Degradable multilayer high-barrier film, and preparation method and application thereof

Abstract

The application belongs to the field of multilayer films, and particularly relates to a degradable multilayer high-barrier film and a preparation method and application thereof; the multilayer high-barrier film comprises: an outer layer / adhesion layer / barrier layer / adhesion layer / outer layer; wherein the outer layer is a blend I of polybutylene adipate terephthalate and inorganic fillers; the adhesion layer is a blend II of polybutylene adipate terephthalate and tackifying resin; and the barrier layer is polyglycolic acid. The application can prepare a multilayer film with good processability, non-layering, biodegradability and high barrier property.

Description

Technical Field

[0001] This invention belongs to the field of multilayer thin films, specifically relating to a biodegradable multilayer high-barrier thin film, its preparation method, and its application. Background Technology

[0002] Polyglycolic acid (PGA) has a glass transition temperature (Tg) of 35°C to 45°C and a peak melting temperature (Tb) of 220°C to 233°C. m PGA, a semi-crystalline aliphatic polyester, possesses excellent mechanical properties, particularly a high elastic modulus of 6–7 GPa, which is crucial for providing substantial support in load-bearing applications. Furthermore, PGA exhibits excellent gas barrier properties, largely unaffected by ambient temperature, making it an ideal material choice for multilayer barrier films when placed in the core layer. Moreover, PGA is rapidly degradable, ultimately breaking down into water and carbon dioxide, making it a globally recognized material for protecting the environment and life. Therefore, developing fully degradable multilayer barrier films based on PGA can solve the problem of the difficulty in recycling traditional composite barrier films. However, PGA's high processing temperature, poor toughness, and poor adhesion to other resins significantly limit its application in high-barrier films.

[0003] Patent document CN113388136A discloses a PGA-reinforced degradable film. The raw materials, by weight, include: 100 parts of degradable polyester, 10-30 parts of polyglycolic acid (PGA), 20-30 parts of bio-based filler, 0.2-1 parts of chain extender, and 5-15 parts of plasticizer. The processing method of this patent is to first obtain a composite material masterbatch through melt extrusion and then use a blow molding machine to blow mold the obtained composite material masterbatch into a multilayer film.

[0004] Patent document CN109566210A discloses a multi-layered composite multifunctional fully biodegradable plastic mulch film, comprising at least one ground-adhering layer and one support layer. The ground-adhering layer contains the following components in parts by weight: 100 parts fully biodegradable polyester, 5-10 parts reinforcing agent, 0-30 parts filler, 5-20 parts ground-adhering modification masterbatch, and 0-5 parts chain extender. The support layer contains the following components in parts by weight: 100 parts fully biodegradable polyester, 5-10 parts reinforcing agent, 0-30 parts filler, 0-8 parts auxiliary agent masterbatch, and 0-5 parts chain extender. This patented multi-layered film lacks a pure PGA layer, thus affecting its barrier performance.

[0005] Patent document CN113232395A discloses a fully biodegradable composite film material and its packaging bag with barrier properties. The composite film material, from top to bottom, includes a cellulose layer, a PGA layer, a PBAT layer, a first adhesive layer sandwiched between the PBAT and PGA layers, and a second adhesive layer between the PGA and cellulose layers. The PBAT, first, PGA, second adhesive, and cellulose layers are bonded together using a composite film-forming technology. This patent combines a cellulose layer (which is printable but has poor elongation and lacks heat-sealing properties) with a barrier-resistant PGA layer through a second adhesive layer. This composite layer is then further combined with a heat-sealing and elongating PBAT layer through a first adhesive layer. The complementary properties of these layers create a composite film material with good surface wetting tension, heat resistance, heat-sealing capability, and low-temperature freezing adaptability, possessing certain barrier properties. Most of the materials are derived from biodegradable raw materials, making it environmentally friendly. However, this patent uses a hot-pressing process, which is complex and inefficient.

