Nitrogen fertilizer added to the soil is readily transformed through a number of undesirable biological and chemical processes, including nitrification, leaching, and evaporation. Many transformation processes reduce the level of nitrogen available for uptake by the targeted plant. One such process is nitrification, a process by which certain widely occurring soil bacteria metabolize the ammonium form of nitrogen in the soil, transforming the nitrogen into nitrite and nitrate forms, which are more susceptible to nitrogen loss through leaching or volatilization via denitrification.
The decrease in available nitrogen due to nitrification necessitates the addition of more nitrogen rich fertilizer to compensate for the loss of agriculturally active nitrogen available to the plants. These concerns intensify the demand for improved management of nitrogen, in order to reduce costs associated with the use of additional nitrogen fertilizer.
Methods for reducing nitrification include treating soil with agriculturally active compounds that inhibit or at least reduce the metabolic activity of at least some microbes in the soil that contribute to nitrification. These compounds include (Trichloromethyl)pyridines, such as nitrapyrin, which have been used as nitrification inhibitors in combination with fertilizers as described in U.S. Pat. No. 3,135,594, the disclosure of which is incorporated herein by reference in its entirety. These compounds help to maintain agriculturally-applied ammonium nitrogen in the ammonium form (stabilized nitrogen), thereby enhancing plant growth and crop yield. These compounds have been used efficaciously with a number of plant crops including corn, sorghum, and wheat.
Compounds such as nitrapyrin are unstable in soil in part because they are very volatile. For example, nitrapyrin has a relatively high vapor pressure (2.8×10−3 mm Hg at 23° Celsius), and because of this it has a tendency to volatilize and must be applied immediately or somehow protected from rapid loss after the fertilizer is treated with nitrapyrin. One approach is to add nitrapyrin to a volatile fertilizer, namely anhydrous ammonia, which itself must be added to the soil in a manner that reduces the amount of the volatile active lost to the atmosphere. This method is problematic in that it requires the use of anhydrous ammonia, which is corrosive and must be injected into the soil. This method of applying nitrapyrin, while stabilizing nitrapyrin below the soil surface, is not preferred. This method is unsuitable for many other fertilizer types and their standard application practices such as dry fertilizer granules, which most often are broadcasted onto the soil surface.
Still other approaches to stabilize nitrapyrin and reduce its loss to the atmosphere include applying it to the surface of the soil and then mechanically incorporating it into the soil, or watering it into the soil generally within 8 hours after its application to reduce its loss to the atmosphere. Still another approach is to encapsulate nitrapyrin for rapid or dump release. Such encapsulated forms of nitrapyrin have been formulated with lignin sulfonates as disclosed in U.S. Pat. No. 4,746,513, the disclosure of which is incorporated herein by reference in its entirety. While these formulations are less volatile than simple nitrapyrin, these formulations are better suited for use with liquid urea ammonium nitrate (“UAN”) or liquid manure fertilizers than with dry fertilizers. Although the release of nitrapyrin is delayed by the encapsulation, the capsules release all of the nitrapyrin upon contact with moisture, exhibiting the same stability and volatility disadvantages of the prior application methods.
Another approach to stabilizing nitrapyrin includes polycondensation encapsulation. Additional information regarding this approach can be found in U.S. Pat. No. 5,925,464, the disclosure of which is incorporated herein by reference in its entirety. Some of these formulations enhance handling safety and storage stability of the nitrapyrin using polyurethane rather than polyurea to form at least a portion of the capsule shell.
In some instances, polyurea microencapsulation has been used to produce enhanced nitrification inhibitor compositions for delayed, steady release of nitrification inhibitors for application with fertilizers. Such encapsulated forms of nitrapyrin are disclosed in U.S. Pat. Nos. 8,377,849 and 8,741,805, the disclosures of which are incorporated herein by reference in their entirety.
There remains a need to deliver nitrification inhibitors such as, for example, (trichloromethyl)pyridines having greater long term stability in the field environment, while maintaining the level of efficacy of unencapsulated inhibitors.
While microcapsule aqueous suspensions (a.k.a. capsule suspensions or “CS”) of microencapsulated nitrapyrin referred to above are more stable than un-encapsulated nitrapyrin in an aqueous solution under certain conditions, it has been observed that crystals of nitrapyrin can form in the aqueous phase of a microcapsule suspension of nitrapyrin. Formation of crystalline nitrapyrin in an aqueous microcapsule suspension of nitrapyrin appears to be favored over a narrow temperature range of about −5° C. to about 15° C., more particularly about 0° C. to about 10° C. (degrees centigrade). The weight percentage of crystalline nitrapyrin in the bulk aqueous phase of the microcapsule suspension accumulates over time. Depending upon how the microcapsule suspensions are handled, the presence of measurable levels of crystalline nitrapyrin in the aqueous phase can be of little-to-no consequence or problematic. The presence of even about 0.1 wt. percent crystalline nitrapyrin or above in the aqueous phase of the microcapsule suspension can be especially problematic if the suspension is applied by spraying the suspension through a fine point nozzle with a sprayer containing inline screens.
