CA1290585C - Controlled release fertilizer gel composition and process for its production - Google Patents

Abstract

CONTROLLED RELEASE FERTILIZER
GEL COMPOSITION AND PROCESS FOR ITS PRODUCTION

ABSTRACT
Methylene diurea, either alone or as a component of methylene urea polymers acts as a gelling agent for producing a gel composition capable of suspending particles which are insoluble in a liquid medium. Methylene diurea as the gelling agent in a liquid medium can be used to obtain novel gel compositions in the absence of added thickener-suspending agents. The methylene diurea is present in an amount greater than the solubility limit of methylene diurea in the liquid medium and in an amount sufficient to provide a gel for suspending insoluble particles. The process for producing the gel composition includes subjecting a dry methylene urea composition in particulate form to a shearing action in a liquid medium wherein the methylene urea includes an amount of methylene diurea greater than the solubility limit of methylene diurea in the liquid medium. Controlled release nitrogen fertilizer compositions are obtained which exhibit agronomic advantages over conventional fluid nitrogen fertilizers and offer material handling and application advantages over dry forms of fertilizers.

Description

B~i f CONTROL~ED ~ELEASE FERTILIZER
GEL COMPOSITION AND PROCESS FOR ITS PRODUCIION

This inventlon relates to a novel gelllng agent, novel gel compositions prepared without added thickener-suspending agents, a controlled release nitrogen fertilizer composition in gel form, and a process for its productlon.
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~ackground of the Invention Suspension fertilizers are fertilizers in which solids are held in suspension-(prevented from settling) by the use of a suspending agent, usually a swelling type clay. Suspension fertilizers are distinguished from slurry fertilizers in which the solids settle rapidly in the absence of agitation to form a firm layer which is difficult to resuspend. Suspensions are further distinguished from clear liquid fertilizers whioh contain all nutrients in a totally dissolved state. Suspensions contain nutrients present in excess o~ their solubility limits as well as totally insoluble materials. This allows for the production of higher fertilizer grades, as well as more varied ratios, and permits the use of less expensive, e.g., less pure, ingredients than is possible with olear liquid fertilizers.
In recent years, the production of suspension fertilizers has grown at a rate faster than any other segment of the fertilizer industry. Factors contributing to thls growth are cost and nutrient analysis, as well as uniformity of fertiiizer mix, handling advantages, and the option to co-apply with components requlrlng low appllcatlon rates. In a good suspension, the mlx 18 uniform throughout the suspenslon. Unlike dry mix rertillzers, suspensions show little tendency toward nutrlent segregation during handllng, storaee and ( 1 ~ 9 0 5 ~ ~ !

appllcation. Because they are a fluld mixture of true solutlon~ and small nutrlent partlcles ln suspension, the 3uspension fertlllzers can be applied more preclsely and unlformly than dry blends Or large fertlllzer particle3. Suspenslons offer ma~or handllng advantages, a~ they are dust free and are easlly moved by pumping, as oontrasted to bag8ed dry rertlllzers whlch requlrs manual handllng. Lastly, suspenslons can often act as carriers for prlmary and secondary elemental agrlcultural nutrients, micronutrlents and pestlcldes whlch must be applled at low application rates. ~These suspension~ not only provlde for uniform appllcatlon, but oftentlmes eliminate the need for multiple applications.
Suspension fertlllzers developed to date are primarily produced with soluble, quick release nutrient sources. These fertilizers can be detrlmental to the safetg of the crop. All soluble rertilizers can also result in substantial losses to the environment which affect~ the efficiency of nutrient uptake. Most common nitrogen sources for suspension fertilizers are quite soluble and have high salt indices. The salt index is a measure Or the phytotoxicity potential of a fertilizer.
The higher the salt index, the greater the potential for plant in~ury due to dessication i.e., burn. Phytotoxic potential has typically been dealt with by using less than desired quantities of fertilizer, requiring repeated applications, or by restrictions in fertilizer placement. The efPiciency Or plant uptake by conventional fertilizers can be limited by substantial environmental losses. ~3ecause of their high solubility, conventional fertilizers are easily leached under irrigatlon practices. Furthermore, since the nitrogen is commonly present in the ammonlacal or nitrate Porm or as urea, there is hlgh potential for additional losse~
tbrough volatlllzatlon or denltrlfication.

1~905~5 ,-( Controlled release nltrogen technolo6ies have been one aYenue to decrease envlronmental lo99 and correspondlngly lncrease the efriclency Or nltrogen uptake by the plant. Because these rertillzers control the rate of nitrogen availabillty, a much greater proportlon ls assimilated by the plant rather than lost to the environment. Control release N-rertilizers pos3es~ low ~alt lndices and are comparatlvely sare to the plants to whlch there are applled. Methylsne ureas, the condensatlon product of urea and formaldehyde, represent one type of controllèd release fertlllzer.
These fertlllzer3 haYe beeD used prlmarlly in dry granular form. The following table lllustrates the relative safety of this type of fertillzer ln terms of salt lndex.
Table 1 Salt Index of Nltrogen Fertlllzers Fertlllzer Source Salt Index Per Equal Welghts Per Unlt of Materials (20~) of Plant (NaN03=100) Nutrlent Ammonium Nitrate 104.7 2.990 Urea 75.4 1.618 Mono Ammonlum Phosphate 29.9 0.485 Methylene Ureas-(Polymer Blend)~ 24.6 0.610 Methylene Ureas-(Ollgomers) MDU~ 29.6 0.697 DMTU 6.9 0.168 TMTU/TMPU 6.6 0.169 TMPU 2.1 0.055 ~MDU = methylene diurea; DMTU = dimethylene triurea; TMTU
- trimethylene tetraurea; TMPU = tetramethylene pentaurea.
~Commerclally avallable dry granules analyzed as containlng: 22.06S Urea, 18.6~ MDU, 7.3~ DMTU, 18.3S
TMTU, and 25.8~ TMPU.

