A biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer and preparation method thereof

Abstract

The invention discloses a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer and a preparation method thereof. The coating material comprises the following raw materials in parts by weight: 0.8-2.5 parts of a bio-based film-forming matrix, 0.5-1.5 parts of a hydrophobic cross-linking agent and 0.013-0.4 parts of a bionic self-healing agent; the bionic self-healing agent is prepared by mixing a phase change agent, a plastic roughening agent, a positive assembly agent and a negative assembly agent in a mass ratio of (10-80): (0.1-1): (10-50): (10-50). The present invention is the first to prepare a new type of super-hydrophobic bio-based coated controlled-release fertilizer that can dynamically self-heal based on a bionic strategy, which solves the defect that traditional super-hydrophobic controlled-release fertilizer membranes are easily swelled and damaged, resulting in the failure of the super-hydrophobic property, and gives the membrane surface the function of being able to regenerate a super-hydrophobic state. When in use, the membrane can sensitively respond to temperature changes to dynamically self-heal its super-hydrophobic properties, thereby accurately controlling the release rate of the coated fertilizer, and perfectly combining the nutrient release law of the coated fertilizer with the fertilizer requirement law of crop growth, thereby achieving the purpose of significantly improving the fertilizer utilization rate.

Description

Technical Field

[0001] The invention relates to the technical field of controlled-release fertilizers, and in particular to a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer and a preparation method thereof. Background Art

[0002] my country's continuous bumper grain harvests are largely due to chemical fertilizers, but their nutrient utilization rate is less than 40%. Excessive fertilization not only causes serious economic losses, but also leads to environmental vicious cycle problems such as soil compaction and farmland degradation. Coated controlled-release fertilizer refers to a new type of fertilizer that coats the surface of fertilizer particles with a layer of film to enable it to be released slowly, and can continuously supply nutrients during the crop growth period. However, traditional coated controlled-release fertilizer film materials are petrochemical film materials, which are difficult to degrade and have high costs, while emerging bio-based film materials have poor water repellency and poor density. Water enters the film quickly, and nutrients are basically released in the early stage, making it difficult or impossible to meet the requirements of nutrient controlled release period.

[0003] Super-hydrophobic bio-based coated controlled-release fertilizer refers to a type of bio-based coated controlled-release fertilizer with a water contact angle greater than 150° on the membrane surface. The membrane surface is constructed with super-hydrophobic low-surface-energy micro-nano protrusions. When the fertilizer comes into contact with water, an air layer will be generated between the membrane shell and the water, slowing down the speed at which the initial nutrient water enters the membrane, thereby extending the nutrient controlled-release period of the bio-based coated controlled-release fertilizer. For example, patent CN107032891B discloses a super-hydrophobic bio-based coated controlled-release fertilizer and a preparation method thereof, wherein a mixed aqueous solution of micron-scale materials and nano-scale materials is sprayed onto the fertilizer surface, dried at 30-150°C for 0.1-3h, then immersed in a solvent containing a low surface energy material for 0.1-3h, and dried at 30-150°C for 0.1-3h. However, this method requires high temperature conditions during coating and the preparation process is cumbersome; patent CN112159269B discloses a plant oil-based polyurethane coated fertilizer and a preparation method thereof, wherein nano carbon black is added to the plant oil-based polyurethane coating. Construct micro-nano super-hydrophobic coating, however, the preparation process needs to include three layers of film inside, middle and outside, and nano carbon black needs to be in the middle layer protected by the outer layer film, with poor mechanical properties, easily damaged and falling off to lose super-hydrophobic performance; Patent CN115677415B discloses a kind of magnetic nano-microcapsule self-assembly super-hydrophobic additive and its application, and magnetic nano-microcapsules will form uniformly distributed super-hydrophobic micro-nano-scale convex structures on the outer surface by self-assembly during the coating process, however, the above-mentioned super-hydrophobic coated controlled-release fertilizers only consider the construction of super-hydrophobic interfaces during the design and preparation of fertilizer membrane shells, lacking consideration of super-hydrophobic state stability and durability. In the actual test scene of the inventor's research and development of super-hydrophobic coated controlled-release fertilizers, due to the substantial increase in osmotic pressure in the membrane shell in the middle and late stages of nutrient release, the membrane shell will inevitably present an expanded state, and the original super-hydrophobic micro-nano-scale rough surface is completely destroyed at this time, and no longer has low surface energy characteristics, thereby permanently losing super-hydrophobic properties, and nutrients are lost rapidly. This is contrary to the research and development purpose of super-hydrophobic controlled-release fertilizers to achieve long-term, stable controlled-release periods. There has been no research on the application durability of super-hydrophobic controlled-release fertilizers at home and abroad.

[0004] In addition, the superhydrophobic controlled-release fertilizers reported so far lack the function of matching the supply and demand of crops, and fail to combine the advantage of superhydrophobic performance improvement that greatly extends the controlled-release period with the actual needs of crops for dynamic changes in nutrient demand, that is, to coordinate the coexistence of the two functions of efficient slow release and precise controlled release of coated fertilizers, which is also the core essence of the research and development of coated controlled-release fertilizers. Although some patents have reported bio-based coated controlled-release fertilizers that can be released in response to changes in environmental factors, such as CN113135793A, which discloses a temperature-responsive coated controlled-release fertilizer and a preparation method thereof, using biomass polyurethane as the inner membrane material and biomass thermosensitive hydrogel as the outer membrane material, and regulating nutrient dissolution through the pore swelling behavior of the thermosensitive hydrogel, the total thickness of the inner and outer membrane layers is greater than 4 mm, and the overall fertilizer particles are too large, which is not suitable for large-scale production, and when the ambient temperature is low, its pores expand. The release is accelerated when the temperature is high, while the opposite is true when the temperature is high. However, most crops basically do not absorb nutrients when the temperature is too low. If a large amount of nutrients are released from the fertilizer at this time, it will not only be a waste but also easily lead to root and seedling burns. CN117362107A discloses a coated controlled-release fertilizer containing a temperature-sensitive block copolymer switch and a preparation method thereof. However, the raw materials need to be polymerized for 17 to 19 hours under the protection of an inert gas, dialyzed for 11 to 13 hours after polymerization, and then frozen, dried, and ground. The steps are too complicated, and the production conditions and stability are difficult to control. The key point is that although the above patented products are made of polymers with environmental response functions, they all have the following shortcomings: (1) The general technical guiding principle for regulating nutrient release of this type of environmentally sensitive fertilizer film is: when the soil environment changes, the pores in the film expand or shrink to accelerate or slow down the release of nutrients, but the factor that restricts its release rate is still achieved by the osmotic pressure difference between the inside and outside of the membrane shell under natural conditions. The difference in the release characteristics of the maximum and minimum rates is not significant, and the response degree is not strong; (2) The more critical point is that the temperature difference between day and night in the field soil is large and the temperature changes rapidly, which is a huge challenge to the rapid response ability of the controlled-release fertilizer film. The previously reported environmentally responsive controlled-release fertilizers have poor response sensitivity and cannot respond to environmental changes quickly, making it difficult to achieve precise controlled release. In summary, it is urgent to develop new bio-based coated controlled-release fertilizers that can be durable and super-hydrophobic and have significant rapid response characteristics. Summary of the invention

[0005] In view of the above-mentioned prior art, the purpose of the present invention is to provide a biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer and a preparation method thereof, wherein the controlled-release fertilizer film material comprises a bio-based film-forming matrix, a hydrophobic cross-linking agent and a biomimetic self-healing agent, which endows the film material surface with the function of being able to regenerate a super-hydrophobic state, and when used, the film material can sensitively respond to temperature changes to dynamically self-heal its super-hydrophobic properties, thereby perfectly combining the nutrient release law of the coated fertilizer with the fertilizer requirement law of crop growth, thereby achieving the purpose of significantly improving the fertilizer utilization rate. The inventive ideas and principles of the present invention are as follows:

