Controlled Release Fertilizer Coating Using Hydrophilic Blend

Abstract

The coated fertilizer composition comprises fertilizer granules and two or more polyurethane layers on the fertilizer granules, wherein the polyurethane layer comprises an isocyanate component containing one or more isocyanate compounds and an isocyanate-reactive component, the isocyanate-reactive component comprising (a) 65% to 80% by weight of a hydrophilic polyether polyol having an OH value in the range of 220 mg KOH / g to 400 mg KOH / g, wherein ethylene oxide is 90% to 100% by weight of the total alkylene oxide content of the hydrophilic polyether polyol and the hydroxyl functionality is 2 to 3, and (b) 20% to 35% by weight of a low EW polyol having the formula CH2OHC(R 1 )(R 2 )CH2OH (wherein R 1 is CH2OH or OH and R 2 is H or a C1-C3 alkyl group), and two or more polyurethane layers on the fertilizer granules which are reaction products of the isocyanate-reactive component with an isocyanate index of 120 to 160, and may further comprise one or more wax layers on the fertilizer granules containing a polyolefin wax.

Description

Technical Field

[0001] Embodiments relate to coated fertilizer compositions having controlled dissolution and release profiles.

[0002] Introduction Coatings on fertilizers have been used for controlled release to increase fertilizer efficacy, reduce the amount and frequency of application, and lower labor costs. This in turn reduces the risk of root burn from over-application of fertilizers and protects against nutrient losses from leaching and denitrification processes. However, defects in the coating can lead to performance variations and early coating degradation. Coating breakdown can then cause uncontrolled release, scheduling disruptions, and plant damage due to unstable concentration gradients.

Summary of the Invention

[0003] The coated fertilizer composition includes fertilizer granules and two or more polyurethane layers on the fertilizer granules, where the polyurethane layer includes an isocyanate component containing one or more isocyanate compounds and an isocyanate-reactive component, the isocyanate-reactive component including (a) 65 wt% to 80 wt% of a hydrophilic polyether polyol having an OH value in the range of 220 mg KOH / g to 400 mg KOH / g, where ethylene oxide is 90 wt% to 100 wt% of the total alkylene oxide content of the hydrophilic polyether polyol and the hydroxyl functionality is 2 to 3, and (b) 20 wt% to 35 wt% of a low EW polyol having the formula CH2OHC(R 1 )(R 2 )CH2OH (wherein R 1 is CH2OH or OH and R 2 is H or a C1-C3 alkyl group), and may include one or more wax layers on the fertilizer granules including a polyolefin wax, which is a reaction product of the isocyanate-reactive component with an isocyanate index of 120 to 160, and the two or more polyurethane layers on the fertilizer granules.

DETAILED DESCRIPTION OF THE INVENTION

[0004] Embodiments relate to a coated fertilizer composition having one or more layers that provide a delayed release profile and controlled dissolution when compared to an uncoated fertilizer. The fertilizer coating may optionally be multilayer and may be a mixture of one or more polyurethane layers with one or more wax layers interspersed therebetween. The coated fertilizer composition may include one or more polyurethane layers produced by reacting an isocyanate component with an isocyanate-reactive component containing a mixture of a hydrophilic polyether polyol and a low equivalent weight (EW) polyol.

[0005] The coated fertilizer compositions disclosed herein utilize hydrophilic polyether polyols and can provide an enhanced fertilizer release profile when compared to similar formulations that utilize hydrophobic polyols such as castor oil or propoxylated polyols. Hydrophilic polyether polyols are typically avoided because they are associated with an unstable release rate, but incorporation of a low EW polyol into the isocyanate-reactive component unexpectedly allows for a substantial increase in the duration of controlled release of the fertilizer. In particular, use of an isocyanate-reactive component containing a polyol component that contains a combination of a low EW polyol and a hydrophilic polyether polyol provides controlled release of the fertilizer over a longer time scale when compared to relatively hydrophobic polyols such as PO-based polyols that result in inadequate controlled release performance. The coated fertilizer compositions disclosed herein may be easier to handle and may have a release period that extends for up to several weeks or months after application.