,~, -, ,, ~ .
5' ~90585 ' In recent years, there has been developed a ~mall class of dispers10ns made by the ln-~itu reactlon Or urea and formaldehyde in an aqueous medlum. These dlspers10ns have a low N-P205-X20 (hereafter "N-P-K") analys1s, for example, an 18-0-0 product whlch has nltrogen a3 the only nutrient source. Due to the method Or manufacture, the methylene urea polymerizatlon reactlons may be incomplete resulting ln the presence of unreacted free formaldehyde and un~table intermedlates in the final product. The unreacted resin has been a source Or human sensit1zation and 1s of questionable agronomic value. The low analysis of these products limit the distribution economics Or the product. Urea formaldehyde dispersions of this class are represented by U.S. Patents 4,29B,512 and 4,332,610.
Another class of flowable methylene urea nitrogen fertilizers has been slurried powders. These powders are manufactured by grinding solid methylene ureas to a powder form and slurry1ng the product into water for spray applications. Distribution economlcs are improved with this approach since methylene ureas can be shipped in concentrated dry form to the market place where they are slurried. However, once in slurried form, these products must be kept under constant agitation to prevent settling of the solid particles and the clogging of equipment.
Summary of the Invention lt is accordingly a primary object of the invention to provide a novel gel composition in which the polymer ingredient itself provides the basis for the gel formation, and the composition is not diluted by the addition of other thickener-suspending a~ents.
It is another ob~ect Or this lnventlon to increase the agronomlc efficiency of nltrogen fertilizer suspenslon products.

~ 1~9~5~5, It i3 snother obJect Or thi~ lnvcntlon to provlde a controlled release nltrogen fertlllzer composltlon ln whlch one Or the agrlculturally actlve ingredlents of the composltlon acts as the 3uspendlng agent for other agrlculturally active lngredlents.
It i9 3tlll another ob~ect of the lnvention to provlde a controlled release nitrogen fertillzer compo31tlon ln which one Or the agrlculturally actlve lngredients acts as a carrler ror pestlcldal 10 rormulations.
It 13 still another ob~eot Or thi3 invention to provlde a novel controlled release nitrogen fertilizer composition which can provide both early lnitial and long la3tlng nutrient release in a composition which is relatively uniform and homogeneous and can be applied at con31stent delivery rates by conventional fertillzer appllcation equlpment.
The additlonal ob~ect3 and advantages, and other features of the pre3ent lnventlon wlll become apparent from the appended clalms, the followlng description and the accompanying drawing, ln whlch:
Fig. 1 ls a photomicrograph Or methylene diurea in distllled water, illu3tratlng a suitable 3tartlng material herein ln a liquid medium, at lOOX
magnification;
FiB3. 2 and 3 are graphs Or methylene diurea concentratlon in the liquid medium versu3 Vi3CoQity Or gel compositions in accordance with the present invention, following preparation of the compositionq and two months thereafter, respectlvely;
Fig. 4 is a graph 3howlng the leachlng rates Or several nitrogen source3, from a fallow 30il, lncludlng methylene diurea, dimethylene triurea, a blend of methylene urea polymers, and urea, as the nitrogen sources;

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Flg. 5 1~ a photomlcrograph Or a gel compo~itlon of the pre~en~ lnventlon containlng partlcle~
of in-~oluble components, at 450X magnlflcatlon;
F~g. 6 19 a photomlcrograph Or another gel _ ~ompo~it~on Or the present inventlon contalnlng partleles of ~nQoluble component~, at 450X magnlflcation; and FiB. 7 1~ a photomlcrograph of another gel composition of the pre~ent lnvent~on, at 450X
magnlf~cation.
The ob~ects and adYantage~ of the lnventlon are achleved through the use of methylene dlurea as a gelling agent and by the formation of a gel compo~ltlon of a liquid medium and methylene diurea alone or methylene-urea polymers, in the ab~nce of added thickener-_~. 3uspendlng agents. In the practlee of the lnYentlon, methylene diurea, either in a mixture of polym~r~ or alone i~ to be present in an am~unt greater than the solubility limit of methylene diurea in the llquld medium and in an amount sufficient to provide a gel structure for ~uspendlng the insoluble port~on of methylene dlurea and ~ther insoluble particles.
As referred to bereln, a ~gel structure~ is deflned ~s ~ well ordered system of solute nnd solvent molecules wlth the rlgldlty of the system normally belng nupplled by a hlgh degree of hydrogen bondlng between the molecules. A
st~ndard physlc~l ~ttrlbute of such ~ gel structures ls thlxotropy whlch is deflned ns n ~el-sol-gel transltlon.
~hlxotropy ls characterlzed by substant~al ch~nges ln vlscosity wlth chnngln~ shear rate. Thlxotroplc 3,0 composltlons ~lso exhlblt viscosltles whlch ch~nge wlth tlme ~t const~nt shear ~s the internal order of the system is decre~sed, thus produclng flownble mnterl~ls. Gels tend to lncre~se ln vlscoslty on aglng ~s the structure becomes more ordered ~nd rlgld, thus requlrlng more force to dlsrupt the gel structure. Functlonnlly, the gel structure 15 utlllzed to prevent partlcle settllng ~nd to malntaln : pA~tlcles ~ suspens~on.

