Anti-ultraviolet polylactic acid composite degradable agricultural mulching film

Abstract

The utility model relates to the field of agricultural mulching films, and provides an anti-ultraviolet polylactic acid composite degradable agricultural mulching film mainly aiming at the problem of insufficient ultraviolet shielding effect of the existing polylactic acid-based agricultural mulching film, which is characterized by comprising a front packaging layer 1, an ultraviolet shielding layer 2 and a back packaging layer 3 which are sequentially stacked, the ultraviolet shielding layer 2 comprises a structural body formed by compounding polylactic acid and a nanoscale ultraviolet shielding material, and the nanoscale ultraviolet shielding material is of a micro-nano composite structure formed by uniformly mixing a nano sheet layer and a micron sheet layer in the ultraviolet shielding layer 2 and is arranged in a polylactic acid matrix in an oriented manner to form a brick mud structure. The mulching film can effectively reduce aging and degradation of the mulching film caused by ultraviolet radiation, can be effectively used for protecting root systems of crops from being damaged by the ultraviolet radiation, and can be expected to be used in the agricultural field, especially in the agricultural field particularly needing anti-ultraviolet shielding.

Description

Technical Field

[0001] This utility model relates to the field of agricultural mulch film, and in particular to a UV-resistant polylactic acid composite biodegradable agricultural mulch film. Background Technology

[0002] Polylactic acid (PLA) is a widely available, non-toxic, biocompatible, and highly processable biodegradable polymer, widely used in packaging films, biodegradable tableware, and fibers. Furthermore, PLA possesses excellent plasticity and some heat-retaining and moisture-retaining properties, making it a promising candidate for agricultural mulch films. However, PLA's insufficient UV shielding ability leads to degradation and aging of PLA mulch films under UV exposure, affecting their lifespan and functionality, and hindering their widespread application in mulch film production.

[0003] Currently, the main strategy for improving the UV shielding of polylactic acid (PLA) mulch films is to add UV absorbers to the PLA granules. UV absorbers are broadly classified into two categories: organic and inorganic. Common organic absorbers include phenols and styrene, but these organic absorbers possess a certain degree of toxicity, causing damage to organisms and the natural environment both during use and after disposal. Inorganic absorbers are inorganic substances such as metal oxides and metal complexes, with typical examples including zinc oxide and titanium dioxide. However, inorganic UV absorbers have drawbacks such as narrow absorption wavelengths, limited photostability, and poor dispersion, which can introduce mechanical defects when added to PLA films. Furthermore, some UV absorbers possess a certain color, which, when added to PLA mulch films, reduces the film's visible light transmittance, affecting the film's color and performance.

[0004] In summary, how to achieve excellent UV shielding effect of polylactic acid (PLA) agricultural mulch film through structural improvements without affecting its mechanical strength, biodegradability, and visible light transmittance is an urgent problem to be solved in this field. Utility Model Content

[0005] This invention addresses the problem of insufficient UV shielding effect in current polylactic acid (PLA)-based agricultural mulch films by providing a UV-resistant PLA composite biodegradable agricultural mulch film. This film not only maintains the film's light transmittance and mechanical properties but also possesses excellent UV shielding capabilities, effectively blocking UV rays, delaying aging and degradation, and extending the film's lifespan.

[0006] The solution adopted in this utility model is: a UV-resistant polylactic acid composite biodegradable agricultural mulch film. This mulch film includes a front sealing layer (sun-receiving surface), a UV-shielding layer, and a back sealing layer (soil-contact surface). Both the front and back sealing layers are composed of a single polylactic acid film, while the UV-shielding layer is composed of polylactic acid and nano-scale UV-shielding materials in a specific ratio. Because the nano-scale UV-shielding materials are uniformly composited and oriented within the polylactic acid matrix to form a brick-and-mortar structure, this layer exhibits excellent UV-shielding performance. Combined with the front and back sealing layers, while effectively ensuring visible light transmission and excellent mechanical properties, the mulch film's superior UV-shielding effect can significantly improve the efficiency and quality of agricultural production.

[0007] The brick-and-mortar structure refers to a structure in which nanoscale ultraviolet shielding materials, such as mica sheets, are equivalent to the "bricks" in a building wall, while polylactic acid matrix is ​​the "mortar." The mica sheets are arranged in an orderly orientation within the thin film matrix to construct the "brick-and-mortar" structure.

[0008] Preferably, the polylactic acid has a weight-average molecular weight of 11,000-11,500 Da, a melt index of 10-12 g / 10min, a melting point of 150-165℃, a glass transition temperature of 60-65℃, and a relative viscosity of 1.5-2.0.

[0009] Preferably, the diameter of the micron-scale sheets is 20-50 μm, the diameter of the nano-scale sheets is 100-500 nm, and the composite ratio of the nano-scale sheets and the micron-scale sheets is 3:7 to 7:3, preferably 1:1.

[0010] Preferably, the micro-nano composite nanoscale ultraviolet shielding material accounts for 1%-20% of the total mass fraction of the ultraviolet shielding layer.