[0006] In view of the many problems existing in the background technology, the inventor was inspired by the rapid self-healing super-hydrophobic behavior of leaves in nature and made an original technical breakthrough. The formation of super-hydrophobic surface requires non-wetting chemicals and surface roughness. The former can be achieved by modification of low surface energy substances, while the latter requires the construction of micro-nano-level morphological feature structures. As is well known, lotus leaves have super-hydrophobic characteristics. When observing lotus leaves under a microscope, it will be found that in addition to having a rough morphology, its surface is also covered with a layer of waxy substances. These two characteristics are combined to create its super-hydrophobicity. Not only that, lotus leaves can also maintain their super-hydrophobicity for a long time, thanks to the regenerative epidermal wax layer on these surfaces. When the micro-nano rough epidermal wax layer with low surface energy on the leaves is destroyed due to external factors, it will temporarily lose hydrophobicity. At this time, the plant matrix can sense and secrete a new wax layer so that it can easily and quickly restore the low surface energy state of the surface to regenerate super-hydrophobicity. As introduced in the background technology, although the superhydrophobic controlled-release fertilizers that have appeared in recent years can significantly improve the nutrient slow-release effect compared to traditional controlled-release fertilizers, in fact, due to the extremely "fragile" micro-nanoscale superhydrophobic structure on its surface, in actual application, it faces the defect of generally losing the superhydrophobic properties in the middle and late stages of nutrient release, which seriously limits the promotion and application of superhydrophobic controlled-release fertilizers.

[0007] The inventive concept of the present application is as follows: Based on the two major defects of existing superhydrophobic controlled-release fertilizers (1) that can only delay the rate of water entering the membrane in the initial stage, and the membrane material suffers physical damage on the surface due to water absorption and expansion in the middle and late stages of nutrient release, and its low surface energy modified material falls off and fails, and the micro-nano rough morphology is destroyed, resulting in permanent loss of superhydrophobicity and inability to achieve slow nutrient release; and (2) that it can only delay the duration of nutrient controlled release but cannot dynamically respond to environmental changes to match crop nutrient needs, and cannot achieve precise nutrient controlled release, the inventor aims to design a bionic dynamic rapid self-healing superhydrophobic controlled-release fertilizer, the specific working principle of which is as follows: (1) The membrane material is modified using a bionic self-healing agent containing low surface energy chemicals and nano-particles. When the swelling change of the fertilizer membrane shell and other factors cause the low surface energy material to fall off or the nano-rough morphology to be damaged, the membrane surface no longer has superhydrophobic characteristics. At this time, the interfacial free energy between it and the air is much greater than the interfacial free energy between the intrinsically hydrophobic membrane material and the air. Due to the dynamic trend of minimizing the overall free energy of the interface, the bionic self-healing agent in the membrane material is driven to spontaneously migrate to the membrane surface to reduce the total interfacial free energy of the system until the initial equilibrium state is reached. After migration, a rough low-surface-energy fibrous structure is formed on the surface, reshaping the surface super-hydrophobicity, similar to the regeneration behavior of the wax layer on the lotus leaf epidermis, thereby covering the nutrient requirements of the crop during the entire growth period; (2) Some components in the bionic self-healing agent (low-surface-energy modified material component) have a critical phase transition interval. When the ambient temperature is higher than this critical temperature interval, the inherent low-surface-energy modified material attached to the surface undergoes a phase transition, gradually changes to a fluid state and loses to the outside world, and the membrane material passively turns to a hydrophilic state. This process is affected by temperature, that is, the higher the temperature, the faster the transition from hydrophobic to hydrophilic. Although the membrane material still has a tendency for the self-healing agent to migrate to the membrane surface, the migration rate is much lower than the rate of flow loss on the attached surface. This rate difference causes the membrane shell surface to be unable to recover to a super-hydrophobic state, ensuring that the fertilizer can continuously and efficiently release nutrients during the peak period of crop nutrient absorption. When the soil temperature at night drops to close to the critical point of phase change, this rate difference will gradually decrease, and the rate of spontaneous outward migration of the original bionic self-healing agent in the membrane material will exceed the rate of flow loss of the low surface energy material attached to the fertilizer membrane shell. The bionic self-healing agent in the migration state will gradually be anchored in the membrane material matrix, and the low surface energy rough structure interface on the membrane surface will be stabilized until it is restored to a superhydrophobic state.

[0008] Therefore, the technical solution of the present application realizes the continuity of the superhydrophobic interface state throughout the nutrient release period of the controlled-release fertilizer, and the change of soil temperature significantly affects the regeneration change of this superhydrophobic interface, thereby achieving the effect of accurately regulating the nutrient release rate of the superhydrophobic fertilizer, effectively improving the fertilizer utilization rate, and solving the pain point that traditional superhydrophobic coated controlled-release fertilizers cannot have both slow release and controlled release, and truly realizing the purpose of organically combining the slow release function and the controlled release function of the coated fertilizer.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a biomimetic dynamic self-healing super-hydrophobic bio-based coating material, comprising the following raw materials in parts by weight:

[0011] 0.8-2.5 parts of bio-based film-forming matrix, 0.5-1.5 parts of hydrophobic cross-linking agent and 0.013-0.4 parts of biomimetic self-healing agent;

[0012] The bionic self-healing agent is prepared by mixing a phase change agent, a plastic roughening agent, a positive assembly agent and a negative assembly agent in a mass ratio of (10-80): (0.1-1): (10-50): (10-50);

[0013] The phase change agent is one or more of n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, n-eicosane, and n-heneicosane;

[0014] The plastic roughening agent is one or more of amino silver nanoparticles, nano holmium oxide, nano samarium oxide, nano neodymium oxide, nano cerium oxide, nano silicon carbide, and nano antimony tin oxide;

[0015] The positive assembly agent is an anionic polyelectrolyte;

[0016] The negative charge assembling agent is a cationic polyelectrolyte.

[0017] Preferably, the anionic polyelectrolyte is one or more of sodium polyacrylate, sodium polyvinyl sulfonate, poly(sodium p-styrene sulfonate), and potassium polyvinyl sulfate; the cationic polyelectrolyte is one or more of poly(4-vinylpyridine), poly(2-vinylpyridine), and polyethyleneimine hydrochloride.

[0018] Preferably, the phase change agent is a mixture of n-octadecane, n-nonadecane and n-eicosane in a mass ratio of 3:2:1. The phase change temperature range after mixing is 29.5-32°C, and it is a pale yellow-white solid at room temperature (25°C).

[0019] Preferably, the plastic roughening agent is nano antimony tin oxide, which is a powdery substance with a diameter between 10 and 200 nm.

[0020] Furthermore, the bionic self-healing agent is prepared by mixing n-octadecane, n-nonadecane, n-eicosane, nano antimony tin oxide, sodium polyacrylate and polyethyleneimine hydrochloride in a mass ratio of 15:10:5:0.6:15:15.

[0021] Preferably, the bio-based film-forming matrix is ​​formed by mixing vegetable oil polyol and filler in a mass ratio of 100:(1-10);

[0022] The filler is one or more of glass fiber, ceramic fiber, rock wool fiber, nickel powder, rare earth tailings and polytetrafluoroethylene powder.

[0023] Preferably, the vegetable oil polyol is prepared by the following method:

[0024] Vegetable oil, methanol, sodium hydroxide and deionized water are mixed in a mass ratio of (100-500):(10-20):(1-5):(10-100) to obtain a reaction system, a catalyst is added to carry out an ester exchange reaction, and water is removed by vacuum rotary evaporation to obtain vegetable oil polyol.

[0025] Preferably, the catalyst is 0.5-1.5% of sodium methoxide by mass of the reaction system.

[0026] Preferably, the conditions for the transesterification reaction are: 105-120° C., and continuous stirring for 0.5-2 h.

