Long-acting water-retention slow-release coated fertilizer and preparation method thereof

Abstract

The invention relates to the technical field of fertilizers, and discloses a long-acting water-retention slow-release coated fertilizer and a preparation method thereof.The coated fertilizer sequentially comprises inner core particles, an inner-layer coating, a binder and an outer slow-release layer from inside to outside, the inner-layer coating is formed by coating the surface of a urea inner core with an inner-layer coating solution, and the binder is formed by coating the inner-layer coating solution with the outer slow-release layer; the binder is a cross-linked polymer of beta-sodium alginate and polyethylene glycol, the outer slow-release layer is a starch-polyacrylamide grafted product, urea is used as an inner core, and the inner core is subjected to multilayer coating, so that the release speed of the fertilizer can be effectively regulated and controlled, rapid loss of nutrients is avoided, and continuous supply of the nutrients in the whole growth cycle of crops is ensured; the quality of agricultural products is improved. In addition, by using the long-acting water-retention slow-release coated fertilizer, the fertilization frequency and the application amount can be reduced, the production cost can be reduced, the environmental pollution caused by excessive fertilization can be reduced, and the dual goals of cost saving, income increasing and ecological environmental protection are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizers, and in particular to a long-acting water-retaining slow-release coated fertilizer and a preparation method thereof. Background Art

[0002] In the vast world of agricultural production, fertilizers are the "food" for plant growth. The selection and application of fertilizers are directly related to the growth of crops and have a decisive impact on the yield and quality of crops. At present, the types of fertilizers mainly include chemical fertilizers, organic fertilizers and microbial fertilizers. Among them, chemical fertilizers are mainly divided into nitrogen fertilizers, potassium fertilizers and phosphorus fertilizers. Although the concentration of nutrients is high and can meet the needs of rapid growth of crops, this type of fertilizer usually contains only one or several nutrients, which is difficult to meet the needs of plants for multiple nutrients. Moreover, after being applied to the soil, it is easy to be lost with water, causing nutrient waste and environmental pollution. Organic fertilizers contain a variety of nutrients, such as nitrogen, phosphorus, potassium, organic matter, etc., which can meet the nutritional needs of plants in many aspects. However, organic fertilizers decompose slowly and take effect slowly. Compared with chemical fertilizers, the nutrient content of organic fertilizers is relatively low, and a large amount of application is required to achieve the expected effect. Microbial fertilizers can increase the number of beneficial microorganisms in the soil, improve the soil environment, increase soil fertility, and promote the growth and development of plants. However, the fertilizer effect of microbial fertilizers is relatively slow, it takes a long time to play a role, and the application effect is unstable.

[0003] With the development of science and technology, slow-release fertilizer, as a new form of fertilizer, is gradually changing the traditional way of fertilization with its unique advantages and characteristics. Slow-release fertilizer, also known as controlled-release fertilizer or long-acting fertilizer, is a fertilizer that can slowly release nutrients according to a set release rate and release period. It uses physical, chemical or biological methods to encapsulate the nutrients in the fertilizer in special materials to form slightly soluble compounds or particles, thereby controlling the release rate and time of the nutrients. However, the existing slow-release fertilizers have unstable performance and poor slow-release effect, and there are still major problems in practical applications. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a long-acting water-retaining slow-release coated fertilizer and a preparation method thereof.

[0006] (II) Technical solution

[0007] A method for preparing a long-acting water-retaining slow-release coated fertilizer, wherein the coated fertilizer comprises, from the inside to the outside, a core particle, an inner coating, a binder and an outer slow-release layer;

[0008] The inner coating is formed by coating the inner coating solution on the surface of the urea core;

[0009] The binder is a cross-linked polymer of β-sodium alginate and polyethylene glycol;

[0010] The outer sustained-release layer is a starch-polyacrylamide graft product;

[0011] The preparation method comprises the following steps:

[0012] The first step is to place urea granules in a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, dry them, and form core granules;

[0013] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 60-70℃ to form the inner coating.