[0011] During the formation of the ultraviolet shielding layer, nanosheets and microsheets are uniformly mixed in the polylactic acid slurry through shear force deformation assembly. This results in the uniform distribution of micro and nanosheets in the polylactic acid film after drying. Furthermore, the orientation force of the film shear force deformation assembly technology enables the nanosheets and microsheets to achieve oriented arrangement in the polylactic acid film matrix.

[0012] Preferably, the nanoscale ultraviolet shielding material is selected from phlogopite sheets with a micro-nano composite structure.

[0013] Preferably, the thickness of the front encapsulation layer is 10-20 μm, the thickness of the ultraviolet shielding layer is 5-10 μm, and the thickness of the back encapsulation layer is 10-20 μm.

[0014] Preferably, the front encapsulation layer, the ultraviolet shielding layer, and the back encapsulation layer are prepared using a layer-by-layer assembly process, followed by hot pressing at 60-65°C. This assembly method eliminates the need for any adhesives between layers, which helps save on manufacturing costs and reduces environmental pollution caused by the volatilization of VOCs from adhesives.

[0015] The beneficial effects of this invention are as follows: Compared to ordinary polylactic acid (PLA) agricultural mulch films on the market, this invention possesses superior biodegradability, heat retention and moisture retention, processability, and flexibility, while also exhibiting excellent ultraviolet (UV) shielding performance. Under intense outdoor sunlight and UV radiation, the oriented micro-nano UV-shielding material in the PLA mulch film has a multi-layered sheet structure. This structure causes multiple reflections and scatterings of UV rays on the mica sheet surface, resulting in multiple attenuations of UV rays and effectively reducing the penetration depth. Furthermore, the synergistic effects of charge transfer and size effect on the mica surface contribute to the film's excellent UV shielding effect. In summary, this PLA biodegradable composite mulch film effectively ensures visible light transmittance and excellent mechanical properties while reducing aging and degradation caused by UV radiation, thereby reducing the frequency of mulch film replacement and saving agricultural film costs. Secondly, the film's excellent UV shielding effectively protects crop roots from UV radiation damage, promotes crop growth and development, improves crop yield and growth quality, and significantly enhances agricultural production efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of a UV-resistant polylactic acid composite biodegradable agricultural mulch film according to the present invention, wherein 1 is the front sealing layer; 2 is the ultraviolet shielding layer; and 3 is the back sealing layer.

[0017] Figure 2 The reflectance test results of the thin film samples prepared in the ultraviolet band for Example 1 and Comparative Example 1 are shown.

[0018] Figure 3 The image shown is a cross-sectional image of the thin film obtained by scanning electron microscopy (GeminiSEM 500 Schottky field emission scanning electron microscope, 3 kV accelerating voltage) in Example 1.

[0019] Figure 4 Cross-sectional images of the sample prepared for Comparative Example 1 using a scanning electron microscope (GeminiSEM 500 Schottky field emission scanning electron microscope, 3 kV accelerating voltage). Detailed Implementation Plan

[0020] To provide a more detailed and intuitive understanding of this utility model, the following description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the utility model. It should be emphasized that the following description only illustrates preferred embodiments of the utility model and is not intended to limit the utility model. Any simple modifications to the utility model fall within the protection scope of this utility model.

[0021] like Figure 1 As shown, a UV-resistant polylactic acid composite biodegradable agricultural mulch film includes a front sealing layer 1, a UV shielding layer 2, and a back sealing layer 3. The front sealing layer and the back sealing layer are composed of a single polylactic acid film. The polylactic acid 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 ultraviolet shielding layer is composed of polylactic acid and nano-scale ultraviolet shielding material in a certain proportion. The aforementioned nano-scale ultraviolet shielding material adopts micro-nano composite mica sheets. The diameter of the micron sheets is 20-50 μm, and the diameter of the nano sheets is 100-500 nm. The composite ratio of nano sheets and micron sheets is 1:1. The micro-nano composite mica sheets account for 1%-20% of the total mass fraction of the ultraviolet shielding layer. The micro-nano sheets are uniformly distributed in the polylactic acid film by shear force deformation assembly.

[0022] The nanoscale ultraviolet shielding material forms a brick-and-mortar structure through its oriented arrangement and uniform composite in a polylactic acid matrix, giving this layer excellent ultraviolet shielding performance. Combined with the front and back encapsulation layers, the overall thickness of the front encapsulation layer is 10-20 μm, the ultraviolet shielding layer is 5-10 μm, and the back encapsulation layer is 10-20 μm. The three layers are prepared using a layer-by-layer assembly process, and then hot-pressed at 60-65℃ after preparation.

