Water-retaining and soil-moisture-preserving bio-based fully-degradable agricultural film capable of enhancing absorption of infrared light waves and preparation method thereof

Abstract

The invention discloses a water-retention soil-moisture-conservation full-bio-based full-degradable agricultural film capable of enhancing absorption of infrared light waves and a preparation method thereof, and the preparation method comprises the following steps: dispersing layered silicate minerals, a surfactant and an infrared absorption enhancing agent in a solvent, and carrying out shearing and stripping to obtain active nanosheets; blending and granulating the polylactic acid, the bio-based filler, the active nanosheet and the functional additive to obtain a master batch; carrying out melt blending on the master batch and degradable polyester to form a degradable film, carrying out in-situ two-way stretching on the degradable film, and synchronously carrying out surface oxygen plasma treatment to obtain the bio-based full-degradable agricultural film. The active nanosheets are combined with the full-biodegradable agricultural film, infrared light wave absorption is effectively enhanced, the soil temperature can be increased, photosynthesis can be improved, plant diseases and insect pests can be relieved, the hydrophilicity of the agricultural film is improved after the active nanosheets are blended and oxygen plasma treatment is conducted, meanwhile, the active nanosheets block water vapor from permeating, and the agricultural film has the advantages of being environmentally friendly and free of pollution. Therefore, the water vapor transmission rate is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of degradable agricultural films, and in particular to a bio-based fully degradable agricultural film capable of enhancing absorption of infrared light waves for water and moisture retention and a preparation method thereof. Background Art

[0002] Agricultural films can increase temperature and moisture retention, promote crop yields, and are widely used in agricultural production. However, traditional agricultural films represented by polyethylene (PE) have significant defects, such as low recycling rates and long degradation cycles in the environment, which lead to continuous accumulation in the soil and difficulty in degradation. Long-term use may also cause soil compaction problems, which is not conducive to the growth and development of crops and yields.

[0003] In addition, the existing agricultural film materials use biodegradable materials as raw materials, add additives such as light stabilizers, barriers, water absorption barriers, etc., and use the method of co-extrusion to obtain composite materials for agricultural films with light aging and hydrolysis resistance. There are the following problems: 1) During the preparation process, the dispersion is poor after adding additives and the co-extrusion method leads to significant defects in water retention performance. Due to the limited water retention capacity, it is difficult to keep the soil moist under drought or high temperature conditions; 2) The composite materials for agricultural films prepared by the co-extrusion method have poor mechanical properties and are easy to break or tear in wind, rain, mechanical operation and other environments. Frequent replacement increases the cost of use for farmers and affects the growth environment of crops. These defects limit the effect of traditional agricultural films in improving agricultural production efficiency and sustainable development. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a bio-based fully degradable agricultural film with enhanced absorption of infrared light waves for water and moisture retention and a preparation method thereof. The highly active nanosheets are combined with the bio-based fully degradable agricultural film to effectively enhance the absorption of infrared light waves, increase soil temperature, increase photosynthesis and reduce the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income; the hydrophilicity of the agricultural film is improved by blending the highly active nanosheets and treating with oxygen plasma, and the highly active nanosheets block the permeation of water vapor, thereby reducing the water vapor permeability and further improving the water and moisture retention effect. In addition, the film and the highly active nanosheets are oriented by blending with high-toughness bio-based polyester and biaxial stretching, further improving the mechanical properties and gas barrier properties of the film. The bio-based fully degradable agricultural film has high water absorption and stability, and has good absorption performance in the infrared band, improves the thermal insulation of agricultural plastic film, increases photosynthesis and reduces the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income, and can be naturally degraded after use, reducing environmental pollution and promoting the sustainable development of agricultural production.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The first object of the present invention is to provide a method for preparing a bio-based fully degradable agricultural film that can enhance the absorption of infrared light waves and retain water and moisture, comprising the following steps:

[0007] The layered silicate mineral, surfactant and infrared absorbent are dispersed in a solvent and subjected to shear exfoliation to obtain active nanosheets;

[0008] Polylactic acid, bio-based fillers, active nanosheets and additives are blended and granulated to obtain a hydrophilic and water-retaining composite masterbatch with enhanced absorption of infrared light waves;

[0009] The hydrophilic and moisture-retaining composite masterbatch with enhanced infrared light absorption and the degradable polyester are melt-blended to form a degradable film, the degradable film is in-situ biaxially stretched and simultaneously subjected to surface oxygen plasma treatment to obtain a bio-based fully degradable agricultural film with enhanced infrared light absorption and moisture retention.

[0010] Furthermore, during the preparation of active nanosheets, the mass ratio of the surfactant to the layered silicate mineral is 0.1 to 10:100, and the mass ratio of the infrared absorber to the layered silicate mineral is 0.1 to 5:100.

[0011] Furthermore, in the preparation process of the composite masterbatch, the mass ratio of polylactic acid to bio-based filler is 3:1-8:1, the mass ratio of polylactic acid to active nanosheets is 4:1-20:1, and the mass ratio of polylactic acid to additives is 5:1-20:1.

[0012] Furthermore, the mass ratio of the hydrophilic and water-retaining masterbatch for enhancing the absorption of infrared light waves to the degradable polyester is 1:1 to 1:5.

