Bio-based coated controlled-release fertilizer based on network interpenetrating modification and preparation method of bio-based coated controlled-release fertilizer

Abstract

The invention discloses a bio-based coated controlled-release fertilizer based on network interpenetrating modification and a preparation method of the bio-based coated controlled-release fertilizer, and belongs to the technical field of controlled-release fertilizer production. The bio-based coating material based on network interpenetrating modification is prepared from a base material A, a base material B and a nutrient release adjusting material according to a mass ratio of (4-30): (4-30): (1-3), the base material A is bio-based epoxy resin; the base material B is polyethyleneimine; the nutrient release adjusting material is a mixture composed of at least two of epoxidized lignin, modified aminated cellulose and modified starch. According to the invention, the controlled release performance of the bio-based membrane material is improved through network interpenetrating modification treatment, and the enveloping reaction can be carried out at normal temperature, so that the energy consumption is greatly reduced, and the cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of slow / controlled release fertilizer production, in particular to a bio-based coated controlled release fertilizer based on network interpenetration modification and a preparation method thereof. BACKGROUND

[0002] At present, the use of chemical fertilizers is huge, and over-fertilization is common. The utilization rate of fertilizers is generally between 30%-60%, and the waste and pollution are serious. Slow / controlled release fertilizers can significantly improve the utilization rate of fertilizers, but the coating materials of the currently marketed controlled release fertilizers are mostly derived from petroleum chemical products, which are high in cost, non-renewable in resources, and not conducive to the sustainable development of the industry.

[0003] In recent years, bio-based materials have attracted widespread attention due to their low cost, renewability and biodegradability, and have been developed and applied to controlled release fertilizer coating. Bio-based coated fertilizers prepared from bio-based materials are low in price, renewable in resources, efficient and environmentally friendly, and have important social and economic benefits. However, the bio-based coated fertilizers synthesized from bio-based coating materials have many pores or a large number of hydrophilic groups, which accelerate the entry of water into the coating material, cause the coating material to swell and absorb water, and increase the permeability, thereby accelerating the release of nutrients and greatly shortening the controlled release period of nutrients, affecting the controlled release quality. Therefore, modification of bio-based coating materials is the only way to promote the development and progress of the industry.

[0004] Interpenetrating polymer network (IPN) is a unique type of polymer composed of two or more interpenetrating polymers. IPN has good thermal stability and mechanical properties, and its structure and properties can be customized through interpenetrating network technology. IPN is widely used in hydrogels, rubbers, polyelectrolyte films and coatings, but there are few reports on the modification of bio-based coating materials for controlled release. SUMMARY

[0005] In view of the problems existing in the prior art, the purpose of the present application is to provide a bio-based coated controlled release fertilizer based on network interpenetration modification and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In a first aspect of the present application, a bio-based coating material based on network interpenetration modification is prepared from a base material A, a base material B and a nutrient release regulating material in a mass ratio of (4-30):(4-30):(1-3). The base material A is a bio-based epoxy resin; the base material B is polyethyleneimine; and the nutrient release regulating material is a mixture of at least two of epoxy lignin, modified aminocellulose and modified starch.

[0007] Preferably, the bio-based epoxy resin is prepared by the following method: The plant oil is dissolved in acetone and placed in a reaction kettle, concentrated sulfuric acid and formic acid are added, the temperature is set to 50-60 DEG C, and 40% concentration of hydrogen peroxide is slowly dropped, the reaction is stopped after 6h, and the lower layer of wastewater is removed after layering.

[0008] More preferably, the plant oil is one or more of palm oil, soybean oil, castor oil.

[0009] More preferably, the mass ratio of plant oil, acetone, concentrated sulfuric acid, formic acid is 15: (10-20): (0.5-1): (1-3).

[0010] Preferably, the epoxidized lignin is prepared by the following method: The lignin is dissolved in sodium hydroxide solution, heated to 65-75 DEG C, then epichlorohydrin is added, and the temperature is kept constant for 2.5-3.5h, the pH is adjusted to neutral, and the epoxidized lignin is prepared by filtration and drying.

[0011] The modified aminated cellulose is prepared by the following method: The waste paper shell is crushed and placed in a glycol solution, concentrated sulfuric acid is used as a catalyst, and ethylenediamine is used as an amination reagent, and the mixture is stirred at 140-160 DEG C for 2-4h.

