A method for preparing a nitrification inhibitor intelligent controlled-release microcapsule

Abstract

The application discloses a preparation method of a nitrification inhibitor intelligent controlled-release microcapsule, and the controlled-release microcapsule is composed of a core material, a solvent, a capsule wall material, a pore-forming agent, a dispersing agent and water; the microcapsule core material is 2-chloro-6-(trichloromethyl) pyridine (CP for short); the capsule wall material is a polyhydroxy acid, specifically polylactic acid or polyglycolic acid; and the pore-forming agent is composed of polyethylene glycol and cyclohexanone in a mass ratio of 5:0.5-1.5. In the application, the polyhydroxy acid material is used as the capsule wall material, the polyethylene glycol and the cyclohexanone are used as the composite pore-forming agent, the specific additive content is controlled, the rich and uniform microchannel structure is formed on the capsule wall material, the micro-pore size can respond to the external environment such as temperature and pH value, the release of the CP coated in the microcapsule can be intelligently controlled, the nitrification inhibition effect of the CP in the soil is improved, the nitrogen fertilizer efficiency is improved, the wall material is green and safe, and the wall material can be fully degraded and has no residue when applied to the soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nitrogen fertilizer synergist and new fertilizer preparation, and particularly relates to a preparation method of a nitrification inhibitor intelligent controlled-release microcapsule. BACKGROUND

[0002] Nitrification is an important link of nitrogen cycle, and the reaction process includes two oxidation processes, i.e., NH3 to NO2 - (ammonia oxidation) and NO2 - to NO3 - (nitrous acid oxidation), and the formation of nitrate nitrogen is beneficial to plant assimilation. However, nitrate nitrogen has strong solubility and negative charge, is not adsorbed by the negatively charged clay minerals in the soil, and is easily leached and lost by water, resulting in low nitrogen utilization rate and accompanying greenhouse gas emission.

[0003] Nitrification inhibitors (NI) are an important means to improve nitrogen utilization rate, can regulate the migration and transformation of soil nitrogen, can reduce the nitrification and denitrification of ammonium nitrogen by inhibiting the activity of nitrification-related functional microorganisms, prolong the residence time of ammonium nitrogen in the soil, effectively reduce the loss of nitrogen and improve the utilization rate of nitrogen, and thus prolong the fertilizer effect, reduce the nitrogen use amount and labor cost.

[0004] Since the mid-1950s, nitrification inhibitors have been widely concerned by many countries. Nitrification inhibitors mainly including pyrazole, pyrimidine, pyridine, thiazole, thiourea and amide compounds have been continuously developed and applied. The widely used nitrification inhibitors mainly include 2-chloro-6(trichloromethyl)pyridine (CP), 3,4-dimethylpyrazole phosphate (DMPP), dicyandiamide (DCD), hydroquinone (HQ), N-butyl thiophosphoric triamide (NBPT), substituted pyrimidine (AM), thiourea (TU) and the like. 2-chloro-6(trichloromethyl)pyridine (CP) is an early applied nitrification inhibitor, and reasonable use can improve crop yield, reduce nitrogen leaching and reduce greenhouse gas emission. At present, CP has been widely used. However, CP has problems of easy volatilization, easy photolysis, easy adsorption by soil organic matter when applied in high-organic-matter soil, and reduced effectiveness. Therefore, it is necessary to develop new dosage forms to improve the effectiveness of CP. In the prior art, patent CN107285968A has prepared CP into a microcapsule suspension preparation and used it in combination with nitrogen fertilizer to prolong the effectiveness of CP. However, the CP loading amount is low, the capsule wall material cannot quickly respond to the surrounding environment, and the material is a high-molecular-weight difficult-to-degrade material, which is not friendly to the soil environment. SUMMARY

[0005] Based on the above technical problems, the present application aims to provide a nitrification inhibitor intelligent controlled-release microcapsule.

[0006] The present application aims to provide a preparation method of the nitrification inhibitor intelligent controlled-release microcapsule. A polyhydroxy acid material with excellent biodegradability is used as the capsule wall material to prepare the CP intelligent controlled-release microcapsule. Compared with the traditional method, the new wall material and its preparation method increase the drug loading capacity while having excellent environmental protection performance.

