Degradable high barrier film and method of making the same

Abstract

This invention discloses a biodegradable high-barrier membrane and its preparation method, relating to the field of barrier membrane technology. The invention first prepares a biodegradable film layer through a three-layer co-extrusion blow molding process, and then obtains a biodegradable high-barrier membrane by electron beam vacuum evaporation of silicon oxide and coating a protective layer, with a water vapor permeability of <0.5 g / (m²). 2 • day), oxygen permeability < 0.5 cm 3 / (m 2 It has high barrier properties (0.1 MPa), good biodegradability, and can meet the packaging material requirements of the food, medical and other industries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of barrier film, in particular to a degradable high-barrier film and a preparation method thereof. BACKGROUND

[0002] Under the background of global "double carbon" target promotion and increasing awareness of ecological environment protection, the "white pollution" problem caused by traditional non-degradable plastic products has become a key bottleneck restricting the sustainable development of the packaging industry. At the same time, as the main raw material of traditional plastics, petroleum resources are becoming increasingly depleted and the cost of exploitation continues to rise, further promoting the research and application demand of degradable high molecular materials in the industry.

[0003] As one of the most widely used fully biodegradable materials, polylactic acid (PLA) has shown great potential in packaging, medical and other fields due to its excellent biocompatibility, transparency and mechanical strength. Under industrial composting conditions, PLA can be completely degraded into water and carbon dioxide, and the degradation products are non-toxic to the environment. However, the presence of a large number of polar groups in the molecular chain structure of PLA results in poor barrier properties for small molecules such as water vapor and oxygen, which cannot meet the stringent requirements of food preservation (such as meat, baked food requires oxygen transmission rate <5 cm 3 / (m 2 ·day·0.1MPa))、medical sterile packaging (requires moisture permeability <1 g / (m 2 ·day))and other scenarios. In addition, PLA has a high glass transition temperature, and is brittle and hard at low temperatures, with poor impact resistance, which limits its independent application.

[0004] As another mainstream degradable elastomer material, poly (butylene adipate-co-terephthalate) (PBAT) has strong molecular chain segment flexibility and a glass transition temperature lower than room temperature, which can effectively improve the brittleness of PLA. In the prior art, researchers can significantly optimize the toughness of the blended material by blending PLA with PBAT. However, due to the thermodynamic incompatibility of the two materials, the blended system is prone to phase separation, resulting in the formation of a large number of micropores inside the film material, which not only does not improve the barrier properties, but also further increases the moisture and oxygen permeability of the PBAT / PLA blended film. At the same time, PBAT itself has weak barrier properties, and the blending of the two still cannot break through the bottleneck of high barrier properties.

[0005] To solve the problem of barrier property of degradable film, the industry has tried coating modification, inorganic nanoparticle filling and other methods. For example, coating polyvinyl alcohol (PVA) coating on the surface of the film can reduce the oxygen permeation rate, but PVA has poor water resistance and is easy to swell and fail when it comes into contact with water; adding montmorillonite, silicon dioxide and other nanoparticles for filling requires a higher addition amount to slightly improve the barrier property, but it will cause the transparency of the film material to decrease and the processing fluidity to become poor. In addition, some high-barrier packaging materials use a composite structure of "degradable substrate + metal foil layer", which can achieve very low moisture and oxygen permeability, but the metal foil cannot be degraded and will still cause secondary pollution after being discarded, which does not meet the environmental protection requirements of the whole life cycle.

[0006] In summary, the existing degradable film material has problems such as low barrier property and poor environmental protection, and it is urgent to develop a film preparation technology with high barrier property and full degradability to fill the gap in the demand for degradable high-barrier materials in the fields of food, medical and other high-end packaging. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a degradable high-barrier film and a preparation method thereof to solve the problem of poor water vapor and oxygen barrier performance of PBAT / PLA blended film in the prior art.

[0008] The technical scheme of the present application is as follows:

[0009] On the one hand, the present application provides a preparation method of a degradable high-barrier film, comprising the following steps:

[0010] S1. Preparing a degradable film layer: preparing a degradable film layer by three-layer co-extrusion and blow molding; wherein the outer layer of the degradable film layer is composed of 90-95% PBAT, 2-5% additives and 2-6% chitosan; the middle layer is composed of 88-93% PBAT, 2-6% additives and 2-6% chitosan; and the inner layer is composed of 60-80% PLA and 20-40% PBAT;

[0011] S2. Electron beam vacuum evaporation of silicon oxide:

[0012] S2.1. Mounting the degradable film layer to the unwinding roller of the vacuum electron beam coating machine;

[0013] S2.2. Closing the vacuum chamber, vacuumizing, starting the coating cooling steel roller and the servo motor for unwinding and winding;