[0012] The modified starch is prepared by the following method: The starch and water are mixed uniformly to prepare a starch slurry, sodium sulfite is added to the starch slurry and stirred for 20-40min, then hydrochloric acid is added for acid hydrolysis for 2-3h; the solution after acid hydrolysis is adjusted to neutral, urea and ammonium persulfate are added, and the mixture is reacted at 55-65 DEG C for 3-5h, cooled to room temperature, precipitated with ethanol, filtered, washed and dried.

[0013] Preferably, the nutrient release regulating material is a mixture of epoxidized lignin and amide modified starch in a mass ratio of 2:1.

[0014] In a second aspect of the present application, the bio-based coating material is used in the preparation of controlled-release fertilizers.

[0015] In a third aspect of the present application, a bio-based coated controlled-release fertilizer is provided, comprising: a fertilizer core and a bio-based coating material wrapped on the surface of the fertilizer core.

[0016] Preferably, the bio-based coating material is added in an amount of 1-10% by weight of the fertilizer core.

[0017] In a fourth aspect of the present application, a preparation method of the bio-based coated controlled-release fertilizer is provided, comprising the following steps: The fertilizer core is added into a coating machine, the base material A and the base material B in the bio-based coating material are added under rotating conditions, pre-reaction is carried out at normal temperature for 3-5 min, the nutrient release adjusting material in the bio-based coating material is added, and reaction is continued for 10-20 min, so that the bio-based coating material is solidified on the surface of the fertilizer core to form a film, and the bio-based coated controlled-release fertilizer is prepared.

[0018] The action mechanism of the bio-based coated controlled-release fertilizer is as follows: The base material A and the base material B are constructed into a network interpenetrating skeleton by a synchronous method, and are used as the main material of the coated fertilizer; the dense coating can block water from entering; and the function of the nutrient release adjusting material is to act as a switch for adjusting the water channel, to be inserted into the network of the base material to further construct a network interpenetrating structure, to adjust the network pore size, and to act as a water conduit to adjust the rate of water entering the film and nutrient release; and the network interpenetrating structure is constructed by a step-by-step method.

[0019] The base material A is a bio-based epoxy resin prepared by purifying one or more mixtures of palm oil, soybean oil and castor oil; and the other base material B which can be network interpenetrated with the base material A is polyethyleneimine. Under normal temperature conditions, nucleophilic ring-opening reaction occurs between the epoxy group of the epoxy resin and the amino group of the polyethyleneimine.

[0020] The specific process is as follows: the nitrogen atom in the amino group of the polyethyleneimine has a lone pair of electrons, and has nucleophilicity, which attacks the carbon atom in the epoxy group of the epoxy resin, so that the three-membered ring structure of the epoxy group is opened. Therefore, the molecular chains of the epoxy resin and the opened polyethyleneimine molecular chains can be connected by covalent bonds, and the molecular chains of them interpenetrate and entangle with each other in space, and finally form a network interpenetrating skeleton structure. The process can be carried out at normal temperature, and the material has the advantages of low cost, good controlled-release effect, environmental protection, low energy consumption, simple preparation process, short preparation time and the like, and is an ideal controlled-release film material.

[0021] The added nutrient release adjusting agent material is a mixture of two or more of epoxidized lignin, modified aminocellulose and modified starch; because different charge groups are present on the molecular chains of these materials, after mixing with the base material at normal temperature, the molecular chains tend to arrange vertically to the network structure of the base material under the action of static electricity. This vertical arrangement mode makes the space between the molecular chains be reasonably utilized, forms a certain channel structure, forms a structure similar to a "lamp twist", and further forms a nanometer or micrometer pore for water to enter and exit, so as to control the rate of water entering and nutrient dissolving. The nutrient release adjusting agent material can form different numbers and pore sizes of micro-nanometer pores on the base material by selecting different materials and different proportions, so as to adjust the rate of water entering the film through these conduits and the rate of dissolving nutrients, and to achieve the purpose of regulating nutrient release.

[0022] Advantages of the present application: (1) The adopted coating process is simple, the reaction can be carried out at room temperature, the curing time is fast, the energy consumption is greatly reduced, the cost is reduced, and it is suitable for large-scale production.

