A biodegradable cushioning air column material master batch and a preparation method thereof

Abstract

The application provides a biodegradable buffer air column material master batch and a preparation method thereof, and the preparation raw materials include, by weight, 60-80 parts of a base resin, 15-30 parts of an epoxidized polysiloxane grafted starch compound, 3-8 parts of a quaternary ammonium salt modified montmorillonite, 3-6 parts of a plasticizer, 0.5-1.5 parts of a lubricant, 0.3-0.8 parts of an antioxidant, 1-2.5 parts of a foaming nucleating agent and 0.3-0.5 parts of a foaming stabilizer. The biodegradable buffer air column material master batch has the advantages of excellent mechanical properties, strong gas barrier property, good processing performance, uniform and stable cell structure and long service life.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a biodegradable buffer air column material masterbatch and its preparation method. Background Technology

[0002] Cushioning air column materials are widely used in logistics and transportation, precision component packaging, and other fields due to their lightweight and excellent cushioning and protection effects. Traditional cushioning air column materials are mostly made of petroleum-based resins, which are difficult to degrade naturally, and the waste can easily accumulate in the environment and form white pollution. With increasingly stringent environmental policies and rising demands for green packaging, cushioning air column materials based on biodegradable polymers are gradually becoming the focus of industry research and application. Related functional masterbatches are the key to controlling the molding, mechanical, and performance characteristics of air column materials.

[0003] Existing biodegradable buffer air column membrane masterbatches generally suffer from poor component compatibility and insufficient interfacial bonding, resulting in low mechanical strength of the blown film after molding, making it difficult to meet the requirements of air column molding and buffering use. At the same time, these masterbatches have weak gas barrier properties and insufficient ability to control the cell structure, making it difficult to balance gas retention, mechanical support and processing uniformity during the use of buffer air columns, thus limiting their application in the field of high-end buffer packaging. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biodegradable buffer air column material masterbatch and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a biodegradable buffer air column material masterbatch, which, by weight, comprises the following raw materials: 60-80 parts of matrix resin, 15-30 parts of epoxidized polysiloxane grafted starch composite, 3-8 parts of quaternary ammonium salt modified montmorillonite, 3-6 parts of plasticizer, 0.5-1.5 parts of lubricant, 0.3-0.8 parts of antioxidant, 1-2.5 parts of foaming nucleating agent, and 0.3-0.5 parts of foaming stabilizer.

[0006] Using the above technical solutions, the matrix resin provides basic film-forming properties and mechanical support for the masterbatch; the epoxidized polysiloxane-grafted starch composite improves the compatibility between starch and matrix resin, while enhancing the mechanical strength of the masterbatch; quaternary ammonium salt-modified montmorillonite significantly improves the gas barrier properties of the masterbatch and enhances interfacial compatibility; plasticizers improve the processing plasticity and flexibility of the masterbatch, reducing processing difficulty; lubricants reduce friction during masterbatch processing and improve processing stability; antioxidants inhibit thermal oxidative degradation during masterbatch processing and use, extending the service life of the masterbatch; foaming nucleating agents regulate the cell structure and uniformity of the material, optimizing the mechanical and barrier properties of the finished product; and foaming stabilizers stabilize cell morphology, prevent abnormal cell growth, and ensure the uniformity of material performance.

[0007] Preferably, the matrix resin is composed of poly(butylene adipate / terephthalate) and polylactic acid in a mass ratio of 3-5:1; and the plasticizer is composed of epoxidized soybean oil and tributyl citrate in a mass ratio of 1.5-2.5:1.

[0008] Using the above technical solution, poly(adipic acid) / butylene terephthalate can provide good flexibility, film-forming properties and impact resistance, while polylactic acid can provide high modulus and rigidity. The combination of the two can achieve complementary properties, so that the matrix resin has suitable toughness and stiffness at the same time. Epoxidized soybean oil can improve the brittleness of polylactic acid and enhance the processing stability of the material, while tributyl citrate can enhance the plasticizing effect of starch. The combination of the two can synergistically improve the processing plasticity and flexibility of the masterbatch and enhance the processing and molding performance of the masterbatch.

[0009] Preferably, the lubricant is N,N'-ethylene bis-stearamide or zinc stearate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1.5 to 2.5:1.

[0010] Using the above technical solution, N,N'-ethylene bis-stearamide or zinc stearate as a lubricant can reduce material friction during the masterbatch melting process, improve material flowability and processing formability, and enhance the stability of the masterbatch processing process. Antioxidant 1010 can inhibit thermal oxidative degradation during masterbatch processing and use, and antioxidant 168 can decompose peroxides generated during processing. The combination of the two can synergistically improve thermal and oxidative stability, delay material aging, and maintain stable mechanical and processing properties.

[0011] Preferably, the foaming nucleating agent is a coated foaming nucleating agent, which is composed of coated sodium bicarbonate and coated citric acid in a mass ratio of 0.8~1.2:1; the foaming stabilizer is composed of dicyandiamide and 2-methylimidazole in a mass ratio of 8~10:1.

[0012] Using the above technical solution, coated sodium bicarbonate and coated citric acid are compounded at a mass ratio of 0.8~1.2:1 to form a foaming nucleating agent, which can decompose and generate gas during masterbatch processing and blown film production, forming a fine and uniform cell structure inside the material, thereby improving the mechanical properties and gas barrier properties of the material; dicyandiamide and 2-methylimidazole are compounded at a mass ratio of 8~10:1 to form a foaming stabilizer, which can inhibit cell merging and collapse, stabilize cell morphology, and improve cell uniformity and structural stability.

[0013] Preferably, the raw materials for preparing the epoxidized polysiloxane grafted starch composite, by weight, include: 60-80 parts corn starch, 20-40 parts maltodextrin, 90-100 parts hydrogen-terminated silicone oil, 2.0-3.5 parts allyl glycidyl ether, 0.2-0.5 parts chloroplatinic acid-isopropanol solution, 120-180 parts toluene, and 0.1-0.3 parts triethylamine.

[0014] Using the above technical solution, corn starch and maltodextrin serve as the basic raw materials for the epoxidized polysiloxane grafted starch complex, providing abundant hydroxyl sites for the grafting reaction. Hydrogen-terminated silicone oil and allyl glycidyl ether react to generate epoxy-containing polysiloxane prepolymers, providing epoxy groups for the grafting reaction. Chloroplatinic acid-isopropanol solution catalyzes the reaction between hydrogen-terminated silicone oil and allyl glycidyl ether, promoting the formation of epoxy-containing polysiloxane prepolymers. Toluene acts as a reaction solvent, improving the compatibility of the raw materials and ensuring uniform reaction. Triethylamine catalyzes the grafting reaction between the epoxy-containing polysiloxane prepolymers and corn starch and maltodextrin, promoting the formation of the epoxidized polysiloxane grafted starch complex.

