Coated granular body and method for producing coated granular body

Abstract

The present invention involves: a coated granular body including a water-soluble granular body and a coating film that covers the water-soluble granular body, wherein the coating film contains a fatty acid salt and a wax, and has inorganic particles having an average particle diameter of 3-18 μm at least on the surface of the coating film; and a method for producing the coated granular body.

Description

Coated Granules and Method for Producing Coated Granules

[0001] The present disclosure relates to coated granules and a method for producing coated granules.

[0002] Conventionally, in terms of the environmental impact due to the leaching of fertilizer components of water-soluble fertilizers or water-soluble pesticides, and labor-saving due to the aging of agricultural workers, more labor-saving and efficient fertilizers or pesticides have been demanded. Under such a background, granulated products with an adjusted elution time containing various agricultural active ingredients have been proposed and put into practical use. One aspect of granulated products with an adjusted elution time is coated fertilizers. Coated fertilizers are fertilizers in which the surface of water-soluble fertilizers is coated with a film formed by laminating organic or inorganic coating materials to adjust the elution time of the internal fertilizer components. Various types of coating materials have been studied to control the elution time of fertilizer components. Patent Document 1 describes a coated granular fertilizer having a film formed from a coating material containing a resin and high-purity talc. Patent Document 2 describes a coated fertilizer coated with a sulfur modifier composed of sulfur and an alicyclic unsaturated hydrocarbon compound. Non-Patent Document 1 describes a coated fertilizer in which a water-soluble fertilizer is coated in the order of a layer of calcium stearate and a layer of paraffin wax. In addition, the present applicant has found a coated fertilizer in which a water-soluble fertilizer is coated with a film containing a fatty acid salt and a wax, and has already filed a patent application.

[0003] Japanese Patent Application Laid-Open No. 2019-156681, Japanese Patent Application Laid-Open No. 2007-084414

[0004] Ebtisam K. Heikal, Salah A. Khalil “Coating Potassium Nitrate and Urea Fertilizers by some Organic and Inorganic Materials to Improve their Dissolution and Releasing Characteristics”, AMSE JOURNALS -2015-Series: Modelling C; Vol. 76;N°1 ; pp 33-45

[0005] Further investigation into coated granules, in which water-soluble granules are coated with a film containing fatty acid salts and wax, revealed that when the surface temperature of the film is cooled to approximately room temperature, depending on the cooling conditions and environment, multiple water-soluble granules may become integrated through the film (hereinafter referred to as "consolidation"), indicating room for improvement. Therefore, this disclosure aims to provide coated granules in which consolidation is suppressed during manufacturing.

[0006] Further detailed investigation into the aforementioned issues revealed that solidification, observed when using a coating containing fatty acid salts and wax, is more likely to occur when the total amount of water-soluble granular material being cooled is large. This is thought to be because the load on the water-soluble granular material and its coating, located below, increases during cooling. Further intensive investigation by the inventors revealed that the above issues can be solved by supplying inorganic particles within a specific size range to the surface of the coating covering the water-soluble granular material before cooling the surface temperature of the coating to below the curing or solidification temperature of the wax, and then cooling the coating after application. More specifically, the above issues can be solved with the following configuration.

[0007] <1> A coated granular material comprising a water-soluble granular material and a coating film covering the water-soluble granular material, wherein the water-soluble granular material is a particle containing an active ingredient for agricultural use, the coating film contains a fatty acid salt and a wax, and at least the surface of the coating film has inorganic particles with an average particle size of 3 to 18 μm. <2> The coated granular material according to <1>, wherein the fatty acid salt comprises a fatty acid salt having 20 or more carbon atoms. <3> The coated granular material according to <1> or <2>, wherein the inorganic particles are at least one selected from the group consisting of talc, calcium carbonate, slaked lime, and silica particles. <4> The coated granular material according to any one of <1> to <3>, wherein the inorganic particles are inorganic particles with an average particle size of 8 to 18 μm. <5> The coated granular material according to any one of <1> to <4>, wherein the inorganic particles are at least one selected from the group consisting of talc, calcium carbonate, and slaked lime. <6> The coated granular material according to any one of <1> to <5>, wherein the angle of repose at 50°C is 36.5° or less. <7> The coated granular material according to any one of <1> to <6>, wherein the inorganic particles have a Mohs hardness of 6 or less. <8> The coated granular material according to any one of <1> to <7>, wherein the coated granular material has a flotation inhibitor on its surface. <9> The coated granular material according to any one of <1> to <8>, wherein the fatty acid salt comprises a fatty acid salt having 31 or more carbon atoms. <10> The coated granular material according to any one of <1> to <9>, wherein the fatty acid salt comprises at least one of a dimeric acid salt and a trimer acid salt. <11> The coated granular material according to any one of <1> to <10>, wherein the fatty acid salt comprises a fatty acid salt having at least one of a branched structure and a cyclic structure. <12> The coated granular material according to any one of <1> to <11>, wherein the wax comprises at least one of petroleum-based wax and plant-based wax. <13> The coated granular material according to any one of <1> to <12>, wherein the coating consists of at least one layer, and the layer located furthest from the water-soluble granular material contains the salt of the fatty acid and the wax. <14> The coated granular material according to any one of <1> to <13>, wherein the water-soluble granular material is a water-soluble granular fertilizer.<15> A method for producing coated granular material comprising a water-soluble granular material, a coating film covering the water-soluble granular material, and inorganic particles on the surface of the coating film, wherein the following steps 1 to 5 are performed in this order: Step 1: A step of making the water-soluble granular material into a fluid or rolling state in a coating device. Step 2: A step of supplying a fatty acid and a wax into the coating device at the coating temperature. Step 3: A step of supplying a metal hydroxide into the coating device at the coating temperature, reacting the fatty acid with the metal hydroxide to produce a fatty acid salt, and forming a layer containing the fatty acid salt and the wax. Step 4: After step 3, a step of supplying inorganic particles having an average particle size of 3 to 18 μm into the coating device at the coating temperature. Step 5: After step 4, a step of lowering the temperature of the layer. <16> The method for producing coated granular material according to <15>, wherein the fatty acid comprises a fatty acid having 20 or more carbon atoms. <17> A method for producing a coated granular material according to <15> or <16>, wherein step 4 is performed in the coating apparatus at a temperature exceeding 40°C. <18> A method for producing a coated granular material according to any one of <15> to <17>, wherein step 2 and step 3 are each performed one or more times after step 3 and before step 4. <19> A method for producing a coated granular material according to any one of <15> to <18>, wherein step 2 includes step 2a, which is a step of supplying the fatty acid and the wax to the surface of the water-soluble granular material. <20> A method for producing a coated granular material according to any one of <15> to <19>, wherein step 6 is performed after step 5. Step 6: A step of applying a floating suppression treatment to the surface of the coated granular material in the coating apparatus at a temperature of 40°C or lower. <21> A method for producing a coated granular material according to any one of <15> to <20>, wherein the water-soluble granular material is a water-soluble granular fertilizer.

[0008] According to this disclosure, it is possible to provide coated granular material in which caking is suppressed during manufacturing.

[0009] This is a schematic diagram showing a cross-section of an example of a coated granular material. The images (a) and (b) are substitute photographs of the coated granular material obtained in Example 1 and Comparative Example 1, taken with light irradiated from the shooting side, and (c) and (d) are substitute photographs of the coated granular material taken with back illumination. Figure (a) is a binarized version of Figure 2(c), and Figure (b) is a binarized version of Figure 2(d).

[0010] The present disclosure will be described in detail below, but the description of the constituent elements described below is an example of an embodiment of the present disclosure and is not limited to these specific contents. It can be implemented in various ways within the scope of its gist. In this specification, "~" is used to mean that the numerical values ​​described before and after it are included as the lower limit and upper limit.

[0011] (Layer) In this specification, "layer" refers to a state in which the raw material supplied for coating has hardened or solidified over the coated particles (water-soluble granules or coated water-soluble granules). A state in which further raw materials are supplied on top of the layer and hardened or solidified may be described as a "laminated layer." Laminates may or may not have boundaries between layers. In this specification, when "first layer," "second layer," etc. are described, for example, the first layer refers to a layer obtained by the hardening or solidification of the coating material derived from the raw material supplied the first time, and the layer may or may not have boundaries, and the component ratio and distribution of the components constituting the layer may be uniform or non-uniform.

[0012] (Coated Particles) In this specification, "coated particles" refers to coated particles (water-soluble granules or coated water-soluble granules) and their coating before being cooled to room temperature (25°C) during the manufacturing process of coated granular materials. The coating covering the coated particles may be in a hardened or solidified state, or in a state where some of the coating material is not hardened or solidified. The "hardened or solidified state" of the coated particles refers to a state in which the coating covering the coated particles is hardened or solidified to the extent that it is supported on the coated particles, and may have elasticity, tackiness, or be deformable. The "state in which some of the coating material is not hardened or solidified" of the coated particles refers to a state in which the coating material is attached to or coated on the coated particles, but is not supported on the coated particles, or if it is supported, it can be detached from the coated particles by applying a weak force. After the above-mentioned coated particles and their coating have been cooled to 25°C or below, they shall be referred to as "coated granules". Furthermore, unless otherwise specified, the term "coated granules" in this specification refers to both a single coated granule and a group of coated granules.

