Preparation method of green anti-aging biomass-based polypropylene-polyethylene composite plastic material for packaging

Abstract

This invention discloses a method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging, relating to the field of polymer materials and plastic composite materials technology. Using bio-based polypropylene and bio-based polyethylene as the matrix, a composite material is prepared by adding natural biomass reinforcement, anti-aging agents, ultraviolet absorbers, antistatic agents, toughening agents, and interface compatibility agents under controlled high-temperature blending conditions. The resulting material exhibits excellent mechanical properties, thermal stability, and UV aging resistance, significantly improving the weather resistance and service life of packaging materials, making it suitable for the field of environmentally friendly packaging. This technology effectively improves the comprehensive performance of bio-based polyolefin composite materials, promoting the development of the green packaging materials industry.

Description

Technical Field

[0001] This invention relates to the field of polymer materials and plastic composite materials, and in particular to a method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging. Background Technology

[0002] Currently, global plastic packaging materials still primarily rely on petroleum-based polymers, such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). These materials offer advantages such as excellent processability, low cost, and lightweight properties, and are widely used in food, daily necessities, and industrial packaging. However, petroleum-based plastics have inherent drawbacks such as being non-renewable and difficult to degrade. After their lifespan, they remain in the environment for a long time, exacerbating white pollution and carbon emissions, becoming a significant challenge for global environmental governance. In response, governments, research institutions, and enterprises worldwide have proposed plastic substitution and recycling strategies to promote the transformation of packaging materials towards green and environmentally friendly directions.

[0003] Bio-based polymer materials, as one of the main technological routes to replace traditional plastics, can significantly reduce dependence on fossil resources because they partially utilize renewable resources (such as plant sugars, cellulose, and starch) as raw materials. According to the latest industry analysis, global bio-based plastic production capacity reached several million tons in 2023, and is expected to maintain rapid growth in the coming years driven by policy support and market demand. Bio-based polylactic acid (PLA), polyhydroxyalkanoates (PHA), and polybutylene adipate / butanediol esters (PBAT) are mainly used in biodegradable films, packaging containers, and single-use packaging.

[0004] In bio-based material systems, bio-based polyolefins (such as Bio-PE and Bio-PP), with their similar chemical structure and processing compatibility with conventional PE and PP, hold promise for a smooth replacement of fossil-based plastics in the functional packaging field. Typical bio-based polyolefin matrices can be obtained by polymerizing monomers such as bio-ethylene and propylene produced through sugarcane ethanol fermentation, exhibiting similar mechanical properties and chemical stability to traditional high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene. Publicly available patent EP2668105A1 describes a container and label combination containing a high proportion of bio-based polyolefins, emphasizing that a bio-based content of 90% or higher can improve overall environmental performance.

[0005] However, unlike fully biodegradable materials (such as PLA and PHA), bio-based polyolefins, while possessing the advantage of renewable raw materials, are essentially still non-degradable polymers. Long-term exposure to outdoor environments can lead to performance degradation due to ultraviolet radiation, heat, and oxidation, manifesting as decreased mechanical properties, surface chalking, and color changes. This not only affects packaging appearance but may also reduce material lifespan and packaging safety. Therefore, it is necessary to introduce functional additives and composite strategies into bio-based polyolefin systems to effectively improve the material's anti-aging properties.

[0006] Patent document CN110079063A proposes various composite material designs and processing schemes to improve the properties of polymer materials. For example, one invention discloses a bio-based alloy material for packaging films, and how to improve the overall performance of the material by adjusting various components (such as thermo-oxidative stabilizers, plasticizers, reinforcing agents, etc.). This technology utilizes thermo-oxidative stabilizers to improve the thermal stability and durability of the material, suggesting that providing a reasonable ratio of additives in the composite system is crucial for material stability.

[0007] Furthermore, another patent in the field of sustainable packaging, CN103328334B, discloses packaging containers and labels containing a high proportion of bio-based polypropylene and polyethylene. Its main components have a high bio-based content, which can significantly improve the renewability of the packaged products. Combined with recycling strategies, this further enhances lifecycle performance. This type of technology provides a realistic comparison and development basis for the biomass-enhanced, anti-aging composite material design proposed in this invention.

