Coated granular fertilizer

Abstract

One embodiment of the present invention relates to a coated granular fertilizer having a granular fertilizer and a coating film that coats the surface of the granular fertilizer, the coating film comprising a biodegradable resin (A) and at least one wax (B) selected from the group consisting of natural waxes (b1) having an ester group and modified products (b2) thereof, the wax (B) being less than 80 mass% in 100 mass% of the coating film.

Description

TECHNICAL FIELD

[0001] One embodiment of the present application relates to coated granular fertilizer. BACKGROUND

[0002] It is known that there is a coated granular fertilizer in which the surface of a granular fertilizer is coated with a coating material such as a synthetic resin. Since the coated granular fertilizer is easy to control the elution of the fertilizer ingredient, it is confirmed to have effects such as achieving labor saving in agricultural work and reducing environmental load of the fertilizer ingredient. The cultivation technique using such a coated granular fertilizer has been gradually popularized and expanded in recent years.

[0003] However, the conventional coated granular fertilizer is coated with a non-degradable resin or the like, and the non-degradable resin or the like contained in the coating after the elution of the fertilizer ingredient remains in the environment to cause a problem. In order to solve such a problem, for example, Patent Literature 1 discloses a coated granular fertilizer as a coated fertilizer in which the coating material in the environment after the elution of the fertilizer ingredient is decomposed, and has a coating layer containing 5% by weight or more and 80% by weight or less of an aliphatic polyester and 20% by weight or more and 95% by weight or less of a polyolefin wax.

[0004] Patent Literature 2 discloses a coated fertilizer as a coated fertilizer including fertilizer particles and a coating layer disposed on the surface of the fertilizer particles, in which the coating layer contains: poly(lactic acid); poly(butylene succinate), cellulose triacetate, or a second polymer containing a combination of the aforementioned at least one; and a sealant. Patent Literature 3 and Patent Literature 4 disclose a coated fertilizer coated with polyhydroxyalkanoate or polybutylene succinate as a biodegradable resin. PRIOR ART DOCUMENTS PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Laid-Open No. 9-263476 Patent Literature 2: Japanese Patent Publication No. 2017-517471 Patent Literature 3: U.S. Patent Application Publication No. 2021 / 0387925 Patent Literature 4: Japanese Patent Laid-Open No. 07-315976 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, in the technology of Patent Literature 1, although the coating layer has biodegradability, the polyolefin wax contained in the coating layer is a stable substance in nature, and thus it takes a long time until it is decomposed in nature after the elution of the fertilizer ingredient ends. Therefore, the remaining of the coating layer fragments becomes a new problem. The coating layer can be fragmented and stay in the ocean for a long time, and there is room for improvement.

[0007] In the technology of Patent Literature 2, the biodegradability of the coating layer cannot be satisfied. Further, as a necessary component, a sealing agent, a polyolefin wax such as polyethylene wax is used. These components take a long time until they are decomposed in the nature, and they become a problem because they remain in the field.

[0008] In the technology of Patent Literature 3, although it has a disintegration property that is easily decomposed in the nature, the permeability of water into the inside of the fertilizer is too high, and thus the dissolution control property, that is, the dissolution of the fertilizer component over a long period of time, cannot be satisfied.

[0009] In the technology of Patent Literature 4, since the water vapor permeability of the biodegradable plastic is high, the dissolution speed of the fertilizer component is fast, and the dissolution of the fertilizer component is not sufficiently suppressed. That is, the coated granular fertilizer of the prior art cannot satisfy both the excellent biodegradability in the environment and the dissolution control property of the fertilizer component. Therefore, one embodiment of the present application provides a coated granular fertilizer which is excellent in biodegradability and also excellent in the dissolution control property of the fertilizer component. Technical solution adopted to solve the technical problem

[0010] The present inventors earnestly studied in order to solve the above technical problem. As a result, the present application was achieved.

[0011] As a configuration example of the present application, for example, the following [1] to [7] can be listed. [1] A coated granular fertilizer having a granular fertilizer and a coating film coating the surface of the granular fertilizer, the coating film containing a biodegradable resin (A), and at least one kind of wax (B) selected from a natural wax having an ester group (bl) and a modified product thereof (b2), The content of the wax (B) in the coating film 100 mass% is less than 80 mass%. [2] The coated granular fertilizer according to [1], wherein the wax (B) is at least one kind selected from rice wax, castor wax, montan wax, beeswax, carnauba wax, candelilla wax, palm wax, soybean oil wax, and sunflower oil wax. [3] The coated granular fertilizer according to [1] or [2], wherein the wax (B) satisfies the following requirement (I): (I) The acid value is 0.5 to 130 according to the acid value measurement method prescribed in JIS K0070. [4] The coated granular fertilizer according to any one of [1] to [3], wherein the biodegradable resin (A) is at least one kind selected from polybutylene succinate, polylactic acid, polybutylene adipate terephthalate, polyhydroxyaliphatic acid, cellulose acetate, and polycaprolactone. [5] The coated granular fertilizer as described in any one of [1] to [4], wherein the biodegradable resin (A) satisfies the following requirement (II): (II) The melt flow rate (MFR) measured according to ISO 1133 at 190°C and under a load of 2.16 kg is in the range of 0.1 to 30 g / 10 min. [6] The coated granular fertilizer as described in any one of [1] to [5], wherein, in 100% by mass of the coating, the mass ratio (A / B) of the biodegradable resin (A) to the wax (B) is 8 / 5 to 5 / 5. [7] The coated granular fertilizer as described in any one of [1] to [6], wherein the proportion of the coating is 3 to 20% by mass relative to 100% by mass of the coated granular fertilizer. Invention Effects

