Degradable high-barrier protective film and preparation method thereof

Abstract

This invention belongs to the field of biodegradable materials technology, and provides a biodegradable high-barrier protective film and its preparation method. The biodegradable high-barrier protective film is characterized by comprising, by weight, the following raw materials: 100 parts PBAT, 6-10 parts TPS, 15-30 parts modified calcium carbonate, 0.5-2 parts compatibilizer, 1.5-3 parts lubricant, and 0.5-2 parts antioxidant; the modified calcium carbonate is obtained by modifying calcium carbonate with clove essential oil and epoxy chain extender ADR-4468. The protective film prepared by this invention not only has good biodegradability but also excellent gas barrier properties and mechanical properties, and can be widely used in food packaging, agricultural production, and medical devices.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable materials technology, specifically relating to a biodegradable high-barrier protective film and its preparation method. Background Technology

[0002] Plastic films possess numerous advantages, including being lightweight and transparent, moisture-proof and antioxidant, having good airtightness, and good toughness, and are widely used in medical and pharmaceutical, food packaging, and agricultural mulch films. While plastic film products have brought great convenience to people's lives, traditional plastic films, mainly made of resins such as polyethylene, polypropylene, or polyvinyl chloride, are discarded and scattered in soil and water bodies after use. They cannot degrade in a short time, thus causing serious damage to the ecological environment and even endangering the survival of humans and animals.

[0003] With the increasing environmental pollution caused by non-degradable packaging materials, biodegradable packaging materials have received widespread attention and research in recent years. Polybutylene terephthalate (PBAT) is a widely used biodegradable polymer material on the market. Because its tensile properties, ductility, impact resistance, and thermal stability are similar to low-density polyethylene (LDPE), it can be used in agricultural and packaging films. However, PBAT has weak crystallinity, which reduces the mechanical properties and gas barrier properties of the film. Furthermore, the ester groups are prone to aging and degradation during use, further exacerbating the damage to the film's gas barrier capabilities. In addition, to expand the application of PBAT films in food preservation, medical devices, and other fields, antibacterial agents are often added directly to impart antibacterial function. However, traditional blending methods suffer from problems such as high antibacterial agent migration rates and poor antibacterial durability, making it difficult to meet the practical requirements for long-lasting antibacterial effects.

[0004] Therefore, improving the mechanical properties, barrier properties, and antibacterial properties of PBAT is key to meeting the high requirements of agricultural films, food packaging, and medical devices. Summary of the Invention

[0005] The purpose of this invention is to provide a biodegradable high-barrier protective film and its preparation method, so as to solve the problem of poor barrier performance of biodegradable films in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions: A biodegradable, high-barrier protective film, comprising, by weight, the following raw materials: 100 parts PBAT, 6-10 parts thermoplastic starch (TPS), 15-30 parts modified calcium carbonate, 0.5-2 parts compatibilizer, 1.5-3 parts lubricant, and 0.5-2 parts antioxidant; The modified calcium carbonate is obtained by modifying calcium carbonate with clove essential oil and epoxy chain extender ADR-4468.

[0007] In a further preferred embodiment, the modified calcium carbonate is prepared by the following steps: S1. Add calcium carbonate to acetonitrile and ultrasonically stir until homogeneous to obtain a mixture. Add epoxy chain extender ADR-4468 to the acetonitrile solution and heat to 60-65°C. Stir until completely dissolved, then add the above mixture. Add deionized water containing sodium hydroxide to the above mixture, heat to 80-85°C, reflux for 4-5 hours. After the reaction is complete, cool to room temperature, filter, wash the filter cake three times with dichloromethane and ethanol respectively, and then dry in a vacuum drying oven at 60°C for 18-24 hours. Grind and sieve to obtain pretreated calcium carbonate. S2. Dissolve the plant essential oil in anhydrous ethanol and stir until completely dissolved. Then add the pretreated calcium carbonate and continue stirring for 5-6 hours. Centrifuge to collect the product and dry it in a vacuum drying oven at 40°C until constant weight to obtain modified calcium carbonate.

[0008] In a further preferred embodiment, the ratio of calcium carbonate, epoxy chain extender ADR-4468, and sodium hydroxide in S1 is 20-22g: 4-4.6g: 2-2.05g.

