U.S. patent application number 10/659432 was filed with the patent office on 2004-03-11 for controlled release fertilizer and method for production thereof.
This patent application is currently assigned to Agrium Inc.. Invention is credited to Babiak, Nicolette M., Geiger, Albert J., Stelmack, Eugene G..
Application Number | 20040045331 10/659432 |
Document ID | / |
Family ID | 24418420 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045331 |
Kind Code |
A1 |
Geiger, Albert J. ; et
al. |
March 11, 2004 |
Controlled release fertilizer and method for production thereof
Abstract
A controlled release fertilizer material comprising a
particulate plant nutrient surrounded by a coating which is the
reaction product of a mixture comprising: a polyol, an isocyanate
and an organic wax.
Inventors: |
Geiger, Albert J.; (Fort
Saskatchewan, CA) ; Stelmack, Eugene G.; (Fort
Saskatchewan, CA) ; Babiak, Nicolette M.; (Gibbons,
CA) |
Correspondence
Address: |
PATENT ADMINSTRATOR
KATTEN MUCHIN ZAVIS ROSENMAN
525 WEST MONROE STREET
SUITE 1600
CHICAGO
IL
60661-3693
US
|
Assignee: |
Agrium Inc.
|
Family ID: |
24418420 |
Appl. No.: |
10/659432 |
Filed: |
September 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10659432 |
Sep 11, 2003 |
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09604161 |
Jun 27, 2000 |
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6663686 |
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Current U.S.
Class: |
71/28 |
Current CPC
Class: |
C05G 5/37 20200201; C05G
5/38 20200201; C05G 5/37 20200201; C05G 5/38 20200201; C05G 5/38
20200201; C05C 9/005 20130101; C05G 5/37 20200201; C05G 5/37
20200201; C08G 18/36 20130101; C05G 5/38 20200201; C05C 9/005
20130101; C05G 5/37 20200201; C05C 9/005 20130101 |
Class at
Publication: |
071/028 |
International
Class: |
C05C 009/00 |
Claims
What is claimed is:
1. A controlled release fertilizer material comprising a
particulate plant nutrient surrounded by a coating which is the
reaction product of a mixture comprising: a polyol, an isocyanate
and an organic wax.
2. The controlled release fertilizer material defined in claim 1,
wherein the plant nutrient comprises a water soluble compound.
3. The controlled release fertilizer material defined in claim 2,
wherein the water soluble compound comprises a compound containing
at least one member selected from the group consisting of nitrogen,
phosphorus, potassium, sulfur and mixtures thereof.
4. The controlled release fertilizer material defined in claim 1,
wherein the plant nutrient comprises urea.
5. The controlled release fertilizer material defined in claim 1,
wherein the polyol comprises from about 2 to about 6 hydroxyl
moieties.
6. The controlled release fertilizer material defined in claim 1,
wherein the polyol comprises at least one C.sub.10-C.sub.22
aliphatic moiety.
7. The controlled release fertilizer material defined in claim 1,
wherein the polyol comprises castor oil.
8. The controlled release fertilizer material defined in claim 1,
wherein the isocyanate is selected from the group consisting of
diphenylmethane diisocyanate, toluene diisocyanate, aliphatic
isocyantes, derivatives thereof, polymers thereof and mixtures
thereof.
9. The controlled release fertilizer material defined in claim 1,
wherein the isocyanate contains from about 1.5 to about 3.0
isocyanate groups per molecule.
10. The controlled release fertilizer material defined in claim 1,
wherein the isocyanate contains from about 10% to about 50%
NCO.
11. The controlled release fertilizer material defined in claim 1,
wherein the isocyanate comprises polymeric diphenylmethane
diisocyanate.
12. The controlled release fertilizer material defined in claim 1,
wherein the organic wax comprises a drop melting point in the range
of from about 50.degree. C. to about 120.degree. C.
13. The controlled release fertilizer material defined in claim 1,
wherein the organic wax is substantially non-tacky below a
temperature of about 40.degree. C.
