A microemulsion type foliar fertilizer containing a silica sol and a method for preparing the same

Abstract

The application discloses a kind of microemulsion type foliage fertilizer containing silica sol and preparation method thereof, belong to agricultural fertilizer technical field.The foliage fertilizer is by the following raw materials with 100% total weight: 30% silica sol 25-32%, UAN 32 8-15%, ethylene glycol 8-15%, EGDA 0.5-3%, n-butanol 2-5%, Cargill oleic acid methyl ester 3-8%, emulsifier 12-18%, deionized water is made up to 100%.The application builds water-in-oil microemulsion system, and silica sol is wrapped in emulsifier interface film, effectively improves the storage stability, dilution stability and compatibility of product with fertilizer and pesticide.The product of the application still keeps clear and transparent after 54 DEG C hot storage 14 days and 0 DEG C cold storage 14 days, and there is no precipitation after being diluted with water by 100-500 times, and there is no flocculation and precipitation after being mixed with potassium dihydrogen phosphate, macroelement water-soluble fertilizer and agricultural package.The field test shows that the product of the application increases yield by 6.32-8.83% on wheat, and anti-lodging capacity is significantly enhanced;On corn, yield is increased by 13.7-16.1%, and hundred-grain weight is increased, and stem mechanical strength is improved;On soybean, yield is increased by 12.2-16.2%, and root growth is promoted, and pod number and grain number are significantly increased.The emulsifier comprises one or more of calcium dodecylbenzenesulfonate, styryl phenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether and polysorbate-80.The application can be suitable for alkaline silica sol, and can also be suitable for neutral silica sol, wherein neutral silica sol is a preferred scheme, and the pH value of final product is close to neutral, and it is more gentle to crop leaves.The preparation method is simple, suitable for industrial production, and can be widely applied to foliage silicon fertilizer application of wheat, corn, soybean and other field crops.

Description

Technical Field

[0001] This invention belongs to the field of agricultural fertilizer technology, specifically relating to a microemulsion foliar fertilizer containing silica sol and its preparation method, and particularly to a silica-containing foliar fertilizer with excellent storage stability, dilution stability and pesticide compatibility. Background Technology

[0002] Silicon is recognized by the international soil science community as the fourth most important nutrient element after nitrogen, phosphorus, and potassium. Studies have shown that applying silicon fertilizer can significantly improve the lodging resistance of gramineous crops such as rice and wheat, enhance the disease resistance, drought resistance, and salt tolerance of fruit trees and vegetables, and improve the quality and yield of agricultural products. With the advancement of green agriculture and quality improvement policies in my country, the market demand for functional liquid silicon fertilizer has been increasing year by year.

[0003] Currently, the silicon source for liquid silicon fertilizers mainly uses silica sol (i.e., a dispersion system of nano-silica in water). Silica sol has excellent properties such as high silicon nutrient content, absence of harmful sodium ions, and the ability to be mixed with fertilizers such as urea, making it an important development direction for foliar fertilizers.

[0004] However, existing silica sol-based foliar fertilizers have the following technical problems in practical applications.

[0005] First, it exhibits poor stability and is prone to gelation. Silica sol is a colloidal dispersion system of nano-sized silica particles (typically 5-20 nm in diameter) in water. Its stability depends on the electrostatic repulsion and steric hindrance of the particle surfaces. Factors such as temperature changes, pH fluctuations, and the introduction of electrolytes can all cause silica sol particles to aggregate, forming irreversible gels. In existing technologies, silica sol freezes into ice at low temperatures. After the temperature recovers, the originally colloidal silica will combine and aggregate, and this aggregation is irreversible.

[0006] Secondly, it has poor compatibility with fertilizers and pesticides. In actual field applications, liquid silica fertilizers typically need to be mixed with water-soluble fertilizers containing macro-elements, potassium dihydrogen phosphate, and pesticides such as insecticides and herbicides before spraying. However, existing silica sol systems are extremely sensitive to polyvalent cations (Ca²⁺, Mg²⁺, etc.). Once mixed with fertilizers containing calcium or magnesium, or pesticides containing metal ions, it easily produces white flocculent precipitates or gels, clogging spray nozzles and severely affecting the effectiveness and efficiency of field operations.

