Degradable bio-based PE composite film and preparation method thereof

Abstract

The invention relates to the technical field of film production, and discloses a degradable bio-based PE composite film and a preparation method thereof.The degradable bio-based PE composite film comprises an outer layer and an inner layer, the outer layer is a modified PE film, and the inner layer is a modified starch aerogel film; the outer layer is prepared from the following raw materials: modified PE, a plasticizer, a heat stabilizer, a lubricant, an antioxidant and an antistatic agent; the inner layer comprises the following raw materials: modified starch, a plasticizer, a cross-linking agent and deionized water. The degradable packaging material has wide application prospects in the fields of food packaging, agricultural mulching films, medical dressings and the like, a reliable technical scheme is provided for industrial popularization of the degradable packaging material, and the current industrial requirement of green development is met.

Description

Technical Field

[0001] This invention relates to the field of thin film production technology, specifically to a biodegradable bio-based PE composite film and its preparation method. Background Technology

[0002] Polyethylene (PE) film is widely used in many industries due to its advantages such as convenient processing, stable mechanical properties and low cost. However, traditional PE film is a non-polar petroleum-based material that is difficult to degrade in the natural environment. Long-term residue will cause serious white pollution and damage the soil ecology and natural environment.

[0003] Existing biodegradable PE composite membranes are mostly prepared by directly blending starch and PE. However, starch is a hydrophilic polar material with extremely poor compatibility with hydrophobic nonpolar PE. Direct mixing easily leads to phase separation, resulting in composite membranes with weak mechanical properties, easy damage, poor water resistance, and easy swelling and failure upon contact with water. Therefore, developing a biodegradable bio-based PE composite membrane that can solve the compatibility problem between PE and starch, has stable mechanical properties, good water resistance, and complete degradation has become a pressing technical challenge for the industry. This is of great significance for promoting the industrial application of environmentally friendly materials and alleviating white pollution. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a biodegradable bio-based PE composite film and its preparation method.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, a biodegradable bio-based PE composite film is provided, comprising an outer layer and an inner layer, wherein the outer layer is a modified PE film and the inner layer is a modified starch aerogel film. The outer layer comprises the following raw materials in parts by weight: 80-100 parts modified PE, 2-3 parts plasticizer, 0.5-1 part heat stabilizer, 1-1.5 parts lubricant, 0.3-0.6 parts antioxidant, and 0.5-1 part antistatic agent; the plasticizer is one of tributyl citrate and polycaprolactone; the heat stabilizer is one of zinc stearate and triphenyl phosphite; the lubricant is one of polyethylene glycol-400 and erucamide; the antioxidant is one of antioxidant 1010, antioxidant 168, and antioxidant 1076; and the antistatic agent is one of Tween-20, glyceryl fatty acid ester, and dodecyl dimethyl betaine. The inner layer comprises the following raw materials in parts by weight: 85-95 parts modified starch, 4-6 parts plasticizer, 3-5 parts crosslinking agent, and 500-800 parts deionized water; the plasticizer is one of polycaprolactone and glyceryl triacetate; the crosslinking agent is one of diethylenetriamine and glyceryl diglycidyl ether.

[0006] Furthermore, the preparation method of modified starch includes the following steps: A1. Weigh 100-120 parts of starch, add 800-1000 parts of deionized water, stir and disperse, then heat to 45-50℃ and keep warm for 20-30 min. Add 1-1.5 parts of sodium dodecyl sulfate, stir for 10-15 min, and slowly add a mixture of 10-15 parts of dodecyl succinic anhydride, 15-18 parts of polypropylene glycol diglycidyl ether and 100-120 parts of anhydrous ethanol. Adjust the pH of the system to 8.0-9.0 with triethylamine, heat to 60-65℃, and react at a constant temperature for 2-3 h. After the reaction is complete, adjust the pH to 6.5-7.0 with 1 mol / L hydrochloric acid, centrifuge at 4000-6000 rpm for 10-15 min, collect the precipitate, and vacuum dry at 60-80℃ to constant weight to obtain the starch-modified intermediate. A2. Take 80-100 parts of starch-modified intermediate, add 600-800 parts of deionized water, heat to 70-75℃, stir evenly, add 1-1.5 parts of ammonium persulfate, keep warm for 10-15 min, slowly add 15-22 parts of dodecyl acrylate, heat to 80-85℃, react at a constant temperature for 2-4 h, add 2-5 parts of glyoxal, continue to react for 1-2 h, cool to room temperature, centrifuge at 4000-6000 rpm for 10-15 min, collect the precipitate, wash with anhydrous ethanol 1-3 times, and vacuum dry at 60-80℃ for 4-6 h to obtain modified starch.

[0007] Furthermore, the preparation method of modified PE includes the following steps: B1. Add 80-100 parts of ferrocene-grafted PE to a reactor, add 600-800 parts of anhydrous toluene, heat to 105-115℃, stir to dissolve, add 0.4-0.6 parts of benzoyl peroxide under a nitrogen atmosphere, keep warm for 10-15 min, slowly add 10-15 parts of hydroxyethyl acrylate, heat to 120-130℃, react for 2-3 h, add 0.06-0.08 parts of hydroquinone to terminate the reaction, pour the reaction solution into 3-5 times the volume of a 1:1 ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate 1-3 times with a 1:1 ethanol-acetone mixture, and vacuum dry at 60-80℃ for 6-8 h to obtain the PE intermediate; B2. Add 60-80 parts of PE intermediate to a reactor, add 500-600 parts of anhydrous toluene, heat to 105-115℃, stir to dissolve, add 0.15-0.2 parts of dibutyltin dilaurate under a nitrogen atmosphere, slowly add 6-10 parts of isophorone diisocyanate, and react at 85-95℃ for 2-4 h. Quickly cool to 30-40℃, pour the reaction solution into 3-5 times the volume of anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, precipitate out, filter and collect the precipitate, wash 1-3 times with anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, and vacuum dry at 60-80℃ for 6-7 h to obtain modified PE.

