High-transparency ultralow-haze PBAT-based flexible film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of biodegradable materials, in particular to a high-transparency ultralow-haze PBAT-based flexible film and a preparation method and application thereof, and the high-transparency ultralow-haze PBAT-based flexible film is composed of poly (butylene adipate-co-butylene terephthalate), poly (butylene succinate-co-butylene terephthalate), an antioxidant, an anti-hydrolysis agent, an anti-blocking agent and a dispersing agent in parts by weight. The polyethylene terephthalate-butylene adipate is used as a main component, the polyethylene terephthalate-butylene adipate can be added as required, and a small amount of other assistants are added to guarantee the performance of the film. According to the invention, PBAT and PBST are blended to improve the optical performance of the film, casting cooling inhibits the formation of a large crystal region, and the transparency is synergistically increased; the problems of low transparency and high haze of the PBAT-based film are solved, the use requirement of the packaging field on the film material is met, and the application of the PBAT material is further widened.

Description

Technical Field

[0001] This invention relates to the field of biodegradable materials technology, specifically to a highly transparent, ultra-low haze PBAT-based flexible film, its preparation method, and its applications. Background Technology

[0002] Polybutylene terephthalate (PBAT), as a high-performance biodegradable material, possesses both flexibility and toughness. Its processing properties are similar to low-density polyethylene (LDPE), making it highly favored in the field of biodegradable film materials and possessing broad application prospects. To improve the transparency of PBAT-based films, existing technologies have proposed various solutions. For example, patent CN 107345053 A discloses an ultra-thin, ultra-transparent, fully biodegradable blown film material and its preparation method. By introducing a special reinforcing, toughening, and transparency-enhancing masterbatch into PBAT and PLA, and blowing the film thickness to below 6 μm, a highly transparent film is obtained. Patent CN 112980161 A discloses another highly transparent PBAT material and its preparation method. First, a biodegradable polyester elastomer is prepared, then blended with poly(3-hydroxybutyrate-co-4-hydroxybutyrate) to obtain a transparent modified resin. Subsequently, it is blended with PBAT, granulated, and blown into a 12 μm film to achieve a high transparency effect. These existing technologies all require the introduction of additional antireflective materials or a significant reduction in film thickness to improve transparency, which has certain limitations.

[0003] Furthermore, the commonly used processing method for PBAT-based films is blown film blowing. While this method offers advantages such as simple equipment and low cost, it has significant technical drawbacks. The low cooling efficiency of blown film blowing allows the semi-crystalline polymer PBAT ample time to grow crystals, forming large crystalline regions. This directly results in films with low transparency and high haze, severely impacting the visibility of the packaged contents. Simultaneously, film thickness itself also affects transparency and haze. Existing technologies, in pursuit of high transparency, excessively thin the film, potentially affecting its mechanical properties and operational stability. Given these shortcomings of existing technologies, developing a highly transparent, ultra-low haze PBAT-based flexible film through formulation optimization and processing improvements, without adding additional anti-reflective agents or significantly reducing film thickness, has become a pressing technical challenge in the field of biodegradable materials. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a highly transparent, ultra-low haze PBAT-based flexible film, its preparation method, and its applications.

[0005] (II) Technical Solution A highly transparent, ultra-low haze PBAT-based flexible film, wherein the film is composed of the following components in parts by weight: 50-100 parts of polybutylene terephthalate (PET); 0-50 parts of PET; 0.1-1 parts of antioxidant; 0.1-1 parts of anti-hydrolysis agent; 0.1-1 parts of opening agent; and 0.1-1 parts of dispersant.

[0006] Preferably, the antioxidant is one or more of antioxidant 168, antioxidant 1010, and antioxidant 1076.

[0007] Preferably, the anti-hydrolysis agent is one or more of monomeric carbodiimide and polymeric carbodiimide.

[0008] Preferably, the opening agent is one or a combination of oleamide, erucamide, and pentaerythritol stearate.

[0009] Preferably, the dispersant is white oil.

[0010] Preferably, the film is composed of the following components in parts by weight: 80 parts polybutylene terephthalate (PBAT), 20 parts polybutylene terephthalate (PBST), 0.2 parts antioxidant 1010, 0.1 parts antioxidant 168, 0.2 parts monomeric carbodiimide, 0.8 parts pentaerythritol stearate, and 0.05 parts white oil.

