Controlled release fertilizer coating using hydrophilic blends

Abstract

A coated fertilizer composition may contain fertilizer particles; two or more polyurethane layers on the fertilizer particles wherein the polyurethane layers are the reaction product of an isocyanate component comprising one or more isocyanate compounds, and an isocyanate reactive component comprising one or more isocyanate compounds, the isocyanate reactive component includes a polyol component containing (a) from 65 wt% to 80 wt% of a hydrophilic polyether polyol having an OH number in the range of from 220 mg KOH / g to 400 mg KOH / g, where ethylene oxide represents from 90 wt% to 100 wt% of the total alkylene oxide content of the hydrophilic polyether polyol, and a hydroxyl functionality is from 2 to 3, and (b) from 20 wt% to 35 wt% of a low EW polyol having the formula CH2OHC (R1) (R2) CH2OH, where R1 is CH2OH or OH, and R2 is H or a C1 to C3 alkyl group; the isocyanate index is from 120 to 160; and one or more wax layers on the fertilizer particles, the one or more wax layers comprising a polyolefin wax.

Description

Technical Field

[0001] Embodiments are directed to coated fertilizer compositions having controlled dissolution and release characteristics. Background Art

[0002] Coatings on fertilizers have been used for controlled release, which improves fertilizer efficacy, reduces the amount and frequency of applications, and reduces labor costs. This in turn reduces the risk of root burn caused by excess fertilizer, and prevents nutrient losses caused by leaching and denitrification processes. However, coating defects can lead to performance irregularities and premature coating degradation. Coating degradation in turn can lead to uncontrolled release, scheduling disruptions, and plant damage from unstable concentration gradients. Summary of the invention

[0003] The coated fertilizer composition may contain a fertilizer granule; two or more polyurethane layers on the fertilizer granule, wherein the polyurethane layers are the reaction product of an isocyanate component comprising one or more isocyanate compounds, and an isocyanate reactive component comprising a polyol component comprising: (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, wherein ethylene oxide accounts for 90 wt % to 100 wt % of the total alkylene oxide content of the hydrophilic polyether polyol, and a hydroxyl functionality of 2 to 3, and (b) 20 wt % to 35 wt % of a polyol having the formula CH2OHC(R 1 )(R 2 )CH2OH low EW polyols, wherein R 1 is CH2OH or OH, and R 2 is H or a C1 to C3 alkyl group; an isocyanate index of 120 to 160; and one or more wax layers on the fertilizer granules, the one or more wax layers comprising a polyolefin wax. DETAILED DESCRIPTION

[0004] Embodiments relate to coated fertilizer compositions having one or more layers that provide slowed release characteristics and controlled dissolution when compared to uncoated fertilizers. In some cases, the fertilizer coating can be multi-layered and have a mixture of one or more polyurethane layers with one or more wax layers interspersed therebetween. The coated fertilizer composition can include one or more polyurethane layers produced by reacting an isocyanate component with an isocyanate-reactive component of a mixture containing 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 enhanced fertilizer release characteristics when compared to similar formulations utilizing hydrophobic polyols such as castor oil or propoxylated polyols. Although hydrophilic polyether polyols are generally avoided and associated with unstable release rates, the incorporation of low EW polyols in isocyanate reactive components can unexpectedly cause a significant increase in the duration of fertilizer controlled release. In particular, the use of an isocyanate reactive component containing a polyol component provides controlled release of fertilizer over a longer time range when compared to relatively hydrophobic polyols such as PO-based polyols that result in poor controlled release performance, and the polyol component contains a combination of low EW polyols and hydrophilic polyether polyols. The coated fertilizer compositions disclosed herein can be easier to handle and have a release period that can be extended to weeks or months after application.

[0006] The coated fertilizer composition may comprise one or more polyurethane layers having a dispersed wax layer capable of releasing the fertilizer in stages and consistently. The coated fertilizer composition may comprise a polyurethane (PU) layer as the innermost layer contacting the particles and a PU layer as the outermost layer, with alternating wax layers between each PU layer. For example, if the number of PU layers = x, then the number of wax layers = (x-1). The coated fertilizer composition may have a total number of layers ranging from 3 to 9. The order 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 the like. Successive layers may coat the fertilizer particles or sublayers of the bottom layer, wherein the coating is considered to cover 90% to 100% of the surface area of ​​the bottom layer surface.

