PBAT-based environment-friendly slow-release coated urea and preparation method thereof

Abstract

The invention belongs to the technical field of fertilizers, and particularly relates to PBAT-based environment-friendly slow-release coated urea and a preparation method thereof. The PBAT-based environment-friendly slow-release coated urea provided by the invention comprises urea particles and a coating layer coating the urea particles, and the coating layer comprises the following raw materials: PBAT, an organic matter modifier and an inorganic matter modifier; the organic matter modifier comprises at least one of methyl cellulose or polyvinyl ether, and the inorganic matter modifier comprises at least one of bentonite or hydrotalcite. The coating material used in the PBAT-based environment-friendly slow-release coated urea has good biodegradability, degradation products have little harm to soil, the time required for the nitrogen nutrient release amount of the PBAT-based environment-friendly slow-release coated urea to reach 90% is 80-120 days, and the PBAT-based environment-friendly slow-release coated urea is suitable for growth of crops such as corn, soybeans and rice.

Description

Technical Field

[0001] This invention belongs to the technical field of fertilizers, specifically relating to a PBAT-based environmentally friendly slow-release coated urea and its preparation method. Background Technology

[0002] According to an SCI academic paper (Industrial Crops and Products, 2022, 189:115803), the world's population is growing exponentially, projected to reach nearly 9.7 billion by 2050. This continuous population growth puts enormous pressure on global food supplies. Chemical fertilizers play an indispensable role in global food security. Nitrogen is one of the three macronutrients (nitrogen, phosphorus, and potassium) required for crop growth; urea, due to its high nitrogen content (≥46wt%) and low cost, has become the most commonly used nitrogen-based fertilizer. However, urea is a neutral organic small molecule that is not easily fixed by soil particles before hydrolysis, causing it to be lost before crops can absorb it. It is estimated that only 30-50% of the nitrogen nutrients in urea can be absorbed by crops. The loss of nitrogen nutrients not only causes economic losses but also leads to serious environmental problems, such as groundwater pollution and eutrophication of water bodies.

[0003] Developing slow-release coated urea is one effective way to solve the above problems. Slow-release coated urea involves coating the surface of urea granules with a thin film, allowing the nitrogen nutrients in the urea to be released slowly, thus giving crops more time to absorb them and improving the utilization rate of nitrogen nutrients in urea. Compared with ordinary urea granules, slow-release coated urea has advantages such as high nutrient utilization rate, sustainable nutrient supply, low application frequency, and low application rate.

[0004] Therefore, how to prepare sustained-release coated urea with better performance has received increasing attention. Summary of the Invention

[0005] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0006] CN117105727A reports a slow-release coated urea based on mineral powder and its preparation equipment. The coated urea includes a core layer of fertilizer granules and a slow-release layer covering the fertilizer granules, which can greatly prolong the release time of nitrogen nutrients in urea. However, this slow-release coated urea requires the use of complex mineral powders (composed of five substances: palygorskite powder, clay, kaolin, calcareous soil, and talc powder) to bind the urea granules, and the composition of the slow-release layer is even more complex (composed of eleven substances: polylactic acid, straw powder, ginkgo leaf powder, tea powder, crab shell powder, velvet fiber, sodium polyacrylate, polyacrylamide, nanocellulose, pentaerythritol diphosphite, and phenyl dihydroxybenzoate). Furthermore, specialized equipment is required to complete the preparation. CN114773123A reports an environmentally friendly slow-release coated urea containing an inner slow-release layer and an outer protective layer, and its preparation method. This is a fertilizer with controlled nutrient release, drought resistance, water conservation, and soil structure improvement properties. However, this type of slow-release coated urea requires two coating processes, increasing the complexity of the process. An academic paper (Taiyuan Science and Technology, 2002, 01: 44-45) reported a polyethylene-coated urea with promising application prospects. However, polyethylene has poor biodegradability; long-term use of polyethylene-coated urea, after the urea nutrients are released, leaves polyethylene residues in the soil, easily causing "white pollution."

[0007] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a PBAT-based environmentally friendly sustained-release coated urea, which has advantages such as simple preparation process, good sustained-release performance, and biodegradable coating material.

