Coated granular fertilizer and method for producing coated granular fertilizer

Abstract

The present invention pertains to a coated granular fertilizer provided with a granular fertilizer and a coating film that coats the granular fertilizer, the coating film containing a hydrogenated vegetable oil and inorganic fibers, and the inorganic fibers being at least one type selected from the group consisting of wollastonite fibers, titanium oxide fibers, carbon fibers, and halloysite fibers.

Description

Cross-references of related applications

[0001] This application claims priority to Japanese Patent Application Nos. 2023-186146 and 2024-154193, which are incorporated herein by reference. Technical Field

[0002] This invention relates to coated granular fertilizer and a method for manufacturing coated granular fertilizer. Background Technology

[0003] Coated granular fertilizers have the following advantages: they can control the dissolution of fertilizer components and maintain their effectiveness over a long period of time, and can reduce the number of times they need to be dispersed. Coated granular fertilizers containing fertilizer components with a resin-containing film on their surface are known in the past (Patent Document 1).

[0004] In order to prevent the resin used in the aforementioned coating from remaining in the soil after the fertilizer components of the coated granular fertilizer dissolve, a coated granular fertilizer having a coating containing a wax that is degradable in the natural environment such as soil has been developed (Patent Document 2).

[0005] Regarding coated granular fertilizers having a wax-containing coating, in order to prevent the coated granular fertilizers from sticking together and clumping during manufacturing, coated granular fertilizers incorporating mineral fibers have been developed (Patent Document 3).

[0006] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 54-003104 Patent Document 2: Japanese Patent Application Publication No. 2002-293684 Patent Document 3: Japanese Patent Publication No. 47-041813 Summary of the Invention

[0007] The problem that the invention aims to solve The inventors of this application have discovered the following problem: when coated granular fertilizers having a coating containing a decomposable wax have insufficient strength, the coating is damaged and the fertilizer components dissolve prematurely when distributed using a spreader such as a side-deep fertilizer applicator.

[0008] The objective of this invention is to provide a coated granular fertilizer having a coating containing a decomposable wax, and a method thereof for manufacturing the same, which can suppress premature leaching of fertilizer components even when distributed using a spreader such as a side-deep fertilizer applicator.

[0009] Methods for solving problems The inventors of this application discovered that coated granular fertilizers with a membrane containing specific inorganic fibers can suppress premature dissolution of fertilizer components even when distributed using a spreader such as a side-deep fertilizer applicator, thus completing this invention.

[0010] That is, the coated granular fertilizer involved in this invention is as follows.

[0011] (1) A coated granular fertilizer, comprising granular fertilizer and a coating covering the aforementioned granular fertilizer, The aforementioned coating contains hydrogenated vegetable oil and inorganic fibers. The aforementioned inorganic fiber is selected from at least one of the following groups: wollastonite fiber, titanium dioxide fiber, carbon fiber, and halloysite fiber.

[0012] (2) The coated granular fertilizer as described in (1) above, wherein, In the aforementioned membrane, the aforementioned inorganic fibers are dispersed in the aforementioned hydrogenated vegetable oil.

[0013] (3) The coated granular fertilizer as described in (1) or (2) above, wherein, The mass ratio of the aforementioned granular fertilizer to the aforementioned coating is more than 1:0.1 and less than 1:0.3.

[0014] (4) The coated granular fertilizer as described in any one of (1) to (3) above, wherein, The content of the aforementioned inorganic fibers in the aforementioned coating is more than 0.1% by mass and less than 30% by mass.

[0015] (5) The coated granular fertilizer as described in any one of (1) to (4) above, wherein, The aforementioned membrane has a first layer containing the aforementioned hydrogenated vegetable oil and a second layer containing the aforementioned hydrogenated vegetable oil and the aforementioned inorganic fibers.

[0016] (6) The coated granular fertilizer as described in (5) above, wherein, The mass of the hydrogenated vegetable oil in the second layer is less than or equal to the mass of the hydrogenated vegetable oil in the first layer.

[0017] (7) The coated granular fertilizer as described in (5) or (6) above, wherein, In the aforementioned second layer, the content of the aforementioned hydrogenated vegetable oil is 70% to 99% by mass, and the content of the aforementioned inorganic fiber is 1% to 30% by mass.

[0018] (8) The coated granular fertilizer as described in any one of (5) to (7) above, wherein, The aforementioned second layer is positioned on the outside compared to the previously mentioned first layer.

[0019] (9) The coated granular fertilizer as described in any one of (5) to (8) above, wherein, The aforementioned second layer is the outermost layer of the aforementioned film.

[0020] (10) The coated granular fertilizer as described in any one of (1) to (9) above, wherein, The aspect ratio of the aforementioned inorganic fibers is between 5 and 12.

[0021] (11) The coated granular fertilizer as described in any one of (1) to (10) above, wherein, The aforementioned inorganic fibers are the aforementioned carbon fibers, the aforementioned titanium dioxide fibers, or the aforementioned halloysite fibers.

[0022] (12) The coated granular fertilizer as described in any one of (1) to (10) above, wherein, The aforementioned inorganic fiber is the aforementioned wollastonite fiber.

[0023] (13) The coated granular fertilizer as described in (12) above, wherein, The aforementioned wollastonite fibers have a fiber length of 15μm to 200μm.

[0024] (14) The coated granular fertilizer as described in (12) or (13) above, wherein, The aforementioned wollastonite fibers have a particle size of 5μm to 60μm.

[0025] (15) The coated granular fertilizer as described in any one of (1) to (14) above, wherein, The aforementioned hydrogenated vegetable oil is selected from at least one of the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

[0026] (16) The coated granular fertilizer as described in any one of (1) to (15) above, wherein, The melting point of the aforementioned hydrogenated vegetable oil is above 60°C and below 100°C.

[0027] In addition, the method for manufacturing the coated granular fertilizer involved in this invention is as follows.

[0028] (17) A method for manufacturing coated granular fertilizer, the method comprising: The process of adding heated and molten hydrogenated vegetable oil to granular fertilizer; and The step of adding a coating composition containing hydrogenated vegetable oil and inorganic fiber to the aforementioned granular fertilizer. The aforementioned inorganic fiber is selected from at least one of the following groups: wollastonite fiber, titanium dioxide fiber, carbon fiber, and halloysite fiber.

[0029] (18) The method for manufacturing coated granular fertilizer as described in (17) above, wherein, In the aforementioned coated composition, the aforementioned inorganic fibers are dispersed in the aforementioned hydrogenated vegetable oil.

[0030] According to the present invention, a coated granular fertilizer having a coating containing a decomposable wax and a method thereof for manufacturing the same is available. Detailed Implementation

[0031] The coated granular fertilizer according to embodiments of the present invention will be described.

[0032] The coated granular fertilizer involved in this embodiment includes granular fertilizer and a coating film covering the granular fertilizer, wherein the coating film comprises hydrogenated vegetable oil and inorganic fibers.

[0033] The aforementioned granular fertilizer contains fertilizer components and may also contain any additives. The aforementioned granular fertilizer can be manufactured by known methods. For example, the aforementioned granular fertilizer can be obtained by granulating the fertilizer components alone using conventional granulation methods, or by granulating the fertilizer components with the aforementioned additives. Examples of such granulation methods include pelletizing, stirred granulation, extrusion granulation, fluidized bed granulation, rolling granulation, compression granulation, drum granulation, disc granulation, coated granulation, or adsorption granulation. The aforementioned granular fertilizer is preferably spherical, but it can also be cuboid, cylindrical, etc.

[0034] The particle size of the aforementioned granular fertilizer is typically 0.1~15.0 mm. Preferably, the particle size is 1~5 mm. It should be noted that the particle size of the aforementioned granular fertilizer is determined using the sieving method specified in JIS Z8801.

