Bio-based flame-retardant toughening agent as well as preparation method and application thereof

Abstract

The invention provides a bio-based flame-retardant toughening agent as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, preparing a bio-based intermediate AA from arginine and amino trimethylene phosphonic acid through an ionic reaction; then, AA and tannic acid react in a water phase, the hydroxyl content and the P / N ratio of a product are controlled by adjusting the mass ratio of AA to TA, and a flame retardant AT is prepared; and finally, blending AT and the epoxy modifier through a solvent to prepare the bio-based flame-retardant toughening agent. The prepared bio-based flame-retardant toughening agent integrates flame-retardant, toughening and reactive compatibilization functions and is introduced into a polylactic acid (PLA) matrix, dynamic vulcanization is achieved through molecular-level synergistic integration of a phenol structure, reactive compatibilization is achieved through an epoxy group, and the synergistic flame-retardant effect of P / N is achieved. In conclusion, the defects of flammability and intrinsic brittleness of the polylactic acid composite material are effectively overcome, the raw materials are green and renewable, and the polylactic acid composite material has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology of polymer materials, specifically relating to a bio-based flame retardant toughening agent and its preparation method and application. Background Technology

[0002] With increasing global emphasis on environmental protection and sustainable development, the impact of plastic pollution on the ecological environment has attracted widespread attention. Developing bio-based and biodegradable polymers has become an effective way to address this problem. Polylactic acid (PLA), as a typical bio-based biodegradable aliphatic polyester, has been widely used in pharmaceutical delivery, food packaging, and the textile industry due to its good biocompatibility. However, the inherent performance defects of PLA severely limit its further application in engineering fields: on the one hand, it is highly flammable, posing a significant fire safety hazard; on the other hand, PLA exhibits extremely high intrinsic brittleness, with an elongation at break typically below 10% and a notched impact strength of only about 3 kJ / m². Therefore, overcoming its flammability and brittleness while maintaining the environmentally friendly characteristics of PLA is of significant technical value for expanding the application range of PLA composite materials.

[0003] Existing flame-retardant and toughening modification technologies for polylactic acid (PLA) typically rely on single traditional flame retardants (such as ammonium polyphosphate, APP), lacking in-depth exploration of multifunctional and efficient synergistic systems. However, existing technologies have significant limitations in practical applications: while attempting to improve the flame retardancy and toughness of PLA, a significant decrease in the tensile strength of the material is often observed. This is primarily due to poor interfacial compatibility between the flame retardant, toughening phase, and PLA matrix, making it difficult to form a stable interfacial bond, thus leading to an imbalance in the mechanical properties of the composite material. Therefore, how to integrate flame-retardant and toughening functions into a synergistic system, while ensuring good compatibility with the PLA matrix, to achieve an improvement in the overall performance of the material, is a pressing technical challenge in this field. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a bio-based flame-retardant toughening agent, its preparation method, and its application. This preparation method is green and environmentally friendly, utilizing bio-based raw materials to construct a multifunctional additive integrating flame retardancy, toughening, and reactive compatibility. This invention also provides a high-strength, flame-retardant, and toughened polylactic acid composite material. By introducing a bio-based flame-retardant toughening agent, this material effectively solves the flammability and brittleness defects of polylactic acid while significantly improving the interfacial compatibility between the flame-retardant toughening agent and the matrix, overcoming the difficulty in simultaneously achieving toughness and flame retardancy in traditional modifications. The preparation method of this invention is simple in process and has mild reaction conditions, making it suitable for industrial production.

[0005] A method for preparing a bio-based flame retardant toughening agent includes the following steps:

[0006] (1) Add aminotrimethylenephosphonic acid to an aqueous solution of arginine, stir evenly to carry out the reaction, and then process to obtain bio-based flame retardant AA.

[0007] (2) Under stirring conditions, bio-based flame retardant AA reacts with tannic acid in water. After the reaction is completed, the flame retardant AT is obtained through post-treatment.

[0008] (3) Under stirring conditions, flame retardant AT and epoxy modifier are solution blended in solvent and then vacuum dried to obtain the bio-based flame retardant toughening agent.

[0009] In step (1) above:

[0010] In this step, arginine (Ar) and aminotrimethylenephosphonic acid (ATMP) undergo an ion exchange reaction in an aqueous phase to prepare a phosphorus-nitrogen type flame retardant. The aqueous solution of arginine is prepared by dissolving arginine in deionized water.

