High-barrier pbat-based biodegradable film and method for preparing the same

Abstract

The application provides a high-barrier PBAT-based biodegradable film and a preparation method thereof. The preparation method comprises the following steps: melt blending a powdered high-barrier biodegradable polyester and PBAT to obtain a blend and performing film blowing to obtain the high-barrier PBAT-based biodegradable film; wherein the temperature of melt blending is lower than the melting temperature of the high-barrier biodegradable polyester and higher than the melting temperature of the PBAT; during the film blowing process, the temperature of the melt conveying zone is lower than the melting temperature of the high-barrier biodegradable polyester and higher than the melting temperature of the PBAT; and the temperature of the die lip zone is higher than the melting temperature of the high-barrier biodegradable polyester. The preparation method can prepare the PBAT-based biodegradable film with good barrier performance under the condition of a lower content of the high-barrier biodegradable polyester.

Description

Technical Field

[0001] This invention relates to a high-barrier PBAT-based biodegradable film and its preparation method, belonging to the field of PBAT films. Background Technology

[0002] In recent years, with increasing attention to eliminating white pollution, the demand for biodegradable materials in the packaging field has surged. Among them, PBAT, due to its good flexibility and biodegradability, has become one of the main substrates for biodegradable films. However, polybutylene terephthalate (PBAT) has low molecular chain polarity and low crystallinity, resulting in poor barrier properties, especially its barrier properties against oxygen (OTR) and water vapor (WVTR), which fall far short of the requirements for high-end packaging such as food and pharmaceuticals, and cannot effectively extend the shelf life of easily oxidized or moisture-sensitive products. Currently, the main methods to improve the barrier properties of biodegradable films include multilayer composites and surface coatings, but these technologies often face challenges such as complex processes, high costs, or decreased degradation performance. Blending modification processes, on the other hand, are relatively simple and have certain advantages in developing film materials that combine low cost and high barrier properties.

[0003] Biodegradable polyesters such as polylactic acid (PLA) and 3-hydroxybutyric acid-3-hydroxyvalerate copolymer (PHBV) are often used as dispersed phase resins in PBAT films to improve the strength, hardness, and barrier properties of biodegradable films. During blown film production, the larger the two-dimensional size of high-barrier dispersed phases such as PLA and PHBV, the more significant the improvement in barrier effect. Larger dispersed phase sizes are more easily converted into larger two-dimensional sheets during blown film production. However, due to the inherent chemical structures of PBAT and PLA or PHBV, maintaining a uniform dispersed phase distribution while increasing the dispersed phase size while keeping the PLA or PHBV content constant presents significant technical challenges. Currently, the main method to increase the dispersed phase size is to increase its dosage; however, increasing the content of rigid PLA and PHBV will lead to a decrease in the film's flexibility.

[0004] Therefore, achieving high-efficiency barrier properties by increasing the dispersed phase size of PBAT in relatively low-barrier materials, thereby forming a larger two-dimensional layered structure during blown film production, remains a significant technical challenge. Consequently, it is necessary to provide a novel method for preparing high-barrier PBAT-based biodegradable films to address these issues. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a high-barrier PBAT-based biodegradable film and its preparation method. This preparation method yields a PBAT-based biodegradable film with good barrier properties at a relatively low content of high-barrier biodegradable polyester.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high-barrier PBAT-based biodegradable thin film, comprising the following steps: Powdered high-barrier biodegradable polyester and PBAT are melt-blended to obtain a blend. The blend was blown into a film to obtain a high-barrier PBAT-based biodegradable film. Among them, the high-barrier biodegradable polyester is selected from PLA and / or PHBV; the weight ratio of PBAT to high-barrier biodegradable polyester is 80~95:5~20; The melt blending temperature is lower than that of high-barrier biodegradable polyester but higher than that of PBAT. During the blown film process, the temperature of the melt conveying zone is lower than the melt temperature of high-barrier biodegradable polyester but higher than the melt temperature of PBAT; the temperature of the die lip zone is higher than the melt temperature of high-barrier biodegradable polyester.

