Manufacturing method of 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 producing a coated fertilizer and a coated fertilizer using the same. [Background technology]

[0002] Fertilizers are substances used to provide nutrients and promote the growth of edible and ornamental plants. They are dissolved in water or moisture and supply nutrients to plants as a nutrient solution. Fertilizers are classified into slow-release fertilizers, fast-release fertilizers, chemical fertilizers, and organic fertilizers. Slow-release fertilizers, as opposed to fast-release fertilizers like ammonium sulfate, which rapidly release their effects after application to the soil, are fertilizers that gradually release their effects. The use of slow-release fertilizers can reduce the amount of chemical fertilizer used and reduce soil and water pollution caused by nutrient runoff. Typical slow-release granular fertilizers (i.e., granular fertilizers) consist of a core layer and a coating layer. Conventionally, the coating layer of granular fertilizers has been formed by spraying a solvent-free powder onto the core, followed by melting and coating at high temperatures, or by coating the granular fertilizer using a solvent-based coating agent. However, this method requires excessive heat and results in the emission of large amounts of volatile organic compounds (VOCs). In particular, polyvinylidene chloride (PVDC)-based coating agents have caused environmental pollution problems 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 caused by polymer capsule materials, elution-controlled fertilizers using photodegradable polymers have been proposed. For example, Patent Document 1 (China Patent No. 103588561) discloses that when hydrophilic titanium dioxide (TiO2) is used, the photodecomposition rate is lower than that of hydrophobic titanium dioxide. However, both hydrophobic and hydrophilic titanium dioxide have the disadvantage of being expensive.

[0004] This led to efforts to develop water-soluble acrylic coating agents that are based on low-temperature curing at temperatures below 100°C. This is because, unlike polyester, vinyl, and urethane water-soluble polymers, their physical properties are easy to adjust and they are inexpensive, making them highly competitive for industrial use.

[0005] In this regard, Patent Document 2 (Korean Patent Registration No. 10-1410859) discloses a method for producing a coated fertilizer in which a water-soluble acrylic polymer is used to form multiple coating layers on the surface of granular fertilizer, and the glass transition temperature and hydrophilicity of the polymer composition constituting each coating layer are controlled to prevent floating in water. The disclosed coated fertilizer is stored in a normal Korean distribution environment (temperature 45°C, humidity 50%, load 50g / cm). 2 Although it exhibits effective performance when used in areas with higher temperatures and humidity than Korea, it suffers from the drawbacks of caking when distributed in hotter and more humid regions than Korea, and the need for multiple coating processes due to its multi-layer coating.Patent Document 3: Korean Patent Registration No. 10-0205709 proposes an anti-caking agent for solid particle fertilizers that uses paraffin wax and paraffin oil as the main ingredients for preventing caking, but its poor wettability (i.e., hydrophilicity) causes it to float in water. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent No. 103588561 [Patent Document 2] Korean Patent Registration No. 10-1410859 [Patent Document 3] Republic of Korea Patent No. 10-0205709 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve the above-described 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 provide a slow-release coating fertilizer that is environmentally friendly.

[0008] However, the problems to be solved by the present invention are not limited to the above-described problems at all, and other problems not mentioned can be clearly understood by those skilled 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 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, and a step of forming a silica (SiO X , 0 < x < 2) surface layer on the surface of the fine powder silicon.

[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 may include a silica (SiO X , 0 < x < 2) surface layer on the surface of the fine powder silicon.

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

[0012] In one embodiment, the fine powder silicon is heat-treated at a temperature of 600 to 800°C for 10 minutes to 1 hour to form a silica surface layer, and 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 hydroxyl 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 to 50 parts by weight per 100 parts by weight of the fine silicon powder.

[0014] In one embodiment, the polymer sponge powder may be a pulverized 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, polypolyphosphazene, polyvinyl acetate, and polyvinyl alcohol.

[0015] According to one embodiment, the hydrophilic substance may include one or more selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose, and 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, and the hydrophilic substance may be included in an amount of 10 to 30 parts by weight based on 100 parts by weight of the fine silicon powder.

