Full-biodegradable mulching film and preparation method thereof

Abstract

The invention relates to a full-biodegradable mulching film and a preparation method thereof, and belongs to the technical field of biodegradable materials. The full-biodegradable mulching film is prepared from the following components in percentage by mass: 60 percent to 65 percent of PBAT, 25 percent to 35 percent of bamboo micro powder master batch, 1 percent to 3 percent of tow protein, 0.2 percent to 0.5 percent of rosemary extract, 1 percent to 3 percent of tea polyphenol, 0.3 percent to 0.7 percent of chain extender, 0.8 percent to 1.2 percent of PETS, 0.3 percent to 0.7 percent of anti-hydrolysis agent, 0.3 percent to 0.7 percent of magnesium sulfate whisker and 0.1 percent to 0.3 percent of antioxidant. According to the invention, PBAT is taken as a main body material, the ultrathin mulching film is prepared through the rigidity enhancement effect of the bamboo micro-powder master batch, the toughening effect of the tow protein and the composite function system of the tea polyphenol and the rosemary extract in combination with a five-layer co-extrusion film blowing process, and the problems that the existing similar mulching film is insufficient in mechanical property, the water vapor barrier rate exceeds the standard, and the mulching film is difficult to be ultrathin are solved.

Description

Technical Field

[0001] The present invention relates to a fully biodegradable ground film and a preparation method thereof, belonging to the technical field of biodegradable materials. Background Art

[0002] PBAT (polybutylene adipate terephthalate) is a biodegradable aliphatic-aromatic copolyester, which is widely used in the field of agricultural ground films due to its good flexibility, processability and biodegradability. However, the existing PBAT ground films still have significant defects in practical applications: firstly, their mechanical strength is insufficient (for example, the tensile strength is generally lower than 25 MPa), resulting in easy cracking of the ground film during ultra-thin processing and use; secondly, the weather resistance is poor, and it is easy to age and degrade under complex environmental conditions, affecting the service life. Chinese patent application CN117343498A discloses a composite biodegradable film, and the tensile strength of the PBAT / PPC blended ground film in this patent application is only 18.34 Mpa at most, which is difficult to meet the requirements of high strength and high durability for ultra-thin ground films. Therefore, developing a PBAT-based composite film with both high mechanical properties, weather resistance and degradability has become an urgent technical problem to be solved in the current field of agricultural ground films. Summary of the Invention

[0003] The present invention provides a fully biodegradable ground film and a preparation method thereof to solve the problems existing in the above-mentioned prior art.

[0004] One of the purposes of the present invention is to provide a fully biodegradable ground film, which includes the following components by mass percentage: 60% - 65% of PBAT, 25% - 35% of bamboo micro-powder masterbatch, 1% - 3% of silk fibroin, 0.2% - 0.5% of rosemary extract, 1% - 3% of tea polyphenols, 0.3% - 0.7% of chain extender, 0.8% - 1.2% of PETS, 0.3% - 0.7% of anti-hydrolysis agent, 0.3% - 0.7% of magnesium sulfate whiskers, and 0.1% - 0.3% of antioxidant.

[0005] On the basis of the above technical solution, the present invention can also be improved as follows: Further, the bamboo micro-powder masterbatch includes the following components by mass percentage: 32% - 36% of bamboo micro-powder, 48% - 52% of carboxymethyl starch, 5% - 7% of sodium citrate, 3% - 5% of cellulose nanocrystals, 3% - 5% of sodium hydroxide, 1% - 3% of sodium trimetaphosphate, and 0 - 1% of glycerol.

[0006] Further, the preparation method of the bamboo micro-powder masterbatch includes the following steps: S1: Add bamboo micro-powder, carboxymethyl starch, sodium citrate, and glycerol with a mass fraction of 0.2 - 0.8% into a liquid medium, stir at 40°C - 60°C for 20 min - 40 min to form a premixed colloid. S2: Drop a sodium trimetaphosphate solution with a mass fraction of 5 - 15% into the premixed colloid, adjust the pH to 8 - 9, and react at 60°C - 80°C for 100 min - 180 min to form a three-dimensional network structure. S3: Then add cellulose nanocrystals and a sodium hydroxide solution with a mass fraction of 2 - 8%, perform ultrasonic dispersion for 10 min - 20 min, and conduct hydrothermal treatment at 80°C - 100°C for 80 min - 100 min. S4: Centrifuge and wash until neutral, vacuum dry at 60°C - 80°C, and pulverize to obtain bamboo micro-powder masterbatch.

