A biodegradable material, its preparation method and its application

Abstract

This invention relates to the field of polymer degradable materials technology, specifically to a biodegradable material, its preparation method, and its applications. The material is based on modified polylactic acid (PLA), supplemented by antioxidants, plasticizers, flame retardants, and inorganic fillers in specific weight proportions. Its unique feature lies in the polymerization of lactic acid and epicatechin imidazole ammonium chloride polymer under stannous octoate catalysis, using chemical bonding to introduce the bioactive groups of epicatechin into the PLA backbone, significantly improving the material's biodegradation rate, mechanical properties, and thermal stability. The bioactive substances and ionic groups in this material promote microbial degradation, achieving complete decomposition in a composting environment within a short time. Simultaneously, through molecular-level reinforcement and ionic cross-linking effects, the strength, toughness, and high-temperature processing performance of PLA are effectively improved. This material can be widely used in disposable tableware, food packaging films, and biodegradable agricultural mulch films.

Description

Technical Field

[0001] This invention relates to the field of polymer degradable materials technology, and in particular to a biodegradable material, its preparation method, and its application. Background Technology

[0002] With the increasing global awareness of environmental protection and the in-depth implementation of sustainable development strategies, biodegradable materials have become an important development direction to replace traditional petroleum-based plastics. Among many biodegradable polymers, polylactic acid (PLA), a thermoplastic polymer derived from renewable resources, is considered one of the most promising green materials due to its good biocompatibility, complete biodegradability, and relatively mature industrial production technology.

[0003] Polylactic acid (PLA) can be produced through the polymerization of lactic acid, which can be extracted from crops such as corn, sugarcane, and cassava, offering the advantages of a wide range of renewable raw material sources. Under suitable composting conditions, PLA can be completely decomposed by microorganisms into carbon dioxide and water, without causing persistent environmental pollution, aligning with the development concept of a circular economy. These properties give PLA enormous application potential in packaging materials, disposable tableware, agricultural films, and medical materials.

[0004] However, despite its numerous advantages, polylactic acid (PLA) still faces a series of technical challenges in practical applications. First, PLA's biodegradation rate is relatively slow, often requiring a considerable amount of time to fully degrade under natural environmental conditions. This limits its use in applications with strict degradation time requirements. Second, pure PLA materials have relatively poor mechanical properties, particularly low impact strength and elongation at break, making it difficult to meet the demands of applications requiring high mechanical performance. Furthermore, PLA suffers from insufficient thermal stability, easily undergoing thermal degradation during high-temperature processing, leading to a decrease in molecular weight and performance deterioration, thus complicating material processing and molding.

[0005] To overcome these technical challenges, researchers have explored various modification strategies. Physical modification methods, including blending with other polymers and adding various fillers and plasticizers, can improve certain properties to some extent, but often come at the cost of other properties, making it difficult to achieve a comprehensive improvement in overall performance. Chemical modification methods improve the properties of polylactic acid by introducing functional groups or constructing special molecular structures, but most methods are complex, costly, and have limited modification effects.

[0006] In recent years, the application of bioactive compounds in polymer modification has attracted widespread attention. These compounds can not only endow materials with special functional properties, but also potentially promote the biodegradation process through bioactive mechanisms. Epicatechin, as a natural bioactive compound, possesses good biocompatibility and unique molecular structure characteristics, providing a new approach for the modification of polylactic acid (PLA). However, how to effectively introduce this functional component into the PLA matrix to achieve chemical bonding rather than simple physical mixing, how to balance various performance indicators to obtain biodegradable materials with excellent overall performance, and how to design a simple, easy-to-implement, and industrially viable preparation process remain key challenges in current technological development. Therefore, developing a modification technology that can simultaneously improve the biodegradability, mechanical properties, and thermal stability of PLA is of great significance for promoting the industrial application of biodegradable materials. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a biodegradable material, a preparation method and its application, so as to solve the problems of slow biodegradation rate, low mechanical strength and poor thermal stability of existing polylactic acid materials, which cannot meet the needs of practical applications.

