U.S. patent application number 12/385295 was filed with the patent office on 2009-10-15 for controlled release agricultural products and processes for making the same.
Invention is credited to Keith D. Cochran, Timothy G. Holt, Gregory S. Pedeen, Taylor Pursell, Arthur R. Shirley, JR..
Application Number | 20090258786 12/385295 |
Document ID | / |
Family ID | 26910691 |
Filed Date | 2009-10-15 |
United States Patent
Application |
20090258786 |
Kind Code |
A1 |
Pursell; Taylor ; et
al. |
October 15, 2009 |
Controlled release agricultural products and processes for making
the same
Abstract
A controlled release agricultural absorbent based product
including particles of an absorbent material containing
capillaries/voids between 10-200 microns in cross-sectional
diameter which is impregnated in an amount of 40-95% of the
capillaries/voids volume with an agriculturally beneficial material
selected from the group consisting of fertilizers, insecticides,
herbicides and fungicides, being produced by a process including
steps of 1) introducing water to particles of absorbent material to
result in absorption of water within the absorbent material, 2)
heating the absorbent particles and water to transform the water
within the absorbent particles to steam, 3) introducing the heated
absorbent particles to an agriculturally beneficial material in
aqueous solution to essentially saturate the absorbent particles
with the agriculturally beneficial material, 4) granulating the
combination of agriculturally beneficial material and saturated
absorbent particles to solidify and harden the mixture, resulting
in the agglomeration of absorbent particles into granules, and 5)
drying the granules.
Inventors: |
Pursell; Taylor;
(Birmingham, AL) ; Shirley, JR.; Arthur R.;
(Florence, AL) ; Cochran; Keith D.; (Killen,
AL) ; Holt; Timothy G.; (Florence, AL) ;
Pedeen; Gregory S.; (Killen, AL) |
Correspondence
Address: |
MANELLI DENISON & SELTER
2000 M STREET NW SUITE 700
WASHINGTON
DC
20036-3307
US
|
Family ID: |
26910691 |
Appl. No.: |
12/385295 |
Filed: |
April 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11017700 |
Dec 22, 2004 |
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12385295 |
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09895876 |
Jul 2, 2001 |
6890888 |
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11017700 |
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60216132 |
Jul 3, 2000 |
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60254178 |
Dec 11, 2000 |
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Current U.S.
Class: |
504/358 ; 71/28;
71/29 |
Current CPC
Class: |
Y10S 514/964 20130101;
A01N 25/12 20130101; C05G 5/40 20200201 |
Class at
Publication: |
504/358 ; 71/28;
71/29 |
International
Class: |
A01N 25/12 20060101
A01N025/12; A01P 13/00 20060101 A01P013/00; C05C 9/00 20060101
C05C009/00; C05B 15/00 20060101 C05B015/00 |
Claims
1-98. (canceled)
99. A controlled release agricultural product comprising: a mixture
of a control release holding substance selected from the group
consisting of plant starches, protein gels, glues, gumming
compositions, crystallizing compounds, gelling clays and synthetic
gel forming compounds; and an agriculturally beneficial material
selected from the group consisting of fertilizers, insecticides,
herbicides and fungicides, said agricultural product being in a
particulate form.
100. The controlled release agricultural product of claim 99
wherein the holding substance is 4-8% wt of the agricultural
product.
101. The controlled release agricultural product of claim 99
wherein the holding substance is a starch selected from the group
consisting of corn starch, rice starch, potato starch, wheat
starch, tapioca starch, starch containing D-glucopyranose polymers,
amylose and amylopectin. starch acetates, starch esters, starch
ethers, starch phosphates
102. The controlled release agricultural product of claim 99
wherein the interspatial blocker is corn starch or wheat
starch.
103-109. (canceled)
110. The controlled release agricultural product of claim 99
wherein the interspatial blocker is a gelling clay.
111. The controlled release agricultural product of claim 99,
wherein the fertilizer is secondary nutrients selected from the
group consisting of sulfur, calcium and magnesium.
112. The controlled release agricultural product of claim 99,
wherein the fertilizer is micronutrients selected from the group
consisting of boron, copper, iron, manganese, molybdenum and
zinc.
113. The controlled release agricultural product of claim 99,
wherein the fertilizer is selected from the group consisting of
nitrogen compounds, phosphorous compounds and potassium
compounds.
114. The controlled release agricultural product of claim 113,
wherein the nitrogen compounds are selected from the group
consisting of urea, ammonia, ammonium nitrate, ammonium sulfate,
calcium nitrate, diammonium phosphate, monoammonium phosphate,
potassium nitrate and sodium nitrate.
115. The controlled release agricultural product of claim 113,
wherein the phosphorous compounds are selected from the group
consisting of diammonium phosphate, monoammonium phosphate,
monopotassium phosphate, dipotassium phosphate, tetrapotassium
pyrophosphate, and potassium metaphosphate.
116. The controlled release agricultural product of claim 113,
wherein the potassium compound is selected from the group
consisting of potassium chloride, potassium nitrate, potassium
sulfate, monopotassium phosphate, dipotassium phosphate,
tetrapotassium pyrophosphate, and potassium metaphosphate.
117. The controlled release agricultural product of claim 113,
wherein the fertilizer contains nitrogen, phosphorous and potassium
compounds in a ratio selected from the group consisting of 29-3-4,
16-4-8, 10-10-10, 15-5-10, 15-0-15, 22-3-14, 20-28-5 and
12-6-6.
118-184. (canceled)
185. A process for preparing a controlled release agricultural
product comprising the following steps: mixing a control release
holding substance selected from the group consisting of plant
starches, protein gels, glues, gumming compositions, crystallizing
compounds, gelling clays and synthetic gel forming compounds with
an agriculturally beneficial material in aqueous solution selected
from the group consisting of fertilizers, insecticides, herbicides
and fungicides; granulating the combination of agriculturally
beneficial material and holding substance to solidify and harden
the mixture, resulting in granules; and drying the granules.
186. The process of claim 185 wherein the holding substance is a
starch selected from the group consisting of corn starch, rice
starch, potato starch, wheat starch, tapioca starch, starch
containing D-glucopyranose polymers, amylose and amylopectin.
starch acetates, starch esters, starch ethers, starch
phosphates
187. The process of claim 185 wherein the holding substance is corn
starch or wheat starch.
188-194. (canceled)
195. The process of claim 185 wherein the holding substance is a
gelling clay.
196. The process of claim 185 wherein the combination of
agriculturally beneficial material and holding substance is heated
while blending mixing.
197. The process of claim 185 wherein the granulated combination of
agriculturally beneficial material and holding substance is
screened to result in granules of a predetermined diameter.
198. The process of claim 185 wherein the combination of
agriculturally beneficial material and holding substance is
introduced into the granulator by spraying means.
199. (canceled)
200. The process of claim 185 wherein the combination of
agriculturally beneficial material and holding substance are
solidified and hardened by a loss of heat and/or increase of
concentration of the agriculturally beneficial material.
Description
[0001] This is a continuation application of U.S. Application No.
11/017,700 filed Dec. 22, 2004, which is a continuation of
application Ser. No. 09/895,876 filed Jul. 2, 2001, now issued as
U.S. Pat. No. 6,890,888.
BACKGROUND OF THE INVENTION
[0002] This invention relates to controlled release agricultural
products and processes for making such products. More particularly,
the present invention is directed to particulate absorbents in
particulate form and holding compositions in particulate form that
provide for controlled release of agriculturally beneficial
materials such as fertilizers, insecticides, herbicides and
fungicides. The particulate absorbents contain capillaries/voids
between 10-200 microns in cross-sectional diameter and are
impregnated in an amount of 40-95% of the capillaries/voids volume
with the agriculturally beneficial material. The process of the
present invention forms the controlled release agricultural
particulate absorbents by blending the absorbent with the
agriculturally beneficial material(s) for a prescribed time. The
blended absorbent is fed into a granulator and after screening, the
product is dried. The process results in an easily handled, free
flowing, controlled release agricultural absorbent based
product.
[0003] There are many slow and extended release fertilizers with
their nutrient release based on time and event related coating
failures or coating permeability, and/or low solubility, and/or
microbial activity in the soil, and/or a ratio of surface area to
nutrient weight of the particle. Of these, the major commercial
products are sulfur coated urea, polymer coated ureas, and
urea--formaldehyde products such as methylene ureas. The production
costs of these materials vary, but all of these commercially
available products have been judged by the consumers' spending
patterns as too expensive for extensive use in agriculture. This
especially occurs in the case of major crops such as wheat and corn
which are grown on moist, dry, and irrigated soils under varying
weather conditions. In addition, these high priced extended release
products are in general not tailored for the short growing periods
of wheat and corn because they do not release their nutrients
completely within the growing period of these crops. The existing
products are tailored for severe water regime nutrient
applications, such as rice, sugar cane, and pineapples and high-end
truck farm crops, such as strawberries, and cranberries, or shrubs,
ornamentals, and flowers. When used for grasses, existing products
are limited because of their high cost for use on lawns, gardens,
parks, golf courses and commercial, governmental, and educational
grounds. The existing products are not extensively used for pasture
lands because of the added processing cost of the fertilizer.
Furthermore, when existing controlled release products are used for
lawn care applications, many purchasers-users primarily desire burn
protection caused by overdosing the lawn while applying the
fertilizer. They do not necessarily desire long term release
properties that the fertilizer may provide.
[0004] Thus, a low cost alternative fertilizer with a much shorter
controlled release period would be superior to the higher cost,
longer controlled/extended release fertilizers.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention includes numerous embodiments of a
controlled release agricultural absorbent based product. The
absorbent based product includes particles of an absorbent material
containing capillaries/voids between 10-200 microns in
cross-sectional diameter which is impregnated in an amount of
40-95% of the capillaries/voids volume with an agriculturally
beneficial material selected from the group consisting of
fertilizers, insecticides, herbicides and fungicides. The absorbent
material includes for example, expanded perlite, shredded
newspaper, saw dusts, cotton lint, ground corn cobs, corn cob
flower, Metrecz absorbent and diatomaceous earth.
[0006] The fertilizer includes nitrogen compounds, phosphorous
compounds and potassium compounds. The nitrogen compounds include
urea, ammonia, ammonium nitrate, ammonium sulfate, calcium nitrate,
diammonium phosphate, monoammonium phosphate, potassium nitrate and
sodium nitrate. The phosphorous compounds include diammonium
phosphate, monoammonium phosphate, monopotassium phosphate,
dipotassium phosphate, tetrapotassium pyrophosphate, and potassium
metaphosphate. The potassium compound includes potassium chloride,
potassium nitrate, potassium sulfate, monopotassium phosphate,
dipotassium phosphate, tetrapotassium pyrophosphate, and potassium
metaphosphate.
[0007] The agriculturally beneficial material also includes
micronutrients, secondary nutrients, growth regulators,
nitrification regulators, as well as the aforementioned
insecticides, herbicides and fungicides.
[0008] The particles of absorbent may be agglomerated into granules
of a predetermined size.
[0009] An important embodiment of the invention is the impregnation
of the particle absorbent with a mixture of an interspatial blocker
and the agriculturally beneficial material. The interspatial
blocker includes plant starches, protein gels, glues, gumming
compositions, crystallizing compounds, gelling clays, and synthetic
gel forming compounds. The presence of the interspatial blocker
acts to regulate the release of the agriculturally beneficial
material.