[0035] Examples of fertilizer components mentioned above include nitrogenous fertilizer components, phosphate fertilizer components, potassium fertilizer components, silicate fertilizer components, magnesium fertilizer components, calcium fertilizer components, manganese fertilizer components, boron fertilizer components, and iron-containing fertilizer components. Examples of nitrogenous fertilizer components include urea, ammonium nitrate, magnesium ammonium nitrate, ammonium chloride, ammonium sulfate, ammonium phosphate, sodium nitrate, potassium nitrate, calcium nitrate, calcium cyanamide, urea-formaldehyde (UF), butylidene diurea (CDU), isobutylidene diurea (IBDU), guanidine urea (GU), and soybean meal. Examples of phosphate fertilizer components include superphosphate, triple superphosphate, calcium magnesium phosphate, humic acid phosphate, calcined phosphate, triple-burned phosphate, magnesium superphosphate, sodium polyphosphate, ammonium polyphosphate, potassium metaphosphate, calcium metaphosphate, magnesium ammonium phosphate, sulfur ammonium phosphate, ammonium nitrate phosphate, and chlorinated ammonium phosphate. Examples of potassium-based fertilizer components include potassium chloride, potassium sulfate, sodium potassium sulfate, magnesium potassium sulfate, potassium bicarbonate, and potassium phosphate. Examples of silicate fertilizer components include calcium silicate. Examples of magnesium-based fertilizer components include magnesium sulfate and magnesium chloride. Examples of calcareous fertilizer components include quicklime and hydrated lime. Examples of manganese-based fertilizer components include manganese sulfate, magnesium manganese sulfate, and manganese slag. Examples of boron-based fertilizer components include boric acid and borates. Examples of iron-containing fertilizer components include iron ore slag. The aforementioned granular fertilizer may contain only one of these fertilizer components, or it may contain two or more of them.

[0036] Examples of additives that may be included in the aforementioned granular fertilizers include, for example, anti-floating agents, composition homogenization promoters, effect expression promoters, colorants, and granulation promoters. Examples of anti-floating agents include, for example, andesite powder, peridotite powder, shale powder, sandstone powder, and silica powder. Examples of composition homogenization promoters include, for example, gypsum, andesite powder, shale powder, sandstone powder, bentonite, clay, humic acid, zeolite, sepiolite, lignite, and peat. Examples of effect expression promoters include, for example, ferric oxide, lime nitrate, ferrous sulfate, zinc sulfate, ferric ethylenediaminetetraacetate, copper sulfate, ferric diethylenetriaminepentaacetate, zinc ethylenediaminetetraacetate, ferrous sulfate, calcium ethylenediaminetetraacetate, and molybdenum ethylenediaminetetraacetate. Examples of colorants include, for example, humic acid and carbon black. Examples of granulation promoters include olivine rock powder, clay, silica powder, diatomaceous earth, zeolite, gypsum, starch, molasses, bentonite, lignosulfonic acid, konjac starch, sepiolite, yeast fermentation concentrate, ammonia, kaolinite, sandstone powder, sulfuric acid, phosphoric acid, talc powder, palygorskite, black liquor, andesite powder, carboxymethyl cellulose, corn starch, rice bran, lightly calcined magnesium oxide, and slaked lime.

[0037] The aforementioned coating may also have a first layer containing the aforementioned hydrogenated vegetable oil and a second layer containing the aforementioned hydrogenated vegetable oil and the aforementioned inorganic fibers. The aforementioned second layer may also contain a higher content of the aforementioned inorganic fibers than the aforementioned first layer. When the aforementioned second layer is located on the outer side compared to the aforementioned first layer, the mass of the aforementioned hydrogenated vegetable oil in the aforementioned second layer is preferably less than the mass of the aforementioned hydrogenated vegetable oil in the aforementioned first layer. Thus, the aforementioned second layer, located on the outer side and containing a high content of the aforementioned inorganic fibers, can be thinner than the aforementioned first layer, located on the inner side, and can be in a state of high inorganic fiber density overall. The aforementioned first layer may be stacked on the aforementioned granular fertilizer, and the aforementioned second layer may be stacked on the first layer from the outer side, or the aforementioned second layer may be stacked on the aforementioned granular fertilizer, and the aforementioned first layer may be stacked on the second layer from the outer side. That is, the aforementioned first layer, which has a lower content of the aforementioned inorganic fibers, may be located on the inner side compared to the aforementioned second layer, or it may be located on the outer side compared to the aforementioned second layer.

[0038] In the case where the aforementioned second layer is formed on the outside of the aforementioned first layer, the mass of the aforementioned hydrogenated vegetable oil in the aforementioned first layer located on the inside of the aforementioned film may be greater than or equal to the mass of the aforementioned hydrogenated vegetable oil in the aforementioned second layer located on the outside.

[0039] The aforementioned coating may have two or more of the aforementioned first layers, or it may have two or more of the aforementioned second layers. In this case, the aforementioned coating preferably has the aforementioned first layer and the aforementioned second layer adjacent to each other in the thickness direction. Furthermore, the aforementioned coating may have a layer structure formed by one aforementioned first layer, the aforementioned second layer connected to the first layer from the inside, and the aforementioned second layer connected to the first layer from the outside, or it may have a layer structure formed by one aforementioned second layer, the aforementioned first layer connected to the second layer from the inside, and the first layer connected to the second layer from the outside.

[0040] The first layer primarily functions to control the dissolution of the aforementioned fertilizer components. Conversely, the second layer primarily functions to protect the inner portion, particularly the first layer, from mechanical impact. Furthermore, the second layer, by containing the aforementioned hydrogenated vegetable oil, also functions to control the dissolution of the aforementioned fertilizer components. Through this layered structure, the coated granular fertilizer, with the second layer primarily functioning as a reinforcing layer, can suppress damage during transportation, storage, and dispensing using the aforementioned distributor, thereby inhibiting premature dissolution of the aforementioned fertilizer components. Additionally, the coated granular fertilizer, with the first layer primarily functioning as a dissolution control layer, can supply the aforementioned fertilizer components to the soil within a specified period. Moreover, compared to a coating formed from a single layer containing the aforementioned hydrogenated vegetable oil and the aforementioned inorganic fibers, the coated granular fertilizer inhibits premature dissolution of the aforementioned fertilizer components, thus enabling easy and long-term supply of the aforementioned fertilizer components to the soil.

[0041] The aforementioned coating can also be formed using a coating composition comprising the aforementioned hydrogenated vegetable oil, the aforementioned inorganic fibers, and any additives. When the aforementioned first layer and the aforementioned second layer each comprise the aforementioned hydrogenated vegetable oil and the aforementioned inorganic fibers, each layer can also be formed using a coating composition comprising the aforementioned hydrogenated vegetable oil and the aforementioned inorganic fibers. That is, in each of the aforementioned first layer and the aforementioned second layer, the aforementioned inorganic fibers can be dispersed in the aforementioned hydrogenated vegetable oil. More specifically, the aforementioned first layer and the aforementioned second layer can also be formed using a coating composition comprising the aforementioned hydrogenated vegetable oil, the aforementioned inorganic fibers, and any additives. The aforementioned first layer and the aforementioned second layer formed by such a coating composition are each in a state where at least half of the aforementioned inorganic fibers are dispersed along the circumference of the aforementioned coated granular fertilizer in the length direction of the inorganic fibers. Therefore, it is believed that when the aforementioned second layer is disposed outside the aforementioned first layer, the cracks generated on the surface of the aforementioned film will function in a detour relative to the path toward the center of the coated granular fertilizer, thereby inhibiting the cracks from traveling toward the aforementioned first layer.