[0006] The coated fertilizer composition may include one or more polyurethane layers having a dispersed wax layer that allows for stepwise and consistent fertilizer release. The coated fertilizer composition may include a polyurethane (PU) layer as the innermost layer in contact with the granules and a PU layer as the outermost layer, with wax layers alternating between each PU layer. For example, if the number of PU layers = x, the number of wax layers = (x - 1). The coated fertilizer composition may have a total number of layers in the range of 3 to 9. A series of layers in the coated fertilizer composition may include a first PU layer, a first wax layer, a second PU layer, a second wax layer, a third PU layer, and so on. The continuous layer can coat the underlying fertilizer granules or sublayer, in which case the coating is considered to cover 90% to 100% of the surface area of the underlying surface.

[0007] The coated fertilizer composition disclosed herein includes one or more fertilizers provided in granular form. Suitable fertilizers include, for example, a urea source, a nitrogen source, a phosphorus source, or a potassium source, such as ammonium nitrate, ammonium sulfate, ammonium nitrate sulfate, calcium nitrate, calcium ammonium nitrate, urea-formaldehyde, monoammonium phosphate, diammonium phosphate, polyphosphoric acid compounds, phosphate rock, superphosphate of lime, triple superphosphate of lime, potassium nitrate, potassium chloride, potassium sulfate, or combinations thereof. In some embodiments, the fertilizer may be granular urea. For example, the fertilizer granules may have a nitrogen:phosphorus:potassium ratio of 46:0:0. The amount of nitrogen source, phosphorus source, or potassium source contained in the fertilizer granules may vary based on the intended end use and may be 0 to 60 wt% for each component based on the total weight of the fertilizer granules.

[0008] The fertilizer granules can have any shape or size desirable for their intended use. In some embodiments, the fertilizer granules are substantially spherical. The fertilizer granules can have an average particle size of from 0.5 mm to 6.0 mm, from 1.0 mm to 5.5 mm, or from 1.5 mm to 5.0 mm. In some embodiments, at least 90% by weight of the fertilizer granules have a particle size of from 2.0 to 4.0 mm. The particle size can be determined according to "Size Analysis-Sieve Method" IFDC S-107 issued by the International Fertilizer Development Center (IFDC), which is a common and internationally approved method for determining fertilizer particle size.

[0009] The coated fertilizer composition can include one or more polyurethane layers produced by reacting an isocyanate component with an isocyanate-reactive component containing a mixture of a hydrophilic polyether polyol and a low EW polyol. The isocyanate component can include at least one compound having an isocyanate group. The isocyanate component can be the same or different in a coated fertilizer composition in which a plurality of PU layers are incorporated.

[0010] The isocyanate component can include one or more isocyanates and polyisocyanates having an average of more than 1.0 isocyanate groups per molecule. The isocyanate component can contain moieties that are aliphatic, cycloaliphatic, alicyclic, arylaliphatic, aromatic, and / or their derivatives. Examples of suitable compounds for use in the isocyanate component include polymethylene polyphenyl isocyanate, toluene 2,4- / 2,6-diisocyanate (TDI), methylene diphenyl diisocyanate (MDI), polymeric MDI, and the like.

[0011] The isocyanate can have an average isocyanate functionality of 1 to 5, 1.5 to 5, 2 to 5, or 3 to 5. The isocyanate can have an isocyanate equivalent weight (EW) in the range of 80 g / eq to 200 g / eq, 90 g / eq to 175 g / eq, or 100 to 175 g / eq. The isocyanate can have an isocyanate content in the range of 20 wt% to 45 wt%, 25 wt% to 45 wt%, or 25 wt% to 40 wt% based on the total weight of the isocyanate.

[0012] The polyurethane layer can have an isocyanate index defined as the stoichiometric excess of isocyanate moieties in the reaction mixture relative to the number of moles of isocyanate-reactive units (active hydrogens available for reaction with the isocyanate moiety) multiplied by 100. An isocyanate index of 100 means that there is no stoichiometric excess such that there is 1.0 mole of isocyanate groups per 1.0 mole of isocyanate-reactive groups multiplied by 100. The isocyanate component can have an isocyanate index in the range of 110 to 170, 120 to 160, or 125 to 155.

