Multilayer composite mulch film and preparation method therefor

Abstract

A multilayer composite mulch film, comprising an outermost layer (1), a secondary outer layer (2), an intermediate layer (3), a secondary inner layer (4) and an innermost layer (5), which are arranged in sequence. The outermost layer (1) comprises a polyethylene compound, an antioxidant and an ultraviolet absorbent, wherein the density of the polyethylene compound is less than or equal to 0.910 g / cm3. The secondary outer layer (2) and the secondary inner layer (4) both comprise a polyethylene compound, an antioxidant and an ultraviolet absorbent, wherein the density of the polyethylene compound is 0.917-0.923 g / cm3. The intermediate layer (3) comprises a polyethylene compound, an antioxidant and an ultraviolet absorbent, wherein the density of the polyethylene compound is greater than or equal to 0.935 g / cm3. The innermost layer (5) comprises a polyethylene compound, an antioxidant, an ultraviolet absorbent and an infrared absorbent, wherein the density of the polyethylene compound is 0.938-0.942 g / cm3. With the density gradually increasing from outside to inside, the multilayer composite mulch film can reflect sunlight that is irradiated from outside to inside to retain as much parallel light as possible, and therefore the proportion of reflected light during the refraction of the mulch film is reduced, the light transmittance of the mulch film is increased, and the haze of the mulch film is reduced, thereby improving the heat preservation effect.

Description

Multilayer composite ground film and preparation method thereof Technical Field

[0001] The present application relates to the technical field of PE films, and in particular to a multi-layer composite ground film and a preparation method thereof. Background Art

[0002] Ground film, also known as ground covering film, is typically transparent or black, but also available in green or silver. It is used for agricultural ground covering. Composite PE ground film, in particular, offers advantages such as low thickness (10-30 μm), high yield, and low cost. Its excellent warming and entropy-retaining properties not only increase ground temperature, conserve water, soil, and fertilizer, but also provide weed control, pest control, drought and waterlogging resistance, salt suppression, seedling protection, improved near-ground light and heat conditions, and a hygienic and clean product. For newly emerged seedlings, it protects their roots and promotes growth.

[0003] However, existing PE mulch films generally have high haze and poor light transmittance. When used as crop shelters in northern China during autumn and winter, the short daylight hours mean that little sunlight reaches the ground where crops are grown, resulting in poor insulation. Furthermore, due to the large temperature difference between day and night in northern China during autumn and winter, temperatures drop dramatically to low temperatures at night due to radiative cooling. Heat absorbed by the ground from sunlight during the day is quickly dissipated as infrared heat radiation at night. Furthermore, current PE mulch films are not very hydrophobic. In environments with large temperature differences, water vapor condenses at low temperatures, easily forming water droplets on the surface of the multi-layer composite mulch film, reflecting sunlight and reducing its transmittance, thus affecting its overall performance.

[0004] Therefore, it is necessary to further improve the hydrophobicity, light transmittance and other properties of PE mulch, so as to facilitate the promotion and application of PE mulch.

[0005] Application Contents

[0006] The purpose of this application is to provide a multi-layer composite ground film with high light transmittance, good warming effect, low haze and strong hydrophobicity.

[0007] To achieve the above-mentioned object, the present application provides a multi-layer composite ground film, comprising an outermost layer, a second outermost layer, an intermediate layer, a second innermost layer, and an innermost layer arranged in sequence. The parameters of the outermost layer, the second outermost layer, the intermediate layer, the second innermost layer, and the innermost layer are as follows.

[0008] The outermost layer includes polyethylene compound, antioxidant and ultraviolet absorber. The density of polyethylene compound is ≤0.910g / cm 3 The antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound. The UV absorber accounts for 5 to 12‰ of the mass of the polyethylene compound.

[0009] The sub-outer layer and the sub-inner layer both include polyethylene compounds, antioxidants and ultraviolet absorbers. The density of the polyethylene compound is 0.917 to 0.923 g / cm 3 The antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound. The UV absorber accounts for 5 to 12‰ of the mass of the polyethylene compound.

