Preparation and control method of PBAT / PBS film imitating shell nano-multilayer structure

Abstract

The application discloses a preparation and regulation method of poly(butylene terephthalate-co-butylene succinate) / poly(butylene succinate) (PBAT / PBS) film imitating shell nano-multilayer structure, which comprises the following steps: (1) preparing PBAT / PBS / chain extender blend granules through melt blending; (2) preparing a PBAT / PBS / chain extender casting film with a co-continuous phase structure characteristic through extrusion; and (3) preparing a PBAT / PBS nano-multilayer biomimetic structure film through phase transformation by unidirectional stretching or bidirectional stretching. The nano-multilayer film prepared by the application has excellent mechanical properties, and the highest breaking strength can reach 120.6 MPa, the highest tear strength can reach 112.8 kN / m, and the highest puncture strength can reach 362.1 N / mm, which are 2.7 times, 1.6 times and 11.1 times higher than those of a film not subjected to the above processing steps, respectively. The imitating shell nano-multilayer structure obtained by the method has the characteristics that the'mud' layers are interconnected, and the 'brick' layers are also interconnected, thereby achieving good tear resistance. The method disclosed by the application can well regulate the thickness of the multilayer structure. In addition, the preparation process of the method is simple, the preparation period is short, mass industrial production can be realized, and the method plays a positive role in high performance of degradable films.

Description

Technical Field

[0001] This invention relates to the field of biodegradable thin film materials and their preparation, and particularly to the preparation and control method of a high-strength, high-toughness poly(butylene terephthalate) (PBAT) / poly(butylene succinate) (PBS) thin film nanomultilayer structure with shell-like characteristics. Background Technology

[0002] High-performance biodegradable films can replace traditional petroleum-based polymer films, reducing pollution. To meet the diverse needs of multiple industries, these films typically require comprehensive properties such as high strength and high toughness, meaning they need high tensile strength and good tear resistance. Films used in the packaging field usually also need high puncture resistance. However, strength and toughness are often contradictory; reinforcement usually leads to a loss of toughness, a problem that limits the application of biodegradable films.

[0003] Natural materials in the world offer us valuable inspiration. Mussels and pearl oysters, with their hard shells, exhibit remarkable toughness, capable of withstanding significant external forces without deformation. The inner layers of these animals' shells consist of alternating layers of calcium carbonate aragonite lamellae and soft organic layers, forming a "brick-and-mortar" layered structure. The aragonite lamellae can withstand substantial external forces, which are then conducted along the soft organic layers, thus contributing to the shell's strength and toughness. This suggests that constructing multi-layered structures can achieve superior mechanical properties to meet our application requirements. Currently, methods for constructing multi-layered shell-like structures primarily employ casting, freeze-drying, and lamination. Among them, the method of constructing a multilayer structure by solution freeze-drying and utilizing the growth and exclusion effect of ice crystals is the most commonly used (An electrode material with a biomimetic shell layered structure and its preparation method and application [P]. Shaanxi Province: CN114156445B, 2023-12-19; ​​A biomimetic shell nacre layer material with a layered structure and its preparation method [P]. Hubei Province: CN111574137B, 2021-04-23.). Ice crystals are grown in the matrix solution, and the ice crystals are removed by freeze-drying. Then, the dispersed phase solution is incorporated by means of filtration, etc., and finally a multilayer structure with alternating matrix and dispersed phase is formed (Adv. Mater. 2016, 28 (1), 50-56; ACS nano, 2022, 16(11), 19067-19086.). However, these methods usually face bottleneck problems such as complex preparation process, low yield and long preparation cycle, which limit the further application of biomimetic shell multilayer materials. Furthermore, the interfacial interactions between the matrix and the dispersed phase deserve consideration, as they affect the material's mechanical properties. Poor interfacial interactions often lead to significant phase separation, severely degrading the material's performance. Therefore, developing a simple, efficient, and large-scale continuous production method for preparing shell-like structural materials, while also addressing interfacial bonding capabilities, has significant practical application value. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a process method for large-scale preparation of nanoscale multilayer structures of PBAT / PBS films. The mechanism involves melt extrusion of a PBAT / PBS / chain extender blend to obtain a PBAT / PBS cast film with a co-continuous phase structure. During this process, a chain extender is added to prevent phase aggregation, improve interfacial interactions, and form a smaller co-continuous phase structure. The cast film is then subjected to a specific temperature range (80~130°C). oC) Thermal stretching forces the cocontinuous phase structure to deform under an external force field. By controlling different stretching ratios, multilayer structures of varying thicknesses are obtained, exhibiting shell-like characteristics. Subsequently, quenching is performed to fix the phase structure morphology, ultimately yielding a PBAT / PBS nanoscale multilayer film with high fracture strength, high tear strength, and high puncture strength while retaining a certain degree of toughness.