[0027] Preferably, the vegetable oil is one or more of palm oil, citronella oil, Chinese tallow oil, banana oil, croton oil, avocado oil and apple seed oil.

[0028] Preferably, the vegetable oil is a mixture of palm oil, citronella oil and croton oil in a mass ratio of (3-10):4:1.

[0029] Preferably, the hydrophobic crosslinking agent is prepared by mixing isocyanate and siloxane compound in a mass ratio of (5-15):1;

[0030] The isocyanate is one or more of cyclohexyl isocyanate, octadecyl isocyanate, m-toluene isocyanate, o-chlorophenyl isocyanate, m-chlorophenyl isocyanate, furanmethyl isocyanate, cycloheptyl isocyanate, 3,5-dichlorophenyl isocyanate, p-phenylene diisocyanate, polyphenyl polymethylene polyisocyanate and diphenylmethane diisocyanate;

[0031] The siloxane compound is one or more of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(chloromethyl)tetramethyldisiloxane, 1,3-dichlorotetramethyldisiloxane, 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane.

[0032] Preferably, the hydrophobic crosslinking agent is prepared by mixing p-phenylene diisocyanate, polyphenyl polymethylene polyisocyanate, 1,3-bis(3-aminopropyl)tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane in a mass ratio of 8:10:0.5:1.

[0033] The second aspect of the present invention provides a method for preparing the above-mentioned coating material, comprising the following steps:

[0034] (1) mixing the vegetable oil polyol with the filler, and ultrasonically shaking at 40-60° C. for 40-80 min to prepare a bio-based film-forming matrix;

[0035] (2) mixing the isocyanate and the siloxane compound, heating at 70-90° C. and stirring for 1-2 hours to prepare a hydrophobic crosslinking agent;

[0036] (3) mixing the phase change agent, the plastic roughening agent, the positive assembly agent and the negative assembly agent, ultrasonically shaking at room temperature for 30-60 minutes, and refrigerating high-speed centrifugation for 20-40 minutes to prepare a bionic self-healing agent;

[0037] (4) The bio-based film-forming matrix and the hydrophobic cross-linking agent are mixed and stirred to obtain a film-forming mixed system, and then a biomimetic self-healing agent is added, and ultrasonic vibration is performed at room temperature for 20-40 minutes to obtain a uniform coating material.

[0038] The third aspect of the present invention provides the use of the above-mentioned bionic dynamic self-healing super-hydrophobic bio-based coating material in the preparation of coated controlled-release fertilizers.

[0039] The fourth aspect of the present invention provides a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer, comprising: fertilizer particles, and the above-mentioned coating material sprayed on the surface of the fertilizer particles.

[0040] Preferably, the spraying amount of the bionic dynamic self-healing super-hydrophobic bio-based coating material is 0.6-10% of the mass of the fertilizer particles.

[0041] A fifth aspect of the present invention provides a method for preparing the above-mentioned biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer, comprising the following steps:

[0042] The fertilizer particles are added into a preheated drum, and then the bionic dynamic self-healing super-hydrophobic bio-based coating material is sprayed or dripped onto the surface of the fertilizer particles. The drum temperature is continuously maintained during the rotation of the drum and the fertilizer is stirred with a glass rod so that the coating material forms a coating. The above operation is repeated 1 to 10 times to prepare a coated controlled-release fertilizer.

[0043] Preferably, the fertilizer granules are selected from one or more of urea granules, diammonium phosphate granules, superphosphate granules, potassium dihydrogen phosphate granules, and potassium sulfate granules.

[0044] Beneficial effects of the present invention:

[0045] (1) The present invention is the first to prepare a novel super-hydrophobic bio-based coated controlled-release fertilizer that can dynamically self-heal based on a bionic strategy, which solves the defect that the traditional super-hydrophobic controlled-release fertilizer film is easy to swell and break, resulting in the failure of the super-hydrophobic property. The present invention uses a bionic self-healing agent prepared by a phase change agent, a plasticizer, an anionic polyelectrolyte and a cationic polyelectrolyte to modify the film material, wherein:

[0046] Phase change agents are a class of low surface energy alkane mixtures. When incorporated into the microstructure of bio-based membrane materials, a self-healing super-hydrophobic surface is constructed. The damaged surface can quickly restore its super-hydrophobicity without any external stimulation. The self-healing mechanism is attributed to the ability of alkane molecules to quickly migrate from the inner matrix to the outer surface to reduce the surface energy, which is driven by the necessary condition of minimizing the total interfacial free energy of the system. This migration mechanism is very similar to the self-healing mechanism of natural wax in plant leaves. The surface energy of the alkane mixtures selected by the present invention is relatively low, which contributes to the rapid self-healing speed of the super-hydrophobic surface.

[0047] Roughening agent is a kind of nanoparticles, which is the core of constructing the nano-scale rough surface of the membrane surface. The present invention utilizes the assembly mechanism of positive and negative charges between anionic polyelectrolytes and cationic polyelectrolytes to mix and encapsulate nanoparticles with phase change agents. Due to the moderate Coulomb interaction between anionic and cationic polyelectrolytes, the formed polyelectrolyte composite cementing group can maintain a stable structure in the membrane material, so the nanoparticles can quickly migrate to the membrane surface with the low surface energy phase change agent. When exposed to external moisture, the cementing group quickly dissociates, and the encapsulated nanoparticles are released, gradually forming a highly rough nano-scale fibrous structure on the membrane surface, and cooperating with the phase change agent to achieve the regeneration of the surface super-hydrophobic state.

[0048] The low surface energy rough interface on the surface of the modified controlled-release fertilizer film can achieve self-healing regeneration after damage, maintaining the stability of the super-hydrophobic state of the film in the middle and late stages of nutrient release. The nutrient controlled release curve in the middle and late stages is more stable (constant temperature conditions), significantly improving the nutrient utilization rate of the bio-based coated controlled-release fertilizer. The bionic strategy of the self-healing super-hydrophobic coated controlled-release fertilizer proposed in the present invention has achieved an original breakthrough in the theory and technology of controlled-release fertilizer.

[0049] (2) The self-healing regeneration behavior of the super-hydrophobic coating designed by the present invention is affected by the environment. Since the phase change agent has a critical phase change interval that is sensitive to soil temperature, it can achieve repeated switching between super-hydrophobicity and hydrophilicity on the membrane surface, and can dynamically respond to crop needs. Compared with the passive nutrient regulation of traditional temperature-sensitive controlled-release membranes that rely on membrane pore size and natural osmotic pressure, the maximum and minimum nutrient release rates of the controlled-release fertilizer of the present invention are greatly different, and can actively match the different nutrient requirements of the critical period and inert period of crop growth, providing a key technical means to solve the contradiction between the long-term efficient slow release and dynamic precise controlled release of coated fertilizers. In addition, since the preparation of the phase change agent involves the combination of a mixture of alkanes with different melting points, its temperature phase change interval is variable, which meets the different requirements of temperature sensitivity for nutrient absorption of different crops.

[0050] (3) The present invention utilizes renewable new plant oil resources as the raw material for controlled-release fertilizer film formation. The amount of plant oil polyol and isocyanate synthesized by ester exchange reaction can be controlled at (1.8-2.3):1. Compared with traditional bio-based coated controlled-release fertilizers, it has a higher content of bio-based components while still maintaining a high film-forming property and cross-linking degree. The bio-based matrix is ​​blended and modified using low glass transition temperature siloxane compounds and easily dispersible fillers, which effectively improves the flow mobility of the bio-based film material, which provides additional degrees of freedom for the diffusion of the biomimetic self-healing agent in the bio-based film network. The synergistic effect of the temperature-sensitive mobility of the phase change agent and the high mobility of the modified bio-based membrane network ensures the rapid migration dynamics of the bionic self-healing agent from the matrix to the outer surface, thereby realizing the rapid self-healing of the superhydrophobic state on the membrane surface (about 30 minutes), ensuring the performance of controlled-release fertilizers to quickly respond to the nutrient absorption characteristics of crops under the scenario of rapid temperature changes caused by the alternation of day and night. It solves the pain point of traditional environmentally sensitive coated controlled-release fertilizers that have slow response speed and lead to inaccurate nutrient release, and promotes the innovation of the controlled-release fertilizer industry.