~05~S
- 6a -It has now been di~covered thak methylene diurea, either alone or ln a mixture Or methylene urea polymer~, ~uch as the mixture obtained as condensatlon products of urea and formaldehyde, when subJected to structure in a gel shearing action in a liquid medium, can form a gel/
composition without the addition sf thiokener-~uspending agents, if the methylene diurea i~ pre~ent in a sufficient amount. Furthermore, in a preferred embodiment of this invention, the shearing action is combined with heating l0 of the liquid medium to promote formation of the gel structure. Although methylene diurea by itself, which is illustrated in distilled water at a concentration of 0.104 grams in 1.04 ml of water in the photomicrograph in Fig. 1, can be utilized to form the gel compo~itions of the present invention, excellent, usable gel composition~ are obtained u~ing commercially available methylene urea polymer compositions. Suitable starting material for the gel compo3itions Or the pre~ent lnvention include dry, granular methylene urea '~
l~905BS

composltions de3crlbed in U.S. Patent No. 3,705,794, is3ued to ~.H. Czurak, et al. on December 12, 1972, and in U.S. Patent No. 4,37B,238, 1ssued to HarYey M. Goertz on March 29, 1983. These compositions are fully cured urea formaldehyde reslns, and contaln no mea~urable amou~ts of unreacted formaldehyde.
It has been found that methylene dlurea in the amount and as proces~ed as descrlbed herein enables the l~ formatlon of a gel composition in the ab~ence of added thickener-suspending agents. By nthickener-suspendlng agents" are meant those composition~ or compounds known to the art, lncluding swelling agents, which have been used to form, assist in the for~ation of, or to stabilize di~perslon~ again~t syneresis. Typical of the thlckener-3uspending agents which can be avolded in the present invention are clay~, particularly swelling type clays, vegetable gums such as xanthan gum, and cellulose materlal~, such a~ sodium carboxymethyl-cellulose and microcry~talline cellulose.
In the process of the present lnYentlon, the dry, granular methylene urea composition is treated in a liquid medium, which can be considered the liquid pha~e of the composition. The liquid phase can be water or other liquids ln which methylene urea i~ sparingly soluble. As considered herein, the term "soluble"
indicates a component or ingredient which dissolves ln the liquid medium, or that amount of the component or ingredient which is pre~ent up to the solubility limlt of the llquid medium. In the ca~e of a "~parlngly soluble"
component or lngredient, a small portion of the component or lngredlent may be ~oluble, i.e., up to its ~olublllty limit in the llquid medium, but is usually present in a yuantity greater than its ~olubility limit in the liquid medium, and the portion greater than that limit is considerbd "in~oluble" herein. An "insoluble" component or ingredlent may haYe 3ubstantially zero solubility in - a -the llquld medlum and 19 consldered "lnsoluble~ hereln.
In addltlon to water, llquld3 ln whlch methylene diurea 19 sparingly soluble, and are therefore userul ln the present lnventlon, are partlcularly exempllfled by llquld fertlllzers ln whlch methylene dlurea is sparlngly soluble, such as: urea ammonium nitrate, ammonium polyphosphate, ammonium thlosulfate, ammonlum nltrate Rolutlons, urea solutions, ammonium sulrate solutlons, phosphorlc acid, and super phosphoric acid, and nitrogen solutions, and partlcularly aqueous solutions thereof.
In order to obtain the gel composltions Or the present invention, methylene diurea must be present in an amount greater than the solubility limit of methylene dlurea in the liquid medium. The solubility limit of methylene diurea in water has been found to be approximately 2.6 grams per 100 milliliters (ml) of water at 77F. Based upon this determination, as a guideline it is preferred to have methylene diurea present in the liquid medium in an amount above 2.6 grams per 100 ml of the liquid medium, and preferably substantially above that amount. It is recognized that the solubillty limit of methylene diurea ln other llquld media will vary above or below lts solubility in water depending upon the medlum and the concentratlon lf a solution, 3uch as an aqueous solution of the medlum. For example, it has been found that the presence of urea in the liquid medium increases the solubility of methylene dlurea, and additional amounts of the latter wlll be required to be in exce~s of the solubility limit in accordance wlth the invention. As it is believed that the structure or solid phase of the resulting gel composition is in large part determined by the methylene dlurea present, it 19 more preferred to ha~e an amount Or methylene dlurea substantially greater than the solubility limit of the methylene diurea ln the liquid medium, and in an amount sufficient to provlde a gel for suspendlng lnsoluble particles thereln. As it 19 desirable to obtaln a gel ~E;''' ~ i~90585 i oomposltlon whlch 18 pourable or flowable, as wlll be herelnafter defined, lt 19 deslrable to have an amount Or methylene dlurea ln the llquld medlum suff1clent to provlde a pourable or flowable gel upon agltation Or the gel composltion. By experlmentatlon, as a guldellne, lt ha3 been determlned that an amount of methylene dlurea in the llquid medlum at below approxlmately 31 Brams per 100 ml of liquid medium 19 preferable to provlde a gel composltion which is pourable or can be made pourable upon agitation Or the gel compo~ition.
The gel compositlons Or the present inventlon can be produced by subjectlng the dry methylene urça composition ln particulate form to a shearing action in the liquld medlum. The shearlng action in the liquid medium is required, as dry milling, for example by hammer milling or alr mllling, has been found to be insufficlent to provlde the products of the present inventlon. It is believed that reduction of the particle slze of the methylene diurea, and hence the dry methylene urea compositlon contalnlng the methylene dlurea, whlch is the preferred starting material herein, to molecular size achieves the purposes of thls invention. Thus, subjecting the methylene urea composition ln liquid medium to the shearlng action as descrlbed herein ls believed to reduce the slze of the particles to molecular size, whereas dry milllng of the same mixture did not produce particles of even submicron size when subsequently added to water, and the resultlng composition was not a gel composltion Or the present inventlon.
Thus, "shearing actlonn, as deflned herein ln accordance with thls bellef i9 the appllcatlon of force to particles in a llquld medlum. Thls action lncreases the solubllity ln the llquld medlum, and hence causes lncreaslng amounts of the component to enter lnto solutlon and subsequently permlts the crystalllzatlon of the component as an lnsoluble component. Shearlng actlon .' , ', , .

