Coated Granular Fertilizer

Abstract

An object of the present invention is to provide a coated granular fertilizer that is degradable and has impact resistance that can prevent the early leaching of fertilizer components after application using a spreader such as a side-stripe fertilizer applicator. [Solution] The present inventors have discovered that the above-mentioned problems can be solved by setting the angle of repose of the granular urea in a specific range in a coated granular fertilizer comprising granular urea and a coating that coats the granular urea, the coating containing hydrogenated vegetable oil. In addition, the present inventors have discovered that the above-mentioned problems can be solved by setting the angle of repose of the coated granular fertilizer in a specific range.

Description

[Technical Field]

[0001] The present invention relates to a coated granular fertilizer. [Background technology]

[0002] Coated granular fertilizers have the advantage of being able to control the elution of fertilizer components and maintain their effectiveness after being spread once, thereby reducing the number of times they need to be spread.

[0003] For example, the coated granular fertilizer described in Patent Document 1 has a coating made of petroleum wax that is degradable in the fertilization environment, such as soil, with the aim of reducing the burden on the environment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-293684 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a coated granular fertilizer that is degradable and has impact resistance that can prevent the early leaching of fertilizer components after application using a spreader such as a side-stripe fertilizer applicator. [Means for solving the problem]

[0006] The present inventors have found that, in a coated granular fertilizer comprising granular urea and a coating that coats the granular urea, the coating containing hydrogenated vegetable oil, the above-mentioned problems can be solved by setting the angle of repose of the granular urea within a specific range. In addition, the present inventors have found that the above-mentioned problems can be solved by setting the angle of repose of the coated granular fertilizer within a specific range.

[0007] That is, the coated granular fertilizer according to the present invention may have the following constitutional aspects, but is not limited to these. [1] The present invention provides a method for producing a urea-containing product, comprising: providing granular urea and a coating that coats the granular urea; the coating contains hydrogenated vegetable oil; The coated granular fertilizer, wherein the melting point of the hydrogenated vegetable oil is 60°C or higher and 100°C or lower. [2] The coated granular fertilizer according to [2], wherein the angle of repose of the granular urea is 31 degrees or less. [3] The coated granular fertilizer according to [1] or [2], wherein the angle of repose of the coated granular fertilizer is 29 degrees or less. [4] The coated granular fertilizer according to any one of [1] to [3], wherein the oil absorption rate of the granular urea is 0.4% or more and 1.0% or less. [5] The coated granular fertilizer according to any one of [1] to [4], wherein the hydrogenated vegetable oil is at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil. [6] The coated granular fertilizer according to [4], wherein the hardened vegetable oil is hardened castor oil. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a coated granular fertilizer that is degradable and has impact resistance that can prevent the early leaching of fertilizer components after application using a spreader such as a side stripe fertilizer applicator. DETAILED DESCRIPTION OF THE INVENTION

[0009] The coated granular fertilizer according to the present invention will now be described.

[0010] The coated granular fertilizer comprises granular urea and a coating that coats the granular urea.

[0011] The coated granular fertilizer comprises granular urea.

[0012] The granular urea is a granular material containing a urea component. The granular urea may be a granular material in which the urea component is granulated alone, or may be a granular material containing the urea component and optional additives. Examples of the optional additives include a floating inhibitor, a composition uniformity promoter, an effect development promoter, a colorant, and a granulation promoter.

[0013] The average particle size of the granular urea is not particularly limited and may be 0.1 to 15.0 mm, 0.5 to 10 mm, or 1 to 5 mm. The average particle size of the granular urea can be measured according to the procedure described in the Examples section below.

[0014] The circularity coefficient of the granular urea may be 0.6 to 1.0, or may be 0.7 to 0.9. The circularity coefficient of the granular urea can be measured according to the procedure described in the Examples section below.

[0015] The aspect ratio of the granular urea may be 1.0 to 1.3, or may be 1.0 to 1.2. The aspect ratio of the granular urea can be measured according to the procedure described in the Examples section below.

