High-mechanical-property PLA degradable composite material and preparation method thereof

Abstract

The application relates to the technical field of degradable materials, and discloses a high-mechanical-property PLA degradable composite material and a preparation method thereof.The high-mechanical-property PLA degradable composite material comprises the following raw materials in parts by weight: 60-80 parts of PLA resin, 15-30 parts of PBS resin, 5-12 parts of Chinese pine powder, 10-15 parts of polycaprolactone, 0.1-3 parts of a modified toughening agent, 0.2-1 part of a modified light stabilizer, 0.1-1 part of antioxidant 1010, 1.5-3 parts of glycerol tristearate, 0.1-0.5 parts of sodium benzoate and 0.1-0.5 parts of silane coupling agent KH-550.The modified toughening agent improves the impact strength and flexibility of the material, and further widens the application scene of the material; the modified light stabilizer enhances the ultraviolet aging resistance of the material, and meanwhile, the material retains excellent degradable characteristics and can be efficiently degraded in a natural environment after being discarded.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, specifically to a high-mechanical-performance PLA biodegradable composite material and its preparation method. Background Technology

[0002] Biodegradable polylactic acid (PLA) is a core component of bio-based biodegradable materials systems, derived from renewable plant resources such as fir wood powder. As a typical biodegradable polymer, PLA can be gradually decomposed into carbon dioxide and water by microorganisms in the natural environment, fundamentally solving the environmental pollution problems caused by the long-term accumulation of traditional petrochemical plastics. However, its inherent properties and technical bottlenecks in the modification process of composite materials limit its application in demanding scenarios. In terms of mechanical properties, pure PLA has inherent defects such as insufficient toughness and low impact strength, making it difficult to meet the requirements of load-bearing structural components and wear-resistant products for material deformation resistance and elongation at break. In terms of UV resistance, PLA is prone to photo-oxidative degradation under long-term outdoor exposure, leading to molecular chain breakage, decreased cross-linking density, surface powdering and yellowing, and degradation of mechanical properties, severely shortening its outdoor service life.

[0003] Patent application number 201811511495.9 discloses a fully biodegradable toughened PLA composite material and its preparation method. It improves the toughness of polylactic acid by adding alginate-based natural polymers, achieving biodegradability and being harmless to humans. However, alginate is hydrophilic, while polylactic acid is hydrophobic, resulting in a significant difference in polarity and increasing the complexity of the formulation design. Patent application number 202111615332.7 discloses a radiation-sterilizable biodegradable material and its preparation method. It uses benzotriazole-based light stabilizers to improve the UV resistance of polylactic acid. However, its molecular weight is relatively small, and long-term use makes it easy for it to migrate to the material surface, making it difficult to simultaneously meet the requirements of UV resistance and mechanical reinforcement when used alone. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a high-mechanical-performance PLA biodegradable composite material and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A high-mechanical-performance PLA biodegradable composite material comprises the following raw materials in parts by weight: 60-80 parts PLA resin, 15-30 parts PBS resin, 5-12 parts cedar wood powder, 10-15 parts polycaprolactone, 0.1-3 parts modified toughening agent, 0.2-1 part modified light stabilizer, 0.1-1 part antioxidant 1010, 1.5-3 parts tristearate, 0.1-0.5 parts sodium benzoate, and 0.1-0.5 parts silane coupling agent KH-550; The modified toughening agent is prepared by the following steps: Step A1: Mix DL-glyceraldehyde and anhydrous ethanol, add 1-(3-aminopropyl)imidazolium dropwise with stirring, reflux at 85°C for 2 hours, and after the reaction is completed, allow to stand and cool, filter, wash, and vacuum dry to obtain intermediate product 1. Furthermore, the ratio of DL-glyceraldehyde, anhydrous ethanol, and 1-(3-aminopropyl)imidazole is 0.8-1 mol: 150-250 mL: 0.8-1 mol; In step A1, DL-glyceraldehyde and 1-(3-aminopropyl)imidazole undergo a Schiff base reaction, introducing a hydroxyl group into the system and providing reaction conditions for the subsequent esterification reaction. The imidazole structure provides conditions for the subsequent nucleophilic substitution reaction.

[0006] Step A2: Mix cashew phenol, triethylamine and dichloromethane, purge with nitrogen, stir in an ice-water bath, add 6-bromohexanoyl chloride dropwise, after the addition is complete, heat to room temperature, stir for 2 hours, add deionized water and stir for 0.5 hours, then extract, wash, dry in liquid phase, filter, distill under reduced pressure and dry in solid phase to obtain intermediate product 2. Furthermore, the ratio of cashew phenol, triethylamine, dichloromethane, 6-bromohexanoyl chloride, and deionized water is 0.8-1 mol: 1.2-1.5 mol: 350-400 mL: 0.96-1.2 mol: 150 mL; In step A2, cashew phenol and 6-bromohexanoyl chloride undergo a nucleophilic substitution reaction. The introduced bromine atom provides the reaction conditions for the subsequent nucleophilic substitution reaction. Cashew phenol has both a benzene ring structure and a 15-carbon straight chain. The benzene ring is rigid, while the 15-carbon straight chain has good toughness. This structure can improve the impact resistance of the system.

