Preparation method of modified ethyl cellulose coated controlled-release fertilizer

Abstract

The invention discloses a preparation method of a modified ethyl cellulose coated controlled-release fertilizer. The preparation method comprises the following steps: S1, preparing an ethyl cellulose core / shell emulsion; s2, preparing a modified ethyl cellulose core / shell emulsion; the preparation method is suitable for the technical field of controlled-release fertilizers, ethyl cellulose is used as a coating material, a coating liquid system is a water system, an organic solvent is not needed, and the defects that when ethyl cellulose is used for preparing a coating liquid, the organic solvent is used, environmental pollution is large, and recovery is difficult are overcome; aiming at the problem of poor hydrophobicity of ethyl cellulose as a coating material, the modified polysiloxane is used for modifying an ethyl cellulose core / shell emulsion, so that the hydrophobicity of the coated controlled-release fertilizer is improved, and the coated controlled-release fertilizer with a long controlled-release period is prepared. The fertilizer has the characteristics of greenness, degradability and long controlled release period, the green and sustainable development process of agriculture is promoted, and a technical means is provided for realizing a dual-carbon target in China.

Description

Technical Field

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

[0002] Controlled-release fertilizers can control the nutrient release and crop nutrient absorption in a one-time fertilization, thereby increasing crop yields and fertilizer utilization, and are an important product of green fertilizers in my country. At present, the mainstream coated controlled-release fertilizers on the market are mainly organic polymer coated controlled-release fertilizers. Although the controlled-release performance is good, there are problems such as difficult degradation of the membrane shell and environmental pollution.

[0003] As my country pays more and more attention to the quality of arable land, the development of new high-efficiency bio-based degradable controlled-release materials has become a technical problem that needs to be overcome in the field of controlled-release fertilizers. The use of biodegradable cellulose materials to develop new green controlled-release fertilizers is a current research hotspot.

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

[0005] As one of the cellulose ether derivatives, ethyl cellulose has good hydrophobicity and has the advantages of biodegradability, renewability, low cost and low thermal expansion coefficient. It is often used as a coating and film material. However, ethyl cellulose has problems such as poor mechanical properties. The developed controlled-release fertilizer has a release period of only a few dozen hours, and it is necessary to further improve its controlled-release performance through modification measures such as hydrophobic toughening.

[0006] Some scholars used ethyl cellulose (EC) and acrylic acid-co-acrylamide (AA-co-AM) as inner and outer coating materials, respectively, and ethanol solution as solvent. The coated fertilizer was prepared by water immersion method. In the test of simulated soil condition experiment, it was shown that the release was complete within 30 days (Ni et al., 2009).

[0007] For example, Lubkowski dissolved ethyl cellulose in ethanol and treated untreated phosphate fertilizer by multiple immersion methods to obtain ethyl cellulose coated phosphate fertilizer. The water immersion method study found that the nutrient release reached 70% at 320 hours, and the nutrient release of untreated phosphate fertilizer reached 80% at about 30 hours (Lubkowski. Poland, 2019).

[0008] In summary, in existing studies, ethyl cellulose is used as a coating material, and the solvents used are basically organic solvents, mostly ethanol. The process conditions used are mainly based on the impregnation method, and the mainstream process (such as the use of a fluidized bed) is relatively rare. There are the following problems:

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

[0010] 2. In previous studies, when ethyl cellulose was used to prepare coated fertilizers, the solvents used to dissolve ethyl cellulose were all organic solvents, which have the problems of high cost, low recovery rate, and toxicity;

[0011] 3. Ethyl cellulose has a large particle size, poor mechanical properties, and poor film-forming properties. The controlled-release properties of ethyl cellulose-coated controlled-release urea alone are poor and do not 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 method for preparing a modified ethyl cellulose coated controlled-release fertilizer.

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

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

[0015] S1 preparation of ethyl cellulose core / shell emulsion;

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

[0017] S3 Preparation of modified ethyl cellulose core / shell emulsion coated controlled release fertilizer.