[0014] S2.3. After the degradable film layer rotates through the guide roller, starting the argon ion wind to clean and activate the surface of the degradable film layer, which is conducive to the adhesion of the subsequent coating layer;

[0015] S2.4 Activating with oxygen to introduce -OH, -COOH polar groups on the surface of the degradable film layer;

[0016] S2.5 Spraying silane coupling agent to the surface of the degradable film layer by a vacuum spraying device, and grafting reaction occurs at the plasma activated sites to form chemical bond linkage of "substrate-silane coupling agent-silicon oxide" with the subsequent silicon oxide evaporation barrier layer, which can enhance the adhesion of the coating layer;

[0017] S2.6 Guiding the degradable film layer through a guide roller into an evaporation steel roller to further activate the degradable film layer and assist the subsequent silicon oxide vapor deposition;

[0018] S2.7 Adjusting the position and power of the electron gun spot, and using electron beam to bombard the silicon oxide target to deposit the silicon oxide evaporation barrier layer by evaporation sublimation;

[0019] S2.8 Introducing nitrogen and using plasma to bombard the silicon oxide evaporation barrier layer to rearrange the atoms of the silicon oxide evaporation barrier layer and reduce the porosity;

[0020] S2.9 Rolling up the degradable film layer with the silicon oxide evaporation barrier layer after passing through the synchronous guide roller, releasing the vacuum, and unrolling and packaging;

[0021] S3 Coating a protective layer on the surface of the silicon oxide evaporation barrier layer, and after solidification and molding, a degradable high-barrier film is obtained; the protective layer is composed of the following components in mass percentage: 3-20% polyurethane, 1-2% ethanol, 0.5-1% water-based film forming agent, and the rest is deionized water.

[0022] Preferably, in step S1, the auxiliary agent is an antioxidant; and the thickness of the degradable film layer prepared in step S1 is 32-60 μm.

[0023] Preferably, in step S2.2, the vacuum is drawn to 4x10 -3 ~6x10 -3 Pa; the linear speed of the servo motor is 250-400 m / min, and the tension is 0.6-1.7 kg.

[0024] Preferably, in step S2.3, the argon ion wind has an argon flow rate of 100-500 SCCM, a direct current power of 600-900 V, and a cleaning and activating time of 5-15 s.

[0025] Preferably, in step S2.4, the oxygen flow rate is 300-600 SCCM, the direct current power is 200-500 V, and the activating time is 5-10 s.

[0026] Preferably, in step S2.5, the concentration of the silane coupling agent is 0.5-2 wt.%, and the spraying thickness is 0.5-1 μm.

[0027] Preferably, in step S2.6, the temperature of the vapor-deposited steel roller is 40~60℃.

[0028] Preferably, in step S2.7, an electron gun is used to emit an electron beam to bombard the silicon oxide target. The electron gun operates at a voltage of 6-10 kV. After preheating for 3-5 minutes, the filament current is adjusted to 1-1.8 mA, and the beam current is adjusted to 400-600 A. The rate of silicon oxide evaporation and sublimation is 3-6 nm / s, and the thickness of the silicon oxide barrier layer is 30-80 nm. The electron beam emitted by the filament is deflected and focused, irradiating the silicon oxide. Under the thermal energy of the electron beam, the silicon oxide rapidly sublimates, and silicon oxide atomic gas is deposited and adhered to the relatively low-temperature biodegradable film layer.

[0029] Preferably, in step S2.8, the nitrogen flow rate is 200~500 SCCM; the plasma frequency is 40~70 kHz; the power is 80~120 W; and the silicon oxide vapor-deposited barrier layer is bombarded for 3~5 seconds. In step S3, a protective layer is coated using a microgravure coating method, with a coating amount of 3~5 g / m². 2 The coating thickness is 1~2μm, and the barrier properties and abrasion resistance of the film are further improved after treatment.

[0030] On the other hand, the present invention provides a biodegradable high-barrier membrane, which is prepared by the above-described method for preparing a biodegradable high-barrier membrane.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] 1. This invention achieves a significant improvement in the barrier performance of biodegradable membranes through a three-layer synergistic structure design of "biodegradable substrate optimization - silica vapor deposition barrier - protective layer coating," combined with a multi-step surface modification process. Specifically, in the PBAT / PLA / chitosan three-layer co-extruded substrate, the amino and hydroxyl groups on the chitosan molecular chain can form hydrogen bonds with PBAT and PLA, reducing phase separation porosity and initially lowering membrane permeability. The electron beam vacuum vapor-deposited silica barrier layer is a dense inorganic film with tightly packed atoms, effectively blocking the permeation paths of water and oxygen molecules, resulting in a substantial decrease in membrane moisture and oxygen permeability. Subsequent plasma bombardment further eliminates pinhole defects in the silica vapor-deposited barrier layer, increasing coating density, and ultimately achieving a water vapor permeability of <0.5 g / (m²). 2 • day), oxygen permeability < 0.5 cm 3 / (m 2 With a pressure of 0.1 MPa per day, it not only meets the needs of ordinary food preservation, but is also suitable for high-end scenarios that are sensitive to water and oxygen, filling the gap in the application of biodegradable materials in the field of high-barrier packaging.