[0008] In summary, while existing technologies encompass bio-based polymer materials and their combinations for packaging applications, there are still shortcomings in the modification design and composite material preparation techniques for bio-based polyolefin systems to improve their resistance to environmental aging. Specifically, achieving a balance between high bio-based content and excellent anti-aging properties, and improving interfacial properties and overall stability through precise formulation design and processing techniques, are crucial. Therefore, proposing a novel biomass-based polypropylene-polyethylene anti-aging composite material and its preparation method has significant technical and commercial value. Summary of the Invention

[0009] Based on the problems raised in the background art above, the present invention proposes a method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging.

[0010] The technical solution is as follows: A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps, in parts by weight: (1) Prepare a mixture of bio-based polypropylene and bio-based polyethylene matrix, wherein the mass ratio of bio-based polypropylene to bio-based polyethylene is 30~70:30~70, and the total is 100 parts; (2) Add 10 to 30 parts by mass of the biomass enhancer to the matrix mixture in step (1); (3) Add 0.5-5.0 parts of anti-aging agent, 2.0-10.0 parts of interface compatibility agent, 0.1-1.0 parts of antistatic agent, 1.0-5.0 parts of toughening agent and 0.5-3.0 parts of ultraviolet absorber, and mix evenly; (4) The mixture after uniform mixing in step (3) is melt-blended and extruded in a twin-screw extruder at a temperature of 170~230℃ and a screw speed of 200~600rpm to fully disperse the components. (5) After cooling, granulating and drying, the extrudate is processed into a final green packaging composite material product by molding at 180~230℃ in injection molding or extrusion molding equipment.

[0011] As a preferred embodiment of the present invention, the biomass enhancer is one of natural cellulose fiber powder, lignin fiber, or crop straw powder, or a compound thereof.

[0012] As a preferred embodiment of the present invention, the method for preparing the anti-aging agent is as follows: By weight, 65-80 parts of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 18-28 parts of 3-vinylquinoline (CAS: 67752-31-2), 90-130 parts of N,N-dimethylacetamide, and 1.0-1.8 parts of triethylenediamine co-catalyst are mixed evenly, and 0.5-1.2 parts of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) are added. Under a nitrogen protective atmosphere, the reaction temperature is controlled at 70-80℃, and ultraviolet light with a wavelength of 365nm and a power of 80-120W is used for irradiation at a distance of 10-25cm. The reaction system is stirred at a rate of 250-350r / min. The reaction time is controlled at 3-5 hours. The residual solvent is removed by vacuum distillation, and then the mixture is dried in a vacuum oven for 5-8 hours to obtain quinoline-modified benzimidazole anti-aging agent.

[0013] In a preferred embodiment of the present invention, the vacuum distillation pressure is 0.005-0.05 MPa and the temperature is 60-70°C.

[0014] In a preferred embodiment of the present invention, the vacuum oven has a temperature of 55-65°C and a pressure of 0.05-0.08 MPa.

[0015] In a preferred embodiment of the present invention, the interface compatibility agent is maleic anhydride-grafted polypropylene or maleic anhydride-grafted polyethylene.

[0016] As a preferred embodiment of the present invention, the antistatic agent is one or more combinations of trihydroxyethylmethyl quaternary ammonium methyl sulfate, stearyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide.

[0017] In a preferred embodiment of the present invention, the toughening agent is ethylene propylene rubber or POE.

[0018] In a preferred embodiment of the present invention, the ultraviolet absorber is UV-328, UV-531 or BP-6.

[0019] Anti-aging agent reaction mechanism: The click chemistry reaction follows a photocatalytic thiol-olefin nucleophilic addition mechanism: the photoinitiator is homolytically cleaved by 365nm ultraviolet light to generate active free radicals, which abstract hydrogen atoms from the thiol group in 1H-benzimidazole-2-thiol to form thiol free radicals. These free radicals attack the carbon-carbon double bond of 3-vinylquinoline to undergo nucleophilic addition. After capturing hydrogen atoms through a carbon free radical intermediate, a stable carbon-sulfur covalent bond is formed, achieving covalent connection between the two. The cocatalyst triethylenediamine promotes the generation of thiol free radicals and polarizes the double bond to enhance the reaction activity through hydrogen bonding. The reaction is highly selective, mild, and efficient, ultimately introducing the quinoline group into the anti-aging agent molecule to form a synergistic adsorption system.

