Multilayer slow-release fertilizer and manufacturing method thereof

Abstract

The invention provides a multi-layer slow-release fertilizer which comprises an outer layer, a middle layer and an inner layer, the whole spherical granular fertilizer is formed, the inner layer comprises a compound fertilizer, the middle layer comprises a plurality of slow-release layers and thin film layers which are mutually stacked, and the outer layer is an elastic water absorption layer; the invention further provides a manufacturing method of the multi-layer slow-release fertilizer. The manufacturing method comprises the steps of raw material processing, inner layer forming, middle layer preparing, outer layer bonding and the like. According to the invention, the inner layer only comprises the compound fertilizer which can be quickly dissolved in water and absorbed by crops, the middle layer is of a structure with a plurality of slow-release layers and thin film layers which are alternately arranged, fertilizer elements in the slow-release layers can be respectively released layer by layer, and even if the slow-release layers absorb too much water, the thin film layers on the inner sides of the slow-release layers can temporarily block the permeation of the water; the situation that the whole structure is damaged due to the fact that the other slow-release layer absorbs water and expands is avoided, only fertilizer in one slow-release layer is released each time, and the fertilizer efficiency is evenly released for a long time under the condition that the whole structure is kept stable.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer production, and in particular to a multi-layer slow-release fertilizer and a manufacturing method thereof. Background Art

[0002] In the development of modern agriculture, in order to pursue high yields, excessive application of chemical fertilizers has become a common phenomenon, among which excessive application of nitrogen fertilizers is particularly serious. Excessive application of nitrogen fertilizers not only increases agricultural production costs, but also easily causes excessive growth of crops in the early stages of growth, damaging the quality of crops; at the same time, large amounts of nitrogen loss cause serious environmental pollution, especially eutrophication of runoff water sources, which has become a long-standing problem plaguing most agricultural areas.

[0003] In order to effectively solve the problem of excessive nitrogen application, the development of slow-release urea has become an effective way. Existing slow-release urea is mainly divided into three categories: 1. Slowing down the release of nitrogen by coating the surface of urea, such as resin-coated urea and sulfur-coated urea; 2. Slowing down the release of nitrogen by changing the physical and chemical properties of urea, such as urea-formaldehyde slow-release fertilizer; 3. Slowing down the release of nitrogen by inhibiting the conversion rate of nitrogen in urea, such as adding nitrification inhibitors and urease inhibitors. Among them, the most widely used and simplest preparation method is slow release by film coating.

[0004] Common resin-coated urea can effectively slow down the release rate of urea in the soil, thereby improving the utilization rate of urea. However, the production cost of resin is too high, up to tens of thousands of yuan per ton; in addition, resin is difficult to be decomposed by microorganisms in the soil and easily becomes a new soil pollutant. With the advancement of technology, new slow-release fertilizers have also emerged, thus solving the problems of traditional resin coating.

[0005] For example, the Chinese utility model patent with publication number CN210103788U proposes a slow-release trace element fertilizer granule, including multiple trace element water-soluble fertilizer granules and ammonium chloride granules, the multiple trace element water-soluble fertilizer granules and the ammonium chloride granules are respectively wrapped with a single trace element layer, and the multiple trace element water-soluble fertilizer granules wrapped with a single trace element layer and the ammonium chloride granules are bonded and granulated into an integrated structure, and the integrated structure is sequentially provided with a medium trace element layer, a slow-release layer, a water-retaining layer, a microbial agent layer and a coating layer. This structure solves the problem of secondary contamination of the traditional outer membrane part by separating the quick-release layer and the slow-release layer, and both contain fertilizer elements.

[0006] However, the above-mentioned slow-release fertilizers and traditional slow-release fertilizers all have a problem, that is, there is only one coating layer on the outermost side as a waterproof structure. When the coating layer is damaged and the fertilizer begins to contact the soil, it will quickly absorb water and swell in a high humidity environment after rain, watering, etc., thereby causing the original multi-layer slow-release structure to break, and moisture will further enter the internal quick-release layer, causing the fertilizer elements to be released quickly, making it difficult to achieve the original technical effect. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a multi-layer slow-release fertilizer and a method for manufacturing the same, which solves the problem in the prior art that the original multi-layer slow-release structure breaks due to water absorption and expansion, resulting in rapid release of fertilizer elements and difficulty in achieving the original technical effect.

