High-performance lightweight biodegradable mulching film and preparation method and application thereof

Abstract

This invention relates to the field of biodegradable polymer materials technology, and provides a high-performance lightweight biodegradable mulch film, its preparation method, and its applications. The high-performance lightweight biodegradable mulch film provided by this invention comprises PBAT, PPC, bamboo powder / PGA functional masterbatch, MDI, citrate ester, epoxidized soybean oil, glycerol, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent. Its preparation method includes: activating bamboo powder and then preparing bamboo powder / PGA masterbatch through a first blending granulation, followed by a second blending granulation to prepare granules, and finally obtaining the high-performance lightweight biodegradable mulch film through blown film forming. The mulch film provided by this invention has low density, high strength, controllable degradation rate, antibacterial properties, is environmentally friendly, has low water vapor permeability, and good moisture retention. Furthermore, the preparation process provided by this invention is stable and can achieve continuous production.

Description

Technical Field

[0001] This invention relates to the field of biodegradable polymer materials technology, and in particular to a high-performance lightweight biodegradable mulch film, its preparation method, and its application. Background Technology

[0002] Mulch film is an indispensable agricultural input in agricultural production, mainly used to cover the soil, playing a role in retaining moisture, keeping the soil warm, suppressing weed growth, and reducing the occurrence of pests and diseases. It is of great significance for increasing crop yield and improving the quality of agricultural products. Currently, the traditional mulch film widely used in agricultural production is mainly made of polyethylene (PE). This type of mulch film has the characteristics of low cost and simple processing, but because it is difficult to degrade, long-term residues in the soil will cause "white pollution", damage the soil structure, and affect crop growth, which has become an important factor restricting the sustainable development of agriculture. To solve this problem, biodegradable mulch film has emerged. It is mainly made of PBAT (polybutylene terephthalate), PLA (polylactic acid), PPC (polypropylene carbonate), etc. After use, it can be completely degraded into water and carbon dioxide by microorganisms in the natural environment, making it an ideal solution to replace traditional PE mulch film.

[0003] However, existing biodegradable mulch films still face the following intractable technical bottlenecks in practical applications: Existing biodegradable mulch films have a high density (1.15~1.25 g / cm³). 3 The high cost of core raw materials makes large-scale promotion difficult; while reducing the density of mulch film through lightweighting can easily lead to a decline in mechanical properties, failing to meet the needs of field use, and there is a technical bias in the industry that "foaming will inevitably reduce strength"; moreover, the degradation rate of current biodegradable mulch film is uncontrollable, and a single system of mulch film cannot match the growth cycle of different crops, which can easily lead to premature disintegration or long-term residue problems.

[0004] In summary, there is an urgent need to provide a low-density, high-strength, and controllable biodegradable mulch film. Summary of the Invention

[0005] In view of this, the present invention provides a high-performance lightweight biodegradable mulch film, its preparation method, and its application. The biodegradable mulch film provided by the present invention has low density, high strength, controllable degradation rate, antibacterial properties, and good moisture retention.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: A high-performance, lightweight, biodegradable mulch film comprises the following components in parts by weight: 50-65 parts of polybutylene terephthalate (PBAT), 20-35 parts of polypropylene carbonate (PPC), 5-10 parts of bamboo powder / polyglycolic acid (PGA) functional masterbatch, 0.3-0.8 parts of diphenylmethane diisocyanate (MDI), 0.5-2 parts of citrate, 0.5-1.5 parts of epoxidized soybean oil, 0.05-0.5 parts of glycerin, 0.05-0.3 parts of stearic acid, 0.02-0.2 parts of calcium stearate, 0.1-0.5 parts of aluminate coupling agent, 0.1-0.5 parts of antioxidant, and 0.05-0.3 parts of opening agent; The bamboo powder / PGA functional masterbatch comprises the following components in parts by weight: 70-80 parts of ultrafine bamboo powder, 10-20 parts of PGA, 1-3 parts of stearic acid, 2-5 parts of aluminate coupling agent, 2-6 parts of epoxidized soybean oil, and 0.5-2 parts of calcium stearate.

[0007] Preferably, the D of the bamboo powder ultrafine powder 90 Particle size ≤10μm, initial moisture content <5wt%.

[0008] Preferably, the antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

[0009] Preferably, the opening agent includes at least one of erucamide and oleamide.

[0010] Preferably, the high-performance lightweight biodegradable mulch film has a flat ellipsoidal cell structure with a cell size of 20~50μm.

[0011] This invention also provides a method for preparing the high-performance lightweight biodegradable mulch film described above, comprising the following steps: According to the component ratio of bamboo powder / polyglycolic acid functional masterbatch, bamboo powder ultrafine powder is dried and mixed with aluminate coupling agent for activation to obtain activated bamboo powder; the activated bamboo powder, polyglycolic acid, stearic acid, epoxidized soybean oil and calcium stearate are subjected to a first blending and granulation to obtain the bamboo powder / polyglycolic acid functional masterbatch. According to the component ratio of high-performance lightweight biodegradable mulch film, polybutylene terephthalate, polypropylene carbonate, bamboo powder / polyglycolic acid functional masterbatch, diphenylmethane diisocyanate, citrate, epoxidized soybean oil, glycerin, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent are subjected to a second blending and granulation to obtain granules; the moisture content of the granules is 800~1500ppm; the temperature of the second blending and granulation is ≤160℃; The granules are blown into a film to obtain the high-performance lightweight biodegradable mulch film; the stretching method of the blown film forming is biaxial stretching, the blow-up ratio is 4.0~6.0, the traction ratio is 4.5~6.5, and the ratio of the blow-up ratio to the traction ratio is 0.9~1.1.

[0012] Preferably, the second blending granulation is carried out using a twin-screw extruder, which is equipped with a main feed port, a side feed port, and a liquid injection port; the twin-screw extruder is equipped with 5 loss-in-weight scales, which are numbered 1# to 5#. The stearic acid, calcium stearate, aluminate coupling agent, antioxidant, opening agent and part of polybutylene terephthalate adipate are fed into the main feed port through the No. 1 loss-in-weight scale; The bamboo powder / polyglycolic acid functional masterbatch is fed into the main feed port through a No. 2 loss-in-weight weigher. The polypropylene carbonate is fed in through the side feed port via a loss-in-weight scale (No. 3). The diphenylmethane diisocyanate and the remaining polybutylene terephthalate adipate were premixed and fed into the main feed port through a loss-in-weight scale (No. 4). The citrate, epoxidized soybean oil, and glycerin were injected from the liquid inlet using a No. 5 loss-in-weight balance.