[0007] In addition, in the present application, through the specific capsule wall material and the composite pore-forming agent, the capsule wall material coats the nitrification inhibitor CP, the pore-forming agent forms a microporous structure on the surface of the capsule wall material, the pore size can be adjusted by the surrounding pH value and temperature, the release speed of CP in the microcapsule responds to the surrounding soil environment, the nitrification inhibition effect of CP in the soil is prolonged, and thus the nitrogen fertilizer efficiency is prolonged.

[0008] Another object of the present application is to provide the application of the nitrification inhibitor intelligent controlled-release microcapsule.

[0009] The object of the present application is achieved by the following technical solutions.

[0010] A nitrification inhibitor intelligent controlled-release microcapsule, characterized in that the controlled-release microcapsule is composed of a core material, a capsule wall material, a solvent, a pore-forming agent, a dispersing agent and water, the capsule wall material is a polyhydroxy acid, specifically polylactic acid or polyglycolic acid, and the pore-forming agent is composed of polyethylene glycol and cyclohexanone in a mass ratio of 5:0.5-1.5.

[0011] Further, the core material of the microcapsule is 2-chloro-6-(trichloromethyl)pyridine (CP) technical material.

[0012] Further, the capsule wall material is a polyhydroxy acid, specifically polylactic acid or polyglycolic acid, and can achieve full degradation and no residue when applied to soil.

[0013] Further, the solvent is at least one of toluene, xylene, acetonitrile, dichloromethane, chloroform, ethanol, cyclohexanone, N,N-dimethylformamide or Mobil S-200.

[0014] Further, the dispersing agent is at least one of fatty alcohol polyoxyethylene ether, polyvinyl alcohol series, fatty alcohol polyoxyethylene ether carboxylate, alkyl glycoside, methylene bis-taurate sodium, methylene bis-naphthalene sulfonate sodium.

[0015] Further, the amount of each component is calculated according to the mass percentage, the amount of each component is 1%-35% of the core material, 10%-30% of the solvent, 1%-5% of the capsule wall material, 1%-5% of the pore-forming agent, 2-8% of the dispersing agent, and the balance is water.

[0016] The preparation method of the nitration inhibitor intelligent controlled release microcapsule is characterized in that the following steps are performed:

[0017] (1) preparing microcapsule core material, capsule wall material, solvent, pore former, dispersant and distilled water;

[0018] (2) mixing the microcapsule core material, capsule wall material, solvent and pore former to obtain an oil phase, and mixing the dispersant into distilled water to obtain an aqueous phase;

[0019] (3) mixing the oil phase and the aqueous phase and performing shear emulsification to form an emulsion;

[0020] (4) performing rotation treatment on the emulsion to form microcapsules, and then performing capsule washing to obtain the nitration inhibitor intelligent controlled release microcapsule.

[0021] Further, the microcapsule core material is 2-chloro-6-(trichloromethyl)pyridine (CP) technical material.

[0022] Further, the capsule wall material is polyhydroxy acid, specifically polylactic acid or polyglycolic acid, which can achieve full degradation and no residue when applied to soil.

[0023] Further, the pore former is polyethylene glycol and cyclohexanone, which are composed of a mass ratio of 5:0.5~1.5.

[0024] Further, the solvent is at least one of toluene, xylene, acetonitrile, dichloromethane, chloroform, ethanol, cyclohexanone, N,N-dimethylformamide or Mobil S-200.

[0025] Further, the dispersant is at least one of fatty alcohol polyoxyethylene ether, polyvinyl alcohol series, fatty alcohol polyoxyethylene ether carboxylate, alkyl glycoside, methylene bis sodium sulfonate, and methylene sodium naphthalene sulfonate.

[0026] Further preferably, the dispersant is fatty alcohol polyoxyethylene ether or polyvinyl alcohol.

[0027] Further, in step (1), the amount of each component is calculated based on the mass percentage, and the amount of each component is 1%~35% of the microcapsule core material, 10%~30% of the solvent, 1%~5% of the capsule wall material, 1%~5% of the pore former, 2~8% of the dispersant, and the balance is water.

[0028] Further, in step (2), the aqueous phase is obtained by heating distilled water to 90~95℃, adding the dispersant, and thoroughly stirring and mixing.

[0029] Further, in step (3), the shear rotation speed is 10000~12000rmp, and the shear time is 1~2min.

