Modified pbat / thermoplastic starch film and preparation method thereof

Abstract

The application discloses a modified PBAT / thermoplastic starch film, which comprises the following components in parts by weight: 60-80 parts of PBAT resin; 20-40 parts of pre-plasticized starch particles; 1-4 parts of polyethylene glycol stearate; 0.5-1.5 parts of talcum powder; and 0.2-1 part of a chain extender. Through modification of the PBAT / thermoplastic starch composite material, the adhesion between the film product and water-based ink is increased under the premise that the compatibility of PBAT and starch is improved, and the prepared film product is excellent in mechanical properties, friendly to the environment and low in cost.

Description

Technical Field

[0001] This invention relates to the field of biodegradable film technology, and in particular to a modified PBAT / thermoplastic starch film and its preparation method. Background Technology

[0002] With increasingly stringent environmental protection requirements in my country, biodegradable materials are finding wider application in the film industry. Commercially available film materials often require printing with inks, which are generally divided into oil-based and water-based inks. Traditional oil-based inks contain volatile organic solvents, posing significant environmental and human health risks during production and use. Water-based inks, with water as their solvent, have extremely low VOC content and cause less environmental pollution. Therefore, oil-based inks used for printing on films are gradually being replaced by water-based inks. To guide the use of water-based inks in the printing of biodegradable plastic packaging, the China Daily Chemical Industry Association officially released the "Water-based Inks for Biodegradable Packaging Printing" standard on February 25, 2024, which officially came into effect on March 25 of the same year.

[0003] Polybutylene terephthalate (PBAT) possesses excellent mechanical properties and biodegradability. Due to its high ductility, it shows broad application prospects in the field of biodegradable film materials. Because PBAT is highly hydrophobic and has weak adhesion to water-based inks, blending it with starch can reduce costs while effectively improving the hydrophilicity of PBAT. Starch decomposes below its melting point due to intermolecular hydrogen bonds. To improve starch processability, polar substances are often used to plasticize and modify it. While plasticized starch exhibits some plasticity, it still contains a large number of hydroxyl groups, resulting in strong hydrophilicity and poor compatibility with hydrophobic PBAT, leading to a decline in the performance of the prepared PBAT / thermoplastic starch materials.

[0004] Currently, to address the difficulties in printing on fully biodegradable plastic films using water-based inks and the resulting insufficient adhesion, existing technologies typically focus on improving the formulation of the water-based inks. The color fading of water-based inks on biodegradable film bags is related to the composition, polarity, and adhesion of both the water-based ink and the biodegradable film bag. Patent application CN114085498A discloses a biodegradable film bag that does not fade when printed with water-based inks and its preparation method. By adding lubricants and emulsifiers to the biodegradable film bag formulation, the smoothness of the film surface is improved, and the film bag's adsorption of water-based inks is enhanced. However, this patent involves corona treatment after film blowing to improve ink adhesion. The corona treatment process is accompanied by noise pollution and produces gases such as ozone, nitrogen dioxide, and nitric oxide, which are harmful to human health. Patent application CN105585823A discloses a biodegradable polyester composition. By adding a certain amount of tetrahydrofuran to the biodegradable polyester composition, printing defects that occur during the printing process can be effectively improved, thus giving the film excellent printing performance. However, the tetrahydrofuran added in this patent is a typical solvent-based volatile substance, which does not meet environmental protection requirements. Patent application CN117384472A discloses a PBAT film that can adhere to water-based inks and its preparation method. By improving the polarity and surface roughness of the film surface, the adhesion of water-based inks to the film is improved. However, this patent improves the compatibility of the two-phase resin by adding a certain amount of maleic anhydride grafted PLA to the PBAT matrix. This results in high production costs, insufficient product ductility, and the peroxide used as the grafting initiator decomposes during processing, releasing irritating gases and generating toxic substances that are harmful to human health. Summary of the Invention

[0005] This invention aims to provide a modified PBAT / thermoplastic starch film and its preparation method. By modifying the PBAT / thermoplastic starch film material, the compatibility between PBAT and starch is improved, and the adhesion of water-based inks on the film is increased. The prepared product has excellent mechanical properties, is environmentally friendly, and has low cost, and has high market prospects.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A modified PBAT / thermoplastic starch film comprising the following components in parts by weight: PBAT resin: 60-80 parts; Pre-plasticized starch granules: 20-40 parts; Polyethylene glycol stearate: 1-4 parts; Talc powder: 0.5-1.5 parts; Chain extender: 0.2-1 part.

