Release-controlled fertilizer composition

Abstract

A controlled-release fertilizer composition includes coated fertilizer particles having granules substantially encapsulated with a polyurethane coating layer formed from a polyol composition and an isocyanate curing agent. The polyurethane coating layer includes inorganic particles. Methods of making and using the controlled-release fertilizer composition are also disclosed.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 857,498, filed on June 5, 2019, entitled "CONTROLLED - RELEASE FERTILIZER COMPOSITIONS", which is hereby incorporated by reference in its entirety.

[0002] Technical Field The present disclosure generally relates to making inorganic particles be included in the polyurethane coating of fertilizer particles. The fertilizer particles form a controlled - release fertilizer composition.

Background Art

[0003] Controlled - release fertilizers offer many advantages compared to conventional fertilizers. For example, controlled - release fertilizers can extend the release of nutrients, minimize the leaching of nutrients into the ground, and minimize the number of fertilizer applications required for optimal plant growth. One way to form a controlled - release fertilizer is to encapsulate granules with a barrier layer to form coated fertilizer particles. However, known encapsulation processes have many drawbacks, including the need for a relatively thick coating, poor nutrient release characteristics, and a time - consuming manufacturing process.

Summary of the Invention

[0004] According to one embodiment, a controlled - release fertilizer composition includes coated fertilizer particles each including granules and one or more layers of polyurethane coating layers. The one or more layers of polyurethane coating layers substantially encapsulate the granules and are formed from the reaction product of a polyol composition and an isocyanate curing agent. The one or more layers of polyurethane coating layers include inorganic particles.

[0005] According to another embodiment, a method for producing a release-controlled fertilizer composition includes coating granules with a polyol composition, dispersing inorganic particles on the polyol composition, and applying an isocyanate curing agent to the polyol composition to form a polyurethane coating layer that substantially encapsulates each granule. The polyol composition is miscible with the isocyanate curing agent.

[0006] According to another embodiment, a method for producing a release-controlled fertilizer composition includes coating granules with an isocyanate curing agent composition, dispersing inorganic particles on the isocyanate curing agent composition, and applying a polyol composition to the isocyanate curing agent composition to form a polyurethane coating layer that substantially encapsulates each granule. The polyol composition is miscible with the isocyanate curing agent.

[0007] According to another embodiment, a method for producing a release-controlled fertilizer composition includes coating granules with a polyol composition, applying an isocyanate curing agent to the polyol composition to form a polyurethane coating layer that substantially encapsulates each granule, and dispersing inorganic particles on the polyurethane coating layer before the polymerization of the polyol composition and the isocyanate curing agent is completed. The polyol composition is miscible with the isocyanate curing agent.

Mode for Carrying Out the Invention

[0008] The polyurethane coating, when applied to the granules, can substantially encapsulate the granules and extend the duration of fertilizer release over a long period. Known polyurethane coatings formed from at least the reaction of a polyol and an isocyanate curing agent have problems with many undesirable attributes, such as poor durability, high coating weight, and a time-consuming manufacturing process.

[0009] The present disclosure generally describes a method for forming coated fertilizer particles for a controlled-release fertilizer composition that includes inorganic particles within a polyurethane coating. By including the inorganic particles, the manufacture of the coated fertilizer particles can be improved, the nutrient release profile of the coated fertilizer particles can be improved, and the coating weight of the polyurethane coating can be reduced.

[0010] These properties can be improved by including suitable inorganic particles in the polyurethane coating, which improves the abrasion resistance and impact resistance of the polyurethane coating and reduces the moisture diffusion rate. Additionally, by including the inorganic particles, the manufacturing time required to form the polyurethane coating can also be shortened.

[0011] However, as will be understood, adding inorganic particles to the polyurethane coating can give rise to, or lead to, several difficulties. For example, adding certain inorganic particles may require that the unpolymerized polyurethane components (e.g., polyol and isocyanate hardener) contain additional additives to stabilize the composition prior to polymerization. Additionally, certain inorganic particles, such as those having certain dimensions, may also cause a substantial increase in the viscosity of the unpolymerized polyurethane components. Such an increase in viscosity can make the processing and manufacture of the controlled-release fertilizer composition more difficult.

[0012] Several ways to overcome these difficulties have been discovered. For example, suitable combinations of inorganic particles and polyols that do not require additional additives for stability have been discovered. Additionally, manufacturing processes have been developed that avoid or minimize the difficulties caused by including inorganic particles in the starting components of the polyurethane coating.