[0013] Furthermore, during melt blending, the temperature is 160°C to 300°C, during in-situ biaxial stretching, the thickness of the degradable film is 10μm to 800μm, the stretching temperature is 120°C to 250°C, and the longitudinal and transverse stretching ratios of the degradable film are both 2 to 20; the power of the surface oxygen plasma treatment is 50W to 8000W, and the time is 0.5min to 120min.

[0014] Furthermore, the layered silicate mineral is at least one of montmorillonite, talc, kaolin, sericite, diatomaceous earth, illite, and vermiculite, with a maximum radial dimension of 100nm to 2000nm and a thickness of 1nm to 10nm; the infrared absorber is at least one of aminomethyltriethoxysilane and aminoethyltriethoxysilane.

[0015] Furthermore, the surfactant is at least one of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecyl sulfate, and dodecyl betaine; and the solvent is at least one of water, ethanol, acetone, xylene, and toluene.

[0016] Furthermore, the bio-based filler is at least one of wood fiber, bamboo fiber, nanocellulose, and chitosan; the auxiliary agent is at least one of epoxy esters, triethyl citrate, white oil, UV-531, Chimassorb 944, stearic acid, stearate, p-phenylenediamine, antioxidant 168, antioxidant 300, antioxidant 1010, dilauryl thiodipropionate, and near-infrared absorber.

[0017] Furthermore, the degradable polyester is at least one of polybutylene succinate, polybutylene succinate-co-hexanediol butanediol, polyhydroxyalkanoate, polyethylene terephthalate / polycaprolactone blend, and polycaprolactone.

[0018] Furthermore, during the blending and granulation, the temperature is 120° C. to 300° C., the mixing time is 10 min to 120 min, and the ratio of the output energy of the blending process to the mass of the entire mixture is 0.1 kWh / kg to 5 kWh / kg.

[0019] The second object of the present invention is to provide a bio-based fully degradable agricultural film that can enhance the absorption of infrared light waves and retain water and moisture.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention combines highly active nanosheets with biodegradable agricultural films to effectively enhance infrared light absorption, increase soil temperature, increase photosynthesis, and reduce the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income; the hydrophilicity of the agricultural film is improved by blending highly active nanosheets and treating it with oxygen plasma, and the highly active nanosheets block the permeation of water vapor, thereby reducing the water vapor permeability and further improving the water and moisture retention effect; the film and highly active nanosheets are oriented by blending high-toughness bio-based polyester and biaxially stretching, thereby further improving the mechanical properties and gas barrier properties of the film; the bio-based fully degradable agricultural film has high water absorption and stability, and has good absorption properties in the infrared band, thereby improving the thermal insulation of agricultural plastic films, increasing photosynthesis and reducing the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income, and can be naturally degraded after use, reducing environmental pollution, and promoting the sustainable development of agricultural production.

[0022] (2) The highly active nanosheets prepared by the present invention have an extremely high specific surface area, so that more infrared absorbers can be evenly distributed on the surface of the material, increasing the contact area with infrared light and significantly improving the absorption efficiency of infrared light; they can effectively scatter and absorb infrared light, extend the path of light inside the material, and increase the probability of light absorption; the highly active nanosheets prepared by the shear exfoliation method can be evenly dispersed in the matrix material to form a stable exfoliation structure; the interface interaction between the highly active nanosheets and the matrix material is strong, which can form a good interface bonding, significantly enhancing the gas barrier properties and mechanical properties.

[0023] (3) The present invention obtains a highly oriented film by stretching the active nanosheet-modified polymer at a high multiple, which promotes the directional arrangement of nanofillers and molecular chains under a strong stretching field, thereby improving the filler orientation, as well as the orderliness and crystallinity of the polymer, greatly reducing the phonon scattering caused by crystal defects and crystal interfaces, and obtaining a polymer film with high infrared absorption.

[0024] (4) The present invention adopts a process combining high-speed shear peeling and biaxial stretching to form uniformly distributed highly oriented lamellae, which can greatly improve the strength, toughness and ductility of the composite film, and significantly improve the mechanical properties, infrared absorption properties and gas barrier properties of the composite material, greatly expanding the scope of application.

[0025] (5) The present invention utilizes a "nano barrier wall" composed of a highly active nanosheet network to effectively block the penetration of gas molecules, greatly reducing the gas barrier properties of the composite material and further improving the water and moisture retention effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The present invention is a process flow chart of the fully degradable agricultural film prepared by the present invention.