[0051] (4) The bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer developed by the present invention can increase the nutrient controlled-release period by 2 to 3 times compared with the coated controlled-release fertilizer without hydrophobic modification, and by 1 times compared with the traditional super-hydrophobic coated controlled-release fertilizer, and has lower cost, simple operation process, low energy consumption, and green environmental protection. The economic, social and ecological benefit potential is significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 : Nutrient release characteristics of the coated controlled-release fertilizer prepared by the present invention under constant temperature conditions (25°C). Wherein a is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 1 under static water constant temperature conditions; b is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 2 under static water constant temperature conditions; c is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 3 under static water constant temperature conditions;

[0053] Figure 2 : Nutrient release characteristics of the coated controlled-release fertilizer prepared by the present invention under variable temperature conditions. Wherein a is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 1 and Comparative Example 1 under static water variable temperature conditions; b is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 2 and Comparative Example 2 under static water variable temperature conditions; c is the nutrient release curve of the coated controlled-release fertilizer prepared in Example 3 and Comparative Example 3 under static water variable temperature conditions;

[0054] Figure 3 : Water contact angle of the film shell of the coated controlled-release fertilizer prepared by the present invention. Wherein a: Example 1; b: Example 2; c: Example 3; d: Comparative Example 1; e: Comparative Example 2; f: Comparative Example 3;

[0055] Figure 4 : The field nutrient release curve of the coated controlled-release fertilizer prepared by the present invention is compared and analyzed with the nutrient absorption rate curve during the crop growth period.

[0056] Figure 5 : The average annual temperature, average precipitation and average sunshine time in the experimental area during the ten years from 2010 to 2020. DETAILED DESCRIPTION

[0057] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0058] As introduced in the background technology section, the current bio-based coated controlled-release fertilizers have poor nutrient release control capabilities due to their natural hydrophilicity relative to traditional petrochemical membrane materials, which severely limits their large-scale commercial promotion in my country's agricultural materials market, especially in the downstream market. Although various methods have been studied to improve its controlled-release performance, such as superhydrophobic modification, in actual application scenarios, since the release of nutrients requires the entry of water for dissolution, no matter how the coating material is designed and prepared, the membrane shell will expand and deform in the middle and late stages of nutrient release, making it difficult or even impossible to maintain the stability of the superhydrophobic structure on the membrane surface, and the controlled-release period can only be forcibly extended by increasing the cost of membrane material usage; in addition, the traditional superhydrophobic modification method only delays the speed at which water enters the membrane in the early stage of nutrient release to extend the total nutrient controlled-release period, but some crops, such as sweet potatoes and green onions, have a maximum nitrogen efficiency period. At the beginning of growth, the nutrient release performance of previous superhydrophobic coated controlled-release fertilizers cannot meet the nutrient needs of crops. The key is that its nutrient release characteristic curve is still relatively single, and can only be changed to a low degree by changing the coating thickness, but the nutrient release is still not precise. Different crops, such as wheat, have a maximum nitrogen efficiency period from jointing to heading, corn has a maximum nitrogen efficiency period from trumpet to early cotton male stage, and cotton has a maximum nitrogen and phosphorus efficiency period in the flowering and boll stage. In addition, the nutrient absorption of almost all crops is affected by environmental factors and changes. This single nutrient release characteristic cannot adapt to the dynamic nutrient needs of crops.

[0059] In view of this, the present invention has conducted in-depth research on super-hydrophobic bio-based coated controlled-release fertilizers. Aiming at the two major technical contradictions of the super-hydrophobic interface state of super-hydrophobic bio-based coated controlled-release fertilizers being fragile and easy to be damaged and the nutrient release being unable to accurately and dynamically respond to the nutrient needs of crops, a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer is prepared. This not only gives the membrane material the regenerative self-healing property after the super-hydrophobic state is damaged to continuously release nutrients, but also realizes accurate and efficient controlled release of nutrients in dynamic response to changes in soil temperature.

[0060] The invention uses vegetable oil as a bio-based raw material, mixes it with methanol (99.5%), 15 mol / L sodium hydroxide solution and deionized water, adds it into a three-necked flask, adds 1% of the system mass of sodium methoxide, heats it to 105-120° C. in an oil bath and stirs it magnetically for 0.5-2 hours, and vacuum-rotates the product at 65° C. for 30 minutes to remove water to prepare vegetable oil polyol. The invention uses sodium methoxide as a catalyst to reduce the activation energy required for the reaction, and the reaction only needs to be carried out in the range of 105-120° C., and by optimizing the reaction conditions, the ester exchange efficiency is improved, and the average hydroxyl value of the polyol product is 221.6 (refer to "HG / T2709-2022 Plastics-Determination of Hydroxyl Value of Polyester Polyol for Producing Polyurethane").

[0061] The aforementioned vegetable oil polyol and filler are mixed in a mass ratio of 100:(1-10), added into a 250 ml beaker, and ultrasonically oscillated at 40-60° C. using an ultrasonic water bath constant temperature oscillator for 40-80 min to allow the filler to be evenly dispersed in the vegetable oil polyol to obtain a bio-based film-forming matrix.

[0062] The invention mixes isocyanate and siloxane compound in a mass ratio of (5-15):1, adds the mixture into a 100 ml single-necked flask, heats the mixture to 70-90° C. in a silicone oil bath, and reacts the mixture for 1-2 hours under constant magnetic stirring to obtain a uniform mixed solution of the two, which is used as a hydrophobic crosslinking agent.

[0063] The invention uses a mixture of different alkanes as a phase change agent, nanoparticles as a plasticizer, a cationic polyelectrolyte as a positively charged assembling agent, and an anionic polyelectrolyte as a negatively charged assembling agent in a mass ratio of (10-80):(0.1-1):(10-50):(10-50), and ultrasonically vibrates for 30-60 minutes at room temperature (25°C), and then puts the mixture into a centrifuge and centrifuges it at 10000-15000 rpm for 30 minutes to serve as a bionic self-healing agent.

[0064] The present invention uniformly mixes the aforementioned bio-based film-forming matrix and the hydrophobic crosslinking agent in a mass ratio of (0.8-2.5): (0.5-1.5) to obtain a film-forming mixed system, then adds 1-10% of the total mass of the film-forming mixed system with a bionic self-healing agent, and ultrasonically vibrates for 20-40 minutes to obtain a coating material.

[0065] Fertilizer particles are added into a rotating drum and preheated to 75° C. After 10 minutes, a coating material is sprayed or coated on the surface of the fertilizer particles in the rotating drum according to 0.6% of the fertilizer mass, and the coating material is continuously stirred with a glass rod. The coating material is heat-cured within 8 to 10 minutes during the rotation of the drum, promoting the synthesis of a bionic dynamic self-healing super-hydrophobic bio-based coating, so that the coating adheres to the surface of the fertilizer particles. The above operation is repeated 1 to 10 times to obtain a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer with a spraying amount of 0.6 to 6%.

[0066] In the above method, the inner diameter of the coating drum is 500 mm and the rotation speed is 25 rpm; the granular urea is preheated by a combination of hot air heating and pot heating; the coating material spraying or coating rate is 2 g / min, and during the coating process, the drum temperature is maintained at 70°C.

[0067] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments.