[0007] This invention controls the melt blending temperature to be lower than the melt temperature of the high-barrier biodegradable polyester but higher than the melt temperature of PBAT, allowing the powdered high-barrier biodegradable polyester to be uniformly dispersed in the PBAT at its initial particle size, forming a blend. Furthermore, the high-barrier biodegradable polyester in this blend does not melt in the melt transport zone of the blown film, but melts in the die lip zone. This results in a layered structure of high-barrier biodegradable polyester with larger two-dimensional dimensions within the PBAT after stretching into a film, thereby improving the barrier properties of the film.

[0008] In some alternative embodiments, the melt blending temperature is 130-150°C. More preferably, the melt blending process includes: melt blending PBAT and powdered high-barrier biodegradable polyester in a twin-screw extruder at a rotation speed of 70 r / min.

[0009] In some alternative implementations, the temperature of the melt conveying zone is 130~150°C; the temperature of the die lip zone is 170~200°C.

[0010] In some preferred embodiments, the weight ratio of PBAT to high-barrier biodegradable polyester is 80-85:15-20, more preferably 80:20.

[0011] In some preferred embodiments, the draw ratio of the blown film is 5 to 9; the blow-up ratio is 4 to 5. A high blow-up ratio combined with a low draw ratio allows for a more effective increase in the lateral dimensions of the dispersed film layer.

[0012] In some preferred embodiments, the particle size of the high-barrier biodegradable polyester is 20-500 μm. In some optional embodiments, the high-barrier biodegradable polyester can be prepared into powder particles with a particle size of 20-500 μm by cryogenic milling, preferably, the average particle size of the powder particles is 20-100 μm.

[0013] In some alternative implementations, the melt index of PBAT is 3-5 g / 10 min (test conditions: 190 °C / 2.16 kg). The Mw is 60,000-90,000 g / mol.

[0014] In some alternative implementations, the melt index of PHBV is 5-10 g / 10 min (test conditions: 190 °C / 2.16 kg). Mw is 100,000-150,000 g / mol.

[0015] This invention also provides a high-barrier PBAT-based biodegradable film, which is prepared by the aforementioned method. In some optional embodiments, the film thickness is 10-100 μm. The high-barrier PBAT-based biodegradable film of this invention exhibits superior barrier properties. Attached Figure Description

[0016] Figure 1 A flowchart illustrating a method for preparing a PBAT-based biodegradable film according to one embodiment of the present invention is shown.

[0017] Figure 2 The SEM image of the brittle fracture surface of the film prepared in Comparative Example 2 by keeping PBAT / PHBV in a molten state throughout the melt blending process is shown.

[0018] Figure 3 The image shows a SEM image of the brittle fracture surface of a film prepared by melting PHBV in Example 4, where PHBV does not melt in the melt delivery zone but melts in the die lip zone. Detailed Implementation

[0019] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0020] The PBAT and PHBV used in the examples and comparative examples were sourced from the following sources: PBAT - Xinjiang Lanshan Tunhe Technology Co., Ltd., brand name TH801; PHBV - Ningbo Tianan Biomaterials Co., Ltd., brand name ENMATY1000P.

[0021] Example 1

[0022] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 95 parts of PBAT and 5 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0023] Example 2

[0024] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV is prepared into powder particles by cryogenic grinding, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 90 parts of PBAT and 10 parts of PHBV powder were melt-blended at 150°C with a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0025] Example 3

[0026] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV is prepared into powder particles by cryogenic grinding, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 85 parts of PBAT and 15 parts of PHBV powder were melt-blended at 150°C with a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0027] Example 4

[0028] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV is prepared into powder particles by cryogenic grinding, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0029] Comparative Example 1

[0030] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 90 parts of PBAT and 10 parts of PHBV powder were melt-blended at 185°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 185℃), zone 2 (connection section between single screw and die, temperature 185℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0031] Comparative Example 2

[0032] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 185°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 185℃), zone 2 (connection section between single screw and die, temperature 185℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0033] Comparative Example 3