[0023] (2) The residual film of the coated controlled-release fertilizer produced by the present application can be degraded and contains certain organic nutrients, and after decomposition, it can provide nutrients for crops.

[0024] (3) The coated controlled-release fertilizer has good controlled-release effect, and can meet the fertilizer requirement law of different crops as needed. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 : Schematic diagram of network interpenetrating structure formation process; in the figure, 1, base material A; 2, base material B; 3, construction of network interpenetrating skeleton; 4, addition of nutrient release regulating material; 5, synthesis of bio-based coating material based on network interpenetrating technology modification.

[0026] Figure 2 : Schematic diagram of controlled-release principle of bio-based coated controlled-release fertilizer of the present application; in the figure, 1, fertilizer particle; 2, network interpenetrating film material; 3, water channel formed by modified material regulation; 4, nutrient release regulator material; 5, water channel.

[0027] Figure 3 : Bio-based film shell cross-section diagram prepared by example 1 and comparative example 1 of the present application, wherein A is the film shell cross-section diagram of comparative example 1, and B is the film shell cross-section diagram of example 1. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0029] Term explanation: "Room temperature" herein refers to a temperature range of 15-25℃.

[0030] As described previously, interpenetrating polymer network (IPN) is a unique type of polymer composed of two or more interpenetrating polymers, which can be used in the fields of hydrogel, rubber, polyelectrolyte film and coating, etc. However, since the raw materials for forming interpenetrating polymer network are mostly homogeneous polymers, they cannot self-assemble to form nanoscale channels through electrostatic or hydrogen bonding, and direct use of interpenetrating polymer network as bio-based coating material has a single diffusion release curve and is prone to burst release in the later stage; moreover, the film has high brittleness, and the film layer is prone to cracking and falling off. Therefore, research on interpenetrating polymer network in the modification of bio-based coating material controlled release is still relatively rare.

[0031] In view of this, the present invention has conducted an in-depth study on the application of interpenetrating polymer networks in bio-based coating materials. The synthesis process of the bio-based coating material modified by the network interpenetration technology of the present invention is as follows: Figure 1 As shown, this invention selects bio-based epoxy resin as substrate A, polyethyleneimine as substrate B, and a mixture of at least two of epoxidized lignin, modified amino cellulose, and modified starch as nutrient release regulating material. Substrate A and substrate B are constructed simultaneously to form an interpenetrating network framework, which serves as the main material of the coated fertilizer. Its dense coating can prevent water from entering. The function of the nutrient release regulating material is to act as a switch to regulate water channels. It is inserted into the network of the substrate to further construct the interpenetrating network structure, adjust the network pore size, and act as a water conduit to regulate the rate of water entering the membrane and nutrient release. This process is a stepwise method for constructing the interpenetrating network structure.

[0032] The controlled release principle of the bio-based coating material of the present invention is as follows: Figure 2 As shown, nutrient release regulator materials are used to form a "wick"-like structure, thereby creating nanoscale or microscale channels for water entry and exit, thus controlling the rate of water entry and nutrient dissolution. By selecting different materials and varying the proportions, nutrient release regulator materials can form different numbers and sizes of micro- and nanoscale channels on the substrate, thereby regulating the rate at which water enters the membrane and nutrients dissolve, ultimately achieving the goal of controlling nutrient release.

[0033] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0034] The test materials used in the embodiments and comparative examples of this invention are all conventional test materials in the art and can be purchased through commercial channels. Experimental methods without specified detailed conditions were performed according to conventional test methods or the supplier's recommended operating instructions. Wherein: CAS number for polyethyleneimine: 9002-98-6.

[0035] The preparation method of bio-based epoxy resin is as follows: Dissolve 15g of palm oil in 20g of acetone and place it in a reaction vessel. Add 0.5g of concentrated sulfuric acid and 2g of formic acid. Set the temperature to 55℃ and slowly add 3g of hydrogen peroxide with a mass concentration of 40%. Stop the reaction after 6 hours, let it stand to separate into layers, and remove the lower layer of wastewater.

[0036] The preparation method of epoxidized lignin is as follows: Dissolve 10 g of lignin in 100 mL of 1 mol / L sodium hydroxide solution, add to a three-necked flask with stirring device, heat to 70°C in water bath, then add 30 mL of epichlorohydrin, constant temperature reflux for 3 h, adjust pH to neutral, dry by suction filtration, and dry to obtain epoxidized lignin.

