U.S. patent application number 12/362057 was filed with the patent office on 2009-05-28 for high nitrogen liquid fertilizer.
This patent application is currently assigned to GEORGIA-PACIFIC CHEMICALS LLC. Invention is credited to Kurt D. Gabrielson, James C. Phillips, Stacey L. Wertz.
Application Number | 20090133457 12/362057 |
Document ID | / |
Family ID | 46326309 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090133457 |
Kind Code |
A1 |
Phillips; James C. ; et
al. |
May 28, 2009 |
HIGH NITROGEN LIQUID FERTILIZER
Abstract
The present invention is directed to liquid fertilizer
composition having a high nitrogen content comprising an aqueous
mixture of a urea-formaldehyde resin and a nitrogen fertilizer
source selected from the group consisting of urea, ammonium
nitrate, and a mixture of urea and ammonium nitrate, wherein the
liquid fertilizer possess surprisingly depressed freeze points and
salt-out temperatures.
Inventors: |
Phillips; James C.;
(Peachtree City, GA) ; Wertz; Stacey L.; (Conyers,
GA) ; Gabrielson; Kurt D.; (Lilburn, GA) |
Correspondence
Address: |
PATENT GROUP GA030-43
133 PEACHTREE STREET, N.E.
ATLANTA
GA
30303-1847
US
|
Assignee: |
GEORGIA-PACIFIC CHEMICALS
LLC
Atlanta
GA
|
Family ID: |
46326309 |
Appl. No.: |
12/362057 |
Filed: |
January 29, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11549462 |
Oct 13, 2006 |
7513928 |
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12362057 |
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11357409 |
Feb 21, 2006 |
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11549462 |
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Current U.S.
Class: |
71/30 |
Current CPC
Class: |
C08G 73/06 20130101;
C08G 61/122 20130101; C05G 5/23 20200201; C08G 12/12 20130101; C05C
9/02 20130101; C05C 1/00 20130101; C08G 61/12 20130101; C05C 9/00
20130101; C05C 1/00 20130101; C05C 9/00 20130101; C05C 9/02
20130101; C05G 5/23 20200201; C05C 1/00 20130101; C05C 9/00
20130101; C05C 9/02 20130101; C05G 5/23 20200201 |
Class at
Publication: |
71/30 |
International
Class: |
C05C 9/00 20060101
C05C009/00 |
Claims
1. An aqueous nitrogen fertilizer solution comprising a mixture of
a urea-formaldehyde resin and a nitrogen fertilizer source selected
from the group consisting of urea, ammonium nitrate and a mixture
of urea and ammonium nitrate.
2. The aqueous nitrogen fertilizer solution of claim 1 wherein the
urea-formaldehyde resin is prepared by reacting urea, formaldehyde
and optionally ammonia in water under an alkaline reaction
condition to yield an aqueous urea-formaldehyde resin solution.
3. The aqueous nitrogen fertilizer solution of claim 2 wherein the
urea-formaldehyde resin is prepared by reacting urea, formaldehyde
and ammonia at a formaldehyde/urea/ammonia mole ratio of
1-4/1/:0.5-1.
4. The aqueous nitrogen fertilizer solution of claim 2 wherein the
urea-formaldehyde resin is prepared by reacting urea, formaldehyde
and ammonia at a formaldehyde/urea/ammonia mole ratio of
0.6-1/1/0.25-0.35.
5. The aqueous nitrogen fertilizer solution of claim 3 wherein the
urea-formaldehyde resin is prepared by reacting a solution of urea,
formaldehyde and ammonia at a temperature from 80.degree. C. to
95.degree. C. and a pH from 7.5 to 10.5 for 45 to 120 minutes.
6. The aqueous nitrogen fertilizer solution of claim 4 wherein the
urea-formaldehyde resin is prepared by reacting a solution of urea,
formaldehyde and ammonia at a temperature from 80.degree. C. to
95.degree. C. and a pH from 7.5 to 10.5 for 45 to 120 minutes.
7. The aqueous nitrogen fertilizer solution of claim 3 wherein the
urea-formaldehyde resin has a cyclic urea content, based on 100%
resin solids, of greater than 20% by weight.
8. The aqueous nitrogen fertilizer solution of claim 7 wherein the
urea-formaldehyde resin has a cyclic urea content, based on 100%
resin solids, of greater than 40% by weight.
9. The aqueous nitrogen fertilizer solution of claim 8 wherein the
urea-formaldehyde resin has a free urea content, based on 100%
resin solids, of less than 10% by weight.