[0010] The middle layer includes polyethylene compound, antioxidant and ultraviolet absorber. The density of polyethylene compound is ≥0.935g / cm 3 The antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound. The UV absorber accounts for 5 to 12‰ of the mass of the polyethylene compound.

[0011] The innermost layer includes polyethylene compound, antioxidant, ultraviolet absorber and infrared absorber. The density of polyethylene compound is 0.938~0.942g / cm 3 The antioxidant accounts for 2 to 7‰ of the weight of the polyethylene compound. The ultraviolet absorber accounts for 5 to 12‰ of the weight of the polyethylene compound. The infrared absorber accounts for 0.5 to 2.5% of the weight of the polyethylene compound.

[0012] The multi-layer composite ground film of the present application has at least the following technical effects.

[0013] (1) The density of the outermost polyethylene compound is lower than 0.910 g / cm 3 The density of the second outer layer of polyethylene compound is 0.917~0.923g / cm 3 The density of the polyethylene compound in the middle layer is higher than 0.935g / cm 3 By gradually increasing the density from the outside to the inside, the sunlight irradiated from the outside to the inside can be refracted to maintain as much parallel light as possible, reducing the reflection ratio during refraction of the ground film, increasing the light transmittance of the ground film, and reducing the haze of the ground film, thereby improving the thermal insulation effect.

[0014] (2) The density of the sub-outer layer and the sub-inner layer is 0.917~0.923g / cm 3 The polyethylene compound can improve the overall puncture resistance and toughness of the mulch.

[0015] (3) The innermost layer density is 0.938~0.942g / cm 3 The polyethylene compound has a high density. When it is prepared, it is pressed with a pressure roller to form a hydrophobic pattern on the outermost layer and reduce the surface tension of the outermost layer of the ground film. As a result, the ground film will gel into water droplets and flow away during the covering process, taking away the soil on it, thereby improving the warming effect of the ground film.

[0016] (4) Adding infrared absorbent to the innermost layer can effectively isolate the loss of far-infrared radiation during the covering process of the ground film, thereby improving the thermal insulation performance of the ground film.

[0017] As a technical solution of the present application, the polyethylene compound in the outermost layer includes a density of 0.915 to 0.920 g / cm 3 , linear low-density polyethylene with a melt index of 0.10 to 0.30 g / 10 min and a density of 0.900 to 0.905 g / cm 3 , ultra-low density polyethylene with a melt index of 0.80-2.00 g / 10 min. Linear low density polyethylene accounts for 40-60 wt.% of the polyethylene compound. Through the regulation of linear low density polyethylene and ultra-low density polyethylene, a density below 0.910 g / cm 3 polyethylene compounds.

[0018] As a technical solution of the present application, the polyethylene compound in the sub-outer layer and the sub-inner layer includes a density of 0.918 to 0.922 g / cm 3 The first metallocene polyethylene with a melt index of 0.30-0.70 g / 10min and a density of 0.914-0.918 g / cm 3 The second metallocene polyethylene has a melt index of 0.10 to 0.25 g / 10 min and a density of 0.925 to 0.930 g / cm 3 , the third metallocene polyethylene has a melt index of 0.10 to 0.50 g / 10 min. The mass ratio of the first metallocene polyethylene, the second metallocene polyethylene and the third metallocene polyethylene is 60 to 80:5 to 20:5 to 20. The first metallocene polyethylene, the second metallocene polyethylene and the third metallocene polyethylene are regulated to obtain a density of 0.917 to 0.923 g / cm 3 The sub-outer and sub-inner layers use ultra-tough metallocene polyethylene to improve the overall puncture resistance and toughness of the mulch.