[0007] Third, the stability due to dilution is insufficient. Most existing silica sol foliar fertilizers are water-based systems, which may remain stable in a concentrated state. However, when diluted with water to the field application concentration, the stabilizer concentration is diluted simultaneously, weakening the protective effect and making it easy to produce precipitation or flocculation.

[0008] In the field of pesticide formulation, synergistic adjuvants formulated with vegetable oils or esterified vegetable oils, organic solvents, emulsifiers, and penetrants have been widely used. These adjuvants can significantly enhance the wetting, spreading, and penetrating abilities of pesticide solutions, increasing the deposition of pesticide droplets on plant surfaces, thereby improving the control efficacy of pesticides. However, these synergistic adjuvants are mainly designed for the active ingredients of pesticides and have not yet addressed the synergistic application with fertilizer components such as silica sol.

[0009] The core technical challenge in introducing silica sol into microemulsion systems containing vegetable oil esters and organic solvents lies in the fact that, as an aqueous dispersion of nano-silica, the stability of silica sol depends on the aqueous environment and the charge balance on the particle surface. The presence of vegetable oil esters and organic solvents alters the polar environment of the system, easily leading to silica sol instability and aggregation. Simultaneously, the electrolyte components in the silica sol may interact with the emulsifier system, disrupting the integrity of the microemulsion structure. Therefore, achieving a stable compounding of silica sol with synergistic additives is a pressing technical problem that needs to be solved. Summary of the Invention

[0010] The technical problem to be solved by the present invention is as follows: In view of the technical defects of existing silica sol foliar fertilizers, such as poor stability, poor compatibility with fertilizers and pesticides, and easy precipitation after dilution, the present invention provides a microemulsion foliar fertilizer containing silica sol and its preparation method.

[0011] This invention constructs a water-in-oil (W / O) microemulsion system, encapsulating silica sol in the form of tiny water droplets within the oil phase / emulsifier interface film. This effectively isolates the silica sol particles from direct attack by external electrolytes, organic solvents, etc., thereby significantly improving the product's storage stability, dilution stability, and compatibility with various fertilizers and pesticides. Furthermore, the methyl oleate and penetrant components in the microemulsion system endow the product with excellent leaf spreading, penetration, and deposition properties.

[0012] This invention is applicable to both alkaline and neutral silica sol raw materials, and both can be stabilized through the microemulsion system of this invention to meet the needs of different application scenarios.

[0013] Technical solution: To achieve the above-mentioned objectives, the present invention provides the following technical solution.

[0014] A microemulsion foliar fertilizer containing silica sol, comprising, by weight percentage, the following raw materials: 30% silica sol, 25-32%; Methyl oleate 2-8%; 1-5% ethylene glycol diacetate; Emulsifier 10-20%; Ethylene glycol 8-15%; n-Butanol 2-5%; Urea ammonium nitrate solution (UAN32) 8-15%; Add deionized water to bring the solution to 100.

[0015] Preferably, the 30% silica sol is an alkaline sodium silica sol with a SiO2 content of 25%-28%, a pH value of 9.0-10.5, and a density of 1.19-1.21 g / cm³ (25℃).

[0016] Preferably, the 30% silica sol is a neutral silica sol with a SiO2 content of 28%-32%, a pH value of 7.0-8.0, and a density of 1.19-1.21 g / cm³ (25℃).

[0017] Preferably, the UAN 32 is a urea-ammonium nitrate aqueous solution with a nitrogen content of 32%, wherein urea nitrogen, ammonium nitrogen, and nitrate nitrogen each account for approximately one-third.

[0018] Preferably, the methyl oleate is an esterified vegetable oil, and the unsaturated fatty acid ester segments contained in its molecular structure can endow the product with excellent leaf surface affinity and permeability.

[0019] Preferably, the emulsifier is a compound emulsifier, comprising one or more of the following emulsifiers: calcium dodecylbenzenesulfonate, styrene-phenol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, and polysorbate-80.