[0008] The PBAT-based environmentally friendly slow-release coated urea of ​​this invention includes urea particles and a coating layer covering the urea particles. The raw materials of the coating layer include PBAT, an organic modifier, and an inorganic modifier. The organic modifier includes at least one of methylcellulose or polyvinyl ether, and the inorganic modifier includes at least one of bentonite or hydrotalcite.

[0009] The advantages and technical effects of the PBAT-based environmentally friendly slow-release coated urea in this invention are as follows: 1. In this invention, the coating material has good biodegradability, and the degradation products have minimal harm to the soil; 2. In this invention, the time required for the PBAT-based environmentally friendly slow-release coated urea to release 90% of its nitrogen nutrients is 80-120 days, making it suitable for the growth of crops such as corn, soybeans, and rice.

[0010] In some embodiments, the mass ratio of the coating layer to the urea particles is 2-8%.

[0011] In some embodiments, the mass ratio of PBAT, organic modifier and inorganic modifier is (8-12):(0.1-4):(0.1-5).

[0012] This invention also provides a method for preparing PBAT-based environmentally friendly sustained-release coated urea, characterized by comprising the following steps:

[0013] (1) Dissolve PBAT and an organic modifier in an organic solvent and perform a first stirring treatment to obtain a PBAT-based solution; then add an inorganic modifier to the PBAT-based solution and perform a second stirring treatment and ultrasonic dispersion treatment to obtain a PBAT-based coating solution;

[0014] (2) Take urea granules for preheating treatment, use PBAT-based coating solution to coat the preheated urea granules and then dry them.

[0015] In some embodiments, in step (1), the organic solvent includes at least one of N,N-dimethylformamide or N-methylpyrrolidone;

[0016] And / or, the mass ratio of the organic solvent, PBAT, organic modifier and inorganic modifier is 100:(8-12):(0.1-4):(0.1-5).

[0017] In some embodiments, in step (1), the temperature of the first stirring treatment is 60-100°C, and the time of the first stirring treatment is 40-100 min;

[0018] And / or, the temperature of the second stirring treatment is 60-100°C, and the time of the second stirring treatment is 30-80 min;

[0019] And / or, the ultrasonic dispersion time is 10 to 30 minutes.

[0020] In some embodiments, in step (2), the radius of the urea particles is 3 to 6 mm.

[0021] In some embodiments, in step (2), the preheating time is 5 to 20 minutes and the preheating temperature is 70 to 100°C.

[0022] In some embodiments, in step (2), the equipment used for the coating process is a rotary drum coating machine, the fan temperature of the rotary drum coating machine is 70-100℃, and the drum speed is 30-70 r / min.

[0023] In some embodiments, in step (2), the drying temperature is 70-100°C and the drying time is 15-60 min. Attached Figure Description

[0024] Figure 1 This is a bar chart showing the water content of each coating material in Examples 1-7 and Comparative Examples 2-4 of the present invention;

[0025] Figure 2 This is a bar chart showing the biodegradation rate of each coating material in Examples 1-7 and Comparative Examples 2-4 of the present invention over two months;

[0026] Figure 3 This is a schematic diagram of the testing device for the nitrogen nutrient release rate of each coating material in Examples 1-7 and Comparative Examples 2-4 of the present invention;

[0027] Figure 4 This is a bar chart showing the nitrogen nutrient release rate of each coating material in Examples 1-7 and Comparative Examples 2-4 of the present invention;

[0028] Figure 5 These are SEM images of the coating materials in Embodiments 1, 6 and Comparative Example 2 of the present invention;

[0029] Figure 6 This is a bar chart showing the time required for the nitrogen nutrient release rate to reach 90% in Examples 1-7 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0030] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0031] The PBAT-based environmentally friendly slow-release coated urea of ​​this invention includes urea particles and a coating layer covering the urea particles. The raw materials of the coating layer include PBAT, an organic modifier, and an inorganic modifier. The organic modifier includes at least one of methylcellulose or polyvinyl ether, and the inorganic modifier includes at least one of bentonite or hydrotalcite.

[0032] The coating material in the PBAT-based environmentally friendly slow-release coated urea of ​​this invention has good biodegradability, and the degradation products have minimal harm to the soil. In this invention, the time required for the nitrogen nutrient release of the PBAT-based environmentally friendly slow-release coated urea to reach 90% is 80-120 days, which is suitable for the growth of crops such as corn, soybeans, and rice.

