researchers usually need to introduce compatibilizers or employ other modification methods. Furthermore, existing PBAT / PLA composites still require further improvement in heat resistance, barrier properties, and processability to meet broader application needs.

[0004] Currently, the poor weather resistance and insufficient mechanical properties of existing PBAT / PLA composite materials remain significant challenges for the industry.

[0005] To this end, a PBAT / PLA composite biodegradable plastic and its preparation process are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a PBAT / PLA composite biodegradable plastic and its preparation process. This invention involves preheating PBAT resin particles and then performing melt grafting to obtain modified PBAT; obtaining hydroxyl-terminated PBS through transesterification polycondensation, and further obtaining a triblock compatibilizer through bulk polymerization; acetylifying nanocellulose to obtain a dispersing reinforcing agent, and then melt-blending it with PLA resin particles to obtain a reinforcing masterbatch; reactively blending the modified PBAT, reinforcing masterbatch, and triblock compatibilizer, followed by vacuum drying, to obtain the biodegradable plastic.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A process for preparing a PBAT / PLA composite biodegradable plastic includes the following steps:

[0009] Unless otherwise specified, all parts in this invention refer to parts by mass, and all average molecular weights refer to exponential molecular weights.

[0010] PBAT resin particles were preheated and then melt-grafted to obtain modified PBAT.

[0011] Among them, the BA unit accounts for 70% of the PBAT resin particles, the BT unit accounts for 30%, and the average molecular weight is 45,000.

[0012] Dimethyl succinate and 1,4-butanediol were mixed and subjected to transesterification polycondensation to obtain hydroxyl-terminated PBS.

[0013] Hydroxyl-terminated PBS and lactide monomers were mixed and subjected to bulk polymerization to obtain a triblock compatibilizer.

[0014] The lactide monomer is racemic 3,6-dimethyl-1,4-dioxane-2,5-dione, CAS: 95-96-5.

[0015] Nanocellulose was acetylated to obtain a dispersion enhancer.

[0016] Among them, the average molecular weight of nanocellulose is 10,000, the average aspect ratio is 100-200, and the average diameter is 10-20 nm.

[0017] PLA resin particles are dried and then melt-blended with a dispersing reinforcing agent to obtain a reinforcing masterbatch.

[0018] The average molecular weight of the PLA resin particles is 65,000.

[0019] Modified PBAT, reinforcing masterbatch, and triblock compatibilizer were reactively blended to obtain a composite resin precursor.

[0020] The composite resin precursor was vacuum dried at 60°C and 1 mbar for 12 hours to obtain a biodegradable plastic.

[0021] Preferably, the melt grafting process is as follows: 100 parts of PBAT resin particles are preheated at 80-85°C for 4 hours, then mixed with 2-4 parts of glycidyl methacrylate and 0.2-0.5 parts of dicumyl peroxide, fed into an extruder at 140-150°C, with the screw speed maintained at 150-200 rpm, treated at 170°C for 10 minutes, heated to 190°C for 20 minutes, and extruded at 180°C to obtain modified PBAT.

[0022] Preferably, the transesterification polycondensation process is as follows: dimethyl succinate and 1,4-butanediol are mixed in a molar ratio of 1:1.1-1.3, tetrabutyl titanate and triphenyl phosphite are added, the temperature is raised to 160-190°C under nitrogen protection, the reaction is continued for 3 hours, the temperature is raised to 220°C at a rate of 5°C / min, the pressure of the reaction system is reduced to 1 mbar, and the reaction is continued for 5 hours to obtain hydroxyl-terminated PBS.

[0023] The amount of tetrabutyl titanate added is 0.02 wt% of the total mass of dimethyl succinate and 1,4-butanediol, and the amount of triphenyl phosphite added is 0.6 wt% of the total mass of dimethyl succinate and 1,4-butanediol.

[0024] Preferably, the bulk polymerization process is as follows: hydroxyl-terminated PBS and lactide monomer are mixed at a molar ratio of 1:100-170, and then a toluene solution of stannous octoate is added. After reacting at 130-160°C for 8 hours, the reaction solution is cooled and recrystallized with methanol to obtain a triblock compatibilizer.

