Multilayer composite mulch film and method of making same

Abstract

The present application provides a kind of multilayer composite mulch film, including the outermost layer, secondary outer layer, intermediate layer, secondary inner layer and innermost layer arranged in turn.The outermost layer includes polyethylene compound, antioxidant and ultraviolet absorbent, the density of polyethylene compound is ≤0.910g / cm 3 .Both secondary outer layer and secondary inner layer include polyethylene compound, antioxidant and ultraviolet absorbent, the density of polyethylene compound is 0.917-0.923g / cm 3 . Intermediate layer includes polyethylene compound, antioxidant and ultraviolet absorbent, the density of polyethylene compound is ≥0.935g / cm 3 . Innermost layer includes polyethylene compound, antioxidant, ultraviolet absorbent and infrared absorbent, the density of polyethylene compound is 0.938-0.942g / cm 3 The multilayer composite mulch film of the present application can keep as much parallel light as possible by gradually increasing the density from outside to inside, reduce the reflection ratio when the mulch film is refracted, increase the light transmittance of the mulch film, reduce the haze of the mulch film, and thus improve the heat preservation effect.

Description

Technical Field

[0001] This invention relates to the field of PE film technology, and in particular to a multilayer composite mulch film and its preparation method. Background Technology

[0002] Mulch film, also known as ground cover film, is usually transparent or black, but can also be green or silver, used for agricultural ground covering. Composite PE mulch film, in particular, features low thickness (10-30µm), high yield, and low cost. It also possesses excellent warming and entropy-retaining properties, not only increasing soil temperature, conserving water, soil, and fertilizer efficiency, but also providing multiple functions such as weed control, pest and disease prevention, drought and flood resistance, salt suppression and seedling protection, improving near-surface light and heat conditions, and ensuring product hygiene. For newly emerged seedlings, it helps protect roots and promote growth.

[0003] However, existing PE mulch films generally have high haze and poor light transmittance. When using PE mulch films as protective greenhouses for crops in northern regions during autumn and winter, the short sunshine hours mean less sunlight reaches the soil surface through the PE mulch film, resulting in poor heat retention for the crops. Furthermore, in northern regions during autumn and winter, the large diurnal temperature range causes a rapid drop in temperature at night due to radiative cooling. Heat absorbed by the soil surface during the day is quickly dissipated at night as infrared heat radiation. Secondly, current PE mulch films have poor hydrophobicity. In environments with large temperature differences, water vapor condenses easily at low temperatures, forming water droplets on the side of the multi-layered composite mulch film closest to the ground surface. This reflects sunlight, reducing the film's sunlight transmittance and affecting its overall performance.

[0004] Therefore, it is necessary to further improve the hydrophobicity, light transmittance and other properties of PE mulch film in order to facilitate its widespread application. Summary of the Invention

[0005] The purpose of this invention is to provide a multilayer composite mulch film with high light transmittance, good warming effect, low haze and strong hydrophobicity.

[0006] To achieve the above objectives, the present invention provides a multi-layer composite mulch film, comprising an outermost layer, a second outermost layer, a middle layer, a second innermost layer, and an innermost layer arranged sequentially. The parameters of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer are as follows.

[0007] The outermost layer consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is ≤0.910 g / cm³. 3 Antioxidants comprise 2–7‰ of the mass of polyethylene compounds. Ultraviolet absorbers comprise 5–12‰ of the mass of polyethylene compounds.

[0008] Both the outermost and innermost layers consist of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds ranges from 0.917 to 0.923 g / cm³. 3 Antioxidants comprise 2–7‰ of the mass of polyethylene compounds. Ultraviolet absorbers comprise 5–12‰ of the mass of polyethylene compounds.

[0009] The intermediate layer comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is ≥0.935 g / cm³. 3 Antioxidants comprise 2–7‰ of the mass of polyethylene compounds. Ultraviolet absorbers comprise 5–12‰ of the mass of polyethylene compounds.