[0020] Beneficial effects of anti-aging agents: The precise introduction of quinoline heterocyclic functional groups and thioether bonds through the click chemical reaction enables the modified anti-aging agent to form a "heterocyclic conjugated structure-sulfur atom" synergistic adsorption system. This system can efficiently adsorb residual monomers, processing impurities, and polar harmful substances generated during degradation in plastic substrates. At the same time, it enhances the ability to shield against ultraviolet light and capture free radicals, extending the anti-aging life of polypropylene-polyethylene composite plastics and solving the technical pain point of traditional anti-aging agents that can only resist aging and cannot purify the substrate.

[0021] The reaction employs a photocatalytic click reaction mechanism, combined with a specific photoinitiator and mild reaction conditions, avoiding the decomposition of raw materials and the generation of by-products caused by high temperature and high pressure. The production process is low-energy and has no harmful gas emissions. The modified anti-aging agent has excellent compatibility with the biomass-based blended substrate, which can significantly improve the tensile strength and elongation at break of the composite plastic, taking into account both environmental friendliness and mechanical property stability, and meeting the environmental protection production needs of green packaging and plastic daily necessities.

[0022] Compared with the prior art, the present invention has the following advantages: Highly environmentally friendly: It uses bio-based polyolefins and renewable biomass resources as raw materials, significantly reducing dependence on fossil resources and improving the sustainability of materials; Improved anti-aging performance: The addition of highly effective anti-aging agents and UV stabilizers can effectively delay the performance degradation of materials under light and heat-oxygen environments; Excellent mechanical properties: By adjusting the interface compatibility agent, the interfacial bonding between the biomass reinforcement and the polyolefin matrix is ​​improved, thereby enhancing the tensile, bending, and impact properties of the material; Suitable for packaging: The composite material has good heat-sealing properties, processability and appearance quality, and can be used in the fields of food and daily green packaging. Detailed Implementation

[0023] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments. Example

[0024] A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 30 kg of bio-based polypropylene and 70 kg of bio-based polyethylene at a mass ratio of 30:70, for a total of 100 kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 300 rpm, and mix for 20 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0025] 2. Step (2) Addition of biomass reinforcement: Weigh 10 kg of biomass reinforcement (natural cellulose fiber powder, particle size 80 mesh), slowly add it to the matrix mixture obtained in step (1), and continue mixing for 30 minutes while maintaining a rotation speed of 300 rpm, so that the reinforcement is evenly dispersed in the matrix.

[0026] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 0.5 kg of anti-aging agent, 2.0 kg of interface compatibility agent (maleic anhydride grafted polypropylene, grafting rate 1.2%), 0.1 kg of antistatic agent (trihydroxyethyl methyl quaternary ammonium methyl sulfate), 1.0 kg of toughening agent (ethylene propylene rubber), and 0.5 kg of ultraviolet absorber (UV-328); adjust the speed of the mixer to 400 rpm and mix at room temperature for 40 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0027] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; screw speed 200rpm, vacuum degree -0.08MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0028] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 25℃) and sent to a pelletizer to be cut into granules with a particle size of 3mm; the granules are placed in a vacuum drying oven and dried for 4 hours at 60℃ and 0.07MPa to remove surface moisture; the dried granules are added to the injection molding equipment, the molding temperature is set to 180℃, the injection pressure is 8MPa and the holding time is 2 seconds, and the injection molding is used to make green packaging pallet products. After cooling and demolding, the final product is obtained.

[0029] The method for preparing the anti-aging agent is as follows: 65 kg of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 18 kg of 3-vinylquinoline (CAS: 67752-31-2), and 90 kg of... (The text abruptly ends here, so the translation stops as well.) N,N-dimethylacetamide and 1.0 kg of triethylenediamine co-catalyst were added to the reactor and mixed thoroughly. 0.5 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) was added, and nitrogen gas was introduced for protection (flow rate 150 mL / min). The reaction temperature was controlled at 70 °C. The mixture was irradiated with ultraviolet light at a wavelength of 365 nm and a power of 80 W, with an irradiation distance of 10 cm, while the reaction system was stirred at a rate of 250 r / min. After reacting for 3 hours, residual solvent was removed by vacuum distillation at a pressure of 0.005 MPa and a temperature of 60 °C. The product was then placed in a vacuum oven and dried at 55 °C and 0.05 MPa for 5 hours to obtain a quinolinyl-modified benzimidazole anti-aging agent. Example