1~9~58S

as applled to methylene dlurea particle9 hereln, 1~ the appllcatlon Or ~ufrlc1ent force to the partlcles ln a liquld medium ln which the particles sre sparingly soluble, to cause a reductlon ln the s1ze Or the particles to molecular ~ize so that lncrea~ing amounts Or the methylene dlurea enters into the Rolution and subsequently recrystallizes to form a gel compositlon with the li~uid medium.
Where mechanlcal force i8 employed to provide the shearing action utilized herein, it has been found that a mechanical force provided b~ a laboratory blender or a high shear turbine rotating at a speed sufricient to provide a tip speed, i.e. the speed of the paddle or blade at its tip contacting the methylene urea in liquid -~ medium, in the range Or above approximately 2,500 feet per minute provides the desired reduction of the methylene diurea particles. Additionally~ high speed centrifugal pumps, which provide the de~ired shearing action, can be utilized to provide the de~ired particle ~ize reduction. It is recognized that the shearing action to reduce the size of the particles as described herein may be provided by other mean~, for example, non-mechanical means.
The choice of the apparatus to provide the shearing action does not appear to affect the quality of the gel /obtained, but may affect the time required to achieve the desired gel composition. The formation of the gel composition can be visually observed with the viscosity of the gel composition increasing with the time the methylene urea composition ln liquid medium is sub~ected to the action. It has been found that the preferred compositions have a viscosity Or from about 100 centipoises to about 5,500 centipoises. Gel compositions of the present invention having a vlscosity at the lower portion of the range are found to be stable and homogenous and retain their flowability, whereas gel B

compositions hav~ng a viscos~ty at the upper portion of the range are lmilarly ~table and homogenou~, but may tend to be non-flowable when stored, and upon agltatlon, again become flowable.
Fig 2 illu~trates the relation~hip bet~een the amount of methylene diurea in the composition and the viscosity of the composition following halting of the shearing actlon, while Fig. 3 illustrates the same relationship after the compo~ltions have been stored for two months. In the~e figures, the concentration of methylene diurea (MDU) i8 shown i~ grams of methylene diurea per 100 grams of liquid phase, i.e. of liquid medium; and the viscosity of the composition is expressed in centipoises.
The viscosity of the gel composition produced in accordance with the present invention will increase with increa~ed processing temperature. The apparatus for providing shearing action, particularly mechanical apparatus therefor, will usually cause an increase in the temperature of the composition as the shearing action progresses. Thus, while temperature of processing, like the time of processing, affects the viscosity of the gel composition, these factors can be readily controlled by observing the change in or measuring the viscosity of the composition during processing. However, it is to be noted that in order to enhance the formation of a gel structure in the gel compositions of this invention, it is preferred to subject the liquid medium containing a requisite amount of methylene diurea to a combination of both shearing action and heating ~f 1.)~905~3S
- lla -It i~ believed that the gelling aBent Or the present invention and the gel composition~ produced therewith, occur due to the limited solubility of methylene diurea in the liquid medium. The shearing action heretofore defined iQ believed to reduce the particle size of the dry polymer particle~, thereby maximizing the solid/liquid interfacial area. In accordance with thi~ theory, as the particle ~ize de¢reases to molecular ~ize, increasing portions Or methylene diurea in contact with the llquid medium di3sol~e into solution, creating an equilibrium with the ~olid phase of particles Or methylene diurea and other ., .,..i OS&15 lnsoluble portionQ Or ingredients or lnsoluble lngredients. In this equilibrium, it 19 belleved that methylene diurea molecule~ are continually golng ~nto solution and crystallizlng out of solution lnto the solid phase. The crystal~ thu~ formed are belleved to create a or gel structure lattlce framework/whi~h entraps other solld partlcles, preventing the latter from settllng. The latt~ce or gel structure framework /contlnues to prevent the ~olld particles from settllng upon storage of the composition, although ir the composition is sufficiently viscous, the composltlon wlll not be pourable or flowable. However, up~n agitation of the composition, it is believed that the lattice framework is broken, which reduces the apparent viscosity and allows movement, -quch as the flowing of the composition, and permits its application as if it were a liquid, for example by spraying.
The belief that the methylene diurea particles, either alone, or ln a blend of methylene urea polymer~
upon processing in accordance with the present invention enter into solution and crystallize out of solution as a solid phase creating a lattice framework, is shown in the photomicrographs in Figs. 5-7. The~e photomicrograph~ of composltions of the present invention are prepared from commercially available methylene urea granular compo~ition3 and liquid media, which are as described - herein and which, will be described in further detail.
In accordance with the present invention, a gelling agent for producing a gel composition capable of suspending particles which are insoluble ln a liquid medium, is obtained by providing methylene diurea capable of being reduced to molecular size in a liquld medium in an amount greater than the solubllity limit of methylene diurea in the llquid medium. The gelling agent can be utilized in the same manner that swelling clays, for example montmorillonite clay, is utilized to form suspension~ of other ingredients which are insoluble in the liquid medium. The gelling agent of the invention is ~90585 partlcularly useful ln prepar1ng agrloulturally actlve suspenslon~, as the methylene dlurea gelllng agent 19 ltself agriculturally actlve as a source Or controlled release nltrogen.
The controlled release fertlllzer gel 5 composltlon of the present lnventlon 19 partlcularly U9erUl, 18 agronomically advantageous, and results ln reduced loss to the env~ronment as compared to the conventlonal 11quld fertlllzers. In additlon, thç
fertillzer gel composltlon Or the lnventlon provldes advantages ln materlal handling and in appllcatlon over dry forms of fertilizer. Moreover, as the release of nitrogen from the fertilizer gel composition described herein is controlled, the fertillzer possesses a low salt lndex and is found to be very safe to the plants to wh1ch they are applled.
These controlled release fertllizer gel composltions are advantageous as they permit the development of prescriptlon fertilizer rormulas tailored to the nutrient reguirements of the crop and the nutrient deficiencies Or the soil. In thls regard, the insoluble or solid phase of the composition can include virtually any agrlcultural chemical, ranging from insoluble methylene urea polymers, to agrlculturally actlve phosphorus and potasslum, and secondary nutrlents, mlcronutrients, pesticidal materlals, such as herbicides and fungicldes, and the like.
The fertilizer gel compositions are also particularly useful ln the productlon and appllcatlon of base suspensions. "Base suspensions", as used herein, are composltions of the present inventlon which can be stored over long periods of time, and then can be applied as the final fertilizer composition, or can be blended with addltional materlals shortly before applloation. By utlllzing agitation prior to applicatlon, these composltlons, even after long periods Or storage, become flowable or pourable, and can be applied as a liquid ,~ - .