[0037] The preparation method of modified aminated cellulose is as follows: Take 10 g of waste paper shell as raw material, crush it, and then put it in 100 ml of 80% ethylene glycol solution, use 0.8 ml of concentrated sulfuric acid as catalyst, 10 ml of ethylenediamine as aminating agent, and react at 150°C for 3 h with continuous stirring. After the reaction is completed, cool to room temperature, adjust pH to neutral, dry by suction filtration and washing, and dry.

[0038] The preparation method of modified starch is as follows: Mix 10 g of starch with 90 ml of water to make a 10% starch slurry, add 0.5 g of sodium sulfite to the starch slurry and stir for 30 min, then add 5 ml of hydrochloric acid for acid hydrolysis reaction for 2.5 hours. Then adjust the solution to neutral, add 5 g of urea and 0.05 g of ammonium persulfate, react at 60°C for 4 h, then cool to room temperature, precipitate with 95% (v / v) ethanol, dry by suction filtration and washing, and dry to obtain modified starch.

[0039] Through the above modification treatment of lignin, cellulose and starch, on the one hand, ionic groups can be introduced to enable insertion into the network interpenetrating structure; on the other hand, functional groups are introduced to improve the reaction activity and compatibility of natural polymers.

[0040] Example 1: Preparation of bio-based coated controlled-release fertilizer based on network interpenetrating modification 1. Raw material composition: Large particle urea and bio-based coating material; Among them: The bio-based coating material is composed of base material A (bio-based epoxy resin), base material B (polyethyleneimine) and nutrient release regulating material (a mixture of epoxidized lignin and modified starch in a mass ratio of 2:1).

[0041] 2. Preparation method: The substrate A and the substrate B are mixed at a mass ratio of 1:1 to obtain a substrate mixture. 10 kg of large-particle urea (particle size 3-5 mm) is added to the coating machine pot, and rotation is started (30 r / min). Then 80 g of the substrate mixture is added to the coating machine, and pre-reaction is carried out at room temperature for 3 minutes. Then 20 g of the nutrient release adjusting material is added, and reaction is carried out at room temperature. After 20 minutes, a film is formed on the surface of the fertilizer particles. This process is repeated 3 times. Finally, rotation is stopped, the fertilizer is taken out, and packaged for storage to obtain the bio-based coated controlled-release fertilizer based on network interpenetrating modification. In the bio-based coated controlled-release fertilizer prepared in this example, the bio-based coating material accounts for 3% of the weight of urea.

[0042] Example 2: Preparation of bio-based coated controlled-release fertilizer based on network interpenetrating modification 1. Raw material composition: Granular diammonium phosphate and bio-based coating material; Wherein: The bio-based coating material is composed of substrate A (bio-based epoxy resin), substrate B (polyethyleneimine), and nutrient release adjusting material (a mixture of epoxidized lignin, modified starch, and modified aminocellulose at a mass ratio of 6:3:1).

[0043] 2. Preparation method: The substrate A and the substrate B are mixed at a mass ratio of 1:1 to obtain a substrate mixture. 10 kg of granular diammonium phosphate is added to the coating machine pot, and rotation is started (35 r / min). Then 80 g of the substrate mixture is added to the coating machine, and pre-reaction is carried out at room temperature for 5 minutes. Then 20 g of the nutrient release adjusting material is added, and reaction is carried out at room temperature. After 20 minutes, a film is formed on the surface of the fertilizer particles. This process is repeated 5 times. Finally, rotation is stopped, the fertilizer is taken out, and packaged for storage to obtain the bio-based coated controlled-release fertilizer based on network interpenetrating modification. In the bio-based coated controlled-release fertilizer prepared in this example, the bio-based coating material accounts for 5% of the weight of urea.

[0044] Example 3: Preparation of bio-based coated controlled-release fertilizer based on network interpenetrating modification 1. Raw material composition: Granular potassium sulfate fertilizer and bio-based coating material; Wherein: The bio-based coating material is composed of substrate A (bio-based epoxy resin), substrate B (polyethyleneimine), and nutrient release adjusting material (a mixture of epoxidized lignin and modified aminocellulose at a mass ratio of 1:1).