[0033] 2. The substrate of the biodegradable high-barrier membrane of the present invention uses three fully biodegradable components: PBAT, PLA, and chitosan. Among them, PBAT and PLA have a biodegradation rate of over 90% under industrial composting conditions in 90 days. Chitosan, as a natural polysaccharide, can be completely decomposed by microorganisms into small molecule organic matter without environmental residue. After the product is disposed of, whether it is naturally composted or industrially degraded, it will not produce microplastic or heavy metal pollution, providing a practical and feasible technical solution to the problem of "white pollution".

[0034] 3. Addressing the industry pain points of "easy detachment of the barrier layer and poor mechanical properties" in biodegradable films, this invention achieves dual protection of structure and performance through multi-process synergy: Argon ion air cleaning removes oil, dust, and other impurities from the surface of the biodegradable film, improving surface roughness and providing a good substrate for subsequent coating adhesion; Oxygen activation introduces a large number of -OH and -COOH polar groups on the surface of the biodegradable film, forming chemical bonds with the amino groups of the silane coupling agent to construct a strong bonding interface of "substrate-silane coupling agent-silica", improving the adhesion of the silica vapor-deposited barrier layer; Plasma bombardment rearranges silica atoms, reducing internal stress in the coating and preventing coating cracking when the film is bent; The final coated protective layer not only improves the wear resistance of the film but also forms an organic-inorganic composite protective system with the silica vapor-deposited barrier layer, balancing high barrier properties and excellent mechanical durability, meeting the mechanical requirements of packaging processing (such as bag making and heat sealing) and transportation. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention.

[0036] Example 1

[0037] The method for preparing the biodegradable high-barrier membrane in this embodiment includes the following steps:

[0038] S1 Preparation of biodegradable film layer

[0039] The raw materials for the biodegradable film are placed in different raw material bins and stirred until homogeneous using a high-speed mixer. After extrusion using a single-screw extruder, the mixture is blow-molded using a blow molding machine to obtain the biodegradable film. The outer layer of the biodegradable film consists of 93% PBAT, 3% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 4% chitosan; the middle layer consists of 90% PBAT, 5% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 5% chitosan; and the inner layer consists of 70% PLA and 30% PBAT.

[0040] The processing temperatures from the outer feed inlet to the die of the single-screw extruder are 175℃, 185℃, 185℃, 190℃, 195℃, and 165℃, respectively; the processing temperatures from the middle feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 160℃, respectively; the processing temperatures from the inner feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 170℃, respectively; the temperatures in the blow molding machine are 170℃, 180℃, and 190℃, respectively; and the traction speed is 7 m / min.

[0041] The outer layer of the biodegradable membrane has a thickness of 10 μm, the middle layer has a thickness of 15 μm, and the inner layer has a thickness of 35 μm.

[0042] S2 electron beam vacuum evaporation of silicon dioxide

[0043] S2.1 Install the biodegradable film layer onto the unwinding roller of the vacuum electron beam coating machine;

[0044] S2.2 Close the vacuum chamber and evacuate to 6×10⁻⁶. -3 After Pa, start the coating cooling steel roller and the servo motor for winding and unwinding. The linear speed of the servo motor is 250m / min and the tension is 0.6kg.

[0045] After the S2.3 biodegradable film rotates and is guided by the guide roller, an electron beam coating system is used to start argon ion air cleaning and activation. The argon flow rate is 100 SCCM, the DC power supply is 600V, and the cleaning and activation time is 5s.

[0046] S2.4 is activated using oxygen at a flow rate of 300 SCCM, a DC power supply of 200V, and an activation time of 5s.

[0047] S2.5 uses a vacuum spraying device to atomize and spray 0.5 wt.% silane coupling agent (MP200) onto the surface of the biodegradable film layer, with a spraying thickness of 0.5 μm;

[0048] The S2.6 biodegradable film layer is guided by the guide roller into the vapor deposition steel roller to further activate the biodegradable film layer. The temperature of the vapor deposition steel roller is 40℃.