[0068] The test materials used in the examples and comparative examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0069] Palm oil (CAS No. 8002-75-3), croton oil (CAS No. 8001-28-3), avocado oil (also known as "avocado oil", CAS No. 8024-32-6), and citronella oil (CAS No. 8001-29-1) were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0070] Example 1: Preparation of biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer:

[0071] (1) Preparation of vegetable oil polyols:

[0072] Palm oil, citronella oil and croton oil are mixed in a mass ratio of 5:4:1 to prepare a vegetable oil raw material, the vegetable oil raw material, methanol, sodium hydroxide and water are mixed in a mass ratio of 150:15:2:50 and added into a single-necked flask to obtain a reaction system, 1% sodium methoxide by mass fraction of the reaction system is added as a catalyst, the oil bath is heated to 105° C. and stirred for 1 hour, and water is removed by vacuum rotary evaporation to obtain a vegetable oil polyol;

[0073] (2) Preparation of bio-based film-forming matrix:

[0074] Vegetable oil polyol, nickel powder and polytetrafluoroethylene powder were mixed in a mass ratio of 50:1:1 and added into a 250 ml beaker, and ultrasonically oscillated at 50°C for 1 h using an ultrasonic water bath constant temperature oscillator to obtain a bio-based film-forming matrix;

[0075] (3) Preparation of hydrophobic crosslinking agent:

[0076] P-phenylene diisocyanate, polyphenyl polymethylene polyisocyanate, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane were mixed in a mass ratio of 8:10:0.5:1, added into a 100 ml single-necked flask, and magnetically stirred in an oil bath at 80°C for 1.5 h to obtain a hydrophobic crosslinking agent;

[0077] (4) Preparation of bionic self-healing agent:

[0078] n-octadecane, n-nonadecane, n-eicosane, nano antimony tin oxide, sodium polyacrylate and polyethyleneimine hydrochloride were mixed in a mass ratio of 15:10:5:0.6:15:15 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min using a refrigerated centrifuge at -20°C to obtain a bionic self-healing agent;

[0079] (5) Preparation of coating materials:

[0080] The bio-based film-forming matrix and the hydrophobic cross-linking agent are uniformly mixed in a mass ratio of 2.5:1 to obtain a film-forming mixed system; 1 mass% of a biomimetic self-healing agent is added to the film-forming mixed system, and ultrasonicated at room temperature of 25°C for 30 minutes to obtain a coating material;

[0081] (6) Preparation of coated controlled-release fertilizer:

[0082] 2 kg of fertilizer granules were added to a drum and preheated to 75°C. After 10 minutes, the coating material was sprayed or coated on the surface of the fertilizer granules. The temperature was kept at 75°C during the rotation of the drum. The coating material was solidified to form a coating to prepare a coated controlled-release fertilizer. The mass of the coating material sprayed or dripped onto the surface of the fertilizer granules each time accounted for 0.6% of the mass of the fertilizer granules. The above steps were repeated 7 times to obtain a biomimetic dynamic superhydrophobic bio-based coated controlled-release fertilizer with a coating thickness of 4.2%.

[0083] According to experimental tests, the film material of the controlled-release fertilizer changes to a hydrophilic state when the temperature is higher than 29.5°C, and the static water nutrient controlled release period (at room temperature of 25°C) is 3 to 4 months.

[0084] Example 2: Preparation of biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer:

[0085] (1) Preparation of vegetable oil polyols:

[0086] Palm oil, citronella oil and avocado oil were mixed in a mass ratio of 3:2:1 to prepare a vegetable oil raw material, which was mixed with methanol, sodium hydroxide and water in a mass ratio of 120:15:3:65 and added into a single-necked flask, and 1% sodium methoxide as a catalyst was added thereto, and the mixture was heated to 110°C in an oil bath and stirred for 1 hour, and water was removed by vacuum rotary evaporation to obtain vegetable oil polyols;

[0087] (2) Preparation of bio-based film-forming matrix:

[0088] The vegetable oil polyol, glass fiber and ceramic fiber were mixed in a mass ratio of 50:1:1 and added into a 250 ml beaker, and ultrasonically oscillated for 1 h using an ultrasonic water bath constant temperature oscillator at 50°C to obtain a bio-based film-forming matrix;

[0089] (3) Preparation of hydrophobic crosslinking agent:

[0090] Cyclohexyl isocyanate, m-toluene isocyanate, 1,3-bis(chloromethyl)tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane were mixed in a mass ratio of 18:5:2:1, added into a 100 ml single-necked flask, and magnetically stirred in an oil bath at 80° C. for 1.5 h to obtain a hydrophobic crosslinking agent;

[0091] (4) Preparation of bionic self-healing agent:

[0092] n-Hexadecane, nano-holmium oxide, poly(4-vinylpyridine) and poly(sodium p-styrene sulfonate) were mixed in a mass ratio of 10:0.1:20:20 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min at -20°C using a refrigerated centrifuge to obtain a bionic self-healing agent;

[0093] (5) Preparation of coating materials:

[0094] The bio-based film-forming matrix and the hydrophobic cross-linking agent are uniformly mixed in a mass ratio of 0.8:1 to obtain a film-forming mixed system; 1 mass% of a biomimetic self-healing agent is added to the film-forming mixed system, and ultrasonicated at room temperature of 25°C for 30 minutes to obtain a coating material;

[0095] (6) Preparation of coated controlled-release fertilizer:

[0096] 2 kg of fertilizer granules are added to a drum, preheated to 75°C, and after 10 minutes, the coating material is sprayed or coated on the surface of the fertilizer granules. The temperature is kept at 75°C during the rotation of the drum, and the coating material is solidified to form a coating to prepare a coated controlled-release fertilizer. The mass of the coating material sprayed or dripped onto the surface of the fertilizer granules each time accounts for 0.6% of the mass of the fertilizer granules. Repeat the above steps 10 times to obtain a biomimetic dynamic superhydrophobic bio-based coated controlled-release fertilizer with a coating thickness of 6%.

[0097] According to experimental tests, the film material of the controlled-release fertilizer changes to a hydrophilic state when the temperature is higher than 18.2°C, and the static water nutrient controlled release period (at room temperature of 25°C) is 5 to 6 months.

[0098] Example 3: Preparation of biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer:

[0099] (1) Preparation of vegetable oil polyols:

[0100] Palm oil, citronella oil and avocado oil were mixed in a mass ratio of 2:1:1 to prepare a vegetable oil raw material, which was mixed with methanol, sodium hydroxide and water in a mass ratio of 200:15:3:60 and added into a single-necked flask, and 1% sodium methoxide as a catalyst was added thereto, and the mixture was heated to 115° C. in an oil bath and stirred for 1 h, and water was removed by vacuum rotary evaporation to obtain vegetable oil polyols;

[0101] (2) Preparation of bio-based film-forming matrix:

[0102] Vegetable oil polyol, rock wool fiber and polytetrafluoroethylene powder were mixed in a mass ratio of 50:1:1 and added into a 250 ml beaker, and ultrasonically oscillated for 1 h using an ultrasonic water bath constant temperature oscillator at 50°C to obtain a bio-based film-forming matrix;

[0103] (3) Preparation of hydrophobic crosslinking agent:

[0104] Octadecyl isocyanate, cycloheptyl isocyanate, 1,3-dichlorotetramethyldisiloxane, and 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane were mixed in a mass ratio of 8:6:1:1, added into a 100 ml single-necked flask, and magnetically stirred in an oil bath at 80° C. for 1.5 h to obtain a hydrophobic crosslinking agent;

[0105] (4) Preparation of bionic self-healing agent:

[0106] n-Heptadecane, n-octadecane, nano-samarium oxide, poly(2-vinylpyridine) and polyethylene sulfate potassium salt were mixed in a mass ratio of 15:10:0.6:15:15 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min using a refrigerated centrifuge at -20°C to obtain a bionic self-healing agent;

[0107] (5) Preparation of coating materials:

[0108] The bio-based film-forming matrix and the hydrophobic cross-linking agent are uniformly mixed in a mass ratio of 2:1 to obtain a film-forming mixed system; 1 mass% of a biomimetic self-healing agent is added to the film-forming mixed system, and ultrasonicated at room temperature of 25°C for 30 minutes to obtain a coating material;

[0109] (6) Preparation of coated controlled-release fertilizer:

[0110] 2 kg of fertilizer granules were added to a drum and preheated to 75°C. After 10 minutes, the coating material was sprayed or coated on the surface of the fertilizer granules. The temperature was kept at 75°C during the rotation of the drum. The coating material was solidified to form a coating to prepare a coated controlled-release fertilizer. The mass of the coating material sprayed or dripped onto the surface of the fertilizer granules each time accounted for 0.6% of the mass of the fertilizer granules. The above steps were repeated 7 times to obtain a biomimetic dynamic superhydrophobic bio-based coated controlled-release fertilizer with a coating thickness of 4.2%.