[0033] In some embodiments, preferably, the mass ratio of the coating layer to the urea particles is 2 to 8%, for example, 2%, 3%, 4%, 5%, 6%, 7%, or 8%.

[0034] In some embodiments, preferably, the mass ratio of PBAT, organic modifier and inorganic modifier is (8-12):(0.1-4):(0.1-5).

[0035] This invention also provides a method for preparing PBAT-based environmentally friendly sustained-release coated urea, characterized by comprising the following steps:

[0036] (1) Dissolve PBAT and an organic modifier in an organic solvent and perform a first stirring treatment to obtain a PBAT-based solution; then add an inorganic modifier to the PBAT-based solution and perform a second stirring treatment and ultrasonic dispersion treatment to obtain a PBAT-based coating solution;

[0037] (2) Take urea granules for preheating treatment, use PBAT-based coating solution to coat the preheated urea granules and then dry them.

[0038] In some embodiments, preferably, in step (1), the organic solvent includes at least one of N,N-dimethylformamide or N-methylpyrrolidone;

[0039] And / or, the mass ratio of the organic solvent, PBAT, organic modifier and inorganic modifier is 100:(8-12):(0.1-4):(0.1-5).

[0040] In some embodiments, preferably, in step (1), the temperature of the first stirring treatment is 60 to 100°C, for example, 60°C, 70°C, 80°C, 90°C or 100°C, and the time of the first stirring treatment is 40 to 100 min, for example, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min or 100 min;

[0041] And / or, the temperature of the second stirring treatment is 60 to 100°C, for example, 60°C, 70°C, 80°C, 90°C or 100°C, and the time of the second stirring treatment is 30 to 80 minutes, for example, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes or 80 minutes;

[0042] And / or, the ultrasonic dispersion time is 10 to 30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

[0043] In some embodiments, preferably, in step (2), the radius of the urea particles is 3-6 mm, for example 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, or 6 mm.

[0044] In some embodiments, preferably, in step (2), the preheating time is 5 to 20 minutes, such as 5 minutes, 10 minutes, 15 minutes or 20 minutes, and the preheating temperature is 70 to 100 degrees Celsius, such as 70 degrees Celsius, 80 degrees Celsius, 90 degrees Celsius or 100 degrees Celsius.

[0045] In some embodiments, preferably, in step (2), the coating process uses a rotary drum coating machine. The fan temperature of the rotary drum coating machine is 70-100°C, for example, 70°C, 80°C, 90°C, or 100°C, and the drum speed is 30-70 r / min, for example, 30 r / min, 40 r / min, 50 r / min, 60 r / min, or 70 r / min.

[0046] In some embodiments, preferably, in step (2), the drying temperature is 70 to 100°C, such as 70°C, 80°C, 90°C or 100°C; and the drying time is 15 to 60 minutes, such as 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0047] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0048] The specifications and manufacturers of some of the raw materials used in the embodiments are shown in Table 1:

[0049] Table 1

[0050]

[0051]

[0052] Example 1

[0053] (1) Add 12g PBAT, 2g methylcellulose and 1g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 80℃ for 90min to obtain a homogeneous PBAT-based solution; add 2g bentonite to the obtained PBAT-based solution, stir at 80℃ for 60min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0054] (2) Turn on the rotary drum coating machine, set the fan temperature to 70℃ and the drum speed to 40r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 15min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 60min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 4%.

[0055] Example 2

[0056] (1) Add 12g PBAT and 2g methylcellulose to 100g N,N-dimethylformamide (DMF) and stir at 90℃ for 70min to obtain a homogeneous PBAT-based solution; add 3g bentonite to the obtained PBAT-based solution, stir at 90℃ for 60min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0057] (2) Turn on the rotary drum coating machine, set the fan temperature to 80℃ and the drum speed to 50r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 10min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 50min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 5%.

[0058] Example 3

[0059] (1) Add 10g PBAT, 2g methylcellulose and 1g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 70℃ for 100min to obtain a homogeneous PBAT-based solution; add 2g bentonite and 0.48g hydrotalcite to the obtained PBAT-based solution, stir at 80℃ for 60min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0060] (2) Turn on the rotary drum coating machine, set the fan temperature to 90℃ and the drum speed to 40r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 8min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 40min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 5%.

