Modified PBAT material, high water vapor barrier biodegradable mulch film and preparation method thereof

Abstract

The application discloses a modified PBAT material, a high-water-vapor-barrier biodegradable mulching film and a preparation method thereof. The modified PBAT material is prepared from terephthalic acid, adipic acid, 1,4-butanediol and epoxidized fatty acid glyceride through ring-opening, esterification and polycondensation reactions, and the high-water-vapor-barrier biodegradable mulching film is obtained by blow molding the modified PBAT material into a film. The epoxidized fatty acid glyceride is introduced into the PBAT molecule, so that the water vapor barrier property, the mechanical property and the aging resistance of the biodegradable mulching film are significantly improved. The raw materials are easy to obtain, and the production process is simple. The existing PBAT polymerization can be technically improved, and the general film blowing equipment is used, so that the large-scale industrial production can be realized.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a modified PBAT material, a high water vapor barrier biodegradable mulch film, and its preparation method. Background Technology

[0002] Mulching has become an important agricultural production technology in my country. However, in recent years, the large-scale application of traditional polyethylene mulch film has led to an increasing accumulation of residual mulch film in farmland, which has increasingly affected the growth space of crop roots, resulting in reduced absorption and utilization of water and nutrients, and a decline in crop yield and quality, seriously affecting the sustainable development of agriculture in my country.

[0003] Biodegradable mulch film is a low-carbon, environmentally friendly material. It not only effectively retains moisture and prevents water and heat loss from the soil during crop germination and seedling stages, but also degrades into water, carbon dioxide, and small molecules by microorganisms in the field after crop maturity, without polluting the soil environment. In agricultural mulching applications, using biodegradable mulch film instead of traditional mulch film is one of the effective means to solve the problem of residual film pollution in farmland. Polybutylene terephthalate (PBAT) has excellent mechanical properties and good biodegradability, making it the mainstream material currently used in the field of biodegradable mulch film. However, PBAT mulch film has poorer water vapor barrier properties than traditional polyethylene mulch film, resulting in insufficient moisture retention.

[0004] Currently, there are two main technical methods to improve the water vapor barrier performance of PBAT mulch films: one is to add high-barrier polymers to form blended or multilayer films, and the other is to add barrier performance enhancers. Patent CN106221165A discloses a high-barrier, fully biodegradable mulch film, which uses PPC with excellent barrier properties to melt-blend with PBAT and PHBH and then blow-forms it into a film to obtain a high-barrier PBAT mulch film. Patent CN118596670A discloses a fully biodegradable multilayer mulch film including an aging-resistant layer and a barrier layer. The function is controlled by adjusting the amount of PGA and ultraviolet absorbers in the two-layer formulation, resulting in a PBAT mulch film product with excellent water vapor barrier performance and moderate hardness. Patent CN110452507A discloses a high-barrier, fully biodegradable mulch film, which improves the barrier performance of PBAT mulch films by adding barrier performance enhancers. Barrier performance enhancers mainly include organic barrier performance enhancers such as low molecular weight polyethylene wax, oxidized polyethylene wax, petrolatum, and 1,4-butanediol, as well as inorganic barrier performance enhancers such as micron-sized talc, nano-sized talc, high-permeability talc, mica flakes, nano-montmorillonite, modified nanocellulose, and nano-attapulgite. Patent CN118063941A discloses a high-barrier, fully biodegradable mulch film that uses a blend of three biodegradable materials: PBAT, PHBH, and PGA. It employs polymethyl methacrylate and ethylene-norbornene copolymer as water vapor barrier agents to improve the barrier performance of PBAT. However, the technological innovations of the above methods are concentrated in the processing stage. Blending PBAT with other polymers leads to low compatibility between polymers, resulting in decreased processing and overall performance, requiring complex formulation design to address. The structure of multilayer films requires multiple formulation designs and multilayer co-extrusion processes, placing high demands on processing equipment and technology. Barrier performance enhancers, especially inorganic ones, generally suffer from insufficient interfacial strength, leading to decreased mechanical and aging resistance properties, necessitating modification or the addition of compatibilizers. Therefore, there is an urgent need for a biodegradable mulch film with good water vapor barrier properties, mechanical properties, and aging resistance, along with its preparation method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a modified PBAT material and its preparation method. The modified PBAT material is synthesized by adding epoxidized fatty acid glycerides (EAG) during the esterification process, thereby improving the mechanical properties and water vapor barrier properties of the material.