[0013] For example, in certain embodiments, unexpectedly, polyurethane coatings formed from mixtures of polyols and isocyanate hardeners can be made to include any of a variety of common inorganic particles, such as clay, fumed silica, and calcium carbonate, without the inclusion of additives or other stabilizers. In certain embodiments, additional examples of inorganic particles suitable for such combinations of polyols and isocyanate hardeners include quartz, aluminum oxide, mica, calcined kaolin, wollastonite, calcite, zirconia, zircon, iron oxide mica, iron oxide, aluminum silicate, talc (also referred to as hydrated magnesium silicate), barium sulfate, lithopone, and combinations thereof, among others.

[0014] In such embodiments, the inorganic particles can generally have any suitable average particle size. For example, in certain embodiments, suitable inorganic particles can have an average particle size of about 50 microns or less, in certain embodiments about 20 microns or less, and in certain embodiments about 5 microns or less. As can be appreciated, inorganic particles with a smaller average particle size can result in a greater increase in viscosity compared to inorganic particles with a larger average particle size. In order to minimize the increase in viscosity and, as a result, the difficulty of manufacturing and processing, it may be desirable to select inorganic particles with a smaller average particle size.

[0015] Even more unexpectedly, it has been found that only a small amount of inorganic particles need to be included in the polyurethane coating to improve the properties of the coating. For example, in various embodiments, the inorganic particles can be included in an amount of about 1% or less of the polyurethane coating, about 0.5% or less of the polyurethane coating, about 0.3% or less of the polyurethane coating, about 0.2% or less of the polyurethane coating, about 0.1% or less of the polyurethane coating, about 0.05% or less of the polyurethane coating, and about 0.01 weight% of the polyurethane coating. As can be appreciated, it can be advantageous for the inorganic particles to be present in such small amounts because the potential for incompatibility between the inorganic particles and the polyurethane components can be minimized, and the increase in viscosity caused by the inclusion of the inorganic particles can be minimized.

[0016] It has further been discovered that various manufacturing processes can be useful in forming the desired release-controlled fertilizer composition. For example, it has been discovered that inorganic particles can be advantageously incorporated into the polyurethane coating substantially surrounding the granules by adding the inorganic particles in such a way that they do not have to be mixed. In these examples, the granules can be encapsulated by applying a polyol composition around the granules, dispersing inorganic particles on the polyol composition, and then finally adding an isocyanate curing agent. As can be understood, by applying the inorganic particles in this way, any processing concerns arising from the inorganic particles increasing the viscosity of the unpolymerized polyurethane components can be substantially avoided. In addition, by including the inorganic particles in this way, good mixing can be ensured while minimizing compatibility problems.

[0017] Other advantageous manufacturing processes have been further developed. For example, in embodiments where the granules are encapsulated by multiple coating layers, it has been discovered that desirable properties can be obtained as a result of including inorganic particles in only specific layers. For example, in embodiments where only the innermost layer of a multilayer polyurethane coating contains inorganic particles, the resulting fertilizer particles can exhibit an advantageous nutrient release profile with a reduced rate of fertilizer utilization compared to alternative fertilizer particles having inorganic particles only in the outermost layer or no inorganic particles. As can be understood, the inorganic particles can be applied to any possible combination of polyurethane coating layers (e.g., the innermost and outermost coating layers, the innermost two coating layers, the innermost two coating layers and the outermost coating layer, a specific intermediate layer, etc.).

[0018] In certain embodiments, additionally or alternatively, inorganic particles can also be applied to the polyurethane coating after the polymerization of the polyols and the isocyanate hardener has already started. By applying the inorganic particles in this way, the polymerization time can be reduced, and any concerns about aggregation caused by incomplete curing or drying of the polyurethane coating can be avoided. In certain embodiments, by adding inorganic particles, the polymerization time can be reduced from about 30 to 60 minutes to about 10 to 20 minutes or less. As can be understood, a greater amount of hardener or catalyst content can be used to reduce the polymerization time.

[0019] Examples of polyols suitable for forming the polyurethane coating include hydrophobic polyols such as aromatic amine-based polyols and polyether polyols (e.g., ethylene oxide polyols and propylene oxide polyols).