[0018] Preferably, the step S1 specifically includes:

[0019] 10-15 parts of ethyl cellulose, 0.4-0.6 parts of plasticizer and 0.3-0.5 parts of stabilizer are melted at high temperature, and after melting, ammonia water is added to dilute to obtain ethyl cellulose core / shell emulsion.

[0020] Preferably, in step S1, the ethyl cellulose is a 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 epoxy soybean oil, and the stabilizer is oleic acid.

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

[0022] Preferably, the step S2 specifically includes:

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

[0024] Preferably, the step S2 further includes:

[0025] Preparation of modified polysiloxane emulsion:

[0026] S2-1: 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid and 40 parts of water were respectively charged into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet, stirred at 350 rpm for 15 minutes at room temperature, and then emulsion polymerized at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion;

[0027] S2-2: At room temperature, first, 0.50 parts of 3-methacryloxytrimethoxysilane was dropped into the polysiloxane emulsion prepared in step S2-1 and stirred for 15 minutes, then modified at 80°C for 4 hours, and the system was cooled to room temperature to obtain a modified polysiloxane emulsion.

[0028] Preferably, the step S3 specifically includes:

[0029] S3-1: Connect the modified ethyl cellulose core / shell emulsion prepared in 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 to 80 parts of fertilizer particles into the preheated coating device for 5 to 10 minutes, and after the fertilizer is preheated, turn on the peristaltic pump to inject the coating liquid;

[0030] S3-2: After the injection is completed, the temperature is lowered to 60°C, and the fertilizer coated with the material is continuously rolled in the coating device for 5 to 15 minutes before being taken out to obtain the modified ethyl cellulose coated controlled-release fertilizer.

[0031] Preferably, 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 fertilizer particle size is 2 to 4 mm, the coating temperature is 60 to 80° C., the coating time is 30 to 45 min, and the coating device is a coating pan, a drum, or a fluidized bed.

[0032] Preferably, in 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 solution, the beneficial effects of the present invention are:

[0034] 1. In the present invention, modified ethyl cellulose core / shell emulsion is used as the coating material, and no organic solvent is needed, which solves the disadvantages of large environmental pollution and difficulty in recycling when using organic solvents to prepare ethyl cellulose coating liquid;

[0035] 2. In the present invention, in order to solve the problem that the ethyl cellulose material coated on the fertilizer has poor hydrophobicity, 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 single ethyl cellulose has a larger particle size of 60 to 80 μm and cannot form a uniform and dense film layer. The ethyl cellulose core / shell emulsion has a smaller particle size of 80 to 200 nm and has better film-forming properties, and can form a uniform film layer on the surface of the fertilizer particles. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0039] Figure 3 Schematic diagram of the water contact angle of the coated controlled-release urea in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention are described in detail below.

[0041] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 10 to 50 is listed for a specific parameter, it is understood that the range of 10 to 40 and 20 to 50 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 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 range of values ​​"a to b" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the range of values ​​"0 to 5" means that all real numbers between "0 to 5" have been fully listed in this article, and "0 to 5" is only an abbreviation of these numerical combinations.

[0042] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, 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 explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0045] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0046] Unless otherwise specified, the reaction is carried out at room temperature and pressure.

[0047] Unless otherwise specified, all parts or percentages are by weight.

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

[0049] In the present invention, the devices or equipment used are all conventional devices or equipment known in the art and are commercially available.

[0050] The following examples further illustrate the specific implementation of the method for preparing a modified ethyl cellulose coated controlled-release fertilizer of the present invention. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer of the present invention is not limited to the description of the following examples.

[0051] Embodiment 1:

[0052] A method for preparing a modified ethyl cellulose coated controlled-release fertilizer, such as Figure 1 As shown, the following steps are included:

[0053] S1 preparation of ethyl cellulose core / shell emulsion;

[0054] S2 prepares modified ethyl cellulose core / shell emulsion;

[0055] S3 Preparation of modified ethyl cellulose core / shell emulsion coated controlled release fertilizer.