[0049] S2.7 Adjust the electron gun spot position and electron gun power, and use the electron beam to bombard the silicon oxide target. The silicon oxide evaporates and sublimates to deposit a film, forming a silicon oxide vapor-deposited barrier layer. The electron gun operates at 6kV. After preheating for 3 minutes, the filament current is adjusted to 1mA and the beam current is adjusted to 400A. The silicon oxide evaporation and sublimation rate is 3nm / s, and the thickness of the silicon oxide vapor-deposited barrier layer is 30nm. The thickness of the silicon oxide vapor-deposited barrier layer is automatically detected using a JYK film thickness controller (Chengdu Jinyake Electric Co., Ltd.).

[0050] S2.8 Nitrogen gas is introduced at a flow rate of 200 SCCM. The silicon oxide vapor-deposited barrier layer is bombarded with plasma for 3 seconds at a plasma frequency of 40 kHz and a power of 80 W.

[0051] S2.9 The biodegradable film layer with silicon oxide vapor-deposited barrier layer enters the synchronous guide roller, is wound up, the vacuum is released, and the roll is unwound and packaged. The tension of the synchronous guide roller is 5kg.

[0052] S3 Protective Coating: A protective layer is applied to the surface of the silicon oxide vapor-deposited barrier layer using a micro-gravure coating method, with a coating amount of 3 g / m². 2 The coating thickness is 1μm. After curing, a biodegradable high-barrier film is obtained. The protective layer is composed of the following components by mass percentage: 10% polyurethane, 1% ethanol, 0.5% aqueous film-forming agent, and the remainder is deionized water.

[0053] Example 2

[0054] The method for preparing the biodegradable high-barrier membrane in this embodiment includes the following steps:

[0055] S1 Preparation of biodegradable film layer

[0056] The raw materials for the biodegradable film are placed in different raw material bins and stirred until homogeneous using a high-speed mixer. After extrusion using a single-screw extruder, the mixture is blow-molded using a blow molding machine to obtain the biodegradable film. The outer layer of the biodegradable film consists of 90% PBAT, 5% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 5% chitosan; the middle layer consists of 88% PBAT, 6% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 6% chitosan; and the inner layer consists of 60% PLA and 40% PBAT.

[0057] The processing temperatures from the outer feed inlet to the die of the single-screw extruder are 175℃, 185℃, 185℃, 190℃, 195℃, and 165℃, respectively; the processing temperatures from the middle feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 160℃, respectively; the processing temperatures from the inner feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 170℃, respectively; the temperatures in the blow molding machine are 170℃, 180℃, and 190℃, respectively; and the traction speed is 7 m / min.

[0058] The outer layer of the biodegradable membrane has a thickness of 5 μm, the middle layer has a thickness of 8 μm, and the inner layer has a thickness of 19 μm.

[0059] S2 electron beam vacuum evaporation of silicon dioxide

[0060] S2.1 Install the biodegradable film layer onto the unwinding roller of the vacuum electron beam coating machine;

[0061] S2.2 Close the vacuum chamber and evacuate to 4×10⁻⁶. -3 After Pa, start the coating cooling steel roller and the servo motor for winding and unwinding. The linear speed of the servo motor is 325m / min and the tension is 1.1kg.

[0062] After the S2.3 biodegradable film rotates and is guided by the guide roller, an electron beam coating system is used to start argon ion air cleaning and activation. The argon flow rate is 300 SCCM, the DC power supply is 750V, and the cleaning and activation time is 10s.

[0063] S2.4 is activated using oxygen at a flow rate of 450 SCCM, a DC power supply of 350 V, and an activation time of 8 s.

[0064] S2.5 uses a vacuum spraying device to atomize and spray 1 wt.% of silane coupling agent (MP200) onto the surface of the biodegradable film layer, with a spraying thickness of 0.7 μm;

[0065] The S2.6 biodegradable film layer is guided by the guide roller into the vapor deposition steel roller to further activate the biodegradable film layer. The temperature of the vapor deposition steel roller is 50℃.

[0066] S2.7 Adjust the electron gun spot position and power, and bombard the silicon oxide target with an electron beam. The silicon oxide evaporates and sublimates to deposit a silicon oxide barrier layer. The electron gun operates at 8kV. After preheating for 4 minutes, the filament current is adjusted to 1.4mA and the beam current to 500A. The silicon oxide evaporation and sublimation rate is 4.5nm / s, and the thickness of the silicon oxide barrier layer is 55nm. The silicon oxide target is a multi-component product modified with epoxy silicone resin, with epoxy silicone resin accounting for 3.6% by mass. The target sintering temperature is 260℃. The thickness of the silicon oxide barrier layer is automatically detected using a JYK film thickness controller (Chengdu Jinyake Electric Co., Ltd.). The crystal frequency is 10MHz, and the fundamental frequency drops to 500kHz during the deposition process.