[0011] Preferably, the method for preparing the highly transparent, ultra-low haze PBAT-based flexible film includes the following steps: S1, in the order of granules-liquid-powder, add PBAT, PBST, dispersant, antioxidant, anti-hydrolysis agent and opening agent to the high-speed mixer step by step and mix evenly; S2: The mixture is fed into a twin-screw extruder, melt-extruded, cooled by air and then pelletized to obtain PBAT-based modified material; S3: Feed the PBAT-based modified material into the casting machine for plasticizing and casting; S4: Cooling of plasticized materials via cooling rollers; S5: The cooled film is wound up to obtain a PBAT-based flexible film.

[0012] 8. The method for preparing a highly transparent, ultra-low haze PBAT-based flexible film according to claim 7, characterized in that the temperature of each zone of the twin-screw extruder is set as follows: zone 1 90℃, zone 2 150℃, zone 3 160℃, zones 4-11 170℃, zone 12 165℃, and screen changing 160℃.

[0013] 9. The method for preparing a highly transparent, ultra-low haze PBAT-based flexible film according to claim 7, characterized in that, in S2, the twin-screw extruder processing temperature is 120-170℃ and the screw speed is 200-300 r / min; in S3, the casting machine extrusion temperature is 140-165℃ and the extrusion speed is 10-20 Hz; in S4, the cooling roller temperature is 15-30℃ and the speed is 15-20 r / min; and in S5, the film winding speed is 15-20 r / min.

[0014] Preferably, the highly transparent, ultra-low haze PBAT-based flexible film is used in one or more garment bags or packaging bags.

[0015] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: 1. By melt-blending PBST polymer into the PBAT substrate, good compatibility and similar physical processing properties are achieved by utilizing the similar molecular structures of the two. At the same time, the synergistic effect generated by the difference in molecular structure effectively breaks the structural regularity of each, slows down the crystallization rate and reduces the crystallinity, fundamentally improving the optical properties of PBAT-based films. This solves the core problems of low transparency and high haze of traditional PBAT-based films, eliminating the need for additional antireflective agents and simplifying the formulation.

[0016] 2. The cooling efficiency is greatly improved by the cooling roller of the casting machine, which shortens the crystal growth time of the semi-crystalline polymer PBAT and further inhibits the formation of large crystal regions. This, together with the formulation optimization, contributes to the high transparency and ultra-low haze characteristics of the film.

[0017] 3. This film has a wide range of applications and can be used in various packaging products, which broadens the application field of PBAT materials, promotes the further popularization and development of biodegradable materials in the packaging industry, and has important economic value and social significance. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for preparing a highly transparent, ultra-low haze PBAT-based flexible thin film disclosed in this invention. Figure 2 This is a line graph comparing the transmittance and haze of the examples and comparative examples; Figure 3 This is a physical image of a PBAT-based flexible film with high transparency and ultra-low haze proposed in this invention. Detailed Implementation

[0019] according to Figures 1 to 3 The specific embodiments of the present invention are as follows: The following detailed description, in conjunction with examples and comparative examples, illustrates the high-transparency, ultra-low-haze PBAT-based flexible film of the present invention and its preparation method. All samples were tested using a uniform standard; the testing methods and equipment are as follows: Transmittance and haze: According to GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics"; Tensile strength and elongation at break: According to GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets"; Tear resistance: Tested according to GB / T 16578.1-2008; Puncture resistance: Tested according to BB / T 0024-2018 test method; Processing stability: scored from 1 to 5, with 5 being the best, evaluating the material's melt state, extrusion smoothness, and film formation integrity; Testing equipment: high-speed mixer, twin-screw extruder, casting machine, haze meter, universal testing machine.

[0020] Example 1 Components and parts by weight: 80 parts PBAT, 20 parts PBST, 0.2 parts antioxidant 1010, 0.1 parts antioxidant 168, 0.2 parts monomeric carbodiimide, 0.8 parts pentaerythritol stearate, and 0.05 parts white oil.

[0021] Preparation steps: S1. Start the high-speed mixer, set the speed to 800 r / min and the temperature to 40℃. First, add PBAT granules and PBST granules, and stir for 5 minutes until there is no obvious agglomeration of granules. Then, add white oil and continue stirring for 3 minutes until the white oil evenly covers the surface of the granules. Finally, add antioxidant 1010, antioxidant 168, monomeric carbodiimide, and pentaerythritol stearate powder in sequence, and continue stirring for 8 minutes. After observing that there is no local color difference in the material, stop stirring and discharge the material for later use.