[0010] The innermost layer comprises polyethylene compounds, antioxidants, ultraviolet absorbers, and infrared absorbers. The density of the polyethylene compounds ranges from 0.938 to 0.942 g / cm³. 3 Antioxidants comprise 2–7‰ of the mass of polyethylene compounds. Ultraviolet absorbers comprise 5–12‰ of the mass of polyethylene compounds. Infrared absorbers comprise 0.5–2.5% of the mass of polyethylene compounds.

[0011] The multilayer composite mulch film of the present invention has at least the following technical effects.

[0012] (1) The density of the outermost polyethylene compound is less than 0.910 g / cm³. 3 The density of the outermost polyethylene compound is 0.917–0.923 g / cm³. 3 The density of the intermediate layer polyethylene compound is higher than 0.935 g / cm³. 3 By gradually increasing the density from the outside to the inside, the sunlight shining from the outside to the inside can be refracted to maintain as much parallel light as possible, reducing the reflection ratio when the mulch film is refracted, increasing the light transmittance of the mulch film, reducing the fog of the mulch film, and thus improving the heat preservation effect.

[0013] (2) The outermost and innermost layers use a density of 0.917–0.923 g / cm³. 3 Polyethylene compounds can improve the overall puncture resistance and toughness of mulch films.

[0014] (3) The density of the innermost layer is 0.938~0.942g / cm³. 3 Polyethylene compounds have a high density. During preparation, pressure rollers are used to pressurize the outermost layer, which creates a hydrophobic texture and reduces the surface tension of the outermost layer of the mulch film. This allows the mulch film to gel into water droplets and flow away during use, carrying away the soil on top, thereby improving the warming effect of the mulch film.

[0015] (4) Adding an infrared absorber to the innermost layer can effectively isolate the loss of far-infrared radiation during the covering process, thereby improving the heat preservation performance of the mulch film.

[0016] As one technical solution of the present invention, the outermost layer contains a polyethylene compound with a density of 0.915–0.920 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.10–0.30 g / 10 min and a density of 0.900–0.905 g / cm³ 3 Ultra-low density polyethylene with a melt flow index of 0.80–2.00 g / 10 min. Linear low-density polyethylene accounts for 40–60 wt.% of the polyethylene compounds. A density below 0.910 g / cm³ is obtained by adjusting the ratio of linear low-density polyethylene to ultra-low-density polyethylene. 3 Polyethylene compounds.

[0017] As one technical solution of the present invention, the polyethylene compounds in the outermost and innermost layers comprise compounds with a density of 0.918–0.922 g / cm³. 3 The first metallocene polyethylene has a melt flow index of 0.30–0.70 g / 10 min and a density of 0.914–0.918 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10–0.25 g / 10 min and a density of 0.925–0.930 g / cm³ 3 A third metallocene polyethylene with a melt flow index of 0.10–0.50 g / 10 min was prepared. The mass ratio of the first, second, and third metallocene polyethylenes was 60–80:5–20:5–20. A density of 0.917–0.923 g / cm³ was obtained by adjusting the composition of the first, second, and third metallocene polyethylenes. 3 Polyethylene compounds. The outermost and innermost layers use ultra-high toughness metallocene polyethylene, which can improve the overall puncture resistance and toughness of the mulch film.

[0018] As one technical solution of the present invention, the polyethylene compound in the intermediate layer includes a first polyethylene and a second polyethylene. The first polyethylene accounts for 40-75 wt.% of the polyethylene compound. The first polyethylene has a density of 0.939-0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.10–0.20 g / 10 min and / or a density of 0.938–0.942 g / cm³ 3 Metallocene polyethylene with a melt flow index of 0.15–0.25 g / 10 min. The second type of polyethylene includes polyethylene with a density of 0.925–0.929 g / cm³. 3Metallocene polyethylene with a melt flow index of 0.05–0.15 g / 10 min and / or a density of 0.923–0.927 g / cm³ 3 Linear low-density polyethylene with a melt flow index of 0.40–0.60 g / 10 min. The intermediate layer can achieve a density ≥0.935 g / cm³ by adjusting the composition of various polyethylenes. 3 Polyethylene compounds. High-density polyethylene is not added to the intermediate layer to avoid a decrease in the light transmittance of the mulch film due to excessive crystallinity in the intermediate layer.