[0020] In certain embodiments, suitable polyols can be a blend of aromatic amine-based polyols having alkylene oxide substituents such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, alkylene oxide-tetrahydrofuran mixtures, epihalohydrins, and alkylene styrenes. For example, suitable aromatic amine-based polyols generally can be derived from aromatic amines of Formula I:

Chemical formula

[0021] Suitable polyether polyols can generally be selected from known organic oxides such as ethylene oxide, propylene oxide, 1,2-butylene oxide, and epichlorohydrin.

[0022] Suitable polyols can also be obtained commercially. For example, suitable aromatic amine-based polyols and polyether polyols are sold under the trademark Pluracol® and are available from BASF Corporation (Wyandotte, Michigan). Further examples of suitable polyols are described in U.S. Patent No. 7,416,785, the disclosure of which is incorporated herein by reference.

[0023] As can be understood, the polyols described herein can form a polyurethane coating layer when reacted with a suitable curing agent such as an isocyanate curing agent. Generally, such polyols and isocyanate curing agents can be mixed in a ratio of about 1:5, about 1:4.5, about 1:4, about 1:3, about 1:2, or about 1:1 to form polyurethane coating layers according to various embodiments. As can be understood, increasing the amount of the curing agent can increase the amount of polyurethane crosslinking and enhance the mechanical strength of the polyurethane coating. The rate of the polymerization reaction can be varied, for example, according to the amount of polyol used to form the coating, the amount of curing agent, and the amount of catalyst if present. In certain embodiments, mutually miscible polyols and isocyanate curing agents can be advantageously selected. As can be understood, miscibility can facilitate production, reduce or eliminate any unreacted components, and reduce the reaction time required to form the polyurethane coating. In certain embodiments, miscible polyols and isocyanate agents can be applied separately to the granules as a result of their miscibility.

[0024] A variety of isocyanate curing agents may be suitable for forming the release-controlled fertilizer compositions described herein. For example, suitable isocyanate curing agents can include aliphatic isocyanates, aromatic isocyanates, heterocyclic isocyanates, and their oligomers or polymers, among others. In certain embodiments, a suitable isocyanate curing agent can have two or more isocyanate groups per molecule.

[0025] In certain embodiments, it may be useful to make the isocyanate curing agent chemically related to the selected polyols, for example, to promote the compatibility and miscibility of the isocyanate curing agent and the selected polyol. In certain such embodiments, a suitable isocyanate curing agent can be an aromatic amine-based isocyanate such as an isocyanate curing agent of a toluene derivative. As can be understood, suitable isocyanate curing agents can also be obtained commercially, and examples can include isocyanate curing agents sold under the trade name Lupranate®. The Lupranate® isocyanate curing agent is available from BASF Corporation (Wyandotte, Michigan).

[0026] Generally, by using the polyols and isocyanate hardeners described herein, any desired type of granule can be encapsulated to control the rate until the desired soil and vegetation can utilize the fertilizer components in the granule. Suitable granules that can be encapsulated by the polyols and isocyanate hardeners described herein can be highly diverse and can include, for example, nitrogen fertilizer compounds, phosphate fertilizer compounds, potassium fertilizer compounds, sulfur fertilizer compounds, potassium fertilizer compounds, calcium fertilizer compounds, various metal fertilizer compounds, micronutrients, and combinations thereof. In certain embodiments, the granule can include a nitrogen-based fertilizer such as urea, ammonium nitrate, or calcium ammonium nitrate. Additionally, or alternatively, the granules described herein can include any other material beneficial to the soil or vegetation, including other NPK fertilizers. For example, suitable granules can further include herbicides, insecticides, fungicides, and fragrances.

[0027] Examples of suitable granules can include fertilizer granules such as potassium nitrate, potassium sulfate, urea, ammonium nitrate, monopotassium sulfate, ammonium phosphate, fertilizers containing micronutrients or trace elements, and urea formaldehyde fertilizers. Further details of urea formaldehyde fertilizers are disclosed in U.S. Pat. Nos. 6,039,781 and 6,579,831, which are incorporated herein by reference in their entireties.

[0028] In certain embodiments, further or alternatively, the granules can be made of an inert material such as corn cob, peanut hull, processed paper pulp, sawdust, aggregated cellulose-based carrier granules, wood fiber core granules, compressed core granules, processed paper pulp, limestone, gypsum, sand, vermiculite, perlite, fuller's earth and clay (e.g., attapulgite clay, bentonite clay, and montmorillonite clay). In certain embodiments, the inert granules can include properties that can make the granules more highly absorbent. For example, granules containing processed paper pulp (e.g., biodac) can absorb more liquid than dolomitic limestone. In certain embodiments, the inert granules can include additives that can enhance the biological function of the granules. For example, the granules can include an aggregate of dispersed particles or fine powder having properties such as improved hardness or crush resistance as described in International Publication No. US12 / 32596, which is incorporated herein by reference. Such granules are known to those skilled in the art.