[0006] Therefore, further development of multilayer thin films with high barrier properties and their preparation methods has become a worthy research direction. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies in preparing high-barrier multilayer films by providing a biodegradable multilayer high-barrier film, its preparation method, and its application. The invention employs a co-extrusion process, with the barrier layer in the multilayer film being pure polyglycolic acid. By designing a multilayer structure and improving the materials of each layer, a multilayer film with good processing performance, non-delamination, biodegradability, and high barrier properties can be obtained.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] In a first aspect, a biodegradable multilayer high-barrier film is provided, the multilayer high-barrier film comprising: an outer layer / adhesive layer / barrier layer / adhesive layer / outer layer arranged sequentially; wherein,

[0010] The outer layer is a blend of polybutylene terephthalate / adipate and inorganic filler I;

[0011] The adhesive layer is a blend of polybutylene terephthalate / adipate and tackifying resin II;

[0012] The barrier layer is polyglycolic acid.

[0013] According to the multilayer high-barrier film provided by the present invention, in one embodiment, the thickness of the multilayer high-barrier film is 50-300μm (e.g., 55μm, 60μm, 80μm, 100μm, 150μm, 200μm, 250μm).

[0014] In one embodiment, the thickness ratio of each layer in the multilayer high-barrier film is, outer layer: adhesive layer: barrier layer = 2:2:1 to 1:1:2, for example, 2:2:1.4, 2:2:2, 2:2:2.5, 2:2:3, 2:2:3.6.

[0015] In some embodiments of the multilayer high-barrier film provided by the present invention, the content of poly(butylene terephthalate) / butylene adipate in the blend I of the poly(butylene terephthalate) and inorganic filler is 60 wt% to 95 wt% (e.g., 65 wt%, 70 wt%, 75 wt%, 80 wt%, 90 wt%), and the content of the inorganic filler is 5 wt% to 40 wt% (e.g., 6 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%).

[0016] In some embodiments, the inorganic filler is selected from one or more of SiO2, calcium carbonate, montmorillonite, and talc.

[0017] In some embodiments of the multilayer high-barrier film provided by the present invention, the content of poly(butylene terephthalate) / butylene adipate in the blend II of the poly(butylene terephthalate) and the tackifying resin is 80 wt% to 95 wt% (e.g., 82 wt%, 85 wt%, 88 wt%, 90 wt%, 93 wt%), and the content of the tackifying resin is 5 wt% to 20 wt% (e.g., 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%).

[0018] In some embodiments, the tackifying resin is a natural series resin.

[0019] In some embodiments, the natural series resins are selected from one or more of rosin, rosin derivatives, and terpene resins.

[0020] In some embodiments, the rosin is selected from resin rosin, tall oil rosin, and wood rosin;

[0021] In some embodiments, the rosin derivative is selected from hydrogenated rosin, disproportionated rosin, polymerized rosin, esterified rosin, and maleic acid-modified rosin;

[0022] In some embodiments, the terpene resin is selected from α-terpene resin, β-terpene resin, and terpene phenolic resin.

[0023] In some embodiments of the multilayer high-barrier film provided by the present invention, the polyglycolic acid has a weight-average molecular weight of 100,000 to 300,000 (e.g., 120,000, 150,000, 200,000, 250,000) and a melt index of 5.0 to 80 g / 10 min (e.g., 6.0 g / 10 min, 10.0 g / 10 min, 15 g / 10 min, 20 g / 10 min, 30 g / 10 min, 40 g / 10 min, 50 g / 10 min, 60 g / 10 min, 70 g / 10 min).

[0024] In a second aspect, a method for preparing the multilayer high-barrier film as described above is provided, comprising the following steps:

[0025] 1) The poly(butylene terephthalate) and inorganic filler (e.g., in a vacuum drying oven) are dried. Preferably, the drying process conditions include: time of 2-4 hours (e.g., 2.5 hours, 3 hours) and temperature of 30-50°C (e.g., 35°C, 40°C, 45°C).