[0007] Step A3: Nitrogen gas was introduced into intermediate product 1, n-hexane and 2,6-di-tert-butyl-4-methylphenol, and intermediate product 2 solution was added dropwise. After the addition was completed, the temperature was raised to 40°C and the reaction was carried out for 24 hours. After the reaction was completed, the temperature was cooled to 25°C, washed, filtered and dried under vacuum to obtain intermediate product 3. Furthermore, the molar ratio of intermediate product 1, n-hexane, 2,6-di-tert-butyl-4-methylphenol, and intermediate product 2 solution is 0.3-0.4 mol: 80-100 mL: 0.12-0.18 mmol: 60-80 mL; Furthermore, the intermediate product 2 solution is prepared by mixing intermediate product 2 and anhydrous ethanol at a volume ratio of 0.6-0.8 mol: 60-80 mL; In step A3, the imidazole in intermediate 1 and the bromine atom in intermediate 2 undergo a nucleophilic substitution reaction. The resulting imidazole-based ionic liquid can enter between PLA molecular chains, increasing the free volume between PLA molecules, weakening the intermolecular forces, and thus increasing the chain segment mobility, thereby enhancing the toughness of PLA.

[0008] Step A4: Mix dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide and toluene, purge with nitrogen, heat to 120°C, add tetrabutyl titanate, and then heat in stages at 160°C, 190°C and 210°C for 4 hours under reflux. Then heat to 230°C, reduce the system pressure to below 50 Pa within 1 hour, and then heat to 250°C for 6 hours under reflux. After the reaction is complete, discharge under nitrogen protection and vacuum dry to obtain the modified toughening agent. Furthermore, the molar ratio of dimethyl terephthalate, dodecanoic acid, intermediate 3, isosorbide, toluene, and tetrabutyl titanate is 0.1-0.2 mol: 0.1-0.2 mol: 0.12-0.24 mol: 0.024-0.048 mol: 30-50 mL: 0.4-0.8 mmol; In step A4, dimethyl terephthalate, dodecanoic acid, intermediate 3, and isosorbide undergo esterification and transesterification reactions, followed by polycondensation to generate a copolyester. Isosorbide has a unique rigid cyclic structure, which gives it strong molecular rigidity and biodegradability. In addition, the copolyester has a similar morphology to PLA chains and has good compatibility. Introducing ionic liquids and cashew phenols into the copolyester can further improve the mechanical properties of the system.

[0009] The modified light stabilizer is prepared by the following steps: Step B1: Mix methyl 4-hydroxycinnamate, epichlorohydrin and tetrabutylammonium bromide, stir and react at 80°C for 2 hours. After the reaction is completed, cool to room temperature, add 20wt% sodium hydroxide aqueous solution in an ice-water bath, react in an ice-water bath for 1 hour, then extract, wash, recrystallize, filter and vacuum dry to obtain cinnamic acid derivative. Furthermore, the ratio of methyl 4-hydroxycinnamate, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution is 0.8-1 mol: 8-10 mol: 0.33-0.34 mol: 400-500 mL; In step B1, methyl 4-hydroxycinnamate and epichlorohydrin undergo a nucleophilic substitution reaction, introducing an epoxy group into the system and providing reaction conditions for the subsequent ring-opening reaction. The introduced methyl cinnamate structure contains an unsaturated conjugated system with an absorption wavelength around 305 nm and a high molar extinction coefficient, which can improve the system's ability to absorb ultraviolet light.

[0010] Step B2: Mix 1-hydroxybenzotriazole, cinnamic acid derivative and N,N-dimethylformamide, heat to 90°C, add tetramethylammonium bromide, heat to 100°C and react for 6 hours. After the reaction is completed, cool to room temperature, wash, separate and distill under reduced pressure to obtain cinnamic acid benzotriazole derivative. Furthermore, the molar ratio of 1-hydroxybenzotriazole, cinnamic acid derivative, N,N-dimethylformamide and tetramethylammonium bromide is 0.1-0.14 mol: 0.5-0.7 mol: 60-100 mL: 0.002-0.003 mol; In step B2, 1-hydroxybenzotriazole and cinnamic acid derivative undergo a ring-opening reaction. The introduced hydroxyl group provides the reaction conditions for the subsequent esterification reaction. The benzotriazole is introduced into the system. This structure can release light energy in the form of heat energy or other forms through molecular tautomerism. It can absorb ultraviolet light in the range of 280-400 nm and is not easily migrated.

[0011] Step B3: Mix anhydrous citric acid, cysteine ​​hydrochloride and deionized water to obtain a mixture. Place it in an 80°C oven for 30 min, shake, and continue to place it in the oven for 1.5 h. Then place it in a 130°C oven and react for 12 h. After the reaction is complete, cool to room temperature, add deionized water, stir, filter under reduced pressure, wash, and dry under vacuum to obtain the pyridinone derivative. Furthermore, the ratio of the mixed solution to deionized water is 3-6 mL: 100-150 mL; Furthermore, the ratio of anhydrous citric acid, cysteine ​​hydrochloride, and deionized water in the mixture is 0.05-0.1 mol: 0.05-0.1 mol: 3-6 mL; In step B3, anhydrous citric acid and cysteine ​​hydrochloride undergo a condensation ring-forming reaction, introducing a carboxyl group into the system and providing reaction conditions for the subsequent esterification reaction. The resulting pyridone structure contains a pyridine ring and a ketone group, forming a conjugated π-electron system that can effectively absorb ultraviolet light.