[0016] According to one embodiment, the second coating layer further comprises a cationic surfactant, and the cationic surfactant may comprise one or more selected from the group consisting of a quaternary ammonium salt, 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 may be 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 may each be 10 mgKOH / g to 100 mgKOH / g, 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 each be 10,000 (mol / g) to 1,000,000 (mol / g). [Effects of the Invention]

[0019] The present invention can improve the wettability (i.e., hydrophilicity) of the coating layer to enhance the effect of preventing floating 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] It is a cross-sectional view showing the configuration of a coating fertilizer according to an embodiment of the present invention.

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. The method may include these steps.

[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 refer to the central portion containing the active ingredients of a fertilizer. The granular fertilizer core 100 may be applied to any commercially available product (granular fertilizer) known in the art or any component applicable to a granular fertilizer, without any limitations. For example, among elements necessary for plant growth, the fertilizer may be composed of three elements of fertilizer: nitrogen (N), phosphorus (P), and potassium (K), or four or five elements by adding calcium (Ca) and magnesium (Mg) to the three elements. The main components of the fertilizer may be composed of ionic compounds (i.e., in the form of salts) and organic fertilizer components, and may be in a granular form, but are not limited thereto. Furthermore, the size (diameter) of the granular fertilizer core 100 can be changed in various ways, 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 refers to an inner coating layer formed on the surface of the granular fertilizer 100 and may contain an acrylic polymer and have the function of adjusting water permeability in order to adjust the dissolution rate of the active ingredients of the fertilizer.

[0027] According to one embodiment, the first coating composition may consist solely of the monomer and water, but may further include 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 a reactive unsaturated acrylate monomer and a carboxy group-containing monomer, and the reactive unsaturated acrylate monomer may be one or a mixture of two or more selected from C1-C18 alkyl acrylates, alkyl methacrylates, cycloalkyl acrylates, cycloalkyl ethacrylates, alkoxyalkyl acrylates, alkoxyalkyl methacrylate esters, C2-C8 hydroxyalkyl acrylates, hydroxyalkyl methacrylate esters, acrylonitrile, methacrylonitrile, and trifluoroethyl methacrylate. The carboxy group-containing monomer may be one or a mixture of two or more selected from acrylic acid, methacrylic acid, vinylbenzoic acid, itaconic acid, maleic acid, fumaric acid, and anhydrides thereof. The acrylic polymer may also be formed by a crosslinking agent containing an acrylic group containing two or more ethylene groups.

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

[0029] According to one embodiment, the chain transfer agent may be an alkyl mercaptan having 2 to 15 carbon atoms, a mercaptocarboxylic acid ester having 2 to 8 carbon atoms, carbon tetrachloride, bromotrichloromethane, or the like. However, the type of the chain transfer agent is not limited as long as it is a compound that can be used to control the molecular weight of the polymer produced.

[0030] According to one embodiment, the acrylic polymer contained in the first coating composition may have a glass transition temperature of 5°C to 80°C, 5°C to 50°C, or preferably 5°C to 40°C, an acid value of 10 to 100 (mgKOH / g), a hydroxyl group 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 from a second coating composition including an acrylic polymer, finely powdered silicon, a polymer sponge powder, and a hydrophilic substance. The second coating layer 300 refers to an outer coating layer formed on the first coating layer 200, and may include an acrylic polymer, finely powdered silicon, a polymer sponge powder, and a hydrophilic substance to improve wettability and prevent solidification at high temperatures and floating in water.

[0032] According to one embodiment, the acrylic polymer contained in the second coating composition may have 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 differ from the acrylic polymer contained in the first coating composition in at least one 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, making it possible to provide a coated fertilizer that is prevented from solidifying and floating in water.

[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 the same or different in at least one or all of the following: 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 differentiated by differentiating the aforementioned 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 acrylic polymer contained in the first coating composition has a glass transition temperature of 10 to 30° C., and the acrylic polymer contained in the second coating composition has a glass transition temperature of 40 to 70° C. That is, the first coating composition has a relatively low glass transition temperature and is excellent in water resistance and moisture blocking properties, so that the elution rate of the fertilizer components can be easily adjusted, and the second coating composition has a relatively high glass transition temperature, so that the inner coating layer can be physically protected from the outside and the solidification phenomenon in which the fertilizer sticks to itself at high temperatures during distribution of the fertilizer can be prevented.

