Preparation method of novel controlled release inhibitor coated urea
By spraying the urea with acrylic modified alkyd resin grafted polyurethane and dicyandiamide and N-butylthiophosphoramide inhibitors on the surface of the urea, the problem of fast release speed and low utilization of enveloped urea in the soil is solved, and the slow release and efficient utilization of urea are achieved.
Patent Information
- Application Number
- CN202510485337.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-17
- Publication Date
- 2025-07-22
AI Technical Summary
The existing enveloped urea releases nutrients in the soil at a fast rate, has a high risk of loss, and the inhibitors are not bound to urea tightly, resulting in low fertilizer utilization.
The acrylic-modified alkyd resin grafted polyurethane envelope technology is combined with dicyandiamide and N-butylthiophosphoramide inhibitors, and sprayed on the urea surface through a fluidized bed coater to form a uniform and tight envelope. The epoxy resin is used as a binder to control the release rate of urea in the soil.
The slow and continuous release of urea in the soil is achieved, which reduces nutrient loss, improves fertilizer utilization and water absorption performance, and meets the long-term growth needs of crops.
Smart Images
Figure CN120349215A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of urea preparation, and specifically to a preparation method of a novel controlled-release inhibitor-coated urea. Background Art
[0002] In the field of agricultural fertilizers, the development and application of controlled-release fertilizer technology have always been a research hotspot. Although traditional coated urea can, to a certain extent, control the release process of nutrients from the film to the outside of the film and extend the release period of the fertilizer in the soil, its effect is still limited. Once the nutrients are released from the coating and enter the soil, the coating material can no longer regulate them, resulting in a relatively fast conversion rate of nutrients in the soil and a high loss risk.
[0003] To solve this problem more effectively, researchers have begun to explore new methods of combining coating technology with inhibitors. By coating the inhibitor together with urea, the nutrients and the inhibitor can be slowly released into the soil simultaneously. In this way, when the nutrients enter the soil, the inhibitor can conduct secondary regulation on them, further slowing down the conversion rate of nutrients and reducing losses, thereby improving the utilization rate of fertilizers.
[0004] However, there are still technical bottlenecks in the currently available coated inhibitor fertilizers on the market, such as the insufficient tight combination of the coating and the inhibitor, the mismatched release rates, or the unsatisfactory effect of the inhibitor. These problems limit the application effect and promotion of coated inhibitor fertilizers. Summary of the Invention
[0005] In view of the deficiencies of the prior art, the present invention provides a preparation method of a novel controlled-release inhibitor-coated urea, which combines the coating technology of acrylic acid-modified alkyd resin grafted polyurethane and the mixed use of dicyandiamide and N-butyl thiophosphoryl triamide inhibitor, and can effectively control the conversion rate of nutrients in the soil, reduce losses, and further improve the utilization rate of fertilizers.
[0006] A preparation method of a novel controlled-release inhibitor-coated urea, the preparation method comprising:
[0007] Step 1, mix 1-3 parts by weight of dicyandiamide and 0.2-0.3 parts by weight of N-butyl thiophosphoryl triamide, and after mixing, dissolve them in an ethanol solvent containing ethyl cellulose. After heating and mixing evenly in a water bath at 60-70°C, spray it on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 70-80°C; compressed air pressure 0.3-0.4 Pa; nozzle atomization pressure 0.1-0.2 Pa. After drying, urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide is obtained.
[0008] Step 2: Add 100 parts by weight of dicyandiamide and urea with N-butyl thiophosphoryl triamide mixed coating into a disk granulator, polish for 8 - 10 minutes, add 2 - 4 parts by weight of a spraying binder, then add 12 - 13 parts by weight of acrylic acid modified alkyd resin grafted polyurethane into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor coated urea.
[0009] Preferably, in the said Step 2, the binder is any one of epoxy resin E-44 and epoxy resin E-51.