[0015] Preferably, the platinum concentration in the chloroplatinic acid-isopropanol solution is 900~1000ppm.

[0016] The above technical solution can effectively catalyze the reaction between hydrogen-containing silicone oil and allyl glycidyl ether, promote the formation of epoxy-containing polysiloxane prepolymer, ensure the smooth preparation of epoxidized polysiloxane grafted starch composite, ensure that the composite has the expected structure and performance, and thus provide support for the comprehensive performance of biodegradable buffer gas column material masterbatch.

[0017] Preferably, the preparation method of the epoxidized polysiloxane-grafted starch composite includes the following steps: 1) Under nitrogen protection, add hydrogen-containing silicone oil and toluene to the reactor and stir at 80~120 r / min for 15~25 min. Add allyl glycidyl ether, heat to 55~65℃, add chloroplatinic acid-isopropanol solution, stir evenly and continue to heat to 80~90℃, and reflux for 4~6 h. 2) After the reaction is completed, the reaction solution is distilled under reduced pressure at 80~90℃ and vacuum degree ≤-0.095MPa for 1~2h to obtain epoxy-containing polysiloxane prepolymer with epoxy value of 0.10~0.15mol / 100g; 3) Add corn starch and maltodextrin to a high-speed mixer and stir at 200-300 r / min at 100-120℃ for 25-35 min. Then cool down to 70-85℃, add triethylamine, and then spray the epoxy-containing polysiloxane prepolymer obtained in step 2) through a pressure atomizing nozzle at an atomization pressure of 0.2-0.4 MPa. After spraying, stir at 1000-1200 r / min for 15-25 min. 4) Transfer the material obtained in step 3) to a closed reactor and react at a constant temperature of 100~120℃ for 2~3 hours. After the reaction is completed, crush the material and pass it through a 200~250 mesh sieve to obtain the epoxidized polysiloxane grafted starch composite.

[0018] Using the above technical solution, through nitrogen protection, reaction under specific temperature and stirring conditions, the hydrogen-containing silicone oil and allyl glycidyl ether can be fully reacted. After vacuum distillation, an epoxy-containing polysiloxane prepolymer that meets the epoxy value requirements is obtained. By drying corn starch and maltodextrin and then atomizing, stirring, and reacting them with the epoxy-containing polysiloxane prepolymer at a constant temperature, effective grafting of polysiloxane segments onto the surface of corn starch and maltodextrin can be achieved. After crushing and sieving, a uniformly structured epoxy polysiloxane-grafted starch composite is obtained.

[0019] This invention also discloses a method for preparing a biodegradable buffer air column material masterbatch, comprising the following steps: S1. Preprocessing: The matrix resin was vacuum dried at 60-80℃ and vacuum degree ≤-0.09MPa for 4-6 hours, and the moisture content was controlled to be ≤0.03%; the quaternary ammonium salt modified montmorillonite was dried by forced air at 80-90℃ for 2-3 hours. Sodium bicarbonate and stearic acid are added to a high-speed mixer at a mass ratio of 1:0.05~0.15 and stirred at 300~500 r / min for 5~10 min at 85~100℃. After cooling to 25~30℃, the mixture is pulverized and passed through a 200~250 mesh sieve to obtain coated sodium bicarbonate particles. Citric acid and paraffin are added to a high-speed mixer at a mass ratio of 1:0.5~0.8 and stirred at 300~500 r / min for 5~10 min at 65~80℃. After cooling to 25~30℃, the mixture is pulverized and passed through a 200~250 mesh sieve to obtain citric acid coated particles. A foaming nucleating agent is obtained by compounding sodium bicarbonate particles and citric acid particles in a certain proportion. S2. Preparation of premix: The dried matrix resin, epoxidized polysiloxane grafted starch complex, quaternary ammonium salt modified montmorillonite, plasticizer, lubricant, antioxidant and foaming stabilizer are added to a high-speed mixer and stirred at 500-800 r / min at 65-85℃ for 8-15 min to obtain a premix. S3, Melt Blending Extrusion: The premix obtained in step S2 is added to the main feed port of the twin-screw extruder, and the foaming and nucleating agent obtained in step S1 is added to the fifth zone of the twin-screw extruder through the side feeding system. After melt blending and extrusion, the material is successively cooled, dried, pelletized, and dried at low temperature to obtain biodegradable buffer air column material masterbatch.

[0020] Using the above technical solution, drying the matrix resin and quaternary ammonium salt modified montmorillonite can remove moisture from the raw materials, ensuring the stability of subsequent processing; coating and compounding sodium bicarbonate and citric acid separately can prepare a stable foaming nucleating agent; mixing the dried raw materials according to the process can obtain a uniform premix, ensuring uniform dispersion of each component; melt blending extrusion by combining main feed and side feed in a twin-screw extruder, followed by subsequent treatments such as cooling, drying, pelletizing, and low-temperature drying, can prepare a biodegradable buffer air column material masterbatch with uniform structure and stable performance.

[0021] Preferably, in step S3, the temperatures of each section of the twin-screw extruder are: Zone 1 130~145℃, Zone 2 145~160℃, Zone 3 155~170℃, Zone 4 155~165℃, Zone 5 150~160℃, and the die head temperature 150~165℃; Zone 4 is equipped with vacuum exhaust, with a vacuum degree of -0.04~-0.06MPa; the screw speed is 180~280r / min, and the feeding frequency is 15~25Hz.

[0022] By adopting the above technical solution, the premixed material can be gradually melted and uniformly mixed, ensuring that the matrix resins such as poly(butylene adipate / terephthalate), polylactic acid, and various additives are fully melted and do not undergo thermal degradation. The vacuum exhaust in the four zones can remove volatiles in the molten system, improving the purity and uniformity of the molten material. The set screw speed and feeding frequency can match the melt blending and extrusion rates, ensuring that the material has an appropriate residence time in the extruder, achieving full blending and uniform extrusion, and providing a guarantee for subsequent cooling, pelleting, and masterbatch performance stability.

[0023] Preferably, in step S3, the melt-blended extruded strip is cooled in a water bath at 20~30℃ and dried with an air knife at an air pressure of 0.2~0.4MPa. Then, it is pelletized at a pelletizing speed of 300~500r / min to obtain pellets with an average particle size of 2~4mm. The pellets are then dried in a forced-air dryer at 45~60℃ for 2~4h to obtain biodegradable buffer air column material masterbatch.

