Preparation method of biomass modified environment degradable polypropylene plastic preservation storage box
By using a blending technology of modified chitosan and biomass fillers, the mechanical properties and processability issues of biodegradable polypropylene materials have been solved, achieving efficient degradation and excellent comprehensive performance of food preservation storage boxes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PUJIANG COUNTY HENGRUI IND & TRADE CO LTD
- Filing Date
- 2026-01-20
- Publication Date
- 2026-06-09
AI Technical Summary
Existing biodegradable polypropylene materials suffer from insufficient mechanical properties, poor processability, poor appearance quality, and difficulty in achieving effective degradation while maintaining practical properties such as strength and temperature resistance.
Modified chitosan grafted with maleic anhydride polypropylene, antioxidants, lubricants, and antistatic agents, along with biomass fillers such as corn stalk powder and wheat stalk powder, are mixed and blended in a twin-screw extruder to form a composite material, which is then injection molded to prepare a food preservation storage box.
It significantly improves the material's natural degradation ability, maintains excellent mechanical strength and processability, and achieves a balance between the environmental protection attributes and performance of the food preservation storage box.
Abstract
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 a biomass-modified environmentally degradable polypropylene plastic food preservation storage box. Background Technology
[0002] Plastic products, due to their lightweight, easy processing, low cost, and excellent mechanical properties, have been widely used in packaging, household utensils, automotive parts, and many other fields since the mid-20th century, becoming an important material in modern industry and daily life. Polyolefin plastics, represented by polypropylene (PP), are particularly favored for their good heat resistance, chemical resistance, and cost advantages, and are extensively used in the production of food containers, food storage boxes, and injection-molded parts. However, traditional polypropylene is a non-degradable petroleum-based polymer material, extremely difficult to decompose in the natural environment, and the large-scale accumulation of waste has caused serious environmental problems such as "white pollution." Existing research shows that plastic waste accounts for a large proportion of total urban solid waste, and its long-term presence can alter soil pH and hinder organic recycling, causing long-term harm to the environment and ecosystem.
[0003] To alleviate the environmental burden caused by non-degradable plastics, the development of biodegradable plastics and bio-based materials has received widespread attention from the scientific and industrial communities. One technical solution involves blending readily degradable synthetic resins, such as aliphatic polyesters or polylactic acid, with polypropylene (PP) to prepare polypropylene compositions with certain degradability. For example, Chinese patent CN110317406A discloses a biodegradable polypropylene composition containing polybutylene succinate (PBAT) and polylactic acid (PLA). By adding a compatibilizer to improve the compatibility between the polymers, the composition acquires degradability while maintaining mechanical properties and appearance quality.
[0004] Another type of technological exploration attempts to introduce bio-based polypropylene (such as polypropylene synthesized from bioethanol) into a composite with traditional petroleum-based polypropylene to form so-called bio-based plastic composite materials. Korean patent KR20240008811A proposes a plastic composite material containing bio-based polypropylene and petroleum-based polypropylene, which improves the environmental friendliness and mechanical properties of the composite material by adjusting the mass ratio of the two, thus achieving a balance between environmental performance and traditional plastic properties.
[0005] In addition, there are methods in biodegradable material systems that combine biodegradable polymers with inorganic fillers, such as the biodegradable resin composition containing inorganic powder disclosed in CN114207030A. Although it is not for polypropylene systems, it reflects the idea of enhancing the processability and mechanical properties of biodegradable materials through composite modification.
[0006] Currently, many methods that directly blend natural polymers such as starch and cellulose with polypropylene as fillers show positive potential in improving environmental biodegradability. However, due to problems such as poor compatibility, severe degradation of mechanical properties, and increased processing difficulty, these methods have not yet been widely adopted in industrial applications. To address this technical challenge, the academic community has conducted extensive research, such as introducing maleic anhydride-grafted polypropylene as a compatibilizer to improve interfacial bonding, enabling the natural polymer filler to be uniformly dispersed in the polypropylene matrix and improving overall performance.
[0007] In summary, while existing technologies have made some progress in the degradability of polypropylene, they still face the following challenges: 1. Biodegradable polypropylene materials typically suffer from defects such as insufficient mechanical properties, poor processability, and poor appearance quality; 2. Maintaining the strength, temperature resistance, and other practical properties of polypropylene materials while improving their degradation performance remains a challenge; 3. The efficient preparation process that effectively integrates biomass fillers and polypropylene matrix while maintaining the excellent properties of both is still immature.
