Degradable plastic colloidal particles and preparation method thereof

Abstract

The invention relates to degradable plastic colloidal particles and a preparation method thereof, and belongs to the technical field of degradable plastic. The colloidal particle comprises the following components in percentage by mass: 15-20 wt% of a photosensitive accelerator, 8-12 wt% of a biodegradation agent, 5-8 wt% of a plasticizer, 0.3-0.5 wt% of a compatilizer, 0.3-0.5 wt% of an antioxidant and the balance of polylactic acid. The photosensitive accelerator is prepared by the following steps: reacting 5-hydroxy-2-nitrobenzyl alcohol with di-tert-butyl dicarbonate ester to generate a phenolic hydroxyl group protection intermediate, oxidizing with chromic acid to obtain a carboxyl-terminated intermediate, reducing hydroxyl groups with trifluoroacetic acid, and polymerizing with lactide. According to the biodegradation agent, lipase and glycogen are loaded on silicon dioxide to form a compound, and then the compound is coated with a layer of compact acetalized polysaccharide film which is easy to hydrolyze and resistant to high temperature by adopting a solvent evaporation method. The plastic degradation efficiency can be effectively improved through a constructed'light triggering-biological enhancement 'bimodal synergistic degradation mechanism.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of plastics, and in particular relates to a degradable plastic rubber particle and a preparation method thereof. BACKGROUND

[0002] Plastic pollution has become one of the most pressing environmental challenges worldwide. Traditional petroleum-based plastics are extremely difficult to decompose in the natural environment due to their excellent durability and stability, and can exist for hundreds of years. However, the "long-lasting" characteristics of this material, after being discarded, have turned into a serious environmental burden, and the accumulation of plastic waste has caused continuous damage to the ecosystem.

[0003] To alleviate the plastic pollution crisis, the industry has developed a variety of degradable plastics, the most common of which is to blend traditional petroleum-based plastics with degradable plastics. Although such products have some degradability compared to pure traditional plastics, they can only be broken into small pieces during the degradation process, and do not truly destroy their core chemical structure. Such microplastic particles are more hidden and more likely to be misfed or ingested by organisms, and then widely invade the soil, water and atmospheric environment, and are further enriched through the food chain, ultimately posing a potential threat to the stability of the ecosystem and human health.

[0004] Against this background, polylactic acid-based degradable plastics have emerged. However, even so, their application still faces two key bottlenecks: slow degradation rate and incomplete degradation, which seriously restricts their actual promotion and environmental benefits. The effective degradation of such materials often depends heavily on industrial composting conditions, including sustained high temperature, specific humidity and special microbial community; and in the natural environment, such harsh conditions are difficult to meet, resulting in extremely slow degradation process, and ultimately failing to achieve rapid recycling and environmental self-cleaning in real application scenarios, and remaining in the environment for a long time, thereby causing a series of environmental problems such as visual pollution, animal misfeeding and ecological accumulation.

[0005] In summary, the fundamental defect of current degradable plastic technology is that the degradation process is uncontrollable and incomplete, and highly dependent on ideal environments created by humans, and cannot achieve rapid and complete degradation under natural conditions. This greatly limits its potential to replace traditional petroleum-based plastics and solve the problem of plastic pollution from the root. SUMMARY

[0006] In order to solve the technical problems mentioned in the background art, the purpose of the present application is to provide a degradable plastic rubber particle and a preparation method thereof.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A degradable plastic glue particle, the weight percentage components of which are: photosensitive promoter 15-20wt%, biodegradation agent 8-12wt%, plasticizer 5-8wt%, compatibility agent 0.3-0.5wt% and antioxidant 0.3-0.5wt%, and the rest is polylactic acid.

[0009] The photosensitive promoter is prepared by the following method:

[0010] Step A1: 5-hydroxy-2-nitrobenzyl alcohol is pre-mixed with anhydrous dichloromethane, cooled to 0°C in an ice water bath, mixed with triethylamine and 4-dimethylaminopyridine, then slowly add di-tert-butyl dicarbonate and stir for 30 min, the temperature rises to room temperature and continue to stir for 10-12 h, after the reaction is completed, filter and rotary evaporation to obtain intermediate 1.