[0008] To achieve the above objectives, the present invention provides a biodegradable material, prepared by weight from the following raw materials: 80-120 parts modified polylactic acid powder, 1-3 parts antioxidant, 2-4 parts plasticizer, 5-15 parts flame retardant and 10-20 parts inorganic filler.

[0009] Preferably, the modified polylactic acid powder is obtained by polymerizing DL-lactic acid and epicatechin imidazole ammonium chloride polymer under stannous octoate catalysis.

[0010] Preferably, the weight ratio of DL-lactic acid, epicatechin imidazole ammonium chloride polymer and stannous octoate is 100-200:5-15:0.5-1.

[0011] Preferably, the specific preparation method of the modified polylactic acid powder is as follows: Under a nitrogen atmosphere, DL-lactic acid, epicatechin imidazole ammonium chloride polymer and stannous octoate are mixed, heated to 105-115℃, and stirred for 1-3 hours. While stirring, a vacuum pump is used to evacuate to a pressure of 4-6 kPa. The temperature is then raised to 165-175℃, and the vacuum degree is maintained at 4-6 kPa. The stirring reaction continues for 8-12 hours. Samples are taken for testing. When the acid value drops below 5 mg KOH / g, the reaction is stopped. The mixture is cooled to 68-72℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate is collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0012] Preferably, the specific steps for obtaining the epicatechin imidazole ammonium chloride polymer are as follows: epicatechin is added to a sodium hydroxide solution, heated to 78-82°C, and stirred for 2-4 hours. Then epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolium chloride are added, and the reaction is stirred for 5-7 hours. The reaction is quenched with acetone, the acetone is removed under reduced pressure, the pH of the solution is adjusted to 6.9-7.2 with hydrochloric acid, dialyzed, and lyophilized to obtain the epicatechin imidazole ammonium chloride polymer.

[0013] Preferably, the weight ratio of epicatechin, sodium hydroxide solution, epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolium chloride is 4.1:15-25:5-10:0.8-2.

[0014] Preferably, the concentration of the sodium hydroxide solution is 25wt%-35wt%.

[0015] Preferably, the dialysis is performed for 3-5 days using a dialysis bag with a molecular weight cutoff of 2800-3200.

[0016] Preferably, the antioxidant is one of triphenyl phosphite, antioxidant 1010, or antioxidant 168.

[0017] Preferably, the plasticizer is one of triethyl citrate, acetylated tributyl citrate, or polyethylene glycol 400.

[0018] Preferably, the flame retardant is one of ammonium polyphosphate, aluminum hydroxide, or zinc borate.

[0019] Preferably, the inorganic filler is one of silica, montmorillonite, alumina, or zirconium oxide.

[0020] Furthermore, the present invention also provides a method for preparing a biodegradable material, comprising the following steps: mixing modified polylactic acid powder, antioxidant, plasticizer, flame retardant and inorganic filler, and melt-extruded and granulating the mixture using a twin-screw extruder at 178-182°C to obtain the biodegradable material.

[0021] Furthermore, the present invention also provides an application of biodegradable materials for the preparation of disposable tableware, food packaging films and biodegradable agricultural mulch films.

[0022] This invention achieves a significant improvement in the overall performance of biodegradable materials by constructing a technical solution for modifying polylactic acid with epicatechin imidazole ammonium chloride polymer, and has the following beneficial effects:

[0023] The bioactive groups in epicatechin imidazole ammonium chloride polymers effectively promote microbial attachment, reproduction, and enzyme activity, accelerating the biodegradation process of the material in a composting environment. The ionic properties of the imidazole salt groups enhance the hydrophilicity of the material, facilitating water penetration and hydrolysis reactions. Simultaneously, its unique ion exchange mechanism promotes the recognition and attack of polymer molecular chains by microbial enzyme systems, thereby significantly shortening the complete degradation time of the material.