[0008] Furthermore, the preparation method of ferrocene-grafted PE includes the following steps: Add 100-120 parts of PE to a reactor, add 600-800 parts of anhydrous toluene, heat to 100-120℃ and stir until completely dissolved to form a PE solution. Under a nitrogen atmosphere, add 0.8-1.2 parts of dicumyl peroxide, keep warm for 10-15 min, then slowly add 4-8 parts of vinyl ferrocene, heat to 125-135℃ and react for 2-4 h. Add 0.08-0.1 parts of hydroquinone to terminate the reaction. Pour the reaction solution into 3-5 times the volume of a 1:1 ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate 1-3 times with a 1:1 ethanol-acetone mixture, and dry under vacuum at 60-80℃ for 6-8 h to obtain ferrocene-grafted PE.

[0009] Furthermore, the outer and inner layers are bonded together using a hot-pressing process to obtain a composite film.

[0010] A second aspect of the present invention provides a method for preparing a biodegradable bio-based PE composite film, comprising the following steps: S1. Weigh the modified PE, plasticizer, heat stabilizer, lubricant, antioxidant, and antistatic agent, add them to a high-speed mixer, stir at 80~90℃ and 800~1000 rpm for 10~15 min, feed them into a single-screw extruder, extrude the molten preform, and extrude it through the die head of a blown film extruder to obtain a modified PE film with a thickness of 0.03~0.04 mm. After cooling at room temperature, wind it up with a winding machine for later use. S2. Weigh the modified starch and plasticizer, add them to the reaction vessel, pour in deionized water, stir at 300~500 rpm, mix at room temperature for 10~15 min, heat to 85~90℃, keep warm for 30~40 min, add crosslinking agent, continue stirring for 1~1.5 h, cool to 50~60℃, degas under vacuum of -0.06~-0.08 MPa for 10~20 min to form starch sol; S3. The degassed crosslinked sol is uniformly coated onto a polytetrafluoroethylene (PTFE) carrier using a casting machine. The wet film thickness is controlled at 200-250 μm and the coating speed is 1-2 m / min. The wet film is allowed to stand at room temperature for 2-3 h to transform into a wet gel film. It is then transferred to a 0-4℃ refrigerator and allowed to stand for 12-16 h. After that, it is immersed in a liquid nitrogen bath for 1-2 min and then transferred to a freeze dryer. The parameters are set as follows: temperature -55~-50℃, vacuum degree ≤1 Pa, and drying time 24-30 h. After drying, the film material is peeled off from the PTFE carrier with a thickness of 50-70 μm. It is then cut into sizes that match the outer PE film to obtain a modified starch aerogel film for later use. S4. Align the modified starch aerogel film with the modified PE film, ensuring no wrinkles or misalignment. Place it between the upper and lower plates of a hot press and control the hot pressing parameters: temperature 120~125℃, pressure 0.8~1.0 MPa, time 30~40 s. After hot pressing, quickly transfer it to a cooling press and cool it at 20~25℃ and 0.3~0.5 MPa for 2~3 min, with a thickness of 0.08~0.10 mm. Place it in an aging chamber at 30~40℃ and 50~60% humidity for 36~72 h to obtain a biodegradable bio-based PE composite film.

[0011] Furthermore, in step S1, the single-screw extruder parameters are controlled as follows: processing temperature: zone 1 130~150℃, zone 2 160~165℃, zone 3 165~170℃, die head 165~168℃, and screw speed 220~250 rpm.

[0012] Furthermore, in step S1, the blown film extrusion is performed by the die head of the blown film extruder, with the blow ratio controlled at 2.5~3.0, the traction speed at 8~10 m / min, and the cooling air temperature at 20~25℃.

[0013] (iii) Beneficial technical effects This invention provides a method for preparing a biodegradable bio-based PE composite film. The outer layer of modified PE is grafted with ferrocene and incorporating polar groups, giving the material excellent photosensitive degradation activity, enabling rapid degradation in the natural environment and avoiding the environmental residue problems of traditional plastic films. The inner layer of modified starch undergoes modification and cross-linking treatment to construct a stable porous aerogel structure, which reduces the exposure of hydrophilic groups, improves water resistance, and effectively blocks heat transfer through the porous structure, giving the composite film good thermal insulation properties. Simultaneously, the polar groups on the modified PE and modified starch molecular chains form a synergistic effect, significantly improving the interfacial compatibility of the two layers. Combined with the stress dispersion effect of the aerogel structure, this significantly optimizes the mechanical properties of the composite film.

[0014] The process of this invention reduces production costs and uses environmentally friendly materials, and has broad application prospects in many fields such as food packaging, agricultural mulch film, and medical dressings. It provides a reliable technical solution for the industrial promotion of biodegradable packaging materials and meets the current industrial needs of green development. Detailed Implementation

[0015] 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.