[0025] The mass concentration of the toluene solution of stannous octoate is 2.5 wt%, and its addition amount is 0.5 wt% of the mass of lactide.

[0026] Preferably, the acetylation modification process is as follows: 0.5-1 parts of nanocellulose are dispersed in 80 parts of glacial acetic acid, and after stirring and reacting at 50°C, 120-160 parts of acetic anhydride and 0.01 parts of iodine are added, and after stirring and reacting at 80-100°C for 3 hours, the resulting precipitate is washed and dried to obtain the dispersion enhancer.

[0027] Preferably, the melt blending process is as follows: 100 parts of PLA resin particles are mixed with 5-18 parts of dispersing reinforcing agent, and extruded at 185°C with a screw speed of 200-400 rpm to obtain reinforcing masterbatch.

[0028] Preferably, the reactive blending process is as follows: modified PBAT and reinforcing masterbatch are fed at 160°C, mixed at 200°C, and a dispersing reinforcing agent is added. The screw speed is controlled at 220 rpm. After the reaction is completed, the mixture is extruded at 180°C to obtain a composite resin precursor. The mass ratio of modified PBAT, reinforcing masterbatch and triblock compatibilizer is 40:30-55:5-9.

[0029] A biodegradable plastic based on PBAT / PLA blend modification includes modified PBAT, reinforcing masterbatch, and dispersing agent.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. PBAT resin particles were modified by melt grafting, and the modified PBAT, reinforcing masterbatch and triblock compatibilizer were partially chemically bonded during the blending process through reactive blending. This constructed a synergistic system of chemical bonding and physical compatibility, resulting in PBAT / PLA blended composite materials with better compatibility, which improved the toughness and weather resistance of biodegradable plastic products.

[0032] 2. The acetylation modification process activates nanocellulose, significantly improving its compatibility with the hydrophobic polyester matrix. It is then melt-blended with PLA resin particles. Before the final reactive blending, the acetylated dispersing agent is dispersed in the PLA matrix, ensuring the full integration of the dispersing agent with the PLA matrix. During the reactive blending process, the compatibility with the PBAT phase is significantly improved, thereby enhancing the weather resistance of the biodegradable plastic products.

[0033] 3. Hydroxyl-terminated PBS was prepared by transesterification polycondensation, and PLA-b-PBS-b-PLA triblock copolymer was synthesized by bulk polymerization with lactide monomer. As a triblock compatibilizer, it fully combined the PBAT phase and PLA phase during reactive mixing, which significantly improved the strength of biodegradable plastic products.

[0034] 4. By adjusting the composition of the triblock compatibilizer and performing melt grafting treatment on PBAT, the fully combined PBAT / PLA mixed phase is ensured to still possess good biodegradability. Simultaneously, the added triblock compatibilizer and reinforcing masterbatch are both biodegradable. The various components synergistically improve the strength and weather resistance of the biodegradable plastic product without introducing non-biodegradable segments, thus giving the biodegradable plastic product excellent biodegradability. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of biodegradable plastics in this invention. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below through some embodiments and experimental examples. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Reference Figure 1 The process flow diagram shown illustrates that this invention provides a PBAT / PLA composite biodegradable plastic and its preparation process. The technical solution is as follows:

[0038] Example 1

[0039] After preheating 100 parts of PBAT resin granules at 80-85℃ for 4 hours, they were mixed with 2 parts of glycidyl methacrylate and 0.2 parts of dicumyl peroxide. The mixture was fed into an extruder at 140℃, with the screw speed maintained at 150 rpm. The mixture was then treated at 170℃ for 10 minutes, heated to 190℃ for 20 minutes, and extruded at 180℃ to obtain modified PBAT.

[0040] Dimethyl succinate and 1,4-butanediol were mixed in a molar ratio of 1:1.1, and tetrabutyl titanate and triphenyl phosphite were added. The mixture was heated to 160°C under nitrogen protection and reacted for 3 hours. Then, the temperature was increased to 220°C at a rate of 5°C / min, and the pressure of the reaction system was reduced to 1 mbar. After reacting for 5 hours, hydroxyl-terminated PBS was obtained.

