Coated granular fertilizer and method for producing coated granular fertilizer

Abstract

This coated granular fertilizer comprises a granular fertilizer and a coating film that coats the granular fertilizer. The coating film contains a hardened vegetable oil and a filler. The filler is one or more types selected from the group consisting of calcium carbonate, mica, clay, wollastonite and bentonite. The filler forms two or more filler layers that overlap in the thickness direction of the coating film.

Description

Coated granular fertilizer and method for producing the coated granular fertilizer CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application Nos. 2024-085866 and 2024-154194, the disclosures of which are incorporated herein by reference.

[0002] The present invention relates to a coated granular fertilizer and a method for producing the coated granular fertilizer.

[0003] Coated granular fertilizers have the advantage of controlling the elution of fertilizer components and maintaining their effectiveness after a single application, thereby reducing the number of times they are applied. For example, the coated granular fertilizer described in Patent Document 1 has a resin coating on the surface of a granular fertilizer containing fertilizer components.

[0004] Furthermore, the coated granular fertilizer described in Patent Document 2 is provided with a coating made of petroleum wax that is degradable in the fertilization environment, such as soil, with the aim of reducing the burden on the environment.

[0005] As a method for producing coated granular fertilizer, for example, as described in Patent Document 3, a method is known in which a coating is formed on the granular fertilizer using a resin dissolved in a solvent such as thinner in order to prevent the coated granular fertilizer from sticking together and forming blocks, and then mineral short fibers are powder-coated before the coating dries and sticks.

[0006] Japanese Patent Publication No. 2003-104787 Japanese Patent Publication No. 2002-293684 Japanese Patent Publication No. 47-041813

[0007] The inventors have discovered that coated granular fertilizers having a coating made of petroleum-based wax have problems in that they are insufficiently degradable in the fertilization environment and also have insufficient impact resistance when used with a spreader such as a side stripe fertilizer applicator, which may result in the leaching of fertilizer components early.

[0008] An object of the present invention is to provide a coated granular fertilizer that is degradable and can suppress the early leaching of fertilizer components after application using a spreader such as a side stripe fertilizer applicator, and a method for producing the same.

[0009] The present inventors discovered that a coated granular fertilizer having a coating with a multilayer structure formed from a hardened plant oil layer and a filler layer is degradable and can suppress the early leaching of fertilizer components even when applied using a spreader such as a side-stripe fertilizer applicator, and thus arrived at the present invention. Specifically, the coated granular fertilizer according to the present invention is as follows: (1) A coated granular fertilizer comprising a granular fertilizer and a coating coating the granular fertilizer, wherein the coating contains hardened plant oil and a filler, the filler being at least one selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite, and the filler forming two or more filler layers overlapping in the thickness direction of the coating. (2) The coated granular fertilizer according to (1) above, wherein the hardened plant oil forms two or more hardened plant oil layers overlapping in the thickness direction of the coating. (3) The coated granular fertilizer according to (2) above, wherein the hardened plant oil layer forms the outermost layer of the coating. (4) The coated granular fertilizer according to any one of (1) to (3) above, wherein the mass ratio of the granular fertilizer to the coating is 1:0.1 or more and 1:0.5 or less. (5) The coated granular fertilizer according to any one of (1) to (4) above, wherein the melting point of the hydrogenated vegetable oil is 60°C or more and 100°C or less.

[0010] The present invention also provides a method for producing a coated granular fertilizer as follows: (6) A method for producing a coated granular fertilizer, comprising: a first step of adding heat-melted hardened vegetable oil to the granular fertilizer in a rolling state; and a second step of adding a filler to the granular fertilizer in a rolling state, wherein the filler is one or more selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite, and wherein the first step and the second step are each repeated two or more times. (7) A method for producing a coated granular fertilizer as set forth in (6) above, wherein the first step and the second step are each repeated two or more times alternately. (8) A method for producing a coated granular fertilizer as set forth in (6) or (7) above, wherein the mass ratio of the granular fertilizer to the total amount of the hardened vegetable oil added in the first step is 1000:100 or more and 1000:280 or less. (9) The method for producing a coated granular fertilizer according to any one of (6) to (8) above, wherein the mass ratio of the granular fertilizer to the total amount of the filler added in the second step is from 1000:20 to 1000:180. (10) The method for producing a coated granular fertilizer according to any one of (6) to (9) above, wherein the mass ratio of the granular fertilizer to the amount of the filler added per second step is from 1000:1 to 1000:50. (11) The method for producing a coated granular fertilizer according to any one of (6) to (10) above, wherein a hardened plant oil layer and a filler layer that coat the granular fertilizer are formed in the first step and the second step, respectively.

[0011] According to the present invention, it is possible to provide a coated granular fertilizer that is degradable and can suppress the early leaching of fertilizer components after application using a spreader such as a side-stripe fertilizer applicator, and a method for producing the same.

[0012] A coated granular fertilizer according to an embodiment of the present invention will be described.

[0013] The coated granular fertilizer according to this embodiment includes a granular fertilizer and a coating that coats the granular fertilizer.

[0014] The granular fertilizer contains fertilizer components. The granular fertilizer may contain any additives. The granular fertilizer can be produced by a known method. For example, the granular fertilizer can be obtained by granulating the fertilizer components themselves alone using a conventional granulation method for granulation of granules, or by mixing the fertilizer components and the additives and granulating the mixture. Examples of such granulation methods include prilling granulation, stirring granulation, extrusion granulation, fluidized bed granulation, rolling granulation, compression granulation, drum granulation, pan granulation, coating granulation, and adsorption granulation. The granular fertilizer is preferably spherical, but may also be rectangular or cylindrical.

[0015] The particle size of the granular fertilizer is usually 0.1 to 15.0 mm. The particle size of the granular fertilizer is preferably 1 to 5 mm. The particle size of the granular fertilizer is measured by the sieving method specified in JIS Z8801.

[0016] Examples of fertilizer components 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, lime nitrogen, formaldehyde-modified urea (UF), acetaldehyde-modified urea (CDU), isobutyraldehyde condensed urea (IBDU), guanylurea (GU), and soybean flour. Examples of phosphate fertilizer components include superphosphate, triple superphosphate, fused phosphate fertilizer, humic acid phosphate fertilizer, calcined phosphate fertilizer, double-burned phosphate, magnesium superphosphate, sodium polyphosphate, ammonium polyphosphate, potassium metaphosphate, calcium metaphosphate, magnesium ammonium phosphate, ammonium sulfate, potassium ammonium phosphate, and ammonium phosphate salt. Examples of the potassium fertilizer component include potassium chloride, potassium sulfate, potassium soda sulfate, potassium magnesium sulfate, potassium bicarbonate, and potassium phosphate. Examples of the silicate fertilizer component include calcium silicate. Examples of the magnesium fertilizer component include magnesium sulfate and magnesium chloride. Examples of the calcium fertilizer component include quicklime and slaked lime. Examples of the manganese fertilizer component include manganese sulfate, manganese magnesium sulfate, and manganese slag. Examples of the boron fertilizer component include boric acid and borates. Examples of the iron-containing fertilizer component include steel slag. The granular fertilizer may contain only one of these fertilizer components, or may contain two or more of them.

[0017] Optional additives that may be contained in the granular fertilizer include, for example, anti-floating agents, composition uniformity promoters, effect development promoters, colorants, and granulation promoters. Examples of the anti-floating agents include andesite powder, peridotite powder, shale powder, sandstone powder, and silica powder. Examples of the composition uniformity promoters include gypsum, andesite powder, shale powder, sandstone powder, humic acid, zeolite, sepiolite, lignite, and peat. Examples of the effect development promoters include ferric oxide, lime nitrate, ferrous sulfate, zinc sulfate, ethylenediaminetetraacetic acid iron, copper sulfate, diethylenetriaminepentaacetic acid iron, ethylenediaminetetraacetic acid zinc, ferric sulfate, ethylenediaminetetraacetic acid calcium, and ethylenediaminetetraacetic acid molybdenum. Examples of the colorants include humic acid and carbon black. Examples of the granulation accelerator include peridotite powder, silica powder, diatomaceous earth, zeolite, gypsum, starch, molasses, lignin sulfonic acid, konjac flying powder, sepiolite, concentrated yeast fermentation waste liquid, ammonia liquid, kaolin, sandstone powder, sulfuric acid, phosphoric acid liquid, attapulgite, pulp waste liquid, andesite powder, carboxymethyl cellulose, corn starch, rice bran, light-burned magnesia, and slaked lime.

[0018] The coating contains hydrogenated vegetable oil and a filler. The filler is one or more selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite. The filler may be one selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite. In the coating, the filler forms two or more filler layers (a calcium carbonate layer, a mica layer, a clay layer, a filler layer, or a bentonite layer) that overlap in the thickness direction. In the coating, the hydrogenated vegetable oil forms two or more hydrogenated vegetable oil layers that overlap in the thickness direction. That is, the coating has a multilayer structure formed from the hydrogenated vegetable oil layer and the filler layer. This improves the impact resistance of the coating and suppresses early leaching of the fertilizer components. More specifically, the two or more filler layers prevent the progression of cracks that may occur in the thickness direction of the coating, thereby suppressing the coating's ability to control the leaching of the fertilizer components. Furthermore, even if a crack occurs, the crack tends to progress along the surface direction of the filler layer, i.e., the crack is less likely to progress inward in the thickness direction toward the granular fertilizer. In the coating, the hardened vegetable oil layer mainly functions to control the elution of the fertilizer components.