[0010] Another embodiment of the present invention includes A
controlled release, particulate, agricultural product that includes
a mixture of a control release holding substance, such as plant
starches, protein gels, glues, gumming compositions, crystallizing
compounds, gelling clays and synthetic gel forming compounds, and
an agriculturally beneficial material including fertilizers,
insecticides, herbicides and fungicides.
[0011] The present invention also includes embodiments of processes
for making the controlled release agricultural absorbent based
product. The process includes, for example, the steps of 1)
introducing water to particles of absorbent material to result in
absorption of water within the absorbent material, 2) heating the
absorbent particles and water to transform the water within the
absorbent particles to steam, 3) introducing the heated absorbent
particles to an agriculturally beneficial material in aqueous
solution to essentially saturate the absorbent particles with the
agriculturally beneficial material, 4) granulating the combination
of agriculturally beneficial material and saturated absorbent
particles to solidify and harden the mixture, resulting in the
agglomeration of absorbent particles into granules, and 5) drying
the granules.
[0012] The present controlled release agricultural absorbent based
product and holding material based product provide for fine control
of the release over both short and long periods of time, for a
variety of agriculturally beneficial materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Further objects and advantages of the present invention will
be better understood by carefully reading the following detailed
description of the presently preferred exemplary embodiments of
this invention in conjunction with the accompanying drawings, of
which:
[0014] FIG. 1 is a flow chart showing one embodiment of the process
of the present invention wherein a controlled release agricultural
absorbent based product is produced containing fertilizer and a gel
forming interspatial blocker.
[0015] FIG. 2 is a photomicrograph showing expanded perlite wherein
the particles appear to be covered with a thin shell.
[0016] FIG. 3 is a photomicrograph showing exfoliated perlite
wherein the internal capillaries and voids are exposed.
[0017] FIG. 4 is a photomicrograph showing the exfoliated perlite
of FIG. 3 at higher magnification to observe the greater exposure
of internal capillaries and voids.
[0018] FIG. 5 is a photomicrograph showing the expanded perlite of
FIG. 2 at the higher magnification as in FIG. 4 in order to compare
the relatively closed surface compared to the exfoliated perlite of
FIG. 4.
[0019] FIG. 6 is a schematic showing the plant growth test plots of
Example 16, demonstrating the utility and effectiveness of the
products of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] One embodiment of the present invention is the newly
developed controlled release fertilizer which extends the release
of plant nutrient from absorbent particles over a period of time by
trapping the plant nutrients in the small capillaries and voids of
an absorbing material. Techniques utilize innovative means to
provide deep penetration and extensive absorption of an
agriculturally beneficial material into the absorbent material.
Where this absorbed material contains plant nutrient, the result is
a fertilizer with controlled nutrient release characteristics. In
most cases, we have been able to further enhance the retention of
the nutrient within the absorbent through use of an interspatial
blocker such as a gelling compound, which helps further trap the
nutrient within the small capillaries and voids of the absorbent
material. We have tried many absorbents and methods of absorption,
along with several gel forming materials, with varying levels of
controlled nutrient release. We have been the most successful where
the absorbents are extremely absorbent which results in a
relatively dense concentration of nutrient. For testing and
development purposes, urea was selected as representative of
nutrient/fertilizer agriculturally beneficial materials. It was the
nutrient most tested. Best results have been achieved when using
perlite as the absorber, although milled newspaper and fine pine
sawdust have been very good as absorbents. Utilizing cornstarch as
the interspatial blocker (a gelling substance) has improved
controlled nutrient release.
[0021] Pollution is an ever increasing problem with respect to both
air pollution and water pollution. Water pollution occurs when
readily soluble fertilizer is solubilized and washed into streams
during rains or is solubilized and is leached into the ground water
before its intended target vegetation is able to capture. Failure
to capture the fertilizer occurs because the target vegetation is
not in need of it when it becomes soluble or because the leaching
rate is too rapid. Some fertilizers, in particular urea, are lost
to the atmosphere through volatilization where urea decomposes to
ammonia, carbon dioxide, biuret, and other volatile compounds.
Therefore, since the vast majority of fertilizer used has no
controlled release properties because they are not available at a
low cost, pollution problems are being caused by inefficient use of
soluble and volatile fertilizers, which must be applied in excess
amounts over the crop's need.
[0022] Those who are familiar with the production, storage,
transportation, and application of fertilizers know that the
nutrient concentration and the physical properties of a fertilizer
are extremely important in its acceptance and use by the
agricultural community.
[0023] Our invention addresses the problems of production, storage,
shipping, and application costs, as well as the need for moderation
in the length of nutrient availability from slow and controlled
release fertilizers. It provides a process that produces a high
analysis granular material, for example 40 to 45% by weight
nitrogen when using perlite and urea, with or without corn starch,
at an extremely low production cost for a controlled release
fertilizer. Concurrently, the invention provides a product with
physical properties equal to and for the most part more desirable
than commercially available urea.
[0024] The nutrient strength of commercial urea is commonly
recognized as 46-0-0, which is 46% nitrogen. The most common slow
release nitrogen, sulfur coated urea, varies from 32% nitrogen to
38% nitrogen depending on its size and the thickness of the coating
it is given to obtain the desired release rate. Therefore,
substantially more weight (typically 28% more) of sulfur coated
urea is required to provide the same amount of nutrient. When this
property of a fertilizer is coupled with the physical property
commonly called bulk density, which is the amount of weight which
occupies a unit of volume, e.g. lbs/ft.sup.3, then we have the full
impact on the cost of storage and distribution of the fertilizer.
In the case of urea and sulfur coated urea, the bulk density is
about the same at 45 to 46 lb/ft.sup.3.
[0025] To achieve a fertilizer which will be accepted by the
agricultural community as a replacement for urea and sulfur coated
urea, we have developed products which approach the bulk density
and exceeds the crushing hardness of urea. Handling characteristics
are much better than for sulfur coated urea. Handling and storage
do not affect the controlled release properties of our product, but
they can, for example, crack the coating of sulfur coated urea. Our
product varies in nitrogen strength from 40.0% nitrogen to 45.0%
nitrogen, with a more preferred range being 43.0% nitrogen to 44.0%
nitrogen. At the same time we had been able to perfect the nutrient
absorption and granule forming aspects of the product such that
bulk densities have been achieved from 25 lb/ft.sup.3 to 43
lb/ft.sup.3, with a more preferred range being 35 lb/ft.sup.3 to 46
lb/ft.sup.3 and the most preferred range being 38 lb/ft.sup.3 to 46
lb/ft.sup.3. The concentrations of nitrogen using urea and perlite
and those bulk densities of final product have been achieved in a
laboratory and a pilot plant while maintaining the controlled
release properties of the fertilizer. In using larger equipment, as
in a full scale plant, with the techniques taught herein, the bulk
density is 46 lb/ft.sup.3, the same as that of urea and sulfur
coated urea while maintaining 44% nitrogen content of the
fertilizer and the controlled release aspects of our product.
[0026] Several innovative methods were developed to increase the
density of the resulting controlled release fertilizer. Such
methods provide a superior, concentrated product, having improved
handling characteristics and controlled release properties. The
product should have a bulk density approaching that of urea to
provide economics of storage, transportation and distribution near
or equal to those of urea.
[0027] In one embodiment of the present invention, our dense,
concentrated product is accomplished by the following important
features: 1) already expanded perlite is further steam exfoliated
beyond its normal popped form to allow better penetration and
filling of its interspatial regions by the urea/corn starch
mixture; 2) urea/corn starch melts are maintained around 95 to 98%
concentration to minimize voids formed from evaporation during the
processing; and 3) the small perlite particles containing urea/corn
starch are granulated together to form dense, spherical
particles.
[0028] In general, the process involves taking a proper absorbent
material and a fertilizer melt or solution and absorbing the
fertilizer melt or solution (which is in a dense saturation state)
into the absorbent material and then solidifying the fertilizer
within the voids of the absorbent such that it is difficult for the
fertilizer to be released by the absorbent when in contact with
water or humid conditions. This is done by utilizing a very
absorbent material with small capillaries and/or voids and
accomplishing the absorbance by keeping the fertilizer and the
absorbent above the fertilizer's initial crystallization
temperature and at viscosities where capillary action easily occurs
while absorption is occurring. For improvements in controlled
release characteristics, an interspatial blocker, such as starches
and/or other gelling compounds are homogenized into the fertilizer
melt or solution before the absorption step of the process. When
solidified, these gelling compounds tend to help trap the soluble
fertilizer nutrients within the capillaries and/or internal voids
of the absorbent. Following absorption and prior to crystallization
of the fertilizer melt or solution within the absorbent, the liquid
filled absorbent is mixed with recycled material, previously
crystallized, to solidify and granulate the liquid filled absorbent
with the recycled material through cooling and/or drying, at least
partially, imparted by these recycled materials within a pugmill,
drum, rotating pan, fluid-bed, or similar standard granulation
equipment or combination of standard granulation equipment. Before
being stored as product, the granulated solids are milled,
screened, further cooled and dried, but not necessarily in that
order, by any of the obvious ways before sending the product to
storage. The material also is easily prepared using the solids
forming techniques which do not use recycle of solid particles for
cooling, such as slating, prilling, rotoforming, low pressure
extrusion, molding, and forming of bulk slabs or molded shapes. As
needed, any of these methods can involve milling of the obtained
solids with screening and further cooling and drying as needed with
fines recycled to the starting melt or solution filled absorbent
for inclusion in the solidification process. The cooling and drying
can be accomplished by the use of most all standard methods
presently known in the art of granulation including, but not
limited to direct gas contact, vacuum enhanced evaporation, and
indirect heat exchange.
[0029] Although the development can extend to many fertilizer
nutrients, we have centered our development work to date on
providing controlled release urea. Other nutrient fertilizers which
can be used to provide controlled release fertilizer include, but
are not limited to the following; ammonia, ammonium nitrate,
ammonium sulfate, calcium nitrate, diammonium phosphate,
monoammonium phosphate, potassium chloride, potassium nitrate,
potassium sulfate, potassium phosphates, such as monopotassium
phosphate, dipotassium phosphate, tetrapotassium pyrophosphate, and
potassium metaphosphate, and sodium nitrate and combinations of
these materials. The urea melt is maintained between 40% and +99.9%
by weight urea; however, a preferred range of the melt would be
between 65% and +99.9% and a most preferred range between 75% and
+99.9% by weight urea. To provide other controlled release
fertilizer, one or more other nutrient materials other than urea
can be absorbed as long as the nutrients are in the fluid phase by
being pure melt or by being solubilized in water or in the melt of
another nutrient or combination of nutrients and/or water. For
example, a full NPK fertilizer can be made by using urea,
monoammonium phosphate, diammonium phosphates, and potassium
chloride in various proportions and concentrations, and then
blending the product with a filler to provide, for example, 29-3-4,
16-4-8, 10-10-10, 15-5-10, 15-0-15, 22-3-14, 20-28-5, and 12-6-6
control release fertilizers. Further, the nutrients can be in the
fluid phase by being in a volatile substance such as e.g. ethanol
or methanol as the solvent, which can be evaporated out as the
material is solidified and dried. In the above manner, it is
possible to prepare controlled release fertilizers containing
various mixtures of nitrogen, phosphorus, and potassium as well as
incorporation of various secondary nutrients (e.g. sulfur, calcium,
and magnesium) and micronutrients (e.g. boron, copper, iron,
manganese, molybdenum, zinc) if not all of the secondary and
micronutrients, and secondary and micronutrients as well as growth
regulators such as, but not limited to, potassium azide, 2
amino-4-chloro-6-methyl pyrimidine,
N-(3,5-dichlorophenyl)succinimide, 3-amino-1,2,4 triazole and
nitrification regulators such as, but not limited to,
2-chloro-6-(trichloromethyl)pyridine, sulfathiazole, dicyandiamide,
thiourea, and guanylthiourea.