[0013] Preferably, the twin-screw extruder includes ten barrel heating zones from the feed end to the discharge end, numbered sequentially from zone 1 to zone 10. The heating temperature of zone 1 is 120~130℃, the heating temperature of zone 2 is 130~145℃, the heating temperature of zone 3 is 145~150℃, the heating temperature of zone 4 is 150~155℃, the heating temperature of zone 5 is 150~155℃, the heating temperature of zone 6 is 155~160℃, the heating temperature of zone 7 is 155~160℃, the heating temperature of zone 8 is 150~155℃, the heating temperature of zone 9 is 150~155℃, and the heating temperature of zone 10 is 145~150℃. The die head temperature of the twin-screw extruder is 150~155℃; The screw speed of the twin-screw extruder is 350~500 rpm.

[0014] Preferably, the blown film forming is performed using a blown film machine; the blown film machine sequentially includes a feeding section, a compression section, a metering section, a die head body, and a die opening; the temperature of the feeding section is 130~140℃, the temperature of the compression section is 145~155℃, the temperature of the metering section is 150~160℃, the temperature of the die head body is 152~154℃, and the temperature of the die opening is 151~153℃; The nozzle gap for blown film forming is 1.2~1.5 mm, and the cooling and shaping height is 150~300 mm.

[0015] The present invention also provides the application of the high-performance lightweight biodegradable mulch film described in the above-described scheme or the high-performance lightweight biodegradable mulch film prepared by the preparation method described in the above-described scheme in the agricultural field.

[0016] This invention provides a high-performance, lightweight, biodegradable mulch film, comprising the following components in parts by weight: The bamboo powder / PGA functional masterbatch comprises the following components by weight: 50-65 parts PBAT, 20-35 parts PPC, 5-10 parts bamboo powder / PGA functional masterbatch, 0.3-0.8 parts MDI, 0.5-2 parts citrate, 0.5-1.5 parts epoxidized soybean oil, 0.05-0.5 parts glycerol, 0.05-0.3 parts stearic acid, 0.02-0.2 parts calcium stearate, 0.1-0.5 parts aluminate coupling agent, 0.1-0.5 parts antioxidant, and 0.05-0.3 parts opening agent; the bamboo powder / PGA functional masterbatch comprises the following components by weight: 70-80 parts ultrafine bamboo powder, 10-20 parts PGA, 1-3 parts stearic acid, 2-5 parts aluminate coupling agent, 2-6 parts epoxidized soybean oil, and 0.5-2 parts calcium stearate. Compared with the prior art, the present invention has the following significant beneficial effects: (1) Significant weight reduction effect: In this invention, MDI is added to the biodegradable mulch film. MDI reacts with the water in the system in situ to generate CO2 microbubbles, thereby reducing the density of the mulch film. The results of the examples show that the density of the mulch film of this invention is stably controlled at 0.60~0.65 g / cm³. 3 Compared to conventional biodegradable mulch film (1.15~1.25g / cm³), 3 The amount of material used per unit area is reduced by 40% to 50%, and the amount of material used per mu is reduced by more than 35%, from 7 to 10 kg to 3 to 5 kg.

[0017] (2) Excellent mechanical properties: The present invention adds bamboo powder / PGA masterbatch to the biodegradable mulch film. The rigidity of bamboo powder and the chain extension and capacity enhancement of MDI work synergistically to improve the mechanical properties of the mulch film. The results of the examples show that the longitudinal and transverse tensile strength of the mulch film of the present invention reaches more than 30 MPa, the puncture strength is ≥3 N, the elongation at break is ≥200%, and the right angle tear strength is ≥80 kN / m, which is significantly better than the existing lightweight biodegradable mulch film (tensile strength ≤25 MPa, puncture strength ≤2.5 N), successfully breaking the technical prejudice that "foaming will reduce strength".

[0018] (3) Controllable degradation rate: By adjusting the PGA content in the masterbatch, the degradation rate of the mulch film can be controlled. The mass retention rate is 78-92% after 90 days and 10-32% after 180 days, which can match the growth needs of short-cycle vegetables (such as lettuce) and long-cycle crops (such as corn).

[0019] (4) Functional Synergistic Optimization: The natural bamboo kun in bamboo powder has antibacterial properties, which can inhibit Gram-positive bacteria in the soil and reduce the incidence of crop root rot; PPC is a CO2-based polymer, and each ton of mulch film produced can fix 100-300 kg of carbon, which is environmentally friendly; the water vapor transmission rate is controlled at 400 g / (m 2Within 24 hours, its moisture retention effect is better than that of conventional PBAT mulch film.

[0020] (5) Significant cost advantage: This invention uses bamboo powder and PPC to partially replace the expensive PBAT, reducing raw material costs by 15-25%. Combined with the reduction in materials used due to lightweighting, the overall cost is more than 30% lower than that of conventional biodegradable mulch film.

[0021] This invention also provides a method for preparing the high-performance lightweight biodegradable mulch film described above. The invention first activates bamboo powder, then prepares bamboo powder / PGA masterbatch through a first blending granulation process. Next, the bamboo powder / PGA masterbatch is combined with other components through a second blending granulation process to prepare granules. Finally, the high-performance lightweight biodegradable mulch film is obtained through blown film forming, wherein the stretching method in the blown film forming is biaxial stretching. This invention uses biaxial stretching to form a flattened ellipsoidal cell structure inside the mulch film, further reducing the mulch film density. Simultaneously, biaxial stretching causes the molecular chains in the cell walls to be highly oriented, improving the mulch film strength, thus achieving both low density and high strength.

