Degradable white breathable reflective mulch film material and preparation method thereof

Abstract

This application relates to the field of reflective covering film material processing technology, and more specifically, to a biodegradable white breathable reflective covering film material and its preparation method, which is prepared from the following raw materials in parts by weight: 40-50 parts polypropylene, 40-50 parts biodegradable material, 1-2 parts anti-UV masterbatch, and 5-9 parts reflective color masterbatch; the biodegradable material is composed of starch-grafted polymer, polyhydroxyalkanoate, and iron stearate coating in a weight ratio of (5-10):(2-5):0.3; by utilizing the biodegradability of starch-grafted polymer and polyhydroxyalkanoate, combined with the slow-release catalytic effect of iron stearate coating, the biodegradability and breathability of the material are significantly improved while ensuring the strength and reflective performance of polypropylene. Simultaneously, the anti-UV masterbatch effectively extends the service life of the material, allowing it to naturally degrade after meeting the needs of the crop growth cycle, solving the problem of the difficulty in degradation and recycling of traditional polypropylene reflective films, thus combining environmental protection and practicality.

Description

Technical Field

[0001] This application relates to the field of reflective covering film material processing technology, and more specifically, to a biodegradable white breathable reflective covering film material and its preparation method. Background Technology

[0002] Polypropylene reflective film is made of bright white plastic that effectively reflects sunlight. Within the visible light range, it reflects most of the light back to the crop canopy, increasing light intensity and photosynthetically active radiation in the lower and middle parts of the crop. Simultaneously, polypropylene itself has a certain degree of weather resistance, maintaining relatively stable performance under the influence of ultraviolet radiation, wind, rain, and other natural factors in outdoor environments. Unlike some ordinary reflective materials, it does not age, discolor, or experience a significant decrease in reflectivity within a short period. Its service life generally lasts for several months or even longer, meeting the needs of a single crop growth cycle.

[0003] However, with the continuous development of agricultural production, the recycling and disposal of polypropylene reflective film after use has become increasingly prominent. Due to its difficulty in natural degradation, if not properly recycled, the polypropylene reflective film remaining in the soil will damage the soil structure, affect the soil's aeration and water permeability, and thus adversely affect the soil ecological environment and the growth of subsequent crops. This, to some extent, restricts the sustainable development of agriculture. Summary of the Invention

[0004] To improve the degradability of polypropylene reflective film, this application provides a degradable white breathable reflective covering film material and its preparation method.

[0005] In a first aspect, this application provides a biodegradable white breathable reflective covering film material, employing the following technical solution:

[0006] A biodegradable white breathable reflective covering film material is prepared from the following raw materials in parts by weight:

[0007] 40-50 parts of polypropylene

[0008] 40-50 parts of biodegradable material

[0009] 1-2 parts of UV-resistant masterbatch

[0010] 5-9 parts of reflective masterbatch;

[0011] The biodegradable material is composed of starch-grafted polymer, polyhydroxy fatty acid ester, and iron stearate encapsulant in a weight ratio of (5-10):(2-5):0.3;

[0012] The iron stearate coating was prepared according to the following method:

[0013] Ferric stearate and polyethylene glycol are mixed and heated in a water bath at 70-80°C. After the ferric stearate is fully dissolved in the polyethylene glycol, the mixture is stirred for 1-2 hours. The mixture is then slowly cooled at room temperature to obtain a solid. The solid is then placed in a vacuum drying oven to obtain a ferric stearate coating.

[0014] The weight ratio of the ferric stearate to the polyethylene glycol is 5:(20-30).

[0015] By adopting the above technical solution, the biodegradable material in this application is composed of starch-grafted polymer, polyhydroxyalkanoate, and ferric stearate coating. Both the starch-grafted polymer and polyhydroxyalkanoate can be gradually decomposed by microorganisms in the natural environment. The ferric stearate coating promotes the entire biodegradation process. These three components work synergistically, enabling the entire reflective covering film material to gradually degrade in the natural environment after its service life, avoiding the problem of long-term residue in the soil damaging soil structure. This effectively solves the problems of difficult recycling and degradation of traditional polypropylene reflective film.

