Method for producing coated fertilizer and coated fertilizer using the same

Abstract

To provide a coated fertilizer having a hydrophilic surface.SOLUTION: A coated fertilizer comprises: a granular fertilizer core; a first coated layer that is formed on a surface of the granular fertilizer core and is composed of a first coating composition including an acrylic polymer; and a second coated layer that is formed on the first coated layer and is composed of a second coating composition including an acrylic polymer, fine silicon powder, polymer sponge powder, and a hydrophilic substance. A silica particle layer is provided on a surface of the fine silicon powder.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a coated fertilizer and a coated fertilizer using the same.

Background Art

[0002] Fertilizers are substances for supplying nutrients to edible plants and ornamental plants and promoting their growth, and are substances for supplying nutrients to plants as nutrient solutions dissolved by water or moisture. Such fertilizers are classified into slow-release fertilizers, quick-acting fertilizers, chemical fertilizers, organic agricultural fertilizers, and the like. Here, slow-release fertilizers are terms contrasted with quick-acting fertilizers in which the effects of fertilizers applied to the soil appear promptly like ammonium sulfate, and are fertilizers whose effects appear gradually. By using slow-release fertilizers, the amount of chemical fertilizers used can be reduced, and pollution of soil and water quality caused by outflow nutrients can be reduced. Ordinary slow-release granular fertilizers (that is, granular fertilizers) are composed of a core layer and a coating layer. Conventionally, in order to form the coating layer of granular fertilizers, a solventless powder was sprayed onto the core and then melted and coated under high temperature, or the granular fertilizers were coated using a solvent-based coating agent. However, this was accompanied by excessive heat costs and caused the release of a large amount of volatile organic compounds (VOCs). In particular, polyvinylidene chloride (PVDC) - based coating agents have caused problems of environmental pollution not only due to the emission of volatile organic compounds (VOCs) but also due to the inclusion of halogen compounds.

[0003] In recent years, in order to prevent environmental pollution by polymer capsule materials, an elution control type fertilizer using a photodegradable polymer has been proposed. For example, Patent Document 1: Chinese Patent No. 103588561 discloses that when hydrophilic titanium dioxide (TiO2) is used, the photodegradation rate is lower than that of hydrophobic titanium dioxide. However, both hydrophobic titanium dioxide and hydrophilic titanium dioxide have the disadvantage of being expensive.

[0004] As a result, efforts have been made to develop a water-soluble acrylic coating agent based on low-temperature curing at 100°C or lower. This is because among water-soluble polymers, unlike polyester-based, vinyl-based, and urethane-based polymers, their physical properties are easy to adjust, and moreover, they are inexpensive, so they have excellent competitiveness in the industry.

[0005] In connection with this, in Patent Document 2: Republic of Korea Registered Patent No. 10-1410859, a method for producing a coated fertilizer having an effect of preventing floating in water is disclosed by forming a plurality of coating layers on the surface of granular fertilizer using a water-soluble acrylic polymer and adjusting the glass transition temperature and hydrophilicity of the polymer composition forming each coating layer. The disclosed coated fertilizer exhibits effective performance when taking the normal distribution environment in Korea (temperature 45°C, humidity 50%, stacking load 50 g / cm 2 ) as a reference, but there are drawbacks such as the problem of solidification occurring when distributed in regions with higher temperature and humidity than Korea, and the problem that a large number of coating steps are required because it consists of multiple coating layers. Note that Patent Document 3: Republic of Korea Registered Patent No. 10-0205709 proposes an anti-solidification agent for solid particle fertilizers that employs paraffin wax and paraffin oil as main components for preventing solidification, but there is a problem of floating in water because of its poor wettability (i.e., hydrophilicity).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to solve the above-mentioned problems, the present invention aims to improve the wettability (i.e., hydrophilicity) of the coating layer to improve the anti-floating effect in water, prevent the solidification phenomenon of granular fertilizers at high temperatures, and moreover, provide an environmentally friendly slow-release coated fertilizer.

[0008] However, the problems to be solved by the present invention are not limited to the above-mentioned problems at all, and other problems not mentioned can be clearly understood by those of ordinary skill in the art from the following description.

Means for Solving the Problems

[0009] A method for manufacturing a coated fertilizer according to an embodiment of the present invention includes the steps of preparing a granular fertilizer core, forming a first coating layer formed from a first coating composition containing an acrylic polymer on the surface of the granular fertilizer core, and forming a second coating layer formed from a second coating composition containing an acrylic polymer, fine powder silicon (Si), polymer sponge powder, and a hydrophilic substance on the first coating layer, and forming a silica (SiO X , 0 < x < 2) surface layer on the surface of the fine powder silicon. The method may include these steps.

[0010] A coated fertilizer according to an embodiment includes a granular fertilizer core, a first coating layer formed on the surface of the granular fertilizer core and formed from a first coating composition containing an acrylic polymer, and a second coating layer formed on the first coating layer and formed from a second coating composition containing an acrylic polymer, fine powder silicon (Si), polymer sponge powder, and a hydrophilic substance, and the surface of the fine powder silicon may be provided with a silica (SiO X , 0 < x < 2) surface layer.

[0011] According to one embodiment, the layer thickness of the surface layer is 10 nm to 50 nm, and the fine powder silicon is porous silicon particles, or a porous aggregate of silicon fibers, silicon nanotubes, silicon rods or silicon wires, or a pulverized product of a silicon fabric (woven fabric). The particle diameter of the fine powder silicon is 80 nm (nanometers) to 15 μm (micrometers), and the density is 0.3 g / m 3 ~0.9 g / m 3 and the specific surface area may be 0.1 m 2 / g to 150 m 2 / g.

[0012] According to one embodiment, the fine powder silicon is heat-treated at a temperature of 600 to 800 for 10 minutes to 1 hour to form a silica surface layer. The fine powder silicon is functionalized with a hydrophilic group on the silica surface layer, and the hydrophilic group may be a thiol group, an amine group or a hydroxy group.

[0013] According to one embodiment, the second coating layer further includes silica particles surface-treated with a hydrophilic group, and the silica particles may be included in an amount of 10 parts by weight to 50 parts by weight based on 100 parts by weight of the fine powder silicon.