[0006] Another objective of this invention is to propose a high water vapor barrier biodegradable mulch film and its preparation method. The biodegradable mulch film prepared using the above-mentioned modified PBAT material has good water vapor barrier performance, mechanical properties and aging resistance. Moreover, the production process is simple and can be carried out on a large scale using general blown film equipment.

[0007] The objective of this invention is achieved through the following technical solutions.

[0008] A first aspect of the present invention is to provide a modified PBAT material comprising a reaction product of terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides.

[0009] The epoxidized fatty acid glycerides are selected from at least one of epoxidized rapeseed oil, epoxidized safflower oil, epoxidized linseed oil, epoxidized sunflower oil, epoxidized corn oil, epoxidized olive oil, epoxidized soybean oil, epoxidized peanut oil, epoxidized cottonseed oil, and epoxidized palm oil.

[0010] The epoxy value of the epoxidized fatty acid glyceride is 0.1 to 3.0 mol / 100g, preferably 0.1 to 1.0 mol / 100g.

[0011] A second aspect of the present invention is to provide a method for preparing the above-mentioned modified PBAT material, comprising the step of reacting a component including terephthalic acid, adipic acid, 1,4-butanediol and epoxidized fatty acid glycerides to obtain the modified PBAT material.

[0012] Preferably, the preparation method of the modified PBAT material specifically includes the following steps:

[0013] (1) Adipic acid and epoxidized fatty acid glycerides were subjected to a ring-opening reaction to obtain compound ESO-AA;

[0014] (2) The compound ESO-AA, 1,4-butanediol and terephthalic acid obtained in step (1) are subjected to esterification reaction under the action of a catalyst;

[0015] (3) The esterification product obtained in step (2) is subjected to polycondensation reaction to obtain the modified PBAT material.

[0016] In the preparation method of the modified PBAT material:

[0017] The molar ratio of terephthalic acid, adipic acid, 1,4-butanediol and epoxidized fatty acid glycerides is 10:(10-100):(20-130):(0.01-5), preferably 10:(10-20):(20-40):(0.05-1);

[0018] The catalyst is selected from at least one of titanium-based catalysts (such as titanium dioxide, titanate catalysts, etc.), antimony-based catalysts (such as antimony trioxide, antimony acetate, antimony glycolate, etc.), germanium-based catalysts (such as germanium dioxide and metal complexes, etc.), and tin-based catalysts (such as stannous chloride and metal complexes, etc.), preferably from at least one of titanate catalysts and antimony-based catalysts. The titanate catalyst can be a commonly used titanate compound, such as, but not limited to, tetrabutyl titanate, diisopropyl titanate, etc., and the antimony-based catalyst includes, but is not limited to, antimony trioxide, antimony acetate, antimony glycolate, etc. The amount of catalyst used is not particularly limited and can be added according to commonly used methods.

[0019] In the preparation method of the modified PBAT material:

[0020] The conditions for the ring-opening reaction are: temperature 160-190℃, time 20-40 min; the ring-opening reaction is preferably carried out in a protective gas atmosphere, and the protective gas can be commonly used nitrogen or an inert gas (such as argon).

[0021] The conditions for the esterification reaction are: temperature 140-220℃, time 1-5h; the esterification reaction is preferably carried out in a protective gas atmosphere, and the protective gas can be commonly used nitrogen or an inert gas (such as argon).

[0022] The conditions for the polycondensation reaction are: temperature 240-260℃, pressure <50Pa, time 0.2-1.5h; after the polycondensation reaction, a protective gas (e.g., nitrogen) is introduced to cool the reaction system.

[0023] In step (2), the order of adding the components such as ESO-AA, 1,4-butanediol, terephthalic acid, and catalyst during the esterification reaction, as well as the order of the esterification reaction, are not particularly limited and can be selected according to the actual reaction. For example, the esterification reaction steps in step (2) can include any of the following methods:

[0024] Method (1): Esterification reaction is carried out by mixing compound ESO-AA, 1,4-butanediol, terephthalic acid and catalyst; or,

[0025] Method (II): Esterification of compounds ESO-AA and terephthalic acid with 1,4-butanediol under the action of a catalyst; or,

[0026] Method (3): Mix ESO-AA, 1,4-butanediol and catalyst, react them, and then add terephthalic acid to continue the esterification reaction.

