Preparation method of a modified ethyl cellulose coated controlled-release fertilizer

Abstract

The present invention discloses a preparation method of a modified ethyl cellulose-coated controlled-release fertilizer, comprising the following steps: S1 preparing an ethyl cellulose core / shell emulsion; S2 preparing a modified ethyl cellulose core / shell emulsion; S3 preparing a modified ethyl cellulose core / shell emulsion-coated controlled-release fertilizer. The present invention is applicable to the technical field of controlled-release fertilizers. Using ethyl cellulose as the coating material and the coating liquid system being an aqueous system, without the use of organic solvents, it solves the disadvantages of using organic solvents, causing large environmental pollution and being difficult to recycle when preparing the coating liquid with ethyl cellulose. Aiming at the problem of poor hydrophobicity of ethyl cellulose as the coating material, a modified polysiloxane is used to modify the ethyl cellulose core / shell emulsion, improving the hydrophobicity of the coated controlled-release fertilizer and preparing a coated controlled-release fertilizer with a longer controlled-release period. This fertilizer has the characteristics of being green and biodegradable and having a long controlled-release period, promoting the process of green and sustainable development of agriculture and providing a technical means for the country to achieve the dual-carbon goal.

Description

Technical Field

[0001] The present invention belongs to the technical field of controlled-release fertilizers, and specifically relates to a preparation method of a modified ethyl cellulose-coated controlled-release fertilizer. Background Art

[0002] Under the condition of one-time fertilization, controlled-release fertilizers can control the synchronization of nutrient release and crop nutrient absorption, improve crop yields and fertilizer utilization rates, and are important products of green fertilizers in China. At present, the mainstream coated controlled-release fertilizers on the market are mainly those coated with organic polymer materials. Although they have good controlled-release performance, there are problems such as difficult degradation of the film shell and environmental pollution.

[0003] With the increasing attention of China to the quality of cultivated land, developing new types of efficient bio-based degradable controlled-release materials has become a technical problem that needs to be broken through in the field of controlled-release fertilizers. Developing green new controlled-release fertilizers using biodegradable cellulose materials is a current research hotspot.

[0004] Cellulose is the most abundant bio-based material in the world, and there have been research reports on using cellulose and its derivatives to develop controlled-release fertilizers. For example, some scholars modified polyols with sodium carboxymethyl cellulose to prepare bio-based modified polyurethane-coated controlled-release fertilizers (Wang et al, 2021), which greatly increased the controlled-release period of the fertilizers, but did not fundamentally change the difficult degradability of polyurethane.

[0005] As one of the cellulose ether derivatives, ethyl cellulose has good hydrophobicity and advantages such as biodegradability, renewability, low cost, and low thermal expansion coefficient, and is often used as coating and film materials. However, ethyl cellulose has problems such as poor mechanical properties, and the release period of the developed controlled-release fertilizers is only dozens of hours, and hydrophobic toughening and other modification measures are needed to further improve its controlled-release performance.

[0006] Some scholars used ethyl cellulose (EC) and acrylic acid-co-acrylamide (AA-co-AM) as the inner coating and outer coating materials respectively, and ethanol solution as the solvent, and prepared coated fertilizers by the water immersion method. The tests in the simulated soil condition experiments showed that the release was complete in 30 days (Ni et al., 2009).

[0007] Another example is that Lubkowski dissolved ethyl cellulose in ethanol and treated untreated phosphate fertilizers by the multiple impregnation method to obtain ethyl cellulose-coated phosphate fertilizers. The water immersion method study found that the nutrient release reached 70% at 320 h, and the nutrient release of untreated phosphate fertilizers reached 80% at about 30 h (Lubkowski. Polish, 2019).