[0016] The angle of repose of the granular urea may be 31 degrees or less, may be 25 to 31 degrees, or may be 30 to 31 degrees. The angle of repose of the granular urea can be measured according to the procedure described in the Examples section below.

[0017] The oil absorption rate of the granular urea may be 0.1 to 1.0%, 0.4 to 1.0%, or 0.5 to 0.9%. The oil absorption rate of the granular urea may be measured according to the procedure described in the Examples section below.

[0018] The granular urea having an average particle size, a circularity coefficient, an aspect ratio, an angle of repose, and an oil absorption rate within specific ranges can be produced by the procedure described in the Examples section below.

[0019] The coating contains hydrogenated vegetable oil.

[0020] The hydrogenated vegetable oil can be obtained by adding hydrogen to a naturally occurring or synthetic vegetable oil containing unsaturated fatty acid triglycerides to saturate the unsaturated bonds of the unsaturated fatty acid triglycerides. The hydrogenated vegetable oil can also be obtained by chemical synthesis. Examples of the hydrogenated vegetable oil include hydrogenated castor oil, hydrogenated rapeseed oil, hydrogenated soybean oil, hydrogenated palm oil, hydrogenated peanut oil, hydrogenated jojoba oil, hydrogenated cottonseed oil, and hydrogenated coconut oil.

[0021] The hydrogenated vegetable oil has moderate decomposition properties in a fertilization environment such as soil. Specifically, the hydrogenated vegetable oil does not decompose immediately in the fertilization environment, allowing the coating to exhibit elution control. Furthermore, the hydrogenated vegetable oil decomposes at a moderate rate so that its remaining in the fertilization environment is not a problem. In other words, a coated granular fertilizer having a coating containing the hydrogenated vegetable oil has excellent decomposition properties and elution control properties. The decomposition properties of the hydrogenated vegetable oil can be measured according to the procedure described in the Examples section below.

[0022] The hydrogenated vegetable oil is solid at 25°C. The melting point of the hydrogenated vegetable oil is 60°C or higher and 100°C or lower, and may be 80°C or higher and 90°C or lower. Hydrogenated vegetable oils with such melting points can be melted by heating and therefore can be handled in a liquid state without using a solvent. Furthermore, using hydrogenated vegetable oils with such melting points can prevent adhesion between the coated granular fertilizers or between the coated granular fertilizers and the rotating drum during production of the coated granular fertilizer, improving the manufacturability of the coated granular fertilizer. The manufacturability of the coated granular fertilizer can be measured according to the procedure described in the Examples section below. The freezing point of the hydrogenated vegetable oil is from 60° C. to 100° C., and may be from 80° C. to 90° C. Although the melting point and the freezing point are generally the same value, the melting point of the hydrogenated vegetable oil may be higher than the freezing point.

[0023] The hydrogenated vegetable oil has low viscosity. By including the hydrogenated vegetable oil with low viscosity in the coating of the coated granular fertilizer, the caking of the coated granular fertilizer particles during production and storage can be suppressed, improving the adhesion of the coated granular fertilizer. The adhesion of the coated granular fertilizer during storage can be measured according to the procedure described in the Examples section below.

[0024] The hydrogenated vegetable oil has lower water vapor permeability than biodegradable resins, and is therefore superior in terms of improving the control of elution of fertilizer components. The hydrogenated vegetable oil has higher fluidity when melted by heating than biodegradable resins, and therefore is less likely to caking during production of the coated granular fertilizer, resulting in good manufacturability of the coated granular fertilizer.

[0025] The content of the hardened vegetable oil in the coating may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0026] The coating may contain only one or more of the hydrogenated vegetable oils. The coating may contain at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

[0027] The coated granular fertilizer preferably does not contain a biodegradable resin, examples of which include polylactic acid, polyhydroxyalkanoate, polybutylene adipate terephthalate, polycaprolactone, polybutylene succinate, polyethylene succinate, polyvinyl alcohol, polyglycolic acid, polyaspartic acid, cellulose fatty acid ester, and polybutylene succinate adipate.