10. The aqueous nitrogen fertilizer solution of claim 4 wherein the
urea-formaldehyde resin has a cyclic urea content, based on 100%
resin solids, of 14 to 20% by weight.
11. The aqueous nitrogen fertilizer solution of claim 3 prepared by
blending an aqueous urea-ammonium nitrate solution having a
nitrogen content from 28 to 32% by weight with an aqueous solution
of a urea-formaldehyde resin.
12. The aqueous nitrogen fertilizer solution of claim 4 prepared by
blending an aqueous urea-ammonium nitrate solution having a
nitrogen content from 28 to 32% by weight with an aqueous solution
of a urea-formaldehyde resin.
13. The aqueous nitrogen fertilizer solution of claim 3 wherein an
aqueous urea-formaldehyde resin solution (UF) is mixed with a
nitrogen fertilizer source selected from the group consisting of an
aqueous solution of urea (U), an aqueous solution of ammonium
nitrate (AN) and an aqueous solution of urea-ammonium nitrate (UAN)
in a weight ratio (UF:U, UF:AN or UF:UAN) of 90:10 to 10:90.
14. The aqueous nitrogen fertilizer solution of claim 4 wherein an
aqueous urea-formaldehyde resin solution (UF) is mixed with a
nitrogen fertilizer source selected from the group consisting of an
aqueous solution of urea (U), an aqueous solution of ammonium
nitrate (AN) and an aqueous solution of urea-ammonium nitrate (UAN)
in a weight ratio (UF:U, UF:AN or UF:UAN) of 90:10 to 10:90.
15. The aqueous nitrogen fertilizer solution of claim 3 wherein an
aqueous urea-formaldehyde resin solution (UF) is mixed with a
nitrogen fertilizer source selected from the group consisting of an
aqueous solution of urea (U), an aqueous solution of ammonium
nitrate (AN) and an aqueous solution of urea-ammonium nitrate (UAN)
in a weight ratio (UF:U, UF:AN or UF:UAN) of 70:30 to 30:70.
16. The aqueous nitrogen fertilizer solution of claim 4 wherein an
aqueous urea-formaldehyde resin solution (UF) is mixed with a
nitrogen fertilizer source selected from the group consisting of an
aqueous solution of urea (U), an aqueous solution of ammonium
nitrate (AN) and an aqueous solution of urea-ammonium nitrate (UAN)
in a weight ratio (UF:U, UF:AN or UF:UAN) of 70:30 to 30:70.
17. The aqueous nitrogen fertilizer solution of claim 3 wherein an
aqueous urea-formaldehyde resin solution (UF) is mixed with a
nitrogen fertilizer source selected from the group consisting of an
aqueous solution of urea (U), an aqueous solution of ammonium
nitrate (AN) and an aqueous solution of urea-ammonium nitrate (UAN)
in a weight ratio (UF:U, UF:AN or UF:UAN) of 30:70 to 50:50.
18. The aqueous nitrogen fertilizer solution of claim 15 wherein
the aqueous urea-formaldehyde resin solution has a solid
concentration of above 70% by weight.
19. The aqueous nitrogen fertilizer solution of claim 16 wherein
the aqueous urea-formaldehyde resin solution has a solid
concentration of above 70% by weight.
20. The aqueous nitrogen fertilizer solution of claim 17 wherein
the aqueous urea-formaldehyde resin solution has a solid
concentration of above 70% by weight.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present invention claims the benefit, as a continuation
application, of co-pending application Ser. No. 11/549,462 filed
Oct. 13, 2006, which is a continuation-in-part application, of
co-pending application Ser. No. 11/357,409 filed Feb. 21, 2006, the
entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to a liquid fertilizer
composition having a high nitrogen content. The invention is
particularly directed to an aqueous liquid fertilizer comprising a
mixture of a concentrated aqueous solution of a urea-formaldehyde
resin and a separate nitrogen fertilizer source selected from the
group consisting of ammonium nitrate, urea and a mixture of
ammonium nitrate and urea. Liquid fertilizers of the present
invention generally possess reduced freeze points and reduced
salt-out temperatures.
BACKGROUND OF THE INVENTION
[0003] Nitrogen is an essential nutrient for supporting the growth
and development of plants, including grasses. Most plants grown to
produce food, either for human or animal consumption, are given
some form of nitrogen fertilizer. Fertilization of lawns also
consumes large amounts of nitrogen fertilizers.
