Biodegradable material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of polymer degradable materials, in particular to a biodegradable material as well as a preparation method and application thereof. The material takes modified polylactic acid as a main body, and an antioxidant, a plasticizer, a flame retardant and an inorganic filler are used as auxiliary materials in parts by weight. The method is characterized in that lactic acid and an epicatechin imidazole ammonium chloride polymer are polymerized under the catalysis of stannous octoate, and an epicatechin bioactive group is introduced into a polylactic acid main chain in a chemical bonding manner, so that the biodegradation rate, the mechanical property and the thermal stability of the material are remarkably improved. Bioactive substances and ionic groups in the material promote microbial degradation, and the material can be completely decomposed in a compost environment in a short time; meanwhile, the strength, the toughness and the high-temperature processability of the polylactic acid are effectively improved through molecular-level enhancement and an ionic cross-linking effect. The material can be widely applied to the fields of disposable tableware, food packaging films, degradable agricultural mulching films and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer degradable materials, and in particular to a biodegradable material, a preparation method and application thereof. Background Art

[0002] With the growing 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 the many biodegradable polymers, polylactic acid, 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. Lactic acid offers the advantages of a broad and renewable raw material source. Under suitable composting conditions, PLA is completely decomposed by microorganisms into carbon dioxide and water, causing no persistent environmental pollution and aligning with the development of a circular economy. These properties give PLA enormous potential for applications in packaging, disposable tableware, agricultural films, and medical materials.

[0004] However, despite the many advantages of polylactic acid, it still faces a series of technical challenges in its actual application. First, the biodegradation rate of polylactic acid is relatively slow, and it often takes a long time to completely degrade under natural environmental conditions. This, to a certain extent, limits its use in certain application scenarios that have strict requirements on degradation time. Secondly, the mechanical properties of pure polylactic acid materials are relatively poor, especially the impact strength and elongation at break are relatively low, which makes it difficult to meet the requirements of some applications that have high requirements on the mechanical properties of materials. In addition, polylactic acid has insufficient thermal stability and is prone to thermal degradation during high-temperature processing, resulting in a decrease in molecular weight and deterioration of performance, which brings difficulties to the processing and molding of the material.

[0005] To overcome these technical challenges, researchers have attempted a variety of modification strategies. Physical modification methods, such as blending with other polymers and adding various fillers and plasticizers, can improve certain properties to a certain extent, but often come at the expense 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 and costly, and the modification effect is limited.

[0006] In recent years, the application of bioactive compounds in polymer modification has attracted widespread attention. These compounds can not only impart special functional properties to materials but may also promote the biodegradation process of materials through bioactive mechanisms. As a natural bioactive compound, epicatechin has 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-use preparation process with industrial potential remain key issues facing current technological development. Therefore, the development of 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 the present invention is to propose a biodegradable material, a preparation method and its application 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 actual applications.

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

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

[0010] Preferably, the weight ratio of the DL-lactic acid, epicatechin imidazolium 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, the temperature is raised to 105-115° C., and the reaction is stirred for 1-3 hours. While stirring the reaction, a vacuum pump is used to evacuate the pressure to 4-6 kPa, and the temperature is then raised to 165-175° C., the vacuum degree is maintained at 4-6 kPa, and the stirring reaction is continued for 8-12 hours. Sampling is performed for detection. When the acid value drops below 5 mg KOH / g, the reaction is stopped, the mixture is cooled to 68-72° C., acetone is added to dissolve it, and then it is poured into deionized water for precipitation. The precipitate is collected by filtration, washed three times with deionized water, and vacuum dried to obtain the modified polylactic acid powder.

[0012] Preferably, the specific steps of the epicatechin imidazolate ammonium chloride polymer are as follows: epicatechin is added to a sodium hydroxide solution, heated to 78-82° C., stirred for 2-4 hours, then epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolate ammonium chloride are added, stirred for reaction 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, then dialyzed, and freeze-dried to obtain the epicatechin imidazolate 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 using a dialysis bag with a molecular weight cut-off of 2800-3200 for 3-5 days.

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

[0017] Preferably, the plasticizer is one of triethyl citrate, acetyl 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 zirconia.

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

[0021] Furthermore, the present invention also provides an application of a biodegradable material for preparing disposable tableware, food packaging film and degradable agricultural mulch film.