[0030] Most specifically, a preparation method of a nitrification inhibitor intelligent controlled release microcapsule, characterized by comprising the following steps:

[0031] (1) preparing materials: according to mass percentage, nitrification inhibitor CP original drug (content ≥98%) 1%~35%, solvent dichloromethane or trichloromethane 10%~30%, capsule wall material polyhydroxy acid 1%~5%, pore former poly 1%~5%, dispersant fatty alcohol polyoxyethylene ether or polyvinyl alcohol 2~8%, and the rest is distilled water, the polyhydroxy acid is PLA or PGA, and the pore former is ethylene glycol and cyclohexanone with a mass ratio of 5:0.5~1.5;

[0032] (2) oil phase preparation: PLA is added to the solvent, and PLA is fully dissolved by fully stirring;

[0033] (3) water phase preparation: distilled water is heated to 90 DEG C, and fatty alcohol polyoxyethylene ether is added to the water, and the fatty alcohol polyoxyethylene ether is fully dissolved by fully stirring;

[0034] (4) emulsification and shearing: the oil phase of step (2) is slowly poured into the water phase of step (3), and the oil phase is added while stirring, and after all the oil phase is added, a high-speed shearing machine is used to shear at 10000 rmp for 1~2 min;

[0035] (5) preparation of microcapsules: the oil phase and water phase mixture in step (4) is transferred to a round-bottom flask, and emulsification is carried out at 350~450 rpm, and the emulsification time is 4~8 min, and the temperature is increased to 40~50 DEG C, and after the solvent is evaporated, the capsule is formed, and then solidification is carried out in a rotary evaporator for 2 h, and the solidification rotation speed is 400 rpm.

[0036] When the polyhydroxy acid material capsule wall material is used to wrap the CP original drug, the dense structure of the capsule wall material effectively improves the encapsulation rate of the CP, but the dense structure also leads to an unsatisfactory slow-release effect, and the CP cannot be released in the early stage, cannot quickly take effect, and is sharply released in the later stage, so that the long-term slow-release effect cannot be achieved.

[0037] In the application, the polyhydroxy acid material capsule wall material is used to wrap the CP original drug, a complex pore former formed by polydiethylene glycol and cyclohexanone is added, micro-pores are distributed in the capsule wall, the pore former diffuses into the membrane after meeting water, and uniform micro-channels are formed on the surface of the capsule wall material, so that the CP is quickly released in the early stage, the effect is quickly achieved, and the distributed micro-channels with different structures control the controlled release of the CP by the capsule wall material, and an effective slow-release effect is formed; meanwhile, the pore size can be controlled by the surrounding pH value and temperature, the release speed of the CP in the microcapsule is adjusted according to the surrounding soil environment, the nitrification inhibition effect of the CP in the soil is prolonged, and the nitrogen fertilizer efficiency is prolonged.

[0038] The present application has the following technical effects:

[0039] In the present application, polyhydroxy acid material is used as the capsule wall material, polyethylene glycol and cyclohexanone are used as the composite pore-forming agent, and the specific additive content is controlled to form a rich and uniform microchannel structure on the capsule wall material, so that the CP inside the coating can form a controllable slow release; at the same time, the pore size can be controlled by the surrounding pH value and temperature, realizing the effect that the release speed of CP in the microcapsule responds to the surrounding soil environment, prolonging the nitration inhibition effect of CP in the soil, thereby prolonging the nitrogen fertilizer efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 : The pore-forming effect of different contents of pore-forming agents on the capsule wall material in the present application is shown in the electron microscope graph.

[0041] Figure 2 : The release curve of CP in the microcapsule prepared by different contents of pore-forming agents in the present application is shown.

[0042] Figure 3 : The release curve of CP in the microcapsule prepared by 1% content of pore-forming agent in the present application at different temperatures.

[0043] Figure 4 : The release curve of CP in the microcapsule prepared by 1% content of pore-forming agent in the present application at different pH values. DETAILED DESCRIPTION

[0044] The present application will be specifically described below through examples, and it is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above content of the present application.

[0045] Example 1:

[0046] A preparation method and application of a nitration inhibitor intelligent controlled-release microcapsule, comprising the following steps:

[0047] (1) Prepare materials: according to the mass percentage, prepare 2-chloro-6-(trichloromethyl) pyridine 30%, solvent dichloromethane 10%, capsule wall material 5%, pore-forming agent 1%, dispersant polyvinyl alcohol (0588) 5%, and the rest is water, wherein the capsule wall material is polylactic acid PLA, and the pore-forming agent is polyethylene glycol and cyclohexanone with a mass ratio of 5:1.