[0007] The melt flow rate of the PBAT resin is 2-5 g / 10 min; The pre-plasticized starch granules are prepared by the following steps: A1. Add 70 parts starch, 10-20 parts glycerin and 10-20 parts distilled water to a mixer and mix them in a mixer at a temperature of 60-80℃ for 3-5 minutes and a speed of 40-60 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0008] Furthermore, the starch is one or more of corn starch, potato starch, and tapioca starch, with corn starch being preferred.

[0009] The talc powder is talc powder that has been surface-treated with a coupling agent.

[0010] The chain extender is a reactive epoxy functional chain extender.

[0011] A method for preparing a modified PBAT / thermoplastic starch film includes the following steps: S1. After drying PBAT resin and preplasticized starch granules in an oven at 80℃ for 4-6 hours, mix all the raw material components together to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder, and perform melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. S3: Add the modified PBAT / thermoplastic starch granules obtained in step S2 to the feeding port of a single-screw extruder, and perform melting, extrusion, blowing, traction, and winding to finally obtain the modified PBAT / thermoplastic starch film material.

[0012] Furthermore, in step S2, the twin-screw extruder speed is 200-400 r / min, the extrusion temperature is 130-170℃, the feed rate is 40-60 kg / h, and the drying conditions are 80℃ for 4-6 h.

[0013] In further step S3, the single-screw extruder speed is 40-60 r / min, the extrusion temperature is 120-160℃, and the film blow-up ratio is 2.0-3.0.

[0014] The beneficial effects of this invention are: 1. The modified PBAT / thermoplastic starch film material prepared by this invention has polyethylene glycol stearate in the raw materials acting as a bridge between the two phases of PBAT resin and starch, allowing thermoplastic starch to be dispersed in the PBAT phase, thereby improving the compatibility between PABT and starch. The resulting modified PBAT / thermoplastic starch film material exhibits excellent mechanical properties at high starch content, meets the requirements for full biodegradability, and reduces production costs, thus achieving high economic benefits.

[0015] 2. The modified PBAT / thermoplastic starch film material prepared by this invention increases the hydrophilicity of the film material due to the thermoplastic starch. Polyethylene glycol stearate, as a conventional surfactant, has a unique linear hydrophobic-hydrophilic structure that can increase the compatibility of PBAT and starch while also acting as a dispersant and emulsifier for water-based inks. The synergistic effect of the two enables water-based inks to adhere more effectively to the modified PBAT / thermoplastic starch film material, improving the adhesion of water-based inks. In addition, the modified PBAT / thermoplastic starch film material can maintain the colorfastness of water-based inks after printing and drying without corona treatment, solving the problem of the difficulty in printing water-based inks on existing PBAT biodegradable plastic films. Replacing oil-based inks with water-based inks reduces VOC emissions, making it safe and environmentally friendly.

[0016] 3. This invention uses a certain weight proportion of glycerol and water to pre-plasticize starch in a mixer. By pre-plasticizing the starch, the processing temperature of the starch is increased, allowing it to be melt-extruded with PBAT resin in a twin-screw extruder at the processing temperature of PBAT resin. Compared with plasticized starch, pre-plasticized starch has a higher ability to be re-plasticized with polyethylene glycol in polyethylene glycol stearate in a twin-screw extruder, which is more conducive to the compatibility of starch and PABT, thereby improving the mechanical properties of the film product. Attached Figure Description

[0018] Figure 1 These are schematic diagrams of the thin film products of Embodiment 1 and Comparative Examples 1-5 of the present invention.

[0019] Figure 2 This is a scanning electron microscope (SEM) image of the modified PBAT / thermoplastic starch composite material of the present invention after twin-screw extrusion.