[0022] The present invention achieves a significant improvement in the comprehensive performance of biodegradable materials by constructing a technical solution of modifying polylactic acid with an epicatechin imidazolium chloride polymer, and has the following beneficial effects:

[0023] The bioactive groups in the epicatechin imidazolium chloride polymer effectively promote microbial attachment, growth, and enzyme activity, accelerating the biodegradation process in composting environments. The ionic properties of the imidazolium salt groups enhance the material's hydrophilicity, facilitating water penetration and hydrolysis. Simultaneously, their unique ion exchange mechanism promotes the recognition and attack of the polymer molecular chains by microbial enzyme systems, significantly shortening the material's complete degradation time.

[0024] The rigid epicatechin backbone structure, introduced through chemical bonding, acts as a molecular reinforcement, effectively increasing the material's tensile strength and modulus. The ionic crosslinked network formed by the imidazolium salt groups exhibits dynamic reversibility, capable of rearrangement and energy dissipation under external forces, significantly improving the material's toughness and impact resistance. This combination of rigidity and flexibility achieves a synergistic improvement in strength and toughness, overcoming the challenge of mutually restrictive mechanical properties encountered in traditional modification methods.

[0025] The rigid polycyclic structure of epicatechin and the aromaticity of the imidazole ring contribute to its excellent thermal stability, effectively raising the material's decomposition temperature. The ionic crosslinking network constrains the movement of polymer segments, delaying chain breakage and volatilization at high temperatures. This expands the material's processing temperature window, improving processing stability and consistent product quality.

[0026] The modified material of the present invention maintains 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 multiple fields such as packaging, agriculture, and medical treatment. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0028] Example 1:

[0029] (1) 4.7 g of epichlorohydrin and 4.7 g of 1-methylimidazole were added to a mixed solution of 20 g of isopropyl alcohol and 10 g of deionized water, the temperature was raised to 50° C., and the mixture was stirred for 7 h. After that, the isopropyl alcohol was removed by extraction with ether, and the distilled water was removed under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride;

[0030] (2) 4.1 g of epicatechin was added to 15 g of sodium hydroxide solution (25 wt%), the temperature was raised to 78° C., and the mixture was stirred for 2 h. Then, 5 g of epichlorohydrin and 0.8 g of 2,3-epoxypropyl-1-methylimidazolium chloride were added, and the mixture was stirred for 5 h. The reaction was quenched with acetone, the acetone was removed under reduced pressure, and the pH of the solution was adjusted to 6.9 with hydrochloric acid. The mixture was dialyzed for 3 days using a dialysis bag with a molecular weight cutoff of 2800, and freeze-dried to obtain an epicatechin imidazolium chloride polymer.

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

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

[0033] Example 2:

[0034] (1) 4.7 g of epichlorohydrin and 4.7 g of 1-methylimidazole were added to a mixed solution of 20 g of isopropyl alcohol and 10 g of deionized water, the temperature was raised to 50° C., and the mixture was stirred for 7 h. After that, the isopropyl alcohol was removed by extraction with ether, and the distilled water was removed under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride;

[0035] (2) 4.1 g of epicatechin was added to 20 g of sodium hydroxide solution (33 wt%), the temperature was raised to 80° C., and the mixture was stirred for 3 h. Then, 7 g of epichlorohydrin and 1.4 g of 2,3-epoxypropyl-1-methylimidazolium chloride were added, and the mixture was stirred for 6 h. The reaction was quenched with acetone, the acetone was removed under reduced pressure, and the pH of the solution was adjusted to 7.1 with hydrochloric acid. The mixture was dialyzed for 4 days using a dialysis bag with a molecular weight cutoff of 3000, and freeze-dried to obtain an epicatechin imidazolium chloride polymer.

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

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

[0038] Example 3:

[0039] (1) 4.7 g of epichlorohydrin and 4.7 g of 1-methylimidazole were added to a mixed solution of 20 g of isopropyl alcohol and 10 g of deionized water, the temperature was raised to 50° C., and the mixture was stirred for 7 h. After that, the isopropyl alcohol was removed by extraction with ether, and the distilled water was removed under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride;

[0040] (2) 4.1 g of epicatechin was added to 25 g of sodium hydroxide solution (35 wt%), the temperature was raised to 82° C., and the mixture was stirred for 4 h. Then, 10 g of epichlorohydrin and 2 g of 2,3-epoxypropyl-1-methylimidazolium chloride were added, and the mixture was stirred for 7 h. The reaction was quenched with acetone, the acetone was removed under reduced pressure, and the pH of the solution was adjusted to 7.2 with hydrochloric acid. The mixture was dialyzed for 5 days using a dialysis bag with a molecular weight cutoff of 3200, and freeze-dried to obtain an epicatechin imidazolium chloride polymer.