[0048] (2) Oil phase preparation: take dichloromethane, add PLA to it, and fully stir to dissolve PLA;

[0049] (3) Preparation of water phase: distilled water was weighed and heated to 90°C, and PVA was added thereto, and the PVA was fully dissolved by stirring.

[0050] (4) Emulsification and shearing: the oil phase was slowly poured into the water phase while stirring. After all the oil phase was added, a high-speed shearing machine was used to shear at 10,000 rpm for 1 min to obtain a nitrite inhibitor intelligent controlled-release microcapsule suspension;

[0051] (5) Preparation of microcapsules: the oil phase and the water phase were mixed and transferred to a round-bottom flask, and emulsified at 400 rpm, and the emulsification time was 5 min. The temperature was increased to 45°C, and after the solvent was evaporated, the microcapsule morphology was observed every 30 min using a biological microscope, and the pictures of the microcapsule formation process were recorded. After the encapsulation was completed, the microcapsules were solidified in a rotary evaporator for 2 h at a rotation speed of 400 rpm.

[0052] (6) Washing of the microcapsules: the suspension prepared in (5) was transferred to a funnel, washed with distilled water, and then dried in the dark. The microcapsules were labeled as CPCS-1 ("1" represents that the pore-forming agent is 1%).

[0053] Examples 2 and 3 and the blank control group were prepared according to the method of Example 1, and the steps were the same as those of Example 1. The main difference was that a pore-forming agent was added in step (3). The microcapsules prepared in step (4) were labeled with codes according to the proportion of the added pore-forming agent. According to the proportion of the added pore-forming agent, the blank control group was labeled as CPCS-0 (the pore-forming agent was 0%), Example 2 was labeled as CPCS-3 (the pore-forming agent was 3%), and Example 3 was labeled as CPCS-5 (the pore-forming agent was 5%). The effects of different amounts of pore-forming agents on the pore size formed in the capsule wall material were as shown in Figure 1 (a, b, c, and d).

[0054] The microcapsules were subjected to a slow-release test in a buffer solution with a pH of 7.0 to test the slow-release effect of CP in the microcapsules and draw a slow-release curve. The release curves of the microcapsules with different concentrations of pore-forming agents in a buffer solution with a pH of 7.0 were as shown in Figure 2 From the graph, it can be seen that the four kinds of microcapsules showed different slow-release behaviors. The microcapsules without the addition of the pore-forming agent CPCS-0 had the longest release time, reaching 53 days. Among the microcapsules containing the pore-forming agent CPCS-1, CPCS-3, and CPCS-5, the microcapsules with a pore-forming agent content of 1% had the longest CP release time, reaching 33 days. When the amount of the pore-forming agent added was 5%, the release speed was relatively fast, and the release balance was basically reached on the 14th day. Therefore, the CP microcapsules prepared by adding three different amounts of the pore-forming agent all had a slow-release effect in a buffer solution with a pH of 7.0, and the microcapsules prepared by adding the pore-forming agent in an amount of 1% had the longest release time, reaching 33 days.

[0055] The release characteristics of CP in the microcapsule with 1% pore-forming agent in buffer solution (pH = 7.0) at different temperatures (10 ℃, 20 ℃ and 30 ℃) are shown in Figure 3 As shown in the figure, the cumulative release rate of CP increases by about 10% for every 10 ℃ increase in temperature. Increasing the temperature can promote the release of CP, indicating that the micro-pore flux can respond to the temperature. Therefore, the release time of CP can be prolonged under low temperature conditions, and high temperature environment should be avoided as much as possible during storage to prevent rapid release. At the same time, the local soil temperature should be considered when using, and the dosage should be adjusted reasonably to achieve the best nitrification inhibition effect.

[0056] The sustained-release effect curve of CP microcapsule with 1% pore-forming agent in buffer solution (20 ℃) at different pH values (5.0, 7.0 and 9.0) is shown in Figure 4 As shown in the figure, the cumulative release rate of CP microcapsule at pH = 7.0 is significantly lower than that under alkaline and acidic conditions. Weak acid and weak base environment can accelerate the release of CP microcapsule, indicating that the micro-pore flux can respond to the pH value. Therefore, the pH value distribution of local soil should be fully considered when preparing CP suspension preparation, and the addition amount of pore-forming agent in the preparation process of CP microcapsule should be adjusted to accurately guide the use range and reasonably adjust the dosage to achieve the best nitrification inhibition effect.