[0008] Therefore, developing a biomass-modified polypropylene material and its preparation method that combines environmental degradability with excellent comprehensive performance, controllable process, and suitability for industrial production has significant practical significance and application value. Summary of the Invention
[0009] Based on the problems raised in the background art, the present invention proposes a method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box.
[0010] The technical solution is as follows: A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps, in parts by weight: Step 1) Ingredient preparation: Prepare the raw material mixture according to the mass parts, including 70-90 parts of polypropylene, 5-20 parts of maleic anhydride grafted polypropylene, 5-20 parts of modified chitosan, 0.1-1.0 parts of antioxidant, 0.1-1.0 parts of lubricant and 0.05-0.5 parts of antistatic agent; Step 2) Biomass pretreatment step: The biomass packing is soaked in 0.5-5.0% alkaline solution or acid solution at 50-90℃ for 20-60 minutes, then washed and dried, and activated and modified to introduce carboxyl, hydroxyl or ester active functional groups on its surface. Step 3) Mixing and blending step: The raw material mixture prepared in step 1) and the biomass filler treated in step 2) are added to a twin-screw extruder with the temperature controlled at 170-230℃ for mixing and blending, and the screw speed is controlled at 30-80 rpm to obtain the composite material. Step 4) Granulation step: The composite material obtained in step 3) is cut into pellets or granulated to form granules; Step 5) Injection molding step: The composite particles obtained in step 4) are injected into an injection molding machine with process parameters set to produce a finished food preservation storage box.
[0011] As a preferred embodiment of the present invention, the method for preparing the modified chitosan is as follows: By weight, 30-45 parts chitosan, 1.5-3.1 parts epoxy cyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 0.9-1.6 parts catalyst potassium ethoxide, 3-7 parts poly(lactic acid-caprolactone) copolymer, and 300-400 parts DMF are added sequentially to a reactor and kept at 50-60°C. After the reaction is completed, the mixture is cooled to room temperature, DMF is removed by distillation, and the mixture is dried under vacuum to obtain modified chitosan.
[0012] As a preferred embodiment of the present invention, the poly(lactic acid-caprolactone) copolymer has a molecular weight of 1000-2000.
[0013] As a preferred embodiment of the present invention, the vacuum drying parameters are: temperature of 55-65℃, pressure of 0.06-0.09MPa, and time of 12-20 hours.
[0014] As a preferred embodiment of the present invention, the antioxidant is one or a combination of Irganox 1010, Irgafos 168 or Irganox 1076.
[0015] As a preferred embodiment of the present invention, the lubricant is one or a combination of stearic acid, ammonium stearate or sodium stearate.
[0016] As a preferred embodiment of the present invention, the alkaline solution is selected from sodium hydroxide, potassium hydroxide or ammonia; the acid solution is selected from sulfuric acid, hydrochloric acid or acetic acid.
[0017] As a preferred embodiment of the present invention, the volume filling rate of the composite material in the mixing and blending step is controlled at 5-35% and the mixing time is controlled at 3-8 minutes.
[0018] As a preferred embodiment of the present invention, the process parameters in the injection molding step are: mold temperature 30-60°C, injection barrel temperature 180-230°C, holding time 5-20 seconds, and cooling time 30-120 seconds.
[0019] As a preferred embodiment of the present invention, the biomass filler is corn stalk powder, wheat stalk powder, rice husk powder, bamboo powder, or a combination thereof.
[0020] Reaction mechanism: Chitosan, as a biomass substrate, undergoes a ring-opening grafting reaction with the epoxy groups of epoxycyclohexyl-cage polysilsesquioxane under the action of a catalyst. At the same time, poly(lactic acid-caprolactone) copolymer participates in molecular chain crosslinking through compatibility. Nano-hydroxyapatite is embedded in the system through interfacial interactions, forming a crosslinked modified structure that combines biomass compatibility and degradation activity, providing a structural basis for subsequent composite with polypropylene substrate.