[0011] Further, the feeding ratio of 5-hydroxy-2-nitrobenzyl alcohol, di-tert-butyl dicarbonate, anhydrous dichloromethane, triethylamine and 4-dimethylaminopyridine is 1 mol:1-1.2 mol:3-3.5 L:1.2-1.5 mol:16-18 g. Under the action of base, di-tert-butyl dicarbonate reacts with the phenolic hydroxyl group in 5-hydroxy-2-nitrobenzyl alcohol to protect the phenolic hydroxyl group, and the specific reaction route is as follows:

[0012] Step A2: Intermediate 1 is pre-mixed with acetone, cooled to 0°C in an ice water bath, slowly add chromic acid reagent and stir for 30 min, the temperature rises to room temperature and continue to stir for 2-3 h, then quench, rotary evaporation and extraction, washing and filtering to obtain intermediate 2.

[0013] Further, the feeding ratio of intermediate 1, chromic acid reagent and acetone is 1 mol:1-1.2 mol:3-3.6 L; the chromic acid reagent oxidizes intermediate 1. The specific reaction route is as follows:

[0014] Step A3: Intermediate 2 is mixed with dichloromethane, then add trifluoroacetic acid and stir at room temperature for 2 h, after the reaction is completed, rotary evaporation to obtain intermediate 3.

[0015] Further, the feeding ratio of intermediate 2, trifluoroacetic acid and dichloromethane is 1.5-1.8 g:10-15 mL:20-30 mL; trifluoroacetic acid deprotects the phenolic ester protecting group on the molecule of intermediate 2, and the specific reaction route is as follows:

[0016] Step A4: Lactide and intermediate 3 are mixed, under argon protection, then add anhydrous tetrahydrofuran and stannous octoate mixture, heat to 130°C and react for 12 h, after the reaction is completed, cool, filter and dry to obtain the photosensitive promoter.

[0017] Further, the feeding ratio of lactide, intermediate 3 and anhydrous toluene is 10-12 mol: 1-1.2 mol: 18-20 L; the amount of stannous octoate catalyst is 1 wt‰; the lactide ring opens and randomly copolymerizes with intermediate 3.

[0018] The biodegradation agent is prepared by the following method:

[0019] Step B1: nitrogen is introduced, dextran is mixed with anhydrous dimethyl sulfoxide, stirred and heated to 50℃, molecular sieves are added and continue to stir for 30 min, and ice water bath is cooled to 0℃. Add p-toluenesulfonic acid pyridine salt mixture, the temperature rises to room temperature and stir for 24 h. Pour the reaction liquid into petroleum ether / ether mixture under vigorous stirring, stand and filter, wash the precipitate, and obtain acetalized polysaccharide.

[0020] Further, the feeding ratio of dextran, p-toluenesulfonic acid pyridine salt, molecular sieves and anhydrous dimethyl sulfoxide is 1 g: 0.1 g: 1 g: 10 mL, and the petroleum ether / ether mixture is mixed by petroleum ether and ether at a volume ratio of 1:1.

[0021] Step B2: the lipase and glycogen are mixed with phosphate buffer solution and stirred uniformly, and porous silica nanospheres are added. Slow stirring at 4℃ for 4 h allows the enzyme and glycogen to be loaded into the pores to obtain an "enzyme-glycogen-silica" complex.

[0022] Further, the feeding ratio of lipase, glycogen, silica nanospheres and phosphate buffer solution is 1 g: 2 g: 5 g: 100 mL.

[0023] Step B3: the acetalized polysaccharide is mixed with dichloromethane, and then the "enzyme-glycogen-silica" complex is added to form a suspension; the emulsifying dispersant is mixed with water and poured into the suspension, and emulsified at a speed of 8000 rpm for 3 min to form a multiple emulsion, which is stirred at room temperature for 4 h, and then centrifuged and washed to obtain a core-shell structure biodegradation enhancer.

[0024] Further, the feeding ratio of "enzyme-glycogen-silica" complex, acetalized polysaccharide, dichloromethane, emulsifying dispersant and water is 50 mg: 100 mg: 4 mL: 100 mg: 10 mL; as the dichloromethane volatilizes during stirring, the acetalized polysaccharide dissolved in dichloromethane gradually precipitates and deposits on the surface of the "enzyme-glycogen-silica" complex to form a dense coating film, which is the biodegradation agent.

[0025] Preferably, the plasticizer is acetyl tri-n-butyl citrate, which has excellent biocompatibility and can effectively improve the processing fluidity of the copolymer and the flexibility of the final product.

[0026] Preferably, the antioxidant is antioxidant 1010, which maintains good antioxidant ability and prevents thermal oxidative degradation during processing.

[0027] Preferably, the compatibilizer is Joncryl ADR-4368, which greatly improves the dispersion uniformity of the biodegradable agent in the modified polylactic acid while enhancing the interfacial bonding of the biodegradable agent with the polymer matrix, preventing agglomeration.