[0022] Furthermore, components such as PPC and PGA have poor thermal stability and are prone to thermal degradation and uneven dispersion when blended with natural plant fibers such as bamboo powder. This leads to membrane bubble vibration, crystal points and holes in the film, resulting in a narrow processing window and making it difficult to achieve continuous industrial production. However, this invention solves the problem of uneven dispersion by pre-forming bamboo powder into masterbatch, strictly controls the moisture content of the granules to ensure uniform foaming, and strictly controls the temperature of the second blending granulation to ≤160℃ (to lower the melting point), which can avoid thermal degradation of PPC. At the same time, PPC is fed into the side feed port of a twin-screw extruder to further prevent its thermal degradation. In summary, the preparation method provided by this invention has good stability and a wide process window, making it suitable for continuous industrial production of 1000 tons per year.

[0023] In summary, this invention provides a high-performance, lightweight biodegradable mulch film through a synergistic technological approach of "plant fiber miniaturization, alloying, compositeization, and lightweighting." It is particularly suitable for ground cover of crops such as vegetables, rice, cotton, and corn in agricultural production, achieving the technical goals of "reducing density, lowering melting point, reducing cost, and improving performance." It solves the problem that existing products cannot simultaneously achieve lightweighting, high strength, stable processing, and controllable degradation, and has broad application prospects. Attached Figure Description

[0024] Figure 1 This is a process flow diagram for preparing high-performance, lightweight, biodegradable mulch film according to the present invention. Detailed Implementation

[0025] This invention provides a high-performance, lightweight, biodegradable mulch film, comprising the following components in parts by weight: PBAT 50~65 parts, PPC 20~35 parts, bamboo powder / PGA functional masterbatch 5~10 parts, MDI 0.3~0.8 parts, citrate 0.5~2 parts, epoxidized soybean oil 0.5~1.5 parts, glycerin 0.05~0.5 parts, stearic acid 0.05~0.3 parts, calcium stearate 0.02~0.2 parts, aluminate coupling agent 0.1~0.5 parts, antioxidant 0.1~0.5 parts, opening agent 0.05~0.3 parts; The bamboo powder / PGA functional masterbatch comprises the following components in parts by weight: 70-80 parts of ultrafine bamboo powder, 10-20 parts of PGA, 1-3 parts of stearic acid, 2-5 parts of aluminate coupling agent, 2-6 parts of epoxidized soybean oil, and 0.5-2 parts of calcium stearate.

[0026] Unless otherwise specified, all raw materials / components used in this invention are commercially available.

[0027] By weight, the high-performance lightweight biodegradable mulch film provided by the present invention comprises 50-65 parts of PBAT, preferably 55-58 parts, specifically 55, 56 or 58 parts; the PBAT is preferably blown film grade, the melt index is preferably 3-5 g / min, and the moisture content is preferably <0.3%; in the present invention, the PBAT is used to provide basic toughness and film-forming properties.

[0028] Based on the weight parts of PBAT, the high-performance lightweight biodegradable mulch film provided by the present invention comprises 20-35 parts of PPC, preferably 25-30 parts, specifically 25, 28, or 30 parts; the molecular weight of the PPC is preferably ≥100,000, and the moisture content is preferably <0.5%. In the present invention, the PPC is used to reduce density and melting point, improve processability, and reduce costs.

[0029] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 5-10 parts of bamboo powder / PGA functional masterbatch, preferably 6-8 parts, specifically 6, 6.67, or 8 parts. In this invention, the bamboo powder / PGA functional masterbatch can improve the rigidity of the mulch film, regulate the degradation rate, and improve dispersibility.

[0030] In this invention, the bamboo powder / PGA functional masterbatch comprises the following components in parts by weight: 70-80 parts of ultrafine bamboo powder, specifically 72, 75, or 78 parts; 10-20 parts of PGA, specifically 15, 15.3, or 16 parts; 1-3 parts of stearic acid, specifically 1.5 or 2 parts; 2-5 parts of aluminate coupling agent, specifically 3 or 4 parts; 2-6 parts of epoxidized soybean oil, specifically 4.5 or 5 parts; and 0.5-2 parts of calcium stearate, specifically 0.75 or 1 part. The aluminate coupling agent is used to activate the surface of the bamboo powder and improve interfacial compatibility; the ultrafine bamboo powder has a D... 90The particle size is preferably ≤10μm, more preferably 8~10μm, and the initial moisture content is preferably <5wt%. This invention controls the particle size of bamboo powder ultrafine powder within the above range, which can take into account both the lightweight effect and mechanical properties of the mulch film.

[0031] In this invention, the type of aluminate coupling agent used to prepare the bamboo powder / PGA functional masterbatch is the same as the type of aluminate coupling agent used to prepare the high-performance lightweight biodegradable mulch film, which will be described in detail later.

[0032] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.3 to 0.8 parts of MDI, preferably 0.4 to 0.6 parts, specifically 0.4, 0.5, or 0.6 parts; the purity of the MDI is ≥99%, and the mass fraction of -NCO is ≥33%. In this invention, the MDI is used for chain extension and compatibilization, in-situ foaming, and to improve interfacial bonding.

[0033] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.5 to 2 parts of citrate ester, preferably 1 to 1.5 parts, specifically 1, 1.1, or 1.5 parts; the acid value of the citrate ester is ≤0.2. In this invention, the citrate ester acts as a plasticizer, which can reduce the processing temperature and improve the flexibility of the mulch film.

[0034] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by the present invention comprises 0.5 to 1.5 parts of epoxidized soybean oil, preferably 0.6 to 1 part, specifically 0.6, 0.8, or 1 part; the epoxy value of the epoxidized soybean oil is preferably ≥6.0%; in the present invention, the epoxidized soybean oil can assist in plasticization, improve thermal stability and compatibility of each component.

[0035] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.05 to 0.5 parts of glycerol, preferably 0.08 to 0.15 parts, specifically 0.08, 0.1, or 0.15 parts. In this invention, the glycerol can regulate the foaming rate and improve the smoothness of the film surface.

[0036] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.05 to 0.3 parts of stearic acid, preferably 0.08 to 0.15 parts, specifically 0.08, 0.1, or 0.15 parts. In this invention, the stearic acid acts as an internal lubricant, promoting component dispersion.

