Infrared light reflecting degradable agricultural mulching film and preparation method thereof

Abstract

The application discloses an infrared light reflecting degradable agricultural mulching film and a preparation method thereof. The agricultural mulching film at least comprises: a base layer as a first layer, which is composed of PLA, PBAT and Nano-OS; a CNF / TiO2-MA functional layer as a second layer, which is arranged on at least one side of the base layer; and a PLA layer as a third layer, which is arranged on at least one side of the CNF / TiO2-MA functional layer. The infrared light reflecting degradable agricultural mulching film has good infrared light reflecting cooling, excellent mechanical properties and biodegradable properties.

Description

Technical Field

[0001] This invention relates to the field of biodegradable agricultural mulch film and infrared light reflection technology, specifically to an infrared light reflecting biodegradable agricultural mulch film and its preparation method. Background Technology

[0002] Traditional agricultural mulch films are typically made of non-biodegradable plastics, which are difficult to degrade after use, causing pollution to the soil and environment. Biodegradable agricultural mulch films, on the other hand, can degrade into harmless substances after their service life, reducing pollution to soil and water bodies and contributing to ecological protection. The environmentally friendly characteristics of biodegradable agricultural mulch films lie in their ability to naturally degrade after use, reducing pollution to soil and water bodies and helping to protect the ecological environment; at the same time, the use of biodegradable agricultural mulch films conserves resources and promotes sustainable development. Furthermore, it can improve soil aeration, promote soil microbial activity, and increase soil fertility and yield, meeting the needs of modern agriculture. The adoption of biodegradable agricultural mulch films is a measure to adapt to future regulations and is currently widely used in actual agricultural production.

[0003] While biodegradable agricultural mulch films offer environmental advantages, they also face numerous challenges. These include unstable degradation rates in some biodegradable mulch films, high production costs, immature technology, and limited functionality. Overcoming these challenges requires multifaceted efforts, including technological innovation and cost reduction, to promote the further development and widespread adoption of biodegradable agricultural mulch films. Summary of the Invention

[0004] Therefore, to address the problems of insufficient biodegradability, high production costs, and limited functionality of existing agricultural mulch films, this invention provides a composite agricultural mulch film with excellent infrared reflection cooling, superior mechanical properties, and biodegradability based on a three-layer structure design. The infrared-reflective biodegradable agricultural mulch film is assembled from a base layer, a functional layer, and an encapsulation layer. When exposed to sunlight, this film effectively reduces soil surface temperature and reflects sunlight. Furthermore, the introduction of nano-oyster shells (Nano-OS) and nano-pearl powder (TiO2-MA) gives the film excellent mechanical properties during use, while significantly increasing its degradation rate upon disposal. This mulch film can effectively improve crop yield and growth quality, and can also significantly improve the efficiency and stability of agricultural production, which is of great significance for promoting sustainable agricultural development.

[0005] Therefore, the present invention provides the following technical solution.

[0006] <1> An infrared-reflective biodegradable agricultural mulch film, comprising at least:

[0007] The base layer, which serves as the first layer, is composed of PLA, PBAT, and Nano-OS.

[0008] As a second CNF / TiO2-MA functional layer, it is disposed on at least one side of the substrate layer; and

[0009] The PLA layer, which serves as the third layer, is disposed on at least one side of the CNF / TiO2-MA functional layer.

[0010] <2> . according to <1> The infrared light reflective biodegradable agricultural mulch film, wherein, based on the total mass of the base layer, PLA accounts for 20%-70% of the mass, PBAT accounts for 20%-70% of the mass, and Nano-OS accounts for 5%-20% of the mass.

[0011] <3> . according to <1> The infrared-reflective biodegradable agricultural mulch film, wherein the CNF used in the CNF / TiO2-MA functional layer of the agricultural mulch film has at least one of the following properties:

[0012] i) The diameter of the CNF is 5-70 nm;

[0013] ii) The aspect ratio of the CNF is 50-400;

[0014] iii) The crystallinity of the CNF is 75-95%;

[0015] iv) The CNF contains at least one hemicellulose component containing carboxyuronic acid;

[0016] v) The surface charge of the CNF is -50 to -10 mV.

[0017] <4> . according to <1> The infrared light reflective biodegradable agricultural mulch film, wherein, based on the total mass of the CNF / TiO2-MA functional layer as the second layer, the mass fraction of CNF is 10%-30%, and the mass fraction of TiO2-MA is 70%-90%.

[0018] <5> . according to <1> The infrared light reflective biodegradable agricultural mulch film has a first layer thickness of 20-40 μm, a second layer thickness of 25-50 μm, and a third layer thickness of 5-20 μm.

[0019] <6> . according to <1> The infrared-reflective biodegradable agricultural mulch film, wherein the PLA has a weight-average molecular weight range of 11000-11500 Da, a melt index range of 10-12 g / 10 min, a melting point range of 150-165℃, a glass transition temperature range of 60-65℃, and a relative viscosity range of 1.5-2.0.

[0020] The PBAT has a crystallization temperature range of 105-110℃, a melting point range of 110-140℃, and a density range of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%.

[0021] The diameter of the Nano-OS sheets ranges from 100 to 300 nm.

[0022] <7> . according to <1> The infrared light reflective biodegradable agricultural mulch film, wherein the CNF is derived from agricultural waste biomass raw materials, selected from one of Sargassum fusiforme, coconut palm, rice straw, corn stalks and bagasse.

[0023] <8> A method for preparing... <1> - <7> The method for degrading agricultural mulch film by infrared light reflection according to any one of the following methods, wherein the method comprises the following steps:

[0024] A) PLA, PBAT and Nano-OS are compounded in proportion to form composite granules, and then the composite granules are blow-molded to form a base film as the first layer;

[0025] B) CNF and TiO2-MA are combined in a certain proportion to prepare a composite slurry, and then the composite slurry is coated on the substrate to obtain the second layer;

[0026] C) Pure PLA is coated onto the second layer to obtain a structure with at least three thin film layers;

[0027] D) The structure is hot-pressed to obtain the infrared-reflective biodegradable agricultural mulch film.