[0026] Weigh out dried poly(butylene terephthalate) and inorganic filler, blend them, and then melt-extrude and granulate them through a twin-screw extruder to obtain the outer resin material.

[0027] 2) The polybutylene terephthalate / butylene adipate and the tackifying resin (e.g., in a vacuum drying oven) are dried. Preferably, the drying process conditions include: a time of 2-4 hours (e.g., 2.5 hours, 3 hours) and a temperature of 30-50°C (e.g., 35°C, 40°C, 45°C).

[0028] Weigh out dried poly(butylene terephthalate) and tackifying resin, blend them, and then melt-extrude and granulate them through a twin-screw extruder to obtain the adhesive layer resin material.

[0029] 3) The outer layer resin material, the adhesive layer resin material, and polyglycolic acid are co-extruded in multiple layers, and the resulting material is obtained by casting or blown film process to obtain the biodegradable multilayer high barrier film.

[0030] According to the preparation method of the present invention, in some embodiments, the adhesion strength of the multilayer high-barrier film is >1 N / cm (e.g., 1.5 N / cm, 2 N / cm, 4 N / cm, 8 N / cm, 10 N / cm), and the water vapor transmission rate is ≤10 g / (m²). 2 ·day), for example, 9g / (m 2 ·day), 5g / (m 2 ·day), 2g / (m 2 ·day), 1g / (m 2 ·day), 0.5g / (m2 ·day), 0.1g / (m 2 ·day), 0.05g / (m 2 ·day), 0.01g / (m 2 •day), oxygen permeability ≤3cm 3 / (m 2 (0.1 MPa, for example, 2.5 cm) 3 / (m 2 ·day·0.1MPa), 2cm 3 / (m 2 ·day·0.1MPa), 1.5cm 3 / (m 2 ·day·0.1MPa), 1.0cm 3 / (m 2 ·day·0.1MPa), 0.5cm 3 / (m 2 ·day·0.1MPa), 0.1cm 3 / (m 2 ·day·0.1MPa), 0.05cm 3 / (m 2 ·day·0.1MPa), 0.01cm 3 / (m 2 (day 0.1MPa).

[0031] According to the preparation method of the present invention, in some embodiments, the melt extrusion process conditions in step 1) include: the temperature of the extruder's conveying section is 130-160℃ (e.g., 140℃, 150℃), the temperature of the melting section is 160-190℃ (e.g., 170℃, 180℃), the temperature of the mixing section is 170-200℃ (e.g., 180℃, 190℃), the temperature of the venting section is 160-190℃ (e.g., 170℃, 180℃), and the temperature of the homogenization section is 150-180℃ (e.g., 160℃, 170℃); and the screw speed is 50-200 rpm (e.g., 60 rpm, 100 rpm, 150 rpm).

[0032] In some implementations, the melt extrusion process conditions described in step 2) include: the temperature of the extruder's conveying section is 130-160°C (e.g., 140°C, 150°C), the temperature of the melting section is 160-190°C (e.g., 170°C, 180°C), the temperature of the mixing section is 170-200°C (e.g., 180°C, 190°C), the temperature of the venting section is 160-190°C (e.g., 170°C, 180°C), and the temperature of the homogenization section is 140-170°C (e.g., 150°C, 160°C); and the screw speed is 50-200 rpm (e.g., 60 rpm, 100 rpm, 150 rpm).

[0033] In some implementations, the process conditions for multilayer co-extrusion in step 3) include:

[0034] The extrusion temperature of the outer layer is 180–220℃ (e.g., 185℃, 190℃, 200℃, 210℃); the extrusion temperature of the adhesive layer is 180–220℃ (e.g., 185℃, 190℃, 200℃, 210℃); the extrusion temperature of the barrier layer is 230–260℃ (e.g., 235℃, 240℃, 250℃, 255℃); and the die head temperature is 240–260℃ (e.g., 235℃, 240℃, 250℃, 255℃).