[0009] In a further preferred embodiment, the ratio of plant essential oil, anhydrous ethanol and pretreated calcium carbonate in S2 is 1-1.25g: 50mL: 2-2.2g.

[0010] In a further preferred embodiment, the plant essential oil in S2 is at least one of cinnamon essential oil and clove essential oil.

[0011] The above technical solution utilizes the epoxy chain extender ADR-4468 as a modifier to graft and modify the surface of calcium carbonate. Calcium carbonate modified with ADR-4468 is more fully dispersed in the PBAT matrix resin, resulting in reduced water vapor permeability and oxygen permeability of the protective film, and improved mechanical properties. This is because ADR-4468 introduces epoxy groups, providing multiple reaction sites for calcium carbonate, enabling in-situ compatibilization, promoting more branching and cross-linking interactions with PBAT, acting as a molecular bridge connecting calcium carbonate and PBAT, enhancing their interfacial compatibility, and thus improving the water vapor and oxygen barrier properties of the PBAT film. Simultaneously, the PBAT protective film prepared from calcium carbonate modified with ADR-4468 also introduces a rigid benzene ring structure, forming a branched topological network and a controllable cross-linking structure, significantly improving mechanical properties, enhancing water vapor barrier performance, and exhibiting excellent degradation resistance.

[0012] Furthermore, to enhance the antibacterial properties of the protective film, this invention introduces plant essential oils. Cinnamon essential oil and clove essential oil are both natural antibacterial agents with excellent antibacterial effects, and are widely available, safe, and environmentally friendly. This invention enhances the antibacterial effect of the protective film by loading plant essential oils onto the porous surface and pores of calcium carbonate. Loading plant essential oils into calcium carbonate not only effectively prevents the excessively rapid evaporation rate of cinnamon and / or clove essential oils in the packaging film, increasing the retention time of plant essential oils in the protective film, but also allows them to be more uniformly dispersed in the PBAT matrix resin, exhibiting a significant slow-release antibacterial effect. Simultaneously, the increased surface roughness of calcium carbonate modified with the epoxy chain extender ADR-4468 significantly improves the adsorption rate of plant essential oils by calcium carbonate.

[0013] In a further preferred embodiment, the compatibilizer is at least one selected from tributyl citrate, triethyl citrate, and tri-n-butyl acetylcitrate.

[0014] In a further preferred embodiment, the lubricant is at least one of stearic acid, zinc stearate, and calcium stearate.

[0015] In a further preferred embodiment, the antioxidant is at least one of antioxidant 1010 and antioxidant 168.

[0016] This invention also provides a method for preparing a biodegradable high-barrier protective film, comprising the following steps: The dried PBAT and TPS are mixed with modified calcium carbonate, compatibilizer, lubricant and antioxidant in a mixer. After being mixed evenly, the mixture is fed into a twin-screw extruder for melt extrusion. Then, it is cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

[0017] In a further preferred embodiment, the temperature of the twin-screw extruder is 115–145°C, and the screw speed is 600–750 rpm / min.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a biodegradable, high-barrier protective film, using PBAT as the base resin, combined with TPS, modified calcium carbonate, compatibilizer, lubricant, and antioxidant to form a composite system with good compatibility and processability. The introduction of TPS improves the biodegradability of the film, while the addition of modified calcium carbonate significantly enhances its barrier and mechanical properties. The compatibilizer improves the interfacial compatibility between PBAT, TPS, and calcium carbonate, reducing phase separation; the lubricant improves the processing fluidity of the material, ensuring uniform film formation, a smooth surface, and stable mechanical properties. The resulting protective film not only exhibits good biodegradability but also excellent gas barrier properties and mechanical properties.

