A high-barrier biodegradable material, its preparation method and application

Abstract

This invention provides a high-barrier biodegradable material, comprising the following components by mass percentage: 20-30% polyglycolic acid, 40-50% polybutylene adipate terephthalate, 15-25% polybutylene succinate, 1.5-3% reactive compatibility chain extender, 0.3-0.8% hydrolysis stabilizer, 0.2-0.5% lubricant, and 0.5-2.5% silica. This invention also provides a method for preparing and applying the high-barrier biodegradable material. This invention uses polyglycolic acid as the high-barrier functional phase, polybutylene adipate terephthalate as the flexible matrix, and polybutylene succinate as the auxiliary modifying phase. In-situ compatibility is achieved through a reactive compatibility chain extender, and the hydrolysis stabilizer inhibits the hydrolytic degradation of polyglycolic acid. This effectively overcomes the defects of polyglycolic acid, such as high brittleness, easy hydrolysis, and difficulty in forming soft films, as well as the poor barrier properties of polybutylene adipate terephthalate and polybutylene succinate.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable materials, and in particular relates to a high-barrier biodegradable material, its preparation method, and its application. Background Technology

[0002] With the continued implementation of global plastic restriction policies, traditional non-degradable plastic packaging such as polyethylene, polypropylene, and nylon is causing serious white pollution to soil and water bodies. This has led to a surge in demand from the food industry for fully degradable, high-barrier, flexible, heat-sealable, and food-safe packaging materials. Currently, the mainstream commercially available biodegradable flexible materials are polybutylene adipate terephthalate (PBAT) and polybutylene succinate (PBS). Both have good molecular chain flexibility, bend resistance, are easy to blown film processing, and have excellent low-temperature toughness, making them the core substrates for flexible packaging films. However, these two materials have a loose molecular structure and low crystallinity, resulting in high permeability of oxygen, carbon dioxide, and water vapor, and extremely poor barrier properties. When used for packaging high-oil, high-moisture, and easily oxidized foods, they can easily cause oil rancidity, food moisture absorption, and oxidative browning, significantly shortening shelf life and failing to meet the preservation requirements of mid-to-high-end foods.

[0003] Polyglycolic acid (PGA) is a highly crystalline aliphatic polyester biodegradable material with tightly packed molecular chains. It possesses outstanding advantages such as ultra-high oxygen barrier properties, low water vapor permeability, oil resistance, high strength, and rapid biodegradation, making it an ideal high-barrier biodegradable substrate. However, PGA has significant drawbacks: it is extremely rigid, brittle, and has poor bending resistance, making it prone to cracking when used alone in film formation; it has poor hydrolytic stability, easily undergoing molecular chain degradation during heat processing and storage; and its narrow processing temperature window makes it difficult to prepare flexible films alone, greatly limiting its large-scale application in food flexible packaging. Existing technologies mostly focus on PLA / PBAT binary blends, single PGA modification, or simple physical blending, failing to simultaneously address technical issues such as poor interfacial compatibility in ternary systems, severe phase separation, PGA hydrolytic aging, high material hardness, and the inability to simultaneously balance barrier properties and toughness. Summary of the Invention

[0004] To address the problems existing in the prior art, the first objective of this invention is to provide a high-barrier biodegradable material, the second objective of this invention is to provide a method for preparing the high-barrier biodegradable material, and the third objective of this invention is to provide applications of the high-barrier biodegradable material.

[0005] To achieve the first objective of this invention, the following technical solution is adopted: A high-barrier biodegradable material, comprising the following components by weight percentage: Polyglycolic acid 20-30%; polybutylene adipate terephthalate 40-50%; polysuccinate 15-25%; reactive compatible chain extender 1.5-3%; hydrolysis stabilizer 0.3-0.8%; lubricant 0.2-0.5%; silica 0.5-2.5%; composite antioxidant 0.5-1%.

[0006] Preferably, by mass percentage, it comprises the following components: Polyglycolic acid 25%, polybutylene adipate 45%, polybutylene succinate 25%, reactive compatibility chain extender 1.5%, hydrolysis stabilizer 0.5%, lubricant 0.5%, silica 1.5%, composite antioxidant 1%.