[0028] <9> . according to <1> The method for preparing the infrared light reflective biodegradable agricultural mulch film, wherein the method for preparing the first layer of composite granules of the agricultural mulch film is a twin-screw internal mixing method, and the internal mixing temperature range of the twin-screw internal mixer is 170℃-220℃.

[0029] <10> . according to <1> The method for preparing the infrared light reflective biodegradable agricultural mulch film includes a method for pre-treating the substrate with hydrophilicity before spraying the composite slurry to form the second layer. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of nano-OS oyster shells. The image shows that the oyster shells, after being treated with a combination of chemical and physical methods, exhibit nanoscale bands at the microscopic level (see [link to image]). Figure 1(The part indicated by the arrow in the image) provides favorable conditions for subsequent composite enhancement. Scanning electron microscopy images of the samples were obtained using a GeminiSEM 500 Schottky field emission scanning electron microscope at an accelerating voltage of 3 kV. All samples were sputtered with platinum at a current of 30 mA for 60 s.

[0031] Figure 2 A is a digital photograph of polylactic acid (PLA) granules. Figure 2 B is a digital photograph of PBAT pellets. Figure 2 C is a digital photograph of the nano-oyster shell dispersion. (Example) Figure 2 As shown in C, the nano-oyster shells obtained after peeling can maintain good stability after being dispersed in water, and no aggregation occurs.

[0032] Figure 3 This is a digital photograph of the first layer of the infrared reflective mulch film according to the present invention. The first layer is the base layer, which is mainly composed of PLA, PBAT, and Nano-OS in a certain proportion, and serves to support the entire agricultural mulch film. As shown in the figure, this layer is relatively uniform and smooth, providing favorable conditions for subsequent lamination.

[0033] Figure 4 The stress-strain tensile curve of the substrate film according to the present invention shows that the mechanical strength of the film is about 50 MPa, which is better than that of pure PLA film (about 30-40 MPa). The film samples were tested using an Instron 5565A universal testing machine.

[0034] Figure 5 To obtain the X-ray diffraction pattern of the substrate thin film according to the present invention, a PANalytical X'pert PROMRD X-ray diffractometer was used. The sample was uniformly placed on a silicon wafer and placed together in the X-ray diffractometer to obtain the data.

[0035] Figure 6 To obtain the X-ray diffraction curve of the infrared reflective mulch film according to the present invention, a PANalytical X'pertPRO MRD X-ray diffractometer was used. The sample was placed uniformly on a silicon wafer and then placed together in the X-ray diffractometer to obtain the data.

[0036] Figure 7The figure shows the reflectance curves of the infrared reflective mulch film, polypropylene mulch film, and PLA mulch film according to the present invention. As can be seen from the figure, the infrared reflective mulch film according to the present invention has high reflectance throughout the entire film, especially in the wavelength range of 250-1000 nm, while the polypropylene mulch film and pure PLA mulch film have lower reflectance. This demonstrates the excellent infrared light reflection function of the infrared reflective mulch film, which effectively reflects and refracts sunlight directly hitting the agricultural mulch film. On the one hand, it effectively reduces the direct sunlight exposure of crops inside the mulch film, lowers the temperature inside the film, improves crop survival rate, and avoids the problem of crop death due to excessively high internal temperature. On the other hand, it allows the shaded side of the crop to also effectively receive reflected sunlight, resulting in uniform light exposure and promoting full maturity of the crop. The tests were conducted using a PerkinElmer LAMBDA 750S UV-Vis-NIR spectrophotometer.

[0037] Figure 8 The images are scanning electron microscope (SEM) images of the fracture surface of the mulch film according to the present invention. Due to the addition of nano-oyster shells, the composite film has the effect of resisting crack propagation and tearing when subjected to external forces, thereby improving the tensile strength of the film. The SEM images of the samples were obtained using a GeminiSEM 500 Schottky field emission scanning electron microscope at an accelerating voltage of 3 kV. All samples were sputtered with platinum at a current of 30 mA for 60 s.

[0038] Figure 9 Scanning electron microscope (SEM) images of TiO2-MA raw materials show that the diameter of the sheets is approximately tens of micrometers. After being combined with CNF, they exhibit excellent reflectivity. SEM images of the samples were obtained using a GeminiSEM 500 Schottky field emission scanning electron microscope at an accelerating voltage of 3 kV. All samples were sputtered with platinum at a current of 30 mA for 60 s.

[0039] Figure 10 The images show digital photographs of the reverse (A) and front (B) sides of the composite film after the second composite layer is applied. As can be seen from the images, the film remains relatively uniform and the surface is relatively smooth after the second functional layer is applied.

[0040] Figure 11 This is a digital photograph of the slurry formed after pure PLA has been melted.

[0041] Figure 12 This is a digital photograph of pure PLA after it has been melted and then composited and encapsulated with the first two layers. The infrared reflective mulch film is obtained after hot pressing.

[0042] Figure 13 The curve shows the temperature change of the soil during an actual soil light test using the composite mulch film prepared in Example 1.

[0043] Figure 14 The figure shows the stress-strain tensile curve of the mulch film in Example 1. The mechanical strength of the film is approximately 130 MPa. The film samples were tested using an Instron 5565A universal testing machine.

[0044] Figure 15 The curve shows the temperature change of the soil during an actual soil light test using the composite mulch film prepared in Example 2.

[0045] Figure 16 The figure shows the stress-strain tensile curve of the mulch film in Example 2. It can be seen from the figure that the mechanical strength of the film is approximately 170 MPa. The film sample was tested using an Instron 5565A universal testing machine.