[0024] Using the above technical solution, the melt-blended extruded strips can be cooled in a water tank to allow the molten strips to solidify and form quickly. Air knife drying can remove moisture from the surface of the strips, preventing moisture from affecting the subsequent pelleting and masterbatch performance. Pelletizing can obtain pellets with uniform particle size. Subsequent blower drying can further remove residual moisture from the pellets, ensuring the dryness and structural stability of the masterbatch, and ensuring the consistency of the masterbatch's subsequent processing and use performance.

[0025] The beneficial effects of this invention are as follows: The matrix resin provides the basic film-forming properties and mechanical support for the masterbatch; the epoxidized polysiloxane-grafted starch composite improves the compatibility between starch and matrix resin, while enhancing the mechanical strength of the masterbatch; quaternary ammonium salt-modified montmorillonite significantly improves the gas barrier properties of the masterbatch and enhances interfacial compatibility; plasticizers improve the processing plasticity and flexibility of the masterbatch, reducing processing difficulty; lubricants reduce friction during masterbatch processing and improve processing stability; antioxidants inhibit thermal oxidative degradation during masterbatch processing and use, extending the service life of the masterbatch; foaming nucleating agents regulate the cell structure and uniformity of the material, optimizing the mechanical and barrier properties of the finished product; foaming stabilizers stabilize cell morphology, prevent abnormal cell growth, and ensure the uniformity of material properties. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0028] Table 1

[0029] Example 1: This embodiment discloses a biodegradable buffer air column material masterbatch, which, by weight, comprises the following raw materials: 60 parts of matrix resin, 15 parts of epoxidized polysiloxane grafted starch composite, 3 parts of quaternary ammonium salt modified montmorillonite, 3 parts of plasticizer, 0.5 parts of lubricant, 0.3 parts of antioxidant, 1 part of foaming nucleating agent, and 0.3 parts of foaming stabilizer.

[0030] The matrix resin is a blend of poly(butylene adipate / terephthalate) and polylactic acid in a 3:1 mass ratio; the plasticizer is a blend of epoxidized soybean oil and tributyl citrate in a 1.5:1 mass ratio. The lubricant is N,N'-ethylenebis-stearamide; the antioxidant is a blend of antioxidant 1010 and antioxidant 168 in a 1.5:1 mass ratio. The foaming nucleating agent is a coated foaming nucleating agent, which is a blend of coated sodium bicarbonate and coated citric acid in a 0.8:1 mass ratio; the foaming stabilizer is a blend of dicyandiamide and 2-methylimidazole in an 8:1 mass ratio.

[0031] The raw materials for preparing the epoxidized polysiloxane grafted starch composite, by weight, include: 60 parts corn starch, 20 parts maltodextrin, 90 parts hydrogen-terminated silicone oil, 2 parts allyl glycidyl ether, 0.2 parts chloroplatinic acid-isopropanol solution, 120 parts toluene, and 0.1 parts triethylamine; the platinum concentration in the chloroplatinic acid-isopropanol solution is 900 ppm.

[0032] The preparation method of the epoxidized polysiloxane-grafted starch composite includes the following steps: 1) Under nitrogen protection, add hydrogen-containing silicone oil and toluene into the reactor, stir at 80 r / min for 15 min, add allyl glycidyl ether, heat to 55℃, add chloroplatinic acid-isopropanol solution, stir evenly, continue to heat to 80℃, and reflux for 4 h. 2) After the reaction is completed, the reaction solution is distilled under reduced pressure at 80℃ and vacuum degree ≤ -0.095MPa for 1h to obtain epoxy-containing polysiloxane prepolymer with an epoxy value of 0.10mol / 100g. 3) Add corn starch and maltodextrin to a high-speed mixer and stir at 200 r / min for 25 min at 100℃. Then cool down to 70℃, add triethylamine, and then spray the epoxy-containing polysiloxane prepolymer obtained in step 2) through a pressure atomizing nozzle at an atomization pressure of 0.2 MPa. After spraying, stir at 1000 r / min for 15 min. 4) Transfer the material obtained in step 3) to a closed reactor and react at 100°C for 2 hours. After the reaction is completed, pulverize and pass through a 200-mesh sieve to obtain the epoxidized polysiloxane grafted starch composite.

[0033] This embodiment also discloses a method for preparing a biodegradable buffer air column material masterbatch, comprising the following steps: S1. Preprocessing: The matrix resin was vacuum dried at 60℃ and vacuum degree ≤ -0.09MPa for 4 hours, and the moisture content was controlled to be ≤ 0.03%; the quaternary ammonium salt modified montmorillonite was dried by forced air at 80℃ for 2 hours. Sodium bicarbonate and stearic acid were added to a high-speed mixer at a mass ratio of 1:0.05 and stirred at 300 r / min for 5 min at 85°C. After cooling to 25°C, the mixture was pulverized and passed through a 200-mesh sieve to obtain sodium bicarbonate coated particles. Citric acid and paraffin were added to a high-speed mixer at a mass ratio of 1:0.5 and stirred at 300 r / min for 5 min at 65℃. After cooling to 25℃, the mixture was pulverized and passed through a 200-mesh sieve to obtain citric acid-coated particles. A foaming nucleating agent is obtained by compounding sodium bicarbonate particles and citric acid particles in a certain proportion. S2. Preparation of premix: The dried matrix resin, epoxidized polysiloxane grafted starch complex, quaternary ammonium salt modified montmorillonite, plasticizer, lubricant, antioxidant and foaming stabilizer were added to a high-speed mixer and stirred at 500 r / min for 8 min at 65℃ to obtain a premix. S3, Melt Blending Extrusion: The premix obtained in step S2 is added to the main feed port of the twin-screw extruder. The foaming and nucleating agent obtained in step S1 is added to the fifth zone of the twin-screw extruder through the side feeding system. The temperatures of each section of the twin-screw extruder are: zone 1 130℃, zone 2 145℃, zone 3 155℃, zone 4 155℃, zone 5 150℃, and die head temperature 150℃. Zone 4 is equipped with vacuum exhaust with a vacuum degree of -0.04MPa. The screw speed is 180r / min and the feeding frequency is 15Hz. The melt-blended extruded strips were cooled in a 20°C water bath and dried with an air knife at a pressure of 0.2 MPa. They were then pelletized at a pelletizing speed of 300 r / min to obtain pellets with an average particle size of 2 mm. The pellets were then dried in a forced-air dryer at 45°C for 2 h to obtain biodegradable buffer air column material masterbatch.