[0111] According to experimental tests, the membrane material of the controlled-release fertilizer changes to a hydrophilic state when the temperature is higher than 26.7°C, and its static water nutrient controlled release period is 4 to 5 months.

[0112] Comparative Example 1:

[0113] The difference between this comparative example and Example 1 is that the components of n-octadecane, n-nonadecane and n-eicosane are omitted in the preparation process of the bionic self-healing agent. The specific preparation method is as follows:

[0114] Nano antimony tin oxide, sodium polyacrylate and polyethyleneimine hydrochloride were mixed in a mass ratio of 0.6:15:15 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min at -20°C using a refrigerated centrifuge to obtain a bionic self-healing agent;

[0115] The remaining preparation steps are the same as those in Example 1 to obtain a coated controlled-release fertilizer.

[0116] Comparative Example 2:

[0117] The difference between this comparative example and Example 2 is that the preparation process of the hydrophobic crosslinking agent omits 1,3-bis(chloromethyl)tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane components, and the specific preparation method is as follows:

[0118] Cyclohexyl isocyanate and m-toluene isocyanate were mixed in a mass ratio of 18:5 and added into a 100 ml single-necked flask, and magnetically stirred for 1.5 h in an oil bath at 80°C to obtain a hydrophobic crosslinking agent;

[0119] The remaining preparation steps are the same as those in Example 2 to obtain a coated controlled-release fertilizer.

[0120] Comparative Example 3:

[0121] The difference between this comparative example and Example 3 is that the preparation process of the bionic self-healing agent omits the poly(2-vinylpyridine) and polyvinyl sulfate potassium salt components. The specific preparation method is as follows:

[0122] n-Heptadecane, n-Octadecane and nano-samarium oxide were mixed in a mass ratio of 15:10:0.6 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min at -20°C using a refrigerated centrifuge to obtain a bionic self-healing agent;

[0123] The remaining preparation steps are the same as those in Example 3 to obtain a coated controlled-release fertilizer.

[0124] Comparative Example 4:

[0125] The difference between this comparative example 4 and example 1 is that the nano antimony tin oxide component is omitted in the preparation process of the bionic self-healing agent. The specific preparation method is as follows:

[0126] n-octadecane, n-nonadecane, n-eicosane, sodium polyacrylate and polyethyleneimine hydrochloride were mixed in a mass ratio of 15:10:5:15:15 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min using a refrigerated centrifuge at -20°C to obtain a bionic self-healing agent;

[0127] The remaining preparation steps are the same as those in Example 1 to obtain a coated controlled-release fertilizer.

[0128] Comparative Example 5:

[0129] The difference between this comparative example 5 and example 1 is that the sodium polyacrylate and polyethyleneimine hydrochloride components are omitted in the preparation process of the bionic self-healing agent. The specific preparation method is as follows:

[0130] n-octadecane, n-nonadecane, n-eicosane and nano antimony tin oxide were mixed in a mass ratio of 15:10:5:0.6 and added into a 100 ml beaker, ultrasonically vibrated for 30 min using an ultrasonic water bath constant temperature oscillator at room temperature, and then centrifuged at 10000 rpm for 30 min using a refrigerated centrifuge at -20°C to obtain a bionic self-healing agent;

[0131] The remaining preparation steps are the same as those in Example 1 to obtain a coated controlled-release fertilizer.

[0132] Test Example 1: Test for determination of nutrient release rate:

[0133] The determination of nutrient release rate refers to the National Standard of the People's Republic of China "GB / T 23348-2009 Slow-release Fertilizer". The specific test method is as follows:

[0134] 1.25℃ constant temperature culture test:

[0135] 10 g of the coated controlled-release fertilizer prepared in Examples 1-3 was placed in glass bottles containing 200 mL of deionized water and stored in a constant temperature incubator at 25°C. Water samples of each fertilizer were taken out on the 1st, 3rd, 5th, 7th, 14th, 21st, and 28th days of cultivation, and the interval for subsequent sampling was 7 days until the cumulative nutrient release rate reached 80%; after each sampling, the remaining water in the bottle was poured out, and 200 mL of deionized water was added to the bottle again. The nitrogen concentration of the water sample was determined using the Kjeldahl method.

[0136] 2. Temperature-variable culture test:

[0137] A variable temperature culture test was designed based on the constant temperature culture test. 10 g of the coated controlled release fertilizer prepared in Examples 1-3 and Comparative Examples 1-3 were placed in glass bottles containing 200 mL of deionized water and stored in an incubator. Some of the treatments changed the temperature conditions during the culture period. Water samples of each fertilizer were taken out at intervals of 3 days; after each sampling, the remaining water in the bottle was poured out, and 200 mL of deionized water was added to the bottle again. The nitrogen concentration of the water sample was determined using the Kjeldahl method.

[0138] like Figure 2 As shown in a, at 25°C, due to the presence of hydrophobic silane in the membrane matrix, the initial release rate of the coated controlled-release fertilizer prepared in Comparative Example 1 is close to that of Example 1. When the temperature rises to 30°C, the bionic self-healing agent in the membrane shell of the coated controlled-release fertilizer prepared in Example 1 reaches its phase change temperature range, the membrane shell turns into a hydrophilic state, and the nutrient release is accelerated. When the temperature drops back to 20°C, the nutrient release of Example 1 slows down, while there is no change in Comparative Example 1, indicating that the phase change agent drives the bionic self-healing of the super-hydrophobic state of the membrane material. Figure 2 b shows that the coated controlled-release fertilizer prepared in Comparative Example 2 is limited in the migration rate of the phase change agent in the absence of the silane compound component, and cannot achieve rapid and precise regulation of nutrients affected by temperature; Figure 2 c shows that in the coated controlled-release fertilizer prepared in Comparative Example 3, in the absence of anionic and cationic polyelectrolyte components, the plasticizer cannot migrate with the phase change healing agent, resulting in limited superhydrophobic self-healing effect and inability to restore the initial superhydrophobic state, resulting in accelerated nutrient release in the later stage.

[0139] Test Example 2: Water contact angle test of coated controlled-release fertilizer:

[0140] Recover the residual membrane shells of the coated controlled-release fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 used in Test Example 1 after the release is completed, cut a relatively flat sheet of film (about 5 mm in diameter), treat the cut sample with an ultrasonic cleaner, dry it naturally, and place it for more than 24 hours. Place the sample to be tested on the test platform of the contact angle measuring instrument, adjust the distance between the needle and the sample, so that the hanging drop dripped out can contact the sample when it is 1±0.3μL and detach from the needle to form a sessile drop, take a picture through the camera system, and calculate its static contact angle by the spherical calculation method.

[0141] like Figure 3 As shown, after variable temperature culture, Example 1 ( Figure 3 a), Example 2 ( Figure 3 b) and Example 3 ( Figure 3 c) The coated controlled-release fertilizers prepared can achieve self-healing of the original super-hydrophobic properties of the membrane material; in contrast, the comparative example 1 ( Figure 3 d) is still in the hydrophilic state after the temperature is restored, which proves the important role of phase change agent in the bionic self-healing process; Comparative Example 2 ( Figure 3 e) and Comparative Example 3 ( Figure 3 f) Although it recovered, it did not reach the super-hydrophobic state. The water contact angle test experiment further verified the conclusion of Experimental Example 1.