[0019] As a technical solution of the present application, the polyethylene compound in the middle layer includes a first polyethylene and a second polyethylene. The first polyethylene accounts for 40 to 75 wt.% of the polyethylene compound. The first polyethylene includes a density of 0.939 to 0.943 g / cm 3 , medium density polyethylene with a melt index of 0.10 to 0.20 g / 10 min and / or a density of 0.938 to 0.942 g / cm 3 , a metallocene polyethylene having a melt index of 0.15 to 0.25 g / 10 min. The second polyethylene comprises a density of 0.925 to 0.929 g / cm 3, metallocene polyethylene with a melt index of 0.05 to 0.15 g / 10 min and / or a density of 0.923 to 0.927 g / cm 3 , linear low-density polyethylene with a melt index of 0.40 to 0.60 g / 10 min. The middle layer can be adjusted to a density of ≥ 0.935 g / cm 3 No high-density polyethylene is added to the middle layer to avoid a decrease in the light transmittance of the ground film due to excessive crystallinity of the middle layer.

[0020] As a technical solution of the present application, the polyethylene compound in the innermost layer includes a third polyethylene and a fourth polyethylene. The third polyethylene accounts for 60 to 80 wt.% of the polyethylene compound. The third polyethylene includes a density of 0.939 to 0.943 g / cm 3 , medium density polyethylene with a melt index of 0.10 to 0.20 g / 10 min, and a density of 0.938 to 0.942 g / cm 3 , a fourth metallocene polyethylene having a melt index of 0.15 to 0.25 g / 10 min and a density of 0.943 to 0.947 g / cm 3 , at least one of the fifth metallocene polyethylenes having a melt index of 0.40 to 0.60 g / 10 min. The fourth polyethylene comprises a density of 0.925 to 0.929 g / cm 3 The sixth metallocene polyethylene has a melt index of 1.00 to 2.00 g / 10 min. By adjusting the third and fourth polyethylenes, a density of 0.938 to 0.942 g / cm 3 The third polyethylene particularly includes medium-density polyethylene, which can stabilize the hydrophobic texture subsequently constructed by pressure roller application.

[0021] As a technical solution of the present application, the antioxidant in each of the outermost layer, the second outermost layer, the middle layer, the second innermost layer and the innermost layer includes a hydroquinone antioxidant, such as Ningkang Chemical T501 product.

[0022] As a technical solution of the present application, the UV absorber in each of the outermost layer, the second outermost layer, the intermediate layer, the second innermost layer, and the innermost layer independently comprises a benzophenone derivative or a benzotriazole derivative. Among them, 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.

[0023] As a technical solution of the present application, the infrared absorber in each of the outermost layer, the second outermost layer, the intermediate layer, the second innermost layer, and the innermost layer independently comprises a dithiolene complex or a transition metal composite oxide. The dithiolene complex is selected from a 1,3-dithiole-2-thione-4,5-dithiol complex or a bis(1,2-bis(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.

[0024] As a technical solution of this application, 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. As the density of the polyethylene compound increases, the thickness of the outermost layer, the second outermost layer, and the middle layer increases, effectively promoting the effective reflection of external sunlight. The innermost layer is further thickened, and pressure rollers are subsequently used to create a stable hydrophobic pattern.

[0025] Another aspect of the present application provides a method for preparing a multi-layer composite ground film. The method comprises uniformly mixing the raw materials for the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer according to a specific ratio, feeding each layer into the extruder of a five-layer co-extrusion film blowing unit, and then sequentially extruding, blowing, cooling, shaping, heating to 75-90°C, and applying pressure using a single-sided patterned roller before winding.

[0026] In the preparation method of the present application, after film blowing and shaping, the film is heated to 75-90°C and then pressurized using a single-sided patterned roller to form a certain microstructure on the film surface, thereby constructing a hydrophobic pattern. Pressurization can be performed by instant high-pressure molding. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic diagram of a five-layer structure of a multi-layer composite ground membrane of the present application. DETAILED DESCRIPTION

[0028] The technical solution of the present application is further illustrated below through specific implementation methods, but does not constitute any limitation to the present application.

[0029] As shown in FIG1 , the multi-layer composite ground membrane of the present application includes, from top to bottom, an outermost layer 1 , a sub-outer layer 2 , an intermediate layer 3 , a sub-inner layer 4 and an innermost layer 5 .