[0027] Figure 2 This is a transmission electron microscope image of the in-situ exfoliation of montmorillonite nanosheets by liquid phase shearing of the present invention. Figure 2 (a) is without in-situ peeling, (b) is with peeling time of 20 min, and (c) is with peeling time of 60 min. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0030] Traditional agricultural films such as polyethylene mainly reduce water evaporation by physical covering, but their materials and structural designs often cannot effectively lock in water, resulting in limited water retention and soil moisture retention effects. Under high temperature and drought conditions, water evaporates rapidly from agricultural films, and soil moisture content is difficult to maintain, affecting the ability of crop roots to absorb water, thereby affecting growth and yield. Existing agricultural film materials use biodegradable materials as raw materials, add additives such as light stabilizers, barriers, water absorption barriers, etc., and adopt a co-blending extrusion method to obtain a composite material for agricultural film that is resistant to light aging and hydrolysis. However, during the preparation process, the co-blending extrusion method after adding additives leads to poor dispersibility and still has significant defects in water retention performance. Due to limited water retention capacity, it is difficult to maintain soil moisture under drought or high temperature conditions, resulting in crops facing the dilemma of insufficient water. This situation is particularly serious under water-scarce climatic conditions, which may lead to limited crop growth and reduced yields. 2) The composite material for agricultural film prepared by the co-blending extrusion method has poor mechanical properties and is easy to break or tear in wind, rain, mechanical operation and other environments. Frequent replacement increases the cost of use for farmers and affects the growth environment of crops. These defects have limited the effectiveness of traditional agricultural films in improving agricultural production efficiency and sustainable development. In addition, most agricultural films have poor absorption of infrared light, especially in cold seasons, and cannot effectively use solar infrared radiation to increase soil temperature, resulting in low temperature in the crop growth environment, slowing growth, affecting germination rate and crop yield, especially at night and in cold seasons, when crops are susceptible to frost and cold damage. In addition, due to the lack of effective infrared light wave absorption capacity, agricultural films cannot fully reduce the impact of greenhouse gases, resulting in excessively high soil temperatures, which may cause poor plant growth or increased pests and diseases. Although there are some so-called degradable agricultural films on the market, their degradation speed and effect often do not meet expectations, and some even produce harmful residues during the degradation process. The residual agricultural films are difficult to completely degrade in the soil, causing long-term environmental pollution and destroying soil structure and ecosystems. Therefore, there is an urgent need to develop a new type of agricultural film material with excellent infrared absorption function and enhanced water retention performance, and to use degradable and environmentally friendly materials to reduce the impact on the environment and support the sustainable development of agriculture.

[0031] Based on the above problems, the present invention provides a method for preparing a bio-based fully degradable agricultural film that can enhance the absorption of infrared light waves and retain water and moisture, such as Figure 1 As shown, the following steps are included:

[0032] S1, dispersing layered silicate minerals, surfactants and infrared absorbents in a solvent, and performing shear exfoliation to obtain highly active nanosheets;

[0033] S2, blending and granulating polylactic acid, bio-based fillers, highly active nanosheets and functional additives to obtain a hydrophilic and water-retaining composite masterbatch with enhanced absorption of infrared light waves;

[0034] S3. Melt-blending the hydrophilic and water-retaining composite masterbatch with enhanced absorption of infrared light waves and the degradable polyester to form a degradable film, in-situ biaxially stretching the degradable film and simultaneously performing surface oxygen plasma treatment to obtain a bio-based fully degradable agricultural film with enhanced absorption of infrared light waves and water retention.

[0035] The invention disperses layered silicate mineral, surfactant and infrared absorber in solvent for shearing and exfoliating, aiming at effectively exfoliating the layered silicate mineral by high shear rate, exfoliating the layered silicate mineral into single-layer or few-layer high-activity nanosheets, and at the same time, with the assistance of surfactant, ensuring uniform dispersion of high-activity nanosheets, improving reaction probability with infrared absorber, forming stable exfoliation structure, improving infrared light absorption capacity and heat preservation effect of material, optimizing heat preservation performance of agricultural film; the adopted shearing and exfoliating method is at least one of high-pressure homogenization method, ultrasonic exfoliation method, liquid phase circulation high-speed shearing method and high-speed centrifugation method, wherein the pressure range of high-pressure homogenization method is 300MPa-600MPa, the ultrasonic power of ultrasonic exfoliation method is 200W-500W, the shear rate of liquid phase circulation high-speed shearing method is 10000rpm-30000rpm, the rotation speed of high-speed centrifugation method is 10000rpm-30000rpm, the temperature is 20℃-80℃, and the processing time range is 10min-120min. In a specific embodiment, a liquid phase circulating high-speed shearing method is used.

[0036] Among them, the blending granulation is to mix polylactic acid, bio-based filler, highly active nanosheets and functional additives, and then place them in a blending device for granulation, the temperature is 120℃~300℃, the mixing time is 10min~120min, and the ratio of the output energy of the blending process to the mass of all the mixtures is 0.1kWh / kg~5kWh / kg. The blending equipment can be at least one of a reciprocating screw extruder, a twin-screw extruder, a high-speed mixer, an open mill, a tumbling internal mixer, a continuous internal mixer, a Z-type kneader, a screw kneader, a vacuum kneader and a horizontal twin-screw mixer. In a specific embodiment, the blending equipment is a twin-screw extruder, wherein the temperatures of the first to sixth zones of the twin-screw extruder are 90℃~250℃ respectively, the head temperature is 90℃~250℃, and the rotation speed is 10rpm~1200rpm.