[0030] A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 45kg of bio-based polypropylene and 55kg of bio-based polyethylene at a mass ratio of 45:55, for a total of 100kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 320rpm, and mix for 25 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0031] 2. Step (2) Addition of biomass reinforcement: Weigh 17.5 kg of biomass reinforcement (lignin fiber, particle size 100 mesh) and slowly add it to the matrix mixture obtained in step (1). Continue mixing for 35 minutes while maintaining a rotation speed of 320 rpm to ensure that the reinforcement is evenly dispersed in the matrix.

[0032] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 2.0 kg of anti-aging agent, 4.5 kg of interface compatibility agent (maleic anhydride grafted polyethylene, grafting rate 1.0%), 0.35 kg of antistatic agent (stearic acid trimethylammonium chloride), 2.5 kg of toughening agent (POE, melt index 2.0 g / 10 min), and 1.2 kg of ultraviolet absorber (UV-531); adjust the speed of the mixer to 420 rpm and mix at room temperature for 45 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0033] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 170℃, homogenization section 190℃, metering section 200℃; screw speed 350rpm, vacuum degree -0.085MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0034] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 30℃) and sent to a pelletizer to be cut into granules with a particle size of 3.5mm; the granules are placed in a vacuum drying oven and dried for 5 hours at 65℃ and 0.07MPa to remove surface moisture; the dried granules are added to an extrusion molding equipment, the molding temperature is set to 200℃, the extrusion speed is 5m / min and the traction speed is 6m / min, and the extrusion molding is used to produce green packaging film products. After cooling and shaping, the final product is obtained.

[0035] The method for preparing the anti-aging agent is as follows: 70 kg of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 21 kg of 3-vinylquinoline (CAS: 67752-31-2), and 105 kg of... (The text abruptly ends here, so the translation stops as well.) N,N-dimethylacetamide and 1.3 kg of triethylenediamine co-catalyst were added to the reactor and mixed thoroughly. 0.7 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) was added, and nitrogen gas was introduced for protection (flow rate 180 mL / min). The reaction temperature was controlled at 73 °C. The mixture was irradiated with ultraviolet light at a wavelength of 365 nm and a power of 95 W, with an irradiation distance of 15 cm, while the reaction system was stirred at a rate of 280 r / min. After reacting for 3.5 hours, residual solvent was removed by vacuum distillation at a pressure of 0.02 MPa and a temperature of 63 °C. The product was then placed in a vacuum oven and dried at 58 °C and 0.06 MPa for 6 hours to obtain a quinolinyl-modified benzimidazole anti-aging agent. Example

[0036] A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 55kg of bio-based polypropylene and 45kg of bio-based polyethylene at a mass ratio of 55:45, for a total of 100kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 350rpm, mix for 30 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0037] 2. Step (2) Addition of biomass reinforcement: Weigh 22.5 kg of biomass reinforcement (natural cellulose fiber powder and lignin fiber are compounded in a mass ratio of 1:1, with a particle size of 120 mesh), and slowly add it to the matrix mixture obtained in step (1). Continue mixing for 40 minutes while maintaining a rotation speed of 350 rpm to ensure that the reinforcement is evenly dispersed in the matrix.

[0038] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 3.5 kg of anti-aging agent, 7.0 kg of interface compatibility agent (maleic anhydride grafted polypropylene and maleic anhydride grafted polyethylene mixed at a mass ratio of 1:1), 0.65 kg of antistatic agent (hexadecyltrimethylammonium chloride), 3.5 kg of toughening agent (ethylene propylene rubber and POE mixed at a mass ratio of 1:1), and 2.2 kg of ultraviolet absorber (BP-6); adjust the speed of the mixer to 450 rpm and mix at room temperature for 50 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0039] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feed section 180℃, homogenization section 210℃, metering section 220℃; screw speed 450rpm, vacuum degree -0.09MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0040] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 35℃) and sent to a pelletizer to be cut into granules with a particle size of 4mm; the granules are placed in a vacuum drying oven and dried for 6 hours at 70℃ and 0.07MPa to remove surface moisture; the dried granules are added to the injection molding equipment, the molding temperature is set to 215℃, the injection pressure is 10MPa and the holding time is 3 seconds, and the injection molding is used to make green packaging turnover boxes. After cooling and demolding, the final product is obtained.