[0030] The multi-layer composite ground film of the present application can be prepared by the following method, which includes:

[0031] (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 uniformly according to the proportions and respectively sent to the extruder of the five-layer co-extrusion film blowing unit;

[0032] (2) Blowing;

[0033] (3) Traction cooling;

[0034] (4) Microstructure construction: After shaping, heat to 75-90°C and apply instantaneous high pressure using a single-sided pattern roller.

[0035] (5) Coiling.

[0036] The following will introduce the multi-layer composite ground membrane of the present application in detail through specific embodiments, but the scope of implementation of the present application is not limited thereto.

[0037] Example 1

[0038] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 11 μm. The performance parameters of each layer are as follows.

[0039] Outermost layer: 1 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3 Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0040] Second outer layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0041] Middle layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0042] Second inner layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0043] The innermost layer is 3 μm thick and contains polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 75% by mass and a density of 0.943g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 The metallocene polyethylene has a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound's mass. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound's mass. 1,3-Dithiolene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the polyethylene compound's mass.

[0044] Example 2

[0045] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 22 μm. The performance parameters of each layer are as follows.

[0046] Outermost layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.909 g / cm 3 Polyethylene compounds include 43% by mass and a density of 0.915g / cm 3 , linear low-density polyethylene with a melt index of 0.30g / 10min and a mass ratio of 57% and a density of 0.905g / cm 3 Ultra-low density polyethylene with a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 3‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 10‰ of the weight of the polyethylene compound.

[0047] Second outer layer: 4 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0048] Middle layer: 6 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0049] Second inner layer: 4 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0050] Innermost layer: 6 μm thick, including polyethylene compound, antioxidant, UV absorber and infrared absorber. The density of polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.940g / cm 3 , metal polyethylene with a melt index of 0.20g / 10min, a mass proportion of 15%, and a density of 0.945g / cm 3 , a metal polyethylene with a melt index of 0.50g / 10min and a mass ratio of 15% and a density of 0.929g / cm 3 , metallocene polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 6‰ of the polyethylene compound's mass. 2-(2-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole UV absorber accounts for 6‰ of the polyethylene compound's mass. 1,3-Dithiole-2-thione-4,5-dimercapto complex infrared absorber accounts for 2.0% of the polyethylene compound's mass.

[0051] Example 3

[0052] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 39 μm. The performance parameters of each layer are as follows.

[0053] Outermost layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3 Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3, linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0054] Second outer layer: 6 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.923 g / cm 3 Polyethylene compounds include 60% by mass and a density of 0.922g / cm 3 The first metallocene polyethylene with a melt index of 0.40g / 10min, a mass ratio of 20%, and a density of 0.917g / cm 3 The second metallocene polyethylene with a melt index of 0.15g / 10min and a mass ratio of 20% and a density of 0.930g / cm 3 , a third metallocene polyethylene with a melt index of 0.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 5‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 10‰ of the weight of the polyethylene compound.

[0055] Middle layer: 12 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.936 g / cm 3 Polyethylene compounds include 75% by mass and 0.940g / cm 3 , metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 25% and a density of 0.925g / cm 3 , linear low-density polyethylene with a melt index of 0.50g / 10min. Ningkang Chemical T501 antioxidant accounts for 5‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 9‰ of the weight of the polyethylene compound.

[0056] Second inner layer: 6 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.923 g / cm 3 Polyethylene compounds include 60% by mass and a density of 0.922g / cm 3 The first metallocene polyethylene with a melt index of 0.40g / 10min, a mass ratio of 20%, and a density of 0.917g / cm 3The second metallocene polyethylene with a melt index of 0.15g / 10min and a mass ratio of 20% and a density of 0.930g / cm 3 , a third metallocene polyethylene with a melt index of 0.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 5‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 10‰ of the weight of the polyethylene compound.