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

[0042] (4) 120 g of modified polylactic acid powder, 3 g of triphenyl phosphite, 4 g of triethyl citrate, 15 g of ammonium polyphosphate and 20 g of silica (average particle size 200 nm) were mixed and melt-extruded into granules using a twin-screw extruder at 182° C. with a screw speed of 50 rpm to obtain a biodegradable material.

[0043] Comparative Example 1:

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

[0045] The specific steps are as follows:

[0046] (1) 4.1 g of epicatechin was added to 20 g of sodium hydroxide solution (33 wt%), the temperature was raised to 80° C., and the mixture was stirred for 3 h. 8.4 g of epichlorohydrin was then added and the mixture was stirred for 6 h. The reaction was quenched with acetone, the acetone was removed under reduced pressure, and the pH of the solution was adjusted to 7.1 with hydrochloric acid. The solution was then dialyzed for 4 days using a dialysis bag with a molecular weight cutoff of 3000 and freeze-dried to obtain an epicatechin polymer.

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

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

[0049] Comparative Example 2:

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

[0051] (1) 4.7 g of epichlorohydrin and 4.7 g of 1-methylimidazole were added to a mixed solution of 20 g of isopropyl alcohol and 10 g of deionized water, the temperature was raised to 50° C., and the mixture was stirred for 7 h. After that, the isopropyl alcohol was removed by extraction with ether, and the distilled water was removed under reduced pressure to obtain 2,3-epoxypropyl-1-methylimidazole ammonium chloride;

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

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

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

[0055] Comparative Example 3:

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

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

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

[0059] Comparative Example 4:

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

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

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

[0063] Performance testing:

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

[0065] Tensile properties test: Referring to GB / T 1040.2-2006, standard type I specimens (thickness 4.0 mm) were prepared using an injection molding machine. The specimens were equilibrated at 23°C and 50% humidity for 48 h. Then, they were 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, a 5.0 mg sample was placed in an aluminum crucible and heated at a rate of 10°C / min from 30°C to 500°C under a nitrogen atmosphere (flow rate of 50 mL / min). Weight loss curves were recorded using a thermogravimetric analyzer. The 5 wt% weight loss temperature and the maximum decomposition temperature were used as thermal stability indicators. The temperature sensor was calibrated with an 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 of Example 2 in Table 1, the biodegradable material prepared by the present invention exhibits good coordination and balance across various performance indicators. In terms of biodegradability, the material exhibits high degradation efficiency, which may be due to the bioactive groups in the epicatechin imidazolium chloride polymer promoting microbial attachment and reproduction, while the imidazolium salt groups may accelerate the hydrolysis 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 backbone structure of epicatechin and the ionic crosslinking network formed by the imidazolium salt, which can both transmit stress and absorb deformation energy to a certain extent. Thermal stability performance indicates that the material has good processing adaptability. This is likely due to the combined effect of the thermal stability of epicatechin and the imidazole ring and the crosslinking network's restriction of thermal motion of the molecular chain, allowing the material to maintain structural stability during high-temperature processing, providing technical support for practical application.

[0071] As can be seen from the data of Example 2 and Comparative Example 1 in Table 1, Example 2 has significant advantages in biodegradability, and the imidazole salt group may promote the identification and degradation of the microbial enzyme system to polymer by its unique ionic properties, and the hydrophilicity of the imidazole ring may enhance the interaction of the material with the moisture in the composting environment, thereby accelerating the carrying out of the hydrolysis reaction. The improvement of Example 2 mechanical property may be relevant to the ionic bond cross-linked network formed by imidazole salts, and this ionic cross-linking is different from traditional covalent cross-linking, has certain reversibility and dynamic characteristics, can be rearranged under external force, thereby improving the toughness and strength of the material. The lifting of thermal stability may be derived from the inherent thermal stability of the imidazole ring structure and the ionic cross-linking to the constraint effect of molecular segment motion, and this constraint effect delays the decomposition process of the material at high temperatures, so that the material can maintain structural integrity at higher temperatures, for processing and use provide a wider temperature window.