[0007] The coated fertilizer composition disclosed herein comprises one or more fertilizers provided in granular form. The fertilizer granules include urea, 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 hydrogen phosphate, polyphosphate compounds, phosphate rock, superphosphate, triple superphosphate, potassium nitrate, potassium chloride, potassium sulfate or a combination 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 the nitrogen source, phosphorus source or potassium source included in the fertilizer granules may vary based on the intended end use, and based on the gross weight of the fertilizer granules, each component may be 0 to 60wt%.

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

[0009] The coated fertilizer composition may comprise one or more polyurethane layers, which are formed 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 may include at least one compound having an isocyanate group. In a coated fertilizer composition comprising a plurality of PU layers, the isocyanate components may be the same or different.

[0010] The isocyanate component may include one or more isocyanates and polyisocyanates having an average of greater than 1.0 isocyanate groups per molecule. The isocyanate component may contain aliphatic, alicyclic, alicyclic, araliphatic, aromatic and / or derivatives thereof. Examples of compounds suitable 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 may have an average isocyanate functionality of 1 to 5, 1.5 to 5, 2 to 5, or 3 to 5. The isocyanate may 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 may 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, which is defined as the molar stoichiometric excess of isocyanate moieties in the reaction mixture relative to the number of moles of isocyanate-reactive units (active hydrogens available to react with isocyanate moieties), multiplied by 100. An isocyanate index of 100 means no stoichiometric excess, such that there are 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 may comprise one or more polyurethane layers produced by the reaction of an isocyanate component with an isocyanate-reactive component containing a polyol component, the 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 may consist essentially of one or more hydrophilic polyether polyols and one or more low EW polyols, wherein "consist essentially or consisting essentially" means that all polyol species within the isocyanate-reactive component are limited to those polyols and amounts described, but other components do not substantially affect the total isocyanate index and / or average OH value.

[0014] The hydrophilic polyether polyols disclosed herein are prepared by polymerization of ethylene oxide with an initiator and optionally another alkylene oxide, wherein ethylene oxide accounts for 90 wt% or more of the total alkylene oxide. In some cases, the weight percentage (wt%) of ethylene oxide in the hydrophilic polyether polyol can range from 90 wt% to 100 wt% or 95 wt% to 100 wt%. Initiators include molecules with hydroxyl functionality ranging from 2 to 8, such as between 2 and 4. Suitable initiators include water, glycerol, ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol, and combinations thereof. Examples of other alkylene oxides that can be used to prepare hydrophilic polyether polyols include propylene oxide, butylene oxide, and combinations thereof. The hydrophilic polyether polyols can be prepared according to known methods and can include VORANOL TM and CARBOWAX TM A commercially available example is sold as HYDRAPLAST®, which is available from The Dow Chemical Company.

[0015] The isocyanate reactive component may include a polyol component containing a mixture of hydrophilic polyether polyols. The hydrophilic polyether polyols disclosed herein may have a hydroxyl functionality of 2 to 4 or 2 to 3. The hydrophilic polyether polyols may 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 as measured according to ASTM D4274-21. The hydrophilic polyether polyols may 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 may include a polyol component comprising a mixture of low EW polyols. The low EW polyols may have the formula CH2OHC(R 1 )(R 2 )CH2OH, where R 1 is CH2OH or OH, and R 2 is H or a C1 to C3 alkyl group. Suitable low EW polyols include C3 to C6 polyols having 2 to 3 hydroxyl functionalities, such as glycerol and trimethylolpropane.

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

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

[0019] The isocyanate reactive component 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 also include a tertiary amine having a weight percentage (wt%) of 15wt% or less, 10wt% or less or 8wt% or less. The isocyanate reactive component may also include a tertiary amine having a weight percentage (wt%) of 1wt% to 20wt%, 1wt% to 15wt% or 5wt% to 15wt%. In some cases, the isocyanate reactive component is substantially composed of 5wt% to 15wt% of a tertiary amine, 15wt% to 35wt% of a low EW polyol and 50wt% to 80wt% of a hydrophilic polyether polyol.

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

[0021] The coated fertilizer composition may comprise one or more polyurethane layers, wherein the polyurethane is included in a weight percentage (wt%) of the coated fertilizer composition in the range of 1.5 wt% to 4 wt%, 2 wt% to 4 wt%, or 2 wt% to 3.5 wt%. The coated fertilizer composition may comprise one or more wax layers, wherein the wax is included in a weight percentage (wt%) of the coated fertilizer composition 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%.

[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 particles after contact 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 particles after contact with water for 14 days.