[0037] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.02 to 0.2 parts of calcium stearate, specifically 0.03 to 0.08 parts, specifically 0.03, 0.05, or 0.08 parts. In this invention, the calcium stearate serves as an external lubricant, capable of reducing friction between the melt and the equipment.

[0038] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.1 to 0.5 parts of aluminate coupling agent, preferably 0.15 to 0.25 parts, specifically 0.15, 0.2, or 0.25 parts; the aluminate coupling agent may specifically be DL-411. In this invention, the aluminate coupling agent is used to improve the interfacial compatibility and bonding force between bamboo powder masterbatch PBAT and PPC matrix, prevent interfacial detachment, promote uniform dispersion of multi-component resin and powder, optimize low-temperature extrusion rheological properties, and stabilize the cell structure.

[0039] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by the present invention includes 0.1 to 0.5 parts of antioxidant, preferably 0.15 to 0.25 parts, specifically 0.15, 0.2, or 0.25 parts; the antioxidant preferably includes at least one of antioxidant 1010 and antioxidant 168, preferably antioxidant 1010 (pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]); in the present invention, the antioxidant is used to inhibit oxidative degradation during processing heat.

[0040] Based on the weight percentage of PBAT, the high-performance lightweight biodegradable mulch film provided by this invention comprises 0.05 to 0.3 parts of an opening agent, preferably 0.08 to 0.15 parts, specifically 0.08, 0.1, or 0.15 parts; the opening agent preferably includes at least one of erucamide and oleamide, preferably erucamide; the amide content of the erucamide is preferably ≥98 wt%. In this invention, the opening agent is used to prevent film adhesion and improve opening performance.

[0041] In this invention, the high-performance lightweight biodegradable mulch film has a flat ellipsoidal cell structure with a cell size of 20~50μm. In an embodiment of this invention, the major axis of the cell structure is 45μm and the minor axis is 18μm.

[0042] In this invention, the bamboo powder ultrafine powder is uniformly dispersed in the mulch film substrate without obvious agglomeration.

[0043] In this invention, the high-performance lightweight biodegradable mulch film has a thickness of 0.01~0.018 mm and a density of 0.60~0.65 g / cm³. 3Both longitudinal and transverse tensile strengths are above 30 MPa, puncture strength is ≥3 N, elongation at break is ≥200%, right-angle tear strength is ≥80 kN / m, and water vapor transmission rate is ≤400 g / (m²). 2 •24h).

[0044] The mulch film provided by this invention has the characteristics of being lightweight, high-strength, and controllable degradable, and has a bamboo kun content of ≥0.05wt%, which has antibacterial function and an inhibition rate of ≥80% for Gram-positive bacteria in the soil.

[0045] The present invention also provides a method for preparing the high-performance lightweight biodegradable mulch film described above, comprising the following steps: According to the component ratio of bamboo powder / PGA functional masterbatch, bamboo powder ultrafine powder is dried and mixed with aluminate coupling agent for activation to obtain activated bamboo powder; the activated bamboo powder, PGA, stearic acid, epoxidized soybean oil and calcium stearate are subjected to a first blending and granulation to obtain the bamboo powder / PGA functional masterbatch. According to the component ratio of high-performance lightweight biodegradable mulch film, PBAT, PPC, bamboo powder / PGA functional masterbatch, MDI, citrate, epoxidized soybean oil, glycerol, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent are subjected to a second blending and granulation to obtain granules; the moisture content of the granules is 800~1500ppm; the temperature of the second blending and granulation is ≤160℃; The granules are blown into a film to obtain the high-performance lightweight biodegradable mulch film; the stretching method of the blown film forming is biaxial stretching, the blow-up ratio is 4.0~6.0, the traction ratio is 4.5~6.5, and the ratio of the blow-up ratio to the traction ratio is 0.9~1.1.

[0046] Figure 1 The following is a process flow diagram for preparing high-performance, lightweight, biodegradable mulch film according to the present invention, in conjunction with... Figure 1 Please provide a detailed explanation.

[0047] This invention relates to a bamboo powder / PGA functional masterbatch, which involves drying ultrafine bamboo powder and then activating it by mixing it with an aluminate coupling agent to obtain activated bamboo powder. The activated bamboo powder, PGA, stearic acid, epoxidized soybean oil, and calcium stearate are then subjected to a first blending and granulation process to obtain the bamboo powder / PGA functional masterbatch. In this invention, the drying temperature of the ultrafine bamboo powder is preferably 100-110℃, specifically 105℃, and the drying time is preferably 2-3 hours, specifically 2.5 hours. The moisture content of the dried ultrafine bamboo powder is <0.5%, and the drying is preferably carried out in a hot air circulating dryer.

[0048] In this invention, the activation temperature is preferably 80-95℃, more preferably 85-90℃, the activation time is preferably 5-15 minutes, specifically 9 minutes, and the activation speed is preferably 800-1000 rpm, specifically 900 rpm; the activation is preferably carried out in a high-speed mixer. After activation, the obtained activated bamboo powder is preferably cooled to below 40℃; the activated bamboo powder should be used within 4 hours to avoid moisture absorption.

[0049] In this invention, before the first blending granulation, it is preferable to premix activated bamboo powder, PGA, stearic acid, epoxidized soybean oil and calcium stearate, and then perform the first blending granulation on the resulting premix. The premixing speed is preferably 60 rpm and the time is preferably 3 to 5 minutes. The premixing is preferably carried out in a low-speed mixer.

[0050] In this invention, the first blending granulation is preferably carried out in a twin-screw extruder, and the length-to-diameter ratio of the twin-screw extruder is preferably 48:1. The twin-screw extruder used for the first blending granulation includes six barrel heating zones from the feed end to the discharge end, which are sequentially labeled as zones 1 to 6. The heating temperature of zone 1 is 145~150℃, preferably 148℃; the heating temperature of zone 2 is 155~160℃, preferably 158℃; the heating temperature of zone 3 is 160~165℃, preferably 163℃; the heating temperature of zone 4 is 165~170℃, preferably 168℃; the heating temperature of zone 5 is 165~170℃, preferably 168℃; and the heating temperature of zone 6 is 160~165℃, preferably 163℃. The die head temperature of the twin-screw extruder is preferably 160~165℃, preferably 163℃.