[0046] Figure 17 The curve shows the temperature change of the soil during an actual soil light test using the composite mulch film prepared in Example 3.

[0047] Figure 18 The figure shows the stress-strain tensile curve of the mulch film in Example 3. It can be seen from the figure that the mechanical strength of the film is approximately 150 MPa. The film sample was tested using an Instron 5565A universal testing machine.

[0048] Figure 19 The temperature change curves of the soil during actual soil illumination testing are shown for comparison between the uncovered mulch film in Example 1 and the infrared light-reflecting agricultural mulch film of the present invention.

[0049] Figure 20 The temperature change curves of the soil during actual soil illumination tests are shown for comparison between the first layer of mulch film alone in Example 2 and the infrared light-reflecting agricultural mulch film of the present invention.

[0050] Figure 21 The temperature change curves of the soil during actual soil illumination testing are compared between the polylactic acid mulch film alone in Example 3 and the infrared light-reflecting agricultural mulch film of the present invention.

[0051] Figure 22 The temperature change curves of the soil during actual soil illumination tests are compared between the commercial polypropylene mulch film in Example 4 and the infrared light-reflecting agricultural mulch film of the present invention.

[0052] Figure 23 The temperature change curves of the soil during actual soil illumination testing are compared between the composite mulch film with the middle layer replaced by commercial polypropylene mulch film in Comparative Example 5 and the infrared light reflective agricultural mulch film of the present invention. Detailed Implementation

[0053] This application provides an infrared-reflective biodegradable agricultural mulch film and its preparation strategy. This mulch film not only has excellent infrared reflection and cooling effects, but also superior mechanical properties and biodegradability. It can effectively improve crop yield and growth quality, significantly enhance the efficiency and stability of agricultural production, and is of great significance for promoting sustainable agricultural development.

[0054] According to one embodiment of this application, an infrared light-reflecting biodegradable agricultural mulch film is provided, which includes at least the following three parts: a base film as the first layer, which is composed of PLA, PBAT and nano oyster shell composite; a second layer located on at least one side of the base film, which is formed by uniformly composited CNF and nano pearlescent powder (TiO2-MA) onto the base foil film; and a pure PLA layer as the third layer, which is located on at least one side, or preferably both sides, of the second layer for the purpose of encapsulation.

[0055] In this disclosure, the term "encapsulation" refers to the formation of one or more thin films on a substrate through techniques such as lamination or deposition to reduce the exchange of substances between the substrate and the external environment, thereby protecting the substrate or the external environment and improving the stability and service life of the product.

[0056] In this disclosure, the term "nano-oyster shell" or "Nano-OS" refers to nanoscale powder materials obtained by chemical and physical means from oyster shells. Oyster shells are the outer shells of oysters, hard shells composed of calcium and other inorganic substances, primarily calcium carbonate, while also containing small amounts of protein and other minerals. Oyster shells are commonly used in the production of handicrafts, pharmaceuticals, and feed additives. They are also used as soil conditioners in agriculture, improving soil aeration and water retention, regulating soil pH, and promoting plant growth.

[0057] In this disclosure, the terms "cellulose nanocellulose" or "CNF" mean that the size of the fibrous material is in the nanoscale range. For example, Sargassum-based cellulose nanofibers obtained from Sargassum have a diameter distribution range of 5-60 nm and satisfy at least one of the following properties: an aspect ratio distribution range of 20-400, a crystallinity distribution range of 80-95%, a surface charge distribution range of -60 to -10 mV, and contain at least one hemicellulose component containing carboxyuronic acid.

[0058] In this disclosure, the term "nano pearlescent powder" or "TiO2-MA" refers to a nano-sized powder extracted and modified from pearlescent powder. Pearlescent powder is a cosmetic ingredient, typically composed of fine glitter or colored particles, providing a shimmering effect. These glitter or colored particles are usually made from non-toxic and harmless components such as silicates, TiO2, and iron oxide. Pearlescent powder has a wide range of applications, commonly used in decoration.

[0059] In this disclosure, PBAT is a biodegradable polyester material composed of a copolymer of poly(butylene adipate) / poly(terephthalate).

[0060] In this disclosure, the base film, serving as the first layer, is composed of PLA, PBAT, and nano-oyster shells. Compared to traditional pure PLA or pure PBAT mulch films, the addition of nano-oyster shells results in mulch films with superior mechanical properties. (See attached...) Figure 4 As can be seen, the mechanical strength of the substrate film is about 50 MPa, which is better than that of pure PLA film (about 30-40 MPa) and pure PBAT film (about 15-25 MPa).

[0061] In some preferred embodiments of this disclosure, the second layer is preferably disposed on both sides of the substrate film serving as the first layer.

[0062] In some preferred embodiments of this disclosure, the third layer is preferably disposed on both sides of the base film serving as the second layer to encapsulate the first and second layers. This can better improve the weather resistance of the mulch film during actual use and ensure that the mulch film can be used in the soil for a long time and maintain its effectiveness.

[0063] In an embodiment of the present invention, the three parts are assembled in the order of the first layer, the second layer, and the third layer.

[0064] In some preferred embodiments of this disclosure, other layers beneficial to agricultural mulch films may be present between the first and second layers to achieve certain specific properties suitable for agricultural mulch films. Similarly, other layers beneficial to agricultural mulch films may also be present between the second and third layers to achieve certain specific properties suitable for agricultural mulch films.

[0065] In the invented infrared light reflective biodegradable agricultural mulch film, based on the total mass of the base film as the first layer, the mass fraction of PLA is 20%-70%, preferably 30%-50%, more preferably 35%-40%; the mass fraction of PBAT is 20%-70%, preferably 30%-55%; and the mass fraction of Nano-OS is 5%-20%, preferably 10%-20%, more preferably 15%-20%.