[0037] Among them, melt blending is to mix the hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves and the degradable polyester, and then place them in a film forming device for extrusion, blow molding or casting at a high temperature of 160°C to 300°C to form a degradable film with a thickness of 10μm to 800μm. The film forming device is at least one of a sheet extruder, a film blow molding machine and a cast film machine; and simultaneously perform in-situ synchronous biaxial stretching, the longitudinal and transverse stretching ratios of the degradable film are both 2 to 20, and the stretched film is subjected to online synchronous oxygen plasma treatment, the power of the surface oxygen plasma treatment is 50W to 8000W, and the time is 0.5min to 120min. Enhanced absorption of infrared light waves After the highly active nanosheets in the hydrophilic and water-retaining composite masterbatch are mixed with the degradable polyester, the interfacial bonding force is enhanced, thereby improving the overall performance of the material. A highly oriented film is obtained by high-multiple stretching of the active nanosheet-modified polymer. Under a strong stretching field, the nanofillers and molecular chains are oriented, the orientation of the fillers, as well as the orderliness and crystallinity of the polymer are improved, the phonon scattering caused by crystal defects and crystal interfaces is greatly reduced, and a polymer film with high infrared absorption can be obtained; and high-toughness bio-based polyester blending and biaxial stretching are used to orient the film and highly active nanosheets, further improving the mechanical properties and gas barrier properties of the film.

[0038] By adding hydrophilic nanofillers and surface oxygen plasma treatment, the hydrophilicity of agricultural films is improved and their water retention performance is enhanced; at the same time, adding mineral materials with good absorption performance in the infrared band helps to reduce the greenhouse effect of soil and plants and promote the sustainable development of agricultural production; the biaxial stretching process improves the mechanical properties of the film, making it more durable in use; adding bio-based fillers to degradable materials reduces the production cost of agricultural films; the agricultural film has low light transmittance and high light blocking properties, can effectively prevent weeds and can be naturally degraded after use, reducing environmental pollution. Bio-based fully degradable agricultural films have high water absorption and stability, and have good absorption properties in the infrared band, which improves the thermal insulation of agricultural plastic films, increases photosynthesis and reduces the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income, and can be naturally degraded after use, reducing environmental pollution and promoting the sustainable development of agricultural production.

[0039] In some specific embodiments, during the preparation of highly active nanosheets, the mass ratio of the layered silicate mineral, surfactant and infrared absorbent is 100:0.1-10:0.1-5. The layered silicate mineral is at least one of montmorillonite, talc, kaolin, sericite, diatomite, illite and vermiculite, with a maximum radial dimension of 100nm-2000nm and a thickness of 1nm-10nm; the infrared absorbent is at least one of aminomethyltriethoxysilane (AMEO), aminoethyltriethoxysilane (AEEOS) and far-infrared powder. The infrared absorbent is added to a mineral material with good absorption performance in the infrared band, and the structure can effectively scatter and absorb infrared light, extend the path of light inside the material, and increase the probability of light absorption, which helps to reduce the greenhouse effect of soil and plants and promote the sustainable development of agricultural production. The surfactant is at least one of cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS), and dodecyl betaine; and the solvent is at least one of water, ethanol, acetone, xylene, and toluene.

[0040] In the present invention, after the layered silicate minerals are effectively stripped by means of a high shear rate, the highly active nanosheets have an extremely high specific surface area, and the structure can effectively scatter and absorb infrared light, extend the path of light inside the material, and increase the probability of light absorption. The active groups in the infrared absorber modify the nanosheets in situ to promote the nanosheets to effectively absorb infrared light; the highly active nanosheets prepared by the shear stripping method can be uniformly dispersed in the matrix material, effectively enhancing the interfacial bonding force; in addition, the interfacial interaction between the highly active nanosheets and the matrix material is strong, and a good interfacial bonding can be formed, thereby improving the overall performance of the material, and utilizing the "nano barrier wall" composed of a network of highly active nanosheets to effectively block the penetration of gas molecules, greatly reducing the gas barrier property of the composite material, and further improving the water and moisture retention effect.

[0041] In some specific embodiments, during the preparation of the composite masterbatch, the mass ratio of polylactic acid, bio-based filler, highly active nanosheets and functional additives is 50-80:30-50:15-20:5-10. Among them, the bio-based filler is at least one of wood fiber, bamboo fiber, nanocellulose and chitosan; the functional additive is at least one of epoxy esters, triethyl citrate, white oil, UV-531, Chimassorb 944, stearic acid, stearate, p-phenylenediamine, antioxidant 168, antioxidant 300, antioxidant 1010, dilauryl thiodipropionate and near-infrared absorber. Among them, the near-infrared absorber has a raw material with strong infrared light absorption ability, such as carbon black, metal oxides (such as iron oxide, chromium oxide, etc.) or infrared dyes (such as IR780, IR820, etc.). By adding functional additives and near-infrared absorbers, it has low light transmittance and high light blocking properties, which can block the growth of weeds while maintaining crop growth.

[0042] In some specific embodiments, the mass ratio of the hydrophilic and water-retaining masterbatch for enhanced absorption of infrared light waves and the degradable polyester is 1:1-5. Among them, the degradable polyester is at least one of polybutylene succinate (PBS), polybutylene succinate-co-hexanediol butanediol (PBAT), polyhydroxyalkanoate (PHA), polyethylene terephthalate / polycaprolactone blend (PES / PCL), and polycaprolactone (PCL). The hydrophilic and water-retaining composite masterbatch for enhanced absorption of infrared light waves and the bio-polyester material are compounded and blended in different proportions to form a good interface interaction, improve the overall performance of the material, and the highly active nanosheets in the composite masterbatch block the penetration of water vapor, thereby reducing the water vapor permeability. The bonding strength in the bio-based filler can be effectively improved through wood fiber, etc., which facilitates the bonding of the bio-based filler with other substances and improves the strength of the agricultural film.

