A fully biodegradable mulching film and a method for preparing the same

Abstract

This invention relates to a fully biodegradable mulch film and its preparation method, belonging to the field of biodegradable materials technology. The fully biodegradable mulch film comprises the following components by mass percentage: 60%~65% PBAT, 25%~35% bamboo micron powder masterbatch, 1%~3% fibrous protein, 0.2%~0.5% rosemary extract, 1%~3% tea polyphenols, 0.3%~0.7% chain extender, 0.8%~1.2% PETS, 0.3%~0.7% anti-hydrolysis agent, 0.3%~0.7% magnesium sulfate whiskers, and 0.1%~0.3% antioxidant. This invention uses PBAT as the main material, leveraging the rigidity-enhancing effect of bamboo micron powder masterbatch, the toughening effect of fibrous protein, and the composite functional system of tea polyphenols and rosemary extract, combined with a five-layer co-extrusion blown film process to prepare an ultra-thin mulch film. This solves the problems of insufficient mechanical properties, excessive water vapor barrier rate, and difficulty in achieving ultra-thinness in existing similar mulch films.

Description

Technical Field

[0001] This invention relates to a fully biodegradable mulch film and its preparation method, belonging to the field of biodegradable materials technology. Background Technology

[0002] PBAT (polybutylene adipate / terephthalate) is a biodegradable aliphatic-aromatic copolyester, widely used in agricultural mulch films due to its good flexibility, processability, and biodegradability. However, existing PBAT mulch films still have significant drawbacks in practical applications: First, their mechanical strength is insufficient (e.g., tensile strength is generally below 25 MPa), making them prone to breakage during ultra-thin processing and use; second, they have poor weather resistance and are prone to aging and degradation under complex environmental conditions, affecting their service life. Chinese patent application CN117343498A discloses a composite biodegradable film, but the highest tensile strength of the PBAT / PPC blend mulch film in this patent application is only 18.34 MPa, which is insufficient to meet the requirements of high strength and high durability for ultra-thin mulch films. Therefore, developing a PBAT-based composite film that combines high mechanical properties, weather resistance, and biodegradability has become a pressing technical challenge in the current agricultural mulch film industry. Summary of the Invention

[0003] This invention provides a fully biodegradable mulch film and its preparation method to solve the problems existing in the prior art as described above.

[0004] One of the objectives of this invention is to provide a fully biodegradable mulch film, comprising the following components by weight percentage: 60%~65% PBAT, 25%~35% bamboo micron powder masterbatch, 1%~3% fibrous protein, 0.2%~0.5% rosemary extract, 1%~3% tea polyphenols, 0.3%~0.7% chain extender, 0.8%~1.2% PETS, 0.3%~0.7% anti-hydrolysis agent, 0.3%~0.7% magnesium sulfate whiskers, and 0.1%~0.3% antioxidant.

[0005] Based on the above technical solution, the present invention can be further improved as follows:

[0006] Furthermore, the bamboo micro powder masterbatch comprises the following components by mass percentage: 32%~36% bamboo micro powder, 48%~52% carboxymethyl starch, 5%~7% sodium citrate, 3%~5% cellulose nanocrystals, 3%~5% sodium hydroxide, 1%~3% sodium trimetaphosphate, and 0~1% glycerol.

[0007] Furthermore, the preparation method of the bamboo micron powder masterbatch includes the following steps:

[0008] S1: Add bamboo micro powder, carboxymethyl starch, sodium citrate and 0.2-0.8% glycerol by mass to a liquid medium and stir at 40℃-60℃ for 20-40 minutes to form a premixed colloid;

[0009] S2: Add 5-15% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 8-9, and react at 60-80℃ for 100-180 min to form a three-dimensional network structure.

[0010] S3: Add cellulose nanocrystals and sodium hydroxide solution with a mass fraction of 2-8%, ultrasonically disperse for 10-20 minutes, and hydrothermally treat at 80-100℃ for 80-100 minutes.

[0011] S4: Centrifuge and wash until neutral, vacuum dry at 60℃~80℃, and pulverize to obtain bamboo micro powder masterbatch.

[0012] Further, in step S1, the liquid medium is a mixture of deionized water and a homogenized solution of carboxymethyl cellulose with a mass fraction of 0.5% to 1.5% at a volume ratio of (90 to 99): (1 to 10), and the mass of the liquid medium is 2.5 to 3.5 times the total mass of bamboo powder, carboxymethyl starch, sodium citrate and glycerol.