[0030] The controlled release absorbent particles are small and
must be granulated for most commercial application. It is possible
to granulate the filled absorbent particles either in their liquid
filled or solidified condition with other non-absorbed materials to
give controlled release properties to only that portion of the
material contained in the absorbent.
[0031] See FIG. 1 for a flow diagram of one embodiment of the
processes of our invention. The blending of cornstarch and urea, if
needed, is done through the use of high shear agitation provided by
a homogenizer. The cornstarch addition in tests carried out in the
laboratory and pilot plant has worked well. Cornstarch addition can
range from 0.01 to 20% by weight cornstarch, with the preferred
range being from 0.2 to 10% by weight cornstarch and the most
preferred range being from 0.5 to 4% by weight cornstarch. The
homogenized mixture is mixed (poured not sprayed) gently with the
exfoliated and/or expanded perlite at near the full absorbing
capability of the perlite, which is approximately 4 to 7.5% for our
exfoliated perlite, by weight of the final product; thus the
absorbed urea and cornstarch makes up approximately 95% of the
weight of the final product. Prior to the mixing, the exfoliated
and/or expanded perlite is preheated significantly above the melt
temperature to prevent premature freezing of the melt before full
penetration into the perlite. Preheating expanded perlite to
temperatures as high as 330.degree. F. has been successful.
Preheating of the perlite is desirable but we have made a good
product just by keeping the mixture of perlite and melt above the
melting point of the urea melt or solution while absorption is
occurring. Although full absorption of the urea and fertilizer into
the exfoliated perlite or other absorbent is the preferred manner
for most products, a reduction in the absorbance will provide a
material with less release extension and can be desirable for some
fertilizers.
[0032] We have been successful by 1) submerging preheated
exfoliated and/or expanded perlite in an excessive amount of
homogeneous urea/corn starch melt or urea melt, and then extracting
the fully absorbed particle from the homogeneous melt for
granulation; 2) pouring the homogeneous urea/cornstarch melt or
urea melt into the preheated exfoliated and/or expanded perlite
with gentle mixing until the absorbing capacity of the perlite is
obtained before granulation; or 3) in mixing simultaneously metered
amounts of exfoliated and/or expanded perlite and urea/cornstarch
melt or urea melt and blending them together with gentle mixing
while maintaining the melt and perlite above the solidification
point of the melt before granulation. Then for all three methods of
blending, the resulting blended material is added directly to a
pan/drum granulator or pugmill, with recycle and allowed to
agglomerate and solidify into granules or is premixed with or
without recycle before adding it to the pan/drum. The resulting
granules are screened and the oversize is milled and recycled to
the screen. The undersize is recycled back to the granulator where
it is agglomerated with the incoming mixed material. In another
option, we have been successful in returning the oversize directly
to the perlite urea/corn starch mixing step, Vessel 2. Steam can be
used to enhance granulation, but our laboratory tests have not
shown this is required. The product granules are quickly and easily
dried in a pilot plant or laboratory fluid-bed operating with
approximately 190.degree. F. entering air. The dried granules are
then cooled and conditioned against caking, if necessary, before
going to storage.
[0033] All of the exfoliated and/or expanded perlites we have used
have worked well. The inside microstructure of an exfoliated and/or
expanded perlite particle is comparable to a honeycomb type
arrangement; the individual cells indicate diameters of 10 to 200
micron, with a preferred range being 25 to 150 microns, and the
most preferred range being 40 to 100 microns. As such, the
exfoliated and/or expanded perlite used can have a loose weight
density of from 2 to 20 lb/ft.sup.3 with a preferred range of 2 to
10 lb/ft.sup.3 and a most preferred range of 2 to 6
lb/ft.sup.3.
[0034] One skilled in the art readily will see that the
agglomeration and otherwise granule forming, drying, milling, and
screening portions of the process are similar to that of a pan/drum
agglomeration type granulation process and that of a fluid-bed or
prilling granulation process and as such the innovative portion of
our process can be easily incorporated into existing and idle
fertilizer granulation plants. See the dashed line enclosure of
FIG. 1 for the existing plant equipment. Tests have shown that
drying can be performed at lower temperatures and without the use
of fluid-beds, e.g. within a standard rotary drying drum. The
milling step which is obviously forbidden in coated products
appears to have no significant adverse effect on the controlled
release characteristics of this new invention when milling uses a
knife bladed hammer mill similar to those used in large urea
granulation plants.
[0035] For the most economical process, it is preferred to have the
urea as a melt of concentration around 78 to 85%. The urea can be
taken directly from the urea synthesis plant and does not need to
pass through an evaporator, concentrator per the normal route
toward granulation or prilling, hence biuret formation which occurs
in the normal granulation urea process of melt concentration and
then granulation at high temperatures is avoided. Further, the
added costs for production of a controlled release urea fertilizer
over that of just urea granules is only the cost of the perlite
and, if used, the cornstarch or other gelling additive, and the
cost of mixing them with the urea. However for more dense products
with enhanced controlled nutrient release characteristics, and the
use of less absorbent, we teach the use of higher concentration
melts up to 99.9% melt.
[0036] The products made by our invention continue to retain
excellent handling characteristics with regard to hardness and
abrasion resistance and can be made in all size ranges desired by
the lawn and garden users as well as the agricultural users. In
some cases, by using 78% to 85% by weight urea melt, we can achieve
better penetration of the cornstarch within the capillaries and
voids of the absorbent material than with +99.9% melt. This
increased penetration is apparently due to several reasons; among
them lower viscosity of the homogeneous mixture, almost no foaming
of the mixture with cornstarch during processing, and reduced
pre-gelling of the cornstarch prior to entrance into the exfoliated
and/or expanded perlite. When the absorption is done without
cornstarch or any additive absorbed into the perlite using the same
methods as with cornstarch, significant reductions in controlled
release characteristics occur.
[0037] All absorbents will not work; it now appears that only those
with capillaries and voids between 10 and 200 microns in cell
diameter can be used. Further it appears that others, which may
work from a controlled release standpoint, have much too small an
absorbing capacity, greatly diluting the nutrient content of the
fertilizer particle and thus increasing the cost.
[0038] In our work to date we have made granular-product of a size
from 1 mm to 4 mm; however, we have made granules ranging in size
from 0.20 mm to 25 mm. These larger and smaller granules have
control release properties and product of this size can be made
with only a change in the process screen size. It is preferable to
have granules of about 0.20 mm when producing a product to be used
on golf greens. The 25 mm product would be used in rice patties.
The most useful range for lawns and most agriculture is 1 mm to 4
mm granules. Material with a size of 6mm to 8 mm will be useful for
forestry fertilization.
[0039] The urea used can contain normal conditioning additives like
formaldehyde, previously reacted urea formaldehyde, clays, ligno
products, or parting agents. The presently produced product has
shown some excellent handling characteristics. Unlike some
controlled release products, it has little tendency to float and it
can be blended with most other fertilizers or used directly without
blending.
[0040] We have successfully made a product using urea melt
concentrations up to +99.9% urea melt without cornstarch addition,
but at a loss of some controlled release characteristics and some
good physical properties because of the absence of the corn starch.
Further processing at above about 98% urea concentration leads to
excessive formation of biuret, a compound which is undesirable to
many agricultural users because of its toxic properties with some
crops, in particular, citrus crops. This requires preheating and/or
keeping the absorbent above the solidification point of the urea
melt and preferably about 20 to 30.degree. F. above that point.
[0041] In our work along with the granulation process techniques
otherwise mentioned, we have experienced success in making the
controlled release absorbent based product when using a compaction
step, by making a homogenous mixture of cornstarch and urea, or
using just urea and then mixing the mixture with the perlite or
other absorbents, i.e. shredded newspaper, various saw dusts,
cotton lint, ground corn cobs, corn cob flower, Metrecz absorbent,
diatomaceous earth, and others. Then we solidify the material by
pouring it out on a flat metal sheet to cool. Following this, the
product is milled to the desired particle size; however, when
employing a compaction step it is typically milled and compacted
into the desired particle size. The controlled release
characteristics of the product are usually reduced by the
compaction step.
[0042] Many other pure nutrients and combination of nutrients can
be made utilizing the process techniques taught by our
disclosure.
[0043] In further embodiments of this invention, insecticides such
as 0,0-diethyl O-(2-isopropyl-6 methyl- 4 pyrimidinyl)
phosphorothioate), herbicides such as 2,4-dichlorophenoxyacetic
acid, fungicides such as ferric-di-methyl-dithiocarbamate, growth
regulators such as gibberellic acid, and other agricultural
chemicals such as methiocarb can be added during the absorption
phase of this process to obtain controlled release characteristics
to a complete set of a crop's chemical and nutrient needs. Table 1
includes some more of these chemicals, but those that can be added
to the product during the absorption phase are not limited by this
list.
[0044] Other plant starches, protein gels and glues, gumming
products, crystallizing compounds, gelling clays, and synthetic gel
forming compounds also work as the gelling and/or inter-spatial
blocking compound. These include but are not limited to the
following: rice starch, potato starch, wheat starch, tapioca
starch, and any starch which contains the D-glucopyranose polymers,
amylose and amylopectin; modified starch of the former listing
(also including corn starch) by acetylation, chlorination, acid
hydrolysis, or enzymatic action which yield starch acetates,
esters, and ethers; starch phosphate, an ester made from the
reaction of a mixture of orthophosphate salts (sodium dihydrogen
phosphate and disodium hydrogen phosphate) with any of the listed
(also including corn starch) starch/or starches; gelatin as made by
hydrolysis of collagen by treating raw materials with acid or
alkali; glue as made from any of the following: collagen, casein,
blood, and vegetable protein such as that of soybeans; gumming
products such as cellulosics, rubber latex, gums, terpene resins,
mucilages, asphalts, pitches, hydrocarbon resins; crystallizing
compounds such as sodium silicate, phosphate cements, calcium-oxide
cements, hydraulic cements (mortar, gypsum); gelling clays in the
form of very fine powders; synthetic gel forming compounds such as
polysulfide sealants, polyethylene, isobutylene, polyamides,
polyvinyl acetate, epoxy, phenolformaldehyde, urea formaldehyde,
polyvinyl butyral, cyanoacrylates, and silicone cements. Plant
starches work particularly well, especially corn and wheat
starches.
[0045] All granules made can be rounded and/or coated, if desired,
with hydrophobic materials such as waxes, polymers, or oils to
further enhance their controlled release characteristics.
[0046] Scanning electron photo micrographs of our expanded perlite
showed the expanded perlite to be an in-depth formation of small
micro sized chambers connected by walls which are about 0.5 micron
thick which formed when water evenly dispersed in the unexpanded
perlite expanded under high temperature. For the most part, the
expansion of the perlite particles, which are sized before
expansion by milling the larger mineral rock, result in particles
which appear to have outer shells with blow-holes in the shells.