[0022] S2: Preheat the temperature of each zone of the twin-screw extruder to the set values: Zone 1 90℃, Zone 2 150℃, Zone 3 160℃, Zones 4-11 170℃, Zone 12 165℃, and the screen changing device 160℃. After the temperature of each zone stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feeding speed to match the extrusion speed, and setting the screw speed to 250 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip enters the air-cooling device with an air velocity of 3 m / s and an air temperature of 25℃. After the strip cools to room temperature, it is cut into cylindrical PBAT-based modified material with a particle size of 3 mm and a length of 3 mm by a pelletizer.

[0023] S3, start the casting machine, preheat the extrusion temperature to 155℃, and simultaneously set the die head temperature to 158℃. After the temperature stabilizes for 20 minutes, add the PBAT-based modified material to the casting machine hopper, set the extrusion speed to 15Hz, and after the material is plasticized by the screw, it is evenly cast onto the surface of the casting roller through the T-die head to ensure that the cast film surface is free of bubbles and wrinkles.

[0024] S4 uses a chrome-plated cooling roller to cool the plasticized material. The cooling roller temperature is set to 25℃ and the rotation speed is 18r / min. The distance between the cooling roller and the casting roller is adjusted to ensure that the material is closely attached to the surface of the cooling roller and is quickly cooled and shaped into a continuous film preform. The thickness of the film preform is controlled by matching the rotation speed of the cooling roller with the extrusion speed.

[0025] S5. Before winding, start the automatic cutter to cut the film blank to a width of 500mm, ensuring that the cut edge is flat and free of burrs; set the winding speed to 18r / min, and finally obtain a PBAT-based flexible film with a thickness of 20μm.

[0026] Example 2 Components and parts by weight: 50 parts PBAT, 50 parts PBST, 0.5 parts antioxidant 1076, 1.0 part polymeric carbodiimide, 0.1 part oleamide, and 0.1 part white oil.

[0027] Preparation steps: S1, start the high-speed mixer, set the speed to 750 r / min and the temperature to 38℃, first add PBAT particles and PBST particles, stir for 6 minutes until the particles are evenly dispersed; after adding white oil, stir for 4 minutes until the white oil is completely integrated into the gaps between the particles; then add antioxidant 1076, polymeric carbodiimide and oleic amide powder, continue stirring for 10 minutes, observe the material status every 2 minutes, and stop stirring and discharge the material after ensuring that there is no powder sedimentation.

[0028] In step S2, the temperatures of each zone of the twin-screw extruder are preheated: zone 1 90℃, zone 2 148℃, zone 3 158℃, zones 4-11 168℃, zone 12 163℃, and the screen changing device 158℃. After each zone temperature stabilizes for 30 minutes without fluctuation, the mixture obtained in step S1 is fed into the extruder at a uniform speed through the hopper. The feed rate is controlled to match the extrusion rate, and the screw speed is set to 200 r / min. After the material is melted and plasticized in the barrel, it is extruded through the die to form a continuous strip. After the material is melted and extruded, the strip is cooled by an air-cooling device (air velocity 2.8 m / s, air temperature 23℃) and then cut into PBAT-based modified materials with a particle size of 3 mm and a length of 3 mm.

[0029] S3, the extrusion temperature of the casting machine is preheated to 140℃, the die temperature is 142℃, and after the temperature stabilizes, PBAT-based modified material is added. The extrusion speed is set to 10Hz, and the material is cast through the T-die to the casting roller to ensure that the width of the cast film is uniform.

[0030] S4, the cooling roller temperature is set to 15℃ and the rotation speed is 15r / min. The temperature is monitored in real time by the surface temperature sensor of the cooling roller to ensure stable cooling effect and the material is cooled and shaped into a film preform.

[0031] S5, the automatic cutter cuts the film blank to a width of 800mm, the winding machine rotates at 15r / min, and the film flatness is checked periodically during the winding process, finally obtaining a PBAT-based flexible film with a thickness of 20μm.

[0032] Example 3 Components and parts by weight: 60 parts PBAT, 40 parts PBST, 0.3 parts antioxidant 1076, 0.2 parts antioxidant 168, 0.6 parts polymeric carbodiimide, 0.4 parts pentaerythritol stearate, and 0.06 parts white oil.