' ,.-. ~

~ ~05~5 fertlllzer, for example by varlous appllcatlon technlques whlch may range from boom spray appllcatlon, to soll inJection, to 3trip band drlbble, to fertlgatlon, l.e., appllcatlon through irrigation systems.
Application of these composltions, partlcularly through fertlgation, ls partlcularly useful ln applicatlons which have preYlously recognlzed the value of controlled release nltrogen ln fertillzatlon. For example, the compositlons are particularly useful ln turf fertilization, including lawn care service by liquid spray application and in fertilization of golf courses by fertigatlon. Ornamental plant productlon addltionally utilizes fertigation as a labor saving means of metering nutrients to the plants, and while with previously utilized fertilizers a large portlon of the nutrients were leached to the environment, application Or the compoqitions of the present invention significantly reduce the 1088 to the environment through leachlng while belng particularly amicable to the meterlng of nutrients by fertigation. The signiflcant reductlon of the 1088 Or nutrients through leaching is illustrated in Fig. 4 of the drawing, wherein urea was found to have the hiehest leaching rate, methylene diurea 1MDU ) and dimethylene triurea (DMTU) the next highest, but considerably lower leaching rate, and a blend of methylene urea polymers having the lowest leaching rate.
Detailed Description of Preferred Embodiments The following examples are illustrative of the practice of the invention and of the gel compositions, controlled release fertilizer compositions and process of the present invention. All parts and percentages are by weight unle~Y otherwise lndlcated.

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EXA~IPLE 1 A controlled rele~se fertlllzer oompo31tion ln gel form was prepared from the followlng ingredlents ln the lndlcated amounts:
Water 192.04 lbs.
Ammonium polyphosphate 23.06 lbs.
Urea 66.44 lb~
Methylene urea~ 77 56 lbs Potassium chloride 44 00 lbs ~ reaction product Or urea and formaldehyde prepared in accordance with my U.S. Pat. No. 4,025,329 from a urea-formaldehyde concentrate, such ~as UFC-85, which is supplied by Georgia-Paciric Corporation, Atlanta, Georgia U.S.A., and contains approximately 25 percent urea and 60 percent formaldehyde.
The reaction product, as dry granules, contained the following as a percentage by weight in the starting material:
Urea 14.32~
Methylene Diurea 14.93%
Dimethylene Triurea 11.21 TMPU 38 07~
TMTU = trimethylene tetraurea; TMPU = tetramethylene pentaurea.
The liquld phase comprising the water and polyphosphate were added to a 40 gallon mixer equipped with a 20 horsepower high shear turbine. The urea was added with the turbine rotating at 2100 rpm (5000 ft. per minute tip speed). The dissolution Or the urea ln the liquid phase decreased the temperature from 70F to 60F, at which time the dry granular methylene urea was added with continued high shear turbine rotation. After 10 minutes, the potasslum chloride was added to the mixer.
The high shear turblne rotation was contlnued for a total of 45 mlnute~. The resultlng gel composltion had a Yl~coslty of 240 centipolses and an average partlcle size of 4.5 mlcrons. After two months the composltion had a Ylscoslty Or 848 centipoises.

,.' , , ~, 5~3~

The controlled rel~ased gel composltlon thus prepared was a 16-2-6 N-P-K controlled release fertlllzer deslgned for turf appllcatlons, derlving approxlmately 30% Or lts nltrogen from controlled release sources ln the composition.