[0028] A preparation method of degradable plastic granules, the specific steps are as follows: polylactic acid, photosensitive promoter, plasticizer, compatibilizer and antioxidant are put into a double screw extruder for melt blending, and the biodegradable agent is added into the blending system through a side feeding port; the formed fine strip is first cooled through a water tank, and then granulated to obtain degradable plastic granules.

[0029] The application has the following beneficial effects: the application uses polylactic acid as the main material, adds a photosensitive promoter and a biodegradable agent to construct a "light-triggered-biological-enhanced" dual-mode synergistic degradation mechanism. The photosensitive promoter with excellent compatibility with polylactic acid structure is prepared by connecting the o-nitrobenzyl photosensitive group with lactide, so that it can be crosslinked and entangled with the polylactic acid backbone; at the same time, enzyme-sugar microcapsules coated with high-temperature-resistant and easily hydrolyzed acetalized polysaccharides are dispersed in the system, finally realizing a breakthrough in the degradation performance of the material. The degradation principle is as follows: after the material is discarded, natural light first triggers the Norrish I type cleavage of the o-nitrobenzyl group, i.e. the cleavage of the ester chain connecting the nitrobenzyl group and the carboxyl group, efficiently cutting off the long polymer chain and promoting the formation of a large number of disintegrating cracks on the surface and inside of the material; with the help of capillary action, water is more easily penetrated into the interior of the material, and after the biodegradable agent encounters water, the acetalized polysaccharide shell rapidly hydrolyzes, exposing the high-efficiency lipase which can accurately cleave the ester bond in the polymer molecular chain; and glycogen acts as a strong chemoattractant, efficiently enriching the microorganisms in the surrounding environment, and finally completely mineralizing the plastic fragments into carbon dioxide, water and biomass.

[0030] The significant advantages brought by the dual-mode mechanism are: not only effectively solving the core pain points of slow degradation rate and incomplete degradation of traditional degradable plastics, but also completely getting rid of the dependence on industrial composting facilities, and realizing rapid and complete degradation in various complex real environments; at the same time, the degradation life of the material can be precisely controlled through molecular structure design. In summary, the application provides an innovative solution that is efficient, environmentally adaptable and economically feasible for replacing traditional plastics and addressing white pollution. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0032] Embodiment 1, preparation of degradable plastics, the specific implementation process is as follows:

[0033] (1) Preparation of photosensitive accelerant

[0034] Step A1: 5-hydroxy-2-nitrobenzyl alcohol is premixed with anhydrous dichloromethane, cooled to 0°C in an ice water bath, and then mixed with triethylamine and 4-dimethylaminopyridine, followed by slowly adding di-tert-butyl dicarbonate and stirring for 30 min, and then the temperature is raised to room temperature and the stirring is continued for 10 h, wherein the feeding ratio of 5-hydroxy-2-nitrobenzyl alcohol, di-tert-butyl dicarbonate, anhydrous dichloromethane, triethylamine and 4-dimethylaminopyridine is 1 mol: 1.2 mol: 3.5 L: 1.5 mol: 18 g. After the reaction is completed, filtration and rotary evaporation are performed to obtain intermediate 1.

[0035] Step A2: Intermediate 1 is premixed with acetone, cooled to 0°C in an ice water bath, and then slowly added with chromic acid reagent and stirred for 30 min, and then the temperature is raised to room temperature and the stirring is continued for 2 h, and then slowly added with isopropyl alcohol to quench the excess oxidant. Most of the acetone is removed by rotary evaporation. The remaining substance is diluted with water and extracted with dichloromethane three times. The organic phase is combined, dried with anhydrous sodium sulfate, filtered and then rotary evaporated to obtain intermediate 2. The feeding ratio of intermediate 1, chromic acid reagent and acetone is 1 mol: 1.2 mol: 3.6 L.

[0036] Step A3: Intermediate 2 is mixed with dichloromethane, and then trifluoroacetic acid is added, and stirred at room temperature for 2 h. The feeding ratio of intermediate 2, trifluoroacetic acid and dichloromethane is 1.5 g: 10 mL: 20 mL; and after the reaction is completed, rotary evaporation is performed to obtain intermediate 3.

[0037] Step A4: Lactide and intermediate 3 are mixed, and then anhydrous tetrahydrofuran and stannous octoate are added under argon protection, and then the temperature is raised to 130°C and reacted for 12 h. The feeding ratio of lactide, intermediate 3 and anhydrous toluene is 10 mol: 1 mol: 18 L; and the amount of stannous octoate catalyst is 1 wt‰; and after the reaction is completed, the temperature is cooled to room temperature, and then filtration is performed to obtain a white solid, which is washed with cold methanol three times. The product is dried under vacuum at 40°C to obtain the photosensitive accelerant.