[0012] Step B4: Mix pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and dichloromethane, seal, and stir in an ice-water bath for 2 hours. After the reaction is complete, add cinnamic acid benzotriazole derivative solution dropwise at room temperature, seal and react for 24 hours. Then wash, dry in liquid phase, filter under reduced pressure, rotary evaporate, purify, and dry under vacuum to obtain the modified light stabilizer. Furthermore, the volume ratio of the pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, dichloromethane, and benzotriazole cinnamic acid derivative solution is 0.03-0.05 mol : 0.003-0.005 mol : 0.06-0.1 mol : 120-160 mL : 40-80 mL; Furthermore, the cinnamic acid benzotriazole derivative solution is prepared by mixing cinnamic acid benzotriazole derivative and dichloromethane in a volume ratio of 0.045-0.075 mol: 40-80 mL; In step B4, the pyridone derivative and the benzotriazole cinnamic acid derivative undergo an esterification reaction. The pyridone structure has strong absorption characteristics in the ultraviolet region. Combined with the benzotriazole and cinnamic acid ester structures, it improves the compatibility with the polymer matrix and also enhances the photostability of the system.

[0013] A method for preparing a high-mechanical-performance PLA biodegradable composite material includes the following steps: Step S1: Weigh the raw materials according to the weight proportions, and put PLA resin, PBS resin, cedar powder, polycaprolactone, modified toughening agent, modified light stabilizer, antioxidant 1010, tristearate, sodium benzoate and silane coupling agent KH-550 into a mixer and mix for 10-30 minutes at a speed of 400-600 rpm to obtain a mixture; Step S2: The mixture is fed into an extruder for extrusion granulation. The screw speed is 100-200 rpm and the extrusion temperature is 160-170℃. Then, it is injection molded to obtain a high-mechanical-performance PLA biodegradable composite material.

[0014] The beneficial effects of this invention are: The high-mechanical-performance PLA biodegradable composite material of this invention can be widely used in packaging materials, 3D printing consumables, automotive interiors, and electronic device housings. The modified toughening agent in the composite material significantly improves its impact strength and flexibility, effectively addressing the drawbacks of pure PLA's brittleness and easy breakage. The modified light stabilizer enhances the material's resistance to UV aging, preventing performance degradation, yellowing, and brittleness in outdoor environments. Simultaneously, the material retains excellent biodegradability, efficiently degrading in the natural environment after disposal, reducing white pollution. It also exhibits strong processing adaptability, maintaining its appearance and performance stably under conventional molding processes. Compared to existing technologies, this invention achieves a synergistic improvement in mechanical properties and weather resistance through a dual-modification system, balancing environmental friendliness and practicality, and has broad application prospects.

[0015] In this invention, the modified toughening agent first undergoes a Schiff base reaction with DL-glyceraldehyde and 1-(3-aminopropyl)imidazole. Then, a nucleophilic substitution reaction is performed with cashew phenol and 6-bromohexanoyl chloride. Cashew phenol possesses both a benzene ring structure and a 15-carbon straight chain; the benzene ring exhibits rigidity, while the 15-carbon straight chain provides good toughness. This structure enhances the system's impact resistance. Subsequently, through the nucleophilic substitution reaction, the generated imidazole-based ionic liquid can enter between PLA molecular chains, increasing the free volume between PLA molecules, weakening the intermolecular forces, and increasing chain segment mobility, thus enhancing PLA toughness. Finally, a polycondensation reaction is used to generate a copolyester. Isosorbide has a unique rigid cyclic structure, giving it high molecular rigidity and biodegradability. Furthermore, the copolyester has a similar morphology to PLA chains, exhibiting good compatibility. Introducing the ionic liquid and cashew phenol into the copolyester further improves the system's mechanical properties.

[0016] In this invention, the modified light stabilizer first undergoes a nucleophilic substitution reaction between methyl 4-hydroxycinnamate and epichlorohydrin. The introduced methyl cinnamate structure contains an unsaturated conjugated system with an absorption wavelength around 305 nm and a high molar extinction coefficient, which can improve the system's ability to absorb ultraviolet light. Then, a ring-opening reaction is used to introduce benzotriazole into the system. This structure can release light energy as heat or other forms through molecular tautomerism, can absorb ultraviolet light in the 280-400 nm range, and is not easily migrated. Subsequently, a condensation ring-forming reaction is performed between anhydrous citric acid and cysteine ​​hydrochloride, resulting in a pyridone structure containing a pyridine ring and a ketone group, forming a conjugated π-electron system that can effectively absorb ultraviolet light. Finally, through an esterification reaction, the pyridone structure exhibits strong absorption characteristics in the ultraviolet region. Combined with the benzotriazole and cinnamate ester structures, it improves both compatibility with the polymer matrix and the photostability of the system. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1: The modified toughening agent was prepared by the following steps: Step A1: Mix DL-glyceraldehyde and anhydrous ethanol, add 1-(3-aminopropyl)imidazole dropwise with stirring, reflux at 85°C for 2 hours, after the reaction is completed, let stand and cool, filter, wash, and vacuum dry to obtain intermediate product 1. The ratio of DL-glyceraldehyde, anhydrous ethanol and 1-(3-aminopropyl)imidazole is 0.8 mol: 150 mL: 0.8 mol. Step A2: Mix cashew nut phenol, triethylamine, and dichloromethane, purge with nitrogen, stir in an ice-water bath, add 6-bromohexanoyl chloride dropwise, and after the addition is complete, heat to room temperature and stir for 2 hours. Then add deionized water and stir for 0.5 hours. After extraction, washing, liquid-phase drying, filtration, vacuum distillation, and solid-phase drying, intermediate product 2 is obtained. The ratio of cashew nut phenol, triethylamine, dichloromethane, 6-bromohexanoyl chloride, and deionized water is 0.8 mol: 1.2 mol: 350 mL: 0.96 mol: 150 mL. Step A3: Nitrogen gas was introduced into intermediate product 1, n-hexane, and 2,6-di-tert-butyl-4-methylphenol. Solution of intermediate product 2 was added dropwise. After the addition was completed, the temperature was raised to 40°C and the reaction was carried out for 24 hours. After the reaction was completed, the temperature was cooled to 25°C, washed, filtered, and dried under vacuum to obtain intermediate product 3. The molar ratio of intermediate product 1, n-hexane, 2,6-di-tert-butyl-4-methylphenol, and solution of intermediate product 2 was 0.3 mol: 80 mL: 0.12 mmol: 60 mL. Solution of intermediate product 2 was prepared by mixing intermediate product 2 and anhydrous ethanol at a molar ratio of 0.6 mol: 60 mL. Step A4: Mix dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, and toluene, purge with nitrogen, heat to 120°C, add tetrabutyl titanate, and then heat in stages at 160°C, 190°C, and 210°C for 4 hours under reflux. Then heat to 230°C, reduce the system pressure to below 50 Pa within 1 hour, and then heat to 250°C for 6 hours under reflux. After the reaction is complete, discharge under nitrogen protection and vacuum dry to obtain the modified toughening agent. The ratio of dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, toluene, and tetrabutyl titanate is 0.1 mol: 0.1 mol: 0.12 mol: 0.024 mol: 30 mL: 0.4 mmol.