[0042] The first layer can be either the innermost or outermost layer of the aforementioned coating. The second layer can be either the innermost or outermost layer of the aforementioned coating. When the second layer is the outermost layer of the aforementioned coating, the coated granular fertilizer exhibits excellent wear resistance.

[0043] The content of the aforementioned hydrogenated vegetable oil in the first layer is preferably 80% by mass or more, more preferably 85% by mass or more, further preferably 90% by mass or more, and even more preferably 95% by mass or more. Alternatively, the content of the aforementioned hydrogenated vegetable oil in the first layer may also be 100% by mass. On the other hand, the content of the aforementioned inorganic fiber in the first layer is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. The first layer may also substantially contain no aforementioned inorganic fiber. A first layer containing a specified amount or more of hydrogenated vegetable oil can fully function as a dissolution control layer.

[0044] The content of the aforementioned inorganic fibers in the second layer is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more. Furthermore, the content of the aforementioned inorganic fibers in the second layer is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less. On the other hand, the content of the aforementioned hydrogenated vegetable oil in the second layer is preferably 65% ​​by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. Additionally, the content of the aforementioned hydrogenated vegetable oil in the second layer may also be 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less. A second layer containing a specified amount or more of inorganic fibers can fully function as a reinforcing layer. Furthermore, by keeping the content of inorganic fibers to a specified amount or less, thickening of the aforementioned coating composition during manufacturing can be suppressed. Therefore, it has the advantages of easily forming a second layer with excellent dispersibility of the aforementioned inorganic fibers and less likelihood of film defects.

[0045] The mass ratio of the first layer to the second layer can be, for example, 1:9 to 9:1. The mass of the first layer is preferably greater than or equal to the mass of the second layer. The mass ratio of the first layer to the second layer is preferably 5:5 to 8:2, and more preferably 6:4 to 8:2.

[0046] The mass ratio of the hydrogenated vegetable oil in the second layer to the hydrogenated vegetable oil in the first layer is preferably 1:0.5 or more, more preferably 1:1 or more, and even more preferably 1:2 or more. This mass ratio is preferably 1:5 or less.

[0047] The mass ratio of the aforementioned granular fertilizer to the aforementioned coating is preferably 1:0.1 or more and 1:0.5 or less, more preferably 1:0.3 or more and 1:0.4 or less, and even more preferably 1:0.3.

[0048] The content of the aforementioned inorganic fibers in the aforementioned coating is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 0.5% by mass or more and 20% by mass or less.

[0049] From an environmental perspective, the aforementioned coating preferably does not contain a non-degradable resin layer. Examples of resins forming the aforementioned non-degradable resin layer include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include olefin resins, diene resins, and polyvinyl chloride. Examples of olefin resins include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, butene-ethylene copolymer, butene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylate copolymer, and ethylene-carbon monoxide copolymer. Examples of diene resins include butadiene copolymer, isoprene polymer, chloroprene polymer, butadiene-styrene copolymer, and styrene-isoprene copolymer. Examples of thermosetting resins include epoxy resins, alkyd resins, phenolic resins, urea resins, melamine resins, and silicone resins.

[0050] Furthermore, from the viewpoint of continuous dissolution control, the aforementioned coating preferably does not contain a biodegradable resin layer. Examples of biodegradable resins include polylactic acid, polyhydroxyalkanoates, polybutylene terephthalate, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, polyaspartic acid, cellulose fatty acid esters, and polybutylene adipate.

[0051] The aforementioned coating preferably does not contain the aforementioned biodegradable resin. The content of the aforementioned biodegradable resin in the aforementioned coating is, for example, 0.5% by mass or less, preferably 0.1% by mass or less. Because of its high water vapor permeability, the aforementioned biodegradable resin is unsuitable as a coating component from the viewpoint of improving the controllability of fertilizer component dissolution. When the aforementioned biodegradable resin is melted by heating, its fluidity is low, and it is prone to solidification during the manufacture of the aforementioned coated granular fertilizer, making it unsuitable as a coating component from a manufacturing perspective. Furthermore, thermoplastic resins in the aforementioned biodegradable resin are difficult to apply to the aforementioned granular fertilizer if they are not soluble in solvents, making them unsuitable as a coating component from a manufacturing perspective. Additionally, resins with low solubility in solvents require the use of highly harmful halogen-based solvents, which is undesirable from an environmental impact perspective. Depending on the type of the aforementioned biodegradable resin, it may decompose only under specific conditions, or decompose almost non-existently in natural environments such as soil and oceans. On the other hand, hydrogenated vegetable oil has the same structure as animal and plant fats and can be decomposed by fat-decomposing bacteria that are widely present in natural environments.

[0052] The thickness of the aforementioned coating is, for example, 50 to 250 μm. The thickness of the aforementioned coating can be measured by observing the cross-section of the aforementioned coated granular fertilizer in BSE mode using a scanning electron microscope (Hitachi High-Tech Corporation, SU-3800). It can be determined by drawing 10 line segments orthogonal to the coating over the aforementioned coated granular fertilizer and averaging their lengths.

[0053] The aforementioned inorganic fiber is selected from at least one of the following groups: wollastonite fiber, titanium dioxide fiber, carbon fiber, and halloysite fiber.

[0054] Wollastonite is a mineral, also known as wollastonite, calcium metasilicate, or calcium silicate, containing calcium silicate represented by CaSiO3 as a silicate. The aforementioned wollastonite fibers are substances from the aforementioned wollastonite that contain needle-like or columnar crystals, possessing physical properties widely used in the fiber industry. Specifically, the aforementioned wollastonite fibers have an aspect ratio of at least 3, preferably 24 or less, more preferably 5 or more and 12 or less. Furthermore, the aforementioned wollastonite fibers preferably have a roundness factor of less than 0.6. In addition, the fiber length of the aforementioned wollastonite fibers is preferably 10 μm or more and 400 μm or less, more preferably 15 μm or more and 200 μm or less, and even more preferably 15 μm or more and 100 μm or less. By making the fiber length 10 μm or more, the aforementioned first layer can function sufficiently as a reinforcing layer. Furthermore, it is believed that by making the fiber length 400 μm or less, the protrusion of the aforementioned wollastonite fibers from the aforementioned first layer can be suppressed, thereby suppressing premature dissolution of fertilizer components caused by such protrusion. It should be noted that these physical properties can be measured using a scanning electron microscope (Hitachi High-Tech Corporation, SU-3800) and images taken in the micron-scale region based on wollastonite fibers. Specifically, wollastonite fibers, serving as the sample, are bonded to the test stage using conductive tape, and platinum sputtering is performed at 20 mA for 120 seconds using an ion sputtering device (Hitachi, Ltd., E-1030) to create the object to be photographed. Then, depending on the sample size, images are taken at magnification of approximately 50 to 3000 times, with approximately 10 to 100 fibers per field of view. Furthermore, image analysis software (MOUNTECH Co., Ltd., Mac-View) is used to measure the fiber length (major axis), minor axis, aspect ratio (major axis / minor axis), and roundness coefficient (4π × area × perimeter) of more than 100 fibers captured in the images, and their average values ​​are calculated. Here, the major axis is defined as the maximum distance between two points on the fiber surface captured in the fiber image. The minor axis is defined as the maximum length of a line segment orthogonal to the major axis. It should be noted that if multiple minor axes exist, their average value is taken as the minor axis.