[0014] According to one embodiment, the polymer sponge powder may be a pulverized product of a polymer sponge structure containing one or more selected from the group consisting of cellulose-based polymers, gelatin, collagen, gellan gum, sodium hyaluronate, sodium alginate, fibroin, chondroitin sulfate, glycosaminoglycan, proteoglycan, elastin, chitosan, heparin, glucosamine, PCL (poly ε-caprolactone), PLA (polylactic acid), aliphatic polyester, PG (polyglycolic acid), polyphosphate ester, polyphosphazene, polyvinyl acetate, and polyvinyl alcohol.

[0015] According to one embodiment, the hydrophilic substance includes one or more selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. The organic acid includes one or two or more selected from the group consisting of butyric acid, lactic acid, propionic acid, valeric acid, acetic acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid, citric acid, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, isostearic acid, and behenic acid. The hydrophilic substance may be included in an amount of 10 parts by weight to 30 parts by weight based on 100 parts by weight of the fine powder silicon.

[0016] According to one embodiment, the second coating layer further includes a cationic surfactant. The cationic surfactant may include one or two or more selected from the group consisting of quaternary ammonium salts, cetyltrimethylammonium chloride (CTAC), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB), didodecyldimethylammonium bromide, and cetrimonium bromide.

[0017] According to one embodiment, the glass transition temperature of the acrylic polymer contained in the first coating composition is 5°C to 40°C, and the glass transition temperature of the acrylic polymer contained in the second coating composition may be 40°C to 80°C.

[0018] According to one embodiment, the acid value of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition is 10 mgKOH / g to 100 mgKOH / g, respectively, and the molecular weight (weight average molecular weight) of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition may be 10,000 (mol / g) to 1,000,000 (mol / g), respectively.

Effects of the Invention

[0019] The present invention can improve the wettability (i.e., hydrophilicity) of the coating layer to improve the anti-floating effect in water, prevent the solidification phenomenon of granular fertilizers at high temperatures, and moreover, provide an environmentally friendly slow-release coating fertilizer.

Brief Description of the Drawings

[0020]

Figure 1

Modes for Carrying Out the Invention

[0021] Hereinafter, the coating fertilizer of the present invention will be specifically described with reference to embodiments and drawings. However, the present invention is not limited to such embodiments and drawings.

[0022] The present invention can provide a slow-release coating fertilizer that can improve wettability, prevent solidification and floating in water by adopting an outer skin layer containing silicon particles and a hydrophilic substance and an inner skin layer based on an acrylic polymer.

[0023] According to an embodiment of the present invention, the present invention provides a method for manufacturing a coating fertilizer. The method for manufacturing a coating fertilizer includes the steps of preparing a granular fertilizer core, forming a first coating layer formed from a first coating composition containing an acrylic polymer on the surface of the granular fertilizer core, and forming a second coating layer formed from a second coating composition containing an acrylic polymer, fine powder silicon (Si), polymer sponge powder, and a hydrophilic substance on the first coating layer, and forming a silica (SiO X , 0 < x < 2) surface layer on the surface of the fine powder silicon. It may also include.

[0024] According to another embodiment, referring to FIG. 1, the coating fertilizer 100 according to the present invention may include a granular fertilizer core 100, a first coating layer 200 (i.e., the inner skin layer) and a second coating layer 300 (the outer skin layer).

[0025] According to one embodiment, the granular fertilizer core 100 may mean a central portion containing the active ingredient of the fertilizer. The granular fertilizer core 100 is applicable without limitation as long as it is a well-known commercially available product (granular fertilizer) in the technical field of the present invention or a component applicable to granular fertilizers. For example, among the elements necessary for plant growth, the three major elements of fertilizer consisting of nitrogen (N), phosphorus (P), and potassium (K) and the three elements may be composed of four elements and five elements by adding calcium (Ca) and magnesium (Mg). The main components of the fertilizer are composed of ionic compounds (i.e., in the form of salts) and organic fertilizer components, and may be granular, but are not limited thereto. Also, the size (diameter) of the granular fertilizer core 100 can be variously changed and may be 1 μm (micrometer) or more, 10 μm (micrometer) or more, 100 μm (micrometer) or more, 300 μm (micrometer) or more, 500 μm (micrometer) or more, 800 μm (micrometer) or more, 1 mm (millimeter) or more, 2 mm (millimeter) or more, or 3 mm (millimeter).

[0026] According to one embodiment, the first coating layer 200 may be formed on the surface of the granular fertilizer core 100 and may be formed from a first coating composition containing an acrylic polymer. The first coating layer 200 means an inner coating layer formed on the surface of the granular fertilizer 100 and may have a function of adjusting the water permeability in order to adjust the elution rate of the active ingredient of the fertilizer by containing an acrylic polymer.

[0027] According to one embodiment, the first coating composition may be composed of only the monomer and water, but may further contain an initiator, a chain transfer agent, a surfactant, etc. According to one embodiment, in the first coating composition, the acrylic polymer is formed by polymerizing a monomer selected from among a reactive unsaturated acrylate monomer and a monomer containing a carboxy group, and the reactive unsaturated acrylate monomer is an alkyl acrylate having 1 to 18 carbon atoms, an alkyl methacrylate, a cycloalkyl acrylate, a cycloalkyl ethacrylate, an alkoxyalkyl acrylate, an alkoxyalkyl methacrylate ester, a hydroxyalkyl acrylate having 2 to 8 carbon atoms, a hydroxyalkyl methacrylate ester, acrylonitrile, methacrylonitrile, and trifluoroethyl methacrylate, and may be one or a mixture of two or more selected therefrom. The monomer containing a carboxy group may be characterized in that it is one or a mixture of two or more selected from acrylic acid, methacrylic acid, vinylbenzoic acid, itaconic acid, maleic acid, fumaric acid, and their anhydrides. Further, the acrylic polymer may be formed by a crosslinking agent containing an acrylic group containing two or more ethylene groups.