[0007] Preferably, the reactive compatibility chain extender is at least one of epoxy chain extender ADR-4468 and ethylene-methyl acrylate-glycidyl methacrylate terpolymer AX8900.

[0008] Preferably, the anti-hydrolysis stabilizer is a single-component or compound anti-hydrolysis agent of carbodiimide. More preferably, the anti-hydrolysis stabilizer is a monomeric carbodiimide. Monomeric carbodiimide has higher reactivity, and the carbodiimide groups in its molecular structure can react more efficiently with the terminal carboxyl groups generated by the hydrolysis of polyglycolic acid, capturing the carboxyl groups and blocking the autocatalytic process of the hydrolysis chain reaction, thereby more effectively delaying the hydrolytic aging of polyglycolic acid. Compared with polymeric carbodiimide, monomeric carbodiimide requires less addition and has higher reaction efficiency, providing better anti-hydrolysis protection without affecting other properties of the material.

[0009] Preferably, the lubricant is one or a combination of two of pentaerythritol stearate and erucamide.

[0010] More preferably, the lubricant is a compound of pentaerythritol stearate and erucamide in a weight ratio of 1:1. Pentaerythritol stearate, as an internal lubricant, can reduce internal friction of the melt, while erucamide, as an external lubricant, can improve the release properties of the melt from the equipment surface. When the two are compounded in a 1:1 ratio, they can produce a synergistic effect, which can improve the surface smoothness of the film while reducing processing energy consumption.

[0011] Preferably, the composite antioxidant is prepared by mixing 2246 hindered phenol and THP-24 phosphite in a weight ratio of 2:8. In this invention, 2246 hindered phenol is used as the primary antioxidant and THP-24 phosphite is used as the secondary antioxidant. In this invention, the compounding of 2246 hindered phenol (primary antioxidant) and THP-24 phosphite (secondary antioxidant) in a weight ratio of 2:8 can produce a strong synergistic stabilizing effect. This can not only significantly improve the thermal stability and color stability of the material during high-temperature processing (preventing degradation and yellowing), but also effectively extend the performance retention of the product during long-term use and storage.

[0012] In this invention, polyglycolic acid, polybutylene adipate terephthalate (PBAT), and polybutylene succinate (PBAT) all belong to the category of polyester biodegradable plastics. Polyester biodegradable plastics refer to a class of polymeric materials whose molecular backbone contains ester bonds (-COO-), which can break down into smaller molecules in nature through microbial action or hydrolysis. Polyglycolic acid (PGA) is an aliphatic polyester obtained through glycolic acid condensation polymerization or glycolide ring-opening polymerization. Its ester bonds are easily hydrolyzed under humid and hot conditions, ultimately degrading into carbon dioxide and water. Simultaneously, its tightly packed molecular chains and high crystallinity endow the material with excellent barrier properties. Polybutylene adipate terephthalate (PBAT) is an aliphatic-aromatic copolyester copolymerized from adipic acid, terephthalic acid, and butanediol. Its molecular chain contains ester bonds, combining the biodegradability of aliphatic polyesters with the good mechanical properties of aromatic polyesters. Its good molecular chain flexibility makes it an ideal substrate for preparing flexible films. Polybutylene succinate (PBS) is an aliphatic polyester obtained by the condensation polymerization of succinic acid and butanediol. Its molecular chain contains ester bonds, resulting in good molecular chain regularity, high crystallinity, and excellent dimensional stability and heat resistance. All three materials mentioned above use ester bonds as the connecting units of their molecular backbone, and are therefore collectively referred to as polyester biodegradable plastics.

[0013] In this invention, the functions and working principles of each component in the high-barrier biodegradable material are as follows: Polyglycolic acid (PGA) is a high-barrier functional phase in materials. PGA is a highly crystalline aliphatic polyester with a tightly ordered molecular chain, effectively blocking the permeation of oxygen, carbon dioxide, and water vapor. It possesses outstanding advantages such as ultra-high oxygen barrier properties, low water vapor permeation, oil resistance, and high strength. The introduction of PGA is key to solving the insufficient barrier properties of PBAT / PBS. However, PGA itself is extremely rigid and brittle, with poor bending resistance, and the ester bonds in its molecular chain are prone to hydrolysis under humid and hot environments, leading to a decrease in molecular weight and performance degradation. Therefore, this invention overcomes the above-mentioned defects of PGA by compounding it with other components and adding functional additives. The PGA content is controlled within the range of 20-30%: below 20%, the barrier performance of the material is not significantly improved, making it difficult to meet the preservation requirements of high-oil and high-moisture foods; above 30%, the flexibility of the material decreases significantly, increasing processing difficulty. Therefore, 20-30% is the optimal range to ensure a balance between barrier performance and flexibility.

