Film coating method for improving film coating rate of microbial fertilizer particles
By coating microbial fertilizer granules with a mixture of PVA-modifier and hydrophilic materials, the problems of short shelf life, difficulty in wetting, and poor compressive strength of microbial fertilizer granules are solved, thereby improving the coating rate and the effectiveness of fertilizer in the soil.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-02
- Publication Date
- 2026-04-14
AI Technical Summary
Existing microbial fertilizer granules suffer from problems such as short shelf life, limited time for maintaining bacterial activity, difficulty in wetting, and poor compressive strength. Furthermore, traditional coating materials are difficult to achieve uniform and stable coating effects.
A mixed solution of PVA modifier and hydrophilic materials such as starch, glucose, and maltose was used to control the surface tension by the modifier to prepare coated microbial fertilizer granules, including a hydrophobic fertilizer core layer and a modified film layer, with a mass ratio of 100:(0.5-10). The coating layer was formed by spraying and drying using a coating machine.
It significantly extends the shelf life of microbial fertilizer granules, improves wettability and compressive strength, reduces the death of live bacteria and powdering, and ensures the effectiveness and stability of fertilizer in the soil.
Smart Images
Figure CN121850804A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microbial fertilizer preparation technology, and provides a coating method to improve the coating rate of microbial fertilizer particles. Background Technology
[0002] Microbial fertilizers, as a new type of bio-agricultural fertilizer, can promote crop growth and improve the soil environment through beneficial microbial communities. These fertilizers are characterized by low input costs and significant ecological benefits, meeting the current needs of green agricultural development. Therefore, promoting the industrialization of microbial fertilizers is of great strategic significance for reducing the use of chemical fertilizers and pesticides and promoting sustainable agricultural development.
[0003] Despite the significant ecological benefits and low production costs of microbial fertilizers, their application still faces three major technical bottlenecks: first, the shelf life of microbial fertilizer granules is short, and the duration of microbial cell activity is limited; second, the hydrophobic nature of microbial fertilizer granules makes wetting difficult; and third, microbial fertilizer granules have poor compressive strength and are prone to loosening and powdering. Constructing biodegradable hydrophilic coatings is an effective way to overcome these limitations. Commonly used materials such as cellulose, starch, chitosan, sodium alginate, lignin, pectin, and polyvinyl alcohol (PVA) possess good hydrophilicity and environmental compatibility, but due to significant interfacial differences with the hydrophobic surface of microbial fertilizers, it is difficult to achieve a uniform and stable coating effect. Therefore, developing novel microbial fertilizer coating technologies has become a key breakthrough point for the current industry development. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and propose a coating method to improve the coating rate of microbial fertilizer granules.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: A coating method for improving the coating rate of microbial fertilizer granules, wherein the prepared coated microbial fertilizer granules include a hydrophobic microbial fertilizer granule core layer and a modified film layer covering the fertilizer core, and the mass ratio of fertilizer core to modified film layer is 100:(0.5-10).
[0006] The microbial fertilizer granules are microbial fertilizer granules such as Trichoderma harzianum, Penicillium barometz, or Aspergillus niger.
[0007] The microbial fertilizer granules can also be microbial fertilizer granules obtained by mixing microbial agents such as Trichoderma harzianum, Penicillium barometz or Aspergillus niger with one or more carriers such as bentonite and diatomaceous earth. The number of live bacteria can be controlled by the weight ratio of the agent to the carrier, ranging from about 100 million / g to 50 billion / g.
[0008] The modifier in the PVA-modifier mixture solution can be a surfactant, wetting agent, dispersant or mixture thereof that alters the surface tension of water (such as sodium dodecyl sulfate, disodium methylene dinaphthalene sulfonate, sodium dodecylbenzene sulfonate or fatty acid salts or mixtures thereof).
[0009] The mass ratio of PVA to modifier in the PVA-modifier mixed solution is 100:(5-50).