[0004] Urea continues to be the most widely used source of nitrogen
fertilizer. While most of the urea is used in a granular form,
liquid fertilizers using urea in some form continue to occupy an
important segment of the fertilizer market. Probably the most
common of the urea-based liquid fertilizers are aqueous urea
solutions and an aqueous solution of urea and ammonium nitrate,
identified as UAN solutions (Ammonium nitrate (AN) solutions
without added urea also are used to some extent as a nitrogen
fertilizer). The most concentrated of these aqueous solutions
contains about 32% by weight nitrogen and is made from about 34 to
35% urea, 46 to 45% ammonium nitrate and the balance water. This
concentrated fertilizer solution has a salt-out temperature of
about 0 to -2.degree. C., which limits the locations where it can
be safely used without added complexity in transportation and
storage. The salt-out temperature can be depressed further by
increasing the water content and thus sacrificing the total
nitrogen concentration of the aqueous fertilizer. So in cold
climates, the maximum nitrogen content of such solutions is usually
about 28% by weight.
[0005] Urea solutions can be prepared at solids contents up to
about 50% by weight. Solutions containing about 20% urea are common
for lawn fertilizer applications. Such solutions also must be
handled appropriately to avoid complications due to urea
crystallization (salt out) at low temperatures.
[0006] Once applied to the soil, urea in such fertilizers is
enzymatically converted to ammonia by urease, an enzyme produced by
endogenous microorganisms in the soil. The ammonia then is
hydrolyzed rapidly to ammonium ions. In the soil, some of the
ammonium ions, whether from the hydrolyzed ammonia or from ammonium
nitrate, are assimilated directly by plants, but most are converted
to nitrate by the process of nitrification. Once in the nitrate
form, the nitrogen is more readily assimilated directly by
plants.
[0007] Although in widespread use, one of the problems with using
urea, AN and UAN solutions as the nitrogen source is that some
fraction of the nitrogen is lost after application in various ways,
including volatilization as ammonia, denitrification to gaseous
nitrogen and nitrate leaching. It has been estimated that the
nitrogen loss for such fertilizers falls somewhere between 30% and
60%.
[0008] The fertilizer art also has developed a wide variety of
liquid fertilizers based on the reaction between urea and
formaldehyde. Such urea-formaldehyde resin fertilizers have been
formulated and used as a way of providing a more controlled
(sometimes characterized as an extended) release of the nitrogen
values so that the availability of the nitrogen hopefully is
tailored more closely to the time-course nitrogen requirements of
the plants. In this way, it is thought that the nitrogen loss
commonly associated with the quick release nitrogen fertilizers,
such as urea and UAN solutions, can be reduced. However, when
formulated at high solids contents to maximize the total nitrogen
value, these liquid fertilizers sometimes present their own
stability problems.
[0009] Notwithstanding these inherent inefficiencies and potential
problems, liquid fertilizers based on such formulations continue to
be an attractive way of applying nitrogen fertilizers to plants.
For that reason, the fertilizer art continues to search for
improved compositions and ways for providing a concentrated
nitrogen fertilizer liquid that is more stable and less prone to
salting-out.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention is based on the discovery that the
combination of concentrated liquid fertilizers containing
controlled release urea-formaldehyde resins with urea solutions,
ammonium nitrate (AN) solutions and urea-ammonium nitrate (UAN)
solutions can produce a liquid fertilizer composition having an
increase in its nitrogen content, relative to the urea, AN and UAN
solutions alone, and having an improved thermal (low temperature)
stability.
[0011] Applicants have specifically discovered that either or both
the freezing point and the salt-out temperature of urea solutions,
ammonium nitrate (AN) solutions and urea ammonium nitrate (UAN)
solutions can be depressed by the addition of liquid fertilizer
compositions of concentrated, controlled release urea-formaldehyde
resins. In this way, fertilizer solutions of higher solids
concentrations (and thus higher nitrogen concentrations) are
possible while reducing the risk of salting out.
[0012] Thus, the present invention is directed to a liquid
fertilizer composition of a high nitrogen content comprising an
aqueous solution of a urea-formaldehyde resin, and a separate
nitrogen fertilizer source selected from the group consisting of
urea, ammonium nitrate and a mixture of urea and ammonium nitrate
(also referred to herein as urea-ammonium nitrate). The invention
also is directed to the related method of using the liquid
fertilizer to fertilize plants, including grasses.
[0013] The first component of the liquid fertilizer composition of
the present invention is an aqueous concentrated urea-formaldehyde
resin solution. This component provides a controlled release
nitrogen property to the liquid fertilizer. This component also
causes the ultimate liquid fertilizer composition to have improved
freeze point and/or salt-out temperature.