[0019] The modified calcium carbonate provided by this invention utilizes the epoxy chain extender ADR-4468 to perform surface grafting modification on calcium carbonate, introducing epoxy groups that allow it to undergo branching and cross-linking reactions with PBAT, forming a molecular bridge structure. This enhances interfacial bonding and effectively reduces the water vapor permeability and oxygen permeability of the film. Furthermore, the epoxy chain extender ADR-4468 introduces a rigid benzene ring structure, enabling the formation of a branched topological network and a controllable cross-linking structure, significantly improving the tensile strength, impact resistance, and other mechanical properties of the film. It also achieves a sustained-release antibacterial function by loading natural antibacterial plant essential oils into the porous structure of the modified calcium carbonate. Utilizing its high adsorption rate and rough surface, the loading capacity and retention time of the essential oils are significantly increased, preventing excessively rapid volatilization and achieving a long-lasting, sustained-release antibacterial effect, meeting the hygiene performance requirements of food packaging, medical devices, and other fields.

[0020] The present invention provides a method for preparing a biodegradable high-barrier protective film, which uses widely available raw materials, has a simple preparation process, and is suitable for large-scale production. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] PBAT was purchased from BASF Ltd.; epoxy chain extender ADR-4468 was purchased from BASF Ltd.; anhydrous ethanol was purchased from Guangzhou Hongyuan Chemical Co., Ltd.; clove oil was purchased from Shanghai Guoyao Group Chemical Reagent Co., Ltd.; acetonitrile was purchased from Chongqing Chuandong Chemical Group Co., Ltd.; other reagents without specified manufacturers were all commercially available products.

[0023] Preparation Example Preparation Example 1 This preparation example provides a modified calcium carbonate, and the preparation steps are as follows: S1. Add 20g of calcium carbonate to 100mL of acetonitrile and stir ultrasonically until homogeneous to obtain a mixture; add 4g of epoxy chain extender ADR-4468 to 30mL of acetonitrile solution, heat to 60℃, stir until completely dissolved, then add the above mixture, and then add 5mL of deionized water containing 2g of sodium hydroxide to the above mixture, heat to 80°C and reflux for 5h. After the reaction is completed, cool to room temperature, filter, wash the filter cake three times with dichloromethane and ethanol respectively, and then dry in a vacuum drying oven at 60°C for 24h. Grind and sieve to obtain pretreated calcium carbonate. S2. Dissolve 1g of clove essential oil in 50mL of anhydrous ethanol and stir until completely dissolved. Then add 2g of pretreated calcium carbonate and continue stirring for 5h. Collect by centrifugation and dry the solid product in a vacuum drying oven at 40°C to constant weight to obtain modified calcium carbonate.

[0024] Preparation Example 2 The only difference from Preparation Example 1 is that the amounts of each component in S1 are different: S1. Add 22g of calcium carbonate to 100mL of acetonitrile and stir ultrasonically until homogeneous to obtain a mixture. Add 4.6g of epoxy chain extender ADR-4468 to 30mL of acetonitrile solution, heat to 60°C, and stir until completely dissolved. Then add the above mixture, followed by 5mL of deionized water containing 2.05g of sodium hydroxide. Heat to 80-85°C and reflux for 5h. After the reaction is complete, cool to room temperature, filter, and wash the filter cake three times with dichloromethane and ethanol respectively. Then dry in a vacuum drying oven at 60°C for 24h, grind and sieve to obtain pretreated calcium carbonate.

[0025] Preparation Example 3 The only difference from Preparation Example 1 is that the amounts of each component in S2 are different: S2. Dissolve 1.25g of plant essential oil in 50mL of anhydrous ethanol and stir until completely dissolved. Then add 2.2g of pretreated calcium carbonate and continue stirring for 6h. Collect by centrifugation and dry the solid product in a vacuum drying oven at 40°C to constant weight to obtain modified calcium carbonate.

[0026] Preparation Example 4 This preparation example provides a modified calcium carbonate, which, compared to Preparation Example 1, does not use a natural antibacterial agent for loading modification of the calcium carbonate. The preparation steps are as follows: 20g of calcium carbonate was added to 100mL of acetonitrile and ultrasonically stirred until homogeneous to obtain a mixture. 4g of epoxy chain extender ADR-4468 was added to 30mL of acetonitrile solution and heated to 60°C. The mixture was stirred until completely dissolved and then added to the above mixture. 5mL of deionized water containing 2g of sodium hydroxide was added to the above mixture. The mixture was heated to 80°C and refluxed for 5h. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the filter cake was washed three times with dichloromethane and ethanol, respectively. The cake was then dried in a vacuum drying oven at 60°C for 24h, ground, and sieved to obtain modified calcium carbonate.