[0055] Specifically, examples of the aforementioned wollastonite fibers include the KGP series (manufactured by KANSAI MATEC Co., Ltd.) such as KGP-H45, the KAP series (manufactured by KANSAI MATEC Co., Ltd.) such as KAP-150, the KTP series such as KTP-H02, the KSP series such as KSP-N01, the WP series (manufactured by Nippon Talc Co., Ltd.) such as WP200, the WFA series (manufactured by Nippon Talc Co., Ltd.) such as WFA80, the WFB series (manufactured by Nippon Talc Co., Ltd.) such as WFB15, the WFC series (manufactured by Nippon Talc Co., Ltd.) such as WFC5, the NYAD series (manufactured by IMERYS) such as NYAD 1250, and the NYGLOS series (manufactured by IMERYS) such as NYGLOS 12. The aforementioned coating may include only one of the above types, or it may include two or more types.

[0056] The aforementioned titanium dioxide fiber is a titanium dioxide material containing needle-like crystals, with an aspect ratio of 3 or higher. The aspect ratio of the aforementioned titanium dioxide fiber is preferably 21 or less, more preferably 10 or less. Furthermore, the roundness coefficient of the aforementioned titanium dioxide fiber is preferably less than 0.6. The fiber length of the aforementioned titanium dioxide fiber is preferably 1 μm or more and 10 μm or less, but can be 10 μm or more and 400 μm or less, or 15 μm or more and 200 μm or less. It should be noted that these physical properties of the aforementioned titanium dioxide fiber can be measured in the same manner as those of the aforementioned wollastonite fiber.

[0057] The aspect ratio of the aforementioned carbon fiber is preferably 3 or more and 20 or less, more preferably 5 or more and 15 or less. Furthermore, the roundness coefficient of the aforementioned carbon fiber is preferably less than 0.6. The fiber length of the aforementioned carbon fiber is preferably 10 μm or more and 400 μm or less, more preferably 15 μm or more and 200 μm or less. It should be noted that these physical properties of the aforementioned carbon fiber can be measured in the same manner as those of the aforementioned wollastonite fiber.

[0058] The particle size of the aforementioned inorganic fibers is preferably 5 μm to 70 μm. More specifically, the particle size of the aforementioned wollastonite fibers is preferably 5 μm to 60 μm. The particle size of the aforementioned titanium dioxide fibers is preferably 15 μm to 25 μm. The particle size of the aforementioned carbon fibers is preferably 60 μm to 70 μm. It should be noted that these particle sizes refer to the median particle size (D50) on a volume basis, which can be measured using a laser diffraction particle size analyzer (Malvern Analytical, Mastersizer 3000) via a dry method.

[0059] The aforementioned halloysite fiber is a mineral comprising a silica-alumina system mineral represented by Al2Si2O5(OH)4·2H2O. The aforementioned halloysite fiber is a halloysite containing needle-like crystals, and its aspect ratio is preferably 3 or more. The aspect ratio of the aforementioned halloysite fiber is preferably 20 or less, more preferably 15 or less. Furthermore, the roundness coefficient of the aforementioned halloysite fiber is preferably less than 0.6. The fiber length of the aforementioned halloysite fiber is preferably 0.1 μm to 5 μm, and can be 0.1 μm to 400 μm or 0.1 μm to 200 μm. It should be noted that these physical properties of the aforementioned halloysite fiber can be measured in the same manner as those of the aforementioned wollastonite fiber.

[0060] The aforementioned inorganic fiber is preferably the aforementioned wollastonite fiber. Specifically, the aforementioned titanium dioxide fiber and the aforementioned carbon fiber are synthetically produced, while the aforementioned wollastonite fiber is a natural product. It is evident that using the aforementioned wollastonite fiber can suppress energy consumption in the manufacture of the aforementioned coated granular fertilizer, which is preferable from an environmental impact perspective. Furthermore, with the aforementioned titanium dioxide fiber, unevenness easily forms on the surface of the aforementioned coated granular fertilizer; with the aforementioned carbon fiber, the aforementioned coated granular fertilizer becomes black. That is, the aforementioned titanium dioxide fiber and the aforementioned carbon fiber impair the appearance of the aforementioned coated granular fertilizer. On the other hand, the aforementioned wollastonite fiber does not have this problem. Moreover, it is believed that the calcium silicate constituting the aforementioned wollastonite fiber, like fertilizer components, can help promote crop cultivation; therefore, even after the aforementioned coating has completed its function and is placed in soil such as paddy fields, the possibility of it having an adverse effect on crop cultivation is small.

[0061] The aforementioned hydrogenated vegetable oil is obtained by adding hydrogen to vegetable oil containing unsaturated fatty acid triglycerides to saturate the unsaturated bonds of the aforementioned unsaturated fatty acid triglycerides. The aforementioned hydrogenated vegetable oil includes chemically synthesized products with the same chemical structure as the aforementioned hydrogenated oil. Examples of such hydrogenated vegetable oils include, for instance, hydrogenated castor oil, hydrogenated rapeseed oil, hydrogenated soybean oil, hydrogenated palm oil, hydrogenated peanut oil, hydrogenated jojoba oil, hydrogenated cottonseed oil, and hydrogenated coconut oil. The aforementioned coating may contain only one of the aforementioned hydrogenated vegetable oils, or it may contain two or more. Preferably, the hydrogenated vegetable oil is selected from at least one of the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

[0062] The aforementioned hydrogenated vegetable oil exhibits moderate decomposability in fertilization environments such as soil. Specifically, the aforementioned hydrogenated vegetable oil does not decompose immediately in the fertilization environment, allowing the aforementioned coating to exert dissolution control properties, and decomposes at a moderate rate to the extent that residues in the fertilization environment will not be a problem. In other words, the coated granular fertilizer having a coating containing the aforementioned hydrogenated vegetable oil exhibits excellent decomposability and dissolution control properties.

[0063] The aforementioned hydrogenated vegetable oil is solid at 25°C. Preferably, the hydrogenated vegetable oil has a melting point of 60°C to 100°C, and more preferably, a melting point of 80°C to 90°C. Hydrogenated vegetable oils with such melting points can be melted by heating. Therefore, they can be processed in a liquid state without the use of solvents. Furthermore, by using hydrogenated vegetable oils with such melting points, it is possible to prevent the fertilizer components from decomposing due to heat during the manufacture of the aforementioned coated granular fertilizer. Additionally, by including the outermost layer of the aforementioned coating with hydrogenated vegetable oil that has low adhesiveness, it is possible to suppress the cohesion of fertilizers during manufacturing and storage.

[0064] Examples of additives that may be included in the aforementioned coating include, for example, the aforementioned anti-floating agent, the aforementioned colorant, and the antibacterial agent. The content of any additive in the aforementioned coating is, for example, 0.1 to 10% by mass.

[0065] The dissolution rate E1 of the aforementioned fertilizer components after standing in water for 7 days at a concentration of 2.5 g / 100 mL satisfies E1 < 30 (%). Furthermore, when the dissolution rate E2 is set as the dissolution rate of the aforementioned fertilizer components after being rapidly recovered from the aforementioned coated granular fertilizer using a side-deep fertilizer applicator (Yanmar Co., Ltd., YK6D) and similarly standing in water for 7 days, E2 - E1 < 15 (%) is displayed. It should be noted that the dissolution rate can be calculated by measuring the concentration of the aforementioned fertilizer components in water collected after a specified time using a UV-Vis spectrophotometer (Shimadzu Corporation, UV-1900i).

[0066] This coated granular fertilizer, possessing both dissolution control and shock resistance, is suitable for cultivation of rice and other rice crops in paddy fields. The aforementioned coated granular fertilizer can also be dispersed alone in paddy fields (soil). Alternatively, the aforementioned coated granular fertilizer can be formulated into a compound fertilizer and dispersed in paddy fields (soil). That is, the aforementioned compound fertilizer can simultaneously contain the aforementioned coated granular fertilizer and the aforementioned granular fertilizer without the aforementioned coating. Furthermore, the aforementioned coated granular fertilizer can also be dispersed in paddy fields (soil) together with coated granular fertilizer not included therein. According to this compound fertilizer, the aforementioned granular fertilizer, by exposing its fertilizer components, can immediately supply a sufficient amount of fertilizer components to rice crops, and the aforementioned coated granular fertilizer can continuously supply fertilizer components for a specified period.