[0013] (Consolidation) In this specification, in the manufacturing process of coated granules, if two or more water-soluble granules are integrated through the coating when the surface temperature of the coated particles is lowered from the coating temperature (described later) to room temperature (25°C), the integrated particles will be referred to as "consolidated particles." Furthermore, when 1 kg is randomly taken from the manufactured coated granules, the consolidation rate obtained by the following formula is judged as "no consolidation" if it is 15% or less, "total consolidation" if it is 80% or more, and "partial consolidation" if it is neither no consolidation nor total consolidation. A consolidation rate of less than 10% is particularly preferred. Consolidation rate (%) = (Mass of consolidated particles / Mass of the taken coated granules) × 100

[0014] [1. Coated Granules] The coated granules of the present disclosure are coated granules comprising a water-soluble granule, a coating covering the water-soluble granule, and inorganic particles on the surface of the coating, wherein the coating contains a fatty acid salt and a wax. It has been found that if the average particle size of the inorganic particles is less than 3 μm, the effect of suppressing caking tends to be insufficient. Although the detailed mechanism is unknown, it is presumed that if the average particle size of the inorganic particles is smaller than 3 μm, even if the inorganic particles are supplied to coated particles that are at a high surface temperature, the inorganic particles become embedded in the coating when the coated particles come into close contact with each other after the supply of inorganic particles, and the area of ​​the contact surface where the coated particles come into close contact cannot be reduced sufficiently, making it difficult to prevent caking.

[0015] The coated granular material described herein is determined to have "inorganic particles on the surface of the coating" if its mass increases after the supply of inorganic particles compared to before the supply, and it passes the peel resistance evaluation described later. In this specification, "having inorganic particles on the surface of the coating" means that at least a portion of the inorganic particles may be exposed on the surface of the coating, some inorganic particles may be embedded in the coating, or the inorganic particles may be attached to or adsorbed on the surface of the coating. Furthermore, even if some inorganic particles are embedded in the coating, the inorganic particles are particles held on the "coating surface" and are not components that constitute the "coating," such as fatty acid salts or waxes.

[0016] Furthermore, if the inorganic particles on the surface of the coating are exposed, they can also be confirmed by surface observation using an electron microscope or the like. Additionally, a simple guideline for determining whether the coating surface contains inorganic particles during manufacturing is to observe whether a decrease in tackiness, visual improvement in fluidity, or visual decrease in gloss is observed on the coating surface after supplying the inorganic particles compared to before supplying them.

[0017] The coated granular material of this disclosure preferably has an angle of repose at 25°C of 34° or less, and more preferably 33° or less, as measured by the method described later. A smaller angle of repose indicates higher particle fluidity. In this embodiment, the coated granular material with an angle of repose at 25°C of 34° or less tended to have reduced gloss and good tackiness in the appearance evaluation. This suggests that at least a portion of the inorganic particles are exposed from the coating surface, and that this exposure creates gaps between particles even when the coated granular material is densely packed, resulting in increased fluidity. The coated granular material of this disclosure may more preferably have an angle of repose at 25°C of 32.0° or less. Furthermore, the lower limit of the angle of repose at 25°C is not particularly limited, but may be, for example, 30° or more, preferably 31° or more.

[0018] Furthermore, it has been found that the coated granular material of this disclosure tends to suppress caking more easily when the angle of repose at 50°C is 36.5° or less, as measured by the method described later. Since 50°C is a temperature near the melting point of the wax used for the coating, it is presumed that the coating particles having appropriate fluidity near the melting point of the wax makes it easier to suppress caking. Therefore, the coated granular material of this disclosure may preferably have an angle of repose at 50°C of 36.5° or less. The coated granular material of this disclosure may more preferably have an angle of repose at 50°C of 36.2° or less, and even more preferably 35° or less. Also, the lower limit of the angle of repose at 50°C is not particularly limited, but may be, for example, 31° or more, and preferably 32° or more.

[0019] The coated granules of this disclosure may contain water, provided that this does not significantly affect elution or caking. The water content of the coated granules tends to correlate with the water content of the water-soluble granules and is not particularly limited. For example, when urea particles are used as the water-soluble granules, the water content of the coated granules may be 0.5% by mass or less. The lower limit is not particularly limited, but may be, for example, 0.01% by mass or more. The water content of this specification can be measured by the method described later.

[0020] <Water-soluble granular material> The water-soluble granular material of this disclosure is a particle containing an active ingredient for agricultural use, wherein the active ingredient is water-soluble. Specifically, examples include granular water-soluble fertilizers and water-soluble pesticides. Furthermore, the water-soluble granular material may be a single component or a composition having multiple components, and the particle may contain only a fertilizer or pesticide as the active ingredient, or a single particle may contain both a water-soluble fertilizer and a water-soluble pesticide.

[0021] The water-soluble fertilizers described above are used as active ingredients (fertilizer components) that directly promote the growth of crops or indirectly promote growth by improving the soil of farmland. The water-soluble fertilizer can be granular (sometimes referred to as water-soluble granular fertilizer), but is not particularly limited. Any known water-soluble granular fertilizer can be used, such as urea, ammonium chloride, ammonium sulfate, ammonium nitrate, potassium chloride, potassium nitrate, sodium nitrate, potassium ammonium phosphate, ammonium phosphate, and calcium ammonium phosphate, with urea being preferred. The water-soluble granular fertilizer may be a fertilizer using one of the above, or a compound fertilizer using two or more. Furthermore, the water-soluble granular fertilizer may contain water-soluble or insoluble impurities, as long as they do not significantly affect its properties as a fertilizer.

[0022] The water-soluble pesticides mentioned above are used as active ingredients for fungicide, insecticide, and control of harmful pests and diseases of crops, as well as for weed control and suppression of weed growth in farmland. Water-soluble pesticides are not particularly limited; they simply need to be contained within particles (sometimes referred to as water-soluble granular pesticides). Any known water-soluble pesticide can be used, such as various insecticides, insect repellents, fungicides, herbicides, plant growth regulators, and rodenticides.

[0023] The size and shape of the water-soluble granules are not particularly limited, and commonly used sizes can be used. For example, for convenience when spreading on a farm using existing machinery, solid particles (e.g., spherical, nearly spherical, rod-shaped, needle-shaped, rectangular, flattened, irregularly shaped, etc.) are preferred, with a particle diameter of 1.0 mm to 5.0 mm after sieving, and more preferably 2.0 mm to 4.0 mm.

[0024] Water-soluble granular materials can be commercially available, or they can be manufactured using known methods such as extrusion granulation or compression granulation.

[0025] <Coating> In the coated granular material of this disclosure, the coating refers to the entire film covering the water-soluble granular material. The film on the water-soluble granular material may be in contact with the surface of the water-soluble granular material, or there may be any film or layer interposed between the water-soluble granular material and the film. The coating may also have any particles on its surface. In this specification, as mentioned above, particles that adhere to or adsorb onto the surface of the coating after coating formation are not included in the components that make up the coating. The above "after coating formation" may refer to the time after step 3 described later has been completed. In the coated granular material of this disclosure, the coating consists of at least one layer, preferably at least two layers, and more preferably at least four layers. There is no particular upper limit to the number of layers that make up the coating, but for example, it may be 100 or less, or 50 or less. In this disclosure, if there are two or more layers covering the water-soluble granular material, the entire film consisting of two or more layers is referred to as the "coating". If there are two or more layers that make up the coating, each layer may have a different composition, or they may all have the same composition. Furthermore, "composition" refers to the components contained in the layer and their respective percentages.

[0026] The coating contains fatty acid salts and wax. Furthermore, if metal oxides added before the completion of step 3, which will be described later, are present in the coating, these metal oxides may also be included as components of the coating. Among the fatty acid salts mentioned above, fatty acids with 20 or more carbon atoms are also called "specific fatty acids," and salts of fatty acids with 20 or more carbon atoms are also called "specific fatty acid salts." In addition, among all the fatty acid salts contained in the coating, salts of fatty acids other than specific fatty acids may be included as long as they do not significantly impair the various properties of the coating, but it is desirable that the main component of the fatty acid salts contained in the coating is the specific fatty acid salt mentioned above. The "main component" mentioned above refers to the component that is present in the largest quantity among the fatty acid salts. For example, if the total mass of fatty acid salts contained in the coating is 100% by mass, the main component may be a component with a content of 60% by mass or more. Preferably, the main component may be a component with a content of 75% by mass or more, more preferably a component with a content of 80% by mass or more, even more preferably a component with a content of 85% by mass or more, and particularly preferably a component with a content of 90% by mass or more. There is no particular upper limit to the content of the main component, but it may be, for example, 100% by mass or less, and preferably 98% by mass or less. Also, if there are two or more salts of specific fatty acids, their total value may be referred to as the "content of salts of specific fatty acids."

[0027] If the coating consists of two or more layers, the salt of the specific fatty acid and the wax may be contained in the same layer or in separate layers (i.e., one layer may contain the salt of the specific fatty acid and not the wax, while another layer may not contain the salt of the specific fatty acid and may contain the wax). However, in this case, it is preferable that the outermost layer contains the salt of the specific fatty acid and the wax. From the viewpoint of improving the yield rate of the coated granules and improving initial elution, it is preferable that the coating consists of at least one layer, and that at least one layer contains the salt of the specific fatty acid and the wax. It is more preferable that the coating consists of at least four layers, and that at least four layers contain the salt of the specific fatty acid and the wax. It is preferable that the coating consists of at least one layer, and that the layer closest to the water-soluble granules (the layer in contact with the surface of the water-soluble granules) contains the salt of the specific fatty acid and the wax. The coating is preferably composed of at least one layer, and the outermost layer (the layer furthest from the water-soluble granules) contains a salt of a specific fatty acid and a wax.