[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 may each be 10 to 100 mgKOH / g, the hydroxyl value of the acrylic polymer contained in the first coating composition and the acrylic polymer contained in the second coating composition may each be 10 to 100 mgKOH / g, 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 each be 10,000 to 1,000,000 (mol / g).

[0036] According to one embodiment, the glass transition temperatures of the first and second coating compositions (i.e., acrylic polymers) may be adjusted by changing the type and content of the polymerized monomers. The first coating composition may include an acrylic polymer polymerized using a soft polymer monomer such as acrylic acid, methyl acrylate, ethyl acrylate, or butyl acrylate as the main monomer, or the second coating composition may include an acrylic polymer polymerized using a hard polymer monomer such as methyl methacrylate, ethyl methacrylate, or butyl methacrylate as the main monomer. For example, the first coating composition may contain 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, of a carboxyl group-containing monomer per 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 carboxyl group-containing monomer per 100 parts by weight of the reactive unsaturated acrylate monomer. The coated fertilizer of the present invention uses conventional acrylic polymers with different glass transition temperatures, but contains fine powdered silicon in the second coating composition to improve anti-caking properties, and maximizes hydrophilicity by allowing hydrophilic substances to be adsorbed onto the fine powdered silicon, thereby maintaining the ability to prevent floating in water.

[0037] According to one embodiment, the acrylic polymer contained in the second coating composition may include an acrylic polymer having an acid value of 55-60 (mgKOH / g), a hydroxyl value of 90-96 (mgKOH / g), and a weight-average molecular weight of approximately 500,000. Alternatively, the acrylic polymer may include an acrylic polymer having an acid value of 45-50 (mgKOH / g), a hydroxyl value of 80-90 (mgKOH / g), and a weight-average molecular weight of approximately 300,000. In other words, by changing the acid value, hydroxyl value, and / or molecular weight of the second coating composition, the dispersibility and adhesive strength of the fine powder can be increased, and wettability (i.e., wettability) can be imparted.

[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 from 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 hydrophilic groups on the silica surface layer. The hydrophilic groups may be thiol groups, amine groups, or hydroxyl groups. Such functionalization with hydrophilic groups may be carried out in the same manner as for the fine powder silica described below, or may be carried out by mixing the fine powder silicon with a compound (in solution) having functional groups, immersing the mixture, and then heat-treating the mixture at 150°C to 200°C. Such porous properties and functionalization with hydrophilic groups improve wettability and hydrophilicity, thereby preventing 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 may be a product typically produced by a process well known in the art of the present invention or a commercially available product. The foam and sponge may have micropores with a diameter of 10 nm to 100 μm (micrometers). The foam and sponge are crushed using a cutter, then pulverized into particles with a diameter of 100 nm to 100 μm (micrometers) by ultrasonic crushing and ball milling. The polymer sponge powder is a porous particle with micropores, which increases wettability through capillary action and can adsorb moisture to prevent floating in water. The polymer sponge powder may be a pulverized 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, polypolyphosphazene, 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 silicon powder. By applying the content ranges mentioned above, the capillary action of the polymer sponge powder can be increased, thereby improving wettability and hydrophilicity, preventing floating in water, and increasing the solidification temperature.

[0043] According to one embodiment, the hydrophilic substance may be a naturally occurring substance or a hydrophilic substance derived from a naturally occurring substance (i.e., a modified form of a natural substance). 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 the manufacturing process of the granular fertilizer involves a heating step, if the hydrophilic substance has low volatility and a low melting point, a high melting point may be preferable because the hydrophilic substance may repeatedly liquefy and solidify in a storage environment where high temperatures (daytime) and room temperatures (nighttime) are alternated, thereby reducing its anti-caking function.

[0044] According to one embodiment, the hydrophilic material 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 silicon powder. By applying the content ranges mentioned above, it is possible to improve wettability and hydrophilicity, prevent floating in water, and increase the solidification temperature.