Additionally, certain commercial embodiments of polyurea microencapsulated nitrification inhibitors, such as, for example, Instinct® or Entrench® (commercial embodiments sold by Dow AgroSciences LLC), are limited by the amount of active ingredient (nitrification inhibitor) that can be microencapsulated and suspended in the aqueous phase without the active ingredient crystallizing into the aqueous phase. For example, in some embodiments, Instinct® and Entrench® comprise about 17% to about 18% by weight active ingredient (nitrapyrin). Crystallization of the active ingredient into the aqueous phase has limited increased levels of active in these aqueous capsule suspensions. Some commercial nitrapyrin capsule suspension formulations have active loadings of 200 g/L, the upper limit of the loading being bound by the solubility of the nitrapyrin in the solvent.
In some of the inventive embodiments of the present disclosure, no solvent is required to dissolve the nitrapyrin (and/or other active ingredient) in the lipophilic phase. In some embodiments, stable aqueous capsule suspension formulations up to 300 g/L nitrapyrin loading are disclosed, without crystallization issues.
Some aspects of the present disclosure include compositions that prevent and/or reduce crystal formation issues observed in presently commercially available formulations of nitrapyrin, including capsule suspensions. Crystal formation in nitrification inhibiting compositions can cause problems including filter blockage during field spray applications. In some instances, crystals that form in the liquid phase of a capsule suspension are high purity crystals, comprising substantially pure organic nitrification inhibitor, such as, for example, nitrapyrin. In some instances, high purity nitrapyrin (99 wt %) crystals form in presently available commercial formulations. Crystal formation, in some instances, is dependent upon the temperature of the formulation in storage, shipping, and/or transport of the formulations.
In some embodiments of the microcapsule suspension formulations of the present disclosure, stable, high-load, agricultural liquid formulations comprising aqueous microcapsule suspensions containing low melting active ingredients are presented. In some embodiments, the microcapsule suspension formulations are prepared without use of an organic solvent to dissolve the low melting point active, such as for example a nitrification inhibitor such as nitrapyrin, and may optionally use small amounts of a polymeric ultra-hydrophobe to prepare the microcapsules. In some embodiments, the microcapsule suspension formulation may include a hydrophobic crystal inhibitor additive to prevent or inhibit crystal formation or growth of the nitrapyrin. In some embodiments, the formulations provide superior physical, chemical, and/or crystallization stability upon storage, and acceptable volatility and nitrification inhibition attributes in applications to the soil.
In some embodiments of the microcapsule suspension formulations disclosed herein, post addition (i.e. after microcapsule formation) of a hydrophobic crystal inhibitor additive to the aqueous phase reduces the rate of crystal formation and/or growth in the aqueous phase at certain temperature storage conditions. In one embodiment, post addition of one or more hydrophobic crystal inhibitor additives provides superior crystal growth reduction in cold temperature storage conditions. In one exemplary embodiment, post-addition of a hydrophobic crystal inhibitor additive that is an aromatic solvent, which includes at least one oil, is present in the aqueous phase of the formulation after the formation of the microcapsules. The term “oil” will herein describe organic solvents that are generally immiscible with water.
In some embodiments, microcapsule suspension formulations already containing crystals of nitrapyrin and without a hydrophobic crystal inhibitor additive in the aqueous phase can be treated with one or more hydrophobic crystal inhibitor additives by addition to the aqueous phase, and the resulting mixture can be stirred at ambient temperature for a length of time, possibly 30 minutes to 5 hours based on the total volume of the microcapsule suspension, until the crystals of nitrapyrin, and/or other crystallized organic inhibitor of nitrapyrin, have disappeared.
The present disclosure therefore provides compositions and methods to prevent and/or reduce crystals and crystal formation in stable, high-load agricultural active compositions containing organic nitrification inhibitors, such as nitrapyrin. In some embodiments, addition of hydrophobic crystal inhibitor additives prevent and/or reduce crystals and crystal formation in capsule suspensions of microencapsulated nitrapyrin. In some embodiments, hydrophobic crystal inhibitor additives provide superior physical stability at about 10° C. stability testing.
In certain embodiments, hydrophobic crystal inhibitor additives of the present disclosure could be applied to any agricultural active composition comprising one or more solvents, one or more agricultural active ingredients, and/or one or more nitrification inhibitors, optionally nitrapyrin.