[0033] Preparation steps: S1. Start the high-speed mixer, set the speed to 820 r / min and the temperature to 39℃. First, add PBAT granules and PBST granules, and stir for 5.5 min until the granules are no longer agglomerated. After adding white oil, stir for 3.5 min until the white oil is evenly distributed. Then add antioxidant 1076, antioxidant 168, polymeric carbodiimide, and pentaerythritol stearate powder, and continue stirring for 9 min. After observing that the material color is uniform, stop stirring and discharge the material for later use.

[0034] S2: Preheat the temperature of each zone of the twin-screw extruder: Zone 1 90℃, Zone 2 149℃, Zone 3 159℃, Zones 4-11 169℃, Zone 12 164℃, and the screen changing device 159℃. After each zone temperature stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feed speed to match the extrusion speed, and setting the screw speed to 230 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip is cooled by an air-cooling device (air velocity 3.0 m / s, air temperature 24℃) and cut into PBAT-based modified materials with a particle size of 3 mm and a length of 3 mm.

[0035] S3, preheat the extrusion temperature of the casting machine to 150℃, the die temperature to 153℃, add the modified material after the temperature stabilizes, set the extrusion speed to 13Hz, adjust the temperature distribution of the T-die to ensure that there are no defects on the film surface caused by temperature differences.

[0036] S4, cooling roller temperature 22℃, rotation speed 17r / min, by matching the speed of the cooling roller and the casting roller to control the thickness of the film blank and ensure sufficient cooling.

[0037] S5, the automatic cutter cuts the film blank to a width of 600mm, the winding machine rotates at 17r / min and maintains consistent film tension during the winding process, finally obtaining a PBAT-based flexible film with a thickness of 20μm.

[0038] Example 4 Components and parts by weight: 70 parts PBAT, 30 parts PBST, 0.4 parts antioxidant 1010, 0.1 parts antioxidant 1076, 0.3 parts monomeric carbodiimide, 0.6 parts oleamide, and 0.07 parts white oil.

[0039] Preparation steps: S1, start the high-speed mixer, set the speed to 780 r / min and the temperature to 41℃, first add PBAT granules and PBST granules, stir for 5 min until the granules are dispersed; after adding white oil, stir for 3 min until the white oil is incorporated into the granules; then add antioxidant 1010, antioxidant 1076, monomeric carbodiimide, and oleic amide powder, continue stirring for 8.5 min, and stop stirring after ensuring that there is no powder residue, and discharge the material.

[0040] S2: Preheat the temperature of each zone of the twin-screw extruder: Zone 1 90℃, Zone 2 151℃, Zone 3 161℃, Zones 4-11 170℃, Zone 12 165℃, and the screen changing device 161℃. After each zone temperature stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feed speed to match the extrusion speed, and setting the screw speed to 270 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip is cooled by an air-cooling device (air velocity 3.1 m / s, air temperature 25℃) and then cut into PBAT-based modified materials with a particle size of 3 mm and a length of 3 mm.

[0041] S3, the extrusion temperature of the casting machine is preheated to 158℃, the die temperature is 160℃, and after the temperature stabilizes, the modified material is added. The extrusion speed is set to 17Hz to ensure that the material is fully plasticized and there are no unmelted particles.

[0042] S4, cooling roller temperature 28℃, rotation speed 19r / min, the surface cleanliness of the cooling roller is controlled to avoid impurities on the film surface, the material is cooled and shaped into film preform.

[0043] S5, the automatic cutter cuts the film blank to a width of 400mm, the winding machine rotates at 19r / min, and after winding is completed, the film thickness deviation is checked to ensure ≤±0.5μm, and finally a PBAT-based flexible film with a thickness of 20μm is obtained.

[0044] Example 5 Components and parts by weight: 90 parts PBAT, 10 parts PBST, 0.3 parts antioxidant 168, 0.2 parts antioxidant 1076, 0.8 parts polymeric carbodiimide, 0.3 parts erucamide, and 0.09 parts white oil.

[0045] Preparation steps: S1, start the high-speed mixer, set the speed to 830 r / min and the temperature to 40℃, first add PBAT granules and PBST granules, stir for 4.5 min until the granules are loose; after adding white oil, stir for 2.5 min until the white oil covers the granules; then add antioxidant 168, antioxidant 1076, polymeric carbodiimide, and erucamide powder, continue stirring for 7.5 min, stop stirring after observing that there are no local density differences in the material, and discharge the material for later use.