[0016] Unless otherwise specified, all components of the bio-based PE composite film formulation of this invention are commercially available. All parts used in this invention are parts by weight; The density of PE is 0.91~0.93 g / cm³. 3 Purchased from Zhejiang Hengyi Petrochemical Co., Ltd. The starch was corn starch with a particle size of 10-20 μm, purchased from Shandong Fuyang Biotechnology Co., Ltd. Polycaprolactone has a molecular weight of 1000~2000; Example

[0017] A biodegradable bio-based PE composite membrane includes an outer layer and an inner layer, wherein the outer layer is a modified PE membrane and the inner layer is a modified starch aerogel membrane. The outer layer comprises the following raw materials in parts by weight: 80 parts modified PE, 2 parts plasticizer, 0.5 parts heat stabilizer, 1 part lubricant, 0.3 parts antioxidant, and 0.5 parts antistatic agent; the plasticizer is tributyl citrate; the heat stabilizer is zinc stearate; the lubricant is polyethylene glycol-400; the antioxidant is antioxidant 1010; and the antistatic agent is Tween-20. The inner layer comprises the following raw materials in parts by weight: 85 parts modified starch, 4 parts plasticizer, 3 parts crosslinking agent, and 500 parts deionized water; the plasticizer is polycaprolactone; and the crosslinking agent is diethylenetriamine.

[0018] The preparation method of modified starch includes the following steps: A1. Weigh 100 parts of starch, add 800 parts of deionized water, stir and disperse, then heat to 45℃ and keep warm for 20 min. Add 1 part of sodium dodecyl sulfate, stir for 10 min, and slowly add a mixture of 10 parts of dodecyl succinic anhydride, 15 parts of polypropylene glycol diglycidyl ether and 100 parts of anhydrous ethanol. Adjust the pH of the system to 8.0 with triethylamine, heat to 60℃, and react at a constant temperature for 2 h. After the reaction is complete, adjust the pH to 6.5 with 1 mol / L hydrochloric acid, centrifuge at 4000 rpm for 10 min, collect the precipitate, and vacuum dry at 60℃ to constant weight to obtain the starch-modified intermediate. A2. Take 80 parts of starch-modified intermediate, add 600 parts of deionized water, heat to 70℃, stir evenly, add 1 part of ammonium persulfate, keep warm for 10 min, slowly add 15 parts of dodecyl acrylate, heat to 80℃, keep warm for 2 h, add 2 parts of glyoxal, continue to react for 1 h, cool to room temperature, centrifuge at 4000 rpm for 10 min, collect the precipitate, wash once with anhydrous ethanol, and vacuum dry at 60℃ for 4 h to obtain modified starch.

[0019] The preparation method of modified PE includes the following steps: B1. Add 80 parts of ferrocene-grafted PE to a reactor, add 600 parts of anhydrous toluene, heat to 105℃, stir to dissolve, add 0.4 parts of benzoyl peroxide under nitrogen atmosphere, keep warm for 10 min, slowly add 10 parts of hydroxyethyl acrylate, heat to 120℃, react for 2 h, add 0.06 parts of hydroquinone to terminate the reaction, pour the reaction solution into 3 times the volume of a 1:1 volume ratio ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate once with a 1:1 volume ratio ethanol-acetone mixture, and vacuum dry at 60℃ for 6 h to obtain the PE intermediate; B2. Add 60 parts of PE intermediate to a reaction vessel, add 500 parts of anhydrous toluene, heat to 105℃, stir to dissolve, add 0.15 parts of dibutyltin dilaurate under a nitrogen atmosphere, slowly add 6 parts of isophorone diisocyanate, react at 85℃ for 2 h, rapidly cool to 30℃, pour the reaction solution into 3 times the volume of anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, precipitate out, filter to collect the precipitate, wash once with anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, and vacuum dry at 60℃ for 6 h to obtain modified PE.

[0020] The preparation method of ferrocene-grafted PE includes the following steps: 100 parts of PE were added to a reaction vessel, followed by 600 parts of anhydrous toluene. The mixture was heated to 100°C and stirred until completely dissolved to form a PE solution. Under a nitrogen atmosphere, 0.8 parts of dicumyl peroxide were added, and the mixture was kept at this temperature for 10 min. Then, 4 parts of vinyl ferrocene were slowly added, and the mixture was heated to 125°C and reacted for 2 h. The reaction was terminated by adding 0.08 parts of hydroquinone. The reaction solution was poured into a 1:1 volume ratio of ethanol-acetone mixture to precipitate the precipitate. The precipitate was collected and washed once with a 1:1 volume ratio of ethanol-acetone mixture. The precipitate was then dried under vacuum at 60°C for 6 h to obtain ferrocene-grafted PE.