[0019] The coating may have a structure in which high-density and low-density regions of the filler are repeated in the thickness direction in a cross section passing through the center of the coated granular fertilizer, with the high-density regions forming the filler layers. In this case, the coating may contain the hardened vegetable oil throughout the thickness direction by having each filler layer contain the hardened vegetable oil. This allows each filler layer to contribute auxiliary to elution control. The coating may have a structure in which high-density and low-density regions of the hardened vegetable oil are repeated in the thickness direction in the cross section, with the high-density regions forming the hardened vegetable oil layers. In the coating, the filler and the hardened vegetable oil may alternately form the filler layers and the hardened vegetable oil layers.

[0020] It is preferable that the hydrogenated vegetable oil forms the innermost layer of the coating. Such a coating is less likely to peel off from the granular fertilizer than when the filler forms the innermost layer. It is also preferable that the hydrogenated vegetable oil forms the outermost layer of the coating. A coated granular fertilizer having such a coating is less likely to have the filler fall off. It is also preferable that the filler forms both the innermost and outermost layers of the coating. It is also preferable that the filler form the innermost layer and the hydrogenated vegetable oil form the outermost layer of the coating. It is also preferable that the hydrogenated vegetable oil form the innermost layer and the filler form the outermost layer of the coating.

[0021] The number of each of the filler layers and the hydrogenated vegetable oil layers in the coating may be, for example, 2 or more, 3 or more, 5 or more, 10 or more, or 15 or more. More specifically, in the case of the calcium carbonate layers, the number of each layer is preferably 2 or more. In the case of the mica layers, the number of each layer is preferably 2 or more. In the case of the clay layers, the number of each layer is preferably 3 or more. In the case of the wollastonite layers, the number of each layer is preferably 2 or more. In the case of the bentonite layers, the number of each layer is preferably 2 or more. On the other hand, the upper limit of the number of each of the filler layers and the hydrogenated vegetable oil layers is not particularly limited, but may be 100 or less, 50 or less, 25 or less, or 20 or less. The number of the hydrogenated vegetable oil layers in the coating may be less than the number of the filler layers, may be equal to the number of the filler layers, or may be greater than the number of the filler layers. The number of the filler layers and the number of the hardened vegetable oil layers can be specified by observing a cross section passing through the center of the coated granular fertilizer using a scanning electron microscope (SU-3800, manufactured by Hitachi High-Technologies Corporation) in BSE mode.

[0022] The mass ratio of the granular fertilizer to the coating is preferably 1:0.1 or more and 1:0.5 or less.

[0023] The content of the filler in the coating is typically 1% by mass or more and 80% by mass or less, and preferably 5% by mass or more and 60% by mass or less. More specifically, in the case of calcium carbonate, the content of calcium carbonate in the coating is preferably 5% by mass or more and 60% by mass or less, and more preferably 30% by mass or more and 50% by mass or less. In the case of mica, the content of mica in the coating is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 30% by mass or less. In the case of clay, the content of clay in the coating is preferably 10% by mass or more and 40% by mass or less. In the case of wollastonite, the content of wollastonite in the coating is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less. In the case of bentonite, the content of bentonite in the coating is preferably 5% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 30% by mass or less. On the other hand, the content of the vegetable hardened oil in the coating is preferably 40% by mass or more. The content of the vegetable hardened oil in the coating may be 95% by mass or less, or may be 90% by mass or less. More specifically, in the case of calcium carbonate, the content of the vegetable hardened oil in the coating is preferably 40% by mass or more and 95% by mass or less, and more preferably 50% by mass or more and 70% by mass or less. In the case of mica, the content of the vegetable hardened oil in the coating is preferably 70% by mass or more and 95% by mass or less. In the case of clay, the content of the vegetable hardened oil in the coating is preferably 60% by mass or more and 90% by mass or less. In the case of wollastonite, the content of the vegetable hardened oil in the coating is preferably 50% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 80% by mass or less. In the case of bentonite, the content of the vegetable hardened oil in the coating is preferably 60% by mass or more and 95% by mass or less, and more preferably 70% by mass or more and 95% by mass or less. In the coating, the content of the filler is preferably smaller than the content of the hydrogenated vegetable oil.

[0024] The mass ratio of the coating to the filler in one filler layer (each filler layer) is preferably 100:0.3 or more and 100:20 or less, more preferably 100:0.3 or more and 100:10 or less. More specifically, in the case of calcium carbonate, the mass ratio here is preferably 100:3 or more and 100:20 or less. In the case of mica, the mass ratio here is preferably 100:0.3 or more and 100:10 or less. In the case of clay, the mass ratio here is preferably 100:3 or more and 100:10 or less. In the case of wollastonite, the mass ratio here is preferably 100:0.3 or more and 100:10 or less, more preferably 100:1 or more and 100:4 or less. In the case of bentonite, the mass ratio here is preferably 100:3 or more and 100:10 or less. The mass of the filler in one filler layer is the average mass calculated by dividing the mass of the filler in the coating by the number of filler layers.

[0025] The mass ratio of the coating to the hydrogenated vegetable oil in one of the hydrogenated vegetable oil layers (each hydrogenated vegetable oil layer) is preferably 100:0.5 or more and 100:40 or less, and more preferably 100:2 or more and 100:40 or less. More specifically, in the case of calcium carbonate, the mass ratio here is preferably 100:2 or more and 100:40 or less. In the case of mica, the mass ratio here is preferably 100:0.5 or more and 100:40 or less. In the case of clay, the mass ratio here is preferably 100:5 or more and 100:25 or less. In the case of wollastonite, the mass ratio here is preferably 100:0.5 or more and 100:40 or less. In the case of bentonite, the mass ratio here is preferably 100:1 or more and 100:40 or less. The mass of the hydrogenated vegetable oil in one hydrogenated vegetable oil layer is an average mass calculated by dividing the mass of the hydrogenated vegetable oil in the coating by the number of hydrogenated vegetable oil layers.

[0026] The mass ratio of the filler mass in the filler layer 1 to the hydrogenated vegetable oil mass in the hydrogenated vegetable oil layer 1 is preferably 1:0.4 or more and 1:30 or less, and more preferably 1:0.4 or more and 1:15 or less. More specifically, in the case of calcium carbonate, the mass ratio here is preferably 1:0.4 or more and 1:15 or less. In the case of mica, the mass ratio here is preferably 1:0.4 or more and 1:15 or less. In the case of clay, the mass ratio here is preferably 1:1 or more and 1:10 or less. In the case of wollastonite, the mass ratio here is preferably 1:1 or more and 1:10 or less. In the case of bentonite, the mass ratio here is preferably 1:1 or more and 1:10 or less. It is believed that a multilayer structure in which each filler layer is separated by a hydrogenated vegetable oil layer of appropriate thickness prevents the progression of cracks that may occur in the thickness direction of the coating, thereby preventing the coating's ability to control the elution of the fertilizer components from being impaired.

[0027] From the viewpoint of environmental impact, it is preferable that the coating does not include a non-degradable resin layer. Examples of resins constituting the non-degradable resin layer include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include olefin-based resins, diene-based resins, and polyvinyl chloride. Examples of olefin-based resins include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, butene-ethylene copolymer, butene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, and ethylene-carbon monoxide copolymer. Examples of diene-based resins include butadiene copolymer, isoprene polymer, chloroprene polymer, butadiene-styrene copolymer, and styrene-isoprene copolymer. Examples of thermosetting resins include epoxy resin, alkyd resin, phenolic resin, urea resin, melamine resin, and silicone resin.

[0028] From the viewpoint of maintaining controlled release, the coating preferably does not include a biodegradable resin layer, such as polylactic acid, polyhydroxyalkanoate, polybutylene adipate terephthalate, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, polyaspartic acid, cellulose fatty acid ester, and polybutylene succinate adipate.

[0029] Preferably, the coating is substantially free of the biodegradable resin. The content of the biodegradable resin in the coating is, for example, 0.5% by mass or less, preferably 0.1% by mass or less. The biodegradable resin has high water vapor permeability, making it unsuitable as a coating component from the viewpoint of improving the control of fertilizer component elution. When melted by heating, the biodegradable resin has low fluidity and is prone to caking during the production of the coated granular fertilizer, making it unsuitable as a coating component from the viewpoint of manufacturability. Furthermore, among the biodegradable resins, thermoplastic resins are difficult to coat on the granular fertilizer unless they are soluble in solvents, making them unsuitable as a coating component from the viewpoint of manufacturability. Furthermore, among the biodegradable resins, those with low solubility in solvents require the use of highly toxic halogen-based solvents, which is undesirable from the viewpoint of environmental impact. Some types of biodegradable resins decompose only under specific environments, and decomposition rarely occurs in natural environments such as soil or the ocean. On the other hand, hydrogenated vegetable oils have a structure similar to that of animal and plant fats and can be decomposed by lipolytic bacteria that are widespread in natural environments.

[0030] The thickness of the coating is, for example, 30 to 500 μm. The thickness of the coating can be measured by observing a cross section passing through the center of the coated granular fertilizer using a scanning electron microscope (SU-3800, manufactured by Hitachi High-Technologies Corporation) in BSE mode. The thickness of the coating can be determined by drawing 10 line segments perpendicular to the coating for the coated granular fertilizer and averaging their lengths.