[0057] Comparative Example 1

[0058] In the process of selecting the pore-forming agent, an equal amount of polyethylene glycol 8000 and cyclohexanone in Example 1 was respectively used as the pore-forming agent, and the rest of the formulation and preparation steps were the same as Example 1. The CP microcapsule prepared by using polyethylene glycol 8000 alone as the pore-forming agent was denoted as CPCS-1-1-1, and the CP microcapsule prepared by using cyclohexanone alone as the pore-forming agent was denoted as CPCS-1-1-2. The surface pore microchannel structure of the wall material in the prepared CP microcapsule is shown in Figure 1 e and f, it can be seen that polyethylene glycol 8000 alone has a certain pore-forming effect on the wall material PLA, but the effect is significantly poorer than Example 1, as shown in Figure 1 e; and cyclohexanone alone cannot form a smooth microchannel structure, as shown in Figure 1 f. However, in Example 1, the combination of polyethylene glycol 8000 and cyclohexanone promotes the pore-forming efficiency of polyethylene glycol 8000 on the surface of PLA, forming a rich microchannel, indicating that the combined pore-forming agent has better effect.

[0059] Meanwhile, in the process of compounding polyethylene glycol and cyclohexanone, it is found that when the ratio of polyethylene glycol and cyclohexanone is between 5:0.5-1.5, the pore-forming effect is obviously improved compared with that of polyethylene glycol alone. When the ratio of cyclohexanone is lower than the above ratio, the pore-forming effect is not greatly affected compared with that of polyethylene glycol, and when the ratio of cyclohexanone exceeds the above ratio, the pore-forming effect is even reduced.

[0060] Comparative Example 2:

[0061] The capsule wall material PLA is replaced with polymethylene polyphenyl isocyanate, and the other components are completely consistent with those in Example 1. The prepared microcapsules are recorded as CPCS-1-2, and the electron microscope scanning result shows no pore-forming effect.

[0062] Comparative Example 3:

[0063] The capsule wall material PLA is replaced with polymethylene polyphenyl isocyanate, and the other components are completely consistent with those in Example 1. The prepared microcapsules are recorded as CPCS-1-2, and the electron microscope scanning result shows no pore-forming effect.

[0064] Encapsulation rate and drug loading determination:

[0065] An analytical balance is used to weigh a certain amount of each microcapsule slurry, which is dispersed in a certain volume of ethanol solution, and then centrifuged at high speed. The supernatant is passed through a 0.45 μm organic filter membrane (Pall Corporation 0.45 μm, Michigan USA), and the filtrate is collected. The CP content is measured by high performance liquid chromatography, and the encapsulation rate is calculated according to the following formula:

[0066]

[0067] An analytical balance is used to weigh a certain amount of each microcapsule powder, which is dispersed in a certain volume of ethanol solution, and then broken by an ultrasonic breaking machine. The broken product is passed through a 0.45 μm organic filter membrane, and the filtrate is collected. The CP content is measured by high performance liquid chromatography, and the drug loading is calculated according to the following formula:

[0068]

[0069] The encapsulation rate and drug loading of the blank control group, each example and each comparative example microcapsule are calculated by the above method, and the results are shown in Table 1.

[0070] Table 1: Microcapsule encapsulation rate and drug loading

[0071]

[0072] It can be seen that, taking PLA as the wall material, the initial high encapsulation rate and drug loading efficiency with the original drug are ensured, and replacing other wall materials will cause a significant decrease in encapsulation rate and drug loading. Taking PLA as the wall material, further adding a pore former to adjust the pore generation on the surface of the wall material will cause a certain decrease in the encapsulation efficiency of the wall material to the original drug, but the drug loading is also improved to a certain extent. When polyethylene glycol 8000 or cyclohexanone is added alone, the drug loading decreases significantly, because the compatibility of polyethylene glycol 8000 with the wall material is poor, and the generated pores are not uniform in dispersion. When cyclohexanone is added alone, the cyclohexanone volatilizes rapidly during the solidification process, causing the wall material to collapse and the dissolved original drug to be carried away by volatilization, resulting in a decrease in encapsulation rate and drug loading. In the process of composite addition, polyethylene glycol 8000 (hydrophilic) and cyclohexanone (oleophilic) form a synergistic effect to improve the uniformity of the pore distribution on the surface of the wall material, thereby inhibiting the excessive decrease in encapsulation rate and improving the drug loading efficiency.

