Environment-friendly degradable disposable plastic meal box and preparation method thereof

Abstract

The present application relates to the technical field of high polymer materials, in particular to an environment-friendly degradable disposable plastic meal box and a preparation method thereof, which comprises the following raw materials in parts by weight: 50-55 parts of bio-based polypropylene resin, 45-50 parts of degradable polyester phase, 3-5 parts of composite additive, 0.1-0.3 parts of antioxidant, 0.1-0.3 parts of hydrolysis-resistant agent, 0.1-0.3 parts of nucleating agent, 0.1-0.2 parts of slip agent and 0.5-2 parts of food-grade color master batch.In the present application, additive A and additive B of the composite additive are used to construct an enzyme-carrying synergistic system, PBAT in the degradable polyester phase is used as a tough skeleton to maintain strength, PHA is rapidly biodegradable, and PCL is easily soluble at low temperature.Through the combination of the three, the adaptive conditions are widened to achieve efficient degradation, and the meal box can be completely degraded into carbon dioxide, water and biomass humus under composting conditions, effectively solving the problem of difficult degradation and environmental pollution of traditional polypropylene disposable meal boxes.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an environmentally friendly, biodegradable disposable plastic lunch box and its preparation method. Background Technology

[0002] Disposable plastic food containers are mainly made of petroleum-based plastics and produced through injection molding or thermoforming processes. They are characterized by low cost, good temperature resistance, and easy molding, and are widely used in scenarios such as takeout, fast food, and fresh food delivery to meet the basic needs of temporarily holding food.

[0003] In existing technologies, petroleum-based lunch boxes are non-biodegradable, causing environmental pollution after disposal, and taking hundreds of years to degrade in the natural environment. Therefore, this invention provides an environmentally friendly, biodegradable disposable plastic lunch box and its preparation method. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly and biodegradable disposable plastic lunch box and its preparation method. The disposable plastic lunch box prepared by this invention has biodegradable characteristics, conforms to the concept of environmental protection, and effectively improves the performance of disposable plastic lunch boxes.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an environmentally friendly and biodegradable disposable plastic lunch box, comprising the following raw materials in parts by weight: 50-55 parts of bio-based polypropylene resin, 45-50 parts of biodegradable polyester phase, 3-5 parts of composite additives, 0.1-0.3 parts of antioxidant, 0.1-0.3 parts of anti-hydrolysis agent, 0.1-0.3 parts of nucleating agent, 0.1-0.2 parts of slip agent, and 0.5-2 parts of food-grade masterbatch.

[0006] Furthermore, the composite additive includes additive A and additive B, wherein additive A is pretreated before the preparation of the composite additive.

[0007] Furthermore, the biodegradable polyester phase is a mixture of polybutylene terephthalate, polyhydroxyalkanoate, and polycaprolactone in a mass ratio of (4-5):(3-4):(2-3), wherein the water content of polybutylene terephthalate and polyhydroxyalkanoate is less than 0.05%, and the water content of polycaprolactone is less than 0.1%.

[0008] Further, the preparation method of the composite additive is as follows: Additive A is dispersed in 0.1M phosphate buffer at a volume ratio of 1:(45-55), and Additive B is added. The mixture is stirred at 4°C for 1.5-2.5 hours, and 0.1wt% sodium alginate is added. The mixture is stirred at 20-30°C for 1 hour, and the solid is collected by centrifugation at 8000 rpm for 5-15 minutes. The solid is then vacuum dried at 55-65°C for 12 hours to obtain the composite additive. The mass of Additive B is 1-1.5 times the mass of Additive A.

[0009] Further, the preparation method of additive A is as follows: microcrystalline cellulose is dispersed in deionized water at a volume ratio of 1:(18-22), then tetramethylpiperidine oxide and sodium bromide are added, the pH value is adjusted to 9.5-10.5 with 0.5M sodium hypochlorite solution, and the mixture is stirred at 20-30℃ for 1.5-2.5h to obtain a reaction solution. The reaction is terminated with 0.5M sodium thiosulfate solution, and the precipitate is collected by centrifugation at 8000rpm for 5-15min. The precipitate is dialyzed to neutral under a molecular weight cutoff of 3500Da to obtain a neutral product. The mixture was dispersed in deionized water at a volume ratio of 1:(90-110), and chitosan oligosaccharide was added. The pH was adjusted to 4.5-5.5 with 0.1M hydrochloric acid solution, and the mixture was stirred at 20-30℃ for 40-80 min to obtain additive A. The microcrystalline cellulose had a particle size of 50 μm, tetramethylpiperidine oxide had a mass of 0.15-0.17% of the microcrystalline cellulose mass, sodium bromide had a mass of 0.15-0.17% of the microcrystalline cellulose mass, sodium hypochlorite had a volume of 1-5% of the reaction liquid volume, and chitosan oligosaccharide had a mass of 2-5% of the neutral product mass.