[0024] The rigid framework structure of epicatechin, introduced through chemical bonding, acts as a molecular-level reinforcing phase, effectively improving the tensile strength and modulus of the material. The ionic cross-linked network formed by imidazole salt groups exhibits dynamic and reversible characteristics, capable of rearrangement and energy dissipation under external forces, significantly improving the toughness and impact resistance of the material. This combination of rigidity and flexibility in molecular design achieves a synergistic improvement in strength and toughness, overcoming the problem of mutual constraints on mechanical properties in traditional modification methods.

[0025] The polycyclic rigid structure of epicatechin molecules and the aromaticity of the imidazole ring contribute to excellent thermal stability, effectively increasing the decomposition temperature of the material. The constraint effect of the ionic cross-linking network on the movement of polymer molecular chain segments delays molecular chain breakage and volatilization at high temperatures, expands the processing temperature window of the material, and improves processing stability and product quality consistency.

[0026] The modified material of this invention retains the good processing properties of polylactic acid and can be used to prepare various products through various molding processes such as injection molding, extrusion, and blow molding. It has broad application prospects in many fields such as packaging, agriculture, and medicine. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] Example 1:

[0029] (1) Add 4.7g epichlorohydrin and 4.7g 1-methylimidazole to a mixed solution of 20g isopropanol and 10g deionized water, heat to 50℃, stir for 7h, then remove isopropanol by extraction with diethyl ether, remove distilled water under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride.

[0030] (2) Add 4.1g epicatechin to 15g sodium hydroxide solution (25wt%), heat to 78℃, stir for 2h, then add 5g epichlorohydrin and 0.8g 2,3-epoxypropyl-1-methylimidazolium chloride, stir for 5h, quench the reaction with acetone, remove acetone under reduced pressure, adjust the pH of the solution to 6.9 with hydrochloric acid, dialyze for 3 days with a dialysis bag with a molecular weight cutoff of 2800, freeze dry to obtain epicatechin imidazolium chloride polymer;

[0031] (3) Under a nitrogen atmosphere, 100g of DL-lactic acid, 5g of epicatechin imidazole ammonium chloride polymer and 0.5g of stannous octoate were mixed, heated to 105℃, and stirred for 1h. While stirring, a vacuum pump was used to evacuate to a pressure of 4kPa. The temperature was then raised to 165℃, and the vacuum was maintained at 4kPa. The stirring was continued for 8h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 68℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0032] (4) Mix 80g of modified polylactic acid powder, 1g of triphenyl phosphite, 2g of triethyl citrate, 5g of ammonium polyphosphate and 10g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 178°C with a screw speed of 50rpm to obtain biodegradable material.

[0033] Example 2:

[0034] (1) Add 4.7g epichlorohydrin and 4.7g 1-methylimidazole to a mixed solution of 20g isopropanol and 10g deionized water, heat to 50℃, stir for 7h, then remove isopropanol by extraction with diethyl ether, remove distilled water under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride.

[0035] (2) Add 4.1g epicatechin to 20g sodium hydroxide solution (33wt%), heat to 80℃, stir for 3h, then add 7g epichlorohydrin and 1.4g 2,3-epoxypropyl-1-methylimidazolium chloride, stir for 6h, quench the reaction with acetone, remove acetone under reduced pressure, adjust the pH of the solution to 7.1 with hydrochloric acid, dialyze for 4 days with a dialysis bag with a molecular weight cutoff of 3000, freeze dry to obtain epicatechin imidazolium chloride polymer;

[0036] (3) Under a nitrogen atmosphere, 150g of DL-lactic acid, 10g of epicatechin imidazole ammonium chloride polymer and 0.75g of stannous octoate were mixed, heated to 110℃, and stirred for 2h. While stirring, a vacuum pump was used to evacuate to a pressure of 5kPa. The temperature was then raised to 170℃, and the vacuum was maintained at 5kPa. The stirring was continued for 10h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 70℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0037] (4) Mix 100g of modified polylactic acid powder, 2g of triphenyl phosphite, 3g of triethyl citrate, 10g of ammonium polyphosphate and 15g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 180°C with a screw speed of 50rpm to obtain biodegradable material.