[0008] In a first aspect, the present invention provides a multi-layer slow-release fertilizer, comprising an outer layer, an intermediate layer and an inner layer, wherein the inner layer is a spherical particle structure, the intermediate layer is a spherical shell covering the outer portion of the inner layer, and the outer layer is a spherical shell covering the outer portion of the intermediate layer, forming a spherical granular fertilizer as a whole;

[0009] The inner layer includes compound fertilizer;

[0010] The intermediate layer includes a plurality of sustained-release layers and film layers stacked on each other, wherein the sustained-release layer is a spherical shell structure sequentially coated from the inside to the outside, and the film layer covers the inner side and the outer side of each sustained-release layer, and the film layer is a degradable film;

[0011] The outer layer is an elastic water-absorbing layer;

[0012] The sustained-release layer comprises the following components calculated by weight: 60-70 parts of corn starch, 15-27 parts of cassava starch, and 40-50 parts of compound fertilizer.

[0013] Preferably, the compound fertilizer comprises the following components calculated by weight: 200-220 parts of urea, 280-290 parts of monoammonium phosphate, 150-180 parts of potassium nitrate, and 180-200 parts of potassium sulfate.

[0014] Preferably, the compound fertilizer further comprises 30-45 parts of EDTA chelated zinc and 15-25 parts of EDTA chelated manganese, calculated by weight.

[0015] Furthermore, the film layer includes a separation membrane and a water-absorbing membrane stacked inside and outside, wherein the separation membrane is located on the inner side.

[0016] Preferably, the separator is made of PBAT or PLA.

[0017] Preferably, the material of the water-absorbing film is one of hydroxypropyl cellulose, polyvinyl alcohol and polyvinyl pyrrolidone.

[0018] Furthermore, the outer layer includes a binder and fly ash.

[0019] In a second aspect, the present invention further proposes a method for manufacturing a multi-layer slow-release fertilizer, comprising the following steps:

[0020] S1. Raw material processing: urea, monoammonium phosphate, potassium nitrate and potassium sulfate are uniformly mixed in proportion to form compound fertilizer powder, and then the compound fertilizer is mixed with corn starch and cassava starch to form a slow-release layer powder;

[0021] S2, inner layer forming: put compound fertilizer powder into the disc granulator, spray water for lubrication, and make inner layer granules;

[0022] S3, preparation of the middle layer: drying the inner layer granules, and then putting them into the disc granulator again, and then continuously adding the sustained-release layer powder, so as to granulate again with the inner layer granules as the core, and covering the surface of the inner layer granules with the sustained-release layer spherical shell structure to form covered granules; then putting the covered granules into the granule coating machine, and forming a coating on the outside by spraying the heated liquid film layer material to obtain the film layer structure; repeating the above steps according to the number of layers required for the middle layer, to obtain the middle layer granules;

[0023] S5. Outer layer bonding: put the middle layer particles into the disc granulator again, replace the lubricating water with adhesive first, spray the middle layer particles, rotate for a certain period of time, so that the adhesive is wrapped on the outer surface of the middle layer particles, and then add fly ash so that the fly ash is wrapped and bonded to the outside to obtain multi-layer slow-release fertilizer product particles.

[0024] Preferably, the adhesive comprises one of guardo gum, sodium lignin sulfonate, and sodium carboxymethyl cellulose, and has a viscosity of 25 to 45 mm / s.