[0038] (2) Preparation of biodegradable agent:

[0039] Step B1 : nitrogen was bubbled into the mixture of dextran and anhydrous dimethyl sulfoxide, stirred and heated to 50°C, molecular sieves were added and stirred for 30 min, and then cooled to 0°C in an ice water bath. Pyridine p-toluenesulfonate was added, and the temperature was raised to room temperature and stirred for 24 h. The reaction solution was poured into a mixture of petroleum ether / ether under vigorous stirring, and after standing, the supernatant was decanted and the precipitate was washed with a large amount of ether three times to completely remove dimethyl sulfoxide, catalyst and by-products. The obtained white solid was dried at 40°C under vacuum for 24 h to obtain the acetalized polysaccharide. The feeding ratio of dextran, pyridine p-toluenesulfonate, molecular sieves and anhydrous dimethyl sulfoxide was 1 g:0.1 g:1 g:10 mL, and the mixture of petroleum ether / ether was mixed by volume ratio of petroleum ether and ether 1:1.

[0040] Step B2: the lipase and glycogen were mixed with phosphate buffer and stirred uniformly, and porous silica nanospheres were added. The enzyme and glycogen were loaded into the pores by stirring at 4°C for 4 h to obtain an "enzyme-glycogen-silica" complex. The lipase used was Novozym 435, and the glycogen was provided by Shanghai Sunshine Reagent Co., Ltd. The feeding ratio of lipase, glycogen, silica nanospheres and phosphate buffer was 1 g:2 g:5 g:100 mL.

[0041] Step B3: the acetalized polysaccharide was mixed with dichloromethane, and then the "enzyme-glycogen-silica" complex was added to form a suspension; the emulsifying dispersant was mixed with water and poured into the suspension, and emulsified at a speed of 8000 rpm for 3 min to form a multiple emulsion, which was stirred at room temperature for 4 h. The reaction solution was centrifuged at 8000 rpm for 10 min, and the supernatant was discarded. The precipitate was washed with deionized water three times to remove PVA. The collected solid particles were redispersed in a small amount of water and dried. Finally, the acetalized polysaccharide microcapsules were obtained. That is, the biodegradable agent with core-shell structure. The feeding ratio of "enzyme-glycogen-silica" complex, acetalized polysaccharide, dichloromethane, emulsifying dispersant and water was 50 mg:100 mg:4 mL:100 mg:10 mL; as the dichloromethane volatilized during stirring, the acetalized polysaccharide dissolved in dichloromethane gradually precipitated and deposited on the surface of the "enzyme-glycogen-silica" complex, forming a dense coating film. That is, the biodegradable agent.

[0042] (3) Preparation of degradable plastic particles

[0043] According to the component preparation, the photosensitizer is 15wt%, which is self-made in this embodiment; the biodegradable agent is 8wt%, which is self-made in this embodiment; the plasticizer is 5wt%, which is tributyl acetylacetic acid (TBC) from Jinan Shengchen Chemical Co., Ltd.; the compatibilizer is 0.3wt%, which is Joncryl® ADR-4368-C from Shanghai Kunzhen Materials Technology Co., Ltd.; the antioxidant is 0.3wt%, which is commercially available antioxidant 1010; and the balance is polylactic acid, which is polylactic acid FY802 from Anhui Fengyuan Group.

[0044] Polylactic acid, photosensitizing accelerator, plasticizer, compatibilizer and antioxidant are put into a twin-screw extruder for melt blending. Biodegradable agent is added to the blending system through the side feed port. The extruded strips are first cooled in a water tank and then granulated to obtain biodegradable plastic granules.

[0045] Example 2: Preparation of biodegradable plastics, the specific implementation process is as follows:

[0046] (1) Preparation of photosensitizing promoter

[0047] Step A1: Premix 5-hydroxy-2-nitrobenzyl alcohol with anhydrous dichloromethane, cool to 0°C in an ice-water bath, add triethylamine and 4-dimethylaminopyridine, then slowly add di-tert-butyl dicarbonate and stir for 30 min. The temperature is then raised to room temperature and the reaction continues for 10 h. The feed ratio of 5-hydroxy-2-nitrobenzyl alcohol, di-tert-butyl dicarbonate, anhydrous dichloromethane, triethylamine, and 4-dimethylaminopyridine is 1 mol:1.2 mol:3.5 L:1.5 mol:18 g. After the reaction is complete, filter and rotary evaporate to obtain intermediate 1.

