Double-layer coated fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of fertilizers, in particular to a double-layer coated fertilizer and a preparation method thereof. The double-layer coated fertilizer consists of a core fertilizer, an inner-layer coating material and an outer-layer coating material, wherein the inner-layer coating material and the outer-layer coating material are coated on the surface of the core fertilizer; the core fertilizer comprises urea, monopotassium phosphate, potassium sulfate, boric acid, zinc sulfate, copper sulfate, manganese sulfate and ammonium molybdate; the inner-layer coating material is a mixture of polyvinyl alcohol and methyl cellulose; the outer layer coating material comprises lignin, polylactic acid and genipin; the mass ratio of the core fertilizer to the inner-layer coating material to the outer-layer coating material is 100: (0.5-3): (3-30). The preparation method comprises the following steps: (1) uniformly spraying an inner-layer coating solution on the surfaces of core fertilizer particles; (2) uniformly spraying an outer layer coating solution; and (3) carrying out air-drying treatment. The double-layer coated fertilizer disclosed by the invention is beneficial to improving the utilization rate of the fertilizer, enhancing the stability of the fertilizer, prolonging the validity period of the fertilizer, reducing the waste of the fertilizer and reducing the pollution to the environment.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, in particular to a double-layer coated fertilizer and a preparation method thereof. Background Art

[0002] In modern agricultural practice, the rational use of fertilizers plays a decisive role in increasing crop yields. However, due to the lack of precise controlled release function, traditional fertilizers usually have low utilization rates after application and cause serious pollution to the environment. For example, excessive application of nutrients such as nitrogen and phosphorus may enter water bodies through surface runoff and soil infiltration, causing eutrophication of water bodies and destroying the balance of aquatic ecosystems.

[0003] To solve this problem, researchers have been exploring effective ways to improve fertilizer utilization. Research has found that coating technology can effectively regulate the release rate of fertilizers to match the crop growth cycle, thereby improving fertilizer utilization efficiency. This technology involves coating the surface of fertilizer particles with a layer of biodegradable or semi-biodegradable coating material to slow down the release rate of nutrients, reduce nutrient loss, and reduce adverse effects on the environment.

[0004] Although coated fertilizer technology has made certain research progress, it still faces many challenges in practical application. For example, the coating materials currently used may be derived from non-renewable petroleum resources, which not only increases production costs, but may also cause secondary pollution to the environment. In addition, the degradation rate of coating materials and the precise control of fertilizer release are still research hotspots in this field. Therefore, the development of new environmentally friendly coating materials and the improvement of the precise control ability of coating technology are of great significance to improving fertilizer utilization and reducing environmental pollution. Summary of the invention

[0005] In view of the above shortcomings in the prior art, the present invention provides a double-layer coated fertilizer, which realizes the controlled release of fertilizer, improves fertilizer utilization, and reduces environmental pollution by combining a core fertilizer with a double-layer coating material. To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A double-layer coated fertilizer comprises a core fertilizer, an inner coating material wrapped on the surface of the core fertilizer, and an outer coating material wrapped on the surface of the inner coating material; the core fertilizer comprises urea, potassium dihydrogen phosphate, potassium sulfate, boric acid, zinc sulfate, copper sulfate, manganese sulfate and ammonium molybdate; the inner coating material is a mixture of polyvinyl alcohol and methyl cellulose; the outer coating material comprises lignin, polylactic acid and genipin; the mass ratio of the core fertilizer, the inner coating material and the outer coating material is 100:0.5-3:3-30.

[0007] Furthermore, the core fertilizer comprises the following components in weight percentage: 40% urea, 25% potassium dihydrogen phosphate, 25% potassium sulfate, 2% boric acid, 2% zinc sulfate, 2% copper sulfate, 2% manganese sulfate, and 2% ammonium molybdate.

[0008] Furthermore, the inner coating material comprises the following components in weight percentage: 5% polyvinyl alcohol, 3% methyl cellulose, and 92% water.

[0009] Furthermore, the outer coating material comprises the following components in weight percentage: 40% lignin, 10% polylactic acid, 5% genipin, and 45% water.

[0010] The method for preparing the double-layer coated fertilizer is characterized by comprising the following steps:

[0011] (1) urea, potassium dihydrogen phosphate, potassium sulfate, boric acid, zinc sulfate, copper sulfate, manganese sulfate and ammonium molybdate are uniformly mixed according to a proportion to form core fertilizer particles;

[0012] (2) mixing polyvinyl alcohol, methyl cellulose and water according to a ratio, heating to 65-75° C., and continuously stirring to form an inner coating solution;

[0013] (3) spraying the inner coating solution obtained in step (2) uniformly on the surface of the core fertilizer particles obtained in step (1);

[0014] (4) mixing lignin, polylactic acid, genipin and water according to a ratio to form an outer coating solution;

[0015] (5) spraying the outer coating solution obtained in step (4) uniformly on the surface of the core fertilizer particles wrapped by the inner coating material obtained in step (3);

[0016] (6) Drying is performed to form a double-layer coated fertilizer.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Improve the utilization rate of fertilizer and reduce fertilizer waste.