[0014] Polybutylene adipate terephthalate (PBAT) is the flexible continuous matrix of the material. The PBAT molecular chain contains aliphatic and aromatic segments, possessing both flexibility and a certain degree of mechanical strength, exhibiting high elongation at break, good heat-sealing properties, and processing fluidity. As a continuous phase, PBAT can encapsulate the PGA dispersed phase, endowing the material with good flexibility and bending resistance, enabling the film material to meet the flexibility requirements of flexible packaging. The PBAT content is controlled within the range of 40-50%: below 40%, the material's flexibility is insufficient, and the film is too stiff; above 50%, the content of PGA and PBS decreases accordingly, leading to a decline in barrier properties and dimensional stability.

[0015] Polybutylene succinate (PBS) is an auxiliary modifying phase for materials. PBS possesses good dimensional stability, weather resistance, and low-temperature impact resistance. It can regulate the crystallization behavior and rheological properties of blended systems, improving the processing window and dimensional stability of finished products. The introduction of PBS can also reduce material costs to some extent and synergistically enhance the overall mechanical properties of materials with PBAT. The PBS content should be controlled within the range of 15%–25%: below 15%, the modification effect is not significant; above 25%, the content of PGA or PBAT decreases accordingly, affecting barrier properties or flexibility.

[0016] Reactive compatibility chain extenders are one of the core additives in this invention. Due to the poor interfacial compatibility among PGA, PBAT, and PBS, simple physical blending easily leads to phase separation, resulting in film delamination and uneven mechanical properties. This invention uses epoxy-based reactive compatibility chain extenders (such as ADR-4468 and AX8900), whose molecular chains contain multiple epoxy functional groups. During melt blending, these extenders can undergo ring-opening addition reactions with the carboxyl and hydroxyl groups at the ends of the PGA, PBAT, and PBS molecular chains, forming covalent bonds between the three resin molecular chains, thereby achieving in-situ compatibility enhancement. The addition of reactive compatibility chain extenders not only improves the interfacial bonding force of the three phases and inhibits phase separation, but also increases the molecular weight of the blend system and reduces melt flowability, thereby improving the mechanical uniformity and heat-sealing strength of the film. The content of the reactive compatibility chain extender is controlled within the range of 1.5% to 3%: below 1.5%, the compatibility enhancement effect is not obvious, and the phase separation problem still exists; above 3%, it may lead to excessive cross-linking, affecting the processing flowability and flexibility of the material.

[0017] Hydrolysis stabilizers are used to inhibit the hydrolytic degradation of PGA during processing and use. The ester bonds in the PGA molecular chain are sensitive to moisture and are prone to hydrolytic breakage under high temperature and humidity conditions, leading to a decline in material performance. This invention employs carbodiimide-based hydrolysis stabilizers, more preferably monomeric carbodiimides. The carbodiimide groups in the monomeric carbodiimide molecule can react with the terminal carboxyl groups generated by PGA hydrolysis, capturing the carboxyl groups and blocking the autocatalytic process of the hydrolysis chain reaction, thereby effectively delaying the hydrolytic aging of PGA and improving the processing stability and shelf life of the material. Compared to polymeric carbodiimides, monomeric carbodiimides have the advantages of higher reactivity and lower addition amounts, achieving excellent hydrolysis resistance at extremely low addition levels. The content of the hydrolysis stabilizer is controlled within the range of 0.3% to 0.8%: below 0.3%, the hydrolysis resistance is insufficient, and the material is easily degraded during processing and storage; above 0.8%, it increases costs and may affect other properties of the material.