[0045] According to one embodiment, the second coating composition may further contain finely powdered silica (SiO2) particles. The term "finely powdered silica" may refer to a finely powdered porous silica gel. Generally, when an acid is added to liquid silicic acid, a silica sol having primary particles is produced. The silanol groups (Si-OH) present on the surfaces of the primary particles undergo dehydration and condensation reactions with the continued addition of phosphoric acid, forming a Si-O-Si network, forming a three-dimensional network structure, which is called silica gel. Such silica gel exhibits porosity, and its finely powdered form may be called finely powdered silica. The finely powdered silica can exhibit various properties depending on the degree of porosity and particle size.

[0046] The fine powder silica has numerous pores in its particles, and the pores have very small diameters, which allows it to exhibit a strong capillary effect on liquids. Furthermore, it is less expensive than colloidal silica or alkoxysilane-based silicas with nanometer-sized particles, and it also has the advantage of exhibiting a quenching effect.

[0047] According to one embodiment, the particle size of the finely powdered silica may be 0.3 μm to 100 μm. Specifically, the particle size of the finely powdered silica may be 0.8 μm to 5 μm, preferably 1 μm to 5 μm. Furthermore, if the particle size of the finely powdered silica exceeds the above-mentioned range, the pore size of the finely powdered silica particles becomes large, reducing the capillary effect on liquids and preventing water from quickly reaching the second coating layer 300 (outer coating layer), which becomes lipophilic upon contact with water. As a result, the ability to prevent floating in water may be reduced.

[0048] According to one embodiment, the oil absorption of the fine powdered 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 powdered silica is 10 m 2 / g~1,000m 2 / g. Preferably, 100m 2 / g~500m 2 / g, more preferably 200m 2 / g~400m 2 / g.

[0049] According to one embodiment, the fine powdered 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, preferably a thiol group. The surface functionalized with the hydrophilic group increases surface wettability and water adsorption. According to one embodiment, the fine powdered silica may be acid-treated in an aqueous acid solution of nitric acid / sulfuric acid (1:1 v / v) for 1 hour, and then functionalized in a solution containing a compound having a functional group at 90°C to 100°C for 1 hour to 2 hours. The compound may be added in an amount of 1 to 15 parts by weight per 100 parts by weight of the fine powdered silica. As the thiol group, ammonium thioglycolate (AmTG), 1,3-diisopropyl-2-thiourea, N-(3-methoxyphenyl)thiourea, 1,3-dihexyl-2-thiourea, or the like can be used. The amine group may be a compound having an amine functional group, and the amine functional group may be butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, hexadecylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, diaminopentane, diaminohexane, diaminoheptane, diaminooctane, diaminononane, diaminodecane, 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 powdered silica may be included in an amount of 1 to 30 parts by weight, 5 to 20 parts by weight, or 10 to 15 parts by weight based on 100 parts by weight of the fine powdered silicon (Si). By applying the above-mentioned content, wettability and moisture adsorption can be increased, thereby improving the function of preventing floating in water.

[0051] According to one embodiment, the second coating composition further comprises a cationic surfactant, which may include one or more surfactants 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 included in an amount of 1 to 30 parts by weight, 5 to 20 parts by weight, or 10 to 15 parts by weight per 100 parts by weight of the finely divided silicon (Si) powder. Applying the above-mentioned content can facilitate the dispersion and mixing of the dispersion (i.e., solids and particles) applied to the second coating composition and reduce the surface contact angle with water.

[0052] According to one embodiment, the second coating composition may further include one or more neutralizing agents 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, finely powdered silica, and a hydrophilic material, and has the effect of increasing the thixotropy of the second coating composition. Thixotropy refers to the property of a suspension not flowing when stationary but becoming flowable upon vibration. The neutralizing agent increases the thixotropy of the second coating composition, thereby providing excellent anti-settling performance without the need for a separate thickener. Furthermore, the neutralizing agent is characterized by its low probability of remaining in the coating layer of the granular fertilizer due to evaporation during the heating and drying process after the coating layer is formed.

[0053] According to one embodiment, the first coating layer 200 and the second coating layer 300 may be configured as a single layer or multiple layers as needed, and the thickness of the first coating layer 200 and the second coating layer 300 may be 10 μm to 1000 μm, 100 μm to 1000 μm, 200 μm to 800 μm, or 300 μm to 500 μm, respectively. The thicknesses of the first coating layer 200 and the second coating layer 300 may be the same or different. Preferably, the second coating layer 300 may be 1.2 to 2 times thicker than the first coating layer to improve the anti-floating function.