[0016] When ferric stearate is encapsulated in polyethylene glycol (PEG), its direct contact with oxygen is reduced, thus lowering the likelihood of oxidation during use. This makes the chemical properties of ferric stearate more stable within the material, less prone to deterioration due to oxidation, and extends the material's lifespan. In the initial stages of use, the tightly encapsulated ferric stearate in PEG is relatively stable and does not easily release, ensuring the material's performance stability throughout its growth cycle and meeting the requirements of crop growth. Once the material has completed its service life and entered the natural environment, PEG degrades relatively quickly under natural conditions. As PEG gradually degrades, ferric stearate is slowly released. The released ferric stearate acts as a catalyst for microbial degradation, promoting the decomposition of the biodegradable material and accelerating the overall degradation rate, allowing it to better integrate into the natural environmental cycle.

[0017] Meanwhile, the addition of biodegradable materials in this application does not completely negate the advantages of polypropylene, but rather endows the material with degradable properties. The presence of polypropylene ensures sufficient strength and stability throughout the service life of the reflective covering film, while the biodegradable materials provide the possibility for subsequent degradation processes.

[0018] Components such as starch-grafted polymers and polyhydroxyalkanoates in biodegradable materials have a relatively loose molecular structure compared to polypropylene. During the film-forming process with other components, they create tiny pores or channels within the reflective coating. These channels allow air molecules to exchange across the membrane, thus achieving breathability.

[0019] The high reflectivity of the reflective masterbatch works in conjunction with the optical properties of polypropylene. The high light transmittance and low scattering of polypropylene allow the effective components in the reflective masterbatch to function better, reflecting most of the visible light back to the crop canopy and enhancing the reflective effect.

[0020] UV-resistant masterbatch can absorb ultraviolet rays, thereby protecting polypropylene and biodegradable materials from excessive UV damage, extending the service life of materials in outdoor environments, and enabling materials to maintain relatively stable performance while meeting the needs of crop growth cycles.

[0021] Preferably, the molecular weight of the polyethylene glycol is 2000-7000.

[0022] By adopting the above technical solution, the molecular weight of polyethylene glycol is optimized to give it moderate viscosity and fluidity, which can be fully mixed with ferric stearate and uniformly encapsulate ferric stearate particles. Ferric stearate can be uniformly dispersed in the polypropylene matrix and can form a continuous and stable film on the surface of ferric stearate. This allows the ferric stearate coating to remain stable in the material and not easily break or fall off, thereby extending the service life of the material.

[0023] Preferably, the polypropylene is modified polypropylene, prepared by the following method:

[0024] 1) Mix polypropylene, acrylic monomer, and DCP initiator in a weight ratio of (90-100):(5-10):0.1, add to a high-speed mixer, mix evenly to fully disperse the components, and obtain a mixture;

[0025] 2) The mixture is added to a twin-screw extruder, extruded, and pelletized to obtain modified polypropylene;

[0026] The temperatures for each zone are set as follows: feeding zone temperature 170-180℃, compression zone temperature 190-200℃, homogenization zone temperature 210-220℃, and screw speed 200-300 r / min.

[0027] By adopting the above technical solutions, the original polypropylene exhibits poor compatibility with biodegradable materials, resulting in interfacial defects that affect material performance. The modified polypropylene, by introducing acrylic acid monomers, increases polarity, improving compatibility with biodegradable materials such as starch-grafted polymers and polyhydroxyalkanoates, reducing interfacial defects, and enhancing overall material performance. The modified polypropylene also shows better compatibility with the components in reflective masterbatches, allowing for more uniform dispersion of the masterbatch within the polypropylene matrix. This uniform dispersion improves the uniformity and stability of the material's reflective properties, ensuring consistent reflectivity of the cover film at different locations.