[0057] The innermost layer is 12 μm thick and contains polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 75% by mass and a density of 0.943g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 The metallocene polyethylene (PE) has a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound's mass. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound's mass. Bis(1,2-bis(4-tert-butylphenyl)-1,2-dithiodiene) nickel complex infrared absorber accounts for 1.5% of the polyethylene compound's mass.

[0058] Comparative Example 1

[0059] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 11 μm. The performance parameters of each layer are as follows.

[0060] Outermost layer: 1 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3 Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0061] Second outer layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0062] Middle layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0063] Second inner layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0064] Innermost layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 75% by mass and a density of 0.943g / cm3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0065] Comparative Example 2

[0066] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 11 μm. The performance parameters of each layer are as follows.

[0067] Outermost layer: 1 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0068] Second outer layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0069] Middle layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0070] Second inner layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0071] The innermost layer is 3 μm thick and contains polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 75% by mass and a density of 0.943g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 The metallocene polyethylene has a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound's mass. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound's mass. 1,3-Dithiolene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the polyethylene compound's mass.

[0072] Comparative Example 3

[0073] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 11 μm. The performance parameters of each layer are as follows.

[0074] Outermost layer: 1 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0075] Second outer layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3 Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0076] Middle layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0077] Second inner layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0078] The innermost layer is 3 μm thick and contains polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compound is 0.939 g / cm 3 Polyethylene compounds include 75% by mass and a density of 0.943g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 The metallocene polyethylene has a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound's mass. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound's mass. 1,3-Dithiolene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the polyethylene compound's mass.

[0079] Comparative Example 4

[0080] The multi-layer composite ground film includes the outermost layer, the second outermost layer, the middle layer, the second inner layer and the innermost layer from top to bottom. The total thickness of the multi-layer composite ground film is 11 μm. The performance parameters of each layer are as follows.

[0081] Outermost layer: 1 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.910 g / cm 3 Polyethylene compounds include 55% by mass and a density of 0.918g / cm 3 , linear low-density polyethylene with a melt index of 0.20g / 10min and a mass ratio of 45% and a density of 0.900g / cm 3 Ultra-low density polyethylene with a melt index of 1.00 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound.

[0082] Second outer layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0083] Middle layer: 3 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.920 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.920g / cm 3 The first metallocene polyethylene with a melt index of 0.50g / 10min, a mass ratio of 20%, and a density of 0.916g / cm 3 The second metallocene polyethylene with a melt index of 0.20g / 10min and a mass ratio of 10% and a density of 0.927g / cm 3 , a third metallocene polyethylene with a melt index of 0.30 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0084] Second inner layer: 2 μm thick, including polyethylene compound, antioxidant and UV absorber. The density of polyethylene compound is 0.937 g / cm 3 Polyethylene compounds include 70% by mass and a density of 0.941g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 30% and a density of 0.927g / cm 3 , metallocene polyethylene with a melt index of 0.10g / 10min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the weight of the polyethylene compound. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the weight of the polyethylene compound.

[0085] The innermost layer is 3 μm thick and contains polyethylene compounds, antioxidants, UV absorbers, and infrared absorbers. The density of the polyethylene compound is 0.939 g / cm 3Polyethylene compounds include 75% by mass and a density of 0.943g / cm 3 , medium density polyethylene with a melt index of 0.14g / 10min and a mass ratio of 25% and a density of 0.927g / cm 3 The metallocene polyethylene has a melt index of 1.50 g / 10 min. Ningkang Chemical T501 antioxidant accounts for 4‰ of the polyethylene compound's mass. 2-Hydroxy-4-methoxybenzophenone UV absorber accounts for 8‰ of the polyethylene compound's mass. 1,3-Dithiolene-2-thione-4,5-dimercapto complex infrared absorber accounts for 1.5% of the polyethylene compound's mass.

[0086] The multilayer composite mulch films of Examples 1 to 3 and Comparative Examples 1 to 4 can be prepared by the following method:

[0087] (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 uniformly according to the proportions and respectively sent to the extruder of the five-layer co-extrusion film blowing unit;

[0088] (2) Blowing;

[0089] (3) Traction cooling; cooling time is 70 seconds;

[0090] (4) Microstructure construction: After shaping, heat to 80 °C and use a single-sided pattern roller for instant high-pressure pressurization.