[0046] S2: Preheat the temperature of each zone of the twin-screw extruder: Zone 1 90℃, Zone 2 150℃, Zone 3 160℃, Zones 4-11 169℃, Zone 12 163℃, and the screen changing device 160℃. After each zone temperature stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feed speed to match the extrusion speed, and setting the screw speed to 240 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip is cooled by an air-cooling device (air velocity 2.9 m / s, air temperature 24℃) and then cut into PBAT-based modified materials with a particle size of 3 mm and a length of 3 mm.

[0047] S3, preheat the extrusion temperature of the casting machine to 152℃, the die temperature to 155℃, add the modified material after the temperature stabilizes, set the extrusion speed to 14Hz, and adjust the T-die lip to ensure that the edges of the cast film are neat.

[0048] S4, cooling roller temperature 20℃, rotation speed 16r / min, cooling time is controlled to avoid internal stress in the film, the material is cooled and shaped into film preform.

[0049] The S5 automatic cutter trims the film blank to a width of 700mm, the winding machine rotates at 16r / min, and the film flatness is monitored in real time during the winding process, finally obtaining a PBAT-based flexible film with a thickness of 20μm.

[0050] Example 6 The difference between this embodiment and Embodiment 1 is that the film thickness is 30 μm.

[0051] Example 7 The difference between this embodiment and Embodiment 1 is that the film thickness is 35 μm.

[0052] Example 8 The difference between this embodiment and Embodiment 1 is that the film thickness is 40 μm.

[0053] Comparative Example 1 (without PBST component) Components and parts by weight: 100 parts PBAT, 0.2 parts antioxidant 1010, 0.1 parts antioxidant 168, 0.2 parts monomeric carbodiimide, 0.8 parts pentaerythritol stearate, and 0.05 parts white oil.

[0054] Preparation steps: S1, start the high-speed mixer, set the speed to 800 r / min and the temperature to 40℃, first add PBAT granules, stir for 5 minutes until there is no obvious agglomeration of granules; then add white oil, continue stirring for 3 minutes until the white oil evenly covers the surface of the granules; finally add antioxidant 1010, antioxidant 168, monomeric carbodiimide, and pentaerythritol stearate powder in sequence, continue stirring for 8 minutes, and after observing that there is no local color difference in the material, stop stirring and discharge the material for later use.

[0055] S2: Preheat the temperature of each zone of the twin-screw extruder to the set values: Zone 1 90℃, Zone 2 150℃, Zone 3 160℃, Zones 4-11 170℃, Zone 12 165℃, and the screen changing device 160℃. After the temperature of each zone stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feeding speed to match the extrusion speed, and setting the screw speed to 250 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip enters the air-cooling device with an air velocity of 3 m / s and an air temperature of 25℃. After the strip cools to room temperature, it is cut into cylindrical PBAT-based modified material with a particle size of 3 mm and a length of 3 mm by a pelletizer.

[0056] S3, start the casting machine, preheat the extrusion temperature to 155℃, and simultaneously set the die head temperature to 158℃. After the temperature stabilizes for 20 minutes, add the PBAT-based modified material to the casting machine hopper, set the extrusion speed to 15Hz, and after the material is plasticized by the screw, it is evenly cast onto the surface of the casting roller through the T-die head to ensure that the cast film surface is free of bubbles and wrinkles.

[0057] S4 uses a chrome-plated cooling roller to cool the plasticized material. The cooling roller temperature is set to 25℃ and the rotation speed is 18r / min. The distance between the cooling roller and the casting roller is adjusted to ensure that the material is closely attached to the surface of the cooling roller and is quickly cooled and shaped into a continuous film preform. The thickness of the film preform is controlled by matching the rotation speed of the cooling roller with the extrusion speed.

[0058] S5. Before winding, start the automatic cutter to cut the film preform to a width of 500mm, ensuring that the cut edge is flat and free of burrs; set the winding speed to 18r / min, and finally obtain a PBAT-based film with a thickness of 20μm.

[0059] Comparative Example 2 (processed using blown film method) Components and parts by weight: 80 parts PBAT, 20 parts PBST, 0.2 parts antioxidant 1010, 0.1 parts antioxidant 168, 0.2 parts monomeric carbodiimide, 0.8 parts pentaerythritol stearate, and 0.05 parts white oil.