[0018] Lubricants are used to reduce the melt viscosity of blended systems and improve flowability and release properties during extrusion film formation. This invention employs lubricants such as calcium stearate and erucamide, which can reduce friction between resin molecular chains and between the melt and the metal surface of the equipment, thereby reducing processing energy consumption and improving film surface smoothness. When PETS stearate and erucamide are blended in a 1:1 weight ratio, PETS stearate acts as an internal lubricant to reduce internal melt friction, while erucamide acts as an external lubricant to improve the release properties between the melt and the equipment surface. The 1:1 blend produces a synergistic effect, combining internal and external lubrication to reduce processing energy consumption while improving film surface smoothness. The lubricant content is controlled within the range of 0.2% to 0.5%: below 0.2%, the lubrication effect is not significant, and processing resistance is high; above 0.5%, it may lead to migration and precipitation on the film surface, affecting heat-sealing performance.

[0019] Silica, acting as an opening agent and anti-blocking agent, forms microscopic protrusions on the film surface when added to film materials. This reduces the contact area between film layers, effectively preventing film adhesion during winding and storage, without affecting the film's transparency and barrier properties. The silica content should be controlled within the range of 0.5% to 2.5%: below 0.5%, the opening effect is not obvious, and the film is prone to adhesion; above 2.5%, it may affect the film's transparency and mechanical properties.

[0020] To achieve the second objective of this invention, the following technical solution is adopted: A method for preparing the aforementioned high-barrier biodegradable material includes the following steps: S1: Raw material pretreatment: Polyglycolic acid is dried in a vacuum environment at 80℃ for 8-12 hours, and the moisture content is controlled to be ≤200ppm; Polybutylene adipate terephthalate and polybutylene succinate are dried in hot air at 60-70℃ for 4-6 hours, and the moisture content is controlled to be ≤500ppm; Reactive compatibility chain extender, anti-hydrolysis stabilizer, lubricant, silica and composite antioxidant are accurately weighed according to the formula, and mixed at high speed for 5-10 minutes to obtain a uniform additive premix; S2: Melt reaction blending and granulation: The dried polyglycolic acid, polybutylene adipate terephthalate, polybutylene succinate resin and additive premix are fed into a co-rotating twin-screw extruder. After segmented temperature-controlled melting, in-situ reaction compatibilization, and strong shear blending, the mixture is extruded, and then subjected to water-cooled traction, air drying, pelletizing, and secondary drying to obtain uniform modified biodegradable composite masterbatch. S3: Film forming: The composite masterbatch is fed into the film forming equipment, and melt extrusion is carried out using blown film process or casting process. After cooling and shaping, traction, tension adjustment and winding, a soft high-barrier biodegradable material is obtained.

[0021] Preferably, in step S2, the co-rotating twin-screw extruder has an L / D ratio ≥ 40, a screw speed of 200–300 r / min, and the processing temperatures of each section of the extruder are as follows: Zone 1 160℃, Zone 2 175℃, Zone 3 190℃, Zone 4 200℃, Zone 5 210℃, Zone 6 215℃, and Die Head 210℃. Using a twin-screw extruder with an L / D ratio ≥ 40 provides longer residence time and stronger shear mixing, ensuring that the reactive compatible chain extender reacts fully with the three resins, achieving uniform in-situ compatibilization. The segmented gradient temperature control method, with gradual heating from Zone 1 to Zone 6, ensures gradual melting of the resin while avoiding thermal degradation of PGA due to excessive residence time at high temperatures.

[0022] Preferably, the blown film process parameters in step S3 are: extruder barrel temperature 180-210℃, die temperature 205℃, blow-up ratio controlled at 1.8-2.5, and traction speed 15-30m / min, to prepare a flexible packaging film with a thickness of 20-50μm.

[0023] Preferably, the casting process parameters in step S3 are: melt extrusion temperature 190-210℃, cooling roller water temperature constant 30-40℃, and winding tension 5-15N, to obtain a high-flatness transparent soft film with a thickness of 15-40μm.

[0024] To achieve the third objective of this invention, the following technical solution is adopted: The application of the aforementioned high-barrier biodegradable material is to prepare fresh fruit and vegetable preservation bags, baked food packaging bags, braised cooked food sealing bags, moisture-proof and antioxidant soft packaging for nuts and high-oil foods, and inner barrier film for food composite packaging.