[0045] 2. Preparation method: Substrate A and Substrate B were mixed at a mass ratio of 2:1 to obtain a substrate mixture. 10 kg of granular potassium sulfate fertilizer was added to the coating machine pot, and the machine was started and rotated (40 rpm). Then, 85 g of the substrate mixture was added to the coating machine. After 5 minutes, 15 g of nutrient release regulator was added, and the reaction proceeded. After 20 minutes, a film was formed on the surface of the fertilizer granules. This process was repeated 5 times. Finally, the rotation was stopped, the fertilizer was removed, packaged, and stored. A bio-based coated controlled-release fertilizer based on network interpenetrating modification was prepared. In this embodiment, the bio-based coating material accounts for 5% of the weight of urea in the bio-based coated controlled-release fertilizer.

[0046] Comparative Example 1: 1. Raw material composition: Large-particle urea and bio-based coating materials; in: The bio-based coating material consists of substrate A (bio-based epoxy resin) and substrate B (polyethyleneimine).

[0047] 2. Preparation method: Substrate A and Substrate B were mixed at a mass ratio of 1:1 to obtain a bio-based coating material. 10 kg of large-particle urea (particle size 3-5 mm) was added to the coating machine pot, and the machine was turned on and rotated (30 r / min). Then, 100 g of the bio-based coating material was added to the coating machine, and the reaction was carried out at room temperature. After 20 minutes, a film was formed on the surface of the fertilizer particles. This process was repeated 3 times. Finally, the rotation was stopped, the fertilizer was removed, packaged, and stored to prepare a bio-based coated controlled-release fertilizer with simple network interpenetration modification.

[0048] Comparative Example 2: 1. Raw material composition: Particulate diammonium phosphate and bio-based coating materials; in: The bio-based coating material consists of substrate A (bio-based epoxy resin) and substrate B (polyethyleneimine).

[0049] 2. Preparation method: Substrate A and Substrate B were mixed at a mass ratio of 1:1 to obtain a bio-based coating material. 10 kg of granular diammonium phosphate was added to the coating machine pot, and the machine was turned on and rotated (35 r / min). 100 g of the bio-based coating material was added to the coating machine, and the reaction was carried out at room temperature. After 20 minutes, a film was formed on the surface of the fertilizer granules. This process was repeated 5 times. Finally, the rotation was stopped, the fertilizer was removed, packaged, and stored to prepare a bio-based coated controlled-release fertilizer with simple network interpenetration modification.

[0050] Comparative Example 3: 1. Raw material composition: Granular potassium sulfate fertilizer and bio-based coating materials; in: The bio-based coating material consists of substrate A (bio-based epoxy resin) and substrate B (polyethyleneimine).

[0051] 2. Preparation method: Substrate A and Substrate B were mixed at a mass ratio of 1:1 to obtain a bio-based coating material. 10 kg of granular potassium sulfate fertilizer was added to the coating machine pot, and the machine was started to rotate (40 r / min). Then, 100 g of the bio-based coating material was added to the coating machine, and the reaction was carried out at room temperature. After 20 minutes, a film was formed on the surface of the fertilizer granules. This process was repeated 5 times. Finally, the rotation was stopped, the fertilizer was removed, packaged, and stored, thus preparing a bio-based coated controlled-release fertilizer with simple network interpenetration modification.

[0052] Experimental Example 1: Electron microscopy was performed on cross-sections of the bio-based membrane shells of the bio-based coated controlled-release fertilizers prepared in Example 1 and Comparative Example 1. The results are as follows: Figure 3 As shown, the bio-based membrane shell of Comparative Example 1 was not modified with nutrient release regulating material, and its membrane shell was loose and porous; while the bio-based membrane shell of Example 1 was modified with nutrient release regulating material, and its structure was more compact.

[0053] Experimental Example 2: The nutrient release time of the bio-based coated controlled-release fertilizers prepared in Examples 1-3 and Comparative Examples 1-3 was measured.

[0054] The method for determining the controlled release time of nutrients is as follows: 10g of the prepared fertilizer is placed in a mesh bag and then placed in 200ml of deionized water at 25℃. Every 7 days, 1ml is taken to measure the nutrient release concentration, and the water is replaced with a fresh 200ml of deionized water until the nutrients are completely released. The nutrient release concentration is determined using the conventional methods for nitrogen, phosphorus, and potassium. The cumulative release rate is obtained by summing the measured nutrient release concentrations.