[0010] The mass fraction of the PVA-modifier mixed solution is 1%-50%.
[0011] The hydrophilic material that can provide glycogen in the aqueous solution that can provide sugar raw materials can be starch, glucose, maltose or dextrin and mixtures thereof, and its mass fraction in the solution is 1%-50%.
[0012] The mixed solution of the PVA-modifier solution and the hydrophilic material solution that can provide glycogen is characterized in that the mass ratio of the PVA-modifier to the hydrophilic material that can provide glycogen is 1:9-9:1, preferably 7:3-3:7.
[0013] The membrane layer of the microbial fertilizer granules is a mixture of PVA and hydrophilic materials that can provide glycogen, such as starch, glucose, maltose, and dextrin. The selection criteria are as follows: materials such as starch, glucose, maltose, and dextrin have advantages such as low cost and renewability, and can provide nutrients for the germination and growth of microbial agents when used for coating microbial fertilizers. However, they have low viscosity and poor film-forming properties, making them difficult to use alone. PVA has excellent film-forming ability and can be used to modify sugar raw materials. It has been reported that the PVA / glycogen composite system has excellent water absorption, mechanical properties, and biodegradability; therefore, the PVA / glycogen system can serve as a basic material for the outer shell membrane of microbial fertilizers. Furthermore, modifiers can alter the surface tension of the PVA / glycogen system solution. The degree of alteration can be controlled by the amount of modifier and the types of compounding agents. By changing the surface tension of the PVA / glycogen system solution, its affinity for microbial fertilizer granules can be improved, thereby increasing the coating rate of the microbial fertilizer granules.
[0014] The coating process of the microbial fertilizer granules includes the following steps, taking PVA / starch-(sodium dodecyl sulfate and disodium methylene dinaphthalene sulfonate) coated microbial fertilizer granules as an example: Step 1—Preparing an aqueous solution of PVA: Add PVA, sodium dodecyl sulfate and disodium methylene dinaphthalene sulfonate to deionized water, and stir continuously at 300 r / min for 2 hours at 105℃ until completely dissolved to form a transparent and homogeneous PVA-modifier solution. Step 2—Preparing a soluble starch solution: Mix soluble starch with deionized water and stir at 300 r / min for 10 minutes at a constant temperature of 75℃ to fully gelatinize the starch and form a transparent solution; Step 3—Preparation of PVA-modifier / starch mixed solution: Mix the two solutions in a predetermined ratio, place them in a 75°C water bath, and stir at 600r / min for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles from the solution, obtaining a clear coating solution for later use. Step 4—Preparation of Coated Microbial Fertilizer Granules: Using a coating machine, the prepared mixed solution is evenly sprayed onto the surface of the microbial fertilizer granules, controlling the spraying rate to ensure complete coverage. The coated granules are dried at a temperature ≤90℃ (preferably ≤40℃) to obtain the final coated microbial fertilizer product.
[0015] Advantages of the product of this invention: 1. The coating membrane in the coated microbial fertilizer granules prepared by the present invention can improve the shelf life of the microbial fertilizer granules and enhance their wettability, which can solve the problems of easy inactivation and difficulty in wetting of traditional microbial fertilizer granules, and has good promotion and application value. Specifically: (1) The coating membrane can effectively isolate the microbial fertilizer granules from the external environment. In particular, its excellent oxygen barrier performance can significantly reduce the germination probability of microorganisms during storage, reduce the number of dead live bacteria, and thus extend the shelf life of the product. At the same time, when the fertilizer is applied to the soil, the coating membrane can be naturally degraded by microorganisms and water in the soil. During the degradation process, the sugars produced by the decomposition of the coating membrane material can also provide nutrients for microorganisms, promote their germination and growth. This characteristic not only ensures storage stability, but also does not affect the efficacy of the fertilizer in the soil, and may even enhance its fertilizer effect. (2) The hydrophilic outer coating membrane overcomes the problem that hydrophobic microbial fertilizers are difficult to wet quickly in water. The coated microbial fertilizer is more easily wetted by water, which is very helpful in improving its germination and survival rate in the soil. (3) The PVA / glycogen composite coating film has good flexibility and can absorb external pressure through elastic deformation, which significantly improves the compression resistance of microbial fertilizer particles and prevents them from breaking or loosening during transportation or use. In addition, the complete coating structure can tightly wrap the microbial agent and effectively reduce the "powdering" phenomenon of fertilizer particles.