[0008] In summary, in existing research, when ethyl cellulose is used as a coating material, the solvents used are basically organic solvents, mostly ethanol. The process conditions mainly use the dipping method, and the mainstream processes (such as using fluidized beds) are less. There are the following problems:

[0009] 1. The mainstream controlled-release fertilizers on the market are mainly controlled-release fertilizers coated with organic polymers, such as polyurethane-coated controlled-release urea and polyethylene-coated controlled-release urea. They have problems such as poor film shell degradability and easy environmental pollution;

[0010] 2. In previous research, when using ethyl cellulose to prepare coated fertilizers, the solvents for dissolving ethyl cellulose are all organic solvents. Organic solvents have problems such as high cost, low recovery rate, and toxicity;

[0011] 3. Ethyl cellulose has a large particle size, poor mechanical properties, and poor film-forming properties. Using ethyl cellulose alone to coat controlled-release urea has poor controlled-release performance and cannot meet the national standards for controlled-release fertilizers. Summary of the Invention

[0012] The purpose of the present invention is to overcome the defects of the prior art and provide a preparation method for a modified ethyl cellulose-coated controlled-release fertilizer.

[0013] To achieve the above purpose, the present invention adopts the following technical solutions:

[0014] A preparation method for a modified ethyl cellulose-coated controlled-release fertilizer includes the following steps:

[0015] S1 Prepare an ethyl cellulose core / shell emulsion;

[0016] S2 Prepare a modified ethyl cellulose core / shell emulsion;

[0017] S3 Prepare a modified ethyl cellulose core / shell emulsion-coated controlled-release fertilizer.

[0018] Preferably, in the step S1, it specifically includes:

[0019] Melt 10-15 parts of ethyl cellulose with 0.4-0.6 parts of plasticizer and 0.3-0.5 parts of stabilizer at high temperature. After melting, add ammonia water for dilution to obtain an ethyl cellulose core / shell emulsion.

[0020] Preferably, in the step S1, the ethyl cellulose is in the form of white powder, with a viscosity of 3-7 mPa·s, 6-9 mPa·s, or 9-11 mPa·s. The plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxidized soybean oil, and the stabilizer is oleic acid.

[0021] Preferably, in the step S1, the viscosity of ethyl cellulose is 9-11 mPa·s, and the plasticizer is dibutyl sebacate.

[0022] Preferably, in the step S2, it specifically includes:

[0023] Mix the ethyl cellulose core / shell emulsion obtained in the step S1 with 9-10 parts of the prepared modified polysiloxane to obtain a modified ethyl cellulose core / shell emulsion.

[0024] Preferably, in the step S2, it further includes:

[0025] Prepare a modified polysiloxane emulsion:

[0026] S2-1: Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 part of dodecylbenzenesulfonic acid and 40 parts of water into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet respectively. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7-8 with ammonia water to obtain a polysiloxane emulsion;

[0027] S2-2: At room temperature, first drop 0.50 part of 3-methacryloxytrimethoxysilane into the polysiloxane emulsion prepared in the step S2-1 and stir for 15 min, then modify at 80 °C for 4 h, and wait for the system to cool to room temperature to obtain a modified polysiloxane emulsion.

[0028] Preferably, in the step S3, it specifically includes:

[0029] S3-1: Connect the modified ethyl cellulose core / shell emulsion prepared in the step S2 as a coating liquid to a peristaltic pump, adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 74-80 parts of fertilizer particles to the preheated coating device for 5-10 min. After the fertilizer is preheated, turn on the peristaltic pump to allow the coating liquid to be injected;

[0030] S3-2; After the injection is completed, lower the temperature to 60 °C, continue to tumble the fertilizer with the coated material in the coating device for 5-15 min and then take it out to obtain the modified ethyl cellulose-coated controlled-release fertilizer.

[0031] Preferably, in the step S3, the fertilizer particles are one or more of potassium chloride, potassium sulfate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen, phosphorus and potassium fertilizers. The particle size of the fertilizer particles is 2-4 mm, the coating temperature is 60-80 °C, the coating time is 30-45 min, and the coating device is a coating pan, a drum or a fluidized bed.

[0032] Preferably, in the step S3, the fertilizer particles are urea, the coating temperature is 80 °C, the coating time is 40 min, and the coating device is a fluidized bed.