[0014] The third step is to place the inner core particles coated with the inner layer film in a granulator, spray the binder, and after the binder is evenly coated on the surface of the inner layer film, continue to spray the starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0015] As a further embodiment of the present invention, the preparation method of the inner coating solution is as follows:

[0016] Step 1: add cyclodextrin into water, stir to form a uniform mixture, then continue to add chloroacetic acid and sodium hydroxide into the mixture, after adding, raise the temperature to 60-70°C, keep warm for 2-4 hours, cool down and discharge the material to obtain modified cyclodextrin;

[0017] Step 2: Dissolve the modified cyclodextrin in water to form a uniform mixed solution, then add chitosan to the mixed solution. After adding, raise the temperature to 40-50°C, stir for 6-9 hours, and then discharge the material to obtain the inner coating solution.

[0018] As a further embodiment of the present invention, in step 1, the mass ratio of cyclodextrin to chloroacetic acid is 1:0.1-0.3.

[0019] As a further embodiment of the present invention, in step 2, the mass ratio of the modified cyclodextrin to chitosan is 1:1.

[0020] As a further solution of the present invention, the preparation method of the binder is:

[0021] Add β-sodium alginate and polyethylene glycol into water, stir mechanically to make them uniform, then add phase transfer catalyst, after adding, gradually increase the temperature to 90-100°C, keep stirring for 6-8h, stop heating, cool and discharge the material, and the adhesive can be obtained.

[0022] As a further embodiment of the present invention, the phase transfer catalyst is p-toluenesulfonic acid or trifluoromethanesulfonic acid.

[0023] As a further embodiment of the present invention, the preparation method of the starch-polyacrylamide graft product is as follows:

[0024] Add starch into water, stir and disperse evenly, turn on the heating, control the temperature to 85-95°C, stir and gelatinize for 1-2 hours, then lower the temperature to 60-70°C, then add the initiator, stir for 10-20 minutes, continue to add acrylamide monomer and cross-linking agent, after the addition is completed, keep warm and stir at 70-80°C for 4-8 hours, cool and discharge the material, and the starch-polyacrylamide grafted product can be obtained.

[0025] As a further embodiment of the present invention, the initiator is potassium persulfate or ammonium persulfate.

[0026] As a further embodiment of the present invention, the cross-linking agent is N,N-methylenebisacrylamide.

[0027] A long-acting water-retaining slow-release coated fertilizer is prepared by adopting the above preparation method.

[0028] (III) Beneficial technical effects

[0029] The present invention uses urea as the core and coats the core with multiple layers, which can effectively regulate the release rate of the fertilizer, avoid rapid loss of nutrients, and ensure the continuous supply of nutrients throughout the entire growth cycle of the crop. Moreover, the use of this kind of fertilizer to apply long-acting water-retaining slow-release coated fertilizer can prevent excessive absorption of nitrogen by crops, thereby inhibiting the occurrence of diseases and improving the quality of agricultural products. In addition, the use of this kind of long-acting water-retaining slow-release coated fertilizer can reduce the number and amount of fertilization, reduce production costs, and reduce environmental pollution caused by excessive fertilization, achieving the dual goals of cost saving and increasing revenue and ecological environmental protection.

[0030] The starch-polyacrylamide grafted product is used as the raw material of the outer slow-release layer. While effectively improving the water retention performance of the fertilizer, it can also regulate the slow-release effect of the fertilizer and realize the intelligent release of the fertilizer. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Preparation Example 1

[0033] Preparation of inner coating solution:

[0034] Step 1: add 2 g of cyclodextrin into water, stir to form a uniform mixture, then add 0.5 g of chloroacetic acid and 0.1 g of sodium hydroxide into the mixture. After the addition, raise the temperature to 65°C, keep the temperature for 3 hours, then cool and discharge the mixture to obtain modified cyclodextrin.