[0014] In accordance with the present invention, the aqueous
concentrated urea-formaldehyde resin solution is prepared by
reacting urea and formaldehyde and optionally ammonia under
alkaline reaction conditions. The use of a formaldehyde (F) to urea
(U) to ammonia (A) mole ratio (F:U:A) in the range of
0.5-4.0:1.0:0.0-1.0 for making the concentrated urea-formaldehyde
resin solution, and more usually in the range of
0.5-2.5:1.0:0.0-0.5 is typical. There are a variety of processes
known in the prior art for making such resins and in the broadest
aspects of the present invention such processes and the resulting
aqueous urea-formaldehyde solutions are intended to be embraced by
the present invention. It is important that the reaction between
the urea, formaldehyde and the optional ammonia be conducted under
alkaline reaction conditions so that methylolated urea species are
formed. Reaction temperatures between 50 and 100.degree. C. are
common, with a reaction time period as short as 30 minutes or as
long as 5 hours being possible.
[0015] In one preferred embodiment of the present invention, the
aqueous urea-formaldehyde resin solution is the aqueous resin
solution described and claimed in Gabrielson, U.S. Pat. No.
6,632,262 (the Gabrielson patent). The Gabrielson patent
specifically describes a controlled release urea-formaldehyde
liquid fertilizer having a nitrogen level of at least 28% by weight
nitrogen. According to the Gabrielson patent, formaldehyde (F),
urea (U) and ammonia (A) are eventually combined in an aqueous
alkaline solution at an F:U:A mole ratio in the range of
0.6-1:1.0:0.25-0.35. The aqueous reaction mixture is heated for at
least 0.75 hour at a temperature of 80.degree. C. to 95.degree. C.,
followed by cooling to less than 50.degree. C. and adjusting the pH
of the aqueous liquid to 9.0 to 10.5. Specific materials and
procedures for preparing the urea-formaldehyde liquid fertilizer
are aptly described in the Gabrielson patent and thus it is not
necessary to repeat those teachings here. Instead, the disclosure
of the Gabrielson patent, U.S. Pat. No. 6,632,262, is incorporated
herein in its entirety by reference.
[0016] Briefly, to prepare this particular aqueous
urea-formaldehyde resin solution of the Gabrielson patent, U.S.
Pat. No. 6,632,262, formaldehyde, urea, and ammonia are combined in
an alkaline solution at a formaldehyde:urea:ammonia mole ratio of
about 0.6-1/1/0.25-0.35, preferably at a mole ratio of about
0.7-0.9/1/0.25-0.3, and most preferably at a ratio of about
0.8:1:0.27. All or most of the water present in the mixture comes
from a urea-formaldehyde concentrate, used as the main source of
formaldehyde, and the ammonia source (aqua-ammonia). Water also may
be added at the completion of the cook to adjust nitrogen
content.
[0017] The solution is heated to about 80.degree. C. to about
95.degree. C., preferably to about 85.degree. C. to about
90.degree. C., and held for at least about 45 minutes, preferably
about 45 minutes to about 120 minutes, more preferably about 60 to
about 75 minutes, to ensure some triazone formation and to complete
reaction of formaldehyde. Approximately 14 to 20% of the urea in
the original mixture is in the form of triazone, preferably about
17 to about 20%. The pH of the solution is at least 7, preferably
about 7.5 to about 10.5, and more preferably about 8.5 to about
9.5.
[0018] Following the initial reaction, the solution then is cooled
to less than about 50.degree. C., preferably to about ambient
temperature and the pH is adjusted, as needed, to be within the
range of about 9 to about 10.5, preferably from about 9.5 to about
10.
[0019] This process provides an aqueous urea-formaldehyde resin
solution in which the triazone content, and mono-, di-, and
tri-substituted urea species has been optimized for maximum
stability.
[0020] The pH may be maintained or adjusted by adding a compound,
such as triethanolamine, borax, sodium or potassium bicarbonate, or
sodium or potassium carbonate, preferably triethanolamine, at the
start of the reaction that will buffer the pH of the aqueous
reaction mixture at the desired pH level. Alternatively, the pH may
be maintained by addition of any suitable base during the reaction.
While any base can be used to increase the pH of the reaction mix,
one common source are alkali metal hydroxides such as potassium
hydroxide, lithium hydroxide, and sodium hydroxide.