[0021] A method for preparing a biodegradable bio-based PE composite film includes the following steps: S1. Weigh the modified PE, plasticizer, heat stabilizer, lubricant, antioxidant, and antistatic agent, add them to a high-speed mixer, stir at 80°C and 800 rpm for 10 minutes, feed them into a single-screw extruder, extrude the molten preform, and extrude it through the die head of a blown film extruder to obtain a modified PE film with a thickness of 0.03 mm. After cooling at room temperature, wind it up with a winding machine for later use. S2. Weigh the modified starch and plasticizer, add them to the reaction vessel, pour them into deionized water, stir at 300 rpm, mix at room temperature for 10 min, heat to 85℃, keep warm for 30 min, add crosslinking agent, continue stirring for 1 h, cool to 50℃, degas under vacuum of -0.06 MPa for 10 min to form starch sol. S3. The degassed crosslinked sol is uniformly coated onto a polytetrafluoroethylene (PTFE) carrier using a casting machine. The wet film thickness is controlled at 200 μm and the coating speed is 1 m / min. The wet film is allowed to stand at room temperature for 2 h to transform into a wet gel film. It is then transferred to a 0℃ refrigerator and allowed to stand for 12 h. After that, it is immersed in a liquid nitrogen bath for 1 min and then transferred to a freeze dryer. The parameters are set as follows: temperature -55℃, vacuum degree ≤1Pa, and drying time 24 h. After drying, the film material is peeled off from the PTFE carrier with a thickness of 50 μm. It is then cut into sizes that match the outer PE film to obtain a modified starch aerogel film for later use. S4. Align the modified starch aerogel film with the modified PE film, ensuring no wrinkles or misalignment, and place it between the upper and lower plates of the hot press. Control the hot pressing parameters: temperature 120℃, pressure 0.8 MPa, time 30 s. After hot pressing, quickly transfer it to the cooling press and cool it at 20℃ and 0.3 MPa for 2 min. The thickness is 0.08 mm. Place it in an aging chamber at 30℃ and 50% humidity for 36 h to obtain a biodegradable bio-based PE composite film.

[0022] In step S1, the single-screw extruder parameters are controlled as follows: processing temperature: zone 1 130℃, zone 2 160℃, zone 3 165℃, die head 165℃, and screw speed 220 rpm.

[0023] In step S1, the blown film extrusion is performed by the die head of the blown film extruder, with the blow-up ratio controlled at 2.5, the traction speed at 8 m / min, and the cooling air temperature at 20℃. Example

[0024] A biodegradable bio-based PE composite membrane includes an outer layer and an inner layer, wherein the outer layer is a modified PE membrane and the inner layer is a modified starch aerogel membrane. The outer layer comprises the following raw materials in parts by weight: 90 parts modified PE, 2.5 parts plasticizer, 0.8 parts heat stabilizer, 1.2 parts lubricant, 0.4 parts antioxidant, and 0.6 parts antistatic agent; the plasticizer is polycaprolactone; the heat stabilizer is triphenyl phosphite; the lubricant is erucamide; the antioxidant is antioxidant 168; and the antistatic agent is glycerol fatty acid ester. The inner layer comprises the following raw materials in parts by weight: 90 parts modified starch, 5 parts plasticizer, 4 parts crosslinking agent, and 600 parts deionized water; the plasticizer is glyceryl triacetate; and the crosslinking agent is glyceryl diglycidyl ether.

[0025] The preparation method of modified starch includes the following steps: A1. Weigh 110 parts of starch, add 900 parts of deionized water, stir and disperse, then heat to 45℃ and keep warm for 25 min. Add 1.3 parts of sodium dodecyl sulfate, stir for 15 min, and slowly add a mixture of 12 parts of dodecyl succinic anhydride, 16 parts of polypropylene glycol diglycidyl ether and 110 parts of anhydrous ethanol. Adjust the pH of the system to 8.5 with triethylamine, heat to 62℃, and react at a constant temperature for 2.5 h. After the reaction is complete, adjust the pH to 6.8 with 1 mol / L hydrochloric acid, centrifuge at 5000 rpm for 12 min, collect the precipitate, and vacuum dry at 70℃ to constant weight to obtain the starch-modified intermediate. A2. Take 90 parts of starch-modified intermediate, add 700 parts of deionized water, heat to 72℃, stir evenly, add 1.2 parts of ammonium persulfate, keep warm for 10 min, slowly add 18 parts of dodecyl acrylate, heat to 82℃, react at a constant temperature for 3 h, add 3 parts of glyoxal, continue to react for 1.5 h, cool to room temperature, centrifuge at 5000 rpm for 10 min, collect the precipitate, wash twice with anhydrous ethanol, and vacuum dry at 70℃ for 5 h to obtain modified starch.

[0026] The preparation method of modified PE includes the following steps: B1. Add 90 parts of ferrocene-grafted PE to a reactor, add 700 parts of anhydrous toluene, heat to 110℃, stir to dissolve, add 0.5 parts of benzoyl peroxide under nitrogen atmosphere, keep warm for 10 min, slowly add 12 parts of hydroxyethyl acrylate, heat to 125℃, react for 3 h, add 0.07 parts of hydroquinone to terminate the reaction, pour the reaction solution into 4 times the volume of a 1:1 volume ratio ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate twice with a 1:1 volume ratio ethanol-acetone mixture, and vacuum dry at 70℃ for 7 h to obtain the PE intermediate; B2. Add 70 parts of PE intermediate to a reaction vessel, add 550 parts of anhydrous toluene, heat to 110℃, stir to dissolve, add 0.18 parts of dibutyltin dilaurate under a nitrogen atmosphere, slowly add 8 parts of isophorone diisocyanate, and react at 90℃ for 3 h. Quickly cool to 35℃, pour the reaction solution into 4 times the volume of anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, precipitate out, filter and collect the precipitate, wash twice with anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, and vacuum dry at 70℃ for 6 h to obtain modified PE.

[0027] The preparation method of ferrocene-grafted PE includes the following steps: 110 parts of PE were added to a reactor, along with 700 parts of anhydrous toluene. The mixture was heated to 110°C and stirred until completely dissolved to form a PE solution. Under a nitrogen atmosphere, 1 part of dicumyl peroxide was added, and the mixture was kept at this temperature for 12 min. Then, 6 parts of vinyl ferrocene were slowly added, and the mixture was heated to 130°C and reacted for 3 h. The reaction was terminated by adding 0.09 parts of hydroquinone. The reaction solution was poured into a 1:1 volume ratio of ethanol-acetone mixture to precipitate the precipitate. The precipitate was collected and washed twice with a 1:1 volume ratio of ethanol-acetone mixture. The precipitate was then dried under vacuum at 70°C for 7 h to obtain ferrocene-grafted PE.