[0013] Furthermore, in step S3, the ultrasonic power is 35~45KHz, and the hydrothermal treatment adopts microwave-assisted hydrothermal treatment.

[0014] A second objective of this invention is to provide a method for preparing the above-mentioned fully biodegradable mulch film, comprising the following steps:

[0015] (1) Premix PBAT and bamboo micro powder masterbatch in a mixer at 70℃~80℃ for 3min~8min, then add silk tow protein, rosemary extract and tea polyphenols and mix evenly.

[0016] (2) Add chain extender, PETS (pentaerythritol stearate), anti-hydrolysis agent, magnesium sulfate whiskers, and antioxidant and melt blend in a twin-screw extruder;

[0017] (3) After underwater pelleting, dry at 50℃~70℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0018] (4) The mulch film particles are formed by a five-layer co-extrusion blown film machine to obtain the fully biodegradable mulch film.

[0019] Furthermore, the barrel temperature of the twin-screw extruder is 100℃~130℃, and the screw speed is 30~80 rpm.

[0020] Furthermore, the five layers of the five-layer co-extrusion blown film unit are layer A, layer B, layer C, layer D and layer E. The temperature of layer A and layer E is 125℃~130℃, the temperature of layer B, layer C and layer D is 120℃~125℃, the die pressure is 8~12Mpa, the film width is 1200~1250mm, the film thickness is 0.006~0.007mm, and the blow-up ratio is 2.5~3.0.

[0021] The technical solution provided by this invention has the following advantages compared with the prior art:

[0022] 1. This invention uses PBAT as the main material, and through the rigidity enhancement effect of bamboo micro powder masterbatch, the in-situ cross-linking toughening effect of the β-sheet structure of filament protein, and the composite functional system of tea polyphenols and rosemary extract (antioxidant + insect repellent), combined with a five-layer co-extrusion blown film process, to prepare an ultra-thin mulch film with a thickness of only 0.006~0.007mm. This mulch film has both high strength and high ductility (tensile strength > 25MPa, elongation at break > 810%), while having a biodegradation induction period of 60 days, and is endowed with UV resistance and insect repellent functions, solving the problems of insufficient mechanical properties, excessive water vapor barrier rate, and difficulty in ultra-thinning of existing mulch films.

[0023] 2. The bamboo micro powder masterbatch of this invention forms a rigid network through nanoscale dispersion, which improves the tensile strength of the film; the β-sheet structure of the tow protein is cross-linked in situ with the PBAT molecular chain during processing to form a tough interface, which synergistically solves the contradiction between strength and toughness; tea polyphenols and rosemary extract constitute an antioxidant-insect repellent composite system. The former quenches ultraviolet free radicals through phenolic hydroxyl groups, while the latter repels insects through volatile components. The two work together to delay the photo-oxidative degradation of the mulch film and reduce insect damage; the five-layer co-extrusion blown film process distributes the functional components in a gradient (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.

[0024] 3. The bamboo micron powder masterbatch of the present invention is prepared by using bamboo micron powder and carboxymethyl starch as the main materials, compounded with functional additives such as cellulose nanocrystals, through a sol-gel method. The bamboo micron powder and cellulose nanocrystals synergistically enhance the tensile strength. The sol-gel method achieves molecular-level composite, which is simple and energy-efficient. The bamboo micron 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. It is particularly suitable for preparing ultra-thin and ultra-tough fully biodegradable mulch films. Detailed Implementation

[0025] The principles and features of the present invention are described below with reference to examples. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0026] Preparation Example 1

[0027] A bamboo micro powder masterbatch comprises 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 tripolyphosphate.

[0028] A method for preparing bamboo micro powder masterbatch includes the following steps:

[0029] S1: Add the above bamboo micro powder, carboxymethyl starch, and sodium citrate to a liquid medium (the liquid medium is a mixture of deionized water and 1% carboxymethyl cellulose homogenate at a volume ratio of 95:5, and the mass of the liquid medium is 3 times the total mass of bamboo micro powder, carboxymethyl starch, and sodium citrate), stir at 50°C for 30 minutes to form a premixed colloid.