[0035] Step 2: Dissolve 1.5 g of modified cyclodextrin in water to form a uniform mixture, then add 1.5 g of chitosan to the mixture. After adding, raise the temperature to 50°C, stir for 8 hours, and then discharge the material to obtain the inner coating solution.

[0036] Preparation Example 2

[0037] Preparation of binder:

[0038] Add 1.2g of sodium β-alginate and 0.5g of polyethylene glycol into water, stir mechanically to make it uniform, then add 0.1g of p-toluenesulfonic acid, after the addition, gradually increase the temperature to 95°C, keep stirring for 8h, stop heating, cool and discharge the material to obtain the adhesive.

[0039] Preparation Example 3

[0040] Preparation of starch-polyacrylamide grafted products:

[0041] Add 1.5g starch into water, stir and disperse evenly, turn on the heating, control the temperature to 90℃, stir and gelatinize for 1h, then lower the temperature to 70℃, add potassium persulfate, stir for 20min, then add 2g acrylamide monomer and 0.2g N,N-methylenebisacrylamide, after the addition is completed, keep warm and stir at 80℃ for 6h, cool and discharge the material to obtain the starch-polyacrylamide grafted product.

[0042] Example 1

[0043] A method for preparing a long-acting water-retaining slow-release coated fertilizer comprises the following steps:

[0044] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0045] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray 0.4g of the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 70℃ to form the inner coating.

[0046] The third step is to place the inner core particles coated with the inner layer in a granulator, spray 0.1g of a binder, and after the binder is evenly coated on the surface of the inner layer, continue to spray 0.5g of the starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0047] Example 2

[0048] A method for preparing a long-acting water-retaining slow-release coated fertilizer comprises the following steps:

[0049] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0050] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray 0.5g of the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 70℃ to form the inner coating.

[0051] The third step is to place the inner core particles coated with the inner layer in a granulator, spray 0.2g of a binder, and after the binder is evenly coated on the surface of the inner layer, continue to spray 0.6g of a starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0052] Example 3

[0053] A method for preparing a long-acting water-retaining slow-release coated fertilizer comprises the following steps:

[0054] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0055] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray 0.8g of the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 70℃ to form the inner coating.

[0056] The third step is to place the inner core particles coated with the inner layer in a granulator, spray 0.1g of a binder, and after the binder is evenly coated on the surface of the inner layer, continue to spray 1g of a starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0057] Example 4

[0058] A method for preparing a long-acting water-retaining slow-release coated fertilizer comprises the following steps:

[0059] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0060] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray 1g of inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 70℃ to form the inner coating.

[0061] The third step is to place the inner core particles coated with the inner coating in a granulator, spray 0.2g of a binder, and after the binder is evenly coated on the surface of the inner coating, continue to spray 1.2g of a starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0062] Example 5

[0063] A method for preparing a long-acting water-retaining slow-release coated fertilizer comprises the following steps:

[0064] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0065] Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray 1.5g of the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 70℃ to form the inner coating.

[0066] The third step is to place the inner core particles coated with the inner layer in a granulator, spray 0.3g of a binder, and after the binder is evenly coated on the surface of the inner layer, continue to spray 1g of a starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

[0067] Comparative Example 1

[0068] A method for preparing a slow-release coated fertilizer comprises the following steps:

[0069] The first step is to put 10g of urea granules into a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle 2g of silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, and dry them to form core granules;

[0070] The second step is to continue to place the core particles in the granulator, control the disc to continue to rotate, and then evenly spray 0.8g of the inner coating solution on the surface of the core particles. After spraying, take it out and dry it at 70℃ to obtain the coated fertilizer.