[0011] Preferably, the molar ratio of arginine to aminotrimethylenephosphonic acid is controlled at (1~6):(1~3). More preferably, it is 1:(0.5~3). Even more preferably, it is 1:1.

[0012] Preferably, the reaction temperature is 20~80 °C. More preferably, it is 30~60 °C. Even more preferably, it is 30~40 °C.

[0013] Preferably, the reaction time is 2 to 6 hours. More preferably, it is 2 to 4 hours. Even more preferably, it is 4 hours.

[0014] As a preferred option, the post-processing procedure is as follows:

[0015] The reaction solution is pre-frozen with liquid nitrogen and then freeze-dried to obtain the corresponding flame retardant.

[0016] Specifically:

[0017] The reaction solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 40-60 h to obtain the bio-based flame retardant AA.

[0018] As a further preferred option, the freeze-drying time is 48 h.

[0019] In step (2) above:

[0020] Preferably, the mass ratio of bio-based flame retardant AA to tannic acid (TA) is (0.5~6):(1~2). Further preferably, it is (0.25~4):1. Even more preferably, it is (0.5~4):1.

[0021] Preferably, the reaction temperature is 20~60 °C. More preferably, it is 20~50 °C. Even more preferably, it is 30~40 °C.

[0022] Preferably, the reaction time is 1 to 5 hours. More preferably, it is 1 to 4 hours.

[0023] As a preferred option, the post-processing procedure is as follows:

[0024] The reaction solution is pre-frozen with liquid nitrogen and then freeze-dried to obtain the corresponding flame retardant.

[0025] Specifically:

[0026] The reaction solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 40-60 h to obtain the bio-based flame retardant AA.

[0027] As a further preferred option, the freeze-drying time is 48 h.

[0028] In step (3) above:

[0029] Preferably, the solvent used for solution blending is selected from one or more of acetone, chloroform, dichloromethane, and toluene. More preferably, it is selected from one or more of acetone, chloroform, and dichloromethane. Even more preferably, it is acetone.

[0030] Preferably, the epoxy-modifying agent is selected from one or more of epoxidized soybean oil (ESO), triglycidyl isocyanurate (TGIC), styrene-glycidyl methacrylate (ADR), glycidyl methacrylate (GMA), and ethylene-methyl methacrylate-glycidyl methacrylate. More preferably, it is selected from one or more of epoxidized soybean oil (ESO), triglycidyl isocyanurate (TGIC), styrene-glycidyl methacrylate (ADR), and glycidyl methacrylate (GMA). Even more preferably, it is epoxidized soybean oil (ESO).

[0031] Preferably, the mass ratio of the flame retardant AT to the epoxy modifier is (1~4):(1~8). More preferably, it is 1:(0.5~3). Even more preferably, it is 1:1.

[0032] Preferably, the reaction temperature is 20~40 °C. More preferably, it is 20~30 °C. Even more preferably, it is 25 °C.

[0033] Preferably, the reaction time is 5 to 30 minutes. More preferably, it is 5 to 20 minutes. Even more preferably, it is 10 minutes.

[0034] Preferably, the vacuum drying temperature is 40~80 °C. More preferably, it is 40~60 °C. Even more preferably, it is 60 °C.

[0035] The present invention also provides a bio-based flame retardant toughening agent, which is prepared by any of the preparation methods described above.

[0036] The present invention also provides a high-strength, flame-retardant, and toughened polylactic acid composite material, which is prepared by melt blending polylactic acid (PLA) and the bio-based flame-retardant and toughening agent as described above.

[0037] Preferably, the high-strength, flame-retardant, and toughened polylactic acid composite material is prepared from the following components by mass percentage:

[0038] The amount of polylactic acid added is 85-99%;

[0039] The addition amount of bio-based flame retardant toughening agent is 1-15%;

[0040] Furthermore, the sum of the mass percentages of polylactic acid and bio-based flame retardant toughening agent is 100%.

[0041] As a preferred option, the high-strength, flame-retardant, and toughened polylactic acid composite material is prepared from 90% PLA and 10% bio-based flame-retardant and toughening agent by mass percentage.

[0042] Preferably, the melt blending time is 6 to 12 minutes. More preferably, it is 8 to 10 minutes. Even more preferably, it is 8 minutes.