[0067] S2.8 Nitrogen gas is introduced at a flow rate of 350 SCCM. The silicon oxide vapor-deposited barrier layer is bombarded with plasma for 4 seconds at a plasma frequency of 55 kHz and a power of 100 W.

[0068] S2.9 The biodegradable film layer with silicon oxide vapor-deposited barrier layer enters the synchronous guide roller, is wound up, the vacuum is released, and the roll is unwound and packaged. The tension of the synchronous guide roller is 10kg.

[0069] S3 Protective Coating: A protective layer is applied to the surface of the silicon oxide vapor-deposited barrier layer using a micro-gravure coating method, with a coating amount of 4 g / m². 2The coating thickness is 1.5μm. After curing, a biodegradable high-barrier film is obtained. The protective layer is composed of the following components by mass percentage: 3% polyurethane, 2% ethanol, 1% aqueous film-forming agent, and the remainder is deionized water.

[0070] Example 3

[0071] The method for preparing the biodegradable high-barrier membrane in this embodiment includes the following steps:

[0072] S1 Preparation of biodegradable film layer

[0073] The raw materials for the biodegradable film are placed in different raw material bins and stirred until homogeneous using a high-speed mixer. After extrusion through a single-screw extruder, the film is blow-molded using a blow molding machine to obtain the biodegradable film. The outer layer of the biodegradable film consists of 95% PBAT, 2% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 3% chitosan; the middle layer consists of 93% PBAT, 2% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a 4:1 mass ratio), and 5% chitosan; and the inner layer consists of 80% PLA and 20% PBAT.

[0074] The processing temperatures from the outer feed inlet to the die of the single-screw extruder are 175℃, 185℃, 185℃, 190℃, 195℃, and 165℃, respectively; the processing temperatures from the middle feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 160℃, respectively; the processing temperatures from the inner feed inlet to the die of the single-screw extruder are 150℃, 160℃, 160℃, 170℃, 170℃, and 170℃, respectively; the temperatures in the blow molding machine are 170℃, 180℃, and 190℃, respectively; and the traction speed is 7 m / min.

[0075] The outer layer of the biodegradable membrane has a thickness of 6 μm, the middle layer has a thickness of 8 μm, and the inner layer has a thickness of 30 μm.

[0076] S2 electron beam vacuum evaporation of silicon dioxide

[0077] S2.1 Install the biodegradable film layer onto the unwinding roller of the vacuum electron beam coating machine;

[0078] S2.2 Close the vacuum chamber and evacuate to 5×10⁻⁶. -3 After Pa, start the coating cooling steel roller and the servo motor for winding and unwinding. The linear speed of the servo motor is 400m / min and the tension is 1.7kg.

[0079] After the S2.3 biodegradable film rotates and is guided by the guide roller, an electron beam coating system is used to start argon ion air cleaning and activation. The argon flow rate is 500 SCCM, the DC power supply is 900V, and the cleaning and activation time is 15s.

[0080] S2.4 is activated using oxygen at a flow rate of 600 SCCM, a DC power supply of 500V, and an activation time of 10s.

[0081] S2.5 uses a vacuum spraying device to atomize and spray 2 wt.% of silane coupling agent (MP200) onto the surface of the biodegradable film layer, with a spraying thickness of 1 μm;

[0082] The S2.6 biodegradable film layer is guided by the guide roller into the vapor deposition steel roller to further activate the biodegradable film layer. The temperature of the vapor deposition steel roller is 60℃.

[0083] S2.7 Adjust the electron gun spot position and power, and bombard the silicon oxide target with an electron beam. The silicon oxide evaporates and sublimates to deposit a silicon oxide barrier layer. The electron gun operates at 10kV. After preheating for 5 minutes, the filament current is adjusted to 1.8mA and the beam current is adjusted to 600A. The silicon oxide evaporation and sublimation rate is 6nm / s, and the thickness of the silicon oxide barrier layer is 80nm. The silicon oxide target is a multi-component product modified with epoxy silicone resin, with epoxy silicone resin accounting for 3.6% by mass. The target sintering temperature is 300℃. The thickness of the silicon oxide barrier layer is automatically detected using a JYK film thickness controller (Chengdu Jinyake Electric Co., Ltd.). The crystal frequency is 12MHz, and the fundamental frequency drops to 600kHz during the deposition process.

[0084] S2.8 Nitrogen gas is introduced at a flow rate of 500 SCCM. The silicon oxide vapor-deposited barrier layer is bombarded with plasma for 5 seconds at a plasma frequency of 70 kHz and a power of 120 W.

[0085] S2.9 The biodegradable film layer with silicon oxide vapor-deposited barrier layer enters the synchronous guide roller, is wound up, the vacuum is released, and the roll is unwound and packaged. The tension of the synchronous guide roller is 20kg.