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

[0055] According to one embodiment, a coating machine capable of producing the granular fertilizer generally includes a drum coating machine, a fan-type coating machine, a fluidized bed coating machine, etc. Although the drum coating machine and the fan-type coating machine are easy to operate and allow for mass production, they are unable to quickly dry the liquid substance contained in the coating substance inside the coating machine, which can lead to entanglement of the fertilizer particles or poor film formation. 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 a granular fertilizer core flowing through a pressurized two-fluid nozzle with the coating composition using a commonly known fluidized bed granular coating machine.

[0057] According to one embodiment, before proceeding with the coating, it is preferable to preheat the inside of the coating machine to evaporate the moisture remaining in the granular fertilizer inside the coating machine and remove dust attached to the granular fertilizer, and to preheat the inside of the coating machine for 5 to 10 minutes while maintaining the temperature at the inlet of the coating machine at about 60 to 100°C and the internal temperature of the coating machine at 60 to 70°C, but the above conditions can be changed depending on the performance and required physical properties of the coating machine.

[0058] According to one embodiment, after the preheating of the coating machine is completed, the cores of the granular fertilizer are coated with the first coating composition. The first coating composition is sprayed using a pump at a rate of 5 g / min to 100 g / min with an air pressure of 0.2 kg / cm of the air-mixing spray nozzle. 2 ~3kg / cm 2 Alternatively, the first coating layer may be formed by spraying the granular fertilizer through a two-fluid nozzle.

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

[0060] According to one embodiment, after the second coating layer is formed using the second coating composition, the coating layer is dried by heat treatment, which can particularly firmly maintain the formation of a film between the first coating layer and the polymer particles in the second coating layer.

[0061] According to one embodiment, the heat treatment step may generally be performed using a hot air blower, maintaining the same amount of hot air as in the coating step, and the heat treatment may be performed at 30 to 100°C for about 5 to 100 minutes, more preferably at 60 to 100°C for 20 to 60 minutes, although the conditions can be changed depending on the performance of the coating machine and the required physical properties. Furthermore, the heat treatment is preferably performed to dry the first coating layer and the second coating layer so that the moisture content in the first coating layer and the second coating layer is 20% by weight or less, more preferably 10% by weight or less.

[0062] The present invention will be described in more detail below with reference to examples and experimental examples. However, these examples and experimental examples can be modified in various ways, and the scope of the present invention is not limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0063] Manufacturing Example 1 Preparation of the First Coating Composition A first coating composition was prepared containing the following acrylic polymer:

[0064] 700 g of ion-exchanged water and 10 g of sodium dodecylbenzenesulfonate were added to a 1 L flask and heated to 80°C. 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 then added dropwise over two hours to produce an acrylic polymer. After the addition was completed, the mixture was held for approximately one hour and then cooled to 60°C to produce a first coating composition. The resulting first coating composition had a solids content of 30%, a particle size of 150 nm, and a viscosity of 120 cps. The acrylic polymer in the first coating composition was confirmed to have a glass transition temperature of 20°C and a weight-average molecular weight of 150,000.

[0065] Manufacturing Example 2-1 Preparation 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 heated to 80°C. 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 then added dropwise over two hours to produce an acrylic polymer. After the addition was completed, the mixture was held for approximately one hour and then cooled to 60°C to produce a second coating composition. The resulting second coating composition had a solids content of 42%, a particle size of 162 nm, and a viscosity of 180 cps. The acrylic polymer in the second coating composition was confirmed to have a glass transition temperature of 40°C and a weight-average molecular weight of 145,000.