[0027] Preparation Example 5 This preparation example provides a modified calcium carbonate. Compared with Preparation Example 1, the surface grafting modification of calcium carbonate was not performed using the epoxy chain extender ADR-4468. The preparation steps are as follows: Dissolve 1g of clove essential oil in 50mL of anhydrous ethanol and stir until completely dissolved. Then add 2g of calcium carbonate and continue stirring for 5h. Collect by centrifugation and dry the solid product in a vacuum drying oven at 40°C to constant weight to obtain modified calcium carbonate.

[0028] Example Example 1 This embodiment provides a biodegradable, high-barrier protective film, comprising the following raw materials by weight: 100 parts PBAT, 6 parts TPS, 15 parts modified calcium carbonate from Preparation Example 1, 0.5 parts tributyl citrate, 1.5 parts stearic acid, and 0.5 parts antioxidant 1010; This embodiment also provides a method for preparing a biodegradable high-barrier protective film, including the following steps: The dried PBAT and TPS were mixed with modified calcium carbonate, compatibilizer, lubricant and antioxidant in a mixer. After being mixed evenly, the mixture was melt-extruded in a twin-screw extruder at a temperature of 115-145℃ and a screw speed of 650 rpm / min. The mixture was then cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

[0029] Example 2 The only difference from Example 1 is that the modified calcium carbonate in Preparation Example 1 is replaced with the modified calcium carbonate in Preparation Example 2, while the amount remains the same.

[0030] Example 3 The only difference from Example 1 is that the modified calcium carbonate in Preparation Example 1 is replaced with the modified calcium carbonate in Preparation Example 3, while the amount remains the same.

[0031] Example 4 The only difference from Example 1 is that: a biodegradable high-barrier protective film, by weight, comprises the following raw materials: 100 parts PBAT, 8 parts TPS, 23 parts modified calcium carbonate from Preparation Example 1, 1.2 parts tributyl citrate, 2.0 parts stearic acid, and 1.3 parts antioxidant 1010.

[0032] Example 5 The only difference from Example 1 is that: a biodegradable high-barrier protective film, by weight, comprises the following raw materials: 100 parts PBAT, 10 parts TPS, 30 parts modified calcium carbonate from Preparation Example 1, 2 parts tributyl citrate, 3 parts zinc stearate, and 2 parts antioxidant 168.

[0033] Example 6 The only difference from Example 1 is that a method for preparing a biodegradable high-barrier protective film includes the following steps: The dried PBAT and TPS were mixed with modified calcium carbonate, compatibilizer, lubricant and antioxidant in a mixer. After being mixed evenly, the mixture was melt-extruded in a twin-screw extruder at a temperature of 115-145℃ and a screw speed of 750 rpm / min. The mixture was then cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

[0034] Comparative Example Comparative Example 1 This comparative example provides a biodegradable, high-barrier protective film, which differs from Example 1 only in that TPS and modified calcium carbonate are not added to the raw materials. By weight, it includes the following raw materials: 100 parts PBAT, 0.5 parts tributyl citrate, 1.5 parts stearic acid, 0.5 parts antioxidant 1010; This comparative example also provides a method for preparing a biodegradable high-barrier protective film, comprising the following steps: The dried PBAT, compatibilizer, lubricant, and antioxidant are added to a mixer and mixed evenly. The mixture is then fed into a twin-screw extruder for melt extrusion. The temperature of the twin-screw extruder is 115–145°C and the screw speed is 650 rpm / min. Subsequently, the mixture is cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

[0035] Comparative Example 2 This comparative example provides a biodegradable, high-barrier protective film, which differs from Example 1 only in that modified calcium carbonate is not added to the raw materials. By weight, it comprises the following raw materials: PBAT 100 parts, TPS 6 parts, tributyl citrate 0.5 parts, stearic acid 1.5 parts, antioxidant 1010 0.5 parts; This embodiment also provides a method for preparing a biodegradable high-barrier protective film, including the following steps: The dried PBAT and TPS, along with compatibilizer, lubricant, and antioxidant, are added to a mixer and mixed thoroughly. The mixture is then fed into a twin-screw extruder for melt extrusion. The temperature of the twin-screw extruder is 115–145°C, and the screw speed is 650 rpm / min. Subsequently, the mixture is cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

[0036] Comparative Example 3 The only difference from Example 1 is that the modified calcium carbonate in Preparation Example 1 is replaced with the modified calcium carbonate in Preparation Example 4, while the amount remains the same.