[0021] In this particular embodiment, the aqueous urea-formaldehyde
resin solution has a free urea content of 45-55 wt %, a cyclic urea
(trazone) content of 14-20 wt %, a monomethylol urea content of
25-35 wt % and a di/trimethylurea content of 5-15 wt % based on the
weight of the urea-formaldehyde resin solution wherein the rest of
the solution is composed predominately of water. The solids
concentration of the aqueous urea-formaldehyde resin solution is
typically between 60 and 92% by weight and preferably 80 and 92%,
measured as the residual solids following heating at 105.degree. C.
The higher solids contents can be obtained by distilling the
aqueous resin solution, usually under a vacuum.
[0022] In another preferred embodiment of the present invention, a
urea-formaldehyde resin of a higher triazone (cyclic urea) content
is utilized as the aqueous solution of a urea-formaldehyde resin.
Applicants have determined that this higher triazone-containing
urea-formaldehyde resin similarly helps to reduce the freeze point
and especially the salt out temperature of solutions made with a
nitrogen fertilizer source selected from the group consisting of
urea, ammonium nitrate and a mixture of ammonium nitrate and urea
(e.g., UAN). It is expected that the resulting solutions will
exhibit desirable extended-release fertilization profiles as well.
Such urea-formaldehyde resins generally have a triazone (cyclic
urea) content (including substituted triazone compounds) of at
least 20% by weight.
[0023] Suitable urea-formaldehyde resins of a higher triazone
(cyclic urea) content can be prepared by reacting formaldehyde,
urea and ammonia at a mole ratio (F:U:A) in the range of
1.0-4.0:1.0:0.5-1.0. These urea-formaldehyde resins of higher
cyclic urea content generally contain at least 20% of triazone and
substituted triazone compounds. In such resins, the ratio of cyclic
ureas to di- and tri-substituted ureas and mono-substituted ureas
varies with the mole ratio of the reactants. For example, a resin
prepared at a mole ratio of 2.0:1.0:0.5 (F:U:A) would be expected
to produce a solution containing approximately 42% cyclic ureas,
approximately 28% di/tri-substituted ureas, approximately 24%
mono-substituted ureas, and approximately 5% free urea.
Alternatively, a urea-formaldehyde resin prepared at a mole ratio
of 1.2:1.0:0.5 (F:U:A) would be expected to produce a solution
containing approximately 26% cyclic ureas, approximately 7%
di/tri-substituted ureas, approximately 32% mono-substituted ureas,
and approximately 35% free urea.
[0024] Methods for making such higher triazone-containing
urea-formaldehyde resins are known to those skilled in the art.
Especially preferred are those urea-formaldehyde resins having a
high content of cyclic urea and a low content of free urea.
Urea-formaldehyde resins of a high cyclic urea content suitable for
use in this preferred aspect of the invention are described, for
example, in U.S. Pat. No. 6,114,491, which is hereby incorporated
by reference in its entirety. As described in Example 1 of this
patent, urea-formaldehyde resins with cyclic urea contents in
excess of 75% can be prepared.
[0025] Still other ways of making triazone (cyclic urea)-containing
urea-formaldehyde resins are known to those skilled in the art and
in its broadest aspects the present invention is not to be limited
to any particular resin type. In this regard, reference is made to
U.S. Pat. Nos. 4,554,005; 4,599,102; 4,778,510 and 5,674,971, which
describe the preparation of urea-formaldehyde resins containing
cyclic ureas. The disclosure of these patents are hereby
incorporated by reference in their entirety.
[0026] As above, it is preferred to produce a liquid concentrate of
the urea-formaldehyde resin having a solids content of above about
60% by weight, preferably above 70% by weight, more preferably
above 80% by weight and especially above 90% by weight, measured as
the residual solids following heating at 105.degree. C. Such
concentrated urea-formaldehyde resins can be prepared by using
concentrated raw materials or by distilling an aqueous resin
solution made at a lower solids concentration, usually under a
vacuum.
[0027] As noted above, a solution of the urea, formaldehyde and
ammonia reactants is heated to about 80.degree. C. to about
95.degree. C., preferably to about 85.degree. C. to about
90.degree. C., and held for at least about 45 minutes, preferably
about 45 minutes to about 120 minutes, more preferably about 60 to
about 75 minutes, to ensure triazone formation and to complete
reaction of formaldehyde. The pH of the solution is at least 7,
preferably about 7.5 to about 10.5, and more preferably about 8.5
to about 9.5.