[0010] Preferably, in the said Step 2, the preparation method of the acrylic acid modified alkyd resin grafted polyurethane is as follows:
[0011] Step 11: Add N,N-dimethylformamide, acrylic acid modified alkyd resin with a mass ratio of 100:(0.3 - 0.5), 4-aminobenzaldehyde and 60 - 70 mL of 5 mol / L hydrochloric acid into a flask, heat under reflux for 4 - 6 h, cool to room temperature after the reaction, adjust the pH to 6.8 - 7.2 with sodium hydroxide solution, carry out vacuum filtration, and perform recrystallization to obtain an intermediate.
[0012] Step 12: Add N,N-dimethylformamide, terminal amino polyurethane with a mass ratio of 100:(90 - 110) and the intermediate into a flask, stir and react at room temperature for 4 - 6 h, carry out the reaction at a temperature of 55 - 65 °C for 18 - 24 h, distill off N,N-dimethylformamide under reduced pressure, wash and dry to obtain the acrylic acid modified alkyd resin grafted polyurethane.
[0013] Beneficial technical effects:
[0014] In the present invention, the acrylic acid modified alkyd resin reacts with 4-aminobenzaldehyde under the action of hydrochloric acid, then terminal amino polyurethane is added to obtain the acrylic acid modified alkyd resin grafted polyurethane. The dicyandiamide and N-butyl thiophosphoryl triamide inhibitors are mixed and sprayed on the outer surface of urea. In the urea containing dicyandiamide and N-butyl thiophosphoryl triamide inhibitors, a binder and the acrylic acid modified alkyd resin grafted polyurethane are sprayed to obtain a novel controlled-release inhibitor coated urea.
[0015] In the novel controlled-release inhibitor-coated urea of the present invention, the acrylic acid-modified alkyd resin grafted polyurethane-coated urea fertilizer has a uniformly distributed film-forming material that is tightly and firmly bonded to the urea. The dicyandiamide and N-butyl thiophosphoric triamide inhibitors are completely coated according to the irregular surface trend of the urea. The junction between the fertilizer core and the inhibitor is tightly combined, and the coating layer tightly covers the irregular outer surface of the inhibitor. The inhibitor is evenly distributed on the surface of the urea, and the inhibitor layer is completely surrounded by the coating layer, which has an obvious controlled-release effect on urea nitrogen, can effectively control the release rate of urea, has excellent weather resistance and color retention, and can ensure the slow and continuous release of urea in the soil, thus meeting the long-term growth needs of crops. As a high molecular compound, polyurethane acts as a coating material in urea, which can effectively delay the entry of water into the coating to dissolve urea, thus achieving a slow-release effect. Brief Description of the Drawings
[0016] Figure 1 It is the preparation reaction formula of acrylic acid-modified alkyd resin grafted polyurethane. Detailed Embodiments
[0017] The preparation method of preparing amino-terminated polyurethane according to the method of the master's degree thesis of Beijing University of Chemical Technology, "Research on Amino-Terminated Polyurethane Toughened Epoxy Resin Adhesive" is as follows:
[0018] Step 1: Place the weighed dehydrated polyethylene glycol in a 250 ml four-necked flask, fill with nitrogen, and add a measured amount of 2,4-toluene diisocyanate. Under the protection of a nitrogen atmosphere, control the temperature of the water bath to 20 °C, and stir and react until the -NCO content reaches the theoretical value to obtain a polyurethane prepolymer terminated with an isocyanate group.
[0019] Step 2: Add a measured amount of m-xylylenediamine-dimethyl sulfoxide solution to the four-necked flask, slowly stir until homogeneous, then fill with nitrogen, and cool down to 2 °C with an ice-salt bath. Drop the prepared polyurethane prepolymer solution from a constant pressure dropping funnel into the above solution at a rate of 20 drops / min. After dropping, slowly heat up to 40 °C and stir and react for 3 h. Then vacuum remove all solvents to obtain amino-terminated polyurethane.