This original perlite expansion can be done by any one of several
known technologies. We find that though the resulting expanded
perlite has potential, it does not allow us to produce the dense
product we desire. Therefore, we subject the expanded perlite to
further treatment in our pilot plant. A small quantity of water is
applied to the expanded perlite, our most preferred amount being
from 0.5 ml of water/gm of perlite to 5.0 ml of water/gm of
perlite. The treated expanded perlite is then introduced into a
heated chamber, most preferably a steam jacketed double shaft
pugmill running at a high rate of speed so as to mechanically
fluidize the particles. This heats the wetted expanded perlite up
again such that the water in the perlite expands within the perlite
but this time in a much more gentle fashion than the original high
temperature and pressure popping technique used in the original
expansion. Air temperatures within the vessel can range from
210.degree. F. to 500.degree. F. with the most desired range being
215.degree. F. to 350.degree. F. The result as shown by the
electron microscope is increased rupture and exfoliation of the
outer shell as the absorbed water expands into steam at atmospheric
pressure. There appears to be less effect on the vast maze of
internal chambers. The retention time that the wetted perlite
spends in the expansion chamber (or pugmill) needs only to be about
30 seconds, but extensive exposure of over an hour is not
detrimental unless the mechanical action is too violent and abrades
the perlite. The perlite with this enhancement to the original
expansion is now ready to be filled with our urea/corn starch
mixture. This step of controlled exfoliation of the perlite with
steam immediately before it is introduced to the absorbing vessel
also drives most of the air from the internals of the previously
expanded perlite replacing it with steam. Since urea and urea
solutions are extremely hydrophilic as are most fertilizers, the
steam in the perlite is absorbed by the fertilizer mixture causing
a psuedo vacuum within the perlite which further assists complete
filling of the perlite with urea/corn starch solution or melt when
the perlite is fully immersed in the molten material. We have
achieved the same exfoliated results in the laboratory using a
small tank fitted with a condenser, in a pressure cooker and with a
microwave oven. In each case, to get a further rupture of the outer
skin of the expanded perlite, water had to be applied to the
expanded perlite prior to heating. Scanning electron photo
micrographs and calculations, based on percentage of components in
the final product and bulk density in the final product, indicate
that in the final product, the exfoliated perlite is impregnated to
between 40 and 95% of its holding capacity and in most cases,
impregnation is between 60 and 90% of its holding capacity. In the
most preferred cases, impregnation is between 80 and 90% of the
capillaries/void volume. Thereby, the impregnated mixture makes up
70 to 95% by weight of the final product. About 60 to 80% of the
urea/corn starch mixture is absorbed into the exfoliated perlite.
The remaining urea and corn starch acts as a binder holding the
individual granules together and that urea is available for quick
release to the soil.
[0047] Another major contributor to the high bulk density is the
fact that we can granulate the material in the same manner as urea
is presently granulated. This is accomplished by spraying the
mixture consisting of molten urea, corn starch, and the small
perlite particles containing absorbed urea/corn starch mixture, and
which vary in size from about 100 micron to 1500 micron in
diameter, but more preferably 150 to 1000 microns, onto existing
recycle granules in a rotating drum. The existing granules thus
grow in size because of the onion skin type build-up from direct
solidification of the mixture sprayed on them and because there is
some agglomeration of small existing granules in the rotating bed
being adhered to large granules by the solidifying mixture which
acts as an adhesive. By such a manner the granules are made
spherical. They are then sized as they leave the granulator as per
a typical urea granulation plant, with the undersize being returned
to the granulator and the oversize being milled and returned to the
granulator either in total or just the undersize part after
rescreening. The resulting product is spherical even though each
granule is made up of a multiplicity of perlite particles filled
with solidified urea and starch and the unabsorbed urea and starch
acting as the adhesive to hold the granule together. Later when the
granules are applied to the soil and water begins to leach-out the
urea nutrient, the corn starch not only acts as a inter-spatial
blocker thus retarding the leaching of the urea it helps hold the
perlite particles together which also enhances controlled release
of the nutrient by, in effect, maintaining a larger center of high
nutrient content, rather than allowing the dispersion of the small
perlite particles in the soil. Also, in effect, maintaining a large
urea granule which obviously goes into solution slower than the
same granule ground to a powder and dispersed in the soil.
[0048] Our granules are extremely hard when made at high density
even without the customary inclusion of 0.3% to 0.5% urea
formaldehyde in urea granules to harden them up and prevent caking.
The exfoliated perlite super-structure apparently gives extra
hardness (crushing strength) to the granules such that the crushing
strength of -6+7 Tyler mesh, (3.4 mm to 2.8 mm in diameter)
materials vary from 8 lbs of force to 10 lbs of force without the
addition of urea formaldehyde as a hardening and conditioning
agent. This is due to using concentrated urea of 95%, and spray
agglomeration granulation. In comparison, typical commercial urea
with 0.3% to 0.5% urea formaldehyde at -6+7 Tyler mesh (3.4 mm to
2.8 mm in diameter) has a hardness (crushing strength) of 5 to 8
lbs of force, but without formaldehyde, are much weaker.
[0049] Urea hardness (crushing strength) varies directly in a
straight line manner with granule diameter, with a curve of the
type y=mx+c, where y=the hardness, x=the diameter of the granule,
m=the slope of the curve, and c=the intercept of the x-axis. Using
this curve equation with the normal intercept as determined by
classical data at 0.75, we can predict the hardness (crushing
strength) of our urea/corn starch product to range 11 to 14 lb of
force when the granules are 4 mm in diameter and 0.9 to 1.1 lb of
force when the granules are 1 mm in diameter.
[0050] With regard to the use of urea formaldehyde as the
recognized manner of preventing urea caking during storage and
shipment, we have used some urea pretreated with 0.4% urea
formaldehyde in our tests to determine any positive or adverse
effect its presence might have on the controlled release
characteristics of our material. Some may wish to re-granulate urea
by melting or dissolving standard commercial product or they may
wish to add urea formaldehyde to resist caking or other reasons. To
demonstrate this was possible we did some limited testing. In our
test work, we were able to make a product with some increased
extension to the release rate.
[0051] To measure the relative solubilities of the products in
soil, an irrigated soil burial test was devised such that granules
could be retrieved for measurement of their nitrogen content. The
following is a description of the test.
Procedure for Controlled Release Soil Test
[0052] 1. Screen the sample to obtain -6+7 Tyler mesh granules for
the test.
[0053] 2. Label a freezer container with the test description.
[0054] 3. Place the freezer container on the 1200 g balance and
tare out.
[0055] 4. Place 300 g of potting soil with a 40% moisture content
into the container and record the weight.
[0056] 5. Over the soil place two (2) pieces of fiberglass mesh
with 14 meshes to the inch and 1/16 inch openings.
[0057] 6. Tare out the container with the soil and fiberglass mesh
screens.
[0058] 7. Spread 5 grams of -6+7 Tyler mesh granules over the
screen in a single layer and record the weight.
[0059] 8. Place a large square of fiberglass mesh over the
granules, with a stainless steel screen cut to fit over it, so that
the shape of the container has been mirrored.
[0060] 9. Once this is shaped, tare out the container and add 150 g
of soil and record the weight.
[0061] 10. Repeat this process for each sample to be tested (in
triplet if possible).
[0062] 11. After all containers are completed, fill a mist spray
bottle with de-ionized water and prime.
[0063] 12. Tare out the weight of the primed mist bottle.
[0064] 13. Mist 4 g of water into each container and immediately
place the lid on container and seal.
[0065] 14. After the fertilizer granules have been submerged in a
humid soil environment for the allotted time (9 hours, 24 hours,
and 3 days), the 150 g of soil is removed from the container.
[0066] 15. Weigh to the nearest 0.0001 g in aluminum weigh pan and
tare out.
[0067] 16. Gently remove the two pieces of fiberglass mesh, which
contains the remaining fertilizer granules.
[0068] 17. Transfer the granules to the aluminum weigh pan and
record the weight of the fertilizer granules.
[0069] 18. Place the fertilizer granules in a laboratory oven to
dry at low temperature (50.degree. C.) for 13 hours.
[0070] 19. Remove the dry sample from the oven, weigh to the
nearest 0.0001 g and record weight.
[0071] 20. Place the dry fertilizer sample into a 125 mL plastic
sample bottle containing 20 g of de-ionized water.
[0072] 21. Allow the sample to dissolve for 3 hours.
[0073] 22. Place approximately 1 ml aliquot of the sample solution
onto the sample stage of a refractometer(e.g., Abbe
Refractometer).
[0074] 23. Record the refractive index and temperature of the
solution.
[0075] 24. Calculate the percent urea retained from the original
fertilizer sample.
[0076] Using the above procedure, plain urea particles went into
solution in the first 9 hours. Perlite granules containing urea and
1% corn starch and made from 85% urea melt retained up to 42% of
their nutrient after 9 hours, 23% after 24 hours, and 11% after 3
days, thus providing an extended control release pattern. Further
extended control release of the granules resulted when 1%
cornstarch was used as a gelling compound with a 95% urea melt; up
to 48% of the nutrient remained in the perlite after 9 hours, 23%
remained after 24 hours, and 11% remained in the perlite after 3
days.
[0077] This is much less controlled retention than the goal of most
sulfur coated ureas and methylene ureas, which are relatively
expensive, longer nutrient availability extending materials.
[0078] Alternatively, cornstarch and cold water (33.degree.
F.-43.degree. F.) can be blended at ratios of as little as 1 to 1
(i.e. cornstarch is equal to or less than 50%) and then mixed with
the urea melt before the absorption step of the process and thus
avoid the homogenizer step in the process. This, however, adds
water to the melt which must be dried out of the product, and for a
continuous plant process would not be desirable.
[0079] While urea was employed in the tests as the principle source
of nitrogen, diammonium phosphate (DAP) was additionally used as a
source of nitrogen, as well as a source of phosphorus.
[0080] The control release fertilizer of the present invention was
applied to outdoor plots of grass as described in Example 16. Two
sample embodiments of the present controlled release fertilizer
were prepared using urea, corn starch and expanded perlite. One
sample fertilizer was prepared using a 1% corn starch solution and
the second sample fertilizer was prepared using a 4% corn starch
solution. An 85% urea solution was employed in preparing both the
1% and 4% sample fertilizers. Test results show that the controlled
release fertilizers provided the shortest time from planting to
tasseling and silking for both sweet corn and field corn.