[0028] The coating preferably does not contain a non-degradable resin. Examples of the non-degradable resin include thermoplastic resins and thermosetting resins. Examples of the thermoplastic resin include olefin-based resins, diene-based resins, and polyvinyl chloride. Examples of the olefin-based resin include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, butene-ethylene copolymer, butene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, and ethylene-carbon monoxide copolymer. Examples of the diene-based resin include butadiene copolymer, isoprene polymer, chloroprene polymer, butadiene-styrene copolymer, and styrene-isoprene copolymer. Examples of the thermosetting resin include epoxy resin, alkyd resin, phenolic resin, urea resin, melamine resin, and silicone resin.

[0029] The coating may contain any additive. Examples of the optional additive include an antibacterial agent. The content of the optional additive in the coating is, for example, 0.1 to 10% by mass.

[0030] The mass ratio of the granular fertilizer to the coating may be 1:0.1 or more and 1:0.5 or less.

[0031] The thickness of the coating is usually 30 to 500 μm. The thickness of the coating can be measured by observing a cross section passing through the center of the coated granular fertilizer using a scanning electron microscope (SU-3800, manufactured by Hitachi High-Technologies Corporation) in BSE mode. The thickness of the coating can be determined by drawing 10 line segments perpendicular to the coating for the coated granular fertilizer and averaging their lengths.

[0032] The method for producing the coated granular fertilizer comprises a first step of rolling the granular urea and a second step of adding the hardened vegetable oil to the rolling granular urea. In the second step, the hardened vegetable oil can be added to the granular urea by dissolving it in a solvent or by heating and melting the hardened vegetable oil. The method of adding the heated and melted hardened vegetable oil to the granular urea does not use a solvent and is therefore preferable from the perspective of reducing environmental impact. The heat-melting temperature is higher than the melting point of the hardened vegetable oil, and may be 70°C, 80°C, 90°C, or 105°C.

[0033] The method for producing the coated granular fertilizer may include a step of adding a lubricant such as liquid paraffin or other optional components between the first step and the second step. The step of adding other optional components may be a step carried out under heating conditions. The method for producing the coated granular fertilizer may include a step of adding optional additives such as a surfactant or an anti-caking agent to the surface of the obtained coated granular fertilizer after the third step.

[0034] The angle of repose of the coated granular fertilizer may be 29 degrees or less, may be 26 to 29 degrees, or may be 28 to 29 degrees. The angle of repose of the coated granular fertilizer can be measured according to the procedure described in the Examples section below.

[0035] The coated granular fertilizer can be used for growing agricultural crops in paddy fields, such as grass crops. The coated granular fertilizer can be applied to paddy fields alone or as a mixed fertilizer with other fertilizers.

[0036] In this specification, the dissolution rate E1 of the fertilizer components when the coated granular fertilizer is left standing in water at a concentration of 2.5 g / 100 mL for 7 days is referred to as the initial dissolution rate. The initial dissolution rate can be measured according to the procedure described in the Examples section below. The dissolution controllability of the coated granular fertilizer can be evaluated based on the value of E1. The coated granular fertilizer satisfies E1<25(%). In this specification, the dissolution rate E3 of the fertilizer components when the coated granular fertilizer is left standing in water at a concentration of 2.5 g / 100 mL for 42 days is referred to as the medium-term dissolution rate. The medium-term dissolution rate can be measured by the same procedure as the initial dissolution rate described in the Examples section below. The dissolution controllability of the coated granular fertilizer can also be evaluated based on the E3 value. When E3 is less than 40%, it can also be evaluated that the medium-term dissolution controllability is good.

[0037] The coated granular fertilizer can be spread on the soil using a spreader such as a side-stripe fertilizer applicator.