[0048] Step A2: Intermediate 1 was premixed with acetone, cooled to 0°C in an ice-water bath, and chromic acid reagent was slowly added while stirring for 30 min. The temperature was then raised to room temperature and stirring continued for 2 h. Isopropanol was then slowly added to quench excess oxidant. Most of the acetone was removed by rotary evaporation. The residue was diluted with water and extracted three times with dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate, filtered, and then rotary evaporated to obtain intermediate 2. The feed ratio of intermediate 1, chromic acid reagent, and acetone was 1 mol:1.2 mol:3.6 L.

[0049] Step A3: Mix intermediate 2 with dichloromethane, then add trifluoroacetic acid, and stir at room temperature for 2 hours. The feed ratio of intermediate 2, trifluoroacetic acid, and dichloromethane is 1.5 g: 10 mL: 20 mL. After the reaction is complete, rotary evaporate to obtain intermediate 3.

[0050] Step A4: Lactide and intermediate 3 were mixed, and under argon protection, anhydrous tetrahydrofuran and stannous octoate were added and mixed. The mixture was heated to 130°C and reacted for 12 hours. The feed ratio of lactide, intermediate 3, and anhydrous toluene was 10 mol:1 mol:18 L; the amount of stannous octoate catalyst was 1 wt%. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain a white solid, and washed three times with cold methanol. The product was vacuum dried at 40°C to obtain a photosensitizer.

[0051] (2) Preparation of biodegradable agents:

[0052] Step B1: Nitrogen gas is introduced, dextran is mixed with anhydrous dimethyl sulfoxide (DMSO), stirred and heated to 50°C, molecular sieve is added and stirring continues for 30 min, then cooled to 0°C in an ice-water bath. Pyridine p-toluenesulfonate is added, and the temperature is raised back to room temperature with stirring for 24 h. The reaction mixture is poured into a petroleum ether / diethyl ether mixture under vigorous stirring, allowed to stand, and the supernatant is discarded. The precipitate is washed three times with a large amount of diethyl ether to thoroughly remove dimethyl sulfoxide, catalyst, and byproducts. The resulting white solid is vacuum dried at 40°C for 24 h to obtain acetalized polysaccharide. The feed ratio of dextran, pyridine p-toluenesulfonate, molecular sieve, and anhydrous dimethyl sulfoxide is 1 g:0.1 g:1 g:10 mL, and the petroleum ether / diethyl ether mixture is a 1:1 volume ratio of petroleum ether and diethyl ether.

[0053] Step B2: Lipase and glycogen were mixed thoroughly with phosphate buffer, and porous silica nanospheres were added. The mixture was stirred at 4°C for 4 hours to load the enzyme and glycogen into the pores, obtaining an "enzyme-glycogen-silica" complex. The lipase used was Novozymes lipase 435, and the glycogen was provided by Shanghai Sunshine Reagent Co., Ltd. The feed ratio of lipase, glycogen, silica nanospheres, and phosphate buffer was 1 g:2 g:5 g:100 mL.

[0054] Step B3: Mix the acetalized polysaccharide with dichloromethane, then add the enzyme-glycogen-silica complex and disperse thoroughly to form a suspension. Mix the emulsifying dispersant with water and pour it into the suspension. Emulsify at 8000 rpm for 3 minutes to form a double emulsion. Stir at room temperature for 4 hours. Centrifuge the reaction solution at 8000 rpm for 10 minutes and discard the supernatant. Wash the precipitate three times with deionized water to remove PVA. Redisperse the collected solid particles in a small amount of water and then dry. Finally, acetalized polysaccharide microcapsules are obtained, which are biodegradable agents with a core-shell structure. The feed ratio of the enzyme-glycogen-silica complex, acetalized polysaccharide, dichloromethane, emulsifying dispersant, and water is 50 mg:100 mg:4 mL:100 mg:10 mL. As the dichloromethane evaporates during stirring, the acetalized polysaccharide dissolved in the dichloromethane gradually precipitates and deposits on the surface of the enzyme-glycogen-silica complex, forming a dense coating film. This film serves as the biodegradable agent.

[0055] (3) Preparation of biodegradable plastic granules

[0056] According to the composition, the photosensitizer is 17wt%, which is self-made in this embodiment; the biodegradable agent is 10wt%, which is self-made in this embodiment; the plasticizer is 7wt%, which is tributyl acetylacetic acid (TBC) from Jinan Shengchen Chemical Co., Ltd.; the compatibilizer is 0.4wt%, which is Joncryl® ADR-4368-C from Shanghai Kunzhen Materials Technology Co., Ltd.; the antioxidant is 0.4wt%, which is commercially available antioxidant 1010; and the balance is polylactic acid, which is polylactic acid FY802 from Anhui Fengyuan Group.