[0020] Furthermore, in the microemulsion foliar fertilizer of the present invention, the weight ratio of methyl oleate to EGDA is 5:1. This ratio range ensures good solubility of the oil phase system and stability of the microemulsion structure. n-Butanol, as both a co-surfactant and a penetration enhancer, can provide excellent foliar penetration while maintaining the stability of the microemulsion system.

[0021] Preparation method: The preparation method of the above-mentioned silica sol microemulsion foliar fertilizer includes the following steps.

[0022] Step 1: Prepare the oil phase. Weigh out EGDA, n-butanol, methyl oleate, and emulsifier according to the formula, place them in a reaction vessel, and stir at 200-400 rpm for 10-20 minutes at room temperature to ensure that the components are mixed evenly and obtain the oil phase mixture.

[0023] Step 2: Prepare the aqueous phase. Weigh out UAN 32, ethylene glycol and deionized water according to the formula, place them in another reaction vessel, and stir at 200-400 rpm for 5-10 minutes at room temperature to ensure that the components are mixed evenly and obtain an aqueous phase mixture.

[0024] Step 3: Emulsification. While continuously stirring, slowly add the aqueous phase mixture obtained in Step 2 to the oil phase mixture obtained in Step 1, controlling the addition time to 10-20 minutes. After the addition is complete, continue stirring for 20-30 minutes until the system forms a transparent and homogeneous liquid.

[0025] Step 4: Add silica sol. While continuously stirring, slowly add 30% of the formulated silica sol to the transparent system obtained in Step 3, controlling the addition time to 5-15 minutes. After the addition is complete, continue stirring for 15-20 minutes to ensure the silica sol is evenly dispersed in the microemulsion system, resulting in a pale yellow transparent liquid product.

[0026] Preferably, the operating temperature of steps one to four is controlled between 15-35℃.

[0027] Preferably, the silica sol is added slowly in a thin stream during step four.

[0028] Dual mechanism of stability and enhancement: This invention achieves stable coexistence of silica sol in environments containing vegetable oil esters and organic solvents by constructing an oil-in-water microemulsion system, while simultaneously endowing the product with excellent foliar enhancement function.

[0029] 1. Stabilization Mechanism. This invention constructs a water-in-oil (W / O) microemulsion system. Methyl oleate and EGDA constitute the continuous oil phase, while the emulsifier forms a dense interfacial film at the oil-water interface. UAN 32, ethylene glycol, and water constitute the dispersed phase (water core). Silica sol nanoparticles are encapsulated within the water core, physically isolated from the external oil phase and organic solvents, thus maintaining the stable aqueous environment upon which they depend. Simultaneously, the interfacial film formed by the emulsifier exhibits selective permeability, effectively preventing external polyvalent cations (Ca²⁺, Mg²⁺, etc.) and organic molecules from entering the water core and attacking the silica sol particles. EGDA, as a high-boiling-point polar solvent, not only participates in the construction of the microemulsion system but also improves the distribution behavior of each component in the oil and water phases, enhancing the overall thermodynamic stability of the formulation.

[0030] This physical isolation stabilization mechanism has remarkable universality: both basic and neutral silica sols are equally protected by the interfacial film after entering the water core of the microemulsion system. Basic silica sols rely on the electrostatic repulsion of the negative charge on the particle surface and the physical barrier of the interfacial film to form a dual stabilizing guarantee; although neutral silica sols have weaker electrostatic repulsion, the physical isolation effect of the interfacial film is sufficient to maintain their stable dispersion within the water core. Therefore, this invention has good applicability to silica sol raw materials with different pH values.

[0031] 2. Synergistic Mechanism. The components in the microemulsion system of this invention work synergistically to enhance the leaf surface effect.

[0032] (a) Enhanced wetting and spreading: Methyl oleate, as an esterified plant oil, has a natural affinity for plant leaf surfaces, which can significantly reduce the contact angle between fertilizer solution and leaf surface, and promote the uniform spreading of fertilizer solution on leaf surface.

[0033] (b) Promoting osmotic absorption: n-Butanol, as a penetrant, can help break down the waxy barrier on the surface of plant leaves, promoting the penetration of silicon and nitrogen nutrients into the mesophyll tissue.

[0034] (c) Rain washout resistance: The adhesive properties of methyl oleate can increase the amount of fertilizer droplets deposited on the plant surface, thereby improving the fertilizer's resistance to rain washout.