[0028] The other component of the liquid fertilizer composition of
the present invention is an aqueous solution of a nitrogen
fertilizer source selected from the group consisting of urea,
ammonium nitrate (AN) and an aqueous solution of urea-ammonium
nitrate (UAN). Urea solutions containing urea in an amount of about
20 to 50% by weight urea are commercially available and are easily
made by dissolving a solid source of urea, such as prilled urea, in
water. AN solutions containing 21% nitrogen and UAN solutions
containing 28%, 30% and 32% nitrogen also are commercially
available, and other customized concentrations and formulations can
be obtained. The present invention is not limited to any particular
source or concentration of urea, AN and/or UAN solutions. A UAN
solution generally is prepared from 50% by weight ammonium nitrate
and 50% by weight urea. Both continuous and batch-type process can
be used for making urea, AN and UAN solutions. In such processes,
especially in the case of UAN solutions, concentrated urea and
ammonium nitrate solutions are measured, mixed and cooled.
[0029] To make the liquid nitrogen fertilizer composition of the
present invention, it only is necessary to prepare a blend of an
aqueous urea-formaldehyde resin solution and the nitrogen
fertilizer source selected from an aqueous solution of urea, an
aqueous solution of ammonium nitrate (AN) or an aqueous solution of
urea-ammonium nitrate (UAN) with thorough mixing. In the case of
urea in particular, it may be suitable to simply dissolve a solid
source of urea into an aqueous urea-formaldehyde resin solution to
accomplish the required blending of the aqueous solutions. No
specialized mixing equipment is needed. In some circumstances
heating may be advisable or necessary to assist the initial,
complete dissolution of the blended materials.
[0030] In accordance with the present invention, the aqueous
urea-formaldehyde resin solution (UF) and the nitrogen fertilizer
source selected from the group consisting of an aqueous solution of
urea (U), an aqueous solution of ammonium nitrate (AN) or an
aqueous solution of urea-ammonium nitrate (UAN) are mixed in a
weight ratio (UF:U; UF:AN or UF:UAN) of 90:10 to 10:90, often in
the range of 80:20 to 20:80, more often in the range of 75:25 to
25:75 and most often in the range of 30:70 to 70:30, usually
depending on the desired ratio of quick release and controlled
release nitrogen desired in the final liquid fertilizer
formulation. In the case of blends of AN or UAN and concentrated
urea-formaldehyde resins of high cyclic urea content (and
preferably of low free urea content), the aqueous urea-formaldehyde
resin solution and the aqueous solution of ammonium nitrate (AN) or
the aqueous solution of urea-ammonium nitrate (UAN) preferably are
mixed in a weight ratio (UF:AN or UF:UAN) of 30:70 to 50:50 a
desirable extended release nitrogen profile can be obtained.
[0031] As noted above, by using a urea-formaldehyde resin of a high
cyclic urea content and especially one having a low urea content,
preferably a urea-formaldehyde resin having a cyclic urea content
above 20%, more preferably above 40% and most preferably above 60%,
(and having a urea content of below 20%, preferably below 10% and
especially below 5%) an aqueous blend of ammonium nitrate (or
urea-ammonium nitrate) and urea-formaldehyde resin having a highly
desirable extended nitrogen release profile can be obtained.
[0032] A concentrated urea-formaldehyde resin can typically exhibit
a nitrogen content of about 25%, so a blend with a UAN solution
(32% nitrogen) at a mixing ratio of urea-formaldehyde resin to UAN
solution of 30:70 will produce a fertilizer solution of about 30%
nitrogen.
[0033] A small amount of other additives also can be included in
the liquid fertilizer compositions of the present invention. For
example, in specific applications, an herbicide, certain
micronutrients, a coloring agent or dye and other known fertilizer
additives may safely be added to the composition without
significantly degrading the thermal stability of the fertilizer
composition.
[0034] The liquid fertilizer composition of the present invention
can be made at high solids concentrations, i.e., at a solids
content of at least 50% by weight, at a solids content of at least
60% by weight, at a solids content of at least 70% by weight and at
a solids content of at least 80% by weight and thus has a high
nitrogen content. The liquid fertilizer composition of the present
invention also has a broader temperature range over which it
remains fluid with no appreciable precipitation of solids and thus
it can be applied to plants, including grasses, in the same manner
as any of the conventional liquid urea, AN and UAN fertilizer
solutions.
[0035] It will be understood that while the invention has been
described in conjunction with specific embodiments thereof, the
foregoing description and following examples are intended to
illustrate, but not limit the scope of the invention. Other
aspects, advantages and modifications will be apparent to those
skilled in the art to which the invention pertains, and these
aspects and modifications are within the scope of the
invention.