14. The controlled release fertilizer material defined in claim 1,
wherein organic wax comprises a C.sub.30+ alpha olefin.
15. The controlled release fertilizer material defined in claim 1,
wherein the coating is present in an amount in the range of from
about 1 to about 10 percent by weight based on the weight of
particulate plant nutrient.
16. The controlled release fertilizer material defined in claim 1,
wherein the coating is present in an amount in the range of from
about 1.5 to about 5.0 percent by weight based on the weight of
particulate plant nutrient.
17. The controlled release fertilizer material defined in claim 1,
wherein the coating is present in an amount in the range of from
about 2.0 to about 4.0 percent by weight based on the weight of
particulate plant nutrient.
18. The controlled release fertilizer material defined in claim 1,
wherein the ratio of NCO groups from the isocyanate to the hydroxyl
groups in the polyol in the mixture is in the range of from about
0.8 to about 3.0.
19. The controlled release fertilizer material defined in claim 1,
wherein the ratio of NCO groups from the isocyanate to the hydroxyl
groups in the polyol in the mixture is in the range of from about
0.8 to about 2.0.
20. The controlled release fertilizer material defined in claim 1,
wherein the ratio of NCO groups from the isocyanate to the hydroxyl
groups in the polyol in the mixture is in the range of from about
0.9 to about 1.1.
21. The controlled release fertilizer material defined in claim 1,
wherein the amount of organic wax in the mixture is up to about 50
percent by weight based on the combined weight of the organic wax
and the polyol.
22. The controlled release fertilizer material defined in claim 1,
wherein the amount of organic wax in the mixture is in the range of
from about 1.0 to about 25 percent by weight based on the combined
weight of the organic wax and the polyol.
23. The controlled release fertilizer material defined in claim 1,
wherein the amount of organic wax in the mixture is in the range of
from about 2.0 to about 10 percent by weight based on the combined
weight of the organic wax and the polyol.
24. A process for producing a controlled release fertilizer
material comprising the steps of: (a) contacting a particulate
plant nutrient with a mixture comprising: a polyol, an isocyanate
and an organic wax to produce a coating surrounding the particulate
plant nutrient; and (b) curing the coating to produce the
controlled release fertilizer material.
25. The process defined in claim 24, wherein the particulate
material is agitated during Step (a).
26. The process defined in claim 24, wherein Step (a) is conducted
at a temperature in the range of from about 50.degree. C. to about
105.degree. C.
27. The process defined in claim 24, wherein Step (a) is conducted
at a temperature in the range of from about 60.degree. C. to about
90.degree. C.
28. The process defined in claim 24, wherein Step (a) is conducted
at a temperature in the range of from about 70.degree. C. to about
80.degree. C.
29. The process defined in claim 24, wherein Step (a) comprises
contacting the particulate plant nutrient with a first stream
comprising the polyol and a second stream comprising the
isocyanate, the first stream and the second stream being
independent of one another.
30. The process defined in claim 29, wherein the first stream
comprises a mixture of the polyol and the organic wax.
31. The process defined in claim 29, wherein Step (a) comprises
contacting the particulate plant nutrient simultaneously with the
first stream and the second stream.
32. The process defined in claim 29, wherein Step (a) comprises
contacting the particulate plant nutrient with the first stream
followed by the second stream.
33. The process defined in claim 24, wherein Steps (a) and (b) are
repeated at least once to produce a controlled release fertilizer
material having a plurality of coating layers.
34. The process defined in claim 24, wherein the plant nutrient
comprises a water soluble compound.
35. The process defined in claim 34, wherein the water soluble
compound comprises a compound containing at least one member
selected from the group consisting of nitrogen, phosphorus,
potassium, sulfur and mixtures thereof.
36. The process defined in claim 24, wherein the plant nutrient
comprises urea.
37. The process defined in claim 24, wherein the polyol comprises
from about 2 to about 6 hydroxyl moieties.
38. The process defined in claim 24, wherein the polyol comprises
at least one C.sub.10-C.sub.22 aliphatic moiety.
39. The process defined in claim 24, wherein the polyol comprises
castor oil.