[0028] Meanwhile, the modified polypropylene interacts with biodegradable materials, promoting the overall degradation performance of the reflective film. Furthermore, the modified polypropylene itself may absorb moisture and microbial activity to some extent, thereby accelerating its degradation, reducing the amount of reflective film residue in the soil, and minimizing damage to the soil's ecological environment.

[0029] Preferably, the acrylic monomer is prepared from methyl acrylate and hydroxyethyl acrylate in a weight ratio of (6-9):3.

[0030] By employing the above technical solution and optimizing the type and dosage ratio of acrylic monomers, the modified polypropylene molecular chains are made more susceptible to water erosion in the natural environment, thereby accelerating the degradation process of polypropylene. The combination of methyl acrylate and hydroxyethyl acrylate introduces functional groups with different properties. The hydroxyl groups in hydroxyethyl acrylate enhance the hydrophilicity of the material, making the reflective film more easily absorb water in the soil environment, thus accelerating the erosion and decomposition of the material by microorganisms. Simultaneously, the introduction of acrylic monomers disrupts the regularity of the polypropylene molecular chains, reducing the crystallinity of the material and accelerating its degradation rate in the natural environment.

[0031] Furthermore, polypropylene itself is a highly crystalline polymer with relatively poor air permeability. However, through grafting modification with acrylic acid monomers, the regularity of the polypropylene molecular chains decreases, reducing crystallinity and creating more microporous structures and air permeability channels within the material. Simultaneously, the hydroxyl groups in hydroxyethyl acrylate have a certain degree of hydrophilicity, allowing them to adsorb a certain amount of moisture, further promoting gas exchange within the material and enhancing the air permeability of the reflective film. This benefits soil aeration and moisture regulation during crop growth, creating a better growing environment for crops.

[0032] The introduction of acrylic monomers alters the surface properties of polypropylene, increasing the material's surface roughness and light scattering ability, enabling the reflective film to more effectively reflect various wavelengths of sunlight.

[0033] Preferably, the reflective masterbatch is prepared by the following method:

[0034] Yttrium-doped zinc oxide, mica powder, barium sulfate and polylactic acid are mixed in a weight ratio of (1-2):(3-5):(6-8):20, then added to a twin-screw extruder, extruded, and pelletized to obtain reflective masterbatch.

[0035] By employing the above technical solutions, yttrium-doped zinc oxide, with its high refractive index, effectively reflects light, particularly ultraviolet and visible light, enhancing the reflectivity of the covering film. The layered structure of mica powder creates a specular reflection, allowing light to be reflected systematically to the crop canopy, improving light energy utilization. Barium sulfate further scatters and reflects light, filling the gaps in the mica powder's reflection and making the reflected light more uniform. These three elements synergistically enhance the reflectivity of the covering film, increasing light intensity and photosynthetically active radiation in the lower and middle parts of the crop.

[0036] Meanwhile, barium sulfate possesses high chemical stability and appropriate porosity, which helps to form tiny channels within the reflective film, allowing air and water vapor to exchange through these channels, thereby enhancing the film's permeability. Polylactic acid (PLA) is a biodegradable material with certain permeability and biodegradability. Its presence in reflective masterbatches not only helps improve the film's permeability but also, to some extent, enhances its biodegradability, reducing environmental pollution.

[0037] Preferably, the average particle size of the mica powder is 0.1-0.5 μm.

[0038] Preferably, the average particle size of the barium sulfate is 0.01-0.2 μm.

[0039] Preferably, the average particle size of the yttrium-doped zinc oxide is 30-50 nm.