[0012] According to one embodiment of the present invention, a coated granular fertilizer with excellent biodegradability and excellent control over the dissolution of fertilizer components can be provided. Attached Figure Description

[0013] Figure 1 The image shows an example of an apparatus for manufacturing coated granular fertilizer. Detailed Implementation

[0014] One embodiment of the present invention relates to coated granular fertilizers. This application claims priority based on Japanese Patent Application No. 2023-075207, filed on April 28, 2023, the contents of which are incorporated herein by reference. The present invention will now be described in detail. <Coated Granular Fertilizer> The granulated fertilizer of the present invention has granulated fertilizer and a coating covering the surface of the granulated fertilizer, the coating comprising a biodegradable resin (A) and at least one wax (B) selected from natural waxes having ester groups (b1) and their modifiers (b2), wherein the wax (B) is less than 80% by mass of 100% by mass of the coating.

[0015] <Biodegradable Resin (A)> One embodiment of the coated granular fertilizer of the present invention comprises a biodegradable resin (A). Hereinafter, the biodegradable resin (A) will also be referred to as "component (A)".

[0016] [Biodegradable] Biodegradable resins are resins that are typically completely consumed by microorganisms and produce only natural byproducts. In this invention, component (A) is simply a resin that has been confirmed to have biodegradability according to testing methods such as JIS or ISO, or a resin that has obtained certification from other public institutions. Examples of biodegradability determination methods based on JIS or ISO test methods include JIS K 6950 (ISO 14851), JIS K 6953-1 (ISO 14855-1), JIS K 6955 (ISO 17556), JIS K 6951 (ISO 14852), and JIS K 6953-2 (ISO 14855).

[0017] As a certification for public institutions, examples include the following. In Japan, the Japan Bioplastics Association (JBPA) has established a biodegradable plastics identification and display system. Once biodegradability is confirmed in tests like the one described above, the plastic is registered in a positive list of biodegradable plastics. Outside of Japan, Belgium's TUV AUSTRIA (also known as TUV) has established a certification system for biodegradability. Once biodegradability is confirmed through tests like those mentioned above, certification can be obtained. In this invention, component (A) preferably has obtained JBPA or TUV biodegradability certification.

[0018] Melt Flow Rate (MFR) The melt flow rate (MFR) of the biodegradable resin (A), as determined according to ISO 1133 at 190°C and a load of 2.16 kg, is preferably in the range of 0.1 to 30 g / 10 min, more preferably in the range of 0.1 to 20 g / 10 min, and even more preferably in the range of 2 to 10 g / 10 min. If the MFR of the biodegradable resin (A) is within the above range, it forms a good film, has fewer defects in the film, and exhibits excellent control over the dissolution of fertilizer components, thus it is preferred.

[0019] Examples of biodegradable resins (A) include aromatic polyester resins, aliphatic polyester resins, aliphatic aromatic polyester resins, and polymers containing polysaccharides and starch. As aromatic polyester resins, examples include polyethylene terephthalate, polyethylene glycol-2,6-naphthalate, polypropylene terephthalate, and polybutylene terephthalate.

[0020] As aliphatic polyester resins, specific examples include polylactic acid (also known as PLA), polylactic acid / polyether copolymers and other polylactic acid resins, polyethylene glycol, polyhydroxybutyrate, poly(3-hydroxybutyrate), poly(3-hydroxybutyrate·3-hydroxyhexanoate), poly(3-hydroxybutyrate·3-hydroxyvalerate) and other polyhydroxy fatty acids, polycaprolactone, polybutylene succinate (also known as PBS), polybutylene adipate (also known as PBAT), etc.

[0021] As aliphatic aromatic polyester resins, examples include polyethylene terephthalate (PET) and polybutylene terephthalate (PET). Aliphatic polyester resins and aromatic polyester resins can be copolymerized from one or more of them.

[0022] Polymers containing polysaccharides and starch include, specifically, cellulose resins such as cellulose acetate, glucosamine resins such as chitosan, and starch polyesters. The biodegradable resin (A) is preferably selected from at least one of polybutylene succinate, polylactic acid, polybutylene terephthalate-adipate, polyhydroxy fatty acids, cellulose acetate, and polycaprolactone. From the perspective of low initial leaching of fertilizer components and excellent leaching control, it is more preferably selected from at least one of polybutylene succinate, polylactic acid, polybutylene terephthalate-adipate, and polycaprolactone. From the perspective of moderate water permeability to the interior of the film, particularly excellent leaching control of fertilizer components, particularly excellent biodegradability of the film in the environment, and the ability to impart film strength that can withstand storage, polybutylene succinate is further preferred.

[0023] Biodegradable resin (A) can be used alone or in combination of two or more types. When using biodegradable resin (A) in combination, it is preferable to combine polybutylene succinate and polybutylene terephthalate, polybutylene succinate and polylactic acid, polybutylene succinate and polycaprolactone, polybutylene terephthalate and polylactic acid, or polybutylene terephthalate and polycaprolactone. From the perspective of excellent film-forming properties, it is more preferable to combine polybutylene succinate and polybutylene terephthalate, or polybutylene succinate and polylactic acid.

[0024] When any two resins (referred to as a1 and a2) are used in combination as biodegradable resin (A), the mass ratio (a1 / a2) of biodegradable resin (a1) to biodegradable resin (a2) at 100% by mass of biodegradable resin (A) is preferably 100 / 1 to 1 / 100.

[0025] When polybutylene succinate and polybutylene terephthalate (PTH) are used as biodegradable resin (A), the mass ratio (a1 / a2) of polybutylene succinate (a1) to polybutylene terephthalate (a2) in 100% by mass of biodegradable resin (A) is preferably 100 / 1 to 50 / 50.