[0043] On the other hand, the present invention provides a bio-based fully degradable agricultural film that enhances the absorption of infrared light waves to retain water and moisture. Fully degradable agricultural film The agricultural film has low light transmittance, high light blocking, high water absorption and stability, high mechanical strength, and good absorption performance in the infrared band, which improves the thermal insulation of agricultural plastic film, and has excellent degradation rate and growth cycle adaptability, increases photosynthesis and reduces the occurrence of pests and diseases, thereby promoting crop growth and increasing production and income, and can be naturally degraded after use, reducing environmental pollution and promoting the sustainable development of agricultural production. The preparation cost is low, the raw materials are simple and easy to obtain, and it is easy to degrade, which is suitable for promotion and use.

[0044] The invention is further described below through specific examples.

[0045] Example 1

[0046] A water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves, comprising the following raw materials in parts by weight: 50 parts of polylactic acid, 30 parts of bamboo fiber, 12.5 parts of montmorillonite nanosheets and 7.5 parts of functional additives;

[0047] The functional additive is composed of the following components in parts by weight: 5 parts of epoxidized soybean oil, 0.5 parts of p-phenylenediamine, 0.5 parts of UV-531, 0.5 parts of calcium stearate, and 1 part of near-infrared absorber iron oxide.

[0048] The preparation method of a water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves comprises the following steps:

[0049] S1, dispersing 10 parts of montmorillonite, 0.1 parts of CTAB and 0.1 parts of aminomethyltriethoxysilane into anhydrous ethanol to form a mixture, wherein the mass content of montmorillonite in the mixture is 0.1wt%, and then grinding at 25°C for 20min using a turbine sand mill with a working energy consumption of 1kWh / kg, and centrifuging to obtain highly active montmorillonite nanosheets with a particle size of 100nm;

[0050] S2, adding polylactic acid, bamboo fiber, high-activity montmorillonite, and functional additives in proportion to a high-speed mixer for hot mixing, mixing at a temperature of 150° C. for 60 min to obtain a primary mixed material, adding the primary mixed material to a twin-screw extruder for extrusion granulation, wherein the temperatures of zones 1 to 6 of the twin-screw extruder are 160° C., 165° C., 175° C., 180° C., 170° C., and 160° C., respectively, the head temperature of the twin-screw extruder is 200° C., the rotation speed is 1200 rpm, and after the ratio of mixing output energy to the mass of all mixtures reaches 0.1 kWh / kg, a hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves is obtained;

[0051] S3. Mix the masterbatch with PBS in a mass ratio of 50:50, and prepare a degradable film by a cast film machine at a temperature of 180°C. The molding thickness of the degradable film is 200μm. At the same time, in-situ synchronous biaxial stretching is performed. During biaxial stretching, the preheating temperature is 120°C, the stretching temperature is 140°C, the cooling temperature is 50°C, the stretching rate is 60mm / min, the transverse stretching ratio is 1.5 times, and the longitudinal stretching ratio is 3 times. At the same time, the surface of the stretched film is treated with oxygen plasma under the treatment conditions of 500W for 10min, so as to obtain a water-retaining, moisture-retaining, fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves, and the thickness is 50μm.

[0052] Example 2

[0053] A water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves, comprising the following raw materials in parts by weight: 40 parts of polylactic acid, 35 parts of wood fiber, 18.5 parts of kaolinite nanosheets and 6.5 parts of functional additives;

[0054] The functional additive is composed of the following components in parts by weight: 5 parts of epoxidized soybean oil, 0.5 parts of p-phenylenediamine, 0.5 parts of UV-531, and 0.5 parts of sodium stearate.

[0055] The preparation method of a water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves comprises the following steps:

[0056] S1. Dispersing 10 parts of kaolinite, 0.5 parts of DTAB and 0.2 parts of aminoethyltriethoxysilane into deionized water to form a mixture, wherein the mass content of kaolinite in the mixture is 1 wt%, and grinding is performed at 25° C. for 60 min using a turbine sand mill with a working energy consumption of 5 kWh / kg, and centrifugation is performed to obtain high-activity kaolinite with a particle size of 80 nm;

[0057] S2, adding polylactic acid, wood fiber, high-activity kaolinite nanosheets, and functional additives in proportion to a tumble mixer and mixing at 180° C. for 30 minutes, and obtaining a hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves after the ratio of the output energy of the tumble mixer to the mass of all the mixture reaches 5 kWh / kg;

[0058] S3. Mix the masterbatch and PBAT in a mass ratio of 50:50, melt at a temperature of 170°C, and prepare a degradable film by blow molding. The molding thickness of the degradable film is 150μm, and in-situ synchronous biaxial stretching is performed. During biaxial stretching, the preheating temperature is 120°C, the stretching temperature is 140°C, the cooling temperature is 50°C, and the stretching rate is 40mm / min, wherein the transverse stretching ratio is 4 times, and the longitudinal stretching ratio is 2 times. The surface of the stretched film is treated with oxygen plasma at 500W for 10min to obtain a water-retaining, moisture-retaining, fully bio-based, and fully degradable agricultural film with enhanced absorption of infrared light waves, having a thickness of 30μm.