[0023] The coated fertilizer granule composition can be prepared using known equipment, conditions and components, such as a drum coater that applies heat. The preparation method may 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 layering step may be repeated as many times as desired. The formation of one or more polyurethane layers in the polyurethane layer may include dividing the isocyanate component and / or the isocyanate-reactive component into portions that are added at different stages of the coating process. For example, a first portion of the isocyanate-reactive component may be added to a 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 is added to the mixture.

[0024] Example

[0025] The following examples are provided to illustrate embodiments of the present invention and are not intended to limit the scope of the invention. Table 1 provides the materials used in the following examples.

[0026]

[0027] In the following examples, urea fertilizer granules were coated with 5 alternating PU (0.9 wt% + 0.9 wt% + 0.9 wt% = 2.7 wt% in total) and wax layers (0.25 wt% + 0.25 wt% = 0.5 wt% in total) using a drum coater and a layer-by-layer component coating process as follows. According to standard industrial practice, the fertilizer (0.5 kg to 2.0 kg) was first dried in an oven at 80°C for at least 6 hours before the coating process was planned to begin. The fertilizer was then transferred to a drum coater heated to 80°C. To produce the coated fertilizer composition, each coating component was added and allowed to coat the granules for 30 seconds before the subsequent component addition. The order of addition was as follows: the first portion (40%) of isocyanate, the isocyanate-reactive component, the remaining 60% of the pre-weighed isocyanate portion, followed by the wax component. The process was repeated to form 5 coating layers: PU-wax-PU-wax-PU. The coated fertilizer compositions were then allowed to cool and age for one week before release testing.

[0028] For the release test, 10 grams of each sample are placed in the corresponding container with 100mL deionized water. Then, after 14 days and 28 days of contact with water, the weight percent of the fertilizer (urea) released is measured by refractive index. In order to measure the refractive index, an initial calibration curve is created by using a refractometer to measure the refractive index of an uncoated urea (SUPERU 46-0-0; 2mm-4mm uncoated urea pellet) aqueous solution with different concentrations. The equation of the weight percent of dissolved urea is solved as follows:

[0029]

[0030] Where X = wt% of urea released. A calibration curve plotting wt% urea in deionized water versus refractive index has a best fit line: y = 0.0013x + 1.333, and R 2 =0.9997.

[0031] The formulation details and test results of the comparative examples (CE) and the inventive examples (IE) are shown in Tables 2 and 3. The isocyanate reactive components for IE1 contained 67.5 wt% Polyol 1, 22.5 wt% glycerol, and 10 wt% TEA. The isocyanate reactive components for IE2 contained 70 wt% Polyol 2, 20 wt% glycerol, and 10 wt% TEA. The isocyanate reactive components for IE2 contained 67.5 wt% Polyol 1, 22.5 wt% TMP, and 10 wt% TEA.

[0032]

[0033]

[0034]

[0035] Comparative Examples CE1-8 show poor urea fertilizer release performance relative to the extended release time of Examples IE1-IE3. Surprisingly, the hydrophilic blend used to form the polyurethane layer of the coated fertilizer provides enhanced control over the fertilizer release time compared to a hydrophobic polyurethane coating such as the propylene oxide based formulation used in CE4.

[0036] While the foregoing is directed to illustrative embodiments, other and further embodiments may be devised without departing from the basic scope of the present invention, which is defined by the claims that follow.

Claims

1. A coated fertilizer, comprising: Fertilizer granules; Two or more polyurethane layers on the fertilizer granule, wherein the polyurethane layers are the reaction product of: (i) an isocyanate component, the isocyanate component comprising one or more isocyanate compounds, and (ii) an isocyanate-reactive component comprising a polyol component consisting of: (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, wherein ethylene oxide accounts for 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 polyol having the formula CH2OHC(R 1 )(R 2 )CH2OH low EW polyols, wherein R 1 is CH2OH or OH, and R 2 is H or a C1 to C3 alkyl group; an isocyanate index of 120 to 160; and One or more wax layers on the fertilizer granules, the one or more wax layers comprising polyolefin wax.

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

3. The coated fertilizer composition according to claim 1, wherein the isocyanate reactive component comprises a tertiary amine added to the isocyanate reactive component in a weight percentage ranging from 5 wt% to 15 wt%.

4. The coated fertilizer composition of claim 1, wherein the coated fertilizer composition releases less than 40% of the total weight of the fertilizer particles after contact with water for 28 days.

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

20.

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

7. A method for preparing the coated fertilizer composition according to claim 1, the method 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; as well as A second polyurethane layer of the two or more polyurethane layers is formed on the first wax layer.

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