[0026] When polybutylene succinate and polylactic acid are used as biodegradable resin (A), the mass ratio (a1 / a2) of polybutylene succinate (a1) to polylactic acid (a2) in 100% by mass of biodegradable resin (A) is preferably 100 / 1 to 50 / 50.

[0027] Biodegradable resin (A) can also be commercially available. Examples of polybutylene succinate include BioPBS manufactured by Mitsubishi Chemical Corporation. Examples of polybutylene terephthalate (PET) include ECOFLEX and ECOVIO from BASF Corporation. Examples of polylactic acid (PLA) include 4060D from Nature Works Corporation. These commercially available products can be used individually or in combination of two or more.

[0028] <At least one wax (B) selected from natural waxes with ester groups (b1) and their modified forms (b2)> One embodiment of the present invention provides a coated granular fertilizer comprising at least one wax (B) selected from natural waxes (b1) having ester groups and their modifiers (b2), wherein the wax (B) comprises less than 80% by mass of 100% by mass of the coating. Hereinafter, at least one wax (B) selected from natural waxes (b1) having ester groups and their modified forms (b2) will also be abbreviated as "component (B)".

[0029] In one embodiment of the present invention, the coated granular fertilizer preferably contains 1% by mass or more of component (B) within 100% by mass of the coating, more preferably 10% by mass or more, further preferably 20% by mass or more, and most preferably 30% by mass or more. When 1% by mass or more of component (B) is contained, the dissolution control of the fertilizer component tends to be excellent.

[0030] In one embodiment of the present invention, the coated granular fertilizer contains less than 80% by mass of component (B) in 100% by mass of the coating, preferably less than 50% by mass, and more preferably less than 40% by mass. The presence of component (B) of less than 80% by mass results in excellent dissolution control of the fertilizer components. Excessive wax content impairs film formation, thus hindering long-term dissolution control of the fertilizer components within the granular fertilizer.

[0031] In component (B), having an ester group means that at least one wax selected from natural waxes (b1) and their modified forms (b2) has one or more ester groups.

[0032] Natural wax (b1) refers to plant waxes, mineral waxes, and animal waxes.

[0033] Examples of plant-based waxes include rice wax, sunflower oil wax, jojoba wax, soybean oil wax, corn oil wax, carnauba wax, candelilla wax, palm wax, coconut wax, candelilla wax, and carnauba wax.

[0034] As a type of mineral wax, lignite wax can be cited as an example. Examples of animal waxes include beeswax and whale wax. From a carbon neutrality perspective, natural wax (b1) is preferably plant-based and animal-based, and more preferably selected from at least one of rice wax, beeswax, carnauba wax, candelilla wax, palm wax, soybean wax, sunflower wax, and whale wax.

[0035] Modified product (b2) refers to a modified natural wax (b1). As a modifier (b2), examples include all or part of the hydrides (also called curings), oxides, saponifications, esterifications, amidation compounds, etc. of natural waxes, with hydrides being preferred.

[0036] As a modifier (b2), examples include castor wax (also known as cured castor oil), semi-cured castor oil wax, hydrogenated rice wax, hydrogenated palm oil wax, hydrogenated soybean oil wax, and partially saponified ester wax of lignite. Since hydrogenated waxes generally have higher melting points and improved film-forming properties during coating, they are preferred. Furthermore, considering that they are widely available and inexpensive, as well as being used in cosmetics, castor wax is preferred.

[0037] From the perspective of fewer defects in the coating, obtaining a good coating, and excellent control over the dissolution of fertilizer components, component (B) is preferably selected from at least one of rice wax, castor wax, lignite wax, beeswax, carnauba wax, candelilla wax, palm wax, soybean oil wax, and sunflower oil wax. From the perspective of widespread availability and stable quality, it is more preferably selected from at least one of lignite wax, rice wax, and castor wax. From the perspective of obtaining a high dissolution inhibition effect, it is even more preferably selected from at least one of rice wax and castor wax. From the perspective of a good balance between hydrophilic and hydrophobic components constituting rice wax and moderate moisture permeability, rice wax is the most preferred.

[0038] [Acid value] Acid value indicates the amount of free fatty acids in oils and fats. It is expressed as the number of mg of potassium hydroxide required to neutralize the free fatty acids contained in 1g of oil or fat. In this invention, according to the acid value determination method specified in JIS K0070, the acid value of component (B) is preferably 0.5 to 130, more preferably 3 to 55, and even more preferably 5 to 25.

[0039] The inventors have discovered that if the acid value of component (B) is below 0.5, its hydrophilicity to the coating decreases, and the controllability of fertilizer component dissolution tends to increase. Although the coating is biodegradable in the environment, its biodegradability tends to be lower. Furthermore, if the acid value is above 130, its hydrophilicity to the coating is high, and fertilizer components tend to dissolve completely in a short period of time.

[0040] Furthermore, the inventors conducted research on the balance between excellent biodegradability in the environment and leaching control of fertilizer components, and found that when the acid value of component (B) is within a specific range, its biodegradability and leaching control are particularly excellent.

[0041] From the viewpoint of lower acid value and improved control over the leaching of fertilizer components, component (B) is preferably selected from at least one of rice wax, castor wax, carnauba wax, candelilla wax, and lignite wax, and more preferably rice wax.

[0042] [Saponification value] Saponification value indicates the amount of free fatty acids and esters in oils and fats. It is expressed as the number of mg of potassium hydroxide required to saponify the esters and neutralize the free fatty acids contained in 1g of oil or fat. In one embodiment of the present invention, according to the saponification value determination method specified in JIS K0070, the saponification value of component (B) is preferably 1 to 190, more preferably 1 to 170, even more preferably 50 to 160, and most preferably 50 to 120 from the viewpoint of particularly excellent dissolution control.