[0020] The preparation method of preparing acrylic acid-modified alkyd resin according to the method of the master's degree thesis of Beijing University of Chemical Technology, "Synthesis and Properties of Waterborne Acrylic Acid-Modified Alkyd Resin Coatings" is as follows:
[0021] Step 11: Add monoglyceride, maleic anhydride, phthalic anhydride, dimethylolpropionic acid and solvent xylene to a four-necked flask equipped with a stirring paddle, thermometer, heating jacket thermocouple, water separator, and reflux condenser. Vent and add condensed water, heat up to 180 °C to make the water-carrying agent xylene reflux stably, and carry out esterification dehydration for about 2.5 hours. When the acid value drops below 70 mgKOH·g -1, the alkyd resin is obtained.
[0022] Step 12, remove the solvent xylene in the resin under reduced pressure by vacuum pumping, and add a cosolvent for dilution. Ventilate and add condensed water, heat up to 100 °C, and drop the mixture of the acrylic acid modified monomer and the initiator into the four-necked flask within 3 hours under reflux, keep warm for 2 hours, then add the remaining initiator, and keep warm for 3 hours, thus obtaining the acrylic acid modified alkyd resin.
[0023] Example 1:
[0024] Step 1, add N,N-dimethylformamide, 200 g of acrylic acid modified alkyd resin, 0.6 g of 4-aminobenzaldehyde and 70 mL of 5 mol / L hydrochloric acid to the flask, heat under reflux, react for 4 h, cool to room temperature after the reaction, adjust the pH to 7.2 with sodium hydroxide solution, filter under reduced pressure, and perform recrystallization in a solution of ethanol:water = 1:1 to obtain the intermediate.
[0025] Step 2, add N,N-dimethylformamide, 300 g of terminal amino polyurethane and 270 g of the intermediate to the flask, stir and react at room temperature for 6 h, carry out the reaction at 65 °C for 18 h, distill off N,N-dimethylformamide under reduced pressure, wash and dry to obtain the acrylic acid modified alkyd resin grafted polyurethane.
[0026] Step 3, mix 2 parts by weight of dicyandiamide and 0.25 parts by weight of N-butyl thiophosphoryl triamide, and after mixing, dissolve them in 1000 parts of an ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a 70 °C water bath, spray it on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 75 °C; compressed air pressure 0.35 Pa; nozzle atomization pressure 0.15 Pa. After drying, obtain the urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide.
[0027] Step 4, add 100 parts by weight of the urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide to a disk granulator, polish for 9 minutes, spray 3 parts by weight of epoxy resin E-44, then add 12 parts by weight of the acrylic acid modified alkyd resin grafted polyurethane to the granulator, and continue to rotate for 8 minutes to obtain the new controlled-release inhibitor coated urea.
[0028] Example 2:
[0029] Step 1, add N,N-dimethylformamide, 200 g of acrylic acid modified alkyd resin, 1 g of 4-aminobenzaldehyde and 60 mL of 5 mol / L hydrochloric acid to the flask, heat under reflux, react for 6 h, cool to room temperature after the reaction, adjust the pH to 6.8 with sodium hydroxide solution, filter under reduced pressure, and perform recrystallization in a solution of ethanol:water = 1:1 to obtain the intermediate.
[0030] Step 2: Add N,N-dimethylformamide, 300 g of terminal amino polyurethane, and 330 g of intermediate into the flask, stir and react at room temperature for 4 h, carry out the reaction at 55 °C for 24 h, remove N,N-dimethylformamide by vacuum distillation, wash and dry to obtain acrylic acid-modified alkyd resin grafted polyurethane.
[0031] Step 3: Mix 3 parts by weight of dicyandiamide and 0.2 parts by weight of N-butyl thiophosphoryl triamide, and after mixing, dissolve them in 1000 parts of ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a water bath at 60 °C, spray them on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 80 °C; compressed air pressure 0.4 Pa; nozzle atomization pressure 0.1 Pa. After drying, urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide is prepared.
[0032] Step 4: Add 100 parts by weight of urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide into a disk granulator, polish for 10 minutes, spray 2 parts by weight of epoxy resin E-51, then add 13 parts by weight of acrylic acid-modified alkyd resin grafted polyurethane into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor-coated urea.