[0010] Further, the pretreatment method for additive A is as follows: Additive A is dispersed in deionized water at a volume ratio of 1:(90-110), ferric chloride hexahydrate and ferrous chloride tetrahydrate are added, nitrogen gas is passed through at a flow rate of 50-100 mL / min for protection, and the mixture is stirred at 75-85℃ and 200-300 rpm for 10-20 min. Ammonia water with a mass fraction of 25% is slowly added, and stirring is continued for 25-35 min. Magnetic separation is performed at an electric field strength of 0.3-0.5T for 5-10 s. The separated additive is washed with deionized water until neutral, and vacuum dried at 55-65℃ for 12 h to obtain pretreated additive A. The mass of ferric chloride hexahydrate is 5.0-5.8% of the mass of additive A, the mass of ferrous chloride tetrahydrate is 1.7-2.5% of the mass of additive A, and the volume of ammonia water is 9-11% of the volume of deionized water.

[0011] Further, the preparation method of additive B is as follows: clean rice husks are crushed to 0.3-0.9 mm, first pyrolyzed at 300-500℃ under nitrogen atmosphere with limited oxygen for 2.5-3.5 h, then added to 1M sulfuric acid solution at a volume ratio of 1:10, stirred at 250-350 rpm at 80℃ for 1.5-2.5 h, the solid is separated, washed with deionized water until neutral, then washed twice with ethanol, vacuum dried at 55-65℃ for 10-15 h, ground to a particle size of 50-100 μm, and the obtained powder is prepared at a volume ratio of 1:(45 -55) was dispersed in 0.1M MES buffer, and 8-12% of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.5-0.7% of N-hydroxysuccinimide were added. The mixture was stirred at 20-30℃ for 20-40 min, and then 1-2% of Novozymes lipase 435 was added. The mixture was stirred at 4℃ for 1.5-2.5 h, centrifuged at 8000 rpm for 5-15 min, the carrier was collected and washed 3 times with deionized water to obtain additive B, which was stored at 4℃.

[0012] Furthermore, the nucleating agent is prepared by modifying nano-talc powder with silane coupling agent KH550 at 60-80℃ for 2 hours, wherein the nano-talc powder has a particle size of less than 100nm and the mass of silane coupling agent KH550 is 1-2% of the mass of nano-talc powder.

[0013] Furthermore, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0014] Furthermore, the anti-hydrolysis agent is carbodiimide Stabaxol P200, the slip agent is oleamide, and the food-grade masterbatch is titanium dioxide.

[0015] Secondly, the present invention provides a method for preparing an environmentally friendly and biodegradable disposable plastic lunch box, characterized by comprising the following steps: S1: Dry the bio-based polypropylene resin at 80-100℃ for 2-4 hours, add it together with the biodegradable polyester phase into a high-speed mixer, premix at 1500-2000 rpm for 5-8 minutes, then add the composite additive, antioxidant, anti-hydrolysis agent, nucleating agent, slip agent and food-grade color masterbatch in sequence, and continue mixing at 1500-2000 rpm for 3-5 minutes to obtain the mixture; S2: The mixture is blended and pelletized using a co-rotating twin-screw extruder with a length-to-diameter ratio ≥40:1, segmented temperature control, and screw speed of 250-350 rpm to obtain blended particles of 2-3 mm. The segmented temperature control parameters are: feeding section 160-170℃, compression section 170-180℃, homogenization section 180-190℃, and die head 175-185℃. S3: The blended particles are melted using a single-screw extruder at a barrel temperature of 170-190℃ and a die temperature of 175-185℃. The mixture is then cast through a T-die, and the cooling roller temperature is 20-40℃ to obtain a sheet with a thickness of 0.3-0.5mm. S4: Heat the thick sheet to 130-150℃, place it in a mold, hold it under vacuum of -0.1MPa and molding pressure of 0.3-0.5MPa for 5-10 seconds, air cool at room temperature to demold and obtain a rough lunch box. Punch and trim the edges, anneal at 60-80℃ for 1.5-2.5 hours to obtain an environmentally friendly and biodegradable disposable plastic lunch box.

[0016] Compared with the prior art, the beneficial effects of the present invention are: In this invention, an enzyme-carrier synergistic system is constructed by additive A and additive B of a composite additive. The pre-treatment reinforcement material in additive A has a magnetic targeting enrichment effect in composting, the chitosan oligosaccharide enhances hydrophilicity, and the microcrystalline cellulose skeleton provides a stable interface for the enzymatic reaction, which not only avoids enzyme loss but also prolongs the activity cycle, ensuring effective degradation. The lipase in additive B preferentially catalyzes the hydrolysis and chain breaking of ester bonds in the degradable polyester phase, and the PBAT in the degradable polyester phase acts as a tough skeleton to maintain strength. PHA is rapidly biodegraded, and PCL is easily soluble at low temperatures. The combination of the three broadens the adaptability conditions and enables efficient degradation. Under composting conditions, the lunch box can be rapidly and completely degraded into carbon dioxide, water, and biomass humus, effectively solving the problems of traditional polypropylene disposable lunch boxes being difficult to degrade and polluting the environment. Attached Figure Description

[0017] Figure 1 The present invention provides a flowchart of an environmentally friendly, biodegradable disposable plastic lunch box and its preparation method. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the raw materials used in the following examples are all commercially available, and the MES buffer was purchased from Fuzhou Feijing Biotechnology Co., Ltd. as PH1772.