[0066] Manufacturing Example 2-2 Preparation of the second coating composition (B) 5g of allyl methacrylate, 25g of methacrylate, 35g of ethyl acrylate, 85g of 2-ethylhexyl acrylate, 130g of 2-hydroxyethyl acrylate, 130g of 2-hydroxyethyl methacrylate, 35g of butyl acrylate, and 70g of acrylic acid were mixed with stirring, and then 1.9g of benzoyl peroxide was added as an initiator and stirred. The mixture was then added dropwise to the flask over a period of 4 hours to produce an acrylic polymer. After the addition, the mixture was refluxed for approximately 1 hour to allow the polymerization reaction to proceed, and then cooled to 60°C to produce a first coating composition. The acrylic polymer in the first coating composition was confirmed to have an acid value of 52.9mgKOH / g, a hydroxyl value of 95.5mgKOH / g, and a weight-average molecular weight of approximately 500,000. 35 g of diethylethanolamine was added to the acrylic polymer, and neutralization titration was performed at room temperature until the pH reached 10, followed by dilution with water to prepare a second coating composition (a water-soluble polyacrylic resin composition). The acrylic polymer in the prepared second coating composition had a solids content of 45%, a particle size of 160 nm, and a viscosity of 150 cps. The acrylic polymer in the second coating composition was confirmed to have a glass transition temperature of 50°C.

[0067] Manufacturing Example 3 Polymer sponge powder Cellulose sponge (pore size (diameter): approximately 0.5 μm to 2 μm) was crushed in a crusher, then ultrasonically crushed for 1 hour, ball milled for 2 hours, and dried to obtain a powder with a particle size of approximately 10 μm.

[0068] Manufacturing Example 4-1 Production of fine silicon powder The porous silicon particles, which consist of silicon skeletons connected by a reticulated network, were heat-treated at a temperature of about 700°C for 10 minutes, and then cooled to form a 30 nm oxide (SiO x , x is 1.4 to 1.8) to obtain a fine powder silicon having a surface layer. The particle diameter of the fine powder silicon was 2 μm on average, the pore diameter was 100 nm to 150 nm, and the specific surface area was 150 m 2 / g and the density is 0.5g / m3 is.

[0069] Manufacturing Example 4-2 Surface functionalization of fine powder silicon The fine powder silicon (Preparation Example 4-1; a 30 nm oxide surface layer was 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. It was then immersed in an ammonium thioglycolate (AmTG) solution (10 parts by weight based on the total mass of the fine powder silicon particles) and dried to obtain a silicon powder surface-modified with thiol groups.

[0070] Production Example 5 Surface functionalization of silica particles Porous silica particles (2μm, oil absorption: 300ml / 100g, pore diameter: average 300nm, specific surface area: 300(m 2 The porous silica particles (1000 mg / g)) were immersed in an aqueous solution of nitric acid / sulfuric acid (1 / 1 volume ratio) for 1 hour, rinsed, and dried at 50°C. They were then immersed in an ammonium thioglycolate (AmTG) solution (dimethylformamide (DMF) solvent, 10 parts by weight 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] Manufacturing Example 6 Manufacturing of fine powder silicon paste The components shown in Table 1 were added to 199 g of water and stirred (linear velocity: 2 m / sec) to produce a silicone paste. In producing the paste, a urethane-based thickener (Coapur-3025 manufactured by Coatex) that does not require pH adjustment was used as an anti-settling agent to minimize viscosity increase and prevent settling.

[0072] [Table 1]

[0073] Manufacturing Example 7 Preparation of the second coating composition (C) A second coating composition containing fine powder silicon paste was prepared by mixing the acrylic polymer of Preparation Example 2 with the fine powder silicon paste of Preparation Example 6. The composition and properties of the prepared second coating composition for improving anti-floating properties are shown in Table 2.

[0074] [Table 2]

[0075] Examples 1 to 4 Preparation of coated fertilizer using acrylic polymer and second coating composition of Table 2 2 kg of granular fertilizer with a particle size of 2 mm to 4 mm was measured and put into a fluidized bed coating machine, and the fluidizing air volume was approximately 200 m 3 The granular fertilizer was levitated in the air at a rate of 40°C / hr, and the fluidized air temperature was set to 60°C, followed by a 10-minute preheating step. After the preheating step was completed, 200 g of the first coating composition prepared in Preparation Example 1 was sprayed onto the surface of the fertilizer for 50 minutes to form a first coating layer. Next, 100 g of each of the second coating compositions prepared in Preparation Examples 7-1, 7-2, 7-3, and 7-4 was sprayed for 15 minutes to form a second coating layer. At this time, the coating temperature was 40°C, the fluidizing air volume was 350 m3 / hr, and the air pressure of the spray nozzle was 2 kg / cm 2 The first coating layer and the second coating layer were formed under the conditions of a spray rate of 13 g / min.