[0043] Depending on the method used to separate and purify the wax components from rice bran, rice waxes with different acid values ​​are currently available. Examples of acid values ​​for rice wax include 7–9, 15–25, 45–55, and 125–135. From the viewpoint of particularly excellent dissolution control, acid values ​​of 7–9, 15–25, and 45–55 are preferred for rice waxes. From the viewpoint of having fewer highly hydrophilic components affecting water vapor permeability and even better dissolution control, 7–9 and 15–25 are more preferred. In component (B), the acid value of rice wax is preferably in the range of 0.5 to 130, more preferably in the range of 0.5 to 55, and from the viewpoint of particularly excellent control over the dissolution of fertilizer components, it is even more preferably in the range of 5 to 25.

[0044] [Biodegradable] Similar to the biodegradable resin (A) mentioned above, component (B) can be any component that has been confirmed to have biodegradability according to JIS or ISO standards, preferably those that have obtained certification, and there is no particular limitation on its type. Component (B) can be used alone or in combination of two or more.

[0045] <Granular Fertilizer> In one embodiment of the present invention, the granular fertilizer used may contain only one or more fertilizer components such as nitrogen, phosphate, and potassium. Specifically, in addition to nitrogenous fertilizers, phosphate fertilizers, and potassium fertilizers, fertilizers containing essential plant elements such as calcium, magnesium, sulfur, iron, manganese, boron, and trace elements, as well as silicon, may be included as needed. Furthermore, fertilizers containing nitrification inhibitors, pesticide components, etc., may be used. Among these, nitrogenous fertilizers containing ammonium sulfate, urea, ammonium nitrate, etc., which have high water solubility and are easily released into the environment, potassium fertilizers containing potassium sulfate, potassium chloride, etc., and chemically formed fertilizers containing urea, ammonium nitrogen, and nitrate nitrogen are preferred. Urea, which has a low unit price per unit fertilizer component, is even more preferred.

[0046] Fertilizer components can be used alone or in combination of two or more. Granular fertilizers may also contain other components without impairing the effects of the present invention. Other components contained in granular fertilizers include, for example, carriers, binders, surfactants, waste molasses, animal oils, vegetable oils, hydrogenated oils, fatty acids, fatty acid metal salts, paraffin wax, waxes, and glycerin. One of these components may be used alone, or two or more may be used in combination.

[0047] The method for manufacturing the granular fertilizer used in one embodiment of the present invention is not particularly limited, and a known granulation method can be used. For example, the granular fertilizer can be manufactured using fluidized bed granulation, rotary granulation, coating granulation, adsorption granulation, etc.

[0048] The shape of the granular fertilizer used in one embodiment of the present invention is not particularly limited, but from the viewpoint of easily and uniformly coating the surface with the film material, a spherical shape is preferred. Regarding the shape of granular fertilizer, specifically, the roundness coefficient obtained by the following formula (2) is preferably 0.7 or more and 1 or less, more preferably 0.75 or more and 1 or less, and most preferably 0.8 or more and 1 or less. The maximum value of the roundness coefficient is 1. The closer it is to 1, the closer the granular fertilizer particles are to a perfect circle. As the particle shape deviates from a perfect circle, the roundness coefficient becomes smaller. Circularity coefficient = {(4π × projected area of ​​the particle) / (outline length of the particle projection image)} 2} ...Formula (2)

[0049] In one embodiment of the present invention, the average particle size of the granular fertilizer is preferably 1 to 10 mm, more preferably 2 to 5 mm. If the average particle size of the granular fertilizer is within this range, it is easier to coat the surface of the granular fertilizer and prepare coated granular fertilizer, which is therefore preferred. As a granular fertilizer, commercially available granular fertilizers or manufactured granular fertilizers can be used, and sieves or similar equipment can be used appropriately to adjust the average particle size to the desired value. In one embodiment of the present invention, the average particle size refers to the average particle size calculated based on particle size distribution methods such as dynamic image analysis.

[0050] In one embodiment of the present invention, commercially available granular fertilizers, such as granular urea (manufactured by PETRONAS Fertilizer (Kedah) Sdn. Bhd.), granular ammonium phosphate (manufactured by Central Green Co., Ltd.), and granular potassium sulfate (manufactured by Asahi AGRIA Co., Ltd.), can be used as commercially available granular fertilizers.

[0051] <Membrane> One embodiment of the present invention provides a coated granular fertilizer comprising granular fertilizer and a coating covering the surface of the granular fertilizer. The coating comprises a biodegradable resin (A) and at least one wax (B) selected from natural waxes (b1) having ester groups and their modifiers (b2), wherein the wax (B) comprises less than 80% by mass of 100% by mass of the coating.

[0052] The coating preferably comprises polybutylene succinate as a biodegradable resin (A) and rice wax as a component (B). Although the rationale for this preference is not clear, the inventors believe that the balance between the alkyl chain length and the ester content of rice wax results in a very high affinity for polybutylene succinate, which improves the film condition during film formation, increases the coating strength, and improves dissolution control. Therefore, it is preferred to include polybutylene succinate as a biodegradable resin (A) and rice wax as a component (B).

[0053] In one embodiment of the coated granular fertilizer of the present invention, the mass ratio (A / B) of the biodegradable resin (A) to at least one wax (B) selected from natural waxes (b1) having ester groups and their modifiers (b2) in 100% by mass of the coating is preferably 8 / 2 to 5 / 5, more preferably 7.5 / 2.5 to 5 / 5, and even more preferably 7 / 3 to 5 / 5 from the perspective of an excellent balance between coating strength and dissolution control.