[0028] According to one embodiment, as the initiator, a water-soluble initiator, an oil-soluble initiator, or a redox initiator can be used, and preferably, a thermally dissociable radical initiator can be used. Specific examples of the water-soluble initiator include ammonium persulfate, sodium persulfate, and potassium persulfate, which may be used alone, or may be used in combination with a reducing agent such as sodium bisulfite or sodium formaldehyde sulfoxylate. As the oil-soluble initiator, t-butyl hydroperoxide, dibutyl peroxide, benzoyl hydroperoxide, perbenzoic acid, hydrogen peroxide, peracetic acid, etc. are used, and they may be used alone or in combination with the above reducing agent.

[0029] According to one embodiment, as the chain transfer agent, alkyl mercaptans having 2 to 15 carbon atoms, mercapto carboxylic acid esters having 2 to 8 carbon atoms, carbon tetrachloride, bromotrichloromethane, etc. can be used. However, as long as it is a compound that can be used for adjusting the molecular weight of the produced polymer, its type is not limited.

[0030] According to one embodiment, the acrylic polymer contained in the first coating composition has a glass transition temperature of 5°C to 80°C, 5°C to 50°C, preferably 5°C to 40°C, an acid value of 10 to 100 (mgKOH / g), a hydroxyl value of 10 to 100 (mgKOH / g), and a molecular weight (weight average molecular weight) of 10,000 to 1,000,000 (mol / g).

[0031] According to one embodiment, the second coating layer 300 may be formed on the first coating layer 200 and may be formed from a second coating composition containing an acrylic polymer, fine powder silicon, polymer sponge powder, and a hydrophilic substance. The second coating layer 300 means an outer coating layer formed on the first coating layer 200, and may contain an acrylic polymer, fine powder silicon, polymer sponge powder, and a hydrophilic substance to improve wettability and have functions of preventing solidification at high temperatures and preventing floating in water.

[0032] According to one embodiment, the acrylic polymer contained in the second coating composition has a glass transition temperature of 5°C to 80°C, 30°C to 80°C, preferably 40°C to 80°C, an acid value of 10 to 100 mgKOH / g, a hydroxyl value of 10 to 100 mgKOH / g, and a molecular weight (weight average molecular weight) of 10,000 to 1,000,000 (mol / g). According to one embodiment, the acrylic polymer contained in the second coating composition may be different from the acrylic polymer contained in the first coating composition in at least one or more or all of the glass transition temperature, acid value, hydroxyl value, and molecular weight. According to one embodiment, the acrylic polymer contained in the second coating composition has a higher glass transition temperature than the acrylic polymer contained in the first coating composition, and a coated fertilizer that prevents solidification and floating in water can be provided.

[0033] According to one embodiment, the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition may be different or the same in at least one or more or a combination or all of the glass transition temperature, acid value, hydroxyl value, and molecular weight (e.g., weight average molecular weight). Preferably, the physical properties required for the first coating layer 200 and the second coating layer 300 may be controlled by differentiating in the mentioned physical properties.

[0034] According to one embodiment, the acrylic polymer contained in the first coating composition has a glass transition temperature of 5 to 40°C, and the acrylic polymer contained in the second coating composition has a glass transition temperature of 40 to 80°C. Preferably, the glass transition temperature of the acrylic polymer contained in the first coating composition is 10 to 30°C, and the glass transition temperature of the acrylic polymer contained in the second coating composition may be 40 to 70°C. That is, since the first coating composition has a relatively low glass transition temperature and is excellent in water resistance and moisture barrier properties, the elution rate of the fertilizer component can be easily adjusted. Since the second coating composition has a relatively high glass transition temperature, it can physically protect the inner coating layer from the outside and prevent the solidification phenomenon in which fertilizers stick to each other at high temperatures during the distribution of fertilizers.

[0035] According to one embodiment, the acid value of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition is 10 to 100 mgKOH / g, respectively. The hydroxyl value of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition is 10 to 100 mgKOH / g, respectively. The molecular weight (weight average molecular weight) of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition may be 10,000 to 1,000,000 (mol / g), respectively.

[0036] According to one embodiment, the glass transition temperatures (i.e., acrylic polymers) of the first and second coating compositions may be adjusted by changing the types and contents of the monomers to be polymerized. In the case of the first coating composition, it may contain an acrylic polymer polymerized using a monomer of a soft polymer such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, etc. as the main monomer, or in the case of the second coating composition, it may contain an acrylic polymer polymerized using a monomer of a hard polymer such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. as the main monomer. For example, in the first coating composition, 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, of a monomer containing a carboxy group can be used with respect to 100 parts by weight of the reactive unsaturated acrylate monomer, and the second coating composition may contain an acrylic polymer polymerized using 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, of a monomer containing a carboxy group with respect to 100 parts by weight of the reactive unsaturated acrylate monomer. The coating fertilizer according to the present invention uses acrylic polymers having different glass transition temperatures that have been conventionally used, and contains fine powder silicon in the second coating composition to improve the solidification prevention function, and adsorbs a hydrophilic substance to the fine powder silicon to maximize the hydrophilicity, thereby having the effect of being able to maintain the function of preventing floating in water.

[0037] According to one embodiment, the acrylic polymer contained in the second coating composition may contain an acrylic polymer having an acid value of 55 to 60 (mgKOH / g), a hydroxyl value of 90 to 96 (mgKOH / g), and a weight average molecular weight of about 500,000. Or, it may contain an acrylic polymer having an acid value of 45 to 50 (mgKOH / g), a hydroxyl value of 80 to 90 (mgKOH / g), and a weight average molecular weight of about 300,000. That is, this can increase the dispersibility and adhesion of the fine powder and impart wettability (i.e., wetting property) by changing the acid value, hydroxyl value, and / or molecular weight of the second coating composition.