[0091] (5) Coiling.

[0092] The parameters of each layer of the multi-layer composite ground membrane of Comparative Example 5 are the same as those of Example 1, and its preparation method can be as follows.

[0093] (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 uniformly according to the proportions and respectively sent to the extruder of the five-layer co-extrusion film blowing unit;

[0094] (2) Blowing;

[0095] (3) Traction cooling; cooling time is 70 seconds;

[0096] (4) Coiling.

[0097] The multilayer composite ground films prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested for their warming performance, thermal insulation performance, light transmittance, haze, and hydrophobicity. The test results are shown in Table 1. The test methods are as follows.

[0098] Warming performance: Cover the experimental field with ground film, measure the surface temperature regularly at 8:00, 13:00 and 18:00 every day, and calculate the temperature increase compared with the temperature without film covering.

[0099] Thermal insulation performance: Cover the experimental field with film, and measure the temperature 5cm underground every two hours from 6:00 to 18:00. Take the average value and calculate the temperature increase compared with the temperature without film.

[0100] Light transmittance: Cut the ground film into test samples of the same size and test them using a film transmittance tester.

[0101] Haze: Cut the ground film into test samples of the same size and test them using a film haze tester.

[0102] Hydrophobicity: Cut the mulch into test samples of the same size and test the contact angle using a contact angle meter.

[0103] Table 1 Performance test results of multi-layer composite ground films of Examples 1 to 3 and Comparative Examples 1 to 5

[0104] As shown in Table 1, compared with Comparative Examples 1-4, the multilayer composite ground films of Examples 1-3 have higher light transmittance, lower haze, and larger contact angles. The surface temperature at 8 a.m. can increase by more than 1.0°C, and 5 cm below the surface can increase by more than 2.0°C. This is because the multilayer composite ground films of the present application, by gradually increasing density from the outside to the inside, can refract sunlight from the outside to the inside to maintain as much parallel light as possible, reducing the reflection ratio during refraction of the ground film, increasing the light transmittance of the ground film, and reducing the haze of the ground film, thereby improving the thermal insulation effect. The addition of an infrared absorber to the innermost layer can effectively isolate the loss of far-infrared radiation during the covering process, thereby improving the thermal insulation performance of the ground film.

[0105] Combining Example 1 and Comparative Example 5, it can be seen that applying instantaneous high-pressure pressure with a pressure roller after inflation and shaping during preparation is beneficial to increasing the contact angle of the multi-layer composite film and can further improve the warming performance.

[0106] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one 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 present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles disclosed herein.

Claims

1. A multi-layer composite plastic film, comprising an outermost layer, a sub-outer layer, a middle layer, a sub-inner layer and an innermost layer arranged in sequence, characterized in that, 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 includes a polyethylene compound, an antioxidant, and an ultraviolet absorber, and the density of the polyethylene compound is ≤ 0.910 g / cm 3 , the antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound, and the ultraviolet absorber accounts for 5 to 12‰ of the mass of the polyethylene compound; The second outermost layer and the second innermost layer both include polyethylene compounds, antioxidants, and ultraviolet absorbers, and the density of the polyethylene compounds is 0.917 to 0.923 g / cm 3 , the antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound, and the ultraviolet absorber accounts for 5 to 12‰ of the mass of the polyethylene compound; The intermediate layer includes a polyethylene-based compound, an antioxidant, and an ultraviolet absorber, and the density of the polyethylene-based compound is ≥ 0.935 g / cm 3 , the antioxidant accounts for 2 to 7‰ of the mass of the polyethylene-based compound, and the ultraviolet absorber accounts for 5 to 12‰ of the mass of the polyethylene-based compound; The innermost layer includes a polyethylene compound, an antioxidant, an ultraviolet absorber, and an infrared absorber. The density of the polyethylene compound is 0.938 to 0.942 g / cm 3 , the antioxidant accounts for 2 to 7‰ of the mass of the polyethylene compound, the ultraviolet absorber accounts for 5 to 12‰ of the mass of the polyethylene compound, and the infrared absorber accounts for 0.5 to 2.5% of the mass of the polyethylene compound.