[0041] The method for preparing the anti-aging agent is as follows: 75 kg of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 25 kg of 3-vinylquinoline (CAS: 67752-31-2), and 120 kg of... (The text abruptly ends here, so the translation stops as well.) N,N-dimethylacetamide and 1.5 kg of triethylenediamine co-catalyst were added to the reactor and mixed thoroughly. 0.9 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) was added, and nitrogen gas was introduced for protection (flow rate 220 mL / min). The reaction temperature was controlled at 77 °C. The mixture was irradiated with ultraviolet light at a wavelength of 365 nm and a power of 105 W, with an irradiation distance of 20 cm, while the reaction system was stirred at a rate of 320 r / min. After 4.5 hours of reaction, residual solvent was removed by vacuum distillation at a pressure of 0.035 MPa and a temperature of 67 °C. The product was then placed in a vacuum oven and dried at 62 °C and 0.07 MPa for 7 hours to obtain a quinolinyl-modified benzimidazole anti-aging agent. Example

[0042] A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 70 kg of bio-based polypropylene and 30 kg of bio-based polyethylene at a mass ratio of 70:30, for a total of 100 kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 380 rpm, and mix for 35 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0043] 2. Step (2) Addition of biomass enhancer: Weigh 30kg of biomass enhancer (crop straw powder, crushed and sieved to 150 mesh), slowly add it to the matrix mixture obtained in step (1), and continue mixing for 45 minutes at a speed of 380rpm to make the enhancer evenly dispersed in the matrix.

[0044] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 5.0 kg of anti-aging agent, 10.0 kg of interface compatibility agent (maleic anhydride grafted polypropylene, grafting rate 1.5%), 1.0 kg of antistatic agent (octadecyltrimethylammonium chloride), 5.0 kg of toughening agent (POE, melt index 3.0 g / 10 min), and 3.0 kg of ultraviolet absorber (UV-328 and UV-531 mixed at a mass ratio of 1:1). Adjust the speed of the mixer to 480 rpm and mix at room temperature for 60 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0045] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 190℃, homogenization section 230℃, metering section 240℃; screw speed 600rpm, vacuum degree -0.095MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0046] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 40℃) and sent to a pelletizer to be cut into granules with a particle size of 4.5mm; the granules are placed in a vacuum drying oven and dried for 7 hours at 75℃ and 0.07MPa to remove surface moisture; the dried granules are added to the extrusion molding equipment, the molding temperature is set to 230℃, the extrusion speed is 8m / min and the traction speed is 9m / min, and the extrusion molding is used to produce green packaging board products. After cooling and shaping, the final product is obtained.

[0047] The method for preparing the anti-aging agent is as follows: 80 kg of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 28 kg of 3-vinylquinoline (CAS: 67752-31-2), and 130 kg of... (The text abruptly ends here, so the translation stops as well.) N,N-dimethylacetamide and 1.8 kg of triethylenediamine co-catalyst were added to the reactor and mixed thoroughly. 1.2 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) was added, and nitrogen gas was introduced for protection (flow rate 250 mL / min). The reaction temperature was controlled at 80 °C. The mixture was irradiated with ultraviolet light at a wavelength of 365 nm and a power of 120 W, with an irradiation distance of 25 cm, while the reaction system was stirred at a rate of 350 r / min. After 5 hours of reaction, residual solvent was removed by vacuum distillation at a pressure of 0.05 MPa and a temperature of 70 °C. The product was then placed in a vacuum oven and dried at 65 °C and 0.08 MPa for 8 hours to obtain a quinolinyl-modified benzimidazole anti-aging agent.

[0048] Comparative Example 1 A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 30 kg of bio-based polypropylene and 70 kg of bio-based polyethylene at a mass ratio of 30:70, for a total of 100 kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 300 rpm, and mix for 20 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0049] 2. Step (2) Addition of biomass reinforcement: Weigh 10 kg of biomass reinforcement (natural cellulose fiber powder, particle size 80 mesh), slowly add it to the matrix mixture obtained in step (1), and continue mixing for 30 minutes while maintaining a rotation speed of 300 rpm, so that the reinforcement is evenly dispersed in the matrix.