[0061] Example 4

[0062] (1) Add 9g PBAT and 2g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 90℃ for 70min to obtain a homogeneous PBAT-based solution; add 3g bentonite and 0.12g hydrotalcite to the obtained PBAT-based solution, stir at 90℃ for 40min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0063] (2) Turn on the rotary drum coating machine, set the fan temperature to 80℃ and the drum speed to 50r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 10min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 50min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 6%.

[0064] Example 5

[0065] (1) Add 9g PBAT, 1g methylcellulose, and 1g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 70℃ for 100min to obtain a homogeneous PBAT-based solution; add 2g bentonite and 0.12g hydrotalcite to the obtained PBAT-based solution, stir at 70℃ for 80min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0066] (2) Turn on the rotary drum coating machine, set the fan temperature to 90℃ and the drum speed to 40r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 8min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 40min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 6%.

[0067] Example 6

[0068] (1) Add 12g PBAT, 1g methylcellulose, and 2g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 70℃ for 100min to obtain a homogeneous PBAT-based solution; add 2g bentonite and 0.12g hydrotalcite to the obtained PBAT-based solution, stir at 70℃ for 80min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0069] (2) Turn on the rotary drum coating machine, set the fan temperature to 70℃ and the drum speed to 40r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 15min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 60min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 3%.

[0070] Example 7

[0071] (1) Add 10g PBAT, 2g methylcellulose and 1g polyethylene ether to 100g N,N-dimethylformamide (DMF) and stir at 70℃ for 100min to obtain a homogeneous PBAT-based solution; add 0.2g bentonite and 0.05g hydrotalcite to the obtained PBAT-based solution, stir at 80℃ for 60min, and then ultrasonically disperse at room temperature for 20min; let the polymer solution stand for 120min, and after the bubbles are removed, obtain the PBAT-based coating solution;

[0072] (2) Turn on the rotary drum coating machine, set the fan temperature to 90℃ and the drum speed to 40r / min; take urea particles with a radius of 3-4mm and preheat them in the rotary drum coating machine for 8min; spray the PBAT-based coating liquid evenly on the surface of the urea particles; finally, dry the prepared coated urea particles in the rotary drum coating machine for 40min to obtain PBAT-based environmentally friendly slow-release coated urea, with a coating layer to urea particle mass ratio of 5%.

[0073] Comparative Example 1

[0074] This comparative example uses uncoated urea particles with a diameter of 3-4 mm.

[0075] Comparative Example 2

[0076] The preparation method of this comparative example is the same as that of Example 3, except that in step (1), the PBAT-based coating solution contains only PBAT and does not contain methylcellulose, polyethylene ether, bentonite and hydrotalcite.

[0077] Comparative Example 3

[0078] The preparation method of this comparative example is the same as that of Example 3, except that in step (1), the PBAT-based coating solution contains only bentonite and hydrotalcite, and does not contain methylcellulose and polyethylene ether.

[0079] Comparative Example 4

[0080] The preparation method of this comparative example is the same as that of Example 3, except that in step (1), the PBAT-based coating solution contains only methylcellulose and polyethylene ether, and does not contain bentonite and hydrotalcite.

[0081] The moisture content of the coating materials in the PBAT-based environmentally friendly sustained-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4 was tested. The test method was as follows: Membrane materials were prepared using the same raw materials as the coating layers in the PBAT-based environmentally friendly sustained-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4. A 2cm × 2cm sample of the membrane material was placed in 50mL of deionized water. After one day, the sample was removed, surface moisture was absorbed with filter paper, and the weight was recorded as m1. The sample was then placed in an electric thermostatic drying oven at 60℃ and dried to constant weight, and the weight was recorded as m2. The formula for calculating the water absorption rate Q is: Test results are as follows Figure 1 As shown.