[0027] A third aspect of the present invention is to provide a high water vapor barrier biodegradable mulch film prepared from a modified PBAT material, wherein the modified PBAT material is the aforementioned modified PBAT material. Specifically, the modified PBAT material comprises the reaction product of terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides.

[0028] The thickness of the high water vapor barrier biodegradable mulch film can be adjusted according to actual needs, for example, the thickness of the high water vapor barrier biodegradable mulch film is 5-20 μm; the water vapor permeability of the high water vapor barrier biodegradable mulch film is less than 8 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa.

[0029] A fourth aspect of the present invention provides a method for preparing the above-mentioned high water vapor barrier biodegradable mulch film, comprising blow molding a component including the modified PBAT material into a film to obtain the high water vapor barrier biodegradable mulch film. The blow molding process can be achieved using commonly used blow molding equipment and process conditions, for example, the blow molding conditions are: screw temperature of 140–160°C, screw length-to-diameter ratio ≥ 20:1, and blow-up ratio ≥ 2:1.

[0030] The technical solution provided by this invention has the following technical effects:

[0031] (1) In the esterification process of PBAT synthesis, the present invention adds epoxidized fatty acid glycerides (EAG) to obtain a modified PBAT material, which significantly improves mechanical properties and aging resistance, and the water vapor barrier rate can be increased by more than 5 times, breaking through the current technical bottleneck in the performance of biodegradable mulch films.

[0032] (2) The present invention directly blow-moldes the modified PBAT material (EAG-PBAT) into a film to obtain a high water vapor barrier biodegradable mulch film. Unlike the existing technologies that use melt blending modification or composite modification, the present invention avoids the performance degradation and poor compatibility problems caused by melt processing to prepare modified components.

[0033] (3) The raw materials for preparing the high water vapor barrier biodegradable mulch film of the present invention are readily available and the production process is simple. By modifying the existing PBAT polymerization process and using general blown film equipment, it can be industrialized on a large scale. Attached Figure Description

[0034] Figure 1 The Fourier transform infrared spectra of the modified PBAT material obtained in Examples 1-3 of this invention, the PBAT material obtained in Comparative Example 1, and ESO (epoxidized soybean oil) are shown.

[0035] Figure 2The images show the proton nuclear magnetic resonance (NMR) spectra of the modified PBAT materials obtained in Examples 1-3 of this invention and the PBAT material obtained in Comparative Example 1.

[0036] Figure 3 The tensile strength and tensile strength retention rate in the transverse and longitudinal directions of the ESO-PBAT mulch film obtained in Examples 4-6 of this invention and the PBAT mulch film obtained in Comparative Example 2 are shown before and after 100 hours of aging. Here, TD represents the transverse direction, MD represents the longitudinal direction, the horizontal axis represents the test sample, the left vertical axis represents the tensile strength (MPa), and the right vertical axis represents the tensile strength retention rate (%).

[0037] Figure 4 The transverse and longitudinal elongation at break and retention rate of the ESO-PBAT mulch film obtained in Examples 4-6 of this invention and the PBAT mulch film obtained in Comparative Example 2 are shown before and after 100 hours of aging. TD represents the transverse direction, MD represents the longitudinal direction, the horizontal axis represents the test sample, the left vertical axis represents the elongation at break (%), and the right vertical axis represents the elongation at break retention rate (%).

[0038] Figure 5 The water vapor barrier properties of the ESO-PBAT mulch film obtained in Examples 4-6 of this invention and the PBAT mulch film obtained in Comparative Example 2 are shown. The horizontal axis represents the test sample, and the vertical axis represents the water vapor transmission coefficient (10⁻⁶). -14 g·cm / cm 2 ·s·Pa). Detailed Implementation

[0039] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] The raw materials used in the following embodiments of the present invention are sourced from the following sources:

[0046] Terephthalic acid (TA), adipic acid (AA), 1,4-butanediol (1,4-BDO), tetrabutyl titanate (TBOT) and antimony trioxide were all purchased from Aladdin Biochemical Technology Co., Ltd.

[0047] Epoxidized soybean oil (ESO) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with an epoxy value of 0.4 mol / 100g.

[0048] The product characterization method used in this invention is as follows:

[0049] Fourier transform infrared spectroscopy (FTIR): performed on a Nicolet LSJ20 instrument with a resolution of 4 cm⁻¹. -1 The scanning frequency is 32 times, and the range is 400–4000 cm. -1 .