Eight gel compositlons were prepared using the same technlque as in Example 1, but wlth varled amounts of methylene diurea in each formulation. Upon processing each of the formulation~ as ind~cated in Example 1, suitable gel compositions were obtained in Example~ 3-9, but as the amount of urea in proportion to the amount of methylene diurea in Example . 2 was quite hlgh, the solubility of the latter was lncreased 90 that insufficient methylene diurea was present, and a stable homogeneous gel composition was not formed. Example 4 is the same as Example 1 above. The vlscoslty Or the resultant compositions obtained, and the urea and methylene diurea content Or each example are as follows:
Viscosity Example Urea NDU Initial 2 Months 2 45.7 5.5 44 80 3 47.8 11.4 252 528 4 36.5 5.3 240 848 38.7 8.1 297 936 6 38.9 8.5 319 1004 7 45.8 10.1 348 1208 8 40.9 16.3 1584 2048 9 -34.1 19.7 2182 2822 Urea and methylene diurea content (MDU) expressed in grams per 100 grams liquid, and viscosity measured in centipoises.
Example 2 never attained adequate viscosity to - suspend the insoluble portlon of the rormulation.
Examples 3-9 formed 3table gel compositlons which retalned lnsoluble components in suspen~ion.

l~()sas Illustrative Or the use of the gelling agent Or the present inventlon to form stable compo~itions wlth liquid~ other than water, and particularly with common agricultural liquid rertilizers, compositions were prepared using a methylene urea reaction product, as dry granules, contalning the following percentage by weight:
Urea 43.0~
Methylene Diurea 19.0S
Dimethylene triurea5.0 TMTU 15.0~
TMPU `18.0%
TMTU - trimethylene tetraurea; TMPU = tetramethylene pentaurea and the following liquid ingredients in the proportion indicated below:
% Methylene Example Liquid ~ Llquid Urea Urea Ammonlum Nitrate (UAN) 70 30 11 Ammonium Polyphosphate (APP) 80 20 12 Ammonium Thiosulfate (ATS) 70 30 25 13 Ammonium Nitrate (AN) 70 30 14 Ammonium Sulfate (AS) 75 25 Phosphoric Acid (PA) 65 35 Proce3sing as set forth in Example 1 using an Oster Blender for 5 minutes having an impeller tip speed of 5367 feet per minute, yielded stable gel compositions having the following N-P-K analysis and percent controlled release nitrogen, with the analysis of the liquid medium being shown for comparison:
N-P-K-S N-P-K-S~~ of Nitrogen as AnalysisAnalysis Controlled Exa~ple Liquid MediumComposition Pelease 11 APP 10-34-016-27-o 35 ,~. -, , , . ,, , !

l'~9~ 85 - lB -13 AN 20-0-0 26-o-o 32 14 AS 8-o-o-9 16-0-0-7 44 s ~N-P-K-S = N-P205-K2O-S analy3ls As heretofore noted, the analysis of the final product can be tailored for a speciric application to include additional amount3 of prlmary nutrients, secondary nutrients such as calcium, magnesium and sulfur, and micronutrients such as zinc, copper, iron, manganese, molybdenum and boron, by in~corporating compounds contalning these elements, as will be hereinafter exemplified.

15 The relationship Or the processing temperature to the viscosity and gelling Or the composition was illustrated by measuring the temperature, visually observing the composition, and determining the viscosity of the composition periodically during processing. In this example, 96 lbs. Or methylene urea reaction product, as dry granules, containing the rollowing in percentage by welght:
Urea 36.97%
Methylene Dlurea 22.83%
2S Dimethylene Triurea 8.21~
TMTU 10.06%
TMPU 21.93~
TMTU = trimethylene tetraurea; TMPU = tetramethylene pentaurea and 224 lbs. of urea ammonium nitrate solution having a N-P-R concentration Or 32-0-0, was placed in a 40 gallon Bard Yac-U-Max high ~hear blender. The temperature of the mixture was lnltially recorded. Thereafter, at ten minute lntervals, one quart samples were withdrawn and 1~051~35 the temperature measured. Thle v13cos1ty Or each 3ample was determined after coollng using a Brookfleld Vlscometer. The temperature Or the content~ Or the blender and the visco~lty Or the samples are presented below:
Vi3cosity Cp9 Sample Temperature F at 25C
Initlal (0 min.) 66 0 10 minutes 88 1700 10 20 minutes 120 3150 - 30 minute3 148 4800 40 minutes 172 ~ ~ot measureable The temperature lncrease occurred due to the shearing action, and no external heat was applied. The viscosity and gelling is believed to be obtained due to the increase in solubility Or the methylene diurea in the polymer blend through the shearing action and the increase in temperature.

The necessity of the shearing action ~n forming the gelling agents and gel compositions of the present invention is demonstrated in Examples 17 - 19 wherein the same dry granular methylene diurea was differently pro¢essed and the resultant mixtures or composition visually observed and their viscosity measured.

In this example, 175 grams Or the methylene urea reaction product described in Example 16 was hammer milled and placed with 525 grams Or di3tilled water in a 600 ml beaker. The ingredients were stirred with moderate agitation for five minute3. The solid particles di3persed wlth 310w stirring, and settled after the stirring was halted. The average particle size Or the lnsoluble portion wa3 determined to be approximately 100 ,~". - .

, . . .
. . . f , .-`.

, 1~905~35 !

microns. The resultant mixture appeared to dupllcate the commerclally available methylene urea fertlllzer in powder form whlch i3 mixed with water in a tank for spray appllcatlon, and began to settle following halting of the agitation.

EXAMPI.E 18 In this example, 175 grams of the methylene urea specified in the preceding example was air milled and placed with 525 grams of distilled water in a 600 ml beaker. The mixture was stirred ~ïth moderate agitation for five minutes. The particles of air milled methylene urea, which had a particle size of 4-5 microns, disper3ed in the water with agitation, but slowly settled following halting of the agitation.