[0019] As one technical solution of this invention, the innermost layer of polyethylene compounds includes a third polyethylene and a fourth polyethylene. The third polyethylene accounts for 60-80 wt.% of the polyethylene compounds. The third polyethylene has a density of 0.939-0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.10–0.20 g / 10 min and a density of 0.938–0.942 g / cm³. 3 The four metallocene polyethylenes have a melt flow index of 0.15–0.25 g / 10 min and a density of 0.943–0.947 g / cm³. 3 The fourth type of polyethylene includes at least one of the fifth metallocene polyethylenes with a melt flow index of 0.40–0.60 g / 10 min. The fourth type of polyethylene includes polyethylene with a density of 0.925–0.929 g / cm³. 3 A sixth-metallocene polyethylene with a melt flow index of 1.00–2.00 g / 10 min was obtained. Densities of 0.938–0.942 g / cm³ could be obtained by adjusting the third and fourth polyethylene layers. 3 Polyethylene compounds. Thirdly, polyethylene, particularly medium-density polyethylene, allows for the subsequent fabrication of hydrophobic textures using pressure rollers.

[0020] As one technical solution of this invention, the antioxidants in the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer include hydroquinone-based antioxidants. For example, Ningkang Chemical's T501 product can be used.

[0021] As a technical solution of the present invention, the ultraviolet absorber in each of the outermost, second outermost, middle, second innermost, and innermost layers independently includes either a benzophenone derivative or a benzotriazole derivative. The benzophenone derivative includes 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octyloxybenzophenone. The benzotriazole derivative includes 2-(2-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-benzotriazole, and 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole.

[0022] As a technical solution of this invention, the infrared absorber in each of the outermost, second outermost, middle, second innermost, and innermost layers independently comprises a dithiocyclopentene complex or a transition metal composite oxide. The dithiocyclopentene complex is selected from 1,3-dithiocyclopentene-2-thionone-4,5-dimercapto complex or bis(1,2-di(4-tert-butylphenyl)-1,2-dithiodiene)nickel complex. The transition metal composite oxide is selected from one or more of tungsten-cesium oxide, indium-tin oxide, and tin-antimony oxide.

[0023] As one technical solution of this invention, the thickness ratio of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer is 1:2~3:3~5:2~3:3~5. The outermost, second outermost, and middle layers become thicker as the density of the polyethylene compound increases, effectively promoting the refraction of sunlight. The innermost layer is further thickened to allow for subsequent pressure application using pressure rollers to create a stable hydrophobic texture.

[0024] Another aspect of the present invention provides a method for preparing a multilayer composite mulch film. The preparation method includes mixing the raw materials of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer evenly according to the formula ratio, feeding them separately to the extruder of a five-layer co-extrusion blown film unit, and then sequentially extruding, blowing, traction cooling, shaping, heating to 75-90°C, and then winding it up after applying pressure with a single-sided patterned roller.

[0025] In the preparation method of this invention, after blown film shaping, the film is heated to 75-90°C, and then pressure is applied using a single-sided patterned roller, which can form a certain microstructure on the film surface and create a hydrophobic texture. The pressure can be applied by instantaneous high-pressure molding. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the 5-layer structure of the multilayer composite mulch film of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further illustrated below through specific embodiments, but these do not constitute any limitation on the present invention.