[0072] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, the introduction of epicatechin improves biodegradability, mechanical properties and thermal stability. The improvement in biodegradability may be closely related to the biological activity characteristics of epicatechin, which enhances the activity of microbial communities in the composting environment, thereby accelerating the biodegradation process of the material. The significant improvement in mechanical properties may be due to the fact that multiple hydroxyl and carboxyl groups in the epicatechin molecule form chemical bonds with the polymer main chain. This intermolecular interaction enhances the cohesive strength of the material, and the rigid skeleton structure of epicatechin may also play a role in reinforcing the phase. However, the relative reduction in elongation at break indicates that the introduction of epicatechin may limit the flexibility of the molecular chain while improving strength. This regulation of rigid-flexible balance reflects the structure-activity 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 formed with the polymer matrix. This structure can effectively resist thermal decomposition and extend the service life of the material.

[0073] As can be seen from the data of Example 2 and Comparative Example 3 in Table 1, chemical bonding and physical mixing produce completely different effects on material properties. The improvement in biodegradability shows that the epicatechin imidazolyl chloride polymer formed by chemical bonding can more effectively exert its biological activity. The improvement in mechanical properties reflects the advantage of chemical bonding in constructing a continuous phase. Compared with simple physical mixing, chemical bonding can achieve 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 improvement in thermal stability may be due to the fact that the stable structure formed by chemical bonding can better resist thermal degradation, while the epicatechin in physical mixing may migrate or decompose at high temperatures, thereby affecting the thermal stability of the material.

[0074] The data from Example 2 and Comparative Example 4 in Table 1 demonstrate that the introduction of the epicatechin imidazolium chloride polymer achieves comprehensive performance optimization of the biodegradable material, with significant improvements across all key performance indicators. This data demonstrates that this functionalized polymer not only effectively promotes the biodegradation process but also synergizes mechanical properties and thermal stability.

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

Claims

1. A biodegradable material, characterized in that: The invention is prepared from the following raw materials: 80-120 parts of modified polylactic acid powder, 1-3 parts of antioxidant, 2-4 parts of plasticizer, 5-15 parts of flame retardant and 10-20 parts of inorganic filler; The modified polylactic acid powder is obtained by polymerizing DL-lactic acid and epicatechin imidazolium chloride polymer under the catalysis of stannous octoate; The specific steps of the epicatechin imidazolate ammonium chloride polymer are as follows: adding epicatechin to a sodium hydroxide solution, heating to 78-82° C., stirring for 2-4 hours, then adding epichlorohydrin and 2,3-epoxypropyl-1-methylimidazolate ammonium chloride, stirring for reaction for 5-7 hours, quenching the reaction with acetone, removing the acetone under reduced pressure, adjusting the pH of the solution to 6.9-7.2 with hydrochloric acid, then dialyzing, and freeze-drying to obtain the epicatechin imidazolate ammonium chloride polymer.

2. The biodegradable material according to claim 1, characterized in that The weight ratio of the DL-lactic acid, epicatechin imidazolium 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, the temperature is raised to 105-115° C., and the mixture is stirred for reaction for 1-3 hours. While stirring the mixture, a vacuum pump is used to evacuate the mixture to a pressure of 4-6 kPa. The mixture is then heated to 165-175° C., the vacuum is maintained at 4-6 kPa, and the mixture is stirred for reaction for 8-12 hours. Sampling is performed for testing. When the acid value drops below 5 mg KOH / g, the reaction is stopped, the mixture is cooled to 68-72° C., acetone is added to dissolve the mixture, and then the mixture is poured into deionized water for precipitation. The precipitate is collected by filtration, washed three times with deionized water, and vacuum dried to obtain the 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 25 wt%-35 wt%.

6. The biodegradable material according to claim 1, characterized in that The dialysis is performed for 3-5 days using a dialysis bag with a molecular weight cut-off 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, acetyl tributyl citrate 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 to 7, characterized in that: The following steps are involved: The modified polylactic acid powder, antioxidant, plasticizer, flame retardant and inorganic filler are mixed, and melt-extruded and granulated at 178-182 DEG C using a twin-screw extruder to obtain a biodegradable material.

9. Use of the biodegradable material according to any one of claims 1 to 7, characterized in that: Used to prepare disposable tableware, food packaging film and degradable agricultural mulch film.

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