[0050] 1H NMR spectrum ( 1 ¹H NMR: Performed on a Bruker Avance III HD 500MHz instrument using CDCl3 as solvent.

[0051] Tensile property test: conducted according to GB / T1040.3-2018 on a SANS CMT6104 instrument, with a tensile speed of 100 mm / min.

[0052] Water vapor barrier performance test: conducted according to GB / T1037-2021 on a Labthink C360M instrument, at a temperature of 23℃ and a relative humidity of 50%.

[0053] Biodegradability test: The method for determining oxygen demand in a closed respirometer was adopted according to GB / T 22047-2008.

[0054] Example 1: Preparation of Modified PBAT Material

[0055] The preparation of modified PBAT materials includes the following steps:

[0056] (1) Ring-opening reaction: Epoxidized soybean oil (ESO) and adipic acid (AA) were mixed in a molar ratio of 1:80 and reacted at 180°C for 30 min under a nitrogen atmosphere to obtain ESO-AA.

[0057] (2) Esterification reaction: 1,4-butanediol (1,4-BDO) with 2.4 times the molar amount of adipic acid (AA) and TBOT with a molar ratio of 1,4-butanediol to tetrabutyl titanate (TBOT) of 90:1 were added to the ESO-AA product after the reaction in step (1), and the reaction was carried out at 160°C for 1 h under a nitrogen atmosphere; then terephthalic acid (TA) and antimony trioxide were added to the system at a molar ratio of adipic acid, terephthalic acid and antimony trioxide of 100:100:3, and the temperature was raised to 200°C for 3 h.

[0058] (3) Polycondensation reaction: The system pressure is controlled to be <50Pa, the temperature is slowly raised to 260℃ within 1h, and after 1h of reaction, N2 is introduced to cool the system to room temperature to obtain modified PBAT resin ESO-PBAT.

[0059] Example 2: Preparation of Modified PBAT Material

[0060] The preparation process of the modified PBAT material is the same as in Example 1, except that the molar ratio of epoxidized soybean oil to adipic acid is 1:100.

[0061] Example 3: Preparation of Modified PBAT Material

[0062] The preparation process of the modified PBAT material is the same as in Example 1, except that the molar ratio of epoxidized soybean oil to adipic acid is 1:120.

[0063] Preparation of PBAT material in Comparative Example 1

[0064] The preparation process of the modified PBAT material is the same as in Example 1, except that epoxidized soybean oil is not added. The preparation of the PBAT material includes the following steps:

[0065] (1) Esterification reaction: Adipic acid (AA) and 1,4-butanediol (1,4-BDO) in a molar ratio of 1:2.4 and TBOT in a molar ratio of 1,4-butanediol and tetrabutyl titanate (TBOT) of 90:1 were mixed and reacted at 160°C for 1 h under a nitrogen atmosphere; then terephthalic acid (TA) and antimony trioxide were added to the system in a molar ratio of 100:100:3 and the temperature was raised to 200°C for 3 h.

[0066] (2) Polycondensation reaction: The system pressure is controlled to be <50Pa, the temperature is slowly raised to 260℃ within 1h, and after 1h of reaction, N2 is introduced to cool the system to room temperature to obtain PBAT resin.

[0067] Test Example 1: Testing of Modified PBAT Materials

[0068] like Figure 1 As shown, the ESO-PBAT prepared in Examples 1-3 showed an area located at 827 cm⁻¹. -1 The characteristic peaks of epoxy; with the increase of ESO content, the ester bond in ESO-PBAT reaches 1720 cm⁻¹. -1 The -C=O stretching vibration peak at 1410 cm⁻¹ is relative to that at 1410 cm⁻¹. -1 The relative intensity of the -CH2- bending vibration peak at that location increases. For example... Figure 2 As shown, a new peak at 3.69–3.75 ppm appeared in ESO-PBAT, representing the methyl proton signal peak linked to the hydroxyl group in the β-hydroxy ester. Additionally, methylene and methyl proton peaks from the ESO structure were observed at 0.85–0.90 ppm and 1.25–1.35 ppm, respectively. The increased proton peaks in the β-hydroxy ester and ESO fragments with increasing ESO concentration suggest that the abundance of the ESO fragment in ESO-PBAT depends on the monomer concentration.