[0019] The modified light stabilizer is prepared by the following steps: Step B1: Methyl 4-hydroxycinnamate, epichlorohydrin, and tetrabutylammonium bromide were mixed and stirred at 80°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and 20wt% sodium hydroxide aqueous solution was added in an ice-water bath. The mixture was reacted in an ice-water bath for 1 hour. After extraction, washing, recrystallization, filtration, and vacuum drying were performed to obtain the cinnamic acid derivative. The ratio of methyl 4-hydroxycinnamate, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution was 0.8mol:8mol:0.33mol:400mL. Step B2: Mix 1-hydroxybenzotriazole, cinnamic acid derivative, and N,N-dimethylformamide, heat to 90°C, add tetramethylammonium bromide, heat to 100°C and react for 6 hours. After the reaction is complete, cool to room temperature, wash, separate, and distill under reduced pressure to obtain cinnamic acid benzotriazole derivative. The molar ratio of 1-hydroxybenzotriazole, cinnamic acid derivative, N,N-dimethylformamide, and tetramethylammonium bromide is 0.1 mol: 0.5 mol: 60 mL: 0.002 mol. Step B3: Mix anhydrous citric acid, cysteine ​​hydrochloride, and deionized water to obtain a mixture. Place the mixture in an 80℃ oven for 30 min, shake, and continue to place it in the oven for 1.5 h. Then place it in a 130℃ oven and react for 12 h. After the reaction is complete, cool to room temperature, add deionized water, stir, filter under reduced pressure, wash, and vacuum dry to obtain the pyridinone derivative. The ratio of the mixture to deionized water is 3 mL:100 mL, and the ratio of anhydrous citric acid, cysteine ​​hydrochloride, and deionized water in the mixture is 0.05 mol:0.05 mol:3 mL. Step B4: Mix pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and dichloromethane, seal, and stir in an ice-water bath for 2 hours. After the reaction is complete, add cinnamic acid benzotriazole derivative solution dropwise at room temperature, seal, and react for 24 hours. Then wash, dry in liquid phase, filter under reduced pressure, rotary evaporate, purify, and dry under vacuum to obtain the modified light stabilizer. The ratio of pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, dichloromethane, and cinnamic acid benzotriazole derivative solution is 0.03 mol: 0.003 mol: 0.06 mol: 120 mL: 40 mL. The cinnamic acid benzotriazole derivative solution is prepared by mixing cinnamic acid benzotriazole derivative and dichloromethane in a ratio of 0.045 mol: 40 mL.

[0020] Example 2: The modified toughening agent was prepared by the following steps: Step A1: Mix DL-glyceraldehyde and anhydrous ethanol, add 1-(3-aminopropyl)imidazole dropwise with stirring, reflux at 85°C for 2 hours, after the reaction is completed, let stand and cool, filter, wash, and vacuum dry to obtain intermediate product 1. The ratio of DL-glyceraldehyde, anhydrous ethanol and 1-(3-aminopropyl)imidazole is 0.9 mol: 200 mL: 0.9 mol. Step A2: Mix cashew nut phenol, triethylamine, and dichloromethane, purge with nitrogen, stir in an ice-water bath, add 6-bromohexanoyl chloride dropwise, and after the addition is complete, heat to room temperature and stir for 2 hours. Then add deionized water and stir for 0.5 hours. After extraction, washing, liquid-phase drying, filtration, vacuum distillation, and solid-phase drying, intermediate product 2 is obtained. The ratio of cashew nut phenol, triethylamine, dichloromethane, 6-bromohexanoyl chloride, and deionized water is 0.9 mol: 1.35 mol: 375 mL: 1.08 mol: 150 mL. Step A3: Nitrogen gas was introduced into intermediate product 1, n-hexane, and 2,6-di-tert-butyl-4-methylphenol. Solution of intermediate product 2 was added dropwise. After the addition was completed, the temperature was raised to 40°C and the reaction was carried out for 24 hours. After the reaction was completed, the temperature was cooled to 25°C, washed, filtered, and dried under vacuum to obtain intermediate product 3. The molar ratio of intermediate product 1, n-hexane, 2,6-di-tert-butyl-4-methylphenol, and solution of intermediate product 2 was 0.35 mol: 90 mL: 0.15 mmol: 70 mL. Solution of intermediate product 2 was prepared by mixing intermediate product 2 and anhydrous ethanol at a molar ratio of 0.7 mol: 70 mL. Step A4: Mix dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, and toluene, purge with nitrogen, heat to 120°C, add tetrabutyl titanate, and then heat in stages at 160°C, 190°C, and 210°C for 4 hours under reflux. Then heat to 230°C, reduce the system pressure to below 50 Pa within 1 hour, and then heat to 250°C for 6 hours under reflux. After the reaction is complete, discharge under nitrogen protection and vacuum dry to obtain the modified toughening agent. The ratio of dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, toluene, and tetrabutyl titanate is 0.15 mol: 0.15 mol: 0.18 mol: 0.036 mol: 40 mL: 0.6 mmol.