[0030] S2: Add 10% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 8, and react at 70℃ for 120 min to form a three-dimensional network structure.

[0031] S3: Add cellulose nanocrystals and 5% sodium hydroxide solution, disperse by ultrasonication (35KHz) for 15min, and then hydrothermally treat at 90℃ for 90min.

[0032] S4: Centrifuge and wash until neutral, vacuum dry at 70℃, and pulverize to obtain bamboo micro powder masterbatch.

[0033] Preparation Example 2

[0034] A bamboo micro powder masterbatch comprises 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 tripolyphosphate.

[0035] A method for preparing bamboo micro powder masterbatch includes the following steps:

[0036] S1: Add the above bamboo micro powder, carboxymethyl starch, and sodium citrate to a liquid medium (the liquid medium is a mixture of deionized water and 0.5% carboxymethyl cellulose homogenate at a volume ratio of 90:10, and the mass of the liquid medium is 2.5 times the total mass of bamboo micro powder, carboxymethyl starch, and sodium citrate), stir at 40°C for 40 min to form a premixed colloid;

[0037] S2: Add 5% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 9, react at 80℃ for 100 min to form a three-dimensional network structure;

[0038] S3: Add cellulose nanocrystals and 2% sodium hydroxide solution, disperse by ultrasonication (40KHz) for 10min, and then hydrothermally treat at 80℃ for 100min.

[0039] S4: Centrifuge and wash until neutral, vacuum dry at 80℃, and pulverize to obtain bamboo micro powder masterbatch.

[0040] Preparation Example 3

[0041] A bamboo micro powder masterbatch comprises 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 tripolyphosphate.

[0042] A method for preparing bamboo micro powder masterbatch includes the following steps:

[0043] S1: Add the above bamboo powder, carboxymethyl starch, and sodium citrate to a liquid medium (the liquid medium is a mixture of deionized water and 1.5% carboxymethyl cellulose homogenate at a volume ratio of 99:1, and the mass of the liquid medium is 3.5 times the total mass of bamboo powder, carboxymethyl starch, and sodium citrate), and stir at 60°C for 20 minutes to form a premixed colloid.

[0044] S2: Add 15% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 8.5, react at 60℃ for 180 min to form a three-dimensional network structure;

[0045] S3: Add cellulose nanocrystals and a 6% sodium hydroxide solution, disperse by ultrasonication (35 kHz) for 20 min, and then perform hydrothermal treatment at 85°C for 95 min.

[0046] S4: Centrifuge and wash until neutral, vacuum dry at 60℃, and pulverize to obtain bamboo micro powder masterbatch.

[0047] Preparation Example 4

[0048] A bamboo micro powder masterbatch comprises 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.

[0049] A method for preparing bamboo micro powder masterbatch includes the following steps:

[0050] S1: Add the above bamboo powder, carboxymethyl starch, and sodium citrate to a liquid medium (the liquid medium is a mixture of deionized water and 1% carboxymethyl cellulose homogenate at a volume ratio of 99:1, and the mass of the liquid medium is 3 times the total mass of bamboo powder, carboxymethyl starch, sodium citrate, and glycerin), and stir at 45°C for 35 minutes to form a premixed colloid.

[0051] S2: Add 8% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 8, and react at 65℃ for 160 min to form a three-dimensional network structure.

[0052] S3: Add cellulose nanocrystals and 4% sodium hydroxide solution, disperse by ultrasonication (35KHz) for 12min, and then hydrothermally treat at 100℃ for 80min.

[0053] S4: Centrifuge and wash until neutral, vacuum dry at 70℃, and pulverize to obtain bamboo micro powder masterbatch.

[0054] Preparation Example 5

[0055] 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 tripolyphosphate.

[0056] A method for preparing bamboo micro powder masterbatch includes the following steps:

[0057] S1: Add the above bamboo powder, carboxymethyl starch, and sodium citrate to a liquid medium (the liquid medium is a mixture of deionized water and 1% carboxymethyl cellulose homogenate at a volume ratio of 90:10, and the mass of the liquid medium is 3 times the total mass of bamboo powder, carboxymethyl starch, and sodium citrate), stir at 55°C for 25 minutes to form a premixed colloid.

[0058] S2: Add 12% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 9, and react at 75℃ for 140 min to form a three-dimensional network structure.