[0038] Example 3:

[0039] (1) Add 4.7g epichlorohydrin and 4.7g 1-methylimidazole to a mixed solution of 20g isopropanol and 10g deionized water, heat to 50℃, stir for 7h, then remove isopropanol by extraction with diethyl ether, remove distilled water under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride.

[0040] (2) Add 4.1g epicatechin to 25g sodium hydroxide solution (35wt%), heat to 82℃, stir for 4h, then add 10g epichlorohydrin and 2g 2,3-epoxypropyl-1-methylimidazolium chloride, stir for 7h, quench the reaction with acetone, remove acetone under reduced pressure, adjust the pH of the solution to 7.2 with hydrochloric acid, dialyze for 5 days with a dialysis bag with a molecular weight cutoff of 3200, freeze dry to obtain epicatechin imidazolium chloride polymer;

[0041] (3) Under a nitrogen atmosphere, 200g of DL-lactic acid, 15g of epicatechin imidazole ammonium chloride polymer and 1g of stannous octoate were mixed, heated to 115℃, and stirred for 3h. While stirring, a vacuum pump was used to evacuate to a pressure of 6kPa. The temperature was then raised to 175℃, and the vacuum was maintained at 6kPa. The stirring was continued for 12h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 72℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0042] (4) Mix 120g of modified polylactic acid powder, 3g of triphenyl phosphite, 4g of triethyl citrate, 15g of ammonium polyphosphate and 20g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 182℃ with a screw speed of 50rpm to obtain biodegradable material.

[0043] Comparative Example 1:

[0044] The difference between Comparative Example 1 and Example 2 is that 2,3-epoxypropyl-1-methylimidazolium chloride in step (2) is replaced with epichlorohydrin;

[0045] The specific steps are as follows:

[0046] (1) Add 4.1g epicatechin to 20g sodium hydroxide solution (33wt%), heat to 80℃, stir for 3h, then add 8.4g epichlorohydrin, stir for 6h, quench the reaction with acetone, remove acetone under reduced pressure, adjust the pH of the solution to 7.1 with hydrochloric acid, dialyze for 4 days with a dialysis bag with a molecular weight cutoff of 3000, freeze dry to obtain epicatechin polymer;

[0047] (2) Under a nitrogen atmosphere, 150g of DL-lactic acid, 10g of epicatechin polymer and 0.75g of stannous octoate were mixed, heated to 110℃ and stirred for 2h. While stirring, a vacuum pump was used to evacuate to a pressure of 5kPa. The temperature was then raised to 170℃ and the vacuum was maintained at 5kPa. The stirring was continued for 10h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 70℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0048] (3) Mix 100g of modified polylactic acid powder, 2g of triphenyl phosphite, 3g of triethyl citrate, 10g of ammonium polyphosphate and 15g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 180°C with a screw speed of 50rpm to obtain biodegradable material.

[0049] Comparative Example 2:

[0050] The difference between Comparative Example 2 and Example 2 is that epicatechin was not added in step (2);

[0051] (1) Add 4.7g epichlorohydrin and 4.7g 1-methylimidazole to a mixed solution of 20g isopropanol and 10g deionized water, heat to 50℃, stir for 7h, then remove isopropanol by extraction with diethyl ether, remove distilled water under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride.

[0052] (2) 7g epichlorohydrin and 1.4g 2,3-epoxypropyl-1-methylimidazolium chloride were added to 20g sodium hydroxide solution (33wt%), heated to 80℃, stirred for 9h, the reaction was quenched with acetone, acetone was removed under reduced pressure, the pH of the solution was adjusted to 7.1 with hydrochloric acid, and then dialyzed for 4 days with a dialysis bag with a molecular weight cutoff of 3000. The polymer was then freeze-dried to obtain the polymer.