[0020] Example 1

[0021] Prepare the following raw materials by weight: 50 parts bio-based polypropylene resin, 45 parts biodegradable polyester phase, 3 parts composite additives, 0.1 parts antioxidant, 0.1 parts anti-hydrolysis agent, 0.1 parts nucleating agent, 0.1 parts slip agent, and 0.5 parts food-grade masterbatch; The biodegradable polyester phase is a mixture of polybutylene terephthalate, polyhydroxyalkanoate, and polycaprolactone in a mass ratio of 4:3:3, wherein the water content of polybutylene terephthalate and polyhydroxyalkanoate is less than 0.05%, and the water content of polycaprolactone is less than 0.1%. The nucleating agent was prepared by modifying nano-talc powder with silane coupling agent KH550 at 60℃ for 2 hours. The nano-talc powder had a particle size of less than 100 nm, and the mass of silane coupling agent KH550 was 1% of the mass of nano-talc powder. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1. The anti-hydrolysis agent is carbodiimide Stabaxol P200, the slip agent is oleamide, and the food-grade masterbatch is titanium dioxide.

[0022] Preparation of Additive A: Microcrystalline cellulose was dispersed in deionized water at a volume ratio of 1:18, and then tetramethylpiperidine oxide and sodium bromide were added. The pH was adjusted to 9.5 with 0.5M sodium hypochlorite solution, and the mixture was stirred at 20℃ for 1.5 h to obtain a reaction solution. The reaction was terminated with 0.5M sodium thiosulfate solution, and the precipitate was collected by centrifugation at 8000 rpm for 5 min. The precipitate was dialyzed to neutral under a molecular weight cutoff of 3500 Da to obtain a neutral product. The neutral product was dispersed in deionized water at a volume ratio of 1:90, and chitosan oligosaccharide was added. The pH was adjusted to 4.5 with 0.1M hydrochloric acid solution, and the mixture was stirred at 20℃ for 40 min to obtain Additive A. The particle size of microcrystalline cellulose was 50 μm, the mass of tetramethylpiperidine oxide was 0.15% of the mass of microcrystalline cellulose, the mass of sodium bromide was 0.15% of the mass of microcrystalline cellulose, the volume of sodium hypochlorite was 1% of the volume of the reaction solution, and the mass of chitosan oligosaccharide was 2% of the mass of the neutral product.

[0023] Pretreatment Additive A: Additive A was dispersed in deionized water at a volume ratio of 1:90. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added. Under nitrogen protection, the mixture was stirred at 75°C and 200 rpm for 10 min. Ammonia solution with a mass fraction of 25% was slowly added, and stirring was continued for 25 min. Magnetic separation was performed under an electric field strength of 0.3T for 5 s. The separated additive was washed with deionized water until neutral and then vacuum dried at 55°C for 12 h to obtain pretreated additive A. The mass of ferric chloride hexahydrate was 5.0% of the mass of additive A, the mass of ferrous chloride tetrahydrate was 1.7% of the mass of additive A, and the volume of ammonia solution was 9% of the volume of deionized water.

[0024] Preparation of Additive B: Clean rice husks were crushed to 0.3 mm, pyrolyzed at 300 °C under nitrogen atmosphere for 2.5 h with limited oxygen, and then added to 1 M sulfuric acid solution at a volume ratio of 1:10. The mixture was stirred at 250 rpm for 1.5 h at 80 °C. The solid was separated, washed with deionized water until neutral, and then washed twice with ethanol. The mixture was vacuum dried at 55 °C for 10 h and ground to a particle size of 50 μm. The resulting powder was dispersed in 0.1 M MES buffer at a volume ratio of 1:45. 8-12% of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.5% of N-hydroxysuccinimide were added. The mixture was stirred at 20 °C for 20 min, and then 1% of Novozymes lipase 435 was added. The mixture was stirred at 4 °C for 1.5-2.5 h, centrifuged at 8000 rpm for 5-15 min, the carrier was collected and washed three times with deionized water to obtain Additive B, which was stored at 4 °C.

[0025] Preparation of composite additive: Additive A was dispersed in 0.1M phosphate buffer at a volume ratio of 1:45, and additive B was added. The mixture was stirred at 4°C for 1.5 h, and 0.1 wt% sodium alginate was added. The mixture was stirred at 20°C for 1 h, and the solid was collected by centrifugation at 8000 rpm for 5 min. The solid was then dried under vacuum at 55°C for 12 h to obtain the composite additive. The mass of additive B was 1 times the mass of additive A.