[0060] Preparation steps: S1. Start the high-speed mixer, set the speed to 800 r / min and the temperature to 40℃. First, add PBAT granules and PBST granules, and stir for 5 minutes until there is no obvious agglomeration of granules. Then, add white oil and continue stirring for 3 minutes until the white oil evenly covers the surface of the granules. Finally, add antioxidant 1010, antioxidant 168, monomeric carbodiimide, and pentaerythritol stearate powder in sequence, and continue stirring for 8 minutes. After observing that there is no local color difference in the material, stop stirring and discharge the material for later use.

[0061] S2: Preheat the temperature of each zone of the twin-screw extruder to the set values: Zone 1 90℃, Zone 2 150℃, Zone 3 160℃, Zones 4-11 170℃, Zone 12 165℃, and the screen changing device 160℃. After each zone temperature stabilizes for 30 minutes without fluctuation, feed the mixture obtained in S1 into the extruder at a uniform speed through the hopper, controlling the feed speed to match the extrusion speed, and setting the screw speed to 250 r / min. After the material melts and plasticizes in the barrel, it is extruded through the die to form a continuous strip. The strip enters the air-cooling device with an air velocity of 3 m / s and an air temperature of 25℃. After the strip cools to room temperature, it is cut into cylindrical PBAT-based modified material with a particle size of 3 mm and a length of 3 mm by a pelletizer. S3 uses a single-screw blown film extruder (model SJ-45, L / D ratio 25:1). The temperatures of each zone are preheated to 120℃ (zone 1), 140℃ (zone 2), 160℃ (zone 3), and 170℃ (die head). After the temperature stabilizes for 30 minutes, the modified S1 material is fed into the blown film extruder hopper. The screw speed is set to 80 r / min and the blow-up ratio to 2.5. After the material melts, it is extruded through the die head to form bubbles. The bubbles are cooled by an air ring with an air velocity of 1.5 m / s and an air temperature of 30℃. The cooled bubbles are then pulled by traction rollers, with the traction speed matched to the screw speed.

[0062] S4. After cooling, the film is guided by rollers to adjust its flatness. The winding speed is set to 10 r / min to finally obtain a PBAT-based film with a thickness of 20 μm.

[0063] The performance test results of the examples and comparative examples are compared in the table below: Table 1

[0064] The highly transparent, ultra-low haze PBAT-based flexible film prepared by this invention exhibits excellent and stable overall performance: the light transmittance of the examples remains at 90.5%-92.5%, and the haze is only 1.2%-1.8%. Even when the film thickness in Examples 6-8 is increased from 20 μm in Example 1 to 30-40 μm, the light transmittance remains stable at 90.5%-91.8%, and the haze is ≤1.8%, consistently maintaining the characteristics of "high transparency and ultra-low haze". In terms of mechanical properties, the tensile strength of the examples reaches 26.3-28.8 MPa, and the elongation at break is 630-720%. Among them, the elongation at break is slightly improved in Examples 6-8 due to the reduction of stress concentration caused by the increase in film thickness, but the mechanical stability is not affected. In terms of processing stability, the scores of the examples are all 4.6-4.8 points, showing strong adaptability to large-scale production.

[0065] In contrast, comparative examples showed that Comparative Example 1, without PBST, had a transmittance of only 88.6% and a haze of 5.8%, while Comparative Example 2, using the blown film method, had a transmittance of 85.7% and a processing stability score of only 3.2, both significantly lower than the examples. This fully demonstrates the effectiveness of the "PBAT-PBST blending + casting and rapid cooling" technical solution. It achieves breakthroughs in optical performance without the need for additional antireflective agents or film thinning, while also maintaining excellent mechanical properties and processing stability. This lays a solid foundation for its application in packaging fields such as garment bags and packaging bags, promoting the high performance and widespread adoption of biodegradable materials.