[0076] Comparative Example 1 The same procedure as in Example 1 was carried out, except that the second coating composition prepared in Preparation Example 7-5 in Table 3 was used.

[0077] Experimental Example 1 Determining the onset temperature of solidification of the second coating composition The first coating composition (Preparation Example 1) was coated onto a PET film with an average thickness of 38 μm using a bar coater and then dried at room temperature for one hour. The second coating composition (Preparation Example 7) was then coated onto the thus-prepared primary coating layer using a bar coater. The coating was then dried at room temperature for one hour and then at 60°C for three hours. The film was then removed from the oven and left in its natural state for 24 hours. Two coated films prepared in the same manner were stacked facing each other and placed in an oven. A metal plate with a fixed unit area was placed on top of the film. A weight was then placed on top of the film, and the temperature was increased in 5°C increments from 25°C, with the heating time being one hour for each unit temperature. After heating for one hour, the opposing surfaces were separated and checked for adhesion. The results are shown in Table 3.

[0078] [Table 3]

[0079] As shown in Table 3, the reference temperature and load are 60°C x 80g / cm 2 Since no solidification occurs at this temperature, it can be confirmed that the solidification prevention function of the second coating composition of the present invention is outstanding. It can also be confirmed that the solidification temperature increases with the application of particles functionalized with hydrophilic groups or the increase in silica particles.

[0080] Experimental Example 2 Confirmation of the anti-floating effect of the second coating composition Using the second coating composition of Preparation Example 7, a test specimen was prepared using the same anti-caking test method as in Experimental Example 1. The prepared test specimen was heated and dried, and then the contact angle was measured (using a contact angle measuring instrument manufactured by Kruss) at a temperature of 25°C and humidity of 50%. Generally, 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° significantly reduces 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 does not contain a hydrophilic substance, has a large contact angle with water, but Production Examples 7-1 to 7-4 have low contact angles, confirming that they have an excellent anti-floating effect.

[0083] Experimental Example 3 Confirmation of floating rate of coated fertilizer in water To measure the floating rate of the coated fertilizers in water, approximately 300 particles of the coated fertilizers prepared in Examples 1 to 4 and Comparative Example 1 were randomly removed and spread widely in a 500 ml beaker, ensuring that the particles did not overlap. Then, using a 100 ml washing bottle, approximately 300 ml of water was carefully poured along the sides of the beaker, and the beaker was stored in a constant temperature bath at 25°C to test the floating rate of the coated fertilizers in water. The container was then sealed with plastic wrap to prevent evaporation, and the floating rate was calculated as the number of fertilizer particles that floated to the top of the water relative to the total number of fertilizer particles, expressed 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, so that the number of granular fertilizers floating on the water surface at the beginning is small, and they are prevented from floating on the water surface for a long period of time.

[0086] Experimental Example 4 Confirmation of the effect of coated fertilizer in suppressing solidification The first coating composition was coated onto a PET film with an average thickness of 38 μm using a bar coater (#10) and then dried at room temperature for one hour. The second coating composition prepared in Preparation Example 7 was then coated onto the surface of the primary coating layer prepared in this manner using a bar coater (#10) from the undiluted state. The coating was then dried at room temperature for one hour and then at 60°C for three hours. The film was then removed from the oven and left in its natural state for 24 hours. Two coated films prepared in the same manner were stacked facing each other and placed in an oven. A metal plate with a fixed unit area was placed on top of the film. A fixed weight was then placed on top of the film, and the temperature was increased by 5°C from 25°C. The heating time was one hour for each unit temperature. After heating for one hour, the opposing surfaces were separated and checked for adhesion. The results of this experiment are shown in Table 6.

[0087] [Table 6]

[0088] As shown in Table 6, Example 1 and Example 4 have higher solidification temperatures than Comparative Example 1, and Example 4 has an even higher solidification temperature when using acrylic polymers with different molecular weights.