40. The process defined in claim 24, wherein the isocyanate is
selected from the group consisting of diphenylmethane diisocyanate,
toluene diisocyanate, aliphatic isocyanates derivatives thereof,
polymers thereof and mixtures thereof.
41. The process defined in claim 24, wherein the isocyanate
contains from about 1.5 to about 3.0 isocyanate groups per
molecule.
42. The process defined in claim 24, wherein the isocyanate
contains from about 10% to about 50% NCO.
43. The process defined in claim 24, wherein the isocyanate
comprises polymeric diphenylmethane diisocyanate.
44. The process defined in claim 24, wherein the organic wax
comprises a drop melting point in the range of from about
50.degree. C. to about 120.degree. C.
45. The process defined in claim 24, wherein the organic wax is
substantially non-tacky below a temperature of about 40.degree.
C.
46. The process defined in claim 24, wherein organic wax comprises
a C.sub.30+ alpha olefin.
47. The process defined in claim 24, wherein the mixture is used in
an amount to provide a coating in an amount in the range of from
about 1 to about 10 percent by weight based on the weight of
particulate plant nutrient.
48. The process defined in claim 24, wherein the mixture is used in
an amount to provide a coating in an amount in the range of from
about 1.5 to about 5.0 percent by weight based on the weight of
particulate plant nutrient.
49. The process defined in claim 24, wherein the mixture is used in
an amount to provide a coating in an amount in the range of from
about 2.0 to about 4.0 percent by weight based on the weight of
particulate plant nutrient.
50. The process defined in claim 24, wherein the ratio of NCO
groups from the isocyanate to the hydroxyl groups in the polyol in
the mixture is in the range of from about 0.8 to about 3.0.
51. The process defined in claim 24, wherein the ratio of NCO
groups from the isocyanate to the hydroxyl groups in the polyol in
the mixture is in the range of from about 0.8 to about 2.0.
52. The process defined in claim 24, wherein the ratio of NCO
groups from the isocyanate to the hydroxyl groups in the polyol in
the mixture is in the range of from about 0.9 to about 1.1.
53. The process defined in claim 24, wherein the amount of organic
wax in the mixture is up to about 50 percent by weight based on the
combined weight of the organic wax and the polyol.
54. The process defined in claim 24, wherein the amount of organic
wax in the mixture is in the range of from about 1.0 to about 25
percent by weight based on the combined weight of the organic wax
and the polyol.
55. The process defined in claim 24, wherein the amount of organic
wax in the mixture is in the range of from about 2.0 to about 10
percent by weight based on the combined weight of the organic wax
and the polyol.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a controlled release
fertilizer and to a method for production thereof.
[0003] 2. Description of the Prior Art
[0004] Fertilizers have been used for many years to supplement
nutrients in growing media.
[0005] In recent years the art has focused on techniques to deliver
controlled amounts of plant nutrients to the soil or other growing
media. This has been done so that, on one hand, the growing plants
are not adversely deprived of nutrients and, on the other hand, an
over supply of nutrients is avoided. An over supply of nutrients
can result in toxicity to the plants or losses from leaching. The
resulting improvement in FUE (fertilizer use efficiency) can reduce
the rate and the frequency of nutrient application.
[0006] U.S. Pat. No. 5,538,531 [Hudson et al. (Hudson)] and the
prior art cited therein provides a useful overview of methods of
conveying controlled release properties to a particulate plant
nutrient. Specifically, Hudson teaches a controlled release,
particulate fertilizer product having a water soluble fertilizer
central mass encased in a plurality of water insoluble, abrasion
resistant coatings. At least one inner coating is a urethane
reaction product derived from recited isocyanates and polyols. The
outer coating is formed from an organic wax having a drop melting
point in the range of from 50.degree. C. to 120.degree. C. The
general teachings of Hudson and those of the Examples in Hudson
make it clear that the Hudson process involves curing the urethane
coating(s) around the particulate plant nutrient and, thereafter,
applying to the cured urethane coating(s) the outer layer of
organic wax.