[0023] Example

[0024] Example 1

[0025] This embodiment prepares a UV-resistant polylactic acid composite biodegradable agricultural mulch film, comprising a front encapsulation layer 1, a UV shielding layer 2, and a back encapsulation layer 3. The front encapsulation layer and the back encapsulation layer are composed of a single polylactic acid film. The polylactic acid has a weight-average molecular weight of 11000 Da, a melt index of 12 g / 10 min, a melting point of approximately 160℃, a glass transition temperature of approximately 60℃, and a relative viscosity of 1.8. The UV shielding layer is composed of polylactic acid and nano-scale UV shielding material in a 9:1 ratio. The diameter of the micron-sized mica flakes ranges from 20 to 50 μm, and the diameter of the nano-flakes ranges from 200 to 500 nm. The composite ratio of the nano-mica flakes and the micron-sized flakes is 1:1. Through a shear force deformation assembly method, the micro- and nano-mica flakes are uniformly distributed within the polylactic acid film, forming an oriented brick-and-mortar structure. It is then combined with the front and back encapsulation layers. The overall thickness of the front encapsulation layer is 15 μm, the thickness of the ultraviolet shielding layer is 8 μm, and the thickness of the back encapsulation layer is 15 μm. The three are prepared by a layer-by-layer assembly process. After preparation, it is hot-pressed at 60℃ to obtain the final sample.

[0026] Compare with Example 1

[0027] This embodiment prepares a UV-resistant polylactic acid composite biodegradable agricultural mulch film, comprising a front encapsulation layer 1, a UV shielding layer 2, and a back encapsulation layer 3. The front encapsulation layer and the back encapsulation layer are composed of a single polylactic acid film. The polylactic acid has a weight-average molecular weight of 11000 Da, a melt index of 12 g / 10 min, a melting point of approximately 160℃, a glass transition temperature of approximately 60℃, and a relative viscosity of 1.8. The UV shielding layer is composed of polylactic acid and nano-scale UV shielding material in a 9:1 ratio. The diameter of the micron-sized mica flakes ranges from 20-50 μm, and the diameter of the nanosheets ranges from 200-500 nm. The composite ratio of the nanosheets and micron-sized flakes is 1:1. Subsequently, the mica flakes and polylactic acid are placed upside down on a table and allowed to dry naturally without any external force to form a film. It is then combined with the front and back encapsulation layers. The overall thickness of the front encapsulation layer is 15 μm, the thickness of the ultraviolet shielding layer is 8 μm, and the thickness of the back encapsulation layer is 15 μm. The three are prepared by a layer-by-layer assembly process. After preparation, it is hot-pressed at 60℃ to obtain the final sample.

[0028] Figure 2 The reflectance of the thin film samples prepared in Example 1 and Comparative Example 1 in the ultraviolet band was tested using a UV-Vis-NIR spectrophotometer (Shimadzu Corporation, Solid 3700 DUV). The curves show that the polylactic acid composite film after orientation and uniform lamination exhibits higher reflectance in the ultraviolet band, demonstrating superior ultraviolet shielding capability compared to the film in Comparative Example 1.

[0029] Figure 3 This is a cross-sectional image of the thin film obtained using a scanning electron microscope (GeminiSEM 500 Schottky field emission scanning electron microscope, 3 kV accelerating voltage) in Example 1. It can be seen that the sheets are oriented and arranged in the thin film substrate, forming a "brick-and-mortar" structure, which enhances the ultraviolet shielding performance.

[0030] Figure 4 Cross-sectional images of the sample prepared for Comparative Example 1 using a scanning electron microscope (GeminiSEM 500 Schottky field emission scanning electron microscope, 3 kV accelerating voltage). As shown in the figure, the mica sheets are randomly arranged in the film, without exhibiting an ordered "brick-and-mortar" structure.

[0031] This utility model relates to a UV-resistant polylactic acid composite biodegradable agricultural mulch film. This polylactic acid biodegradable composite agricultural mulch film effectively ensures visible light transmittance and excellent mechanical and processability properties, while also possessing excellent UV shielding performance. It effectively reduces the penetration depth of ultraviolet rays, resulting in a better UV shielding effect, meeting the UV shielding requirements of agricultural mulch films, and improving crop yield and agricultural production efficiency.

Claims

1. A UV-resistant polylactic acid composite biodegradable agricultural mulch film, characterized in that: It includes a front encapsulation layer (1) that serves as the light-receiving surface, an ultraviolet shielding layer (2), and a back encapsulation layer (3) that serves as the soil contact surface, which are stacked in sequence. In the ultraviolet shielding layer (2), phlogopite is oriented and arranged in a polylactic acid matrix to form a brick-and-mortar structure. The phlogopite has a micro-nano composite structure in which nanosheets and microsheets are uniformly combined. The diameter of the micron-scale sheets is 20-50 μm, and the diameter of the nanosheets is 100-500 nm. The thickness of the ultraviolet shielding layer (2) is 5-10 μm.

2. The UV-resistant polylactic acid composite biodegradable agricultural mulch film according to claim 1, characterized in that: The above The thickness of the front encapsulation layer (1) is 10-20 μm, and the thickness of the back encapsulation layer (3) is 10-20 μm.

3. The UV-resistant polylactic acid composite biodegradable agricultural mulch film according to claim 1, characterized in that: The front encapsulation layer (1), the ultraviolet shielding layer (2), and the back encapsulation layer (3) are directly stacked together by hot pressing.

4. The UV-resistant polylactic acid composite biodegradable agricultural mulch film according to claim 1, characterized in that: There is no adhesive layer between the front encapsulation layer (1), the ultraviolet shielding layer (2), and the back encapsulation layer (3).

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