[0067] The aforementioned coated granular fertilizer can be used for dispersing into the soil using spreaders such as side-deep fertilizer applicators. These spreaders typically include a fertilizer hopper, a release device, and a fertilizer hose with an opening at the front end, configured to supply fertilizer into the hose and air into the opening. With this configuration, the spreader transports the fertilizer toward the opening via free fall and airflow within the hose, dispersing it into the soil and other external environments. During this process, the fertilizer is subjected not only to the impact of passing through the release device but also to impacts caused by collisions between fertilizer particles and against the inner wall of the hose. According to the aforementioned coated granular fertilizer, the coating, which functions as a reinforcing layer, can suppress damage caused by such impacts and inhibit premature dissolution of the fertilizer components.

[0068] Next, the manufacturing method of the aforementioned coated granular fertilizer will be described.

[0069] The aforementioned method for manufacturing coated granular fertilizer includes a coating forming step of forming the aforementioned coating on the surface of the granular fertilizer.

[0070] In the aforementioned coating formation process, granular fertilizer in a rolling state is brought into contact with the aforementioned hydrogenated vegetable oil heated to above its melting point, forming the aforementioned first layer on the granular fertilizer. The aforementioned hydrogenated vegetable oil, further heated to above its melting point, is dispersed in the aforementioned inorganic fibers to prepare a heated coating composition. Granular fertilizer having the aforementioned first layer in a rolling state is brought into contact with the heated coating composition, and the aforementioned second layer is stacked on the surface of the aforementioned first layer. After cooling, the aforementioned coated granular fertilizer is obtained. Thus, in the aforementioned coated granular fertilizer manufactured through the process of contacting the granular fertilizer having the aforementioned first layer after pre-preparing the coating composition, the inorganic fibers are uniformly dispersed in the aforementioned second layer, thereby providing advantages such as preventing the aggregation of inorganic fibers, smoothness of the coating, and excellent strength. It should be noted that after forming the aforementioned second layer on the surface of the aforementioned granular fertilizer, the aforementioned coated granular fertilizer can also be obtained by forming the aforementioned first layer on the surface of the aforementioned second layer. Alternatively, the aforementioned coated granular fertilizer can also be obtained by forming only the aforementioned second layer on the surface of the aforementioned granular fertilizer.

[0071] Prior to the aforementioned film-forming step, a pretreatment step may be included, in which the aforementioned granular fertilizer, which is in a rolling state using a rolling device, is heated with hot air while being in contact with paraffin wax. This treatment improves the rolling properties of the aforementioned granular fertilizer within the rolling device and makes the coating composition easier to adhere to the aforementioned granular fertilizer. Furthermore, after the aforementioned film-forming step, a post-treatment step may be included, in which any additives such as surfactants and anti-caking agents are added to the surface of the aforementioned film. It should be noted that the aforementioned pretreatment step and the aforementioned post-treatment step are not part of the aforementioned film-forming step.

[0072] It should be noted that the coated granular fertilizer and the method for manufacturing the coated granular fertilizer of the present invention are as described above, but the coated granular fertilizer and the method for manufacturing the coated granular fertilizer of the present invention are not limited to the configuration of the above embodiments. Various modifications can be made to the coated granular fertilizer and the method for manufacturing the coated granular fertilizer of the present invention without departing from its spirit.

[0073] For example, as another embodiment of the coated granular fertilizer involved in this invention, the coating of the granular fertilizer may consist of only a single layer comprising hydrogenated vegetable oil and inorganic fibers. In this case, in order for the aforementioned single layer to function as both a reinforcing layer and a dissolution control layer, for example, the content of the aforementioned single layer relative to the aforementioned granular fertilizer may be set to 20% by mass or more, the content of the aforementioned inorganic fibers in the aforementioned single layer may be set to 10% by mass or more and 30% by mass or less, and the content of the aforementioned hydrogenated vegetable oil in the aforementioned single layer may be set to 70% by mass or more and 90% by mass or less.

[0074] In this case, by dispersing the aforementioned inorganic fibers in the aforementioned hydrogenated vegetable oil that has been heated to above the melting point to prepare a coating composition in a heated state, and by contacting the aforementioned granular fertilizer in a rolling state with the coating composition and cooling it, a coated granular fertilizer having a coating film formed by a single layer can be obtained.

[0075] Example The present invention will be described in more detail below with reference to specific embodiments, but the invention is not limited to the embodiments described below. In the examples, unless otherwise stated, "%" means "mass %".

[0076] Granular fertilizer Large-particle urea: Urea (manufactured by China BlueChemical Limited, particle size (D50) approximately 3mm) Hydrogenated vegetable oil Hydrogenated castor oil: fatty acid triglycerides (hydrogenated castor oil manufactured by Ito Oil Co., Ltd., melting point 80~90℃) Hydrogenated rapeseed oil: fatty acid triglycerides ("Extremely hydrogenated rapeseed oil" manufactured by Yokogaki Oil & Fat Industry Co., Ltd., melting point 67°C) Hydrogenated soybean oil: fatty acid triglycerides ("Extremely hydrogenated soybean oil" manufactured by Yokogaki Oil & Fat Industry Co., Ltd., melting point 67°C) [Inorganic Fibers] Wollastonite fiber 1 (manufactured by KANSAI MATEC Co., Ltd., "KGP-H45") Wollastonite fiber 2 (manufactured by KANSAI MATEC Co., Ltd., "KGP-H40") Wollastonite fiber 3 (manufactured by KANSAI MATEC Co., Ltd., "KTP-H02") Wollastonite fiber 4 (manufactured by Nippon Talc Co., Ltd. as "WFB15") Wollastonite fiber 5 (manufactured by KANSAI MATEC Co., Ltd., "KGP-H85") Wollastonite fiber 6 (manufactured by Nippon Talc Co., Ltd. as "WFA80") Wollastonite Fiber 7 (manufactured by KANSAI MATEC Co., Ltd., "KSP-N01") Carbon fiber 1 (DIALEAD K223HM (200μ) manufactured by Mitsubishi Chemical Corporation) Carbon fiber 2 (manufactured by Teijin Corporation, "HT M100 40MU") Titanium oxide fiber 1 (manufactured by Ishihara Sangyo Co., Ltd., "FTL-100") Titanium oxide fiber 2 (manufactured by Ishihara Sangyo Co., Ltd., "FTL-400") Halloysite fiber 1 (FIMATEC LTD., manufactured "HP-M") Halloysite fiber 2 (FIMATEC LTD., manufactured "HP-A") [filler] Fiberglass 1 (manufactured by Central Glass Co., Ltd., "EFDE-50-01") Fiberglass 2 (manufactured by Central Glass Co., Ltd., "EFH150-01") Talc (manufactured by Nippon Talc Co., Ltd. as "Micro-Ace P-2") Calcium carbonate (manufactured by SHIRAISHI CALCIUM KAISHA, LTD. as "Vigot-15") [Petroleum-based waxes] NIPPON SEIRO CO., LTD. manufactures "HNP-51" (hereinafter referred to as Paraffin Wax). Hydrocarbon (S.KATO & CO., "Sasol C80") (hereinafter referred to as FT Wax). [Plant-based wax] S.KATO&CO. manufactures "Purified Carnauba Wax No. 2" (hereinafter referred to as Carnauba Wax). S.KATO&CO. manufactures "Purified Candelilla Wax" (hereinafter referred to as Candelilla Wax). [other] Kao Corporation manufactures "LUNAX S-98" (hereinafter referred to as stearic acid). "NISSAN ELECTOL WEP-5" (hereinafter referred to as fatty acid ester) manufactured by Nippon Oil Co., Ltd. Kao Corporation manufactures "KALCOL 220-80" (hereinafter referred to as betainol). [Example 1] Hydrogenated castor oil (72 parts by weight) was heated and melted at 105°C, and then mixed with wollastonite fiber 1 (18 parts by weight) which had been heated to 105°C to obtain a coating composition in which wollastonite fiber 1 was dispersed in hydrogenated castor oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was added to a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (MORESCO, Moresco White P-350P) (10 parts by weight) was added, and the rolling state was maintained for 5 minutes. Next, hydrogenated castor oil (210 parts by weight) heated to 105°C was added to the above-mentioned large-particle urea with paraffin coating, and the rolling state was maintained for more than 3 minutes under heating conditions to form the first layer. The granular fertilizer with the first layer was kept in a rolling state under heating conditions, and the aforementioned coating composition heated to 105°C was added and the rolling state was maintained under heating conditions until the total amount of hydrogenated castor oil and coating composition added reached 300 parts by weight, thereby forming the second layer. After cooling to near room temperature, coated granular fertilizer was obtained.