2. The multi-layer composite plastic film according to claim 1, characterized in that The polyethylene compound in the outermost layer includes linear low density polyethylene with a density of 0.915 - 0.920 g / cm 3 , and ultra-low density polyethylene with a density of 0.900 - 0.905 g / cm 3 , and a melt index of 0.80 - 2.00 g / 10 min. The proportion of the linear low density polyethylene in the polyethylene compound is 40 - 60 wt.%.

3. The multi-layer composite plastic film according to claim 1, wherein The polyethylene compounds in the second outermost layer and the second innermost layer include a first metallocene polyethylene with a density of 0.918 to 0.922 g / cm 3 , a second metallocene polyethylene with a density of 0.914 to 0.918 g / cm 3 , a melt index of 0.10 to 0.25 g / 10 min, and a third metallocene polyethylene with a density of 0.925 to 0.930 g / cm 3 , a melt index of 0.10 to 0.50 g / 10 min. The mass ratio of the first metallocene polyethylene, the second metallocene polyethylene, and the third metallocene polyethylene is 60 to 80:5 to 20:5 to 20.

4. The multi-layer composite plastic film according to claim 1, wherein The polyethylene compounds in the intermediate layer include a first polyethylene and a second polyethylene, and the proportion of the first polyethylene in the polyethylene compounds is 40-75 wt.%, and the first polyethylene includes medium density polyethylene with a density of 0.939-0.943 g / cm 3 , and metallocene polyethylene with a density of 0.938-0.942 g / cm 3 , and a melt index of 0.15-0.25 g / 10 min. The second polyethylene includes metallocene polyethylene with a density of 0.925-0.929 g / cm 3 , and a melt index of 0.05-0.15 g / 10 min and / or linear low density polyethylene with a density of 0.923-0.927 g / cm 3 , and a melt index of 0.40-0.60 g / 10 min.

5. The multi-layer composite plastic film according to claim 1, wherein The polyethylene compounds in the innermost layer include a third polyethylene and a fourth polyethylene, and the proportion of the third polyethylene in the polyethylene compounds is 60-80 wt.%, and the third polyethylene includes medium-density polyethylene with a density of 0.939-0.943 g / cm 3 , metallocene polyethylene with a density of 0.938-0.942 g / cm 3 , and at least one of fourth metallocene polyethylene with a melt index of 0.15-0.25 g / 10 min and fifth metallocene polyethylene with a density of 0.943-0.947 g / cm 3 , and a melt index of 0.40-0.60 g / 10 min. The fourth polyethylene includes sixth metallocene polyethylene with a density of 0.925-0.929 g / cm 3 , and a melt index of 1.00-2.00 g / 10 min.

6. The multi-layer composite plastic film according to claim 1, wherein In each of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer, the antioxidant includes hydroquinone antioxidants.

7. The multi-layer composite plastic film according to claim 1, wherein, In each of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer, the ultraviolet absorber independently includes benzophenone derivatives or benzotriazole derivatives.

8. The multi-layer composite plastic film according to claim 1, wherein In each of the outermost layer, the second outermost layer, the middle layer, the second innermost layer, and the innermost layer, the infrared absorber independently includes dithiocyclopentene-based complexes or transition metal composite oxides.

9. The multi-layer composite plastic film according to claim 1, characterized in that, 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.

10. The preparation method of the multi-layer composite plastic film according to any one of claims 1 to 9, characterized in that It includes: Mix 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, send them to the extruders of the five-layer coextrusion blown film unit respectively, and then successively carry out extrusion, inflation, traction cooling, shaping, and then heat to 75-90 °C, and wind up after pressing with a single-sided pattern roller.

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