[0029] According to certain embodiments, the step of coating the granules can include applying a selected polyol to the granules to be encapsulated, followed by applying inorganic particles and an isocyanate hardener. For example, after applying a polyol mixture to the granules, inorganic particles can be applied. Once the inorganic particles are applied, an isocyanate hardener can be applied to form a polyurethane coating layer that substantially completely surrounds the granules. By including inorganic particles in the polyol before applying the isocyanate hardener, any problems caused by the inclusion of inorganic particles can be minimized. Alternatively, after applying the isocyanate hardener to the granules, inorganic particles can be applied. Once the inorganic particles are applied, a polyol can be applied to form a polyurethane coating layer.

[0030] Generally, the polyol mixture and the isocyanate hardener can be applied in a weight ratio of about 1:1. In other embodiments, other ratios can be selected as alternatives. In certain embodiments, two or more coating layers can be applied sequentially. For example, in certain embodiments, two, three, four, or more coating layers can be applied to encapsulate the granules and form coated fertilizer particles. The inorganic particles can be included in each layer or only in specific layers. Generally, the selected polyol, inorganic particles, and isocyanate hardener can be applied using any suitable coating process, including, for example, spray coating, roll coating, dip coating, and other known coating processes.

[0031] In certain embodiments, the controlled-release fertilizer composition described herein can be formed by roll coating urea. In such embodiments, the urea can be heated to a temperature of about 170°F in a rotating drum. Once heated, the selected polyol or polyol blend can be applied to coat the urea granules. Thereafter, the inorganic particles can be dispersed over the granules. Finally, the isocyanate hardener can be applied and reacted with the polyols to form a polyurethane coating layer. Additional polyurethane coating layers can be formed in the same manner.

[0032] In certain embodiments, the coated granules can be heated for an additional period of time to ensure that the polymerization is complete. For example, in certain embodiments, the coated granules can be held at about 170°F for 30 to 60 minutes to ensure that the polymerization of the polyurethane layer is complete. In certain embodiments, the inorganic particles can be dispersed over the entire surface of the coated granules during this additional period of time. In such embodiments, the coated granules can be heated for only about 5 to 20 minutes.

[0033] As can be understood, alternative processes may also be suitable. For example, the selected polyol and inorganic particles can be premixed before being applied to the granules. Alternatively, the inorganic particles can be premixed with the isocyanate hardener. In certain embodiments, the polyol, inorganic particles, and isocyanate hardener can each be premixed together before being applied to the granules.

[0034] As can be understood, various embodiments can further include various optional components. For example, certain embodiments include a catalyst to accelerate the polymerization reaction between the selected polyol and the isocyanate hardener. Certain such embodiments can include from about 0.5% to about 5%, from 0.75% to about 3%, or from about 1% to about 2% catalyst, based on the weight of the polyol. Suitable catalysts can include amine-based catalysts such as triethanolamine, trimethylamine, triethylamine, tetraethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (“DBU”), 1,5-diazabicyclo[4.3.0]non-5-ene (“DBN”), dimethylethylamine, dimethylisopropylamine, and the like. Alternatively, suitable catalysts can be metal salt catalysts such as ferric acetylacetonate and dibutyltin dilaurate (“DBTL”). In certain such embodiments, ferric acetylacetonate can be included at from about 50 parts per million (“ppm”) to about 1,000 ppm, from about 100 ppm to about 750 ppm, or from about 200 ppm to about 500 ppm, based on the polyol.

[0035] As can be understood, other optional constituents can be further included in the controlled-release fertilizer composition, the granules, and / or the coating layer. For example, a desiccant such as calcium sulfate can be used to remove moisture before the encapsulation step or to help reduce agglomeration of the granules. In addition, a colorant can be included to facilitate identification of the controlled-release fertilizer composition.