[0053] (3) Under a nitrogen atmosphere, 150g of DL-lactic acid, 10g of polymer and 0.75g of stannous octoate were mixed, heated to 110℃ and stirred for 2h. While stirring, a vacuum pump was used to evacuate to a pressure of 5kPa. The temperature was then raised to 170℃ and the vacuum was maintained at 5kPa. The stirring was continued for 10h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 70℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0054] (4) Mix 100g of modified polylactic acid powder, 2g of triphenyl phosphite, 3g of triethyl citrate, 10g of ammonium polyphosphate and 15g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 180°C with a screw speed of 50rpm to obtain biodegradable material.

[0055] Comparative Example 3:

[0056] The difference between Comparative Example 3 and Example 2 is that epicatechin imidazole ammonium chloride polymer in step (3) is replaced with epicatechin;

[0057] (1) Under a nitrogen atmosphere, 150g of DL-lactic acid, 10g of epicatechin and 0.75g of stannous octoate were mixed, heated to 110℃ and stirred for 2h. While stirring, a vacuum pump was used to evacuate to a pressure of 5kPa. The temperature was then raised to 170℃ and the vacuum was maintained at 5kPa. The stirring was continued for 10h. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 70℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

[0058] (2) Mix 100g of modified polylactic acid powder, 2g of triphenyl phosphite, 3g of triethyl citrate, 10g of ammonium polyphosphate and 15g of silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 180°C with a screw speed of 50rpm to obtain biodegradable material.

[0059] Comparative Example 4:

[0060] The difference between Comparative Example 4 and Example 2 is that epicatechin imidazole ammonium chloride polymer was not added in step (3);

[0061] (1) Under a nitrogen atmosphere, 150g of DL-lactic acid and 0.75g of stannous octoate were mixed, heated to 110°C, and stirred for 2 hours. While stirring, a vacuum pump was used to evacuate to a pressure of 5kPa. The temperature was then raised to 170°C, and the vacuum was maintained at 5kPa. The stirring was continued for 10 hours. Samples were taken for testing. When the acid value dropped to below 5mg KOH / g, the reaction was stopped. The mixture was cooled to 70°C, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate was collected by filtration, washed three times with deionized water, and dried under vacuum to obtain polylactic acid powder.

[0062] (2) Mix 100g polylactic acid powder, 2g triphenyl phosphite, 3g triethyl citrate, 10g ammonium polyphosphate and 15g silica (average particle size 200nm), and melt extrude and granulate the mixture using a twin-screw extruder at 180°C with a screw speed of 50rpm to obtain biodegradable material.

[0063] Performance testing:

[0064] Biodegradability test: Referring to GB / T 19277.1-2011, the granulated samples of Examples 1-3 and Comparative Examples 1-4 were crushed into particles with an average particle size of 1.5 mm. 5.00 g of the sample was accurately weighed and mixed with fresh compost at a ratio of 1:10 (w / w) in a biodegradation test reactor. Humidified air (flow rate 0.02 L / min) was continuously introduced at 58℃ and 50% humidity. The amount of CO2 released was measured every 24 hours using the barium hydroxide absorption method. Monitoring was conducted continuously for 45 days, and the biodegradation rate was calculated. The results are shown in Table 1.

[0065] Tensile property test: Referring to GB / T 1040.2-2006, standard type I specimens (thickness 4.0 mm) were prepared using an injection molding machine, equilibrated for 48 h at 23℃ and 50% humidity, and stretched at a rate of 50 mm / min using a universal testing machine. The tensile strength and elongation at break were recorded. The results are shown in Table 1.