[0086] S3 Protective Coating: A protective layer is applied to the surface of the silicon oxide vapor-deposited barrier layer using a micro-gravure coating method, with a coating amount of 5 g / m². 2 The coating thickness is 2μm. After curing, a biodegradable high-barrier film is obtained. The protective layer is composed of the following components by mass percentage: 20% polyurethane, 2% ethanol, 1% aqueous film-forming agent, and the remainder is deionized water.

[0087] Comparative Example 1

[0088] The difference from Example 1 is that step S2.3 is not performed.

[0089] Comparative Example 2

[0090] The difference from Example 1 is that step S2.4 is not performed.

[0091] Comparative Example 3

[0092] The difference from Example 1 is that step S2.5 is not performed.

[0093] Comparative Example 4

[0094] The difference from Example 1 is that step S2.6 is not performed.

[0095] Comparative Example 5

[0096] The difference from Example 1 is that step S2.8 is not performed.

[0097] Comparative Example 6

[0098] The difference from Example 1 is that step S3 is not performed.

[0099] Comparative Example 7

[0100] The difference from Example 1 is that in step S1, the outer layer of the biodegradable membrane is composed of 97% PBAT and 3% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 4:1); the middle layer is composed of 95% PBAT and 5% antioxidant (antioxidant 1010 and antioxidant 168 are compounded in a mass ratio of 4:1).

[0101] The performance of the biodegradable films prepared in Examples 1-3 and Comparative Examples 1-7 was tested using the following methods:

[0102] Water vapor transmission rate: Determined according to the first method, weight gain method, second method or third method in General Chapter 4010 of Part IV of the Chinese Pharmacopoeia 2025 edition, "Determination of Water Vapor Transmission Rate of Pharmaceutical Packaging Materials".

[0103] Oxygen permeability: Determined according to Method I or Method II in General Chapter 4007 of Part IV of the Chinese Pharmacopoeia 2025, "Determination of Gas Permeability of Pharmaceutical Packaging Materials".

[0104] Biodegradation rate: determined in accordance with GB / T 19277.1 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions by means of determination of carbon dioxide released - Part 1: General method".

[0105] The test results are shown in Table 1:

[0106] Table 1 Performance test results of the biodegradable membranes prepared in Examples 1-3 and Comparative Examples 1-7

[0107]

[0108] As can be seen from the test data in Table 1, the water vapor and oxygen permeability of Examples 1-3 are superior to those of Comparative Examples 1-7. This demonstrates that the present invention, through argon ion cleaning and activation, oxygen activation, spraying of silane coupling agent, heating of the evaporating steel roller to further activate the biodegradable film layer, plasma bombardment, surface coating process, and the addition of chitosan to the outer and middle layers, can effectively improve the barrier performance and biodegradability of the biodegradable high-barrier membrane. The water vapor permeability of the biodegradable high-barrier membranes prepared in Examples 1-3 is <0.5 g / (m²). 2 • day), oxygen permeability < 0.5 cm 3 / (m 2 The pressure (0.1 MPa per day) meets the packaging requirements for pharmaceuticals sensitive to water and oxygen. The reasons are analyzed below:

[0109] Argon ion cleaning and activation before vapor deposition achieves the dual effect of removing surface contaminants and introducing active sites, enhancing the subsequent oxygen activation process. Oxygen activation before silicon oxide vapor deposition forms numerous highly reactive oxygen-containing groups on the biodegradable film surface, enabling the subsequent silane coupling agent to form chemical bonds with the biodegradable film, thus strengthening the adhesion. The silane coupling agent, with an inorganic affinity group at one end and an organic affinity group at the other, enhances the adhesion between silicon oxide and the biodegradable film, increases coating density, and helps improve the barrier properties of the biodegradable film. Heating the vapor deposition steel roller raises the substrate surface temperature, causing adsorbed water vapor and impurities to rapidly desorb and volatilize, further cleaning the substrate surface. Simultaneously, the increased temperature activates the molecular chain mobility on the substrate surface, breaking some weak chemical bonds and forming active sites, which facilitates the bonding of silicon oxide particles with the substrate, significantly improving the adhesion between the coating and the substrate. Nitrogen ion bombardment of the silicon oxide coating surface provides controllable micro-etching and densification, filling defects such as pinholes and microcracks formed during coating deposition and reducing gas and water vapor penetration. Simultaneously, it increases the surface roughness of the coating, providing surface energy for subsequent protective layer application. A polyurethane coating provides a protective layer and improves wear resistance. Furthermore, the polyurethane coating can combine with silicon oxide, creating a high-performance organic-inorganic composite protective system through multi-dimensional effects of "wear resistance protection, defect filling, interfacial synergy, and performance enhancement." Chitosan, a natural cationic polysaccharide, is rich in polar groups such as -OH and -NH2 on its molecular chain. Chitosan molecules readily form hydrogen bond networks, filling the intermolecular gaps in PLA / PBAT substrates and reducing gas and water vapor penetration channels. Especially in high-humidity environments, the hygroscopic and swelling properties of chitosan further seal pores, helping to address the sharp decline in barrier performance of biodegradable membranes under high humidity conditions.