In this example, 175 grams of the methylene urea specified in the two preceding examples were placed in 525 grams of distilled water in a Ross Laboratory blender. The blender was actuated for five minutes. The blender was determined to have a tip speed of 2,663 feet per minute. The resulting composition was a gel composition in accordance with the present invention, as noted below.
The viscosity of the mixtures or composition obtained in Examples 17 - 19 was determined with a ~rookfield Viscometer after blending, and the rate of settling out of each mixture or composition was recorded as the percent of clear solution at the time intervals noted below:
S of Clear Viscosity Solution After ExampleCp8 at 25C 1/2 hr.1 hr 1-1/2 hrs. 2 hr~.
17 20 44.1 50.0 50.0 52.9 18.20 8.8 20.6 26.5 32.4 19 510 0.0 0.0 0.0 0.0 1~90S85 Example3 17 - 19 demonstrate that the rormation of a homogeneous gel, and obtalnlng a vlscoslty withln the desired range i9 obtained only upon the methylene urea belng 3ub~ected to 3hearlng ln a liquld media ln whlch methylene dlurea ls only sparlngly sDluble.

This example lllustrates the manufacture Or the gel composltlon of the present lnvention ln commercial equipment, and the use of a common agrlcultural llquld fertilizer as the l~quld medium for~the ¢omposition. The composition was manufactured in a Vac-U-Max 60-1600-30 blender, which is a 1600 gallon mixing vat equipped wlth a 60 horsepower high shear turbine and a 30 horsepower centrifugal recirculatlng pump. 7200 lbs. of urea ammonium nitrate solution, at a N-P-K analysis of 32-0-0 was pumped into the vat. The hlgh shear turbine was actuated and 2800 lbs. of dry methylene urea of the oomposition defined in Example 1 were added by conveyor to the top of the mixing vat at a rate of 133 lbs. per minute. The contents of the vat were mixed under high shear for a total of two hours. At the end of this time, the viscosity of the resultant composition was sufricient to hold particulate matter in suspension and of a particle size suitable for in~ection into irrigation systems. The contents of the vat were pumped to a ~torage tank, where it was held successfully for four months without settling. The viscosity of the composition was determined to be 900 centipoises with a particle size of 99% of the compositlon smaller than 45 microns. The product was analyzed to have a N-P-~analysis of 34-0-0 with 20% of the total nltrogen derived from methylene urea polymers.

' ~90~35 !

Thls example lllustrates the oapabillty of the gel composltions Or the present lnventlon to create pre~crlption fertlllzer rormulas, l.e. formulas tallored to the needs of speclfic plants and ~oll condltions. The partlcular composltlon noted below wa~ created to meet the nutrlent requlrements for potato productlon ln a partlcular 80il, and was designed to have the following fertilizer requlrements:
Nutrlent Pounds per Acre N 100.~00 P20580.00 K20150.00 S 30.0 Zn 5.00 Cu 1.00 Fe 1.65 B 0.50 A~ in the previous example, the composition was manu~actured in a Vac-U-Max 60-1600-30 blender. The ingredient~ and order of their addition to the vat were as follows:
Water 544 lbs.
APP 10-30-03,280 lbs.
AS ô-0-0-9 4,100 lbs.
Methylene ~rea1,400 lbs.
KCl 3,075 lbs.
Ferrous sulfate t20~ Fe)101 lbs.
Solubor (20.5~ B) 30 lbs.
Copper Sulfate (25S Cu) 49 lb~.
Zinc sulfate (36~ Zn) 171 lbs.
APP is a base liquid of ammonium polyphosphate having the indicated N-P-K analy~is, AS is an ammonium sulfate solu-tion having the indicated analysi~, and the methyleneurea was the commercially available dry granular product de~cribed in Example 20.
~ he first three ingredients were added to the mlxer wlth the turbine agltator rotating. The methylene urea was added vla a conveyor at the rate lndicated in the previous example. After 30 minutes, the viscosity of the composltlon was sufficient to prevent settllng of the 1'~90~85 ~

partlculate3. At thls tlme, the potassium chlorlde wa3 added via the conveyor1 and the micronutrlents were added by mean3 Or an eductor ln the reclrculatlon loop. The total process1ng tlme was approxlmately 40 minute3. Due to the short processing tlme, quantlties Or large (30 mesh) methylene urea particles were vlsible ln the composition. The composition was succes3rully applied through soil in~ection equipment in a pre-plant application to potatoes.

EXAMPLE 22~
This example illustrate3 the agronomic advantage of the controlled release fertilizer compositions Or the present invention over conventional fertilizer3 containing no controlled release nitrogen.
The compositions produced in Example~ 20 and 21 were utilized in a potato trlal involving both preplant fertilizer application as well a3 "fertigation", the applicatlon of fertilizer through an irrigation system.
The test comprised three treatments as follows: In Treatment 1, the controlled release composition Or -Example 21 was utilized in a preplant application and the controlled relea3e composition Or Example 20 applied by fertigation. In Treatment 2 the fertigation application was the same as in Treatment 1, but urea ammonium nitrate - 25 solution (32-0-0 analysis) was substituted for methylene urea in the formula of of Example 21. Treatment 3 was the grower's standard fertili~ation practice, and utilized no controlled release nitrogen. In this treatment urea ammonium nitrate t32-o 0 analysis) was utilized instead of methylene urea in both the preplant and fertigation applications. The improvement using the methylene urea controlled release nitrogen composition3 in accordance with the present invention on total yield and grade is presented below:

.

1~9(1 585 Treatment 1 2 3 Methylene Urea Preplant (100 lbN/acre) yes no no Fertigatlon (62.5 lbNJacre) yes yes no lield (cwt/acre)~ 603 541 419 Grade (Percent) Carton3 53.5 34.813.8 10's 32.5 39.741.7 B's 12.7 22.735.8 - lO Culls 1.2` 2~8 8.7 ~Field weights.