[0036] In certain embodiments, a wax can be applied to the outside of the coated fertilizer particles to impart additional water resistance to the controlled-release fertilizer composition. In such embodiments, the coated fertilizer particles can be heated to a suitable temperature (e.g., about 70° C.) and then coated with molten wax, and the particles can be rotated so that the entire coated fertilizer particles are uniformly coated with wax. However, in certain embodiments, based on the strength of the polyurethane coating formed herein, the wax coating can be omitted.

[0037] As can be appreciated, the release profile of the coated fertilizer particles can depend on a variety of different factors. For example, the rate at which the fertilizer present in the granules is released into the desired soil and vegetation can depend on the physical durability and water permeability of the encapsulating material, as well as the overall coating weight of the coating material (e.g., the thickness and number of polyurethane coating layers). It has been discovered that by including a small amount of inorganic particles, the physical durability of the encapsulating material can be improved and the water permeability can be reduced. A more durable encapsulating material can facilitate the formation of a controlled-release fertilizer composition having excellent handling characteristics.

[0038] A controlled-release fertilizer composition having a lower coating weight can be extremely beneficial. A lower coating weight can mean that the controlled-release fertilizer composition can contain more fertilizer for a given weight and / or volume of the fertilizer composition. In addition, reducing the coating weight can, in certain embodiments, reduce the amount of coating that will be applied to the granules, reducing the consumption of time, materials, and energy and simplifying the manufacture of the controlled-release fertilizer composition. Further, reducing the coating weight can also reduce the amount of polymer expended in the field. As can be appreciated, each coating applied around the fertilizer particles can increase both the time and the difficulty of the manufacturing process.

[0039] As can be understood, the release-controlled fertilizer composition described herein can be blended with additional fertilizer compounds. For example, additional slow-release nitrogen compounds such as triazone, urea-triazone (such as tetrahydro-s-triazone or 5-methylenuride-2-oxohexahydro-s-triazine), methylene urea products, and isobutylidene diurea ("IBDU") can be blended with the coated fertilizer particles to further adjust the nitrogen release profile over time according to the purpose. Also, by adding such fertilizer compounds, it may be possible for the release-controlled fertilizer composition to contain any suitable amount of nitrogen. For example, in certain embodiments, the release-controlled fertilizer composition can contain from about 1% to about 99% by weight of nitrogen. In certain embodiments, the fertilizer composition can contain from about 20% to about 70% by weight of nitrogen, including, for example, from about 20% to about 50% by weight of nitrogen. In various embodiments, the amount of nitrogen in the fertilizer composition can be about 1%, about 2%, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, or about 99% by weight.

[0040] Furthermore, or alternatively, various types of quick-release nitrogen compounds can be blended with the release-controlled fertilizer composition. Examples of suitable quick-release nitrogen compounds can include urea, urea ammonium sulfate ("UAS"), one or more of ammonium sulfate, and the like.

[0041] In certain embodiments, the release-controlled fertilizer composition described herein can further be mixed with one or more unencapsulated components. For example, the fertilizer composition can be mixed with unencapsulated phosphorus, potassium, calcium, magnesium, manganese, molybdenum, sulfur, or zinc.

[0042] The release-controlled fertilizer composition described herein can be applied to seeds, seedlings, plants, lawns by spreading the composition or (e.g., using a mechanical spreader) spraying it, and this composition can be applied to soil, seeds, seedlings, plants, lawns, farms, crops, or other agricultural environments.

[0043] In certain embodiments, the fertilizer composition described herein is from about 0.1 lb (0.1 pound) of nitrogen per 1000 ft 2 (1000 square feet) to about 6 lb of nitrogen per 1000 ft 2 and can be applied. In certain embodiments, the fertilizer composition can be formulated as an immediately useable formulation or an immediately sprayable formulation.

[0044] Examples The following examples are included to illustrate certain aspects and embodiments of the present disclosure and are not intended to limit the present disclosure to these described embodiments.

[0045] Each of the examples was prepared in accordance with the following procedure. 1000 g of granular urea was charged into a rotating drum heated to 170°F. When the granular urea reached 170°F, 2.2 g of Dustrol® 3088 was uniformly distributed over the entire charged granules while heating and rotating the drum coater. Dustrol® 2088 is an additive for dust suppression. This process was continued for 3 minutes. Depending on the desired polymer thickness, a mixture (w / w) - polyol of 4.5 parts by weight of Pluracol® 1500 and Pluracol® 1578 was distributed over the entire granules coated with Dustrol® 3088. Tumbling and heating were continued for an additional 1 minute. HiSil 233 (0.25 g), an amorphous silica inorganic particle blend, was uniformly sprayed over the entire granules in the drum, and tumbling was continued for an additional 2 minutes. Next, Lupranate® M20 (4.5 g), an isocyanate curing agent, was charged into the drum and uniformly sprayed over the entire granule bed. A single layer of polyurethane layer was formed by the combination of HiSil 233, polyol, and isocyanate. This layer formation was repeated until the desired total polymer coating weight was achieved. Thereafter, the coating was heated for an additional 30 to 60 minutes to ensure completion of the reaction. This also eliminated the need for bag sets during storage.