[0110] Comparative Example 1 lacked the argon ion air cleaning and activation steps, resulting in decreased barrier properties. This is because the core function of argon ion air cleaning and activation is to remove impurities such as oil and dust from the membrane surface and improve surface roughness. Without this step, residual contaminants on the membrane surface will hinder the interfacial bonding of subsequent oxygen activation, silane coupling agent spraying, and silicon oxide evaporation, leading to tiny gaps between the coating and the substrate, forming water and oxygen permeation channels. Insufficient surface roughness reduces the coating adhesion area, weakens the bonding force, and makes it prone to microcracks, further reducing the barrier effect.

[0111] In Comparative Example 2, the absence of the oxygen activation step significantly reduced the barrier performance. This is because the key function of oxygen activation is to introduce polar groups such as -OH and -COOH onto the surface of the biodegradable film. These groups are the core sites for the subsequent silane coupling agent grafting reaction. Without oxygen activation, the number of polar groups on the film surface is extremely small. The silane coupling agent cannot form stable chemical bonds with the substrate and can only adhere through physical adsorption, leading to the breakage of the chemical bond link between the substrate, silane coupling agent, and silicon oxide. The silicon oxide vapor-deposited barrier layer has a loose interface with the substrate, containing numerous micropores that allow water and oxygen molecules to easily penetrate. Furthermore, the coating is prone to peeling off, further deteriorating the barrier performance.

[0112] Comparative Example 3 lacked the silane coupling agent spraying step, resulting in decreased barrier properties. This is because the core function of the silane coupling agent is to build a "bridge" between the organic substrate and the inorganic silica coating. One end of the coupling agent binds to the polar groups on the substrate surface, while the other end forms a chemical bond with the silica. Without this step, there is no chemical bond between the substrate and the silica coating, relying solely on physical bonding. This leads to poor interfacial compatibility, easily generating gaps and microcracks, which become channels for water and oxygen permeation. The coating density decreases, failing to form a continuous and dense barrier layer, resulting in a significant increase in moisture and oxygen permeability.

[0113] Comparative Example 4 lacked the further activation step of the vapor-deposited steel roller, resulting in a decrease in barrier properties. This is because the activation effect of the vapor-deposited steel roller is manifested in two aspects: heating can promote the rapid desorption and volatilization of water vapor and residual impurities adsorbed on the substrate surface, further cleaning the surface and preventing impurities from affecting the coating deposition; the increase in temperature activates the molecular chain movement on the substrate surface, breaking some weak chemical bonds to form active sites, enhancing the bonding force between silicon oxide particles and the substrate. Without this step, trace amounts of water vapor and impurities remain on the substrate surface, and there are insufficient active sites, resulting in weak adhesion and reduced density of the silicon oxide coating, thus reducing barrier performance.

[0114] Comparative Example 5 lacks the plasma bombardment step, resulting in a decrease in barrier properties. This is because the core function of plasma bombardment is to rearrange the atoms in the silicon oxide coating to fill defects such as pinholes and microcracks. During the silicon oxide evaporation process, the coating is prone to forming tiny pinholes and pores due to uneven deposition rates. These defects are important channels for water and oxygen permeation. Without plasma bombardment, these defects cannot be repaired, resulting in insufficient coating density. At the same time, the internal stress of the coating is relatively high, and new cracks are easily generated during film bending or processing, leading to a deterioration in barrier performance.

[0115] Comparative Example 6 lacked the protective layer coating step, resulting in a decrease in barrier properties. This is because the protective layer (polyurethane + ethanol + water-based film-forming agent) serves as both physical protection and defect filling: the silicon oxide coating is an inorganic thin film, which is brittle and has poor abrasion resistance. Without the protective layer, the coating is prone to wear and cracking during subsequent processing (bag making, heat sealing) or transportation, forming numerous permeation channels; the protective layer can fill the tiny defects on the surface of the silicon oxide coating, forming an organic-inorganic composite protective system, further blocking water and oxygen permeation; without the protective layer, the silicon oxide coating is directly exposed to the environment and is easily detached due to moisture and external forces, leading to a significant decrease in barrier performance.