[0016] 2. By using modifiers such as surfactants, wetting agents, dispersants and their mixtures to regulate and change the surface tension of the PVA / glycogen system solution, the affinity of the solution to hydrophilic coating materials can be improved, thereby increasing the coating rate of microbial fertilizer particles. Attached Figure Description
[0017] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration: Figure 1 This is an optical photograph (undried) of the coated microbial fertilizer prepared in Example 1. Figure 2 This is an optical photograph (undried) of the coated microbial fertilizer prepared in Comparative Example 1. Figure 3 These are optical photographs of the coated microbial fertilizer prepared in Example 1 before and after being pressed with weights; Figure 4 These are optical photographs of the coated microbial fertilizer prepared in Example 2 before and after being pressed with weights; Figure 5 These are optical photographs of the coated microbial fertilizer prepared in Example 3 before and after being pressed with weights; Figure 6 These are optical photographs of the coated microbial fertilizer prepared in Comparative Example 1 before and after being pressed with weights; Figure 7 These are optical photographs of the coated microbial fertilizer prepared in Comparative Example 2 before and after being pressed with weights. Figure 8 These are optical photographs of the coated microbial fertilizer prepared in Comparative Example 3 before and after being pressed with weights. Figure 9 Optical photographs of the microbial fertilizer in Comparative Example 4 before and after being pressed with weights. Figure 10 These are optical photographs of the microbial fertilizer in Comparative Example 5 before and after being pressed by weights. Figure 11 These are optical photographs of the microbial fertilizer in Comparative Example 6 before and after being pressed with weights. Detailed Implementation
[0018] The technical effects of the coated microbial fertilizer granules and their preparation method of the present invention will be further explained below with reference to specific embodiments. However, the specific implementation methods mentioned in these embodiments are only examples of the technical solutions of the present invention and are not intended to limit the scope of implementation of the present invention. Any improvements or substitutions based on the above principles and on the basis of the present invention should be within the protection scope of the present invention. Example 1
[0019] To prepare a PVA-modifier mixed solution, add PVA (10% by mass), sodium dodecyl sulfate (3% by mass), and disodium methylene dinaphthalene sulfonate (3% by mass) to deionized water. Stir continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA-modifier mixed solution. To prepare a 10% (by mass) soluble starch solution, mix soluble starch with deionized water and stir at 300 rpm for 10 minutes at a constant temperature of 75°C. The starch is fully gelatinized to form a transparent solution. A PVA / starch mixed solution is prepared by mixing the two solutions in a 1:1 ratio and placing them in a 75℃ water bath. The mixture is stirred at 600 rpm for 30 minutes to ensure thorough mixing. The mixed solution is then transferred to an ultrasonic cleaner and ultrasonically treated for 15 minutes to completely remove air bubbles, yielding a clear coating solution for later use. Using a coating machine, the prepared mixed solution is evenly sprayed onto the surface of Harz raspberry microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coating coverage. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Example 2
[0020] To prepare a PVA-modifier mixed solution, add PVA (10% by mass), sodium dodecyl sulfate (3% by mass), and disodium methylene dinaphthalene sulfonate (3% by mass) to deionized water. Stir continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA-modifier mixed solution. To prepare a 10% (by mass) soluble starch solution, mix soluble starch with deionized water and stir at 300 rpm for 10 minutes at a constant temperature of 75°C. The starch is fully gelatinized to form a transparent solution. A PVA / starch mixed solution is prepared by mixing the two solutions in a 1:1 ratio and placing them in a 75℃ water bath. The mixture is stirred at 600 rpm for 30 minutes to ensure thorough mixing. The mixed solution is then transferred to an ultrasonic cleaner and ultrasonically treated for 15 minutes to completely remove air bubbles, yielding a clear coating solution for later use. Using a coating machine, the prepared mixed solution is evenly sprayed onto the surface of Penicillium baicale microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Example 3