[0028] Figure 1 is a schematic diagram showing a cross-section of an example of a coated granular material of the present disclosure. The coated granular material 1 in Figure 1 includes a water-soluble granular material F and a coating film L covering the water-soluble granular material F. The coating film L is composed of four layers, in order from the layer closest to the water-soluble granular material F: a first layer L1, a second layer L2, a third layer L3, and a fourth layer L4. At least one of the first layer L1, second layer L2, third layer L3, and fourth layer L4 contains a salt of a specific fatty acid, and at least one of the layers contains wax. It is preferable that at least one of the first layer L1, second layer L2, third layer L3, and fourth layer L4 contains a salt of a specific fatty acid and wax. It is more preferable that the fourth layer L4 contains a salt of a specific fatty acid and wax. It is particularly preferable that the first layer L1, the second layer L2, the third layer L3, and the fourth layer L4 contain salts of specific fatty acids and waxes. Although the boundaries between layers L1 to L4 are clearly shown in Figure 1, the boundaries may be unclear. Also, the thickness of each layer may be the same or different.

[0029] An example of the coated granular material of this disclosure has inorganic particles Z with an average particle size of 3 to 18 μm further on the surface of L4 in Figure 1. As described above, the inorganic particles Z may be attached to and adsorbed on the surface of L4, or they may be partially embedded in L4 and partially exposed. Furthermore, if a portion is embedded, the inorganic particles may be embedded down to the lower layer (L1 to L3) on the water-soluble granular material side of L4, as long as it does not significantly affect elution.

[0030] The film thickness can be adjusted as appropriate to the desired elution pattern, for example, from 10 μm to 250 μm, from 30 μm to 200 μm, or from 50 μm to 150 μm. The total film thickness is the sum of the thicknesses of each layer. The thickness of each layer constituting the film is not particularly limited and can be adjusted as appropriate depending on the film thickness, but for example, a thickness of 5 μm to 30 μm is preferred in terms of ease of coating.

[0031] The total mass of the coating is preferably 1.0 to 30% by mass, more preferably 2.0 to 25% by mass, and even more preferably 3.0 to 20% by mass, relative to the total mass of the coated granules. The ratio of the total mass of the coating to the total mass of the coated granules is also called the coating rate. Coating rate (%) = (Total mass of coating / Total mass of coated granules) × 100

[0032] The coating may contain water, as long as it does not significantly affect the caking or elution performance. The water content is not particularly limited, but may be, for example, 5% by mass or less. The lower limit is not particularly limited, but may be, for example, 0.01% by mass or more. The water content of the coating in this specification can be obtained by the method described later.

[0033] <Inorganic Particles> The inorganic particles used in this disclosure have an average particle size of 3 to 18 μm. As mentioned above, if the average particle size is less than 3 μm, the performance in suppressing solidification may be insufficient. Also, if the average particle size exceeds 18 μm, the adhesion rate of the inorganic particles may decrease, and coating defects may be more likely to occur. The average particle size of the inorganic particles is preferably 5 to 18 μm, more preferably 8 to 18 μm, and even more preferably 11 to 18 μm. Furthermore, the average particle size of the inorganic particles may be preferably 16 μm or less, that is, preferably 5 to 16 μm or less, more preferably 8 to 16 μm or less, and even more preferably 11 to 16 μm or less.

[0034] Furthermore, in this specification, the average particle size of inorganic particles was determined by adding 0.1 g of inorganic particles to a glass bottle containing 10 g of isopropyl alcohol (IPA), and then dispersing the dispersion for 5 minutes in an ultrasonic cleaner (AS ONE Corporation, US-3KS). The average particle size was then measured using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, SALD-2200).

[0035] The inorganic particles are not particularly limited as long as their average particle size is within the above range and they do not dissolve in wax or water. Examples include talc, calcium carbonate, silica particles (silica fume, settling silica, etc.), slaked lime, mica, clay, diatomaceous earth, kaolin, montmorillonite, clay, alumina, bentonite, carbon, zeolite, sulfur powder, and metal oxides such as iron oxide. Preferably, talc, silica particles, calcium carbonate, and slaked lime are used; more preferably, talc, silica fume, calcium carbonate, and slaked lime are used; even more preferably, talc, calcium carbonate, and slaked lime are used; and still more preferably, talc. The inorganic particles may contain water as long as it does not impair adhesion to the coating surface or the performance of the coated granules. For example, the water content measured by a Karl Fischer moisture meter may be 10% by mass or less, preferably 6% by mass or less, and more preferably 5% by mass or less. The lower limit is not particularly limited, but for example, it may be 0.05% by mass or more, preferably 0.1% by mass or more.

[0036] The shape of the inorganic particles is not particularly limited, and known particle shapes such as spherical, nearly spherical, rod-shaped, needle-shaped, plate-shaped, rectangular, flattened, or irregular in shape may be used. Furthermore, from the viewpoint of being less likely to be embedded in the coating, it is preferable to use shapes other than spherical, i.e., rod-shaped, needle-shaped, plate-shaped, rectangular, flattened, or irregular in shape. In addition, the inorganic particles may be non-porous or porous.

[0037] The inorganic particles are preferably contained in an amount of 0.1 to 5.0% by mass, when the total mass of the coated granular material is considered to be 100% by mass. More preferably, the amount may be 0.5 to 2.0% by mass. Within this range, it is possible to suppress the aforementioned solidification more efficiently.

[0038] Among the inorganic particles mentioned above, those with a lower Mohs hardness tend to have less of a decrease in the quality rate of the coated granules, and are therefore preferred. Specifically, it is preferable to use inorganic particles with a Mohs hardness of 1 to 7, more preferably 1 to 6, and even more preferably 1 to 4.

[0039] <Float Inhibitor> In addition to the inorganic particles, it is preferable that the coated granular material of this disclosure has a float inhibition treatment applied to its surface by a method described later. By applying the float inhibition treatment, it is possible to suppress the floating of particles in water when the coated granular material is used in hydroponics or the like.

[0040] The flotation suppression treatment preferably involves attaching or adsorbing a flotation inhibitor onto the surface of the coated granular material. The flotation inhibitor is not particularly limited and can be any known agent that is difficult to peel off in the peel resistance evaluation described later and is capable of suppressing flotation. Furthermore, the shape of the flotation inhibitor may be in the form of a layer, in the form of granules, or as a liquid agent that has solidified or hardened. In other words, the coated granular material of this disclosure preferably has inorganic particles with an average particle size of 3 to 18 μm on the surface of the coating, and further has a flotation inhibitor.

[0041] Examples of flotation inhibitors include anionic surfactants such as fatty acid soaps, alkylbenzene sulfonates, alkyl sulfate sulfonates, alkyl ether sulfates, fatty acid ester sulfates, fatty acid amide sulfonates, sulfosuccinates, and phosphate esters; cationic surfactants such as alkyltrimethylammonium salts, alkylpyridinium salts, alkyl quaternary ammonium salts, and alkylamine salts; amphoteric surfactants such as amino acid-based amphoteric surfactants (e.g., sodium laurylaminopropionate), betaine-based surfactants, and imidazoline-based surfactants; nonionic surfactants such as polyethylene glycol, glycol ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, sorbitan fatty acid esters, polyethylene glycol fatty acid esters, sucrose fatty acid esters, glycerin fatty acid esters, and glycerin alkyl ethers; and silica particles (silica fume, settling silica). In particular, silica particles are preferred because they are less likely to peel off in water and have high flotation inhibitory performance, and silica fume may be preferred. Furthermore, when talc with an average particle size of 3 to 18 μm was used as the inorganic particles, using silica particles as a flotation inhibitor tended to make peeling in water less likely, which is preferable.

[0042] The coated granular material of this disclosure preferably has a flotation inhibitor on its surface. The flotation inhibitor only needs to be located outside the coating (in a position where it can come into contact with water before the coating in water), and may be attached to or adsorbed on the coating surface, partially embedded in the coating, or attached to or adsorbed on the surface of the inorganic particles, similar to the inorganic particles. Furthermore, if the inorganic particles are hydrophobic, it is preferable that at least a portion of the flotation inhibitor be located outside the inorganic particles.

[0043] The flotation inhibitor is preferably contained in an amount of 0.1 to 3.0% by mass when the total mass of the coated granules is considered as 100% by mass. More preferably, it may be 0.3 to 1.0% by mass. When within the above range, the flotation rate, as described later, can be set to 10% or less.

[0044] <Other Optional Components> The coated granular material of the present disclosure may further have an arbitrary material on the above coating for the purpose of preventing damage, further suppressing floating in water, suppressing caking during storage, etc. Examples include talc, silica, diatomaceous earth, etc. These arbitrary materials can be integrated with the coated granular material by applying them to the surface of the coated granular material or forming a layer covering the coated granular material. Also, as will be described later, it may be mixed into the coating as one component of the coating material. Further, the coated granular material of the present disclosure may contain unreacted raw materials (for example, fatty acids such as specific fatty acids, metal hydroxides, etc.) and reaction by-products during coating formation described later in the coating film.

[0045] Hereinafter, the constituent components constituting the coating will be described.

[0046] (Salt of Fatty Acid) The salt of fatty acid is not particularly limited as long as it can form a wax and a coating. However, as described above, using the salt of a specific fatty acid is preferable from the viewpoints of ease of coating and ease of controlling the elution timing.

[0047] (Salt of Specific Fatty Acid) The salt of specific fatty acid uses the salt of fatty acid having 20 or more carbon atoms. It preferably contains the salt of fatty acid having 21 or more carbon atoms, and more preferably contains the salt of fatty acid having 31 or more carbon atoms. Further, it is more preferable that the main component of the salt of fatty acid contained in the coating is the salt of fatty acid having 31 or more carbon atoms. The upper limit of the number of carbon atoms of the salt of specific fatty acid is not particularly limited, but may be, for example, 100 or less.