[0021] Technical effect (1) Significantly improves the natural degradation ability of polypropylene materials. After the product is discarded, it can be gradually decomposed in the natural environment, avoiding residual pollution; (2) Optimize the preservation and sealing performance of the storage box, which can effectively block the influence of the external environment and maintain the quality stability of the stored items; (3) Innovatively achieve synergistic effects between biomass modifiers and degradation aids, ensuring the strength of the material while endowing it with environmental protection attributes, breaking through the limitation of traditional plastic storage boxes that "performance and environmental protection cannot be achieved at the same time". At the same time, it maintains excellent mechanical strength and processability. Detailed Implementation
[0022] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, structures, features and effects of the present invention, in conjunction with preferred embodiments, is provided below. Example
[0023] A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass percentages: 70 kg of polypropylene, 5 kg of maleic anhydride-grafted polypropylene (grafting rate 1.0%), 5 kg of modified chitosan, 0.1 kg of antioxidant (Irganox 1010), 0.1 kg of lubricant (stearic acid), and 0.05 kg of antistatic agent (trihydroxyethylmethyl quaternary ammonium methyl sulfate). Add the above raw materials to a high-speed mixer in sequence and mix at 300 rpm for 20 minutes at room temperature to obtain a uniform raw material mixture.
[0024] 2. Step 2) Biomass pretreatment steps: Weigh 5 kg of biomass filler (corn straw powder, particle size 80 mesh), put it into the reaction tank, add 0.5% sodium hydroxide alkaline solution (liquid-solid ratio 5:1), and soak at 50℃ for 20 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 80℃ for 4 hours; then use citric acid solution (concentration 1%) for activation modification, soak at room temperature for 15 minutes to introduce carboxyl active functional groups, wash and dry again for later use.
[0025] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) together to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; control the screw speed at 30 rpm, the composite material volume filling rate at 5%, and the mixing time at 3 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0026] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 25℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 3mm, and collected and placed in a temporary storage tank for later use.
[0027] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, set the process parameters: mold temperature 30℃, injection barrel temperature 180℃ (front section 170℃, middle section 180℃, rear section 175℃), holding time 5 seconds, cooling time 30 seconds, injection pressure 8MPa; start the equipment to complete injection molding, after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0028] The modified chitosan is prepared as follows: 30 kg of chitosan, 1.5 kg of epoxy cyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 0.9 kg of potassium ethoxide catalyst, 3 kg of poly(lactic acid-caprolactone) copolymer (molecular weight 1000), and 300 kg of DMF are sequentially added to a reaction vessel according to the following proportions by weight: After sealing the reaction vessel, the temperature is raised to 50°C, and the mixture is stirred at 250 rpm for 3 hours; after the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation under a pressure of 0.06 MPa and a temperature of 70°C; the remaining product is placed in a vacuum oven, and dried for 12 hours at a temperature of 55°C and a pressure of 0.06 MPa to obtain the modified chitosan. Example
[0029] A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass percentages: 75 kg of polypropylene, 10 kg of maleic anhydride-grafted polypropylene (grafting rate 1.2%), 10 kg of modified chitosan, 0.35 kg of antioxidant (Irgafos 168), 0.35 kg of lubricant (ammonium stearate), and 0.2 kg of antistatic agent (trimethylammonium stearate chloride). Add the above raw materials to a high-speed mixer in sequence and mix at 320 rpm for 25 minutes at room temperature to obtain a uniform raw material mixture.
[0030] 2. Step 2) Biomass pretreatment steps: Weigh 10 kg of biomass filler (wheat straw powder, particle size 100 mesh), put it into the reaction tank, add 2.0% hydrochloric acid solution (liquid-solid ratio 6:1), and soak at 65℃ for 35 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 85℃ for 5 hours; then use propylene oxide solution (concentration 2%) for activation modification, soak at 40℃ for 20 minutes to introduce hydroxyl active functional groups, wash and dry again for later use.
[0031] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 170℃, homogenization section 190℃, metering section 200℃; control the screw speed at 45 rpm, the composite material volume filling rate at 15%, and the mixing time at 4.5 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0032] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 30℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 3.5mm, and collected and placed in a temporary storage tank for later use.