[0013] The coated fertilizer composition can include one or more polyurethane layers produced from the reaction of an isocyanate-reactive component containing an isocyanate component and a polyol component containing a mixture of one or more hydrophilic polyether polyols and one or more low EW polyols each having at least one isocyanate-reactive hydrogen atom group such as a hydroxyl group and / or an amine group. The polyol component can consist essentially of one or more hydrophilic polyether polyols and one or more low EW polyols, where "consisting essentially of" or "consisting of essentially" means that all polyol species within the isocyanate-reactive component are limited to only the polyols described and in the amounts such that other components do not substantially affect the overall isocyanate index and / or average OH number.

[0014] The hydrophilic polyether polyols disclosed herein are produced by the polymerization of ethylene oxide with an initiator and optionally another alkylene oxide, and the ethylene oxide is 90% by weight or more of the total alkylene oxides. In some cases, the ethylene oxide may be in a weight percentage (wt%) in the range of 90 wt% to 100 wt% or 95 wt% to 100 wt% of the hydrophilic polyether polyol. Examples of initiators include molecules having a hydroxyl functionality in the range of 2 to 8, such as 2 to 4. Suitable initiators include water, glycerol, ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol, or combinations thereof. Examples of other alkylene oxides that can be utilized to prepare the hydrophilic polyether polyol include propylene oxide, butylene oxide, and combinations thereof. The hydrophilic polyether polyol can be prepared according to known methods, and commercially available examples sold under the trade names VORANOL™ and CARBOWAX™ available from The Dow Chemical Company can be cited.

[0015] The isocyanate-reactive component can include a polyol component containing a mixture of hydrophilic polyether polyols. The hydrophilic polyether polyols disclosed herein can have a hydroxyl functionality of 2 to 4 or 2 to 3. The hydrophilic polyether polyol can have an average hydroxyl value (OH value) of 220 mg KOH / g to 400 mg KOH / g, 220 mg KOH / g to 350 mg KOH / g, or 240 mg KOH / g to 350 mg KOH / g when measured according to ASTM D4274-21. The hydrophilic polyether polyol can have a weight average molecular weight in the range of 200 Da to 1000 Da, 300 Da to 1000 Da, 300 Da to 800 Da, or 220 Da to 760 Da.

[0016] The isocyanate-reactive component can include a polyol component containing a mixture of low EW polyols. The low EW polyol is CH2OHC(R 1 )(R2 ))CH2OH (wherein R 1 is CH2OH or OH, and R 2 is H or a C1-C3 alkyl group). Suitable low EW polyols include C3-C6 polyols having 2-3 hydroxyl functional groups such as glycerol and trimethylolpropane.

[0017] The low EW polyol can have an equivalent weight of 110 or less, 100 or less, or 60 or less. The low EW polyol can have an average hydroxyl value of 500 mg KOH / g or more, 750 mg KOH / g or more, or 900 mg KOH / g or more when determined according to ASTM D4274-21.

[0018] The isocyanate-reactive component can include one or more hydrophilic polyether polyols in a weight percentage of the isocyanate-reactive component of 65 wt% - 85 wt%, 65 wt% - 80 wt%, 67 wt% - 80 wt%, 65 wt% - 75 wt%, or 67 wt% - 75 wt%. The isocyanate-reactive component can include one or more low EW polyols in a weight percentage of the isocyanate-reactive component in the range of 15 wt% - 35 wt%, 20 wt% - 35 wt%, 20 wt% - 33 wt%, 15 wt% - 25 wt%, or 15 wt% - 33 wt%. In some embodiments, the isocyanate-reactive component can have a mass ratio of hydrophilic polyether polyol to low EW polyol in the range of 65:35 - 85:15, 67:33 - 85:15, 67:33 - 80:20, or 75:25 - 80:20.