[0007] It is also known in the art to pre-coat particulate plant
nutrient with an organic wax or similar material as a means to
regular or otherwise improve the surface of the particulate plant
nutrient prior to coating thereof with the urethane forming
reagents.
[0008] Despite these advances in the art, there is still room for
improvement. Specifically, it would be desirable to have a
controlled release fertilizer and process for production thereof
which would allow for the ready customization of the release rate
profile of a given particulate plant nutrient having applied
thereto a given amount of urethane coating(s). It would also be
desirable to be able to achieve a desirable release rate profile
for a given particulate plant nutrient using significantly reduced
amounts of coating materials.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a novel
controlled release fertilizer which obviates or mitigates at least
one of the above-mentioned disadvantages of the prior art.
[0010] Accordingly, in one of its aspects the present invention
provides a controlled release fertilizer material comprising a
particulate plant nutrient surrounded by a coating which is the
reaction product of a mixture comprising: a polyol, an isocyanate
and an organic wax.
[0011] In another of its aspects, the present invention provides a
process for producing a controlled release fertilizer material
comprising the steps of:
[0012] (a) contacting a particulate plant nutrient with a mixture
comprising: a polyol, an isocyanate and an organic wax to produce a
coating surrounding the particulate plant nutrient; and
[0013] (b) curing the coating to produce the controlled release
fertilizer material.
[0014] Thus, we have surprisingly and unexpectedly discovered that
an improved controlled release fertilizer material and process for
production thereof may be achieved from a coating which is the
reaction product of a mixture comprising: a polyol, an isocyanate
and an organic wax. Specifically, while it is known use wax as a
pre-coat before application of the urethane layer and/or as
post-coat after application of the urethane layer, the advantages
of incorporating the wax with the urethane forming reagents has
heretofore been unknown. This advantages include:
[0015] (i) the ability to extend the release rate profile for a
give plant nutrient having a given amount of urethane coating
thereon;
[0016] (ii) the ability to achieve a desirable release rate profile
using significantly less coating that used with comparable prior
art coating techniques; and
[0017] (iii) the ability to obtain such a product via one-step
process (i.e., compared to the multi-step processes of the prior
art).
[0018] Other advantages will become apparent to those of skill in
art having the present specification in hand.
BRIEF DESCRIPTION OF THE DRAWING
[0019] Embodiments of the present invention will be described with
reference to the accompanying FIGURE in which there is illustrated
the release rate profile a controlled release fertilizer in
accordance with the present invention and the release rate profiles
of prior art controlled release fertilizers.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Accordingly, in one of its aspects, the present invention
relates to a controlled release fertilizer material comprising a
particulate plant nutrient surrounded by a coating.
[0021] The choice of particulate plant nutrient material useful for
the present controlled release fertilizer material is not
particularly restricted and is within the purview of a person
skilled in the art.
[0022] For example, the plant nutrient material used may selected
from those disclosed in Hudson. Preferably, such a plant nutrient
comprises a water soluble compound, more preferably a compound
containing at least one member selected from the group consisting
of nitrogen, phosphorus, potassium, sulfur and mixtures thereof. A
preferred such plant nutrient comprises urea. Other useful examples
of plant nutrients are taught in U.S. Pat. No. 5,571,303
[Bexton]--e.g., ammonium sulfate, ammonium phosphate and mixtures
thereof.
[0023] Preferably, the coating surrounds the plant nutrient
material in an amount in the range of from about 1.0 to about 10
percent by weight, more preferably from about 1.5 to about 5.0
percent by weight, most preferably from about 2.0 to about 4.0
percent by weight, based on the weight of the plant nutrient
material.
[0024] The coating is the reaction product of a mixture comprising:
a polyol, an isocyanate and an organic wax.