[0142] According to Fowkes theory, combined with water contact angle data, the surface energy of the membrane material is calculated. The surface energy calculation formula is as follows:

[0143]

[0144] In the formula, Rsv is the surface energy of the membrane material, and Rlv=72.8.

[0145] Table 1 Surface energy of membrane materials with different treatments of controlled-release fertilizers

[0146]

[0147] It can be seen from Table 1 that the surface energies of the membranes prepared in Examples 1-3 are significantly lower than those of the membranes prepared in Comparative Examples 1-3, which further verifies the conclusion of Experimental Example 1 regarding the differences in nutrient controlled-release characteristics of different controlled-release fertilizers.

[0148] Test Example 3: Field Planting Test:

[0149] Field planting tests were conducted using the coated controlled-release fertilizers prepared in Example 1, Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 4, and Comparative Example 5 of the present invention. The specific test methods are as follows:

[0150] The test crops are summer corn and winter wheat, the corn variety is Zhengdan 958, and the wheat variety is Shannong 28. The test area is Linzi District, Zibo City, Shandong Province, with a warm temperate monsoon continental climate. From 2010 to 2020, the average temperature is 14.11℃, the average precipitation is 631.01mm, and the average sunshine time is 2240.97h ( Figure 5 ). The test soil type is lime light moist rudimentary soil (tidal soil), which is a soil for planting corn-wheat rotation for many years, and the planting method is corn-wheat rotation. The basic physical and chemical properties of the 0-20cm soil layer are: organic matter content is 8.65g / kg, nitrate nitrogen content is 20.05mg / kg, ammonium nitrogen content is 7.37mg / kg, available phosphorus content is 18.9mg / kg, and pH value is 9.05.

[0151] The area of ​​a single test plot is 20m 2(6.67m long × 3m wide), 5 rows of corn were planted in each plot during the corn season, with a row spacing of 60cm and a plant spacing of 24.7cm. The corn seeds were buried at a depth of 5cm, and the fertilizer was buried at a depth of 10-15cm, 10cm away from the seed row. The ratio of corn seed rows to fertilizer rows was 1:1, and the nitrogen application rate was 300kg / ha (pure), and the nitrogen materials for different treatments were ordinary urea and the coated controlled-release fertilizers prepared in Example 1, Comparative Example 1, Comparative Example 4, and Comparative Example 5, respectively. The yield was measured and harvested in early October;

[0152] In the wheat season, three rows of wheat are planted in each plot, with large and small rows, the large row width is 25 cm, and the small row width is 15 cm. Fertilizer is applied in the middle of the large row, which is the same as the width of the large and small rows of the "seed and fertilizer sowing at the same time" currently being promoted. The wheat seeds are buried at a depth of 3 cm, and fertilizers are applied in the large rows by digging trenches, with a burial depth of 10-15 cm. The ratio of wheat seed rows to fertilizer rows is 2:1, and the nitrogen application rate is 225 kg / ha (pure). The nitrogen materials for different treatments are ordinary urea and the coated controlled-release fertilizers prepared in Example 2, Comparative Example 2, Comparative Example 4, and Comparative Example 5, respectively. The yield is measured and harvested at the end of May. Urea in the ordinary urea treatment is provided by Shandong Agricultural Fertilizer Technology Co., Ltd. In each treatment, the phosphate fertilizer in the test fertilizer is heavy superphosphate, and the phosphorus application rate is 135 kg / ha (pure); potassium sulfate is used as potassium fertilizer, and the potassium application rate is 180 kg / ha (pure).

[0153] After sowing, the crops were managed by watering, spraying pesticides and weeding according to farmers' habits. The biomass, number of grains per ear (number of ears), thousand / hundred-grain weight and actual yield were measured and harvested, and the relevant data were statistically analyzed using SPAS Statistics 26 software.

[0154] Table 2 Yield and composition of summer corn and winter wheat under different fertilization treatments

[0155]

[0156] Note: 100-grain weight is used for summer maize, and 1,000-grain weight is used for winter wheat; if the same letter is used at the end of the data in the same column, the difference is not significant (p<0.05).

[0157] As can be seen from Table 2, the summer corn treated with the fertilizer of Example 1 had significantly higher biomass, number of grains per ear, and 100-grain weight than the treatments of Comparative Example 1, Comparative Example 4, Comparative Example 5, and ordinary urea. In terms of yield, the yield increase rate of Example 1 was increased by 13.59% compared with the ordinary urea treatment, while the yield increase rates of Comparative Example 1, Comparative Example 4, and Comparative Example 5 were increased by 6.69%, 3.43%, and 2.63%, respectively, compared with the ordinary urea treatment, indicating that the phase change agent, plastic roughness agent, positive assembly agent, and negative assembly agent in the bionic self-healing agent of the present application have a synergistic effect on increasing the yield of summer corn.

[0158] The winter wheat treated with the fertilizer of Example 2 had a more significant yield-increasing effect than the fertilizers of Comparative Example 2, Comparative Example 4, Comparative Example 5 and common urea. This proves that the nutrient release characteristics of the coated controlled-release fertilizers prepared in Examples 1 and 2 are suitable for fertilization on summer corn and winter wheat, respectively.

[0159] Test Example 4: In order to compare the matching degree between the nutrient release characteristics of the bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer and the nutrient absorption during the crop growth period, the field nutrient release rate of the coated controlled-release fertilizer prepared by Example 1 and Example 2 used in Test Example 3, as well as the nutrient utilization rate of summer corn and winter wheat were tested respectively, and the field nutrient release curve of the measured coated controlled-release fertilizer was plotted and compared with the nutrient absorption rate curve during the crop growth period. The determination of the field nutrient release rate refers to "DB37 / T 3827-2019 Technical Specifications for Field Testing of Nutrient Release Rate and Application Period of Slow-Release Fertilizers", and the specific test method is as follows:

[0160] Weigh 10g of the coated controlled-release fertilizer prepared in Example 1 and put it into a small mesh bag, seal it, make 12 bags, bury the fertilizer bag in the soil at 15cm on the day of summer corn transplanting, cover it with soil, and sample 3 bags every 6 hours within 1 day; weigh 10g of the coated controlled-release fertilizer prepared in Example 2 and put it into a small mesh bag, seal it, make 15 bags, bury the fertilizer bag in the soil at 15cm on the day of winter wheat transplanting, cover it with soil, and sample 3 bags at the seedling stage, tillering stage, jointing stage, heading stage, and full maturity stage. Rinse the taken fertilizer samples and completely dry them to constant weight, use the weight loss method to test the residual nutrient content, and calculate the field nutrient release rate of the coated controlled-release fertilizer.