[0028] like Figure 1 As shown, the multilayer composite mulch film of the present invention includes, from top to bottom, an outermost layer 1, a second outermost layer 2, a middle layer 3, a second innermost layer 4, and an innermost layer 5.

[0029] The multilayer composite mulch film of the present invention can be prepared by the following method, the preparation method comprising:

[0030] (1) Extrusion: The raw materials of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are mixed evenly according to the ratio and sent to the extruder of the five-layer co-extrusion blown film unit respectively;

[0031] (2) Blowing;

[0032] (3) Traction cooling;

[0033] (4) Microstructure construction: After shaping, heat to 75-90℃ and apply high pressure instantly using a single-sided patterned roller.

[0034] (5) Roll up.

[0035] The multilayer composite mulch film of the present invention will be described in detail below through specific embodiments, but the scope of the present invention is not limited thereto.

[0036] Example 1

[0037] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 11 μm. The performance parameters of each layer are as follows.

[0038] The outermost layer, 1 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3 Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0039] The outermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0040] Intermediate layer: 3 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0041] The innermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0042] The innermost layer, 3 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds. 1,3-Dithiocyclopentene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the mass of the polyethylene compounds.

[0043] Example 2

[0044] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 22 μm. The performance parameters of each layer are as follows.

[0045] The outermost layer, 2 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.909 g / cm³. 3 Polyethylene compounds comprise 43% by mass and have a density of 0.915 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.30 g / 10 min and a mass percentage of 57% and a density of 0.905 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 3‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 10‰ of the mass of the polyethylene compound.

[0046] The outermost layer, 4 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0047] Intermediate layer: 6 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0048] The innermost layer, 4 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0049] The innermost layer, 6 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.940 g / cm³. 3 Metallic polyethylene with a melt flow index of 0.20 g / 10 min, a mass percentage of 15%, and a density of 0.945 g / cm³. 3 Metallic polyethylene with a melt flow index of 0.50 g / 10 min and a mass percentage of 15% and a density of 0.929 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 6‰ of the mass of the polyethylene compounds. 2-(2-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole UV absorber accounts for 6‰ of the mass of the polyethylene compounds. 1,3-Dithiocyclopentene-2-thionone-4,5-dimercapto complex infrared absorber accounts for 2.0% of the mass of the polyethylene compounds.

[0050] Example 3

[0051] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 39 μm. The performance parameters of each layer are as follows.

[0052] The outermost layer, 3 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3 Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0053] The outermost layer, 6 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.923 g / cm³. 3 Polyethylene compounds include those comprising 60% by mass and having a density of 0.922 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.40 g / 10 min, a mass percentage of 20%, and a density of 0.917 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.15 g / 10 min and a mass percentage of 20% and a density of 0.930 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 5‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 10‰ of the mass of the polyethylene compound.

[0054] Intermediate layer: 12 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.936 g / cm³. 3 Polyethylene compounds include those with a mass percentage of 75% and a content of 0.940 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 25% and a density of 0.925 g / cm³ were used. 3 Linear low-density polyethylene with a melt flow index of 0.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 5‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 9‰ of the mass of the polyethylene compound.

[0055] The innermost layer, 6 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.923 g / cm³. 3 Polyethylene compounds include those comprising 60% by mass and having a density of 0.922 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.40 g / 10 min, a mass percentage of 20%, and a density of 0.917 g / cm³. 3Metallocene polyethylene with a melt flow index of 0.15 g / 10 min and a mass percentage of 20% and a density of 0.930 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 5‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 10‰ of the mass of the polyethylene compound.

[0056] The innermost layer, 12 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the mass of the polyethylene compound. Bis(1,2-di(4-tert-butylphenyl)-1,2-dithiodiene)nickel complex infrared absorber accounts for 1.5% of the mass of the polyethylene compound.

[0057] Comparative Example 1

[0058] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 11 μm. The performance parameters of each layer are as follows.