[0066] Thermal stability test: Referring to GB / T 19466.3-2004, 5.0 mg of sample was placed in an aluminum crucible and heated from 30 °C to 500 °C at a rate of 10 °C / min under a nitrogen atmosphere (flow rate 50 mL / min). The weight loss curve was recorded using a thermogravimetric analyzer, and the 5 wt% weight loss temperature and the maximum decomposition temperature were taken as thermal stability indicators. The temperature sensor was calibrated with indium standard before each test. The results are shown in Table 1.

[0067] Table 1 Performance Test Results

[0068]

[0069] Data Analysis:

[0070] As can be seen from the data in Example 2 of Table 1, the biodegradable material prepared by this invention exhibits good coordination and balance in various performance indicators. In terms of biodegradability, the material demonstrates high degradation efficiency, which may be due to the bioactive groups in the epicatechin imidazole ammonium chloride polymer promoting microbial attachment and reproduction, while the imidazole salt groups may accelerate the hydrolysis process of the polymer chain through ion exchange. Mechanical property data show that the material maintains high tensile strength while possessing good ductility. This improvement in mechanical properties may be related to the rigid framework structure of epicatechin and the ionic crosslinking network formed by the imidazole salt. This crosslinking network can both transmit stress and absorb deformation energy to a certain extent. The thermal stability indicates that the material has good processing adaptability. This may be the result of the combined effect of the thermal stability of epicatechin and the imidazole ring, and the restrictive effect of the crosslinking network on the thermal motion of the molecular chains, enabling the material to maintain structural stability during high-temperature processing, providing technical support for practical applications.

[0071] As can be seen from the data in Table 1 for Example 2 and Comparative Example 1, Example 2 exhibits significant advantages in biodegradability. The imidazole salt group may promote the recognition and degradation of the polymer by the microbial enzyme system through its unique ionic properties. Simultaneously, the hydrophilicity of the imidazole ring may enhance the interaction between the material and moisture in the composting environment, thereby accelerating the hydrolysis reaction. The improved mechanical properties of Example 2 may be related to the ionic crosslinking network formed by the imidazole salt. This ionic crosslinking differs from traditional covalent crosslinking, possessing certain reversibility and dynamic characteristics, and can rearrange under external forces, thus improving the material's toughness and strength. The improved thermal stability may stem from the inherent thermal stability of the imidazole ring structure and the constraint effect of ionic crosslinking on the movement of molecular chain segments. This constraint effect delays the decomposition process of the material at high temperatures, allowing the material to maintain structural integrity at higher temperatures and providing a wider temperature window for processing and use.

[0072] As can be seen from the data in Example 2 and Comparative Example 2 in Table 1, the introduction of epicatechin improved biodegradability, mechanical properties, and thermal stability. The improved biodegradability is likely closely related to the bioactivity of epicatechin, which enhances the activity of the microbial community in the composting environment, thereby accelerating the biodegradation process. The significant improvement in mechanical properties may stem from the chemical bonds formed between multiple hydroxyl and carboxyl groups in the epicatechin molecule and the polymer backbone. This intermolecular interaction enhances the cohesive strength of the material, while the rigid framework structure of epicatechin may act as a reinforcing phase. However, the relative decrease in elongation at break indicates that while the introduction of epicatechin improves strength, it may limit the flexibility of the molecular chain. This balance between rigidity and flexibility reflects the structure-property relationship in material design. The significant improvement in thermal stability may be related to the thermal stability of the epicatechin molecule and the stable structure it forms with the polymer matrix. This structure effectively resists thermal decomposition and extends the material's service life.

[0073] As can be seen from the data in Table 1 for Example 2 and Comparative Example 3, chemical bonding and physical mixing produce drastically different effects on material properties. The improved biodegradability indicates that the epicatechin imidazole ammonium chloride polymer formed through chemical bonding can more effectively exert its bioactive effects. The improved mechanical properties reflect the advantages of chemical bonding in constructing a continuous phase. Compared to simple physical mixing, chemical bonding enables effective bonding between components at the molecular level, forming a more stable and uniform network structure, thereby improving the overall mechanical properties of the material. The improved thermal stability may stem from the fact that the stable structure formed by chemical bonding better resists thermal degradation, while physically mixed epicatechin may migrate or decompose at high temperatures, thus affecting the thermal stability of the material.