[0073] Controlled release experiment:

[0074] The CP microcapsules prepared in the embodiments of the application were tested for nitrogen control release experiment. The test soil was taken from the 0-20 cm plough layer of the test field of Jilin Agricultural University in June 2024, and the soil type was meadow black soil. The test nitrogen fertilizer was urea (N content 46.3%, Sinochem Fertilizer Co., Ltd.). The CP microcapsules were compared with the blank control group and the sample prepared in Example 1. The test was set up with no fertilizer, single urea, urea + 0.5% CP, urea + 0.5% CPCS-0 and urea + 0.5% CPCS-1, a total of 5 treatments, 3 times of repetition. The soil water content was adjusted to 65% of the field water holding capacity, and placed in a 25°C artificial climate incubator for 42 days. After incubation for 1, 3, 7, 14, 21, 28 and 42 days, the soil samples were taken, and the ammonium nitrogen and nitrate nitrogen contents were determined by the conventional method.

[0075] The change of ammonium nitrogen content in the soil is shown in Table 2.

[0076] Table 2: Change of ammonium nitrogen content in soil (unit: mg / kg)

[0077]

[0078] The concentration of ammonium nitrogen in the soil without fertilization treatment did not change significantly with the increase of incubation time, and remained at 12.85-13.53 mg / kg; the concentration of ammonium nitrogen in the soil with urea treatment increased first and then decreased with the increase of incubation time, and reached the maximum value of 422.35 mg / kg at the third day; the concentration of ammonium nitrogen in the soil with urea+0.5%CP treatment increased first and then decreased with the increase of incubation time, but compared with the urea treatment alone, the decrease of ammonium nitrogen content was significantly inhibited, and the overall ammonium nitrogen content was significantly improved, and the concentration of ammonium nitrogen in the soil still reached 122.36 mg / kg at 42 days; the concentration of ammonium nitrogen in the soil with urea+0.5%CPCS-0 treatment increased first and then decreased with the increase of incubation time, but the concentration of ammonium nitrogen in the soil was significantly lower than that of urea+0.5%CP treatment, and the decrease was larger in the early stage and significantly slower in the later stage, which was related to the fact that CP in CPCS-0 was difficult to release in the early stage and was released in the later stage; the concentration of ammonium nitrogen in the soil with urea+0.5%CPCS-1 treatment increased first and then decreased with the increase of incubation time, but the concentration of ammonium nitrogen in the soil was significantly higher than that of urea+0.5%CP treatment, which might be related to the fact that CP in CPCS-1 reached the full-process controllable slow release, which improved the effectiveness of CP; compared with urea+0.5%CPCS-0 treatment and urea+0.5%CPCS-1 treatment, it can be seen that the CP release in 0.5%CPCS-1 meets the actual production needs more complexly.

[0079] The change of the content of nitrate nitrogen in the soil is shown in Table 3.

[0080] Table 3: Change of nitrate nitrogen content in soil (unit: mg / kg)

[0081]

[0082] The concentration of nitrate nitrogen in the soil without fertilization treatment did not change significantly with the increase of incubation time, and remained at 20.38-22.94 mg / kg; the concentration of nitrate nitrogen in the soil with urea treatment increased first and then tended to be stable with the increase of incubation time, and reached the maximum value of 356.36 mg / kg at the 14th day; the concentration of nitrate nitrogen in the soil with urea + 0.5% CP treatment also increased first and then tended to be stable with the increase of incubation time, but compared with the urea treatment, it showed a significant inhibitory effect at the 3rd day; the concentration of nitrate nitrogen in the soil with urea + 0.5% CP S-0 treatment increased first and then tended to be stable, but it was significantly higher than that of the urea + 0.5% CP treatment; the concentration of nitrate nitrogen in the soil with urea + 0.5% CP S-1 treatment increased first and then tended to be stable, but it was significantly lower than that of the urea + 0.5% CP treatment; compared with the urea + 0.5% CP S-0 treatment and the urea + 0.5% CP S-1 treatment, it can be seen that the CP in 0.5% CP S-1 is released slowly, which improves the effectiveness of CP and thus improves the inhibitory effect on the conversion of urea to nitrate nitrogen in the soil, and the controlled release of CP in 0.5% CP S-1 is more in line with the actual production needs.