[0043] Preferably, the melt blending temperature is 160~200 °C. More preferably, it is 170~190 °C. Even more preferably, it is 180 °C.

[0044] Preferably, the melt blending speed is 50-80 rpm. More preferably, it is 50-70 rpm. Even more preferably, it is 60 rpm.

[0045] The preparation method of the bio-based flame retardant and toughening agent of the present invention firstly prepares a bio-based intermediate AA by ionic reaction of arginine (Ar) and aminotrimethylenephosphonic acid (ATMP); then, AA is reacted with tannic acid (TA) in an aqueous phase, and the hydroxyl content and P / N ratio of the product are controlled by adjusting the mass ratio of AA to TA to obtain the flame retardant AT; finally, AT is solvent-blended with epoxidized soybean oil (ESO) to prepare the bio-based flame retardant and toughening agent. The bio-based flame retardant and toughening agent prepared by the present invention integrates flame retardant, toughening, and reactive compatibilization functions. When introduced into a polylactic acid (PLA) matrix, dynamic vulcanization is achieved through molecular-level synergistic integration of phenolic structures, reactive compatibilization is achieved using epoxy groups, and the synergistic flame retardant effect of P / N is exerted. In summary, the present invention effectively solves the defects of flammability and intrinsic brittleness of polylactic acid composite materials, and the raw materials are green and renewable, showing good application prospects.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) Unique molecular structure design achieves "multi-functionality": The preparation method of the bio-based flame retardant toughening agent of the present invention cleverly combines the rigid flame retardant skeleton AT with the flexible toughening segment epoxy modifier. The resulting bio-based flame retardant toughening agent, when applied to PLA, can effectively improve the mechanical and flame retardant properties of PLA. Among them, the introduced phenolic structure (tannic acid) can achieve molecular-level synergistic integration, promote the dynamic vulcanization process, and significantly dissipate energy during tensile and impact processes; the epoxy modifier provides excellent plasticizing and toughening effects; and the bio-based flame retardant AT provides excellent flame retardant effects.

[0048] (2) Excellent interfacial compatibility and reactive compatibilization: In the preparation method of the bio-based flame retardant toughening agent of the present invention, the reaction conditions are mild and the time is short, and the epoxy groups are not consumed by the hydroxyl groups, thus retaining sufficient epoxy groups. During the processing, the epoxy groups can undergo ring-opening reactions with the terminal hydroxyl and carboxyl groups of PLA, which significantly enhances the interfacial bonding force between the filler and the PLA matrix, thereby improving toughness while maintaining high tensile strength.

[0049] (3) Green and sustainable: In the preparation method of the bio-based flame retardant toughening agent of the present invention, the raw materials selected are mainly derived from renewable biomass resources, and the preparation process is mainly carried out in aqueous phase or low-toxicity solvent, which meets the requirements of green chemistry and sustainable development.

[0050] (4) The bio-based flame retardant toughening agent of the present invention is used to prepare PLA composite materials that have a balance of tensile stress, toughness and flame retardant properties, and has broad application prospects in industrial films, food packaging and other fields. The PLA composite material with added bio-based flame retardant toughening agent exhibits a synergistic flame retardant effect between the gas phase and the condensed phase during combustion, and this synergistic flame retardant effect endows the PLA composite material with excellent flame retardant properties. Attached Figure Description

[0051] Figure 1 SEM image of the PLA / 4AT-ESO composite material prepared in Example 1 of this invention;

[0052] Figure 2 The image shows a SEM image of the PLA / 2AT-ESO composite material prepared in Example 2 of this invention.

[0053] Figure 3 SEM image of the PLA / 1AT-ESO composite material prepared in Example 3 of this invention;

[0054] Figure 4 SEM image of the PLA / 0.5AT-ESO composite material prepared in Example 4 of this invention. Detailed Implementation

[0055] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0056] In the following embodiments and application examples:

[0057] Polylactic acid was purchased from Natureworks, USA, model number 4032D.

[0058] Arginine (Ar), aminotrimethylenephosphonic acid (ATMP), tannic acid (TA), and epoxidized soybean oil (ESO) were all purchased from Maclean's Reagent Co., Ltd.

[0059] Limiting Oxygen Index (LOI): Measured according to ASTM D2863 standard using a JF-3 oxygen index meter (Jiangning Analytical Instruments Co., Ltd., China), with dimensions of 100 × 6.5 × 3 mm. 3 Rectangular sheet material.