[0069] Example 4: Preparation of High Water Vapor Barrier Biodegradable Mulch Film

[0070] The modified PBAT material ESO-PBAT prepared in Example 1 was crushed and then extruded and blown into film to prepare ESO-PBAT mulch film. The screw processing temperature of the blown film device was 160°C, the die head temperature was 140°C, the screw length-to-diameter ratio was 20:1, and the blow-up ratio was 2:1. A uniform ESO-PBAT mulch film with a thickness of approximately 10 μm was obtained.

[0071] Example 5: Preparation of a high water vapor barrier biodegradable mulch film

[0072] The preparation method of the high water vapor barrier biodegradable mulch film is the same as that in Example 4, except that the modified PBAT material used is the ESO-PBAT prepared in Example 2.

[0073] Example 6: Preparation of High Water Vapor Barrier Biodegradable Mulch Film

[0074] The preparation method of the high water vapor barrier biodegradable mulch film is the same as that in Example 4, except that the modified PBAT material used is the ESO-PBAT prepared in Example 3.

[0075] Comparative Example 2: Preparation of Biodegradable Mulch Film

[0076] The preparation method of the biodegradable mulch film is the same as that in Example 4, except that the PBAT resin used is the PBAT resin prepared in Comparative Example 1.

[0077] Test Example 2: Testing of High Water Vapor Barrier Biodegradable Mulch Film

[0078] The PBAT mulch films prepared in Examples 4-6 and Comparative Example 1 were subjected to laboratory artificial climate aging tests. The artificial climate aging performance of the mulch films was tested using an Atlas test chamber (Ci 4000) equipped with a 6500W xenon lamp, according to GB / T 16422.2-2014. The blackboard temperature (BPT) of the dark chamber was 65°C, and the relative humidity (RH) was 50%. A 2-hour exposure cycle was used, with each cycle including 108 minutes of UV radiation and 12 minutes of simultaneous water spray and UV radiation. The incident light intensity was 0.55 W / m². 2 The wavelength was 340 nm. After 100 hours of artificial climate aging, the samples were taken out for tensile property testing.

[0079] like Figure 3 As shown, compared with the PBAT mulch film without ESO monomer in Comparative Example 2, the ESO-PBAT mulch films prepared in Examples 4-6 showed an increase of over 10% in transverse tensile strength and over 28% in longitudinal tensile strength, with the improvement effect gradually increasing with the increase of ESO introduction. Figure 4 As shown, compared with the PBAT mulch film without ESO monomer in Comparative Example 2, the ESO-PBAT mulch films prepared in Examples 4-6 showed an increase of over 100% in transverse elongation at break and over 15% in longitudinal elongation at break, with the improvement effect gradually increasing with the increase of ESO introduction. After 100 hours of artificial climate aging, the retention rate of transverse tensile strength increased from 71% to 95%, and the retention rate of longitudinal tensile strength increased from 76% to 95%; the retention rate of transverse elongation at break increased from 70% to 86%, and the retention rate of longitudinal elongation at break increased from 66% to 80%, with the improvement effect gradually increasing with the increase of ESO introduction. This indicates that the introduction of ESO has a significant effect on improving the tensile properties and aging resistance of ESO-PBAT mulch films, and the improvement effect is positively correlated with the amount of ESO introduced.

[0080] like Figure 5As shown, the water vapor permeability of the PBAT mulch film without ESO monomer in Comparative Example 2 was 3.23 × 10⁻⁶. -13 g·cm / cm 2 In Examples 4-6, the introduction of ESO reduced the water vapor permeability of the ESO-PBAT mulch film to 5.28 × 10⁻⁶ Pa. -14 g·cm / cm 2 The water vapor barrier performance was improved by more than 5 times, and the water vapor permeability of ESO-PBAT mulch film gradually decreased with the increase of ESO introduction, indicating that the introduction of ESO has a significant effect on improving the water vapor barrier performance of ESO-PBAT mulch film, and the improvement effect is positively correlated with the amount of ESO introduced.

[0081] The relative biodegradability of the mulch films prepared in Examples 4-6 reached over 90%, with the required time being 117 days, 113 days, and 98 days, respectively, all lower than 180 days. This indicates that the biodegradability of the ESO-PBAT mulch film meets the requirements of GB / T 35795-2017.