[0031] The calcium carbonate is CaCO ３The calcium carbonate may be heavy calcium carbonate obtained by crushing and classifying limestone, or light calcium carbonate obtained by a chemical reaction. The calcium carbonate is usually a powder composed of irregular particles. Specific examples of the calcium carbonate include light calcium carbonate (manufactured by New Lime Co., Ltd.), the Hakuenka series (manufactured by Shiraishi Kogyo Co., Ltd.), the CALUSEO series (manufactured by Shiraishi Kogyo Co., Ltd.), the Callite series (manufactured by Shiraishi Kogyo Co., Ltd.), the Whiten series (manufactured by Shiraishi Kogyo Co., Ltd.), the Valkofil series (manufactured by Shiraishi Kogyo Co., Ltd.), Brilliant-1500 (manufactured by Shiraishi Kogyo Co., Ltd.), Viscolite-TH10 (manufactured by Shiraishi Kogyo Co., Ltd.), the Miclone series (manufactured by New Lime Co., Ltd.), the Calflex series (manufactured by New Lime Co., Ltd.), and the Viscal series (manufactured by New Lime Co., Ltd.). The coating may contain only one of these, or may contain two or more of them.

[0032] The mica is also called mica, and is usually obtained by crushing and classifying silicate minerals. Natural mica is preferred as the silicate mineral. Examples of natural mica include muscovite, phlogopite, biotite, and sericite. Muscovite is also called hard mica or muscovite. Phlogopite is also called soft mica or phlogopite. Sericite is also called sericite. The mica is usually a powder composed of plate-like or scale-like particles. However, as shown in the examples below, a coating having only one mica layer has insufficient impact resistance. In contrast, a coating having two or more mica layers exhibits excellent impact resistance. Specific examples of the mica include Suzorite 325-HK (manufactured by Mi Kogyo Co., Ltd.), Suzorite series (manufactured by Mi Kogyo Co., Ltd.), Sericite GMS series (manufactured by Kinseimatec Co., Ltd.), TC mica (manufactured by Kinseimatec Co., Ltd.), Helios series (manufactured by Tobii Kogyo Co., Ltd.), and NK-G / M series (manufactured by Nihon Koken Kogyo Co., Ltd.). The coating may contain only one type of these, or may contain two or more types.

[0033] Examples of the clay include Al ２ O ３ 4SiO ２ ・H ２ Clay obtained by crushing and classifying pyrophyllite (rose stone) represented by O, Al ２ O ３ 2SiO ２ ・2H ２ Examples of clays include clays obtained by crushing and classifying kaolinite represented by the formula (I) O. These clays are usually powders composed of plate-like or scale-like particles. ８ Si １２ O ３０ (OH) ４ (OH ２ ) ４ ・8H ２ The clay may be a clay obtained by crushing and classifying sepiolite represented by O. The clay is usually a powder composed of needle-shaped particles. Specific examples of the clay include Dry Clay (Shokozan Mining Co., Ltd.), Clay S (Shokozan Mining Co., Ltd.), A Clay (Shokozan Mining Co., Ltd.), DL Clay (Shokozan Mining Co., Ltd.), SP Clay (Shokozan Mining Co., Ltd.), B Clay (Shokozan Mining Co., Ltd.), Rhodoseki Clay (Shokozan Mining Co., Ltd.), and Miraclay (registered trademark, Omi Mining Co., Ltd.). The coating may contain only one of these, or may contain two or more of them.

[0034] The wollastonite is a type of mineral, also called wollastonite, wollastonite, or wollastonite, and is a silicate, CaSiO ３The wollastonite contains calcium silicate represented by the formula: The wollastonite is typically a powder composed of needle-like or columnar particles and has physical properties commonly used in the textile field. For example, the wollastonite has an aspect ratio of at least 3, preferably 24 or less, and more preferably 5 or more and 12 or less. The wollastonite also preferably has a circularity coefficient of less than 0.6. Furthermore, the fiber length of the wollastonite 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. These physical properties can be measured based on images of the wollastonite in the micrometer range captured using a scanning electron microscope (SU-3800, manufactured by Hitachi High-Tech Corporation). Specifically, a sample of wollastonite is adhered to a test table using conductive tape, and platinum sputtering is performed for 120 seconds at 20 mA using an ion sputtering device (E-1030, manufactured by Hitachi, Ltd.) to prepare a specimen. Next, the sample is photographed at a magnification of approximately 50 to 3000 times depending on the size, so that there are approximately 10 to 100 fibers per field of view, and a photographed image is obtained. Then, using image analysis particle size distribution software (Mac-View, manufactured by Mountec Co., Ltd.), the fiber length (i.e., the major axis), minor axis, aspect ratio (major axis / minor axis), and circularity coefficient (4π × area × perimeter) of 100 or more fibers photographed in the photographed image are measured, and the average value of these is calculated. Here, the major axis is defined as the maximum value of the distance between two points on the fiber surface photographed in the fiber image. The minor axis is defined as the maximum value of the length of a line segment perpendicular to the major axis. When multiple maximum values ​​exist, the average value of these is taken as the minor axis.Specific examples of the wollastonite include the KGP series such as KGP-H45, the KAP series such as KAP-150 (manufactured by Kansai Matec Co., Ltd.), the KTP series such as KTP-N01, the KSP series such as KSP-N01 (manufactured by Kansai Matec Co., Ltd.), the WP series such as WP200 (manufactured by Nippon Talc Co., Ltd.), the WFA series such as WFA90 (manufactured by Nippon Talc Co., Ltd.), the WFB series such as WFB5 (manufactured by Nippon Talc Co., Ltd.), the WFC series such as WFC5 (manufactured by Nippon Talc Co., Ltd.), the NYAD series such as NYAD 1250 (manufactured by IMERYS), and the NYGLOS series such as NYGLOS 12 (manufactured by IMERYS). The coating may contain only one of these, or may contain two or more of them.

[0035] The bentonite is (Na, Ca) ０．３３ (Al, Mg) ２ Si ４ O １０ (OH) ２ ・nH ２ The bentonite is produced from clay containing O as a main component. The bentonite is usually a powder composed of plate-like particles. Specific examples of the bentonite include Esben (Japan Organic Clay Co., Ltd.) and Fuji (Hojun Co., Ltd.). The coating may contain only one of these, or may contain two or more of them.

[0036] The calcium carbonate preferably has a particle size of 1 μm to 35 μm. The mica preferably has a particle size of 1 μm to 25 μm, more preferably 5 μm to 20 μm. The clay preferably has a particle size of 1 μm to 25 μm, more preferably 5 μm to 20 μm. The wollastonite preferably has a particle size of 1 μm to 60 μm, more preferably 5 μm to 60 μm. The bentonite preferably has a particle size of 1 μm to 25 μm, more preferably 10 μm to 25 μm. The filler layer formed by these fillers is suitable for imparting the above-mentioned impact resistance to the coating. Specifically, in a filler layer formed of fillers with a relatively large particle size of 1 μm or more, linear portions are formed in which a plurality of the fillers are connected in the circumferential direction, which is thought to make it easier to prevent cracks from progressing in the thickness direction of the coating, or in other words, to make it easier for cracks to progress along the surface direction of the filler layer. Note that the particle size of the calcium carbonate, mica, clay, wollastonite, or bentonite refers to the volume-based median diameter (D50), and can be measured by a dry method using a laser diffraction particle size measuring device (Mastersizer 3000, manufactured by Malvern Analytical).

[0037] The hydrogenated vegetable oil is obtained by adding hydrogen to a vegetable oil containing unsaturated fatty acid triglycerides to saturate the unsaturated bonds of the unsaturated fatty acid triglycerides. The hydrogenated vegetable oil also includes chemically synthesized products with the same chemical structure as the hydrogenated vegetable oil. Examples of such hydrogenated vegetable oils include 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 coating may contain only one of the hydrogenated vegetable oils, or two or more of them. The coating preferably uses at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

[0038] The hydrogenated vegetable oil has moderate decomposition properties in a fertilization environment such as soil. Specifically, the hydrogenated vegetable oil can exert elution control properties in the coating without immediately decomposing in the fertilization environment, and can decompose at a moderate rate so that its remaining in the fertilization environment is not a problem. In other words, a coated granular fertilizer having a coating containing the hydrogenated vegetable oil has excellent decomposition properties and elution control properties.

[0039] The hydrogenated vegetable oil is solid at 25°C. The hydrogenated vegetable oil preferably has a melting point of 60°C or higher and 100°C or lower, and more preferably a melting point of 80°C or higher and 90°C or lower. Hydrogenated vegetable oils with such melting points can be melted by heating. Therefore, they can be handled in a liquid state without using a solvent. Furthermore, by using hydrogenated vegetable oils with such melting points, it is possible to prevent the fertilizer components from being decomposed by heat during the production of the coated granular fertilizer. Furthermore, by including a low-viscosity hydrogenated vegetable oil in the outermost layer of the coated granular fertilizer, caking of the fertilizer particles during production and storage is suppressed.

[0040] Examples of optional additives that may be contained in the coating include the anti-floating agent, the colorant, and the antibacterial agent. The content of the optional additives in the coating is, for example, 0.1 to 10% by mass.

[0041] The coated granular fertilizer can have a fertilizer component elution rate E1 that satisfies E1 < 30% when left standing in water for 7 days at a concentration of 2.5 g / 100 mL. Furthermore, when the coated granular fertilizer is applied using a side stripe fertilizer applicator (Yanmar Co., Ltd., YK6D) and then promptly recovered, and then left standing in water for 7 days in the same manner as above, and the elution rate E2 is defined as E2 - E1 < 15%. The coated granular fertilizer can have a fertilizer component elution rate E3 that satisfies E3 < 60% when left standing in water for 42 days at a concentration of 2.5 g / 100 mL. Furthermore, when the coated granular fertilizer is applied using the side stripe fertilizer applicator and then promptly recovered, and then left standing in water for 42 days in the same manner as above, and the elution rate E4 is defined as E4 - E3 < 15%. The elution rate can be calculated by measuring the concentration of the fertilizer components in water collected after a predetermined time has elapsed using an ultraviolet-visible spectrophotometer (UV-1900i, manufactured by Shimadzu Corporation).