[0020] Figure 3 The graph shows the contact angle test data of the modified PBAT / thermoplastic starch film of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0022] Example 1 This embodiment provides a modified PBAT / thermoplastic starch film. In this embodiment, the modified PBAT / thermoplastic starch film is prepared through the following steps: S1: Weigh 70 parts of PBAT resin and 30 parts of preplasticized starch granules and dry them at 80℃ for 4 hours. Mix 2 parts of polyethylene glycol stearate, 0.5 parts of chain extender, 1 part of talc powder, and the dried PBAT resin and preplasticized starch granules evenly to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder for melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. The twin-screw extruder speed is 300 rpm, the extrusion temperature is 130℃-170℃, and the feed rate is 50 kg / h. The drying conditions are 80℃ for 4 hours.

[0023] S3. The modified PBAT / thermoplastic starch granules obtained in step S2 are added to the feed port of a single-screw extruder blown film mill, and then melted, extruded, blown, drawn, and wound to finally obtain a modified PBAT / thermoplastic starch film material. The single-screw extruder blown film mill has a rotation speed of 50 r / min, an extrusion temperature of 120-160℃, a film blow-up ratio of 2.5, and a film thickness of 20 μm.

[0024] In this embodiment, the pre-plasticized starch granules are prepared through the following steps: A1. Add 70 parts starch, 15 parts glycerin and 15 parts distilled water to a mixer and mix them in a mixer at 80°C for 3 minutes at a speed of 50 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0025] The pre-plasticized starch granules prepared in this embodiment contain a large number of hydroxyl groups. The hydrophilic structure of polyethylene glycol (PEG) stearate segments undergoes hydrogen bonding with the pre-plasticized starch during melt extrusion in a twin-screw extruder. This causes the hydrophilic structure of PEG stearate to align with the starch phase. Since stearate chains are non-polar, during melt extrusion with hydrophobic PBAT in a twin-screw extruder, the hydrophobic structure of PEG stearate aligns with the PBAT phase. PEG, being a hydrophilic chain, is compatible with starch, while stearate, being a hydrophobic chain, is compatible with PBAT. Further plasticizing the pre-plasticized starch granules using a twin-screw extruder, with PEG stearate acting as a bridge between the two phases, improves the compatibility of the PBAT / thermoplastic starch material.

[0026] In this embodiment, the PBAT resin is grade TH801T, the melt flow rate is 2-5 g / 10 min (190℃, 2.16 kg), and the manufacturer is Xinjiang Lanshan Tunhe New Materials Co., Ltd. The starch is corn starch, food grade, manufactured by Shouguang Xinfeng Starch Co., Ltd. Glycerin, manufactured by Tianjin Bodi Chemicals Co., Ltd. Polyethylene glycol stearate, manufactured by Quzhou Chenkang Chemical Co., Ltd. Talc, brand name OP-10, is manufactured by Specialty Minerals in the United States; talc is used as a film opening agent.

[0027] The chain extender, brand name SG-20, is manufactured by Jia Yi Rong Polymer Co., Ltd.; the ester group stability of modified PBAT / thermoplastic starch materials is poor and they are easily degraded under strong shear. In order to prevent further degradation, a chain extender needs to be added.

[0028] Example 2 The difference between this embodiment and embodiment 1 is that in this embodiment: The starch is potato starch, food grade, manufactured by Zhejiang Yicun Biotechnology Co., Ltd. In this embodiment, the modified PBAT / thermoplastic starch film is prepared through the following steps: S1: Weigh 60 parts of PBAT resin and 40 parts of preplasticized starch granules and dry them at 80℃ for 5 hours. Mix 3 parts of polyethylene glycol stearate, 1 part of chain extender, 0.5 parts of talc powder, and the dried PBAT resin and preplasticized starch granules evenly to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder for melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. The twin-screw extruder speed is 200 rpm, the extrusion temperature is 130℃-170℃, and the feed rate is 40 kg / h. The drying conditions are 80℃ for 5 hours.

[0029] S3. The modified PBAT / thermoplastic starch granules obtained in step S2 are added to the feed port of a single-screw extruder blown film mill, and then melted, extruded, blown, drawn, and wound to finally obtain a modified PBAT / thermoplastic starch film material. The single-screw extruder blown film mill has a rotation speed of 60 r / min, an extrusion temperature of 120-160℃, a film blow-up ratio of 3.0, and a film thickness of 20 μm.