[0057] Polylactic acid, photosensitizing accelerator, plasticizer, compatibilizer and antioxidant are put into a twin-screw extruder for melt blending. Biodegradable agent is added to the blending system through the side feed port. The extruded strips are first cooled in a water tank and then granulated to obtain biodegradable plastic granules.

[0058] Example 3: Preparation of biodegradable plastics, the specific implementation process is as follows:

[0059] (1) Preparation of photosensitizing promoter

[0060] Step A1: Premix 5-hydroxy-2-nitrobenzyl alcohol with anhydrous dichloromethane, cool to 0°C in an ice-water bath, add triethylamine and 4-dimethylaminopyridine, then slowly add di-tert-butyl dicarbonate and stir for 30 min. The temperature is then raised to room temperature and the reaction continues for 10 h. The feed ratio of 5-hydroxy-2-nitrobenzyl alcohol, di-tert-butyl dicarbonate, anhydrous dichloromethane, triethylamine, and 4-dimethylaminopyridine is 1 mol:1.2 mol:3.5 L:1.5 mol:18 g. After the reaction is complete, filter and rotary evaporate to obtain intermediate 1.

[0061] Step A2: Intermediate 1 was premixed with acetone, cooled to 0°C in an ice-water bath, and chromic acid reagent was slowly added while stirring for 30 min. The temperature was then raised to room temperature and stirring continued for 2 h. Isopropanol was then slowly added to quench excess oxidant. Most of the acetone was removed by rotary evaporation. The residue was diluted with water and extracted three times with dichloromethane. The combined organic phases were dried over anhydrous sodium sulfate, filtered, and then rotary evaporated to obtain intermediate 2. The feed ratio of intermediate 1, chromic acid reagent, and acetone was 1 mol:1.2 mol:3.6 L.

[0062] Step A3: Mix intermediate 2 with dichloromethane, then add trifluoroacetic acid, and stir at room temperature for 2 hours. The feed ratio of intermediate 2, trifluoroacetic acid, and dichloromethane is 1.5 g: 10 mL: 20 mL. After the reaction is complete, rotary evaporate to obtain intermediate 3.

[0063] Step A4: Lactide and intermediate 3 were mixed, and under argon protection, anhydrous tetrahydrofuran and stannous octoate were added and mixed. The mixture was heated to 130°C and reacted for 12 hours. The feed ratio of lactide, intermediate 3, and anhydrous toluene was 10 mol:1 mol:18 L; the amount of stannous octoate catalyst was 1 wt%. After the reaction was completed, the mixture was cooled to room temperature, filtered to obtain a white solid, and washed three times with cold methanol. The product was vacuum dried at 40°C to obtain a photosensitizer.

[0064] (2) Preparation of biodegradable agents:

[0065] Step B1: Nitrogen gas is introduced, dextran is mixed with anhydrous dimethyl sulfoxide (DMSO), stirred and heated to 50°C, molecular sieve is added and stirring continues for 30 min, then cooled to 0°C in an ice-water bath. Pyridine p-toluenesulfonate is added, and the temperature is raised back to room temperature with stirring for 24 h. The reaction mixture is poured into a petroleum ether / diethyl ether mixture under vigorous stirring, allowed to stand, and the supernatant is discarded. The precipitate is washed three times with a large amount of diethyl ether to thoroughly remove dimethyl sulfoxide, catalyst, and byproducts. The resulting white solid is vacuum dried at 40°C for 24 h to obtain acetalized polysaccharide. The feed ratio of dextran, pyridine p-toluenesulfonate, molecular sieve, and anhydrous dimethyl sulfoxide is 1 g:0.1 g:1 g:10 mL, and the petroleum ether / diethyl ether mixture is a 1:1 volume ratio of petroleum ether and diethyl ether.

[0066] Step B2: Lipase and glycogen were mixed thoroughly with phosphate buffer, and porous silica nanospheres were added. The mixture was stirred at 4°C for 4 hours to load the enzyme and glycogen into the pores, obtaining an "enzyme-glycogen-silica" complex. The lipase used was Novozymes lipase 435, and the glycogen was provided by Shanghai Sunshine Reagent Co., Ltd. The feed ratio of lipase, glycogen, silica nanospheres, and phosphate buffer was 1 g:2 g:5 g:100 mL.