[0051] In this invention, the screw speed of the first blending granulation is preferably 300~500 rpm, more preferably 400 rpm, and the vacuum exhaust pressure is preferably -0.06~-0.09 MPa, specifically -0.08 MPa.

[0052] In this invention, the material extruded from a twin-screw extruder is subjected to underwater pelletizing to obtain the bamboo powder / PGA functional masterbatch.

[0053] In this invention, the moisture content of the bamboo powder / PGA functional masterbatch is preferably <500ppm, the particle size is preferably 3~4mm, and the cross-section is free of white spots and pores.

[0054] After obtaining the bamboo powder / PGA functional masterbatch, the present invention performs a second blending and granulation of PBAT, PPC, bamboo powder / PGA functional masterbatch, MDI, citrate, epoxidized soybean oil, glycerol, stearic acid, calcium stearate, aluminate coupling agent, antioxidant and opening agent according to the component ratio of high performance lightweight biodegradable mulch film to obtain granules. In this invention, the second blending granulation is preferably carried out using a twin-screw extruder. The twin-screw extruder used for the second blending granulation is equipped with a main feed port, a side feed port, and a liquid injection port. The twin-screw extruder used for the second blending granulation is equipped with 5 loss-in-weight feeders, which are numbered 1# to 5#. The stearic acid, calcium stearate, aluminate coupling agent, antioxidant, opening agent, and part of PBAT are fed into the main feed port through the 1# loss-in-weight feeder. In a specific embodiment of this invention, the PBAT, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent are preferably premixed for 5 minutes, and then the resulting premix is ​​fed into the 1# loss-in-weight feeder. The bamboo powder / PGA functional masterbatch is fed into the main feed port through the 2# loss-in-weight feeder. PC is fed in through the side feed port via a loss-in-weight balance (#3); the side feed port is located at the rear section of the twin-screw extruder. Feeding PPC from the rear section avoids thermal degradation. MDI and the remaining PBAT are fed in through the main feed port via a loss-in-weight balance (#4), with a mass ratio of 1:2. In a specific embodiment of the invention, it is preferable to premix the MDI and the remaining PBAT in a fume hood for 2 minutes before feeding, mixing and using immediately. Citrate, epoxidized soybean oil, and glycerol are injected through the liquid injection port via a loss-in-weight balance (#5). In a specific embodiment of the invention, it is preferable to premix the citrate, epoxidized soybean oil, and glycerol for 10 minutes before feeding the resulting premix via the loss-in-weight balance (#5).

[0055] In this invention, the temperature of the second blending granulation is ≤160℃, specifically 120~160℃. Specifically, the second blending granulation twin-screw extruder includes ten barrel heating zones from the feed end to the discharge end, numbered 1 to 10. The heating temperature of zone 1 is 120~130℃, preferably 125℃; the heating temperature of zone 2 is 130~145℃, preferably 140℃; the heating temperature of zone 3 is 145~150℃, preferably 148℃; the heating temperature of zone 4 is 150~155℃, preferably 153℃; and the heating temperature of zone 5 is 150~155℃. The preferred temperature for zone 6 is 153℃, the preferred temperature for zone 7 is 155~160℃, the preferred temperature for zone 8 is 150~155℃, the preferred temperature for zone 9 is 150~155℃, the preferred temperature for zone 10 is 145~150℃, the preferred temperature for zone 10 is 148℃, and the preferred temperature for zone 10 is 150~155℃, the preferred temperature for zone 10 is 150~155℃; the preferred temperature for zone 10 is 150℃.

[0056] In this invention, the screw speed of the twin-screw extruder used for the second blending granulation is preferably 350~500 rpm, specifically 450 rpm, and the length-to-diameter ratio is preferably 64:1.

[0057] In this invention, the moisture content of the granules is 800-1500 ppm, preferably 1000-1200 ppm. In a specific embodiment of this invention, during the second blending granulation, the vacuum valve of the twin-screw extruder is closed and locked. When the granule moisture content is <800 ppm, water is sprayed at a rate of 50-100 mL / min through the side feed port for humidification. When the moisture content is >1500 ppm, the amount of liquid additive is reduced and the moisture content of the raw material is checked. This invention controls the moisture content of the granules within the above range, ensuring that MDI reacts with moisture in situ to generate uniform microbubbles.

[0058] After obtaining the granules, the present invention performs blown film forming to obtain the high-performance lightweight biodegradable mulch film. In the present invention, the blown film forming is performed using a blown film machine; the blown film machine sequentially includes a feeding section, a compression section, a metering section, a die head body, and a die opening. The temperature of the feeding section is preferably 130~140℃, specifically 133℃; the temperature of the compression section is preferably 145~155℃, specifically 148℃; the temperature of the metering section is preferably 150~160℃, specifically 153℃; the temperature of the die head body is preferably 152~154℃, specifically 153℃; and the temperature of the die opening is preferably 151~153℃, specifically 152℃. The present invention controls the temperature of the die head body at 152~154℃, which can balance film formation and cell stability.

[0059] In this invention, the length-to-diameter ratio of the screw of the blown film machine is preferably ≥36:1, and can specifically be 38:1.

[0060] In this invention, the blown film forming includes sequentially performing melting, extrusion, blowing, traction, cooling, and winding; the stretching method of the blown film forming is bidirectional stretching; the blow-up ratio of the blown film forming is 4.0~6.0, preferably 5.5~5.8, specifically 5.0, 5.7, or 6.0; the traction ratio is 4.5~6.5, preferably 5.5~6.0, specifically 5.2, 6.0, or 6.2; the ratio of the blow-up ratio to the traction ratio is 0.9~1.1, specifically 0.95, 0.96, or 0.97; the film nozzle gap of the blown film forming is preferably 1.2~1.5 mm, specifically 1.2 or 1.5 mm; the cooling and shaping height is 150~300 mm, specifically 180, 200, or 220 mm.