[0033] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, and set the process parameters: mold temperature 40℃, injection barrel temperature 200℃ (front section 190℃, middle section 200℃, rear section 195℃), holding time 10 seconds, cooling time 60 seconds, injection pressure 10MPa; start the equipment to complete the injection molding, and after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0034] The modified chitosan is prepared as follows: 36 kg of chitosan, 2.0 kg of epoxy cyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 1.2 kg of potassium ethoxide catalyst, 4.5 kg of poly(lactic acid-caprolactone) copolymer (molecular weight 1400), and 330 kg of DMF are sequentially added to a reaction vessel according to the following proportions by weight: After sealing the reaction vessel, the temperature is raised to 53°C, and the mixture is stirred at 280 rpm for 3.5 hours; after the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation under a pressure of 0.07 MPa and a temperature of 72°C; the remaining product is placed in a vacuum oven, and dried for 15 hours at a temperature of 58°C and a pressure of 0.07 MPa to obtain the modified chitosan. Example
[0035] A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass proportions: 85 kg of polypropylene, 15 kg of maleic anhydride-grafted polypropylene (grafting rate 1.5%), 15 kg of modified chitosan, 0.65 kg of antioxidant (Irganox 1010 and Irganox 1076 mixed in a 1:1 ratio), 0.65 kg of lubricant (stearic acid and sodium stearate mixed in a 1:1 ratio), and 0.35 kg of antistatic agent (hexadecyltrimethylammonium bromide). Add the above raw materials to a high-speed mixer in sequence and mix at 350 rpm for 30 minutes at room temperature to obtain a uniform raw material mixture.
[0036] 2. Step 2) Biomass pretreatment steps: Weigh 15 kg of biomass filler (rice husk powder, particle size 120 mesh), put it into a reaction tank, add 3.5% potassium hydroxide alkaline solution (liquid-solid ratio 7:1), and soak at 75℃ for 45 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 90℃ for 6 hours; then use acetic anhydride solution (concentration 3%) for activation modification, soak at 50℃ for 25 minutes to introduce ester active functional groups, wash and dry again for later use.
[0037] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feed section 180℃, homogenization section 210℃, metering section 220℃; control the screw speed at 60 rpm, the composite material volume filling rate at 25%, and the mixing time at 6 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0038] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 35℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 4mm, and collected and placed in a temporary storage tank for later use.
[0039] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, and set the process parameters: mold temperature 50℃, injection barrel temperature 210℃ (front section 200℃, middle section 210℃, rear section 205℃), holding time 15 seconds, cooling time 90 seconds, injection pressure 12MPa; start the equipment to complete the injection molding, and after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0040] The modified chitosan is prepared as follows: 40 kg of chitosan, 2.5 kg of epoxy cyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 1.4 kg of potassium ethoxide catalyst, 5.5 kg of poly(lactic acid-caprolactone) copolymer (molecular weight 1700), and 370 kg of DMF are sequentially added to a reaction vessel according to the following proportions by weight: After sealing the reaction vessel, the temperature is raised to 57°C, and the reaction is stirred at 300 rpm for 4.5 hours; after the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation under a pressure of 0.08 MPa and a temperature of 75°C; the remaining product is placed in a vacuum oven, and dried for 18 hours at a temperature of 62°C and a pressure of 0.08 MPa to obtain the modified chitosan. Example
[0041] A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass proportions: 90 kg of polypropylene, 20 kg of maleic anhydride-grafted polypropylene (grafting rate 1.8%), 20 kg of modified chitosan, 1.0 kg of antioxidant (Irganox 1076), 1.0 kg of lubricant (sodium stearate), and 0.5 kg of antistatic agent (a 1:1 mixture of stearyltrimethylammonium chloride and hexadecyltrimethylammonium bromide); Add the above raw materials sequentially to a high-speed mixer and mix at 380 rpm for 35 minutes at room temperature to obtain a uniform raw material mixture.
[0042] 2. Step 2) Biomass pretreatment steps: Weigh 20 kg of biomass filler (bamboo powder, particle size 150 mesh), put it into a reaction tank, add 5.0% acetic acid solution (liquid-solid ratio 8:1), control the temperature at 90℃ and soak for 60 minutes; stir once every 5 minutes, each stirring for 30 seconds; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, put it into a forced-air drying oven at 95℃ and dry for 7 hours; then use a mixed solution of citric acid and acetic anhydride (volume ratio 1:1, total concentration 4%) for activation modification, soak at 60℃ for 30 minutes, and at the same time introduce carboxyl and ester active functional groups, wash and dry again for later use.
[0043] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) together to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 190℃, homogenization section 230℃, metering section 240℃; control the screw speed at 80 rpm, the composite material volume filling rate at 35%, and the mixing time at 8 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0044] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 40℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 4.5mm, and collected and placed in a temporary storage tank for later use.