[0054] In one embodiment of the present invention, the coated granular fertilizer preferably contains 15 to 85% by mass of component (A) in 100% by mass of the coating, and more preferably 50 to 80% by mass from the perspective of good film-forming properties. If component (A) is within the above range, good film-forming tends to be achieved. Furthermore, if component (A) exceeds 85% by mass, the initial dissolution of the fertilizer component tends to be lower, but there is a tendency for dissolution control to deteriorate over long-term dissolution of the fertilizer component. It is believed that if the mass of component (B) in the film is less than 15% by mass, the fertilizer dissolution inhibition effect of component (B) will be smaller, and the dissolution rate of fertilizer components will tend to be faster.

[0055] When component (A) is 100% by mass and component (B) is completely absent, although the initial dissolution of fertilizer components decreases, there is a tendency to worsen the dissolution control of fertilizer components in the long term.

[0056] In one embodiment of the coated granular fertilizer of the present invention, component (B) is less than 80% by mass in 100% by mass of the coating. Preferably, the coating contains 15-75% by mass of component (B), and more preferably 20-50% by mass from the perspective of good control over the dissolution of the fertilizer component. If the content of component (B) in 100% by mass of the coating is less than 15% by mass, the initial dissolution of the fertilizer component tends to be greater. Furthermore, if it exceeds 85% by mass, the coating strength is insufficient, and the initial dissolution of the fertilizer component tends to be greater.

[0057] The coating may include fillers as other components without impairing the effects of the present invention. Examples of fillers include, for instance, plate-shaped fillers such as talc, mica, and hydrotalcite; calcium carbonate, silica, clay, bentonite, montmorillonite, montmorillonite, various ore powders, inorganic substances such as sulfur, organic fillers such as starch and cellulose nanofibers, and organic fillers such as carbon, as well as surfactants. One type of filler may be used alone, or two or more may be used in combination.

[0058] From the perspective of relatively low cost, inorganic fillers are preferred. From the perspective of improving film strength and reducing the tendency of dissolution control to deteriorate less with the addition of fillers, plate-shaped fillers are preferred, and talc is even more preferred.

[0059] The median particle size of the filler is preferably below 100 μm, more preferably 1 to 50 μm. If the median particle size is within this range, problems such as film peeling during film formation and clogging of the coating resin composition in nozzles are less likely to occur due to excessively large median particle size. Even if the filler's median particle size is larger than the film thickness and protrudes from the film surface, the desired effect can be achieved as long as a portion of it enters the film and adheres to it. The median particle size can be determined using known methods such as the laser diffraction particle size distribution measuring device described above.

[0060] In the case of blended fillers, although it depends on the type of filler, it is preferable to include 0 to 80% by mass of filler in 100% by mass of the coating, more preferably 0 to 30% by mass. If the filler content in 100% by mass of the coating material exceeds 80% by mass, the dissolution controllability tends to deteriorate significantly.

[0061] The coating may contain a compatibilizer as another component without impairing the effects of the present invention. Examples of compatibilizers include, for example, unsaturated carboxylic acid modified polyolefins such as maleic anhydride modified polypropylene and maleic anhydride modified polyethylene; copolymers of styrene or α-olefins with maleic anhydride or maleic esters; aliphatic carboxylic acid modified polyolefin waxes; styrene-based thermoplastic elastomers such as SBS (styrene-butadiene-styrene) and SEBS (styrene-ethylene-butene-styrene); and rubbers such as EPR (ethylene-propylene). Compatibilizers can be used alone or in combination of two or more.

[0062] Furthermore, from the viewpoint of reducing biodegradability, the coating is preferably substantially free of waxes other than component (B). The coating is preferably substantially free of, for example, polyolefin waxes such as polyethylene wax, paraffin wax, microcrystalline wax, and aliphatic hydrocarbon waxes.

[0063] The fact that the coating does not contain wax other than component (B) means that wax that exists as an impurity of each component, or that is mixed in from raw materials or the like when manufacturing the coated granular fertilizer of one embodiment of the present invention, may be included in the coating, but wax other than component (B) is not actively added to the coating.

[0064] Specifically, "substantially free of wax other than component (B)" means that the content of wax other than component (B) in the coated granular fertilizer of the present invention is generally 0 to 1% by mass in 100% by mass of the coating, preferably 0 to 0.5% by mass, and more preferably 0 to 0.1% by mass.

[0065] In one embodiment of the present invention, the ratio of the film to 100% by mass of the coated granular fertilizer is defined as the coating rate, which can be expressed as the following formula (3). Coverage rate (%) = (mass of film) / (mass of coated granular fertilizer) × 100 ...Formula (3)

[0066] In addition, the mass of the coating is calculated by subtracting the mass of the granular fertilizer before coating from the mass of the coated granular fertilizer. Furthermore, each mass can be calculated using the average of 350 coated granular fertilizers or 350 granular fertilizers before coating. In one embodiment of the coated granular fertilizer of the present invention, the proportion of the coating relative to 100% by mass of the coated granular fertilizer is preferably 3 to 20% by mass, more preferably 4 to 15% by mass, and even more preferably 5 to 12% by mass. If the proportion of the coating is within the range described above, the leaching control of the fertilizer components is excellent, and therefore preferred.