[0038] In this specification, the elution rate E2 of the fertilizer components when the coated granular fertilizer is spread using a side stripe fertilizer applicator (Yanmar Co., Ltd., YK6D), quickly recovered, and left to stand in water for 7 days in the same manner as above is referred to as the elution rate after initial mechanical fertilization. E2 of the coated granular fertilizer can be measured according to the procedure described in the Examples section below. The impact resistance of the coated granular fertilizer can be evaluated based on the value of E2 - E1. The coated granular fertilizer satisfies E2 - E1 < 25 (%). In this specification, the elution rate E4 of the fertilizer components when the coated granular fertilizer is spread using a side stripe fertilizer applicator (Yanmar Co., Ltd., YK6D) and then quickly recovered and left to stand in water for 42 days in the same manner as above is referred to as the elution rate after medium-term mechanical fertilization. The medium-term impact resistance of the coated granular fertilizer can be measured using the same procedure as for the initial impact resistance, which will be described in the Examples section below. The impact resistance of the coated granular fertilizer can also be evaluated based on the value of E4 - E3. Impact resistance can also be evaluated as good when E4 - E3 is less than 45%.

[0039] When the coated granular fertilizer is spread on soil using the spreader, the coated granular fertilizer may collide with each other inside the spreader or with the inner wall of the spreader, thereby applying an impact to the coated granular fertilizer. Even in such cases, the coated granular fertilizer can suppress the early leaching of fertilizer components. The mechanism by which such an effect is obtained has not been completely clarified, and various factors are thought to be involved, but the following mechanism is thought to be one contributing factor. The coated granular fertilizer has an angle of repose within a specific range, which is thought to improve the rolling properties of the coated granular fertilizer inside the spreader and make the coating less susceptible to damage caused by collisions between the coated granular fertilizers. This is thought to prevent the leaching of fertilizer components from occurring early after spreading using a spreader such as a side stripe fertilizer applicator. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0041] [Granular urea] Granular urea obtained from Qatar Fertiliser Company and China Blue Chemical Limited was sorted using a soybean sorter (DS-1, manufactured by Minoru Sangyo Co., Ltd.) (sample amount: 5 g, tilt angle: 20 degrees, sorting time: 60 seconds) to prepare Granular Urea 1 to 6 and Comparative Granular Urea 1 to 2, each having the following average particle size, circularity coefficient, aspect ratio, angle of repose, and oil absorption rate. Granular urea 1: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 26 degrees, oil absorption rate 0.17% Granular urea 2: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 28 degrees, oil absorption rate 0.16% Granular urea 3: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 30 degrees, oil absorption rate 0.88% Granular urea 4: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.65% Granular urea 5: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.57% Granular urea 6: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 31 degrees, oil absorption rate 0.51% Comparison granular urea 1: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 32 degrees, oil absorption rate 0.16% Comparative granular urea 2: average particle diameter 3 mm, circularity coefficient 0.8, aspect ratio 1.1, angle of repose 32 degrees, oil absorption rate 0.27% [Vegetable hydrogenated oil] "Hydrogenated Castor Oil" manufactured by Ito Oil Mills, melting point 80-90°C (hereinafter referred to as "Hydrogenated Castor Oil 1") "Extremely hydrogenated rapeseed oil" manufactured by Yokoseki Oil & Fat Industries Co., Ltd., melting point 67°C (hereinafter referred to as "extremely hydrogenated rapeseed oil") [Petroleum wax] "HNP-51" manufactured by Nippon Seiro Co., Ltd. (hereinafter referred to as paraffin wax) "Sasol C80" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as FT Wax) [Plant-based wax] "Refined Carnauba Wax No. 2" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as "Carnauba Wax") "Refined Candelilla Wax" manufactured by Kato Yoko Co., Ltd. (hereinafter referred to as "Candelilla Wax") [others] "Lunac S-98" manufactured by Kao Chemical Corporation (hereinafter referred to as stearic acid) "Nissan Electol WEP-5" manufactured by NOF Corporation (hereinafter referred to as "fatty acid ester") "Kalcol 220-80" manufactured by Kao Chemical Corporation (hereinafter referred to as behenyl alcohol)