[0026] Preparation of environmentally friendly and biodegradable disposable plastic lunch boxes: S1: Dry the bio-based polypropylene resin at 80°C for 2 hours, add it together with the biodegradable polyester phase to a high-speed mixer, premix at 1500 rpm for 5 minutes, then add the composite additive, antioxidant, anti-hydrolysis agent, nucleating agent, slip agent and food-grade color masterbatch in sequence, and continue to mix at 1500 rpm for 3 minutes to obtain the mixture. S2: The mixture is blended and pelletized using a co-rotating twin-screw extruder with a length-to-diameter ratio ≥40:1, segmented temperature control, and a screw speed of 250 rpm to obtain 2 mm blended particles. The segmented temperature control parameters are: feeding section 160℃, compression section 170℃, homogenization section 180℃, and die head 175℃. S3: The blended particles are melted in a single screw extruder at 170°C in the barrel and 175°C in the die. The mixture is then cast through a T-die and cooled by a roller at 20°C to obtain a 0.3mm thick sheet. S4: Heat the thick sheet to 130℃, place it in the mold, hold it under vacuum of -0.1MPa and molding pressure of 0.3MPa for 5 seconds, and demold it at room temperature to obtain a rough lunch box. Punch and trim the edges, and anneal at 60℃ for 1.5 hours to obtain an environmentally friendly and biodegradable disposable plastic lunch box.

[0027] Example 2

[0028] Prepare the following raw materials by weight: 53 parts bio-based polypropylene resin, 48 parts biodegradable polyester phase, 4 parts composite additives, 0.2 parts antioxidant, 0.2 parts anti-hydrolysis agent, 0.2 parts nucleating agent, 0.15 parts slip agent, and 1.2 parts food-grade masterbatch; The biodegradable polyester phase is a mixture of polybutylene terephthalate, polyhydroxyalkanoates, and polycaprolactone in a mass ratio of 4.5:3.5:2.5, wherein the water content of polybutylene terephthalate and polyhydroxyalkanoates is less than 0.05%, and the water content of polycaprolactone is less than 0.1%. The nucleating agent was prepared by modifying nano-talc powder with silane coupling agent KH550 at 70℃ for 2 hours. The nano-talc powder had a particle size of less than 100 nm, and the mass of silane coupling agent KH550 was 1.5% of the mass of nano-talc powder. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1. The anti-hydrolysis agent is carbodiimide Stabaxol P200, the slip agent is oleamide, and the food-grade masterbatch is titanium dioxide.

[0029] Preparation of Additive A: Microcrystalline cellulose was dispersed in deionized water at a volume ratio of 1:20, and then tetramethylpiperidine oxide and sodium bromide were added. The pH was adjusted to 10 with 0.5M sodium hypochlorite solution, and the mixture was stirred at 25℃ for 2 hours to obtain a reaction solution. The reaction was terminated with 0.5M sodium thiosulfate solution, and the precipitate was collected by centrifugation at 8000 rpm for 10 minutes. The precipitate was dialyzed to neutral under a molecular weight cutoff of 3500 Da to obtain a neutral product. The neutral product was dispersed in deionized water at a volume ratio of 1:100, and chitosan oligosaccharide was added. The pH was adjusted to 5 with 0.1M hydrochloric acid solution, and the mixture was stirred at 25℃ for 60 minutes to obtain Additive A. The particle size of microcrystalline cellulose was 50 μm, the mass of tetramethylpiperidine oxide was 0.16% of the mass of microcrystalline cellulose, the mass of sodium bromide was 0.16% of the mass of microcrystalline cellulose, the volume of sodium hypochlorite was 3% of the volume of the reaction solution, and the mass of chitosan oligosaccharide was 3% of the mass of the neutral product.

[0030] Pretreatment Additive A: Additive A was dispersed in deionized water at a volume ratio of 1:100. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added. Nitrogen gas was purged at a flow rate of 75 mL / min for protection. The mixture was stirred at 80°C and 250 rpm for 15 min. Ammonia solution with a mass fraction of 25% was slowly added. The mixture was stirred for another 30 min. Magnetic separation was performed under an electric field strength of 0.4T for 8 s. The separated additive was washed with deionized water until neutral and then vacuum dried at 60°C for 12 h to obtain pretreated additive A. The mass of ferric chloride hexahydrate was 5.4% of the mass of additive A, the mass of ferrous chloride tetrahydrate was 2.1% of the mass of additive A, and the volume of ammonia solution was 10% of the volume of deionized water.