[0025] The beneficial effects of this invention are: (1) This invention achieves synergistic and complementary performance through the scientific compounding of PGA, PBAT, and PBS ternary resins. PGA provides ultra-high oxygen barrier, water vapor barrier, and oil resistance; PBAT imparts high elongation and flexibility to the material; and PBS enhances the material's dimensional stability and low-temperature impact resistance. The compounding of the three perfectly compensates for the performance defects of individual materials and solves the industry pain points of insufficient barrier performance of PBAT / PBS and the brittleness and easy hydrolysis of PGA. The oxygen permeability of the obtained material is ≤5cm³ / (m²·24h·0.1MPa), and the water vapor permeability is ≤3g / (m²·24h), which is more than an order of magnitude higher than that of pure PBAT or PBAT / PBS binary systems.

[0026] (2) This invention employs a reactive compatibility chain extender for in-situ compatibility modification. Through chemical reactions during melt blending, covalent bonds are formed between the molecular chains of PGA, PBAT, and PBS, significantly improving the interfacial compatibility of the three phases, inhibiting phase separation, resulting in a film free of delamination and white spots, and greatly improving mechanical uniformity. Simultaneously, a carbodiimide-based hydrolysis stabilizer (more preferably a monomeric carbodiimide) effectively captures the terminal carboxyl groups generated by PGA hydrolysis, blocking the hydrolysis chain reaction and solving the problems of short storage life and rapid performance degradation of degradable materials. The resulting material has an elongation at break ≥400%, completely solving the problem of PGA's inability to prepare soft films.

[0027] (3) The preparation process of this invention is highly versatile. It adopts conventional twin-screw granulation and blown film / casting equipment throughout the process, without the need for large-scale equipment modification. The process is simple, the production efficiency is high, and it is suitable for large-scale industrial mass production. The material can be widely used in the field of flexible preservation packaging for fresh fruits and vegetables, baked pastries, braised cooked food, and nuts and oils. Detailed Implementation

[0028] The invention can be further understood through the specific embodiments given below, but they are not intended to limit the invention. Example 1

[0029] This embodiment 1 provides a high-barrier biodegradable material, which comprises the following components by mass percentage: Polyglycolic acid (PGA) 20%, polybutylene adipate terephthalate (PBAT) 50%, polybutylene succinate (PBS) 25%, epoxy chain extender ADR-4468 1.5%, carbodiimide hydrolysis stabilizer 0.3%, pentaerythritol stearate 0.2%, erucamide 0.5%, silica 1.5%, 2246 hindered phenol 0.2%, THP-24 phosphite 0.8%.

[0030] The preparation method of the high-barrier biodegradable material in Example 1 includes the following steps: S1: Raw material pretreatment: PGA was dried in an 80℃ vacuum drying oven for 10 hours, with the moisture content controlled to ≤200ppm; PBAT and PBS were dried in a 65℃ hot air drying oven for 5 hours, with the moisture content controlled to ≤500ppm; ADR-4468, carbodiimide, pentaerythritol stearate, erucamide, silica, 2246 hindered phenol and THP-24 phosphite were weighed according to the formula, and mixed at high speed for 8 minutes to obtain a uniform additive premix; S2: Melt reaction blending and granulation: The dried PGA, PBAT, and PBS resins and additive premixes are fed into a co-rotating twin-screw extruder (length-to-diameter ratio L / D=40). The screw speed is 250 r / min. The processing temperatures of each section of the extruder are as follows: Zone 1 160℃, Zone 2 175℃, Zone 3 190℃, Zone 4 200℃, Zone 5 210℃, Zone 6 215℃, and Die head 210℃. After segmented temperature-controlled melting, in-situ reaction compatibilization, and strong shear blending, the mixture is extruded, then water-cooled traction, air-drying, pelletizing, and secondary drying to obtain uniform modified biodegradable composite masterbatch. S3: Film forming: The composite masterbatch is fed into the blown film unit and melt extruded using the blown film process. The extruder barrel temperature is 190-210℃, the die temperature is 205℃, the blow-up ratio is controlled at 2.0, and the traction speed is 20m / min. A flexible packaging film with a thickness of 35μm is prepared and marked as sample Y1. Example 2