[0066] In the invented infrared light reflective biodegradable agricultural mulch film, based on the total mass of the base film as the second layer, the mass fraction of CNF is 10%-30%, preferably 15%-30%, more preferably 15%-25%; the mass fraction of TiO2-MA is 70%-90%, preferably 75%-90%, more preferably 85%-90%.

[0067] In some preferred embodiments of this disclosure, CNF and TiO2-MA, which serve as the second layer, are uniformly composited onto the base film. This facilitates the formation of a relatively flat infrared reflection region, thereby achieving efficient and uniform reflection of infrared light.

[0068] In some preferred embodiments of this disclosure, the thickness of the first layer of the composite agricultural mulch film is 20-40 μm, preferably 25-35 μm, and more preferably 20-30 μm.

[0069] In some preferred embodiments of this disclosure, the thickness of the second layer of the composite agricultural mulch film is 25-50 μm, preferably 30-45 μm, and more preferably 35-40 μm.

[0070] In some preferred embodiments of this disclosure, the thickness of the third layer of the composite agricultural mulch film is 5-20 μm, preferably 5-15 μm, and more preferably 10-15 μm.

[0071] In addition, this disclosure provides a method for preparing an infrared-reflective biodegradable agricultural mulch film, the method comprising the following steps:

[0072] A) PLA, PBAT and Nano-OS are compounded in proportion to form composite granules, and then the composite granules are blow-molded to form a film as a substrate;

[0073] B) CNF and TiO2-MA are combined in a certain proportion to prepare a composite slurry, and then the composite slurry is coated, preferably sprayed, onto the substrate to obtain the second layer;

[0074] C) Pure PLA is preferably coated onto the second layer by scraping to obtain a structure with at least three thin film layers;

[0075] D) The structure is hot-pressed to obtain the infrared-reflective biodegradable agricultural mulch film.

[0076] In one specific embodiment of this disclosure, the method for preparing the infrared-reflective biodegradable agricultural mulch film includes the following steps:

[0077] A) PLA, PBAT and Nano-OS are compounded in proportion to form composite granules, and then the composite granules are blow-molded to form a base film as the first layer;

[0078] B) CNF and TiO2-MA are combined in a certain proportion to prepare a composite slurry, and then the composite slurry is coated on the substrate to obtain the second layer;

[0079] C) Pure PLA is coated onto the second layer to obtain a structure with at least three thin film layers;

[0080] D) The structure is hot-pressed to obtain the infrared-reflective biodegradable agricultural mulch film.

[0081] In the first layer obtained, the specific composite ratio range of PLA, PBAT and Nano-OS granules is as follows: the mass fraction of PLA is 20%-70%, preferably 30%-50%, more preferably 35%-40%; the mass fraction of PBAT is 20%-70%, preferably 30%-55%; and the mass fraction of Nano-OS is 5%-20%, preferably 10%-20%, more preferably 15%-20%.

[0082] In the obtained second layer, the mass fraction of CNF is 10%-30%, preferably 15%-30%, more preferably 15%-25%; the mass fraction of TiO2-MA is 70%-90%, preferably 75%-90%, more preferably 85%-90%.

[0083] C) The third layer is composed of pure PLA and serves as an encapsulation layer.

[0084] D) The composite agricultural mulch film is formed by pressing three layers of film together using a hot press.

[0085] According to a specific embodiment of this disclosure, in the method for preparing the infrared-reflective biodegradable agricultural mulch film of the present invention, the preparation method of the first layer of composite granules of the agricultural mulch film is a twin-screw mixer. A certain proportion of PLA, PBAT, and Nano-OS powders are added to a twin-screw mixer for compounding. The mixing temperature range of the twin-screw mixer is 170℃-220℃, preferably 180℃-200℃. Specifically, the PLA has a weight-average molecular weight range of 11000-11500 Da, a melt index range of 10-12 g / 10 min, a melting point range of 150-165℃, a glass transition temperature range of 60-65℃, and a relative viscosity range of 1.5-2.0; the PBAT has a crystallization temperature range of 105-110℃, a melting point range of 110-140℃, and a density range of 1.0-1.3 g / ml. -1The crystallinity ranges from 30% to 35%; the diameter of the above Nano-OS sheets ranges from 100 to 300 nm, preferably from 200 to 300 nm.

[0086] According to a specific embodiment of this disclosure, in the method for preparing the infrared light reflective biodegradable agricultural mulch film of the present invention, the first layer of the composite agricultural mulch film is prepared by blow molding, and the blowing method is one of flat extrusion upper blowing, flat extrusion lower blowing, and flat extrusion flat blowing, preferably the flat extrusion upper blowing method for preparing the film.

[0087] According to a specific embodiment of this disclosure, in the method for preparing the infrared-reflective biodegradable agricultural mulch film of the present invention, the second layer of the composite agricultural mulch film is prepared by spraying. On a substrate of the first layer, a certain concentration of CNF / TiO2-MA composite slurry is coated, preferably by spraying, onto the first layer after hydrophilic treatment. The mass fraction of CNF dispersion is 10%-20%, and the mass fraction of TiO2-MA is 80%-90%. Subsequently, it is placed in an oven for drying. The oven temperature range is 80-100℃, preferably 85-95℃, more preferably 90-95℃; the drying time is 5-8 h, preferably 5-7 h, more preferably 6-7 h. The flow rate and pressure range of the spray gun is 0.3-0.5 MPa, preferably 0.35-0.45 MPa; the atomization pressure is 0.05-0.15 MPa, preferably 0.01-0.15 MPa. The hydrophilic treatment of the first layer is achieved through one of plasma treatment, corona treatment, and chemical modification, with plasma treatment being the preferred method. The purpose of the hydrophilic treatment is primarily to alter the surface properties of the first-layer base film, making its surface hydrophilic. This promotes the adsorption and diffusion of the CNF / TiO2-MA composite slurry, allowing the slurry to spread more evenly and form a dense infrared reflective layer. The hydrophilic treatment time is 10-30 min, preferably 10-25 min, and more preferably 10-15 min.