[0034] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 185℃), zone 2 (connection section between single screw and die, temperature 185℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0035] Comparative Example 4

[0036] This comparative example provides a method for preparing a PBAT thin film, which includes the following steps: 1) In a twin-screw extruder, 100 parts of PBAT were melt-blended at 185°C at a rotation speed of 70 r / min to obtain PBAT granules; 2) PBAT granules are sequentially passed through the melt conveying zone (single screw extruder, temperature 185℃), zone 2 (connection section between single screw and die, temperature 185℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0037] Figure 2 The SEM image of the brittle fracture surface of the film prepared in Comparative Example 2 by keeping PBAT / PHBV in a molten state throughout the melt blending process is shown. The layered structure of PHBV in the blown film has a small thickness, with dimensions not exceeding 10 μm in the two-dimensional direction.

[0038] Figure 3 The image shows a SEM image of the brittle fracture surface of the film prepared in Example 4 by melting PHBV in the melt blending zone and melting it in the die lip zone without melting it. The layered structure of PHBV in the blown film has a high thickness and a two-dimensional dimension exceeding 20 μm. This demonstrates that the present invention can form a PHBV layered structure with a larger two-dimensional dimension in PBAT at the same mass ratio.

[0039] Table 1 shows the barrier performance test results of the films obtained in Examples 1-4 and Comparative Examples 1-4.

[0040] Table 1

[0041] In Example 1, 95 parts of PBAT remained in a molten state throughout the melt blending process, while 5 parts of PHBV powder remained unmelted. However, the PHBV completely melted before the exit die area, resulting in a blown film with a water vapor permeability coefficient of 4.97 × 10⁻⁶. - 13 g·cm / m 2 The oxygen permeability coefficient is 1.61 × 10⁻⁶ s·Pa. -13 cm 3 ·cm / (cm 2 ·s·Pa).

[0042] In Example 2, 90 parts of PBAT remained in a molten state throughout the melt blending process, while 10 parts of PHBV powder remained unmelted. However, the PHBV completely melted before the exit die area, resulting in a blown film with a water vapor transmission coefficient of 3.16 × 10⁻⁶. - 13 g·cm / m 2 The oxygen permeability coefficient is 1.21 × 10⁻⁶ Pa·s. -13 cm 3 ·cm / (cm 2 ·s·Pa). In Comparative Example 1, PBAT / PHBV (90:10) remained in a molten state throughout, and the water vapor transmission coefficient of the blown film was 4.49×10. -13 g·cm / m 2 The oxygen permeability coefficient is 1.52 × 10⁻⁶ Pa·s. -13 cm 3 ·cm / (cm 2 ·s·Pa). Compared to Example 2, the water vapor transmission coefficient and oxygen transmission coefficient of the blown film in Comparative Example 1 were significantly reduced.

[0043] In Example 3, 85 parts of PBAT remained in a molten state throughout the melt blending process, while 15 parts of PHBV powder remained unmelted. However, the PHBV completely melted before the exit die area, resulting in a blown film with a water vapor transmission coefficient of 2.36 × 10⁻⁶. - 13 g·cm / m 2 The oxygen permeability coefficient is 0.93 × 10⁻⁶ Pa·s. -13 cm 3 ·cm / (cm 2 ·s·Pa).