[0005] The advantage of this invention is that it can prepare PBAT / PBS nanolayered thin film materials with shell-like structures using simple processing equipment and a simple, industrially scalable process, which can easily achieve mass production. This is of great significance for broadening the methods for preparing and controlling the structure of high-performance bio-based biodegradable thin film materials.

[0006] The technical solution of the present invention for achieving the above objectives is as follows: (1) Preparation of PBAT / PBS / chain extender blend granules: PBAT resin, PBS resin and chain extender are extruded through a twin-screw extruder at 110-190 °C. o C is melt-extruded and granulated to obtain PBAT / PBS / chain extender blend granules; (2) Preparation of PBAT / PBS / chain extender cast film with co-continuous phase structure: The granules from step (1) are fed into a single-screw extruder at 120~180°C. o After C is melted, it is extruded through a die and cooled by a cooling roller to form a cast film with a co-continuous phase structure; (3) Preparation of PBAT / PBS / chain extender biomimetic nano-multilayer structure film: The cast film from step (2) is sent to a stretching device for uniaxial or biaxial stretching. The stretching ratio is controlled by setting the stretching ratio of the stretching device. The stretching temperature is 80~130℃. o Between C, after cooling and annealing, a PBAT / PBS / chain extender nano-multilayer structure film is formed.

[0007] The chain extender in step 1 can be a substance containing polyepoxy functional groups, a diamine, or other chain extenders commonly used in the art.

[0008] Preferably, the melting temperature in step 1 is 110~190°C. o C, further optimized to 125-175 o C.

[0009] Preferably, the melting temperature in step 2 is 120~180°C. o C, further optimized to 130-165 o C.

[0010] Preferably, the stretching temperature in step 3 is 80~120℃. o C, further optimized to 90-110 oC.

[0011] Preferably, in step 3, the uniaxial stretching ratio is 2 to 5, and the biaxial stretching ratio is 2×2 to 5×5.

[0012] Preferably, the stretching rate used in step 3 for hot stretching is 1-100 mm / min, more preferably 50-100 mm / min. Preferably, the thickness of the stretched film is 10-200 μm.

[0013] Preferably, in step 1, a twin-screw extruder is used for melting, extrusion, and granulation; the screw speed is 100-200 r / min.

[0014] Preferably, the chain extender in step 1 has a mass fraction of 1-2 wt%.

[0015] Preferably, in step 2, a single-screw extruder is used for melting and extrusion; the screw speed is 50-150 r / min.

[0016] Preferably, in step 2, the cocontinuous phase structure can be transformed into a multilayer structure, wherein the mass ratio of PBAT to PBS is 1:(0.5~1.5).

[0017] In this invention, the content of the chain extender is 1~3 wt%, and the mass ratio of PBAT to PBS is 1:(0.5~1.5). The above-mentioned range is the range value finally determined after a large number of experiments. It can ensure the normal progress of the preparation process and ensure that the final film has excellent mechanical properties. Moreover, those skilled in the art cannot obtain this value with a few experiments.

[0018] Beneficial effects The method for preparing PBAT / PBS film-like shell nanolayered structures provided by this invention is simple, efficient, and continuous compared to existing methods such as freeze-drying, casting, and lamination, and is suitable for large-scale production and manufacturing.

[0019] Compared with the prior art, the present invention has the following advantages: (1) This invention utilizes PBAT / PBS / chain extender to form a cocontinuous phase structure of smaller size, applies a tensile force field to force the cocontinuous phase structure to deform, and finally forms a nanoscale multilayer structure with typical characteristics of a shell structure.

[0020] (2) Due to the nature of the cocontinuous phase structure, the PBAT phases remain interconnected after deformation, and the PBS phases are also interconnected. That is, in the shell structure, the "mud" is interconnected while the "bricks" are also interconnected.

[0021] (3) The nano-multilayer structure film prepared by the present invention has ultra-high puncture resistance, with a puncture strength of up to 362.1 N / mm, and its tear resistance and tensile properties are also greatly improved.