[0025] The choice of polyol is not particularly restricted and is
within the purview of a person skilled in the art. For example, the
polyol may be a hydroxyl-terminated backbone of a member selected
from the group comprising polyether, polyester, polycarbonate,
polydiene and polycaprolactone. Preferably, such a polyol is
selected from the group comprising hydroxyl-terminated
polyhydrocarbons, hydroxyl-terminated polyformals, fatty acid
triglycerides, hydroxyl-terminated polyesters,
hydroxymethyl-terminated polyesters, hydroxymethyl-terminated
perfluoromethylenes, polyalkyleneether glycols,
polyalkylenearyleneether glycols and polyalkyleneether triols. More
preferred polyols are selected from the group comprising
polyethylene glycols, adipic acid-ethylene glycol polyester,
poly(butylene glycol), poly(propylene glycol) and
hydroxyl-terminated polybutadiene--see, for example, British patent
No. 1,482,213. The most preferred such polyol is a polyether
polyol. Preferably, such a polyether polyol has a molecular weight
in the range of from about 200 to about 20,000, more preferably
from about 2,000 to about 10,000, most preferably from about 2,000
to about 8,000.
[0026] A particularly preferred class of polyols are those
disclosed in Hudson. Preferably, such a polyol comprises from about
2 to about 6 hydroxyl moieties. More preferably, such a polyol
comprises at least one C.sub.10-C.sub.22 aliphatic moiety. Most
preferably, the polyol comprises castor oil.
[0027] Additionally, the polyol may be derived from natural sources
such as soybean, corn, canola and the like (i.e., to produce
naturally occurring modified oils). An example of such a synthetic
polyol comprising a canola base is commercially available from
Urethane Soy Systems Corp. (Princeton, Ill.).
[0028] The isocyanate suitable for used in producing the coating is
not particularly restricted and the choice thereof is within the
purview of a person skilled in the art. Generally, the isocyanate
compound suitable for use may be represented by the general
formula:
Q(NCO).sub.i
[0029] wherein i is an integer of two or more and Q is an organic
radical having the valence of i. Q may be a substituted or
unsubstituted hydrocarbon group (e.g. an alkylene or arylene
group). Moreover, Q may be represented by the general formula:
Q.sup.1-Z-Q.sup.1
[0030] wherein Q.sup.1 is an alkylene or arylene group and Z is
chosen from the group comprising --O--, -O-Q.sup.1-, --CO--, --S--,
--S-Q.sup.1-S-- and --SO.sub.2--. Examples of isocyanate compounds
which fall within the scope of this definition include
hexamethylene diisocyanate, 1,8-diisocyanato-p-methane, xylyl
diisocyanate, (OCNCH.sub.2CH.sub.2CH.sub.2OCH.sub.2O).sub.2,
1-methyl-2,4-diisocyanatoc- yclohexane, phenylene diisocyanates,
tolylene diisocyanates, chlorophenylene diisocyanates,
diphenylmethane-4,4'-diisocyanate, naphthalene-1,5-diisocyanate,
triphenylmethane-4,4',4"-triisocyanate and
isopropylbenzene-alpha-4-diisocyanate.
[0031] In another embodiment, Q may also represent a polyurethane
radical having a valence of i. In this case Q(NCO).sub.i is a
compound which is commonly referred to in the art as a prepolymer.
Generally, a prepolymer may be prepared by reacting a
stoichiometric excess of an isocyanate compound (as discussed
hereinabove) with an active hydrogen-containing compound (as
discussed hereinabove), preferably the polyhydroxyl-containing
materials or polyols discussed above. In this embodiment, the
polyisocyanate may be, for example, used in proportions of from
about 30 percent to about 200 percent stoichiometric excess with
respect to the proportion of hydroxyl in the polyol.
[0032] In another embodiment, the isocyanate compound suitable for
use in the process of the present invention may be selected from
dimers and trimers of isocyanates and diisocyanates, and from
polymeric diisocyanates having the general formula:
[Q"(NCO).sub.i].sub.j
[0033] wherein both i and j are integers having a value of 2 or
more, and Q" is a polyfunctional organic radical, and/or, as
additional components in the reaction mixture, compounds having the
general formula:
L(NCO).sub.i
[0034] wherein i is an integer having a value of 1 or more and L is
a monofunctional or polyfunctional atom or radical. Examples of
isocyanate compounds which fall with the scope of this definition
include ethylphosphonic diisocyanate, phenylphosphonic
diisocyanate, compounds which contain a .dbd.Si--NCO group,
isocyanate compounds derived from sulphonamides (QSO.sub.2NCO),
cyanic acid and thiocyanic acid.