[0033] Example 3:
[0034] Step 1: Add N,N-dimethylformamide, 200 g of acrylic acid-modified alkyd resin, 0.8 g of 4-aminobenzaldehyde, and 65 mL of 5 mol / L hydrochloric acid into the flask, heat under reflux and react for 5 h. After the reaction, cool to room temperature, adjust the pH to 7 with sodium hydroxide solution, carry out vacuum filtration, and carry out recrystallization in a solution of ethanol:water = 1:1 to obtain the intermediate.
[0035] Step 2: Add N,N-dimethylformamide, 300 g of terminal amino polyurethane, and 300 g of intermediate into the flask, stir and react at room temperature for 5 h, carry out the reaction at 60 °C for 20 h, remove N,N-dimethylformamide by vacuum distillation, wash and dry to obtain acrylic acid-modified alkyd resin grafted polyurethane.
[0036] Step 3: Mix 3 parts by weight of dicyandiamide and 0.3 parts by weight of N-butyl thiophosphoryl triamide, and after mixing, dissolve them in 1000 parts of ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a water bath at 60 °C, spray them on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 80 °C; compressed air pressure 0.4 Pa; nozzle atomization pressure 0.2 Pa. After drying, urea with a mixed coating of dicyandiamide and N-butyl thiophosphoryl triamide is prepared.
[0037] Step 4: Add 100 parts by weight of dicyandiamide and N-butylthiophosphoryl triamide mixed-coated urea into a disk granulator, polish for 10 minutes, spray 4 parts by weight of epoxy resin E-51, then add 13 parts by weight of acrylic acid-modified alkyd resin grafted polyurethane into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor-coated urea.
[0038] Example 4:
[0039] Step 1: Add N,N-dimethylformamide, 200 g of acrylic acid-modified alkyd resin, 1 g of 4-aminobenzaldehyde and 70 mL of 5 mol / L hydrochloric acid into a flask, heat under reflux for 6 h, cool to room temperature after the reaction, adjust the pH to 7 with sodium hydroxide solution, perform vacuum filtration, and carry out recrystallization in a solution of ethanol:water = 1:1 to obtain an intermediate.
[0040] Step 2: Add N,N-dimethylformamide, 300 g of terminal amino polyurethane and 300 g of the intermediate into a flask, stir and react at room temperature for 4 h, carry out the reaction at 65 °C for 24 h, distill off N,N-dimethylformamide under reduced pressure, wash and dry to obtain acrylic acid-modified alkyd resin grafted polyurethane.
[0041] Step 3: Mix 1 part by weight of dicyandiamide and 0.2 part by weight of N-butylthiophosphoryl triamide, and after mixing, dissolve them in 1000 parts of an ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a water bath at 70 °C, spray it on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 70 °C; compressed air pressure 0.3 Pa; nozzle atomization pressure 0.1 Pa. After drying, obtain dicyandiamide and N-butylthiophosphoryl triamide mixed-coated urea.
[0042] Step 4: Add 100 parts by weight of dicyandiamide and N-butylthiophosphoryl triamide mixed-coated urea into a disk granulator, polish for 8 minutes, spray 2 parts by weight of epoxy resin E-44, then add 12 parts by weight of acrylic acid-modified alkyd resin grafted polyurethane into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor-coated urea.
[0043] Comparative Example 1:
[0044] Step 1: Add N,N-dimethylformamide, 200 g of acrylic acid-modified alkyd resin, 0.6 g of 4-aminobenzaldehyde and 70 mL of 5 mol / L hydrochloric acid into a flask, heat under reflux for 4 h, cool to room temperature after the reaction, adjust the pH to 7.2 with sodium hydroxide solution, perform vacuum filtration, and carry out recrystallization in a solution of ethanol:water = 1:1 to obtain an intermediate.
[0045] Step 2: Add N,N-dimethylformamide, 300 g of terminal amino polyurethane, and 270 g of the intermediate into a flask, stir and react at room temperature for 6 h, carry out the reaction at 65 °C for 18 h, remove N,N-dimethylformamide by vacuum distillation, wash and dry to obtain acrylic acid-modified alkyd resin grafted polyurethane.