TABLE-US-00001 TABLE 1 CHEMICAL NAME
2-(2-Methyl-4-chlorophenoxy)propionic acid
2-Methyl-4-chlorophenoxyacetic acid 3,6-Dichloro-o-anisic acid
Pyrethrins 2-chloro-4-ethylamino-s-triazine Benefin:
N-butyl-N-ethyl-alpha, alpha, alpha, trifluoro-
2,6-dinitro-p-toluidine Trifluralin: alpha, alpha, alpha,
trifluoro-2, trifluoro- 2,6-dinitro-N,N-dipropyl-p-toluidine
Dithiopyr 3,5-pyridenedicarbothiocic acid, 2-
(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,S-
dimethyl ester Chlorpyrifos[O,O-diethyl-O-(3,5,6-trichloro-2-
pyridyl)phosphorothioate O,O-Diethyl
S-(2-(ethylthio)ethyl)phosphorodithioate
(2,2,2-trichloro-1-hydroxethyl)phosphonate
1-((6-chloro-3-pyridinyl)methyl)-N-nitro-2- imidazolidinimine
Cyano(4-fluoro-3-phenoxyphenyl)methyl 3-(2,2-
dichloroethenyl)-2,2-dimethylcyclopropane carboxylate
(2,4,6,8-tetramethyl-1,3,5,7-tetraoxycyclo-octane) Prodiamine,
(N3,N3-Di-n-propyl-2,4-nitro-
6(trifluoromethyl)-m-phenylenediamine)
[0081] More specifically, our invention encompasses taking urea
melt of concentrations 40% to 99.9%, or more preferably 65% to
99.9%, and most preferably 75% to 99.9% made by any means and corn
starch made by a means and blending them together into a completely
homogeneous mixture and in such a way that the gelling properties
of the corn starch are not destroyed and foam formation is
minimized. We blend under atmospheric pressure and do not let the
temperature of the mixture exceed 295.degree. F. or a point where
the vapor pressure of the mixture exceeds 450 mm of Hg while
maintaining the temperature of the mixture above the point of first
crystallization for urea. More preferably, we do not exceed
280.degree. F. or a point where the vapor pressure of the mixture
exceeds 350 mm of Hg and most preferably we do not exceed
270.degree. F. or a point where the vapor pressure exceeds 300 mm
of Hg. This prevents foaming which hinders the later absorption
step, limits formation of biuret, and limits thermal damage to the
corn starch.
[0082] We minimize the mixing step and use only enough
homogenization to completely mix the corn starch within the urea
solution. We use urea solution with more than 40% urea content up
to 99.9% urea; however, to provide a more dense product and to get
better extension of the release, we more prefer to use urea
solution with a urea content between 65% and 99.9% and most prefer
a urea solution between 75% urea and 99.5% urea. Further, we keep
the melt at least 0.5.degree. F. above the point of first
crystallization for the urea/corn starch mixture; however, we
prefer to keep it at least above 2.degree. F., and most prefer to
keep it at least 5.degree. F. above the point of first
crystallization. Once the mixture has been made, it is important to
quickly absorb it to prevent damage to the corn starch gel and to
prevent excessive biuret formation. We pump and meter the mixture
without temperature adjustment into a pugmill where it is mixed
with the absorbing exfoliated perlite. Although others who utilize
our technology may wish to adjust the temperature, we find
temperatures adjusted at this point can cause foaming or
crystallization which at this point are very harmful in obtaining
maximum absorption into the expanded perlite. Expanded perlite by
any of most standard means is heated to above the point of first
crystallization of the mixture to avoid premature freezing of the
mixture in the outer chambers of the perlite and thus prevent full
penetration. The metered perlite can be heated by a fluid-bed or
any number of ways and passed to the absorber, however, we prefer
to provide a secondary step of limited exfoliation to the perlite
as follows for much better absorption and controlled release. A
mixture of perlite and water may be heated to steam the perlite, or
hot steam may be introduced directly to the perlite to steam the
perlite.
[0083] The preferably hot steam filled perlite is fed to the
absorber where it absorbs the mixture to near completeness. More
urea/corn starch mixture is used than the absorbing capacity of the
perlite so that the perlite is essentially totally submerged in the
urea/corn starch mixture. This allows the excellent penetration and
fill of the perlite particles. To give the mixture time to
completely penetrate into the perlite before being crystallized or
gel setting the absorbers side walls are heated at the same
temperature as the perlite-slurry and the top is covered to prevent
evaporation. Although we do this in continuous fashion in a
pugmill, it is obvious to those schooled in the art that some other
absorber vessels may work just as well or to a limited degree as
long as early crystallization of the mixture is not allowed. There
must be excess in urea/corn starch over that which absorbs for this
mixture is used as the mortar which covers and joins the individual
pieces of perlite, now partially or totally filled with the
urea/corn starch mixture, together into granules made up of a
multiplicity of these filled perlite particles. Retention time in
the absorber can be from 10 seconds to several hours, however, we
prefer to provide the time to obtain maximum penetration and yet
minimize the time with respect to avoiding excess formation of
biuret and damage to the corn starch gel. Thus we more prefer 30
seconds to 30 minutes within the absorber, and most prefer 1 minute
to 15 minutes within the absorber.
[0084] Once the urea/corn starch mixture is absorbed into the
exfoliated perlite to the extend desired, the mixture is still a
slurry of urea/corn starch containing perlite in a mixture of urea
and corn starch, as such it is pumped by mechanical, pressure or
suction means into the granulator. We have found that a course
dispersion spray such as is used in most commercial drum
granulators is preferred although we have been successful in
pouring the material into the rolling bed of granules and in
pressure spraying the material with steam. When doing this, recycle
as undersize and milled oversize and product, if needed, is fed
back to the drum to provide cooling as needed and to assist in
particle formation and agglomeration. Much of the cooling is
provided by the evaporation of water from the granules. We have
found that the best temperature for granulation is to provide
entering recycle at from 110.degree. F. to 220.degree. F., but more
preferably between 130.degree. F. and 210.degree. F., and most
preferably, between 150.degree. F. and 205.degree. F., with the
perlite/corn starch slurry fed into the drum at from 32.degree. F.
to 295.degree. F., but more preferably, from 115.degree. F. to
280.degree. F., but most preferably, between 160.degree. F. and
270.degree. F., but not allowing the temperature of the granules in
the drum to exceed 235.degree. F. The rolling action and spraying
action combine to form hard spherical granules with a good gel
structure and with controlled release properties.
[0085] The difference between normally expanded perlite and
exfoliated perlite as taught by our invention is shown by the
following photo micrographs. FIG. 2 shows the expanded perlite to
be spherical to oblong in shape with an average size of about 0.5
millimeters=500 microns. Some openings are apparent on some of the
material, but most of the particles appear to be covered over with
a thin shell. After steam exfoliation within the pugmill of the
pilot plant, as shown in FIG. 3, the outer covering is efficiently
removed revealing the expanse of the internals. In essence, totally
changing the absorbency of the perlite. A close up of an exfoliated
granule in FIG. 4 shows just how open the perlite is to penetration
by the urea and/or urea/corn starch mixture. A close up photo
micrograph of expanded perlite, as in FIG. 5, in contrast to FIG.
4, shows limited exposure to the perlite internals to the urea or
urea/corn starch mixtures. It also reveals a much easier means of
egress by the absorbed mixture when it is in the soil, thus
allowing the control and extension of nutrient release by the
amount and type of blocking agent mixed with the urea or other
nutrient.
[0086] With reference to FIG. 1, one embodiment of the process of
our invention includes taking fertilizer nutrient as a solution or
as a melt and homogenously mixing it with a gelling material, i.e.
blocking agent, in vessel (1) containing a high sheer homogenizer.
However, if the mixture is, e.g. a starch or similar material, and
the solution is relatively cold, a homogenous mixture of the
solution and the blocking agent can be obtained with less mixing
force.
[0087] The homogenous solution is then pumped in a continuous
manner by a metering pump (2) to a blender (3) to mix with an
absorbent. The absorbent is likewise continuously fed to the
blender by being metered by a solids feeder (4) to a blending type
heat exchanger (5) to which water is also metered through a pump
(6) and added to the absorbent prior to complete heating of the
absorbent and in a manner that it is evenly dispersed among and
within the particles of the absorbent. Heat (7) is applied
indirectly to the absorbent and water in the heat exchanger in a
controlled manner to cause the water to expand to steam as the
absorbent passes through the heat exchanger, this prepares the
absorbent for maximum absorbency when it reaches the blender (3).
Heat (8) is applied to the blender to individually heat the
contents and maintain good temperature control for optimum
absorbency. In the blender the absorbent absorbs the mixture
prepared in vessel (1) but not all of it; leaving an essentially
filled absorbent with excess of that mixture in a very viscous but
flowable condition to be discharged from blender (3) to feeder (9).
Thereby it can be introduced into the granulator (10) by a number
of means. The filled absorbent particle with the absorbent mixture
are granulated within the granulator such that the mixture
crystallizes both within the absorbent particles and outside the
absorbent particles, the latter thus acting as the glue to hold the
individual particles together into the form of a granule containing
many particles. The granules discharge from the granulator after
the particles and their contents and the accompanying mixture,
making up the granules, are solidified by the loss of heat and/or
increase concentration. The heat of crystallization is removed by
incoming recycle provided by the undersize from a sizing screen
(11) and/or cooling gases passing through the granulator and/or
heat losses passing through the shell of the granulator and/or by
evaporation of water or other solvent from the granules or
evaporation cooling from other means within the granulator. In some
cases heat will replace cooling to evaporate the solvent, thus
increasing concentration of the mixture, both within and outside
the absorbent, and resulting in solidification of the mixture.
Within the granulator, the particles from feeder (9), not only
agglomerate among themselves, they also build on and agglomerate
with the incoming recycle of undersize. Discharge from granulator
(10) then free flows to screen (11) where the oversize is separated
and sent to a mill (12) and then back to the screen (11). As an
option to allow the best sphericity product, the milled material is
all returned to the granulator. The on-size material leaving screen
(11) free flows to a dryer/cooler (13) where it is dried to the
desired completeness and cooled to a proper storage temperature.
optionally, portions or all of the undersize and milled oversize
can be returned to the blender (3) as is needed to improve
granulation.
[0088] More specifically, we prefer that the heat exchanger (3) be
a moderately high tip speed pugmill with heated sidewalls, and that
heat be provided by steam whose pressure at saturation can be
easily regulated for a constant temperature control. The heat
exchanger (3) should be vented but only to let out the air and
steam which would otherwise build to a pressure condition within
the heat exchanger. We prefer to maintain as much as possible a
steam atmosphere within the pugmill, which is produced by
evaporation of the water dispersed into the absorbent, and to
discharge the exfoliated and/or steam containing absorbent directly
to the blender (3). The blender is preferred to be a pugmill with
moderate to slow tip speed, such that the mixing is gentle but
thorough. The material should reach a moderate oatmeal consistency
as it exits the pugmill blender (3). We prefer the feeder (9) to be
a low pressure developing pump or screw conveyor.
[0089] In other feeding means, we have been successful with a steam
eductor whereby the filled absorbent and excess mixture is sprayed
onto the granules in the granulator. The granulation system which
consists of the granulator, screen, mill and drying and cooling
means and associated supporting equipment can be most any classical
commercially existing system including spray drum granulators, pan
granulators, pugmill granulators, pour and crumble granulators,
fluid-bed granulators, prill towers, and other forms of solid
forming operations. The process is designed such that only minimal
alterations are required to most every large (equal to or greater
than 5 tons/hr) granulation plant now in operation which produce
granules or prills of urea, monoammonium phosphate, diammonium
phosphate, sulfur, ammonium sulfate, and ammonium nitrate,
potassium nitrate, calcium nitrate, potassium phosphate, sodium
nitrate, and mixtures of these products and others.
[0090] The following examples show how the present invention has
taken the above concepts and developed them into a unique extended
release agricultural product and method of making and using
same.
[0091] Thus, the invention is demonstrated with reference to the
following examples, which are of an illustrative nature only and
which are to be construed as non-limiting.