[0030] In this embodiment, the pre-plasticized starch granules are prepared through the following steps: A1. Add 70 parts starch, 10 parts glycerin and 20 parts distilled water to a mixer and mix them at 60℃ for 5 minutes at 40r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0031] Example 3 The difference between this embodiment and embodiment 1 is that in this embodiment: The starch is cassava starch, food grade, manufactured by Shandong Guante Biotechnology Co., Ltd. In this embodiment, the modified PBAT / thermoplastic starch film is prepared through the following steps: S1: Weigh 80 parts of PBAT resin and 20 parts of preplasticized starch granules and dry them at 80℃ for 6 hours. Mix 1 part of polyethylene glycol stearate, 0.2 parts of chain extender, 1.5 parts of talc powder, and the dried PBAT resin and preplasticized starch granules evenly to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder for melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. The twin-screw extruder speed is 400 rpm, the extrusion temperature is 130℃-170℃, and the feed rate is 60 kg / h. The drying conditions are 80℃ for 6 hours.

[0032] S3. The modified PBAT / thermoplastic starch granules obtained in step S2 are added to the feed port of a single-screw extruder blown film mill, and then melted, extruded, blown, drawn, and wound to finally obtain a modified PBAT / thermoplastic starch film material. The single-screw extruder blown film mill has a rotation speed of 40 r / min, an extrusion temperature of 120-160℃, a film blow-up ratio of 2.0, and a film thickness of 20 μm.

[0033] In this embodiment, the pre-plasticized starch granules are prepared through the following steps: A1. Add 70 parts starch, 20 parts glycerin and 10 parts distilled water to a mixer and mix them at 70°C for 4 minutes at a speed of 60 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0034] Example 4 The difference between this embodiment and embodiment 1 is that in this embodiment: The starch is a mixture of corn starch and tapioca starch in a 1:1 mass ratio. In this embodiment, the modified PBAT / thermoplastic starch film is prepared through the following steps: S1: Weigh 65 parts of PBAT resin and 35 parts of preplasticized starch granules and dry them at 80℃ for 4 hours. Mix 4 parts of polyethylene glycol stearate, 1 part of chain extender, 1.5 parts of talc powder, and the dried PBAT resin and preplasticized starch granules evenly to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder for melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. The twin-screw extruder speed is 400 rpm, the extrusion temperature is 130℃-170℃, and the feed rate is 50 kg / h. The drying conditions are 80℃ for 4 hours.

[0035] S3. The modified PBAT / thermoplastic starch granules obtained in step S2 are added to the feed port of a single-screw extruder blown film mill, and then melted, extruded, blown, drawn, and wound to finally obtain a modified PBAT / thermoplastic starch film material. The single-screw extruder blown film mill has a rotation speed of 60 r / min, an extrusion temperature of 120-160℃, a film blow-up ratio of 2.5, and a film thickness of 20 μm.

[0036] In this embodiment, the pre-plasticized starch granules are prepared through the following steps: A1. Add 70 parts starch, 15 parts glycerin and 15 parts distilled water to a mixer and mix them in a mixer at a temperature of 60℃ for 3 minutes and a speed of 60 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0037] Example 5 The difference between this embodiment and Embodiment 1 is that, in this embodiment, the modified PBAT / thermoplastic starch film is prepared through the following steps: S1: Weigh 70 parts of PBAT resin and 30 parts of preplasticized starch granules and dry them at 80℃ for 4 hours. Mix 2 parts of polyethylene glycol stearate, 0.6 parts of chain extender, 1 part of talc powder, and the dried PBAT resin and preplasticized starch granules evenly to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder for melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. The twin-screw extruder speed is 300 rpm, the extrusion temperature is 130℃-170℃, and the feed rate is 40 kg / h. The drying conditions are 80℃ for 4 hours.

[0038] S3. The modified PBAT / thermoplastic starch granules obtained in step S2 are added to the feed port of a single-screw extruder blown film mill, and then melted, extruded, blown, drawn, and wound to finally obtain a modified PBAT / thermoplastic starch film material. The single-screw extruder blown film mill has a rotation speed of 50 r / min, an extrusion temperature of 120-160℃, a film blow-up ratio of 2.0, and a film thickness of 20 μm.