[0067] [Dissolution control of fertilizer components] The controllability of fertilizer component dissolution in coated granular fertilizers can be evaluated, for example, by the dissolution rate (%) of fertilizer components when the coated granular fertilizer is immersed in water. The dissolution rate (%) of fertilizer components can be expressed as the following formula (4). Dissolution rate (%) = (mass of dissolved fertilizer components) / (mass of fertilizer components contained in the coated granular fertilizer) × 100 ...Formula (4)

[0068] The dissolution rate of fertilizer components can be determined, for example, by allowing granular fertilizer to stand in water at 25°C and then quantitatively analyzing the fertilizer components that dissolve in the water over time. As a quantitative analysis method for fertilizer components, the method proposed by the Environmental Technology Research Institute of the Ministry of Agriculture, Forestry and Fisheries can be cited as an example ("Detailed Explanation of Fertilizer Analysis Methods," edited by Masayoshi Koshino, 1988, published by Yokendo). Fertilizer components are generally water-soluble. If there are defects in the coating, many fertilizer components will dissolve during fertilization, resulting in insufficient control over dissolution.

[0069] Regarding the leaching control of the coated granular fertilizer according to one embodiment of the present invention, according to the above-described "Detailed Explanation of Fertilizer Analysis Method", the leaching rate in water at 25°C on the 7th day is preferably less than 100%, more preferably less than 98%, even more preferably less than 80%, even more preferably less than 45%, and even more preferably less than 30%.

[0070] <Method for manufacturing coated granular fertilizer> The method for manufacturing the coated granular fertilizer according to one embodiment of the present invention is not particularly limited. The coated granular fertilizer can be manufactured by coating the surface of a core material with a coating material comprising component (A), component (B), and other components within the scope that does not impair the effects of the present invention.

[0071] Coated granular fertilizers can be manufactured using known techniques such as spraying a melt-dispersed coating material onto the surface of a core material, spraying a coating material containing a coating material dissolved or dispersed in a solvent onto the surface of a core material (solution spraying), spraying monomers onto the surface of a core material to react and resinify them (coating), and impregnation of the core material into a coating material. Among these, the solution spraying method is preferred.

[0072] When dissolving or dispersing the coating material in a solvent, there are no particular restrictions on the solvent as long as it can dissolve or disperse the coating material, but solvents with boiling points above 30°C and below 150°C are preferred. If the boiling point is below 30°C, it is difficult to condense and recover the material; if it exceeds 150°C, it is difficult to dry it. From the viewpoint of non-flammability or flame retardancy, halogenated solvents or water are preferred. Examples of halogenated solvents include dichloromethane, chloroform, dichloroethane, trichloroethane, trichloroethylene, and perchloroethylene. Solvents can be mixed. From the viewpoint of environmental impact, solvents other than halogenated solvents are preferred, including toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, butyl acetate, tetrahydrofuran, dimethoxyethane, and diethoxyethane.

[0073] There are no particular limitations on the apparatus used for coating. Examples of coating methods include pan coating, jet coating, fluidized bed coating, rotary coating, dry coating, or combinations thereof. The present invention preferably uses jet coating or fluidized bed coating. Example

[0074] Next, an embodiment of the present invention will be shown in further detail, but the invention is not limited thereto. Furthermore, unless otherwise specified, "%" in the following embodiments represents mass%.

[0075] <Preparation of Materials> In the examples and comparative examples, commercially available products were used to prepare coated granular fertilizers. The physical properties are as follows.

[0076] [Granular fertilizer] Granular urea (manufactured by PETRONAS Fertilizer (Kedah) Sdn. Bhd.), roundness coefficient 0.9.

[0077] [Ingredients (A)] • Polybutylene succinate (also known as PBS-1) BioPBS manufactured by Mitsubishi Chemical Corporation TM FZ91, density 1.26 g / cm³ 3 (ISO 1183), melting point 115℃ (ISO 3146), melt flow rate (MFR: 190℃, 2.16kg) 0.1~30. It is listed in JBPA's Positive List of Biodegradable Plastics, classification A-1 (Biodegradable Synthetic Polymers), and is a product that has obtained biodegradability certification. • Polybutylene terephthalate (also known as PBAT-1) ECOFLEX manufactured by BASF TM Density 1.26 g / cm³3 (ISO 1183), melting point 110-120℃ (ISO 3146), melt flow rate (MFR: 190℃, 2.16kg) 2.7~4.9. It is listed in JBPA's Positive List of Biodegradable Plastics, classification A-1 (Biodegradable Synthetic Polymers), and is a product that has obtained biodegradability certification. Polylactic acid (also known as PLA-1) 4060D manufactured by Natural Workshop has a density of 1.24 g / cm³. 3 (ISO 1183), melting point 160℃ (ISO 3146), melt flow rate (MFR: 190℃, 2.16kg) 10. Listed in JBPA's Positive List of Biodegradable Plastics, classification A-1 (Biodegradable Synthetic Polymers), it is a product that has obtained biodegradability certification.

[0078] [Ingredient (B)] Rice wax (also written as RBW-1) Acid value (mgKOH / g) 15-25, saponification value (mgKOH / g) 92.5, melting point (°C) approximately 79. Materials with TUV biodegradability certification are used. Rice wax (also written as RBW-2) Acid value (mgKOH / g) 130, saponification value (mgKOH / g) 170, melting point (°C) 78. Materials with TUV biodegradability certification are used. Castor wax (also written as C Wax) Acid value (mgKOH / g) 3, saponification value (mgKOH / g) 175-186, melting point (°C) 86. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO17556). Rice wax (also written as RBW-3) Acid value (mgKOH / g) 45-55, saponification value (mgKOH / g) 115, melting point (°C) approximately 78. Materials with TUV biodegradability certification are used.