[0067] Step B3: Mix the acetalized polysaccharide with dichloromethane, then add the enzyme-glycogen-silica complex and disperse thoroughly to form a suspension. Mix the emulsifying dispersant with water and pour it into the suspension. Emulsify at 8000 rpm for 3 minutes to form a double emulsion. Stir at room temperature for 4 hours. Centrifuge the reaction solution at 8000 rpm for 10 minutes and discard the supernatant. Wash the precipitate three times with deionized water to remove PVA. Redisperse the collected solid particles in a small amount of water and then dry. Finally, acetalized polysaccharide microcapsules are obtained, which are biodegradable agents with a core-shell structure. The feed ratio of the enzyme-glycogen-silica complex, acetalized polysaccharide, dichloromethane, emulsifying dispersant, and water is 50 mg:100 mg:4 mL:100 mg:10 mL. As the dichloromethane evaporates during stirring, the acetalized polysaccharide dissolved in the dichloromethane gradually precipitates and deposits on the surface of the enzyme-glycogen-silica complex, forming a dense coating film. This film serves as the biodegradable agent.

[0068] (3) Preparation of biodegradable plastic granules

[0069] According to the composition, the photosensitizer is 20 wt%, which is self-made in this embodiment; the biodegradable agent is 12 wt%, which is self-made in this embodiment; the plasticizer is 8 wt%, which is tributyl acetylacetic acid (TBC) from Jinan Shengchen Chemical Co., Ltd.; the compatibilizer is 0.5 wt%, which is Joncryl® ADR-4368-C from Shanghai Kunzhen Materials Technology Co., Ltd.; the antioxidant is 0.5 wt%, which is commercially available antioxidant 1010; and the balance is polylactic acid (PLA), which is PLA FY802 from Anhui Fengyuan Group.

[0070] Polylactic acid, photosensitizing accelerator, plasticizer, compatibilizer and antioxidant are put into a twin-screw extruder for melt blending. Biodegradable agent is added to the blending system through the side feed port. The extruded strips are first cooled in a water tank and then granulated to obtain biodegradable plastic granules.

[0071] Comparative Example 1 was carried out in accordance with the method of Example 3, without adding photosensitizing promoters and biodegradable agents, and the balance was supplemented by polylactic acid to 100 wt%, and the rest of the implementation process was exactly the same.

[0072] Comparative Example 2 was carried out in accordance with the method of Example 3, but without adding photosensitizing promoters, and the balance was supplemented by polylactic acid to 100 wt%, and the rest of the implementation process was exactly the same.

[0073] Comparative Example 3 follows the same implementation method as Example 3, except that the photosensitizer is replaced with an equal amount of titanium dioxide photosensitizer, and the rest of the implementation process is exactly the same.

[0074] The biodegradable plastic granules prepared above were hot-pressed into films using a micro film press. The prepared films were then cut into 2cm × 2cm samples, and the samples were subjected to simulated natural degradation. The specific method was as follows:

[0075] A 5cm thick layer of humus soil was laid at the bottom of a constant temperature and humidity chamber. The temperature inside the chamber was controlled at 30±2℃ and the humidity at 90%RH. The samples were placed on the surface of the humus soil to simulate a natural accumulation state and were irradiated with a 30W fluorescent lamp. The surface condition of the samples was observed at 7, 28, and 60 days, and the weight loss rate was calculated by weighing. The specific test results are shown in the table below:

[0076] A comprehensive analysis of the test data in the table above shows that the biodegradable plastic prepared by this invention possesses excellent degradation performance, specifically characterized by rapid degradation rate and thorough degradation. A comparison of the data from the examples and comparative examples reveals that the addition of the photosensitizing accelerator significantly accelerates the photo-oxidative degradation process, and without the photosensitizing accelerator, the biodegrading agent is difficult to function effectively. Furthermore, the photosensitizing group of this invention exhibits higher photosensitivity and a superior synergistic effect with the biodegrading agent. Further comparison of Examples 1, 2, and 3 shows that the degradation rate increases with the increase of the photosensitizing accelerator content, demonstrating that the photo-triggered mechanism is both highly efficient and controllable. In addition, the significant jump in degradation rate in the examples indicates that the introduction of enzymes and glycogen plays a strong synergistic role, rather than a simple additive effect. In summary, the biodegradable plastic prepared by the examples of this invention exhibits excellent degradation performance, fully meeting all the requirements for degradation behavior in biodegradable plastics. Its "photodegradation-bioreinforcement" two-step process is smoothly integrated, successfully achieving a cascade reaction from physical chain breaking to complete biomineralization. This material system holds promise for solving the problem of microplastic residues.