[0022] (4) The process of this invention is simple. It only requires simple blending, extrusion and stretching to make the film have a nano-multilayer structure similar to a seashell. It has high production efficiency and is suitable for large-scale continuous production in industry.

[0023] (5) The method for preparing the shell-like multilayer structure mentioned in this invention is not limited to using PBAT / PBS to form a cocontinuous phase structure. Other blend materials that can be used to prepare cocontinuous phase structures can also be prepared into nano-multilayer structures using this method. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the method flow and a schematic diagram of the changes in the internal structure of the thin film of the present invention.

[0025] Figure 2 This is a schematic diagram of the chain extender structure used in the examples.

[0026] Figure 3 This is a diagram illustrating the reaction mechanism of chain extenders with PBAT and PBS.

[0027] Figure 4 Scanning electron microscope images of Examples 35, 39 and Comparative Examples 8, 12. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-described invention are still within the scope of protection of the present invention.

[0029] The general process of the preparation method of the PBAT / PBS film imitation seashell nanolayered structure described in this invention is as follows: Figure 1 As shown.

[0030] In this embodiment, the chain extender used is ADR, specifically Joncryl ADR-4468. This is an acrylate containing polyepoxy functional groups. During melt extrusion, it can react with the end groups (hydroxyl or carboxyl groups) of PBAT and PBS molecular chains to form block copolymers, improving the interfacial interaction between PBAT and PBS, preventing phase aggregation, and resulting in a co-continuous phase structure with smaller phase size after melt extrusion. Subsequent stretching then yields a nanoscale layered structure. Its molecular structure is as follows: Figure 2It is worth noting that the chain extender ADR used in this invention is to illustrate the role of the chain extender; other commonly used chain extenders in the art can achieve the same effect as this invention.

[0031] Examples 1-48 are shown in Table 1 below: (1) Preparation of PBAT / PBS / chain extender blend granules: PBAT resin, PBS resin and chain extender Joncryl ADR-4468 (ADR) were extruded through a twin-screw extruder at 110-190 rpm. o C-type melt extrusion and granulation yield PBAT / PBS / ADR blend granules. The twin-screw extruder operates at a temperature range of 110~190°C from the feed inlet to the die. o C. The screw speed is 100–200 r / min. (The mass ratio of PBAT to PBS is abbreviated as mass ratio, and the ADR addition is a mass percentage.) (2) Preparation of PBAT / PBS / ADR cast films with co-continuous phase structure characteristics: The granules from step (1) are fed into a single-screw extruder at 120~180°C. o After C melts, it is extruded through a die and cooled by cooling rollers to form a cast film with a co-continuous phase structure. The temperature range from the feed port to the die in the single-screw extruder is 120~180°C. o C, the screw speed is 50~150 r / min.

[0032] (3) Preparation of PBAT / PBS / ADR biomimetic nano-multilayer structure film: The cast film from step (2) is sent to a stretching device for uniaxial or biaxial stretching. The stretching ratio is controlled by setting the stretching ratio of the stretching device, which is between 80 and 130. o Hot stretching is performed at C, followed by quenching to form a PBAT / PBS / ADR nano-multilayer structure film. The temperature of the stretching rollers is 80~120℃. o C. The speed of the stretching roller is 1.0~100.0 m / min, the unidirectional stretching ratio is controlled at 2~5, and the bidirectional stretching ratio is controlled at 2×2~5×5.

[0033] Comparative Examples 1-9 are shown in Table 1 below: (1) Preparation of PBAT / PBS / chain extender blend granules: PBAT resin, PBS resin and chain extender Joncryl ADR-4468 (ADR) were extruded through a twin-screw extruder at 110-190 rpm. o C-type melt extrusion and granulation yield PBAT / PBS / ADR blend granules. The twin-screw extruder operates at a temperature range of 110~190°C from the feed inlet to the die. o C. The screw speed is 100-200 r / min. (The mass ratio of PBAT to PBS is abbreviated as mass ratio, and the ADR addition is a mass percentage).

[0034] (2) Preparation of PBAT / PBS / ADR cast films with co-continuous phase structure characteristics: The granules from step (1) are fed into a single-screw extruder at 120~180°C. o After C melts, it is extruded through a die and cooled by cooling rollers to form a cast film with a co-continuous phase structure. The temperature range from the feed port to the die in the single-screw extruder is 120~180°C. o C, the screw speed is 50~150 r / min. The stretch ratio of the resulting cast film is set to 0.