[0035] See also, for example, British patent No. 1,453,258.
[0036] Non-limiting examples of suitable isocyanates include:
1,6-hexamethylene diisocyanate, 1,4-butylene diisocyanate,
furfurylidene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene
diisocyanate, 2,4'-diphenylmethane diisocyanate,
4,4'-diphenylmethane diisocyanate, 4,4'-diphenylpropane
diisocyanate, 4,4'-diphenyl-3,3'-dimethyl methane diisocyanate,
1,5-naphthalene diisocyanate, 1-methyl-2,4-diisocyanate-5-c-
hlorobenzene, 2,4-diisocyanato-s-triazine,
1-methyl-2,4-diisocyanato cyclohexane, p-phenylene diisocyanate,
m-phenylene diisocyanate, 1,4-naphthalene diisocyanate, dianisidine
diisocyanate, bitoluene diisocyanate, 1,4-xylylene diisocyanate,
1,3-xylylene diisocyanate, bis-(4-isocyanatophenyl)methane,
bis-(3-methyl-4-isocyanatophenyl)methane- , polymethylene
polyphenyl polyisocyanates and mixtures thereof.
[0037] A particularly preferred group of isocyanates are those
described in Hudson.
[0038] Preferably, the polyol and isocyanate are used in amounts
such that the ratio of NCO groups in the isocyanate to the hydroxyl
groups in the polyol is in the range of from about 0.8 to about
3.0, more preferably from about 0.8 to about 2.0, most preferably
from about 0.9 to about 1.1.
[0039] The wax used in the mixture to produce the coating may be
selected from those described in Hudson and from silicon waxes
(commercially available from Dow Corning). Thus, the preferred wax
comprises a drop melting point in the range of from about
50.degree. C. to about 120.degree. C. More preferably, the wax is
substantially non-tacky below a temperature of about 40.degree. C.
Most preferably, the wax comprises a C.sub.30+ alpha olefin.
[0040] Preferably, the organic wax is present in the mixture in an
amount of up to about 50 percent by weight, based on the combined
weight of the organic wax and the polyol. More preferably, the
organic wax is present in the mixture in an amount in the range of
from about 1.0 to about 25 percent by weight, based on the combined
weight of the organic wax and the polyol. Most preferably, the
organic was is present in the mixture in an amount in the range of
from about 2.0 to about 10 percent by weight based, on the combined
weight of the organic wax and the polyol.
[0041] Step (a) in the present process comprises contacting a
particulate plant nutrient with a mixture comprising: a polyol, an
isocyanate and an organic wax to produce a coating surrounding the
particulate plant nutrient. The precise mode of applying the
mixture to the plant nutrient is not particularly restricted--see
for, example column 5, lines 31-63 of Hudson.
[0042] In the present process, it is preferred to conduct Step (a)
at a temperature in the range of from about 50.degree. C. to about
105.degree. C., more preferably in the range of from about
60.degree. C. to about 90.degree. C., most preferably in the range
of from about 70.degree. C. to about 80.degree. C.
[0043] Preferably, Step (a) comprises contacting the particulate
plant nutrient with a first stream comprising the polyol and a
second stream comprising the isocyanate, the first stream and the
second stream being independent of one another. More preferably,
the first stream comprises a mixture of the polyol and the organic
wax. In this embodiment, the particulate plant nutrient may be
contacted simultaneously with the first stream and the second
stream. Alternatively, the particulate plant nutrient with the
first stream followed by the second stream. In a further preferred
embodiment, Steps (a) and (b) of the present process are repeated
at least once to produce a controlled release fertilizer material
having a plurality of coating layers.
[0044] Embodiments of the present invention will be illustrated
with reference to the following Examples which should not be used
to limit or construe the invention.
