Chemistry: fertilizers – Processes and products – Organic material-containing
Reexamination Certificate
2001-08-08
2003-10-14
Sayala, Chhaya (Department: 1761)
Chemistry: fertilizers
Processes and products
Organic material-containing
C071S064100, C071S064110
Reexamination Certificate
active
06632262
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a controlled release urea-formaldehyde liquid fertilizer resin having a nitrogen level of at least about 28 wt % and a method of preparing the resin.
BACKGROUND OF THE INVENTION
Urea-formaldehyde based liquid fertilizers have been used for some time to provide nitrogen to the soil. In addition to nitrogen, phosphorous and potassium are considered major nutrients essential for plant growth. Over time, these major nutrients become deficient in the soil because plants use relatively large amounts of such nutrients. In addition to the major nutrients, secondary and micro-nutrients are also needed, but are usually deficient less often and are used in smaller amounts in fertilizer formulations. It is desirable to have a urea-formaldehyde base resin that contains the necessary nitrogen component, is stable, and capable of solubilizing different levels of phosphorus, potassium, and micro-nutrients from various sources while maintaining stability.
In the past, long term stability of high nitrogen (around 30%) liquid urea-formaldehyde fertilizers was achieved by forming either a high percentage (more than 30%) of cyclic triazone structures or by condensing the urea-formaldehyde resin into small urea-formaldehyde polymer chains.
Several patents issued to Hawkins describe the preparation of urea-formaldehyde resins having high triazone contents. U.S. Pat. No. 4,554,005 describes a reaction that produces at least about 30% triazone and has a preferred urea, formaldehyde, ammonia ratio of 1.2/1.0/0.28. Hawkins further describes preparing 30% nitrogen, liquid UF resin (containing 50% controlled release and 50% quick release nitrogen (50/50)) by starting with a 28% nitrogen liquid UF resin which is 70% controlled release and 30% quick release (70/30) and adding urea. There is only one (70/30) resin known in the industry which can be used to consistently produce a clear, storage-stable 50/50 resin containing 30% nitrogen by fortification with urea. This product is currently produced by Tessenderlo Kerley Inc. and marketed as N-SURE®.
U.S. Pat. No. 4,599,102 describes a reaction that produces at least about 30% triazone and has a urea, formaldehyde, ammonia ratio of 1.2/1.0/0.5. Both of these resins have a high percentage of ammonia. U.S. Pat. No. 4,776,879 describes a reaction that produces at least about 75% triazone in water insoluble forms. This material is then crystallized out and re-dissolved at low solids levels for use. U.S. Pat. No. 4,778,510 describes a reaction that produces at least about 48% triazone. The nitrogen is the useful part of the fertilizer to the plant and thus the higher the percentage of nitrogen, the more efficient the fertilizer.
Other patents describe condensing the resin into small chains. U.S. Pat. No. 4,781,749 to Moore reacts 1.5 to 2.5 mols formaldehyde per mole of urea in the presence of ammonium compounds such as ammonia. This initial mole ratio is below the initial mole ratio of 5 to 4 mols formaldehyde per mole of urea of the present invention. The pH is maintained at near neutral conditions (6.9-8.5) throughout the reaction. Condensed UF chains have lower solubility than methylolated ureas and could continue to advance, leading to extremely slow release.
U.S. Pat. No. 3,970,625 to Moore et al. describes a process for preparing urea-formaldehyde concentrates for use as slow release fertilizers or as adhesives. Urea and formaldehyde are mixed in a molar ratio of 1/4.4-7.3 with no more than 0.015 wt. % of ammonia present in the urea. The pH is adjusted to 8.8-9.5 and the mixture is heated to 50-60° C. for 30-60 minutes. Thereafter, water is removed by distillation under reduced pressure until solids comprise 60-90% of the remaining residue. For producing fertilizers, the residue is heated for another 48 hours at a temperature of 45-50° C.