[0050] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: anti-aging agent 1010 0.5kg, interface compatibility agent (maleic anhydride grafted polypropylene, grafting rate 1.2%) 2.0kg, antistatic agent (trihydroxyethyl methyl quaternary ammonium methyl sulfate) 0.1kg, toughening agent (ethylene propylene rubber) 1.0kg, ultraviolet absorber (UV-328) 0.5kg; adjust the speed of the mixer to 400rpm, mix at room temperature for 40 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0051] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; screw speed 200rpm, vacuum degree -0.08MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0052] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 25℃) and sent to a pelletizer to be cut into granules with a particle size of 3mm; the granules are placed in a vacuum drying oven and dried for 4 hours at 60℃ and 0.07MPa to remove surface moisture; the dried granules are added to the injection molding equipment, the molding temperature is set to 180℃, the injection pressure is 8MPa and the holding time is 2 seconds, and the injection molding is used to make green packaging pallet products. After cooling and demolding, the final product is obtained.

[0053] Comparative Example 2 A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 30 kg of bio-based polypropylene and 70 kg of bio-based polyethylene at a mass ratio of 30:70, for a total of 100 kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 300 rpm, and mix for 20 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0054] 2. Step (2) Addition of biomass reinforcement: Weigh 10 kg of biomass reinforcement (natural cellulose fiber powder, particle size 80 mesh), slowly add it to the matrix mixture obtained in step (1), and continue mixing for 30 minutes while maintaining a rotation speed of 300 rpm, so that the reinforcement is evenly dispersed in the matrix.

[0055] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 0.5 kg of anti-aging agent, 2.0 kg of interface compatibility agent (maleic anhydride grafted polypropylene, grafting rate 1.2%), 0.1 kg of antistatic agent (trihydroxyethyl methyl quaternary ammonium methyl sulfate), 1.0 kg of toughening agent (ethylene propylene rubber), and 0.5 kg of ultraviolet absorber (UV-328); adjust the speed of the mixer to 400 rpm and mix at room temperature for 40 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0056] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; screw speed 200rpm, vacuum degree -0.08MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0057] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 25℃) and sent to a pelletizer to be cut into granules with a particle size of 3mm; the granules are placed in a vacuum drying oven and dried for 4 hours at 60℃ and 0.07MPa to remove surface moisture; the dried granules are added to the injection molding equipment, the molding temperature is set to 180℃, the injection pressure is 8MPa and the holding time is 2 seconds, and the injection molding is used to make green packaging pallet products. After cooling and demolding, the final product is obtained.

[0058] The preparation method of the anti-aging agent is as follows: 18 kg of 3-vinylquinoline (CAS: 67752-31-2), 90 kg of N,N-dimethylacetamide, and 1.0 kg of triethylenediamine co-catalyst are added to a reaction vessel and mixed evenly; 0.5 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) is added, and nitrogen gas is introduced for protection (flow rate 150 mL / min), and the reaction temperature is controlled at 70℃; ultraviolet light with a wavelength of 365 nm and a power of 80 W is used for irradiation, with the irradiation distance maintained at 10 cm, while the reaction system is stirred at a rate of 250 r / min; after reacting for 3 hours, the residual solvent is removed by vacuum distillation under a pressure of 0.005 MPa and a temperature of 60℃; the product is placed in a vacuum oven and dried at 55℃ and 0.05 MPa for 5 hours to obtain the quinoline-modified benzimidazole anti-aging agent.

[0059] Comparative Example 3 A method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging includes the following steps: 1. Step (1) Preparation of matrix mixture: Weigh 30 kg of bio-based polypropylene and 70 kg of bio-based polyethylene at a mass ratio of 30:70, for a total of 100 kg; add the two matrix materials to a high-speed mixer in sequence, set the speed to 300 rpm, and mix for 20 minutes at room temperature until the materials are evenly dispersed to obtain a bio-based polypropylene-polyethylene matrix mixture.