[0035] In a third aspect, the application of the multilayer high-barrier film as described above or the multilayer high-barrier film prepared by the method described above in the packaging field, especially in food, electronics, and pharmaceutical packaging.

[0036] In this invention, the outer layer is a blend of polybutylene terephthalate / adipate and inorganic filler, which can increase the crystallization temperature, accelerate crystallization, and effectively solve the problem of roller sticking.

[0037] Although PGA has excellent barrier properties and is an ideal material for improving the barrier performance of multilayer films, when pure PGA is used as the barrier layer in a multilayer film, there is often a problem of poor adhesion between pure PGA and other layer structures (such as PBAT). This is one of the technical obstacles that this invention aims to solve. In addition, PGA has a very high melting point, resulting in a large temperature difference between it and other tough biodegradable plastics in multilayer films. This leads to poor processing performance in co-extrusion. At the high processing temperature of PGA, other biodegradable resins are difficult to cool and crystallize, leading to roller sticking problems. This is also one of the problems that this application aims to solve by using pure PGA as the core layer to prepare multilayer high-barrier films.

[0038] Moreover, PGA has poor toughness, so it is necessary to select an outer layer with high toughness as a protective layer to improve the overall toughness of the film; and in order to maintain the fully biodegradable performance, the selection of the type of applicable outer layer material is crucial.

[0039] Compared to existing technologies, this invention, through its multilayer structure, employs a blend of PBAT and inorganic fillers in the outer layer. This improves the adhesion and rolling issues that occur in multilayer films at high processing temperatures, enhances the overall toughness of the multilayer film, and maintains its fully biodegradable properties. Furthermore, the adhesive layer, a blend of PBAT and tackifying resin, improves the adhesion between PBAT and PGA. While improving processability and the adhesion of pure PGA to other layers, the use of pure PGA in the barrier layer maintains the high barrier properties of the multilayer film. This invention, through multilayer co-extrusion technology, produces a high-barrier multilayer film with excellent processability, no delamination, and full biodegradability. Detailed Implementation

[0040] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0041] <Source of Raw Materials>

[0042] Polyglycolic acid, with a weight-average molecular weight of 130,000 and a melt index of 26 g / 10 min (240℃, 2.16 kg), was purchased from Shanghai Pujing Chemical Technology Co., Ltd.

[0043] Polybutylene terephthalate (PBAT), BASF C1200, purchased from BASF;

[0044] Talc (powder), 2500 mesh, purchased from Changzhou Rongao Chemical New Materials Co., Ltd.

[0045] Tackifying resin, terpene resin, purchased from Changzhou Jiatong Chemical Co., Ltd.

[0046] Other raw materials used in the examples and comparative examples are all commonly available commercial products, and will not be described in detail here.

[0047] Example 1

[0048] A method for preparing a biodegradable multilayer high-barrier film includes the following steps:

[0049] (1) Preparation of outer layer resin A1: PBAT and talc were dried in a vacuum drying oven at 50°C for 4 hours; 1000g of dried PBAT and 300g of talc were weighed and melt-extruded and granulated in a twin-screw extruder to obtain outer layer resin A1, wherein,

[0050] The conditions for melt extrusion are as follows: the temperature of the conveying section is 150℃, the temperature of the melting section is 190℃, the temperature of the mixing section is 190℃, the temperature of the exhaust section is 190℃, the temperature of the homogenization section is 170℃, and the screw speed is 100 rpm.

[0051] (2) Preparation of adhesive layer resin B1: 950g of dried PBAT and 50g of terpene resin were melt-extruded and granulated in a twin-screw extruder to obtain adhesive layer resin B1.

[0052] The conditions for melt extrusion are as follows: the temperature of the conveying section is 150℃, the temperature of the melting section is 190℃, the temperature of the mixing section is 190℃, the temperature of the exhaust section is 190℃, the temperature of the homogenization section is 170℃, and the screw speed is 100 rpm.