[0038] According to one embodiment, the content of the fine powder silicon may be 1 to 50 parts by weight with respect to 100 parts by weight of the second coating composition. According to one embodiment, the fine powder silicon may be a porous silicon gas pore body having a silica (SiO x ) layer on its surface. The fine powder silicon may be porous silicon particles composed of a silicon skeleton body connected in a three-dimensional network-like shape, or a porous aggregate of silicon nanotubes, rods and / or wires and / or a pulverized product of a silicon fabric (woven fabric). The silicon skeleton body may be a nanotube (hollow) silicon skeleton body. The silicon fabric is woven into a fiber bundle composed of a plurality of silicon fibers. The particle diameter of the fine powder silicon may be 80 nm to 15 μm (micrometer), 200 nm to 15 μm (micrometer), 500 nm to 10 μm (micrometer), or 1 μm (micrometer) to 5 μm (micrometer). The density of the fine powder silicon is 0.3 g / m 3 ~0.9 g / m 3 , and the specific surface area may be 0.1 to 150 m 2 / g. The pore diameter (diameter) of the fine powder silicon may be 1 nm to 1 μm (micrometer). The diameter (or thickness) of the silicon fiber, nanotube, rod and wire may be 100 nm to 200 μm.

[0039] According to one embodiment, the fine powder silicon (particles without a silica (SiO x )(0 < x < 2) layer) may be heat-treated at a temperature of 500°C to 900°C for 10 minutes to 1 hour to form a silica surface layer (SiO x ). The surface layer may have a layer thickness of 1 nm to 50 nm, 5 nm to 50 nm, 10 nm to 50 nm, 20 nm to 50 nm, or 30 nm to 50 nm.

[0040] According to one embodiment, the fine powder silicon may be functionalized with a hydrophilic group on the silica surface layer. The hydrophilic group may be a thiol group, an amine group, or a hydroxy group. Such functionalization with a hydrophilic group may proceed in the same manner as the fine powder silica mentioned below, or alternatively, after mixing and immersing the fine powder silicon and a compound having a functional group (in a solution state), heat treatment may be performed at 150°C to 200°C to proceed. By achieving such porous characteristics and functionalization with hydrophilic groups, wettability and hydrophilicity can be improved to prevent floating in water.

[0041] According to one embodiment, the polymer sponge powder may be a pulverized product of a polymer porous foam and / or a polymer porous sponge structure. The foam and sponge are usually products produced by well-known processes in the technical field of the present invention or may be commercially available products. The foam and sponge may contain fine pores with a pore diameter of 10 nm to 100 μm (micrometer). After being crushed by a cutting machine, the foam and sponge are pulverized into particles with a particle size of 100 nm to 100 μm (micrometer) by performing ultrasonic pulverization and ball milling processes. The polymer sponge powder is a porous particle having fine pores, which can increase wettability by capillary action and adsorb moisture to prevent floating in water. The polymer sponge powder may be a pulverized product of a polymer sponge structure containing one or more selected from the group consisting of cellulose-based polymers, gelatin, collagen, gellan gum, sodium hyaluronate, sodium alginate, fibroin, chondroitin sulfate, glycosaminoglycan, proteoglycan, elastin, chitosan, heparin, glucosamine, PCL (poly ε-caprolactone), PLA (polylactic acid), aliphatic polyester, PG (polyglycolic acid), polyphosphoric acid ester, polyphosphazene, polyvinyl acetate, and polyvinyl alcohol.

[0042] According to one embodiment, the polymer sponge powder may be included in an amount of 10 to 30 parts by weight, 10 to 20 parts by weight, or 15 to 20 parts by weight based on 100 parts by weight of the fine powder silicon. By applying the mentioned content range, the capillary phenomenon caused by the polymer sponge powder can be increased to improve wettability and hydrophilicity, prevent floating in water, and increase the generation temperature of solidification.

[0043] According to one embodiment, as the hydrophilic substance, those existing as natural substances or hydrophilic substances derived from natural substances (i.e., modified products of natural substances) can be used. The hydrophilic substance may include one or more selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. The organic acid may include one or more selected from the group consisting of butyric acid, lactic acid, propionic acid, valeric acid, acetic acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid, citric acid, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, isostearic acid, and behenic acid. Since there is a heating process in the manufacturing process of the granular fertilizer, when the hydrophilic substance has low volatility and a low melting point, liquefaction and solidification are repeated in a storage environment where high temperature (daytime) and normal temperature (nighttime) are repeated, resulting in a decrease in the solidification prevention function. Therefore, in some cases, it is preferable that the melting point is high.

[0044] According to one embodiment, the hydrophilic substance may be included in an amount of 10 to 30 parts by weight, 10 to 20 parts by weight, or 15 to 20 parts by weight based on 100 parts by weight of the fine powder silicon. By applying the mentioned content range, wettability and hydrophilicity can be improved, floating in water can be prevented, and the generation temperature of solidification can be increased.

[0045] According to one embodiment, the second coating composition may further contain fine powder silica (SiO2) particles. The fine powder silica may mean pulverized porous silica gel. Generally, when an acid is added to liquid silicic acid, a silica sol having primary particles is generated, and the silanol groups (Si-OH) present on the surface of the primary particles are promoted to undergo dehydration and condensation reactions by the continuous addition of phosphoric acid to form a Si-O-Si network and a three-dimensional network structure, which is called silica gel. Such silica gel exhibits porosity, and the pulverized product thereof may be fine powder silica. The fine powder silica can exhibit various properties depending on the degree of porosity and particle size.

[0046] The fine powder silica contains a large number of pores in the particles, and due to the very small pore diameter of the pores, it has the characteristic of showing a strong capillary effect on liquids. Also, it has the advantage of being inexpensive compared to colloidal silica or alkoxysilane-based materials having a particle diameter in the nanometer range, and has the characteristic of showing a light extinction effect.

[0047] According to one embodiment, the particle diameter of the fine powder silica may be 0.3 μm (micrometer) to 100 μm (micrometer). Specifically, the particle diameter of the fine powder silica may be 0.8 μm (micrometer) to 5 μm (micrometer), and preferably may be 1 μm (micrometer) to 5 μm (micrometer). Also, when the particle diameter of the fine powder silica exceeds the above-described range, the pore diameter of the pores in the fine powder silica particles becomes large, the capillary effect on liquids decreases, and when in contact with water, water cannot quickly spread to the second coating layer 300 (outer coating layer) having lipophilicity, and as a result, there is a risk of reducing the function of preventing floating in water.