[0046] In certain examples, HiSil 233 was added only to one or more of the individual polymer layers. For example, it is possible to sequentially distribute Dustrol® 3088, HiSil 233, polyol, and an isocyanate curing agent to form a first layer. Next, the polymer layers from the second layer onwards may contain polyol and isocyanate without HiSil 233. As can be understood, the inorganic particles (HiSil 233) can be incorporated into layer 2 to layer n (where layer n represents the final polymer layer required to achieve a coating of a specific thickness).

[0047] In other examples, HiSil 233 was added to the coated granule bed 10 - 20 minutes after adding the final polymer layer. The total cycle time for such a coating process was reduced from 30 - 60 minutes to 10 - 20 minutes as exemplified above.

[0048] In certain examples, a wax coating was applied. In such examples, the polymer - coated granules were transferred to a heated second rotary drum coater (160°F), and 8.8 g of molten wax (Evacote® 7089A per 1000 g of polymer - coated granules) was uniformly distributed over the entire granule bed. The wax coating was continued for 3 minutes and cooled to 100°F or less before removal.

[0049] The nutrient release profiles of various fertilizer compositions were determined by adding 10 g of the fertilizer composition to a bottle containing 100 g of deionized water maintained at room temperature (e.g., about 22°C) and sealing the bottle. The bottle was rolled daily to uniformly disperse the released nitrogen throughout the water. Aliquots of the water were taken at measured time intervals and the amount of nitrogen released from the fertilizer composition was measured. The nutrient release profile indicates the rate at which the nutrients of the fertilizer composition are released into the soil.

[0050] Table 1 shows the nutrient release profiles of some exemplary fertilizer compositions formed from encapsulation of urea granules. The urea granules were encapsulated with various coating weights of a polyurethane formed from a 50 / 50 blend of Pluracol® 1500 and Pluracol® 1578 obtained from BASF Corporation (Wyandotte, Michigan), and the same amount of Lupranate® M20 also obtained from BASF. Each exemplary fertilizer composition contained four layers of polyurethane. Lupranate® M20 is a modified 4,4'-methylenediphenyl isocyanate having a functionality of about 2.7.

[0051] Examples 1 and 2 are comparative examples as they do not contain inorganic particles. In Example 1, the total coating weight is 4.3%, while in Example 2, the total coating weight is 9.6%. The inventive Example 3 contains 0.2 wt% of Hi-Sil 233 from PPG Industries Inc. (Monroeville, Pennsylvania) as the inorganic particles. Half of the Hi-Sil 233 was evenly dispersed in each of the four layers of the polyurethane coating.

Table 1

[0052] As shown in Table 1, Example 3 had a substantially slower nutrient release profile than either of Comparative Examples 1 and 2, even though the total coating weight was only 4.5%.

[0053] For the exemplary fertilizer compositions, abrasion resistance was also measured. The abrasion resistance of 100 g of the exemplary fertilizer composition in a tin can was characterized by mixing it with a stainless steel ball bearing. The sealed tin can was then placed in a paint shaker (Tornado II Portable Paint Shaker, Model 51000) with a constant vibration frequency for 1 minute. Then, the nutrient release values for these examples were measured according to the nutrient release profiles in Table 1. Examples 1 and 3 in Table 1 were evaluated.

Table 2

[0054] As shown in Table 2, the inclusion of only 0.2% of amorphous silica substantially improved the abrasion resistance of the polyurethane coating. These results indicate that a polyurethane coating containing inorganic particles can have significantly greater resistance to abrasion damage.

[0055] In Table 3, the effect of including inorganic particles only in one of the polyurethane layers of the three-layer polyurethane coating was evaluated. Each exemplified fertilizer composition had a total coating weight of 2.7% and was formed from the same components as Examples 1 to 3. Example 4 did not contain Hi-Sil 233, Example 5 contained Hi-Sil 233 in the innermost layer, Example 6 contained Hi-Sil 233 in the middle layer, and Example 7 contained Hi-Sil 233 in the outermost layer.