[0059] The outermost layer, 1 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3 Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0060] The outermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0061] Intermediate layer: 3 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0062] The innermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0063] The innermost layer, 3 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³.3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the mass of the polyethylene compound.

[0064] Comparative Example 2

[0065] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 11 μm. The performance parameters of each layer are as follows.

[0066] The outermost layer, 1 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0067] The outermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0068] Intermediate layer: 3 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0069] The innermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0070] The innermost layer, 3 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound. 1,3-Dithiocyclopentene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the mass of the polyethylene compound.

[0071] Comparative Example 3

[0072] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 11 μm. The performance parameters of each layer are as follows.

[0073] The outermost layer, 1 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0074] The outermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3 Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0075] Intermediate layer: 3 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0076] The innermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0077] The innermost layer, 3 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3 Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds. 1,3-Dithiocyclopentene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the mass of the polyethylene compounds.

[0078] Comparative Example 4

[0079] The multi-layer composite mulch film consists of, from top to bottom, the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer. The total thickness of the multi-layer composite mulch film is 11 μm. The performance parameters of each layer are as follows.

[0080] The outermost layer, 1 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.910 g / cm³. 3 Polyethylene compounds include those comprising 55% by mass and having a density of 0.918 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 45% and a density of 0.900 g / cm³. 3 Ultra-low density polyethylene with a melt flow index of 1.00 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compound.

[0081] The outermost layer, 2 μm thick, consists of polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0082] Intermediate layer: 3 μm thick, comprising polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.920 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.920 g / cm³. 3 The first metallocene polyethylene with a melt flow index of 0.50 g / 10 min, a mass percentage of 20%, and a density of 0.916 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.20 g / 10 min and a mass percentage of 10% and a density of 0.927 g / cm³. 3 A third metallocene polyethylene with a melt flow index of 0.30 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0083] The innermost layer, 2 μm thick, comprises polyethylene compounds, antioxidants, and UV absorbers. The density of the polyethylene compounds is 0.937 g / cm³. 3 Polyethylene compounds include those comprising 70% by mass and having a density of 0.941 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 30% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds.

[0084] The innermost layer, 3 μm thick, comprises polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compounds is 0.939 g / cm³. 3Polyethylene compounds include those comprising 75% by mass and having a density of 0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.14 g / 10 min and a mass percentage of 25% and a density of 0.927 g / cm³. 3 Metallocene polyethylene with a melt flow index of 1.50 g / 10 min. Ningkang Chemical's T501 antioxidant accounts for 4‰ of the mass of the polyethylene compounds. 2-Hydroxy-4-methoxybenzophenone ultraviolet absorber accounts for 8‰ of the mass of the polyethylene compounds. 1,3-Dithiocyclopentene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the mass of the polyethylene compounds.

[0085] The multilayer composite mulch films of Examples 1-3 and Comparative Examples 1-4 can be prepared by the following method:

[0086] (1) Extrusion: The raw materials of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are mixed evenly according to the ratio and sent to the extruder of the five-layer co-extrusion blown film unit respectively;

[0087] (2) Blowing;

[0088] (3) Traction cooling; cooling time is 70 seconds;

[0089] (4) Microstructure construction: After shaping, heat to 80°C and apply instantaneous high pressure using a single-sided patterned roller.

[0090] (5) Roll up.

[0091] The parameters of each layer of the multilayer composite mulch film in Comparative Example 5 are the same as those in Example 1, and its preparation method is as follows.

[0092] (1) Extrusion: The raw materials of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer are mixed evenly according to the ratio and sent to the extruder of the five-layer co-extrusion blown film unit respectively;

[0093] (2) Blowing;

[0094] (3) Traction cooling; cooling time is 70 seconds;

[0095] (4) Roll up.

[0096] The multilayer composite mulches prepared in Examples 1-3 and Comparative Examples 1-5 were tested for their warming performance, heat preservation performance, light transmittance, haze, and hydrophobicity. The test results are shown in Table 1. The test methods are as follows.