[0059] Example 3

[0060] A fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves and water retention, comprising the following raw materials in parts by weight: 40 parts of polylactic acid, 35 parts of wood fiber, 18 parts of kaolinite nanosheets and 7 parts of functional additives;

[0061] The functional additives are composed of the following components in parts by weight: 5 parts of epoxidized soybean oil, 0.5 parts of antioxidants, 0.5 parts of UV-531, 0.5 parts of sodium stearate, and 0.5 parts of near infrared absorber iron oxide.

[0062] The preparation method of a water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves comprises the following steps:

[0063] S1. Dispersing 10 parts of kaolinite, 1.5 parts of SDS and 0.5 parts of aminomethyltriethoxysilane in anhydrous ethanol to form a mixture, wherein the mass content of kaolinite in the mixture is 0.1wt%, grinding the mixture at 25°C for 100min using a turbine sand mill with a working energy consumption of 10kWh / kg, and centrifuging to obtain high-activity kaolinite nanosheets with a particle size of 50nm;

[0064] S2, adding polylactic acid, wood fiber, high-activity kaolinite nanosheets, and functional additives to an open mill for blending and granulation according to a certain proportion, mixing at a temperature of 200° C. for 60 min, and obtaining a hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves after the ratio of output energy to the mass of all the mixture reaches 0.1 kWh / kg;

[0065] S3. The masterbatch and PBAT are mixed in a mass ratio of 30:70, and a degradable film is prepared by tape casting at a temperature of 150°C. The molding thickness of the degradable film is 100 μm, and in-situ synchronous biaxial stretching is performed. During biaxial stretching, the preheating temperature is 90°C, the stretching temperature is 120°C, the cooling temperature is 50°C, and the stretching rate is 50 mm / min, wherein the transverse stretching ratio is 1.5 times, and the longitudinal stretching ratio is 1.5 times. The surface of the stretched film is treated with oxygen plasma online synchronously, and the treatment condition is 500W for 20min, to obtain a water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves, and the thickness is 40 μm.

[0066] Comparative Example 1

[0067] A bio-based fully degradable agricultural film, composed of the following raw materials in parts by weight: 50 parts of polylactic acid, 30 parts of bamboo fiber, 12.5 parts of montmorillonite nanosheets and 7 parts of functional additives;

[0068] The functional additive is composed of the following components in parts by weight: 5 parts of epoxidized soybean oil, 0.5 parts of p-phenylenediamine, 0.5 parts of UV-531, 0.5 parts of calcium stearate and 1 part of near infrared absorber iron oxide.

[0069] The preparation method of bio-based fully degradable agricultural film comprises the following steps:

[0070] S1. Disperse montmorillonite in anhydrous ethanol, wherein the mass content of montmorillonite is 0.1 wt %, grind at 25° C. for 20 min using a turbine sand mill with a working energy consumption of 1 kWh / kg, and centrifuge to obtain montmorillonite nanosheets with a particle size of 100 nm.

[0071] S2, adding polylactic acid, bamboo fiber, montmorillonite nanosheets, and functional additives in proportion to a high-speed mixer for hot mixing, mixing at a temperature of 150° C. for 60 min to obtain a primary mixed material, adding the primary mixed material to a twin-screw extruder for extrusion granulation, wherein the temperatures of zones 1 to 6 of the twin-screw extruder are 160° C., 165° C., 175° C., 180° C., 170° C., and 160° C., respectively, the head temperature of the twin-screw extruder is 200° C., the rotation speed is 1200 rpm, and after the ratio of mixing output energy to the mass of all mixtures reaches 0.1 kWh / kg, a hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves is obtained;

[0072] S3. Mix the masterbatch with PBS in a mass ratio of 50:50, and prepare a degradable film by a cast film machine at a temperature of 180°C. The molding thickness of the degradable film is 200μm. At the same time, in-situ synchronous biaxial stretching is performed. During biaxial stretching, the preheating temperature is 120°C, the stretching temperature is 140°C, the cooling temperature is 50°C, and the stretching rate is 60mm / min. The transverse stretching ratio is 1.5 times, and the longitudinal stretching ratio is 3 times. The surface of the stretched film is treated with oxygen plasma under the treatment conditions of 500W for 10min to obtain a bio-based fully degradable agricultural film with a thickness of 50μm.

[0073] Comparative Example 2

[0074] A water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves, comprising the following raw materials in parts by weight: 40 parts of polylactic acid, 35 parts of wood fiber, 18.5 parts of kaolinite nanosheets and 6.5 parts of functional additives;

[0075] The functional additive is composed of the following components in parts by weight: 5 parts of epoxidized soybean oil, 0.5 parts of p-phenylenediamine, 0.5 parts of UV-531, and 0.5 parts of sodium stearate.

