SOLVENT FOR THIOPHOSPHORIC TRIAMIDE OR DICYANDIAMIDE SOLUTIONS, AND RELATED METHODS

Abstract

Solvents useful with thiophosphoric triamide urease inhibitors, that provide stable solution of a thiophosphoric triamide, such as for distribution (in low or high concentrations) onto a fertilizer or other liquid or solid material that contains urea.

Claims

1. A solution comprising: a thiophosphoric triamide urease inhibitor, and a solvent comprising triethyl phosphate.

2. The solution of claim 1 wherein the thiophosphoric triamide is N-(n-butyl)-thio-phosphoric triamide.

3. The solution of claim 1 wherein the thiophosphoric triamide is present in the solution in an amount between about 15 and 50 weight percent, by weight of the solution.

4. The solution of claim 1 wherein the triethyl phosphate is present in the solution in an amount between about 50 and 85 weight percent, by weight of the solution.

5. The solution of claim 1 wherein the thiophosphoric triamide is present in the solution in an amount between about 20 and 35 weight percent, by weight of the solution.

6-8. (canceled)

9. The solution of claim 1 comprising a co-solvent selected from alkyl lactate, dimethyl sulfoxide, triethyl phosphate, N-methyl pyrrolidone, a glycol, a glycol derivative, propylene glycol, sulfolane, and combinations thereof.

10. The solution of claim 1 comprising a co-solvent selected from: a mixture of triethyl and ethyl lactate; a mixture of triethyl phosphate and dimethyl sulfoxide; and a mixture of triethyl phosphate, ethyl lactate, and dimethyl sulfoxide.

11. The solution of claim 9 wherein the thiophosphoric triamide is present in the solution in an amount between about 15 and 50 weight percent, by weight of the solution.

12-14. (canceled)

15. The solution of claim 9 wherein the co-solvent is present in the solution in an amount up to about 50 weight percent, by weight of the solution.

16-17. (canceled)

18. The solution of claim 1 further comprising a dye.

19. A method of preparing a urea-based fertilizer, the method comprising providing a solution of claim 1 and incorporating the solution into the urea-based fertilizer.

20. The method according to claim 19 wherein the urea-based fertilizer comprises solid particles and the method comprises impregnating the solid particles with the solution.

21. The method according to claim 19 wherein the urea-based fertilizer comprises a liquid and the method comprises incorporating the solution uniformly into the liquid.

22. The method according to claim 19 wherein the urea-based fertilizer is selected from the group consisting of: urea (46-0-0), urea ammonium nitrate solutions (28-32 percent), and urea ammonium sulfate (33-0-0-12S).

23. The solution of claim 1 further comprising dicyandiamide.

24. (canceled)

25. A solution comprising dicyandiamide and a solvent comprising triethyl phosphate.

26. The solution of claim 25 wherein the dicyandiamide is present in the solution in an amount between about 15 and 50 weight percent, by weight of the solution.

27-31. (canceled)

32. The solution of claim 25 further comprising a co-solvent selected from alkyl lactate, dimethyl sulfoxide, triethyl phosphate, N-methyl pyrrolidone, a glycol, a glycol derivative, propylene glycol, sulfolane, and combinations thereof.

33-34. (canceled)

35. The solution of claim 25 consisting essentially of dicyandiamide, triethyl phosphate, and dimethyl sulfoxide.

36. The solution of claim 25 comprising a co-solvent comprising dimethyl sulfoxide.

37. (canceled)

Description

DETAILED DESCRIPTION

[0027] Following is a description of solvents, solvent-containing compositions such as solutions, and agricultural products and derivatives thereof. These compositions and solutions can include urea-based fertilizer compositions that contain a urease inhibitor from the group of thiophosphoric triamide urease inhibitors. The compositions can alternately or additionally contain a nitrification inhibitor such as dicyandiamide (DCD). A composition includes triethyl phosphate as a solvent, either alone or as part of a solvent system containing triethyl phosphate with one or more co-solvent.

[0028] The thiophosphoric triamide urease inhibitor may be an alkyl thiophosphoric triamide, e.g., an N-alkyl thiophosphoric triamide, for example N-(n-butyl)-thio-phosphoric triamide, also referred to herein as NBPT. It is understood that the terms thiophosphoric triamide, alkyl thiophosphoric triamide, N-alkyl thiophosphoric triamide, and N-(n-butyl)-thio-phosphoric triamide as used throughout this application refer not only to the specific materials in a pure form, but also to commercial grades of such materials, which may contain up to 50 percent, preferably not more than 20 percent, of impurities, depending on the method of synthesis and purification scheme, if any, used in preparation of the material.

[0029] Industrial grade thiophosphoric triamides are often waxy and sticky materials that are difficult to handle and process to derivative products using conventional industrial equipment and methods. Thiophosphoric triamides are also of low solubility in water, in aqueous solutions such as ammonium hydroxide solutions, and in various common organic solvents such as toluene, benzene, hexane, dichloromethane, and others. Lower alcohols are good solvents for the N-alkyl thiophosphoric triamides but are flammable, presenting safety problems. Also, alkyl thiophosphoric triamides are considered to be unstable in many aqueous and non-aqueous solvents.