[0046] Step 3: Add 100 parts by weight of urea into a disk granulator, polish for 9 minutes, spray 3 parts by weight of epoxy resin E-44, then add 12 parts by weight of acrylic acid-modified alkyd resin grafted polyurethane into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor-coated urea.
[0047] Comparative Example 2:
[0048] Step 1: Add N,N-dimethylformamide, 300 g of terminal amino polyurethane, and 0.6 g of 4-aminobenzaldehyde into a flask, stir and react at room temperature for 6 h, carry out the reaction at 65 °C for 18 h, remove N,N-dimethylformamide by vacuum distillation, wash and dry to obtain a Schiff base compound.
[0049] Step 2: Mix 2 parts by weight of dicyandiamide and 0.25 parts by weight of N-butyl thiophosphoryl triamide, and dissolve the mixture in 1000 parts of an ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a 70 °C water bath, spray it on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 75 °C; compressed air pressure 0.35 Pa; nozzle atomization pressure 0.15 Pa. After drying, obtain urea with a dicyandiamide and N-butyl thiophosphoryl triamide mixed coating.
[0050] Step 3: Add 100 parts by weight of urea with a dicyandiamide and N-butyl thiophosphoryl triamide mixed coating into a disk granulator, polish for 9 minutes, spray 3 parts by weight of epoxy resin E-44, then add 12 parts by weight of the Schiff base compound into the granulator, and continue to rotate for 8 minutes to obtain a novel controlled-release inhibitor-coated urea.
[0051] Comparative Example 3:
[0052] Step 1: Add N,N-dimethylformamide, 200 g of acrylic acid-modified alkyd resin, 0.6 g of 4-aminobenzaldehyde, and 70 mL of 5 mol / L hydrochloric acid into a flask, heat under reflux for 4 h, cool to room temperature after the reaction, adjust the pH to 7.2 with sodium hydroxide solution, carry out vacuum filtration, and carry out recrystallization in a solution of ethanol:water = 1:1 to obtain an intermediate.
[0053] Step 2: Mix 2 parts by weight of dicyandiamide and 0.25 part by weight of N-butylthiophosphoryl triamide. After mixing, dissolve them in 1000 parts of an ethanol solvent containing 250 parts of ethyl cellulose. After heating and mixing evenly in a water bath at 70 °C, spray it on the outer surface of 100 parts by weight of urea through a fluidized bed coater. The operating parameters of the fluidized bed coater are: inlet air temperature 75 °C; compressed air pressure 0.35 Pa; nozzle atomization pressure 0.15 Pa. After drying, urea with a mixed coating of dicyandiamide and N-butylthiophosphoryl triamide is obtained.
[0054] Step 3: Add 100 parts by weight of urea with a mixed coating of dicyandiamide and N-butylthiophosphoryl triamide to a disk granulator, polish for 9 minutes, spray 3 parts by weight of epoxy resin E-44, then add 12 parts by weight of an intermediate to the granulator, and continue to rotate for 8 minutes to obtain a new controlled-release inhibitor-coated urea.
[0055] Weigh 50 g of the fertilizers of Examples 1-4 and Comparative Examples 1-3 respectively and put them into the dissolution cups of an RCZ-8B type intelligent dissolution tester with a capacity of 1 L. Then add 1 L of distilled water to each dissolution cup. Set the temperature of the dissolution tester at 25 °C and the rotation speed of the stirring rod at 60 r / min. Take a sample regularly within 40 days after the fertilizers are put in. Take 2 mL of each sample each time and put it into a 100 mL volumetric flask, and make up the volume with distilled water. To keep the water volume in the dissolution cup unchanged, add 2 mL of distilled water back each time after sampling. Put 5 g of the coated fertilizer into a 100 mL beaker, add 60 mL of distilled water to soak it, and crush it with a glass rod. After it is completely dissolved, filter it into a 2000 mL volumetric flask, repeatedly wash the fertilizer residue film on the beaker and filter paper with distilled water, make up the volume with distilled water (stock solution), then dilute it 100 times, and use an automatic flow analyzer to measure the content of urea nitrogen released into the water within 40 days.