[0028] A method for preparing a biodegradable bio-based PE composite film includes the following steps: S1. Weigh the modified PE, plasticizer, heat stabilizer, lubricant, antioxidant, and antistatic agent, add them to a high-speed mixer, stir at 85℃ and 900 rpm for 15 min, feed them into a single-screw extruder, extrude the molten preform, extrude it through the die head of a blown film extruder to obtain a modified PE film with a thickness of 0.03 mm, cool it at room temperature, and then wind it up with a winding machine for later use. S2. Weigh the modified starch and plasticizer, add them to the reaction vessel, pour them into deionized water, stir at 400 rpm, mix at room temperature for 10 min, heat to 88℃, keep warm for 30 min, add crosslinking agent, continue stirring for 1 h, cool to 55℃, degas under vacuum of -0.07 MPa for 15 min to form starch sol. S3. The degassed crosslinked sol is uniformly coated onto a polytetrafluoroethylene (PTFE) carrier using a casting machine. The wet film thickness is controlled at 220 μm and the coating speed is 1.5 m / min. The wet film is allowed to stand at room temperature for 3 h to transform into a wet gel film. It is then transferred to a 2℃ refrigerator and allowed to stand for 15 h. After that, it is immersed in a liquid nitrogen bath for 1 min and then transferred to a freeze dryer. The parameters are set as follows: temperature -55℃, vacuum degree ≤1Pa, and drying time 24 h. After drying, the film material is peeled off from the PTFE carrier with a thickness of 50 μm. It is then cut into sizes that match the outer PE film to obtain a modified starch aerogel film for later use. S4. Align the modified starch aerogel film with the modified PE film, ensuring no wrinkles or misalignment, and place it between the upper and lower plates of the hot press. Control the hot pressing parameters: temperature 122℃, pressure 0.8 MPa, time 30 s. After hot pressing, quickly transfer it to the cooling press and cool it at 22℃ and 0.4 MPa for 2 min. The thickness is 0.10 mm. Place it in an aging chamber at 35℃ and 55% humidity for 48 h to obtain a biodegradable bio-based PE composite film.

[0029] In step S1, the single-screw extruder parameters are controlled as follows: processing temperature: zone 1 140℃, zone 2 162℃, zone 3 168℃, die head 165℃, and screw speed 220 rpm.

[0030] In step S1, the blown film extrusion is performed by the die head of the blown film extruder, with the blow-up ratio controlled at 2.5, the traction speed at 10 m / min, and the cooling air temperature at 25℃. Example

[0031] A biodegradable bio-based PE composite membrane includes an outer layer and an inner layer, wherein the outer layer is a modified PE membrane and the inner layer is a modified starch aerogel membrane. The outer layer comprises the following raw materials in parts by weight: 100 parts modified PE, 3 parts plasticizer, 1 part heat stabilizer, 1.5 parts lubricant, 0.6 parts antioxidant, and 1 part antistatic agent; the plasticizer is tributyl citrate; the heat stabilizer is zinc stearate; the lubricant is polyethylene glycol-400; the antioxidant is antioxidant 1076; and the antistatic agent is dodecyl dimethyl betaine. The inner layer comprises the following raw materials in parts by weight: 95 parts modified starch, 6 parts plasticizer, 5 parts crosslinking agent, and 800 parts deionized water; the plasticizer is polycaprolactone; and the crosslinking agent is diethylenetriamine.

[0032] The preparation method of modified starch includes the following steps: A1. Weigh 120 parts of starch, add 1000 parts of deionized water, stir and disperse, then heat to 50℃ and keep warm for 30 min. Add 1.5 parts of sodium dodecyl sulfate, stir for 15 min, and slowly add a mixture of 15 parts of dodecyl succinic anhydride, 18 parts of polypropylene glycol diglycidyl ether and 120 parts of anhydrous ethanol. Adjust the pH of the system to 9.0 with triethylamine, heat to 65℃, and react at a constant temperature for 3 h. After the reaction is complete, adjust the pH to 7.0 with 1 mol / L hydrochloric acid, centrifuge at 6000 rpm for 15 min, collect the precipitate, and vacuum dry at 80℃ to constant weight to obtain the starch-modified intermediate. A2. Take 100 parts of starch-modified intermediate, add 800 parts of deionized water, heat to 75℃, stir evenly, add 1.5 parts of ammonium persulfate, keep warm for 15 min, slowly add 22 parts of dodecyl acrylate, heat to 85℃, keep warm for 4 h, add 5 parts of glyoxal, continue to react for 2 h, cool to room temperature, centrifuge at 6000 rpm for 15 min, collect the precipitate, wash 3 times with anhydrous ethanol, and vacuum dry at 80℃ for 6 h to obtain modified starch.