[0042] A coated granular fertilizer having such release controllability and impact resistance can be suitably used for cultivating agricultural crops in paddy fields, such as the cultivation of grass crops. The coated granular fertilizer may be sprayed alone onto the paddy field (soil). Alternatively, the coated granular fertilizer may be sprayed onto the paddy field (soil) as a compound fertilizer. That is, the compound fertilizer may contain the granular fertilizer without the coating together with the coated granular fertilizer. Alternatively, the coated granular fertilizer may be sprayed onto the paddy field (soil) together with other coated granular fertilizers that are not included therein. With such a compound fertilizer, the granular fertilizer with exposed fertilizer components can supply sufficient amounts of the fertilizer components to grass crops immediately after spraying, and the coated granular fertilizer can sustain the supply of the fertilizer components for a predetermined period of time.

[0043] The coated granular fertilizer can be used for spreading on soil using a spreader such as a side-stripe fertilizer applicator. These spreaders typically include a fertilizer hopper, a dispensing device, and a fertilizer hose with an opening at its tip, configured to supply fertilizer and air toward the opening into the fertilizer hose. This configuration allows the spreader to transport the fertilizer toward the opening by free fall and air flow within the fertilizer hose, thereby spreading the fertilizer on the soil or other fertilization environments. In this case, the fertilizer is subjected to impacts not only when passing through the dispensing device, but also when the fertilizer collides with other fertilizer particles or with the inner wall of the fertilizer hose. With the coated granular fertilizer, the coating containing two or more filler layers suppresses damage caused by such impacts and prevents early leaching of the fertilizer components.

[0044] Next, a method for producing the coated granular fertilizer will be described.

[0045] The method for producing coated granular fertilizers includes a coating process including a first step of adding the hardened vegetable oil to the granular fertilizer in a rolling state and a second step of adding the filler to the granular fertilizer in a rolling state. In the first step, the hardened vegetable oil can be dissolved in a solvent or heated and melted before being added to the granular fertilizer. The method of adding the heated and melted hardened vegetable oil to the granular fertilizer is preferable from the perspective of environmental impact because it does not use a solvent. In the second step, the filler can be dispersed in a solvent or added in powder form to the granular fertilizer. The method of adding the filler in powder form to the granular fertilizer is preferable from the perspective of environmental impact because it does not use a solvent. When the steps of adding the filler and the hardened vegetable oil to the granular fertilizer separately are employed, a defect-free coating is more easily formed, thereby enabling the production of coated granular fertilizers with excellent elution controllability. In the coating process, the first and second steps are each repeated two or more times. As a result, in the coating step, the hardened vegetable oil layer and two or more filler layers that coat the granular fertilizer are formed.

[0046] The first step may be performed as the initial step of the coating process. That is, the first step may involve adding the hardened vegetable oil to the granular fertilizer, which is the starting material for the coating process. Forming the hardened vegetable oil layer in the innermost layer of the coating in this manner is preferable from the viewpoint of improving the release controllability of the coated granular fertilizer. The amount of hardened vegetable oil added in the first step as the initial step is preferably greater than the amount of hardened vegetable oil added per first step from the second step onwards. The amount of hardened vegetable oil added in the first step as the initial step is preferably greater than the average amount added in the first step from the second step onwards. This allows the density of the filler layer to increase with distance from the center of the coated granular fertilizer, which is considered preferable from the viewpoint of impact resistance. The second step may be performed as the initial step of the coating process. That is, the second step may involve adding the filler to the granular fertilizer, which is the starting material for the coating process. This is considered to prevent the granular fertilizer from caking during production while rolling.

[0047] The amount of the hydrogenated vegetable oil used in the first step as the initial step is preferably greater than the amount of the filler used in each of the second steps. The amount of the hydrogenated vegetable oil used in the first step as the initial step is preferably greater than the average amount added in the second step.

[0048] Furthermore, the mass ratio of the amount of the hydrogenated vegetable oil added in the first step per time from the second time onward to the amount of the filler added in the second step per time is preferably 1:0.4 or more and 1:3 or less, thereby further improving the elution controllability and impact resistance of the coating.

[0049] The first step may be carried out as the final step of the coating step, thereby forming the hardened vegetable oil layer as the outermost layer of the coating.

[0050] It is preferable that any m+1th first step is not carried out consecutively with the mth first step. For example, the step following the mth first step is preferably a step using a component other than the hydrogenated vegetable oil, more specifically, the second step of adding the filler to the intermediate obtained in the mth first step is preferred. Similarly, it is preferable that any n+1th second step is not carried out consecutively with the nth second step. For example, the step following the nth second step is preferably a step using a component other than the filler, more specifically, the first step of adding the hydrogenated vegetable oil to the intermediate obtained in the nth second step is preferred.

[0051] In the coating formation process, the first step and the second step may be alternately repeated. In the coating formation process, the first step and the second step are preferably each performed at least twice, more preferably five or more times, and may be performed ten or more times, or may be performed fifteen or more times. The upper limit of the number of times each of the first step and the second step is performed may be 100 or less, 50 or less, 25 or less, or 20 or less. In the coating formation process, the number of times the first step is performed and the number of times the second step is performed may be the same or different. In the first step following the second step, the hydrogenated vegetable oil may be partially impregnated into the filler layer formed in the second step. This may form adjacent filler layers and hydrogenated vegetable oil layers connected by the hydrogenated vegetable oil.

[0052] The first step of adding the heated and melted hardened vegetable oil to the granular fertilizer in a rolling state can be carried out as the first step of the coating process. The second step of adding the filler can be carried out following the first step. Furthermore, the first step and the second step can be carried out alternately from the second time onwards, and the first step or the second step can be carried out as the final step of the coating process.

[0053] The second step of adding the filler to the granular fertilizer in a rolling state can be carried out as the first step of the coating process. The first step of adding the hydrogenated vegetable oil can be carried out following the first step. Furthermore, the second step and the first step can be carried out alternately from the second time onwards, and the first step or the second step can be carried out as the final step of the coating process.

[0054] In the coating process, the mass ratio of the granular fertilizer to the total amount of hydrogenated vegetable oil (the amount of hydrogenated vegetable oil added in all of the first processes) is typically 1000:50 to 1000:500, and preferably 1000:100 to 1000:280. In addition, in the coating process, the mass ratio of the granular fertilizer to the total amount of filler (the amount of filler added in all of the second processes) is typically 1000:1 to 1000:500, and preferably 1000:20 to 1000:180.

[0055] In the coating process, the mass ratio of the granular fertilizer to the amount of hydrogenated vegetable oil added per one cycle of the first process is typically from 1000:1 to 1000:500, and preferably from 1000:2 to 1000:240. In addition, in the coating process, the mass ratio of the granular fertilizer to the amount of filler added per one cycle of the second process is preferably from 1000:0.1 to 1000:150, and more preferably from 1000:1 to 1000:50.

[0056] The number of times each of the first step and the second step may be, for example, 2 or more, 3 or more, 5 or more, 10 or more, or 15 or more. The upper limit of the number of times each of the first step and the second step is not particularly limited, but may be 100 or less, 50 or less, 25 or less, or 20 or less.

[0057] The method for producing coated granular fertilizer may further include a pre-treatment step, prior to the coating formation step, of contacting the granular fertilizer, which has been rolled using a rolling device, with paraffin while heating it with hot air. This step has the advantage of improving the rolling properties of the granular fertilizer within the rolling device, making it easier for the hydrogenated vegetable oil to adhere to the granular fertilizer. Furthermore, the method for producing coated granular fertilizer may further include a post-treatment step, following the coating formation step, of adding any additive, such as a surfactant or an anti-caking agent, to the surface of the coating. The pre-treatment step and the post-treatment step are not the coating formation step.

[0058] The coated granular fertilizer and the method for producing the coated granular fertilizer according to the present invention are as described above, but the coated granular fertilizer and the method for producing the coated granular fertilizer according to the present invention are not limited to the configurations of the above-described embodiments. The coated granular fertilizer and the method for producing the coated granular fertilizer according to the present invention can be modified in various ways without departing from the gist thereof.