EXAMPLE 1
Repeated from Example 2 of U.S. Pat. No. 6,632,262
[0036] The following ingredients were combined by adding in the
following order: UFC, first addition of ammonium hydroxide, first
addition of urea, second addition of ammonium hydroxide, and second
addition of urea. The combination was heated to 85.degree. C. to
90.degree. C. and held for 60 minutes. The pH was monitored every
15 minutes and adjusted as necessary to maintain a pH between 8.6
and 10 using 25% caustic.
TABLE-US-00001 Ingredient Concentration Weight % UFC, 85% 85 37.9
Ammonium hydroxide 28 0.5 Urea, prill 100 28.4 Ammonium hydroxide 8
15.4 Urea, prill 100 18.3 Caustic 25 to adjust pH Formic Acid 23 to
adjust pH Water to adjust % N
[0037] The combination was then cooled to 25.degree. C. and
analyzed for % nitrogen and % free urea (by .sup.13C-NMR).
[0038] Results: % Nitrogen was 29.9; pH was 10.1; % Free urea was
50% which corresponds to <50% quick release. Blends exhibited
excellent stability.
[0039] The nitrogen concentration (and the solids concentration)
can be increased by vacuum distillation of the resulting
urea-formaldehyde resin liquid fertilizer product.
EXAMPLE 2
Repeated from Example 1 of U.S. Pat. No. 6,114,491
[0040] Preparation of Urea-formaldehyde Resins of high Cyclic Urea
Content [0041] a) A urea-formaldehyde resin containing cyclic urea
was prepared at a mole ratio of 2.0:1.0:0.5,
formaldehyde:urea:ammonia (F:U:A), by charging a reaction vessel
with formaldehyde, ammonia, and urea while maintaining the
temperature below about 65.degree. C. Once all the reactants were
in the reaction vessel, the resulting solution was heated to about
90.degree. C., for about 1 hour until the reaction was complete.
Once the reaction was complete, the solution was cooled to room
temperature. C.sup.13-NMR indicated approximately 42.1% of the urea
was contained in the triazone ring structure, 28.5% of the urea was
di/tri-substituted, 24.5% of the urea was mono-substituted, and
4.9% of the urea was free. [0042] b) A second urea-formaldehyde
resin containing cyclic urea was prepared in the same manner as a)
except for the mole ratio of 1.2:1.0:0.5 (F:U:A) was used.
C.sup.13-NMR indicated approximately 25.7% of the urea was
contained in the triazone ring structure, 7.2% of the urea was
di/tri-substituted, 31.9% of the urea was mono-substituted, and
35.2% of the urea was free. [0043] c) A third urea-formaldehyde
resin containing cyclic urea was prepared in the same manner as a)
except for the mole ratio (F:U:A) of 3:1:1 and it was heated to
about 90.degree. C. for 1 hour and then 100.degree. C. for 2 hours.
C.sup.13-NMR indicated approximately 76.0% of the urea was
contained in the triazone ring structure, 15.3% of the urea was
di/tri-substituted, 8.1% of the urea was mono-substituted, and 0.6%
of the urea was free. [0044] d) A fourth urea-formaldehyde resin
containing cyclic urea was prepared in the same manner as a) except
for the mole ratio (F:U:A) of 4:1:1 and it was heated to about
90.degree. C. for 3 hours and the pH was controlled around 7.5.
C.sup.13-NMR indicated approximately 79.2% of the urea was
contained in the triazone ring structure, 17.7% of the urea was
di/tri-substituted, 1.6% of the urea was mono-substituted, and 1.5%
of the urea was free.
EXAMPLE 3
[0045] Aqueous urea-formaldehyde resin solutions prepared
substantially in accordance with the procedure of Example 1 were
processed (using vacuum distillation) to a solids content of about
80% by weight and 92% by weight respectively. These aqueous
urea-formaldehyde resin solutions are identified in the following
Table as UF-1 and UF-2, respectively. Mixtures of the
urea-formaldehyde resin solutions and a commercially available 21%
nitrogen by weight AN solution and a commercially available 32%
nitrogen by weight UAN solution were prepared at various weight
ratios as shown in the following Table. The total solids content of
the various aqueous formulations, measured as the residual solids
following heating at 105.degree. C., and the nitrogen content
(weight %) of the aqueous formulations also are reported in the
Table. The freeze points and the salt out temperatures for the
various solutions were measured by the Galbraith Laboratories,
Knoxville, Tenn. and also are reported in the following Table.
[0046] All of the blends embraced by the present invention stored
at a temperature of 23-25.degree. C. have remained free of solids
for 180 days.