[0021] The modified light stabilizer is prepared by the following steps: Step B1: Methyl 4-hydroxycinnamate, epichlorohydrin, and tetrabutylammonium bromide were mixed and stirred at 80°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and 20wt% sodium hydroxide aqueous solution was added in an ice-water bath. The mixture was then reacted in an ice-water bath for 1 hour. After extraction, washing, recrystallization, filtration, and vacuum drying were performed to obtain the cinnamic acid derivative. The ratio of methyl 4-hydroxycinnamate, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution was 0.9mol:9mol:0.335mol:450mL. Step B2: Mix 1-hydroxybenzotriazole, cinnamic acid derivative, and N,N-dimethylformamide, heat to 90°C, add tetramethylammonium bromide, heat to 100°C and react for 6 hours. After the reaction is complete, cool to room temperature, wash, separate, and distill under reduced pressure to obtain cinnamic acid benzotriazole derivative. The molar ratio of 1-hydroxybenzotriazole, cinnamic acid derivative, N,N-dimethylformamide, and tetramethylammonium bromide is 0.12 mol: 0.6 mol: 80 mL: 0.0025 mol. Step B3: Mix anhydrous citric acid, cysteine ​​hydrochloride, and deionized water to obtain a mixture. Place the mixture in an 80°C oven for 30 min, shake, and continue to place it in the oven for 1.5 h. Then place it in a 130°C oven and react for 12 h. After the reaction is complete, cool to room temperature, add deionized water, stir, filter under reduced pressure, wash, and dry under vacuum to obtain a pyridone derivative. The ratio of the mixture to deionized water is 4.5 mL: 125 mL, and the ratio of anhydrous citric acid, cysteine ​​hydrochloride, and deionized water in the mixture is 0.075 mol: 0.075 mol: 4.5 mL. Step B4: Mix pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and dichloromethane, seal, and stir in an ice-water bath for 2 hours. After the reaction is complete, add cinnamic acid benzotriazole derivative solution dropwise at room temperature, seal, and react for 24 hours. Then wash, dry in liquid phase, filter under reduced pressure, rotary evaporate, purify, and dry under vacuum to obtain the modified light stabilizer. The ratio of pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, dichloromethane, and cinnamic acid benzotriazole derivative solution is 0.04 mol: 0.004 mol: 0.08 mol: 140 mL: 60 mL. The cinnamic acid benzotriazole derivative solution is prepared by mixing cinnamic acid benzotriazole derivative and dichloromethane in a ratio of 0.06 mol: 60 mL.

[0022] Example 3: The modified toughening agent was prepared by the following steps: Step A1: Mix DL-glyceraldehyde and anhydrous ethanol, add 1-(3-aminopropyl)imidazole dropwise with stirring, reflux at 85°C for 2 h, after the reaction is completed, let stand and cool, filter, wash, and vacuum dry to obtain intermediate product 1. The ratio of DL-glyceraldehyde, anhydrous ethanol and 1-(3-aminopropyl)imidazole is 1 mol: 250 mL: 1 mol. Step A2: Mix cashew nut phenol, triethylamine, and dichloromethane, purge with nitrogen, stir in an ice-water bath, add 6-bromohexanoyl chloride dropwise, and after the addition is complete, heat to room temperature and stir for 2 hours. Then add deionized water and stir for 0.5 hours. After extraction, washing, liquid-phase drying, filtration, vacuum distillation, and solid-phase drying, intermediate product 2 is obtained. The ratio of cashew nut phenol, triethylamine, dichloromethane, 6-bromohexanoyl chloride, and deionized water is 1 mol: 1.5 mol: 400 mL: 1.2 mol: 150 mL. Step A3: Nitrogen gas was introduced into intermediate product 1, n-hexane, and 2,6-di-tert-butyl-4-methylphenol. Solution of intermediate product 2 was added dropwise. After the addition was completed, the temperature was raised to 40°C and the reaction was carried out for 24 hours. After the reaction was completed, the temperature was cooled to 25°C, washed, filtered, and dried under vacuum to obtain intermediate product 3. The molar ratio of intermediate product 1, n-hexane, 2,6-di-tert-butyl-4-methylphenol, and solution of intermediate product 2 was 0.4 mol: 100 mL: 0.18 mmol: 80 mL. Solution of intermediate product 2 was prepared by mixing intermediate product 2 and anhydrous ethanol at a molar ratio of 0.8 mol: 80 mL. Step A4: Mix dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, and toluene, purge with nitrogen, heat to 120°C, add tetrabutyl titanate, and then heat in stages at 160°C, 190°C, and 210°C for 4 hours under reflux. Then heat to 230°C, reduce the system pressure to below 50 Pa within 1 hour, and then heat to 250°C for 6 hours under reflux. After the reaction is complete, discharge under nitrogen protection and vacuum dry to obtain the modified toughening agent. The molar ratio of dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide, toluene, and tetrabutyl titanate is 0.2 mol: 0.2 mol: 0.24 mol: 0.048 mol: 50 mL: 0.8 mmol.