[0056] Furthermore, step S1 specifically includes:

[0057] 10 parts of ethyl cellulose, 0.4 parts of plasticizer and 0.3 parts of stabilizer are melted at high temperature, and after melting, ammonia water is added to dilute to obtain ethyl cellulose core / shell emulsion.

[0058] Among them, ethyl cellulose is a white powder structure with a viscosity of 3 to 7 mPa.s, the plasticizer is dibutyl adipate, and the stabilizer is oleic acid.

[0059] Furthermore, step S2 specifically includes:

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

[0061] Furthermore, step S2 further includes:

[0062] Preparation of modified polysiloxane emulsion:

[0063] S2-1: 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid and 40 parts of water were respectively charged into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet, stirred at 350 rpm for 15 minutes at room temperature, and then emulsion polymerized at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion;

[0064] S2-2: At room temperature, first, 0.50 parts of 3-methacryloxytrimethoxysilane was dropped into the polysiloxane emulsion prepared in step S2-1 and stirred for 15 minutes, and then modified at 80°C for 4 hours. After the system was cooled to room temperature, a modified polysiloxane emulsion was obtained.

[0065] Furthermore, step S3 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 into the preheated coating device for 5 minutes, and after the fertilizer is preheated, turn on the peristaltic pump to inject the coating liquid;

[0067] After the S3-2 injection is completed, the temperature is lowered to 60° C., and the fertilizer coated with the material is tumbled in the coating device for 5 minutes before being taken 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-potassium fertilizers. The fertilizer particle size is 2 mm, the coating temperature is 60°C, the coating time is 30 minutes, and the coating device is a coating pot.

[0069] Embodiment 2:

[0070] A method for preparing a modified ethyl cellulose coated controlled-release fertilizer, such as Figure 1 As shown, the following steps are included:

[0071] S1 preparation of ethyl cellulose core / shell emulsion;

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

[0073] S3 Preparation of modified ethyl cellulose core / shell emulsion coated controlled release fertilizer.

[0074] Furthermore, step S1 specifically includes:

[0075] 13 parts of ethyl cellulose, 0.5 parts of plasticizer and 0.4 parts of stabilizer are melted at high temperature, and after melting, ammonia water is added to dilute to obtain ethyl cellulose core / shell emulsion.

[0076] Among them, ethyl cellulose is a white powder structure with a viscosity of 6 to 9 mPa.s, the plasticizer is dibutyl phthalate, and the stabilizer is oleic acid.

[0077] Furthermore, step S2 specifically includes:

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

[0079] Furthermore, step S2 further includes:

[0080] Preparation of modified polysiloxane emulsion:

[0081] S2-1: 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid and 40 parts of water were respectively charged into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet, stirred at 350 rpm for 15 minutes at room temperature, and then emulsion polymerized at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion;

[0082] S2-2: At room temperature, first, 0.50 parts of 3-methacryloxytrimethoxysilane was dropped into the polysiloxane emulsion prepared in step S2-1 and stirred for 15 minutes, and then modified at 80°C for 4 hours. After the system was cooled to room temperature, a modified polysiloxane emulsion was obtained.

[0083] Furthermore, step S3 specifically includes:

[0084] S3-1: Connect the modified ethyl cellulose core / shell emulsion prepared in 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 76.6 parts of fertilizer particles into the preheated coating device for 8 minutes, and after the fertilizer is preheated, turn on the peristaltic pump to inject the coating liquid;

[0085] After the S3-2 sampling is completed, the temperature is lowered to 60° C., and the fertilizer coated with the material is tumbled in the coating device for 10 minutes before being taken 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, and compound nitrogen-phosphorus-potassium fertilizer. The fertilizer particle size is 3 mm, the coating temperature is 70°C, the coating time is 38 minutes, and the coating device is a roller.

[0087] Embodiment 3:

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

[0089] S1 preparation of ethyl cellulose core / shell emulsion;

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

[0091] S3 Preparation of modified ethyl cellulose core / shell emulsion coated controlled release fertilizer.