[0033] The preparation method of modified PE includes the following steps: B1. Add 100 parts of ferrocene-grafted PE to a reactor, add 800 parts of anhydrous toluene, heat to 115℃, stir to dissolve, add 0.6 parts of benzoyl peroxide under nitrogen atmosphere, keep warm for 15 min, slowly add 15 parts of hydroxyethyl acrylate, heat to 130℃, react for 3 h, add 0.08 parts of hydroquinone to terminate the reaction, pour the reaction solution into 5 times the volume of a 1:1 volume ratio ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate 3 times with a 1:1 volume ratio ethanol-acetone mixture, and vacuum dry at 80℃ for 8 h to obtain the PE intermediate; B2. Add 80 parts of PE intermediate to a reaction vessel, add 600 parts of anhydrous toluene, heat to 115℃, stir to dissolve, add 0.2 parts of dibutyltin dilaurate under a nitrogen atmosphere, slowly add 10 parts of isophorone diisocyanate, and react at 95℃ for 4 h. Quickly cool to 40℃, pour the reaction solution into 5 times the volume of anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, precipitate out, filter and collect the precipitate, wash 3 times with anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, and vacuum dry at 80℃ for 7 h to obtain modified PE.

[0034] The preparation method of ferrocene-grafted PE includes the following steps: 120 parts of PE were added to a reaction vessel, followed by 800 parts of anhydrous toluene. The mixture was heated to 120°C and stirred until completely dissolved to form a PE solution. Under a nitrogen atmosphere, 1.2 parts of dicumyl peroxide were added, and the mixture was kept at this temperature for 15 min. Then, 8 parts of vinyl ferrocene were slowly added, and the mixture was heated to 135°C and reacted for 4 h. The reaction was terminated by adding 0.1 parts of hydroquinone. The reaction solution was poured into 5 times its volume of a 1:1 volume ratio ethanol-acetone mixture to precipitate the precipitate. The precipitate was collected and washed three times with a 1:1 volume ratio ethanol-acetone mixture. The precipitate was then dried under vacuum at 80°C for 8 h to obtain ferrocene-grafted PE.

[0035] A method for preparing a biodegradable bio-based PE composite film includes the following steps: S1. Weigh the modified PE, plasticizer, heat stabilizer, lubricant, antioxidant, and antistatic agent, add them to a high-speed mixer, stir at 90℃ and 1000 rpm for 15 min, feed them into a single screw extruder, extrude the molten preform, and extrude it through the die head of a blown film extruder to obtain a modified PE film with a thickness of 0.04 mm. After cooling at room temperature, wind it up with a winding machine for later use. S2. Weigh the modified starch and plasticizer, add them to the reaction vessel, pour in deionized water, stir at 500 rpm, mix at room temperature for 15 min, heat to 90℃, keep warm for 40 min, add crosslinking agent, continue stirring for 1.5 h, cool to 60℃, degas under vacuum of -0.08 MPa for 20 min to form starch sol. S3. The degassed crosslinked sol is uniformly coated onto a polytetrafluoroethylene (PTFE) carrier using a casting machine. The wet film thickness is controlled at 250 μm and the coating speed is 2 m / min. The wet film is allowed to stand at room temperature for 3 h to transform into a wet gel film. It is then transferred to a 4℃ refrigerator and allowed to stand for 16 h. After that, it is immersed in a liquid nitrogen bath for 2 min and then transferred to a freeze dryer. The parameters are set as follows: temperature -50℃, vacuum degree ≤1Pa, and drying time 30 h. After drying, the film material is peeled off from the PTFE carrier with a thickness of 70 μm. It is then cut into sizes that match the outer PE film to obtain a modified starch aerogel film for later use. S4. Align the modified starch aerogel film with the modified PE film, ensuring no wrinkles or misalignment, and place it between the upper and lower plates of the hot press. Control the hot pressing parameters: temperature 125℃, pressure 1.0 MPa, time 40 s. After hot pressing, quickly transfer it to the cooling press and cool it at 25℃ and 0.5 MPa for 3 min. The thickness is 0.10 mm. Place it in an aging chamber at 40℃ and 60% humidity for 72 h to obtain a biodegradable bio-based PE composite film.

[0036] In step S1, the single-screw extruder parameters are controlled as follows: processing temperature: zone 1 150℃, zone 2 165℃, zone 3 170℃, die head 168℃, and screw speed 250 rpm.

[0037] In step S1, the blown film extrusion is performed by the die head of the blown film extruder, with the blow-up ratio controlled at 3.0, the traction speed at 10 m / min, and the cooling air temperature at 25℃.

[0038] Comparative Example 1: Modified PE was replaced with an equal mass of PE, and the remaining components and processes were the same as in Example 1.

[0039] Comparative Example 2: The modified starch was replaced with an equal mass of starch, and the remaining components and processes were the same as in Example 1.

[0040] Comparative Example 3: The modified starch aerogel membrane was replaced with a conventional modified starch membrane, and the remaining components and processes were the same as in Example 1; The conventional method for preparing modified starch film is as follows: Weigh 85 parts of modified starch and 2 parts of plasticizer, add them to a reaction vessel, pour in 500 parts of deionized water, stir at 300 rpm, mix at room temperature for 10 min, heat to 85℃, and keep warm for 30 min to form a starch paste; add 3 parts of crosslinking agent diethylenetriamine, continue stirring for 1 h, control the system temperature at 60℃, and obtain starch sol; degas under vacuum of -0.06 MPa for 15 min, and uniformly coat it on a polytetrafluoroethylene carrier using a casting machine, controlling the wet film thickness at 200 μm and the coating speed at 1 m / min, let it stand at 25℃ for 2 h, transfer it to a hot air drying oven, set the temperature to 60℃, the air speed to 1 m / s, and the drying time to 4 h. After drying, cool the film material to room temperature along with the carrier, and peel it off from the polytetrafluoroethylene carrier to obtain a conventional modified starch film with a thickness of 50 μm.