[0023] The modified light stabilizer is prepared by the following steps: Step B1: Methyl 4-hydroxycinnamate, epichlorohydrin, and tetrabutylammonium bromide were mixed and stirred at 80°C for 2 hours. After the reaction was completed, the mixture was cooled to room temperature, and 20wt% sodium hydroxide aqueous solution was added in an ice-water bath. The mixture was then reacted in an ice-water bath for 1 hour. After extraction, washing, recrystallization, filtration, and vacuum drying were performed to obtain the cinnamic acid derivative. The ratio of methyl 4-hydroxycinnamate, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution was 1 mol: 10 mol: 0.34 mol: 500 mL. Step B2: Mix 1-hydroxybenzotriazole, cinnamic acid derivative, and N,N-dimethylformamide, heat to 90°C, add tetramethylammonium bromide, heat to 100°C and react for 6 hours. After the reaction is complete, cool to room temperature, wash, separate, and distill under reduced pressure to obtain cinnamic acid benzotriazole derivative. The molar ratio of 1-hydroxybenzotriazole, cinnamic acid derivative, N,N-dimethylformamide, and tetramethylammonium bromide is 0.14 mol: 0.7 mol: 100 mL: 0.003 mol. Step B3: Mix anhydrous citric acid, cysteine ​​hydrochloride, and deionized water to obtain a mixture. Place the mixture in an 80°C oven for 30 min, shake, and continue in the oven for 1.5 h. Then place it in a 130°C oven and react for 12 h. After the reaction is complete, cool to room temperature, add deionized water, stir, filter under reduced pressure, wash, and dry under vacuum to obtain the pyridinone derivative. The ratio of the mixture to deionized water is 6 mL:150 mL, and the ratio of anhydrous citric acid, cysteine ​​hydrochloride, and deionized water in the mixture is 0.1 mol:0.1 mol:6 mL. Step B4: Mix pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and dichloromethane, seal, and stir in an ice-water bath for 2 hours. After the reaction is complete, add cinnamic acid benzotriazole derivative solution dropwise at room temperature, seal, and react for 24 hours. Then wash, dry in liquid phase, filter under reduced pressure, rotary evaporate, purify, and dry under vacuum to obtain the modified light stabilizer. The ratio of pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, dichloromethane, and cinnamic acid benzotriazole derivative solution is 0.05 mol: 0.005 mol: 0.1 mol: 160 mL: 80 mL. The cinnamic acid benzotriazole derivative solution is prepared by mixing cinnamic acid benzotriazole derivative and dichloromethane in a ratio of 0.075 mol: 80 mL.

[0024] Example 4: A method for preparing a high-mechanical-performance PLA biodegradable composite material, comprising the following steps: 60 parts PLA resin, 15 parts PBS resin, 5 parts cedar wood powder, 10 parts polycaprolactone, 0.1 parts modified toughening agent prepared in Example 1, 0.2 parts modified light stabilizer prepared in Example 1, 0.1 parts antioxidant 1010, 1.5 parts tristearate, 0.1 parts sodium benzoate, and 0.1 parts silane coupling agent KH-550; Step S1: Weigh the raw materials according to the weight proportions, and put PLA resin, PBS resin, cedar powder, polycaprolactone, modified toughening agent prepared in Example 1, modified light stabilizer prepared in Example 1, antioxidant 1010, tristearate, sodium benzoate and silane coupling agent KH-550 into a mixer and mix for 10 minutes at a speed of 400 rpm to obtain a mixture; Step S2: The mixture is fed into an extruder for extrusion granulation at a screw speed of 100 rpm and an extrusion temperature of 160°C. Then, it is injection molded to obtain a high-mechanical-performance PLA biodegradable composite material.

[0025] Example 5: A method for preparing a high-mechanical-performance PLA biodegradable composite material, comprising the following steps: 70 parts PLA resin, 20 parts PBS resin, 8 parts cedar wood powder, 13 parts polycaprolactone, 1 part of the modified toughening agent prepared in Example 2, 0.6 parts of the modified light stabilizer prepared in Example 2, 0.5 parts of antioxidant 1010, 2 parts of glyceryl tristearate, 0.3 parts of sodium benzoate, and 0.3 parts of silane coupling agent KH-550; Step S1: Weigh the raw materials according to the weight proportions, and put PLA resin, PBS resin, cedar powder, polycaprolactone, modified toughening agent prepared in Example 2, modified light stabilizer prepared in Example 2, antioxidant 1010, tristearate, sodium benzoate and silane coupling agent KH-550 into a mixer and mix for 20 minutes at a speed of 500 rpm to obtain a mixture; Step S2: The mixture is fed into an extruder for extrusion granulation at a screw speed of 150 rpm and an extrusion temperature of 165°C. After that, it is injection molded to obtain a high-mechanical-performance PLA biodegradable composite material.