EXAMPLE 1
[0045] In this Example, a controlled release fertilizer material
was prepared according to the teachings of U.S. Pat. No. 5,538,531
[Hudson et al. (Hudson)]. Accordingly, it will be recognized that
this Example is provided for comparative purposes only and is
outside the scope of the present invention.
[0046] The apparatus used in this Example was capable of applying
coating components to a 7.5 kg batch. The apparatus consisted of a
Plexiglas horizontal drum 16 inches in diameter and 20 inches in
length. The drum end plates had a central 5 inch hole through which
the coating components and the substrate are added. The drum
internals consisted of four substantially evenly spaced
longitudinal baffles, each baffle being about 1 inch in height. The
drum was rotated at 75 fpm peripheral speed or about 18 rpm using a
Separ.TM., variable speed drive, horizontal drum roller. The
internal temperature of the drum and substrate was maintained at
about 75.degree. C. using variable setting electric heating guns.
The heating guns were positioned to direct hot air through the
holes in the drum end plates.
[0047] The coating components were added at a substantially
consistent rate using individual Masterflex.TM. peristaltic pumps
and a modified Amacoil.TM. Machinery auto-sampler. The sampler
portion was removed and an individual stainless steel tubing for
each component was attached to the drive assembly. This allowed the
coating components to be distributed the full length of the drum at
a substantially constant travel speed.
[0048] The substrate used in this Example was granulated urea
(46-0-0). This substrate had a SGN (Size Guide Number) of 240. The
substrate (7.5 kg) was preheated in an oven to about 75.degree. C.
and was allowed to roll in the coating drum until the temperature
has stabilized to 75.degree. C.
[0049] The polyol used in this Example was commercially available
castor oil in an amount of 42.95 g. The isocyanate used in this
Example was polymeric diphenylmethane diisocyanate (BASF PAPI No.
17) in an amount of 19.52 g. The two components are simultaneously
added to the coating apparatus through individual lines or pipettes
near the top of the rolling bed. The 2.5 weight percent coat was
applied to the substrate in three substantially equal layers with
about six minutes between application if each layer--i.e., the
weight of the total coat was 2.5 weight percent based on the weight
of the substrate.
[0050] A C.sub.30+ alpha olefin wax commercially available from
Chevron was pre-heated to about 150.degree. C. and then was applied
in a single layer to the urethane coated substrate. The wax was
used in an amount to provide a weight of 1.5 weight percent based
on the weight of the substrate. Six minutes after the wax was
applied, the drum and contents are cooled with a controlled stream
of pressurized air to about 35.degree. C.
[0051] Thus, in this Example, the sum of the urethane coat and the
wax layer was 4 weight percent based on the weight of the
substrate.
[0052] The water release rate profile for the controlled release
fertilizer material was then determined. In the analysis, a
Technicon AutoAnalyzer.TM. was calibrated and used pursuant to the
teachings of Automated Determination of Urea and Ammoniacal
Nitrogen (University of Missouri, 1980). The following procedure
was used:
[0053] 1. Accurately weigh 15 grams (.+-.0.1 mg) of the sample into
a weigh dish. Record the weight of sample. Transfer the sample to
125 mL Erlenmeyer flask.
[0054] 2. Add 75 mL of demineralized water and stopper the
flask.
[0055] 3. Gently swirl the sample and water until all the particles
are submersed.
[0056] 4. Let the sample stand for a specified time at a constant
temperature (typically at room temperature).
[0057] 5. Gently swirl the flask to mix the solution and decant
only the solution to a 100 mL volumetric flask.
[0058] 6. Rinse the sample with demineralized water adding to the
volumetric flask.
[0059] 7. Bulk to volume of volumetric flask and mix
thoroughly.
[0060] 8. If the test is to be repeated for another time period,
repeat starting at Step 2.
[0061] 9. Once the Technicon AutoAnalyzer II is on line, transfer
some of this solution (or perform the required dilutions if
necessary) to the Technicon sample cups for analysis.
[0062] 10. Record the results as parts per million N--NH.sub.3
(read directly from a Shimadzu Integrator).