[0161] Crop samples were taken at the same time as the above-mentioned fertilizer samples were taken. Three holes of aboveground plants were taken from each plot in the no-fertilization treatment, Example 1 treatment, and Example 2 treatment, and the aboveground fresh weight was weighed. The aboveground plant sample of one hole close to the average value was sterilized at 105°C for 20 minutes, and then completely dried at 80°C to constant weight, and the aboveground dry weight was weighed, and the plant moisture content and aboveground biomass were calculated. The dried plant sample was crushed and ground with a sample grinder, and after passing through a 100-mesh sieve, the total nitrogen of the aboveground plant was determined through the steps of weighing, digestion, volume determination, and Kjeldahl nitrogen determination, and then the crop nutrient utilization rate was calculated in combination with the aboveground biomass data. SPAS Statistics 26 and origin 2024 software were used to analyze and process the relevant data and plot the graphs. The crop nutrient absorption rate calculation formula is as follows:

[0162]

[0163] Figure 4 The present invention is a comparative analysis diagram of the field nutrient release curve of the coated controlled-release fertilizer prepared by the present invention and the nutrient utilization rate curve during the crop growth period. Figure 4a is a comparative analysis diagram of the field nutrient release curve of the coated controlled-release fertilizer prepared in Example 1 of the present invention and the nutrient absorption rate curve of a certain day during the growth period of corn; the results show that the coated controlled-release fertilizer prepared in Example 1 of the present invention can quickly release nutrients when the temperature is high during the day (higher than 29.5°C); after the temperature drops at night, it recovers to a super-hydrophobic state to slowly release nutrients. Summer corn is a short-day thermophilic crop with strong photosynthetic capacity and fast nutrient absorption when the daytime temperature is high. Example 1 of the present invention uses n-octadecane, n-nonadecane, and n-eicosane as phase change agents. After testing, the controlled-release fertilizer will be converted into a hydrophilic state when the temperature is higher than 29.5°C, and thanks to the high flow migration efficiency of the modified bio-based membrane material, it can quickly realize the rapid self-healing of the super-hydrophobic membrane material under the condition of rapid temperature difference changes, and the conversion rate only takes about 30 minutes, thereby meeting the high nutrient absorption demand of corn when the temperature is high during the day, and the rapid self-healing super-hydrophobic property slows down the nutrient release when the nutrient absorption efficiency decreases at night, realizing the precise matching of field nutrient release and corn nutrient absorption;

[0164] Figure 4 b is a comparative analysis diagram of the field nutrient release curve of the coated controlled-release fertilizer prepared in Example 2 of the present invention and the nutrient utilization rate curve of the wheat growth period. The results show that the field nutrient release trend of the coated controlled-release fertilizer prepared in Example 2 of the present invention is relatively synchronized with the nutrient absorption trend of the main growth period of wheat, among which GS10: seedling stage; GS21: tillering stage; GS31: jointing stage; GS55: heading stage; GS92: full maturity stage. Winter wheat has a long growth period of 230 to 270 days, and it is more suitable to grow at 16 to 21°C. Example 2 uses n-hexadecane as a phase change agent, and the melting point of the phase change agent is 18.2°C. After testing, the film material of the controlled-release fertilizer will change to a hydrophilic state at a temperature higher than 18.2°C, and the nutrient release will accelerate, thereby accurately supplying the large amount of nutrient demand of wheat when the soil environment reaches this temperature range. The dynamic superhydrophobic self-healing ability ensures that the nutrient controlled release can cover the long full growth period of wheat.

[0165] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A biomimetic dynamic self-healing super-hydrophobic bio-based coating material, characterized in that: The invention comprises the following raw materials in parts by weight: 0.8-2.5 parts of bio-based film-forming matrix, 0.5-1.5 parts of hydrophobic cross-linking agent and 0.013-0.4 parts of biomimetic self-healing agent; The bionic self-healing agent is prepared by mixing a phase change agent, a plastic roughening agent, a positive charge assembly agent and a negative charge assembly agent in a mass ratio of (10-80): (0.1-1): (10-50): (10-50); The phase change agent is one or more of n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, n-eicosane, and n-heneicosane; The plastic roughening agent is one or more of amino silver nanoparticles, nano holmium oxide, nano samarium oxide, nano neodymium oxide, nano cerium oxide, nano silicon carbide, and nano antimony tin oxide; The positive assembly agent is an anionic polyelectrolyte; The negative charge assembly agent is a cationic polyelectrolyte; The bio-based film-forming matrix is ​​formed by mixing vegetable oil polyol and filler in a mass ratio of 100:(1-10); The filler is one or more of glass fiber, ceramic fiber, rock wool fiber, nickel powder, rare earth tailings and polytetrafluoroethylene powder; The hydrophobic crosslinking agent is prepared by mixing isocyanate and siloxane compound in a mass ratio of (5-15):1; The isocyanate is one or more of cyclohexyl isocyanate, octadecyl isocyanate, m-toluene isocyanate, o-chlorophenyl isocyanate, m-chlorophenyl isocyanate, furanmethyl isocyanate, cycloheptyl isocyanate, 3,5-dichlorophenyl isocyanate, p-phenylene diisocyanate, polyphenyl polymethylene polyisocyanate and diphenylmethane diisocyanate; The siloxane compound is one or more of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 1,3-bis(chloromethyl)tetramethyldisiloxane, 1,3-dichlorotetramethyldisiloxane, 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane and 1,3-bis(4-hydroxybutyl)tetramethyldisiloxane; The bionic dynamic self-healing super-hydrophobic bio-based coating material is prepared by the following method: (1) mixing the vegetable oil polyol with the filler, and ultrasonically shaking at 40-60° C. for 40-80 min to prepare a bio-based film-forming matrix; (2) mixing the isocyanate and the siloxane compound, heating at 70-90° C. and stirring for 1-2 hours to prepare a hydrophobic crosslinking agent; (3) mixing the phase change agent, the plastic roughening agent, the positive assembly agent and the negative assembly agent, ultrasonically shaking at room temperature for 30-60 minutes, and refrigerating high-speed centrifugation for 20-40 minutes to prepare a bionic self-healing agent; (4) The bio-based film-forming matrix and the hydrophobic cross-linking agent are mixed and stirred to obtain a film-forming mixed system, and then a bionic self-healing agent is added, and ultrasonic vibration is performed at room temperature for 20-40 minutes to obtain a bionic dynamic self-healing super-hydrophobic bio-based coating material.

2. The biomimetic dynamic self-healing super-hydrophobic bio-based coating material according to claim 1, characterized in that: The anionic polyelectrolyte is one or more of sodium polyacrylate, sodium polyvinyl sulfonate, poly(sodium p-styrene sulfonate), and potassium polyvinyl sulfate; the cationic polyelectrolyte is one or more of poly(4-vinylpyridine), poly(2-vinylpyridine), and polyethyleneimine hydrochloride.

3. The biomimetic dynamic self-healing super-hydrophobic bio-based coating material according to claim 1, characterized in that: The bionic self-healing agent is prepared by mixing n-octadecane, n-nonadecane, n-eicosane, nano antimony tin oxide, sodium polyacrylate and polyethyleneimine hydrochloride in a mass ratio of 15:10:5:0.6:15:

15.

4. The biomimetic dynamic self-healing super-hydrophobic bio-based coating material according to claim 1, characterized in that: The vegetable oil polyol is prepared by the following method: The vegetable oil, methanol, sodium hydroxide and deionized water are mixed in a mass ratio of (100-500): (10-20): (1-5): (10-100) to obtain a reaction system, a catalyst is added to carry out an ester exchange reaction, and water is removed by vacuum rotary evaporation to obtain a vegetable oil polyol; The vegetable oil is one or more of palm oil, citronella oil, Chinese tallow oil, banana oil, croton oil, avocado oil and apple seed oil.

5. Use of the bionic dynamic self-healing super-hydrophobic bio-based coating material according to any one of claims 1 to 4 in the preparation of coated controlled-release fertilizers.

6. A biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer, characterized in that: include: Fertilizer particles, and the biomimetic dynamic self-healing super-hydrophobic bio-based coating material according to any one of claims 1 to 4 sprayed on the surface of the fertilizer particles, wherein the spraying amount of the biomimetic dynamic self-healing super-hydrophobic bio-based coating material is 0.6 to 10% of the mass of the fertilizer particles.

7. The method for preparing the biomimetic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer according to claim 6, characterized in that: The following steps are involved: The fertilizer particles are added into a preheated drum, and then the bionic dynamic self-healing super-hydrophobic bio-based coating material is sprayed or dripped onto the surface of the fertilizer particles. During the rotation of the drum, the drum temperature is continuously maintained and the fertilizer is stirred with a glass rod so that the coating material forms a coating. The spraying or dripping operation of the bionic dynamic self-healing super-hydrophobic bio-based coating material is repeated 1 to 10 times to prepare a bionic dynamic self-healing super-hydrophobic bio-based coated controlled-release fertilizer.

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