[0061] In a specific embodiment of the present invention, during the blown film forming process, the air ring is fully open for strong cooling; the blown film machine is equipped with a bubble stabilizing cage, which is used to stabilize the bubble during blown film forming to ensure the stability of the film bubble, especially when the blow-up ratio is ≥5.5, to avoid the film bubble shaking; online thickness measurement is performed during blown film forming, and the thickness deviation is controlled within ±8%.

[0062] This invention also provides the application of the high-performance lightweight biodegradable mulch film described in the above-described scheme or the high-performance lightweight biodegradable mulch film prepared by the preparation method described in the above-described scheme in the agricultural field. In this invention, the high-performance lightweight biodegradable mulch film can be used for ground cover of crops, with a preferred application rate of 3-5 kg ​​per acre; the crops can specifically be vegetables, rice, cotton, corn, or wheat.

[0063] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0064] Example 1 1. Raw material formula The raw material formulation of the high-performance lightweight biodegradable mulch film in this embodiment is shown in Table 1.

[0065] Table 1 Raw Material Formula and Remarks

[0066] The bamboo powder / PGA functional masterbatch formulation is as follows (approximately 100 kg): 75 kg of ultrafine bamboo powder (D... 90 =8.5μm), PGA 15.3 kg, stearic acid 1.5 kg, aluminate coupling agent 3 kg, epoxidized soybean oil 4.5 kg, calcium stearate 0.75 kg.

[0067] 2. Preparation method Step 1: Bamboo powder activation Bamboo powder ultrafine powder was dried at 105℃ for 2.5 hours until the moisture content was 0.4wt%. Then, aluminate coupling agent was added according to the ratio of bamboo powder / PGA functional masterbatch, and the mixture was mixed at 90℃ and 900 rpm for 9 minutes to obtain activated bamboo powder.

[0068] Step 2: Masterbatch Granulation According to the ratio in the bamboo powder / PGA functional masterbatch, activated bamboo powder and other raw materials are added to a twin-screw extruder (length-to-diameter ratio of 48:1) for processing. The temperature of the twin-screw extruder from zone one to the die head is 148→158→163→168→168→163→163℃, the screw speed is 400 rpm, the vacuum degree is -0.08 MPa, and the masterbatch moisture content is 420 ppm.

[0069] Step 3: Granulation of main ingredients According to the component ratio of high-performance lightweight biodegradable mulch film, PBAT, PPC, bamboo powder / PGA functional masterbatch, MDI, citrate, epoxidized soybean oil, glycerin, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent are added to a twin-screw extruder for blending and granulation to obtain granules. During blending and granulation, five loss-in-weight scales are used for feeding according to set parameters, including: a portion of PBAT, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent. The oral premix is ​​fed into the feeder through the self-feeding port of the loss-in-weight balance (1#) after 5 minutes of premixing; the bamboo powder / PGA functional masterbatch is fed into the feeder through the self-feeding port of the loss-in-weight balance (2#); PPC is fed into the feeder through the side feeder of the loss-in-weight balance (3#); the premix of MDI and the remaining PBAT (mass ratio 1:2, premixed in the fume hood for 2 minutes, to be used immediately after mixing) is fed into the feeder through the self-feeding port of the loss-in-weight balance (4#); the citrate, epoxidized soybean oil, and glycerin are injected into the feeder through the liquid injection port of the loss-in-weight balance (5#) after 10 minutes of premixing.

[0070] The twin-screw extruder has an aspect ratio of 64:1. The temperature from zone one to the die head is as follows: 125→140→148→153→153→158→158→153→153→148→150℃. The screw speed is 450 rpm, the vacuum is closed, and the moisture content of the resulting granules is 1120 ppm.

[0071] Step 4: Film blowing and forming The granules obtained from the granulation of the main material are directly (without drying) fed into the blown film unit. After melting, extrusion, blowing, traction, cooling, and winding, biodegradable mulch film is obtained. The blown film unit has a length-to-diameter ratio of 38:1. The temperatures of the feeding section, compression section, metering section, die head body, and die orifice are 133→148→153→153→152℃ respectively. The film orifice gap is 1.2 mm, the blowing ratio is 5.7, the traction ratio is 6.0 (the ratio of blowing ratio to traction ratio is 0.95), the cooling and shaping height is 220 mm, the air ring is fully open, and a bubble stabilizing cage is provided.

[0072] 3. Product performance test results The performance of the obtained biodegradable mulch film was tested, and the testing standards and results are shown in Table 2.

[0073] Table 2 Testing Standards and Test Results

[0074] Example 2 The process is basically the same as in Example 1, except that the blown film process parameters are adjusted as follows: film opening gap: 1.5 mm; blow-up ratio: 5.0; traction ratio: 5.2 (the ratio of blow-up ratio to traction ratio is 0.96); cooling and shaping height: 200 mm.

[0075] Product performance: Density 0.63 g / cm³ 3 Longitudinal tensile strength: 31.2 MPa; transverse tensile strength: 30.5 MPa; puncture strength: 3.2 N; water vapor transmission rate: 410 g / (m²). 2 • 24h); Compared with Example 1, the yield increased by 25%, and the performance met the usage requirements.

[0076] Example 3 The process is basically the same as in Example 1, except that the blown film process parameters are adjusted: blow ratio: 6.0; traction ratio: 6.2 (the ratio of blow ratio to traction ratio is 0.97); cooling and shaping height: 180 mm; and a reinforced bubble cage is used.

[0077] Product performance: Density 0.59 g / cm³ 3 Longitudinal tensile strength: 30.8 MPa; transverse tensile strength: 31.2 MPa; puncture strength: 3.1 N; water vapor transmission rate: 395 g / (m²). 2 •24h); The lightweight effect is more significant, while the strength still meets the standard.

[0078] Example 4 The raw material formula was adjusted to: PBAT 55 kg, PPC 25 kg, bamboo powder / PGA masterbatch 6.0 kg, MDI 0.4 kg, citrate 1.0 kg, epoxidized soybean oil 0.6 kg, glycerin 0.08 kg, stearic acid 0.08 kg, calcium stearate 0.03 kg, aluminate coupling agent 0.15 kg, antioxidant 1010 0.15 kg, erucamide 0.08 kg; The process parameters for granulation and blown film forming of the main material are as follows: granule moisture content 1050 ppm, die temperature 152℃, blow-up ratio 5.5, and draw ratio 5.8 (the ratio of blow-up ratio to draw ratio is 0.95). All other conditions are the same as in Example 1.