[0059] S3: Add cellulose nanocrystals and 8% sodium hydroxide solution, disperse by ultrasonication (35KHz) for 18min, and then perform microwave-assisted hydrothermal treatment at 90℃ (880W) for 10min.

[0060] S4: Centrifuge and wash until neutral, vacuum dry at 70℃, and pulverize to obtain bamboo micro powder masterbatch. Example 1

[0061] A fully biodegradable mulch film, comprising the following components by weight percentage: 63% PBAT, 30% bamboo micron powder masterbatch obtained in Preparation Example 1, 2% fibrous protein, 0.3% rosemary extract, 2% tea polyphenols, 0.5% chain extender, 1.0% PETS, 0.5% anti-hydrolysis agent, 0.5% magnesium sulfate whiskers, and 0.2% antioxidant.

[0062] A method for preparing a fully biodegradable mulch film includes the following steps:

[0063] (1) 63 kg of PBAT and 30 kg of bamboo micro powder masterbatch obtained in Preparation Example 1 were premixed in a mixer at 75°C for 5 min, and then 2 kg of silk tow protein, 0.3 kg of rosemary extract and 2 kg of tea polyphenols were added and mixed evenly.

[0064] (2) Add 0.5 kg of chain extender (BASF ADR-4468), 1 kg of PETS (pentaerythritol stearate), 0.5 kg of hydrolysis inhibitor (Stabaxol p400), 0.5 kg of magnesium sulfate whiskers, and 0.2 kg of antioxidant (1076) and melt-blend them in a twin-screw extruder (barrel temperature 115℃, screw speed 50 rpm);

[0065] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0066] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 10Mpa, blown ratio 2.7) to obtain a fully biodegradable mulch film. Example 2

[0067] A fully biodegradable mulch film comprises, by weight percentage: 62% PBAT, 32% bamboo micron powder masterbatch obtained in Preparation Example 2, 1.5% fibrous protein, 0.2% rosemary extract, 2.5% tea polyphenols, 0.3% chain extender, 0.8% PETS, 0.3% anti-hydrolysis agent, 0.3% magnesium sulfate whiskers, and 0.1% antioxidant.

[0068] A method for preparing a fully biodegradable mulch film includes the following steps:

[0069] (1) 62 kg of PBAT and 32 kg of bamboo micro powder masterbatch obtained in Preparation Example 2 were premixed in a mixer at 70°C for 5 min, and then 1.5 kg of silk tow protein, 0.2 kg of rosemary extract and 2.5 kg of tea polyphenols were added and mixed evenly.

[0070] (2) Add 0.3 kg of chain extender (BASF ADR-4468), 0.8 kg of PETS (pentaerythritol stearate), 0.3 kg of hydrolysis inhibitor (Stabaxol p400), 0.3 kg of magnesium sulfate whiskers, and 0.1 kg of antioxidant (1076) and melt-blend them in a twin-screw extruder (barrel temperature 100℃, screw speed 30 rpm);

[0071] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0072] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 8Mpa, blow-up ratio 2.5) to obtain a fully biodegradable mulch film. Example 3

[0073] A fully biodegradable mulch film, by weight percentage, comprises the following components: 65% PBAT, 25% bamboo micron powder masterbatch obtained in Preparation Example 3, 3% fibrous protein, 0.5% rosemary extract, 3% tea polyphenols, 0.7% chain extender, 1.1% PETS, 0.7% anti-hydrolysis agent, 0.7% magnesium sulfate whiskers, and 0.3% antioxidant.

[0074] A method for preparing a fully biodegradable mulch film includes the following steps:

[0075] (1) 65 kg of PBAT and 25 kg of bamboo micro powder masterbatch obtained in Preparation Example 3 were premixed in a mixer at 70°C for 5 min, and then 3 kg of silk tow protein, 0.5 kg of rosemary extract and 3 kg of tea polyphenols were added and mixed evenly.

[0076] (2) 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℃, screw speed 40 rpm);

[0077] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0078] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 9Mpa, blow-up ratio 2.6) to obtain a fully biodegradable mulch film. Example 4

[0079] A fully biodegradable mulch film, by weight percentage, comprises the following components: 60% PBAT, 35% bamboo micron powder masterbatch obtained in Preparation Example 4, 1% fiber tow protein, 0.4% rosemary extract, 1% tea polyphenols, 0.3% chain extender, 1.0% PETS, 0.4% anti-hydrolysis agent, 0.7% magnesium sulfate whiskers, and 0.2% antioxidant.

