Slow-release liquid boron-containing coating agent, boron-containing granular fertilizer and preparation method of boron-containing granular fertilizer

Abstract

The invention discloses a slow-release liquid boron-containing coating agent, a boron-containing granular fertilizer and a preparation method thereof, and belongs to the technical field of agricultural fertilizers and slow and controlled release, the slow-release liquid boron-containing coating agent comprises the following components by mass: 10-20 parts of boric acid, 5-15 parts of triethanolamine, 5-10 parts of a plasticizer, 40-60 parts of a polyvinyl alcohol aqueous solution, 10-30 parts of water, and 0.05-0.2 part of a preservative; boric acid and triethanolamine form a complex, and boric acid and polyvinyl alcohol form stable five-membered ring borate. The boron-containing coating agent disclosed by the embodiment of the invention is a boron-containing material which is in a liquid state, forms a film at a low temperature and can be sprayed on the surface of a fertilizer to form a slow-release film layer, so that the boron-containing coating agent not only can be combined with fertilizer particles, but also can slowly release boron in soil, and the utilization rate and the continuous supply capacity of boron are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural fertilizers and slow-release and controlled-release technologies, in particular to a slow-release liquid boron-containing coating agent, a boron-containing granular fertilizer and a preparation method thereof. Background Art

[0002] Boron, as one of the trace elements necessary for plant growth and development, plays an important role in cell wall formation, carbohydrate metabolism, hormone transport, pollen germination, pollination and fertilization. Boron deficiency can lead to problems such as necrosis of the top growth point of the plant, fruit deformity, and reduced fruit set rate, seriously affecting the yield and quality of crops. At present, commonly used liquid boron fertilizers are mainly applied by drip irrigation and foliar spraying, and have the characteristics of fast dissolution and fast absorption. However, these water-soluble boron sources are easily carried away by runoff and leaching in the soil. After application to the soil, they are released quickly, making it difficult to maintain effective concentrations for a long time, resulting in crops being prone to late boron deficiency throughout the entire growth period. At the same time, it is difficult to accurately control the release rate of some solid boron fertilizers, which are not suitable for the continuous nutritional needs of crops.

[0003] In addition, existing slow-release fertilizer technologies mostly use hot-melt coating or chemical coating methods, such as sulfur coating and resin coating. However, this type of coating process is mostly used for bulk nutrients such as nitrogen, phosphorus, and potassium. The coating of trace elements, especially boron, has the following defects: 1. The film material is not easily compatible with boron, which will affect its release behavior; 2. The film making temperature is high and the cost is high, making it difficult to adapt to the use scenarios of trace elements.

[0004] Currently, there is a lack of systematic development of liquid boron source coating systems, and no liquid boron sustained-release technology suitable for large-scale coating application has been disclosed. Summary of the Invention

[0005] In order to address the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a slow-release liquid boron-containing coating agent, a boron-containing granular fertilizer and a preparation method thereof. The coating agent is a liquid, low-temperature film-forming boron-containing material that can be sprayed on the fertilizer surface to form a slow-release film layer. It can not only combine with the fertilizer particles, but also slowly release boron in the soil, thereby improving the utilization rate and continuous supply capacity of boron.

[0006] The technical solution adopted by the present invention to solve the technical problem is: Provided is a sustained-release liquid boron-containing coating agent, comprising the following components, calculated by mass: 10-20 parts of boric acid, 5-15 parts of triethanolamine, 5-10 parts of plasticizer, 40-60 parts of polyvinyl alcohol aqueous solution, 10-30 parts of water, and 0.05-0.2 parts of preservative; The boric acid forms a complex with triethanolamine, and the boric acid forms a stable five-membered ring borate with polyvinyl alcohol.

[0007] Furthermore, the molar ratio of triethanolamine to boric acid is 1.0-1.5:1.

[0008] Furthermore, the plasticizer is glycerol or propylene glycol.

[0009] Furthermore, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10%.

[0010] Furthermore, the polyvinyl alcohol has a degree of alcoholysis of 86% to 99% and an average molecular weight of 30,000 to 80,000.

[0011] Furthermore, the preservative is one of phenoxyethanol, octanediol, pentylene glycol, kasone, and benzisothiazolinone.

[0012] The invention discloses a slow-release boron-containing granular fertilizer, which is made of a fertilizer core and a liquid coating agent sprayed on the surface of the fertilizer core.

[0013] Furthermore, the fertilizer core is one of urea, monoammonium phosphate, potassium sulfate, potassium chloride or NPK compound fertilizer.

[0014] Furthermore, the mass of the liquid coating agent is 0.8 to 1.2‰ of the fertilizer core.