[0066] The following table compares the notch tear strength and puncture resistance of the examples and comparative examples: Table 2

[0067] The PBAT-based films prepared by this invention exhibit excellent and balanced mechanical properties: the notch tear strength of the embodiments is significantly improved, reaching 152.30–218.93 kN / m in the MD direction and 124.70–133.98 kN / m in the TD direction, which is significantly higher than that of the comparative examples (Comparative Example 1 MD 148.20, TD 118.50; Comparative Example 2 MD 128.40, TD 105.30), indicating that the embodiments all have excellent tear resistance; the puncture resistance is also outstanding, with the breaking force of the embodiments being 17.50–25.20 N and the elongation being 84–115 mm. In particular, Embodiment 5 shows the best performance in both breaking force (25.20 N) and elongation (115 mm), demonstrating that it has both high strength and high toughness; In contrast, comparative examples show that Comparative Example 1, without PBST blending, has a puncture and tear resistance of only 18.90 N, while Comparative Example 2, using blown film technology, exhibits the lowest mechanical properties (16.20 N tear resistance, 72 mm elongation, and significantly lower MD / TD tear strength), indicating insufficient structural uniformity and mechanical load-bearing capacity. This further confirms the effectiveness of the "PBAT-PBST blending + casting and rapid cooling" technology in terms of mechanical reinforcement: it not only significantly improves the tear and puncture resistance of the film but also maintains good toughness, giving it outstanding application potential in packaging bags, protective films, and other applications requiring high mechanical reliability, thus promoting the practical application of biodegradable materials in high-strength applications.

[0068] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PBAT based flexible film with high transparency, ultra-low haze, characterized in that, The film is composed of the following components by weight: 50-100 parts of polybutylene adipate terephthalate; 0-50 parts of polybutylene succinate terephthalate; 0.1-1 part of antioxidant; 0.1-1 part of anti-hydrolysis agent; 0.1-1 part of opening agent; 0.1-1 part of dispersing agent.

2. The high transparent, ultra-low haze PBAT based flexible film as claimed in claim 1, wherein: The antioxidant is one or more of antioxidant 168, antioxidant 1010, and antioxidant 1076.

3. The high transparent, ultra-low haze PBAT based flexible film as claimed in claim 2, wherein: The anti-hydrolysis agent is one or more of monomeric carbodiimide and polymeric carbodiimide.

4. The high transparent, ultra-low haze PBAT based flexible film as claimed in claim 3, wherein: The opening agent is one or more of oleic acid amide, erucic acid amide, and pentaerythritol stearate in combination.

5. The high transparent, ultra-low haze PBAT based flexible film as claimed in claim 4, wherein: The dispersing agent is white oil.

6. The high transparent, ultra-low haze PBAT based flexible film as claimed in claim 5, wherein: The film is composed of the following components by weight: 80 parts of polybutylene adipate terephthalate (PBAT), 20 parts of polybutylene succinate terephthalate (PBST), 0.2 parts of antioxidant 1010, 0.1 parts of antioxidant 168, 0.2 parts of monomeric carbodiimide, 0.8 parts of pentaerythritol stearate, and 0.05 parts of white oil.

7. A process for the preparation of high transparent, ultra-low haze PBAT based flexible film as claimed in any one of claims 1-6, characterized in that, The method comprises the following steps: S1. In the order of particle-liquid-powder, PBAT, PBST, dispersing agent, antioxidant, anti-hydrolysis agent, and opening agent are added step by step into a high-speed mixer and mixed uniformly; S2. The mixed material is sent into a double-screw extruder, melted and extruded, cooled by air, and pelletized to obtain PBAT-based modified material; S3. The PBAT-based modified material is sent into a casting machine for plasticizing and casting; S4. The plasticized material is cooled by a cooling roller; S5. The cooled film is wound at a speed of 15-20 r / min to obtain a PBAT-based flexible film.

8. The process for the preparation of high transparent, ultra-low haze PBAT based flexible film as claimed in claim 7, wherein, The temperature of each zone of the double-screw extruder is set as follows: 90°C for zone 1, 150°C for zone 2, 160°C for zone 3, 170°C for zones 4-11, 165°C for zone 12, and 160°C for screen change.

9. The process for the preparation of high transparent, ultra-low haze PBAT based flexible film as claimed in claim 7, wherein, In S2, the processing temperature of the double-screw extruder is 120-170°C, and the screw rotation speed is 200-300 r / min; in S3, the extrusion temperature of the casting machine is 140-165°C, and the extrusion speed is 10-20 Hz; in S4, the cooling roller temperature is 15-30°C, and the speed is 15-20 r / min; and in S5, the film winding speed is 15-20 r / min.

10. Use of the PBAT-based flexible film according to any one of claims 1-6, having high transparency and ultra-low haze, characterized in that, The film is used in one or more of a clothes hanging bag and a packaging bag.

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