[0021] To prepare a PVA-modifier mixed solution, add PVA (10% by mass), sodium dodecyl sulfate (3% by mass), and disodium methylene dinaphthalene sulfonate (3% by mass) to deionized water. Stir continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA-modifier mixed solution. To prepare a 10% (w / w) soluble starch solution, mix soluble starch with deionized water and stir at 300 rpm for 10 minutes at a constant temperature of 75°C. A process is performed to fully gelatinize the starch, forming a transparent solution. A PVA / starch mixed solution is prepared by mixing the two solutions in a 1:1 ratio and placing them in a 75℃ water bath. The mixture is then stirred at 600 rpm for 30 minutes to ensure thorough mixing. The solution is then transferred to an ultrasonic cleaner and sonicated for 15 minutes to completely remove air bubbles, yielding a clear coating solution. Using a coating machine, the prepared mixed solution is evenly sprayed onto the surface of Aspergillus niger microbial fertilizer granules with bentonite as the carrier, controlling the spraying rate to ensure complete coating coverage. The coated granules are then dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Comparative Example 1
[0022] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Harz raspberry microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Comparative Example 2
[0023] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Penicillium baicale microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Comparative Example 3
[0024] Prepare a 10% PVA solution by adding PVA to deionized water and stirring continuously at 300 rpm for 2 hours at 105°C until completely dissolved to form a transparent and homogeneous PVA solution. Prepare a 10% soluble starch solution by mixing soluble starch with deionized water and stirring at 300 rpm for 10 minutes at a constant temperature of 75°C to fully gelatinize the starch and form a transparent solution. Prepare a PVA / starch mixed solution by mixing the two solutions in a 1:1 ratio and placing them in a 75°C water bath. Stir at 600 rpm for 30 minutes to ensure thorough mixing. Transfer the mixed solution to an ultrasonic cleaner and sonicate for 15 minutes to completely remove air bubbles, obtaining a clear coating solution for later use. Using a coating machine, uniformly spray the prepared mixed solution onto the surface of Aspergillus niger microbial fertilizer granules with bentonite as the "carrier," controlling the spraying rate to ensure complete coverage of the coating layer. The coated granules are dried at a temperature ≤40℃ to obtain the final coated microbial fertilizer product. Comparative Example 4
[0025] Harz raspberry microbial fertilizer granules using bentonite as a "carrier". Comparative Example 5
[0026] Penicillium baicale microbial fertilizer granules using bentonite as a "carrier". Comparative Example 6
[0027] Aspergillus niger microbial fertilizer granules using bentonite as a "carrier".
[0028] like Figure 1 and Figure 2As shown, after introducing a modifier (such as...) Figure 1 The coating effect of PVA / starch on microbial fertilizer granules was significantly improved; however, directly coating microbial fertilizer granules with PVA / starch solution (such as...) Figure 2 Many particles will exhibit incomplete coating. Table 1 compares the coating rates of the coated microbial fertilizer particles prepared in Examples 1-3 with those prepared in Comparative Examples 1-3.
[0029] Table 1
[0030] As shown in Table 1, the coating rate of the coated microbial fertilizer granules prepared by Examples 1-3 of the present invention is better than that of the microbial fertilizer granules prepared by the corresponding comparative examples 1-3.