[0025] Preferably, in step S5, during the disc granulation process, the temperature is maintained at 50-55°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention comprises an outer layer, an intermediate layer and an inner layer, wherein the inner layer only comprises compound fertilizer, which can be quickly dissolved in water and absorbed by crops, and the intermediate layer is a structure of alternating several slow-release layers and thin film layers, which can release fertilizer elements in the slow-release layers layer by layer. Even if the slow-release layer collapses due to excessive water absorption, the thin film layer inside it will temporarily block the penetration of water, thereby preventing the other slow-release layer inside from swelling due to water absorption and causing damage to the overall structure. In this way, only one layer of fertilizer in the slow-release layer is released each time, and the next layer will gradually take effect after the thin film layer is decomposed, thereby maintaining the stability of the overall structure and releasing the fertilizer effect for a long time and evenly;

[0028] 2. The film layer of the middle layer includes a degradable separator and a water-absorbing film, wherein the separator is located on the inner side. Therefore, the outer water-absorbing film can absorb a large amount of water after the outer sustained-release layer is decomposed, so as to maintain the humidity of the separator, so that it can be decomposed faster and avoid the internal sustained-release layer from being difficult to be exposed to the outside. In addition, by controlling the thickness of the separator, the release speed of the sustained-release layer can be adjusted, which is flexibly applicable to crops with different growth cycles;

[0029] 3. The outer layer of the present invention uses an adhesive and fly ash to form an elastic water-absorbing layer. The loose porous structure of the fly ash can quickly absorb moisture in the soil and wrap it around the outside of the middle layer, so that the outermost film layer is in a humid environment, thereby quickly decomposing and releasing fertility; at the same time, the outer layer has excellent elastic properties. Even if the inner slow-release layer expands after absorbing water, it will not cause the outer layer to be damaged or crushed, so it continues to wrap around the outside of the middle layer, providing a highly humid environment, allowing the slow-release layer therein to be effectively released and the film layer to be quickly decomposed, thereby maintaining stable fertility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a cross-sectional schematic diagram of an embodiment of the present invention.

[0031] Figure 2 Schematic diagram of a partial cross-section of a thin film layer in an embodiment of the present invention.

[0032] In the above figures: 1, inner layer; 2, middle layer; 3, outer layer; 21, sustained-release layer; 22, film layer; 221, separator membrane; 222, water-absorbing membrane. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0034] Embodiment 1:

[0035] like Figure 1As shown, an embodiment of the present invention proposes a multi-layer slow-release fertilizer, including an outer layer 3, a middle layer 2 and an inner layer 1, wherein the inner layer 1 is a spherical particle structure, the middle layer 2 is coated on the outside of the inner layer 1 in a spherical shell shape, and the outer layer 3 is coated on the outside of the middle layer 2 in a spherical shell shape, forming a granular fertilizer that is spherical as a whole.

[0036] The inner layer 1 includes compound fertilizer. In this embodiment, the compound fertilizer includes the following components calculated by weight: 200 parts of urea, 280 parts of monoammonium phosphate, 150 parts of potassium nitrate, and 180 parts of potassium sulfate.

[0037] The middle layer 2 includes a plurality of mutually stacked slow-release layers 21 and a film layer 22, wherein the slow-release layer 21 is a spherical shell structure sequentially coated from the inside to the outside, and the film layer 22 covers the inner side and the outer side of each slow-release layer 21, and the film layer 22 is a degradable film. It should be noted that the connection between the middle layer 2 and the inner layer 1 and the outer layer 3 is a film layer 22, which is used to separate moisture. In this embodiment, the slow-release layer 21 includes the following components calculated by weight: 60 parts of corn starch, 15 parts of cassava starch, and 40 parts of compound fertilizer.