[0060] 2. Step (2) Addition of biomass reinforcement: Weigh 10 kg of biomass reinforcement (natural cellulose fiber powder, particle size 80 mesh), slowly add it to the matrix mixture obtained in step (1), and continue mixing for 30 minutes while maintaining a rotation speed of 300 rpm, so that the reinforcement is evenly dispersed in the matrix.

[0061] 3. Step (3) Addition and mixing of additives: Add various additives in sequence: 0.5 kg of anti-aging agent, 2.0 kg of interface compatibility agent (maleic anhydride grafted polypropylene, grafting rate 1.2%), 0.1 kg of antistatic agent (trihydroxyethyl methyl quaternary ammonium methyl sulfate), 1.0 kg of toughening agent (ethylene propylene rubber), and 0.5 kg of ultraviolet absorber (UV-328); adjust the speed of the mixer to 400 rpm and mix at room temperature for 40 minutes to ensure that all additives are fully integrated with the materials and there is no local agglomeration.

[0062] 4. Step (4) Melt blending extrusion: The mixture obtained in step (3) is fed into a twin-screw extruder. The temperatures of each section of the extruder are set as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; screw speed 200rpm, vacuum degree -0.08MPa. The material is melt-blended in the barrel and extruded into strip melt through the T-die. The melt flowability is continuously monitored during the extrusion process to ensure that each component is fully dispersed.

[0063] 5. Step (5) Cooling, granulation and molding: The extruded strip melt is cooled to room temperature in a water cooling tank (water temperature 25℃) and sent to a pelletizer to be cut into granules with a particle size of 3mm; the granules are placed in a vacuum drying oven and dried for 4 hours at 60℃ and 0.07MPa to remove surface moisture; the dried granules are added to the injection molding equipment, the molding temperature is set to 180℃, the injection pressure is 8MPa and the holding time is 2 seconds, and the injection molding is used to make green packaging pallet products. After cooling and demolding, the final product is obtained.

[0064] The preparation method of the anti-aging agent is as follows: 65 kg of 1H-benzimidazole-2-thiol (CAS: 134469-07-1), 90 kg of N,N-dimethylacetamide, and 1.0 kg of triethylenediamine co-catalyst are added to a reaction vessel and mixed evenly; 0.5 kg of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone (CAS: 7473-98-5) is added, and nitrogen gas is introduced for protection (flow rate 150 mL / min), and the reaction temperature is controlled at 70℃; ultraviolet light with a wavelength of 365 nm and a power of 80 W is used for irradiation, with the irradiation distance maintained at 10 cm, while the reaction system is stirred at a rate of 250 r / min; after reacting for 3 hours, the residual solvent is removed by vacuum distillation under a pressure of 0.005 MPa and a temperature of 60℃; the product is placed in a vacuum oven and dried at 55℃ and 0.05 MPa for 5 hours to obtain a quinolinyl-modified benzimidazole anti-aging agent.

[0065] Test method: 1. Accelerated UV aging: UV aging test was conducted according to ASTM G154 / ASTM D4329 standards to simulate the long-term light exposure effect on materials in outdoor environment. Light source and cycle: UV-A ultraviolet lamp (center wavelength ~340 nm), black panel temperature 60℃, timed cycle of light and humidity stages; aging time 500h; 2. Tensile property test: The tensile strength and elongation at break were determined according to ASTM D638 or equivalent national standards before and after aging. 3. Thermal stability and thermal analysis: DSC was used to assess changes in crystallinity and thermal behavior; 4. Mechanical retention rate: The retention rate of performance after aging relative to the initial state is calculated as an anti-aging indicator.

[0066] Test results: Table 1. Tensile property test results before and after aging Initial tensile strength (MPa) 500-hour aging tensile strength (MPa) Retention rate (%) Example 1 32.5 30.1 92.62% Example 2 33.2 30.9 93.07% Example 3 33.7 31.6 93.77% Example 4 34.2 32.2 94.15% Comparative Example 1 28.5 25.6 89.82% Comparative Example 2 29.1 26.4 90.72% Comparative Example 3 29.3 26.8 91.47% Example 1 maintained approximately 92% tensile strength retention under 500 hours of accelerated aging, which is superior to the comparative material. This retention rate is an important evaluation method for assessing weather resistance; when the retention rate after aging is >50%, it is generally considered that the material can still meet functional requirements.