[0092] Furthermore, step S1 specifically includes:

[0093] 15 parts of ethyl cellulose, 0.6 parts of plasticizer and 0.5 parts of stabilizer are melted at high temperature, and after melting, ammonia water is added to dilute to obtain ethyl cellulose core / shell emulsion.

[0094] Among them, ethyl cellulose is a white powder structure with a viscosity of 9 to 11 mPa.s, the plasticizer is one of dibutyl adipate, dibutyl phthalate, dibutyl sebacate, and epoxy soybean oil, and the stabilizer is oleic acid.

[0095] Furthermore, step S2 specifically includes:

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

[0097] Furthermore, step S2 further includes:

[0098] Preparation of modified polysiloxane emulsion:

[0099] S2-1: 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid and 40 parts of water were respectively charged into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet, stirred at 350 rpm for 15 minutes at room temperature, and then emulsion polymerized at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion;

[0100] S2-2: At room temperature, first, 0.50 parts of 3-methacryloxytrimethoxysilane was dropped into the polysiloxane emulsion prepared in step S21 and stirred for 15 minutes, and then modified at 80°C for 4 hours. After the system was cooled to room temperature, a modified polysiloxane emulsion was obtained.

[0101] Furthermore, step S3 specifically includes:

[0102] S3-1: Connect the modified ethyl cellulose core / shell emulsion prepared in 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 73.9 parts of fertilizer particles into the preheated coating device for 10 minutes, and after the fertilizer is preheated, turn on the peristaltic pump to inject the coating liquid;

[0103] After the S3-2 injection is completed, the temperature is lowered to 60° C., and the fertilizer coated with the material is tumbled in the coating device for 15 minutes before being taken out to obtain the modified ethyl cellulose coated controlled-release fertilizer.

[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 fertilizer particle size is 4 mm, the coating temperature is 80°C, the coating time is 45 minutes, and the coating device is a fluidized bed.

[0105] Embodiment 4:

[0106] The preparation of ethylcellulose coated controlled release material T1 comprises the following steps:

[0107] (1) 10 parts of ethyl cellulose, 0.3 parts of dibutyl sebacate, and 0.7 parts of oleic acid are added to a high-pressure homogenizer, melted under high temperature and high pressure, and ammonia water is added to dilute to form an ethyl cellulose core / shell emulsion.

[0108] (2) 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethylsilane, and 40 parts of H2O were respectively charged into a 100 ml three-necked round flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet. After stirring at 350 rpm for 15 minutes at room temperature, emulsion polymerization was carried out at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion. At room temperature, a certain mass of 0.5 parts of 3-methacryloyloxytrimethoxysilane was first dropped into the prepared polysiloxane latex and stirred for 15 minutes, and then modified at 80°C for 4 hours; the system was cooled to room temperature to obtain a modified polysiloxane emulsion.

[0109] (3) 11 parts of ethyl cellulose core / shell emulsion and 9 parts of polysiloxane emulsion were mixed to obtain a modified ethyl cellulose core / shell emulsion.

[0110] Embodiment 5:

[0111] The preparation of ethylcellulose coated controlled release material T2 comprises the following steps:

[0112] (1) 14 parts of ethyl cellulose, 0.6 parts of dibutyl sebacate, and 0.4 parts of oleic acid are added to a high-pressure homogenizer, melted under high temperature and high pressure, and ammonia water is added to dilute to form an ethyl cellulose core / shell emulsion.

[0113] (2) 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethylsilane, and 40 parts of H2O were respectively charged into a 100 ml three-necked round flask equipped with a mechanical stirrer, a reflux condenser, and a nitrogen inlet. After stirring at 350 rpm for 15 minutes at room temperature, emulsion polymerization was carried out at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion. At room temperature, a certain mass of 0.5 parts of 3-methacryloxytrimethoxysilane was first dropped into the prepared polysiloxane latex and stirred for 15 minutes, and then modified at 80°C for 4 hours; the system was cooled to room temperature to obtain a modified polysiloxane emulsion.