[0033] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0034] 1. In the present invention, the modified ethyl cellulose core / shell emulsion is used as the coating material, and no organic solvent is required, solving the problems of large environmental pollution and difficult recovery existing when preparing the ethyl cellulose coating solution using organic solvents;

[0035] 2. In the present invention, aiming at the problem of poor hydrophobicity of the ethyl cellulose material coated on the fertilizer, the present invention uses modified polysiloxane to improve the hydrophobicity of the fertilizer and prepares an ethyl cellulose coated controlled-release fertilizer with good hydrophobicity;

[0036] 3. In the present invention, compared with the single use of ethyl cellulose, the particle size of single ethyl cellulose is larger, 60 - 80 μm, and it is impossible to form a uniform and dense film layer. The particle size of the ethyl cellulose core / shell emulsion is smaller, 80 - 200 nm, and the film-forming property is better, and a uniform film layer can be formed on the surface of the fertilizer particles. Description of the Drawings

[0037] Figure 1 is the flow chart of the present invention;

[0038] Figure 2 is the nutrient release curve graph in the embodiment of the present invention;

[0039] Figure 3 is the schematic diagram of the water contact angle of the coated controlled-release urea in the embodiment of the present invention. Detailed Description of the Invention

[0040] The following is a detailed description of the specific embodiments of the present invention.

[0041] The "scope" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular scope. The scope defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope. For example, if a range of 10 to 50 is listed for a specific parameter, it is understood that ranges of 10 to 40 and 20 to 50 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" are fully listed in this article, and "0 to 5" is only an abbreviated representation of these numerical combinations.

[0042] If there is no special description, all embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0043] If there is no special description, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0044] If there is no special description, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0045] If there is no special description, the "including" and "containing" mentioned in this application mean open-ended or can also be closed-ended. For example, the "including" and "containing" can mean that other components not listed can also be included or contained, or can only include or contain the listed components.

[0046] If there is no special description, the reaction is carried out under normal temperature and normal pressure conditions.

[0047] If there is no special description, all parts or percentages are by weight or weight percentage.

[0048] In the present invention, all substances used are known substances, which can be purchased or synthesized by known methods.

[0049] In the present invention, all devices or equipment used are conventional devices or equipment known in the field and can be purchased.

[0050] The following further illustrates the specific implementation manners of the preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to the present invention with reference to embodiments. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to the present invention is not limited to the description of the following embodiments.

[0051] Example 1:

[0052] A preparation method of a modified ethyl cellulose-coated controlled-release fertilizer, as Figure 1 shown, includes the following steps:

[0053] S1: Prepare an ethyl cellulose core / shell emulsion;

[0054] S2: Prepare a modified ethyl cellulose core / shell emulsion;

[0055] S3: Prepare a modified ethyl cellulose core / shell emulsion-coated controlled-release fertilizer.

[0056] Further, in step S1, it specifically includes:

[0057] Melt 10 parts of ethyl cellulose with 0.4 part of plasticizer and 0.3 part of stabilizer at high temperature. After melting, add ammonia water for dilution to obtain an ethyl cellulose core / shell emulsion.

[0058] Among them, the ethyl cellulose is in a white powdery structure, its viscosity is 3-7 mPa·s, the plasticizer is dibutyl adipate, and the stabilizer is oleic acid.

[0059] Further, in step S2, it specifically includes:

[0060] Mix the ethyl cellulose core / shell emulsion obtained in step S1 with 9 parts of prepared polysiloxane to obtain a modified ethyl cellulose core / shell emulsion.

[0061] Further, in step S2, it also includes:

[0062] Prepare a modified polysiloxane emulsion:

[0063] S2-1: Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 part of dodecylbenzenesulfonic acid and 40 parts of water into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90°C for 10 h, then cool to room temperature, and neutralize with ammonia water to pH 7-8 to obtain a polysiloxane emulsion;

[0064] S2-2: At room temperature, first drop 0.50 part of 3-methacryloyloxytrimethoxysilane into the polysiloxane emulsion prepared in step S2-1 and stir for 15 min, then carry out modification at 80 °C for 4 h. After the system cools to room temperature, a modified polysiloxane emulsion is obtained.