[0035] (d) Solubilizing and stabilizing effects of EGDA: As a high-boiling-point polar solvent, EGDA not only participates in the construction of microemulsion systems, but also improves the distribution behavior of fertilizer components in the oil-water two-phase system, thereby enhancing the overall stability of the formulation.

[0036] Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects.

[0037] 1. Mixing stability. When the product of this invention is mixed with potassium dihydrogen phosphate, water-soluble fertilizers containing macro-elements, agricultural packages containing insecticides and herbicides in conventional proportions, no flocculent precipitation, stratification, or gelation occurs, thus solving the technical problem of precipitation that easily occurs when existing silica sol foliar fertilizers are mixed with other fertilizers and pesticides.

[0038] 2. Storage stability. After being stored at 54℃ for 14 days and then at 3℃ for 14 days, the product of this invention remains clear and transparent, without sedimentation, stratification, or gelation, demonstrating excellent heat and cold resistance.

[0039] 3. Dilution stability. When diluted with water at 50, 100, and 200 times, the product of this invention remains clear and transparent or slightly milky white, without precipitation, flocculation, or stratification, making it suitable for conventional field spraying concentrations.

[0040] 4. Leaf Deposition and Absorption Efficiency. This invention utilizes the leaf affinity of methyl oleate and the penetration-promoting effects of ethylene glycol diacetate and n-butanol to significantly improve the wetting and spreading ability of the fertilizer solution on the leaf surface and the efficiency of nutrient penetration and absorption. Tests show that the surface tension of the product of this invention is ≤32 mN / m, the contact angle on the rice leaf surface is ≤45°, and the deposition of silicon nutrients on the leaf surface is more than 30% higher than that of conventional water-based silicon fertilizers, effectively solving the problems of easy rolling and low absorption rate of traditional water-based foliar fertilizers.

[0041] 5. It combines the functions of both fertilizer and adjuvant. The microemulsion system of this invention itself has the functional characteristics of a synergistic adjuvant. When used, it can achieve excellent wetting, spreading and penetration effects without the need for additional tank-mixing adjuvants, simplifying field operations and reducing the cost of use for farmers.

[0042] 6. High transparency and excellent appearance. The product of this invention is a pale yellow transparent liquid, indicating that the microemulsion system is uniformly dispersed and has a uniform particle size, resulting in a good commercial appearance.

[0043] 7. Simple production process. The preparation method of this invention can be completed at room temperature, without heating or high pressure, and is easy to operate, making it suitable for industrial production.

[0044] 8. Wide adaptability of raw materials. This invention is applicable to both alkaline and neutral silica sol raw materials. When using neutral silica sol raw materials, the final product has a pH value close to neutral (6.5-7.5), resulting in better compatibility with various fertilizers and pesticides, and is gentler on crop leaves, making it suitable for a wider range of application scenarios. Attached Figure Description

[0045] Figure 1 The image shown is of the product in Embodiment 1 of the present invention, which is a pale yellow transparent liquid.

[0046] Figure 2 These are comparative photographs of the appearance of the product of Example 1 (left) and Comparative Example 1 (without emulsifier, right) after being stored at 54°C for 7 days. As can be seen from the figures, the product of this invention remains clear and transparent, while Comparative Example 1 shows obvious layering.

[0047] Figure 3 The image shows the appearance of the product of Example 1 of this invention after being diluted 200 times, indicating that it is a clear and transparent liquid. Detailed Implementation

[0048] Example 1: Based on a total weight of 100g, the formula is as follows: methyl oleate 5.0g, ethylene glycol diacetate 3.0g, compound emulsifier 15g, UAN32 10.0g, 30% silicon source (alkaline, pH 9.0-10.5) 28g, ethylene glycol 10g, n-butanol 3g, and deionized water to make up to 100g.

[0049] In this embodiment, the main components of the compound emulsifier are a mixture of calcium dodecylbenzenesulfonate, styrene-based phenolic polyoxyethylene ether, dodecylphenol polyoxyethylene ether, and Tween 80 in a certain proportion. The weight ratio of methyl ester to EGDA is 5:1, and n-butanol is used as a regulator at a dosage of 3%.