[0082] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A modified PBAT material comprising the reaction product of terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides, wherein the epoxidized fatty acid glycerides are selected from at least one of epoxidized rapeseed oil, epoxidized safflower oil, epoxidized linseed oil, epoxidized sunflower oil, epoxidized corn oil, epoxidized olive oil, epoxidized soybean oil, epoxidized peanut oil, epoxidized cottonseed oil, and epoxidized palm oil; The preparation method of the modified PBAT material specifically includes the following steps: (1) Adipic acid and epoxidized fatty acid glycerides were subjected to a ring-opening reaction to obtain compound EAG-AA; (2) The compound EAG-AA, 1,4-butanediol and terephthalic acid obtained in step (1) are subjected to esterification reaction under the action of a catalyst; (3) The esterification product obtained in step (2) is subjected to polycondensation reaction to obtain the modified PBAT material; The molar ratio of terephthalic acid, adipic acid, 1,4-butanediol and epoxidized fatty acid glycerides is 10:(10~100):(20~130):(0.01~5).

2. The modified PBAT material according to claim 1, characterized in that, The epoxy value of the epoxidized fatty acid glycerides is 0.1~3.0 mol / 100g.

3. The modified PBAT material according to claim 2, characterized in that, The epoxy value of the epoxidized fatty acid glycerides is 0.1~1.0 mol / 100g.

4. A method for preparing the modified PBAT material according to any one of claims 1 to 3, comprising the step of reacting components including terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides to obtain the modified PBAT material.

5. The preparation method according to claim 4, characterized in that, The preparation method of the modified PBAT material specifically includes the following steps: (1) Adipic acid and epoxidized fatty acid glycerides were subjected to a ring-opening reaction to obtain compound EAG-AA; (2) The compound EAG-AA, 1,4-butanediol and terephthalic acid obtained in step (1) are subjected to esterification reaction under the action of a catalyst; (3) The esterification product obtained in step (2) is subjected to polycondensation reaction to obtain the modified PBAT material.

6. The preparation method according to claim 5, characterized in that, The molar ratio of terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides is 10:(10~100):(20~130):(0.01~5); and / or, The catalyst is selected from at least one of titanium-based catalysts, antimony-based catalysts, germanium-based catalysts, and tin-based catalysts.

7. The preparation method according to claim 6, characterized in that, The molar ratio of terephthalic acid, adipic acid, 1,4-butanediol, and epoxidized fatty acid glycerides is 10:(10~20):(20~40):(0.05~1); and / or, The catalyst is selected from at least one of titanate catalysts and antimony-based catalysts.

8. The preparation method according to claim 5, characterized in that, The conditions for the ring-opening reaction are: temperature 160~190 ℃, time 20~40 min; and / or, The conditions for the esterification reaction are: temperature 140~220 ℃, time 1~5 h; and / or, The conditions for the polycondensation reaction are: temperature 240~260 ℃, pressure <50 Pa, and time 0.2~1.5 h.

9. The preparation method according to claim 5, characterized in that, The esterification reaction in step (2) can be performed in any of the following ways: Method (1): Esterification reaction is carried out by mixing compound EAG-AA, 1,4-butanediol, terephthalic acid and catalyst; or, Method (II): Esterification of compound EAG-AA and terephthalic acid with 1,4-butanediol under the action of a catalyst; or, Method (3): Mix compound EAG-AA, 1,4-butanediol and catalyst, react them, and then add terephthalic acid to continue the esterification reaction.

10. A high water vapor barrier biodegradable mulch film, prepared from a modified PBAT material, wherein the modified PBAT material is the modified PBAT material according to any one of claims 1 to 3 or the modified PBAT material obtained by the preparation method according to any one of claims 4 to 9.

11. The high water vapor barrier biodegradable mulch film according to claim 10, characterized in that, The thickness of the high water vapor barrier biodegradable mulch film is 5~20 μm; and / or, The water vapor permeability of the high water vapor barrier biodegradable mulch film is less than 8 × 10⁻⁶. -14 g∙cm / cm 2 ∙s∙Pa.

12. A method for preparing the high water vapor barrier biodegradable mulch film according to claim 10 or 11, comprising blow molding a film containing the modified PBAT material to obtain the high water vapor barrier biodegradable mulch film.

13. The preparation method according to claim 12, characterized in that, The conditions for blow molding film formation are: screw temperature 140~160 ℃, screw length-to-diameter ratio ≥20:1, and blow ratio ≥2:1.

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