[0074] As can be seen from the data in Table 1 for Example 2 and Comparative Example 4, the introduction of the epicatechin imidazole ammonium chloride polymer achieved comprehensive performance optimization of the biodegradable material, with all key indicators showing a significant improvement trend. The data indicate that this functionalized polymer not only effectively promotes the biodegradation process of the material but also plays a synergistic role in mechanical properties and thermal stability.

[0075] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A biodegradable material, characterized in that, It is prepared from the following raw materials: 80-120 parts modified polylactic acid powder, 1-3 parts antioxidant, 2-4 parts plasticizer, 5-15 parts flame retardant and 10-20 parts inorganic filler; The modified polylactic acid powder was obtained by polymerizing DL-lactic acid and epicatechin imidazole ammonium chloride polymer under stannous octoate catalysis; The specific steps for obtaining the epicatechin imidazole ammonium chloride polymer are as follows: epicatechin is added to sodium hydroxide solution, heated to 78-82℃, and stirred for 2-4 hours. Then epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolium chloride are added, and the reaction is stirred for 5-7 hours. The reaction is quenched with acetone, acetone is removed under reduced pressure, the pH of the solution is adjusted to 6.9-7.2 with hydrochloric acid, dialyzed, and lyophilized to obtain the epicatechin imidazole ammonium chloride polymer.

2. The biodegradable material according to claim 1, characterized in that, The weight ratio of DL-lactic acid, epicatechin imidazole ammonium chloride polymer and stannous octoate is 100-200:5-15:0.5-1.

3. The biodegradable material according to claim 1, characterized in that, The specific preparation method of the modified polylactic acid powder is as follows: Under a nitrogen atmosphere, DL-lactic acid, epicatechin imidazole ammonium chloride polymer and stannous octoate are mixed, heated to 105-115℃, and stirred for 1-3 hours. While stirring, a vacuum pump is used to evacuate to a pressure of 4-6 kPa. The temperature is then raised to 165-175℃, and the vacuum degree is maintained at 4-6 kPa. The stirring reaction continues for 8-12 hours. Samples are taken for testing. When the acid value drops below 5 mg KOH / g, the reaction is stopped. The mixture is cooled to 68-72℃, dissolved in acetone, and then poured into deionized water to precipitate. The precipitate is collected by filtration, washed three times with deionized water, and dried under vacuum to obtain modified polylactic acid powder.

4. The biodegradable material according to claim 1, characterized in that, The weight ratio of epicatechin, sodium hydroxide solution, epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolium chloride is 4.1:(15-25):(5-10):(0.8-2).

5. The biodegradable material according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 25wt%-35wt%.

6. The biodegradable material according to claim 1, characterized in that, The dialysis is performed for 3-5 days using dialysis bags with a molecular weight cutoff of 2800-3200.

7. The biodegradable material according to claim 1, characterized in that, The antioxidant is one of triphenyl phosphite, antioxidant 1010, or antioxidant 168; the plasticizer is one of triethyl citrate, tributyl acetylacetate, or polyethylene glycol 400; the flame retardant is one of ammonium polyphosphate, aluminum hydroxide, or zinc borate; and the inorganic filler is one of silica, montmorillonite, alumina, or zirconium oxide.

8. A method for preparing a biodegradable material according to any one of claims 1-7, characterized in that, Includes the following steps: Modified polylactic acid powder, antioxidants, plasticizers, flame retardants and inorganic fillers are mixed and melt-extruded into granules at 178-182℃ using a twin-screw extruder to obtain biodegradable materials.

9. An application of a biodegradable material according to any one of claims 1-7, characterized in that, Used in the preparation of disposable tableware, food packaging films and biodegradable agricultural mulch films.

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