[0042] [Example 1] Granular urea 1 (1,000 parts by mass) was placed in a rotating tank and tumbling. The granular urea 1 was heated to approximately 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling was continued for 5 minutes. The paraffin-coated granular urea 1 was kept in a rolling state, and hardened castor oil 1 (210 parts by mass) that had been heated and melted at 105°C was added, and the rolling state was maintained under heating conditions for 3 minutes or more. Thereafter, the mixture was cooled to about room temperature to obtain a coated granular fertilizer (hereinafter referred to as this coated granular fertilizer 1).

[0043] [Examples 2 to 6] In Examples 2 to 6, coated granular fertilizers were obtained in the same manner as in Example 1, except that one of granular ureas 2 to 6 was used instead of granular urea 1 (hereinafter, these are referred to as coated granular fertilizers 2 to 6, respectively).

[0044] [Comparative Examples 1 to 2] In Comparative Examples 1 and 2, coated granular fertilizers were obtained in the same manner as in Example 1, except that comparative granular urea 1 or 2 was used instead of granular urea 1 (hereinafter referred to as comparative coated granular fertilizers 1 and 2, respectively).

[0045] Comparative Example 3 Granular urea (1,000 parts by mass) was placed in a rotating tank and tumbling. The granular urea was heated to approximately 70°C with hot air, and then liquid paraffin (Moresco White P-350P, manufactured by MORESCO Corporation) (10 parts by mass) was added, and the tumbling was continued for 5 minutes. The paraffin-coated urea granules were tumbling, and FT wax (210 parts by mass) melted at 105°C was added. The tumbling state was maintained under heating conditions for 3 minutes or more. After that, the mixture was cooled to near room temperature to obtain a coated granular fertilizer (hereinafter referred to as comparative coated granular fertilizer 3).

[0046] Comparative Example 4 A coated granular fertilizer (hereinafter referred to as comparative coated granular fertilizer 4) was obtained in the same manner as in Comparative Example 3, except that carnauba wax was used instead of FT wax.

[0047] [Comparative Examples 5 to 6] Coated granular fertilizers were obtained in the same manner as in Comparative Example 3, except that paraffin wax or stearic acid was used instead of FT wax and the heating temperature of the granular urea was set to 55°C (hereinafter referred to as comparative coated granular fertilizers 5 and 6, respectively).

[0048] [Evaluation of average particle size, circularity coefficient, and aspect ratio of granular urea] The granular urea 1 was placed on a glass slide and photographed at a magnification of about 20 times, in accordance with the size of the granular urea 1, so that about 5 to 10 particles per field of view were photographed. An optical microscope (HRX-01, manufactured by Hirox Co., Ltd.) was used for the photographing. When placing the granular urea 1 on the glass slide, care was taken to prevent the granular urea 1 from coming into contact with each other and to ensure a strong contrast between the background color and the granular urea 1, so that the outline of the granular urea 1 would be clear. The captured image of the granular urea 1 was used to automatically recognize the outline of the granular urea 1 using the easy recognition tool (data acquisition mode: color difference, tolerance: 72) of image analysis particle size distribution measurement software (Mac-View, manufactured by Mountec Co., Ltd.), and image analysis was performed to measure the particle diameter (Heywood diameter), circularity coefficient (4π × area × perimeter), and aspect ratio (major diameter / minor diameter). Here, the major diameter is defined as the maximum distance between two points on the surface of the granular urea 1 captured in the image. The minor diameter is defined as the maximum length of the line segment perpendicular to the major diameter. The particle size, circularity coefficient, and aspect ratio of 100 or more particles were measured. The average values of these measurement results were defined as the average particle size, circularity coefficient, and aspect ratio, respectively. The average particle size, circularity coefficient, and aspect ratio of Granular Urea 2 to 6 and Comparative Granular Urea 1 to 2 were also measured in the same manner.