[0044] In Example 4, PBAT remained in a molten state throughout the melt blending process, while PHBV powder remained unmelted. However, PHBV completely melted before the exit die zone, resulting in a blown film with a water vapor transmission coefficient of 1.86 × 10⁻⁶.-13 g·cm / m 2 The oxygen permeability coefficient is 0.64 × 10⁻⁶ s·Pa. -13 cm 3 ·cm / (cm 2 In Comparative Example 2, PBAT / PHBV (80:20) remained in a molten state throughout, and the water vapor transmission coefficient of the blown film was 2.81 × 10⁻⁶. -13 g·cm / m 2 The oxygen permeability coefficient is 1.08 × 10⁻⁶ s·Pa. -13 cm 3 ·cm / (cm 2 In Comparative Example 3, PBAT / PHBV (80:20) was in a non-molten state in the twin-screw extruder and in a molten state in the single-screw extruder. This resulted in a certain degree of dispersion of the molten PHBV, leading to a decrease in the sheet size after blown film production. Consequently, the water vapor permeability coefficient of the blown film was 2.30 × 10⁻⁶. - 13 g·cm / m 2 The oxygen permeability coefficient is 0.93 × 10⁻⁶ Pa·s. -13 cm 3 ·cm / (cm 2 ·s·Pa). Compared to Example 4, the water vapor permeability and oxygen permeability of the blown films in Comparative Example 2 and Comparative Example 3 were significantly reduced.

[0045] In Comparative Example 4, the water vapor transmission coefficient of 100 parts of PBAT was 6.33 × 10⁻⁶. -13 g·cm / m 2 The oxygen permeability coefficient is 1.85 × 10⁻⁶ s·Pa. -13 cm 3 ·cm / (cm 2 ·s·Pa).

[0046] Example 5

[0047] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 130°C with a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0048] Example 6

[0049] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 140°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single-screw extruder, temperature 150℃), zone 2 (connection section between the single screw and the die, temperature 165℃), zone 3 (die section, temperature 180℃), and the die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5. Example 7 This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 140℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0050] Example 8

[0051] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 145℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0052] Example 9

[0053] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 170℃) and die lip zone (temperature 170℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0054] Example 10

[0055] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 190℃) and die lip zone (temperature 190℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0056] Example 11

[0057] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 200℃) and die lip zone (temperature 200℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0058] Comparative Example 5

[0059] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 120°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0060] Comparative Example 6

[0061] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 130℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0062] Comparative Example 7

[0063] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a speed of 70 r / min to obtain a blend of PBAT and PHBV. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 160℃) and die lip zone (temperature 160℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.5.

[0064] Table 2 shows the barrier performance test results of the films obtained in Examples 4-11 and Comparative Examples 5-7.

[0065] Table 2

[0066] In Examples 4-6, the twin-screw temperature was between 130 and 150°C, and the water vapor permeability and oxygen permeability of the blown films did not change significantly.

[0067] In Examples 4, 7, and 8, the temperature in the melt conveying zone (single screw extruder) was between 140 and 150°C, and the water vapor permeability and oxygen permeability of the blown films did not change significantly.

[0068] In Examples 4, 9, 10, and 11, the temperature in the die lip region was between 170 and 200°C, and the water vapor permeability and oxygen permeability of the blown film did not change significantly.

[0069] In Comparative Example 5, the twin-screw temperature was below 130°C, and the viscosity was too high to allow for twin-screw conveying.

[0070] In Comparative Example 6, the temperature in the melt conveying zone (single screw extruder) was below 140°C, and the viscosity was too high to be conveyed by a single screw.

[0071] In Comparative Example 7, the temperature in the die lip area was below 170°C, PHBV could not melt, the extruded film suffered severe cracking, and blown film could not be produced.

[0072] Example 12

[0073] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 4.

[0074] Example 13

[0075] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 5.

[0076] Example 14

[0077] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 5 and the blow-up ratio is 4.5.

[0078] Example 15

[0079] This embodiment provides a method for preparing a PBAT-based biodegradable thin film, such as... Figure 1 As shown, it includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 9 and the blow-up ratio is 4.5.

[0080] Comparative Example 8

[0081] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 1.

[0082] Comparative Example 9

[0083] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 2.

[0084] Comparative Example 10

[0085] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 6.5 and the blow-up ratio is 3.

[0086] Comparative Example 11

[0087] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio and blow-up ratio are 4.5 during blown film production.

[0088] Comparative Example 12

[0089] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 10 and the blow-up ratio is 4.5.