[0080] A method for preparing a fully biodegradable mulch film includes the following steps:

[0081] (1) 603 kg of PBAT and 35 kg of bamboo micro powder masterbatch obtained in Preparation Example 4 were premixed in a mixer at 75°C for 5 min, and then 1 kg of silk tow protein, 0.4 kg of rosemary extract and 1 kg of tea polyphenols were added and mixed evenly.

[0082] (2) 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);

[0083] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0084] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 11Mpa, blow-up ratio 2.8) to obtain a fully biodegradable mulch film. Example 5

[0085] A fully biodegradable mulch film, by weight percentage, comprises the following components: 63.5% PBAT, 29% bamboo micron powder masterbatch obtained in Preparation Example 5, 2.2% fibrous protein, 0.3% rosemary extract, 2% tea polyphenols, 0.6% chain extender, 1.2% PETS, 0.6% anti-hydrolysis agent, 0.4% magnesium sulfate whiskers, and 0.2% antioxidant.

[0086] A method for preparing a fully biodegradable mulch film includes the following steps:

[0087] (1) 63.5 kg PBAT and 30 kg of bamboo micro powder masterbatch obtained in Preparation Example 5 were premixed in a mixer at 80°C for 5 min, and then 2.2 kg of silk tow protein, 0.3 kg of rosemary extract and 2 kg of tea polyphenols were added and mixed evenly.

[0088] (2) 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 them in a twin-screw extruder (barrel temperature 125℃, screw speed 70 rpm);

[0089] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0090] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 12Mpa, blow-up ratio 2.9) to obtain a fully biodegradable mulch film. Example 6

[0091] A fully biodegradable mulch film, by weight percentage, comprises the following components: 61% PBAT, 31% bamboo micron powder masterbatch obtained in Preparation Example 5, 2.5% fibrous protein, 0.5% rosemary extract, 2% tea polyphenols, 0.4% chain extender, 1.0% PETS, 0.7% anti-hydrolysis agent, 0.6% magnesium sulfate whiskers, and 0.3% antioxidant.

[0092] A method for preparing a fully biodegradable mulch film includes the following steps:

[0093] (1) 61 kg of PBAT and 31 kg of bamboo micro powder masterbatch obtained in Preparation Example 5 were premixed in a mixer at 80°C for 5 min, and then 2.5 kg of silk tow protein, 0.5 kg of rosemary extract and 2 kg of tea polyphenols were added and mixed evenly.

[0094] (2) 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℃, screw speed 80 rpm);

[0095] (3) After underwater pelleting, dry at 60℃ until the moisture content is ≤0.5% to obtain mulch film granules;

[0096] (4) The mulch film particles are formed by a five-layer co-extrusion blown film unit (A / E layer temperature 130℃, B / C / D layer temperature 125℃, die head pressure 12Mpa, blow-up ratio 3.0) to obtain a fully biodegradable mulch film.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 is that bamboo micro powder is used instead of bamboo micro powder masterbatch.

[0099] Comparative Example 2

[0100] 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.

[0101] Comparative Example 3

[0102] The difference between this comparative example and Example 1 is that it does not contain filament protein, and the corresponding filament protein is replaced with PBAT.

[0103] Comparative Example 4

[0104] The difference between this comparative example and Example 1 is that it does not contain tea polyphenols, and the corresponding tea polyphenols are replaced with rosemary extract.

[0105] Comparative Example 5

[0106] The difference between this comparative example and Example 1 is that it does not contain rosemary extract, and the corresponding rosemary extract is replaced with tea polyphenols.

[0107] Comparative Example 6

[0108] The difference between this comparative example and Example 1 is that it does not contain tea polyphenols and rosemary extract; instead, the corresponding tea polyphenols and rosemary extract are replaced with PBAT.

[0109] Performance testing:

[0110] The mulch films obtained in Examples 1-6 and Comparative Examples 1-6 were subjected to mechanical property tests, water vapor transmission rate tests, and degradation induction period tests.

[0111] The test results are shown in Table 1.