[0083] The nitration inhibition rate can represent the degree of inhibition of soil nitrification by the nitrification inhibitor. Table 4 is the dynamic change of the soil nitrification inhibition rate under the condition of urea as the nitrogen source during the incubation of 3-42 days, which reflects the differences between different treatments.

[0084] Table 4: Change of soil nitrification inhibition rate (unit: %)

[0085]

[0086] From Table 4, it can be seen that the nitration inhibition rate of urea + 0.5% CP treatment was between 8.35% and 74.56% within 3d-42 days, and it showed an increasing trend first and then a decreasing trend with the increase of culture time. The nitration inhibition rate of urea + 0.5% CPCS-0 treatment showed an increasing trend first and then a decreasing trend with the increase of culture time within 3d-42 days, and the nitration inhibition rate was between 3.38% and 12.02%. The nitration inhibition rate of urea + 0.5% CPCS-1 treatment was between 11.75% and 81.09% within 3d-42 days, and the nitration inhibition rate of urea + 0.5% CPCS-1 treatment was significantly higher than that of urea + 0.5% CPCS-0 and urea + 0.5% CP treatment at the same time point. The overall effect of the three treatments on the nitration inhibition rate was 0.5% CPCS-0 < 0.5% CP < 0.5% CPCS-1, which indicated that CP in CPCS-0 treatment without adding pore-forming agent could not release CP according to the actual demand, and could not effectively play a role in nitration inhibition, while the pore structure formed on the surface of CPCS-1 treatment could release CPO slowly, so that its nitration inhibition effect was significantly higher than that of CP treatment.

[0087] Example 4

[0088] A preparation method of a nitration inhibitor intelligent controlled-release microcapsule, comprising the following steps:

[0089] (1) Preparing materials: according to mass percentage, nitration inhibitor CP technical material (content ≥98%) 35%, solvent trichloromethane 30%, capsule wall material PGA 1%, pore-forming agent poly4%, dispersing agent fatty alcohol polyoxyethylene ether 2%, and the rest is distilled water, the polyhydroxy acid is, and the pore-forming agent is ethylene glycol and cyclohexanone with a mass ratio of 5:0.5;

[0090] (2) Preparing oil phase: adding PLA to the solvent and fully stirring to dissolve PLA;

[0091] (3) Preparing water phase: heating distilled water to 90℃, adding fatty alcohol polyoxyethylene ether thereto, and fully stirring to dissolve fatty alcohol polyoxyethylene ether;

[0092] (4) Emulsifying and shearing: slowly pouring the oil phase of step (2) into the water phase of step (3), adding while stirring, and using a high-speed shearing machine to shear at 10000 rmp for 2 min after adding all;

[0093] (5) Preparing microcapsule: transferring the mixture of the oil phase and the water phase in step (4) to a round-bottom flask, emulsifying at 350 rpm, emulsifying for 8 min, increasing the temperature to 50℃, evaporating the solvent, and then solidifying in a rotary evaporator for 2 h at a solidification speed of 400 rpm.

[0094] The encapsulation rate of the nitrification inhibitor intelligent controlled release microcapsule prepared in this embodiment is 81.72%, and the drug loading is 66.93%. According to the above method, when combined with urea and applied to soil, the soil nitrate nitrogen content is 285.52 mg / kg, the soil ammonium nitrogen content is 136.14 mg / kg, and the digestion inhibition rate is highest at 80.25% on the 7th day.

[0095] Example 5

[0096] A preparation method of a nitrification inhibitor intelligent controlled release microcapsule, comprising the following steps:

[0097] (1) Prepare materials: according to mass percentage, nitrification inhibitor CP crude drug (content ≥98%) 10%, solvent dichloromethane or trichloromethane 20%, capsule wall material polyhydroxy acid 1%, pore former poly 1%, dispersant fatty alcohol polyoxyethylene ether 8%, and the rest is distilled water, the polyhydroxy acid is PLA, and the pore former is ethylene glycol and cyclohexanone with a mass ratio of 5:1.5;

[0098] (2) Oil phase preparation: add PLA to the solvent, and fully stir to dissolve the PLA;

[0099] (3) Water phase preparation: take distilled water and heat to 90°C, and then add fatty alcohol polyoxyethylene ether to it, and fully stir to dissolve the fatty alcohol polyoxyethylene ether;

[0100] (4) Emulsification and shearing: slowly pour the oil phase of step (2) into the water phase of step (3), add while stirring, and then use a high-speed shearing machine to shear at 10000 rmp for 2 min;

[0101] (5) Preparation of microcapsules: transfer the oil phase and water phase mixture in step (4) to a round-bottom flask, emulsify at 450 rpm, emulsify for 4 min, increase the temperature to 40°C, evaporate the solvent, and then solidify in a rotary evaporator for 2 h at a rotation speed of 400 rpm.