[0041] The amount of tetrabutyl titanate added is 0.02 wt% of the total mass of dimethyl succinate and 1,4-butanediol, and the amount of triphenyl phosphite added is 0.6 wt% of the total mass of dimethyl succinate and 1,4-butanediol.

[0042] Hydroxyl-terminated PBS and lactide monomer were mixed at a molar ratio of 1:100, and a toluene solution of stannous octoate was added. After reacting at 130°C for 8 hours, the reaction solution was cooled and recrystallized with methanol to obtain a triblock compatibilizer.

[0043] The mass concentration of the toluene solution of stannous octoate is 2.5 wt%, and its addition amount is 0.5 wt% of the mass of lactide.

[0044] 0.5 parts of nanocellulose were dispersed in 80 parts of glacial acetic acid. After stirring and reacting at 50°C, 120 parts of acetic anhydride and 0.01 parts of iodine were added. After stirring and reacting at 80°C for 3 hours, the resulting precipitate was washed and dried to obtain the dispersion enhancer.

[0045] 100 parts of PLA resin granules were mixed with 5 parts of dispersing reinforcing agent and extruded at 185°C and a screw speed of 200 rpm to obtain reinforcing masterbatch.

[0046] Modified PBAT and reinforcing masterbatch were fed at 160°C, mixed at 200°C, and a dispersing reinforcing agent was added. The screw speed was controlled at 220 rpm. After the reaction was completed, the mixture was extruded at 180°C to obtain a composite resin precursor. The mass ratio of modified PBAT, reinforcing masterbatch, and triblock compatibilizer was 40:30:5.

[0047] The composite resin precursor was vacuum dried at 60°C and 1 mbar for 12 hours to obtain a biodegradable plastic.

[0048] Examples 2-20 differ from Example 1 in operating parameters, but are identical in process steps. The relevant changes in operating parameters are summarized in Tables 1, 2, and 3.

[0049] Table 1. Changes in operating parameters for Examples 1-20 (Part 1)

[0050]

[0051]

[0052] Table 2. Changes in operating parameters for Examples 1-20 (II)

[0053]

[0054]

[0055] Table 3. Changes in operating parameters for Examples 1-20 (Part 3)

[0056]

[0057] Comparative Example 1

[0058] Unlike Example 1, no melt grafting process was performed, but all other process parameters remained the same.

[0059] Comparative Example 2

[0060] Unlike Example 1, no triblock compatibilizer was added, but all other process parameters were the same.

[0061] Comparative Example 3

[0062] Unlike Example 1, a blend of PBS and PLA was used instead of a triblock compatibilizer, wherein the molar ratio of PBS to PLA was 1:100, the average molecular weight of PBS was 35,000, the average molecular weight of PLA was 65,000, and other process parameters were the same.

[0063] Comparative Example 4

[0064] Unlike Example 6, no acetylation modification was performed, but all other process parameters remained the same.

[0065] Comparative Example 5

[0066] Unlike Example 6, the dispersant reinforcement was directly blended with other components during reactive blending, without the melt blending step to prepare the reinforced masterbatch. All other process parameters were the same.

[0067] Comparative Example 6

[0068] Unlike Example 11, no transesterification polycondensation was performed. Instead, PBS with an average molecular weight of 35,000 was used to replace hydroxyl-terminated PBS in the bulk polymerization process. All other process parameters were the same.

[0069] Comparative Example 7

[0070] Unlike Example 11, no bulk polymerization was performed. PLA with an average molecular weight of 65,000 was blended with hydroxyl-terminated PBS, and all other process parameters were the same.

[0071] Comparative Example 8

[0072] Unlike Example 11, epoxidized linseed oil was used instead of the triblock compatibilizer, while all other process parameters remained the same.

[0073] Comparative Example 9

[0074] Unlike Example 16, an equal amount of talc powder was used instead of acetylated nanocellulose, while all other process parameters remained the same.

[0075] Comparative Example 10

[0076] Unlike Example 16, no reinforcing masterbatch was added, but all other process parameters remained the same.

[0077] Experimental Example 1

[0078] The toughness and weather resistance of the biodegradable plastic products prepared in Examples 1-5 and Comparative Examples 1-3 were tested, and the relevant results are summarized in Table 4.