[0088] According to a specific embodiment of this disclosure, in the method for preparing the infrared-reflective biodegradable agricultural mulch film of the present invention, the CNF used in the second layer of the composite agricultural mulch film is derived from agricultural waste biomass raw materials, specifically one of Sargassum fusiforme, coconut palm, rice straw, corn stalks, and bagasse. The CNF possesses at least one of the following properties:

[0089] i) The diameter of the CNF is 5-70 nm (e.g., it can be 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, 55 nm, 70 nm, etc., or within the range formed by these values, such as 5-10 nm, 35-40 nm, etc.), preferably 15-45 nm, more preferably 20-40 nm;

[0090] ii) The aspect ratio of the CNF is 50-400 (e.g., it can be 50, 10, 120, 140, 300, etc., or within the range formed by these values, such as 10-120, 150-350, etc.), and the aspect ratio is preferably 150-250, more preferably 200-250;

[0091] iii) The crystallinity of the CNF is 75-95% (e.g., it can be 75%, 90%, 92%, etc., or within the range formed by these values, such as 86%-88%, etc.), preferably 86-90%, and more preferably 88-90%;

[0092] iv) The CNF contains at least one or more hemicellulose components containing carboxyuronic acid (e.g., at least one selected from Man-UA, Glc-UA and Gul-UA), preferably containing both Man-UA and Glc-UA, more preferably containing both Man-UA, Glc-UA and Gul-UA.

[0093] v) The surface charge of the CNF is -50 to -10 mV (e.g., it can be -50, -40, -35, -25, -10, etc., or within the range formed by these values, such as -40 to -30, etc.), preferably -50 to -20, more preferably -30 to -20.

[0094] According to a specific embodiment of this disclosure, in the method for preparing the infrared light-reflecting biodegradable agricultural mulch film of the present invention, the TiO2-MA powder used in the second layer of the composite agricultural mulch film has at least one of the following properties:

[0095] i) The mesh size of the TiO2-MA is 300-800 mesh (e.g., it can be 300 mesh, 350 mesh, 380 mesh, 400 mesh, 500 mesh, 600 mesh, 700 mesh and 800 mesh, etc., or within the range formed by these values, such as 400-600 mesh, 500-550 mesh, etc.), preferably 400-600 mesh, more preferably 500-550 mesh;

[0096] ii) The color of the TiO2-MA is one or a combination of white, silver and pink (for example, it can be a 1:1 mixture of white and silver, a 1:1 mixture of white and pink, a mixture of the three in equal proportions, etc.), preferably a 7:3 mixture of white and silver, more preferably a 1:1 mixture of white and silver.

[0097] According to a specific embodiment of this disclosure, in the method for preparing the infrared light-reflecting biodegradable agricultural mulch film of the present invention, the third layer of the composite agricultural mulch film is prepared by scraping coating, and the composite film is obtained after drying at room temperature for 20-60 minutes after scraping coating. The scraping coating is performed using one of a coating machine, a micrometer scraper, a fixed-value scraper, and a coating rod, preferably using a coating machine, and more preferably using a micrometer scraper for film scraping.

[0098] According to a specific embodiment of this disclosure, the method for preparing the infrared-reflective biodegradable agricultural mulch film of the present invention involves hot pressing of the composite agricultural mulch film. The pressing pressure range of the pressing machine is 1-2 MPa, preferably 1-1.5 MPa, more preferably 1-1.2 MPa; the hot pressing temperature range is 40-80℃, preferably 50-75℃, more preferably 60-75℃.

[0099] In summary, this disclosure provides an infrared-reflective biodegradable agricultural mulch film and its preparation method, relating to the fields of infrared light reflection and agricultural mulch film technology. The described infrared-reflective biodegradable agricultural mulch film is composed of three layers. The first layer is a base layer, mainly composed of polylactic acid (PLA), polybutylene adipate / terephthalate (PBAT), and nano-oyster shells (Nano-OS) in a specific ratio, serving to support the entire agricultural mulch film. The second functional layer is formed by uniformly composited cellulose nanofibers (CNF) and nano-pearl powder (TiO2-MA) onto the base film. The addition of TiO2-MA effectively achieves reflective cooling while also providing supplemental lighting for crops, effectively reducing the temperature of the film-covered area. The third encapsulation layer is formed by laminating a thin layer of pure PLA onto the first and second layers to achieve encapsulation. The three-layer composite agricultural mulch film preparation strategy proposed in this invention integrates excellent infrared reflective cooling, mechanical properties, and biodegradability. By covering the soil surface with this high-performance agricultural mulch film, Nano-OS, with its excellent water absorption, effectively promotes the degradation of the mulch film. The second layer possesses excellent infrared light reflection capabilities, effectively reflecting and refracting sunlight directly hitting the mulch film. This effectively reduces direct sunlight exposure to crops inside the mulch film, lowers the internal temperature, improves crop survival rates, and prevents crop death due to excessive internal temperature. Furthermore, it allows the shaded side of the crop to receive reflected sunlight, ensuring uniform light exposure and promoting full maturity. The mulch film of this invention not only has excellent infrared reflection and cooling effects but also superior mechanical properties and biodegradability, effectively improving crop yield and growth quality, and significantly increasing agricultural production efficiency. Therefore, it is expected to have promising industrial applications.

[0100] To further understand the present invention, an infrared light-reflecting biodegradable agricultural mulch film and its preparation method are further described below with reference to embodiments. The scope of protection of the present invention is not limited to the following embodiments.

[0101] Example

[0102] Polylactic acid (PLA), polybutylene adipate / terephthalate (PBAT), nano pearlescent powder (TiO2-MA), multi-source cellulose nanocellulose (CNF), and nano oyster shell (Nano-OS) were all purchased from Anhui Zhongke Micro-Nano New Materials Co., Ltd.