[0048] According to one embodiment, the oil absorption amount of the fine powder silica may be 100 ml / 100 g to 1,000 ml / 100 g, preferably 100 ml / 100 g to 500 ml / 100 g, and more preferably 200 ml / 100 g to 400 ml / 100 g. According to one embodiment, the specific surface area of the fine powder silica is 10 m 2 / g to 1,000 m 2 / g. Preferably, it may be 100 m 2 / g to 500 m 2 / g, and more preferably 200 m 2 / g to 400 m 2 / g.

[0049] According to one embodiment, the fine powder silica may be silica particles surface-treated with a hydrophilic group. The hydrophilic group may be a thiol group, an amine group, or a hydroxy group, and preferably may be a thiol group. The surface wettability can be increased by the surface functionalized with the hydrophilic group, and the adsorption of moisture can be increased. According to one embodiment, after subjecting the fine powder silica to acid treatment in an acid aqueous solution of nitric acid / sulfuric acid (1:1 v / v) for 1 hour, the functionalization process may be advanced at 90°C to 100°C for 1 hour to 2 hours in a solution containing a compound having a functional group. The compound may be added in an amount of 1 part by weight to 15 parts by weight based on 100 parts by weight of the fine powder silica. Examples of the thiol group include ammonium thioglycolate (AmTG), 1,3-diisopropyl-2-thiourea, N-(3-methoxyphenyl)thiourea, or 1,3-dihexyl-2-thiourea. As the amine group, a compound having an amine functional group is applicable, and the amine functional group may be butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, hexadecylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminooctane, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, methylpropylamine, ethylpropylamine, propylbutylamine, ethylbutylamine, ethylpentylamine, propylpentylamine, butylpentylamine, tributylamine, or trihexylamine.

[0050] According to one embodiment, the fine powder silica may be contained in an amount of 1 to 30 parts by weight, 5 to 20 parts by weight, or 10 to 15 parts by weight with respect to 100 parts by weight of the fine powder silicon (Si). By applying the mentioned content, wettability and moisture adsorption can be increased, and the function of preventing floating in water can be improved.

[0051] According to one embodiment, the second coating composition further contains a cationic surfactant, and the surfactant may include one or more selected from the group consisting of quaternary ammonium salts, cetyltrimethylammonium chloride (CTAC), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB), didodecyldimethylammonium bromide, and cetrimonium bromide. The cationic surfactant may be contained in an amount of 1 to 30 parts by weight, 5 to 20 parts by weight, or 10 to 15 parts by weight with respect to 100 parts by weight of the fine powder silicon (Si). By applying the mentioned content, the dispersion and mixing of the dispersion (i.e., solids and particles) applied to the second coating composition can be carried out well, and the surface contact angle with water can be reduced.

[0052] According to one embodiment, the second coating composition may further include at least one neutralizing agent selected from the group consisting of dimethylethanolamine (DMEA), isopropanolamine (MIPA), and monoethanolamine (MEA). The neutralizing agent is used to neutralize an acidic silica paste containing water, fine powder silica, and a hydrophilic substance, and has the effect of increasing the thixotropy of the second coating composition. Thixotrophy means the property that a suspension has no fluidity in a stationary state but has fluidity during vibration. The neutralizing agent increases the thixotropy of the second coating composition, and has the effect of showing very good sedimentation prevention performance without separately adding a thickening agent. In addition, the neutralizing agent is characterized in that it has a low probability of remaining in the coating layer of the granular fertilizer after being evaporated in the heating and drying process after the formation of the coating layer.

[0053] According to one embodiment, the first coating layer 200 and the second coating layer 300 may be configured as a single layer or a multi-layer as needed. The layer thicknesses of the first coating layer 200 and the second coating layer 300 may be 10 μm (micrometers) to 1000 μm (micrometers), 100 μm (micrometers) to 1000 μm (micrometers), 200 μm (micrometers) to 800 μm (micrometers), or 300 μm (micrometers) to 500 μm (micrometers), respectively. The layer thicknesses of the first coating layer 200 and the second coating layer 300 may be the same or different from each other. Preferably, in order to improve the floating prevention function, the second coating layer 300 may be 1.2 to 2 times thicker than the first coating layer.

[0054] According to one embodiment, the present invention may include the steps of coating a surface of a granular fertilizer core with a first coating composition containing an acrylic polymer to form a first coating layer, forming a second coating layer formed from a second coating composition on the first coating layer, and heat-treating and drying the granular fertilizer on which the first coating layer and the second coating layer are formed.

[0055] According to one embodiment, as the coating machine capable of manufacturing the granular fertilizer, generally, a drum coating machine, a fan - type coating machine, a fluidized - bed coating machine, etc. can be used. However, although the drum coating machine and the fan - type coating machine are easy to operate and can be mass - produced, they cannot quickly dry the liquid substances contained in the coating material in the coating machine. As a result, the fertilizers may get entangled with each other or the formation of the film may be poor. Therefore, in the present invention, it is preferable to use a fluidized - bed coating machine.

[0056] The coated fertilizer can be produced by coating the surface of the granular fertilizer core flowing through a pressure - type two - fluid nozzle using a generally known fluidized - bed granular coating machine with the coating composition.

[0057] According to one embodiment, before proceeding with the coating, in order to evaporate the moisture remaining in the granular fertilizer and remove the dust adhering to the granular fertilizer inside the coating machine, it is preferable to preheat the inside of the coating machine and then proceed with the coating. The temperature at the inlet of the coating machine may be set to about 60 - 100°C, and the internal temperature of the coating machine may be maintained at 60°C - 70°C for 5 - 10 minutes for preheating. However, the above conditions can be changed according to the performance of the coating machine and the required physical properties.

[0058] According to one embodiment, once the preheating of the coating machine is completed, the core of the granular fertilizer is coated with the first coating composition. The first coating composition is pumped at a rate of 5 g / min - 100 g / min and sprayed through a two - fluid nozzle with an air pressure of 0.2 kg / cm 2 ~3 kg / cm 2 to be primarily coated on the surface of the granular fertilizer to form a first coating layer.