[0056] According to the standard of GB / T23348-2009, weigh 30 g of the coated urea of Examples 1-4 and Comparative Examples 1-3 respectively, wrap the fertilizers with a mesh bag, place them in a 250 mL small beaker, accurately add 200 mL of distilled water, immerse them all in the water, and place them in a constant temperature incubator at 25 °C. After 84 days, use the Kjeldahl method to measure the N cumulative release rate of the coated urea. Set 3 measurements for each sample and take the average value.
[0057] Accurately weigh 5 g of the coated urea, put it into a 0.15 mm nylon mesh bag, seal it, and place it in a beaker containing 250 mL of distilled water. Soak it at room temperature for a period of time (about 3 h), take out the mesh bag, hang it until there is no water dripping to constant weight, weigh it, and calculate the water absorption ratio WA of the coated urea. WA = (M / M0) - 1, where M and M0 represent the mass of the coated urea after full water absorption and swelling and the mass of the dry coated urea respectively.
[0058] Table 1 shows the urea nitrogen content of the new controlled-release inhibitor-coated urea within 40 days
[0059] 12 days (%) 15 days (%) 30 days (%) 40 days (%) Example 1 20.12 27.12 62.18 71.12 Example 2 20.20 25.20 65.64 72.08 Example 3 22.97 22.97 64.49 72.43 Example 4 21.34 26.34 63.20 76.74 Comparative Example 1 33.34 78.96 85.21 86.74 Comparative Example 2 31.27 77.89 83.64 84.08 Comparative Example 3 29.16 74.52 84.49 85.43
[0060] Table 2 shows the test performance of the new controlled-release inhibitor-coated urea
[0061]
[0062]
[0063] As shown in Table 1, comparing Examples 1-4 with Comparative Examples 1-3, the dissolution amount of urea nitrogen content in Examples 1-4 shows a linear increasing trend within 40 days, indicating that the nutrient release is gentle and the urea controlled-release ability is strong. This is because in the examples, the acrylic acid-modified alkyd resin grafted polyurethane-coated urea fertilizer has a uniform distribution of the coating material during film formation, and is tightly and firmly bonded to the urea; the dicyandiamide and N-butyl thiophosphoryl triamide inhibitors are completely coated according to the irregular surface trend of the urea, and the junction between the fertilizer core and the inhibitor is tightly combined. The coating layer tightly covers the irregular outer surface of the inhibitor, and the inhibitor is evenly distributed on the surface of the urea. The inhibitor layer is completely surrounded by the coating layer, which has an obvious controlled-release effect on the urea nitrogen.
[0064] As shown in Table 2, the N cumulative release rate of the urea in the examples is lower than that of the urea in Comparative Examples 1-3, indicating that the slow-release performance of the urea in Examples 1-4 is better than that of the urea in Comparative Examples 1-3. The water absorption ratio of the urea in Examples 1-4 is higher than that of the urea in Comparative Examples 1-3, indicating that the water absorption performance of the urea in Examples 1-4 is better than that of the urea in Comparative Examples 1-3. This is because the acrylic acid-modified alkyd resin as the coating material of the urea can effectively control the release rate of the urea, has excellent weather resistance and color retention, and can ensure the slow and continuous release of the urea in the soil, thus meeting the long-term growth needs of crops. Polyurethane, as a high molecular compound, acts as a coating material in the urea, can effectively delay the entry of water into the coating to dissolve the urea, so as to achieve the slow-release effect. The polyurethane coating material can chelate protease and various trace elements, can promote root growth and strengthen the stem, and has a positive promoting effect on the growth of crops.