[0055] The results showed that the nutrient release time of the bio-based coated controlled-release fertilizer prepared in Example 1 was about 90 days, which was 3 times longer than that of the bio-based coated controlled-release fertilizer prepared in Comparative Example 1.

[0056] The nutrient release time of the bio-based coated controlled-release fertilizer prepared in Example 2 is about 120 days, which is 4 times longer than that of the bio-based coated controlled-release fertilizer prepared in Comparative Example 2.

[0057] The nutrient release time of the bio-based coated controlled-release fertilizer prepared in Example 2 is about 150 days, which is 5 times longer than that of the bio-based coated controlled-release fertilizer prepared in Comparative Example 3.

[0058] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A bio-based coating material based on network interpenetration modification, characterized in that, It is prepared from substrate A, substrate B and nutrient release regulating material in a mass ratio of (4-30):(4-30):(1-3); The substrate A is a bio-based epoxy resin; the substrate B is polyethyleneimine; and the nutrient release regulating material is a mixture of at least two of epoxidized lignin, modified amino cellulose, and modified starch.

2. The bio-based coating material according to claim 1, characterized in that, The bio-based epoxy resin is prepared by the following method: Vegetable oil was dissolved in acetone and placed in a reaction vessel. Concentrated sulfuric acid and formic acid were added, and the temperature was set to 50-60℃. Hydrogen peroxide was slowly added dropwise. The reaction was stopped after 6 hours, and the mixture was allowed to stand and separate into layers. The lower layer of wastewater was then removed.

3. The bio-based coating material according to claim 2, characterized in that, The vegetable oil is one or more of palm oil, soybean oil, and castor oil.

4. The bio-based coating material according to claim 2, characterized in that, The mass ratio of vegetable oil, acetone, concentrated sulfuric acid, and formic acid is 15:(10-20):(0.5-1):(1-3).

5. The bio-based coating material according to claim 1, characterized in that, The epoxidized lignin is prepared by the following method: Lignin was dissolved in sodium hydroxide solution, heated to 65-75℃, and epichlorohydrin was added. The mixture was reacted at a constant temperature for 2.5-3.5 hours. The pH was adjusted to neutral, and the mixture was then filtered and dried to prepare epoxidized lignin. The modified aminoated cellulose is prepared by the following method: The waste paperboard was crushed and placed in an ethylene glycol solution. Concentrated sulfuric acid was used as a catalyst and ethylenediamine was used as an amination reagent. The mixture was stirred at 140-160℃ for 2-4 hours. The modified starch is prepared by the following method: Mix starch and water evenly to make a starch slurry. Add sodium sulfite to the starch slurry and stir for 20-40 minutes. Then add hydrochloric acid and react for 2-3 hours. Adjust the solution after the acid reaction to neutral, add urea and ammonium persulfate, and react at 55-65℃ for 3-5 hours. Cool to room temperature, precipitate with ethanol, filter, wash and dry.

6. The bio-based coating material according to claim 1 or 5, characterized in that, The nutrient release regulating material is a mixture of epoxidized lignin and amamide-modified starch in a mass ratio of 2:

1.

7. The use of the bio-based coating material according to any one of claims 1-6 in the preparation of controlled-release fertilizers.

8. A bio-based coated controlled-release fertilizer, characterized in that, include: The fertilizer core and the bio-based coating material as described in any one of claims 1-6, which is wrapped around the surface of the fertilizer core.

9. The bio-based coated controlled-release fertilizer according to claim 8, characterized in that, The amount of bio-based coating material added is 1-10% of the weight of the fertilizer core.

10. The method for preparing the bio-based coated controlled-release fertilizer according to claim 8 or 9, characterized in that, Includes the following steps: The fertilizer core is added into a coating machine. Under rotating conditions, substrate A and substrate B of the bio-based coating material are added first, and the pre-reaction is carried out at room temperature for 3-5 minutes. Then, the nutrient release regulating material of the bio-based coating material is added, and the reaction is continued for 10-20 minutes. The film is solidified on the surface of the fertilizer core to prepare a bio-based coated controlled-release fertilizer.

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