[0041] Performance testing: 1. Photodegradation rate: Referring to GB / T 20197-2006 standard, the outer modified PE film was placed in an accelerated UV aging chamber (wavelength 340 nm, irradiance 0.71 W / (m²)). 2 •nm), temperature 40℃), irradiated for 30 days, and the degradation rate was calculated by weighing: Photodegradation rate (%) = (initial mass - mass after aging) / initial mass × 100%; Five parallel samples were tested in each group, and the average value was taken.

[0042] 2. Thermal insulation performance: A thermal conductivity tester was used at a test temperature of 25℃. The sample thickness was the actual thickness of the composite film. Three parallel samples were tested in each group, and the average value was taken.

[0043] 3. Waterproof performance: Water absorption test. Cut the inner membrane into 2 cm × 2 cm samples, vacuum dry to constant weight, weigh, and then soak in 25℃ deionized water for 24 h. Take it out, blot the free water on the surface with filter paper, weigh it again, and calculate the water absorption rate.

[0044] 4. Tensile strength and elongation at break: Referring to GB / T 1040.3-2006, the composite films of Examples 1-3 and Comparative Examples 1-3 were cut into standard dumbbell-shaped strips of 15 mm × 100 mm. Ten parallel samples were prepared for each group, ensuring that the edges of the strips were free of gaps and wrinkles. The strips were placed in an environment of 25℃ and 55% relative humidity for 24 h to eliminate internal stress in the membrane material. A universal testing machine was used, with the tensile rate set to 50 mm / min and the clamp spacing to 50 mm. The testing machine was started until the strip broke, and the maximum tensile force and gauge length elongation at break were recorded.

[0045] Table 1. Test results of photodegradation rate, thermal insulation performance, and waterproof performance.

[0046] Table 2. Results of tensile strength and elongation at break tests

[0047] As shown in the table above, the photodegradation rate of the outer layer in Examples 1-3 reached 65.8%-72.3%. The modified PE introduced ferrocene photosensitive groups, which can induce main chain breakage under ultraviolet light. In contrast, Comparative Example 1 had a photodegradation rate of 12.3%, using pure PE, which has no photosensitive activity and extremely poor degradation ability. The thermal conductivity of Examples 1-3 was 0.028-0.032 W / (m·K), indicating excellent thermal insulation performance. This is because the porous structure of the inner modified starch aerogel effectively blocks heat transfer. The thermal conductivity of Comparative Example 3 was 0.045 W / (m·K), as it did not use aerogel technology and had a dense inner layer with low heat conduction resistance. The water absorption rate of Examples 1-3 was 16.5%-18.2%, while that of Comparative Example 2 was 45.7%. The modification of starch effectively improved the waterproof performance. The tensile strength (12.6~14.2 MPa) and elongation at break (85.2~92.5%) of Examples 1-3 demonstrate good interfacial compatibility between modified PE and modified starch. The porous structure of the aerogel can disperse tensile stress, and the combination of additives optimizes the toughness of the membrane material. In Comparative Example 1, due to the poor compatibility between pure PE and the inner layer, delamination is easily achieved during stretching, resulting in a significant decrease in strength and elongation. In Comparative Example 2, the unmodified starch is brittle and has weak interfacial bonding, resulting in poor mechanical properties.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biodegradable bio-based PE composite film, characterized in that, It consists of an outer layer and an inner layer. The outer layer is a modified PE film, and the inner layer is a modified starch aerogel film. The outer layer comprises the following raw materials in parts by weight: 80-100 parts modified PE, 2-3 parts plasticizer, 0.5-1 part heat stabilizer, 1-1.5 parts lubricant, 0.3-0.6 parts antioxidant, and 0.5-1 part antistatic agent; The inner layer comprises the following raw materials in parts by weight: 85-95 parts modified starch, 4-6 parts plasticizer, 3-5 parts crosslinking agent, and 500-800 parts deionized water.

2. The biodegradable bio-based PE composite film according to claim 1, characterized in that, The preparation method of modified starch includes the following steps: A1. Weigh 100-120 parts of starch, add 800-1000 parts of deionized water, stir and disperse, then heat to 45-50℃ and keep warm for 20-30 min. Add 1-1.5 parts of sodium dodecyl sulfate, stir for 10-15 min, and slowly add a mixture of 10-15 parts of dodecyl succinic anhydride, 15-18 parts of polypropylene glycol diglycidyl ether and 100-120 parts of anhydrous ethanol. Adjust the pH of the system to 8.0-9.0 with triethylamine, heat to 60-65℃, and react at a constant temperature for 2-3 h. After the reaction is complete, adjust the pH to 6.5-7.0 with 1 mol / L hydrochloric acid, centrifuge at 4000-6000 rpm for 10-15 min, collect the precipitate, and vacuum dry at 60-80℃ to constant weight to obtain the starch-modified intermediate. A2. Take 80-100 parts of starch-modified intermediate, add 600-800 parts of deionized water, heat to 70-75℃, stir evenly, add 1-1.5 parts of ammonium persulfate, keep warm for 10-15 min, slowly add 15-22 parts of dodecyl acrylate, heat to 80-85℃, react at a constant temperature for 2-4 h, add 2-5 parts of glyoxal, continue to react for 1-2 h, cool to room temperature, centrifuge at 4000-6000 rpm for 10-15 min, collect the precipitate, wash with anhydrous ethanol 1-3 times, and vacuum dry at 60-80℃ for 4-6 h to obtain modified starch.