[0030] Dicyandiamide is a known chemical compound, effective as a nitrification inhibitor, and having the formula (1):

##STR00001##

Dicyandiamide, also known as “2-cyanoganidine,” can be made by known methods of treating cyanamide with base, and is commercially available. Dicyandiamide can be provided in the form of a concentrated solid ingredient, e.g., a flake, pellet, or granule, that contains a high concentration of the DCD, e.g., at least 50, 75, or 90 weight percent DCD. The dicyandiamide also preferably contains a low amount of moisture, such as less than 5, 2, or 1 percent water based on the total weight of the DCD composition.

[0031] According to the present description, triethyl phosphate can be a useful solvent for a nitrification inhibitor such as DCD; for a urease inhibitor such as a thiophosphoric triamide, an alkyl thiophosphoric triamide, a N-alkyl thiophosphoric triamides, or a N-(n-butyl)-thio-phosphoric triamide; or for a combination of the nitrification inhibitor (e.g., DCD) and one or more of these urease inhibitors.

[0032] Triethyl phosphate, which is the triester of ethanol and phosphoric acid, can alternately be referred to as phosphoric acid triethyl ester, ethyl phosphate, triethylphosphate, tris(ethyl) phosphate, or triethoxyphosphine oxide. Triethyl phosphate is a colorless liquid at room temperature and has the following chemical formula:

##STR00002##

[0033] The relative amount of the nitrification inhibitor, the urease inhibitor, or both, in a composition that contains triethyl phosphate as a solvent, can be any amount or amounts useful to allow an effective amount of the nitrification inhibitor, urease inhibitor, or both, to dissolve in the solvent to allow the resultant solution to be processed as desired.

[0034] Exemplary amounts of thiophosphoric triamide and triethyl phosphate, as a solvent, a solution that does not contain co-solvent, can be, e.g., from 15 to 50 weight percent thiophosphoric triamide, and from 50 to 80 weight percent triethyl phosphate, for example from 20 to 35 weight percent thiophosphoric triamide and from 65 to 80 weight percent triethyl phosphate, The solution may consist of or may consist essentially of the thiophosphoric triamide and triethyl phosphate.

[0035] Exemplary amounts of DCD, with triethyl phosphate as a solvent, in a solution that does not contain co-solvent, can be, e.g., from 15 to 50 weight percent DCD, and from 50 to 85 weight percent triethyl phosphate, for example from 20 to 35 weight percent DCD and from 65 to 80 weight percent triethyl phosphate. The solution may consist of or may consist essentially of the DCD and triethyl phosphate.

[0036] Exemplary amounts of DCD and NBPT, with triethyl phosphate as a solvent, in a solution that does not contain co-solvent, can be, e.g., from 15 to 50 weight percent DCD and NBPT, and from 50 to 85 weight percent triethyl phosphate, for example from 20 to 35 weight percent DCD and NBPT and from 65 to 80 weight percent triethyl phosphate. The solution may consist of or may consist essentially of the DCD, NBPT, and triethyl phosphate.

[0037] Optionally, the solution may also contain at least one additional solvent (referred to as a “co-solvent”). The amount and type of co-solvent can be as desired, with certain preferred co-solvents including alkyl lactate (e.g., ethyl lactate), dimethyl sulfoxide, triethyl phosphate, N-methyl pyrrolidone, glycols, glycol derivatives such as propylene glycol, sulfolane, and combinations thereof.

[0038] The solution can include triethyl phosphate as the only solvent, or may contain a single co-solvent or a mixture of two or more co-solvents. Where a mixture of co-solvents is used, examples of preferred co-solvent mixtures include a mixture of triethyl and alkyl (e.g., ethyl) lactate; a mixture of triethyl phosphate and dimethyl sulfoxide; and a mixture of triethyl phosphate, alkyl (e.g. ethyl) lactate, and dimethyl sulfoxide.

[0039] Exemplary amounts of thiophosphoric triamide, triethyl phosphate, and co-solvent (a single co-solvent or a mixture) in a solution that contains co-solvent can be, e.g., from 15 to 50 weight percent thiophosphoric triamide, from 50 to 85 weight percent triethyl phosphate, and up to about 50 weight percent co-solvent, for example from 20 to 30 weight percent thiophosphoric triamide, and from 70 to 80 weight percent triethyl phosphate, and up to about 30, 25, 15, or 10 weight percent co-solvent based on the weight of the solution. The solution may consist of or may consist essentially of the thiophosphoric triamide, the triethyl phosphate, and the co-solvent.

[0040] Exemplary amounts of DCD and co-solvent (a single co-solvent or a mixture) in a solution that contains co-solvent can be, e.g., from 15 to 50 weight DCD, from 50 to 85 weight percent triethyl phosphate, and up to about 75 or 80 weight percent co-solvent, for example from 20 to 30 weight percent DCD, and from 70 to 80 weight percent triethyl phosphate, and up to about 80, 75, 70, 60, 50, 30, 25, 15, or 10 weight percent co-solvent based on the weight of the solution. The solution may consist of or may consist essentially of the DCD, the triethyl phosphate, and the co-solvent.