[0079] The toughness test method is as follows: use a 0.5mm×100mm×20mm specimen to perform tensile property test along the long axis, and record its maximum breaking strength (N / m) and elongation at break (%).

[0080] The weather resistance test method is as follows: record the initial toughness data of the specimen, using 0.55 W / m 2 The sample was irradiated with 340nm ultraviolet light at 40℃ for 100 hours. The retention rate (%) of its maximum breaking strength and elongation at break was then tested. The higher the retention rate, the better the weather resistance.

[0081] Table 4. Toughness and weather resistance of the biodegradable plastic products prepared in Examples 1-5 and Comparative Examples 1-3

[0082]

[0083] As shown in Table 4, the biodegradable plastic products prepared in Examples 1-5 exhibit good toughness and good toughness retention after UV treatment, along with excellent weather resistance. Comparative Example 1, without melt grafting treatment, showed a significant decrease in toughness but a negligible decrease in weather resistance, indicating that melt grafting modification is crucial for improving material toughness and provides a foundation for subsequent chemical bonding. Comparative Example 2, without the addition of a triblock compatibilizer, showed a significant decrease in toughness and a marked loss in weather resistance, indicating that the triblock compatibilizer effectively improved the compatibility of PBAT / PLA, significantly enhancing both the material's toughness and weather resistance. Comparative Example 3, using a blend of PBS and PLA instead of the triblock compatibilizer, showed a significant decrease in toughness, but little impact on weather resistance, indicating that the pre-synthesized PLA-b-PBS-b-PLA triblock compatibilizer with a specific structure is far superior to simple physical blends in improving compatibility and performance.

[0084] In summary, this invention utilizes the reaction sites provided by modified PBAT, the bridging effect of the triblock compatibilizer, and the reactive blending process conditions to form a synergistic system of chemical bonding and physical compatibility. This strengthens interfacial bonding and exhibits significant advantages in toughness and weather resistance. This strongly demonstrates the effectiveness of melt-grafted modified PBAT, the addition of PLA-b-PBS-b-PLA triblock compatibilizer, and the construction of a synergistic system of chemical bonding and physical compatibility through reactive blending, thereby improving the toughness and weather resistance of biodegradable plastic products.

[0085] Experiment Example 2

[0086] The weather resistance and acid resistance of the biodegradable plastic products prepared in Examples 6-10 and Comparative Examples 4-5 were tested, and the relevant results are summarized in Table 5.

[0087] The weather resistance test method is the same as in Experiment Example 1. The acid resistance test method is as follows: record the initial toughness data of the sample, soak it in 10wt% hydrochloric acid for 7 days, and record the retention rate (%) of its maximum breaking strength and elongation at break. The higher the retention rate, the better the acid resistance.

[0088] Table 5. Weather resistance and acid resistance of the biodegradable plastic products prepared in Examples 6-10 and Comparative Examples 4-5

[0089]

[0090] As shown in Table 5, the biodegradable plastic products prepared in Examples 6-10 exhibited good performance in terms of weather resistance and acid resistance. Comparative Example 4, which did not undergo acetylation modification of the nanocellulose, showed a decrease in both UV aging resistance and acid resistance. This indicates that acetylation effectively reduced the hydrophilicity of the nanocellulose, enhanced its interfacial compatibility with the hydrophobic PLA matrix, and thus improved the composite material's resistance to environmental aging. Comparative Example 5, which did not involve melt blending to prepare the reinforcing masterbatch, directly added the dispersing reinforcing agent to the reactive blend. This resulted in a slight decrease in weather resistance, and the acid resistance showed a similar trend. This suggests that pre-dispersing the acetylated nanocellulose in PLA through melt blending to prepare the masterbatch helps overcome the agglomeration problem of nanocellulose, achieving more uniform dispersion in the PLA matrix, thereby more effectively exerting its reinforcing and stabilizing effects and further improving the material's weather resistance.

[0091] In summary, acetylation improves the intrinsic compatibility between nanocellulose and PLA, while the masterbatch preparation step optimizes their physical dispersion. The combination of these two factors ensures that the activated reinforcing agent is fully and uniformly incorporated into the PLA matrix. This not only stabilizes the PLA phase, but also allows this well-dispersed and compatible PLA-nanocellulose composite phase to better interact with PBAT in the final reactive blend, forming a more stable overall structure and thus maximizing the product's weather resistance.