[0034] Example 2: This embodiment discloses a biodegradable buffer air column material masterbatch, which, by weight, comprises the following raw materials: 80 parts of matrix resin, 30 parts of epoxidized polysiloxane grafted starch composite, 8 parts of quaternary ammonium salt modified montmorillonite, 6 parts of plasticizer, 1.5 parts of lubricant, 0.8 parts of antioxidant, 2.5 parts of foaming nucleating agent, and 0.5 parts of foaming stabilizer.

[0035] The matrix resin is a blend of poly(butylene adipate / terephthalate) and polylactic acid in a mass ratio of 5:1; the plasticizer is a blend of epoxidized soybean oil and tributyl citrate in a mass ratio of 2.5:1. The lubricant is zinc stearate; the antioxidant is a blend of antioxidant 1010 and antioxidant 168 in a mass ratio of 2.5:1. The foaming nucleating agent is a coated foaming nucleating agent, which is a blend of coated sodium bicarbonate and coated citric acid in a mass ratio of 1.2:1; the foaming stabilizer is a blend of dicyandiamide and 2-methylimidazole in a mass ratio of 10:1.

[0036] The raw materials for preparing the epoxidized polysiloxane grafted starch composite, by weight, include: 80 parts corn starch, 40 parts maltodextrin, 100 parts hydrogen-terminated silicone oil, 3.5 parts allyl glycidyl ether, 0.5 parts chloroplatinic acid-isopropanol solution, 180 parts toluene, and 0.3 parts triethylamine; the platinum concentration in the chloroplatinic acid-isopropanol solution is 1000 ppm.

[0037] The preparation method of the epoxidized polysiloxane-grafted starch composite includes the following steps: 1) Under nitrogen protection, add hydrogen-containing silicone oil and toluene into the reactor, stir at 120 r / min for 25 min, add allyl glycidyl ether, heat to 65℃, add chloroplatinic acid-isopropanol solution, stir evenly, continue to heat to 90℃, and reflux for 6 h. 2) After the reaction is completed, the reaction solution is distilled under reduced pressure at 90℃ and vacuum degree ≤ -0.095MPa for 2h to obtain epoxy-containing polysiloxane prepolymer with an epoxy value of 0.15mol / 100g. 3) Add corn starch and maltodextrin to a high-speed mixer and stir at 300 r / min for 35 min at 120℃. Then cool down to 85℃, add triethylamine, and then spray the epoxy-containing polysiloxane prepolymer obtained in step 2) through a pressure atomizing nozzle at an atomization pressure of 0.4 MPa. After spraying, stir at 1200 r / min for 25 min. 4) Transfer the material obtained in step 3) to a closed reactor and react at a constant temperature of 120°C for 3 hours. After the reaction is completed, pulverize and pass through a 250-mesh sieve to obtain an epoxidized polysiloxane grafted starch composite.

[0038] This embodiment also discloses a method for preparing a biodegradable buffer air column material masterbatch, comprising the following steps: S1. Preprocessing: The matrix resin was vacuum dried at 80℃ and vacuum degree ≤ -0.09MPa for 6 hours, and the moisture content was controlled to be ≤ 0.03%; the quaternary ammonium salt modified montmorillonite was dried by forced air at 90℃ for 3 hours. Sodium bicarbonate and stearic acid were added to a high-speed mixer at a mass ratio of 1:0.15 and stirred at 500 r / min for 10 min at 100℃. After cooling to 30℃, the mixture was pulverized and passed through a 250-mesh sieve to obtain sodium bicarbonate coated particles. Citric acid and paraffin were added to a high-speed mixer at a mass ratio of 1:0.8 and stirred at 500 r / min for 10 min at 80℃. After cooling to 30℃, the mixture was pulverized and passed through a 250-mesh sieve to obtain citric acid-coated particles. A foaming nucleating agent is obtained by compounding sodium bicarbonate particles and citric acid particles in a certain proportion. S2. Preparation of premix: The dried matrix resin, epoxidized polysiloxane grafted starch complex, quaternary ammonium salt modified montmorillonite, plasticizer, lubricant, antioxidant and foaming stabilizer are added to a high-speed mixer and stirred at 800 r / min for 15 min at 85℃ to obtain a premix. S3, Melt Blending Extrusion: The premix obtained in step S2 is added to the main feed port of the twin-screw extruder. The foaming and nucleating agent obtained in step S1 is added to the fifth zone of the twin-screw extruder through the side feeding system. The temperatures of each section of the twin-screw extruder are: zone 1 145℃, zone 2 160℃, zone 3 170℃, zone 4 165℃, zone 5 160℃, and die head temperature 165℃. Zone 4 is equipped with vacuum exhaust with a vacuum degree of -0.06MPa. The screw speed is 280r / min, and the feeding frequency is 25Hz. The melt-blended extruded strips were cooled in a 30°C water bath and dried with an air knife at a pressure of 0.4 MPa. They were then pelletized at a pelletizing speed of 500 r / min to obtain pellets with an average particle size of 4 mm. The pellets were then dried in a forced-air dryer at 60°C for 4 h to obtain biodegradable buffer air column material masterbatch.

[0039] Example 3: This embodiment discloses a biodegradable buffer air column material masterbatch, which, by weight, comprises the following raw materials: 70 parts of matrix resin, 22 parts of epoxidized polysiloxane grafted starch composite, 5 parts of quaternary ammonium salt modified montmorillonite, 5 parts of plasticizer, 1 part of lubricant, 0.5 parts of antioxidant, 2 parts of foaming nucleating agent, and 0.4 parts of foaming stabilizer.

[0040] The matrix resin is a blend of poly(butylene adipate / terephthalate) and polylactic acid in a 4:1 mass ratio; the plasticizer is a blend of epoxidized soybean oil and tributyl citrate in a 2:1 mass ratio. The lubricant is N,N'-ethylenebis-stearamide; the antioxidant is a blend of antioxidant 1010 and antioxidant 168 in a 2:1 mass ratio. The foaming nucleating agent is a coated foaming nucleating agent, which is a blend of coated sodium bicarbonate and coated citric acid in a 1:1 mass ratio; the foaming stabilizer is a blend of dicyandiamide and 2-methylimidazole in a 9:1 mass ratio.

[0041] The raw materials for preparing the epoxidized polysiloxane grafted starch composite, by weight, include: 70 parts corn starch, 30 parts maltodextrin, 95 parts hydrogen-terminated silicone oil, 2.5 parts allyl glycidyl ether, 0.3 parts chloroplatinic acid-isopropanol solution, 150 parts toluene, and 0.2 parts triethylamine; the platinum concentration in the chloroplatinic acid-isopropanol solution is 950 ppm.