[0103] Example 1 of agricultural mulch film

[0104] A) Weigh the PLA, PBAT, and Nano-OS sheet materials in a ratio of 2:7:1. The PLA has a weight-average molecular weight of 11000-11500 Da, a melt index of 10-12 g / 10 min, a melting point of 150-165℃, a glass transition temperature of 60-65℃, and a relative viscosity of 1.5-2.0. The PBAT has a crystallization temperature of 105-110℃, a melting point of 110-140℃, and a density of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%; the diameter of the above Nano-OS sheets ranges from 100 to 300 nm.

[0105] B) The three raw materials are mixed and then added to a twin-screw internal mixer for compounding. The mixing temperature of the twin-screw internal mixer is 180℃. The compound granules are then extruded. The model of the twin-screw internal mixer is: Wuhan Ruiming Experimental Instrument Manufacturing Co., Ltd., Micro Twin-Screw Extruder SJZS-10;

[0106] C) The obtained granules are blown by flat extrusion to obtain the first base film. The composite film blow molding machine is MFSJ-2L, and the thickness of the base film is about 25 μm.

[0107] D) The obtained film is placed in the vacuum chamber of a plasma treatment machine for hydrophilic surface treatment, which takes 25 minutes. The model of the vacuum plasma machine is: Shanghai Maohong Plasma Technology Co., Ltd., Jinjunhong C-10S plasma surface treatment equipment;

[0108] E) Take a certain amount of coconut fiber cellulose nanofibers (CNF) and TiO2-MA. The CNF has a diameter of 5-70 nm, an aspect ratio of 50-400, a crystallinity of 90%, and contains hemicellulose components such as Man-UA uronic acid. The TiO2-MA has a mesh size of 300 mesh and a white:silver ratio of 1:1. Combine the CNF and TiO2-MA in a 2:8 ratio to obtain a spraying slurry. Then, spray the composite slurry onto a plasma-treated substrate using a spray gun and dry it in an oven for 6 hours at 90℃. The spray gun's flow rate and pressure range is 0.3-0.5 MPa, and the atomization pressure is 0.05-0.15 MPa; the thickness is approximately 40 μm.

[0109] F) Then, pure PLA slurry was scraped onto the above composite film using a spiral micrometer scraper. After drying at room temperature for 20 minutes, the thickness of the PLA layer was about 10 μm, resulting in an integrated agricultural mulch film.

[0110] G) The composite film is then sandwiched with a polytetrafluoroethylene (PTFE) film, and two mirror panels are placed on the outside of the PTFE film. The film is then placed on a tablet press and hot-pressed for 50 minutes to finally obtain the composite agricultural mulch film. The hot-pressing temperature is 60℃ and the pressure is 1 MPa. The tablet press model is YP-40T laboratory powder tablet press.

[0111] H) The obtained composite film was placed in actual soil for experimental testing, and the composite film showed excellent mechanical properties and actual cooling effect.

[0112] I) The obtained first-layer composite film was placed in actual soil for experimental testing. The designed experimental conditions were as follows: first, a solar radiation meter was used to calibrate and determine the solar radiation intensity at height and range, and the calibrated solar irradiance was approximately 975 W / m². 2 The soil was then placed into a box with a diameter of approximately 10 cm, to a depth of approximately 4 cm. A thermocouple was inserted to a depth of 2 cm, and an infrared reflective mulch film was placed over the soil. The thermocouple continuous recording mode was then activated to record the soil temperature change curve under sunlight over 9 hours. The solar radiation measuring instrument model was: Yigu, thermoelectric solar radiation measuring instrument, YGC-TBQ, MF6563; the thermocouple model was: Kaipusen, high-precision portable thermocouple thermometer, KPS-YET, CZ3452.

[0113] J) The initial soil temperature was approximately 24.05℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 26.65℃, with the actual temperature increase being only about 2.6℃.

[0114] Example 2 of agricultural mulch film

[0115] A) Weigh a certain amount of PLA, PBAT, and Nano-OS sheet materials in a ratio of 3:5.5:1.5. The PLA has a weight-average molecular weight of 11000-11500 Da, a melt index of 10-12 g / 10 min, a melting point of 150-165℃, a glass transition temperature of 60-65℃, and a relative viscosity of 1.5-2.0. The PBAT has a crystallization temperature of 105-110℃, a melting point of 110-140℃, and a density of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%; the diameter of the above Nano-OS sheets ranges from 200 to 300 nm.

[0116] B) The three raw materials are mixed and then added to a twin-screw internal mixer for compounding. The mixing temperature of the twin-screw internal mixer is 180℃. The compound granules are then extruded. The model of the twin-screw internal mixer is: Wuhan Ruiming Experimental Instrument Manufacturing Co., Ltd., Micro Twin-Screw Extruder SJZS-10;

[0117] C) The obtained granules are blown by flat extrusion and blow molding to obtain the first base film. The composite film blow molding machine is MFSJ-2L, and the thickness of the base film is about 20 μm.

[0118] D) The obtained film is placed in the vacuum chamber of a plasma treatment machine for hydrophilic surface treatment, which takes 12 minutes. The model of the vacuum plasma machine is: Shanghai Maohong Plasma Technology Co., Ltd., Jin Junhong C-10S plasma surface treatment equipment;

[0119] E) Take a certain amount of coconut fiber cellulose nanofibers (CNF) and TiO2-MA. The CNF has a diameter of 5-70 nm, an aspect ratio of 50-400, a crystallinity of 90%, and contains hemicellulose components such as Man-UA uronic acid. The TiO2-MA has a mesh size of 300 mesh and a white to silver composition of 1:1. After compounding with CNF in a 2:8 ratio, the composite slurry is sprayed onto a plasma-treated substrate using a spray gun and dried in an oven for 6.5 h at 90℃. The spray gun has a flow rate and pressure range of 0.3-0.5 MPa and an atomization pressure of 0.05-0.15 MPa; the thickness is approximately 40 μm.