[0097] Temperature increase performance: The experimental field was covered with mulch film, and the surface temperature was measured at 8:00, 13:00 and 18:00 every day. The temperature increase compared with the uncovered field was calculated.

[0098] Thermal insulation performance: The experimental field was covered with mulch film. From 6:00 to 18:00, the temperature at 5cm below ground was measured every two hours. The average value was taken and the temperature increase compared to the uncovered field was calculated.

[0099] Light transmittance: Cut the mulch film into test samples of the same size and test them using a thin film transmittance tester.

[0100] Haze: Cut the plastic film into test samples of the same size and test them using a thin film haze tester.

[0101] Hydrophobic properties: The plastic film was cut into test samples of the same size, and the contact angle was measured using a contact angle measuring instrument.

[0102] Table 1. Performance test results of multilayer composite mulch films in Examples 1-3 and Comparative Examples 1-5

[0103]

[0104]

[0105] As shown in Table 1, compared with Comparative Examples 1-4, the multi-layer composite mulch films of Examples 1-3 have higher light transmittance, lower haze, and larger contact angles. Furthermore, the surface temperature at 8:00 AM can increase by more than 1.0°C, and the temperature at a depth of 5cm can increase by more than 2.0°C. This is because the multi-layer composite mulch film of this invention, through a gradual increase in density from the outside to the inside, allows sunlight refracted from the outside in to maintain as much parallel light as possible, reducing the reflection ratio during refracting, increasing the light transmittance of the mulch film, reducing the haze, and thus improving the heat preservation effect. The addition of an infrared absorber to the innermost layer allows the mulch film to effectively block the loss of far-infrared radiation during use, thereby improving the heat preservation performance of the mulch film.

[0106] As can be seen from Example 1 and Comparative Example 5, applying instantaneous high pressure with a pressure roller after blow-forming and shaping during preparation is beneficial to increasing the contact angle of the multilayer composite film and can further improve its temperature-increasing performance.

[0107] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles disclosed herein.

Claims

1. A multi-layer composite mulch film, comprising an outermost layer, a second outermost layer, a middle layer, a second innermost layer, and an innermost layer arranged sequentially, characterized in that, During preparation, after blown film shaping, the film is heated to 75-90°C, and then pressure rollers are used to apply pressure to create a hydrophobic texture on the outermost layer. The parameters of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer are as follows: The outermost layer comprises a polyethylene compound, an antioxidant, and a UV absorber, wherein the density of the polyethylene compound is ≤0.910 g / cm³. 3 The antioxidant accounts for 2-7‰ of the mass of the polyethylene compound, and the ultraviolet absorber accounts for 5-12‰ of the mass of the polyethylene compound; Both the outermost and innermost layers comprise polyethylene compounds, antioxidants, and ultraviolet absorbers, wherein the density of the polyethylene compounds is 0.917~0.923 g / cm³. 3 The antioxidant accounts for 2-7‰ of the mass of the polyethylene compound, and the ultraviolet absorber accounts for 5-12‰ of the mass of the polyethylene compound; The intermediate layer comprises a polyethylene compound, an antioxidant, and a UV absorber, wherein the density of the polyethylene compound is ≥0.935 g / cm³. 3 The antioxidant accounts for 2-7‰ of the mass of the polyethylene compound, and the ultraviolet absorber accounts for 5-12‰ of the mass of the polyethylene compound; The innermost layer comprises a polyethylene compound, an antioxidant, a UV absorber, and an infrared absorber, wherein the density of the polyethylene compound is 0.938~0.942 g / cm³. 3 The antioxidant accounts for 2-7‰ of the mass of the polyethylene compound, the ultraviolet absorber accounts for 5-12‰ of the mass of the polyethylene compound, and the infrared absorber accounts for 0.5-2.5% of the mass of the polyethylene compound. The thickness ratio of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer is 1:2~3:3~5:2~3:3~5.