[0048] The salt of a specific fatty acid may be a salt of a monobasic acid, a salt of a dibasic acid, or a salt of a tribasic acid, but it preferably contains at least one of the salt of a dibasic acid and the salt of a tribasic acid. Also, the salt of the specific fatty acid contained in the film may be only one type or two or more types. The salt of the specific fatty acid preferably contains at least one of the salt of a dimer acid and the salt of a trimer acid. More preferably, at least 60% by mass in total of the total amount of the salt of the specific fatty acid contained in the film may be at least one of the salt of a dimer acid or the salt of a trimer acid. Even more preferably, it may contain at least 60% by mass in total of the salt of a dimer acid, and even more preferably, it may contain at least 70% by mass in total of the salt of a dimer acid. The upper limit of the content rate of the salt of a dimer acid is not particularly limited, but for example, it may be 100% by mass or less, 90% by mass or less, or 85% by mass or less.

[0049] The salt of the specific fatty acid preferably contains a salt of a fatty acid having at least one of a branched structure and a cyclic structure. Since the specific fatty acid having the above structure tends to improve the compatibility with wax and retain wax inside the salt of the fatty acid of the film, it is suitable. More preferably, the main component of the salt of the fatty acid contained in the film is a salt of a fatty acid having at least one of a branched structure and a cyclic structure. Here, the branched structure refers to a structure in which at least one hydrogen atom of the hydrocarbon chain of the fatty acid is replaced by carbon, and the cyclic structure refers to a cyclic body of hydrocarbons.

[0050] The salt of the specific fatty acid may be a salt of a saturated fatty acid or a salt of an unsaturated fatty acid. The salt of the specific fatty acid is preferably a salt of an aliphatic carboxylic acid having 20 or more carbon atoms. The salt of the specific fatty acid is preferably a salt of a vegetable fatty acid having 20 or more carbon atoms. Specific examples of the specific fatty acid of the salt of the specific fatty acid will be described later.

[0051] The salt of the specific fatty acid is preferably a metal salt of the specific fatty acid, and more preferably at least one of an alkali metal salt of the specific fatty acid and an alkaline earth metal salt of the specific fatty acid. For example, it is even more preferable that it is at least one selected from the group consisting of a sodium salt of the specific fatty acid, a potassium salt of the specific fatty acid, a lithium salt of the specific fatty acid, a calcium salt of the specific fatty acid, and a magnesium salt of the specific fatty acid. Since the salt of the specific fatty acid itself tends to be difficult to coat onto a water-soluble granular material, a salt obtained by the manufacturing method described later is used. Specifically, a coating of the salt of the specific fatty acid can be obtained by reacting the specific fatty acid with a metal hydroxide on a water-soluble granular material. From the viewpoint of readily reacting with the specific fatty acid to form a salt of the specific fatty acid, it is preferable to use calcium hydroxide as the metal hydroxide. That is, it is particularly preferable that the salt of the specific fatty acid is a calcium salt of the specific fatty acid.

[0052] The content of the salt of the specific fatty acid is not particularly limited, as long as the desired coating is obtained. For example, it is preferably 1 to 99% by mass, more preferably 5 to 95% by mass, and even more preferably 10 to 90% by mass, relative to the total mass of the coating.

[0053] (Wax) The wax is not particularly limited. Preferably, the wax is one that becomes liquid at the coating temperature, and more preferably a wax with a melting point of 50 to 100°C. Examples include petroleum-based waxes such as paraffin wax, plant-based waxes such as carnauba wax, polymer waxes such as polyethylene wax, hardened oils such as hardened palm oil and hardened beef tallow, and synthetic ester waxes. Preferably, the melting point may be 55 to 100°C.

[0054] The wax preferably contains at least one of petroleum-based wax and plant-based wax. Furthermore, when the total mass of all waxes contained in the film is taken as 100, it is more preferable that the combined content of petroleum-based wax and plant-based wax is 80% by mass or more, and it is even more preferable that all waxes contained in the film are at least one of petroleum-based wax and plant-based wax.

[0055] The wax content is not particularly limited as long as it contains an amount that can suppress lamination defects. For example, it is preferably 1 to 40% by mass, more preferably 2.5 to 30% by mass, and even more preferably 5 to 20% by mass, based on the total mass of the coating.

[0056] (Other Components) In addition to salts of specific fatty acids and waxes, the coating may contain other components. Examples of other components include resins, talc, diatomaceous earth, silica, and sulfur powder. When these are used as optional components in the coating, they can be incorporated into the coating as the coating material hardens or solidifies by supplying them before the coating material supplied to the coating device hardens or solidifies. The content of the other components may be 0 to 20% by mass or 0 to 10% by mass relative to the total mass of the coating.

[0057] The coating may or may not contain resin (for example, polyethylene, polyester, acrylic resin, polyurethane, etc.), but from the viewpoint of reducing the burden on the environment, it is preferable not to contain resin.

[0058] If the coated granular material of this disclosure contains fertilizer, it may be mixed with other fertilizers to form a compound fertilizer. Examples of other fertilizers include, but are not limited to, high-grade compound fertilizers such as NK and NPK compound fertilizers, nitrogenous fertilizers such as ammonium chloride, ammonium sulfate, and urea, phosphate fertilizers such as monoammonium phosphate and diammonium phosphate, potassium fertilizers such as potassium chloride and potassium silicate, organic fertilizers such as fish meal, meat and bone meal, vegetable oil residue and its powder, silica gel, and magnesium fertilizers such as magnesium ammonium phosphate.

[0059] [2. Method for Manufacturing Coated Granules] The method for manufacturing coated granules according to the present disclosure will be described below. The method for manufacturing coated granules according to the present disclosure is a method for manufacturing coated granules comprising a water-soluble granule, a coating film covering the water-soluble granule, and inorganic particles on the surface of the coating film, wherein the following steps 1 to 5 are performed in this order. Step 1: A step of making the water-soluble granules into a fluid or rolling state in a coating device. Step 2: A step of supplying a fatty acid and a wax into the coating device at the coating temperature. Step 3: A step of supplying a metal hydroxide into the coating device at the coating temperature, reacting the fatty acid and the metal hydroxide to produce a fatty acid salt, and forming a layer containing the fatty acid salt and the wax. Step 4: After step 3, a step of supplying inorganic particles with an average particle size of 3 to 18 μm into the coating device at the coating temperature. Step 5: After step 4, a step of lowering the temperature of the layer.

[0060] The following describes one preferred embodiment of the present disclosure when a specific fatty acid salt is used as the fatty acid salt, but the present disclosure is not limited to the following description.

[0061] (Step 1) Step 1 will now be described. In Step 1, the water-soluble granular material is made into a fluid or tumbling state in the coating apparatus. Making the water-soluble granular material into a fluid or tumbling state improves the uniformity of the film thickness. The coating apparatus is not particularly limited, but a device such as a rotating drum can be suitably used. In Step 1, the temperature inside the apparatus may be maintained at approximately the coating temperature in advance, and the water-soluble granular material may be heated before Step 2. The coating temperature may be determined by the melting points of the specific fatty acid, wax, and water-soluble granular material used, and is not particularly limited, but for example it is 20 to 150°C, preferably 40 to 100°C, more preferably 50 to 100°C, even more preferably 60 to 100°C, and even more preferably 65 to 100°C. Note that the coating temperature is the temperature at which Steps 2, 3, and 4 are performed. In addition, the humidity inside the apparatus may be adjusted so as not to interfere with Steps 2 to 4, which will be described later.

[0062] (Step 2) Step 2 will now be explained. In Step 2, the specific fatty acid and wax are supplied into a coating device where the coating temperature is maintained. In Step 2, the specific fatty acid and wax are supplied onto a water-soluble granular material that is in a flowing or rolling state. When supplied into the coating device in Step 2, it is preferable that the specific fatty acid and wax are in liquid form. When performing Step 2, it is preferable that the water-soluble granular material is maintained in a rolling or flowing state. Also, when performing Step 2, it is preferable that the device is heated in order to maintain the coating temperature, similar to Step 1. The method of supplying the specific fatty acid and wax is not particularly limited, and examples include spraying and dropping methods, but is not limited to these. Furthermore, any components (e.g., water, solvent, various additives, etc.) may be included as long as it is possible to maintain the solid state of the water-soluble granular material and does not impair the compatibility between the specific fatty acid and wax, or the reactivity between the specific fatty acid and metal hydroxide described later.

[0063] The specific fatty acids and waxes may be supplied separately, or they may be supplied after some or all of the components have been mixed beforehand. If supplied separately, they may be supplied simultaneously, sequentially, or at different times, with some supplied simultaneously.

[0064] Preferably, step 2 includes step 2a, which supplies a specific fatty acid and wax to the surface of the water-soluble granular material. Step 2a and step 3, described later, form a layer that is closest to the water-soluble granular material and contains a salt of the specific fatty acid and wax. For example, when the coated granular material 1 shown in Figure 1 is produced by method 1 including step 2a, the first layer L1 becomes a layer containing a salt of the specific fatty acid and wax.

[0065] (Specific Fatty Acids) The specific fatty acids can be any fatty acids with 20 or more carbon atoms that are capable of forming salts of the specific fatty acids mentioned above and are liquid at the coating temperature. It is preferable to include fatty acids with 21 or more carbon atoms, and more preferable to include fatty acids with 31 or more carbon atoms. There is no particular upper limit to the number of carbon atoms in the specific fatty acids, but for example, it may be 100 or less. The specific fatty acids may be monobasic acids, dibasic acids, or tribasic acids, but it is preferable to include at least one of dibasic acids and tribasic acids. It is preferable to include at least one of dimeric acids and trimer acids. It is preferable to include fatty acids having at least one of a branched structure and a cyclic structure. The specific fatty acids may be saturated fatty acids or unsaturated fatty acids. It is preferable that the specific fatty acids are aliphatic carboxylic acids with 20 or more carbon atoms. It is preferable that the specific fatty acids are plant-derived fatty acids with 20 or more carbon atoms.