[0065] Furthermore, in step S3, it specifically includes:

[0066] S3-1 Connect the modified ethyl cellulose core / shell emulsion prepared in step S2 as the coating liquid to a peristaltic pump, adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 80.3 parts of fertilizer particles to the preheated coating device for 5 min. After the fertilizer is preheated, turn on the peristaltic pump to allow the coating liquid to be injected;

[0067] S3-2 After the injection is completed, lower the temperature to 60 °C, continue to tumble the fertilizer with the coated material in the coating device for 5 min and then take it out to obtain the modified ethyl cellulose-coated controlled-release fertilizer.

[0068] Among them, the fertilizer particles are one of potassium chloride, potassium sulfate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen, phosphorus, and potassium fertilizers. The particle size of the fertilizer particles is 2 mm, the coating temperature is 60 °C, the coating time is 30 min, and the coating device is a coating pan.

[0069] Example 2:

[0070] A preparation method of a modified ethyl cellulose-coated controlled-release fertilizer, as Figure 1 shown, includes the following steps:

[0071] S1 Prepare an ethyl cellulose core / shell emulsion;

[0072] S2 Prepare a modified ethyl cellulose core / shell emulsion;

[0073] S3 Prepare a modified ethyl cellulose core / shell emulsion-coated controlled-release fertilizer.

[0074] Furthermore, in step S1, it specifically includes:

[0075] Melt 13 parts of ethyl cellulose with 0.5 part of plasticizer and 0.4 part of stabilizer at high temperature. After melting, add ammonia water for dilution to obtain an ethyl cellulose core / shell emulsion.

[0076] Among them, the ethyl cellulose is in a white powder structure, its viscosity is 6 - 9 mPa·s, the plasticizer is dibutyl phthalate, and the stabilizer is oleic acid.

[0077] Furthermore, in step S2, it specifically includes:

[0078] Mix the ethyl cellulose core / shell emulsion obtained in step S1 with 9.5 parts of the prepared polysiloxane to obtain a modified ethyl cellulose core / shell emulsion.

[0079] Furthermore, in step S2, it further includes:

[0080] Prepare a modified polysiloxane emulsion:

[0081] S2-1: Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid, and 40 parts of water into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7-8 with ammonia water to obtain a polysiloxane emulsion;

[0082] S2-2: At room temperature, first drop 0.50 parts of 3-methacryloxytrimethoxysilane into the polysiloxane emulsion prepared in step S2-1 and stir for 15 min, then carry out modification at 80 °C for 4 h, and wait for the system to cool to room temperature to obtain a modified polysiloxane emulsion.

[0083] Furthermore, in step S3, it specifically includes:

[0084] S3-1 Connect the modified ethyl cellulose core / shell emulsion prepared in step S2 as the coating liquid to a peristaltic pump, adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 76.6 parts of fertilizer particles to the preheated coating device for 8 min. After the fertilizer is preheated, turn on the peristaltic pump to allow the coating liquid to be injected;

[0085] S3-2 After the injection is completed, lower the temperature to 60 °C, continue to tumble the fertilizer with the coated material in the coating device for 10 min and then take it out to obtain the modified ethyl cellulose-coated controlled-release fertilizer.

[0086] Among them, the fertilizer particles are potassium chloride, potassium sulfate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, urea, compound nitrogen, phosphorus and potassium fertilizers. The particle size of the fertilizer particles is 3 mm, the coating temperature is 70 °C, the coating time is 38 min, and the coating device is a drum.

[0087] Example 3:

[0088] A method for preparing a modified ethyl cellulose-coated controlled-release fertilizer, as Figure 1 shown, includes the following steps:

[0089] S1 Prepare an ethyl cellulose core / shell emulsion;

[0090] S2 Prepare a modified ethyl cellulose core / shell emulsion;

[0091] S3 Prepare a modified ethyl cellulose core / shell emulsion coated controlled-release fertilizer.

[0092] Furthermore, in step S1, it specifically includes:

[0093] Melt 15 parts of ethyl cellulose with 0.6 parts of plasticizer and 0.5 parts of stabilizer at high temperature. After melting, add ammonia water for dilution to obtain an ethyl cellulose core / shell emulsion.

[0094] Among them, the ethyl cellulose is in the form of a white powder, with a viscosity of 9 - 11 mPa·s. The plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxidized soybean oil, and the stabilizer is oleic acid.