[0042] The preparation method of the epoxidized polysiloxane-grafted starch composite includes the following steps: 1) Under nitrogen protection, add hydrogen-containing silicone oil and toluene into the reactor, stir at 100 r / min for 20 min, add allyl glycidyl ether, heat to 60℃, add chloroplatinic acid-isopropanol solution, stir evenly, continue to heat to 85℃, and reflux for 5 h. 2) After the reaction is completed, the reaction solution is distilled under reduced pressure for 1.5 h at 85℃ and vacuum degree ≤ -0.095MPa to obtain epoxy-containing polysiloxane prepolymer with an epoxy value of 0.12mol / 100g. 3) Add corn starch and maltodextrin to a high-speed mixer and stir at 250 r / min for 30 min at 110℃. Then cool down to 77℃, add triethylamine, and then spray the epoxy-containing polysiloxane prepolymer obtained in step 2) through a pressure atomizing nozzle at an atomization pressure of 0.3 MPa. After spraying, stir at 1100 r / min for 20 min. 4) Transfer the material obtained in step 3) to a closed reactor and react at a constant temperature of 110°C for 2.5 hours. After the reaction is completed, pulverize and pass through a 220-mesh sieve to obtain the epoxidized polysiloxane grafted starch composite.

[0043] This embodiment also discloses a method for preparing a biodegradable buffer air column material masterbatch, comprising the following steps: S1. Preprocessing: The matrix resin was vacuum dried at 70℃ and vacuum degree ≤ -0.09MPa for 5h, and the moisture content was controlled to be ≤0.03%; the quaternary ammonium salt modified montmorillonite was dried by forced air at 85℃ for 2.5h. Sodium bicarbonate and stearic acid were added to a high-speed mixer at a mass ratio of 1:0.1 and stirred at 400 r / min for 7 min at 90℃. After cooling to 28℃, the mixture was pulverized and passed through a 220 mesh sieve to obtain sodium bicarbonate coated particles. Citric acid and paraffin were added to a high-speed mixer at a mass ratio of 1:0.7 and stirred at 400 r / min for 7 min at 70℃. After cooling to 27℃, the mixture was pulverized and passed through a 220 mesh sieve to obtain citric acid-coated particles. A foaming nucleating agent is obtained by compounding sodium bicarbonate particles and citric acid particles in a certain proportion. S2. Preparation of premix: The dried matrix resin, epoxidized polysiloxane grafted starch composite, quaternary ammonium salt modified montmorillonite, plasticizer, lubricant, antioxidant and foaming stabilizer were added to a high-speed mixer and stirred at 650 r / min for 11 min at 75°C to obtain a premix. S3, Melt Blending Extrusion: The premix obtained in step S2 is added to the main feed port of the twin-screw extruder. The foaming and nucleating agent obtained in step S1 is added to the fifth zone of the twin-screw extruder through the side feeding system. The temperatures of each section of the twin-screw extruder are: zone 1 135℃, zone 2 150℃, zone 3 160℃, zone 4 160℃, zone 5 155℃, and die head temperature 158℃. Zone 4 is equipped with vacuum exhaust with a vacuum degree of -0.05MPa. The screw speed is 230r / min and the feeding frequency is 20Hz. The melt-blended extruded strips were cooled in a 25°C water bath and dried with an air knife at a pressure of 0.3 MPa. They were then pelletized at a pelletizing speed of 400 r / min to obtain pellets with an average particle size of 3 mm. The pellets were then dried in a forced-air dryer at 52°C for 3 h to obtain biodegradable buffer air column material masterbatch.

[0044] Comparative Example 1: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between this material and Example 3 is that the epoxidized polysiloxane grafted starch complex is not added, and it is replaced in equal amounts with polybutylene adipate / terephthalate (PBAT).

[0045] Comparative Example 2: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between this material and Example 3 is that quaternary ammonium salt modified montmorillonite is not added, and PBAT is replaced in equal amounts.

[0046] Comparative Example 3: A biodegradable buffer air column material masterbatch and its preparation method are disclosed, which differ from Example 3 only in that the epoxidized polysiloxane grafted starch composite is replaced with an equal amount of ordinary corn starch.

[0047] Comparative Example 4: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between this and Example 3 is that the epoxidized polysiloxane grafted starch composite is replaced with an equal amount of corn starch that has only been surface-treated with silane coupling agent KH-570.

[0048] Comparative Example 5: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between this and Example 3 is that the quaternary ammonium salt modified montmorillonite is replaced with an equal amount of unmodified sodium-based montmorillonite.

[0049] Comparative Example 6: A biodegradable buffer air column material masterbatch and its preparation method are disclosed, which differ from Example 3 only in that the amount of plasticizer is reduced to 0.5 parts.

[0050] Comparative Example 7: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between the masterbatch and Example 3 is that the amount of foaming nucleating agent is reduced to 0.2 parts.

[0051] Comparative Example 8: A biodegradable buffer air column material masterbatch and its preparation method are disclosed, which differ from Example 3 only in that no lubricant is added.

[0052] Comparative Example 9: A biodegradable buffer air column material masterbatch and its preparation method are disclosed. The only difference between this and Example 3 is that the maltodextrin in the epoxidized polysiloxane grafted starch complex is replaced with corn starch in an equal amount.

[0053] The mechanical properties, processing properties, barrier properties, antibacterial properties, biodegradability, and air column bag application properties of the masterbatches obtained in Examples 1-3 and Comparative Examples 1-9 were tested. The testing methods and standards are as follows: 1. Mechanical property testing The tests were conducted according to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets". The specimens were dumbbell-shaped, 10 mm wide, with a gauge length of 50 mm, and a tensile speed of 200 mm / min. Each sample was tested 5 times, and the average value was taken.

[0054] Puncture resistance was tested according to GB / T 10004-2008 "Dry lamination and extrusion lamination of plastic composite films and bags for packaging". The puncture needle diameter was 1 mm, the testing speed was 50 mm / min, and each sample was tested 5 times, and the average value was taken.

[0055] 2. Processing performance test The test was conducted according to GB / T 3682.1-2018 "Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method". The temperature was 190℃, the load was 2.16 kg, and each sample was tested three times, with the average value taken.