[0019] 2. By controlling the release of fertilizers, the pollution to the environment is reduced.

[0020] 3. The double-layer coating structure enhances the stability of the fertilizer and extends its shelf life. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1:

[0023] 40 kg of urea, 25 kg of potassium dihydrogen phosphate, 25 kg of potassium sulfate, 2 kg of boric acid, 2 kg of zinc sulfate, 2 kg of copper sulfate, 2 g of manganese sulfate and 2 g of ammonium molybdate are mixed evenly to form core fertilizer particles.

[0024] 0.05 kg of polyvinyl alcohol, 0.03 kg of methyl cellulose and 0.92 kg of water were mixed, heated to 75°C, and stirred continuously to form an inner coating solution.

[0025] The inner coating solution is evenly sprayed on the surface of the core fertilizer particles, so that 1 kg of the inner coating solution is adsorbed on the surface of 100 kg of the core fertilizer particles.

[0026] 4 kg of lignin, 1 kg of polylactic acid, 0.5 kg of genipin and 4.5 kg of water were mixed to form an outer coating solution.

[0027] The outer coating solution is evenly sprayed on the surface of the core fertilizer particles wrapped by the inner coating material, so that 10 kg of the outer coating solution is adsorbed on the surface of 1 kg of the inner coating fertilizer particles.

[0028] The treated fertilizer particles are dried to form double-coated fertilizer.

[0029] Embodiment 2:

[0030] The difference between Example 2 and Example 1 is that 0.1 kg of polyvinyl alcohol, 0.06 kg of methyl cellulose and 1.84 kg of water are mixed, heated to 70°C, and stirred continuously to form an inner coating solution, so that 2 kg of the inner coating solution is adsorbed on the surface of 100 kg of core fertilizer particles, and 8 kg of lignin, 2 kg of polylactic acid, 1 kg of genipin and 9 kg of water are mixed to form an outer coating solution, so that 20 kg of the outer coating solution is adsorbed on the surface of 2 kg of inner coating fertilizer particles.

[0031] Embodiment 3:

[0032] The difference between Example 3 and Example 1 is that 0.15 kg of polyvinyl alcohol, 0.09 kg of methyl cellulose and 2.76 kg of water are mixed, heated to 65°C, and stirred continuously to form an inner coating solution, so that 3 kg of the inner coating solution is adsorbed on the surface of 100 kg of core fertilizer particles, and 12 kg of lignin, 3 kg of polylactic acid, 1.5 kg of genipin and 13.5 kg of water are mixed to form an outer coating solution, so that 30 kg of the outer coating solution is adsorbed on the surface of 3 kg of inner coating fertilizer particles.

[0033] The above content is a further detailed description of the present invention in combination with specific implementation methods. It cannot be considered that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, simple modifications and substitutions made without departing from the concept of the present invention should be deemed to belong to the scope of protection of the present invention.

Claims

1. A double-layer coated fertilizer, characterized in that: It consists of a core fertilizer, an inner coating material wrapped on the surface of the core fertilizer, and an outer coating material wrapped on the surface of the inner coating material; the core fertilizer contains urea, potassium dihydrogen phosphate, potassium sulfate, boric acid, zinc sulfate, copper sulfate, manganese sulfate and ammonium molybdate; the inner coating material is a mixture of polyvinyl alcohol and methyl cellulose; the outer coating material includes lignin, polylactic acid and genipin; the mass ratio of the core fertilizer, the inner coating material and the outer coating material is 100:0.5~3:3~30.

2. The double-layer coated fertilizer according to claim 1, characterized in that: The core fertilizer comprises the following components in weight percentage: 40% urea, 25% potassium dihydrogen phosphate, 25% potassium sulfate, 2% boric acid, 2% zinc sulfate, 2% copper sulfate, 2% manganese sulfate, and 2% ammonium molybdate.

3. The double-layer coated fertilizer according to claim 1, characterized in that: The inner coating material comprises the following components in percentage by weight: 5% polyvinyl alcohol, 3% methyl cellulose and 92% water.

4. The double-layer coated fertilizer according to claim 1, characterized in that: The outer coating material comprises the following components in weight percentage: 40% lignin, 10% polylactic acid, 5% genipin, and 45% water.

5. The method for preparing a double-layer coated fertilizer according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) urea, potassium dihydrogen phosphate, potassium sulfate, boric acid, zinc sulfate, copper sulfate, manganese sulfate and ammonium molybdate are uniformly mixed according to a proportion to form core fertilizer particles; (2) mixing polyvinyl alcohol, methyl cellulose and water according to a ratio, heating to 65-75° C., and continuously stirring to form an inner coating solution; (3) spraying the inner coating solution obtained in step (2) uniformly on the surface of the core fertilizer particles obtained in step (1); (4) mixing lignin, polylactic acid, genipin and water according to a ratio to form an outer coating solution; (5) spraying the outer coating solution obtained in step (4) uniformly on the surface of the core fertilizer particles wrapped by the inner coating material obtained in step (3); (6) Drying is performed to form a double-layer coated fertilizer.