EXAMPLE 1
[0092] Samples of controlled release urea were granulated using an
85% urea solution, with and without corn starch equal to 1% of the
final product, and pre-heated perlite 3-S. The urea and corn starch
were combined in a laboratory beaker. A laboratory scale
homogenizer was used to evenly disperse the corn starch in the urea
solution. In separate tests, a sufficient amount of perlite, both
pre-heated to 300.degree. F. and un-heated, was added to the
urea/corn starch mixture to obtain almost complete absorption of
the mixture. The mixture was removed from the beaker and allowed to
solidify. Once the mixture had solidified and cooled, it was
crumbled using a laboratory blender on the chop setting, and then
screened to obtain -6+7 Tyler mesh (3.4 mm to 2.8 mm in diameter)
fertilizer granules. These granules were then dried in a laboratory
fluid-bed. The resulting materials were evaluated by placing 1 gm
of sample in a test tube with 6 grams of water held at 75.degree.
F. for 1, 2, and 3 days, at which time the samples were drawn out
of the test tube using a pipette after rotating the test tube end
on end three times to create a homogenous solution. Urea retention
in the perlite in all cases was over 250% better when it contained
1% corn starch instead of no 7corn starch and at least 35% better
in all cases when the perlite was heated.
EXAMPLE 2
[0093] A pilot plant was set-up where urea was melted by a steam
tube melter then blended with water to make an 85% solution and
continuously fed at 109 lb/hr to a mix tank equipped with a
homogenizer where corn starch powder was added at the rate of 1
lb/hr. The urea solution and the mix tank were maintained at a
temperature of 210.degree. F. Expanded 3-S perlite was continuously
fed to a fluid-bed pre-heater at 7 lb/hr where it was heated with
air until it was 320.degree. F. to 327.degree. F. (No water was
applied to the perlite before hand and no steam was used to
exfoliate it.) The perlite and the urea/corn starch mixture were
then fed to a pugmill where most of the urea/corn starch mixture
was absorbed while being held at a temperature of 196-197.degree.
F. The resulting slurry of perlite containing urea and corn starch
plus excess urea and corn starch mixture was fed to a second
pugmill. Oversize granules produced during the pilot plant
operation were milled utilizing a Jacobson knife-bladed hammermill
to obtain additional product size material and recycle. Recycle was
added to the pugmill at a rate slightly over 2.5 to 1 that of the
product made. The temperature of product leaving the pugmill was
136.degree. F. The product and recycle were rounded and pre-dried
in a rotating drum at 130.degree. F. after which the product was
dried in a fluid-bed dryer using 140.degree. F. air.
[0094] The resulting product had a bulk density of 26 lb/ft.sup.3,
a perlite content of 8.8%, and a corn starch concentration of 1%
giving a nitrogen content of 41.5+%; which resulted in a 9 hour
dissolution rate in the aforementioned soil test of 43%, 23% after
24 hours, and 10% after 3 days.
EXAMPLE 3
[0095] Eighteen (18) grams of expanded 3-S perlite was placed in a
laboratory vessel having an agitator and small vent. 20 ml of water
were added to the vessel and mixed with the perlite, and it was
heated so that it steamed for 1 hour at 220.degree. F. 350 grams of
a mixture of 85% urea solution with 1% of corn starch homogenized
with it was added to the steaming perlite and mixed well. The
mixture was poured onto a plastic surface to harden and then
crumbled in a lab blender. The crumbled material was screened to
-6+10 Tyler mesh (3.4 mm to 1.7 mm in diameter) and dried in a lab
fluid-bed. The resulting material had a bulk density of 35
lb/ft.sup.3. The material was then placed in a rotating drum and
rounded by blowing hot air on it at 240.degree. F. The bulk density
of the resulting material was 38 lb/ft.sup.3.
EXAMPLE 4
[0096] Eighteen (18) grams of expanded 3-S perlite was placed in a
laboratory vessel and treated in the same manner as Example II
except 350 grams of a 95% urea-1% corn starch mixture was added to
the steaming perlite and mixed well. After crumbling, screening,
and drying, the resulting material had a bulk density of 35
lb/ft.sup.3 and after rounding, a bulk density of 37
lb/ft.sup.3.
EXAMPLE 5
[0097] The same test was performed as Example 3, but a 98% urea-1%
corn starch mixture was added to the steaming perlite. The
resulting material had a bulk density of 38 lb/ft.sup.3 and after
rounding, a bulk density of 40 lb/ft.sup.3.
EXAMPLE 6
[0098] The same test was performed as Example 3, but a pure urea
melt was added to the 18 grams of steam perlite resulting in a bulk
density of 41 lb/ft.sup.3 and after rounding 43 lb/ft.sup.3.
EXAMPLE 7
[0099] The apparatus of Example 2 was altered to allow additional
exfoliation of the expanded perlite in order to get increased
absorbency and increased bulk density per lab examples 3, 4, 5, and
6. The perlite was fed into a double shaft pugmill heated by a
steam jacket at 85 psia or 316.degree. F. The shafts were rotated
at 130 rpm to give them a tip speed of 3.4 ft/sec. As the perlite
was metered to the pugmill, it was moistened at the rate of
approximately 1.1 grams of perlite per gram of water at the inlet
end of the pugmill to allow absorption of the water into the
perlite before the water was heated to the point of becoming steam.
The water was applied through a tygon tube which dripped on the
most active part of the bed in the pugmill. Retention time of the
perlite in the pugmill was about 30 minutes. Photo micrographs
showed the perlite exiting the pugmill to have enhanced exfoliation
of the outer shell. The perlite was introduced to the urea/corn
starch mixture in a second pugmill with its double shaft running at
72 rpm for a tip speed of 0.98 ft/sec. The temperature of the
perlite-urea/corn starch mixture was controlled by a steam jacket
at 271.degree. F. through the use of 45 psia steam. The urea/corn
starch mixture was prepared by melting granular urea and diluting
it with water to 95% solution in the same mix tank as corn starch
was homogenously blended into the mixture. The homogenizer operated
at 3130 rpm and was powered by a 2 hp motor. The mixing was done in
a semi-continuous manner. Residence time in the mixing tank was
about 14 minutes during which it was under constant homogenization.
Every 3 to 4 minutes, some of the mixture was withdrawn from the
mixing vessel and put into a pump tank to provide continuous feed
to the pugmill absorber. Once the withdrawal had occurred,
additional amounts of urea and water to give a 95% urea solution
were added to the mix vessel and corn starch was gradually poured
into the vessel. The steam to the melter was 115 psia; however,
temperatures of the mixing vessel was controlled at 269.degree. F.
In another change from Example 2, the perlite-urea/corn starch
slurry leaving the absorber was sprayed by means of a steam eductor
onto a rolling bed of granules in a rotating drum. The second
pugmill mentioned in Example 2 was removed and the recycle and
slurry were fed directly to the 4 ft dia. drum which was rotating
at 15 rpm. Feed rate of urea .RTM. 95% solution was 100.8 lb/hr
with a corn starch feed rate of 1 lb/hr. Perlite fed at 4.2 lb/hr
and recycle was fed back to the granulation drum at 27 lb/hr. Bed
temperature within the granulation drum was controlled at
217.degree. F. by means of blowing hot air at 227.degree. F. onto
the rotating bed. Material discharged by the drum was fed to a
vibrating type screener for separation into product, oversize, and
undersize. The undersize and oversize milled by a knife-bladed
hammermill was fed back to the drum. Granulation was excellent,
forming spherical granules and very little oversize. The product
size granules of -6+10 Tyler mesh (3.4 mm to 1.7 mm in diameter)
size were dried and found to have a bulk density of up to 43
lb/ft.sup.3. In the soil burial tests previously mentioned, 33%,
16%, and 6% of the urea remained in the perlite after 9 hours, 24
hours, and 3 days, respectively. After drying the product, actual
perlite content was 5.2% and corn starch was 1%. Nitrogen content
of the product was 43+%. The hardness (crushing strength) of the
urea by the recognized TVA crushing strength test as taught by TVA
Bulletin Y-147 was 9+ lbs of force for -6+7% Tyler mesh (3.4 mm to
2.8 mm in diameter) granules. Gel formation around and within the
granules however, did not appear as good as the laboratory products
when they were viewed as submerged in a watch glass filled with
water and with a surface stereo microscope. The individual perlite
particles separated to a larger extent than normal while in water
rather than being bound together by the gel.
EXAMPLE 8
[0100] Using the same equipment as in Example 7 but with
alterations to the operating conditions, the good gelling
properties reappeared in the final product. The same feed rates
were maintained as in Example 7 and the same method of operation
was used for enhanced exfoliation. However, the pugmill rpm was
reduced to 97 rpm and thus the tip speed was reduced to 2.5 ft/sec.
The temperature maintained in the urea melting and corn starch
homogenization steps were reduced; mix tank retention time was
reduced to 31/2 minutes and homogenization was reduced from 14
minutes to 1 minute. Temperatures in the mix tank were reduced to
258.degree. F. and that in the pump tank to 262.degree. F. The urea
melt temperature fed to the mixing vessel was reduced to
283.degree. F. and the pugmill absorber temperature was reduced to
266.degree. F. The temperature to the perlite steaming pugmill was
reduced to 313.degree. F. Steam pressure in the slurry venturi
nozzle was operated at 30 psig. The resulting bulk density of the
-6+10 Tyler mesh product was 39 lb/ft.sup.3. Urea remaining after 9
hours in the perlite after the soil burial tests was 44%, 10%, and
4.5% for 9 hours, 24 hours, and 3 days, respectively.
EXAMPLE 9
[0101] A 95% urea solution was homogenized to contain 1% corn
starch and then for the most part absorbed by perlite equal to 4.5%
of the final product in the same equipment as in Example 7.
However, the granulation of the material was done by spreading the
molten slurry onto the bed of the rotating drum by hand through use
of a ice scoop of the open-top half-pipe style. The scoop allowed
the material to be distributed across the rolling bed of the drum
simulating a course spray discharge longitudinally across the
rolling bed and falling curtains of particles as presently
experienced in the large drum of a urea granulation plant.
Otherwise the manner of operation was like that of Example 8. Urea
melt at 100% and about 283.degree. F. was fed to the mixing vessel.
The mixture temperature was varied from 268.degree. F. to
255.degree. F. during the 4 hour operation as water and then corn
starch was blended into it to make the aforementioned mixture. Feed
rates for the urea, water, and corn starch were 111 lb/hr, 6 lb/hr,
and 1 lb/hr respectively. There was essentially no heel left in the
mix tank between blends. Once the blend was made, it was
immediately discharged to the pump tank, thus providing continuous
feed for the absorber. The urea/corn starch mixture was fed to the
absorber along with the perlite which had been further exfoliated
just prior to its introduction to the absorber. About 1 ml of
H.sub.2O per gram of perlite was introduced to the feed end of the
pugmill and allowed to absorb into the perlite. It expanded into
steam in the steam heated pugmill operating at 320.degree. F., thus
further exfoliating the perlite. The absorber was run at from
268.degree. F. to 255.degree. F. as the operation progressed.