In certain embodiments, in the absence of the addition of one or more hydrophobic crystal inhibitor additives to the aqueous phase, the microcapsule suspension formulations of the present application may form nitrapyrin crystals in the aqueous phase at cold storage temperatures of about 10° C. These nitrapyrin crystals may be about 99% pure. Over time, such crystals may compose up to 0.5 weight percent of the overall microcapsule suspension formulation. Crystals may also form at other temperatures, such as 0° C.-5° C., and 15° C. Solvent-based, hydrophobic crystal inhibitor additives such as aromatic solvents and ester compounds can increase the physical stability of the microcapsule suspension formulations, particularly at mild cold storage temperatures of about 10° C., preventing or at least reducing crystal formation in the aqueous phase of the microcapsule suspension.
Illustratively, post-added aromatic solvents used as hydrophobic crystal inhibitor additives include: Aromatic 100 Fluid, also known as solvent naphtha or light aromatic; Aromatic 150 Fluid, also known as solvent naphtha, heavy aromatic, high flash aromatic naphtha type II, heavy aromatic solvent naphtha, hydrocarbons, C10 aromatics, >1% naphthalene, A150, S150 (Solvesso 150); and Aromatic 200 Fluid, also known as solvent naphtha, heavy aromatic, high flash aromatic naphtha type II, heavy aromatic solvent naphtha, hydrocarbons, C10-13 aromatics, >1% naphthalene, A200, and 5200 (Solvesso 200).
The aromatic solvents used in some embodiments, are naphthalene depleted (“ND”), or contain less than about 1% naphthalene. Said solvents can be added to the microcapsule suspension formulation prior to crystal formation as a preventative measure, or added to the microcapsule suspension formulation after crystal formation as a remedial measure to remove or reduce the presence of crystals.
The ester compounds used in some embodiments as hydrophobic crystal inhibitor additives include: 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate.
Additionally, the microcapsule suspension formulations of the present disclosure can be combined or used in conjunction with pesticides, including arthropodicides, bactericides, fungicides, herbicides, insecticides, miticides, nematicides, nitrification inhibitors, such as dicyandiamide, urease inhibitors such as N-(n-butyl) thiophosphoric triamide, and the like or pesticidal mixtures and synergistic mixtures thereof. In such applications, the microcapsule suspension formulation of the present disclosure can be tank mixed with the desired pesticide(s) or they can be applied sequentially.
In a first embodiment, a microcapsule suspension formulation is disclosed comprising: (a) a suspended phase of a plurality of microcapsules having a volume median particle size of from about 1 to about 10 microns, wherein the microcapsules comprise: (1) a microcapsule wall produced by an interfacial polycondensation reaction between a polymeric isocyanate and a polyamine to form a polyurea shell; (2) at least one organic nitrification inhibiting compound encapsulated within the polyurea shell; (3) at least one polymeric ultra-hydrophobe compound encapsulated within the polyurea shell; and (b) an aqueous phase.
In a second embodiment, the aqueous phase of the microcapsule suspension formulation of the first embodiment further includes at least one additional ingredient selected from the group consisting of: hydrophobic crystal inhibitor additive, dispersant, nonionic polymer surfactant, antifoam, biocide, and mixtures thereof.
In a third embodiment, the microcapsules of any of the prior embodiments comprise 2-chloro-6-(trichloromethyl)pyridine.
In a fourth embodiment, the formulation of any of the prior embodiments further comprises an agricultural active ingredient selected from the group consisting of: arthropodicides, bactericides, fungicides, herbicides, insecticides, miticides, nematicides, fertilizers, dicyandiamide, urease inhibitors, and pesticidal mixtures and synergistic mixtures thereof.
In a fifth embodiment, the formulation of any of the prior embodiments comprises between about 25 weight percent and about 35 weight percent 2-chloro-6-(trichloromethyl)pyridine.
In a sixth embodiment, the formulation of any of the prior embodiments comprises between about 0.1 weight percent and about 2.00 weight percent of the at least one polymeric ultra-hydrophobe compound.
In a seventh embodiment, the microcapsules of any of the prior embodiments comprise a polybutene.
In an eighth embodiment, the aqueous phase of the microcapsule suspension formulation of any of the prior embodiments comprises between about 1.0 weight percent and about 4.0 weight percent of the hydrophobic crystal inhibitor additive.
In a ninth embodiment, the hydrophobic crystal inhibitor additive of any of the prior embodiments is at least one compound selected from the group consisting of: aromatic solvents such as, for example, naphthalene depleted heavy aromatics, and ester compounds such as, for example, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and mixtures thereof.
In a tenth embodiment, the aqueous phase of the microcapsule suspension formulation of any of the prior embodiments comprises between about 1.0 weight percent and about 10 weight percent nonionic polymer surfactant.
In an eleventh embodiment, the nonionic polymer surfactant of any of the prior embodiments is a polyvinyl alcohol.