[0037] Comparative Example 4 The only difference from Example 1 is that the modified calcium carbonate in Preparation Example 1 is replaced with the modified calcium carbonate in Preparation Example 5, while the amount remains the same.

[0038] Comparative Example 5 The only difference from Example 1 is that: Replace 15 parts of modified calcium carbonate in Preparation Example 1 with 15 parts of clove oil.

[0039] Comparative Example 6 The only difference from Example 1 is that: a biodegradable high-barrier protective film, by weight, comprises the following raw materials: 80 parts PBAT, 6 parts TPS, 15 parts modified calcium carbonate from Preparation Example 1, 0.5 parts tributyl citrate, 1.5 parts stearic acid, and 0.5 parts antioxidant 1010.

[0040] Comparative Example 7 The only difference from Example 1 is that: a biodegradable high-barrier protective film, by weight, comprises the following raw materials: 80 parts PBAT, 15 parts TPS, 15 parts modified calcium carbonate from Preparation Example 1, 0.5 parts tributyl citrate, and 0.5 parts antioxidant 1010.

[0041] Performance testing The protective films obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were subjected to the following performance tests: (1) Mechanical property testing: tensile strength and elongation at break are tested according to GB / T1040.3. The 2006 standard test included a tensile speed of 50 mm / min ± 10%.

[0042] (2) Water vapor transmission rate: Tested according to standard GB / T 1037-2021.

[0043] (3) Oxygen permeability: Tested according to the method of GB / T 19789-2021 standard.

[0044] (4) Antibacterial performance test: according to standard GB / T 20944.1 In 2007, the in vitro antibacterial activity of E. coli was assessed by the agar diffusion method.

[0045] The test results are shown in Tables 1 and 2: Table 1

[0046] Table 2

[0047] As can be seen from Tables 1-2, the protective films prepared in Examples 1-6 of this invention, while ensuring good biodegradability, achieve excellent mechanical properties, high barrier properties, and long-lasting antibacterial effects through the synergistic effect of modified calcium carbonate with TPS, compatibilizers, and other components. At the same time, the preparation process is simple, and they have broad application prospects in food packaging, agricultural production, and medical devices.

[0048] Comparing Comparative Examples 1-4 with Example 1, it can be seen that Comparative Example 1, without the addition of TPS and modified calcium carbonate, produced a protective film with significantly lower mechanical properties, barrier properties, and antibacterial properties than Example 1. Comparative Example 2, without modified calcium carbonate, produced a protective film with slightly improved mechanical and barrier properties compared to Comparative Example 1, but still significantly lower than Example 1, and with poor antibacterial properties. Comparative Example 3, with calcium carbonate modified only by an epoxy chain extender and without essential oil loading, produced mechanical and barrier properties similar to Example 1, but with poor antibacterial properties. Comparative Example 4, with calcium carbonate loaded only with essential oil and without modification, suffered from poor compatibility and uneven dispersion due to the lack of surface grafting modification, resulting in decreased mechanical and barrier properties, and lower antibacterial durability than Example 1.

[0049] It is evident that the introduction of epoxy chain extender ADR-4468 not only enhances the interfacial compatibility between calcium carbonate and PBAT, forming a branched cross-linked network and a rigid benzene ring structure, significantly reducing the permeation of water vapor and oxygen, but also provides a rough surface and porous structure with high adsorption rate for plant essential oils; at the same time, the loading of clove essential oil endows the film with excellent sustained-release antibacterial effect, and does not lose its durability due to excessive evaporation.

[0050] Comparing Comparative Example 5 with Example 1, it can be seen that although the initial antibacterial rate was high when 15 parts of clove essential oil were added directly, the essential oil was volatile and had a low retention rate, which led to a rapid decline in the antibacterial effect in the later stage.