[0031] Preparation of Additive B: Clean rice husks were crushed to 0.6 mm, pyrolyzed at 400 °C under nitrogen atmosphere with limited oxygen for 3 h, and then added to 1 M sulfuric acid solution at a volume ratio of 1:10. The mixture was stirred at 300 rpm for 2 h at 80 °C. The solid was separated, washed with deionized water until neutral, and then washed twice with ethanol. The mixture was vacuum dried at 60 °C for 12 h and ground to a particle size of 75 μm. The resulting powder was dispersed in 0.1 M MES buffer at a volume ratio of 1:50. 8-12% of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.6% of N-hydroxysuccinimide were added. The mixture was stirred at 25 °C for 30 min, and then 1.5% of Novozymes lipase 435 was added. The mixture was stirred at 4 °C for 1.5-2.5 h, centrifuged at 8000 rpm for 5-15 min, the carrier was collected and washed three times with deionized water to obtain Additive B, which was stored at 4 °C.

[0032] Preparation of composite additive: Additive A was dispersed in 0.1M phosphate buffer at a volume ratio of 1:50, and additive B was added. The mixture was stirred at 4℃ for 2 hours, and 0.1wt% sodium alginate was added. The mixture was stirred at 25℃ for 1 hour, and the solid was collected by centrifugation at 8000rpm for 10 minutes. The solid was then dried under vacuum at 60℃ for 12 hours to obtain the composite additive. The mass of additive B was 1.2 times that of additive A.

[0033] Preparation of environmentally friendly and biodegradable disposable plastic lunch boxes: S1: Dry the bio-based polypropylene resin at 90°C for 3 hours, add it together with the biodegradable polyester phase into a high-speed mixer, premix at 1800 rpm for 7 minutes, then add the composite additive, antioxidant, anti-hydrolysis agent, nucleating agent, slip agent and food-grade color masterbatch in sequence, and continue mixing at 1800 rpm for 4 minutes to obtain the mixture. S2: The mixture is blended and pelletized using a co-rotating twin-screw extruder with a length-to-diameter ratio ≥40:1, segmented temperature control, and a screw speed of 300 rpm to obtain 2.5 mm blended particles. The segmented temperature control parameters are: feeding section 165℃, compression section 175℃, homogenization section 185℃, and die head 180℃. S3: The blended particles are melted in a single screw extruder at 180°C for both the barrel and the die, and then cast through a T-die at 30°C to obtain a 0.4mm thick sheet. S4: Heat the thick sheet to 140℃, place it in the mold, hold it under vacuum of -0.1MPa and molding pressure of 0.4MPa for 8 seconds, air cool at room temperature to demold and obtain the rough product of the lunch box, punch and trim the edges, anneal at 70℃ for 2 hours to obtain an environmentally friendly and biodegradable disposable plastic lunch box.

[0034] Example 3

[0035] Prepare the following raw materials by weight: 55 parts bio-based polypropylene resin, 50 parts biodegradable polyester phase, 5 parts composite additives, 0.3 parts antioxidant, 0.3 parts anti-hydrolysis agent, 0.3 parts nucleating agent, 0.2 parts slip agent, and 2 parts food-grade masterbatch; The biodegradable polyester phase is a mixture of polybutylene terephthalate, polyhydroxyalkanoate, and polycaprolactone in a mass ratio of 5:4:2, wherein the water content of polybutylene terephthalate and polyhydroxyalkanoate is less than 0.05%, and the water content of polycaprolactone is less than 0.1%. The nucleating agent was prepared by modifying nano-talc powder with silane coupling agent KH550 at 80℃ for 2 hours. The nano-talc powder had a particle size of less than 100 nm, and the mass of silane coupling agent KH550 was 2% of the mass of nano-talc powder. The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1. The anti-hydrolysis agent is carbodiimide Stabaxol P200, the slip agent is oleamide, and the food-grade masterbatch is titanium dioxide.

[0036] Preparation of Additive A: Microcrystalline cellulose was dispersed in deionized water at a volume ratio of 1:22, and then tetramethylpiperidine oxide and sodium bromide were added. The pH was adjusted to 10.5 with 0.5M sodium hypochlorite solution, and the mixture was stirred at 30℃ for 2.5 h to obtain a reaction solution. The reaction was terminated with 0.5M sodium thiosulfate solution, and the precipitate was collected by centrifugation at 8000 rpm for 15 min. The precipitate was dialyzed to neutral under a molecular weight cutoff of 3500 Da to obtain a neutral product. The neutral product was dispersed in deionized water at a volume ratio of 1:110, and chitosan oligosaccharide was added. The pH was adjusted to 5.5 with 0.1M hydrochloric acid solution, and the mixture was stirred at 30℃ for 80 min to obtain Additive A. The particle size of microcrystalline cellulose was 50 μm, the mass of tetramethylpiperidine oxide was 0.17% of the mass of microcrystalline cellulose, the mass of sodium bromide was 0.17% of the mass of microcrystalline cellulose, the volume of sodium hypochlorite was 5% of the volume of the reaction solution, and the mass of chitosan oligosaccharide was 5% of the mass of the neutral product.