[0053] (3) Multilayer co-extrusion: Polyglycolic acid is added to the inner hopper, resin B1 is added to the core hopper, and resin A1 is added to the outer hopper. The mixture is co-extruded by three screw extruders (the working temperatures of the inner, core, and outer layers are 240-260℃, 190-210℃, and 190-210℃, respectively). The five layers (outer, middle, and inner) are co-extruded and cast into a film through a die, and then wound up. The die temperature is 240-260℃ and the roll temperature is 10-40℃. A biodegradable multilayer high-barrier film is obtained.

[0054] The thickness of the prepared multilayer high-barrier film is 150 μm; the thickness ratio of each layer is outer layer: adhesive layer: barrier layer = 1:1:1. The performance test results of the film are shown in Table 1.

[0055] Example 2

[0056] A method for preparing a biodegradable multilayer high-barrier film includes the following steps:

[0057] (1) Preparation of outer layer resin A1: Same as in Example 1;

[0058] (2) Preparation of adhesive layer resin B2: 900g of dried PBAT and 100g of terpene resin were melt-extruded and granulated in a twin-screw extruder to obtain adhesive layer resin B2.

[0059] The conditions for melt extrusion are as follows: the temperature of the conveying section is 150℃, the temperature of the melting section is 190℃, the temperature of the mixing section is 190℃, the temperature of the exhaust section is 190℃, the temperature of the homogenization section is 170℃, and the screw speed is 100 rpm.

[0060] (3) Multilayer co-extrusion: Polyglycolic acid is added to the inner hopper, resin B2 is added to the core hopper, and resin A1 is added to the outer hopper. The mixture is co-extruded by three screw extruders (the working temperatures of the inner, core, and outer layers are 240-260℃, 190-210℃, and 190-210℃, respectively). The five layers (outer, middle, and inner) are co-extruded and cast into a film through a die, and then wound up. The die temperature is 240-260℃ and the roll temperature is 10-40℃. A biodegradable multilayer high-barrier film is obtained.

[0061] The thickness of the prepared multilayer high-barrier film is 150 μm; the thickness ratio of each layer is outer layer: adhesive layer: barrier layer = 1:1:1. The performance test results of the film are shown in Table 1.

[0062] Example 3

[0063] A method for preparing a biodegradable multilayer high-barrier film includes the following steps:

[0064] (1) Preparation of outer layer resin A2: PBAT and SiO2 were dried in a vacuum drying oven at 50°C for 4 hours; 1000g of dried PBAT and 200g of SiO2 were weighed and melt-extruded and granulated in a twin-screw extruder to obtain outer layer resin A2; wherein,

[0065] The conditions for melt extrusion are as follows: the temperature of the conveying section is 150℃, the temperature of the melting section is 190℃, the temperature of the mixing section is 190℃, the temperature of the exhaust section is 190℃, the temperature of the homogenization section is 170℃, and the screw speed is 100 rpm.

[0066] (2) Preparation of adhesive layer resin B1: Same as in Example 1;

[0067] (3) Multilayer co-extrusion: The process conditions and operating steps are the same as those in step (3) of Example 1.

[0068] The thickness of the prepared multilayer high-barrier film is 150 μm; the thickness ratio of each layer is outer layer: adhesive layer: barrier layer = 1:1:1. The performance test results of the film are shown in Table 1.

[0069] Example 4

[0070] A method for preparing a biodegradable multilayer high-barrier film includes the following steps:

[0071] (1) Preparation of outer layer resin A3: Refer to Example 1, except that 1000g of dried PBAT and 60g of talc are weighed and melt-extruded and granulated in a twin-screw extruder to obtain outer layer resin A3.