[0059] According to one embodiment, once the formation of the first coating layer is completed, the supply of the first coating composition is interrupted, and the second coating composition is sprayed in the same manner as the primary coating method to form a secondary coating on the surface of the granular fertilizer on which the first coating layer is formed, thereby forming a second coating layer. At this time, it is preferable to adjust the coating rate of the first coating layer to be about 5 to 15%, and the coating rate of the second coating layer to be about 2% to 25%, 10% to 25%, 15% to 25%, 20% to 25% or 2% to 5%. The above conditions can be changed according to the performance of the coating machine and the required physical properties.

[0060] According to one embodiment, after the second coating layer is formed by the second coating composition, heat treatment is performed to dry the coating layer. In particular, the formation of the film can be firmly maintained between the polymer particles in the first coating layer and the second coating layer by the heat treatment.

[0061] According to one embodiment, the heat treatment step may generally be performed using a hot air blower. The amount of hot air is maintained at the same amount as the coating step. The heat treatment is performed at 30 to 100 °C for about 5 to 100 minutes, and more preferably at 60 to 100 °C for 20 to 60 minutes. However, the above conditions can be changed according to the performance of the coating machine and the required physical properties. Also, it is preferable to dry the water content in the first coating layer and the second coating layer to be 20% by weight or less by the heat treatment, and more preferably to be 10% by weight or less.

[0062] Hereinafter, the present invention will be described more specifically with reference to Examples and Experimental Examples. However, these Examples and Experimental Examples can be changed into various other forms, and the scope of the present invention is not limited to the Examples detailed below in any way. The Examples of the present invention are provided to more fully explain the present invention to those having average knowledge in the industry.

[0063] Production Example 1 Production of the First Coating Composition The first coating composition containing the following acrylic polymer was produced.

[0064] 700 g of ion-exchanged water and 10 g of sodium dodecylbenzenesulfonate were added to a 1-L flask, and then the temperature was raised to 80°C. Next, a monomer mixture consisting of 160 g of styrene, 50 g of butyl acrylate, 80 g of 2-ethyl acrylate, and 10 g of acrylic acid and 3 g of ammonium persulfate were added dropwise over 2 hours to produce an acrylic polymer. After the addition was complete and the mixture was held for about 1 hour, it was cooled to 60°C to produce a first coating composition. The produced first coating composition had a solid content of 30%, a particle size of 150 nm, and a viscosity of 120 cps. In addition, it was confirmed that the acrylic polymer in the first coating composition had a glass transition temperature of 20°C and a weight-average molecular weight of 150,000.

[0065] Production Example 2-1 Production of the Second Coating Composition (A) 800 g of ion-exchanged water and 20 g of sodium dodecylbenzenesulfonate were added to a 1-L flask, and then the temperature was raised to 80°C. Next, a monomer mixture consisting of 380 g of styrene, 100 g of butyl acrylate, 100 g of 2-ethyl acrylate, and 20 g of acrylic acid and 6 g of ammonium persulfate were added dropwise over 2 hours to produce an acrylic polymer. After the addition was complete and the mixture was held for about 1 hour, it was cooled to 60°C to produce a second coating composition. The produced second coating composition had a solid content of 42%, a particle size of 162 nm, and a viscosity of 180 cps. In addition, it was confirmed that the acrylic polymer in the second coating composition had a glass transition temperature of 40°C and a weight-average molecular weight of 145,000.

[0066] Production Example 2-2 Production of the Second Coating Composition (B) 5 g of allyl methacrylate, 25 g of methacrylate, 35 g of ethyl acrylate, 85 g of 2-ethylhexyl acrylate, 130 g of 2-hydroxyethyl acrylate, 130 g of 2-hydroxyethyl methacrylate, 35 g of butyl acrylate, and 70 g of acrylic acid were stirred and mixed. Then, 1.9 g of benzoyl peroxide was added as an initiator and stirred. Subsequently, it was dropped into the prepared flask over 4 hours to produce an acrylic polymer. After the dropping was completed, the polymerization reaction was advanced while maintaining the reflux conditions for about 1 hour, and it was cooled to 60 °C to produce a first coating composition. It was confirmed that the acrylic polymer in the first coating composition had an acid value of 52.9 mgKOH / g, a hydroxyl value of 95.5 mgKOH / g, and a weight average molecular weight of about 500,000. 35 g of diethylethanolamine was added to the acrylic polymer and neutralized by titration at room temperature until the pH reached 10, and then diluted with water to produce a second coating composition (water-soluble polyacrylic resin composition). The acrylic polymer in the produced second coating composition had a solid content of 45%, a particle diameter of 160 nm, and a viscosity of 150 cps. In addition, it was confirmed that the acrylic polymer in the second coating composition had a glass transition temperature of 50 °C.

[0067] Production Example 3 Polymer sponge powder Cellulose sponge (pore diameter (diameter): about 0.5 μm to 2 μm) was crushed by a crusher, then ultrasonically pulverized over 1 hour, ball milled over 2 hours and dried to obtain a powder with a particle diameter of about 10 μm.

[0068] Production Example 4-1 Production of fine powder silicon Porous silicon particles composed of a silicon skeleton body connected by a network were heat-treated at a temperature of about 700 °C for 10 minutes, then cooled to obtain fine powder silicon having an oxide (SiO x , x is 1.4 to 1.8) surface layer. The particle diameter of the fine powder silicon is on average 2 μm, the pore diameter is 100 nm to 150 nm, the specific surface area is 150 m 2 / g, and the density is 0.5 g / m3 It is.

[0069] Production Example 4-2 Surface Functionalization of Fine Powder Silicon The produced fine powder silicon (Production Example 4-1; an oxide surface layer of 30 nm is formed) was immersed in an aqueous solution of nitric acid / sulfuric acid (1 / 1 volume ratio) for 1 hour, and then dried at a temperature of 50°C. Subsequently, it was immersed in an ammonium thioglycolate (AmTG) solution (10 parts by weight was added based on the total mass of the fine powder silicon particles), and dried to obtain silicon powder surface-modified with thiol groups.