[0038] like Figure 2 As shown, the film layer 22 includes a separator 221 and a water-absorbing film 222 which are stacked in three layers, wherein the separator 221 is located on the inner side. The separator 221 is made of PBAT, and the water-absorbing film 222 is made of hydroxypropyl cellulose. The thickness of both is not more than 6um. In this embodiment, a 3um thick film material is used. That is, the separator 221 is made of a degradable plastic material and has a waterproof function. It can be quickly decomposed by microorganisms in a humid environment in the soil; and the water-absorbing film 222 is coated on the outside of the separator 221 to absorb water and maintain the high humidity environment outside the separator 221, so as to promote its rapid decomposition. Because the thickness of the separator 221 is extremely small, it can begin to decompose and rupture within a few days, removing the barrier to water, so that the internal slow-release layer 21 can quickly absorb water and release. At the same time, the water-absorbing film 222 is also a soluble material, which will slowly dissolve after absorbing a large amount of water, and will not hinder the release of the inner layer 1 separator 221 and the slow-release layer 21 in the end.

[0039] The outer layer 3 is an elastic water-absorbing layer, comprising a binder and fly ash. The binder is guar gum with a viscosity of 25 mm / s.

[0040] A method for manufacturing a multi-layer slow-release fertilizer in this embodiment includes the following steps:

[0041] S1. Evenly mix urea, monoammonium phosphate, potassium nitrate and potassium sulfate in proportion to form a compound fertilizer powder, and then mix the compound fertilizer with corn starch and cassava starch to form a slow-release layer powder;

[0042] S2, putting compound fertilizer powder into a disc granulator, spraying water for lubrication, and making inner layer granules;

[0043] S3, drying the inner layer granules, and then putting them into the disc granulator again, and then continuously adding the sustained-release layer powder, so as to granulate again with the inner layer granules as the core, and covering the surface of the inner layer granules with the sustained-release layer spherical shell structure to form covered granules; then putting the covered granules into the granule coating machine, and forming a coating on the outside by spraying the heated liquid film layer material, so as to obtain the film layer 22 structure; repeating the above steps according to the number of layers required for the intermediate layer 2, to obtain the intermediate layer granules;

[0044] S5. Put the middle layer particles into the disc granulator again, maintain the temperature at 50°C, replace the lubricating water with an adhesive, spray the middle layer particles, rotate for a certain period of time, so that the adhesive is wrapped on the outer surface of the middle layer particles, and then add fly ash so that the fly ash is wrapped and bonded to the outside to obtain multi-layer slow-release fertilizer product particles.

[0045] Embodiment 2:

[0046] This embodiment proposes a multi-layer slow-release fertilizer, including an outer layer 3, a middle layer 2 and an inner layer 1, wherein the inner layer 1 is a spherical particle structure, the middle layer 2 is coated on the outside of the inner layer 1 in a spherical shell shape, and the outer layer 3 is coated on the outside of the middle layer 2 in a spherical shell shape, forming a granular fertilizer that is spherical as a whole.

[0047] The inner layer 1 includes compound fertilizer. In this embodiment, the compound fertilizer includes the following components calculated by weight: 210 parts of urea, 285 parts of monoammonium phosphate, 165 parts of potassium nitrate, and 190 parts of potassium sulfate. It also includes 30 parts of EDTA chelated zinc and 15 parts of EDTA chelated manganese.

[0048] The middle layer 2 includes a plurality of mutually stacked slow-release layers 21 and a film layer 22, wherein the slow-release layer 21 is a spherical shell structure sequentially coated from the inside to the outside, and the film layer 22 covers the inner and outer sides of each slow-release layer 21, and the film layer 22 is a degradable film. In this embodiment, the slow-release layer 21 includes the following components calculated by weight: 65 parts of corn starch, 21 parts of cassava starch, and 45 parts of compound fertilizer. The film layer 22 includes a separator 221 and a water-absorbing film 222, which are stacked in three layers, and the separator 221 is located on the inside. The material of the separator 221 is PLA. The material of the water-absorbing film 222 is polyvinyl alcohol.

[0049] The outer layer 3 is an elastic water-absorbing layer, comprising a binder and fly ash. The binder is sodium lignin sulfonate with a viscosity of 35 mm / s.