[0056] 3. Barrier performance test The oxygen transmission rate was tested according to GB / T 19789-2005 "Test Method for Oxygen Permeability of Plastic Films and Sheets for Packaging Materials - Coulometric Test". The temperature was 23℃, the relative humidity was 50%, and the test area was 50cm². 2 Each sample was tested three times, and the average value was taken. Results are expressed in cm. 3 ·mm / (m 2 The unit is ·d·Pa).

[0057] 4. Antibacterial performance test The test was conducted according to GB / T 31402-2015 "Test Method for Antibacterial Properties of Plastic Surfaces". The bacterial strain used was *Escherichia coli*. Each sample was tested three times, and the average value was taken. The antibacterial rate was calculated using the following formula: Antibacterial rate (%) = (Number of viable bacteria in control sample - Number of viable bacteria in antibacterial sample) / Number of viable bacteria in control sample × 100% 5. Biodegradability test The test was conducted according to GB / T 19277.1-2011 "Determination of the final aerobic biodegradability of materials under controlled composting conditions - Method for determining the release of carbon dioxide - Part 1: General Method". The temperature was 58℃, humidity 50-55%, and the test duration was 180 days. Each sample was tested three times, and the average value was taken.

[0058] 6. Performance testing of air column bags The masterbatch was blown into a film with a thickness of 40±5μm using a blown film extrusion machine under the same conditions, and then used to prepare air column bags with a specification of 20cm×30cm. The bags were inflated to 0.10MPa and placed in an environment of 25℃ and 50% humidity for 7 days. The pressure was measured, and the pressure retention rate was calculated. Pressure retention rate (%) = Pressure after 7 days / Initial pressure × 100% Five air column bags were tested for each sample, and the average value was taken.

[0059] The results are shown in Tables 2 and 3.

[0060] Table 2 Test results of mechanical and processing properties

[0061] Table 3. Test results of barrier properties, applicability, and degradation performance.

[0062] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-9 are analyzed as follows: Comparative Example 1: Without the addition of epoxidized polysiloxane-grafted starch composite, PBAT was replaced in equal amounts. Tensile strength decreased from 29.5 MPa to 17.5 MPa (a decrease of 40.7%), elongation at break decreased from 465% to 285% (a decrease of 38.7%), puncture strength decreased from 91.5 N to 52.5 N (a decrease of 42.6%), melt flow rate increased from 3.5 g / 10 min to 4.9 g / 10 min (an increase of 40%), and oxygen permeability decreased from 1.8 cm⁻¹. 3 ·mm / (m 2 The concentration of dPa rose to 3.8 cm. 3 ·mm / (m 2 The 7-day pressure retention rate decreased from 92.0% to 67.5% (a decrease of 26.6%), the 180-day degradation rate decreased from 90.5% to 72.5% (a decrease of 19.9%), and the antibacterial rate of E. coli decreased from 95.5% to 75.5% (a decrease of 20.9%). In this comparative example, the absence of epoxidized polysiloxane-grafted starch composite resulted in the loss of a reactive compatibilizing interface between the starch and the PBAT / PLA matrix, preventing the formation of an "anchor-chain" structure. This led to a significant reduction in stress transfer efficiency, manifested as a comprehensive decline in mechanical properties. Simultaneously, the poor compatibility between starch particles and the matrix resulted in the formation of microscopic pore defects at the interface, shortening the gas molecule diffusion path and significantly increasing oxygen permeability. Furthermore, the lack of hydrophobic protection from polysiloxane segments and the reactivity of epoxy groups led to decreased thermal stability of the starch during processing, with partial decomposition producing small molecules, resulting in a significant increase in melt flowability. The reduced material density also significantly worsened gas barrier properties and pressure retention capacity. The phase separation caused by the poor compatibility between starch and the matrix affected the uniform dispersion of the quaternary ammonium salt-modified montmorillonite and the stable, sustained release of quaternary ammonium salts between layers.

[0063] Comparative Example 2: Montmorillonite without quaternary ammonium salt modification was replaced with an equal amount of PBAT. Tensile strength decreased from 29.5 MPa to 23.2 MPa (a decrease of 21.4%), puncture strength decreased from 91.5 N to 73.5 N (a decrease of 19.7%), and oxygen permeability decreased from 1.8 cm⁻¹. 3 ·mm / (m 2 ·d·Pa) rose to 5.5cm 3 ·mm / (m 2The pressure retention rate decreased from 92.0% to 65.5% (a decrease of 28.8%), and the antibacterial rate against E. coli decreased from 95.5% to 78.5% (a decrease of 17.8%). The absence of quaternary ammonium salt modified montmorillonite caused the material to lose its layered barrier "maze" effect, significantly reducing the resistance to gas molecule diffusion and leading to an increase in oxygen permeability of more than two times. Simultaneously, the physical reinforcement and heterogeneous nucleation effects of the montmorillonite layers in the matrix disappeared, making the material prone to stress concentration under stress, resulting in a decrease in tensile strength and puncture resistance. Furthermore, the absence of quaternary ammonium salt antibacterial active ingredients directly led to a significant decrease in the antibacterial rate, and due to the lack of layered barrier effect on gas permeation, the gas leakage rate inside the gas column bag accelerated, and the pressure retention rate decreased significantly.

[0064] Comparative Example 3: Replacing the epoxidized polysiloxane-grafted starch composite with ordinary corn starch resulted in a decrease in tensile strength from 29.5 MPa to 19.0 MPa (a decrease of 35.6%), elongation at break from 465% to 315% (a decrease of 32.3%), puncture strength from 91.5 N to 56.5 N (a decrease of 38.3%), melt flow rate from 3.5 g / 10 min to 5.0 g / 10 min (an increase of 42.9%), and oxygen permeability from 1.8 cm⁻¹. 3 ·mm / (m 2 The pressure (dPa) rose to 3.5 cm. 3 ·mm / (m 2 The degradation rate (increased by 94.4%), the 7-day pressure retention rate decreased from 92.0% to 66.0% (a decrease of 28.3%), and the 180-day degradation rate decreased from 90.5% to 75.5% (a decrease of 16.6%). Ordinary corn starch is rich in hydroxyl groups on its surface, which have a large polarity difference from the PBAT / PLA polyester matrix, resulting in extremely poor interfacial compatibility. This leads to easy agglomeration of starch granules during processing, forming interfacial defects and stress concentration points. Under external force, this easily triggers crack propagation, causing a significant decrease in mechanical properties. Simultaneously, the micropores at the interface provide channels for gas permeation, nearly doubling the oxygen permeability. Furthermore, unmodified starch has poor thermal stability, and during melt processing, partial degradation produces small-molecule volatiles, leading to an abnormally high melt flow rate. The overall material structure is not dense, resulting in a significant reduction in gas barrier properties and pressure retention capacity. In addition, the poor compatibility between ordinary corn starch and the matrix led to phase separation, which reduced the uniformity of dispersion of quaternary ammonium salt modified montmorillonite in the system. The lamellar aggregation hindered the effective slow release of quaternary ammonium salt, and the antibacterial rate dropped from 95.5% to 80.0% (a decrease of 16.2%).