[0070] Production Example 5 Surface Functionalization of Silica Particles Porous silica particles (2 μm, oil absorption: 300 ml / 100 g, pore diameter: average 300 nm, specific surface area: 300 (m 2 / g))) were immersed in an aqueous solution of nitric acid / sulfuric acid (1 / 1 volume ratio) for 1 hour, then washed away, and dried at a temperature of 50°C. Subsequently, it was immersed in an ammonium thioglycolate (AmTG) solution (dimethylformamide (DMF) solvent, 10 parts by weight was added based on the total mass of the porous silica particles), heated to 90°C, and held for 30 minutes. After washing and drying, silica powder surface-modified with thiol groups was obtained.

[0071] Production Example 6 Production of Fine Powder Silicon Paste After adding the components shown in Table 1 to 199 g of water, a silicon paste was produced while stirring (linear velocity: 2 m / sec). In the production of the paste, a urethane-based (coapur-3025 manufactured by Coatex) thickener that does not require pH adjustment was used as an anti-settling agent to prevent sedimentation while minimizing the increase in viscosity.

[0072] [Table 1]

[0073] Production Example 7 Manufacture of the Second Coating Composition (C) The acrylic polymer of Production Example 2 and the fine powder silicon paste of Production Example 6 were mixed to produce a second coating composition containing the fine powder silicon paste. The composition and properties of the produced second coating composition for improving anti-floating are shown in Table 2.

[0074]

Table 2

[0075] Examples 1 to 4 Manufacture of Coated Fertilizer Using Acrylic Polymer and the Second Coating Composition in Table 2 2 kg of granular fertilizer with a particle size of 2 mm to 4 mm was quantitatively measured and put into a fluidized bed coater, and the fluidized air volume was set to about 200 m 3 / hr to float the granular fertilizer in the air, and the temperature of the fluidized air was set to 60°C, and a preheating process was carried out for 10 minutes. After the preheating process was completed, 200 g of the first coating composition produced in Production Example 1 was sprayed onto the surface of the fertilizer for 50 minutes to form a first coating layer. Next, 100 g each of the second coating compositions produced in Production Examples 7-1, 7-2, 7-3, and 7-4 were sprayed for 15 minutes to form a second coating layer. At this time, the coating temperature was 40°C, the fluidized air volume was 350 m3 / hr, the air pressure of the spray nozzle was 2 kg / cm 2 The first coating layer and the second coating layer were coated under the conditions that the spray amount was 13 g / min.

[0076] Comparative Example 1 The method of Example 1 was followed except that the second coating composition produced in Production Example 7-5 in Table 3 was used.

[0077] Experimental Example 1 Measurement of the Generation Temperature of Solidification of the Second Coating Composition The PET film with an average thickness of 38 μm was coated with the first coating composition (Production Example 1) using a bar coater and then dried at room temperature for 1 hour. After that, the second coating composition (Production Example 7) was coated as a stock solution on the coating surface of the primary coating layer thus prepared using a bar coater, and then dried at room temperature for 1 hour and further dried at 60 °C for 3 hours. After that, it was taken out of the oven and left to stand in a natural state for 24 hours. Two coated films prepared in the same manner as this method were stacked facing each other, and then this film was put into an oven and a metal plate having a certain unit area was placed on the film. After placing a certain weight on it, the temperature was raised from 25 °C by 5 °C each time, and the heating time was 1 hour for each unit temperature. After heating for 1 hour, the two facing surfaces were separated to check for the presence or absence of adhesion. The results are shown in Table 3.

[0078]

Table 3

[0079] As shown in Table 3, since solidification does not occur at 60 °C x 80 g / cm 2 which is the reference temperature and load, it can be confirmed that the solidification prevention function of the second coating composition of the present invention is excellent. Also, it can be confirmed that the solidification occurrence temperature becomes higher by the application of particles functionalized with hydrophilic groups or the increase in silica particles.

[0080] Experimental Example 2 Confirmation of the floating prevention effect of the second coating composition Using the second coating composition of Preparation Example 7, a test specimen was prepared in the same manner as in the solidification prevention test method of Experimental Example 1. The prepared test specimen was heated and dried, and then the contact angle was measured (using a contact angle measuring device manufactured by KRUSS) under conditions of a temperature of 25°C and a humidity of 50%. In general, a contact angle of 60° or less indicates average anti-floating ability, and a contact angle of 50° or less indicates excellent anti-floating ability. A contact angle of more than 80° noticeably deteriorates the anti-floating ability, and a contact angle of 90° or more is considered to be water repellent. The results of the experiment are shown in Table 4.

[0081] [Table 4]

[0082] The second coating composition of Production Example 7-5, which did not contain a hydrophilic substance, had a large contact angle with water, whereas Production Examples 7-1 to 7-4 had low contact angles, confirming that they had an excellent anti-floating effect.

[0083] Experimental Example 3 Confirmation of floating rate of coated fertilizer in water In order to measure the floating rate of the coated fertilizer in water, about 300 pieces of the coated fertilizer prepared in Examples 1 to 4 and Comparative Example 1 were randomly taken out and widely spread in a 500 ml beaker so that the particles would not overlap each other, and then about 300 ml of water was carefully filled along the wall of the beaker using a 100 ml washing bottle, and the beaker was stored in a thermostatic chamber at 25°C to carry out the floating rate test of the granular coated fertilizer in water. At this time, the water was sealed with vinyl wrap to prevent evaporation, and the floating rate in water was calculated as the number of fertilizer particles floating on the water relative to the total number of fertilizer particles as a percentage. The experimental results are shown in Table 5.

[0084] [Table 5]

[0085] Referring to Table 5, it can be seen that in Examples 1 to 4, the capillary phenomenon and wettability are improved, the number of granular fertilizers floating on the water surface initially is small, and it is prevented from floating on the water surface over a long period of time.