[0120] F) Then, pure PLA slurry was scraped onto the above composite film using a spiral micrometer scraper. After drying at room temperature for 25 minutes, the thickness of the PLA layer was about 15 μm, resulting in an integrated agricultural mulch film.

[0121] G) The composite film is then sandwiched between polytetrafluoroethylene (PTFE) films, and two mirror panels are placed on the outside of the PTFE film. The film is then placed on a tablet press and hot-pressed for 50 minutes to finally obtain the composite agricultural mulch film. The hot-pressing temperature is 75℃ and the pressure is 1.1 MPa. The tablet press model is YP-40T laboratory powder tablet press.

[0122] H) The obtained composite film was placed in actual soil for experimental testing, and the composite film showed excellent mechanical properties and actual cooling effect.

[0123] I) The initial soil temperature was approximately 24.69℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 26.77℃, with the actual temperature increase being only about 2.08℃.

[0124] Example 3 of agricultural mulch film

[0125] A) Weigh a certain amount of PLA, PBAT, and Nano-OS sheet materials in a ratio of 3:5.5:1.5. The PLA has a weight-average molecular weight of 11000-11500 Da, a melt index of 10-12 g / 10 min, a melting point of 150-165℃, a glass transition temperature of 60-65℃, and a relative viscosity of 1.5-2.0. The PBAT has a crystallization temperature of 105-110℃, a melting point of 110-140℃, and a density of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%; the diameter of the above Nano-OS sheets ranges from 200 to 300 nm.

[0126] B) The three raw materials are mixed and then added to a twin-screw internal mixer for compounding. The mixing temperature of the twin-screw internal mixer is 180℃. The compound granules are then extruded. The model of the twin-screw internal mixer is: Wuhan Ruiming Experimental Instrument Manufacturing Co., Ltd., Micro Twin-Screw Extruder SJZS-10;

[0127] C) The obtained granules are blown by flat extrusion and blow molding to obtain the first base film. The composite film blow molding machine is MFSJ-2L, and the thickness of the base film is about 25 μm.

[0128] D) The obtained film is placed in the vacuum chamber of a plasma treatment machine for hydrophilic surface treatment, which takes 15 minutes. The model of the vacuum plasma machine is: Shanghai Maohong Plasma Technology Co., Ltd., Jinjunhong C-10S plasma surface treatment equipment;

[0129] E) Take a certain amount of Sargassum fusiforme cellulose nanofibers and TiO2-MA. The Sargassum fusiforme CNF has a diameter of 5-70 nm, an aspect ratio of 50-400, a crystallinity of 90%, and contains hemicellulose components such as Man-UA uronic acid. The TiO2-MA has a mesh size of 300 mesh and a white:silver ratio of 7:3. A spraying slurry is prepared by combining Sargassum fusiforme CNF and TiO2-MA in a ratio of 2.5:7.5. The composite slurry is then sprayed onto a plasma-treated substrate using a spray gun and dried in an oven for 6.5 h at 90℃. The spray gun's flow rate and pressure range is 0.3-0.5 MPa, and the atomization pressure is 0.05-0.15 MPa; the thickness is approximately 30 μm.

[0130] F) Then, pure PLA slurry was scraped onto the above composite film using a spiral micrometer scraper. After drying at room temperature for 20 minutes, the thickness of the PLA layer was about 10 μm, resulting in an integrated agricultural mulch film.

[0131] G) The composite film is then sandwiched between polytetrafluoroethylene (PTFE) films, and two mirror panels are placed on the outside of the PTFE film. The film is then placed on a tablet press and hot-pressed for 50 minutes to finally obtain the composite agricultural mulch film. The hot-pressing temperature is 75℃ and the pressure is 1.1 MPa. The tablet press model is YP-40T laboratory powder tablet press.

[0132] H) The obtained composite film was placed in actual soil for experimental testing, and the composite film showed excellent mechanical properties and actual cooling effect.

[0133] I) The initial soil temperature was approximately 22.89℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 22.93℃, with an actual temperature increase of only about 0.04℃.

[0134] Comparative Example 1

[0135] A) The soil was placed directly under the simulated sunlight without any covering film for about 8 hours, and the temperature change of the soil was continuously recorded using thermocouples.

[0136] B) The initial soil temperature was approximately 31.7℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 48.75℃, with an actual temperature increase of approximately 17℃.

[0137] Comparative Example 2

[0138] A) Weigh a certain amount of PLA, PBAT, and Nano-OS sheet materials in a ratio of 2:7:1. The PLA has a weight-average molecular weight of 11000-11500 Da, a melt index of 10-12 g / 10 min, a melting point of 150-165℃, a glass transition temperature of 60-65℃, and a relative viscosity of 1.5-2.0. The PBAT has a crystallization temperature of 105-110℃, a melting point of 110-140℃, and a density of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%; the diameter of the above Nano-OS sheets ranges from 100 to 300 nm.

[0139] B) The three raw materials are mixed and then added to a twin-screw internal mixer for compounding. The mixing temperature of the twin-screw internal mixer is 180℃. The compound granules are then extruded. The model of the twin-screw internal mixer is: Wuhan Ruiming Experimental Instrument Manufacturing Co., Ltd., Micro Twin-Screw Extruder SJZS-10;

[0140] C) The obtained granules are blown into a film by flat extrusion blow molding. The composite film blow molding machine is MFSJ-2L, and the film thickness is about 25 μm.

[0141] D) The obtained first layer composite film was placed in actual soil for experimental testing. It was placed under simulated sunlight for about 8 hours, and the temperature change of the soil was continuously recorded using thermocouples.

[0142] The initial soil temperature was approximately 27.31℃, and thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 50.35℃, with an actual temperature increase of approximately 23.04℃.