[0007] Further, in step S1, the liquid medium is a mixture of deionized water and a carboxymethyl cellulose homogeneous solution with a mass fraction of 0.5% - 1.5% in a volume ratio of (90 - 99):(1 - 10), and the mass of the liquid medium is 2.5 - 3.5 times the total mass of bamboo micro-powder, carboxymethyl starch, sodium citrate, and glycerol.

[0008] Further, in step S3, the power of ultrasonic is 35 - 45 KHz, and the hydrothermal treatment adopts microwave-assisted hydrothermal treatment.

[0009] The second object of the present invention is to provide a preparation method of the above-mentioned fully biodegradable ground film, including the following steps: (1) Premix PBAT and bamboo micro-powder masterbatch in a mixer at 70°C - 80°C for 3 min - 8 min, and then add silk fibroin, rosemary extract, and tea polyphenol and mix evenly. (2) Then add a chain extender, PETS (pentaerythritol stearate), an anti-hydrolysis agent, magnesium sulfate whiskers, and an antioxidant and conduct melt blending in a twin-screw extruder. (3) After underwater pelletizing, dry at 50°C - 70°C until the moisture content ≤ 0.5% to obtain ground film pellets. (4) Form the ground film pellets through a five-layer co-extrusion blown film machine to obtain the fully biodegradable ground film.

[0010] Further, the barrel temperature of the twin-screw extruder is 100°C - 130°C, and the screw speed is 30 - 80 revolutions per minute.

[0011] Further, the five layers of the five-layer coextrusion blown film unit are layer A, layer B, layer C, layer D, and layer E. The temperatures of layer A and layer E are 125°C to 130°C, the temperatures of layer B, layer C, and layer D are 120°C to 125°C, the die head pressure is 8 to 12 Mpa, the film-forming width is 1200 to 1250 mm, the film-forming thickness is 0.006 to 0.007 mm, and the blow-up ratio is 2.5 to 3.0.

[0012] The technical solution provided by the present invention has the following beneficial effects compared with the prior art: 1. The present invention uses PBAT as the main material, through the rigid enhancement effect of bamboo micro-powder masterbatch, the in-situ cross-linking toughening effect of the β-sheet structure of silk fibroin, and the composite functional system of tea polyphenols-rosemary extract (antioxidant + insect prevention), combined with the five-layer coextrusion blown film process, to prepare an ultra-thin ground film with a thickness of only 0.006 to 0.007 mm; this ground film has both high strength and high ductility (tensile strength > 25 MPa, elongation at break greater than 810%), and at the same time has a biodegradation induction period of 60 days, and is given the functions of anti-ultraviolet and insect prevention, solving the problems of insufficient mechanical properties, excessive water vapor barrier rate, and difficulty in ultra-thinning of existing ground films.

[0013] 2. The bamboo micro-powder masterbatch of the present invention forms a rigid network through nano-scale dispersion, improving the tensile strength of the film; the β-sheet structure of silk fibroin in-situ cross-links with the PBAT molecular chain during processing to form a tough interface, synergistically solving the strength-toughness contradiction; tea polyphenols and rosemary extract form an antioxidant-insect prevention composite system, the former quenches ultraviolet free radicals through phenolic hydroxyl groups, and the latter repels insects through volatile components, and the two synergistically delay the photo-oxidative degradation of the ground film and reduce pest damage; the five-layer coextrusion blown film process distributes the functional components in a gradient manner (the outer layer is enriched with anti-UV / insect repellent agents, and the inner layer strengthens the mechanical structure), achieving a balance between performance and functionality.

[0014] 3. The bamboo micro-powder masterbatch of the present invention is prepared by sol-gel method with bamboo micro-powder and carboxymethyl starch as the main materials, and compounded with functional aids such as cellulose nanocrystals. The bamboo micro-powder and cellulose nanocrystals synergistically enhance the tensile strength, and the sol-gel method realizes molecular-level compounding, with simple process and low energy consumption; the bamboo micro-powder masterbatch prepared by the present invention has good tensile strength, high elongation at break, enhanced thermal stability, and significantly improved water resistance and flexibility, and is particularly suitable for preparing ultra-thin and super-tough fully biodegradable ground films. Specific Embodiments

[0015] The principles and features of the present invention will be described below in conjunction with examples. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0016] Preparation Example 1 A bamboo micro-powder masterbatch, comprising the following components by mass percentage: 34% bamboo micro-powder, 50% carboxymethyl starch, 6% sodium citrate, 4% cellulose nanocrystals, 4% sodium hydroxide, and 2% sodium trimetaphosphate.