Table 3

[0056] In Table 3, it is confirmed that including inorganic particles in any of the polyurethane layers reduces the nutrient release profile of the fertilizer composition compared to a fertilizer composition without inorganic particles. Also, Table 3 shows that placing the inorganic particles in the innermost layer is most beneficial.

[0057] As used herein, all percentages (%) are weight percentages of the entire composition and, unless otherwise indicated, are also expressed as weight / weight %, %(w / w), w / w, w / w% or simply %.

[0058] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and the functionally equivalent range surrounding that value.

[0059] All upper numerical limits given throughout this specification are to be considered to include any lower numerical limits, as if such lower numerical limits were explicitly recited in this specification. All lower numerical limits given throughout this specification are to be considered to include any higher numerical limits, as if such higher numerical limits were explicitly recited in this specification. All numerical ranges given throughout this specification are to be considered to include any narrower numerical ranges that fall within such broader numerical ranges, as if such narrower numerical ranges were explicitly recited in this specification.

[0060] All documents cited in this specification, including any cross-referenced or related patents or applications, are incorporated herein by reference in their entirety, unless explicitly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed in this specification, or that it alone, or in any combination with any other reference or references, teaches, suggests, or discloses any such invention. Further, any meaning or definition of a term in this specification that conflicts with any meaning or definition of the same term in a document incorporated by reference shall be determined by the meaning or definition assigned to that term in the document.

[0061] The foregoing description of the embodiments and examples has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the described forms. Many modifications are possible in light of the above teachings. Some of those modifications have been considered, and others will be apparent to those skilled in the art. The embodiments were chosen and described to illustrate examples of various embodiments. Of course, the scope is not limited to the examples or embodiments described herein, and those skilled in the art can employ it in any number of applications and equivalents. Rather, the scope is intended to be defined by the appended claims.

Claims

1. Coated fertilizer particles comprising granules and one or more layers of polyurethane coating layer, wherein the one or more layers of polyurethane coating layer substantially encapsulate the granules; A controlled-release fertilizer composition comprising: The one or more layers of polyurethane coating layer are formed from a reaction product of an aromatic amine-based polyol composition and an isocyanate curing agent; At least one of the one or more layers of polyurethane coating layer contains inorganic particles; The inorganic particles contain amorphous silica, and the inorganic particles are contained in an amount of 1% by weight or less of the polyurethane coating.

2. The coated fertilizer particles according to claim 1, comprising two or more layers of polyurethane coating layer, wherein the innermost layer of the two or more layers of polyurethane coating layer contains inorganic particles.

3. The controlled-release fertilizer composition according to claim 1 or claim 2, wherein each of the one or more layers of polyurethane coating layer contains inorganic particles.

4. The inorganic particles further comprise one or more of clay, calcium carbonate, quartz, aluminum oxide, mica, calcined kaolin, wollastonite, calcite, zirconia, zircon, mica-like iron oxide, iron oxide, aluminum silicate, talc, barium sulfate, and lithopone. The controlled-release fertilizer composition according to any one of claims 1 to 3.

5. The controlled-release fertilizer composition according to any one of claims 1 to 3, wherein the inorganic particles consist of amorphous silica.

6. The coated fertilizer particles according to any one of claims 1 to 5, comprising one or more selected from the group consisting of nitrogen compounds, phosphate fertilizer compounds, potassium fertilizer compounds, sulfur fertilizer compounds, potassium fertilizer compounds, calcium fertilizer compounds, and metal compounds.

7. The controlled-release fertilizer composition according to claim 6, wherein the granule contains one or more selected from the group consisting of a nitrogen fertilizer compound, a phosphate fertilizer compound, a potassium fertilizer compound, a sulfur fertilizer compound, a potassium fertilizer compound, a calcium fertilizer compound, and a metal fertilizer compound.

8. The controlled-release fertilizer composition according to any one of claims 1 to 7, wherein the coated fertilizer particles contain urea.

9. The controlled-release fertilizer composition according to claim 8, wherein the granule contains urea.

10. The controlled-release fertilizer composition according to any one of claims 1 to 9, wherein the coated fertilizer particles contain one or more selected from the group consisting of a herbicide, an insecticide, and a fungicide.