[0031] Further tests were conducted using 40N weights to assess the compressive strength and looseness of different microbial fertilizer granules. The test results are shown below. Figure 3-11 The microbial fertilizer granules in Comparative Examples 4-6 all exhibited varying degrees of breakage and "powdering" after being pressed by a 40N weight. However, similar to Comparative Examples 1-3, the coated microbial fertilizer granules prepared in Examples 1-3 showed little difference in compressive strength before and after being pressed by a 40N weight, indicating that the compressive strength and "powdering" defects of the microbial fertilizer granules were significantly improved. Furthermore, the introduction of the modifier had little impact on the compressive strength of the coated microbial fertilizer granules.
[0032] The storage time and other indicators of the coated microbial fertilizer granules prepared in the examples and comparative examples were tested. The number of viable bacteria in the microbial fertilizer granules at different storage times was determined according to NY / T2321: the product was stored in a cool, dry, and ventilated warehouse, and then its shelf life was determined. A commonly available compound microbial fertilizer granule was selected as a control group, and the trend of its number of viable bacteria after 120 days of storage was tested. The test results are shown in Table 2.
[0033] Table 2
[0034] As shown in Table 2, the effective viable count retention rate of the coated microbial fertilizer granules prepared by Examples 1-3 of the present invention is better than that of the microbial fertilizer granules in Comparative Examples 4-6, and the viable count retention rate is basically equivalent to that of the microbial fertilizer granules coated only with hydrophilic materials in Comparative Examples 1-3.
[0035] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A coating method for improving the coating rate of microbial fertilizer granules, wherein the prepared coated microbial fertilizer granules have the following characteristics, comprising a microbial granule core layer and a modified film layer coating the outer layer of the fertilizer; The coating process of the microbial fertilizer granules includes the following steps: Prepare a polyvinyl alcohol (PVA)-modifier mixed solution and an aqueous solution that can provide sugar raw materials. Then mix the two, remove air bubbles and set aside. Use a coating machine to evenly spray the mixed solution onto the surface of the microbial fertilizer granules. After drying, the coated microbial fertilizer granules are produced.
2. The coating method for improving the coating rate of microbial fertilizer granules according to claim 1, characterized in that, The core layer of the microbial particles is composed of microbial fertilizer particles such as Trichoderma harzianum, Penicillium barometz, or Aspergillus niger.
3. The microbial particle core layer according to claim 1, characterized in that, The microbial fertilizer granules containing Trichoderma harzianum, Penicillium baicale, or Aspergillus niger can be microbial fertilizer granules obtained by mixing Trichoderma harzianum, Penicillium baicale, or Aspergillus niger with one or more carriers such as bentonite or diatomaceous earth.
4. The PVA-modifier mixed solution according to claim 1, characterized in that, The modifier is a surfactant, wetting agent, dispersant, or mixture thereof that can change the surface tension of water (such as sodium dodecyl sulfate, disodium methylene dinaphthalene sulfonate, sodium dodecylbenzene sulfonate, or fatty acid salts or mixtures thereof).
5. The PVA-modifier mixed solution according to claim 1, characterized in that, The mass ratio of PVA to modifier is 100:(5-50).
6. The PVA-modifier mixed solution according to claim 1, characterized in that, The mass fraction of the solution is 1%-50%.
7. The aqueous solution that can provide sugar raw materials according to claim 1, characterized in that, The hydrophilic material that can provide glycogen can be starch, glucose, maltose or dextrin and mixtures thereof, and the mass fraction of the solution is 1%-50%.
8. The mixed solution of the PVA-modifier solution and the hydrophilic material solution that can provide glycogen according to claim 1, characterized in that, The mass ratio of PVA modifier to hydrophilic material that can provide glycogen is 1:9-9:
1.
9. The coated microbial fertilizer granules according to claim 1, characterized in that, The mass ratio of the microbial fertilizer granule core layer to the modified film layer is 100:(0.5-10).