[0065] Comparative Example 4: When corn starch treated with silane coupling agent KH-570 was used to replace epoxidized polysiloxane-grafted starch composite, the tensile strength decreased from 29.5 MPa to 21.2 MPa (a decrease of 28.1%), the elongation at break decreased from 465% to 365% (a decrease of 21.5%), the puncture strength decreased from 91.5 N to 64.5 N (a decrease of 29.5%), the melt flow rate increased from 3.5 g / 10 min to 4.6 g / 10 min (an increase of 31.4%), and the oxygen permeability decreased from 1.8 cm⁻¹. 3 ·mm / (m 2 The concentration of dPa rose to 3.2 cm. 3 ·mm / (m 2 The pressure retention rate (dPa) increased by 77.8%, while the 7-day pressure retention rate decreased from 92.0% to 71.5% (a decrease of 22.3%). Silane coupling agent treatment can only form physical adsorption or weak chemical bonding on the starch surface, and cannot introduce long-chain polysiloxane flexible segments and highly active epoxy groups onto the starch molecules as in the in-situ grafting reaction of this invention, resulting in limited interfacial compatibilization effect. This physical modification is difficult to form a chemical bond bridge between the starch and the matrix, and the stress transfer efficiency is lower than that of the chemical grafting system, leading to a significant decrease in mechanical properties. At the same time, insufficient interfacial bonding strength makes it easy to form micro-interfacial pores inside the material, increasing gas permeation channels, resulting in increased oxygen permeability and decreased pressure retention capacity of the gas column bag.

[0066] Comparative Example 5: Replacing quaternary ammonium salt modified montmorillonite with unmodified sodium-based montmorillonite reduced oxygen permeability from 1.8 cm⁻¹. 3 ·mm / (m 2 The concentration of dPa rose to 4.8 cm. 3 ·mm / (m 2 The 7-day pressure retention rate decreased from 92.0% to 73.5% (a decrease of 20.1%), and the antibacterial rate against E. coli decreased from 95.5% to 86.5% (a decrease of 9.4%). Sodium-based montmorillonite has a hydrophilic surface and poor compatibility with the PBAT / PLA matrix, making it difficult to effectively peel and disperse during melt processing. The sheets tend to agglomerate and accumulate, failing to form an effective gas-barrier "maze" path, leading to a significant increase in oxygen permeability. Uneven sheet dispersion also results in uneven distribution of antibacterial active sites and weak interfacial bonding with the matrix, significantly reducing both the antibacterial rate and the pressure retention rate of the air column bag.

[0067] Comparative Example 6: When the amount of plasticizer was reduced to 0.5 parts, the elongation at break decreased from 465% to 315% (a decrease of 32.3%), the melt flow rate decreased from 3.5 g / 10 min to 2.1 g / 10 min (a decrease of 40.0%), and the oxygen permeability decreased from 1.8 cm⁻¹. 3 ·mm / (m 2 The concentration of dPa rose to 2.3 cm.3 ·mm / (m 2 The pressure retention rate (dPa) decreased by 27.8% (from 92.0% to 87.0%, a decrease of 5.4%). The absence of the plasticizer, a compound of epoxidized soybean oil and tributyl citrate, made it difficult to plasticize the PLA segments and the starch particles could not be effectively plasticized and dispersed, resulting in increased overall brittleness of the material, manifested as a significant decrease in elongation at break. At the same time, the lubricating effect of the plasticizer was greatly reduced, the melt viscosity increased, the fluidity decreased, and the melt flow rate decreased significantly. Due to the uneven plasticization of the material, the internal micro-phase separation structure was easily formed, resulting in local defects, which slightly reduced the gas barrier performance and the pressure retention rate of the gas column bag also decreased accordingly.

[0068] Comparative Example 7: When the amount of foaming nucleating agent was reduced to 0.2 parts, the oxygen permeability decreased from 1.8 cm. 3 ·mm / (m 2 The concentration of dPa rose to 3.0 cm. 3 ·mm / (m 2 The pressure retention rate decreased from 92.0% to 82.0% (a decrease of 10.9%), while the pressure retention rate increased by 66.7% (dPa). The fine and uniform closed-cell structure formed by the decomposition of the foaming nucleating agent during processing shortens the diffusion path of gas molecules and results in high density of the cell walls. With reduced foaming nucleating agent dosage, the internal pores of the material become larger and unevenly distributed, and defects appear in the cell walls, allowing gas molecules to permeate more easily, leading to increased oxygen permeability and decreased pressure retention capacity of the gas column bag.

[0069] Comparative Example 8: Without lubricant, the melt flow rate decreased from 3.5 g / 10 min to 2.8 g / 10 min (a decrease of 20.0%). The absence of lubricant increased the internal frictional resistance of the melt and reduced processing fluidity, manifested as a significant decrease in melt flow rate; however, due to the low amount of lubricant added, its impact on the material's mechanical properties, barrier properties, and antibacterial properties was relatively limited, with small changes in each indicator.

[0070] Comparative Example 9: When the maltodextrin in the epoxidized polysiloxane-grafted starch composite was replaced with an equal amount of corn starch, the tensile strength decreased from 29.5 MPa to 22.5 MPa (a decrease of 23.7%), the elongation at break decreased from 465% to 380% (a decrease of 18.3%), the puncture strength decreased from 91.5 N to 69.5 N (a decrease of 24.0%), and the oxygen permeability decreased from 1.8 cm⁻¹. 3 ·mm / (m 2 The concentration of dPa rose to 3.1 cm. 3 ·mm / (m 2The 7-day pressure retention rate decreased from 92.0% to 79.0% (a decrease of 14.1%), the antibacterial rate against E. coli decreased from 95.5% to 90.5% (a decrease of 5.2%), and the 180-day degradation rate decreased from 90.5% to 82.0% (a decrease of 9.4%). After maltodextrin was replaced by starch, the starch-polysiloxane entanglement network was difficult to form effectively, the interaction between polysiloxane segments and starch molecules weakened, and the interfacial bonding strength decreased. This led to interfacial slippage under stress, resulting in a significant reduction in tensile strength, elongation at break, and puncture resistance. Simultaneously, the lack of the entanglement network increased the internal free volume of the material, decreased gas barrier properties, and consequently reduced the pressure retention rate of the air column bag. Furthermore, the absence of dextrin also affected the overall uniformity of the material and the dispersion stability of the antibacterial components.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A biodegradable buffer air column material masterbatch, characterized in that, The raw materials for its preparation, by weight, include: 60-80 parts of matrix resin, 15-30 parts of epoxidized polysiloxane grafted starch composite, 3-8 parts of quaternary ammonium salt modified montmorillonite, 3-6 parts of plasticizer, 0.5-1.5 parts of lubricant, 0.3-0.8 parts of antioxidant, 1-2.5 parts of foaming nucleating agent, and 0.3-0.5 parts of foaming stabilizer.