[0092] Experimental Example 3

[0093] The mechanical strength of the biodegradable plastic products prepared in Examples 11-15 and Comparative Examples 6-8 was tested, and the relevant results are summarized in Table 6.

[0094] Mechanical strength includes toughness and puncture resistance. The test method for toughness is the same as in Experiment Example 1. The test method for puncture resistance is as follows: Prepare a 0.5mm×100mm×100mm sample, use a hemispherical probe with a diameter of 3.2mm to press down at a speed of 25mm / min, and record the peak puncture force (N). The larger the peak puncture force, the better the puncture resistance of the sample.

[0095] Table 6 Mechanical strength of the biodegradable plastic products prepared in Examples 11-15 and Comparative Examples 6-8

[0096]

[0097] As shown in Table 6, the biodegradable plastic products prepared in Examples 11-15 have similar toughness to those in Examples 1-10 and good puncture resistance, making them suitable as base materials for products such as packaging bags, straws, and tableware. Comparative Example 6 directly used ordinary PBS instead of the hydroxyl-terminated PBS prepared through transesterification polymerization in subsequent bulk polymerization. Its mechanical strength was lower than that of the product prepared in Example 11, indicating that precisely controlled synthesis of hydroxyl-terminated PBS through transesterification polymerization is fundamental to the successful preparation of triblock copolymers with excellent compatibility and is crucial for improving the final material strength. Comparative Example 7 did not undergo bulk polymerization treatment; it only blended PLA with hydroxyl-terminated PBS. Toughness decreased significantly, but puncture resistance decreased less. This demonstrates that bulk polymerization is necessary to link the hydroxyl-terminated PBS with lactide monomers to form a specific PLA-b-PBS-b-PLA block structure, which effectively bridges the PBAT and PLA phases. Physical blending cannot achieve the same compatibility and strength improvement. Comparative Example 8 used epoxidized linseed oil instead of the triblock compatibilizer synthesized in this invention. The toughness decreased less, but the puncture resistance decreased significantly. This indicates that the PLA-b-PBS-b-PLA triblock copolymer synthesized by the specific method in this invention can more effectively improve the compatibility of the PBAT / PLA system and significantly improve the tensile strength and puncture resistance of the material compared with epoxidized linseed oil.

[0098] In summary, this invention prepares hydroxyl-terminated PBS through transesterification polycondensation, and then performs bulk polymerization to generate PLA-b-PBS-b-PLA triblock copolymer as a compatibilizer, which can effectively combine the PBAT and PLA phases and significantly improve the toughness and puncture resistance of biodegradable plastic products.

[0099] Experiment Example 4

[0100] The biodegradability and weather resistance of the biodegradable plastic products prepared in Examples 16-20 and Comparative Examples 9-10 were tested, and the relevant results are summarized in Table 7.

[0101] The weather resistance test method is the same as in Experiment Example 1. The biodegradability test method is as follows: the sample is made into fragments with a particle size of less than 2 mm, and buried in humus soil at a temperature of 25°C. After 30 days of treatment, the mass of the residual sample is measured, and the biodegradability rate (%) of the sample in 30 days is calculated. The higher the biodegradability rate, the better the biodegradability.

[0102] The humus soil used has a pH range of 6.0-7.0, an organic matter content of 55%, and a natural moisture content of 25%.

[0103] Table 7. Degradability and weather resistance of the biodegradable plastic products prepared in Examples 16-20 and Comparative Examples 9-10

[0104]

[0105] As shown in Table 7, the biodegradable plastic products prepared in Examples 16-20 exhibit good biodegradability and weather resistance. The 25°C humus environment is not a specialized composting environment and has a poor decomposition effect on biodegradable materials; however, Examples 16-20 still decomposed more than 20% within 30 days, demonstrating excellent biodegradability. Comparative Example 9, using an equal amount of non-biodegradable talc to replace biodegradable acetylated nanocellulose as a reinforcing filler, showed a certain degree of decrease in weather resistance and a significant reduction in biodegradation rate, directly proving that introducing non-biodegradable segments significantly reduces the overall biodegradability of the material. Comparative Example 10, without the addition of reinforcing masterbatch, showed a slight decrease in weather resistance and a slight decrease in biodegradation rate, indicating that the biodegradable reinforcing masterbatch added in this invention not only synergistically improves the weather resistance of the material but also, due to its own biodegradability and influence on the matrix morphology, is not sacrificed; on the contrary, it helps maintain the overall biodegradation rate of the material.