[0060] Vertical burning test: Conducted according to ASTM D3801 standard on a CZF-6 vertical burning tester (Jiangning Analytical Instruments Co., Ltd., China). The sample sheet size was 100×13×3 mm. 3 .

[0061] Tensile test: Perform tensile tests at a speed of 10 mm / min according to ISO527-2 / 5A standard. Each sample shall be tested at least 5 times and the average value shall be taken.

[0062] In the following embodiments and application examples:

[0063] Example 1

[0064] Preparation process of bio-based flame retardant toughening agent 4AT-ESO:

[0065] (1) Arginine and aminotrimethylenephosphonic acid were added to deionized water at a molar ratio of 1:1 and stirred at 30 °C for 4 h to obtain a solution. The obtained solution was then poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant AA.

[0066] (2) Tannic acid powder was added to deionized water and stirred until the powder dissolved to obtain a tannic acid solution. Then, flame retardant AA was added to the tannic acid solution and stirred at 35 °C for 4 h. The mass ratio of flame retardant AA to tannic acid was 4:1. After the reaction was completed, the solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant 4AT.

[0067] (3) The specific steps for preparing the bio-based flame retardant toughening agent 4AT-ESO are as follows: Flame retardant 4AT and epoxidized soybean oil are added to acetone in a mass ratio of 1:1 and mixed and stirred. The stirring time is 10 min and the temperature is 25℃. Finally, the stirred solution is placed in a vacuum oven for drying at a temperature of 60℃ to obtain the bio-based flame retardant toughening agent 4AT-ESO.

[0068] Example 2

[0069] Preparation process of bio-based flame retardant toughening agent 2AT-ESO:

[0070] (1) Arginine and aminotrimethylenephosphonic acid were added to deionized water at a molar ratio of 1:1 and stirred at 30 °C for 4 h to obtain a solution. The obtained solution was then poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant AA.

[0071] (2) Tannic acid powder was added to deionized water and stirred until the powder dissolved to obtain a tannic acid solution. Then, flame retardant AA was added to the tannic acid solution and stirred at 35 °C for 4 h. The mass ratio of flame retardant AA to tannic acid was 2:1. After the reaction was completed, the solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant 2AT.

[0072] (3) The specific steps for preparing the bio-based flame retardant toughening agent 2AT-ESO are as follows: Flame retardant 4AT and epoxidized soybean oil are added to acetone in a mass ratio of 1:1 and mixed and stirred. The stirring time is 10 min and the temperature is 25℃. Finally, the stirred solution is placed in a vacuum oven for drying at a temperature of 60℃ to obtain the bio-based flame retardant toughening agent 2AT-ESO.

[0073] Example 3

[0074] Preparation process of bio-based flame retardant toughening agent 1AT-ESO:

[0075] (1) Arginine and aminotrimethylenephosphonic acid were added to deionized water at a molar ratio of 1:1 and stirred at 30 °C for 4 h to obtain a solution. The obtained solution was then poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant AA.

[0076] (2) Tannic acid powder was added to deionized water and stirred until the powder dissolved to obtain a tannic acid solution. Then, flame retardant AA was added to the tannic acid solution and stirred at 35 °C for 4 h. The mass ratio of flame retardant AA to tannic acid was 1:1. After the reaction was completed, the solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant 1AT.

[0077] (3) The specific steps for preparing the bio-based flame retardant toughening agent 1AT-ESO are as follows: Flame retardant 4AT and epoxidized soybean oil are added to acetone in a mass ratio of 1:1 and mixed and stirred. The stirring time is 10 min and the temperature is 25℃. Finally, the stirred solution is placed in a vacuum oven for drying at a temperature of 60℃ to obtain the bio-based flame retardant toughening agent 1AT-ESO.

[0078] Example 4

[0079] Preparation process of bio-based flame retardant toughening agent 0.5AT-ESO:

[0080] (1) Arginine and aminotrimethylenephosphonic acid were added to deionized water at a molar ratio of 1:1 and stirred at 30 °C for 4 h to obtain a solution. The obtained solution was then poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant AA.