[0015] A method for preparing a slow-release boron-containing granular fertilizer comprises the following steps: (1) Dissolve polyvinyl alcohol in water at 60-80°C to prepare a PVA solution; (2) Add triethanolamine, plasticizer, and boric acid to the PVA solution in sequence at 30-60°C and stir until completely dissolved; (3) After cooling to room temperature, add preservatives and filter to remove micro-impurities to obtain the coating solution; (4) Spray the coating liquid evenly on the surface of the fertilizer particles; (5) Drying at 25-60°C for 1-6 hours to obtain a slow-release film layer, thereby obtaining a slow-release boron-containing granular fertilizer.

[0016] Boric acid forms a complex with triethanolamine, the principle is: The B atom in boric acid can form a stable five-membered ring complex structure (i.e., borate ester structure) with the oxygen atoms of the two adjacent hydroxyl groups on the PVA chain: PVA structural fragment: –CH(OH)–CH2–CH(OH)–CH2– After boric acid complexation, a five-membered ring is formed: The principle of the reaction is: Boric acid complexes with vicinal diol to form a five-membered ring borate ester; Its chemical expression is: B(OH)3 + 2–CH(OH)– → [–CH–O–B–O–CH–] + H2O Among them, –CH(OH)– represents the ortho-hydroxyl unit in PVA; a bridged borate complex is formed in the middle. Glycerol, with its trihydroxy structure, is more compatible with polyvinyl alcohol and is particularly suitable for long-term sustained-release applications. Propylene glycol dries quickly (2.5-3 hours at 25°C), but its boron complex stability is relatively poor, making it more suitable for rapid production or low-temperature application.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention forms a stable complex by combining triethanolamine and boric acid at a specific molar ratio, and combines it with the plasticizing effect of glycerol to solve the problem of easy leaching of traditional boron fertilizers in the soil, thereby improving the chemical stability of the boron element. At the same time, glycerol is used to adjust the flexibility of the film layer to avoid drying and cracking. 2. The present invention adopts PVA with an alcoholysis degree of 86% to 99% and a molecular weight of 30,000 to 80,000 as the film-forming matrix, which can form a dense and water-resistant film layer at a low temperature of 25 to 60°C, avoiding high temperature destruction of boron activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 This is a process flow chart for the production of slow-release boron-containing granular fertilizer. DETAILED DESCRIPTION

[0019] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] 1. Preparation of sustained-release liquid boron-containing coating agent Example 1: The following components were weighed in parts by mass: 10 parts of boric acid, 15 parts of triethanolamine, 15 parts of water, 10 parts of glycerol, 40 parts of polyvinyl alcohol (PVA, 98% water-soluble, Mw≈60,000) aqueous solution, and 0.1 part of kason.

[0022] Its preparation method is: (1) Heat deionized water to 75°C, slowly add polyvinyl alcohol while stirring, and stir for 30 minutes until it is completely dissolved to form a transparent solution; (2) Cool to 55°C, add triethanolamine and propylene glycol in sequence, and continue stirring for 10 minutes; (3) Slowly add boric acid powder and stir for 30 min until the boric acid is completely dissolved; (4) Cool to room temperature, add kasonide and stir for 5 minutes, filter to remove micro impurities, and obtain a clear, transparent and stable liquid coating agent product.

[0023] Example 2: The following components were weighed in parts by mass: 10 parts of boric acid, 15 parts of triethanolamine, 15 parts of water, 10 parts of propylene glycol, 40 parts of polyvinyl alcohol (PVA, 98% water-soluble, Mw≈60,000) aqueous solution, and 0.1 parts of kason.

[0024] Its preparation method is: (1) Heat deionized water to 75°C, slowly add polyvinyl alcohol while stirring, and stir for 30 minutes until it is completely dissolved to form a transparent solution; (2) Cool to 55°C, add triethanolamine and propylene glycol in sequence, and continue stirring for 10 minutes; (3) Slowly add boric acid powder and stir for 30 min until the boric acid is completely dissolved; (4) Cool to room temperature, add kasonide and stir for 5 minutes, filter to remove micro impurities, and obtain a clear, transparent and stable liquid coating agent product.

[0025] 2. Coating Preparation of Slow-Release Boron-Containing Granular Fertilizer Example 3: Materials: Compound fertilizer (N-P2O5-K2O 15-15-15): 5 kg; Liquid coating agent prepared in Example 1: 50 g; Method: (1) Put the granular compound fertilizer into the drum coating machine, rotate it slowly, and use an air pump to evenly spray the liquid coating agent onto the fertilizer surface; (2) After spraying, dry it with hot air at 45°C for 4 hours; after drying, boron-containing slow-release compound fertilizer granules with smooth surface and uniform coating are obtained.

[0026] Example 4: The method is the same as that of Example 3, using the liquid coating agent prepared in Example 2.

[0027] During the spraying process, it was found that the film uniformity of the coating agent using propylene glycol was better than that using propylene glycol, the solution viscosity was higher, and it was easier to spray.