[0082] from Figure 1 As can be seen, the unmodified PBAT coating material (Comparative Example 2) had the lowest moisture content (1.50%). The coating material (Comparative Example 3), prepared by adding 2g of bentonite and 0.48g of hydrotalcite to Comparative Example 2, had a higher moisture content of 2.20%, indicating that the addition of bentonite and hydrotalcite made the membrane more absorbent. This is attributed to the good water absorption and retention properties of bentonite and the good hydrophilicity of hydrotalcite. The coating material (Comparative Example 4), prepared by adding 2g of methylcellulose and 1g of polyethylene ether to Comparative Example 2, had a significantly higher moisture content (3.80%). The percentage indicates that the addition of organic matter (methylcellulose, polyethylene ether) is more beneficial to improving the hydrophilicity of the membrane material than that of inorganic matter (bentonite, hydrotalcite). Comparing Example 7 and Comparative Example 4, it can be seen that when the amount of bentonite and hydrotalcite added is 0.2g and 0.05g (less), respectively, the effect on the water content of the membrane is not significant (~3.80%). Comparing Comparative Example 2 and Examples 1-7, it can be seen that different amounts of inorganic matter (bentonite, hydrotalcite) and organic matter (methylcellulose, polyethylene ether) will increase the hydrophilicity of the membrane material to varying degrees.

[0083] The biodegradability of the coating material in the PBAT-based environmentally friendly slow-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4 was tested. The test method was as follows: the corresponding membrane material was prepared using the same raw materials as the coating layer in the PBAT-based environmentally friendly slow-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4. First, the dry membrane sample (mass denoted as M0) was mixed with a small amount of soil and placed in a non-woven bag, which was then buried in the same flowerpot at a soil depth of 10 cm. Then, deionized water was added to the flowerpot at regular intervals to maintain the soil moisture content at ~20 wt%. Every 7 days, a sample was taken from the flowerpot, the surface soil was rinsed with anhydrous ethanol, and then it was dried. The mass was denoted as M. t The formula for calculating the biodegradation rate (De, %) is as follows: Test results are as follows Figure 2 As shown.

[0084] from Figure 2 As can be seen, the coating materials of Examples 1-7 and Comparative Examples 2-4 exhibited good biodegradability within two months, ranging from 15% to 48%. Compared with Comparative Example 2, the coating materials of Examples 1-7 and Comparative Examples 3-4 had higher biodegradability rates. This was mainly due to the addition of methylcellulose, polyethylene ether, bentonite, and hydrotalcite, which increased the hydrophilicity of the membrane material, thus promoting the adhesion of microorganisms to the surface of the membrane material and enhancing enzyme activity.

[0085] The nitrogen nutrient release rate of the coating material in the PBAT-based environmentally friendly slow-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4 was tested. The test method was as follows: the corresponding membrane material was prepared using the same raw material as the coating layer in the PBAT-based environmentally friendly slow-release coated urea prepared in Examples 1-7 and Comparative Examples 2-4, and the membrane material was fixed between the supply pool and the receiving pool of the device (e.g., Figure 3 As shown in the diagram, 80 mL of saturated urea solution was placed in the supply tank, and 80 mL of deionized water was placed in the receiving tank. Every 24 hours, 1 mL of sample was taken from the receiving tank to determine the nutrient content, while simultaneously adding 1 mL of deionized water to the receiving tank. The nutrient permeability coefficient P of the membrane material... s (cm 2 The formula for calculating / day is: V is the solution volume in the receiving cell, mL; l is the membrane thickness, mm; A is the effective area of ​​the membrane sample, cm². 2 t is the test time, day; It is the concentration of the saturated urea solution in the supply tank, in g / mL; It is the rate of change of urea solution concentration in the receiving cell over time, g / (mL·day), and the test results are as follows. Figure 4 As shown.

[0086] from Figure 4 As can be seen, the changes in the nitrogen nutrient release coefficients of the coating materials in Examples 1-7 and Comparative Examples 2-4 show a consistent trend with the changes in water content. The transmembrane diffusion capacity of ions / molecules is related to the hydrophilicity of the coating material; generally speaking, the more hydrophilic the membrane material, the stronger the transmembrane diffusion capacity of ions / molecules.

[0087] The coating materials in the PBAT-based environmentally friendly sustained-release coated urea prepared in Examples 1, 6, and 2 were characterized by SEM, and the results are as follows: Figure 5 As shown, from Figure 5 It can be seen that the addition of methylcellulose, polyethylene ether, bentonite and hydrotalcite has little effect on the surface morphology of the membrane, and the membrane surface exhibits a slightly "uneven" state.