[0045] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, and set the process parameters: mold temperature 60℃, injection barrel temperature 230℃ (front section 220℃, middle section 230℃, rear section 225℃), holding time 20 seconds, cooling time 120 seconds, injection pressure 15MPa; start the equipment to complete the injection molding, and after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0046] The modified chitosan is prepared as follows: 45 kg of chitosan, 3.1 kg of epoxy cyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 1.6 kg of potassium ethoxide catalyst, 7 kg of poly(lactic acid-caprolactone) copolymer (molecular weight 2000), and 400 kg of DMF are sequentially added to a reactor. After sealing the reactor, the temperature is raised to 60°C, and the mixture is stirred at 320 rpm for 5 hours. After the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation at a pressure of 0.09 MPa and a temperature of 80°C. The remaining product is placed in a vacuum oven, and dried at a temperature of 65°C and a pressure of 0.09 MPa for 20 hours to obtain the modified chitosan.
[0047] Comparative Example 1 A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass percentages: 70 kg of polypropylene, 5 kg of maleic anhydride-grafted polypropylene (grafting rate 1.0%), 5 kg of chitosan, 0.1 kg of antioxidant (Irganox 1010), 0.1 kg of lubricant (stearic acid), and 0.05 kg of antistatic agent (trihydroxyethylmethyl quaternary ammonium methyl sulfate). Add the above raw materials to a high-speed mixer in sequence and mix at 300 rpm for 20 minutes at room temperature to obtain a uniform raw material mixture.
[0048] 2. Step 2) Biomass pretreatment steps: Weigh 5 kg of biomass filler (corn straw powder, particle size 80 mesh), put it into the reaction tank, add 0.5% sodium hydroxide alkaline solution (liquid-solid ratio 5:1), and soak at 50℃ for 20 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 80℃ for 4 hours; then use citric acid solution (concentration 1%) for activation modification, soak at room temperature for 15 minutes to introduce carboxyl active functional groups, wash and dry again for later use.
[0049] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) together to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; control the screw speed at 30 rpm, the composite material volume filling rate at 5%, and the mixing time at 3 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0050] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 25℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 3mm, and collected and placed in a temporary storage tank for later use.
[0051] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, set the process parameters: mold temperature 30℃, injection barrel temperature 180℃ (front section 170℃, middle section 180℃, rear section 175℃), holding time 5 seconds, cooling time 30 seconds, injection pressure 8MPa; start the equipment to complete injection molding, after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0052] Comparative Example 2 A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass percentages: 70 kg of polypropylene, 5 kg of maleic anhydride-grafted polypropylene (grafting rate 1.0%), 5 kg of modified chitosan, 0.1 kg of antioxidant (Irganox 1010), 0.1 kg of lubricant (stearic acid), and 0.05 kg of antistatic agent (trihydroxyethylmethyl quaternary ammonium methyl sulfate). Add the above raw materials to a high-speed mixer in sequence and mix at 300 rpm for 20 minutes at room temperature to obtain a uniform raw material mixture.
[0053] 2. Step 2) Biomass pretreatment steps: Weigh 5 kg of biomass filler (corn straw powder, particle size 80 mesh), put it into the reaction tank, add 0.5% sodium hydroxide alkaline solution (liquid-solid ratio 5:1), and soak at 50℃ for 20 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 80℃ for 4 hours; then use citric acid solution (concentration 1%) for activation modification, soak at room temperature for 15 minutes to introduce carboxyl active functional groups, wash and dry again for later use.
[0054] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) together to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; control the screw speed at 30 rpm, the composite material volume filling rate at 5%, and the mixing time at 3 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0055] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 25℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 3mm, and collected and placed in a temporary storage tank for later use.
[0056] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, set the process parameters: mold temperature 30℃, injection barrel temperature 180℃ (front section 170℃, middle section 180℃, rear section 175℃), holding time 5 seconds, cooling time 30 seconds, injection pressure 8MPa; start the equipment to complete injection molding, after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0057] The modified chitosan is prepared as follows: 30 kg of chitosan, 0.9 kg of potassium ethoxide catalyst, 3 kg of poly(lactic acid-caprolactone) copolymer (molecular weight 1000), and 300 kg of DMF are added sequentially to a reaction vessel according to the following weight ratios: After sealing the reaction vessel, the temperature is raised to 50°C, and the mixture is stirred at 250 rpm for 3 hours; after the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation under a pressure of 0.06 MPa and a temperature of 70°C; the remaining product is placed in a vacuum oven, and dried for 12 hours at a temperature of 55°C and a pressure of 0.06 MPa to obtain the modified chitosan.