[0059] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0060] [Granular fertilizer] Urea (manufactured by China Blue Chemical Limited, particle size (D50) approximately 3 mm) (hereinafter referred to as large granular urea) [Hydrogenated vegetable oil] "Hydrogenated castor oil" manufactured by Ito Oil Mills, melting point 80-90°C (hereinafter referred to as "Hydrogenated castor oil 1") [Calcium carbonate] "Light calcium carbonate" manufactured by New Lime Co., Ltd. (hereinafter referred to as "Calcium carbonate 1") [Mica] "TC mica" manufactured by Kinsei Matec Co., Ltd. (hereinafter referred to as "Mica 1") "Suzorite 325-HK" manufactured by Tomoe Engineering Co., Ltd. (hereinafter referred to as "Mica 2") "GMS-C" manufactured by Kinsei Matec Co., Ltd. (hereinafter referred to as "Mica 3") [Clay] "SP clay" manufactured by Shokozan Mining Co., Ltd. (hereinafter referred to as "Clay 1") "Clay S" manufactured by Shokozan Mining Co., Ltd. (hereinafter referred to as "Clay 2") "Mira clay" manufactured by Omi Mining Co., Ltd. P-300" (hereinafter referred to as Clay 3) [Wollastonite] "KGP-H45" manufactured by Kansai Matec Co., Ltd. (hereinafter referred to as Wollastonite 1) "KSP-N01" manufactured by Kansai Matec Co., Ltd. (hereinafter referred to as Wollastonite 2) [Bentonite] "Esben" manufactured by Hojun Co., Ltd. (hereinafter referred to as Bentonite 1) "Fuji" manufactured by Hojun Co., Ltd. (hereinafter referred to as Bentonite 2) [Mineral inorganic fibers] "EFDE50-01" manufactured by Central Glass Fiber Co., Ltd. (hereinafter referred to as Glass Fiber 1) "EFH150-01" manufactured by Central Glass Fiber Co., Ltd. (hereinafter referred to as Glass Fiber 2) [Petroleum-based wax] "HNP-51" manufactured by Nippon Seiro Co., Ltd. (hereinafter referred to as Paraffin wax) Hydrocarbon ("Sasol C80" manufactured by Kato Yoko Co., Ltd.) (hereinafter referred to as FT wax) [Plant-based waxes] "Refined Carnauba Wax No. 2" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as carnauba wax) "Refined Candelilla Wax" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as candelilla wax) [Others] "Lunac S-98" manufactured by Kao Chemical Corporation (hereinafter referred to as stearic acid) "Nissan Electol WEP-5" manufactured by NOF Corporation (hereinafter referred to as fatty acid ester) "Kalcol 220-80" manufactured by Kao Chemical Corporation (hereinafter referred to as behenyl alcohol)

[0061] Example 1 Large granular urea (1,000 parts by mass) was placed in a rotating tank and heated to approximately 70°C with hot air. Liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was then added, and the rolling state was continued for 5 minutes. The paraffin-coated large granular urea was then rolled, and castor oil 1 (150 parts by mass) melted at 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes, and a first step (1) was carried out to form a first hardened vegetable oil layer. Next, calcium carbonate 1 (30 parts by mass) was added, and the rolling state was maintained under heated conditions for at least 3 minutes, and a first step (2) was carried out to form a first calcium carbonate layer outside the first hardened vegetable oil layer. Next, a second step (1) was carried out in the same manner as the first step (1) except that the amount of castor oil 1 used was 20 parts by mass, and a second hardened vegetable oil layer was formed outside the first calcium carbonate layer. Next, the second step was carried out a second time in the same manner as the second step of the first time, to form a second calcium carbonate layer on the outside of the second hardened vegetable oil layer. Next, the first step was carried out a third time in the same manner as the first step of the second time, to form a third hardened vegetable oil layer on the outside of the second calcium carbonate layer. Next, the second step was carried out a third time in the same manner as the second step of the first time, to form a third calcium carbonate layer on the outside of the third hardened vegetable oil layer. Next, the first step was carried out a fourth time in the same manner as the first step of the second time, to form a fourth hardened vegetable oil layer on the outside of the third calcium carbonate layer. Thereafter, the fertilizer was cooled to near room temperature, to obtain a coated granular fertilizer having a coating with a multilayer structure formed of four hardened vegetable oil layers and three calcium carbonate layers.

[0062] [Example 2] The first step was repeated ten times and the second step was repeated nine times, and a coated granular fertilizer having a coating with a multilayer structure formed of ten layers of hardened vegetable oil and nine layers of calcium carbonate was obtained in the same manner as in Example 1, except that the amount of castor hydrogenated oil 1 used in the first first step was 30 parts by mass and the amount of calcium carbonate 1 used in each second step was 10 parts by mass.

[0063] [Example 3] A coated granular fertilizer provided with a coating having a multilayer structure formed of three layers of hardened vegetable oil and two layers of calcium carbonate was obtained in the same manner as in Example 1, except that the amount of hardened castor oil 1 used in the first step was 240 parts by mass and the amount of calcium carbonate 1 used in each second step was 10 parts by mass.

[0064] [Example 4] A coated granular fertilizer having a coating with a multilayer structure formed of four layers of hardened vegetable oil and three layers of calcium carbonate was obtained in the same manner as in Example 1, except that the amount of hardened castor oil 1 used in the first step was 210 parts by mass and the amount of calcium carbonate 1 used in each second step was 10 parts by mass.

[0065] Example 5 A coated granular fertilizer having a coating with a multilayer structure formed of 19 layers of hydrogenated vegetable oil and 18 layers of calcium carbonate was obtained in the same manner as in Example 1, except that the first step was repeated 19 times and the second step was repeated 18 times, and the amount of castor hydrogenated oil 1 used in the first step was 12 parts by mass, the amount of castor hydrogenated oil 1 used in the first step from the second step onwards was 6 parts by mass, and the amount of calcium carbonate 1 used in each second step was 10 parts by mass.

[0066] [Example 6] A coated granular fertilizer having a coating film with a multilayer structure formed of four layers of hardened vegetable oil and three layers of calcium carbonate was obtained in the same manner as in Example 1, except that the amount of hardened castor oil 1 used in the first step was 90 parts by mass and the amount of calcium carbonate 1 used in each of the second steps was 50 parts by mass.

[0067] Comparative Example 1 Castor hardened oil 1 (210 parts by mass) was heated and melted at 105°C, and mixed with calcium carbonate 1 (90 parts by mass) heated to 105°C to obtain a coating composition in which calcium carbonate 1 was dispersed in castor hardened oil 1. Large urea granules (1,000 parts by mass) were charged into a rotating drum and tumbling. The large urea granules were heated to about 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling state was continued for 5 minutes. Next, the coating composition heated to 105°C was added to the paraffin-coated large urea granules in the tumbling state, and the tumbling state was maintained under heating conditions for 3 minutes or more, followed by cooling to near room temperature to obtain a coated granular fertilizer.

[0068] Comparative Example 2: The paraffin-coated large urea particles obtained in the same manner as in Comparative Example 1 were rolled, and 190 parts by mass of hardened castor oil 1 heated to 105°C was added. The rolling state was maintained under heating for at least 3 minutes to form a first hardened vegetable oil layer. Next, 90 parts by mass of calcium carbonate 1 was added, and the rolling state was maintained under heating for at least 3 minutes to form a first calcium carbonate layer outside the first hardened vegetable oil layer. Next, a second hardened vegetable oil layer was formed outside the first calcium carbonate layer in the same manner as in the first step, except that 20 parts by mass of hardened castor oil 1 was used. The resulting mixture was then cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating consisting of two hardened vegetable oil layers and one calcium carbonate layer.

[0069] Comparative Example 3 A coated granular fertilizer was obtained in the same manner as in Comparative Example 1, except that 300 parts by mass of hardened castor oil 1 was used and no filler (calcium carbonate 1) was used.

[0070] Example 7 Large granular urea (1,000 parts by mass) was placed in a rotating tank and heated to approximately 70°C with hot air. Liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was then added, and the rolling state was continued for 5 minutes. The paraffin-coated large granular urea was then rolled, and castor oil 1 (150 parts by mass) melted at 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes. This carried out the first step, forming a first hydrogenated vegetable oil layer. Next, mica 1 (30 parts by mass) was added, and the rolling state was maintained under heated conditions for at least 3 minutes. This carried out the first step, forming a first mica layer on the outside of the first hydrogenated vegetable oil layer. Next, the second step was carried out in the same manner as the first step, except that the amount of castor oil 1 used was 20 parts by mass. This formed a second hydrogenated vegetable oil layer on the outside of the first mica layer. Next, the second step was carried out a second time in the same manner as the second step of the first time, to form a second mica layer on the outside of the second hardened vegetable oil layer. Next, the first step was carried out a third time in the same manner as the first step of the second time, to form a third hardened vegetable oil layer on the outside of the second mica layer. Next, the second step was carried out a third time in the same manner as the second step of the first time, to form a third mica layer on the outside of the third hardened vegetable oil layer. Next, the first step was carried out a fourth time in the same manner as the first step of the second time, to form a fourth hardened vegetable oil layer on the outside of the third mica layer. Thereafter, the fertilizer was cooled to near room temperature, to obtain a coated granular fertilizer equipped with a coating having a multilayer structure formed of four hardened vegetable oil layers and three mica layers.

[0071] [Example 8] A coated granular fertilizer having a coating with a multilayer structure formed of 10 layers of hydrogenated vegetable oil and 9 layers of mica was obtained in the same manner as in Example 7, except that the first step was repeated 10 times and the second step was repeated 9 times, and the amount of castor hydrogenated oil 1 used in the first first step was 30 parts by mass, and the amount of mica 1 used in each second step was 10 parts by mass.

[0072] Example 9 A coated granular fertilizer having a coating with a multilayer structure formed from 91 layers of hydrogenated vegetable oil and 90 layers of mica was obtained in the same manner as in Example 7, except that the first step 91 times and the second step 90 times were alternately repeated, and the amount of castor hydrogenated oil 1 used in the first step was 30 parts by mass, the amount of castor hydrogenated oil 1 used in the first step from the second step onwards was 2 parts by mass, and the amount of mica 1 used in each second step was 1 part by mass.

[0073] [Example 10] A coated granular fertilizer having a coating with a multilayer structure formed of three layers of hydrogenated vegetable oil and two layers of mica was obtained in the same manner as in Example 7, except that the first step was repeated three times and the second step was repeated twice, and the amount of castor hydrogenated oil 1 used in the first step was 240 parts by mass, and the amount of mica 1 used in each second step was 10 parts by mass.