[0019] The isocyanate-reactive components disclosed herein may include one or more tertiary amines. Suitable tertiary amines include triethanolamine, triisopropanolamine, N-methyl-diethanolamine, N-ethyl-diethanolamine, and N,N-dimethyl-ethanolamine. The isocyanate-reactive component may further include tertiary amine in a weight percentage (wt%) of 15 wt% or less, 10 wt% or less, or 8 wt% or less. The isocyanate-reactive component may further include tertiary amine in a weight percentage (wt%) in the range of 1 wt% to 20 wt%, 1 wt% to 15 wt%, or 5 wt% to 15 wt%. In some cases, the isocyanate-reactive component consists essentially of 5 wt% to 15 wt% tertiary amine, 15 wt% to 35 wt% low EW polyol, and 50 wt% to 80 wt% hydrophilic polyether polyol.

[0020] The coated fertilizer composition may include one or more wax layers prepared from one or more waxes, and the waxes used in each layer may be the same or different. Suitable waxes include polyolefin waxes having a carbon number in the range of C20 to C35, and examples include alpha olefin waxes, natural and synthetic waxes, and the like.

[0021] The coated fertilizer composition may include one or more polyurethane layers containing polyurethane in a weight percentage (wt%) in the range of 1.5 wt% to 4 wt%, 2 wt% to 4 wt%, or 2 wt% to 3.5 wt% of the coated fertilizer composition. The coated fertilizer composition may include one or more wax layers containing wax in a weight percentage (wt%) in the range of 0.2 wt% to 1 wt%, 0.2 wt% to 0.9 wt%, or 0.3 wt% to 0.7 wt% of the coated fertilizer composition.

[0022] The coated fertilizer compositions disclosed herein can release less than 30%, less than 40%, or less than 45% of the total weight of the fertilizer granules after being contacted with water for 28 days. The coated fertilizer compositions disclosed herein can release less than 10%, less than 15%, or less than 20% of the total weight of the fertilizer granules after being contacted with water for 14 days.

[0023] The coated fertilizer granule composition can be prepared using known devices, conditions, and components such as a drum coater with the application of heat. The preparation method can include providing the fertilizer granules to a drum coater, forming a first polyurethane layer on the fertilizer granules, forming a first hydrophobic layer on the first polyurethane layer, and forming a second polyurethane layer on the first hydrophobic layer. The layer formation process can be repeated the desired number of times. The formation of one or more polyurethane layers may include dividing the isocyanate component and / or the isocyanate-reactive component into portions that are added at various stages of the coating process. By way of example, a first portion of the isocyanate-reactive component can be added to the drum coater to coat the fertilizer granules, followed by the addition of the isocyanate component, and then a second portion of the isocyanate-reactive component can be added to the mixture.

Example

[0024] The following examples are presented to illustrate embodiments of the invention and are not intended to limit its scope. Table 1 provides the materials used in the following examples.

[0025]

Table 1

[0026] In the following examples, urea fertilizer granules were coated with alternating five layers of PU layers (0.9 wt% + 0.9 wt% + 0.9 wt% = total 2.7 wt%) and wax layers (0.25 wt% + 0.25 wt% = total 0.5 wt%) using a roller drum coater and a component coating process for each layer as follows. Prior to the scheduled start of the coating process, first, the fertilizer (0.5 kg to 2.0 kg) was dried in an oven at 80 °C for at least 6 hours according to standard industry practice. Next, the fertilizer was transferred to a drum coater heated to 80 °C. To produce the coated fertilizer composition, each coating component was added and the particles were coated for 30 seconds before adding the subsequent component. The order of addition was as follows. The first portion (40%) of the isocyanate, the isocyanate-reactive component, the remaining 60% of the pre-weighed isocyanate portion were added, followed by the wax component. This process was repeated to form five coating layers, i.e., PU - wax - PU - wax - PU. Next, the coated fertilizer composition was cooled and aged for 1 week before the release test.