[0035] Comparative Examples 10-13 are shown in Table 1 below: (1) Preparation of PBAT / PBS blend granules: PBAT resin and PBS resin were processed by a twin-screw extruder at 110-190 rpm. o C-type melt extrusion and granulation yield PBAT / PBS blend granules. The twin-screw extruder operates at a temperature range of 110~190°C from the feed inlet to the die. o C. The screw speed is 100–200 r / min. (The mass ratio of PBAT to PBS is abbreviated as mass ratio.) (2) Preparation of PBAT / PBS cast film with co-continuous phase structure: The granules from step (1) are fed into a single-screw extruder at 120~180°C. o After C melts, it is extruded through a die and cooled by cooling rollers to form a cast film with a co-continuous phase structure. The temperature range from the feed port to the die in the single-screw extruder is 120~180°C. o C, the screw speed is 50~150 r / min. The stretch ratio of the resulting cast film is set to 0.

[0036] Comparative Examples 14-17 are shown in Table 1 below: (1) Preparation of PBAT granules: PBAT raw material is melt-extruded and granulated using a twin-screw extruder to obtain PBAT granules. The temperature range of the twin-screw extruder from the feed port to the die is 110~190°C. o C, the screw speed is 100~200 r / min.

[0037] (2) Preparation of PBAT cast film: The granules from step (1) are fed into a single-screw extruder, melted, and extruded through a die. After cooling by a cooling roller, a cast film is formed. The temperature range from the feed port to the die in the single-screw extruder is 120~180°C. o C, the screw speed is 50~150 r / min.

[0038] (3) Preparation of PBAT stretched film: The cast film from step (2) is sent to a stretching device for biaxial stretching. The stretching ratio is controlled by changing the stretching ratio, and the film is quenched to form a PBAT stretched film. The temperature of the stretching roller is 80~120℃. o C, the stretching roller speed is 1.0~100.0 m / min, and the biaxial stretching ratio is controlled at 2×2~5×5.

[0039] Comparative Example 18 is shown in Table 1 below: (1) Preparation of PBAT granules: PBAT raw material is melt-extruded and granulated using a twin-screw extruder to obtain PBAT granules. The temperature range of the twin-screw extruder from the feed port to the die is 110~190°C. o C, the screw speed is 100~200 r / min.

[0040] (2) Preparation of PBAT cast film: The granules from step (1) are fed into a single-screw extruder, melted, and extruded through a die. After cooling by a cooling roller, a cast film is formed. The temperature range from the feed port to the die in the single-screw extruder is 120~180°C. o C, the screw speed is 50~150 r / min. The stretch ratio of the resulting cast film is set to 0.

[0041] Table 1 Mechanical properties of Examples 1-48 and Comparative Examples 1-18 under different preparation process conditions

[0042] In this invention, the content of the chain extender is 1~3 wt%, and the mass ratio of PBAT to PBS is 1:(0.5~1.5). The above-mentioned range is the range value finally determined after a large number of experiments. It can ensure the normal progress of the preparation process and ensure that the final film has excellent mechanical properties. Moreover, those skilled in the art cannot obtain this value with a few experiments.

[0043] Material characterization experiments 1) Microscopic morphology: To investigate the nanomultilayer structure of the thin films, the microstructure of the films was observed using scanning electron microscopy. Examples 35 and 39 and Comparative Examples 8 and 12 are used as examples, and the results are as follows: Figure 2As shown, Comparative Examples 8 and 12 both formed very typical co-continuous structures, with the two phases interconnected. However, in Comparative Example 8, the phase region size is finer than in Comparative Example 12. The phase region size in Comparative Example 12 is 1.5-1.8 μm, while in Comparative Example 8 it is 1-1.3 μm. This confirms that the introduction of the chain extender effectively improved the interfacial interaction between the two phases, reduced the phase region size, and facilitated subsequent stretching to form a thinner sheet structure. In Example 35, after uniaxial stretching, the PBAT / PBS / ADR film exhibited a significant multilayer structure, with the nanolayer thickness approximately 500-1000 nm. Similarly, in Example 39, after biaxial stretching, the PBAT / PBS / ADR film also exhibited a significant multilayer structure, with an even thinner nanolayer thickness of approximately 100-300 nm. The formed nanolayer structure is similar to the cross-sectional structure of a seashell, achieving the purpose of mimicking a seashell structure. It was also found that in the multilayer structure of this invention, PBAT and PBS still maintain their interconnected characteristics. That is, in the mimicking seashell structure, the "mud" is interconnected, and the "bricks" are also interconnected. The method described in this invention has successfully prepared nanoscale multilayer structures.