[0074] Example 11 A coated granular fertilizer having a coating film with a multilayer structure formed of four layers of hydrogenated vegetable oil and three layers of mica was obtained in the same manner as in Example 7, except that the amount of castor hydrogenated oil 1 used in the first step was 210 parts by mass and the amount of mica 1 used in each of the second steps was 10 parts by mass.

[0075] [Example 12] A coated granular fertilizer having a coating film with a multilayer structure formed of four layers of hardened vegetable oil and three layers of mica was obtained in the same manner as in Example 11, except that mica 2, which has a different particle size, was used instead of mica 1.

[0076] [Example 13] A coated granular fertilizer having a coating film with a multilayer structure formed of 10 layers of hardened vegetable oil and 9 layers of mica was obtained in the same manner as in Example 8, except that mica 3, which has a different particle size, was used instead of mica 1.

[0077] Comparative Example 4 Castor hydrogenated oil 1 (210 parts by mass) was heated and melted at 105°C, and mixed with mica 1 (90 parts by mass) heated to 105°C to obtain a coating composition in which mica 1 was dispersed in castor hydrogenated oil 1. Large urea granules (1,000 parts by mass) were charged into a rotating tank and tumbling. The large urea granules were heated to about 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling state was continued for 5 minutes. Next, the coating composition heated to 105°C was added to the paraffin-coated large urea granules in the tumbling state, and the tumbling state was maintained under heating conditions for 3 minutes or more, and then cooled to near room temperature to obtain a coated granular fertilizer.

[0078] [Comparative Example 5] The paraffin-coated large urea particles obtained in the same manner as in Comparative Example 4 were rolled, and 190 parts by mass of hydrogenated castor oil 1 heated to 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes to form a first hydrogenated vegetable oil layer. Next, 90 parts by mass of mica 1 was added, and the rolling state was maintained under heated conditions for at least 3 minutes to form a first mica layer outside the first hydrogenated vegetable oil layer. Next, a second hydrogenated vegetable oil layer was formed outside the first mica layer in the same manner as in the first step, except that the amount of hydrogenated castor oil 1 used was 20 parts by mass, and then the resultant mixture was cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating formed of two hydrogenated vegetable oil layers and one mica layer.

[0079] Example 14 Large granular urea (1,000 parts by mass) was placed in a rotating tank and heated to approximately 70°C with hot air. Liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was then added, and the rolling state was continued for 5 minutes. The paraffin-coated large granular urea was then rolled, and castor oil 1 (150 parts by mass) melted at 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes. This carried out the first step, forming a first hardened vegetable oil layer. Next, clay 1 (30 parts by mass) was added, and the rolling state was maintained under heated conditions for at least 3 minutes. This carried out the first step, forming a first clay layer outside the first hardened vegetable oil layer. Next, the second step was carried out in the same manner as the first step, except that the amount of castor oil 1 used was 20 parts by mass. This formed a second hardened vegetable oil layer outside the first clay layer. Next, the second step was carried out a second time in the same manner as the second step of the first time, to form a second clay layer on the outside of the second hardened vegetable oil layer. Next, the first step was carried out a third time in the same manner as the first step of the second time, to form a third clay layer on the outside of the second clay layer. Next, the second step was carried out a third time in the same manner as the second step of the first time, to form a third clay layer on the outside of the third hardened vegetable oil layer. Next, the first step was carried out a fourth time in the same manner as the first step of the second time, to form a fourth hardened vegetable oil layer on the outside of the third clay layer. Thereafter, the fertilizer was cooled to near room temperature, to obtain a coated granular fertilizer equipped with a coating having a multilayer structure formed of four hardened vegetable oil layers and three clay layers.

[0080] Example 15 A coated granular fertilizer having a coating with a multilayer structure formed of 10 layers of hydrogenated vegetable oil and 9 layers of clay was obtained in the same manner as in Example 14, except that the first step was repeated 10 times and the second step was repeated 9 times, and the amount of hydrogenated castor oil 1 used in the first first step was 30 parts by mass, and the amount of clay 1 used in each second step was 10 parts by mass.

[0081] [Example 16] A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hydrogenated vegetable oil and three layers of clay was obtained in the same manner as in Example 14, except that the amount of hydrogenated castor oil 1 used in the first step was 210 parts by mass and the amount of clay 1 used in each of the second steps was 10 parts by mass.

[0082] Example 17 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hydrogenated vegetable oil and three layers of clay was obtained in the same manner as in Example 14, except that the amount of hydrogenated castor oil 1 used in the first step was 120 parts by mass and the amount of clay 1 used in each of the second steps was 40 parts by mass.

[0083] [Example 18] A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of clay was obtained in the same manner as in Example 16, except that clay 2, which had a different particle size, was used instead of clay 1.

[0084] [Example 19] A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of clay was obtained in the same manner as in Example 16, except that clay 3, which has a different particle size, was used instead of clay 1.

[0085] Comparative Example 6 Castor hardened oil 1 (210 parts by mass) was heated and melted at 105°C, and mixed with clay 1 (90 parts by mass) heated to 105°C to obtain a coating composition in which clay 1 was dispersed in castor hardened oil 1. Large urea granules (1,000 parts by mass) were charged into a rotating tank and tumbling. The large urea granules were heated to about 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling state was continued for 5 minutes. Next, the coating composition heated to 105°C was added to the paraffin-coated large urea granules in the tumbling state, and the tumbling state was maintained under heating conditions for 3 minutes or more, and then cooled to near room temperature to obtain a coated granular fertilizer.

[0086] Comparative Example 7: The paraffin-coated large urea particles obtained in the same manner as in Comparative Example 1 were rolled, and 190 parts by mass of hardened castor oil 1 heated to 105°C was added. The rolling state was maintained under heating for at least 3 minutes to form a first hardened vegetable oil layer. Next, 90 parts by mass of clay 1 was added, and the rolling state was maintained under heating for at least 3 minutes to form a first clay layer outside the first hardened vegetable oil layer. Next, a second hardened vegetable oil layer was formed outside the first clay layer in the same manner as in the first step, except that the amount of hardened castor oil 1 used was 20 parts by mass, and then the resultant mixture was cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating formed of two hardened vegetable oil layers and one clay layer.

[0087] [Comparative Example 8] The paraffin-coated large urea particles obtained in the same manner as in Comparative Example 1 were rolled, and 270 parts by mass of hardened castor oil 1 heated to 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes to form a first hardened vegetable oil layer. Next, 10 parts by mass of clay 1 was added, and the rolling state was maintained under heated conditions for at least 3 minutes to form a first clay layer outside the first hardened vegetable oil layer. Next, a second hardened vegetable oil layer was formed outside the first clay layer in the same manner as in the first step, except that the amount of hardened castor oil 1 used was 20 parts by mass, and then the resultant mixture was cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating formed of two hardened vegetable oil layers and one clay layer.

[0088] Example 20: Large granular urea (1,000 parts by mass) was placed in a rotating tank and heated to approximately 70°C with hot air. Liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was then added, and the tumbling state was continued for 5 minutes. The paraffin-coated large granular urea was then tumbling, and castor oil 1 (150 parts by mass) melted at 105°C was added. The tumbling state was maintained under heated conditions for at least 3 minutes. A first step was then carried out, forming a first wollastonite layer on the outside of the first hardened vegetable oil layer. Next, wollastonite 1 (30 parts by mass) was added, and the tumbling state was maintained under heated conditions for at least 3 minutes. A first step was then carried out, forming a first wollastonite layer on the outside of the first hardened vegetable oil layer. Next, the second first step was carried out in the same manner as the first first step, except that the amount of castor hardened oil 1 used was 20 parts by mass, thereby forming a second hardened vegetable oil layer on the outside of the first wollastonite layer. Next, the second second step was carried out in the same manner as the first second step, thereby forming a second wollastonite layer on the outside of the second hardened vegetable oil layer. Next, the third first step was carried out in the same manner as the second first step, thereby forming a third hardened vegetable oil layer on the outside of the second wollastonite layer. Next, the third second step was carried out in the same manner as the first second step, thereby forming a third wollastonite layer on the outside of the third hardened vegetable oil layer. Next, the fourth first step was carried out in the same manner as the second first step, thereby forming a fourth hardened vegetable oil layer on the outside of the third wollastonite layer. Thereafter, the fertilizer was cooled to near room temperature to obtain a coated granular fertilizer having a coating with a multilayer structure formed of four hardened vegetable oil layers and three wollastonite layers.

[0089] Example 21 A coated granular fertilizer having a coating with a multilayer structure formed of 10 layers of hardened vegetable oil and 9 layers of wollastonite was obtained in the same manner as in Example 20, except that the first step was repeated 10 times and the second step was repeated 9 times, and the amount of castor hardened oil 1 used in the first first step was 30 parts by mass, and the amount of wollastonite 1 used in each second step was 10 parts by mass.

[0090] Example 22 A coated granular fertilizer having a coating with a multilayer structure formed of 19 vegetable hardened oil layers and 18 wollastonite layers was obtained in the same manner as in Example 20, except that the first step was repeated 19 times and the second step was repeated 18 times, and the amount of castor hardened oil 1 in the first step was 30 parts by mass, the amount of castor hardened oil 1 in the first step from the second step onwards was 10 parts by mass, and the amount of wollastonite 1 in each second step was 5 parts by mass.

[0091] Example 23 A coated granular fertilizer having a coating with a multilayer structure formed from 91 vegetable hardened oil layers and 90 wollastonite layers was obtained in the same manner as in Example 20, except that the first step 91 times and the second step 90 times were alternately repeated, and the amount of castor hardened oil 1 used in the first step was 30 parts by mass, the amount of castor hardened oil 1 used in the first step from the second step onwards was 2 parts by mass, and the amount of wollastonite 1 used in each second step was 1 part by mass.