[0090] Comparative Example 13

[0091] This comparative example provides a method for preparing a PBAT-based biodegradable film, which includes the following steps: 1) PHBV was prepared into powder particles by cryogenic milling, with a size distribution of 20~100μm; 2) In a twin-screw extruder, 80 parts of PBAT and 20 parts of PHBV powder were melt-blended at 150°C at a rotation speed of 70 r / min to obtain a PBAT and PHBV blend. 3) The blend is sequentially passed through the melt conveying zone (single screw extruder, temperature 150℃), zone 2 (connection section between single screw and die, temperature 165℃), zone 3 (die section, temperature 180℃) and die lip zone (temperature 180℃) for blown film production. The stretch ratio is 15 and the blow-up ratio is 4.5.

[0092] Table 3 shows the barrier performance test results of the films obtained in Examples 4, 12-15 and Comparative Examples 8-13.

[0093] Table 3

[0094] As can be seen from Examples 4, 12, 13 and Comparative Examples 8-10, when the blow-up ratio is between 4 and 5, the water vapor permeability coefficient and oxygen permeability coefficient of the blown film are relatively small, and the film has better barrier properties.

[0095] As shown in Examples 4, 14, and 15, and Comparative Examples 11-13, when the blow-up ratio is between 5 and 9, the blown film has lower water vapor permeability and oxygen permeability, resulting in better film barrier performance. When the draw ratio is less than 5, the extrudate cannot be drawn in time, causing accumulation and preventing film formation. When the draw ratio is greater than 9, rapid stretching makes the dispersed phase more prone to forming a fibrous structure, making it difficult to form a lamellar structure, leading to a decrease in barrier performance.

[0096] In summary, as shown in Tables 1-3, compared to films prepared by full melt processing, the water vapor permeability and oxygen permeability of the films prepared by the method of this invention are reduced by 30-40%. Therefore, using the method of this invention to form a PHBV layered structure with larger two-dimensional dimensions in PBAT is beneficial for improving the barrier properties of PBAT films.

Claims

1. A method for preparing a high-barrier PBAT-based biodegradable thin film, wherein, Includes the following steps: Powdered high-barrier biodegradable polyester and PBAT are melt-blended to obtain a blend. The blend is blown into a film to obtain a high-barrier PBAT-based biodegradable film; Wherein, the high-barrier biodegradable polyester is selected from PLA and / or PHBV; the weight ratio of PBAT to the high-barrier biodegradable polyester is 80~95:5~20; The melt blending temperature is lower than the melt temperature of the high-barrier biodegradable polyester but higher than the melt temperature of the PBAT. During the blown film process, the temperature of the melt conveying zone is lower than the melt temperature of the high-barrier biodegradable polyester but higher than the melt temperature of the PBAT, and the temperature of the die lip zone is higher than the melt temperature of the high-barrier biodegradable polyester.

2. The method for preparing the high-barrier PBAT-based biodegradable film according to claim 1, wherein, The melt blending temperature is 130~150℃.

3. The method for preparing the high-barrier PBAT-based biodegradable film according to claim 1, wherein, The temperature of the melting conveying zone is 130~150℃.

4. The method for preparing the high-barrier PBAT-based biodegradable film according to claim 3, wherein, The temperature of the die lip area is 170~200℃.

5. The method for preparing a high-barrier PBAT-based biodegradable film according to claim 1 or 2, wherein, The weight ratio of the PBAT to the high-barrier biodegradable polyester is 80~85:15~20.

6. The method for preparing a high-barrier PBAT-based biodegradable film according to claim 1, wherein, The draw ratio of the blown film is 5 to 9.

7. The method for preparing a high-barrier PBAT-based biodegradable film according to claim 1, wherein, The blown film has a blow-up ratio of 4 to 5.

8. The method for preparing a high-barrier PBAT-based biodegradable film according to claim 1, wherein, The high-barrier biodegradable polyester has a particle size of 20~500μm.

9. A high-barrier PBAT-based biodegradable film, wherein, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The high-barrier PBAT-based biodegradable film according to claim 9, wherein, The thickness of the high-barrier PBAT-based biodegradable film is 10~100μm.

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