[0081] (2) Tannic acid powder was added to deionized water and stirred until the powder dissolved to obtain a tannic acid solution. Then, flame retardant AA was added to the tannic acid solution and stirred at 35 °C for 4 h. The mass ratio of flame retardant AA to tannic acid was 0.5:1. After the reaction was completed, the solution was poured into a polytetrafluoroethylene petri dish, pre-frozen with liquid nitrogen, and then freeze-dried for 48 h to obtain flame retardant 0.5AT.

[0082] (3) The specific steps for preparing the bio-based flame retardant toughening agent 1AT-ESO are as follows: Flame retardant 4AT and epoxidized soybean oil are added to acetone in a mass ratio of 1:1 and mixed and stirred. The stirring time is 10 min and the temperature is 25℃. Finally, the stirred solution is placed in a vacuum oven for drying at a temperature of 60℃ to obtain the bio-based flame retardant toughening agent 0.5AT-ESO.

[0083] Application Example 1

[0084] After the dried PLA (90g) and the bio-based flame retardant toughening agent 4AT-ESO (10g) prepared in Example 1 were mixed evenly, they were simultaneously added to a mixer and mixed at 180 ℃ and 60 rpm for 8 min to obtain PLA / 4AT-ESO composite material, which was designated as blend #1.

[0085] Test specimens were prepared by compression molding at 180 °C and 10 MPa using a hot press, and were designated as specimen #1.

[0086] Application Example 2

[0087] After the dried PLA (90g) and the bio-based flame retardant toughening agent 2AT-ESO (10g) prepared in Example 2 were mixed evenly, they were simultaneously added to a mixer and mixed at 180 ℃ and 60 rpm for 8 min to obtain PLA / 2AT-ESO composite material, which was designated as blend #2.

[0088] Test specimens were prepared by compression molding at 180 °C and 10 MPa using a hot press, and were designated as specimen #2.

[0089] Application Example 3

[0090] After the dried PLA (90g) and the bio-based flame retardant toughening agent 1AT-ESO (10g) prepared in Example 3 were mixed evenly, they were simultaneously added to a mixer and mixed at 180 ℃ and 60 rpm for 8 min to obtain the PLA / 1AT-ESO composite material, which was designated as blend #3.

[0091] Test specimens were prepared by compression molding at 180 °C and 10 MPa using a hot press, and were designated as specimen #3.

[0092] Application Example 4

[0093] The dried PLA (90g) and the bio-based flame retardant toughening agent 0.5AT-ESO (10g) prepared in Example 1 were mixed evenly and then added to a mixer. The mixture was then mixed at 180 °C and 60 rpm for 8 min to obtain the PLA / 0.5AT-ESO composite material, which was designated as blend #4.

[0094] Test specimens were prepared by compression molding at 180 °C and 10 MPa using a hot press, and were designated as specimen #4.

[0095] Comparative Example

[0096] Add 100g of dried PLA to a mixer and mix at 180 ℃ and 60 rpm for 8 min to obtain pure PLA material, which is designated as blend #5.

[0097] Test specimens were prepared by compression molding at 180 °C and 10 MPa using a hot press, and were designated as specimen #5.

[0098] Product characteristics:

[0099] SEM images of the PLA / AT-ESO composite materials prepared in Examples 1-4 are shown below. Figures 1-4 .Depend on Figures 1-4 It can be seen that after introducing the bio-based flame retardant toughening agent, the low-temperature fracture surface of the PLA composite material exhibits significant differences in phase morphology and interfacial adhesion characteristics. With increasing TA content, the phase region size of AT-ESO initially decreases and then increases, while interfacial adhesion shows a phenomenon of first strengthening and then weakening. When the bio-based flame retardant toughening agents prepared in Examples 1-3 are applied to PLA composite materials, the PLA composite materials exhibit good interfacial compatibility. However, when the bio-based flame retardant prepared in Example 4 is applied to PLA composite materials, the phase morphology and interfacial adhesion of the PLA composite materials deteriorate. This indicates that the interfacial compatibility of the PLA composite materials prepared in Examples 1-3 is relatively ideal, and the interfacial adhesion between the filler and the matrix is ​​strong.

[0100] Performance testing:

[0101] Mechanical properties, limiting oxygen index, and vertical burning tests were conducted on polylactic acid composite materials (test specimens) obtained in accordance with test cases 1-4 and comparative examples of ISO527-2 / 5A, ASTM D2863, and ASTM D3801 standards. The results are shown in Table 1.