11. The controlled-release fertilizer composition according to claim 10, wherein the granule contains one or more selected from the group consisting of a herbicide, an insecticide, and a fungicide.

12. The controlled-release fertilizer composition according to any one of claims 1 to 11, wherein the coated fertilizer particles contain one or more layers of polyurethane coating layer of about 1 wt% to about 15 wt%.

13. The controlled-release fertilizer composition according to any one of claims 1 to 12, wherein the coated fertilizer particles contain 4 layers of polyurethane coating layer.

14. The controlled-release fertilizer composition according to any one of claims 1 to 13, wherein the coated fertilizer particles further contain a wax coating layer surrounding the one or more layers of polyurethane coating layer.

15. The controlled-release fertilizer composition according to any one of claims 1 to 14, wherein the aromatic amine polyol composition contains an alkylene oxide substituent and further contains a polyether polyol.

16. The release-controlled fertilizer composition according to claim 15, wherein the alkylene oxide substituent contains one or more of ethylene oxide and propylene oxide.

17. The release-controlled fertilizer composition according to claim 15, wherein the polyether polyol contains one or more of ethylene oxide polyol and propylene oxide polyol.

18. The release-controlled fertilizer composition according to any one of claims 1 to 17, wherein the isocyanate curing agent contains a polymeric isocyanate or an aromatic isocyanate.

19. The release-controlled fertilizer composition according to any one of claims 1 to 18, wherein the isocyanate curing agent contains 4,4'-methylenediphenyl diisocyanate.

20. The release-controlled fertilizer composition according to any one of claims 1 to 19, wherein the ratio of the aromatic amine-based polyol composition to the isocyanate curing agent is from about 1:4 to about 1:

1.

21. The release-controlled fertilizer composition according to any one of claims 1 to 20, wherein the one or more layers of polyurethane coating layer contains a catalyst selected from one of an amine-based catalyst or a metal salt catalyst.

22. The release-controlled fertilizer composition according to any one of claims 1 to 21, having a nutrient release profile of about 30 days or more.

23. A fertilization method comprising applying the release-controlled fertilizer composition according to any one of claims 1 to 22 to the soil in a designated area.

24. Coating the granules with an aromatic amine-based polyol composition; Dispersing inorganic particles in the aromatic amine-based polyol composition, wherein the inorganic particles contain amorphous silica; Applying an isocyanate curing agent to the aromatic amine polyol composition to form a polyurethane coating layer that substantially encapsulates each granule; A method for producing a controlled-release fertilizer composition comprising: A method for producing a controlled-release fertilizer composition, wherein the aromatic amine polyol composition is miscible with the isocyanate curing agent and the inorganic particles are contained in an amount of 1% by weight or less of the polyurethane coating.

25. The method according to claim 24, further comprising forming one or more additional polyurethane coating layers to substantially encapsulate each granule.

26. The method according to claim 25, wherein each of the one or more additional polyurethane coating layers contains inorganic particles.

27. The method according to claim 25, wherein each of the one or more additional polyurethane coating layers substantially does not contain inorganic particles.

28. The method according to any one of claims 24 to 27, wherein the aromatic amine polyol composition and the isocyanate curing agent are contained in a ratio of about 1:4 to about 1:

1.

29. Coating the granules with an isocyanate curing agent composition; Dispersing inorganic particles in the isocyanate curing agent composition, wherein the inorganic particles contain amorphous silica; Applying an aromatic amine polyol composition to the isocyanate curing agent composition to form a polyurethane coating layer that substantially encapsulates each granule; A method for producing a controlled-release fertilizer composition comprising: A method for producing a controlled-release fertilizer composition, wherein the aromatic amine polyol composition is miscible with the isocyanate curing agent and the inorganic particles are contained in an amount of 1% by weight or less of the polyurethane coating.

30. Coating the granules with an aromatic amine polyol composition; Applying an isocyanate curing agent to the aromatic amine polyol composition to form a polyurethane coating layer substantially encapsulating each granule; Dispersing inorganic particles in the polyurethane coating layer before the polymerization of the aromatic amine polyol composition and the isocyanate curing agent is completed, wherein the inorganic particles contain amorphous silica; A method for producing a release-controlled fertilizer composition comprising: A method for producing a release-controlled fertilizer composition, wherein the aromatic amine polyol composition is miscible with the isocyanate curing agent, and the inorganic particles are contained in an amount of 1% by weight or less of the polyurethane coating.

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