[0076] The preparation method of a water-retaining and moisture-retaining fully bio-based and fully degradable agricultural film with enhanced absorption of infrared light waves comprises the following steps:

[0077] S1. Dispersing 10 parts of kaolinite, 0.5 parts of DTAB and 0.2 parts of aminoethyltriethoxysilane into deionized water to form a mixture, wherein the mass content of kaolinite in the mixture is 0.1wt%, grinding the mixture at 25°C for 60min using a turbine sand mill with a working energy consumption of 5kWh / kg, and centrifuging to obtain high-activity kaolinite nanosheets with a particle size of 80nm;

[0078] S2, adding polylactic acid, wood fiber, high-activity kaolinite nanosheets, and functional additives in proportion to a tumble mixer and mixing at 180° C. for 30 minutes, and obtaining a hydrophilic and water-retaining masterbatch with enhanced absorption of infrared light waves after the ratio of the output energy of the tumble mixer to the mass of all the mixture reaches 5 kWh / kg;

[0079] S3. Mix the masterbatch and PBAT in a mass ratio of 50:50, melt at a temperature of 170°C, and prepare a degradable film by blow molding. The molding thickness of the degradable film is 150μm, and perform oxygen plasma treatment on the surface of the film. The treatment condition is 500W for 10min to obtain a bio-based fully degradable agricultural film with a thickness of 30μm.

[0080] The bio-based fully degradable agricultural films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to structural characterization and performance testing, and the results are as follows.

[0081] The structure of the montmorillonite nanosheets in situ exfoliated by liquid phase shearing in Example 1 was tested by transmission electron microscopy. Figure 2 This is a transmission electron microscope image of the in-situ exfoliation of montmorillonite nanosheets by liquid phase shearing of the present invention. Figure 2 (a) is without in-situ peeling, (b) is peeling time 20min, (c) is peeling time 60min. Figure 2 As shown, after liquid phase shear in-situ exfoliation, the layers of montmorillonite nanosheets are effectively exfoliated, and the layered silicate minerals are exfoliated into few-layer nanosheets, increasing the specific surface area. The nanosheets prepared by the shear exfoliation method can be uniformly dispersed in the matrix material to form a stable composite structure.

[0082] The light transmittance test method is as follows: fix the bio-based fully degradable agricultural film prepared in Examples 1 to 3 and Comparative Examples 1 to 2, place it under a xenon light source, and use a photometer to measure the light intensity transmitted. Record the results and evaluate the light transmittance.

[0083] The mechanical property test method is as follows: the bio-based fully degradable agricultural films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 are cut to obtain tensile specimens, and the tensile properties are tested using a universal tensile machine (model 4403, sensor 100N) of Instron Company of the United States according to the plastic tensile property test standard ASTM D638-2003 of the American Society for Testing and Materials. At least 3 parallel test samples are guaranteed for each group, and the results are averaged.

[0084] The method for testing the moisture barrier performance of ground film is as follows: According to GB / T-1037, the test method for water vapor permeability of plastic film, using a humidity control instrument and a humidity sensor, the bio-based fully degradable agricultural film samples prepared in Example 1 to Example 3 and Comparative Example 1 to Comparative Example 2 are placed in high humidity and low humidity environments respectively, the humidity difference on both sides is measured, and the transmittance is calculated.

[0085] The water absorption test method is as follows: prepare a certain number of material samples and ensure that the sample sizes are consistent. Dry the samples at 60°C to constant weight and record the initial weight (W0). Place the samples under different humidity conditions (in an environmental chamber with 90% relative humidity) to ensure that the number of samples under each humidity condition is consistent. Keep for a certain period of time (such as 24 hours) to ensure that the samples fully absorb water. Take out the samples and quickly absorb excess water on the surface with filter paper. Weigh the weight of the sample (W1). Water absorption calculation: η = (1-W0 / W1) * 100%.

[0086] Water retention test: Place the sample (W1) after water absorption in a constant temperature and humidity chamber for a certain period of time to conduct a water retention test. Experimental steps: Maintain humidity: Place the sample after water absorption under different environmental humidity conditions (in an environmental chamber with 90% relative humidity) to simulate the water retention performance under different environmental conditions. Weighing: Take out the sample at a predetermined time interval (such as every 4 hours) and weigh the sample (W2). Water retention calculation: Water retention rate (%) η = 100% * (W2-W0) / (W1-W0).

[0087] Table 1 Test results of mechanical properties and water vapor permeability of biodegradable agricultural films

[0088]

[0089] As shown in Table 1, the tensile strength of the embodiments is generally higher than that of the comparative examples, especially the tensile strength of Example 3 is the highest, reaching 48.5MPa. This shows that the treatment method of high-activity nanosheets (such as high-activity montmorillonite and kaolinite) (such as higher working energy consumption, longer grinding time, etc.) enables them to obtain higher dispersibility and surface activity. These highly active nanosheets can be better combined with the matrix resin (such as polylactic acid and PBAT), which improves the uniform distribution of highly active nanosheets and the tensile strength of bio-based fully degradable agricultural film. The tensile strength of Comparative Examples 1-2 is low, indicating that the uneven dispersion of the nanosheets and the insufficient optimization of the mixing process result in poor strength of the material. The elongation at break of Examples 1-3 is between 170% and 185%, which is significantly higher than that of the comparative example, indicating that the material has better toughness and ductility. The highest elongation at break of Example 2 is 185%, indicating that the combination of bio-based fillers and highly active kaolinite nanosheets improves the toughness of the material. The elongations at break of Comparative Examples 1 and 2 are 163% and 159% respectively, which are relatively low. The materials are more likely to break when subjected to tensile stress.