[0031] This embodiment 2 provides a high-barrier biodegradable material, which comprises the following components by mass percentage: Polyglycolic acid (PGA) 25%, polybutylene adipate terephthalate (PBAT) 45%, polybutylene succinate (PBS) 25%, ethylene-methyl acrylate-glycidyl methacrylate terpolymer AX8900 2.5%, carbodiimide hydrolysis stabilizer 0.5%, pentaerythritol stearate 0.25%, erucamide 0.25%, silica 1.0%, 2246 hindered phenol 0.1%, THP-24 phosphite 0.4%.

[0032] The preparation method of the high-barrier biodegradable material in Example 2 is basically the same as that in Example 1, except for the formulation composition; the final thin film material is labeled as sample Y2. Example 3

[0033] This embodiment 3 provides a high-barrier biodegradable material, which comprises the following components by mass percentage: Polyglycolic acid (PGA) 30%, polybutylene adipate terephthalate (PBAT) 50.0%, polybutylene succinate (PBS) 15%, epoxy chain extender ADR-4468 3%, monomer carbodiimide hydrolysis stabilizer 0.5%, erucamide 0.5%, silica 0.5%, 2246 hindered phenol 0.1%, THP-24 phosphite 0.4%.

[0034] The preparation method in this embodiment is basically the same as that in Example 1, except for the formulation composition. The final thin film material is labeled as sample Y3.

[0035] Comparative Example 1 This comparative example uses pure polybutylene adipate terephthalate (PBAT) resin to prepare a single-layer film via blown film process, and is labeled as sample D1.

[0036] Comparative Example 2 This comparative example uses pure polyglycolic acid (PGA) resin and attempts to prepare a film using a blown film process, labeled as sample D2. This film exhibits severe brittleness during preparation and cannot be properly wound up.

[0037] Comparative Example 3 This comparative example provides a PBAT / PBS binary blend material, which, by mass percentage, comprises the following components: The film was prepared using a mixture of 70% polybutylene adipate-terephthalate (PBAT) and 30% polybutylene succinate (PBS). No PGA, compatibility chain extenders, or hydrolysis stabilizers were added. The film was prepared using a blown film process and labeled as sample D3.

[0038] Performance testing The performance of sample Y1 prepared in Example 1, sample Y2 prepared in Example 2, sample Y3 prepared in Example 3, and comparative samples D1, D2, and D3 were tested respectively. The test items and methods are as follows: ①Oxygen permeability: The oxygen permeability was determined by differential pressure method according to GB / T 1038 standard. The test conditions were 23℃ and 0% relative humidity. The test result was measured in cm³ / (m²·24h·0.1MPa).

[0039] ② Water vapor transmission rate: The test was conducted in accordance with GB / T 16928 standard. The test conditions were 38℃ and 90% relative humidity. The test result was measured in g / (m²·24h).

[0040] ③ Elongation at break: According to GB / T 1040 standard, dumbbell-shaped spline was used, and the tensile rate was 200 mm / min. The longitudinal and transverse elongation at break were tested, and the average value was taken. The results are expressed as a percentage.

[0041] ④ Material condition evaluation: The flexibility, heat-sealing performance and surface condition of the film are comprehensively evaluated by visual inspection and touch.

[0042] The test results are shown in Table 1.

[0043]

[0044] The results in Table 1 show that: Regarding the oxygen permeability results: the oxygen permeability of Examples 1, 2, and 3 were 4.8, 3.2, and 2.1 cm³ / (m²·24h·0.1MPa), respectively, while Comparative Example 1 (pure PBAT) had 62.5, Comparative Example 2 (pure PGA) had 1.3, and Comparative Example 3 (PBAT / PBS binary blend) had 58.2. The oxygen permeability of the embodiments of the present invention is much lower than that of the pure PBAT and PBAT / PBS binary blend systems, decreasing by more than 92% compared to Comparative Example 1 and by more than 94% compared to Comparative Example 3. Although pure PGA has the lowest oxygen permeability (1.3), its elongation at break is extremely low (only 35%), which cannot meet the flexibility requirements of flexible packaging. The present invention, through ternary compounding, significantly improves the flexibility of the material while maintaining high barrier performance. This result fully demonstrates that PGA, as a high-barrier functional phase, effectively blocks oxygen permeation due to its dense molecular chain arrangement and high crystallinity. The introduction of PBAT and PBS did not significantly disrupt the barrier network structure of PGA. The oxygen permeability of Example 2 (25% PGA content) was 3.2, and that of Example 3 (30% PGA content) was 2.1, indicating that higher PGA content results in better barrier performance. Users can choose appropriate formulations based on specific packaging requirements.