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

[0115] Embodiment 6:

[0116] The preparation of ethylcellulose coated urea (CRF1) comprises the following steps:

[0117] (1) Connect 20 parts of 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 and adjust the temperature to 80°C to preheat the fluidized bed.

[0119] (3) Add 80 parts of weighed large-particle urea into the preheated fluidized bed for 5 to 10 minutes.

[0120] (4) After the urea is preheated, turn on the peristaltic pump to inject the coating solution.

[0121] (5) After the injection is completed, the temperature is lowered to 60°C, and the urea coated with the material is continued to be fluidized in the fluidized bed for 5 to 15 minutes, and then taken out. Thus, the coated controlled-release urea with a coating rate of 20% is obtained, and its water contact angle is 90°.

[0122] Embodiment 7:

[0123] The preparation of ethylcellulose coated controlled release urea (CRF2) comprises the following steps:

[0124] (1) Connect 25 parts of 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 and adjust the temperature to 80°C to preheat the fluidized bed.

[0126] (3) Add 75 parts of weighed large-particle urea into the preheated fluidized bed for 5 to 10 minutes.

[0127] (4) After the urea is preheated, turn on the peristaltic pump to inject the coating solution.

[0128] (5) After the injection is completed, the temperature is lowered to 60°C, and the urea that has been coated with the material is continued to be fluidized in the fluidized bed for 5 to 15 minutes, and then taken out to obtain coated controlled-release urea with a coating rate of 25% and a water contact angle of 100°.

[0129] Comparative Example 1:

[0130] The preparation of unmodified ethylcellulose coated urea (CRF) comprises the following steps:

[0131] The unmodified ethyl cellulose core / shell emulsion is connected to a peristaltic pump as a coating liquid, the peristaltic pump is adjusted to 10 ml / min, the coating device is turned on, the temperature is adjusted to 80°C, the coating device is preheated, 75 to 80 parts of fertilizer particles are added to the preheated coating device for 5 to 10 minutes, and after the urea coating is completed, the peristaltic pump is turned on to inject the coating liquid. After the injection is completed, the temperature is lowered to 60°C, and the urea that has been coated is continuously rolled in the coating device for 5 to 15 minutes before being taken out to obtain an unmodified ethyl cellulose coated controlled release fertilizer (CRF).

[0132] Comparative Example 2:

[0133] The preparation of polyurethane coated controlled-release urea (PCU) comprises the following steps:

[0134] 1000 parts of large-particle urea were added to a fluidized bed at 75°C and heated for 5 minutes. 5 parts of liquid paraffin were added for pretreatment, and 18.87 parts of polyether polyol and 21.13 parts of isocyanate were dripped onto the surface of large-particle urea and reacted for 5 to 10 minutes to obtain polyurethane-coated controlled-release urea (PCU).

[0135] Test example 1:

[0136] Fertilizer nitrogen release rate determination, including:

[0137] Weigh 10 portions of the coated fertilizers of Example 6 (CRF1), 7 (CRF2), and Comparative Example 1 (CRF), put them in a nylon mesh bag, put them in a plastic bottle with a lid, then add 200 mL of deionized water, cover the bottle cap, and soak them in a constant temperature box at 25°C. Set up three replicates for each sample, and take 1 mL of sample each time to measure the release rate of the coated fertilizer. After the measurement, pour out all the extract in the plastic bottle, and add 200 mL of deionized water to continue soaking. The sampling and measurement times are 1, 3, 5, 7, 9, and 11. The determination method adopts the p-dimethylaminobenzaldehyde-spectrophotometry, in which, Figure 2 This is a nutrient release curve.