Slurry leaving the absorber was discharged to hand operated ice
scoops. The granulation was done in the 4 ft diameter by 18'' long
drum rotating at 3.5 rpm, but increased to 7.5 rpm as the operation
progressed. Some of the absorber discharge was put into a aluminum
sheet and allowed to solidify in a slab. The drum recycle was 33
lb/hr and the temperature of the bed was maintained at between
192.degree. F. to 201.degree. F. using the recycle and the hot air
blower for control. Material from the drum was screened to a
product of -6+10 Tyler mesh and the oversize milled without drying
and recycled to the screen. Undersize was fed to the drum as the
recycle. As the temperature was varied in the homogenizer vessel
from 268.degree. F. to 255.degree. F., the mixture changed from
clear to opaque and the gel strength in the final product as
observed by the stereo microscope increased significantly, as did
the soil burial test results, which went from a urea retention in
the perlite of 33% urea and 13% in 9 and 24 hours respectively, to
a retention of 47% urea and 23% urea in the perlite in 9 and 24
hours respectively, as the test progressed. The bulk density was
acceptable for the entire run but decreased with an increase in gel
strength from 38 lb/ft.sup.3 to 36.5 lb/ft.sup.3.
EXAMPLE 10
[0102] The pilot plant of Example 9 was operated in the same manner
and rates as the best means of Example 9. However, corn starch was
applied at a strength of only 0.5% of the mixture. The resulting
-6+10 Tyler mesh (3.4 mm to 1.7 mm in diameter) product had an
increased bulk density of 39 lb/ft.sup.3 and soil burial result
showed 45%, 16%, and 6% of the urea retained after 9 hours, 24
hours, and 3 days respectively.
EXAMPLE 11
[0103] The pilot plant of Example 9 was operated in the same manner
and rates as the best means of Example 9 except there was no
addition of corn starch. Although the 95% solution of urea was
absorbed by the perlite, it could not be granulated in the drum.
The material was weak and turned to dust in the rotating drum. The
perlite urea slurry was successfully poured out on an aluminum
sheet and solidified as a slab. The material which was poured and
solidified was milled into granules, but it created large
quantities of dust and would be unacceptable in a plant
operation.
EXAMPLE 12
[0104] A 95% urea solution was homogenized with corn starch to give
a 6% corn starch product in the same manner as Example 1, but no
perlite was added. The material was slowly poured on a bed of
rotating granules in a pan granulator and granulated. The resulting
product which contained no perlite was screened to -6+10 Tyler mesh
(3.4 mm to 1.7 mm in diameter) product and had a bulk density of 32
lb/ft.sup.3. In the soil burial, it had a urea retention of 27%,
15% and 6% in the solidified corn starch after 9 hours, 24 hours,
and 3 days respectively.
EXAMPLE 13
[0105] The same test was done as above but had only 1% corn starch
in the final product. The final product of -6+10 Tyler mesh (3.4 mm
to 1.7 mm in diameter) granules had a bulk density of 40
lb/ft.sup.3. In the soil burial tests, urea retention in the
perlite was 10%, 3% and 1% after 9 hours, 24 hours, and 3 days
respectively.
EXAMPLE 14
[0106] Using a standard pressure cooker, but without pressure
development, expanded perlite was moistened with water at 20 ml of
H.sub.2O/18 grams of perlite in the laboratory and the vessel was
heated to exfoliate the perlite. Urea containing the customary 0.3%
to 0.5% formaldehyde used to condition it in most agricultural
operations, was dissolved in H.sub.2O to make a 95% solution. Corn
starch was homogenized into the urea solution at 1% by weight. The
urea/corn starch mixture was poured into the perlite such that the
perlite content was 5% of the dried product and allowed to absorb
the urea formaldehyde/corn starch mixture. The resulting material
was poured onto an aluminum sheet to cool. Then it was crumbled
with a laboratory blender on the chop cycle, screened to -6+10
Tyler mesh and dried. The resulting material had a bulk density of
33 lb/ft.sup.3 and in the soil burial test retained 51% urea, 31%
urea, and 15% urea in the perlite after 9 hours, 24 hours, and 3
days respectively.
EXAMPLE 15
[0107] In the same manner as Example 14, material was produced in
the laboratory where by urea, diammonium phosphate and potassium
chloride were dissolved in water to make an 85% solution of the
nutrients. The solution at 240.degree. F. was added to perlite to
contain 8% of the perlite which had been further expanded in the
manner of Example 14. The resulting product had a nutrient content
of 29% nitrogen, 3% P.sub.2O.sub.5, and 4% K.sub.2O and a bulk
density of 41 lb/ft.sup.3. It showed excellent physical
properties.
EXAMPLE 16
[0108] Established grass plots of 5 ft by 15 ft were all equally
clipped on Aug. 15, 2000 to prepare for the application of
fertilizers. On Aug. 16, 2000, the selected fertilizer blends were
surface applied onto the individual plots. The fertilizer blends
were as follows:
[0109] Commerical-1 Fertilizer (Vigoro) 29-3-4: derived from
polymer coated urea; polymer coated sulfur coated urea, urea,
diammonium phosphate, muriate of potash, ferrous sulfate, and
ferric oxide and containing 7.3% slowly available urea nitrogen
from polymer coated urea and polymer coated sulfur.
[0110] Urea based blend to make a 29-3-4 fertilizer containing:
TABLE-US-00002 Urea = 59.85% Diammonium phosphate = 6.55% Muriate
of potash = 6.45% Ferrous sulfate and ferric oxides = 2.00% Clay =
4.2% Limestone = 20.95% TOTAL = 100.00%
[0111] Commercial-2 Fertilizer (Scotts Turf Builder) 29-3-4:
derived from monoammonium phosphate, urea, methylene ureas, muriate
of potash and containing 8.7% slowly available methylene diurea and
dimethylenetriurea nitrogen.
[0112] Urea-perlite- at 0.92% corn starch based blend to make a
29-3-4 fertilizer which consisted of the base of controlled release
fertilizer as formulated to be:
TABLE-US-00003 Urea: 92.44% Corn starch: .92% Perlite 3-S: 6.64%
TOTAL: 100.00% and which made up 64.75% of the blend the remainder
of the blend containing diammonium phosphate 6.55% muriate of
potash 6.45% ferrous sulfate and ferric oxides 2.00% clay 4.20%
limestone 16.05% TOTAL 100.00%
[0113] Urea-perlite- at 3.60% corn starch based blend to make a
29-3-4 fertilizer which consisted of the base of controlled release
fertilizer as formulated to be:
TABLE-US-00004 Urea: 89.94% Corn starch: 3.60% Perlite 3-S: 6.46%
TOTAL: 100.00% and which made up 66.45% of the blend the remainder
of the blend containing diammonium phosphate 6.55% muriate of
potash 6.45% ferrous sulfate and ferric oxides 2.00% clay 4.20%
limestone 14.35% TOTAL 100.00%
[0114] The application rate for the grass trials was 1 lb of
nitrogen per 1000 ft.sup.2 of surface based on the normal practice
of the lawn care industry. Equal applications of phosphorus and
potassium were contained in all the blends. Each application of
fertilizer was replicated. The fertilizers were watered in
moderately, immediately following the fertilizer application. The
plot diagram in FIG. 6 shows the fertilizer applied by types,
rates, and plot location. Three and four multiple rates of the urea
perlite-0.92% corn starch and 3.60% corn starch containing
fertilizers were applied to some plots as indicated on FIG. 6, to
test leaf burning tendencies of the urea-perlite-corn starch
products and to see the grass yield performance at the higher
application rates.
[0115] The grass was cut on a 7 day interval. The grass cutting
height was established at 3 inches. A moisture meter was used to
determine irrigation requirements. Depending upon soil and
atmosphere temperatures and humidity, the plots were irrigated as
required, approximately three times weekly.
[0116] Visual observation and harvesting of the grass were two
methods used to evaluate the performance of the controlled release
fertilizer.
[0117] A greening rating of each plot was taken each Wednesday
prior to cutting the grass and irrigating. The greening rating was
based on a scale of 1 to 5 with 5 being the best possible and 1 the
lowest rating. At the same time, the grass plots were examined for
any indication of blade damage due to too much fertilizer
availability.
[0118] The grass clippings were weighed after each cutting. One
grass sample from each type of fertilized plot was analyzed for the
nitrogen content each week.
[0119] The grass greening test data is shown by plots and
fertilizer types and rates in Table 2. The first greening rating
was made on Aug. 23, 2000 exactly one week after the fertilizer
application was made on Aug. 16, 2000. The urea-perlite-0.92% corn
starch and urea-perlite-3.60% corn starch based fertilizers
produced a quick greening of the grass and continued to perform in
an excellent manner until the killing frosts of October 8.sup.th
and 9.sup.th. In particular, the fertilizers containing the
urea-perlite-0.92% corn starch based blend maintained an excellent
rating and at the conclusion of the trial on Oct. 11, 2000, had an
average rating of 3.27 on the A-4 plot and a 3.67 average rating on
the B-6 plot. This was overall superior to any other tested
fertilizer when applied at the rate of 1 lb for nitrogen per 1,000
ft.sup.2 of surface. There was never any evidence of blade damage
due to excessive availability of the fertilizer.
TABLE-US-00005 TABLE 2 GRASS PLOTS GREENING TEST DATA.sup.1,2,3,4
Aug. 23, Aug. 30, Sep. 6, Sep. 13, Sep. 20, Sep. 27, Oct. 04, Oct.
11, Plot # Plot Description 2000 2000 2000 2000 2000 2000 2000 2000
SUM AVG A-1 Commercial-1 Fertilizer 2.68 2.33 3.00 3.55 3.10 2.33
2.65 1.50 21.14 2.64 29-3-4 (1X) A-2 Urea Blend (29-3-4) (1X) 2.93
2.50 2.93 3.68 3.00 2.35 2.65 1.50 21.54 2.69 A-3 Commercial-2
Fertilizer 2.73 2.45 2.80 3.68 3.05 2.25 2.30 1.50 20.76 2.60
29-3-4 (1X) A-4 Urea-Perlite, at 0.92% 3.23 3.95 4.08 4.23 3.65
2.85 2.65 1.50 26.14 3.27 Corn Starch (29-3-4) (1X) A-5
Urea-Perlite, at 0.92% 4.45 4.43 4.55 4.68 4.13 3.32 3.20 1.50
30.26 3.78 Corn Starch (29-3-4) (4X) A-6 Urea-Perlite, at 0.92%
3.50 4.20 4.65 4.68 4.25 3.45 3.30 1.50 29.53 3.69 Corn Starch
(29-3-4) (3X) A-7 No Fertilizer 2.45 2.25 2.28 3.00 2.93 3.60 3.60
1.50 21.61 2.70 B-1 Urea-Perlite, at 3.60% 3.25 2.70 2.88 3.75 3.23
2.88 3.70 1.50 23.89 2.99 Corn Starch (29-3-4) (1X) B-2
Urea-Perlite, at 3.60% 4.23 4.55 4.43 4.63 4.03 3.43 3.90 1.50
30.70 3.84 Corn Starch (29-3-4) (4X) B-3 Commercial-1 Fertilizer
2.95 2.55 2.88 4.05 3.03 3.00 3.15 1.50 23.11 2.89 29-3-4 (1X) B-4
Urea Blend (29-3-4) (1X) 3.00 4.03 3.78 4.05 3.65 3.18 3.25 1.50
26.44 3.31 B-5 Commercial-2 Fertilizer 2.88 4.18 4.00 4.05 3.58
3.23 3.13 1.50 26.55 3.32 29-3-4 (1X) B-6 Urea-Perlite, at 0.92%
3.75 4.33 4.30 4.38 3.83 3.50 3.80 1.50 29.39 3.67 Corn Starch
(29-3-4) (1X) B-7 Urea-Perlite, at 0.92% 4.48 4.75 4.93 4.85 4.15
4.00 4.30 1.50 32.96 4.12 Corn Starch (29-3-4) (4X) C-1
Urea-Perlite, at 0.92% 4.00 4.20 4.33 4.55 4.00 3.52 4.00 1.50
30.10 3.76 Corn Starch (29-3-4) (3X) C-2 Urea-Perlite, at 3.60%
3.63 3.98 4.13 4.35 3.35 2.95 3.90 1.50 27.79 3.47 Corn Starch
(29-3-4) (1X) C-3 Urea-Perlite, at 3.60% 4.25 4.60 4.80 4.75 4.13
3.48 3.90 1.50 31.41 3.93 Corn Starch (29-3-4) (4X) Note .sup.1A
(1X) application rate is 1 pound of nitrogen per thousand square
feet, 3X and 4X are 3 and 4 pounds of nitrogen per 1000 square feet
respectively Note .sup.2The ratings were made on seven day
Intervals Note .sup.3Visual observation are on a scale of 1 to 5 (5
being the highest rating) Note .sup.4Fertilizer application was
applied on Aug. 16, 2000
[0120] The cumulative wet weight grass clipping weights for the
replicated plots are shown in Table 3. The urea-perlite and 0.92%
corn starch based blend at 1.times. application rate, at the
conclusion of the trials on Oct. 11, 2000, had 97% more total
weight produced than that produced by the urea based blend, 108%
more than that produced by the Commerical-1 fertilizer 29-3-4
blend, and 48% more than that produced by the Commerical-2
fertilizer 29-3-4 blend. In addition, the urea-perlite-0.92% corn
starch based blend maintained superior grass growth over the entire
duration of the eight week test.