[0040] By employing the above technical solutions and optimizing the average particle size of mica powder, barium sulfate, and yttrium-doped zinc oxide, the reflectivity of the reflective film for visible light is improved, increasing the brightness and uniformity of the reflected light. Specifically, the sheet-like structure of mica powder enables multiple reflections and scatterings of light upon incident light, enhancing the residence time of light on the reflective film surface. Barium sulfate, with its small particle size, high refractive index, and good chemical stability, is evenly distributed throughout the reflective film, forming dense reflection points that scatter and reflect light, resulting in good reflectivity at different angles and improving the uniformity and overall reflectivity of the film. Yttrium-doped zinc oxide, with its smallest particle size, high specific surface area, and excellent ultraviolet light reflection performance, is more evenly distributed throughout the reflective film, forming a dense protective layer that effectively absorbs and reflects ultraviolet light. The combined use of these three components causes multiple reflections and scatterings of light across the surfaces of particles of different sizes, enhancing the brightness and uniformity of the reflective film.

[0041] At the same time, the three particles have different sizes, which can form a tiny porous structure. These gaps can provide channels for the diffusion of gas molecules, allowing air and water vapor to exchange through these channels, thereby enhancing the breathability of the reflective film.

[0042] Preferably, the UV-resistant masterbatch is prepared by the following method:

[0043] Polylactic acid, UV stabilizer and dispersant are mixed in a weight ratio of (5-6):(0.5-1):(1-2), and then fed into a twin-screw extruder for extrusion granulation to obtain UV stabilizer masterbatch.

[0044] By employing the above technical solutions, polylactic acid is used as the matrix material to provide a carrier for UV stabilizers and other agents, ensuring their uniform dispersion within the reflective film and enhancing its overall performance. UV stabilizers effectively absorb and shield ultraviolet rays, preventing photodegradation and extending the film's lifespan. Dispersants improve the compatibility and dispersibility of components, reducing performance differences caused by component aggregation and resulting in more uniform reflective film performance. Lubricants reduce friction between components during processing, improving flowability and enhancing production efficiency and product quality.

[0045] Secondly, this application provides a method for preparing a biodegradable white breathable reflective covering film material, using the following technical solution:

[0046] A method for preparing a biodegradable white breathable reflective covering film material includes the following preparation steps:

[0047] Polypropylene, biodegradable materials, UV-resistant masterbatch, and reflective color masterbatch are mixed and then extruded and granulated to obtain a biodegradable white breathable reflective covering film.

[0048] By employing the above technical solutions, the raw materials are fully dispersed and blended during the mixing process, ensuring the uniformity and stability of the covering film. The synergistic effect of polypropylene and biodegradable materials gives the covering film both good mechanical properties and weather resistance, and it can gradually degrade after use, reducing environmental pollution. The addition of anti-UV masterbatch effectively improves the covering film's UV resistance and aging resistance, extending its service life. Reflective masterbatch gives the covering film good reflective properties, increasing the light intensity and photosynthetically active radiation in the lower and middle parts of the crop. At the same time, the covering film prepared by this process also has good air permeability, which is beneficial to soil aeration and moisture regulation.

[0049] In summary, this application has the following beneficial effects:

[0050] 1. Improved degradability: By adding biodegradable materials (starch-grafted polymers, polyhydroxyalkanoates, and iron stearate coatings), the reflective film is more easily decomposed by microorganisms in the natural environment, reducing long-term soil pollution and solving the problem of the difficulty in degrading traditional polypropylene reflective film.

[0051] 2. Maintain reflective properties: Adding reflective masterbatch to the formula ensures that the covering film can still effectively reflect most of the light in the visible light range, increasing the light intensity and photosynthetically active radiation in the lower part of the crop, thereby maintaining and improving crop yield and quality.

[0052] 3. Good air permeability: The biodegradable white breathable reflective covering film has good air permeability, which is beneficial to soil aeration and moisture regulation. Detailed Implementation

[0053] Preparation Example

[0054] Preparation Example 1

[0055] A UV-resistant masterbatch is prepared by the following method:

[0056] Mix 50g of polylactic acid, 0.5g of UV stabilizer (UV-531), and 1g of dispersant (calcium stearate) in a weight ratio of 5:0.5:1:2, then feed the mixture into a twin-screw extruder for extrusion granulation to obtain UV stabilizer masterbatch.