[0017] A method for preparing a bamboo micro-powder masterbatch, comprising the following steps: S1: Add the above-mentioned bamboo micro-powder, carboxymethyl starch, and sodium citrate into a liquid medium (the liquid medium is a mixed solution of deionized water and 1% carboxymethyl cellulose homogeneous solution mixed according to a volume ratio of 95:5, and the mass of the liquid medium is 3 times the total mass of the bamboo micro-powder, carboxymethyl starch, and sodium citrate), stir at 50 °C for 30 min to form a premixed colloid; S2: Dropwise add a 10% sodium trimetaphosphate solution into the premixed colloid, adjust the pH to 8, and react at 70 °C for 120 min to form a three-dimensional network structure; S3: Then add cellulose nanocrystals and a 5% sodium hydroxide solution, disperse by ultrasonic wave (power 35 KHz) for 15 min, and perform hydrothermal treatment at 90 °C for 90 min; S4: Centrifuge and wash until neutral, dry in vacuum at 70 °C, and pulverize to obtain the bamboo micro-powder masterbatch.

[0018] Preparation Example 2 A bamboo micro-powder masterbatch, comprising the following components by mass percentage: 36% bamboo micro-powder, 48% carboxymethyl starch, 5% sodium citrate, 5% cellulose nanocrystals, 5% sodium hydroxide, and 1% sodium trimetaphosphate.

[0019] A method for preparing a bamboo micro-powder masterbatch, comprising the following steps: S1: Add the above-mentioned bamboo micro-powder, carboxymethyl starch, and sodium citrate into a liquid medium (the liquid medium is a mixed solution of deionized water and 0.5% carboxymethyl cellulose homogeneous solution mixed according to a volume ratio of 90:10, and the mass of the liquid medium is 2.5 times the total mass of the bamboo micro-powder, carboxymethyl starch, and sodium citrate), stir at 40 °C for 40 min to form a premixed colloid; S2: Dropwise add a 5% sodium trimetaphosphate solution into the premixed colloid, adjust the pH to 9, and react at 80 °C for 100 min to form a three-dimensional network structure; S3: Then add cellulose nanocrystals and a 2% sodium hydroxide solution, disperse by ultrasonic wave (power 40 KHz) for 10 min, and perform hydrothermal treatment at 80 °C for 100 min; S4: Centrifuge and wash until neutral, dry in vacuum at 80 °C, and pulverize to obtain the bamboo micro-powder masterbatch.

[0020] Preparation Example 3 A bamboo micro-powder masterbatch includes the following components by mass percentage: 32% bamboo micro-powder, 52% carboxymethyl starch, 7% sodium citrate, 3% cellulose nanocrystals, 3% sodium hydroxide, and 3% sodium trimetaphosphate.

[0021] A method for preparing a bamboo micro-powder masterbatch includes the following steps: S1: Add the above-mentioned bamboo micro-powder, carboxymethyl starch, and sodium citrate into a liquid medium (the liquid medium is a mixed solution of deionized water and a 1.5% carboxymethyl cellulose homogeneous solution mixed in a volume ratio of 99:1, and the mass of the liquid medium is 3.5 times the total mass of the bamboo micro-powder, carboxymethyl starch, and sodium citrate), stir at 60°C for 20 min to form a premixed colloid; S2: Dropwise add a 15% sodium trimetaphosphate solution into the premixed colloid, adjust the pH to 8.5, and react at 60°C for 180 min to form a three-dimensional network structure; S3: Then add cellulose nanocrystals and a 6% sodium hydroxide solution, disperse by ultrasonic wave (power 35 KHz) for 20 min, and perform hydrothermal treatment at 85°C for 95 min; S4: Centrifuge and wash until neutral, vacuum dry at 60°C, and pulverize to obtain the bamboo micro-powder masterbatch.

[0022] Preparation Example 4 A bamboo micro-powder masterbatch includes the following components by mass percentage: 35% bamboo micro-powder, 49% carboxymethyl starch, 6% sodium citrate, 3% cellulose nanocrystals, 4% sodium hydroxide, 2% sodium trimetaphosphate, and 1% glycerol.