[0026] Example 6: A method for preparing a high-mechanical-performance PLA biodegradable composite material, comprising the following steps: 80 parts PLA resin, 30 parts PBS resin, 12 parts cedar wood powder, 15 parts polycaprolactone, 3 parts modified toughening agent prepared in Example 3, 1 part modified light stabilizer prepared in Example 3, 1 part antioxidant 1010, 3 parts tristearate, 0.5 parts sodium benzoate, and 0.5 parts silane coupling agent KH-550; Step S1: Weigh the raw materials according to the weight proportions, and put PLA resin, PBS resin, cedar powder, polycaprolactone, modified toughening agent prepared in Example 3, modified light stabilizer prepared in Example 3, antioxidant 1010, tristearate, sodium benzoate and silane coupling agent KH-550 into a mixer and mix for 30 minutes at a speed of 600 rpm to obtain a mixture; Step S2: The mixture is fed into an extruder for extrusion granulation at a screw speed of 200 rpm and an extrusion temperature of 170°C. Then, it is injection molded to obtain a high-mechanical-performance PLA biodegradable composite material.

[0027] Comparative Example 1: This comparative example is a PLA biodegradable composite material. The difference between this example and Example 6 is that the modified toughening agent prepared in Example 3 is replaced with ethylene-vinyl acetate copolymer. All other aspects are the same.

[0028] Comparative Example 2: This comparative example is a PLA biodegradable composite material. The difference between this example and Example 6 is that the UV absorber UV-326 is used instead of the modified light stabilizer prepared in Example 3. All other aspects are the same.

[0029] Comparative Example 3: This comparative example is a PLA biodegradable composite material. The difference between this example and Example 6 is that the modified toughening agent prepared in Example 3 is replaced by ethylene-vinyl acetate copolymer, and the modified light stabilizer prepared in Example 3 is replaced by UV-326 ultraviolet absorber. All other aspects are the same.

[0030] The composite materials prepared in Examples 4-6 and Comparative Examples 1-3 were subjected to performance tests: Tensile strength and elongation at break tests: The material is made into dumbbell-shaped specimens and placed in a laboratory environment for 48 hours. According to the requirements of GB / T 1040.2-2006, the test is carried out using an electronic universal testing machine with a tensile speed of 10 mm / min. Five specimens are measured in each group and the average value is taken. Impact resistance test: The material is made into rectangular strips and placed in a laboratory environment for 48 hours. According to the requirements of GB / T1843-2008, an electronic cantilever beam impact tester is used to conduct impact tests. Five strips are measured in each group and the average value is taken. UV aging resistance test: Each composite material was irradiated with a 350nm UV lamp at room temperature for 48 hours, with the material 10cm away from the UV lamp source. The UV aging resistance was measured by the retention rate of tensile strength. The higher the value, the better the UV aging resistance. Degradation performance test: The material was pressed into a film using a hydraulic press, and then the percentage of biodegradation after 180 days was determined according to the requirements of GB / T 19277.1-2011.

[0031] The test results are shown in Table 1: Table 1: Performance Test Results

[0032] As shown in Table 1, the PLA biodegradable composite material prepared by this invention possesses high mechanical properties. The tensile strength of the composite materials prepared in the examples is all above 35.3 MPa, the elongation at break is above 193%, and the impact strength is above 87.5 KJ / m. 2 The relative biodegradability is also above 92.7%. Comparing Example 6 and Comparative Example 1, it can be seen that the toughness and rigidity of the material are significantly improved after adding the modified toughening agent prepared in this invention, indicating that the modified toughening agent prepared in this invention improves the mechanical properties of the PLA composite material. Comparing Example 6 and Comparative Example 2, it can be seen that the modified light stabilizer prepared in this invention improves the system's UV aging resistance, proving that the composite material prepared in this invention has high mechanical properties, UV aging resistance, and biodegradability.

[0033] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A high-mechanical-performance PLA biodegradable composite material, characterized in that, The raw materials include the following parts by weight: 60-80 parts PLA resin, 15-30 parts PBS resin, 5-12 parts cedar wood powder, 10-15 parts polycaprolactone, 0.1-3 parts modified toughening agent, 0.2-1 part modified light stabilizer, 0.1-1 part antioxidant 1010, 1.5-3 parts tristearate, 0.1-0.5 parts sodium benzoate, and 0.1-0.5 parts silane coupling agent KH-550; The modified toughening agent is prepared by the following steps: Step A1: Mix DL-glyceraldehyde and anhydrous ethanol, add 1-(3-aminopropyl)imidazolium dropwise with stirring, reflux at 85°C for 2 hours, and after the reaction is completed, allow to stand and cool, filter, wash, and vacuum dry to obtain intermediate product 1. Step A2: Mix cashew phenol, triethylamine and dichloromethane, purge with nitrogen, stir in an ice-water bath, add 6-bromohexanoyl chloride dropwise, after the addition is complete, heat to room temperature, stir for 2 hours, add deionized water and stir for 0.5 hours, then extract, wash, dry in liquid phase, filter, distill under reduced pressure and dry in solid phase to obtain intermediate product 2. Step A3: Nitrogen gas was introduced into intermediate product 1, n-hexane and 2,6-di-tert-butyl-4-methylphenol, and intermediate product 2 solution was added dropwise. After the addition was completed, the temperature was raised to 40°C and the reaction was carried out for 24 hours. After the reaction was completed, the temperature was cooled to 25°C, washed, filtered and dried under vacuum to obtain intermediate product 3. Step A4: Mix dimethyl terephthalate, dodecanoic acid, intermediate product 3, isosorbide and toluene, purge with nitrogen, heat to 120°C, add tetrabutyl titanate, and then heat in stages at 160°C, 190°C and 210°C for 4 hours under reflux. Then heat to 230°C, reduce the system pressure to below 50 Pa within 1 hour, and then heat to 250°C for 6 hours under reflux. After the reaction is complete, discharge under nitrogen protection and vacuum dry to obtain the modified toughening agent.