[0057] Preparation Example 2

[0058] A UV-resistant masterbatch is prepared by the following method:

[0059] Polylactic acid 55, UV inhibitor 0.8g (UV-2908) and dispersant 1.5g (polyethylene wax) were mixed in a weight ratio of 5.5:0.8:1.5:2 and then fed into a twin-screw extruder for extrusion granulation to obtain UV inhibitor masterbatch.

[0060] Preparation Example 3

[0061] A UV-resistant masterbatch is prepared by the following method:

[0062] 60g of polylactic acid, 1g of UV stabilizer (UV-328) and 2g of dispersant (oleamide) were mixed in a weight ratio of 6:1:1:2 and then fed into a twin-screw extruder for extrusion granulation to obtain UV stabilizer masterbatch.

[0063] Preparation Example 4

[0064] A reflective masterbatch is prepared by the following method:

[0065] Mix 10g of yttrium-doped zinc oxide, 30g of mica powder, 60g of barium sulfate and 200g of polylactic acid in a weight ratio of 1:3:6:20, then add the mixture to a twin-screw extruder, extrude and pelletize to obtain reflective masterbatch.

[0066] The average particle size of the mica powder is 0.1 μm.

[0067] The average particle size of barium sulfate is 0.01 μm.

[0068] The average particle size of yttrium-doped zinc oxide is 30 nm.

[0069] Preparation Example 5

[0070] A reflective masterbatch is prepared by the following method:

[0071] Mix 15g of yttrium-doped zinc oxide, 40g of mica powder, 70g of barium sulfate and 200g of polylactic acid in a weight ratio of 1.5:5:7:20, then add the mixture to a twin-screw extruder, extrude, and pelletize to obtain reflective masterbatch.

[0072] The average particle size of the mica powder is 0.3 μm.

[0073] The average particle size of barium sulfate is 0.1 μm.

[0074] The average particle size of yttrium-doped zinc oxide is 40 nm.

[0075] Preparation Example 6

[0076] A reflective masterbatch is prepared by the following method:

[0077] Mix 20g of yttrium-doped zinc oxide, 50g of mica powder, 80g of barium sulfate and 200g of polylactic acid in a weight ratio of 1:5:8:20, then add the mixture to a twin-screw extruder, extrude and pelletize to obtain reflective masterbatch.

[0078] The average particle size of the mica powder is 0.5 μm.

[0079] The average particle size of barium sulfate is 0.2 μm.

[0080] The average particle size of yttrium-doped zinc oxide is 50 nm.

[0081] Preparation Example 7

[0082] A reflective masterbatch, the difference between this preparation example and preparation example 4 is that no mica powder is added.

[0083] Preparation Example 8

[0084] A reflective masterbatch, the difference between this preparation example and preparation example 4 is that barium sulfate is not added.

[0085] Preparation Example 9

[0086] A reflective masterbatch, the difference between this preparation example and preparation example 4 is that the average particle size of the mica powder is 1 μm.

[0087] Example

[0088] The polypropylene was purchased from Shanghai Yuanye Biotechnology Co., Ltd., with product number S52842.

[0089] The polylactic acid (PLA) was purchased from Guangzhou Yuanda New Materials Co., Ltd. The PLA is 100% pure and packaged in 1kg packages.

[0090] The starch-grafted polycaprolactone copolymer was purchased from Xi'an Ruixi Biotechnology Co., Ltd., model number R-22000.

[0091] Example 1

[0092] A biodegradable white breathable reflective covering film material is prepared by the following method:

[0093] 400g of polypropylene, 400g of biodegradable material, 10g of UV-resistant masterbatch (from Preparation Example 1), and 50g of reflective color masterbatch (from Preparation Example 4) were mixed and then extruded and granulated to obtain a biodegradable white breathable reflective covering film.