[0066] As the specific fatty acids described above, known saturated fatty acids and conjugated fatty acids with 20 or more carbon atoms can be suitably used. Commercial products may also be used, or they may be synthesized by known methods. Specific examples of such specific fatty acids include, as commercial products, SB-20, IPU-22, IPS-22 (all manufactured by Okamura Oil Co., Ltd.), Cyclocarboxypropyloleic acid (manufactured by ALFA Chemistry), Tsunodigm 205, Tsunodigm 216, Tsunodigm 346 (all manufactured by Tsukuno Oleochemicals), etc. In the case of plant-derived fatty acids, examples include oleic acid, linoleic acid, linolenic acid, erucic acid, dehydrated condensed castor oil fatty acids, etc., modified to have 20 or more carbon atoms, or those that have been dimerized or trimerized.

[0067] (Step 3) Step 3 will now be described. In Step 3, a metal hydroxide is supplied into a coating apparatus where the coating temperature is maintained, and the metal hydroxide is reacted with a specific fatty acid to produce a salt of the specific fatty acid, forming a layer containing the salt of the specific fatty acid and wax, which is then used as coating particles. When supplied into the coating apparatus in Step 3, the metal hydroxide is preferably in powder form. If it is in powder form, it is preferable that the water content and particle shape be adjusted to an extent that does not impair the reactivity between the specific fatty acid and the metal hydroxide. For example, when the total mass of the specific fatty acid used in Step 2, the wax, and the metal hydroxide used in Step 3 in the coating apparatus before the reaction between the specific fatty acid and the metal hydroxide is taken as 100, the water content may be 50% by mass or less, more preferably in the range of 0.1 to 30% by mass. When performing Step 3, it is desirable that the water-soluble granular material be kept in a rolling or flowing state. Also, when performing Step 3, it is preferable that the apparatus be heated to maintain the coating temperature, similar to Step 1. The method of supplying the metal hydroxide is not particularly limited. For example, if the metal hydroxide is a liquid, methods such as spraying or dropping can be used, similar to step 2. If it is a solid, methods such as mechanically supplying it while dispersing it (mechanical method) or supplying it together with a gas (airflow method) can be used, but are not limited to these. The supply may be the entire amount at once, or it may be supplied sequentially over a predetermined period of time. It may also be supplied in portions at predetermined time intervals.

[0068] (Metal Hydroxide) The metal hydroxide preferably contains at least one alkali metal hydroxide and alkaline earth metal hydroxide, and more preferably contains at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and magnesium hydroxide. From the viewpoint of ease of handling, lithium hydroxide, calcium hydroxide, and magnesium hydroxide, which do not exhibit deliquescent properties, are preferred, and as mentioned above, calcium hydroxide is even more preferred because it reacts well with specific fatty acids. The metal hydroxide may also contain water, such as a hydrate. The ratio of the mass of the metal hydroxide used in step 3 to the mass of the specific fatty acid used in step 2 (mass of metal hydroxide / mass of specific fatty acid) is preferably 10 / 1 to 0.5 / 1, and more preferably 5 / 1 to 1 / 1.

[0069] It is preferable to perform steps 2 and 3 one or more times after step 3. It is preferable to perform four or more cycles, with one cycle consisting of performing steps 2 and 3 in that order each. For example, when the coated granular material 1 shown in Figure 1 is manufactured by method 1, which involves performing steps 2 and 3 in that order once each for four cycles, the first layer L1, the second layer L2, the third layer L3, and the fourth layer L4 will all be layers containing salts of specific fatty acids and wax. In addition, metal hydroxides that did not react with the specific fatty acids may be present in the coating. In this case, since the metal hydroxides are supplied into the apparatus before coating formation, they are not included in the particles that adhere or adsorb after coating formation and do not fall under the category of "inorganic particles" described later.

[0070] (Step 4) Step 4 will now be described. In Step 4, after Step 3, inorganic particles with an average particle size of 3 to 18 μm are supplied into the coating apparatus, where the coating temperature is maintained. The inorganic particles used are as described above, and it is preferable that the supplied inorganic particles are in powder form. Also, when performing Step 4, it is preferable to heat the inside of the apparatus in order to maintain the coating temperature, similar to Step 1.

[0071] When supplying the inorganic particles in step 4, the coated particles obtained after step 3 may or may not maintain a flowing or rolling state. For example, the entire amount of inorganic particles may be supplied with the flowing or rolling state stopped. Also, if the inorganic particles are supplied in two or more separate batches, a step may be inserted between the supply batches to ensure that the supplied inorganic particles are in a flowing or rolling state to the extent that they spread throughout the coating device.

[0072] The method of supplying inorganic particles is not particularly limited. Examples include, but are not limited to, a method of supplying them mechanically while dispersing them (mechanical type) or a method of supplying them together with a gas (airflow type). The supply may be all at once or it may be supplied sequentially over a predetermined period of time. To shorten the manufacturing time, the amount supplied in one go may preferably be 1 / 3 or more of the planned supply amount, more preferably 1 / 2 or more, and even more preferably the entire amount.

[0073] The total amount of inorganic particles supplied is not particularly limited as long as it is sufficient to suppress caking, but it is preferable that the amount is 0.005 to 0.05 times the total mass of coated particles in the coating apparatus (the calculated total mass of coated granular material expected to be obtained, assuming that the coated particles immediately before step 4 have been cooled), because this allows for efficient suppression of caking relative to the supply amount.

[0074] After supplying the inorganic particles, the coated particles are brought into a flowing or rolling state to coat the surface of the coated particles with the inorganic particles. At this time, depending on the amount of inorganic particles supplied, if the time spent in the flowing or rolling state is too long, the inorganic particles may be gradually pushed into the coating, which can easily reduce the solidification suppression performance. Therefore, it is preferable to mix the supplied inorganic particles and the coated particles in the coating device to the extent that no extreme bias is visible to the naked eye. For example, when supplying an amount of inorganic particles equal to 0.005 times or more the total mass of the coated particles, the time spent in the flowing or rolling state may be 5 minutes or less, preferably 4 minutes or less, and more preferably 3 minutes or less.

[0075] In the method for producing coated granular material according to this disclosure, solidification during cooling is suppressed by supplying inorganic particles in a temperature environment in which the wax does not harden or solidify. Preferably, step 4 may be carried out in a coating apparatus at a temperature above 40°C. More preferably, it may be 45°C or higher, and even more preferably 50°C or higher. After step 3, when the coating temperature is maintained, the coating has a framework formed of fatty acid salts, and although the temperature is not such that the wax hardens or solidifies, it is presumed that the wax is incorporated into the framework and exists as a coating. However, the wax itself within the framework does not harden or solidify, the surface of the coating is deformable, and at least a portion of the wax can seep out from within the framework. Therefore, if the temperature drops while pressure is applied that causes the coated particles to become one, solidification as described above is likely to occur. Furthermore, as is the case when using mass production equipment, the larger the amount of coated particles being cooled, the greater the load on the coated particles located lower down, which tends to make solidification more likely. Therefore, by cooling while in a flowing or rolling state, the increase in the load on specific coated particles is suppressed, and the occurrence of solidification is more easily suppressed. However, if the temperature is lowered while the device is stationary due to equipment limitations, the load on the specific coating particles increases, and this state is maintained until the temperature drops completely, making solidification particularly likely. Here, if inorganic particles of a predetermined size as described in this disclosure are supplied before the wax hardens or solidifies, and then the temperature is lowered, solidification can be suppressed. Although the detailed mechanism is unknown, it is presumed that the inorganic particles act as spacers between the coatings, reducing the surface area of ​​the contact surfaces between the coating particles, thereby suppressing solidification.

[0076] (Step 5) In Step 5, the temperature of the layer after Step 4 (which may be the coated particles obtained in Step 4) is lowered from the coating temperature to a temperature below the temperature at which the wax hardens or solidifies. The temperature after cooling should be any temperature at which the wax hardens or solidifies, but may be, for example, 40°C or lower, preferably 38°C or lower, more preferably 35°C or lower, and even more preferably 25°C or lower. At this time, Step 5 may be performed after discharge from the coating apparatus or inside the coating apparatus, but if further processing is to be performed on the surface of the coated granular material after Step 5, it is preferable to cool the material inside the coating apparatus. Also, when cooling the material inside the coating apparatus, it may be cooled while in a flowing state or in a rolling state. Also, if no particular processing is performed after Step 5, the coated particles may be discharged outside the coating apparatus and cooled for the purpose of improving productivity.

[0077] The method of cooling can be any known method and is not particularly limited. Examples include a method of allowing the material to cool without heating until it reaches a predetermined temperature, a method of air cooling by blowing a gas or liquid at a predetermined temperature onto it, a method of keeping it in a flowing or rolling state until it reaches a predetermined temperature, and a method of cooling using a cooling device.

[0078] (Float Inhibition Treatment) It is preferable to perform a float inhibition treatment by supplying a float inhibitor to the coated granular material or coated particles after or before step 5. The float inhibitor to be used is as described above. When supplying the float inhibitor, it may be in liquid form, powder form, a solution using a solvent, or a dispersion using a dispersion medium. When using a solvent or dispersion medium, the temperature inside the coating device may be adjusted to remove the solvent or dispersion medium, as long as it does not impair the caking inhibition performance. When performing the float inhibition treatment, the coated granular material or coated particles may or may not be in a rolling state or a flowing state. The float inhibitor may be supplied in its entirety at once or in multiple portions.

[0079] If the flotation inhibitor is lipophilic, it may be supplied simultaneously with step 4, or after step 4 and before step 5. Alternatively, if it can be processed at a temperature below the coating temperature, it may be supplied after step 5. If the flotation inhibitor is not lipophilic, it is preferable to perform step 6, which will be described later.