[0090] The water vapor transmission rate of Examples 1 to 3 is 189 g·m -2 / 24h~204g·m -2 / 24h, which is lower than that of the comparative example, indicating that the uniform distribution of highly active nanosheets and good interface bonding enhance the water barrier of the material, thereby significantly reducing the water vapor permeability, which helps to maintain soil moisture. The water vapor permeability of comparative examples 1 and 2 is relatively high, which is 258g·m -2 / 24h and 226·m -2 / 24h, indicating that the water vapor barrier properties of these agricultural films are poor, which is not conducive to water and moisture retention. In addition, the improved nanosheet treatment and additive formulation have also optimized the optical properties of the material, making the light transmittance of Examples 1-3 (6.8%-9.3%) lower than that of Comparative Examples 1-2 (38.3%-66.3%), which is conducive to the photosynthesis of plants under the agricultural film. The water retention rate of Examples 1-3 (95%-99%) is significantly higher than that of the comparative example (70%-82%). The enhanced water barrier properties and uniformly dispersed nanosheets increase the water retention rate, making the agricultural film have a significant advantage in water and moisture retention.

[0091] In summary, 1. The water-retaining and moisture-retaining all-bio-based and fully degradable agricultural film proposed in the present invention has high mechanical strength, takes into account the water-retaining and heat-retaining effects, and has excellent degradation rate and growth cycle adaptability, low preparation cost, simple and easy-to-obtain raw materials, and is easy to degrade, suitable for promotion and use. 2. The degradable plastic agricultural film proposed in the present invention has low light transmittance and high light-blocking properties by adding bio-based fillers, which can block the growth of weeds while maintaining the growth of crops. The bonding strength in the bio-based fillers can be effectively improved by wood fibers, etc., which facilitates the bonding of bio-based fillers with other substances and improves the strength of the agricultural film. 3. The bio-degradable agricultural film proposed in the present invention is compounded with hydrophilic nanofillers and bio-polyester materials in different proportions, wherein the layered montmorillonite blocks water vapor transmission, thereby reducing the water vapor transmission rate; further, the present invention performs in-situ modification on the layered nano-montmorillonite to increase the amino group to effectively absorb infrared light. Therefore, the biodegradable mulch film prepared by the present invention has good infrared absorption and water retention properties.

[0092] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0093] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture, characterized in that: The following steps are involved: The layered silicate mineral, surfactant and infrared absorbent are dispersed in a solvent and subjected to shear exfoliation to obtain active nanosheets; The polylactic acid, bio-based filler, active nanosheets and additives are blended and granulated to obtain a hydrophilic and water-retaining composite masterbatch with enhanced absorption of infrared light waves; The hydrophilic and water-retaining composite masterbatch with enhanced absorption of infrared light waves and the degradable polyester are melt-blended to form a degradable film, and the degradable film is in-situ biaxially stretched and simultaneously subjected to surface oxygen plasma treatment to obtain a bio-based fully degradable agricultural film with enhanced absorption of infrared light waves and water retention.

2. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: In the process of preparing active nanosheets, the mass ratio of surfactant to layered silicate mineral is 0.1-10:100, and the mass ratio of infrared absorber to layered silicate mineral is 0.1-5:

100.

3. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: During the preparation of the composite masterbatch, the mass ratio of polylactic acid to bio-based filler is 3:1-8:1, the mass ratio of polylactic acid to active nanosheets is 4:1-20:1, and the mass ratio of polylactic acid to additives is 5:1-20:

1.

4. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: The mass ratio of the hydrophilic and water-retaining composite masterbatch for enhancing the absorption of infrared light waves to the degradable polyester is 1:1 to 1:

5.

5. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: During melt blending, the temperature is 160°C to 300°C. During in-situ biaxial stretching, the thickness of the degradable film is 10μm to 800μm, the stretching temperature is 120°C to 250°C, and the longitudinal and transverse stretching ratios of the degradable film are both 2 to 20. The power of the surface oxygen plasma treatment is 50W to 8000W, and the time is 0.5min to 120min.

6. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: The layered silicate mineral is at least one of montmorillonite, talc, kaolin, sericite, diatomaceous earth, illite and vermiculite, with a maximum radial dimension of 100nm to 2000nm and a thickness of 1nm to 10nm; the infrared absorber is at least one of aminomethyltriethoxysilane and aminoethyltriethoxysilane.

7. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: The surfactant is at least one of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecyl sulfate and dodecyl betaine; and the solvent is at least one of water, ethanol, acetone, xylene and toluene.

8. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: The bio-based filler is at least one of wood fiber, bamboo fiber, nanocellulose, and chitosan; the auxiliary agent is at least one of epoxy esters, triethyl citrate, white oil, UV-531, Chimassorb 944, stearic acid, stearate, p-phenylenediamine, antioxidant 168, antioxidant 300, antioxidant 1010, dilauryl thiodipropionate, and near-infrared absorber.

9. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: The degradable polyester is at least one of polybutylene succinate, polybutylene succinate-co-hexanediol butanediol, polyhydroxyalkanoate, polyethylene terephthalate / polycaprolactone blend, and polycaprolactone.

10. The method for preparing the bio-based fully degradable agricultural film capable of enhancing the absorption of infrared light waves and retaining water and moisture according to claim 1, characterized in that: During blending and granulation, the temperature is 120°C to 300°C, the mixing time is 10min to 120min, and the ratio of the output energy of the blending process to the mass of all the mixture is 0.1kWh / kg to 5kWh / kg.

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