[0077] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0078] The above description is merely an example and illustration 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 invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A degradable plastic pellet, characterized in that, The specific components are: photosensitive promoter 15-20wt%, biodegradable agent 8-12wt%, plasticizer 5-8wt%, compatibility agent 0.3-0.5wt% and antioxidant 0.3-0.5wt%, and the balance is polylactic acid; The photosensitive promoter is prepared by the following method: Step A1: 5-hydroxy-2-nitrobenzyl alcohol is pre-mixed with anhydrous dichloromethane, cooled to 0°C in an ice water bath, mixed with triethylamine and 4-dimethylaminopyridine, then slowly add di-tert-butyl dicarbonate and stir for 30 min, the temperature rises to room temperature and continue to stir for 10-12 h, after the reaction is completed, filter and rotary evaporation to obtain intermediate 1; Step A2: Intermediate 1 is pre-mixed with acetone, cooled to 0°C in an ice water bath, slowly add chromic acid reagent and stir for 30 min, the temperature rises to room temperature and continue to stir for 2-3 h, then quench, rotary evaporation, dilution, extraction, washing, drying, filtration and rotary evaporation to obtain intermediate 2; Step A3: Intermediate 2 is mixed with dichloromethane, then add trifluoroacetic acid and stir for 2 h at room temperature, after the reaction is completed, rotary evaporation to obtain intermediate 3; Step A4: Lactide and intermediate 3 are mixed, under argon protection, then add anhydrous tetrahydrofuran and stannous octoate and mix, heat to 130°C and react for 12 h, after the reaction is completed, cool, filter, dry to obtain the photosensitive promoter.

2. The degradable plastic pellet according to claim 1, wherein, The feeding ratio of 5-hydroxy-2-nitrobenzyl alcohol, di-tert-butyl dicarbonate, anhydrous dichloromethane, triethylamine and 4-dimethylaminopyridine is 1 mol:1-1.2 mol:3-3.5 L:1.2-1.5 mol:16-18 g.

3. The degradable plastic pellet according to claim 2, wherein, The feeding ratio of intermediate 1, chromic acid reagent and acetone is 1 mol:1-1.2 mol:3-3.6 L.

4. The degradable plastic pellet according to claim 3, wherein, The feeding ratio of intermediate 2, trifluoroacetic acid and dichloromethane is 1.5-1.8 g:10-15 mL:20-30 mL.

5. The degradable plastic pellet according to claim 4, wherein, The feeding ratio of lactide, intermediate 3 and anhydrous toluene is 10-12 mol:1-1.2 mol:18-20 L.

6. The degradable plastic pellet according to claim 1, wherein, The biodegradable agent is prepared by the following method: Step B1: Under nitrogen protection, dextran is mixed with anhydrous dimethyl sulfoxide, stirred and heated to 50°C, then add molecular sieves and continue to stir for 30 min, cool to 0°C in an ice water bath, then add p-toluenesulfonic acid pyridine salt and mix, the temperature rises to room temperature and stir for 24 h, then wash with petroleum ether / ether mixture, stand, filter, wash the precipitate to obtain acetalized polysaccharide; Step B2: Lipase and glycogen are mixed with phosphate buffer solution and stirred uniformly, then add porous silica nanospheres, slowly stir for 4 h at 4°C, then dry to obtain "enzyme-glycogen-silica" complex; Step B3: Acetalized polysaccharide is mixed with dichloromethane, then add "enzyme-glycogen-silica" complex to form a suspension, then mix emulsifying dispersant with water and pour into the suspension, stir and emulsify, then stir for 4 h at room temperature, centrifuge, wash the precipitate to obtain core-shell structure biodegradable enhancer.

7. The degradable plastic pellet according to claim 6, wherein, The feeding ratio of dextran, p-toluenesulfonic acid pyridine salt, molecular sieves and anhydrous dimethyl sulfoxide is 1 g:0.1 g:1 g:10 mL.

8. The degradable plastic pellet according to claim 7, wherein, The feeding ratio of lipase, glycogen, silica nanospheres and phosphate buffer is 1 g:2 g:5 g:100 mL.

9. The degradable plastic pellet according to claim 8, wherein, The feeding ratio of "enzyme-glycogen-silica" complex, acetalized polysaccharide, dichloromethane, emulsifying dispersant and water is 50 mg:100 mg:4 mL:100 mg:10 mL.

10. The method of producing degradable plastic pellets according to any one of claims 1-9, characterized in that, Specifically, polylactic acid, photosensitive accelerator, plasticizer, compatibilizer and antioxidant are fed into a twin-screw extruder for melt blending, a biodegradable agent is added into the blending system through a side feeding port, and extrusion granulation is performed to obtain degradable plastic granules.

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