[0071] Test Case

[0072] a. Referring to the standard GB / T 23348-2009, the release rate of the coated fertilizers in the embodiments and comparative examples was tested;

[0073] b. Water retention performance test: 5 g of the coated fertilizer in the embodiment and the comparative example were weighed and mixed with 1 kg of dry soil passed through a 20-mesh sieve, and the weight was recorded as M. After stirring evenly, a sample was formed. Tap water was then added to the sample to saturate the sample. After 7 days, the weight was weighed and recorded as m. The ratio of m to M was calculated to obtain the soil water holding capacity and evaluate the water retention performance of the fertilizer. The test results are recorded in the following table:

[0074]

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0076] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a long-acting water-retaining slow-release coated fertilizer, characterized in that: The coated fertilizer comprises, from the inside to the outside, a core particle, an inner coating, a binder and an outer slow-release layer; The inner coating is formed by coating the inner coating solution on the surface of the urea core; The binder is a cross-linked polymer of β-sodium alginate and polyethylene glycol; The outer sustained-release layer is a starch-polyacrylamide graft product; The preparation method comprises the following steps: The first step is to place urea granules in a granulator, then spray atomized water on the surface of the urea granules to wet the urea granules, then sprinkle silicon dioxide on the surface of the urea granules, rotate the disc to make the silicon dioxide evenly coat the outside of the urea granules, take them out, dry them, and form core granules; Step 2: Keep the core particles in the granulator, control the disc to rotate continuously, and then spray the inner coating solution evenly on the surface of the core particles. After spraying, take them out and dry them at 60-70℃ to form the inner coating. The third step is to place the inner core particles coated with the inner layer film in a granulator, spray the binder, and after the binder is evenly coated on the surface of the inner layer film, continue to spray the starch-polyacrylamide grafted product, and after it is evenly coated, take it out and dry it completely to obtain the coated fertilizer.

2. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 1, characterized in that: The preparation method of the inner coating solution is as follows: Step 1: add cyclodextrin into water, stir to form a uniform mixture, then continue to add chloroacetic acid and sodium hydroxide into the mixture, after adding, raise the temperature to 60-70°C, keep warm for 2-4 hours, cool down and discharge the material to obtain modified cyclodextrin; Step 2: Dissolve the modified cyclodextrin in water to form a uniform mixed solution, then add chitosan to the mixed solution. After adding, raise the temperature to 40-50°C, stir for 6-9 hours, and then discharge the material to obtain the inner coating solution.

3. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 2, characterized in that: In step 1, the mass ratio of cyclodextrin to chloroacetic acid is 1:0.1-0.

3.

4. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 2, characterized in that: In step 2, the mass ratio of the modified cyclodextrin to chitosan is 1:

1.

5. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 1, characterized in that: The preparation method of the binder is: Add β-sodium alginate and polyethylene glycol into water, stir mechanically to make them uniform, then add phase transfer catalyst, after adding, gradually increase the temperature to 90-100°C, keep stirring for 6-8h, stop heating, cool and discharge the material, and the adhesive can be obtained.

6. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 5, characterized in that: The phase transfer catalyst is p-toluenesulfonic acid or trifluoromethanesulfonic acid.

7. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 1, characterized in that: The preparation method of the starch-polyacrylamide graft product is as follows: Add starch into water, stir and disperse evenly, turn on the heating, control the temperature to 85-95°C, stir and gelatinize for 1-2 hours, then lower the temperature to 60-70°C, then add the initiator, stir for 10-20 minutes, continue to add acrylamide monomer and cross-linking agent, after the addition is completed, keep warm and stir at 70-80°C for 4-8 hours, cool and discharge the material, and the starch-polyacrylamide grafted product can be obtained.

8. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 7, characterized in that: The initiator is potassium persulfate or ammonium persulfate.

9. The method for preparing a long-acting water-retaining slow-release coated fertilizer according to claim 7, characterized in that: The cross-linking agent is N,N-methylenebisacrylamide.

10. A long-acting water-retaining slow-release coated fertilizer, characterized in that: The method is prepared according to claim 1.

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