[0039] In this embodiment, the pre-plasticized starch granules are prepared through the following steps: A1. Add 70 parts starch, 15 parts glycerin and 15 parts distilled water to a mixer and mix them in a mixer at 80°C for 3 minutes at a speed of 50 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that polyethylene glycol stearate is not used in this comparative example; instead, polyethylene glycol stearate is replaced with the same amount of PBAT resin by weight. All other conditions are the same as in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that preplasticized starch granules are not used in this comparative example; instead, the preplasticized starch granules are replaced with the same number of parts by weight of PBAT resin. All other conditions are the same as in Example 1.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that polyethylene glycol stearate is not used in this comparative example. Instead, polyethylene glycol stearate is replaced with the same weight parts of polyethylene glycol and stearic acid, and the molar ratio of polyethylene glycol to stearic acid is 1:1. The other conditions are the same as in Example 1.

[0043] In this comparative example, the polyethylene glycol grade is PEG400, and the manufacturer is Jiangsu Haian Petrochemical Plant. The stearic acid grade is SA1801, and the manufacturer is Sven Indonesia.

[0044] Comparative Example 4 The difference between this comparative example and Example 1 is that polyethylene glycol stearate is not used in this comparative example; instead, polyethylene glycol stearate is replaced with the same amount of monoglyceride by weight. All other conditions are the same as in Example 1.

[0045] In this comparative example, the monoglyceride was food grade and manufactured by Shandong Huiheng Biotechnology Co., Ltd.

[0046] Comparative Example 5 The difference between this comparative example and Example 1 is that the filler is different; that is, the preplasticized starch granules are replaced with the same number of parts by weight of calcium carbonate. The other conditions are the same as in Example 1.

[0047] In this comparative example, the calcium carbonate grade is VS-525, and the manufacturer is Dongguan Wuquan New Material Co., Ltd.

[0048] Comparative Example 6 The difference between this comparative example and Example 1 is that the starch is not pre-plasticized in this comparative example; that is, the pre-plasticized starch granules are replaced with the same weight of corn starch. The other conditions are the same as in Example 1.

[0049] Experimental Example The modified PBAT / thermoplastic starch films prepared in Examples 1-5 and Comparative Examples 1-6 were subjected to performance tests, and the performance testing methods included: 1) Maximum tensile load: The maximum tensile load of the specimen was tested according to the national standard GB / T 1040-2018, with a tensile rate of 500 mm / min.

[0050] 2) Nominal strain at fracture: The nominal strain at fracture of the specimen was tested according to the national standard GB / T 1040-2018, with a tensile rate of 500 mm / min.

[0051] 3) Printing quality: According to the national standard GB / T 38082-2019 for biodegradable plastic shopping bags, the printed performance description is observed by the naked eye and is divided into four levels: excellent, good, average, and poor.

[0052] 4) Printing peel rate: The test was conducted according to the description of the printing peel rate item in the national standard GB / T 38082-2019 Biodegradable Plastic Shopping Bags.

[0053] Samples were cut from areas of the bag with the most printed ink for a print peel rate test. The printed side of the sample was placed face up, and the four sides of the sample were fixed to a smooth surface with transparent tape, exposing the test area: 100mm × 100mm. During the operation, the measurement area should not be touched by hand. A 15mm wide and 175mm long adhesive tape with a peel strength of 6.5N / 15mm ± 1.0N / 15mm was applied to the printed surface of the sample, folded at 75mm, and then rolled back and forth once with a 1kg roller. The peel was then quickly performed by hand. After peeling, the peeled area and residual area of ​​the printed ink were measured using a 0.5mm graduated steel ruler. The print peel rate was calculated using the following formula. Three samples were used, and the average value was taken, rounded to 1%.

[0054] η = Sb / Sc × 100% In the formula: η—printing ink peeling rate; Sb—peeling area; Sc—residual area.