[0102] Table 1. Performance test results of polylactic acid composite materials prepared in Application Examples 1-4 and Comparative Examples

[0103]

[0104] As shown in Table 1, compared to sample #5, samples #1 through #4 exhibited varying degrees of increased tensile strain while maintaining a certain level of tensile strength. However, the increase in sample #4 was not significant. This indicates that the bio-based flame retardant toughening agent undergoes both crosslinking and interfacial grafting reactions during melt blending, improving the interfacial compatibility of the blend. However, the excessively high tannic acid content in Example #4, when applied to PLA composites, promotes excessive crosslinking of ESO, consuming too many epoxy groups and reducing interfacial grafting efficiency. Regarding flame retardant performance testing, compared to sample #5, samples #1 through #4 showed improvements in both limiting oxygen index and UL-94 rating, indicating that the introduction of the bio-based flame retardant toughening agent improved the flame retardant performance of the blend. Since sample #1 had the highest content of the bio-based flame retardant AA, it exhibited the best flame retardant performance, with a limiting oxygen index of 26.6% and passing the UL-94 V-0 rating. Simultaneously, due to the improved interfacial compatibility, sample #1 maintained excellent levels of tensile strength and tensile strain. Therefore, spline #1 is the optimal high-strength, flame-retardant, and toughened PLA composite material.

[0105] In summary, the bio-based flame retardant toughening agent, its preparation method, and its application of the present invention achieve an ideal balance between tensile strength and toughness while maintaining excellent flame retardant properties.

Claims

1. A method for preparing a bio-based flame retardant and toughening agent, characterized in that, Includes the following steps: (1) Add aminotrimethylenephosphonic acid to an aqueous solution of arginine, stir evenly to carry out the reaction, and then process to obtain bio-based flame retardant AA. (2) Under stirring conditions, bio-based flame retardant AA reacts with tannic acid in water. After the reaction is completed, the flame retardant AT is obtained through post-treatment. (3) Under stirring conditions, flame retardant AT and epoxy modifier are solution blended in solvent and then vacuum dried to obtain the bio-based flame retardant toughening agent.

2. The method for preparing the bio-based flame retardant and toughening agent according to claim 1, characterized in that, In step (1), the molar ratio of arginine to aminotrimethylenephosphonic acid is controlled at (1~6):(1~3). The reaction temperature is 20~80 ℃, and the reaction time is 2~6 h.

3. The method for preparing the bio-based flame retardant and toughening agent according to claim 1, characterized in that, In step (2), the mass ratio of bio-based flame retardant AA to tannic acid is (0.5~6):(1~2); The reaction temperature is 20~60 ℃, and the reaction time is 1~5 h.

4. The method for preparing the bio-based flame retardant and toughening agent according to claim 1, characterized in that, In step (3), the solvent used for solution blending is selected from one or more of acetone, chloroform, dichloromethane, and toluene; The epoxy modifier is selected from one or more of epoxidized soybean oil, triglycidyl isocyanurate, styrene-glycidyl methacrylate, glycidyl methacrylate, and ethylene-methyl methacrylate-glycidyl methacrylate.

5. The method for preparing the bio-based flame retardant and toughening agent according to claim 1, characterized in that, In step (3), the mass ratio of the flame retardant AT to the epoxy modifier is (1~4):(1~8). The reaction temperature is 20~40 ℃, and the reaction time is 5~30 min.

6. The method for preparing the bio-based flame retardant toughening agent according to claim 1, characterized in that, In steps (1) and (2), the post-processing is the same, as follows: The reaction solution is pre-frozen with liquid nitrogen and then freeze-dried to obtain the corresponding flame retardant.

7. A bio-based flame retardant and toughening agent, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

8. A high-strength, flame-retardant, toughened polylactic acid composite material, characterized in that, The composite material is prepared by melt blending polylactic acid and the bio-based flame retardant toughening agent described in claim 7.

9. The high-strength, flame-retardant, toughened polylactic acid composite material according to claim 8, characterized in that, It is prepared from the following components by mass percentage: The amount of polylactic acid added is 85-99%; The addition amount of bio-based flame retardant toughening agent is 1-15%; Furthermore, the sum of the mass percentages of polylactic acid and bio-based flame retardant toughening agent is 100%.

10. The high-strength, flame-retardant, toughened polylactic acid composite material according to claim 8, characterized in that, The melt blending time is 6~12 min, the melt blending temperature is 160~200 ℃, and the melt blending speed is 50~80 rpm.

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