[0077] [Example 2] Except for using wollastonite fiber 2 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0078] [Example 3] Except for using wollastonite fiber 4 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0079] [Example 4] Except for using wollastonite fiber 5 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0080] [Example 5] Except for using wollastonite fiber 6 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0081] [Example 6] Except that wollastonite fiber 7 is used instead of wollastonite fiber 1, coated granular fertilizer is obtained using the same method as in Example 1.

[0082] [Example 7] The amount of hydrogenated castor oil used to form the second layer was set to 63 parts by mass, and the amount of wollastonite fiber 1 was set to 27 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0083] [Example 8] The amount of hydrogenated castor oil used to form the second layer was set to 63 parts by mass, and wollastonite fiber 3 was used instead of wollastonite fiber 1, with the amount of wollastonite fiber added set to 27 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0084] [Example 9] The amount of hydrogenated castor oil used to form the second layer was set to 63 parts by mass, and wollastonite fiber 5 was used instead of wollastonite fiber 1, with the amount of wollastonite fiber added set to 27 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0085] [Example 10] The amount of hydrogenated castor oil used to form the second layer was set to 81 parts by mass, and the amount of wollastonite fiber 1 was set to 9 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0086] [Example 11] The amount of hydrogenated castor oil added to form the second layer was set to 81 parts by mass, and wollastonite fiber 5 was used instead of wollastonite fiber 1, with the amount of wollastonite fiber added set to 9 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0087] [Example 12] The amount of hydrogenated castor oil used to form the second layer was set to 87.7 parts by mass, and wollastonite fiber 5 was used instead of wollastonite fiber 1, with the amount of wollastonite fiber added set to 2.3 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0088] [Example 13] The amount of hydrogenated castor oil used to form the second layer was set to 89.1 parts by weight, and wollastonite fiber 5 was used instead of wollastonite fiber 1, with the amount of wollastonite fiber added set to 0.9 parts by weight. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0089] [Example 14] The amount of hydrogenated castor oil used to form the first layer was set to 150 parts by weight, the amount of hydrogenated castor oil used to form the second layer was set to 120 parts by weight, and the amount of wollastonite fiber 1 was set to 30 parts by weight. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0090] [Example 15] The amount of hydrogenated castor oil added to form the first layer was set to 90 parts by mass, the amount of hydrogenated castor oil added to form the second layer was set to 168 parts by mass, and the amount of wollastonite fiber 1 added was set to 42 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0091] [Example 18] The amount of hydrogenated castor oil added to form the first layer was set to 280 parts by mass, the amount of hydrogenated castor oil added to form the second layer was set to 96 parts by mass, and the amount of wollastonite fiber 1 added was set to 24 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 1.

[0092] [Example 16] Hydrogenated castor oil (240 parts by weight) was heated and melted at 105°C and mixed with wollastonite fiber 1 (60 parts by weight) which had been heated to 105°C to obtain a coating composition in which wollastonite fiber 1 was dispersed in hydrogenated castor oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was placed into a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (MORESCO Co., Ltd., Moresco White P-350P) (10 parts by weight) was added, and the rolling state was continued for 5 minutes. Next, the aforementioned coating composition, which had been heated to 105°C, was added to the above-mentioned large-particle urea with paraffin coating in the rolling state, and the rolling state was maintained under heating conditions until the total amount of the added coating composition reached 300 parts by weight, thereby forming a layer. After cooling to near room temperature, coated granular fertilizer with a coating film formed by a single layer containing hydrogenated castor oil and wollastonite fiber 1 was obtained.

[0093] [Example 17] The amount of hydrogenated castor oil added to form the second layer was set to 168 parts by mass, and the amount of wollastonite fiber 1 added was set to 42 parts by mass. Otherwise, the coated granular fertilizer having a coating formed only by a single layer containing hydrogenated castor oil and wollastonite fiber 1 was obtained by the same method as in Example 16.

[0094] [Example 19] Hydrogenated rapeseed oil (72 parts by mass) was heated and melted at 105°C, and then mixed with wollastonite fiber 1 (18 parts by mass) which had been heated to 105°C to obtain a coating composition in which wollastonite fiber 1 was dispersed in hydrogenated rapeseed oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was added to a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 55°C using hot air, and then liquid paraffin (MORESCO, Moresco White P-350P) (10 parts by weight) was added, and the rolling state was maintained for 5 minutes. Next, hydrogenated rapeseed oil (210 parts by weight) heated to 105°C was added to the above-mentioned large-particle urea with paraffin coating, and the rolling state was maintained for more than 3 minutes under heating conditions to form the first layer. The granular fertilizer with the first layer was kept in a rolling state under heating conditions, and the aforementioned coating composition heated to 105°C was added and the rolling state was maintained under heating conditions until the total amount of hydrogenated rapeseed oil and coating composition added reached 300 parts by weight, thereby forming the second layer. After cooling to near room temperature, coated granular fertilizer was obtained.

[0095] [Example 20] Except for the use of hydrogenated soybean oil instead of hydrogenated rapeseed oil, coated granular fertilizer was obtained using the same method as in Example 19.

[0096] [Example 21] Except for using carbon fiber 1 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0097] [Example 22] The amount of hydrogenated castor oil used to form the second layer was set to 63 parts by mass, and the amount of carbon fiber 1 was set to 27 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 21.

[0098] [Example 23] Except for using carbon fiber 2 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0099] [Example 24] Except for using titanium dioxide fiber 1 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0100] [Example 25] Except that titanium dioxide fiber 2 is used instead of wollastonite fiber 1, coated granular fertilizer is obtained using the same method as in Example 1.

[0101] [Example 26] The amount of hydrogenated castor oil used to form the second layer was set to 63 parts by mass, and the amount of titanium dioxide fiber 2 was set to 27 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 25.

[0102] [Example 27] Except for using halloysite fiber 1 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0103] [Example 28] Except for using halloysite fiber 2 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0104] [Example 29] Hydrogenated castor oil (120 parts by weight) was heated and melted at 105°C and mixed with wollastonite fiber 1 (30 parts by weight) which had been heated to 105°C to obtain a coating composition in which wollastonite fiber 1 was dispersed in hydrogenated castor oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was placed in a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (MORESCO Co., Ltd., Moresco White P-350P) (10 parts by weight) was added, and the rolling state was maintained for 5 minutes. Next, the aforementioned coating composition, heated to 105°C, was added to the above-mentioned large-particle urea with paraffin coating in the rolling state, and the rolling state was maintained for more than 3 minutes under heating conditions to form the second layer as the innermost layer. The granular fertilizer with the innermost layer was kept in a rolling state under heating conditions, and hydrogenated castor oil, heated to 105°C, was added and the rolling state was maintained under heating conditions until the total amount of hydrogenated castor oil and coating composition added reached 300 parts by weight, thereby forming the outermost layer. After cooling to near room temperature, coated granular fertilizer was obtained.