[0055] The performance test results of the modified PBAT / thermoplastic starch films prepared in Examples 1-5 and Comparative Examples 1-6 are shown in Table 1: Table 1. Performance test results of modified PBAT / thermoplastic starch films prepared in Examples 1-5 and Comparative Examples 1-6 Tensile strength and elongation at break are the most important parameters of film mechanical properties, directly reflecting the strength and ductility of the film. As can be seen from Examples 1-5, within the scope of the technical solution provided in this invention, a modified PBAT / thermoplastic starch film exhibits excellent tensile properties in different directions, while also showing good printing performance and peeling rate for water-based inks.

[0056] Compared with Example 1, Comparative Example 1 did not use polyethylene glycol stearate, which resulted in a certain deficiency in its tensile properties. At the same time, its printing performance and peel rate for water-based inks were also poor. This was due to the poor compatibility between PBAT and starch.

[0057] Compared with Example 1, Comparative Example 2 did not use preplasticized starch, and its printing performance and peel rate for water-based inks were the worst. This is because PBAT is hydrophobic, and without starch as a filler to increase its hydrophilicity, its adhesion to water-based inks was not improved.

[0058] Compared with Example 1, Comparative Examples 3 and 4 show that Comparative Example 3 replaced polyethylene glycol stearate with polyethylene glycol and stearic acid monomers of equal functionality, and Comparative Example 4 replaced polyethylene glycol stearate with another surfactant monoglyceride in equal parts by weight. It can be seen that the tensile properties, printing performance with water-based inks, and peel rate of both comparative examples are not as good as those of Example 1. This indicates that polyethylene glycol stearate, as a specific additive for PBAT / thermoplastic starch, has unexpectedly excellent effects.

[0059] Compared with Example 1, Comparative Example 5 replaced the preplasticized starch granules with surface-treated calcium carbonate. It can be seen that after replacing calcium carbonate as the filler of the present invention, the film's extensibility is greatly reduced, and the printing performance and peel rate of water-based inks also decrease. The ultimate goal of the present invention is to prepare a film material with good water-based ink printing ability and excellent mechanical properties. The reason why starch is used as a filler in the present invention is that starch has strong hydrophilicity, which can improve the hydrophilicity of PABT, and starch has extensibility similar to PBAT. Calcium carbonate cannot achieve this effect.

[0060] Compared with Example 1, Comparative Example 6 directly melt-blended and extruded starch and PBAT in a twin-screw extruder without pre-plasticizing the starch to increase the processing temperature. It was found that the granules prepared by this method had poor processing performance and could not effectively form a 20μm thick film product.

[0061] Figure 1 This is a schematic diagram of the thin film products of Embodiment 1 and Comparative Examples 1-5 of the present invention.

[0062] Depend on Figure 1 As can be seen, the film surfaces of the products in Example 1, Comparative Examples 3, and 4 are relatively smooth. Comparative Example 1, lacking polyethylene glycol stearate, exhibits more wrinkles on its film surface. This is attributed to the poor compatibility between PBAT and thermoplastic starch, leading to instability during blown film production. Comparative Example 2, without added starch, lacks a hydrophilic phase in the polyethylene glycol stearate, resulting in fine crystal points on the film. These crystal points may be due to polyethylene glycol stearate acting as a nucleating agent to induce crystallization of PBAT during blown film production. In Comparative Example 5, the filler was replaced with calcium carbonate instead of starch. Due to the different filler types, polyethylene glycol stearate failed to achieve compatibility, resulting in a more mottled product surface and affecting its appearance.

[0063] Figure 2 This is a scanning electron microscope (SEM) image of the modified PBAT / thermoplastic starch composite material after twin-screw extrusion according to the present invention. The SEM model is FP2031 / 11, manufactured by FEI Corporation, USA. The accelerating voltage is 15 kV, and the magnification is 2500x. Figure 2 (a) is a SEM image of Comparative Example 1 without the addition of polyethylene glycol stearate. Figure 2 (b) is a SEM image of 2 parts of polyethylene glycol stearate added in Example 1.

[0064] like Figure 2 As shown in (a), in the absence of polyethylene glycol stearate, many pores can be observed in the microstructure of the PBAT / thermoplastic starch composite material, such as... Figure 2 As shown in (b), after adding 2 parts of polyethylene glycol stearate, the pores in the microstructure of the PBAT / thermoplastic starch composite material disappeared, indicating that polyethylene glycol stearate can effectively improve the compatibility of PBAT and thermoplastic starch, thereby improving the mechanical properties of the PBAT / thermoplastic starch film.