[0041] Exemplary amounts of DCD, thiophosphoric triamide, triethyl phosphate, and co-solvent (a single co-solvent or a mixture) in a solution that contains co-solvent can be, e.g., from 15 to 50 weight percent DCD and thiophosphoric triamide, from 50 to 85 weight percent triethyl phosphate, and up to about 75 or 80 weight percent co-solvent, for example from 20 to 30 weight percent DCD and thiophosphoric triamide, and from 70 to 80 weight percent triethyl phosphate, and up to about 80, 75, 70, 60, 50, 30, 25, 15, or 10 weight percent co-solvent based on the weight of the solution. The solution may consist of or may consist essentially of the DCD, thiophosphoric triamide, the triethyl phosphate, and the co-solvent.

[0042] The amount of the co-solvent in the solution may depend on the type of co-solvent. Exemplary levels of alkyl (e.g., ethyl) lactate can be up to about 30, e.g., up to about 25 weight percent based on total weight of the solution; exemplary levels of dimethyl sulfoxide can be up to about 80, 75, 70, 50, 25, or 10 weight percent, e.g., up to about 5 weight percent based on total weight of the solution; exemplary levels of a combination of ethyl lactate and dimethyl sulfoxide can be up to about 30, e.g., up to about 25 weight percent of the combination based on total weight of the solution; exemplary levels of N-methyl pyrrolidone can be up to about 10, e.g., up to about 5 weight percent based on total weight of the solution; exemplary levels of a glycol or glycol derivative (e.g., propylene glycol) can be up to about 15, e.g., up to about 10 weight percent based on total weight of the solution; exemplary levels of sulfolane can be up to about 15, e.g., up to about 10 weight percent based on total weight of the solution.

[0043] Optionally, though not required, a composition as described may contain other additives or adjuvants such as, at least one dye, at least one surfactant, stabilizer, etc. Exemplary embodiments of the solution do not contain any additional added ingredient or material such as an additive or adjuvant, and can specifically exclude a dye, surfactant, emulsifier, or stabilizer.

[0044] Preferred solutions can be long-term storage-stable and capable of being incorporated into a liquid or solid urea-containing fertilizer or other useful derivative composition. Examples of solutions as described can remain stable (e.g., without separation, crystallization, or undue chemical breakdown) over extended periods of time (e.g., 1 week, 2 weeks, 4 weeks) and at a temperature in a range from about 30 degrees F to about 120 degrees F. Example solutions can remain stable (e.g., without separation, crystallization, or undue chemical breakdown) for at least 1 week, 2 weeks, or 4 weeks when stored at 72 degrees Fahrenheit.

[0045] Preferred solutions exhibit flow and viscosity properties that allow processing of the solution to incorporate the solution into a derivative product. Preferred solutions can be processed to impregnate, coat, or otherwise incorporate thiophosphoric triamide urease inhibitor or DCD (or both) into or onto a urea-based solid or liquid fertilizer. This may be accomplished by use of any of a variety of known fertilizer bulk blending, coating, or processing equipment. Preferably incorporation of the solution into a solid fertilizer can result in thorough and consistent impregnation of the solid fertilizer by the solution and the urease inhibitor or DCD (or both). Alternately, preferred solutions can be miscible with a liquid fertilizer, allowing the solution to be uniformly mixed or blended into the liquid fertilizer.

[0046] Exemplary fertilizers into which the solution can be incorporated can include urea-based fertilizers such as: urea (46-0-0), urea ammonium nitrate solutions (UAN) (28-32 percent), and urea ammonium sulfate (33-0-0-12S), among others.

Example Solutions:

[0047] Following are examples of solutions of NBPT dissolved in solvent that contains triethyl phosphate and optional co-solvent.

TABLE-US-00001 General Formulation NBPT 20-50% Triethyl phosphate 20-75% Other solvents  0-50%

TABLE-US-00002 Examples Component % w/w NBPT 26.70% Triethyl phosphate 73.30% 100.00%  NBPT 26.70% Triethyl phosphate 48.30% Ethyl lactate   25% 100.00%  NBPT 26.70% Triethyl phosphate 68.30% DMSO  5.00% 100.00%  NBPT 26.70% Triethyl phosphate 48.30% Ethyl lactate   20% DMSO    5% 100.00%  NBPT 26.70% Triethyl phosphate 68.30% N-methyl pyrrolidone    5% 100.00%  NBPT 26.70% Triethyl phosphate 63.30% Propylene glycol   10% 100.00%  NBPT 26.70% Triethyl phosphate 63.30% Sulfolane   10% 100.00%  DCD   20% Triethyl phosphate   10% DMSO   70% DCD   20% NBPT    5% Triethyl phosphate   10% DMSO   65%