[0028] And set up control example 1: Materials: Compound fertilizer (N-P2O5-K2O 15-15-15): 5 kg; Boron fertilizer: 5 g; Method: (1) Put the granular compound fertilizer into the drum coating machine, rotate it slowly, and use an air pump to evenly spray the liquid coating agent onto the fertilizer surface; (2) After spraying, dry it with hot air at 45℃ for 4h; (3) After drying, boron-containing slow-release compound fertilizer granules with smooth surface and uniform coating are obtained.

[0029] 3. Performance Testing 1. Boric acid release rate test The slow-release granular fertilizers of Example 3 and Example 4 and the boron-containing compound fertilizer of Control Example 1 were subjected to a water soaking test to test the boron nutrient release rate at different times. The results are shown in Table 1. The time in Table 1 corresponds to the nutrient release rate at that time.

[0030] Table 1 Cumulative dissolution rate of boron nutrients Results show that this coating significantly slows the dissolution rate of boron nutrients, demonstrating a sustained-release effect. The mechanism is that triethanolamine and boric acid form a stable complex at a specific molar ratio (1.0-1.5:1), combined with the plasticizing effect of a plasticizer, to address the leaching problem of traditional boron fertilizers (such as borax and boric acid) in soil. This system significantly enhances the chemical stability of boron, while the plasticizer modulates the film's flexibility, preventing brittle cracking upon drying.

[0031] 2. Application effect of slow-release granular fertilizer on watermelon Watermelons were divided into four experimental treatments, using the slow-release granular fertilizers of Examples 3 and 4, the boron-containing compound fertilizer of Control Example 1, and the N-P2O5-K2O 15-15-15 compound fertilizer as base fertilizer, with a dosage of 50 kg per mu. The experimental structure is shown in Table 2.

[0032] Table 2 Yield and quality indicators of each experimental treatment The results showed that the slow-release granular fertilizer of Example 3 outperformed the other experimental groups in terms of yield per mu and quality indicators (Vc content, sugar content, soluble solids, and soluble protein content). The quality indicators of the boron-containing compound fertilizer treatment of Control Example 1 were higher than those of the compound fertilizer treatment but lower than those of the boron-containing compound fertilizer treatment of Example 4.

[0033] Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also includes other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, the above-mentioned features can be replaced with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A sustained-release liquid boron-containing coating agent, characterized in that: The composition comprises the following components by weight: 10 to 20 parts of boric acid, 5 to 15 parts of triethanolamine, 5 to 10 parts of plasticizer, 40 to 60 parts of polyvinyl alcohol aqueous solution, 10 to 30 parts of water, and 0.05 to 0.2 parts of preservative; The boric acid forms a complex with triethanolamine, and the boric acid forms a stable five-membered ring borate with polyvinyl alcohol.

2. The sustained-release liquid boron-containing coating agent according to claim 1, characterized in that: The molar ratio of triethanolamine to boric acid is 1.0-1.5:

1.

3. The sustained-release liquid boron-containing coating agent according to claim 1, characterized in that: The plasticizer is glycerol or propylene glycol.

4. The sustained-release liquid boron-containing coating agent according to claim 1, characterized in that: The mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10%.

5. The sustained-release liquid boron-containing coating agent according to claim 1, characterized in that: The polyvinyl alcohol has an alcoholysis degree of 86% to 99% and an average molecular weight of 30,000 to 80,000.

6. The sustained-release liquid boron-containing coating agent according to claim 1, characterized in that: The preservative is one of phenoxyethanol, octanediol, pentylene glycol, kasonide and benzisothiazolinone.

7. A slow-release boron-containing granular fertilizer, characterized in that: The fertilizer is made of a fertilizer core and the liquid coating agent according to any one of claims 1 to 6 sprayed on the surface of the fertilizer core.

8. The slow-release boron-containing granular fertilizer according to claim 7, characterized in that The fertilizer core is one of urea, monoammonium phosphate, potassium sulfate, potassium chloride or NPK compound fertilizer.

9. The slow-release boron-containing granular fertilizer according to claim 7, characterized in that The mass of the liquid coating agent is 0.8 to 1.2‰ of the fertilizer core.

10. A method for preparing the slow-release boron-containing granular fertilizer according to any one of claims 7 to 9, characterized in that: The following steps are involved: (1) Dissolve polyvinyl alcohol in water at 60-80°C to prepare a PVA solution; (2) Add triethanolamine, plasticizer, and boric acid to the PVA solution in sequence at 30-60°C and stir until completely dissolved; (3) After cooling to room temperature, add preservatives and filter to remove micro-impurities to obtain the coating solution; (4) Spray the coating liquid evenly on the surface of the fertilizer particles; (5) Drying at 25-60°C for 1-6 hours to obtain a slow-release film layer, thereby obtaining a slow-release boron-containing granular fertilizer.

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