[0095] Furthermore, in step S2, it specifically includes:

[0096] Mix the ethyl cellulose core / shell emulsion obtained in step S1 with 10 parts of the prepared modified polysiloxane to obtain a modified ethyl cellulose core / shell emulsion.

[0097] Furthermore, in step S2, it also includes:

[0098] Prepare a modified polysiloxane emulsion:

[0099] S2-1: Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid, and 40 parts of water into a three-necked round-bottom flask equipped with a mechanical stirrer, reflux condenser, and nitrogen inlet. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7 - 8 with ammonia water to obtain a polysiloxane emulsion;

[0100] S2-2: At room temperature, first drop 0.50 parts of 3-methacryloxytrimethoxysilane into the polysiloxane emulsion prepared in step S21 and stir for 15 min, then carry out modification at 80 °C for 4 h. Wait for the system to cool to room temperature to obtain a modified polysiloxane emulsion.

[0101] Furthermore, in step S3, it specifically includes:

[0102] S3-1 Connect the modified ethyl cellulose core / shell emulsion prepared in step S2 as the coating liquid to a peristaltic pump. Adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 73.9 parts of fertilizer particles to the preheated coating device for 10 min. After the fertilizer is preheated, turn on the peristaltic pump to allow the coating liquid to be injected;

[0103] After the sample injection in S3-2 is completed, the temperature is reduced to 60 °C. The fertilizer coated with the material is taken out after continuing to tumble in the coating device for 15 min, and the modified ethylcellulose-coated controlled-release fertilizer is obtained.

[0104] Among them, the fertilizer particles are potassium chloride, potassium sulfate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen, phosphorus, and potassium fertilizers. The particle size of the fertilizer particles is 4 mm, the coating temperature is 80 °C, the coating time is 45 min, and the coating device is a fluidized bed.

[0105] Example 4:

[0106] Preparation of the ethylcellulose-coated controlled-release material T1 includes the following steps:

[0107] (1) Add 10 parts of ethylcellulose, 0.3 part of dibutyl sebacate, and 0.7 part of oleic acid to a high-pressure homogenizer, melt under high temperature and pressure, and simultaneously add ammonia water for dilution to form an ethylcellulose core / shell emulsion.

[0108] (2) Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethylsilane, and 40 parts of H2O into a 100 ml three-necked round flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7-8 with ammonia water to obtain a polysiloxane emulsion. At room temperature, first drop a certain mass of 0.5 part of 3-methacryloxytrimethoxysilane into the prepared polysiloxane latex and stir for 15 min, then carry out modification at 80 °C for 4 h; cool the system to room temperature to obtain the modified polysiloxane emulsion.

[0109] (3) Mix 11 parts of the ethylcellulose core / shell emulsion and 9 parts of the polysiloxane emulsion to obtain a modified ethylcellulose core / shell emulsion.

[0110] Example 5:

[0111] Preparation of the ethylcellulose-coated controlled-release material T2 includes the following steps:

[0112] (1) Add 14 parts of ethylcellulose, 0.6 part of dibutyl sebacate, and 0.4 part of oleic acid to a high-pressure homogenizer, melt under high temperature and pressure, and simultaneously add ammonia water for dilution to form an ethylcellulose core / shell emulsion.

[0113] (2) Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethylsilane, and 40 parts of H2O into a 100 ml three-necked round-bottom flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet. After stirring at 350 rpm for 15 minutes at room temperature, carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7 - 8 with ammonia water to obtain a polysiloxane emulsion. At room temperature, first drop 0.5 part of 3-methacryloxytrimethoxysilane of a certain mass into the prepared polysiloxane latex and stir for 15 min, then carry out modification at 80 °C for 4 h; cool the system to room temperature to obtain the modified polysiloxane emulsion.

[0114] (3) Mix 15 parts of ethyl cellulose core / shell emulsion and 10 parts of polysiloxane emulsion to obtain a modified ethyl cellulose core / shell emulsion.

[0115] Example 6:

[0116] Preparation of ethyl cellulose-coated urea (CRF1), including the following steps:

[0117] (1) Connect 20 parts of the modified ethyl cellulose core / shell emulsion T1 to a peristaltic pump and adjust the peristaltic pump to 10 ml / min.