[0045] Regarding the water vapor transmission rate results: the water vapor transmission rates of Examples 1, 2, and 3 were 2.9, 2.1, and 1.5 g / (m²·24h), respectively, while those of Comparative Example 1 were 18.6, Comparative Example 2 was 1.0, and Comparative Example 3 was 16.3. The water vapor transmission rates of the embodiments of this invention are significantly lower than those of pure PBAT and the PBAT / PBS binary blend system, decreasing by more than 84% compared to Comparative Example 1 and by more than 87% compared to Comparative Example 3. This result is also attributed to the high crystallinity and dense structure of PGA, whose tightly packed molecular chains effectively block the diffusion of water vapor molecules. For the preservation packaging of high-fat and high-moisture foods, low water vapor transmission rate means effective prevention of food moisture absorption and oil oxidation rancidity, significantly extending shelf life.

[0046] Regarding the elongation at break results: the elongation at break of Examples 1, 2, and 3 were 465%, 420%, and 385%, respectively, while Comparative Example 1 was 510%, Comparative Example 2 was only 35%, and Comparative Example 3 was 480%. Although the elongation at break of the embodiments of the present invention is slightly lower than that of pure PBAT and the PBAT / PBS binary blend system, it is much higher than that of pure PGA. Compared with pure PGA, the elongation at break of the embodiments of the present invention is increased by more than 10 times, completely solving the problem of the high brittleness of PGA materials and the inability to prepare soft films. This result shows that PBAT, as a flexible continuous matrix, can effectively absorb and disperse external forces with its highly flexible molecular chains, giving the material good bending resistance and flexibility. Example 1 (PGA content 20%) had the highest elongation at break (465%), while Example 3 (PGA content 30%) had the lowest elongation at break (385%). This indicates that the higher the PGA content, the stronger the rigidity of the material, and the slightly reduced the flexibility. However, an elongation at break of 385% can still meet the requirements of most food flexible packaging.

[0047] Regarding the material properties: The film of Example 1 exhibits high flexibility and is easily heat-sealed, making it suitable for packaging applications requiring high flexibility. The film of Example 2 demonstrates a balanced softness and hardness with optimal overall barrier performance, making it the best choice for general use. The film of Example 3 possesses ultra-high barrier performance, but with slightly increased rigidity, making it suitable for high-end food packaging with extremely long shelf-life requirements. The film of Comparative Example 1 is extremely soft but has very poor barrier performance, making it unsuitable for packaging high-oil and high-moisture foods. The film of Comparative Example 2 is extremely brittle, unable to be properly rolled up and used, and therefore unsuitable for flexible packaging. The film of Comparative Example 3 is relatively soft, but its barrier performance is also insufficient, failing to meet the preservation requirements of mid-to-high-end foods.

[0048] In summary, the high-barrier biodegradable material, its preparation method, and its applications provided by this invention, through the scientific compounding of PGA, PBAT, and PBS ternary resins, combined with the in-situ compatibilization of reactive compatibility chain extenders and the protective effect of carbodiimide anti-hydrolysis stabilizers (more preferably monomeric carbodiimides), significantly outperforms existing technologies in multiple key indicators such as oxygen permeability, water vapor permeability, elongation at break, and overall material condition. The material of this invention possesses both high barrier properties and high flexibility, and can be directly produced on conventional blown film or casting equipment without equipment modification. It can be widely used in the field of flexible preservation packaging for fresh fruits and vegetables, baked goods, braised foods, and nuts and oils, meeting food contact safety standards and biodegradability requirements, and has extremely high industrialization value and broad market application prospects.