[0037] Pretreatment Additive A: Additive A was dispersed in deionized water at a volume ratio of 1:110. Ferric chloride hexahydrate and ferrous chloride tetrahydrate were added. Nitrogen gas was purged at a flow rate of 100 mL / min for protection. The mixture was stirred at 85°C and 300 rpm for 20 min. Ammonia solution with a mass fraction of 25% was slowly added. The mixture was stirred for another 35 min. Magnetic separation was performed for 10 s under an electric field strength of 0.5 T. The separated additive was washed with deionized water until neutral and then vacuum dried at 65°C for 12 h to obtain pretreated additive A. The mass of ferric chloride hexahydrate was 5.8% of the mass of additive A, the mass of ferrous chloride tetrahydrate was 2.5% of the mass of additive A, and the volume of ammonia solution was 11% of the volume of deionized water.

[0038] Preparation of Additive B: Clean rice husks were crushed to 0.9 mm, pyrolyzed at 500 °C under nitrogen atmosphere for 3.5 h with limited oxygen, and then added to 1 M sulfuric acid solution at a volume ratio of 1:10. The mixture was stirred at 350 rpm for 2.5 h at 80 °C. The solid was separated, washed with deionized water until neutral, and then washed twice with ethanol. The mixture was vacuum dried at 65 °C for 15 h and ground to a particle size of 100 μm. The resulting powder was dispersed in 0.1 M MES buffer at a volume ratio of 1:55. 8-12% of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.7% of N-hydroxysuccinimide were added. The mixture was stirred at 30 °C for 40 min, and then 2% of Novozymes lipase 435 was added. The mixture was stirred at 4 °C for 1.5-2.5 h, centrifuged at 8000 rpm for 5-15 min, the carrier was collected and washed three times with deionized water to obtain Additive B, which was stored at 4 °C.

[0039] Preparation of composite additive: Additive A was dispersed in 0.1M phosphate buffer at a volume ratio of 1:55, and additive B was added. The mixture was stirred at 4℃ for 2.5h, and 0.1wt% sodium alginate was added. The mixture was stirred at 30℃ for 1h, and the solid was collected by centrifugation at 8000rpm for 15min. The solid was then dried under vacuum at 65℃ for 12h to obtain the composite additive. The mass of additive B was 1.5 times the mass of additive A.

[0040] Preparation of environmentally friendly and biodegradable disposable plastic lunch boxes: S1: Dry the bio-based polypropylene resin at 100℃ for 4 hours, add it together with the biodegradable polyester phase into a high-speed mixer, premix at 2000 rpm for 8 minutes, then add the composite additive, antioxidant, anti-hydrolysis agent, nucleating agent, slip agent and food-grade color masterbatch in sequence, and continue to mix at 2000 rpm for 5 minutes to obtain the mixture. S2: The mixture is blended and pelletized using a co-rotating twin-screw extruder with a length-to-diameter ratio ≥40:1, segmented temperature control, and a screw speed of 350 rpm to obtain 3 mm blended particles. The segmented temperature control parameters are: 170℃ for the feeding section, 180℃ for the compression section, 190℃ for the homogenization section, and 185℃ for the die head. S3: The blended particles are melted in a single screw extruder at 190°C in the barrel and 185°C in the die. The mixture is then cast through a T-die and cooled by a roller at 40°C to obtain a 0.5mm thick sheet. S4: Heat the thick sheet to 150℃, place it in the mold, hold it under vacuum of -0.1MPa and molding pressure of 0.5MPa for 10s, air cool at room temperature to demold and obtain the rough product of the lunch box, punch and trim the edges, anneal at 80℃ for 2.5h to obtain the environmentally friendly and biodegradable disposable plastic lunch box.

[0041] Comparative Example 1: The difference between this comparative example and Example 1 is that this comparative example does not contain composite additives.

[0042] Comparative Example 2 differs from Example 1 in that additive A was not added during the preparation of the composite additive in this comparative example.

[0043] Comparative Example 3 differs from Example 1 in that the biodegradable polyester phase in this comparative example is replaced with an equal amount of polycaprolactone.

[0044] Performance testing: The environmentally friendly biodegradable disposable plastic lunch boxes prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test data are recorded in the table below: Table 1 Testing items Biodegradation percentage (%) Total migration (mg / dm²) Example 1 92.8 0.7 Example 2 94.2 0.8 Example 3 93.4 0.9 Comparative Example 1 67.8 1.0 Comparative Example 2 73.5 0.8 Comparative Example 3 81.6 0.7 In the performance test, the degradation ability test was conducted in accordance with GB / T 19277.1-2025, and the percentage of biodegradation of the experimental material was calculated based on the cumulative amount of carbon dioxide released. Migration experiments were conducted in accordance with GB 31604.8-2021, testing the total migration amount in water-based food simulants. The total migration amount must be ≤10mg / dm² to meet the national food safety standards.

[0045] The biodegradation percentages of the environmentally friendly biodegradable disposable plastic lunch boxes prepared in Examples 1-3 and Comparative Examples 1-3 were 92.8%, 94.2%, 93.4%, 67.8%, 73.5%, and 81.6%, respectively.