[0092] [Example 24] A coated granular fertilizer provided with a coating having a multilayer structure formed of three layers of hardened vegetable oil and two layers of wollastonite was obtained in the same manner as in Example 20, except that the amount of hardened castor oil 1 used in the first step was 240 parts by mass and the amount of wollastonite 1 used in each of the second steps was 10 parts by mass.

[0093] Example 25 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of wollastonite was obtained in the same manner as in Example 20, except that the amount of hardened castor oil 1 used in the first step was 210 parts by mass and the amount of wollastonite 1 used in each of the second steps was 10 parts by mass.

[0094] Example 26 A coated granular fertilizer having a coating with a multilayer structure formed from 15 layers of vegetable hardened oil and 14 layers of wollastonite was obtained in the same manner as in Example 20, except that the first step was repeated 15 times and the second step was repeated 14 times, and the amount of castor hardened oil 1 used in the first step was 20 parts by mass, the amount of castor hardened oil 1 used in the second and subsequent first steps was 10 parts by mass, and the amount of wollastonite 1 used in each second step was 10 parts by mass.

[0095] Example 27 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of wollastonite was obtained in the same manner as in Example 25, except that wollastonite 2, which has a different particle size, was used instead of wollastonite 1.

[0096] Comparative Example 9 Castor hardened oil 1 (210 parts by mass) was heated and melted at 105°C, and mixed with wollastonite 1 (90 parts by mass) heated to 105°C to obtain a coating composition in which wollastonite 1 was dispersed in castor hardened oil 1. Large urea granules (1,000 parts by mass) were charged into a rotating drum and tumbling. The large urea granules were heated to about 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling state was continued for 5 minutes. Next, the coating composition heated to 105°C was added to the paraffin-coated large urea granules in the tumbling state, and the tumbling state was maintained under heating conditions for 3 minutes or more, followed by cooling to near room temperature to obtain a coated granular fertilizer.

[0097] [Comparative Example 10] The paraffin-coated large urea particles obtained in the same manner as in Comparative Example 1 were rolled, and 270 parts by mass of hardened castor oil 1 heated to 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes to form a first hardened vegetable oil layer. Next, 10 parts by mass of wollastonite 1 was added, and the rolling state was maintained under heated conditions for at least 3 minutes to form a first wollastonite layer outside the first hardened vegetable oil layer. Next, a second hardened vegetable oil layer was formed outside the first wollastonite layer in the same manner as in the first step, except that the amount of hardened castor oil 1 used was 20 parts by mass, and then the mixture was cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating formed of two hardened vegetable oil layers and one wollastonite layer.

[0098] Example 28 Large granular urea (1,000 parts by mass) was placed in a rotating tank and heated to approximately 70°C with hot air. Liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was then added, and the rolling state was continued for 5 minutes. The paraffin-coated large granular urea was then rolled, and castor oil 1 (150 parts by mass) melted at 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes. A first step was then carried out, forming a first bentonite layer on the outside of the first hardened vegetable oil layer. Next, bentonite 1 (30 parts by mass) was added, and the rolling state was maintained under heated conditions for at least 3 minutes. A first step was then carried out, forming a first bentonite layer on the outside of the first hardened vegetable oil layer. Next, the second first step was carried out in the same manner as the first first step, except that the amount of castor hardened oil 1 used was 20 parts by mass, thereby forming a second hardened vegetable oil layer on the outside of the first bentonite layer. Next, the second second step was carried out in the same manner as the first second step, thereby forming a second bentonite layer on the outside of the second hardened vegetable oil layer. Next, the third first step was carried out in the same manner as the second first step, thereby forming a third hardened vegetable oil layer on the outside of the second bentonite layer. Next, the third second step was carried out in the same manner as the first second step, thereby forming a third bentonite layer on the outside of the third hardened vegetable oil layer. Next, the fourth first step was carried out in the same manner as the second first step, thereby forming a fourth hardened vegetable oil layer on the outside of the third bentonite layer. Thereafter, the fertilizer was cooled to near room temperature, thereby obtaining a coated granular fertilizer having a coating with a multilayer structure formed of four hardened vegetable oil layers and three bentonite layers.

[0099] Example 29 A coated granular fertilizer having a coating with a multilayer structure formed of 10 layers of hardened vegetable oil and 9 layers of bentonite was obtained in the same manner as in Example 28, except that the first step was repeated 10 times and the second step was repeated 9 times, and the amount of hardened castor oil 1 used in the first step was 30 parts by mass, and the amount of bentonite 1 used in each second step was 10 parts by mass.

[0100] Example 30 A coated granular fertilizer provided with a coating having a multilayer structure formed of three layers of hardened vegetable oil and two layers of bentonite was obtained in the same manner as in Example 28, except that the amount of hardened castor oil 1 used in the first step was 240 parts by mass and the amount of bentonite 1 used in each of the second steps was 10 parts by mass.

[0101] Example 31 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of bentonite was obtained in the same manner as in Example 28, except that the amount of hardened castor oil 1 used in the first step was 210 parts by mass and the amount of bentonite 1 used in each of the second steps was 10 parts by mass.

[0102] Example 32 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of bentonite was obtained in the same manner as in Example 28, except that the amount of hardened castor oil 1 used in the first step was 120 parts by mass and the amount of bentonite 1 used in each of the second steps was 40 parts by mass.

[0103] Example 33 A coated granular fertilizer provided with a coating having a multilayer structure formed of four layers of hardened vegetable oil and three layers of bentonite was obtained in the same manner as in Example 31, except that bentonite 2, which has a different particle size, was used instead of bentonite 1.

[0104] Comparative Example 11 Castor hardened oil 1 (210 parts by mass) was heated and melted at 105°C, and mixed with bentonite 1 (90 parts by mass) heated to 105°C to obtain a coating composition in which bentonite 1 was dispersed in castor hardened oil 1. Large urea granules (1,000 parts by mass) were charged into a rotating drum and tumbling. The large urea granules were heated to about 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling state was continued for 5 minutes. Next, the coating composition heated to 105°C was added to the paraffin-coated large urea granules in the tumbling state, and the tumbling state was maintained under heating for 3 minutes or more, and then the mixture was cooled to near room temperature to obtain a coated granular fertilizer.

[0105] [Comparative Example 12] The paraffin-coated large urea obtained in the same manner as in Comparative Example 1 was rolled, and 270 parts by mass of hardened castor oil 1 heated to 105°C was added. The rolling state was maintained under heated conditions for at least 3 minutes to form a first hardened vegetable oil layer. Next, 10 parts by mass of bentonite 1 was added, and the rolling state was maintained under heated conditions for at least 3 minutes to form a first bentonite layer outside the first hardened vegetable oil layer. Next, a second hardened vegetable oil layer was formed outside the first bentonite layer in the same manner as in the first step, except that 20 parts by mass of hardened castor oil 1 was used. The resulting mixture was then cooled to near room temperature to obtain a coated granular fertilizer having a multilayered coating formed of two hardened vegetable oil layers and one bentonite layer.

[0106] Comparative Examples 13 and 14 Coated granular fertilizers were obtained in the same manner as in Example 4, except that glass fibers 1 and 2 were used instead of calcium carbonate 1.

[0107] Comparative Examples 15 and 16 Coated granular fertilizers were obtained in the same manner as in Example 2, except that glass fibers 1 and 2 were used instead of calcium carbonate 1.

[0108] Comparative Examples 17 and 20 Coated granular fertilizers were obtained in the same manner as in Example 2, except that paraffin wax or stearic acid was used instead of hardened castor oil 1 and the heating temperature of the large urea particles was set to 55°C.

[0109] Comparative Examples 18 and 19 Coated granular fertilizers were obtained in the same manner as in Example 2, except that FT wax or carnauba wax was used instead of hardened castor oil 1.

[0110] [Evaluation of soil degradability of vegetable hydrogenated oils, petroleum-based waxes, etc.] (Method of preparing evaluation samples) 10 g of evaluation samples, such as vegetable hydrogenated oils and petroleum-based waxes shown in Table 1, were placed in a thermostatic chamber set at 105°C and melted. The molten evaluation samples were cast onto a glass plate using a film applicator (manufactured by Allgood Co., Ltd., gap 600 μm), cooled and solidified at room temperature, and a film with a thickness of approximately 300 μm was created. (Evaluation method) 20 g of soil (collection location: Kasai City, Hyogo Prefecture) was placed in a plastic cup (50 mL). The prepared film was cut into a 2 cm square, approximately 100 mg test piece and weighed (M1). The test piece was placed on the soil, and 20 g of soil was added from above. The test piece was then lightly tapped on the ground approximately 10 times and packed. The sample and a cup of water for moistening were arranged on a tray, placed in a plastic bag, and loosely tied at the top. The test pieces were placed in an incubator set at 28°C, and the weight of the cup was measured every two weeks from the start of the test. If any changes were observed, water was added using a spray bottle. After one month, the test pieces were recovered from the soil, lightly washed, and thoroughly dried at room temperature overnight or more. The mass of the test pieces was measured again (M2), and the mass loss rate (W = M2 / M1 x 100 (%)) was calculated. (Evaluation criteria) A: Mass loss rate W is 20% or more but less than 40% B: Mass loss rate W is 10% or more but less than 20% or 40% or more but less than 60% C: Mass loss rate W is less than 10% or 60% or more A rating of A indicates that the soil decomposition of the coated granular fertilizer as a coating is good. The results are shown in Table 1.