[0050] A method for manufacturing a multi-layer slow-release fertilizer in this embodiment includes the following steps:

[0051] S1. Evenly mix urea, monoammonium phosphate, potassium nitrate and potassium sulfate in proportion to form a compound fertilizer powder, and then mix the compound fertilizer with corn starch and cassava starch to form a slow-release layer powder;

[0052] S2, putting compound fertilizer powder into a disc granulator, spraying water for lubrication, and making inner layer granules;

[0053] S3, drying the inner layer granules, and then putting them into the disc granulator again, and then continuously adding the sustained-release layer powder, so as to granulate again with the inner layer granules as the core, and covering the surface of the inner layer granules with the sustained-release layer spherical shell structure to form covered granules; then putting the covered granules into the granule coating machine, and forming a coating on the outside by spraying the heated liquid film layer material, so as to obtain the film layer 22 structure; repeating the above steps according to the number of layers required for the intermediate layer 2, to obtain the intermediate layer granules;

[0054] S5. Put the middle layer particles into the disc granulator again, maintain the temperature at 53°C, replace the lubricating water with an adhesive, spray the middle layer particles, rotate for a certain period of time, so that the adhesive is wrapped on the outer surface of the middle layer particles, and then add fly ash so that the fly ash is wrapped and bonded to the outside to obtain multi-layer slow-release fertilizer product particles.

[0055] Embodiment 3:

[0056] This embodiment proposes a multi-layer slow-release fertilizer, including an outer layer 3, a middle layer 2 and an inner layer 1, wherein the inner layer 1 is a spherical particle structure, the middle layer 2 is coated on the outside of the inner layer 1 in a spherical shell shape, and the outer layer 3 is coated on the outside of the middle layer 2 in a spherical shell shape, forming a granular fertilizer that is spherical as a whole.

[0057] The inner layer 1 includes compound fertilizer. In this embodiment, the compound fertilizer includes the following components calculated by weight: 220 parts of urea, 290 parts of monoammonium phosphate, 180 parts of potassium nitrate, and 200 parts of potassium sulfate. It also includes 45 parts of EDTA chelated zinc and 25 parts of EDTA chelated manganese.

[0058] The middle layer 2 includes a plurality of mutually stacked sustained-release layers 21 and a film layer 22, wherein the sustained-release layer 21 is a spherical shell structure sequentially coated from the inside to the outside, and the film layer 22 covers the inner and outer sides of each sustained-release layer 21, and the film layer 22 is a degradable film. In this embodiment, the sustained-release layer 21 includes the following components calculated by weight: 70 parts of corn starch, 27 parts of cassava starch, and 50 parts of compound fertilizer. The film layer 22 includes a separator 221 and a water-absorbing film 222 stacked in three layers of inner and outer layers, wherein the separator 221 is located on the inner side. The material of the separator 221 is PLA. The material of the water-absorbing film 222 is polyvinyl pyrrolidone.

[0059] The outer layer 3 is an elastic water-absorbing layer, comprising a binder and fly ash. The binder is sodium carboxymethyl cellulose with a viscosity of 45 mm / s.

[0060] A method for manufacturing a multi-layer slow-release fertilizer in this embodiment includes the following steps:

[0061] S1. Evenly mix urea, monoammonium phosphate, potassium nitrate and potassium sulfate in proportion to form a compound fertilizer powder, and then mix the compound fertilizer with corn starch and cassava starch to form a slow-release layer powder;

[0062] S2, putting compound fertilizer powder into a disc granulator, spraying water for lubrication, and making inner layer granules;

[0063] S3, drying the inner layer granules, and then putting them into the disc granulator again, and then continuously adding the sustained-release layer powder, so as to granulate again with the inner layer granules as the core, and covering the surface of the inner layer granules with the sustained-release layer spherical shell structure to form covered granules; then putting the covered granules into the granule coating machine, and forming a coating on the outside by spraying the heated liquid film layer material, so as to obtain the film layer 22 structure; repeating the above steps according to the number of layers required for the intermediate layer 2, to obtain the intermediate layer granules;