[0079] Product performance: Density 0.64 g / cm³ 3 The longitudinal tensile strength is 30.2 MPa, the transverse tensile strength is 29.8 MPa, the puncture strength is 3.1 N, and the elongation at break is 220%; the performance meets the requirements, and the feasibility of the formulation has been verified.

[0080] Example 5 The raw material formula was adjusted to: PBAT 58 kg, PPC 30 kg, bamboo powder / PGA masterbatch 8.0 kg, MDI 0.6 kg, citrate 1.5 kg, epoxidized soybean oil 1.0 kg, glycerin 0.15 kg, stearic acid 0.15 kg, calcium stearate 0.08 kg, aluminate coupling agent 0.25 kg, antioxidant 1010 0.25 kg, erucamide 0.15 kg; Process parameters for main material granulation and blown film forming: granule moisture 1180 ppm, die temperature 154℃, blow-up ratio 6.0, traction ratio 6.2 (the ratio of blow-up ratio to traction ratio is 0.97).

[0081] Product performance: Density 0.61 g / cm³ 3 The longitudinal tensile strength is 31.5 MPa, the transverse tensile strength is 30.8 MPa, the puncture strength is 3.3 N, and the elongation at break is 235%. The performance is stable and there is no strength reduction caused by excessive foaming.

[0082] Example 6 Similar to Example 1, except that the PGA content in the bamboo powder / PGA masterbatch was adjusted, thereby changing the PGA content in the mulch film, and the degradation rate of the finished mulch film was investigated. The test results of PGA content and degradation rate in the mulch film are shown in Table 3.

[0083] Table 3. Test results of PGA content and degradation rate in plastic film.

[0084] The test method for degradation rate was as follows: soil burial test was conducted according to GB / T 35795-2017, with soil pH 6.8, humidity 60%, temperature 25℃, and burial depth 10~15 cm.

[0085] Example 7 The inhibitory effect of plastic film on Bacillus subtilis in soil was tested using the inhibition zone method. Mulch film sample: Example 1; Bacterial strain: Bacillus subtilis; Culture conditions: 37℃, 24 hours; Test results: The diameter of the inhibition zone was 15.2 mm, and the inhibition rate was 82%.

[0086] Conclusion: Natural bamboo kun (content ≥0.05%) in bamboo powder endows the mulch film with good antibacterial function and can reduce the incidence of crop root rot.

[0087] Comparative Example 1 The process is basically the same as in Example 1, except that in step three, vacuum degassing is turned on, the moisture content of the granules is controlled at <300ppm, and foaming is not controlled.

[0088] Product performance: Density 1.18 g / cm³ 3 The longitudinal tensile strength is 21.5 MPa, the transverse tensile strength is 18.3 MPa, and the puncture strength is 2.1 N. It has no in-situ foaming, high density and low strength, and cannot achieve a combination of lightweight and high strength.

[0089] Comparative Example 2 It is basically the same as Example 1, except that MDI is not added.

[0090] Product performance: Density 1.12 g / cm³ 3 The longitudinal tensile strength is 16.8 MPa, the transverse tensile strength is 14.2 MPa, and the puncture strength is 1.8 N. It lacks chain extension and foaming effects, has poor interfacial bonding, and its mechanical properties are significantly reduced.

[0091] Comparative Example 3 It is basically the same as Example 1, except that: the inflation ratio is 3.5, the traction ratio is 3.5 (ratio 1.0), and there is no stable bubble cage.

[0092] Product performance: Density 0.85 g / cm³ 3 The longitudinal tensile strength is 24.5 MPa, the transverse tensile strength is 15.6 MPa, and the puncture strength is 2.4 N; the biaxial tensile strength is insufficient, the strength is low and the longitudinal and transverse strengths are unbalanced.

[0093] Comparative Example 4 The results are basically the same as in Example 1, except that no bamboo powder / PGA masterbatch is added and the PBAT is increased to 62.67 kg.

[0094] Product performance: Density 0.64 g / cm³ 3 The longitudinal tensile strength is 25.2 MPa, the transverse tensile strength is 24.8 MPa, and the puncture strength is 2.6 N. Due to the lack of rigidity enhancement from bamboo powder and the regulation effect of PGA, the strength does not reach 30 MPa, and the degradation rate is uncontrollable.

[0095] Comparative Example 5 The process is basically the same as in Example 1, except that: in step one, no aluminate coupling agent is added, and the bamboo powder is used directly.

[0096] Product performance: Density 0.65 g / cm³ 3 The longitudinal tensile strength is 24.5 MPa, the transverse tensile strength is 22.8 MPa, the puncture strength is 2.5 N, and crystal points are present on the film surface; the bamboo powder is unevenly dispersed, the interfacial bonding is weak, and the performance is degraded.

[0097] Comparative Example 6 (High-temperature processing, PGA melting) The process is basically the same as in Example 1, except that the granulation temperature of the main material in step three is increased to 180°C (when the PGA is completely melted).

[0098] Product performance: Density 0.70 g / cm³ 3 The longitudinal tensile strength is 22.8 MPa, the transverse tensile strength is 21.5 MPa, and the puncture strength is 2.3 N. PPC and PGA undergo thermal degradation, and the reinforcing effect of PGA disappears after melting, resulting in a significant deterioration in performance.