[0051] Comparing Comparative Examples 6 and 7 with Example 1, it can be seen that the reduced PBAT content in Comparative Example 6 led to a corresponding increase in the relative proportion of modified calcium carbonate. Although the increased amount of modified calcium carbonate filler prolonged the gas diffusion path to some extent, resulting in a slight decrease in water vapor and oxygen permeability compared to pure PBAT, the insufficient PBAT matrix content disrupted the continuity of the melt and the integrity of the film formation, leading to microscopic defects within the film. Therefore, its water vapor and oxygen permeability were still significantly higher than in Example 1. In Comparative Example 7, the reduced PBAT content and increased TPS content, along with the absence of lubricant, resulted in poor material flowability and uneven component dispersion during extrusion, leading to cracks on the film surface and within the film, further reducing barrier and antibacterial properties.

[0052] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. It should be understood that, in the various embodiments of this application, the sequence number of each process does not imply a sequential order of execution; some or all steps may be performed in parallel or sequentially; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0053] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0055] 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 high-barrier protective film, characterized in that, By weight, it includes the following ingredients: PBAT 100 parts, TPS 6-10 parts, modified calcium carbonate 15-30 parts, compatibilizer 0.5-2 parts, lubricant 1.5-3 parts, antioxidant 0.5-2 parts; The modified calcium carbonate is obtained by modifying calcium carbonate with clove essential oil and epoxy chain extender ADR-4468.

2. The biodegradable high-barrier protective film according to claim 1, characterized in that, The modified calcium carbonate is prepared by the following steps: S1. Add calcium carbonate to acetonitrile and ultrasonically stir until homogeneous to obtain a mixture. Add epoxy chain extender ADR-4468 to the acetonitrile solution and heat to 60-65°C. Stir until completely dissolved, then add the above mixture. Add deionized water containing sodium hydroxide to the above mixture, heat to 80-85°C, reflux for 4-5 hours. After the reaction is complete, cool to room temperature, filter, wash the filter cake three times with dichloromethane and ethanol respectively, and then dry in a vacuum drying oven at 60°C for 18-24 hours. Grind and sieve to obtain pretreated calcium carbonate. S2. Dissolve the plant essential oil in anhydrous ethanol and stir until completely dissolved. Then add the pretreated calcium carbonate and continue stirring for 5-6 hours. Centrifuge to collect the product and dry it in a vacuum drying oven at 40°C until constant weight to obtain modified calcium carbonate.

3. The biodegradable high-barrier protective film according to claim 2, characterized in that, The ratio of calcium carbonate, epoxy chain extender ADR-4468, and sodium hydroxide in S1 is 20-22g: 4-4.6g: 2-2.05g.

4. The biodegradable high-barrier protective film according to claim 2, characterized in that, In S2, the ratio of plant essential oil, anhydrous ethanol, and pretreated calcium carbonate is 1–1.25 g: 50 mL: 2–2.2 g.

5. The biodegradable high-barrier protective film according to claim 1, characterized in that, The plant essential oil mentioned in S2 is at least one of cinnamon essential oil and clove essential oil.

6. The biodegradable high-barrier protective film according to claim 1, characterized in that, The compatibilizer is at least one of tributyl citrate, triethyl citrate, and tri-n-butyl acetylcitrate.

7. The biodegradable high-barrier protective film according to claim 1, characterized in that, The lubricant is at least one of stearic acid, zinc stearate, and calcium stearate.

8. The biodegradable high-barrier protective film according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010 and antioxidant 168.

9. The method for preparing a biodegradable high-barrier protective film according to claim 1, characterized in that, Includes the following steps: The dried PBAT and TPS are mixed with modified calcium carbonate, compatibilizer, lubricant and antioxidant in a mixer. After being mixed evenly, the mixture is fed into a twin-screw extruder for melt extrusion. Then, it is cast in a casting machine, cooled and shaped, and then pulled and wound to obtain a protective film.

10. The method for preparing a biodegradable high-barrier protective film according to claim 9, characterized in that, The temperature of the twin-screw extruder is 115–145℃, and the screw speed is 600–750 rpm / min.

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