[0023] A method for preparing a bamboo micro-powder masterbatch includes the following steps: S1: Add the above-mentioned bamboo micro-powder, carboxymethyl starch, and sodium citrate into a liquid medium (the liquid medium is a mixed solution of deionized water and a 1% carboxymethyl cellulose homogeneous solution mixed in a volume ratio of 99:1, and the mass of the liquid medium is 3 times the total mass of the bamboo micro-powder, carboxymethyl starch, sodium citrate, and glycerol), stir at 45°C for 35 min to form a premixed colloid; S2: Dropwise add an 8% sodium trimetaphosphate solution into the premixed colloid, adjust the pH to 8, and react at 65°C for 160 min to form a three-dimensional network structure; S3: Then add cellulose nanocrystals and a 4% sodium hydroxide solution, disperse by ultrasonic wave (power 35 KHz) for 12 min, and perform hydrothermal treatment at 100°C for 80 min; S4: Centrifuge and wash until neutral, vacuum dry at 70°C, and pulverize to obtain the bamboo micro-powder masterbatch.

[0024] Preparation Example 5 A bamboo micro-powder masterbatch comprises the following components by mass percentage: 33% bamboo micro-powder, 51% carboxymethyl starch, 5.5% sodium citrate, 4.5% cellulose nanocrystals, 4% sodium hydroxide, and 2% sodium trimetaphosphate.

[0025] A method for preparing a bamboo micro-powder masterbatch includes the following steps: S1: Add the above-mentioned bamboo micro-powder, carboxymethyl starch, and sodium citrate into a liquid medium (the liquid medium is a mixed solution of deionized water and 1% carboxymethyl cellulose homogeneous solution mixed in a volume ratio of 90:10, and the mass of the liquid medium is 3 times the total mass of the bamboo micro-powder, carboxymethyl starch, and sodium citrate), stir at 55 °C for 25 min to form a premixed colloid; S2: Drop a 12% sodium trimetaphosphate solution into the premixed colloid, adjust the pH to 9, and react at 75 °C for 140 min to form a three-dimensional network structure; S3: Then add cellulose nanocrystals and an 8% sodium hydroxide solution, disperse by ultrasonic wave (power 35 KHz) for 18 min, and perform microwave (power 880 W) assisted hydrothermal treatment at 90 °C for 10 min; S4: Centrifuge and wash until neutral, dry in vacuum at 70 °C, and pulverize to obtain the bamboo micro-powder masterbatch. Example 1

[0026] A fully biodegradable mulch film comprises the following components by mass percentage: 63% PBAT, 30% bamboo micro-powder masterbatch obtained in Preparation Example 1, 2% silk fibroin, 0.3% rosemary extract, 2% tea polyphenols, 0.5% chain extender, 1.0% PETS, 0.5% anti-hydrolysis agent, 0.5% magnesium sulfate whisker, and 0.2% antioxidant.

[0027] A method for preparing a fully biodegradable mulch film includes the following steps: (1) Premix 63 kg of PBAT and 30 kg of the bamboo micro-powder masterbatch obtained in Preparation Example 1 in a mixer at 75 °C for 5 min, and then add 2 kg of silk fibroin, 0.3 kg of rosemary extract, and 2 kg of tea polyphenols and mix evenly; (2) Then add 0.5 kg of chain extender (BASF ADR-4468), 1 kg of PETS (pentaerythritol stearate), 0.5 kg of anti-hydrolysis agent (Stabaxol p400), 0.5 kg of magnesium sulfate whisker, and 0.2 kg of antioxidant (1076) and perform melt blending in a twin-screw extruder (barrel temperature 115 °C, screw speed 50 rpm); (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain mulch film pellets; (4) The biodegradable film granules are formed by a five-layer co-extrusion blown film machine of A / B / C / D / E (the temperature of layer A / E is 130 °C, the temperature of layer B / C / D is 125 °C, the die head pressure is 10 Mpa, and the blow-up ratio is 2.7) to obtain a fully biodegradable mulch film. Example 2

[0028] A fully biodegradable mulch film, by mass percentage, includes the following components: 62% PBAT, 32% bamboo micro-powder masterbatch obtained from Preparation Example 2, 1.5% fiber protein, 0.2% rosemary extract, 2.5% tea polyphenol, 0.3% chain extender, 0.8% PETS, 0.3% anti-hydrolysis agent, 0.3% magnesium sulfate whisker, 0.1% antioxidant.