In a twelfth embodiment, the aqueous phase of the microcapsule suspension formulation of any of the prior embodiments includes at least one additive selected from the group consisting of: modified styrene acrylic polymeric surfactant, aqueous emulsion of polydimethylsiloxane concentrate, xanthan gum, microcrystalline cellulose, carboxymethyl-cellulose sodium, propylene glycol, a biocide and mixtures thereof.
In a thirteenth embodiment, the formulation of any of the prior embodiments comprises between about 40 weight percent and about 70 weight percent of the aqueous phase.
In a fourteenth embodiment, a method is disclosed for making a microcapsule suspension formulation comprising the steps of: (a) preparing a lipophilic phase comprising at least one lipophilic isocyanate and at least one polymeric ultra-hydrophobe by mixing said at least one lipophilic isocyanate and at least one polymeric ultra-hydrophobe with at least one molten, low melting-point organic nitrification inhibiting compound; (b) preparing an aqueous phase by dissolving and mixing in water at least one additive selected from the group consisting of: dispersants, nonionic polymer surfactants antifoams, biocides, and mixtures thereof; (c) combining the lipophilic phase and aqueous phase to form an oil-in-water emulsion; and (d) combining the oil-in-water emulsion with a solution of at least one polyamine in water to generate microcapsules.
In a fifteenth embodiment, the lipophilic phase of any of the prior embodiments comprises 2-chloro-6-(trichloromethyl)pyridine.
In a sixteenth embodiment, the lipophilic phase of any of the prior embodiments comprises between about 75 weight percent and about 90 weight percent 2-chloro-6-(trichloromethyl)pyridine.
In a seventeenth embodiment, the lipophilic phase of any of the prior embodiments comprises between about 0.1 weight percent and about 3.00 weight percent of the at least one polymeric ultra-hydrophobe compound.
In an eighteenth embodiment, the lipophilic phase of any of the prior embodiments comprises a polybutene.
In a nineteenth embodiment, the method of any of the prior embodiments further comprises the step of: adding at least one additive selected from the group consisting of: dispersants, antifoams, biocides, an aqueous emulsion of polydimethylsiloxane concentrate, a xanthan gum, a microcrystalline cellulose, a carboxymethyl-cellulose sodium, an anti-freeze additive selected from at least one of ethylene glycol, propylene glycol or glycerol, a hydrophobic crystal inhibitor additive and mixtures thereof, after the step of combining the oil-in-water emulsion with a solution of at least one polyamine in water to generate microcapsules. The method of any of the prior embodiments may also further comprise the step of adding at least one additive selected from the group consisting of: hydrophobic crystal inhibitor additive, dispersant, antifoam, biocide, and mixtures thereof after the step of combining the oil-in-water emulsion with a solution of at least one polyamine in water to generate microcapsules that form the aqueous microcapsule suspension.
In a twentieth embodiment, the final microcapsule suspension of any of the prior embodiments comprises between about 1.0 weight percent and about 4.0 weight percent of at least one hydrophobic crystal inhibitor additive.
In a twenty-first embodiment, the hydrophobic crystal inhibitor additive of any of the prior embodiments is at least one compound selected from the group consisting of: aromatic solvents, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and mixtures thereof.
In a twenty-second embodiment, the aqueous phase of any of the prior embodiments comprises between about 1.0 weight percent and about 10 weight percent of a nonionic polymer surfactant
In a twenty-third embodiment, the nonionic polymer surfactant of any of the prior embodiments is a polyvinyl alcohol.
In a twenty-fourth embodiment, the final microcapsule suspension or the aqueous phase of any of the prior embodiments includes at least one additive selected from the group consisting of: a modified styrene acrylic polymeric surfactant, an aqueous emulsion of polydimethylsiloxane concentrate, a xanthan gum, a microcrystalline cellulose, a carboxymethyl-cellulose sodium, a propylene glycol, and mixtures thereof.
In a twenty-fifth embodiment, the aqueous phase of any of the prior embodiments includes at least one additive selected from the group consisting of: modified styrene acrylic polymeric surfactant, nonionic polymer, aqueous emulsion of polydimethylsiloxane concentrate, xanthan gum, microcrystalline cellulose, carboxymethyl-cellulose sodium, and mixtures thereof.
In a twenty-sixth embodiment, the formulation of any of the prior embodiments comprises between about 40 weight percent and about 70 weight percent of the aqueous phase.
In a twenty-seventh embodiment, the method of any of the prior embodiments further comprises the step of: controlling the temperature of the oil-in-water emulsion while mixing the lipophilic and aqueous phases to produce oily globules of a desired size.
In a twenty-eighth embodiment, the method of any of the prior embodiments further comprises the step of adding to the formulation an agricultural active ingredient selected from the group consisting of: pesticides, arthropodicides, bactericides, fungicides, herbicides, insecticides, miticides, nematicides, fertilizers, dicyandiamide, urease inhibitors, and pesticidal mixtures and synergistic mixtures thereof.