[0080] (Step 6) Step 6 will now be described. In Step 6, after the temperature has been lowered in Step 5, a flotation suppression treatment is performed on the surface of the coated granular material in the coating apparatus at a temperature of 40°C or lower. Step 6 is preferably performed when using a flotation suppressant that does not have lipophilicity, and is particularly preferable when supplying silica particles, which are particulate flotation suppressants, to the surface of the coated granular material. The inventors have found that if the temperature inside the coating apparatus when supplying silica particles as a flotation suppressant is somewhat high, the flotation suppression performance decreases. The detailed mechanism is unknown, but the decrease in the above-mentioned flotation suppression performance tended to decrease as the temperature inside the coating apparatus when supplying the flotation suppressant decreased, so it is presumed that some kind of interaction occurs between the wax contained in the coating and the silica particles, and as a result the flotation suppression performance is inhibited. From the above viewpoint, the temperature inside the coating apparatus may preferably be 38°C or lower, more preferably 35°C or lower, and even more preferably 30°C or lower. The lower limit is not particularly limited, but for example it may be 5°C or higher.

[0081] The method of supplying silica particles is not particularly limited. For example, methods include supplying them mechanically while dispersing them (mechanical method) or supplying them together with a gas (airflow method), but are not limited to these. The entire amount may be supplied at once, or it may be supplied sequentially over a predetermined period of time. It may also be supplied in portions at predetermined time intervals. Furthermore, the coated granular material may be in a rolling or flowing state during or after supply.

[0082] If step 6 is performed inside the coating apparatus, the coated granular material is discharged outside the coating apparatus after step 6. At this time, if it is necessary to lower the temperature of the coated granular material, it is preferable to lower the temperature in the same manner as in step 5 described above.

[0083] After each of the above steps, the surface of the coated granules may be dried or the reaction of any unreacted specific fatty acids may be accelerated.

[0084] [3. Measurement Methods and Evaluation Methods] The measurement methods and evaluation methods for each evaluation item of the coated granular material described herein are shown below.

[0085] (Adhesion Rate) The adhesion rate was calculated using the following method. First, immediately before performing the flotation suppression treatment, the entire amount of coated particles or coated granular material in the coating device was removed, cooled to room temperature (25°C), and its mass was measured. This mass was defined as the "mass of coated granular material before adhesion." Next, the removed coated granular material and the flotation suppressant (hereinafter sometimes referred to as "additive") whose adhesion rate was to be measured were supplied into the coating device. After performing various treatments, the entire amount of coated granular material was removed from the coating device, and its mass was measured. This mass was defined as the "mass of coated granular material after adhesion." Using the obtained masses, the adhesion rate was calculated using the following formula: Adhesion Rate (%) = {(Mass of coated granular material after adhesion - Mass of coated granular material before adhesion) / Mass of additive} × 100

[0086] (Average particle size) The average particle size is determined by measuring the D50 value of the dispersion, which is obtained by adding 0.1 g of inorganic particles to a glass bottle containing 10 g of isopropyl alcohol (IPA) and dispersing it in an ultrasonic cleaner for 5 minutes, using a laser diffraction particle size distribution analyzer (SALD-2200, manufactured by Shimadzu Corporation).

[0087] (Angle of Repose) The angles of repose of the coated granular material at 25°C and 50°C shall be measured three times in accordance with "JIS R 9301-2-2:1999 Alumina Powder - Part 2: Method for Measuring Physical Properties - 2: Angle of Repose", and the average value shall be taken as the angle of repose value at each temperature. Specifically, the measurement can be performed using the injection method shown below. First, prepare a funnel (funnel diameter 90 mm, nozzle diameter 15 mm, nozzle length 27 mm) and a horizontal stand (diameter 70 mm), and place the horizontal stand 60 mm below the tip of the funnel nozzle. Next, take 300 g of coated granular material that has been left to stand in a constant temperature chamber at 25°C or 50°C for 5 hours, drop it into the funnel nozzle, and deposit the coated granular material on the horizontal stand. Next, measure the angle between the horizontal stand and the slope of the pile of deposited coated granular material using an angle gauge. Perform the above measurement a total of three times, and the average value shall be taken as the angle of repose.

[0088] (Good Product Rate) Approximately 10 g of particles are randomly selected from the manufactured coated granules, and the total mass is measured. Next, the selected particles are placed in 150 ml of deionized water at 25°C and subjected to ultrasonic vibration for 5 minutes using an ultrasonic cleaner. After that, the undissolved coated granules are sorted out, dried at 60°C for 2 hours or more, and then their mass is measured. From the obtained value, the ratio of the total mass of undissolved coated granules to the total mass (mass %) is calculated and determined as the good product rate.

[0089] (Floating Rate) Place deionized water in a beaker, add 25 coated granules at 25°C, and observe the floating status after 1 hour. Calculate the ratio of the coated granules that floated to the total number (25 granules) and define this as the floating rate (%).

[0090] (Peeling Resistance) The ease with which the inorganic particles and flotation inhibitor on the surface of the coating can be peeled off the obtained coated granules is evaluated by the following method. Pass: 5 g of coated granules is added to 50 g of water at 25°C, and the turbidity of the water is measured after 1 minute. The measured turbidity value is less than 10 NTU. Fail: 5 g of coated granules is added to 50 g of water at 25°C, and the turbidity of the water is measured after 1 minute. The measured turbidity value is 10 NTU or more. In this specification, turbidity is expressed in NTU (Nephelometric Turbidity Unit) and is measured by a scattered light method based on a formazin standard solution. 1 NTU corresponds to the turbidity when 1 mg of formazin is dispersed in 1 liter of distilled water.

[0091] (Moisture content of coated granules and coating) The moisture content of coated granules and water-soluble granules is measured using the Karl Fischer method (heat vaporization method) in accordance with JIS K0068 (2001), and the moisture content of the coating is calculated. The moisture quantification apparatus used is a combination of a heat vaporization apparatus (ADP-611, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) and a Karl Fischer moisture meter (MKA-610, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). For the measurement samples, 200 randomly selected and crushed coated granules and 200 randomly selected and crushed water-soluble granules are used. The water-soluble granules are to be used after being left to stand for the time required for coating at the coating temperature during coating formation of the coated granules to be measured. The prepared measurement samples are placed in the apparatus, and the temperature is fixed at 100°C and heated to vaporize the moisture in the samples. Heating is continued until there is no change in the mass of the measurement samples. The vaporized water is introduced into a titration cell using a carrier gas, and the values ​​quantified by volumetric titration using a Karl Fischer moisture meter are defined as the water content of the coated granules and the water content of the water-soluble granules. The water content of the coating is calculated using the following formula: {(Water content of coated granules × Mass of coated granules) - (Water content of water-soluble granules × Mass of water-soluble granules)} / {(Mass of coated granules) - (Mass of water-soluble granules)} × 100

[0092] Examples of the present disclosure are described below. However, the present disclosure is not limited to the following examples.

[0093] [Materials Used] The materials used in the preparation of the coated granules in the examples and comparative examples are described below. The moisture content shown below was measured using a Karl Fischer moisture meter.

[0094] <Water-soluble granular material> Urea with a particle size of 2.0 mm to 4.0 mm, which is a water-soluble fertilizer, was used. <Specific fatty acid> Tsunodigm 216 from Tsukuno Oleochemicals (which has a branched structure and contains the most dimeric unsaturated fatty acid (36 carbon atoms)) was used. <Wax> Paraffin wax from Nippon Seiro (melting point: 60°C) was used. <Metal hydroxide> Fine particle slaked lime M-300 from Inoue Mitsuyoshi Shoten (water content 0.9% by mass) was used.

[0095] <Inorganic Particle 1> Talc manufactured by Matsumura Sangyo Co., Ltd. (product name: Crown Talc PP, average particle size 14 μm, Mohs hardness 1, moisture content 0.1 mass%) was used. <Inorganic Particle 2> Silica fume manufactured by Tomoe Kogyo Co., Ltd. (product name: EFACO, average particle size 10 μm, Mohs hardness 7, moisture content 0.6 mass%) was used. <Inorganic Particle 3> Fine particle slaked lime manufactured by Inoue Mitsuyoshi Shoten (product name: M-300, average particle size 5 μm, Mohs hardness 2, moisture content 0.9 mass%) was used. <Inorganic Particle 4> Fine particle calcium carbonate manufactured by Sankyo Seifun Co., Ltd. (product name: Calcy F#9860, average particle size 9 μm, Mohs hardness 3, moisture content 0.3 mass%) was used. <Inorganic Particle 5> Fine particle calcium carbonate manufactured by Sankyo Seifun Co., Ltd. (product name: Escalon #3500, average particle size 1 μm, Mohs hardness 3, moisture content 0.6 mass%) was used. <Inorganic Particle 6> Calcium carbonate manufactured by Sankyo Seifun Co., Ltd. (product name: Special Grade #3, average particle size 22 μm, Mohs hardness 3, moisture content 0.2 mass%) was used. <Inorganic Particle 7> Talc manufactured by Matsumura Sangyo Co., Ltd. (product name: Crown Talc 250M, average particle size 25 μm, Mohs hardness 1, moisture content 0.1 mass%) was used.