[0029] A preparation method of a fully biodegradable mulch film includes the following steps: (1) Premix 62 kg of PBAT and 32 kg of the bamboo micro-powder masterbatch obtained from Preparation Example 2 in a mixer at 70 °C for 5 min, and then add 1.5 kg of fiber protein, 0.2 kg of rosemary extract, and 2.5 kg of tea polyphenol and mix evenly; (2) Then add 0.3 kg of chain extender (BASF ADR-4468), 0.8 kg of PETS (pentaerythritol stearate), 0.3 kg of anti-hydrolysis agent (Stabaxol p400), 0.3 kg of magnesium sulfate whisker, and 0.1 kg of antioxidant (1076) and melt-blend in a twin-screw extruder (the barrel temperature is 100 °C, and the screw speed is 30 revolutions / min); (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain film granules; (4) The film granules are formed by a five-layer co-extrusion blown film machine of A / B / C / D / E (the temperature of layer A / E is 130 °C, the temperature of layer B / C / D is 125 °C, the die head pressure is 8 Mpa, and the blow-up ratio is 2.5) to obtain a fully biodegradable mulch film. Example 3

[0030] A fully biodegradable mulch film, by mass percentage, includes the following components: 65% PBAT, 25% bamboo micro-powder masterbatch obtained from Preparation Example 3, 3% fiber protein, 0.5% rosemary extract, 3% tea polyphenol, 0.7% chain extender, 1.1% PETS, 0.7% anti-hydrolysis agent, 0.7% magnesium sulfate whisker, 0.3% antioxidant.

[0031] A preparation method of a fully biodegradable mulch film includes the following steps: (1) Premix 65 kg of PBAT and 25 kg of the bamboo micro-powder masterbatch obtained from Preparation Example 3 in a mixer at 70 °C for 5 min, and then add 3 kg of fiber protein, 0.5 kg of rosemary extract, and 3 kg of tea polyphenol and mix evenly; (2) Then add 0.7 kg of chain extender (BASF ADR-4468), 1.1 kg of PETS (pentaerythritol stearate), 0.7 kg of hydrolysis inhibitor (Stabaxol p400), 0.7 kg of magnesium sulfate whiskers, and 0.3 kg of antioxidant (1076) and melt-blend them in a twin-screw extruder (barrel temperature 110 °C, screw speed 40 rpm); (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain film pellets; (4) Mould the film pellets through an A / B / C / D / E five-layer coextrusion blown film unit (temperature of layer A / E is 130 °C, temperature of layer B / C / D is 125 °C, die head pressure 9 Mpa, blow-up ratio 2.6) to obtain a fully biodegradable mulch film. Example 4

[0032] A fully biodegradable mulch film, by mass percentage, comprises the following components: 60% PBAT, 35% bamboo micro-powder masterbatch obtained in Preparation Example 4, 1% silk fibroin, 0.4% rosemary extract, 1% tea polyphenol, 0.3% chain extender, 1.0% PETS, 0.4% hydrolysis inhibitor, 0.7% magnesium sulfate whiskers, 0.2% antioxidant.

[0033] A preparation method of a fully biodegradable mulch film, comprising the following steps: (1) Premix 603 kg of PBAT and 35 kg of bamboo micro-powder masterbatch obtained in Preparation Example 4 in a mixer at 75 °C for 5 min, and then add 1 kg of silk fibroin, 0.4 kg of rosemary extract, and 1 kg of tea polyphenol and mix evenly; (2) Then add 0.3 kg of chain extender (BASF ADR-4468), 1 kg of PETS (pentaerythritol stearate), 0.4 kg of hydrolysis inhibitor (Stabaxol p400), 0.7 kg of magnesium sulfate whiskers, and 0.2 kg of antioxidant (1076) and melt-blend them in a twin-screw extruder (barrel temperature 120 °C, screw speed 60 rpm); (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain film pellets; (4) Mould the film pellets through an A / B / C / D / E five-layer coextrusion blown film unit (temperature of layer A / E is 130 °C, temperature of layer B / C / D is 125 °C, die head pressure 11 Mpa, blow-up ratio 2.8) to obtain a fully biodegradable mulch film. Example 5

[0034] A fully biodegradable mulch film, by mass percentage, comprises the following components: 63.5% of PBAT, 29% of the bamboo micro powder masterbatch obtained in Preparation Example 5, 2.2% of silk fibroin, 0.3% of rosemary extract, 2% of tea polyphenols, 0.6% of chain extender, 1.2% of PETS, 0.6% of hydrolysis inhibitor, 0.4% of magnesium sulfate whiskers, 0.2% of antioxidant.