[0138] Test Example 2:

[0139] Determination of water contact angle, including:

[0140] The fertilizer samples of Example 6 (CRF1), 7 (CRF2), and Comparative Example 1 (CRF) were flatly attached to the measuring table with double-sided tape, and the sample position was adjusted to be directly below the syringe needle. The dripping system was turned on, and a drop of ultrapure water was suspended at the needle. The measuring table was moved upward to allow the drop to adhere to the surface of the fertilizer sample, and a photo was taken immediately. The baseline position was found and the contact angle was calculated. Figure 3 is the water contact angle of coated controlled-release urea.

[0141] Test Example 3:

[0142] Membrane shell degradation rate experiment, including:

[0143] The coated controlled-release fertilizers of Example 6 (CRF1), 7 (CRF2), and Comparative Example 2 (PCU) were soaked in clean water and rinsed several times to completely remove the fertilizer on the membrane shell, and the residual membrane was filtered out, dried, and sieved, leaving the membrane shell larger than 2 mm for use. A certain amount of membrane shell was placed in a net bag, buried in the soil, and taken out after 3 months to measure the degradation rate. The degradation rate of the membrane shell treated with CRF1 was 10%, the degradation rate of the membrane shell treated with CRF2 was 13%, and the degradation rate of the membrane shell treated with PCU was 1.5%.

[0144] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for preparing a modified ethyl cellulose coated controlled-release fertilizer, characterized in that: The following steps are involved: S1 preparation of ethyl cellulose core / shell emulsion; S2 prepares modified ethyl cellulose core / shell emulsion; S3 Preparation of modified ethyl cellulose core / shell emulsion coated controlled release fertilizer.

2. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 1, characterized in that: The step S1 specifically includes: 10-15 parts of ethyl cellulose, 0.4-0.6 parts of plasticizer and 0.3-0.5 parts of stabilizer are melted at high temperature, and after melting, ammonia water is added to dilute to obtain ethyl cellulose core / shell emulsion.

3. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 2, characterized in that: In step S1, the ethyl cellulose is a 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 epoxy soybean oil; and the stabilizer is oleic acid.

4. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 1, characterized in that: The step S2 specifically includes: The ethyl cellulose core / shell emulsion obtained in step S1 is mixed with 9 to 10 parts of the prepared modified polysiloxane to obtain a modified ethyl cellulose core / shell emulsion.

5. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 1, characterized in that: The step S2 further includes: Preparation of modified polysiloxane emulsion: S2-1: 9 parts of octamethylcyclotetrasiloxane, 1 part of tetraethoxysilane, 0.22 parts of dodecylbenzenesulfonic acid and 40 parts of water were respectively charged into a three-necked round flask equipped with a mechanical stirrer, a reflux condenser and a nitrogen inlet, stirred at 350 rpm for 15 minutes at room temperature, and then emulsion polymerized at 90°C for 10 hours, then cooled to room temperature, and neutralized with ammonia water to pH 7-8 to obtain a polysiloxane emulsion; S2-2: At room temperature, first, 0.50 parts of 3-methacryloxytrimethoxysilane was dropped into the polysiloxane emulsion prepared in step S2-1 and stirred for 15 minutes, and then modified at 80°C for 4 hours. After the system was cooled to room temperature, a modified polysiloxane emulsion was obtained.

6. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 1, characterized in that: The step S3 specifically includes: S3-1: Connect the modified ethyl cellulose core / shell emulsion prepared in 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 to 80 parts of fertilizer particles into the preheated coating device for 5 to 10 minutes, and after the fertilizer is preheated, turn on the peristaltic pump to inject the coating liquid; S3-2: After the injection is completed, the temperature is lowered to 60°C, and the fertilizer coated with the material is continuously rolled in the coating device for 5 to 15 minutes before being taken out to obtain a modified ethyl cellulose coated controlled-release fertilizer.

7. The method for preparing 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 composite nitrogen-phosphorus-potassium fertilizers, the fertilizer particle size is 2 to 4 mm, the coating temperature is 60 to 80° C., and the coating time is 30 to 45 min.

8. The method for preparing a modified ethyl cellulose coated controlled-release fertilizer according to claim 7, characterized in that: In step S3, the coating device is one of a coating pan, a fluidized bed and a spouted bed.

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