[0096] [Example 1] 100 kg of water-soluble granular material was placed in a drum-type rolling coating device with a diameter of 1.4 m, and the temperature inside the coating device was maintained at 70°C using a hot air generator while rolling at 10 rpm (Step 1). Next, while maintaining the temperature at 70°C and the rolling state, a liquid mixture of specific fatty acid (284.1 g) and wax (170.5 g) was prepared and dropped into the device from the supply port (Step 2a). Next, while maintaining the temperature at 70°C and the rolling state, after 3 minutes, metal hydroxide (1000 g) and water (110 g) were supplied into the device, and the rolling state was maintained for 3 minutes (Step 3). In Step 3, the metal hydroxide and specific fatty acid reacted, and a coating was formed on the surface of the water-soluble granular material. Next, the following was repeated 13 times, with each cycle being considered one cycle. (1 cycle) At 70°C, while maintaining a rolling state, a liquid mixture of specific fatty acid (284.1 g) and wax (170.5 g) was dripped into the apparatus from the supply port (step 2). After 3 minutes, metal hydroxide (1000 g) and water (110 g) were supplied into the apparatus and the rolling state was maintained for 3 minutes (step 3). Next, the rolling state was stopped once, and while maintaining 70°C, inorganic particles 1 (1000 g) were supplied into the apparatus, and the rolling state was maintained for 1 minute and 30 seconds after the entire amount of inorganic particles 1 had been supplied (step 4). Next, the obtained coated granules were discharged from the apparatus and allowed to stand to cool slowly to room temperature (25°C) to obtain coated granules (step 5). The coating rate of the obtained coated granules was 11.5%, and the inorganic particle content (the percentage of inorganic particles when the total mass of the coated granules is 100% by mass) was 1.0% by mass.

[0097] [Example 2] Coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 2 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.2%, and the inorganic particle content was 1.0% by mass.

[0098] [Example 3] Coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 3 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.4%, and the inorganic particle content was 1.0% by mass.

[0099] [Example 4] Coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 4 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.2%, and the inorganic particle content was 1.0% by mass.

[0100] [Comparative Example 1] Except that step 4 was omitted, the rolling state was maintained at 70°C for 6 minutes after step 3, and then the coated granules were discharged from the apparatus and allowed to stand to cool slowly to room temperature (25°C) to obtain coated granules in the same manner as in Example 1. The coating rate of the obtained coated granules was 10.8%.

[0101] [Comparative Example 2] A coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 5 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.3%, and the inorganic particle content was 1.0% by mass.

[0102] [Comparative Example 3] A coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 6 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.1%, and the inorganic particle content was 1.0% by mass.

[0103] [Comparative Example 4] Coated granular material was obtained in the same manner as in Example 1, except that inorganic particle 7 was used as the inorganic particle. The coating rate of the obtained coated granular material was 11.2%, and the inorganic particle content was 1.0% by mass.

[0104] [Measurements and Evaluations] The obtained coated granules were measured and evaluated using the methods described below.

[0105] (Strip Resistance) The ease with which the inorganic particles and flotation inhibitor on the surface of the coating could be removed from the obtained coated granules was evaluated using the following method. Pass: 5 g of coated granules was added to 50 g of water at 25°C, and the turbidity of the water was measured after 1 minute. The measured turbidity value was less than 10 NTU. Fail: 5 g of coated granules was added to 50 g of water at 25°C, and the turbidity of the water was measured after 1 minute. The measured turbidity value was 10 NTU or more.

[0106] (Visual Evaluation) The surface gloss of the obtained coated granules was observed visually. In addition, the presence or absence of tackiness was confirmed from the amount of coated granules adhering to the inner wall of the coating device after discharge to the outside of the coating device. Both gloss and tackiness were evaluated according to the following criteria. <Gloss Evaluation> A: More than 80% of the coated granules relative to the total number have less gloss than the coated granules obtained in Comparative Example 1. B: Less than 80% and more than 20% of the coated granules relative to the total number have less gloss than the coated granules obtained in Comparative Example 1. C: Less than 20% of the coated granules relative to the total number have less gloss than the coated granules obtained in Comparative Example 1. <Tackiness Evaluation> A: The mass of coated granules adhering to the inner wall of the device after discharge is less than 0.1% by mass relative to the urea charged. B: The mass of coated granules adhering to the inner wall of the device after discharge is 0.1% by mass or more and less than 1% by mass relative to the urea charged. C; The mass of the coating granular material adhering to the inner wall of the device after discharge is 1% by mass or more relative to the urea used in the charge.

[0107] (Good Product Rate) Approximately 10 g of particles were randomly selected from the manufactured coated granules, and the total mass was measured. Next, the selected particles were placed in 150 ml of deionized water at 25°C and subjected to ultrasonic vibration for 5 minutes using an ultrasonic cleaner. After that, the undissolved coated granules were sorted out, dried at 60°C for more than 2 hours, and then their mass was measured. From the obtained values, the ratio of the total mass of undissolved coated granules to the total mass (mass %) was calculated and defined as the good product rate.

[0108] (Consolidation Rate) One kilogram was randomly selected from the manufactured coated granules, and the consolidation rate obtained using the following formula was judged as "no consolidation" if it was 15% or less, "total consolidation" if it was 80% or more, and "partial consolidation" if it was neither no consolidation nor total consolidation. Consolidation rate (%) = (Mass of consolidated particles / Mass of selected coated granules) × 100

[0109] (Angle of Repose) The angle of repose was measured using the injection method described below. First, a funnel (funnel diameter 90 mm, nozzle diameter 15 mm, nozzle length 27 mm) and a horizontal stand (diameter 70 mm) were prepared, and the horizontal stand was placed 60 mm below the tip of the funnel nozzle. Next, 300 g of coated granular material, which had been left to stand in a constant temperature chamber at 25°C or 50°C for 5 hours, was taken and dropped into the funnel nozzle, and the coated granular material was deposited on the horizontal stand. Next, the angle between the horizontal stand and the slope of the pile of deposited coated granular material was measured using an angle gauge. The above measurement was performed a total of three times, and the average value was taken as the angle of repose.

[0110] (Moisture content of coated granules and coating) The moisture content of the coated granules and urea was measured using the Karl Fischer method (heat vaporization method) in accordance with JIS K0068 (2001), and the moisture content of the coating was calculated. As the moisture quantification device, a device combining a heat vaporization device (ADP-611, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) and a Karl Fischer moisture meter (MKA-610, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used. For the measurement samples, 200 granules of coated granules were randomly selected from the coating device before step 4 was performed, and after being cooled to room temperature (25°C), they were crushed. For the urea, 200 particles were randomly selected from the raw material urea particles, left to stand at 70°C for the time taken for steps 1 to 3 of Example 1, and then crushed after being cooled to room temperature (25°C). The prepared sample for measurement was placed in the apparatus and heated at a fixed temperature of 100°C to vaporize the water in the sample. Heating was continued until there was no further change in the mass of the sample for measurement. The vaporized water was introduced into a titration cell using a carrier gas, and the values ​​quantified by volumetric titration using a Karl Fischer moisture meter were defined as the water content of the coated granules and the water content of the water-soluble granules. The water content of the coating was calculated using the following formula: {(water content of coated granules × mass of coated granules) - (water content of water-soluble granules × mass of water-soluble granules)} / {(mass of coated granules) - (mass of water-soluble granules)} × 100. As a result, in Examples 1 to 4 and Comparative Examples 1 to 4, the water content of the coated granules was 0.2 to 0.3 mass%, and the water content of the coating was 2 mass%.

[0111] The results are shown in Table 1 below. Note that the "Mohs hardness" values ​​in the table are catalog values. Also, "-" indicates that there is no data to record.

[0112]

[0113] In all examples, coated granular materials with good anti-caking performance were obtained. Therefore, caking could be suppressed by supplying inorganic particles with an average particle size of 3 to 18 μm to the coating surface. Furthermore, since the yield rate did not decrease significantly in any of the examples or comparative examples, it is considered that the method disclosed herein suppresses damage to the coating caused by supplying inorganic particles. In addition, since changes were observed in both the gloss evaluation and tackiness evaluation, which are appearance evaluations, compared to Comparative Example 1 in which inorganic particles were not added, it is possible to simply determine that inorganic particles were attached to the surface of the coating in both cases.

[0114] In Comparative Example 2, which used inorganic particles 5 with a small average particle size, partial solidification was observed. This is presumed to be because the small average particle size allowed the particles to be incorporated into the coating, preventing the solidification suppression performance from being fully realized. Furthermore, the appearance evaluation showed less change in gloss and tackiness compared to the Examples, suggesting that there were fewer inorganic particles on or near the surface of the coating. In addition, in Comparative Examples 3 and 4, which used inorganic particles 6 and 7 with a large average particle size, overall solidification was observed. This is presumed to be because the large average particle size prevented the coating from densely covering the surface. Similar to Comparative Example 2, the appearance evaluation suggests that there were fewer inorganic particles on or near the surface of the coating.

[0115] [Confirmation of Surface Condition] Surface photographs were taken of the coated granular materials obtained in Example 1 and Comparative Example 1 using a microscope and observed. Figure 2(a) shows the image of Example 1, which was photographed with the light source irradiated from the microscope side. Next, without moving the photographed sample, the light source was irradiated from the coated granular material side (sometimes referred to as "back illumination"), and the image of Example 1 was taken with the microscope facing the direction of the light source's propagation, as shown in Figure 2(c). Similarly, Figure 2(b) shows the image of Comparative Example 1, which was photographed with the light source irradiated from the microscope side using the same method, and Figure 2(d) shows the image of Comparative Example 1, which was photographed with back illumination using a microscope. Furthermore, Figures 3(a) and 3(b) show the images obtained by binarizing Figures 2(c) and 2(d), respectively.