TABLE-US-00002 TABLE % Freeze Point Salt-Out Temp. SAMPLE Solids %
N .degree. C. .degree. C. UF-1 80.7 34.6 -- -- UF-2 92.1 39.7 -- --
UAN 80.9 31.9 -- 0 50% UAN/50% UF-1 78.8 33.2 <-19.7 No distinct
crystal formation 50% UAN/50% UF-2 84.4 35.7 <-20 No distinct
crystal formation 70% UAN/30% UF-1 78.8 33.0 <-19.9 -3.1 70%
UAN/30% UF-2 82.1 34.2 <-20 -6.6 AN 65.4 21.6 -- 6 50% AN/50%
UF-1 72.7 29.1 <-20 No distinct crystal formation 50% AN/50%
UF-2 77.8 31.2 <-20 -10.3 70% AN/30% UF-1 69.5 26.8 <-20 -3.5
70% AN/30% UF-2 72.6 28.4 <-20 -0.7
[0047] The notation "no distinct crystal formation" indicates that
the solution remained clear and that there was no visible formation
of solids before the solution reached its freeze point.
[0048] The data in the Table shows that the addition of the
urea-formaldehyde solution (UF-1 and UF-2) to the AN and/or UAN
solutions suppressed the salt-out temperatures of both the AN and
the UAN solutions. Moreover, because of the higher nitrogen content
of the urea-formaldehyde solutions, it was possible to achieve
nitrogen contents in the blends above 32% by weight, the maximum
nitrogen content of UAN solutions.
EXAMPLE 4
[0049] An aqueous urea-formaldehyde resin solution prepared
substantially in accordance with the procedure of Example 2a) was
processed (using vacuum distillation) to a solids content of about
70% by weight. This aqueous urea-formaldehyde resin solution is
identified in the following Table as UFP. Mixtures of the
urea-formaldehyde resin solution and a commercially available 32%
nitrogen by weight UAN solution (80% by weight solids) were
prepared at various weight ratios as shown in the following Table.
The freeze points and the salt out temperatures for the various
solutions were measured by the Galbraith Laboratories, Knoxville,
Tenn. and also are reported in the following Table. For the UAN
solutions, salt out occurs within 48 hours at 3.degree. F.
(-16.degree. C.); while the 70% UAN-32/30% UFP mixture has remained
solids free for over 120 days at 3.degree. F. (-16.degree. C.).
TABLE-US-00003 TABLE % Solids % Freeze Point Salt-Out Temp. SAMPLE
(approx.) N .degree. C. .degree. C. UFP 70 25 -40 <-40 UAN28 70
28 -- -10 UAN32 80 32 -- 0 50% UAN32/50% UFP 75 29 -37 -27 70%
UAN32/30% UFP 77 30 -40 -31
[0050] The data in the Table shows that the addition of the
urea-formaldehyde solution (UFP) to UAN solution suppressed the
salt-out temperature.
EXAMPLE 5
[0051] Compositions of the present invention were compared against
other available sources of nitrogen fertilizer including urea, ESN
(a slow release granular product available from Agrium), UAN
solution, and Nitamin.RTM. 30L (an extended release nitrogen liquid
fertilizer product available from Georgia-Pacific). Fertilizer
incubation tests were conducted by the International Fertilizer
Development Center and the results of their testing is reported
below. In particular, presented in the Table below are the six week
concentrations of ammonium and nitrate. As understood by those
skilled in the art, the longer the fertilizer is in the ammonium
form, the more extended is the nitrogen release profile.
Additionally, eventual conversion to the nitrate form is desired as
once in the nitrate form, the nitrogen is more readily assimilated
directly by plants. As shown in the table below, blends of the
present invention have especially desirable release profiles
similar to Nitamin.RTM. 30L (U.S. Pat. No. 6,632,262). For
comparison, the high cyclic urea content urea-formaldehyde resin
used in preparing the UF/UAN blends of the present invention also
was tested and is reported in the table as the Urea-formaldehyde
polymer (UFP).
TABLE-US-00004 TABLE Six Week Ammonium Six Week Nitrate Product
Concentration Concentration Urea 2 80 ESN 4 84 UAN 10 94 Nitamin
.RTM. 30L 33 55 30% Concentrated UF: 70% 32 66 UAN 50% Concentrated
UF: 50% 44 50 UAN UFP 60 23
[0052] While the invention has been described with respect to
specific examples including presently preferred modes of carrying
out the invention, those skilled in the art will appreciate that
there numerous variations and permutations of the above described
systems and techniques that fall within the spirit and scope of the
invention as set forth in the appended claims.
* * * * *