[0046] The total migration test results of the environmentally friendly biodegradable disposable plastic lunch boxes prepared in Examples 1-3 and Comparative Examples 1-3 were 0.7 mg / dm², 0.8 mg / dm², 0.9 mg / dm², 1.0 mg / dm², 0.8 mg / dm², and 0.7 mg / dm², respectively.

[0047] It is evident that the degradation capacity of the environmentally friendly biodegradable disposable plastic lunch boxes prepared in Comparative Examples 1-3 is lower than that in Examples 1-3, and the total migration of the environmentally friendly biodegradable disposable plastic lunch boxes prepared in Comparative Examples 1-3 meets the national food safety standards. This indicates that: the composite additives, as the core degradation components, achieve the directional enrichment of enzymes through magnetic targeting effect by magnetically pretreated additive A; the microcrystalline cellulose framework provides a stable interface for the enzymatic reaction; and the chitosan oligosaccharide component enhances the hydrophilicity of the matrix and accelerates the attachment of soil microorganisms, thus avoiding enzyme protein loss and extending the enzyme degradation activity cycle, ensuring the continuous and efficient degradation reaction. Additive B, with its loaded lipase, can precisely catalyze the degradation of polyester. The ester bonds of the phase undergo directional hydrolysis and chain scission, providing the core enzymatic driving force for the degradation reaction. The biodegradable polyester phase, in a ternary compound of PBAT, PHA, and PCL, serves as a co-degradation component. PBAT forms a tough skeleton to ensure the structural strength of the lunch box during its use, preventing premature degradation and failure. PHA possesses natural and efficient biodegradability, becoming the main degradation component. PCL's low-temperature solubility broadens its adaptability to different degradation environments. The three complement each other to form a cascade degradation pathway, deeply synergizing with the enzymatic system of the composite additives to improve the overall degradation efficiency. At the same time, all raw materials are food-grade components with low total migration from food contact, enabling the lunch box to completely degrade into carbon dioxide and water under composting conditions. Comparative Example 1, without any composite additives, relied solely on the degradation of the polyester phase itself, resulting in a significantly reduced biodegradation percentage that did not meet the complete degradation standard. Comparative Example 2, without additive A, relied solely on the degradation by lipases from additive B. Due to the synergistic effect of magnetic depletion targeting, interfacial support, and enhanced hydrophilicity, the biodegradation percentage was relatively low. Comparative Example 3, using polycaprolactone instead of the ternary composite polyester phase, lacked the structural support of PBAT and the efficient degradation characteristics of PHA, resulting in a slightly lower biodegradation percentage than the examples.

[0048] By comparing and analyzing the relevant data in the table, it can be seen that the environmentally friendly biodegradable disposable plastic lunch box prepared by this invention has biodegradable properties and conforms to the concept of environmental protection. This indicates that the environmentally friendly biodegradable disposable plastic lunch box provided by this invention has a broader market prospect and is more suitable for promotion.

[0049] In the description of this specification, 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 invention. In this specification, 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.

[0050] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An environmentally friendly, biodegradable, disposable plastic lunch box, characterized in that, The raw materials include the following parts by weight: 50-55 parts bio-based polypropylene resin, 45-50 parts biodegradable polyester phase, 3-5 parts composite additives, 0.1-0.3 parts antioxidant, 0.1-0.3 parts anti-hydrolysis agent, 0.1-0.3 parts nucleating agent, 0.1-0.2 parts slip agent, and 0.5-2 parts food-grade masterbatch; The composite additive includes additive A and additive B, wherein additive A is pretreated before the preparation of the composite additive.

2. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The biodegradable polyester phase is a mixture of polybutylene terephthalate, polyhydroxyalkanoate and polycaprolactone in a mass ratio of (4-5):(3-4):(2-3), wherein the water content of polybutylene terephthalate and polyhydroxyalkanoate is less than 0.05% and the water content of polycaprolactone is less than 0.1%.

3. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The preparation method of the composite additive is as follows: Additive A is dispersed in 0.1M phosphate buffer at a volume ratio of 1:(45-55), and Additive B is added. The mixture is stirred at 4℃ for 1.5-2.5h, and 0.1wt% sodium alginate is added. The mixture is stirred at 20-30℃ for 1h, and the solid is collected by centrifugation at 8000rpm for 5-15min. The solid is then vacuum dried at 55-65℃ for 12h to obtain the composite additive. The mass of Additive B is 1-1.5 times the mass of Additive A.

4. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The preparation method of additive A is as follows: microcrystalline cellulose is dispersed in deionized water at a volume ratio of 1:(18-22), then tetramethylpiperidine oxide and sodium bromide are added, the pH value is adjusted to 9.5-10.5 with 0.5M sodium hypochlorite solution, and the mixture is stirred at 20-30℃ for 1.5-2.5h to obtain a reaction solution. The reaction is terminated with 0.5M sodium thiosulfate solution, and the precipitate is collected by centrifugation at 8000rpm for 5-15min. The precipitate is dialyzed to neutral under a molecular weight cutoff of 3500Da to obtain a neutral product. The neutral product is then distributed according to volume... Disperse the product in deionized water at a ratio of 1:(90-110), add chitosan oligosaccharide, adjust the pH to 4.5-5.5 with 0.1M hydrochloric acid solution, stir at 20-30℃ for 40-80 min to obtain additive A, wherein the particle size of microcrystalline cellulose is 50μm, the mass of tetramethylpiperidine oxide is 0.15-0.17% of the mass of microcrystalline cellulose, the mass of sodium bromide is 0.15-0.17% of the mass of microcrystalline cellulose, the volume of sodium hypochlorite is 1-5% of the volume of the reaction liquid, and the mass of chitosan oligosaccharide is 2-5% of the mass of the neutral product.

5. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The pretreatment method for additive A is as follows: Additive A is dispersed in deionized water at a volume ratio of 1:(90-110), ferric chloride hexahydrate and ferrous chloride tetrahydrate are added, nitrogen gas is passed through at a flow rate of 50-100 mL / min for protection, and the mixture is stirred at 75-85℃ and 200-300 rpm for 10-20 min. Ammonia water with a mass fraction of 25% is slowly added, and stirring is continued for 25-35 min. Magnetic separation is performed at an electric field strength of 0.3-0.5T for 5-10 s. The separated additive is washed with deionized water until neutral, and vacuum dried at 55-65℃ for 12 h to obtain pretreated additive A. The mass of ferric chloride hexahydrate is 5.0-5.8% of the mass of additive A, the mass of ferrous chloride tetrahydrate is 1.7-2.5% of the mass of additive A, and the volume of ammonia water is 9-11% of the volume of deionized water.

6. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The preparation method of additive B is as follows: Clean rice husks are crushed to 0.3-0.9 mm, first pyrolyzed at 300-500℃ under nitrogen atmosphere with limited oxygen for 2.5-3.5 h, then added to 1M sulfuric acid solution at a volume ratio of 1:10, stirred at 250-350 rpm at 80℃ for 1.5-2.5 h, the solid is separated, washed with deionized water until neutral, then washed twice with ethanol, vacuum dried at 55-65℃ for 10-15 h, and ground to a particle size of 50-100 μm. The obtained powder is then prepared at a volume ratio of 1:(45-5... 5) Disperse in 0.1M MES buffer, add 8-12% of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.5-0.7% of N-hydroxysuccinimide by weight of powder, stir at 20-30℃ for 20-40 min, then add 1-2% of Novozymes lipase 435 by weight of powder, stir at 4℃ for 1.5-2.5 h, centrifuge at 8000 rpm for 5-15 min, collect the carrier and wash it 3 times with deionized water to obtain additive B, and store at 4℃.

7. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The nucleating agent is prepared by modifying nano-talc powder with silane coupling agent KH550 at 60-80℃ for 2 hours. The nano-talc powder has a particle size of less than 100nm, and the mass of silane coupling agent KH550 is 1-2% of the mass of nano-talc powder.

8. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1.

9. The environmentally friendly biodegradable disposable plastic lunch box according to claim 1, characterized in that, The anti-hydrolysis agent is carbodiimide Stabaxol P200, the slip agent is oleamide, and the food-grade masterbatch is titanium dioxide.

10. The method for preparing an environmentally friendly, biodegradable, disposable plastic lunch box according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Dry the bio-based polypropylene resin at 80-100℃ for 2-4 hours, add it together with the biodegradable polyester phase into a high-speed mixer, premix at 1500-2000 rpm for 5-8 minutes, then add the composite additive, antioxidant, anti-hydrolysis agent, nucleating agent, slip agent and food-grade color masterbatch in sequence, and continue mixing at 1500-2000 rpm for 3-5 minutes to obtain the mixture; S2: The mixture is blended and pelletized using a co-rotating twin-screw extruder with a length-to-diameter ratio ≥40:1, segmented temperature control, and screw speed of 250-350 rpm to obtain blended particles of 2-3 mm. The segmented temperature control parameters are: feeding section 160-170℃, compression section 170-180℃, homogenization section 180-190℃, and die head 175-185℃. S3: The blended particles are melted using a single-screw extruder at a barrel temperature of 170-190℃ and a die temperature of 175-185℃. The mixture is then cast through a T-die, and the cooling roller temperature is 20-40℃ to obtain a sheet with a thickness of 0.3-0.5mm. S4: Heat the thick sheet to 130-150℃, place it in a mold, hold it under vacuum of -0.1MPa and molding pressure of 0.3-0.5MPa for 5-10 seconds, air cool at room temperature to demold and obtain a rough lunch box. Punch and trim the edges, anneal at 60-80℃ for 1.5-2.5 hours to obtain an environmentally friendly and biodegradable disposable plastic lunch box.

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