2. The high-mechanical-performance PLA biodegradable composite material according to claim 1, characterized in that, In step A1, the ratio of DL-glyceraldehyde, anhydrous ethanol, and 1-(3-aminopropyl)imidazole is 0.8-1 mol: 150-250 mL: 0.8-1 mol.

3. The high-mechanical-performance PLA biodegradable composite material according to claim 1, characterized in that, In step A2, the ratio of cashew phenol, triethylamine, dichloromethane, 6-bromohexanoyl chloride, and deionized water is 0.8-1 mol: 1.2-1.5 mol: 350-400 mL: 0.96-1.2 mol: 150 mL.

4. The high-mechanical-performance PLA biodegradable composite material according to claim 1, characterized in that, In step A3, the ratio of intermediate product 1, n-hexane, 2,6-di-tert-butyl-4-methylphenol, and intermediate product 2 solution is 0.3-0.4 mol: 80-100 mL: 0.12-0.18 mmol: 60-80 mL. Intermediate product 2 solution is prepared by mixing intermediate product 2 and anhydrous ethanol at a ratio of 0.6-0.8 mol: 60-80 mL.

5. The high-mechanical-performance PLA biodegradable composite material according to claim 1, characterized in that, In step A4, the ratio of dimethyl terephthalate, dodecanoic acid, intermediate 3, isosorbide, toluene, and tetrabutyl titanate is 0.1-0.2 mol: 0.1-0.2 mol: 0.12-0.24 mol: 0.024-0.048 mol: 30-50 mL: 0.4-0.8 mmol.

6. The high-mechanical-performance PLA biodegradable composite material according to claim 1, characterized in that, The modified light stabilizer is prepared by the following steps: Step B1: Mix methyl 4-hydroxycinnamate, epichlorohydrin and tetrabutylammonium bromide, stir and react at 80°C for 2 hours. After the reaction is completed, cool to room temperature, add 20wt% sodium hydroxide aqueous solution in an ice-water bath, react in an ice-water bath for 1 hour, then extract, wash, recrystallize, filter and vacuum dry to obtain cinnamic acid derivative. Step B2: Mix 1-hydroxybenzotriazole, cinnamic acid derivative, and N,N-dimethylformamide, heat to 90°C, add tetramethylammonium bromide, heat to 100°C and react for 6 hours. After the reaction is complete, cool to room temperature, wash, separate, and distill under reduced pressure to obtain cinnamic acid benzotriazole derivative. The molar ratio of 1-hydroxybenzotriazole, cinnamic acid derivative, N,N-dimethylformamide, and tetramethylammonium bromide is 0.1-0.14 mol: 0.5-0.7 mol: 60-100 mL: 0.002-0.003 mol. Step B3: Mix anhydrous citric acid, cysteine ​​hydrochloride and deionized water to obtain a mixture. Place it in an 80°C oven for 30 min, shake, and continue to place it in the oven for 1.5 h. Then place it in a 130°C oven and react for 12 h. After the reaction is complete, cool to room temperature, add deionized water, stir, filter under reduced pressure, wash, and dry under vacuum to obtain the pyridinone derivative. Step B4: Mix pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and dichloromethane, seal, and stir in an ice-water bath for 2 hours. After the reaction is complete, add cinnamic acid benzotriazole derivative solution dropwise at room temperature, seal and react for 24 hours. Then wash, dry in liquid phase, filter under reduced pressure, rotary evaporate, purify, and dry under vacuum to obtain the modified light stabilizer.

7. The high-mechanical-performance PLA biodegradable composite material according to claim 6, characterized in that, In step B1, the ratio of methyl 4-hydroxycinnamate, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide aqueous solution is 0.8-1 mol: 8-10 mol: 0.33-0.34 mol: 400-500 mL.

8. The high-mechanical-performance PLA biodegradable composite material according to claim 6, characterized in that, In step B3, the ratio of the mixture to deionized water is 3-6 mL: 100-150 mL, and the ratio of anhydrous citric acid, cysteine ​​hydrochloride, and deionized water in the mixture is 0.05-0.1 mol: 0.05-0.1 mol: 3-6 mL.

9. A high-mechanical-performance PLA biodegradable composite material according to claim 6, characterized in that, In step B4, the ratio of the pyridone derivative, 4-dimethylaminopyridine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, dichloromethane, and benzotriazole cinnamic acid derivative solution is 0.03-0.05 mol: 0.003-0.005 mol: 0.06-0.1 mol: 120-160 mL: 40-80 mL. The benzotriazole cinnamic acid derivative solution is prepared by mixing the benzotriazole cinnamic acid derivative and dichloromethane in a ratio of 0.045-0.075 mol: 40-80 mL.

10. A method for preparing a high-mechanical-performance PLA biodegradable composite material according to any one of claims 1-9, characterized in that, The high-mechanical-performance PLA biodegradable composite material is prepared by the following steps: Step S1: Weigh the raw materials according to the weight proportions, and put PLA resin, PBS resin, cedar powder, polycaprolactone, modified toughening agent, modified light stabilizer, antioxidant 1010, tristearate, sodium benzoate and silane coupling agent KH-550 into a mixer and mix for 10-30 minutes at a speed of 400-600 rpm to obtain a mixture; Step S2: The mixture is fed into an extruder for extrusion granulation. The screw speed is 100-200 rpm and the extrusion temperature is 160-170℃. Then, it is injection molded to obtain a high-mechanical-performance PLA biodegradable composite material.

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