[0099] In summary, this invention discloses a high-performance, lightweight, biodegradable mulch film with synergistic four-pronged approach, its preparation method, and its applications. This mulch film is made from PBAT, PPC, bamboo powder / PGA functional masterbatch, MDI, and other additives. Performance optimization is achieved through the synergistic technology of "plant fiber micronization, alloying, composite formation, and lightweighting." The preparation method includes four steps: bamboo powder activation, functional masterbatch preparation, main material blending and granulation, and blown film forming. The core of this method lies in: the bamboo powder is micronized and activated with a coupling agent, then combined with PGA to form a functional masterbatch; the PBAT / PPC / functional masterbatch is chain-extended and compatibilized with MDI and in-situ foamed, combined with biaxial stretching to form a flat ellipsoidal pore structure, with the blow-up ratio to traction ratio controlled at 0.9~1.1. The resulting mulch film has a density of 0.60~0.65 g / cm³. 3 With longitudinal and transverse tensile strength ≥30 MPa and puncture strength ≥3 N, the overall cost is reduced by more than 30%. Moreover, the degradation rate is controllable, the processing is stable, and it has antibacterial function. It solves the technical problem that existing biodegradable mulch films cannot simultaneously achieve lightweight, high strength, and low cost. It is suitable for agricultural coverage of various crops and has broad prospects for promotion and application.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-performance, lightweight, biodegradable mulch film, characterized in that, The components include the following parts by weight: 50-65 parts of polybutylene terephthalate (PET), 20-35 parts of polypropylene carbonate, 5-10 parts of bamboo powder / polyglycolic acid functional masterbatch, 0.3-0.8 parts of diphenylmethane diisocyanate, 0.5-2 parts of citrate, 0.5-1.5 parts of epoxidized soybean oil, 0.05-0.5 parts of glycerin, 0.05-0.3 parts of stearic acid, 0.02-0.2 parts of calcium stearate, 0.1-0.5 parts of aluminate coupling agent, 0.1-0.5 parts of antioxidant, and 0.05-0.3 parts of opening agent; The bamboo powder / polyglycolic acid functional masterbatch comprises the following components in parts by weight: 70-80 parts of ultrafine bamboo powder, 10-20 parts of polyglycolic acid, 1-3 parts of stearic acid, 2-5 parts of aluminate coupling agent, 2-6 parts of epoxidized soybean oil, and 0.5-2 parts of calcium stearate.

2. The high-performance lightweight biodegradable mulch film according to claim 1, characterized in that, The bamboo powder ultrafine powder D 90 Particle size ≤10μm, initial moisture content <5wt%.

3. The high-performance lightweight biodegradable mulch film according to claim 1, characterized in that, The antioxidant includes at least one of antioxidant 1010 and antioxidant 168.

4. The high-performance lightweight biodegradable mulch film according to claim 1, characterized in that, The opening agent includes at least one of erucamide and oleamide.

5. The high-performance lightweight biodegradable mulch film according to claim 1, characterized in that, The high-performance lightweight biodegradable mulch film has a flat ellipsoidal cell structure with a cell size of 20~50μm.

6. The method for preparing the high-performance lightweight biodegradable mulch film according to any one of claims 1 to 5, characterized in that, Includes the following steps: According to the component ratio of bamboo powder / polyglycolic acid functional masterbatch, bamboo powder ultrafine powder is dried and mixed with aluminate coupling agent for activation to obtain activated bamboo powder; the activated bamboo powder, polyglycolic acid, stearic acid, epoxidized soybean oil and calcium stearate are subjected to a first blending and granulation to obtain the bamboo powder / polyglycolic acid functional masterbatch. According to the component ratio of high-performance lightweight biodegradable mulch film, polybutylene terephthalate, polypropylene carbonate, bamboo powder / polyglycolic acid functional masterbatch, diphenylmethane diisocyanate, citrate, epoxidized soybean oil, glycerin, stearic acid, calcium stearate, aluminate coupling agent, antioxidant, and opening agent are subjected to a second blending and granulation to obtain granules; the moisture content of the granules is 800~1500ppm; the temperature of the second blending and granulation is ≤160℃; The granules are blown into a film to obtain the high-performance lightweight biodegradable mulch film; the stretching method of the blown film forming is biaxial stretching, the blow-up ratio is 4.0~6.0, the traction ratio is 4.5~6.5, and the ratio of the blow-up ratio to the traction ratio is 0.9~1.

1.

7. The preparation method according to claim 6, characterized in that, The second blending and granulation is carried out using a twin-screw extruder, which is equipped with a main feed port, a side feed port, and a liquid injection port; the twin-screw extruder is equipped with 5 loss-in-weight scales, which are numbered 1# to 5# respectively; The stearic acid, calcium stearate, aluminate coupling agent, antioxidant, opening agent and part of polybutylene terephthalate adipate are fed into the main feed port through the No. 1 loss-in-weight scale; The bamboo powder / polyglycolic acid functional masterbatch is fed into the main feed port through a No. 2 loss-in-weight weigher. The polypropylene carbonate is fed in through the side feed port via a loss-in-weight scale (No. 3). The diphenylmethane diisocyanate and the remaining portion of polybutylene terephthalate adipate were fed into the main feed port through a loss-in-weight scale (No. 4). The citrate, epoxidized soybean oil, and glycerin were injected from the liquid inlet using a No. 5 loss-in-weight balance.

8. The preparation method according to claim 7, characterized in that, The twin-screw extruder comprises ten barrel heating zones from the feed end to the discharge end, numbered sequentially from zone 1 to zone 10. The heating temperature of zone 1 is 120~130℃, zone 2 is 130~145℃, zone 3 is 145~150℃, zone 4 is 150~155℃, zone 5 is 150~155℃, zone 6 is 155~160℃, zone 7 is 155~160℃, zone 8 is 150~155℃, zone 9 is 150~155℃, and zone 10 is 145~150℃. The die head temperature of the twin-screw extruder is 150~155℃; The screw speed of the twin-screw extruder is 350~500 rpm.

9. The preparation method according to claim 6, characterized in that, The blown film forming is carried out using a blown film machine; the blown film machine includes, in sequence, a feeding section, a compression section, a metering section, a die head body, and a die opening; the temperature of the feeding section is 130~140℃, the temperature of the compression section is 145~155℃, the temperature of the metering section is 150~160℃, the temperature of the die head body is 152~154℃, and the temperature of the die opening is 151~153℃; The nozzle gap for blown film forming is 1.2~1.5 mm, and the cooling and shaping height is 150~300 mm.

10. The application of the high-performance lightweight biodegradable mulch film according to any one of claims 1 to 5 or the high-performance lightweight biodegradable mulch film prepared by the preparation method according to any one of claims 6 to 9 in the agricultural field.

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