[0079] Rice wax (also written as RBW-4) Acid value (mgKOH / g) 8.8, saponification value (mgKOH / g) 80, melting point (°C) approximately 80.2. According to JIS K6955 (ISO17556), it is confirmed to have a biodegradability of over 60% within 180 days. • Lignite wax (also known as MoW-1) Acid value (mgKOH / g) 13-25, saponification value (mgKOH / g) 180, melting point (°C) 73-79. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO17556). • Lignite wax (also known as MoW-2) Acid value (mgKOH / g) 121.5, saponification value (mgKOH / g) 155, melting point (°C) 79-85. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO17556). • Lignite wax (also known as MoW-3) Acid value (mgKOH / g) 143.5, saponification value (mgKOH / g) 170, melting point (°C) 79-85. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO17556). Candelilla wax (also known as CanW-1) Acid value (mgKOH / g) 17.9, melting point (°C) 71.5. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO 17556). • Carnauba wax (also known as CarW-1) Acid value (mgKOH / g) 7.5, melting point (°C) 83.5. Confirmed to have a biodegradability of over 60% within 180 days according to JIS K6955 (ISO 17556).

[0080] 〔other〕 Polyethylene wax (also denoted as PE(1000)) The weight-average molecular weight (Mw) is approximately 1000, the acid value (mgKOH / g) is 0, and the melting point (°C) is 110. According to JIS K6955 (ISO17556), it is confirmed that it is almost non-biodegradable within 180 days.

[0081] <Examples 1-14, Comparative Examples 1-2> (Example 1) [Manufacturing of coated granular fertilizers] use Figure 1 The manufacturing apparatus shown coats the surface of granular fertilizer (granular urea) by the following method. Figure 1 Inside the manufacturing apparatus, hot air flows from the lower to the upper part of the flow layer 1, passes through the dust collector 6, and is cooled by the condenser 7, where the solvent is condensed and recovered. The gas passing through the condenser 7 is then heated by the blower 8 through the heater 12 and directed back into the flow layer 1 as hot air, forming a cycle.

[0082] As particle 3, granular urea (PETRONAS Fertilizer (Kedah) Sdn. Bhd "urea") was used, sieved to a particle size of 3.0-4.0 mm, with an average particle size of 3.3 mm and a roundness coefficient of 0.9. Particle size and average particle size were determined by dynamic image analysis (Millitrac JPA: manufactured by Nikkiso Corporation).

[0083] 400g of granular urea is added through the inlet located on the side of the flow layer 1. The urea is then allowed to flow through a combination of hot air introduced from the bottom of the flow layer 1 and an agitator located at the bottom of the flow layer 1. The hot air flow rate and temperature are adjusted to bring the particle temperature to 60±2℃. The hot air flow rate is measured and adjusted using a flow meter located between the blower 8 and the flow layer 1. The hot air temperature is adjusted by measuring the particle temperature and the exhaust temperature (temperature at the top of the flow layer 1).

[0084] Towards Figure 1 In the dissolving tank 9, 60% by mass of polybutylene succinate (PBS-1) as the coating material, 40% by mass of rice wax (RBW-1), and 3200% by mass of trichloroethylene as the coating solvent were added. The mixture was stirred at 80±2°C for 90 minutes to dissolve the materials evenly, thus preparing a uniform spray solution 5. Furthermore, the dissolving tank 9 was continuously stirred until the coating process was completed.

[0085] The spray liquid 5 is delivered to the nozzle 2 located above the flow layer 1 at a flow rate of approximately 35.5 ml / min to purge the flowing granular urea spray. The trichloroethylene contained in the purged spray liquid is condensed and recovered by the condenser 7, stored in the tank 11, and guided to the dissolution tank 9.

[0086] The aforementioned coating operation begins when the temperature of the flowing granular urea reaches 60°C and continues until the coating rate reaches 8.4% by mass. Afterward, the particle temperature is maintained at 60±2°C, the hot air temperature is adjusted, and the hot air is blown for only 10 minutes to carry out drying. At the end of the drying process, the coated granular urea is discharged through the extraction port 13 at the bottom of the flow layer 1, and then ventilated for 0.5 to 1 hour to degas and remove trichloroethylene, thus obtaining coated granular fertilizer. The coating of the obtained granular fertilizer was confirmed to be biodegradable according to JIS K6955 (ISO 17556).

[0087] The manufacturing conditions for coated granular fertilizers are briefly as follows. Granular urea: 400g Temperature of particles in the coating: 60℃ Dissolution temperature: 79±2℃ Spray liquid temperature: 79±2℃ Hot air temperature: 70~80℃ Spray flow rate: 35.5 ml / min Coverage rate: 8.4%

[0088] Coverage rate The coverage rate is calculated using the following formula (5). Coverage rate (%) = (mass of film) / (mass of coated granular fertilizer) × 100 ...Formula (5) In addition, the mass of the coating material is calculated by subtracting the mass of the granular fertilizer before coating from the mass of the coated granular fertilizer. Furthermore, each mass is calculated using the average of 350 coated granular fertilizer samples or 350 uncoated granular fertilizer samples.

[0089] (Example 2) Except for adding 60% by mass of PBS-1 and 40% by mass of C Wax as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 3) Except for adding 80% by mass of PBS-1 and 20% by mass of RBW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 4) Except for adding 60% by mass of PBS-1 and 40% by mass of RBW-2 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 5) Except for adding 90% by mass of PBS-1 and 10% by mass of RBW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Comparative Example 1) Except for adding 20% ​​by mass of PBS-1 and 80% by mass of RBW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Comparative Example 2) Except for adding 60% by mass of PBS-1 and 40% by mass of PE(1000) as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1.

[0090] (Example 6) Except for adding 60% by mass of PBS-1 and 40% by mass of RBW-3 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 7) Except for adding 60% by mass of PBS-1 and 40% by mass of RBW-4 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 8) Except for adding 60% by mass of PBS-1 and 40% by mass of MoW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 9) Except for adding 60% by mass of PBS-1 and 40% by mass of MoW-2 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 10) Except for adding 60% by mass of PBS-1 and 40% by mass of CanW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1.