[0116] In Comparative Example 7, the absence of chitosan in the outer and middle layers resulted in a decrease in barrier properties. This is because the core function of chitosan is to fill the pores of the substrate and reduce permeation channels: the chitosan molecular chain is rich in polar groups such as -OH and -NH2, which can form hydrogen bonds with PBAT and PLA, inhibiting phase separation in the blend system, reducing micropores inside the substrate, and thus reducing the permeation pathways of water and oxygen molecules; chitosan has hygroscopic swelling properties in high humidity environments, which can further block the pores of the substrate and prevent a sharp drop in barrier performance; without chitosan, phase separation of the PBAT / PLA blend substrate intensifies, internal pores increase, and moisture and oxygen permeability naturally increase.

[0117] In summary, the water vapor permeability of the biodegradable high-barrier membrane prepared by this invention is <0.5 g / (m²). 2 • day), oxygen permeability < 0.5 cm 3 / (m 2 With a strength of 0.1 MPa, it has high barrier properties and good biodegradability, does not pollute the environment, meets the needs of environmentally friendly material development and use, and can meet the requirements of packaging materials in the food, medical and other industries.

Claims

1. A method for preparing a biodegradable high-barrier membrane, characterized in that, Includes the following steps: S1 Preparation of biodegradable membrane layer: A biodegradable membrane layer is prepared by three-layer co-extrusion and blow molding; wherein, the outer layer of the biodegradable membrane layer is composed of 90~95% PBAT, 2~5% additives and 2~6% chitosan; the middle layer is composed of 88~93% PBAT, 2~6% additives and 2~6% chitosan; and the inner layer is composed of 60~80% PLA and 20~40% PBAT; S2 electron beam vacuum evaporation of silicon oxide: S2.1 Install the biodegradable film layer onto the unwinding roller of the vacuum electron beam coating machine; S2.2 Close the vacuum chamber, evacuate the vacuum, and start the servo motors for coating cooling steel rollers and winding / unwinding. S2.3 After the biodegradable film rotates and is guided by the guide roller, argon ion air cleaning and activation are initiated; S2.4 is activated using oxygen; S2.5 Spray the silane coupling agent onto the surface of the biodegradable film layer; The S2.6 biodegradable film layer is guided by the guide roller and enters the vapor deposition steel roller. The temperature of the vapor deposition steel roller is 40~60℃, which further activates the biodegradable film layer. S2.7 uses an electron beam to bombard a silicon oxide target, causing the silicon oxide to evaporate, sublimate, and deposit as a film, forming a silicon oxide vapor-deposited barrier layer; S2.8 Nitrogen gas is introduced, and plasma is used to bombard the silicon oxide vapor-deposited barrier layer; S2.9 Rewind, release vacuum, unwrap and package; S3 Protective Coating: A protective layer is applied to the surface of the silicon oxide vapor-deposited barrier layer using a micro-gravure coating method, with a coating amount of 3~5 g / m². 2 The coating thickness is 1~2μm. After curing, a biodegradable high-barrier film is obtained. The protective layer is composed of the following components by mass percentage: 3~20% polyurethane, 1~2% ethanol, 0.5~1% aqueous film-forming agent, and the remainder is deionized water.

2. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S1, the additive is an antioxidant; the thickness of the biodegradable film obtained in step S1 is 32~60μm.

3. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.2, a vacuum is drawn to 4×10⁻⁶. -3 ~6×10 -3 Pa; the linear speed of the servo motor is 250~400m / min, and the tension is 0.6~1.7kg.

4. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.3, the argon flow rate of the argon ion wind is 100~500 SCCM, the DC power supply is 600~900V, and the cleaning and activation time is 5~15s.

5. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.4, the oxygen flow rate is 300~600 SCCM, the DC power supply is 200~500V, and the activation time is 5~10s.

6. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.5, the concentration of the silane coupling agent is 0.5~2wt.%, and the spraying thickness is 0.5~1μm.

7. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.7, an electron gun is used to emit an electron beam to bombard the silicon oxide target. The working voltage of the electron gun is 6~10kV. After preheating for 3~5 minutes, the filament current is adjusted to 1~1.8mA and the beam current is adjusted to 400~600A. The rate of silicon oxide evaporation and sublimation is 3~6nm / s, and the thickness of the silicon oxide evaporation barrier layer is 30~80nm.

8. The method for preparing the biodegradable high-barrier membrane as described in claim 1, characterized in that, In step S2.8, the nitrogen flow rate is 200~500 SCCM; the plasma frequency is 40~70 kHz; the power is 80~120 W; and the silicon oxide vapor-deposited barrier layer is bombarded for 3~5 seconds.

9. A biodegradable high-barrier membrane, characterized in that, It is prepared by the method for preparing a biodegradable high-barrier membrane as described in any one of claims 1-8.

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