[0118] (2) Turn on the fluidized bed, adjust the temperature to 80 °C, and preheat the fluidized bed.

[0119] (3) Pour 80 parts of large granular urea weighed into the preheated fluidized bed for 5 - 10 min.

[0120] (4) After the urea is preheated, turn on the peristaltic pump to allow the coating liquid to be injected.

[0121] (5) After the injection is completed, lower the temperature to 60 °C, and continue to fluidize the urea coated with the material in the fluidized bed for 5 - 15 min, then take it out. That is, a coated controlled-release urea with a coating rate of 20% and a water contact angle of 90° is obtained.

[0122] Example 7:

[0123] Preparation of ethyl cellulose-coated controlled-release urea (CRF2), including the following steps:

[0124] (1) Connect 25 parts of the modified ethyl cellulose core / shell emulsion T2 to a peristaltic pump and adjust the peristaltic pump to 10 ml / min.

[0125] (2) Turn on the fluidized bed, adjust the temperature to 80 °C, and preheat the fluidized bed.

[0126] (3) Pour 75 parts of large granular urea weighed into the preheated fluidized bed for 5 - 10 min.

[0127] (4) After the urea preheating is completed, turn on the peristaltic pump to allow the coating liquid to be injected.

[0128] (5) After the injection is completed, lower the temperature to 60 °C, and continue to fluidize the urea with the coated material in the fluidized bed for 5 - 15 min, then take it out to obtain the coated controlled-release urea with a coating rate of 25%, and its water contact angle is 100°.

[0129] Comparative Example 1:

[0130] Preparation of unmodified ethyl cellulose-coated urea (CRF), including the following steps:

[0131] Connect the unmodified ethyl cellulose core / shell emulsion as the coating liquid to the peristaltic pump, adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 75 - 80 parts of fertilizer particles to the preheated coating device for 5 - 10 min. After the urea coating is completed, turn on the peristaltic pump to allow the coating liquid to be injected. After the injection is completed, lower the temperature to 60 °C, and continue to tumble the urea with the coated material in the coating device for 5 - 15 min and then take it out to obtain unmodified ethyl cellulose-coated controlled-release fertilizer (CRF).

[0132] Comparative Example 2:

[0133] Preparation of polyurethane-coated controlled-release urea (PCU), including the following steps:

[0134] Add 1000 parts of large granular urea to a fluidized bed at 75 °C, heat and fluidize for 5 min. Add 5 parts of liquid paraffin for pretreatment, and simultaneously drop 18.87 parts of polyether polyol and 21.13 parts of isocyanate onto the surface of the large granular urea, and react for 5 - 10 min to obtain polyurethane-coated controlled-release urea (PCU).

[0135] Test Example 1:

[0136] Determination of fertilizer nitrogen release rate, including:

[0137] Weigh 10 parts of the coated fertilizers of Example 6 (CRF1), 7 (CRF2), and Comparative Example 1 (CRF), put them in a nylon mesh bag, place them in a plastic bottle with a lid, then add 200 mL of deionized water, cover the bottle cap, and soak in a constant temperature incubator at 25 °C. Each sample is set with three replicates, and 1 mL of the sample is taken each time to measure the release rate of the coated fertilizer. After the measurement, pour out all the leaching solution in the plastic bottle, and then add 200 mL of deionized water to continue soaking. The sampling and determination times are the 1st, 3rd, 5th, 7th, 9th, and 11th. The determination method uses p-dimethylaminobenzaldehyde - spectrophotometry, where, Figure 2 It is the nutrient release curve graph.

[0138] Test Example 2:

[0139] Measurement of water contact angle, including:

[0140] The fertilizer samples of Example 6 (CRF1), Example 7 (CRF2), and Comparative Example 1 (CRF) were flatly pasted on the measurement table with double-sided tape, and the sample position was adjusted so that it was directly below the syringe needle. The drip system was opened to make a drop of ultrapure water hover at the needle tip. The measurement table was moved upward to make the liquid drop adhere to the surface of the fertilizer sample, and a photo was taken immediately. The position of the reference line was found and the contact angle was calculated. Figure 3 It is the water contact angle of the coated controlled-release urea.