[0089] Experimental Example 5 Confirmation of the slow release effect of coated fertilizer To confirm the slow-release effect of the coated fertilizers according to the present invention, 2.5 g of the coated fertilizers of Examples 1 and 2 were placed in 250 ml flasks, filled with distilled water, sealed, and placed in a thermostatic chamber at 30°C. The nitrogen components of the fertilizers that had eluted into the water through the coating layer were measured using high performance liquid chromatography (HPLC) with a refractive index detector. The content of the eluted components was measured, and the elution rate was calculated. The results are shown in Table 7.

[0090] [Table 7]

[0091] Referring to Table 7, it was confirmed that the slow-release properties of the coated fertilizer according to the present invention were not reduced. That is, the present inventors have provided a slow-release coated granular fertilizer that has improved wettability, preventing floating in water and solidification at high temperatures.

[0092] The above-described embodiments of the present invention have been disclosed for illustrative purposes only, and those skilled in the art having ordinary skill in the art may make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions fall within the scope of the appended claims.

Claims

1. providing a granular fertilizer core; forming a first coating layer on the surface of the granular fertilizer core, the first coating layer being formed from a first coating composition including an acrylic polymer; Silica (SiO Ｘ , 0<x<2) surface layer; forming a second coating layer on the first coating layer, the second coating layer being made of a second coating composition including an acrylic polymer, fine powdered silicon having a surface layer of silica formed thereon, a polymer sponge powder, and a hydrophilic substance; Including, The hydrophilic substance includes at least one selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. A method for producing a coated fertilizer.

2. The fine powder silicon is heat treated at a temperature of 600°C to 800°C for 10 minutes to 1 hour to form a silica surface layer. A method for producing the coated fertilizer according to claim 1.

3. a granular fertilizer core; a first coating layer formed on the surface of the granular fertilizer core and made of a first coating composition including an acrylic polymer; a second coating layer formed on the first coating layer and made of a second coating composition including an acrylic polymer, finely powdered silicon (Si), a polymer sponge powder, and a hydrophilic substance; Equipped with The surface of the fine powder silicon is coated with silica (SiO Ｘ , 0<x<2) surface layer, The hydrophilic substance includes at least one selected from the group consisting of organic acids, carboxymethyl cellulose, hydroxymethyl cellulose, and hydroxyethyl cellulose. A coated fertilizer characterized by:

4. the thickness of the surface layer is 10 nm to 50 nm; The fine powder silicon is a porous silicon particle, or a porous aggregate of silicon fiber, silicon nanotube, silicon rod or silicon wire, or a pulverized silicon fabric (woven fabric); The particle size of the fine powder silicon is 80 nm (nanometers) to 15 μm (micrometers), and the density is 0.3 g / m ３ ~0.9g / m ３ and the specific surface area is 0.1 m ２ / g~150m ２ / g The coated fertilizer according to claim 3.

5. The fine powder silicon is functionalized with a hydrophilic group on a silica surface layer, The hydrophilic group is a thiol group, an amine group, or a hydroxy group. The coated fertilizer according to claim 3.

6. the second coating layer further contains silica particles surface-treated with a hydrophilic group; The silica particles are contained in an amount of 10 to 50 parts by weight per 100 parts by weight of the fine powder silicon. The coated fertilizer according to claim 3.

7. The polymer sponge powder is The polymer sponge structure is a pulverized product containing one or more selected from the group consisting of cellulose 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 3.

8. The organic acid is Contains one or more acids 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 to 30 parts by weight based on 100 parts by weight of the fine powder silicon. The coated fertilizer according to claim 3.

9. the second coating layer further contains a cationic surfactant, The cationic surfactant is Quaternary ammonium salts, including one or more selected from the group consisting of cetyltrimethylammonium chloride (CTAC), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB), didodecyldimethylammonium bromide, and cetrimonium bromide. The coated fertilizer according to claim 3.

10. 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 3.

11. the acid value of the acrylic polymer contained in the first coating composition and the acid value of the acrylic polymer contained in the second coating composition are each 10 mgKOH / g to 100 mgKOH / g; 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 is 10,000 (mol / g) to 1,000,000 (mol / g). The coated fertilizer according to claim 3.

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