[0105] [Example 30] Hydrogenated castor oil (199.5 parts by weight) was melted at 105°C and mixed with wollastonite fibers 1 (10.5 parts by weight) that had been heated to 105°C, to obtain a coating composition 1 in which wollastonite fibers 1 are dispersed in hydrogenated castor oil. Separately, hydrogenated castor oil (72 parts by weight) was melted at 105°C and mixed with wollastonite fibers 1 (18 parts by weight) that had been heated to 105°C, to obtain a coating composition 2 in which wollastonite fibers 1 are dispersed in hydrogenated castor oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was placed into a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (MORESCO Co., Ltd., Moresco White P-350P) (10 parts by weight) was added, and the rolling state was continued for 5 minutes. Next, the aforementioned coating composition 1, heated to 105°C, was added to the above-mentioned large-particle urea coated with paraffin in the rolling state, and the rolling state was maintained for more than 3 minutes under heating conditions to form the innermost layer. The granular fertilizer with the innermost layer was kept in a rolling state under heating conditions, and the aforementioned coating composition 2, heated to 105°C, was added to form the outermost layer. After cooling to near room temperature, coated granular fertilizer was obtained.

[0106] [Example 31] Hydrogenated castor oil (40 parts by weight) was melted at 105°C and mixed with 10 parts by weight of wollastonite fibers 1, which had been heated to 105°C, to obtain a coating composition 1 in which wollastonite fibers 1 are dispersed in hydrogenated castor oil. Separately, hydrogenated castor oil (32 parts by weight) was melted at 105°C and mixed with 8 parts by weight of wollastonite fibers 1, which had been heated to 105°C, to obtain a coating composition 2 in which wollastonite fibers 1 are dispersed in hydrogenated castor oil. Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was added to a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (manufactured by Moresco Co., Ltd., Moresco White) was added. [P-350P] (10 parts by weight), continue rolling for 5 minutes. Next, add the aforementioned coating composition 1, heated to 105°C, to the above-mentioned rolled paraffin-coated granular urea, and maintain rolling under heating conditions for at least 3 minutes to form the innermost second layer. While the granular fertilizer having the innermost second layer is in a rolling state under heating conditions, add hydrogenated castor oil (210 parts by weight), heated to 105°C, and maintain rolling under heating conditions for at least 3 minutes to form the intermediate first layer. While the granular fertilizer having the intermediate first layer is in a rolling state under heating conditions, add the aforementioned coating composition 2, heated to 105°C, to form the outermost second layer. Cool to near room temperature to obtain coated granular fertilizer.

[0107] [Comparative Example 1] Glass fiber 1 was used in the formation of the second layer, with the amount of glass fiber 1 added set to 10.5 parts by weight and the amount of hydrogenated castor oil added set to 199.5 parts by weight. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 16.

[0108] [Comparative Example 2] Except for using glass fiber 1 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0109] [Comparative Example 3] Except for using glass fiber 1 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 14.

[0110] [Comparative Example 4] Except for using glass fiber 2 instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0111] [Comparative Example 5] Except for the use of talc in the formation of the second layer, the coated granular fertilizer was obtained using the same method as in Comparative Example 1.

[0112] [Comparative Example 6] Except for using talc instead of glass fiber 1, coated granular fertilizer was obtained using the same method as in Comparative Example 2.

[0113] [Comparative Example 7] The amount of hydrogenated castor oil added was set to 210 parts by weight, and the amount of talc added was set to 90 parts by weight. Otherwise, coated granular fertilizer was obtained using the same method as in Comparative Example 5.

[0114] [Comparative Example 8] Except for using calcium carbonate instead of wollastonite fiber 1, coated granular fertilizer was obtained using the same method as in Example 1.

[0115] [Comparative Example 9] Glass fiber 1 was used instead of wollastonite fiber 1. The amount of hydrogenated castor oil added to the innermost layer was set to 142.5 parts by mass, and the amount of glass fiber 1 added was set to 7.5 parts by mass. The amount of hydrogenated castor oil added to the outermost layer was set to 120 parts by mass, and the amount of glass fiber 1 added was set to 30 parts by mass. Otherwise, the coated granular fertilizer was obtained using the same method as in Example 30.

[0116] [Comparative Example 10] Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was placed into a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 70°C using hot air, and then liquid paraffin (MORESCO Co., Ltd., Moresco White P-350P) (10 parts by weight) was added, and the rolling state was continued for 5 minutes. Next, hydrogenated castor oil (80 parts by weight) heated to 105°C was continuously added to the above-mentioned rolling large-particle urea containing paraffin, and the rolling state was maintained under heating conditions until the total mass of hydrogenated castor oil added reached 80 parts by weight, thereby forming a layer. After cooling to near room temperature, coated granular fertilizer with a film formed by a layer containing only hydrogenated castor oil was obtained.

[0117] [Comparative Example 11] Except that the amount of hydrogenated castor oil added was set to 100 parts by weight, coated granular fertilizer was obtained using the same method as in Comparative Example 10.

[0118] [Comparative Example 12] Except that the amount of hydrogenated castor oil added was set to 210 parts by weight, coated granular fertilizer was obtained using the same method as in Comparative Example 10.

[0119] [Comparative Example 13] Except that the amount of hydrogenated castor oil added was set to 300 parts by weight, coated granular fertilizer was obtained using the same method as in Comparative Example 10.

[0120] [Comparative Example 14] Granular fertilizer (large-particle urea, particle size (D50) approximately 3 mm, 1000 parts by weight) was placed into a rotating tank and kept in a rolling state. The large-particle urea was heated to approximately 55°C using hot air, and then liquid paraffin (MORESCO Co., Ltd., Moresco White P-350P) (10 parts by weight) was added, and the rolling state was continued for 5 minutes. Next, hydrogenated rapeseed oil (30 parts by weight) heated to 105°C was added to the above-mentioned rolling large-particle urea with paraffin coating, and the rolling state was maintained under heating conditions until the total mass of the added hydrogenated rapeseed oil reached 300 parts by weight, thereby forming a layer. After cooling to near room temperature, coated granular fertilizer with a coating formed by layers containing only each hydrogenated vegetable oil was obtained.

[0121] [Comparative Example 15] Except for the use of hydrogenated soybean oil instead of hydrogenated rapeseed oil, coated granular fertilizer having a coating formed by a layer containing only hydrogenated soybean oil was obtained by using the same method as Comparative Example 14.

[0122] [Evaluation of the soil decomposability of hydrogenated vegetable oils, petroleum-based waxes, etc.] (Evaluation of the sample preparation method) 10g of the evaluation objects, such as hydrogenated vegetable oil and petroleum-based wax shown in Table 1, were placed in a thermostat set to 105°C and molten. The molten evaluation objects were cast onto a glass plate using a film coater (manufactured by allgood Co., Ltd., with a gap of 600μm) and allowed to cool and solidify at room temperature to produce a film with a thickness of approximately 300μm.