[0141] Test Example 3:

[0142] Film shell degradation rate experiment, including:

[0143] The coated controlled-release fertilizers of Example 6 (CRF1), Example 7 (CRF2), and Comparative Example 2 (PCU) were soaked in clear water and rinsed repeatedly to completely remove the fertilizer on the film shell. The residual film was filtered out, dried, and sieved, and the part of the film shell larger than 2 mm was reserved for use. A certain amount of the film shell was put into a mesh bag and buried in the soil. It was taken out after 3 months to measure the degradation rate. The degradation rate of the film shell of Treatment CRF1 was 10%, the degradation rate of Treatment CRF2 was 13%, and the degradation rate of the film shell of Treatment PCU was 1.5%.

[0144] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A preparation method of a modified ethyl cellulose-coated controlled-release fertilizer, characterized in that, It includes the following steps: S1 Prepare ethyl cellulose core / shell emulsion Melt 10 - 15 parts of ethyl cellulose, 0.4 - 0.6 parts of plasticizer, and 0.3 - 0.5 parts of stabilizer at high temperature. After melting, add ammonia water for dilution to obtain ethyl cellulose core / shell emulsion; S2 Prepare modified ethyl cellulose core / shell emulsion S2 - 1: Charge 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid, and 40 parts of water into a three - necked round - bottom flask equipped with a mechanical stirrer, reflux condenser, and nitrogen inlet. Stir at 350 revolutions per minute at room temperature for 15 minutes, then carry out emulsion polymerization at 90 °C for 10 h, then cool to room temperature, and neutralize to pH 7 - 8 with ammonia water to obtain polysiloxane emulsion; S2 - 2: At room temperature, first drop 0.50 parts of 3 - methacryloxytrimethoxysilane into the polysiloxane emulsion prepared in step S2 - 1 and stir for 15 min, then carry out modification at 80 °C for 4 h. After the system cools to room temperature, obtain modified polysiloxane emulsion; Mix the ethyl cellulose core / shell emulsion obtained in step S1 with 9 - 10 parts of the prepared modified polysiloxane to obtain modified ethyl cellulose core / shell emulsion; S3 Prepare modified ethyl cellulose core / shell emulsion - coated controlled - release fertilizer S3 - 1: Connect the modified ethyl cellulose core / shell emulsion prepared in step S2 as the coating liquid to a peristaltic pump. Adjust the peristaltic pump to 10 ml / min, turn on the coating device, adjust the temperature to 80 °C, preheat the coating device, add 74 - 80 parts of fertilizer particles to the preheated coating device for 5 - 10 min. After the fertilizer is preheated, turn on the peristaltic pump to allow the coating liquid to be injected; S3 - 2: After the injection is completed, lower the temperature to 60 °C, continue to tumble the fertilizer coated with the material in the coating device for 5 - 15 min and then take it out to obtain modified ethyl cellulose - coated controlled - release fertilizer.

2. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to claim 1, characterized in that, In step S1, the ethyl cellulose is in white powder form with a viscosity of 3 - 7 mPa·s; the plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxidized soybean oil; the stabilizer is oleic acid.

3. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to claim 1, characterized in that, In step S1, the ethyl cellulose is in white powder form with a viscosity of 6 - 9 mPa·s; the plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxidized soybean oil; the stabilizer is oleic acid.

4. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to claim 1, characterized in that In step S1, the ethyl cellulose is in white powder form with a viscosity of 9 - 11 mPa·s; the plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxidized soybean oil; the stabilizer is oleic acid.

5. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to claim 1, characterized in that, In step S3, the fertilizer particles are one or more of potassium chloride, potassium sulfate, ammonium sulfate, monoammonium phosphate, diammonium phosphate, urea, and compound nitrogen - phosphorus - potassium fertilizers. The particle size of the fertilizer particles is 2 - 4 mm, the coating temperature is 60 - 80 °C, and the coating time is 30 - 45 min.

6. The preparation method of a modified ethyl cellulose-coated controlled-release fertilizer according to claim 5, characterized in that, In step S3, the coating device is one of a coating pan, a fluidized bed, and a spouted bed.

Images