[0067] Table 2 Crystallization test results before and after aging Initial crystallinity % Crystallinity % after 500 h aging Example 1 43.1 44.8 Example 2 43.3 45.3 Example 3 43.7 46.0 Example 4 43.8 46.2 Comparative Example 1 41.9 48.7 Comparative Example 2 42.4 48.6 Comparative Example 3 42.6 48.5 The comparative examples showed a significant increase in crystallinity (usually due to the chain breakage and recombination effect caused by photo-oxidation), which may be accompanied by more severe embrittlement. Example 1 showed less change in crystallinity, indicating that the system was more stable.

[0068] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. Other modifications can be easily made by those skilled in the art. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details shown and described herein.

Claims

1. A process for the preparation of an anti-aging biomass based polypropylene-polyethylene composite plastic material for green packaging, characterized by, Includes the following steps, measured in parts by weight: (1) Prepare a mixture of bio-based polypropylene and bio-based polyethylene matrix, wherein the mass ratio of bio-based polypropylene to bio-based polyethylene is 30~70:30~70, and the total is 100 parts; (2) Add 10 to 30 parts by mass of the biomass enhancer to the matrix mixture in step (1); (3) Add 0.5-5.0 parts of anti-aging agent, 2.0-10.0 parts of interface compatibility agent, 0.1-1.0 parts of antistatic agent, 1.0-5.0 parts of toughening agent and 0.5-3.0 parts of ultraviolet absorber, and mix evenly; (4) The mixture after uniform mixing in step (3) is melt-blended and extruded in a twin-screw extruder at a temperature of 170~230℃ and a screw speed of 200~600rpm to fully disperse the components. (5) After cooling, granulating and drying, the extrudate is processed into the final green packaging composite material product in injection molding or extrusion molding equipment at 180~230℃. The anti-aging agent oil was prepared by reacting 1H-benzimidazole-2-thiol, 3-vinylquinoline, N,N-dimethylacetamide, triethylenediamine as a co-catalyst, and 2-hydroxy-2-methyl-1-phenyl-1-propanone.

2. A process for the preparation of an anti-aging biomass based polypropylene- polyethylene composite plastic material for green packaging as claimed in claim 1, wherein: The biomass enhancer is one of natural cellulose fiber powder, lignin fiber, or crop straw powder, or a compound thereof.

3. A process for the preparation of an anti-aging biomass based polypropylene-polyethylene composite plastic material for green packaging as claimed in claim 1, wherein: The method for preparing the anti-aging agent: By weight, 65-80 parts of 1H-benzimidazole-2-thiol, 18-28 parts of 3-vinylquinoline, 90-130 parts of N,N-dimethylacetamide, and 1.0-1.8 parts of triethylenediamine co-catalyst are mixed evenly, and 0.5-1.2 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone photoinitiator are added. Under a nitrogen protective atmosphere, the reaction temperature is controlled at 70-80℃, and ultraviolet light with a wavelength of 365nm and a power of 80-120W is used for irradiation at a distance of 10-25cm. The reaction system is stirred at a rate of 250-350r / min. The reaction time is controlled at 3-5 hours. The residual solvent is removed by vacuum distillation, and then the mixture is dried in a vacuum oven for 5-8 hours to obtain quinoline-modified benzimidazole anti-aging agent.

4. The preparation method of an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 3, characterized in that: The vacuum distillation pressure is 0.005-0.05 MPa, and the temperature is 60-70℃.

5. The preparation method of an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 3, characterized in that: The vacuum oven has a temperature of 55-65℃ and a pressure of 0.05-0.08MPa.

6. The method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 1, characterized in that: The interface compatibility agent is maleic anhydride-grafted polypropylene or maleic anhydride-grafted polyethylene.

7. The method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 1, characterized in that: The antistatic agent is one or more combinations of trihydroxyethylmethyl quaternary ammonium methyl sulfate, stearyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, octadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, or hexadecyltrimethylammonium bromide.

8. The method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 1, characterized in that: The toughening agent is ethylene propylene rubber or POE.

9. The method for preparing an anti-aging biomass-based polypropylene-polyethylene composite plastic material for green packaging according to claim 1, characterized in that: The ultraviolet absorber is UV-328, UV-531, or BP-6.