[0088] The nitrogen nutrient release performance of the PBAT-based environmentally friendly slow-release coated urea prepared in Examples 1-7 and Comparative Examples 1-4 was characterized, and the results are as follows: Figure 6 As shown, the specific method is as follows:

[0089] First, the air-dried soil was sieved through a 65-mesh sieve. Then, 50 grams of the dry soil were placed in a 100 mL plastic cup. Next, 0.5 grams of PBAT-based environmentally friendly slow-release coated urea granules were added to a non-woven fabric bag, which was then placed in the cup. 10 mL of deionized water was added to the cup to maintain the soil moisture content at approximately 20 wt%. Throughout the experiment, the soil moisture content in the cup was maintained at 20 wt%, and weighed every 3 days, with water added as needed. Periodically, the PBAT-based environmentally friendly slow-release coated urea granules were removed from the non-woven fabric bag, dried, ground into powder, dissolved in deionized water, and the remaining nitrogen content was measured.

[0090] from Figure 6 As can be seen from the data, the time required for the nitrogen nutrient release rate of Examples 1 to 7 to reach 90% was 80 to 115 days, indicating that this example has the effect of slowly releasing nitrogen nutrients.

[0091] The time required for the nitrogen nutrient release rate of Comparative Example 1 to reach 90% was 3 days, indicating that the sustained-release performance of the urea granules in this comparative example was poor compared to Examples 1-7. The time required for the nitrogen nutrient release rate of Comparative Example 2 to reach 90% was 150 days, indicating that the nitrogen nutrient sustained-release period of this comparative example was longer than that of Examples 1-7, and demonstrating that organic and inorganic modifications can regulate the nitrogen nutrient sustained-release time of urea granules. The time required for the nitrogen nutrient release rate of Comparative Example 3 to reach 90% was 138 days, indicating that inorganic modification alone can also regulate the nitrogen nutrient sustained-release time of urea granules compared to Comparative Example 2. The time required for the nitrogen nutrient release rate of Comparative Example 4 to reach 90% was 108 days, indicating that organic modification alone can also regulate the nitrogen nutrient sustained-release time of urea granules compared to Comparative Example 2, but to a greater extent than inorganic modification.

[0092] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0093] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A PBAT-based environmentally friendly sustained-release coated urea, characterized in that, The invention comprises urea particles and a coating layer covering the urea particles. The raw materials of the coating layer include PBAT, an organic modifier, and an inorganic modifier. The organic modifier includes at least one of methylcellulose or polyvinyl ether, and the inorganic modifier includes at least one of bentonite or hydrotalcite.

2. The PBAT-based environmentally friendly sustained-release coated urea according to claim 1, characterized in that, The mass ratio of the coating layer to urea particles is 2-8%.

3. The PBAT-based environmentally friendly sustained-release coated urea according to claim 1 or 2, characterized in that, In the coating layer, the mass ratio of PBAT, organic modifier and inorganic modifier is (8-12):(0.1-4):(0.1-5).

4. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Dissolve PBAT and an organic modifier in an organic solvent and perform a first stirring treatment to obtain a PBAT-based solution; then add an inorganic modifier to the PBAT-based solution and perform a second stirring treatment and ultrasonic dispersion treatment to obtain a PBAT-based coating solution; (2) Take urea granules for preheating treatment, use PBAT-based coating solution to coat the preheated urea granules and then dry them.

5. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (1), the organic solvent includes at least one of N,N-dimethylformamide or N-methylpyrrolidone; And / or, the mass ratio of the organic solvent, PBAT, organic modifier and inorganic modifier is 100:(8-12):(0.1-4):(0.1-5).

6. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (1), the temperature of the first stirring treatment is 60-100℃, and the time of the first stirring treatment is 40-100min; And / or, the temperature of the second stirring treatment is 60-100°C, and the time of the second stirring treatment is 30-80 min; And / or, the ultrasonic dispersion time is 10 to 30 minutes.

7. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (2), the radius of the urea particles is 3-6 mm.

8. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (2), the preheating time is 5 to 20 minutes and the preheating temperature is 70 to 100°C.

9. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (2), the coating process uses a rotary drum coating machine with a fan temperature of 70-100℃ and a drum rotation speed of 30-70 r / min.

10. The method for preparing PBAT-based environmentally friendly sustained-release coated urea according to claim 4, characterized in that, In step (2), the drying temperature is 70-100℃ and the drying time is 15-60 min.

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