[0143] Comparative Example 3

[0144] A) Take a certain mass of pure PLA granules and melt them in a high-temperature oven. The PLA has a weight-average molecular weight range of 11000-11500 Da, a melt index range of 10-12 g / 10 min, a melting point range of 150-165℃, a glass transition temperature range of 60-65℃, and a relative viscosity range of 1.5-2.0.

[0145] B) Pure PLA slurry was scraped onto the substrate using a spiral micrometer scraper, dried at room temperature for 30 min, and then peeled off to obtain pure PLA agricultural mulch film with a thickness of approximately 20 μm.

[0146] C) The obtained single-layer polylactic acid film was placed in actual soil for experimental testing. It was placed under simulated sunlight for about 8 hours, and the temperature change of the soil was continuously recorded using thermocouples.

[0147] D) The initial soil temperature was approximately 26.68℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 45.03℃, with an actual temperature increase of approximately 18.35℃.

[0148] Comparative Example 4

[0149] A) Commercial polypropylene mulch film was placed on the soil and exposed to simulated sunlight for about 8 hours. The temperature changes of the soil were continuously recorded using thermocouples.

[0150] B) The initial soil temperature was approximately 27.28℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 48.77℃, with an actual temperature increase of approximately 21.49℃.

[0151] Comparative Example 5

[0152] A) The preparation process and specific implementation method of the material in Comparative Example 5 are the same as those in Example 1, except that the second layer, namely the composite layer of CNF and TiO2-MA, is replaced with the commonly used PP agricultural mulch film material.

[0153] B) Cover the soil with composite mulch film and place it under simulated sunlight for about 8 hours. Use thermocouples to continuously record the temperature changes of the soil.

[0154] C) The initial soil temperature was approximately 24.37℃. Thermocouples were used to record the soil temperature at a solar irradiance of approximately 975 W / m². 2 Under light intensity, the soil temperature change curve over a period of approximately 8 hours of illumination showed that the final soil temperature was approximately 44.64℃, with an actual temperature increase of approximately 20.27℃.

[0155] The results of the above embodiments and comparative examples clearly show that the infrared light-reflecting biodegradable agricultural mulch film according to the present invention can effectively reduce the soil surface temperature when exposed to sunlight, and has a very good effect of reflecting sunlight.

[0156] The above descriptions of specific embodiments and examples are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles and spirit, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. An infrared-reflective biodegradable agricultural mulch film, comprising at least: The base layer, which serves as the first layer, is composed of PLA, PBAT, and nano-oyster shell composite. As a second layer, a cellulose nanofiber / nanopearl functional layer is disposed on at least one side of the substrate layer; and The PLA layer, serving as the third layer, is disposed on at least one side of the cellulose nanofiber / nanopearl functional layer. in, Based on the total mass of the substrate layer, the mass fraction of PLA is 20%-70%, the mass fraction of PBAT is 20%-70%, and the mass fraction of nano-oyster shells is 5%-20%. Based on the total mass of the cellulose nanofiber / nanopearl functional layer, which serves as the second layer, the mass fraction of cellulose nanofiber is 10%-30%, while the mass fraction of nanopearl is 70%-90%. The first layer has a thickness of 20-40 μm, the second layer has a thickness of 25-50 μm, and the third layer has a thickness of 5-20 μm.

2. The infrared-reflective biodegradable agricultural mulch film according to claim 1, wherein, The cellulose nanocellulose used in the cellulose nanocellulose / nanopearl functional layer of the agricultural mulch film has at least one of the following properties: i) The diameter of the cellulose nanofibers is 5-70 nm; ii) The aspect ratio of the cellulose nanocellulose is 50-400; iii) The crystallinity of the cellulose nanocellulose is 75-95%; iv) The cellulose nanocellulose contains at least one hemicellulose component containing carboxylic uronic acid; v) The surface charge of the cellulose nanocellulose is -50 to -10 mV.

3. The infrared-reflective biodegradable agricultural mulch film according to claim 1, wherein the PLA has a weight-average molecular weight range of 11000-11500 Da, a melt index range of 10-12 g / 10 min, a melting point range of 150-165℃, a glass transition temperature range of 60-65℃, and a relative viscosity range of 1.5-2.

0. The PBAT has a crystallization temperature range of 105-110℃, a melting point range of 110-140℃, and a density range of 1.0-1.3 g / ml. -1 The crystallinity ranges from 30% to 35%. The diameter of the nano-oyster shell sheets ranges from 100 to 300 nm.

4. The infrared light-reflecting biodegradable agricultural mulch film according to claim 1, wherein, The cellulose nanocellulose is derived from agricultural waste biomass raw materials, selected from one of Sargassum fusiforme, coconut palm, rice straw, corn stalks, and bagasse.

5. A method for preparing an infrared-reflective biodegradable agricultural mulch film according to any one of claims 1-4, wherein, The method includes the following steps: A) PLA, PBAT and nano oyster shells are compounded in proportion to form composite granules, and then the composite granules are blow-molded to form a base film as the first layer; B) A composite slurry is prepared by combining cellulose nanofiber and nano pearl powder in a certain proportion, and then the composite slurry is coated on the substrate to obtain the second layer; C) Pure PLA is coated onto the second layer to obtain a structure with at least three thin film layers; D) The structure is hot-pressed to obtain the infrared-reflective biodegradable agricultural mulch film.

6. The method for preparing infrared light reflective biodegradable agricultural mulch film according to claim 5, wherein the method for preparing the first layer of composite granules of the agricultural mulch film is a twin-screw internal mixing method, and the internal mixing temperature range of the twin-screw internal mixer is 170℃-220℃.

7. The method for preparing infrared light reflective biodegradable agricultural mulch film according to claim 5, wherein the substrate is pre-treated with hydrophilicity before spraying the composite slurry to form the second layer.

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