[0094] The biodegradable material is composed of starch-grafted polymer (starch-grafted polycaprolactone copolymer), polyhydroxy fatty acid ester, and iron stearate coating in a weight ratio of 5:2:0.3.

[0095] Ferric stearate coatings were prepared by the following method:

[0096] Mix 50g of ferric stearate and 200g of polyethylene glycol, heat in a water bath at 70℃, and continue stirring for 1 hour after the ferric stearate is fully dissolved in the polyethylene glycol. Allow the mixture to cool slowly at room temperature to obtain a solid. Place the solid in a vacuum drying oven to obtain a ferric stearate coating.

[0097] The molecular weight of polyethylene glycol is 2000.

[0098] The difference between Examples 2-3 and Example 1 lies in the types, amounts, and parameters of raw materials used to prepare the biodegradable white breathable reflective covering film material. Specific differences are shown in Table 1.

[0099] Table 1. Raw material types, dosages, and parameters for preparing biodegradable white breathable reflective covering film materials in Examples 1-3.

[0100]

[0101]

[0102] The ferric stearate coating in Example 2 was prepared according to the following method:

[0103] Mix 50g of ferric stearate and 250g of polyethylene glycol, heat in a water bath at 75℃, and continue stirring for 1.5h after the ferric stearate is fully dissolved in the polyethylene glycol. Allow the mixture to cool slowly at room temperature to obtain a solid. Place the solid in a vacuum drying oven to obtain a ferric stearate coating.

[0104] The molecular weight of polyethylene glycol is 5000.

[0105] The ferric stearate coating in Example 3 was prepared according to the following method:

[0106] Mix 50g of ferric stearate and 300g of polyethylene glycol, heat in a water bath at 80℃, and continue stirring for 2 hours after the ferric stearate is fully dissolved in the polyethylene glycol. Allow the mixture to cool slowly at room temperature to obtain a solid. Place the solid in a vacuum drying oven to obtain a ferric stearate coating.

[0107] The molecular weight of polyethylene glycol is 7000.

[0108] Example 4

[0109] A biodegradable white breathable reflective covering film material, the difference between this embodiment and Example 1 is that the polypropylene is modified polypropylene, prepared by the following method:

[0110] 1) Mix 450g of polypropylene, 250g of acrylic monomer, and 0.5g of DCP initiator in a weight ratio of 90:5:0.1. Add the mixture to a high-speed mixer and mix thoroughly to ensure that all components are fully dispersed, thus obtaining a mixture.

[0111] 2) The mixture is added to a twin-screw extruder, extruded, and pelletized to obtain modified polypropylene;

[0112] The temperatures for each zone are set as follows: feeding zone temperature is 170℃, compression zone temperature is 190℃, homogenization zone temperature is 210℃, and screw speed is 200r / min.

[0113] The acrylic monomer was prepared by mixing methyl acrylate and hydroxyethyl acrylate in a weight ratio of 6:3.

[0114] Example 5

[0115] A biodegradable white breathable reflective covering film material, the difference between this embodiment and Example 1 is that the polypropylene is modified polypropylene, prepared by the following method:

[0116] 1) Mix 500g of polypropylene, 50g of acrylic monomer, and 0.5g of DCP initiator in a weight ratio of 100:10:0.1. Add the mixture to a high-speed mixer and mix thoroughly to ensure that all components are fully dispersed, thus obtaining a mixture.

[0117] 2) The mixture is added to a twin-screw extruder, extruded, and pelletized to obtain modified polypropylene;

[0118] The temperatures for each zone are set as follows: feeding zone temperature is 180℃, compression zone temperature is 200℃, homogenization zone temperature is 220℃, and screw speed is 300r / min.

[0119] The acrylic monomer was prepared by mixing methyl acrylate and hydroxyethyl acrylate in a weight ratio of 9:3.