[0049] Evaluation of the angle of repose of granular urea and coated granular fertilizers. Granular urea 1 (375 g) was added to a 500 mL stainless steel cylindrical container, the mouth of the container was sealed with a smooth, rigid plate (material: SUS, dimensions: length 50 cm or more, width 50 cm or more), and the container and plate were inverted. The container was then lifted straight up at a speed of approximately 1 cm / sec. The angles formed by the inclined surface of the resulting conical deposit of granular urea 1 and the plate were measured from all four sides, and the average value was defined as the angle of repose. The angles of repose of granular urea 2 to 6 and comparative granular urea 1 to 2 were also measured using the same method. The angles of repose of present coated granular fertilizers 1 to 6 and comparative coated granular fertilizer 1 were also measured using the same method.

[0050] [Evaluation of oil absorption rate of granular urea] Granular urea 1 (20 g) was added to a 200 mL PP cup and allowed to stand in a 70°C incubator for 1 hour. 20 mg of liquid paraffin was added to the cup and stirred with a spatula for 1 minute (step 1). The cup was again allowed to stand in a 70°C incubator for 30 minutes, allowing 20 mg of liquid paraffin to be absorbed into the granular urea 1 (step 2). The cup was removed from the incubator, and a small amount of granular urea 1 was firmly grasped to visually confirm whether liquid paraffin had adhered to the glove (step 3). Steps 1 to 3 were repeated until liquid paraffin had adhered to the glove. Based on the amount of liquid paraffin added up to step 3, when adhesion of liquid paraffin to the glove was confirmed, the saturated oil absorption was calculated using the following formula 1. The saturated oil absorption was measured three times, and the average value was defined as the oil absorption. The oil absorption of granular ureas 2 to 6 and comparative granular ureas 1 and 2 was also measured in the same manner.

[0051] [Number 1] Saturated oil absorption rate (%) = (total amount of liquid paraffin added (g) / mass of granular urea (g)) x 100

[0052] [Evaluation of decomposition of vegetable hardened oils, petroleum waxes, etc.] (Method of preparing evaluation samples) Ten grams of samples of the hydrogenated vegetable oils and petroleum waxes shown in Table 1 were placed in a thermostatic chamber set to 105°C and melted. The molten samples were cast onto a glass plate using a film applicator (Allgood Co., Ltd., gap 600 μm), and then cooled and solidified at room temperature to form films with a thickness of approximately 300 μm. (Evaluation method) 20 g of soil (collection location: Kasai City, Hyogo Prefecture) was placed in a plastic cup (50 mL). The prepared film was cut into a 2 cm square piece, approximately 100 mg in weight, to prepare a test specimen, which was then weighed (M1). The test specimen was placed on top of the soil, and 20 g of soil was added from above. The specimen was then lightly struck against the ground approximately 10 times to seal it. The plastic cup and a cup of water for moistening were arranged on a tray, placed in a plastic bag, and the top was loosely tied. The test specimen was placed in a thermostatic chamber set at 28°C. The weight of the cup was measured every two weeks from the start of the test, and if any change was observed, water was added with a spray bottle. After one month, the test specimen was collected, lightly washed, and thoroughly dried at room temperature overnight. The mass of the test specimen was measured (M2), and the mass loss rate (W = M2 / M1 × 100 (%)) was calculated. (Evaluation criteria) A: Mass reduction rate W is 20% or more but less than 40% B: Mass reduction rate W is 10% or more but less than 20% or 40% or more but less than 60% C: Mass reduction rate W is less than 10% or 60% or more When the rating is A, the decomposition property of the coating of the coated granular fertilizer can be evaluated as good. The results are shown in Table 1.