[0065] Figure 3This is a graph showing the contact angle test data of the modified PBAT / thermoplastic starch film of the present invention. According to the testing standard GB / T 30693-2014 for plastic film contact angle, the contact angle of the composite film was measured under static conditions using a contact angle meter with a water droplet volume of 0.4 mL. The contact angle meter model was SDC-200S, manufactured by Dongguan Shengding Precision Instruments Co., Ltd.

[0066] from Figure 3 It is known that as the amount of polyethylene glycol stearate increases, the contact angle gradually decreases, and the smaller the contact angle, the higher the hydrophilicity of the material. Polyethylene glycol stearate is a nonionic surfactant with a linear structure. Its molecular structure contains a large number of hydrophilic functional groups of polyethylene glycol. Due to the certain molecular weight of polyethylene glycol, it is difficult for it to penetrate into the starch molecular chain. A large amount of polyethylene glycol remains on the surface of the material molecules, increasing the number of hydroxyl groups on the film surface. At the same time, increasing the amount of polyethylene glycol stearate increases the amount of hydrophilic polyethylene glycol on the surface of the PBAT / thermoplastic starch film, thereby increasing the hydrophilicity of the film. The increase in hydrophilicity is beneficial to the adhesion of water-based inks to the film surface.

[0067] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A modified PBAT / thermoplastic starch film, characterized in that: Includes the following components in parts by weight: PBAT resin: 60-80 parts; Pre-plasticized starch granules: 20-40 parts; Polyethylene glycol stearate: 1-4 parts; Talc powder: 0.5-1.5 parts; Chain extender: 0.2-1 part.

2. The modified PBAT / thermoplastic starch film according to claim 1, characterized in that: The melt flow rate of the PBAT resin is 2-5 g / 10 min.

3. The modified PBAT / thermoplastic starch film according to claim 1, characterized in that: The pre-plasticized starch granules are prepared by the following steps: A1. Add 70 parts starch, 10-20 parts glycerin and 10-20 parts distilled water to a mixer and mix them in a mixer at a temperature of 60-80℃ for 3-5 minutes and a speed of 40-60 r / min. A2. The product obtained in A1 is sealed and left to stand for 8 hours, then cut into granules to finally obtain pre-plasticized starch granules.

4. The modified PBAT / thermoplastic starch film according to claim 1, characterized in that: The starch is one or more of corn starch, potato starch, and tapioca starch.

5. The modified PBAT / thermoplastic starch film according to claim 1, characterized in that: The talc powder is talc powder that has been surface-treated with a coupling agent.

6. The modified PBAT / thermoplastic starch film according to claim 1, characterized in that: The chain extender is a reactive epoxy functional chain extender.

7. A method for preparing the modified PBAT / thermoplastic starch film according to any one of claims 1-6, characterized in that: Includes the following steps: S1. After drying PBAT resin and preplasticized starch granules in an oven at 80℃ for 4-6 hours, mix all the raw material components together to obtain a premix. S2. Add the premix obtained in step S1 to the main feed port of a twin-screw extruder, and perform melt blending, extrusion, granulation, and drying to obtain modified PBAT / thermoplastic starch granules. S3: Add the modified PBAT / thermoplastic starch granules obtained in step S2 to the feeding port of a single-screw extruder, and perform melting, extrusion, blowing, traction, and winding to finally obtain the modified PBAT / thermoplastic starch film material.

8. The method for preparing the modified PBAT / thermoplastic starch film according to claim 7, characterized in that: In step S2, the twin-screw extruder speed is 200-400 r / min, the extrusion temperature is 130-170℃, the feed rate is 40-60 kg / h, and the drying conditions are 80℃ for 4-6 h.

9. The method for preparing the modified PBAT / thermoplastic starch film according to claim 7, characterized in that: In step S3, the single-screw extruder speed is 40-60 r / min, the extrusion temperature is 120-160℃, and the film blow-up ratio is 2.0-3.0.

Images