[0058] Comparative Example 3 A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box includes the following steps: 1. Step 1) Ingredient preparation: Weigh the raw materials according to the following mass percentages: 70 kg of polypropylene, 5 kg of maleic anhydride-grafted polypropylene (grafting rate 1.0%), 5 kg of modified chitosan, 0.1 kg of antioxidant (Irganox 1010), 0.1 kg of lubricant (stearic acid), and 0.05 kg of antistatic agent (trihydroxyethylmethyl quaternary ammonium methyl sulfate). Add the above raw materials to a high-speed mixer in sequence and mix at 300 rpm for 20 minutes at room temperature to obtain a uniform raw material mixture.
[0059] 2. Step 2) Biomass pretreatment steps: Weigh 5 kg of biomass filler (corn straw powder, particle size 80 mesh), put it into the reaction tank, add 0.5% sodium hydroxide alkaline solution (liquid-solid ratio 5:1), and soak at 50℃ for 20 minutes; stir once every 5 minutes for 30 seconds each time; after soaking, wash repeatedly with deionized water until the pH of the washing solution is neutral, and put it into a forced-air drying oven at 80℃ for 4 hours; then use citric acid solution (concentration 1%) for activation modification, soak at room temperature for 15 minutes to introduce carboxyl active functional groups, wash and dry again for later use.
[0060] 3. Step 3) Mixing and blending step: Add the raw material mixture from step 1) and the biomass filler processed in step 2) together to a twin-screw extruder. Set the temperatures of each section of the extruder as follows: feeding section 160℃, homogenization section 170℃, metering section 180℃; control the screw speed at 30 rpm, the composite material volume filling rate at 5%, and the mixing time at 3 minutes to ensure that all components are fully integrated and dispersed to obtain a uniform composite material.
[0061] 4. Step 4) Granulation step: The composite material obtained in step 3) is extruded into strip melt through the extruder die and sent to a water cooling tank (water temperature 25℃) to cool to room temperature; then sent to a pelletizer to cut into particles with a particle size of 3mm, and collected and placed in a temporary storage tank for later use.
[0062] 5. Step 5) Injection molding step: Add the composite particles from step 4) to the injection molding machine, set the process parameters: mold temperature 30℃, injection barrel temperature 180℃ (front section 170℃, middle section 180℃, rear section 175℃), holding time 5 seconds, cooling time 30 seconds, injection pressure 8MPa; start the equipment to complete injection molding, after cooling and demolding, the finished food preservation storage box is obtained after trimming.
[0063] The modified chitosan is prepared as follows: 30 kg of chitosan, 1.5 kg of epoxycyclohexyl-cage polysilsesquioxane (CAS No. 187333-74-0), 0.9 kg of potassium ethoxide catalyst, and 300 kg of DMF are added sequentially to a reaction vessel according to the following weight ratios: After sealing the reaction vessel, the temperature is raised to 50°C, and the mixture is stirred at 250 rpm for 3 hours; after the reaction is completed, the mixture is cooled to room temperature, and the DMF is removed by vacuum distillation under a pressure of 0.06 MPa and a temperature of 70°C; the remaining product is placed in a vacuum oven, and dried for 12 hours at a temperature of 55°C and a pressure of 0.06 MPa to obtain the modified chitosan.
[0064] Test method: 1. Tensile property test method Tensile tests were conducted according to EN ISO 527-1 / -2 standards using a universal testing machine. The testing environment was 23 ± 2 ℃ and 50 ± 5% relative humidity. The gauge length and clamp spacing were set according to standards. The tensile rate was 50 mm / min.
[0065] 2. Biodegradability (Aerobic) Test Method Using the ASTM D5988-18 aerobic biodegradation test method, the sample was pulverized and mixed into standard compost soil, and CO2 emissions were measured to assess the degradation rate. The test period was set at 90 days, and the temperature was maintained at 25–35 °C.
[0066] 3. Thermal performance testing methods The thermal properties of the samples were determined using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC determined the melting temperature and crystallization behavior, while TGA determined the thermal decomposition initiation and maximum degradation temperatures.
[0067] Test results: Table 1 Mechanical Performance Test Results Tensile strength (MPa) Elongation at break (%) Example 1 32.2 21.5 Example 2 32.6 20.8 Example 3 33.1 20.5 Example 4 33.5 20.2 Comparative Example 1 30.0 23.6 Comparative Example 2 31.5 23.0 Comparative Example 3 31.8 22.8 Compared with the comparative example, the tensile strength of the sample in the example was increased; the elongation at break was slightly decreased, indicating that the rigidity was increased but the toughness was reduced.