[0086] Experimental Example 4 Confirmation of the effect of suppressing the solidification phenomenon of the coated fertilizer The first coating composition was coated on a PET film with an average thickness of 38 μm using a bar coater (#10), and then dried at room temperature for 1 hour. After that, the second coating composition produced in Production Example 7 was coated on the surface of the primary coating layer thus prepared with the stock solution using a bar coater (#10), and then dried at room temperature for 1 hour and further dried at 60 °C for 3 hours. After that, it was taken out of the oven and left in a natural state for 24 hours. After stacking two coating films prepared in the same manner face to face, the film was placed in an oven, and a metal plate with a certain unit area was placed on the film. After placing a certain weight on it, the temperature was raised from 25 °C to 5 °C at a time and heated. The heating time was 1 hour for each unit temperature. After heating for 1 hour, the two facing surfaces were pulled apart to check for adhesion. The results of the above experiment are shown in Table 6.

[0087]

Table 6

[0088] As shown in Table 6, it can be seen that in Example 1 and Example 4, the solidification temperature is higher than that in Comparative Example 1, and in Example 4, it is even higher when applying acrylic polymers with a difference in molecular weight.

[0089] Experimental Example 5 Confirmation of the slow-release effect of the coated fertilizer To confirm the slow-release effect of the coating fertilizer according to the present invention, 2.5 g of the coating fertilizers of Example 1 and Example 2 were placed in a 250 ml flask, filled with distilled water, sealed, and left standing in a constant temperature bath at 30°C. Then, the nitrogen component of the fertilizer eluted into the water through the coating layer was measured using high performance liquid chromatography (HPLC) with a refractive index detector (RI Detector). The content of the eluted component was measured to calculate the elution rate. The results are shown in Table 7.

[0090] [Table 7]

[0091] Referring to Table 7, it was confirmed that the slow-release property of the coating fertilizer according to the present invention does not decrease. That is, the present inventors can provide a slow-release coated granular fertilizer with improved wettability, capable of preventing floating in water and solidification at high temperatures.

[0092] The above-described embodiments of the present invention are disclosed for illustrative purposes only, and those skilled in the art with ordinary knowledge in the present invention can make various modifications, changes, and additions within the scope of the idea of the present invention, and such modifications, changes, and additions belong to the scope of the claims.

Claims

1. A step of preparing a granular fertilizer core; A step of forming a first coating layer formed from a first coating composition containing an acrylic polymer on the surface of the granular fertilizer core; A step of forming a second coating layer formed from a second coating composition containing an acrylic polymer, fine powder silicon (Si), polymer sponge powder, and a hydrophilic substance on the first coating layer; A step of forming a silica (SiO Ｘ , 0 < x < 2) surface layer on the surface of the fine powder silicon; including A method for producing a coated fertilizer, characterized by the above.

2. A granular fertilizer core; A first coating layer formed on the surface of the granular fertilizer core and formed from a first coating composition containing an acrylic polymer; A second coating layer formed on the first coating layer and formed from a second coating composition containing an acrylic polymer, fine powder silicon (Si), polymer sponge powder, and a hydrophilic substance; provided with A silica (SiO Ｘ , 0 < x < 2) surface layer is provided on the surface of the fine powder silicon A coated fertilizer, characterized by the above.

3. The layer thickness of the surface layer is 10 nm to 50 nm, The fine powder silicon is porous silicon particles, or a porous aggregate of silicon fibers, silicon nanotubes, silicon rods or silicon wires, or a pulverized product of a silicon fabric (woven fabric), The particle diameter of the fine powder silicon is 80 nm (nanometers) to 15 μm (micrometers), and the density is 0.3 g / m ３ ~0.9 g / m ３ and the specific surface area is 0.1 m ２ / g to 150 m ２ / g The coated fertilizer according to claim 2.

4. The fine powder silicon is heat-treated at a temperature of 600 to 800 for 10 minutes to 1 hour to form a silica surface layer, The fine powder silicon is functionalized with a hydrophilic group on the silica surface layer, The hydrophilic group is a thiol group, an amine group or a hydroxy group. The coated fertilizer according to claim 2.

5. The second coating layer further includes silica particles surface-treated with a hydrophilic group, The silica particles are contained in an amount of 10 to 50 parts by weight with respect to 100 parts by weight of the fine powder silicon. The coated fertilizer according to claim 2.

6. The polymer sponge powder is A pulverized product of a polymer sponge structure containing one or more selected from the group consisting of cellulose-based polymers, gelatin, collagen, gellan gum, sodium hyaluronate, sodium alginate, fibroin, chondroitin sulfate, glycosaminoglycan, proteoglycan, elastin, chitosan, heparin, glucosamine, PCL (poly ε-caprolactone), PLA (polylactic acid), aliphatic polyester, PG (polyglycolic acid), polyphosphate ester, polyphosphazene, polyvinyl acetate, and polyvinyl alcohol. The coated fertilizer according to claim 2.

7. The hydrophilic substance is One or more selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose, The organic acid is It contains one or more selected from the group consisting of butyric acid, lactic acid, propionic acid, valeric acid, acetic acid, glycolic acid, sorbic acid, fumaric acid, formic acid, malic acid, tartaric acid, citric acid, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, isostearic acid and behenic acid. The hydrophilic substance is contained in an amount of 10 parts by weight to 30 parts by weight with respect to 100 parts by weight of the fine powder silicon. The coated fertilizer according to claim 2.

8. The second coating layer further contains a cationic surfactant. The cationic surfactant contains one or more selected from the group consisting of quaternary ammonium salts, cetyltrimethylammonium chloride (cetyltrimethylammonium chloride; CTAC), dodecyltrimethylammonium bromide (dodecyltrimethylammonium bromide; DTAB), cetyltrimethylammonium bromide (CTAB), didodecyldimethylammonium bromide and cetrimonium bromide. The coated fertilizer according to claim 2.

9. The glass transition temperature of the acrylic polymer contained in the first coating composition is 5°C to 40°C. The glass transition temperature of the acrylic polymer contained in the second coating composition is 40°C to 80°C. The coated fertilizer according to claim 2.

10. The acid values of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition are each 10 mgKOH / g to 100 mgKOH / g. The molecular weights (weight average molecular weights) of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition are each 10,000 (mol / g) to 1,000,000 (mol / g). The coated fertilizer according to claim 2.

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