[0072] (2) Preparation of adhesive layer resin B2: Same as in Example 2;

[0073] (3) Multilayer co-extrusion: Polyglycolic acid is added to the inner hopper, resin B2 is added to the core hopper, and resin A3 is added to the outer hopper. The mixture is co-extruded by three screw extruders (the working temperatures of the inner, core, and outer layers are 240-260℃, 190-210℃, and 190-210℃, respectively). The five layers (outer, middle, and inner) are co-extruded and cast into a film through a die, and then wound up. The die temperature is 240-260℃ and the roll temperature is 10-40℃. A biodegradable multilayer high-barrier film is obtained.

[0074] The thickness of the prepared multilayer high-barrier film is 150 μm; the thickness ratio of each layer is outer layer: adhesive layer: barrier layer = 1:1:1. The performance test results of the film are shown in Table 1.

[0075] Comparative Example 1

[0076] The method for preparing multilayer thin films includes the following steps:

[0077] Polyglycolic acid is added to the inner hopper, PBAT is added to the core hopper, and PBAT is added to the outer hopper. The mixture is then co-extruded using three screw extruders (the inner, core, and outer layers operate at temperatures of 240–260°C, 190–210°C, and 190–210°C, respectively). The resulting five layers (outer, middle, and inner) are co-extruded and cast into a film through a die, then wound up. The die temperature is 240–260°C, and the roll temperature is 10–40°C, thus producing a multilayer film.

[0078] The thickness of the prepared multilayer film was 150 μm; the thickness ratio of each layer was 1:1:1 for the outer layer, adhesive layer, and barrier layer. The performance of the film is shown in Table 1.

[0079] Comparative Example 2

[0080] The method for preparing multilayer thin films includes the following steps:

[0081] PBAT is added to the inner hopper, the core hopper, and the outer hopper. The mixture is then co-extruded using three screw extruders (with operating temperatures of 190–210°C for the inner, core, and outer layers, respectively). The resulting five layers (outer, middle, and inner) are co-extruded and cast into a film using a die, which is then wound up. The die temperature is 190–210°C, and the roll temperature is 10–40°C.

[0082] The thickness of the prepared multilayer film was 100 μm; the thickness ratio of each layer was 1:1:1 for the outer layer, adhesive layer, and barrier layer. The performance of the film is shown in Table 1.

[0083] The multilayer thin film structures obtained in the above embodiments and comparative examples can be schematically represented as: A / B / C / B / A.

[0084] Test method:

[0085] (1) Melt index, measured according to GB / T 3682-2000 method;

[0086] (2) Water vapor transmission rate, measured according to the method of GB / T 30412-2013;

[0087] (3) Oxygen permeability, measured according to GB / T 1038-2000 method;

[0088] (4) Peel strength test, measured according to GBT2792-2014 method;

[0089] (5) Testing and judgment criteria for processability: Excellent, good, and poor processability means that "excellent" means that the processability is based on the condition that the roller does not stick and continuous production is possible; "good" means that the processability is based on the condition that the roller sticks slightly and continuous production is possible; and "poor" means that the processability is based on the condition that the roller sticks and continuous production is not possible.

[0090] Table 1. Performance test results of the multilayer thin films prepared in each embodiment and comparative example.

[0091]

[0092] The test results in Table 1 show that, comparing Examples 1-4 with Comparative Example 2, using composite PGA as a barrier layer in the multilayer film can significantly improve the barrier performance of the film. Comparing Examples 1-4 with Comparative Example 1, selecting appropriate components as the adhesive layer and appropriate components as the outer layer in the multilayer film can improve the adhesion problem and processability of the multilayer barrier film. Examples 1-4 show that changing the content of the tackifying resin and the type and content of inorganic fillers can control the peel strength and processability of the multilayer film.

[0093] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A biodegradable multilayer high-barrier film, characterized in that, The multilayer high-barrier film comprises: an outer layer / adhesive layer / barrier layer / adhesive layer / outer layer arranged in sequence; wherein... The outer layer is a blend of polybutylene terephthalate / adipate and inorganic filler I; The adhesive layer is a blend of polybutylene terephthalate / adipate and tackifying resin II; The barrier layer is polyglycolic acid; In the blend I of polybutylene terephthalate (PET) and inorganic filler, the content of PET is 60wt%~95wt% and the content of inorganic filler is 5wt%~40wt% based on the total weight of blend I. The inorganic filler is selected from one or more of SiO2, calcium carbonate, montmorillonite and talc; The multilayer high-barrier film is prepared by multilayer co-extrusion technology.