[0112] Table 1. Test data of plastic film performance

[0113]

[0114] As can be seen from Table 1, the thickness of the mulch film prepared in Examples 1-6 of the present invention is only 0.006mm~0.007mm, and the tensile strength is greater than 25MPa, the elongation at break is greater than 810%, and the water vapor transmission rate is less than 380g / (m²·24h). By comparing Examples 1-6 with Comparative Examples 1-6, it can be seen that the mulch film of the present invention achieves a significant improvement in mechanical properties while achieving an ultra-thin thickness, and the water vapor transmission rate is lower than that of the comparative examples, indicating that the ultra-thin mulch film of the present invention has high mechanical properties, weather resistance, and biodegradability.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fully biodegradable mulch film, characterized in that, By weight percentage, it includes the following components: PBAT 60%~65%, bamboo micro powder masterbatch 25%~35%, silk tow protein 1%~3%, rosemary extract 0.2%~0.5%, tea polyphenols 1%~3%, chain extender 0.3%~0.7%, PETS 0.8%~1.2%, anti-hydrolysis agent 0.3%~0.7%, magnesium sulfate whiskers 0.3%~0.7%, antioxidant 0.1%~0.3%; The bamboo micro powder masterbatch comprises the following components by mass percentage: 32%~36% bamboo micro powder, 48%~52% carboxymethyl starch, 5%~7% sodium citrate, 3%~5% cellulose nanocrystals, 3%~5% sodium hydroxide, 1%~3% sodium trimetaphosphate, and 0~1% glycerol.

2. The fully biodegradable mulch film according to claim 1, characterized in that, The preparation method of the bamboo micro powder masterbatch includes the following steps: S1: Add bamboo micro powder, carboxymethyl starch, sodium citrate and 0.2%~0.8% glycerol by mass to the liquid medium and stir at 40℃~60℃ for 20min~40min to form a premixed colloid; S2: Add 5%~15% sodium trimetaphosphate solution to the premixed colloid, adjust the pH to 8~9, react at 60℃~80℃ for 100min~180min to form a three-dimensional network structure; S3: Add cellulose nanocrystals and sodium hydroxide solution with a mass fraction of 2%~8%, ultrasonically disperse for 10min~20min, and hydrothermally treat at 80℃~100℃ for 80min~100min; S4: Centrifuge and wash until neutral, vacuum dry at 60℃~80℃, and pulverize to obtain bamboo micro powder masterbatch.

3. The fully biodegradable mulch film according to claim 2, characterized in that, In step S1, the liquid medium is a mixture of deionized water and carboxymethyl cellulose homogenate with a mass fraction of 0.5% to 1.5% at a volume ratio of (90 to 99): (1 to 10), and the mass of the liquid medium is 2.5 to 3.5 times the total mass of bamboo powder, carboxymethyl starch, sodium citrate and glycerol.

4. The fully biodegradable mulch film according to claim 2, characterized in that, In step S3, the power of the ultrasound is 35~45KHz, and the hydrothermal treatment is microwave-assisted hydrothermal treatment.

5. A method for preparing a fully biodegradable mulch film as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Premix PBAT and bamboo micro powder masterbatch in a mixer at 70℃~80℃ for 3min~8min, then add silk tow protein, rosemary extract and tea polyphenols and mix evenly. (2) Add chain extender, PETS, anti-hydrolysis agent, magnesium sulfate whiskers and antioxidant and melt blend in a twin-screw extruder; (3) After underwater pelleting, dry at 50℃~70℃ until the moisture content is ≤0.5% to obtain mulch film granules; (4) The mulch film particles are formed by a five-layer co-extrusion blown film machine to obtain the fully biodegradable mulch film.

6. The method for preparing the fully biodegradable mulch film according to claim 5, characterized in that, The barrel temperature of the twin-screw extruder is 100℃~130℃, and the screw speed is 30~80 rpm.

7. The method for preparing the fully biodegradable mulch film according to claim 5, characterized in that, The five layers of the five-layer co-extrusion blown film unit are layer A, layer B, layer C, layer D and layer E. The temperature of layer A and layer E is 125℃~130℃, the temperature of layer B, layer C and layer D is 120℃~125℃, the die pressure of the five-layer co-extrusion blown film unit is 8~12Mpa, the film width is 1200mm~1250mm, the film thickness is 0.006mm~0.007mm, and the blow-up ratio is 2.5~3.0.

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