[0050] Preparation: Weigh EGDA, n-butanol, methyl oleate, and emulsifier according to the formula, place them in a reaction vessel, and stir at 200-400 rpm for 10-20 minutes at room temperature to ensure homogeneity and obtain an oil phase mixture. Weigh UAN 32, ethylene glycol, and deionized water according to the formula, place them in another reaction vessel, and stir at 200-400 rpm for 5-10 minutes at room temperature to ensure homogeneity and obtain an aqueous phase mixture. While continuously stirring, slowly add the aqueous phase mixture to the oil phase mixture obtained in step one, controlling the addition time to 10-20 minutes. After the addition is complete, continue stirring for 20-30 minutes until a transparent and homogeneous liquid is formed. Slowly add 28g of 30% silica sol to the above system, adding over approximately 5 minutes. After the addition is complete, continue stirring for 15 minutes to obtain a pale yellow transparent liquid product.

[0051] Performance Testing: The product of this invention is a pale yellow, transparent, homogeneous liquid; pH 8.0-9.0; surface tension 28-32 mN / m; contact angle 40-45°; good thermal stability at 54℃ for 14 days, with no precipitation, stratification, or gelation; good cold stability at 3℃ for 14 days, with no precipitation, stratification, or gelation; good cold stability at -20℃ for 14 days, and remains a pale yellow, transparent liquid after thawing at room temperature; good stability after dilution 200 times and standing for 2 hours, with no precipitation; leaf deposition is 22% higher than conventional water-based silicon fertilizer; after mixing with a 1:1 stock solution of water-soluble fertilizers such as nitrogen, phosphorus, and potassium and standing for 2 hours, no precipitation or gelation; after mixing with conventional herbicides and insecticides and standing for 2 hours, no precipitation or gelation.

[0052] Example 2: Based on a total weight of 100g, the formula is as follows: methyl oleate 5.0g, ethylene glycol diacetate 3.0g, compound emulsifier 15.0g, UAN32 10.0g, 30% silicon source (neutral, pH 6.5-7.5) 28g, ethylene glycol 10g, n-butanol 3g, and deionized water to make up to 100g.

[0053] In this embodiment, the main components of the compound emulsifier are a mixture of calcium dodecylbenzenesulfonate, styrene-based phenolic polyoxyethylene ether, dodecylphenol polyoxyethylene ether, and Tween 80 in a certain proportion. The weight ratio of methyl ester to EGDA is 5:1, and n-butanol is used as a regulator at a dosage of 3%.

[0054] Preparation: Same as in Example 1.

[0055] Performance Testing: The product of this invention is a pale yellow, transparent, homogeneous liquid; pH 6.5-7.5; surface tension 28-32 mN / m; contact angle 40-45°; good thermal stability at 54℃ for 14 days, with no precipitation, stratification, or gelation; good cold stability at 3℃ for 14 days, with no precipitation, stratification, or gelation; good cold stability at -20℃ for 14 days, remaining a pale yellow, transparent liquid after thawing at room temperature; good stability after dilution 200 times and standing for 2 hours, with no precipitation; leaf deposition is 25% higher than conventional water-based silicon fertilizer; after mixing with a 1:1 stock solution of water-soluble fertilizers such as nitrogen, phosphorus, and potassium and standing for 2 hours, no precipitation or gelation; after mixing with conventional herbicides and insecticides and standing for 2 hours, no precipitation or gelation.

[0056] The results of this embodiment show that when using neutral silica sol raw materials, the final product has a pH value closer to neutral (6.8-7.2), and the product's thermal storage stability, dilution stability, and mixing compatibility are comparable to those of alkaline silica sol raw materials. The neutral product is gentler on crop leaves, has better compatibility when mixed with acidic pesticides, and is suitable for a wider range of application scenarios. Therefore, Example 2 is a preferred embodiment of the present invention.

[0057] Comparative Example 1: Based on a total weight of 100g, no emulsifier was added, and the remaining components and preparation methods were the same as in Example 1, with deionized water added to bring the total weight to 100g.