[0064] S5. Put the middle layer particles into the disc granulator again, maintain the temperature at 55°C, replace the lubricating water with an adhesive, spray the middle layer particles therein, rotate for a certain period of time, so that the adhesive is wrapped around the outer surface of the middle layer particles, and then add fly ash so that the fly ash is wrapped and bonded to the outside to obtain multi-layer slow-release fertilizer product particles.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A multi-layer slow-release fertilizer, characterized in that: The fertilizer comprises an outer layer, a middle layer and an inner layer, wherein the inner layer is a spherical particle structure, the middle layer is a spherical shell covering the outer part of the inner layer, and the outer layer is a spherical shell covering the outer part of the middle layer, so as to form a spherical granular fertilizer as a whole; The inner layer includes compound fertilizer; The intermediate layer includes a plurality of sustained-release layers and film layers stacked on each other, wherein the sustained-release layer is a spherical shell structure sequentially coated from the inside to the outside, and the film layer covers the inner side and the outer side of each sustained-release layer, and the film layer is a degradable film; The outer layer is an elastic water-absorbing layer; The sustained-release layer comprises the following components calculated by weight: 60-70 parts of corn starch, 15-27 parts of cassava starch, and 40-50 parts of compound fertilizer.

2. A multi-layer slow-release fertilizer as claimed in claim 1, characterized in that: The compound fertilizer comprises the following components calculated by weight: 200-220 parts of urea, 280-290 parts of monoammonium phosphate, 150-180 parts of potassium nitrate and 180-200 parts of potassium sulfate.

3. A multi-layer slow-release fertilizer as claimed in claim 2, characterized in that: The compound fertilizer also includes 30-45 parts of EDTA chelated zinc and 15-25 parts of EDTA chelated manganese calculated by weight.

4. A multi-layer slow-release fertilizer as claimed in claim 1, characterized in that: The film layer comprises a separation film and a water-absorbing film which are stacked inside and outside, wherein the separation film is located on the inner side.

5. A multi-layer slow-release fertilizer as claimed in claim 4, characterized in that: The separation membrane is made of PBAT or PLA.

6. A multi-layer slow-release fertilizer as claimed in claim 4, characterized in that: The material of the water-absorbing film is one of hydroxypropyl cellulose, polyvinyl alcohol and polyvinyl pyrrolidone.

7. A multi-layer slow-release fertilizer as claimed in claim 1, characterized in that: The outer layer includes a binder and fly ash.

8. A method for manufacturing a multi-layer slow-release fertilizer as claimed in claim 1, characterized in that: The steps include: S1. Raw material processing: urea, monoammonium phosphate, potassium nitrate and potassium sulfate are uniformly mixed in proportion to form compound fertilizer powder, and then the compound fertilizer is mixed with corn starch and cassava starch to form a slow-release layer powder; S2, inner layer forming: put compound fertilizer powder into the disc granulator, spray water for lubrication, and make inner layer granules; S3, preparation of the intermediate layer: drying the inner layer granules, and then putting them into the disc granulator again, and then continuously adding the sustained-release layer powder, so as to granulate again with the inner layer granules as the core, and covering the surface of the inner layer granules with the sustained-release layer spherical shell structure to form covered granules; then putting the covered granules into the granule coating machine, and forming a coating on the outside by spraying the heated liquid film layer material to obtain the film layer structure; repeating the above steps according to the number of layers required for the intermediate layer, to obtain the intermediate layer granules; S5. Outer layer bonding: put the middle layer particles into the disc granulator again, replace the lubricating water with adhesive first, spray the middle layer particles, rotate for a certain period of time, so that the adhesive is wrapped on the outer surface of the middle layer particles, and then add fly ash so that the fly ash is wrapped and bonded to the outside to obtain multi-layer slow-release fertilizer product particles.

9. The manufacturing method according to claim 8, characterized in that: The adhesive comprises one of guardo gum, sodium lignin sulfonate and sodium carboxymethyl cellulose, and has a viscosity of 25 to 45 mm / s.

10. The manufacturing method according to claim 8, characterized in that: In step S5, during the disc granulation process, the temperature is maintained at 50-55°C.

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