[0091] (Example 11) Except for adding 60% by mass of PBS-1 and 40% by mass of CarW-1 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1. (Example 12) Except for adding 60% by mass of PBAT-1 and 40% by mass of RBW-1 as coating materials to the dissolving tank 9, coated granular fertilizer was obtained in the same manner as in Example 1. (Example 13) Except for adding 60% by mass of PLA-1 and 40% by mass of RBW-1 as coating materials to the dissolving tank 9, coated granular fertilizer was obtained in the same manner as in Example 1. (Example 14) Except for adding 60% by mass of PBS-1 and 40% by mass of MoW-3 as coating materials to the dissolving tank 9, the coated granular fertilizer was obtained in the same manner as in Example 1.

[0092] [Determination of dissolution rate] For the coated granular fertilizers obtained in the examples and comparative examples, the dissolution rate of fertilizer components in water was determined. 10g of the coated granular fertilizer from the examples and comparative examples, and 200ml of distilled water pre-adjusted to 25°C were added to a 250ml capped plastic container and placed in an incubator set at 25°C. After 7 days, all the water was extracted from the container, and the amount of urea contained in the extracted water (urea dissolution amount) was quantitatively analyzed (using the dimethylaminobenzaldehyde method, "Detailed Explanation of Fertilizer Analysis Method, Second Revised Edition," edited by Yueye Zhengyi, Yangxiantang, 1988) to determine the amount of urea dissolved. Meanwhile, the urea content in the same batch of coated granular fertilizer was determined in advance using the dimethylaminobenzaldehyde method. The dissolution rate was calculated using the following formula (6). Dissolution rate (%) = (Amount of urea dissolved) / (Amount of urea contained in the coated granular fertilizer) × 100 ...Formula (6) The dissolution rate in water at 25°C on day 7 is shown in Table 1.

[0093] 〔evaluate〕 Regarding the controllability of fertilizer component dissolution, the following criteria were used for evaluation based on the above dissolution rate test results. Furthermore, regarding biodegradability, the evaluation was based on the biodegradability of component (B). Dissolution control ○: Dissolution rate less than 80%, excellent dissolution control. △: Dissolution rate less than 98% to above 80%, with dissolution control capability. ×: Dissolution rate above 98%, no dissolution control. • Biodegradable ○: Confirmed to have biodegradability as measured according to JIS or ISO standards ×: Unable to confirm biodegradability as measured according to JIS or ISO standards Overall evaluation ◎ = Both dissolution control and biodegradability are rated as ○ ○ = Dissolution control is rated △, biodegradability is rated ○ × = Either dissolution control or biodegradability is ×

[0094] [Table 1]

[0095] [Inspection] As shown in Table 1, according to Example 1, the combination of polybutylene succinate (PBS-1) and rice wax (RBW-1) results in excellent dissolution control and biodegradability.

[0096] According to Example 2, it can be seen that even if component (B) is changed to castor wax (C Wax), the dissolution control and biodegradability are still excellent. According to Example 3, it can be seen that when the mass ratio (A / B) of component (A) to component (B) is 8 / 2, the dissolution control and biodegradability are excellent. Comparing Example 1 and Example 4, it can be seen that even if component (B) is rice wax (RBW-2) with a higher acid value, it is still possible to ensure either dissolution control or biodegradability. However, rice wax (RBW-1) with a lower acid value tends to have superior dissolution control. Comparing Example 3 and Example 5, it can be seen that 10% by mass of rice wax (RBW-1) can ensure either dissolution control or biodegradability, but the dissolution control tends to be superior when the mass of rice wax in the coating is higher.

[0097] According to Comparative Example 1, if the mass percentage of rice wax (RBW-1) is greater than 80% by mass, dissolution control cannot be guaranteed. According to Comparative Example 2, it can be seen that if polyethylene wax (PE(1000)) is used to replace component (B), biodegradability is severely impaired.

Claims

1. A coated granular fertilizer having granular fertilizer and a coating covering the surface of the granular fertilizer, said coating comprising a biodegradable resin (A) and at least one wax (B) selected from natural waxes having ester groups (b1) and their modifiers (b2). Of the 100% by weight of the coating, the wax (B) is less than 80% by weight.

2. The coated granular fertilizer as described in claim 1, wherein, The wax (B) is selected from at least one of rice wax, castor wax, lignite wax, beeswax, carnauba wax, candelilla wax, palm wax, soybean wax, and sunflower wax.

3. The coated granular fertilizer as described in claim 1 or 2, wherein, The wax (B) satisfies the following requirement (I): (I) The acid value is 0.5 to 130 according to the acid value determination method specified in JIS K0070.

4. The coated granular fertilizer as described in claim 1, wherein, The biodegradable resin (A) is selected from at least one of polybutylene succinate, polylactic acid, polybutylene terephthalate, polyhydroxy fatty acid, cellulose acetate, and polycaprolactone.

5. The coated granular fertilizer as described in claim 1, wherein, The biodegradable resin (A) meets the following requirement (II): (II) The melt flow rate (MFR) measured according to ISO 1133 at 190°C and under a load of 2.16 kg is in the range of 0.1 to 30 g / 10 min.

6. The coated granular fertilizer as described in claim 1 or 2, wherein, In 100% by mass of the coating, the mass ratio (A / B) of the biodegradable resin (A) to the wax (B) is 8 / 2 to 5 / 5.

7. The coated granular fertilizer as described in claim 1 or 2, wherein, The proportion of the coating is 3 to 20% by mass relative to 100% by mass of the coated granular fertilizer.

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