[0116] From Figures 2(a) and 2(b), the image of Example 1 showed greater surface irregularities compared to the image of Comparative Example 1. These irregularities are thought to be due to the adhesion of talc to the coating surface. In addition, as seen in region A, locally bright areas were observed. From Figures 2(c) and 2(d), compared to the image of Comparative Example 1, the image of Example 1 showed a dark region B and a bright region C, and the boundary between regions B and C was also clear. Since talc is a particle with low light transmittance, it is expected that region B is an area where talc is attached to the coating surface, and region C is an area where talc is not attached to the coating surface. Furthermore, the locally bright area seen in region A in Figure 2(a) is dark in Figure 2(c) and corresponds to region B. Thus, it was inferred that the bright area seen in Figure 2(a) is talc, and since Figure 2(a) is an image taken from the side of the light source, the talc exposed on the surface is reflecting the irradiated light. Figure 3(a) is a binarized version of Figure 2(c), and in both cases, regions A and B, which are expected to originate from the talc, and region C, which is expected to originate from the coating, can be seen. On the other hand, Figure 3(b) is a binarized version of Figure 2(d), and although black dots are seen almost uniformly throughout, localized black regions corresponding to regions A and B were not observed. From the above, it can be said that Example 1 has talc (inorganic particles) on the coating surface, and Comparative Example 1 does not have inorganic particles on the coating surface.

[0117] [Float Inhibition Treatment] The coated granular material that had undergone solidification inhibition treatment was further subjected to float inhibition treatment using the method described below. The additives used for float inhibition treatment are as follows.

[0118] <Added Particle 1> The inorganic particle 2 mentioned above was used. <Added Particle 2> Sucrose ester particles manufactured by Tokyo Chemical Industry Co., Ltd. were used. <Added Particle 3> Bentonite (average particle size 2 μm; average particle size is catalog value) manufactured by Nacalai Tesque Co., Ltd. was used. <Added Particle 4> Kaolin (average particle size 5 μm) manufactured by Nacalai Tesque Co., Ltd. was used. <Added Particle 5> The inorganic particle 1 mentioned above was used. <Added Particle 6> The inorganic particle 7 mentioned above was used. <Additive 1> An aqueous solution with a concentration of 10% by mass was prepared by mixing Oromin 50 manufactured by Miyoshi Oil & Fat Co., Ltd. with ion-exchanged water, and the resulting aqueous solution was used. <Additive 2> An aqueous solution with a concentration of 10% by mass was prepared by mixing funnel oil 40 manufactured by Taiko Oil & Fat Chemical Industry Co., Ltd. with ion-exchanged water, and the resulting aqueous solution was used. <Additive 3> An aqueous solution with a concentration of 10% by mass was prepared by mixing Peletex PC-2421 manufactured by Miyoshi Oil & Fat Co., Ltd. with ion-exchanged water, and the resulting aqueous solution was used.

[0119] [Test Example 1] First, the same procedure as in Example 1 described above was followed up to step 4. Next, the rolling state was stopped and the temperature inside the coating device was lowered to 30°C. The added particles 1 (1000g) were then introduced into the device from the supply port, and the device was rolled for 1 minute and 30 seconds. Next, the particles were discharged from the coating device to obtain coated granules.

[0120] [Test Example 2] After step 4, the added particle 1 was added without cooling, and the temperature was cooled to 25°C after being discharged from the coating device. The coated granular material was obtained in the same manner as in Test Example 1.

[0121] [Test Examples 3-7] Coated granular materials were obtained in the same manner as in Test Example 1, except that the type and amount of added particles were as shown in Table 2.

[0122] [Test Example 8] First, the same procedure as in Example 1 described above was followed up to step 4. Next, while maintaining the rolling state, 1000 g of additive 1 was supplied from the supply port, and the rolling state was maintained for 1 minute and 30 seconds. Then, it was discharged outside the coating device and allowed to cool slowly to room temperature (25°C) and dry to obtain coated granules.

[0123] [Test Examples 9-12] Coated granular material was obtained in the same manner as in Test Example 8, except that the additives used and their supply amounts were as shown in Table 2.

[0124] [Various Measurements and Evaluations] The floating suppression treatment for coated granular material was evaluated using the methods shown below.

[0125] (Peeling Resistance) The peeling resistance was evaluated using the same method as described above. However, since Test Examples 8 to 12 use water-soluble liquid additives, they cannot be evaluated using this method. Therefore, "-" is indicated in Table 2.

[0126] (Adhesion Rate) The adhesion rate was calculated using the following method. First, immediately before performing the flotation suppression treatment, all coated particles or coated granules were removed from the coating device, cooled to room temperature (25°C), and their mass was measured. This was defined as the "mass of coated particles or coated granules before adhesion." Next, the removed coated particles or coated granules were returned to the coating device, and after performing the various treatments described above, all coated granules were removed from the coating device and their mass was measured. This was defined as the "mass of coated granules after adhesion." Using the obtained masses, the adhesion rate was calculated using the following formula: Adhesion Rate (%) = {(Mass of coated granules after adhesion - Mass of coated particles or coated granules before adhesion) / Mass of additive} × 100

[0127] (Evaluation of flotation rate) Deionized water was placed in a beaker, and 25 coated granules that had undergone flotation suppression treatment were added at 25°C. The flotation status was observed after 1 hour. The ratio of coated granules that floated to the total number (25 granules) was calculated and expressed as the flotation rate (%).

[0128]

[0129] Test Examples 1 and 2, shown in Table 2, revealed that by using silica fume at a supply temperature of 40°C or lower, it is possible to achieve both high flotation suppression performance and high peel resistance. In other words, by supplying the flotation inhibitor (silica fume) at a temperature of 40°C or lower, it is possible to have talc, which has caking suppression performance, and silica fume, which has flotation suppression performance, coexist on the coating surface. Test Example 3, which used sucrose ester particles used as a surfactant, also showed high flotation suppression performance, but tended to have low peel resistance in water. Furthermore, Test Examples 4 to 7, which used bentonite, kaolin, and talc, tended to have low flotation suppression performance, and also tended to have low peel resistance in water. Additives 1 to 3 were all aqueous solutions of known surfactants, and all showed high flotation suppression performance.

[0130] According to this disclosure, it is possible to provide coated granular material in which caking is suppressed during manufacturing.

[0131] Although this disclosure has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of this disclosure. This application is based on Japanese Patent Application No. 2024-190804, filed on 30 October 2024, the contents of which are incorporated herein by reference.

[0132] 1. Coated granular material F. Water-soluble granular material L. Coating L1. First layer L2. Second layer L3. Third layer L4. Fourth layer Z. Inorganic particles

Claims

1. A coated granular material comprising a water-soluble granular material and a coating film covering the water-soluble granular material, wherein the water-soluble granular material is a particle containing an active ingredient for agricultural use, the coating film contains a fatty acid salt and a wax, and at least the surface of the coating film has inorganic particles with an average particle size of 3 to 18 μm.

2. The coated granular material according to claim 1, wherein the fatty acid salt comprises a fatty acid salt having 20 or more carbon atoms.

3. The coated granular material according to claim 1 or 2, wherein the inorganic particles are at least one selected from the group consisting of talc, calcium carbonate, slaked lime, and silica particles.

4. The coated granular material according to claim 1 or 2, wherein the inorganic particles are inorganic particles with an average particle size of 8 to 18 μm.

5. The coated granular material according to claim 1 or 2, wherein the inorganic particles are at least one selected from the group consisting of talc, calcium carbonate, and slaked lime.

6. The coated granular material according to claim 1 or 2, wherein the coated granular material has an angle of repose of 36.5° or less at 50°C.

7. The coated granular material according to claim 1 or 2, wherein the inorganic particles have a Mohs hardness of 6 or less.

8. The coated granular material according to claim 1 or 2, wherein the coated granular material has a floating inhibitor on its surface.

9. The coated granular material according to claim 1, wherein the fatty acid salt comprises a fatty acid salt having 31 or more carbon atoms.

10. The coated granular material according to claim 1 or 2, wherein the salt of the fatty acid comprises at least one of a salt of a dimeric acid and a salt of a trimer acid.

11. The coated granular material according to claim 1 or 2, wherein the salt of the fatty acid comprises a salt of a fatty acid having at least one of a branched structure and a cyclic structure.

12. The coated granular material according to claim 1 or 2, wherein the wax comprises at least one of a petroleum-based wax and a plant-based wax.

13. The coated granular material according to claim 1 or 2, wherein the coating consists of at least one layer, and the layer located furthest from the water-soluble granular material contains the fatty acid salt and the wax.

14. The coated granular material according to claim 1 or 2, wherein the water-soluble granular material is a water-soluble granular fertilizer.

15. A method for producing coated granular material comprising a water-soluble granular material, a coating film covering the water-soluble granular material, and inorganic particles on the surface of the coating film, wherein the following steps 1 to 5 are performed in this order: Step 1: A step of making the water-soluble granular material a fluid or rolling state in a coating device. Step 2: A step of supplying a fatty acid and a wax into the coating device at the coating temperature. Step 3: A step of supplying a metal hydroxide into the coating device at the coating temperature, reacting the fatty acid and the metal hydroxide to produce a fatty acid salt, and forming a layer containing the fatty acid salt and the wax. Step 4: After step 3, a step of supplying inorganic particles with an average particle size of 3 to 18 μm into the coating device at the coating temperature. Step 5: After step 4, a step of lowering the temperature of the layer.

16. The method for producing coated granular material according to claim 15, wherein the fatty acid comprises a fatty acid having 20 or more carbon atoms.

17. The method for producing coated granular material according to claim 15 or 16, wherein step 4 is performed in the coating apparatus at a temperature exceeding 40°C.

18. The method for producing coated granular material according to claim 15 or 16, wherein step 2 and step 3 are each performed one or more times after step 3 and before step 4.

19. The method for producing coated granular material according to claim 15 or 16, wherein step 2 includes step 2a of supplying the fatty acid and the wax to the surface of the water-soluble granular material.

20. A method for producing coated granular material according to claim 15 or 16, further comprising performing the following step 6 after step 5: Step 6: A step of applying a floating suppression treatment to the surface of the coated granular material in the coating apparatus at 40°C or below.

21. The method for producing coated granular material according to claim 15 or 16, wherein the water-soluble granular material is a water-soluble granular fertilizer.

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