[0121] In Table 3, the first number is the combined weights and the
second number is the cumulative weights. The no fertilizer plot did
not have a replicated plot.
TABLE-US-00006 TABLE 3.sup.1,2,3,4,5,6,7,8 GRASS CLIPPING
DATA(GRAMS) Aug. 23, Aug. 30, Sep. 6, Sep. 13, Sep. 20, Sep. 27,
Oct. 4, Oct. 11, PLOT DESCRIPTION.sup.9,10 2000 2000 2000 2000 2000
2000 2000 2000 ZERO FERTILIZER 15 54/69 38/107 66/173 53/226 54/280
18/298 6/304 UREA (29-3-4) (1X) 82 192/274 215/489 270/759 102/861
101/962 53/1015 13/1028 COMMERCIAL-1 FERTILIZER 65 150/215 198/413
266/629 147/776 142/918 48/966 6/972 (29-3-4) (1X) COMMERCIAL-2 123
260/383 324/707 338/1045 162/1207 101/1308 60/1368 5/1373 LAWN
FERTILIZER 29-3-4 (1X) UREA-PERLITE, AT 0.92% CORN STARCH 228
481/709 497/1206 428/1634 145/1779 162/1941 75/2016 10/2026
(29-3-4) (1X) UREA-PERLITE, AT 0.92% CORN STARCH 487 1790/2277
1406/3683 1026/4709 465/5174 350/5524 79/5603 33/5636 (29-3-4) (4X)
UREA-PERLITE, AT 0.92% CORN STARCH 66 600/666 1094/1760 919/2679
469/3148 264/3412 111/3523 23/3546 (29-3-4) (3X) UREA-PERLITE, AT
3.60% CORN STARCH 146 352/498 445/943 450/1393 142/1535 125/1660
81/1741 5/1746 (29-3-4) (1X) UREA-PERLITE, AT 3.60% CORN STARCH 449
1730/2179 1312/3491 1164/4655 322/4977 272/5249 167/5416 17/5433
(29-3-4) (4X) SOIL TEMPERATURE.sup.4,5 72 69 75 65 66 61 57 52 SOIL
MOISTURE.sup.7 7.4 7.0 7.0 7.4 8.8 10.0 9.0 9.0 NOTES:
.sup.1AVERAGE CLIPPING WEIGHTS FOR THE DUPLICATE PLOTS. THE CONTROL
PLOT WAS NOT DUPLICATED. .sup.2TEST PLOTS WERE FERTILIZED ON AUG.
16, 2000. .sup.3LENGTH OF CUTTING INTERVAL = SEVEN DAYS
.sup.4HEIGHT OF CUTTING = 3 INCHES .sup.5SOIL TEMPERATURE IN DEGREE
FAHRENHEIT (AVERAGE OVER SEVEN DAY PERIOD) .sup.6SOIL TEMPERATURE
HAS A SIGNIFICANT CORRELATION ON 419 TIFTON BERMUDA GRASS GROWTH.
.sup.7CUMMULATIVE WEIGHT FOLLOWS WEIGHT OF CLIPPINGS FOR EACH DATE.
.sup.8SOIL MOISTURE WAS MAINTAINED BETWEEN 7 AND 10 UTILIZING A
SOIL MOISTURE METER. .sup.9REFERS TO BASE MATERIAL USED IN THE
N--P--K BLEND WHICH WAS APPLIED TO THE DUPLICATE PLOTS .sup.10ALL
FERTILIZERS WERE BLENDED TO GIVE A 29-3-4 N--P--K ANALYSIS
The nitrogen concentration data by sample is shown in Table 4.
Besides showing excellent total grass production on each cutting,
the urea-perlite-0.92% corn starch blend at the base application
rate of 1 lb per 1,000 ft.sup.2 maintained excellent nitrogen
content. The test results clearly indicate that the
urea-perlite-0.92% and 3.60% corn starch blends provide the ability
not only to quickly green and then maintain grass green while
preventing blade burn damage, but they also allow tremendous
increase in growth and nitrogen recovery by this grass and most
likely many other grasses as well as other food and foliage
producing vegetation.
TABLE-US-00007 TABLE 4 NITROGEN CONCENTRATION DATA BY
PLOTS.sup.1,2,3,4,5 Aug. 23, Aug. 30, Sep. 6, Sep. 13, Sep. 20,
Sep. 27, Oct. 4, Plot # Plot Description 2000 2000 2000 2000 2000
2000 2000 A-7 No Fertilizer 2.29% 2.15% 2.79% 2.81% 2.70% 2.76%
2.41% B-3 Commercial-1 Fertilizer 29-3-4 (1X) 2.41% 2.83% 2.79%
2.70% 2.88% 2.68% 2.39% B-4 Urea Blend (29-3-4) (1X) 2.50% 3.02%
3.25% 2.87% 3.05% 2.67% 2.48% B-5 Commercial-2 Fertilizer 29-3-4
(1X) 2.73% 3.19% 3.05% 2.82% 3.00% 2.73% 2.47% B-6 Urea-Perlite, at
0.92% Corn Starch (29-3-4) (1X) 3.46% 3.57% 3.22% 3.20% 3.02% 3.13%
2.85% B-7 Urea-Perlite, at 0.92% Corn Starch (29-3-4) (4X) 4.20%
4.38% 4.19% 3.90% 3.24% 3.91% 3.66% C-1 Urea-Perlite, at 0.92% Corn
Starch (29-3-4) (3X) 3.35% 4.34% 3.70% 3.60% 3.53% 3.39% 3.12% C-2
Urea-Perlite, at 3.60% Corn Starch (29-3-4) (1X) 3.10% 3.31% 3.07%
3.02% 3.11% 2.87% 2.67% C-3 Urea-Perlite, at 3.60% Corn Starch
(29-3-4) (4X) 3.85% 4.18% 4.09% 3.75% 3.93% 3.50% 3.34% Note
.sup.1Fertilizer application was applied on Aug. 16, 2000 Note
.sup.21X application rate represents 1 pound of nitrogen per
thousand square feet Note .sup.3Grass clippings from this duplicate
test plot areas were analyzed for nitrogen content. Note
.sup.4Grass samples analyzed by Thornton Laboratories Tampa,
Florida Note .sup.5Grass clippings harvested on seven day
intervals
EXAMPLE 17
[0122] In the same manner as Example 14, material was produced in
the laboratory where by using a pressure cooker, but without
pressure development, expanded perlite was moistened with water at
20 ml of H.sub.2O per 18 grams of perlite in the laboratory and
vessel was heated to exfoliate the perlite. Urea was dissolved in
H.sub.2O to make a 95% solution. Unmodified wheat starch was
homogenized into the urea solution at 1% by weight. The urea/wheat
starch mixture was poured into the exfoliated perlite such that the
perlite content was 5.2% of the dried product and allowed to absorb
the urea/wheat starch mixture. The resulting material was poured
onto an aluminum sheet to cool. Then it was crumbled with a
laboratory blender on the chop cycle, screened to -6+10 Tyler mesh
and dried. The resulting material had a bulk density of 33
lb/ft.sup.3 and in soil burial tests, retained 61% of the urea
after 9 hours and 30% after 24 hours.
EXAMPLE 18
[0123] Urea was dissolved in H.sub.2O to make a 95% solution. Corn
starch was homogenized into the urea solution at 1% by weight. The
urea/corn starch mixture was poured into a vessel containing
newspaper which had been chopped in a laboratory blender to a near
lint condition. The newspaper was not steamed, wetted, or
pre-heated before being exposed to the urea/corn starch mixture.
The newspaper content was 3.5% of the final product. The resulting
material was poured on an aluminum sheet to cool. Then it was
crumbled with a laboratory blender on the chop cycle, screened to
-6+10 Tyler mesh and dried. The resulting material had a bulk
density of 30 lb/ft.sup.3 and in a soil burial test, retained 46%
of the urea after 9 hours and 17% of the urea after 24 hours.
EXAMPLE 19
[0124] Using a standard pressure cooker but without pressure
development, expanded perlite was moistened with water at 20 ml of
H.sub.2O per 36 grams of perlite in the laboratory and the vessel
was heated to exfoliate the perlite. 700 grams of urea was
dissolved in H.sub.2O along with 3 grams of magnesium oxide such
that the solution became 85% urea. The solution was poured into the
vessel containing the 36 gram of exfoliated perlite and mixed. The
resulting material was poured onto an aluminum foil to harden. The
hardened mixture was crumbled in the laboratory blender and
screened to -6+10 Tyler mesh. The granules were dried. The bulk
density was 28 lbs/ft.sup.3.
EXAMPLE 20
[0125] A urea/corn starch homogenous mixture was prepared in the
laboratory using a 95% solution of urea and homogenizing corn
starch into the urea solution at 265.degree. F. to make a mixture
containing 8% corn starch. The mixture was poured onto a metal pan
and allowed to solidify after which it was crumbled using a
laboratory blender on the chop cycle, screened, and dried. In the
soil burial test, 62% of the urea remained in the corn starch gel
after 9 hours. The products bulk density was 41 lb/ft.sup.3.
EXAMPLE 21
[0126] In the same manner as Example 20, a mixture containing 6%
corn starch was made and granulated by pouring it in a laboratory
pan granulator. The resulting product was screened, dried, and soil
tested. In the soil burial test, 25%, 21% and 15% of the original
urea remained in the corn starch gel after 9 hours, 24 hours, and 3
days, respectively. The products bulk density was 32
lb/ft.sup.3.
[0127] While only a few exemplary embodiments of this invention
have been described in detail, those skilled in the art will
recognize that there are many possible variations and modifications
which may be made in the exemplary embodiments while yet retaining
many of the novel and advantageous features of this invention.
Accordingly, it is intended that the following claims cover all
such modifications and variations.
* * * * *