2. The multi-layer composite mulch film as described in claim 1, characterized in that, The outermost layer contains polyethylene compounds with a density of 0.915~0.920 g / cm³. 3 Linear low-density polyethylene with a melt flow index of 0.10~0.30 g / 10min and a density of 0.900~0.905 g / cm³ 3 The ultra-low density polyethylene has a melt index of 0.80~2.00 g / 10 min, and the linear low density polyethylene accounts for 40~60 wt.% of the polyethylene compound.

3. The multi-layer composite mulch film as described in claim 1, characterized in that, The polyethylene compounds in the outermost and innermost layers comprise compounds with a density of 0.918~0.922 g / cm³. 3 The first metallocene polyethylene has a melt flow index of 0.30~0.70 g / 10min and a density of 0.914~0.918 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.10~0.25 g / 10 min and a density of 0.925~0.930 g / cm³ 3 The third metallocene polyethylene has a melt index of 0.10~0.50 g / 10 min, and the mass ratio of the first metallocene polyethylene, the second metallocene polyethylene and the third metallocene polyethylene is 60~80:5~20:5~20.

4. The multi-layer composite mulch film as described in claim 1, characterized in that, The polyethylene compound in the intermediate layer includes a first polyethylene and a second polyethylene, wherein the first polyethylene accounts for 40-75 wt.% of the polyethylene compound, and the first polyethylene has a density of 0.939-0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.10~0.20 g / 10min and / or a density of 0.938~0.942 g / cm³ 3 The second polyethylene comprises metallocene polyethylene with a melt flow index of 0.15~0.25 g / 10 min, and has a density of 0.925~0.929 g / cm³. 3 Metallocene polyethylene with a melt flow index of 0.05~0.15 g / 10 min and / or a density of 0.923~0.927 g / cm³ 3 Linear low-density polyethylene with a melt index of 0.40~0.60 g / 10min.

5. The multi-layer composite mulch film as described in claim 1, characterized in that, The innermost layer of polyethylene compounds includes a third polyethylene and a fourth polyethylene, wherein the third polyethylene accounts for 60-80 wt.% of the polyethylene compounds, and the third polyethylene has a density of 0.939-0.943 g / cm³. 3 Medium-density polyethylene with a melt flow index of 0.10~0.20 g / 10min and a density of 0.938~0.942 g / cm³ 3 The four metallocene polyethylenes have a melt flow index of 0.15~0.25 g / 10 min and a density of 0.943~0.947 g / cm³. 3 The fourth polyethylene comprises at least one of the fifth metallocene polyethylenes having a melt flow index of 0.40 to 0.60 g / 10 min, wherein the fourth polyethylene comprises a density of 0.925 to 0.929 g / cm³. 3 Metallocene-6 polyethylene with a melt flow index of 1.00~2.00 g / 10 min.

6. The multi-layer composite mulch film as described in claim 1, characterized in that, The antioxidants described in the outermost, second outermost, middle, second innermost, and innermost layers include hydroquinone antioxidants.

7. The multilayer composite mulch film as described in claim 1, characterized in that, The ultraviolet absorbers in each of the outermost, second outermost, middle, second innermost, and innermost layers independently include benzophenone derivatives or benzotriazole derivatives.

8. The multi-layer composite mulch film as described in claim 1, characterized in that, The infrared absorber includes dithiocyclopentene complexes or transition metal complex oxides.

9. The method for preparing a multilayer composite mulch film according to any one of claims 1 to 8, characterized in that, include: The raw materials for the outermost, second outermost, middle, second innermost, and innermost layers are mixed evenly according to the formula ratio and then sent to the extruder of the five-layer co-extrusion blown film unit. They are then extruded, blown, traction cooled, and shaped in sequence, and then heated to 75~90℃. After being pressed by a single-sided patterned roller, they are wound up.

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