[0111]

[0112] [Evaluation of manufacturability of coated granular fertilizers] (Evaluation method) The degree of sticking between the coated granular fertilizers or between the coated granular fertilizers and the rotating tub that occurred during the production of the coated granular fertilizers of Comparative Examples 17 to 20 and Example 2 was evaluated visually. The results are shown in Table 2. (Evaluation criteria) ◯: Almost no sticking occurred between the coated granular fertilizers or between the coated granular fertilizers and the rotating tub. ×: Significant sticking occurred between the coated granular fertilizers or between the coated granular fertilizers and the rotating tub.

[0113]

[0114] Table 2 shows the results of evaluating the productivity of coated granular fertilizers when paraffin, FT wax, carnauba wax, stearic acid, or hardened castor oil 1 was used.

[0115] [Evaluation of sticking during storage] (Evaluation method) 50 g of the coated granular fertilizer of Example 1 was placed in a cylindrical container, and with a 5 kg weight placed on top, it was left to stand for 24 hours in an incubator set at 40°C. After standing, the coated granular fertilizer was removed from the container, and the degree of sticking of the coated granular fertilizer to each other was evaluated visually. The results are shown in Table 3. (Evaluation criteria) ◯: Almost no sticking of the coated granular fertilizer to each other occurred. ×: Significant sticking of the coated granular fertilizer to each other occurred.

[0116]

[0117] [Measurement of Filler Particle Size] The particle size of the filler was defined as the median diameter (D50) obtained in particle size distribution measurement using the following measuring instrument: A dry laser diffraction particle size measuring instrument (Mastersizer 3000, manufactured by Malvern Analytical) was used for the measurement.

[0118] [Initial Dissolution Controllability] 2.5 g (60 to 80 granules) of the prepared coated granular fertilizer was placed in a sample bottle, 100 mL of water was added, and the fertilizer was allowed to stand at 25°C. After 7 days, 0.6 mL of water was collected from the sample bottle, and the urea concentration was measured using an ultraviolet-visible 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 4 to 23. (Evaluation Criteria) A: Dissolution rate E1 is less than 10% B: Dissolution rate E1 is 10% or more but less than 30% C: Dissolution rate E1 is 30% or more A rating of A or B indicates that the dissolution controllability is good.

[0119] [Initial Impact Resistance] The urea elution rate E2 (%) of coated granular fertilizers after 7 days of application using a side stripe fertilizer applicator (manufactured by Yanmar Co., Ltd.) was measured in the same manner as above, and evaluation was performed based on the value of E2 - E1. The results are shown in Tables 4 to 23. (Evaluation Criteria) A: E2 - E1 is less than 5% B: E2 - E1 is 5% or more but less than 15% C: E2 - E1 is 15% or more A rating of A or B can be considered to indicate good impact resistance.

[0120] [Medium-term release controllability] After 42 days in the same manner as in Evaluation 1, 0.6 ml of water was collected from the sample bottle, and the release rate E3 (%) of urea from the coated granular fertilizer was calculated. The results are shown in Tables 4 to 22. (Evaluation criteria) A: Release rate E3 is less than 30% B: Release rate E3 is 30% or more and less than 60% C: Release rate E3 is 60% or more When the evaluation is A or B, the release controllability can be evaluated as good.

[0121] [Medium-term impact resistance] The urea elution rate E4 (%) of coated granular fertilizers after 42 days of application using a side stripe fertilizer applicator (manufactured by Yanmar Co., Ltd.) was measured in the same manner as above, and evaluation was performed based on the E4-E3 values. The results are shown in Tables 4 to 22. (Evaluation criteria) A: E4-E3 is less than 5% B: E4-E3 is 5% or more but less than 15% C: E4-E3 is 15% or more A rating of A or B indicates that the impact resistance is good.

[0122]

[0123] The results in Table 4 show that the coated granular fertilizer having multiple calcium carbonate layers was superior in elution controllability and impact resistance compared to the coated granular fertilizer having a coating with dispersed calcium carbonate, the coated granular fertilizer having one calcium carbonate layer, and the coated granular fertilizer having no calcium carbonate layer.

[0124]

[0125] Table 5 shows the results of evaluation of the elution controllability and impact resistance when the mass ratio of the coating to calcium carbonate in the calcium carbonate layer is fixed.

[0126]

[0127] Table 6 shows the results of evaluation of the release controllability and impact resistance when the number of calcium carbonate layers was fixed.

[0128]

[0129] The results in Table 7 show that the coated granular fertilizer having multiple mica layers was superior in leaching control and impact resistance compared to the coated granular fertilizer having a coating with dispersed mica, the coated granular fertilizer having one mica layer, and the coated granular fertilizer having no mica layer.

[0130]

[0131] Table 8 shows the results of evaluation of the elution controllability and impact resistance when the mass ratio of the coating to the mica in the mica layer is fixed.

[0132]

[0133] Table 9 shows the results of evaluation of the elution controllability and impact resistance when the number of mica layers was fixed.

[0134]

[0135] Table 10 shows the results of evaluating the elution controllability and impact resistance when the particle size of mica was changed.

[0136]

[0137] The results in Table 11 show that the coated granular fertilizer having multiple clay layers was superior in leaching control and impact resistance compared to the coated granular fertilizer having a coating with dispersed clay, the coated granular fertilizer having one clay layer, and the coated granular fertilizer having no clay layer.

[0138]

[0139] Table 12 shows the results of evaluation of the elution controllability and impact resistance when the mass ratio of the coating to clay 1 in the clay layer 1 was fixed.

[0140]

[0141] Table 13 shows the results of evaluation of elution control and impact resistance when the number of clay layers was fixed.

[0142]

[0143] Table 14 shows the results of evaluating the elution controllability and impact resistance when the particle size of the clay was changed.

[0144]

[0145] The results in Table 15 show that the coated granular fertilizer having multiple wollastonite layers was superior in leaching control and impact resistance compared to the coated granular fertilizer having a coating with dispersed wollastonite and the coated granular fertilizer having no wollastonite layer.

[0146]

[0147] Table 16 shows the results of evaluation of the elution controllability and impact resistance when the mass ratio of the coating to the wollastonite 1 in the wollastonite layer 1 was fixed.

[0148]

[0149] Table 17 shows the results of evaluation of the elution controllability and impact resistance when the number of wollastonite layers was fixed.

[0150]

[0151] Table 18 shows the results of evaluating the elution controllability and impact resistance when the particle size of wollastonite was changed.

[0152]

[0153] The results in Table 19 show that the coated granular fertilizer having multiple bentonite layers was superior in elution control and impact resistance compared to the coated granular fertilizer having a coating with dispersed bentonite, the coated granular fertilizer having one bentonite layer, and the coated granular fertilizer having no bentonite layer.

[0154]

[0155] Table 20 shows the results of evaluation of the elution controllability and impact resistance when the mass ratio of the coating to the bentonite 1 in the 1 bentonite layer was fixed.

[0156]

[0157] Table 21 shows the results of evaluation of the elution controllability and impact resistance when the number of bentonite layers was fixed.

[0158]

[0159] Table 22 shows the results of evaluating the elution controllability and impact resistance when the particle size of bentonite was changed.

[0160]

[0161] Table 23 shows the results of evaluation of elution control and impact resistance when glass fiber was used in place of calcium carbonate, mica, clay, wollastonite, or bentonite.

Claims

1. A coated granular fertilizer comprising a granular fertilizer and a coating that coats the granular fertilizer, the coating containing hardened vegetable oil and a filler, the filler being one or more types selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite, and the filler forming two or more filler layers that overlap in the thickness direction of the coating.

2. The coated granular fertilizer according to claim 1, wherein the hardened vegetable oil forms two or more layers of hardened vegetable oil that overlap in the thickness direction of the coating.

3. The coated granular fertilizer according to claim 2, wherein the hardened vegetable oil layer forms the outermost layer of the coating.

4. The coated granular fertilizer according to claim 1, wherein the mass ratio of the granular fertilizer to the coating is 1:0.1 or more and 1:0.5 or less.

5. The coated granular fertilizer according to any one of claims 1 to 4, wherein the melting point of the hydrogenated vegetable oil is 60°C or higher and 100°C or lower.

6. A method for producing a coated granular fertilizer, comprising: a first step of adding heated and melted vegetable hardened oil to granular fertilizer in a rolling state; and a second step of adding a filler to the granular fertilizer in a rolling state, wherein the filler is one or more selected from the group consisting of calcium carbonate, mica, clay, wollastonite, and bentonite, and the first step and the second step are each repeated two or more times.

7. The method for producing a coated granular fertilizer according to claim 6, wherein the first step and the second step are each repeated alternately two or more times.

8. A method for producing a coated granular fertilizer according to claim 6 or 7, wherein the mass ratio of the granular fertilizer to the total amount of the hydrogenated vegetable oil added in the first step is 1000:100 or more and 1000:280 or less.

9. A method for producing a coated granular fertilizer according to claim 6 or 7, wherein the mass ratio of the granular fertilizer to the total amount of the filler added in the second step is 1000:20 or more and 1000:180 or less.

10. A method for producing a coated granular fertilizer according to claim 6 or 7, wherein the mass ratio of the granular fertilizer to the amount of filler added per second step is 1000:1 or more and 1000:50 or less.

11. The method for producing a coated granular fertilizer according to claim 6 or 7, wherein a hardened vegetable oil layer and a filler layer that coat the granular fertilizer are formed by the first step and the second step, respectively.

Images