2. The multilayer high-barrier film according to claim 1, characterized in that, The thickness of the multilayer high-barrier film is 50-300 μm.

3. The multilayer high-barrier film according to claim 1, characterized in that, The thickness ratio of each layer in the multilayer high-barrier film is from 2:2:1 to 1:1:2, where the outer layer is the adhesive layer and the barrier layer is the barrier layer.

4. The multilayer high-barrier film according to claim 1, characterized in that, In the blend II of poly(butylene terephthalate) and tackifying resin, the content of poly(butylene terephthalate) is 80wt%~95wt% and the content of tackifying resin is 5wt%~20wt% based on the total weight of blend II.

5. The multilayer high-barrier film according to claim 1, characterized in that, The tackifying resin is a natural series resin.

6. The multilayer high-barrier film according to claim 5, characterized in that, The natural series resins are selected from one or more of rosin, rosin derivatives, and terpene resins.

7. The multilayer high-barrier film according to claim 1, characterized in that, The polyglycolic acid has a weight-average molecular weight of 100,000 to 300,000 and a melt index of 5.0 to 80 g / 10 min.

8. The method for preparing a multilayer high-barrier film according to any one of claims 1-7, characterized in that, Includes the following steps: 1) Dry the polybutylene terephthalate / butylene adipate and inorganic filler; Weigh out dried poly(butylene terephthalate) and inorganic filler, blend them, and then melt-extrude and granulate them through a twin-screw extruder to obtain the outer resin material. 2) Dry the polybutylene terephthalate / adipate and the tackifying resin; Weigh out dried poly(butylene terephthalate) and tackifying resin, blend them, and then melt-extrude and granulate them through a twin-screw extruder to obtain the adhesive layer resin material. 3) The outer layer resin material, the adhesive layer resin material, and polyglycolic acid are co-extruded in multiple layers, and then subjected to casting or blown film processes to obtain the biodegradable multilayer high-barrier film.

9. The preparation method according to claim 8, characterized in that, The adhesion strength of the multilayer high-barrier film is >1 N / cm, and the water vapor permeability is ≤10 g / (m²). 2 (day), oxygen permeability ≤3 cm 3 / (m 2 ·day·0.1MPa).

10. The preparation method according to claim 8, characterized in that, The melt extrusion process conditions described in step 1) include: the temperature of the extruder's conveying section is 130-160℃, the temperature of the melting section is 160-190℃, the temperature of the mixing section is 170-200℃, the temperature of the venting section is 160-190℃, and the temperature of the homogenizing section is 150-180℃; the screw speed is 50-200 rpm; and / or The melt extrusion process conditions described in step 2) include: the temperature of the extruder's conveying section is 130-160℃, the temperature of the melting section is 160-190℃, the temperature of the mixing section is 170-200℃, the temperature of the venting section is 160-190℃, the temperature of the homogenizing section is 140-170℃, and the screw speed is 50-200 rpm.

11. The preparation method according to claim 8, characterized in that, The process conditions for multilayer co-extrusion mentioned in step 3) include: The extrusion temperature of the outer layer is 180~220℃; the extrusion temperature of the adhesive layer is 180~220℃; the extrusion temperature of the barrier layer is 230~260℃; and the die head temperature is 240~260℃.

12. The application of the multilayer high-barrier film as described in any one of claims 1-7 or the multilayer high-barrier film prepared by the preparation method as described in any one of claims 8-11 in the packaging field.

13. The application according to claim 12, characterized in that, The multilayer high-barrier film is used in food, electronics, and pharmaceutical packaging.

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