[0058] The results showed that the system immediately separated into layers after the aqueous phase was added to the oil phase during the preparation process, failing to form a transparent and homogeneous microemulsion system. After being stored at 54°C for 7 days, the system showed obvious separation, indicating that the emulsifier is the key component for forming a stable microemulsion system.

[0059] Comparative Example 2: Based on a total weight of 100g, no silicon source was added, and the remaining components and preparation methods were the same as in Example 1, with deionized water added to bring the total weight to 100g.

[0060] Comparative Example 3: Based on a total weight of 100g, the amount of 30% neutral silicon source added was 40g, and the remaining components and preparation methods were the same as in Example 1. Deionized water was added to bring the total weight to 100g.

[0061] The results showed that after 7 days of heat storage at 54℃, the system became noticeably white and viscous, and gelled, indicating that excessive silica sol content was detrimental to the stability of the microemulsion system. Field test

[0062] Table 1 Experimental Design

[0063] Each treatment was randomly assigned to a block design with three replicates per treatment, and foliar spraying was performed during the critical growth stages of the crop.

[0064] Table 2 Test Results in conclusion

[0065] Field trials on wheat showed that spraying with the silicon fertilizer of this invention significantly increased the number of spikes per unit area, the number of grains per spike, and the thousand-grain weight. In winter wheat trials, experimental groups 1 and 2 showed a yield increase of 52.3-67.3 kg / mu compared to the control group without silicon fertilizer, representing an increase of 9.4%-10.7%. The wheat plants in the silicon fertilizer-sprayed groups exhibited significantly enhanced internode strength at the base of the stems and significantly improved resistance to bending. Spraying with silicon fertilizer can effectively improve the lodging resistance of wheat and alleviate yield reduction caused by lodging.

[0066] Field trials of maize showed that after spraying the silicon fertilizer of this invention, the yield per mu of maize increased by 13.7%-16.1% compared with the control group, the 100-grain weight increased by 2.6g-2.9g, and the ear length and stem mechanical strength were also improved.

[0067] Field trials on soybeans showed that after spraying the silicon fertilizer of this invention, the yield of soybeans per mu increased by 12.2%-16.2% compared with the control group, the 100-seed weight increased by 1.5-2.8g, the root growth of soybeans was significantly promoted, the number of root nodules also increased compared with the control group, and the lodging resistance index of the plants was significantly improved.

[0068] The silica sol microemulsion foliar fertilizer provided by this invention can be widely used to improve lodging resistance and increase yield in field crops such as wheat, corn, and soybeans, as well as to improve the quality and enhance the stress resistance of fruit trees, vegetables, and cash crops. The product can be directly mixed with conventional fertilizers and pesticides without special handling, making it suitable for large-scale agricultural application.

Claims

1. A microemulsion foliar fertilizer containing silica sol, characterized in that, Based on a total weight of 100%, it consists of the following raw materials in weight percentage: 30% silica sol 25-32%, UAN 32 8-15%, ethylene glycol 8-15%, EGDA 0.5-3%, n-butanol 2-5%, methyl oleate 3-8%, emulsifier 12-18%, and deionized water to make up to 100%.

2. The silica sol-containing microemulsion foliar fertilizer according to claim 1, characterized in that, The 30% silica sol is an alkaline sodium silica sol with a SiO2 content of 25%-28% and a pH value of 9.0-10.

5.

3. The silica sol-containing microemulsion foliar fertilizer according to claim 1, characterized in that, The 30% silica sol is a neutral silica sol with a SiO2 content of 28%-32% and a pH value of 7.0-8.

0.

4. The silica sol-containing microemulsion foliar fertilizer according to claim 1, characterized in that, The UAN 32 is a urea-ammonium nitrate aqueous solution with a nitrogen content of 32%.

5. The silica sol-containing microemulsion foliar fertilizer according to claim 1, characterized in that, The emulsifier is a compound of emulsifiers such as calcium dodecylbenzenesulfonate, styrene-phenol polyoxyethylene ether, and polysorbate-80.

6. The application of the silica sol-containing microemulsion foliar fertilizer according to any one of claims 1-5 in foliar fertilization of crops.

7. The application according to claim 6, characterized in that, The foliar fertilizer should be diluted with water 100-500 times before spraying.

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