[0065] Compared with Example 1, the deficiency of Comparative Example 1 is that dicyandiamide and N-butyl thiophosphoryl triamide inhibitors are not added. Adding dicyandiamide to coated urea can control the nitrification process after urea dissolution, that is, prevent or slow down the conversion of ammonium nitrogen to nitrate nitrogen, thereby reducing nitrogen loss. N-butyl thiophosphoryl triamide is a highly efficient soil urease inhibitor, which can slow down the process of urea being decomposed into ammonia by urease in the soil, thereby reducing the gas-phase loss of ammonia and improving the utilization rate of urea. Dicyandiamide and N-butyl thiophosphoryl triamide play a synergistic role in controlled-release inhibitor-coated urea. By controlling the dissolution rate of urea and the biochemical conversion process, the utilization rate of urea and the persistence of fertilizer efficiency are improved.
[0066] Compared with Example 1, the deficiency of Comparative Example 2 is that the Schiff base compound replaces the acrylic acid-modified alkyd resin grafted polyurethane, lacking the acrylic acid-modified alkyd resin. The acrylic acid-modified alkyd resin has a certain coating rate and can form a protective film outside the urea, with better slow-release performance for urea.
[0067] Compared with Example 1, the deficiency of Comparative Example 3 is that there is no polyurethane. As a high molecular compound, polyurethane is used as a coating material in urea, which can effectively delay the entry of water into the coated interior to dissolve urea, thereby achieving a slow-release effect and enabling nutrients and water to be continuously absorbed by crops.
Claims
1. A preparation method of a novel controlled-release inhibitor-coated urea, characterized in that, The preparation method includes: Step 1: Mix 1-3 parts by weight of nitrification inhibitor and 0.2-0.3 parts by weight of urease inhibitor. After mixing, dissolve them in an ethanol solvent containing ethyl cellulose. After heating and mixing evenly in a water bath at 60-70°C, spray them on the outer surface of 100 parts by weight of urea through a fluidized bed coater. After drying, obtain urea with a mixed coating of nitrification inhibitor and urease inhibitor; Step 2: Add 100 parts by weight of urea with a mixed coating of nitrification inhibitor and urease inhibitor to a disk granulator, polish for 8-10 minutes, add 2-4 parts by weight of spraying binder, and then add 12-13 parts by weight of acrylic acid-modified alkyd resin grafted polyurethane to the granulator, and continue to rotate for 8 minutes to obtain a new type of controlled-release inhibitor-coated urea.
2. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 1, characterized in that, In the said Step 1, the nitrification inhibitor is dicyandiamide, and the urease inhibitor is N-butyl thiophosphoryl triamide.
3. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 1, characterized in that, In the said Step 1, the operating parameters of the fluidized bed coater are: inlet air temperature 70-80°C; compressed air pressure 0.3-0.4 Pa; nozzle atomization pressure 0.1-0.2 Pa.
4. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 1, wherein, In the said Step 2, the binder is any one of epoxy resin E-44 and epoxy resin E-51.
5. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 1, characterized in that, In the said Step 2, the preparation method of acrylic acid-modified alkyd resin grafted polyurethane is: Step 11: Add N,N-dimethylformamide, 4-aminobenzaldehyde, acrylic acid-modified alkyd resin and 5 mol / L hydrochloric acid to a flask, heat under reflux for 4-6 h. After the reaction, cool to room temperature, adjust to neutral with sodium hydroxide solution, carry out vacuum filtration, and perform recrystallization to obtain an intermediate; Step 12: Add N,N-dimethylformamide, terminal amino polyurethane and the intermediate to a flask, stir and react at room temperature for 4-6 h, carry out for 18-24 h at a temperature of 55-65°C, distill off N,N-dimethylformamide under reduced pressure, wash and dry to obtain acrylic acid-modified alkyd resin grafted polyurethane.
6. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 5, characterized in that, In the said Step 11, the mass ratio of acrylic acid-modified alkyd resin to 4-aminobenzaldehyde is 100:(0.3-0.5).
7. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 5, characterized in that, In the said Step 11, the dosage of hydrochloric acid is 60-70 mL.
8. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 5, characterized in that, In the said Step 11, adjust to a pH of 6.8-7.2 with sodium hydroxide solution.
9. The preparation method of the novel controlled-release inhibitor-coated urea according to claim 5, characterized in that, In the said Step 12, the mass ratio of terminal amino polyurethane to the intermediate is 100:(90-110).