[0123] (Evaluation Method) 20g of soil (collected from Kasai City, Hyogo Prefecture) was placed in a 50mL plastic cup. A 2cm square piece, approximately 100mg in size, was cut from the prepared membrane to make a test piece, which was then weighed (M1). The test piece was placed on top of the aforementioned soil, and 20g of soil was added from above. The sample was then gently tapped on the ground approximately 10 times before being packaged. The sample and a cup filled with water for humidification were placed on a tray, and the bag was placed in a plastic bag and gently sealed. The bag was placed in a thermostat set to 28°C. The weight of the cup was measured every half month from the start of the experiment, and water was added using a sprayer after each change was observed. After one month, the test piece was retrieved from the soil, gently washed, and allowed to dry completely at room temperature overnight. The mass of the test piece was measured again (M2), and the mass reduction rate was calculated (W = M2 / M1 × 100 (%)).

[0124] (Evaluation Criteria) A: The quality reduction rate W is 20% or more but less than 40%. B: The quality reduction rate W is 10% or more but less than 20%, or 40% or more but less than 60%. C: The mass reduction rate W is less than 10% or more than 60%. When the rating is A, the soil covered with granular fertilizer as a mulch has good decomposition properties. The results are shown in Table 1.

[0125] [Table 1] [evaluate] <Evaluation of the particle size of inorganic particles> The particle size of wollastonite fiber 1 is defined as the median particle size (D50) obtained in the particle size distribution determination using the measuring device shown below. The measuring device is a dry corresponding laser diffraction particle size analyzer (Mastersizer 3000, Malvern Analytical), and the determination is performed dry.

[0126] The particle size of wollastonite fibers 2-7, carbon fiber 1, carbon fiber 2, titanium dioxide fiber 1, titanium dioxide fiber 2, glass fiber 1, glass fiber 2, talc or calcium carbonate is also defined and determined using the same method.

[0127] <Evaluation of fiber length, aspect ratio, and roundness coefficient of inorganic particles> Images of the micron-scale region of wollastonite fiber 1 were captured using a scanning electron microscope (SU-3800, Hitachi High-Tech Corporation). Wollastonite fiber 1 was bonded to the sample stage using conductive tape, and platinum sputtering was performed at 20 mA for 120 seconds using an ion sputtering device (E-1030, Hitachi, Ltd.). Images were then taken at magnifications of approximately 50 to 30,000 times, with a density of approximately 10 to 100 particles per field of view, depending on the size of the wollastonite fiber 1. Image analysis software (Mac-View, MOUNTECH Co., Ltd.) was used to analyze the captured images of wollastonite fiber 1, determining the fiber length (major diameter), aspect ratio (=major diameter / minor diameter), and roundness coefficient (=4π × area × perimeter). Analysis was performed on samples with a density of 100 or more particles, and the average value was obtained. This average value was defined as the fiber length.

[0128] For wollastonite fibers 2-7, carbon fiber 1, carbon fiber 2, titanium dioxide fiber 1, titanium dioxide fiber 2, halloysite fiber 1, halloysite fiber 2, glass fiber 1, glass fiber 2, talc, or calcium carbonate, the fiber length, aspect ratio, and roundness coefficient are defined and measured using the same method. Here, the major axis is defined as the maximum distance between two points on the fiber surface captured in the fiber image. The minor axis is defined as the maximum length of a line segment orthogonal to the major axis. It should be noted that if multiple maxima exist, their average value is taken as the minor axis.

[0129] [Evaluation Method: Dissolution Control] 2.5g (60-80 granules) of the prepared coated granular fertilizer was placed in a sample bottle, and 100mL of water was added. The bottle was then allowed to stand at 25℃. Every 7 days, 0.6mL of water was collected from the sample bottle, and the urea concentration was determined using a UV-Vis spectrophotometer (UV-1900i, manufactured by Shimadzu Corporation). Based on the measured urea concentration, the urea dissolution rate E1 (%) from the coated granular fertilizer was calculated. The results are shown in Tables 2-8.

[0130] (Evaluation Criteria) A: Dissolution rate E1 is less than 10%. B: Dissolution rate E1 is 10% or higher and less than 30%. C: Dissolution rate E1 is above 30%. If the rating is A or B, it can be considered as having good dissolution control.

[0131] [Evaluation Method: Impact Resistance] A 2 kg sample, obtained by mixing compound fertilizer (TAMA KASEI S) and the prepared coated granular fertilizer at a 4:1 ratio, was distributed using a side-deep fertilizer applicator (Yanmar Co., Ltd., YK6D). The urea dissolution rate E2 (%) of the distributed coated granular fertilizer was determined using the same method as described above, and the results were evaluated based on the value of E2-E1. The results are shown in Tables 2-8.

[0132] (Evaluation Criteria) A: E2 - E1 is less than 5% B: E2-E1 is above 5% and less than 15%. C: E2-E1 is above 15% If the rating is A or B, it can be considered as having good impact resistance.

[0133] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6] [Table 7] [Table 8]

Claims

1. A coated granular fertilizer, comprising granular fertilizer and a coating covering the granular fertilizer, The coating comprises hydrogenated vegetable oil and inorganic fibers. The inorganic fiber is selected from at least one of the following groups: wollastonite fiber, titanium dioxide fiber, carbon fiber, and halloysite fiber.

2. The coated granular fertilizer as described in claim 1, wherein, In the membrane, the inorganic fibers are dispersed in the hydrogenated vegetable oil.

3. The coated granular fertilizer as described in claim 1 or 2, wherein, The mass ratio of the granular fertilizer to the film is between 1:0.1 and 1:0.

3.

4. The coated granular fertilizer as described in claim 1 or 2, wherein, The content of the inorganic fibers in the membrane is more than 0.1% by mass and less than 30% by mass.

5. The coated granular fertilizer as described in claim 1 or 2, wherein, The membrane has a first layer comprising the hydrogenated vegetable oil and a second layer comprising the hydrogenated vegetable oil and the inorganic fibers.

6. The coated granular fertilizer as described in claim 5, wherein, The mass of the hydrogenated vegetable oil in the second layer is less than the mass of the hydrogenated vegetable oil in the first layer.

7. The coated granular fertilizer as described in claim 5, wherein, In the second layer, the content of the hydrogenated vegetable oil is more than 70% by mass and less than 99% by mass, and the content of the inorganic fiber is more than 1% by mass and less than 30% by mass.

8. The coated granular fertilizer as described in claim 7, wherein, The second layer is positioned on the outside compared to the first layer.

9. The coated granular fertilizer as described in claim 8, wherein, The second layer is the outermost layer of the film.

10. The coated granular fertilizer as described in claim 1 or 2, wherein, The aspect ratio of the inorganic fiber is between 5 and 12.

11. The coated granular fertilizer as described in claim 1 or 2, wherein, The inorganic fiber is the carbon fiber, the titanium dioxide fiber, or the halloysite fiber.

12. The coated granular fertilizer as described in claim 1, wherein, The inorganic fiber is the wollastonite fiber.

13. The coated granular fertilizer as described in claim 12, wherein, The fiber length of the wollastonite fiber is between 15 μm and 200 μm.

14. The coated granular fertilizer as described in claim 12 or 13, wherein, The particle size of the wollastonite fibers is between 5 μm and 60 μm.

15. The coated granular fertilizer as described in claim 12, wherein, The hydrogenated vegetable oil is selected from at least one of the following groups: hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

16. The coated granular fertilizer as described in claim 15, wherein, The hydrogenated vegetable oil has a melting point between 60°C and 100°C.

17. A method for manufacturing coated granular fertilizer, the method comprising: The process of adding heated and molten hydrogenated vegetable oil to granular fertilizer; and The step of adding a coating composition comprising hydrogenated vegetable oil and inorganic fiber to the granular fertilizer. The inorganic fiber is selected from at least one of the following groups: wollastonite fiber, titanium dioxide fiber, carbon fiber, and halloysite fiber.

18. The method for manufacturing coated granular fertilizer as described in claim 17, wherein, In the coating composition, the inorganic fibers are dispersed in the hydrogenated vegetable oil.

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