[0035] A method for preparing a fully biodegradable mulch film comprises the following steps: (1) Premix 63.5 kg of PBAT and 30 kg of the bamboo micro powder masterbatch obtained in Preparation Example 5 in a mixer at 80 °C for 5 min, and then add 2.2 kg of silk fibroin, 0.3 kg of rosemary extract, and 2 kg of tea polyphenols and mix evenly; (2) Then add 0.6 kg of chain extender (BASF ADR-4468), 1.2 kg of PETS (pentaerythritol stearate), 0.6 kg of hydrolysis inhibitor (Stabaxol p400), 0.45 kg of magnesium sulfate whiskers, and 0.2 kg of antioxidant (1076) and melt-blend in a twin-screw extruder (barrel temperature 125 °C, screw speed 70 rpm); (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain mulch film pellets; (4) Form the mulch film pellets by a five-layer co-extrusion blown film unit of A / B / C / D / E (temperature of A / E layers 130 °C, temperature of B / C / D layers 125 °C, die head pressure 12 Mpa, blow-up ratio 2.9) to obtain the fully biodegradable mulch film. Example 6

[0036] A fully biodegradable mulch film, by mass percentage, comprises the following components: 61% of PBAT, 31% of the bamboo micro powder masterbatch obtained in Preparation Example 5, 2.5% of silk fibroin, 0.5% of rosemary extract, 2% of tea polyphenols, 0.4% of chain extender, 1.0% of PETS, 0.7% of hydrolysis inhibitor, 0.6% of magnesium sulfate whiskers, 0.3% of antioxidant.

[0037] A method for preparing a fully biodegradable mulch film comprises the following steps: (1) Premix 61 kg of PBAT and 31 kg of the bamboo micro powder masterbatch obtained in Preparation Example 5 in a mixer at 80 °C for 5 min, and then add 2.5 kg of silk fibroin, 0.5 kg of rosemary extract, and 2 kg of tea polyphenols and mix evenly; (2) Then add 0.4 kg of chain extender (BASF ADR-4468), 1 kg of PETS (pentaerythritol stearate), 0.7 kg of hydrolysis inhibitor (Stabaxol p400), 0.6 kg of magnesium sulfate whiskers, and 0.3 kg of antioxidant (1076) and melt-blend them in a twin-screw extruder (barrel temperature 130 °C, screw speed 80 rpm). (3) After underwater pelletizing, dry at 60 °C until the moisture content ≤ 0.5% to obtain film granules. (4) Mould the film granules through an A / B / C / D / E five-layer co-extrusion blown film unit (temperature of layer A / E is 130 °C, temperature of layer B / C / D is 125 °C, die head pressure is 12 Mpa, blow-up ratio is 3.0) to obtain a fully biodegradable film.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that bamboo micro-powder is used instead of bamboo micro-powder masterbatch.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that it does not contain bamboo micro-powder masterbatch, and the corresponding bamboo micro-powder masterbatch is replaced by PBAT.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that it does not contain fibroin, and the corresponding fibroin is replaced by PBAT.

[0041] Comparative Example 4 The difference between this comparative example and Example 1 is that it does not contain tea polyphenols, and the corresponding tea polyphenols are replaced by rosemary extract.

[0042] Comparative Example 5 The difference between this comparative example and Example 1 is that it does not contain rosemary extract, and the corresponding rosemary extract is replaced by tea polyphenols.

[0043] Comparative Example 6 The difference between this comparative example and Example 1 is that it does not contain tea polyphenols and rosemary extract, and the corresponding tea polyphenols and rosemary extract are replaced by PBAT.

[0044] Performance test: Conduct mechanical property tests, water vapor transmission rate tests, and degradation induction period tests on the films obtained in Examples 1-6 and Comparative Examples 1-6.

[0045] The test results are shown in Table 1.