[0106] In summary, by selecting and synergistically regulating each component, this invention successfully improves the strength and weather resistance of the material while avoiding the introduction of non-degradable components, thus ensuring the excellent overall degradability of the composite material.

[0107] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of PBAT / PLA composite degradable plastic, characterized by: The preparation process is as follows, based on parts by weight: PBAT resin particles are preheated and then subjected to melt grafting treatment to obtain modified PBAT. The melt grafting treatment process is as follows: 100 parts of the PBAT resin particles are preheated at 80-85°C for 4 hours, then mixed with 2-4 parts of glycidyl methacrylate and 0.2-0.5 parts of dicumyl peroxide, fed into an extruder at 140-150°C, with the screw speed maintained at 150-200 rpm, treated at 170°C for 10 minutes, heated to 190°C for 20 minutes, and extruded at 180°C to obtain the modified PBAT. Dimethyl succinate and 1,4-butanediol were mixed at a molar ratio of 1:1.1-1.3 and subjected to transesterification polycondensation to obtain hydroxyl-terminated PBS. The transesterification polycondensation process was as follows: the dimethyl succinate and 1,4-butanediol were mixed, tetrabutyl titanate and triphenyl phosphite were added, the mixture was heated to 160-190°C under nitrogen protection, and after continuous reaction, the temperature was increased to 220°C at a heating rate of 5°C / min, and the pressure of the reaction system was reduced to 1 mbar. After continuous reaction for 5 hours, the hydroxyl-terminated PBS was obtained. The hydroxyl-terminated PBS and lactide monomer were mixed and subjected to bulk polymerization to obtain a triblock compatibilizer. The bulk polymerization process was as follows: the hydroxyl-terminated PBS and lactide monomer were mixed at a molar ratio of 1:100-170, a toluene solution of stannous octoate was added, and the mixture was reacted at 130-160°C. After cooling the reaction solution, it was recrystallized with methanol to obtain the triblock compatibilizer. Nanocellulose is acetylated to obtain a dispersion enhancer. The acetylation modification process is as follows: 0.5-1 parts of the nanocellulose are dispersed in 80 parts of glacial acetic acid by mass, stirred and reacted, 120-160 parts of acetic anhydride and 0.01 parts of iodine are added, and stirred and reacted at 80-100℃. The resulting precipitate is washed and dried to obtain the dispersion enhancer. PLA resin particles are dried and then melt-blended with the dispersing reinforcing agent to obtain reinforcing masterbatch; The modified PBAT, the reinforcing masterbatch, and the triblock compatibilizer are reactively blended to obtain a composite resin precursor; The mass ratio of the modified PBAT, the reinforcing masterbatch, and the dispersing agent is 40:30-55:5-9. The biodegradable plastic is obtained by vacuum drying the composite resin precursor.

2. The preparation process of the PBAT / PLA composite degradable plastic according to claim 1, characterized in that: The melt blending process is as follows: 100 parts by mass of the PLA resin particles are mixed with 5-18 parts by mass of the dispersing reinforcing agent, and the mixture is extruded at 185°C with a screw speed of 200-400 rpm to obtain the reinforcing masterbatch.

3. The preparation process of the PBAT / PLA composite degradable plastic according to claim 1, characterized in that: The reactive blending process is as follows: the modified PBAT and the reinforcing masterbatch are fed and mixed, and the dispersing reinforcing agent is added. After the reaction is completed, the mixture is extruded at 180°C to obtain the composite resin precursor.

4. A degradable plastic based on PBAT / PLA blend modification, characterized in that: The biodegradable plastic is prepared by the preparation process described in any one of claims 1-3; The biodegradable plastic includes: modified PBAT, reinforcing masterbatch, and triblock compatibilizer.

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