3. The biodegradable bio-based PE composite film according to claim 1, characterized in that, The preparation method of modified PE includes the following steps: B1. Add 80-100 parts of ferrocene-grafted PE to a reactor, add 600-800 parts of anhydrous toluene, heat to 105-115℃, stir to dissolve, add 0.4-0.6 parts of benzoyl peroxide under a nitrogen atmosphere, keep warm for 10-15 min, slowly add 10-15 parts of hydroxyethyl acrylate, heat to 120-130℃, react for 2-3 h, add 0.06-0.08 parts of hydroquinone to terminate the reaction, pour the reaction solution into 3-5 times the volume of a 1:1 ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate 1-3 times with a 1:1 ethanol-acetone mixture, and vacuum dry at 60-80℃ for 6-8 h to obtain the PE intermediate; B2. Add 60-80 parts of PE intermediate to a reactor, add 500-600 parts of anhydrous toluene, heat to 105-115℃, stir to dissolve, add 0.15-0.2 parts of dibutyltin dilaurate under a nitrogen atmosphere, slowly add 6-10 parts of isophorone diisocyanate, and react at 85-95℃ for 2-4 h. Quickly cool to 30-40℃, pour the reaction solution into 3-5 times the volume of anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, precipitate out, filter and collect the precipitate, wash 1-3 times with anhydrous ethanol-ethyl acetate mixture with a volume ratio of 1:1, and vacuum dry at 60-80℃ for 6-7 h to obtain modified PE.

4. The biodegradable bio-based PE composite film according to claim 3, characterized in that, The preparation method of ferrocene-grafted PE includes the following steps: Add 100-120 parts of PE to a reactor, add 600-800 parts of anhydrous toluene, heat to 100-120℃ and stir until completely dissolved to form a PE solution. Under a nitrogen atmosphere, add 0.8-1.2 parts of dicumyl peroxide, keep warm for 10-15 min, then slowly add 4-8 parts of vinyl ferrocene, heat to 125-135℃ and react for 2-4 h. Add 0.08-0.1 parts of hydroquinone to terminate the reaction. Pour the reaction solution into 3-5 times the volume of a 1:1 ethanol-acetone mixture to precipitate, collect the precipitate, wash the precipitate 1-3 times with a 1:1 ethanol-acetone mixture, and dry under vacuum at 60-80℃ for 6-8 h to obtain ferrocene-grafted PE.

5. The biodegradable bio-based PE composite film according to claim 1, characterized in that, The outer and inner layers are laminated together by a hot-pressing process to obtain a composite film.

6. A method for preparing a biodegradable bio-based PE composite film according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Weigh the modified PE, plasticizer, heat stabilizer, lubricant, antioxidant, and antistatic agent, add them to a high-speed mixer, stir at 80~90℃ and 800~1000 rpm for 10~15 min, feed them into a single-screw extruder, extrude the molten preform, and extrude it through the die head of a blown film extruder to obtain a modified PE film with a thickness of 0.03~0.04 mm. After cooling at room temperature, wind it up with a winding machine for later use. S2. Weigh the modified starch and plasticizer, add them to the reaction vessel, pour in deionized water, stir at 300~500 rpm, mix at room temperature for 10~15 min, heat to 85~90℃, keep warm for 30~40 min, add crosslinking agent, continue stirring for 1~1.5 h, cool to 50~60℃, degas under vacuum of -0.06~-0.08 MPa for 10~20 min to form starch sol; S3. The degassed crosslinked sol is uniformly coated onto a polytetrafluoroethylene (PTFE) carrier using a casting machine. The wet film thickness is controlled at 200-250 μm and the coating speed is 1-2 m / min. The wet film is allowed to stand at room temperature for 2-3 h to transform into a wet gel film. It is then transferred to a 0-4℃ refrigerator and allowed to stand for 12-16 h. After that, it is immersed in a liquid nitrogen bath for 1-2 min and then transferred to a freeze dryer. The parameters are set as follows: temperature -55~-50℃, vacuum degree ≤1 Pa, and drying time 24-30 h. After drying, the film material is peeled off from the PTFE carrier with a thickness of 50-70 μm. It is then cut into sizes that match the outer PE film to obtain a modified starch aerogel film for later use. S4. Align the modified starch aerogel film with the modified PE film, ensuring no wrinkles or misalignment. Place it between the upper and lower plates of a hot press and control the hot pressing parameters: temperature 120~125℃, pressure 0.8~1.0 MPa, time 30~40 s. After hot pressing, quickly transfer it to a cooling press and cool it at 20~25℃ and 0.3~0.5 MPa for 2~3 min, with a thickness of 0.08~0.10 mm. Place it in an aging chamber at 30~40℃ and 50~60% humidity for 36~72 h to obtain a biodegradable bio-based PE composite film.

7. The method for preparing a biodegradable bio-based PE composite film according to claim 6, characterized in that, In step S1, the single-screw extruder parameters are controlled as follows: processing temperature: zone 1 130~150℃, zone 2 160~165℃, zone 3 165~170℃, die head 165~168℃, screw speed 220~250 rpm.

8. The method for preparing a biodegradable bio-based PE composite film according to claim 6, characterized in that, In step S1, the blown film extrusion is performed by the die head of the blown film extruder, with the blow-up ratio controlled at 2.5~3.0, the traction speed at 8~10 m / min, and the cooling air temperature at 20~25℃.

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