[0120] Example 6

[0121] A biodegradable white breathable reflective covering film material, the difference between this embodiment and Example 1 is that the reflective masterbatch comes from Preparation Example 7.

[0122] Example 7

[0123] A biodegradable white breathable reflective covering film material, the difference between this embodiment and Example 1 is that the reflective masterbatch comes from Preparation Example 8.

[0124] Example 8

[0125] A biodegradable white breathable reflective covering film material, the difference between this embodiment and Example 1 is that the reflective masterbatch comes from Preparation Example 9.

[0126] Comparative Example

[0127] Comparative Example 1

[0128] A biodegradable white breathable reflective covering film material. The difference between this comparative example and Example 1 is that the biodegradable material is a starch-grafted polymer.

[0129] Comparative Example 2

[0130] A biodegradable white breathable reflective covering film material. The difference between this comparative example and Example 1 is that the iron stearate coating is replaced with iron stearate.

[0131] Comparative Example 3

[0132] A biodegradable white breathable reflective covering film material. The difference between this comparative example and Example 1 is that the biodegradable material is composed of starch grafted polymer and polyhydroxy fatty acid ester in a weight ratio of 5:2.

[0133] Comparative Example 4

[0134] A biodegradable white breathable reflective covering film material. The difference between this comparative example and Example 1 is that the biodegradable material is polylactic acid.

[0135] Comparative Example 5

[0136] A biodegradable white breathable reflective covering film material. The difference between this comparative example and Example 1 is that the reflective masterbatch is replaced with barium sulfate.

[0137] Detection methods / test methods

[0138] The biodegradable white breathable reflective covering film materials prepared in Examples 1-8 and Comparative Examples 1-5 were extruded, cast, stretched, and heat-set to form biodegradable white breathable reflective covering films with a thickness of 0.1 mm.

[0139] Degradability: The degradation rate of the degradable white breathable reflective covering film was tested using the composting method according to GB / T 19277.1-2011 standard.

[0140] Reflectivity: After calibrating the spectrophotometer to standard settings, place the biodegradable white breathable reflective coating sample to be tested on the integrating sphere of the spectrophotometer, ensuring the sample surface is flat and in close contact with the integrating sphere. The spectrophotometer will automatically measure reflectivity in the wavelength range of 400-1100 nm at 10 nm intervals, recording the reflectivity value corresponding to each wavelength. Record the average reflectivity in the visible light band (400-700 nm) and the average reflectivity in the near-infrared band (700-1100 nm).

[0141] Breathability: The water vapor permeability of the biodegradable white breathable reflective cover film was determined at a temperature of 23°C using a moisture permeability meter sold by MOCON Corporation, USA, under the trade name Permatran-w3 / 61, in accordance with ASTM 1434-8.

[0142] Durability: A sample of the biodegradable white breathable reflective covering film was cut into 10cm x 10cm pieces and placed in a UV aging test chamber. The chamber parameters were set, such as a UV intensity of 0.85 W / m². 2 ±0.02W / m 2 The temperature was 60℃±2℃, the humidity was 50%±5%, and the test period was 600 hours. Observations were made on the surface to record any changes such as discoloration, cracking, or shrinkage. The experimental data are shown in Table 2.

[0143] Table 2. Experimental data of Examples 1-8 and Comparative Examples 1-5

[0144]

[0145]

[0146] The experimental data from Example 1 and Comparative Examples 1-5 show that the biodegradable white breathable reflective covering film in Example 1 is superior to that in Comparative Examples 1-5 in terms of degradation rate, reflectivity, and water vapor permeability. This indicates that the biodegradable material formulation (a combination of starch-grafted polymer, polyhydroxy fatty acid ester, and iron stearate coating) and the modified polypropylene preparation method used in the examples can effectively improve the overall performance of the covering film and better balance its degradability, reflectivity, and breathability, thus meeting the needs of agricultural applications.