[0044] 2) Mechanical properties: Regarding mechanical properties, as shown in Table 1, the preparation method of the nano-multilayer structure provided by this invention can effectively enhance the mechanical properties of PBAT / PBS / ADR films. Taking Examples 25-32 and Comparative Example 7 as examples, the biaxially stretched multilayer PBAT / PBS films exhibit excellent mechanical properties, with a maximum tensile strength of 120.6 MPa, a maximum tear strength of 112.8 kN / m, and a maximum puncture resistance of 362.1 N / mm. Compared with the unstretched cocontinuous phase PBAT / PBS film (tensile strength 44.2 MPa, tear strength up to 69.3 kN / m, and puncture resistance up to 32.5 N / mm), the performance is significantly improved, indicating that the biomimetic nano-multilayer structure significantly improves the mechanical properties of the material. In addition, taking Examples 25-32 and Comparative Examples 14-17 as examples, the mechanical properties of the nano-multilayer PBAT / PBS films formed by the cocontinuous phase structure are also significantly higher than those of the stretched PBAT film. Meanwhile, the stretch ratio also affects the mechanical properties of the nano-multilayer PBAT / PBS film. Taking Examples 29-32 as examples, the film with a biaxial stretch ratio of 5×5 exhibits the highest tensile strength, tear strength, and puncture resistance. Furthermore, compared to Examples 1-24, the content of the chain extender also affects the mechanical properties of the film. Extensive testing revealed that low levels of chain extender (1-2% by mass) improve mechanical properties, while high levels (3% by mass) have the opposite effect.

[0045] In summary, the method for preparing the nano-multilayer structure described in this invention has demonstrated significant improvement effects, and the resulting blend film exhibits high tensile strength, tear strength, and puncture resistance. Furthermore, this preparation method is simple, efficient, and requires minimal equipment; it can be implemented for continuous industrial production, making it highly suitable for large-scale industrial manufacturing.

[0046] Although the present invention has been described above in conjunction with exemplary embodiments, it should be clear to those skilled in the art that various modifications and variations can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing and controlling a PBAT / PBS film-like shell-like nanolayered structure, characterized in that, Includes the following steps: (1) Preparation of PBAT / PBS / chain extender blend granules: PBAT resin, PBS resin and chain extender are extruded through a twin-screw extruder at 110-190 °C. o C. Melt extrusion and granulation yield PBAT / PBS / chain extender blend granules; wherein, to form a co-continuous phase structure, the mass ratio of PBAT to PBS is 1:(0.5~1.5), and the amount of chain extender added is controlled at 1-3% by mass fraction; (2) Preparation of PBAT / PBS / chain extender cast film with co-continuous phase structure: The granules from step (1) are fed into a single-screw extruder at 120~180°C. o After C is melted, it is extruded through a die and cooled by a cooling roller to form a cast film with a co-continuous phase structure. (3) Preparation of PBAT / PBS / chain extender biomimetic nano-multilayer structure film: The cast film from step (2) is sent to a stretching device for uniaxial or biaxial stretching. The stretching ratio is controlled by setting the stretching ratio of the stretching device. The stretching temperature is 80~130℃. o Between C, after cooling and annealing, a PBAT / PBS / chain extender nano-multilayer structure film is formed; PBAT and PBS first form a cocontinuous phase structure, and the cocontinuous phase structure is induced to deform by an external force field, eventually forming a layered structure; this structure has a shell-like "brick-mud" nano-multilayer structure, with PBAT maintaining cocontinuous characteristics, and PBS also maintaining cocontinuous characteristics, that is, in the shell-like structure, the "mud" is interconnected, and the "bricks" are also interconnected.

2. The method for preparing and controlling the PBAT / PBS film-like shell nanolayered structure according to claim 1, characterized in that: The uniaxial stretch ratio is controlled at 2~5, and the biaxial stretch ratio is controlled at 2×2~5×5.

3. The nano-multilayered thin film prepared by the method for preparing and controlling the shell-like nano-multilayered structure of PBAT / PBS thin film according to claim 1, characterized in that: The thickness of each layer in the multilayer structure is 100~1000 nm.

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