[0027] For the release test, 10 grams of each sample was placed in a separate container with 100 mL of deionized water. Then, refractive index measurements were taken on the 14th and 28th days after contact with water to determine the weight percent of the released fertilizer (urea). To determine the refractive index, an initial calibration curve was created by measuring the refractive index of aqueous solutions of uncoated urea (SUPERU46 - 0 - 0; uncoated urea prills 2 - 4 mm) at various concentrations using a refractometer. To determine the weight percent of dissolved urea, the equation was solved as follows.

[0028] [Number] Where X is the weight percent of the released urea. The calibration curve plotting the weight percent of urea in deionized water against the refractive index had the best fit line: y = 0.0013x + 1.333, and R 2 = 0.9997.

[0029] Details of the formulation compositions and test results of the comparative examples (CE) and inventive examples (IE) of the present invention are shown in Tables 2 and 3. The isocyanate-reactive component of IE1 contained 67.5 wt% of polyol 1, 22.5 wt% of glycerol, and 10 wt% of TEA. The isocyanate-reactive component of IE2 contained 70 wt% of polyol 2, 20 wt% of glycerol, and 10 wt% of TEA. The isocyanate-reactive component of IE2 contained 67.5 wt% of polyol 1, 22.5 wt% of TMP, and 10 wt% of TEA.

[0030] [Table 2]

[0031] [Table 3]

[0032] Comparative examples CE1-8 show that the release performance of the urea fertilizer is inferior compared to the extended release times of inventive examples IE1-IE3. Surprisingly, the hydrophilic blend used to form the polyurethane layer of the coated fertilizer improves control over the fertilizer release time compared to hydrophobic polyurethane coatings such as the propylene oxide-based formulation used in CE4.

[0033] While the foregoing is directed to exemplary embodiments, other further embodiments may be devised without departing from its basic scope, which is determined by the following claims.

Claims

1. A coated fertilizer, comprising: fertilizer granules; and two or more polyurethane layers on the fertilizer granules, wherein the polyurethane layer is (i) a reaction product of an isocyanate component containing one or more isocyanate compounds and (ii) An isocyanate-reactive component comprising: (a) 65% to 80% by weight of a hydrophilic polyether polyol having an OH value in the range of 220 mg KOH / g to 400 mg KOH / g, wherein ethylene oxide is 90% to 100% by weight of the total alkylene oxide content of the hydrophilic polyether polyol and the hydroxyl functionality is 2 to 3; and (b) 20% to 35% by weight of a low EW polyol having the formula CH ２ OHC(R １ )(R ２ )CH ２ OH (wherein R １ is CH ２ OH or OH, and R ２ is H or a C1-C3 alkyl group), the polyol component having an isocyanate index of 120 to 160, an isocyanate-reactive component, two or more polyurethane layers on the fertilizer granules; and one or more wax layers on the fertilizer granules containing a polyolefin wax. The coated fertilizer comprising the above.

2. The coated fertilizer composition according to claim 1, wherein the hydrophilic polyether polyol has a weight average molecular weight in the range of 300 Da to 800 Da.

3. The coated fertilizer composition according to claim 1, wherein the isocyanate-reactive component contains a tertiary amine added to the isocyanate-reactive component in a weight percentage in the range of 5 wt% to 15 wt%.

4. The coated fertilizer composition according to claim 1, wherein the coated fertilizer composition releases less than 40% of the total weight of the fertilizer granules after being contacted with water for 28 days.

5. The coated fertilizer composition according to claim 1, wherein the isocyanate-reactive component contains the hydrophilic polyether polyol and one or more of the low EW polyols in a ratio of 75:25 to 80:

20.

6. The coated fertilizer composition according to claim 1, wherein the isocyanate-reactive component consists essentially of 5 wt% to 15 wt% tertiary amine, 15 wt% to 35 wt% low EW polyol, and 50 wt% to 70 wt% hydrophilic polyether polyol.

7. A method for producing the coated fertilizer composition according to claim 1, comprising: forming a first polyurethane layer of the two or more polyurethane layers on the fertilizer granules; forming a first wax layer of the one or more wax layers on the first polyurethane layer; and forming a second polyurethane layer of the two or more polyurethane layers on the first wax layer. The method comprising the above.

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