[0147] The experimental data from Examples 1 and 4-5 show that the use of modified polypropylene significantly improved the degradation rate, reflectivity, and water vapor permeability of the biodegradable white breathable reflective covering film. This indicates that the introduction of modified polypropylene can significantly improve the biodegradability of the covering film while maintaining good reflectivity and breathability, making it more environmentally friendly and efficient in agricultural applications.

[0148] The experimental data from Examples 1 and 6-8 show that the proper combination of mica powder and barium sulfate in the reflective masterbatch plays an important role in improving the reflectivity and breathability of the biodegradable white breathable reflective covering film. The absence of either component or the use of mica powder with a larger particle size will significantly reduce the reflectivity and breathability of the covering film, while having a relatively smaller impact on the degradation rate.

[0149] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A biodegradable white breathable reflective covering film material, characterized in that, It is prepared from the following raw materials in parts by weight: 40-50 parts of polypropylene 40-50 parts of biodegradable material 1-2 parts of UV-resistant masterbatch 5-9 parts of reflective masterbatch; The biodegradable material is composed of starch-grafted polymer, polyhydroxy fatty acid ester and iron stearate encapsulation in a weight ratio of (5-10):(2-5):0.3; The iron stearate coating was prepared according to the following method: Ferric stearate and polyethylene glycol are mixed and heated in a water bath at 70-80°C. After the ferric stearate is fully dissolved in the polyethylene glycol, the mixture is stirred for 1-2 hours. The mixture is then slowly cooled at room temperature to obtain a solid. The solid is then placed in a vacuum drying oven to obtain a ferric stearate coating. The weight ratio of the ferric stearate to the polyethylene glycol is 5:(20-30). The polypropylene is a modified polypropylene, prepared by the following method: 1) Mix polypropylene, acrylic acid monomer, and DCP initiator in a weight ratio of (90-100):(5-10): Mix 0.1g of the mixture and add it to a high-speed mixer. Mix thoroughly to ensure that all components are fully dispersed and a mixture is obtained. 2) The mixture is added to a twin-screw extruder, extruded, and pelletized to obtain modified polypropylene; The temperatures for each zone are set as follows: feeding zone temperature is 170-180℃, compression zone temperature is 190-200℃, homogenization zone temperature is 210-220℃, and screw speed is 200-300 r / min; The acrylic monomer is prepared from methyl acrylate and hydroxyethyl acrylate in a weight ratio of (6-9):3; The reflective masterbatch is prepared by the following method: Yttrium-doped zinc oxide, mica powder, barium sulfate and polylactic acid are mixed in a weight ratio of (1-2):(3-5):(6-8):20, then added to a twin-screw extruder, extruded, and pelletized to obtain reflective masterbatch; The UV-resistant masterbatch was prepared by the following method: Polylactic acid, UV stabilizer and dispersant are mixed in a weight ratio of (5-6):(0.5-1):(1-2), and then fed into a twin-screw extruder for extrusion granulation to obtain UV stabilizer masterbatch.

2. The biodegradable white breathable reflective covering film material according to claim 1, characterized in that: The molecular weight of the polyethylene glycol is 2000-7000.

3. The biodegradable white breathable reflective covering film material according to claim 1, characterized in that: The average particle size of the mica powder is 0.1-0.5 μm.

4. The biodegradable white breathable reflective covering film material according to claim 1, characterized in that: The average particle size of the barium sulfate is 0.01-0.2 μm.

5. The biodegradable white breathable reflective covering film material according to claim 1, characterized in that: The yttrium-doped zinc oxide has a thickness of 30-50 nm.

6. A method for preparing a biodegradable white breathable reflective covering film material as described in any one of claims 1-5, characterized in that, The preparation steps include the following: Polypropylene, biodegradable materials, UV-resistant masterbatch, and reflective color masterbatch are mixed and then extruded and granulated to obtain a biodegradable white breathable reflective covering film material.

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