[0102] The encapsulation rate of the nitrification inhibitor intelligent controlled release microcapsule prepared in this embodiment is 82.24%, and the drug loading is 67.17%. According to the above method, when combined with urea and applied to soil, the soil nitrate nitrogen content is 286.74 mg / kg, the soil ammonium nitrogen content is 133.47 mg / kg, and the digestion inhibition rate is highest at 80.96% on the 7th day.

Claims

1. A process for the preparation of a nitration inhibitor smart controlled release microcapsule characterized in that, The following steps are taken: (1) Prepare the microcapsule core material, capsule wall material, solvent, pore former, dispersant and distilled water, the microcapsule core material is 2-chloro-6-(trichloromethyl) pyridine original drug, the pore former is polyethylene glycol and cyclohexanone, and the mass ratio is 5:0.5-1.5; (2) Mix the microcapsule core material, capsule wall material, solvent and pore former to obtain an oil phase, and mix the dispersant into distilled water to obtain an aqueous phase; (3) Mix the oil phase and the aqueous phase and perform shear emulsification to form an emulsion; (4) Perform rotation treatment on the emulsion to form microcapsules, and then perform washing to obtain the nitrification inhibitor intelligent controlled release microcapsules.

2. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 1, wherein: The capsule wall material is a polyhydroxy acid, specifically polylactic acid or polyglycolic acid.

3. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 2, wherein: The solvent is at least one of toluene, xylene, acetonitrile, dichloromethane, chloroform, ethanol, cyclohexanone, N,N-dimethylformamide or Mobil S-200.

4. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 3, wherein: The dispersant is at least one of fatty alcohol polyoxyethylene ether, polyvinyl alcohol, fatty alcohol polyoxyethylene ether carboxylate, alkyl glycoside, methylene bis sodium sulfonate, and methylene sodium naphthalene sulfonate.

5. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 4, wherein: In step (1), the amount of each component is calculated based on the mass percentage, and the amount of each component is 1%-35% of the microcapsule core material, 10%-30% of the solvent, 1%-5% of the capsule wall material, 1%-5% of the pore former, 2-8% of the dispersant, and the rest is water.

6. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 5, wherein: In step (2), the aqueous phase is prepared by heating distilled water to 90-95°C, adding a dispersant, and thoroughly stirring to obtain an aqueous phase.

7. A process for the preparation of a nitration inhibitor smart controlled release microcapsule as claimed in claim 6, wherein the process comprises: In step (3), the shear speed is 10,000-12,000 rpm, and the shear time is 1-2 minutes.

8. A process for the preparation of a nitration inhibitor smart controlled release microcapsule characterized in that, The following steps are taken: (1) Prepare the materials: according to the mass percentage, the content of nitrification inhibitor 2-chloro-6-(trichloromethyl) pyridine (CP) original drug is 1%-35%, the solvent dichloromethane or trichloromethane is 10%-30%, the capsule wall material is a polyhydroxy acid, the pore former is 1%-5%, the dispersant is fatty alcohol polyoxyethylene ether or polyvinyl alcohol, and the rest is distilled water, the polyhydroxy acid is PLA or PGA, and the pore former is polyethylene glycol and cyclohexanone with a mass ratio of 5:0.5-1.5; (2) Oil phase preparation: add PLA to the solvent and stir thoroughly to dissolve the PLA; (3) Water phase preparation: heat distilled water to 90°C, and then add fatty alcohol polyoxyethylene ether to the water and stir thoroughly to dissolve the fatty alcohol polyoxyethylene ether; (4) Emulsification and shearing: slowly pour the oil phase of step (2) into the water phase of step (3) while stirring, and then use a high-speed shearing machine at 10,000 rpm for 1-2 minutes; (5) Prepare the microcapsules: transfer the mixture of the oil phase and the water phase in step (4) to a round-bottom flask, emulsify at 350-450 rpm, emulsify for 4-8 minutes, increase the temperature to 40-50°C, evaporate the solvent, and then solidify in a rotary evaporator for 2 hours at a rotation speed of 400 rpm.

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