[0046] Table 1 Data table of film performance test

[0047] As can be seen from Table 1: The thickness of the plastic films prepared in Examples 1-6 of the present invention is only 0.006 mm to 0.007 mm, and the tensile strength is greater than 25 MPa, the elongation at break is greater than 810%, and the water vapor transmission rate is less than 380 g / (m²·24 h); By comparing Examples 1-6 with Comparative Examples 1-6, it can be seen that on the basis of the ultra-thin thickness of the plastic film of the present invention, its mechanical properties have been significantly improved, and the water vapor transmission rate is less than that of the comparative examples, indicating that the ultra-thin plastic film of the present invention has both high mechanical properties, weather resistance and degradability.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A fully biodegradable mulch film, characterized in that, By mass percentage, it includes the following components: 60% - 65% of PBAT, 25% - 35% of bamboo micro-powder masterbatch, 1% - 3% of fibroin, 0.2% - 0.5% of rosemary extract, 1% - 3% of tea polyphenols, 0.3% - 0.7% of chain extender, 0.8% - 1.2% of PETS, 0.3% - 0.7% of anti-hydrolysis agent, 0.3% - 0.7% of magnesium sulfate whiskers, and 0.1% - 0.3% of antioxidant.

2. The fully biodegradable ground film according to claim 1, wherein The bamboo micro-powder masterbatch, by mass percentage, includes the following components: 32% - 36% of bamboo micro-powder, 48% - 52% of carboxymethyl starch, 5% - 7% of sodium citrate, 3% - 5% of cellulose nanocrystals, 3% - 5% of sodium hydroxide, 1% - 3% of sodium trimetaphosphate, and 0 - 1% of glycerol.

3. The fully biodegradable plastic film according to claim 2, wherein The preparation method of the bamboo micro-powder masterbatch includes the following steps: S1: Add bamboo micro-powder, carboxymethyl starch, sodium citrate, and glycerol with a mass fraction of 0.2% - 0.8% into a liquid medium, stir at 40°C - 60°C for 20 min - 40 min to form a premixed colloid. S2: Drop a sodium trimetaphosphate solution with a mass fraction of 5% - 15% into the premixed colloid, adjust the pH to 8 - 9, react at 60°C - 80°C for 100 min - 180 min to form a three-dimensional network structure. S3: Then add cellulose nanocrystals and a sodium hydroxide solution with a mass fraction of 2% - 8%, ultrasonically disperse for 10 min - 20 min, and perform hydrothermal treatment at 80°C - 100°C for 80 min - 100 min. S4: Centrifuge and wash until neutral, vacuum dry at 60°C - 80°C, and pulverize to obtain the bamboo micro-powder masterbatch.

4. The fully biodegradable ground film according to claim 3, characterized in that, In step S1, the liquid medium is a mixed solution of deionized water and a carboxymethyl cellulose homogeneous solution with a mass fraction of 0.5% - 1.5% mixed in a volume ratio of (90 - 99):(1 - 10), and the mass of the liquid medium is 2.5 - 3.5 times the total mass of bamboo micro-powder, carboxymethyl starch, sodium citrate, and glycerol.

5. The fully biodegradable ground film according to claim 3, characterized in that, In step S3, the power of the ultrasonic wave is 35 - 45 KHz, and the hydrothermal treatment adopts microwave-assisted hydrothermal treatment.

6. A method for preparing a fully biodegradable mulch film according to any one of claims 1-5, characterized in that, It includes the following steps: (1) Premix PBAT and the bamboo micro-powder masterbatch in a mixer at 70°C - 80°C for 3 min - 8 min, then add fibroin, rosemary extract, and tea polyphenols and mix evenly. (2) Then add the chain extender, PETS, anti-hydrolysis agent, magnesium sulfate whiskers, and antioxidant and melt-blend in a twin-screw extruder. (3) After underwater pelletizing, dry at 50°C - 70°C until the moisture content ≤ 0.5% to obtain the film mulch granules. (4) Form the film mulch granules through a five-layer co-extrusion blown film machine to obtain the fully biodegradable film mulch.

7. The preparation method of the fully biodegradable ground film according to claim 6, characterized in that, The barrel temperature of the twin-screw extruder is 100°C - 130°C, and the screw speed is 30 - 80 revolutions per minute.

8. The preparation method of the fully biodegradable plastic film according to claim 6, wherein The five layers of the five-layer coextrusion blown film unit are layer A, layer B, layer C, layer D and layer E. The temperatures of layer A and layer E are 125°C to 130°C, the temperatures of layer B, layer C and layer D are 120°C to 125°C. The die head pressure of the five-layer coextrusion blown film unit is 8 to 12 Mpa, the film forming width is 1200 mm to 1250 mm, the film forming thickness is 0.006 mm to 0.007 mm, and the blow-up ratio is 2.5 to 3.0.

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