[0068] Table 2 Environmental degradation performance test results Biodegradation rate (%) Example 1 48.8 Example 2 50.1 Example 3 51.7 Example 4 53.3 Comparative Example 1 40.6 Comparative Example 2 46.2 Comparative Example 3 47.0 The examples show significantly higher aerobic biodegradability than the comparative examples, indicating that biomass fillers promote polymer chain breakage and microbial activity, thereby enhancing the environmental degradation trend.
[0069] Table 3 Thermal performance test results Melting temperature Tm (DSC) Thermal decomposition onset temperature (TGA) Example 1 162.2 365.5 Example 2 162.7 366.4 Example 3 162.4 366.0 Example 4 162.3 365.8 Comparative Example 1 165.0 374.2 Comparative Example 2 164.3 372.0 Comparative Example 3 163.8 371.6 The melting temperature of the example was slightly lower than that of the comparative example, indicating that the filler and interfacial compatibilizer affected the crystallization behavior; the thermal decomposition initiation temperature was slightly lower, but the processing window was still suitable for injection molding.
[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box, characterized in that, Includes the following steps, measured in parts by weight: Step 1) Ingredient preparation: Prepare the raw material mixture according to the mass parts, including 70-90 parts of polypropylene, 5-20 parts of maleic anhydride grafted polypropylene, 5-20 parts of modified chitosan, 0.1-1.0 parts of antioxidant, 0.1-1.0 parts of lubricant and 0.05-0.5 parts of antistatic agent; Step 2) Biomass pretreatment step: Soak the biomass packing material in 0.5-5.0% alkaline solution or acid solution at 50-90℃ for 20-60 minutes, then wash and dry it, and activate and modify it to introduce carboxyl, hydroxyl or ester active functional groups on its surface. Step 3) Mixing and blending step: The raw material mixture prepared in step 1) and the biomass filler treated in step 2) are added to a twin-screw extruder with the temperature controlled at 170-230℃ for mixing and blending, and the screw speed is controlled at 30-80 rpm to obtain the composite material. Step 4) Granulation step: The composite material obtained in step 3) is cut into pellets or granulated to form granules; Step 5) Injection molding step: The composite particles obtained in step 4) are injection molded into a finished food preservation storage box by setting the process parameters in an injection molding machine. The modified chitosan is prepared by reacting chitosan, epoxy cyclohexyl-cage polysilsesquioxane, potassium ethoxide catalyst, and poly(lactic acid-caprolactone) copolymer.
2. The preparation method of a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The preparation method of the modified chitosan: By weight, 30-45 parts chitosan, 1.5-3.1 parts epoxy cyclohexyl-cage polysilsesquioxane, 0.9-1.6 parts catalyst potassium ethoxide, 3-7 parts poly(lactic acid-caprolactone) copolymer, and 300-400 parts DMF are added sequentially to a reactor and kept at 50-60°C. After the reaction is completed, the mixture is cooled to room temperature, DMF is removed by distillation, and the mixture is dried under vacuum to obtain modified chitosan.
3. The preparation method of a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 2, characterized in that: The poly(lactic acid-caprolactone) copolymer has a molecular weight of 1000-2000.
4. The preparation method of a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 2, characterized in that: The vacuum drying parameters are: temperature 55-65℃, pressure 0.06-0.09MPa, and time 12-20 hours.
5. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The antioxidant is one or a combination of Irganox 1010, Irgafos 168, or Irganox 1076.
6. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The lubricant is one or a combination of stearic acid, ammonium stearate or sodium stearate.
7. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The alkaline solution is selected from sodium hydroxide, potassium hydroxide, or ammonia; the acid solution is selected from sulfuric acid, hydrochloric acid, or acetic acid.
8. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: In the mixing and blending step, the volume filling rate of the composite material is controlled at 5-35% and the mixing time is controlled at 3-8 minutes.
9. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The process parameters for the injection molding step are: mold temperature 30-60℃, injection barrel temperature 180-230℃, holding time 5-20 seconds, and cooling time 30-120 seconds.
10. The method for preparing a biomass-modified environmentally degradable polypropylene plastic food preservation storage box according to claim 1, characterized in that: The biomass filler is corn straw powder, wheat straw powder, rice husk powder, bamboo powder, or a combination thereof.