EXAMPLE 2
[0063] The methodology in Example 1 was repeated with the exception
that, prior to application of the urethane forming polyol and
isocyanate, the substrate was pre-coated with the C.sub.30+ alpha
olefin wax (pre-heated to about 150.degree. C.) applied as a single
layer. The wax was used in an amount to provide a weight of 0.3
weight percent based on the weight of the substrate. Accordingly,
it will be recognized that this Example is provided for comparative
purposes only and is outside the scope of the present
invention.
[0064] A three-layer polyurethane coating as applied to the
pre-coated substrate as described in Example 1 (44.0 g castor oil
and 18.4 g isocyanate). Again, the weight of the total polyurethane
coat was 2.5 weight percent based on the weight of the substrate. A
600 g portion of the urethane coated substrate was removed.
[0065] Thereafter, a three-layer coating of the C.sub.30+ alpha
olefin wax (pre-heated to about 150.degree. C.) was applied to the
remaining urethane coated substrate. The wax was used in an amount
to provide a weight of 1.5 weight percent based on the weight of
the substrate (in this case, about 35 g was per layer of the
three-layer coating).
[0066] The water release rate profile for the controlled release
fertilizer material was then determined using the test procedure
described above in Example 1.
EXAMPLE 3
[0067] In this Example, a controlled release fertilizer was
prepared in accordance with the present invention.
[0068] The apparatus used to apply the coating components was a SS
horizontal insulated drum having a 12 inch diameter a 51/2 inches
in width. An enclosed back plate was attached to a variable speed
drive. The front plate had a central 8 inch opening through which
the substrate and the coating components are added. The drum
internals consist of four substantially evenly spaced longitudinal
baffles, each about 1/2 inch high. The drum was rotated at 75 fpm
peripheral speed or about 24 rpm. The internal temperature of the
drum and substrate was maintained at about 75.degree. C. using a
variable setting electric heating gun. The coating components are
added using individual automatic macro pipettes capable of adding
1/3 the weight of each coating component in a single addition.
[0069] The same substrate (1 kg) as used in Examples 1 and 2 was
pre-heated to 75.degree. C. in the (smaller) apparatus described
above. Castor oil (5.63 g) at 140.degree. C. was mixed with
C.sub.30+ alpha olefin wax (0.33 g). A coating was applied to the
substrate consisting of three layers of 5.96 g (5.5 wt. % C.sub.30+
in castor oil) of the castor oil/wax mixture and 2.35 g isocyanate
added simultaneously for a total coating weight of 2.5%. The time
period between application of successive layers of urethane was
approximately 6 minutes. Six minutes after the final urethane layer
Was applied the product was cooled.
[0070] The water release rate profile for the controlled release
fertilizer material was then determined using the test procedure
described above in Example 1.
[0071] The water release rate profiles for the controlled release
fertilizer material produced in Examples 1-3 are illustrated in the
accompanying FIGURE.
[0072] As shown, when it is desired to have material with a release
profile of nitrogen extending over 6-8 months, the water release
rate profile for the material produced in Example 3 (the invention)
is significantly better than that for the material produced in
Example 1 (the Hudson material). Further, this was achieved using
significantly less coating in Example 3 (2.5 weight percent based
on the weight of the substrate) compared with Example 1 (4.0 weight
percent based on the weight of the substrate).
[0073] With reference to Example 2 (wax pre-coat and post-coat),
while the water release rate profile is closer to that achieved in
Example 3 (the invention), this was achieved using a three-step
process whereas the material of Example 3 was made using a one-step
process.
[0074] Accordingly, the material of Example 3 and the production
thereof is a significant advance over the prior art.
[0075] While the present invention has been described in
detail,.including reference to the Examples, it will of course be
readily understood that a number of modifications to the
exemplified embodiment will be apparent to those of skill in the
art with this specification in hand, which modifications do not
depart from the spirit and scope of the present invention.
[0076] All publications, patents and patent applications referred
to herein are incorporated by reference in their entirety to the
same extent as if each individual publication, patent or patent
application was specifically and individually indicated to be
incorporated by reference in its entirety.
* * * * *