[0049] The above description is merely an embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A high-barrier biodegradable material, characterized in that, By mass percentage, it includes the following components: Polyglycolic acid 20-30%; polybutylene adipate terephthalate 40-50%; polysuccinate 15-25%; reactive compatible chain extender 1.5-3%; hydrolysis stabilizer 0.3-0.8%; lubricant 0.2-0.5%; silica 0.5-2.5%; composite antioxidant 0.5-1%.

2. The high-barrier biodegradable material according to claim 1, characterized in that, By mass percentage, it includes the following components: Polyglycolic acid 25%, polybutylene adipate 45%, polybutylene succinate 25%, reactive compatibility chain extender 1.5%, hydrolysis stabilizer 0.5%, lubricant 0.5%, silica 1.5%, composite antioxidant 1%.

3. The high-barrier biodegradable material according to claim 1 or 2, characterized in that, The reactive compatibility chain extender is at least one of epoxy chain extender ADR-4468 and ethylene-methyl acrylate-glycidyl methacrylate terpolymer AX8900.

4. The high-barrier biodegradable material according to claim 1 or 2, characterized in that, The hydrolysis stabilizer is a single-component or compound hydrolysis stabilizer of carbodiimide type; the lubricant is one or a compound combination of pentaerythritol stearate and erucamide.

5. The high-barrier biodegradable material according to claim 1 or 2, characterized in that, The composite antioxidant is prepared by mixing 2246 hindered phenol and THP-24 phosphite in a weight ratio of 2:

8.

6. A method for preparing a high-barrier biodegradable material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Raw material pretreatment: Polyglycolic acid is dried in a vacuum environment at 80℃ for 8-12 hours, and the moisture content is controlled to be ≤200ppm; Polybutylene adipate terephthalate and polybutylene succinate are dried in hot air at 60-70℃ for 4-6 hours, and the moisture content is controlled to be ≤500ppm; Reactive compatibility chain extender, anti-hydrolysis stabilizer, lubricant, silica and composite antioxidant are accurately weighed according to the formula, and mixed at high speed for 5-10 minutes to obtain a uniform additive premix; S2: Melt reaction blending and granulation: The dried polyglycolic acid, polybutylene adipate terephthalate, polybutylene succinate resin and additive premix are fed into a co-rotating twin-screw extruder. After segmented temperature-controlled melting, in-situ reaction compatibilization, and strong shear blending, the mixture is extruded, and then subjected to water-cooled traction, air drying, pelletizing, and secondary drying to obtain uniform modified biodegradable composite masterbatch. S3: Film forming: The composite masterbatch is fed into the film forming equipment, and melt extrusion is carried out using blown film process or casting process. After cooling and shaping, traction, tension adjustment and winding, a soft high-barrier biodegradable material is obtained.

7. The preparation method according to claim 6, characterized in that, In step S2, the length-to-diameter ratio (L / D) of the co-rotating twin-screw extruder is ≥40, the screw speed is 200-300 r / min, and the processing temperatures of each section of the extruder are as follows: Zone 1 160℃, Zone 2 175℃, Zone 3 190℃, Zone 4 200℃, Zone 5 210℃, Zone 6 215℃, and Die head 210℃.

8. The preparation method according to claim 6, characterized in that, The blown film process parameters in step S3 are as follows: extruder barrel temperature 180-210℃, die temperature 205℃, blow-up ratio controlled at 1.8-2.5, and traction speed 15-30m / min, to prepare a flexible packaging film with a thickness of 20-50μm.

9. The preparation method according to claim 6, characterized in that, The casting process parameters in step S3 are: melt extrusion temperature 190-210℃, cooling roller water temperature constant 30-40℃, winding tension 5-15N, to obtain a high-flatness transparent soft film with a thickness of 15-40μm.

10. The application of a high-barrier biodegradable material as described in any one of claims 1 to 5, characterized in that, Used for preparing fresh fruit and vegetable preservation bags, baked food packaging bags, braised cooked food sealing bags, moisture-proof and antioxidant soft packaging for nuts and high-oil foods, and inner barrier film for food composite packaging.

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