2. The biodegradable buffer air column material masterbatch according to claim 1, characterized in that, The matrix resin is composed of poly(butylene adipate / terephthalate) and polylactic acid in a mass ratio of 3-5:1; the plasticizer is composed of epoxidized soybean oil and tributyl citrate in a mass ratio of 1.5-2.5:

1.

3. The biodegradable buffer air column material masterbatch according to claim 1, characterized in that, The lubricant is N,N'-ethylene bis-stearamide or zinc stearate; the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1.5 to 2.5:

1.

4. The biodegradable buffer air column material masterbatch according to claim 1, characterized in that, The foaming nucleating agent is a coated foaming nucleating agent, which is composed of coated sodium bicarbonate and coated citric acid in a mass ratio of 0.8~1.2:1; the foaming stabilizer is composed of dicyandiamide and 2-methylimidazole in a mass ratio of 8~10:

1.

5. The biodegradable buffer air column material masterbatch according to claim 1, characterized in that, The raw materials for preparing the epoxidized polysiloxane grafted starch composite, by weight, include: 60-80 parts corn starch, 20-40 parts maltodextrin, 90-100 parts hydrogen-terminated silicone oil, 2.0-3.5 parts allyl glycidyl ether, 0.2-0.5 parts chloroplatinic acid-isopropanol solution, 120-180 parts toluene, and 0.1-0.3 parts triethylamine.

6. The biodegradable buffer air column material masterbatch according to claim 5, characterized in that, The platinum concentration in the chloroplatinic acid-isopropanol solution is 900~1000 ppm.

7. The biodegradable buffer air column material masterbatch according to claim 5 or 6, characterized in that, The preparation method of the epoxidized polysiloxane-grafted starch composite includes the following steps: 1) Under nitrogen protection, add hydrogen-containing silicone oil and toluene to the reactor and stir at 80~120 r / min for 15~25 min. Add allyl glycidyl ether, heat to 55~65℃, add chloroplatinic acid-isopropanol solution, stir evenly and continue to heat to 80~90℃, and reflux for 4~6 h. 2) After the reaction is completed, the reaction solution is distilled under reduced pressure at 80~90℃ and vacuum degree ≤-0.095MPa for 1~2h to obtain epoxy-containing polysiloxane prepolymer with epoxy value of 0.10~0.15mol / 100g; 3) Add corn starch and maltodextrin to a high-speed mixer and stir at 200-300 r / min at 100-120℃ for 25-35 min. Then cool down to 70-85℃, add triethylamine, and then spray the epoxy-containing polysiloxane prepolymer obtained in step 2) through a pressure atomizing nozzle at an atomization pressure of 0.2-0.4 MPa. After spraying, stir at 1000-1200 r / min for 15-25 min. 4) Transfer the material obtained in step 3) to a closed reactor and react at a constant temperature of 100~120℃ for 2~3 hours. After the reaction is completed, crush the material and pass it through a 200~250 mesh sieve to obtain the epoxidized polysiloxane grafted starch composite.

8. A method for preparing a biodegradable buffer air column material masterbatch according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Preprocessing: The matrix resin was vacuum dried at 60-80℃ and vacuum degree ≤-0.09MPa for 4-6 hours, and the moisture content was controlled to be ≤0.03%; the quaternary ammonium salt modified montmorillonite was dried by forced air at 80-90℃ for 2-3 hours. Sodium bicarbonate and stearic acid are added to a high-speed mixer at a mass ratio of 1:0.05~0.15 and stirred at 300~500 r / min for 5~10 min at 85~100℃. After cooling to 25~30℃, the mixture is pulverized and passed through a 200~250 mesh sieve to obtain coated sodium bicarbonate particles. Citric acid and paraffin are added to a high-speed mixer at a mass ratio of 1:0.5~0.8 and stirred at 300~500 r / min for 5~10 min at 65~80℃. After cooling to 25~30℃, the mixture is pulverized and passed through a 200~250 mesh sieve to obtain citric acid coated particles. A foaming nucleating agent is obtained by compounding sodium bicarbonate particles and citric acid particles in a certain proportion. S2. Preparation of premix: The dried matrix resin, epoxidized polysiloxane grafted starch complex, quaternary ammonium salt modified montmorillonite, plasticizer, lubricant, antioxidant and foaming stabilizer are added to a high-speed mixer and stirred at 500-800 r / min at 65-85℃ for 8-15 min to obtain a premix. S3, Melt Blending Extrusion: The premix obtained in step S2 is added to the main feed port of the twin-screw extruder, and the foaming and nucleating agent obtained in step S1 is added to the fifth zone of the twin-screw extruder through the side feeding system. After melt blending and extrusion, the material is successively cooled, dried, pelletized, and dried at low temperature to obtain biodegradable buffer air column material masterbatch.

9. The method for preparing the biodegradable buffer gas column material masterbatch according to claim 8, characterized in that, In step S3, the temperatures of each section of the twin-screw extruder are as follows: Zone 1 130~145℃, Zone 2 145~160℃, Zone 3 155~170℃, Zone 4 155~165℃, Zone 5 150~160℃, and the die head temperature 150~165℃; Zone 4 is equipped with vacuum exhaust, with a vacuum degree of -0.04~-0.06MPa; the screw speed is 180~280r / min, and the feeding frequency is 15~25Hz.

10. The method for preparing the biodegradable buffer air column material masterbatch according to claim 8, characterized in that, In step S3, the melt-blended extruded strip is cooled in a water bath at 20~30℃ and dried with an air knife at an air pressure of 0.2~0.4MPa. Then, it is pelletized at a pelletizing speed of 300~500r / min to obtain pellets with an average particle size of 2~4mm. The pellets are then dried in a forced-air dryer at 45~60℃ for 2~4h to obtain biodegradable buffer air column material masterbatch.

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