U.S. Pat. No. 5,449,394 to Moore relates to liquid non-polymeric controlled-release nitrogen plant food compositions containing the condensation products of one part ammonia, two parts urea and three parts formaldehyde at a base buffered pH slightly above 7. The reaction is accomplished at a temperature of about 100° C. for 30-300 minutes. Water may be removed by evaporation until the nitrogen content of the formulation is between 20 and 30%. The solution is cooled before polymerization producing chains of more than 3 urea moieties can occur.
U.S. Pat. No. 3,677,736 to Formaini describes a process for manufacturing a liquid fertilizer suspension by preparing an aqueous mixture of urea and formaldehyde having a urea to formaldehyde ratio of 1-2:1 (F:U ratio of 0.5-1:1). Ammonia is then added in an amount of 0.3-6% by weight and the mixture is heated while maintaining the pH in the range of above 7. After heating, the resulting reaction product is diluted with water and an acidic material is added to adjust the pH to 1-4, then the solution is acidified and reheated. The pH is then adjusted to a pH of between 5 and 8.
It is desirable to make a stable urea-formaldehyde resin suitable for fertilizer use that uses significantly less triazone and no acid condensation, and has a higher nitrogen concentration than prior art resins. It is also desirable to have a resin that contains at least 50% controlled release nitrogen and will provide stable solutions with phosphate and potassium salts and other micro-nutrients.
BRIEF SUMMARY OF THE INVENTION
The invention is directed to a method of making a stable urea-formaldehyde resin suitable for fertilizer use which uses significantly less triazone than the Hawkins' process and no condensation reaction like the Moore processes, has a high nitrogen concentration, and yet is very stable, for instance, for at least two months at 25° C.
In particular, the invention is directed to a urea-formaldehyde liquid resin prepared by the method comprising:
1) combining formaldehyde, urea, and ammonia in a basic solution at a formaldehyde/urea/ammonia ratio of about 0.6-1/1/0.25-0.35;
2) heating the solution to about 80° C. to about 95° C., while maintaining a pH of at least 7 for at least 45 minutes;
3) cooling the solution to less than about 50° C., and adjusting the pH to about 9.0 to about 10.5;
wherein the nitrogen content of the resin is at least about 28 wt % based on 100% resin solids with about 50 to about 60 wt % of the nitrogen being controlled release and about 40 to about 50 wt % of the nitrogen being quick release.
The fertilizer resin exhibits superior miscibility with various phosphate, potassium, and micro-nutrient sources while maintaining water clarity and excellent storage stability.
DETAILED DESCRIPTION OF THE INVENTION
The invention is directed to a controlled release liquid urea-formaldehyde fertilizer prepared from a solution prepared by the reaction of formaldehyde, urea, and ammonia.
The nitrogen level of the urea-formaldehyde resin is at least about 28%, preferably at least about 30 wt %, and more preferably between about 30 and 32 wt %. The final mole ratio of formaldehyde:urea:ammonia is about 0.6-1:1:0.25-0.35. The nitrogen content is about 50 wt % to about 60 wt % controlled release, preferably about 55 to about 60 wt % and about 40 to about 50 wt % quick release, preferably about 40 wt % to about 45 wt %.
Quick release nitrogen refers to free urea. Controlled release nitrogen refers to substituted urea. Structure I below is a free urea and II-VII are each a substituted urea with IV-VII representing various triazones.
The fertilizer of the invention has the ability to solubilize varying concentrations of potassium and phosphate salts while maintaining excellent storage stability. The resin can be prepared in a reactor without isolation and eliminates the need for the end user to add or mix in urea. No acid condensation steps are required in the instant invention.
In accordance with the process of the invention:
Formaldehyde, urea, and ammonia are combined in a basic solution at a formaldehyde/urea/ammonia ratio of about 0.6-1/1/0.25-0.35, preferably about 0.7-0.9/1/0.25-0.3, and most preferably about 0.8/1/0.27. All or
Banner & Witcoff , Ltd.
Georgia-Pacific Resins Inc.
Sayala Chhaya
LandOfFree
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