[0053] [Table 1]

[0054] [Evaluation of the manufacturability of coated granular fertilizer] (Evaluation method) The degree of sticking between the coated granular fertilizers or between the coated granular fertilizers and the rotating drum during the production of the present coated granular fertilizers 1 to 6 and the comparative coated granular fertilizers 1 and 2 was evaluated visually. The results are shown in Tables 2 and 4. (Evaluation criteria) ◯: Almost no sticking occurred between the coated granular fertilizer particles or between the coated granular fertilizer and the rotating drum. ×: Significant sticking occurred between the coated granular fertilizer particles or between the coated granular fertilizer and the rotating drum.

[0055] [Table 2]

[0056] [Evaluation of adhesion of coated granular fertilizer during storage] (Evaluation method) 50 g of the coated granular fertilizer 1 was placed in a cylindrical container, and a 5 kg weight was placed on top of it. The container was then left to stand in an incubator set at 40°C for 24 hours. The coated granular fertilizer 1 was then removed from the container, and the degree of adhesion of the coated granular fertilizer 1 to each other was visually evaluated. The results are shown in Table 3. (Evaluation criteria) ○: There was almost no adhesion between the coated granular fertilizers. ×: Significant adhesion occurred between the coated granular fertilizers.

[0057] [Table 3]

[0058] [Initial dissolution rate] 2.5 g of present coated granular fertilizer 1 (60 to 80 granules) was placed in a sample bottle, 100 mL of water was added, and the bottle was allowed to stand at 25°C. After 7 days, 0.6 mL of water was sampled from the sample bottle, and the urea concentration was measured using an ultraviolet-visible spectrophotometer (UV-1900i, Shimadzu Corporation). Based on the measured urea concentration, the urea elution rate E1 (%) from present coated granular fertilizer 1 was calculated. The results are shown in Table 4. E1 was calculated in the same way for present coated granular fertilizers 2 to 6 and comparative coated granular fertilizers 1 and 2. (Evaluation criteria) A: Dissolution rate E1 is less than 13% B: Dissolution rate E1 is 13% or more and less than 25% C: Dissolution rate E1 is 25% or more When the evaluation is A or B, the initial release controllability can be evaluated as good.

[0059] [Initial impact resistance] This coated granular fertilizer 1 was spread using a side stripe fertilizer applicator (Yanmar Co., Ltd., YK6D) and then collected. The collected coated granular fertilizer 1 (2.5 g, 60-80 granules) was placed in a sample bottle, 100 mL of water was added, and the bottle was left to stand at 25°C. After 7 days, the urea concentration was measured using the same method as above. Based on the measured urea concentration, the elution rate E2 (%) after initial mechanical fertilization was calculated. E2 was calculated in the same way for coated granular fertilizers 2-6 and comparative coated granular fertilizers 1-2. Initial impact resistance was evaluated based on the value of E2 - E1. The results are shown in Table 4. (Evaluation criteria) A: E2-E1 is less than 15% B: E2-E1 is 15% or more but less than 25% C: E2-E1 is 25% or more When the evaluation is A or B, the impact resistance can be evaluated as good.

[0060] [Table 4]

Claims

1. The present invention provides a method for producing a urea-containing product, comprising: providing granular urea and a coating that coats the granular urea; the coating contains hydrogenated vegetable oil; The melting point of the hardened vegetable oil is 60°C or higher and 100°C or lower, The angle of repose of the granular urea is 31 degrees or less. Coated granular fertilizer.

2. 2. The coated granular fertilizer according to claim 1, wherein the oil absorption rate of the granular urea is 0.4% or more and 1.0% or less.

3. 3. The coated granular fertilizer according to claim 1, wherein the hydrogenated vegetable oil is at least one selected from the group consisting of hydrogenated castor oil, hydrogenated rapeseed oil, and hydrogenated soybean oil.

4. 4. The coated granular fertilizer according to claim 3, wherein the hydrogenated vegetable oil is hydrogenated castor oil.

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