To demonstrate the amount of methylene diurea required to form the compositions Or the present inventlon, samples of the formulation Or Example 1 were diluted with water prior to proces3ing with the shearing action applied by means Or the Ross blender described in Example 19. The dilution factor, the methylene diurea concentration, and the visco~ity Or the re~ultant mixture or composition, and the amount Or settling therein after two hours, is shown below:
Dilution Settling SampleFactor MDUViscosity(2 hrs.) 1 50~ 1.88 1 12.5 2 37S 2.54120 0.0 3 25% 3.31130 0.0 4 12~ 4.23350 0.0 0~ 5.34700~ 0.0 MDU = concentration in Brams per 100 grams liquid, viscosity in Cps.
~Viscosity after four months.
Samples Or gel compositlons Or the present invention were examined under a microscope to demonstrate recrystallizatlon Or methylene diurea to the lattlce frame;~?ork ln accordance with this invention. Methylene urea, as set forth in Example 9, was rormulated and ,~. - .

;~ , .
t 1~0585 prepared ln accordance wlth Example 1 at room temperature, and a representatlve portlon of the resultant composltion was placed on a sllde. A
photomlcrograph thereof 19 shown ln Fig. 5. Another S sourcc of methylene urea, as set forth ln Example 6, was formulated and prepared ln accordance with Example 1 at room temperature, and a repre~entative portion of the re~ultant composition wa~ placed on a sllde. A
photomlcrograph thereof is shown ln Fig. 6. It is noted that the lattice framework ln the compositlon shown ln Fig. 6 consisted mostly of fine particles in the order of from about 0.5 to 3 microns, whereas the lattice framework of the composition shown in Fig. 5 consisted of a mixture of intermediate ~nd small partlcles. The difference ln the size of the particles ls believed to result from the dlfference ln the amount of methylene diurea as compared to urea in the starting material and liquid medium, with the hiBher concentration yielding larger particles following processing. Methylene urea, agaln as set forth in Example 9, was processed in accordance with Example 1, except that the temperature of the blending material was heated to approximately 120~ F, and after processing, slowly cooled. A representative portion of the resultant composition was placed on a slide, and a photomicrograph thereof in shown in Fig.
7. The lattice framework of the composition included extensive formation Or needle-like structures approximately 1-30 microns in length, the needle-like structures being similar to those formed (but without the lattice structure) when pure methylene diurea was heated in distilled water without the application Or shearing action, and then rapidly cooled.
In order to determine pourability as discussed herein, as a measure of whether or not a composition can be pumped or treated as a liquid, the following test was utillzed: sample3 stored in 8-16 ounce sample bottle3 were stirred twloe with a stirring rod around the inside ,~,, -.

l~sosa~
- 2~ -~urface of ~he contalnei. The container i9 then inverted downward at a 45 angle for two mlnute~. The percent by volume of the composltlon which flow out of the contalner in one mlnute l~ utilized as the pourabllity index of the materlal. Suitable pourability of the gel compositions of the present ln~entlon ~as determined upon at least 85S Or the composltion flowlng out of the contalner withln one mlnute.
The invention ha~ been illustrated with specific examples of fertillzer compositions. In addition, the invention also resid~s in the gelllng agent provided by methylene diurea and methylene urea compositions which provide gel compositions upon processing as indicated herein. The invention also resides in gel compositions useful to ~uspend lnsoluble ingredients for improved flowability and for other purposes. The controlled release fertillzer gel compositions of the lnventlon are particularly useful as a means o~ conveylng many other nutrients, as well as micronutrients, and control chemicals such herbicides, fungicides and insecticides suspended in the composition for flowable application desired. Examples of other ingredients are shown in the aforementioned U.S. patent~.

Other pesticides whlch may be used are shown in the Pesticide Manual, 6th Edltlon, Briti~h Crop Protection Counsel 1980. Other herbicides which may be used are shown in Weed Control 2d Edition, 1962 Robbins et al., McGraw-Hill Book Company, Inc., New York, NY.
Other ~ertilizer nutrients which may be used in combination are shown in Commercial Fertilizers, 5th Editlon, 1955, Collings, McGraw-Hill ~ook, Inc., New York, NY.

Claims (24)

1. A gel composition comprising:
a gel structure formed by subjecting a liquid medium containing particulate methylene urea polymers in the absence of added thickener - suspending agents to a shearing action, said shearing action comprising the application of force to the particles in said liquid medium, said methylene urea polymers in said liquid medium including methylene diurea particles in an amount greater than the solubility limit of methylene diurea in the liquid medium and in an amount sufficient, upon subjecting said methylene diurea particles in said liquid medium to said shearing action, to provide a gel structure for suspending insoluble particles therein, and said methylene diurea particles being subjected to sufficient force by said shearing action to cause a reduction of the size of the methylene diurea particles to molecular size whereby the methylene diurea enters into solution and subsequently recrystallizes from said liquid medium substantially in crystalline form to form said gel structure with said liquid medium.

2. The gel composition as defined in claim 1 wherein the amount of methylene diurea is sufficient to provide a pourable gel upon agitation of said gel composition.

3. The gel composition as defined in claim 1 wherein said composition contains particles which are insoluble in said liquid medium and which are suspended in said composition.

4. The gel composition as defined in claim 1 wherein said composition contains at least one component in addition to methylene diurea and which is insoluble in said liquid medium.

5. A controlled release nitrogen fertilizer gel composition, comprising:
a gel structure formed by subjecting a liquid medium containing particulate methylene urea polymers in the absence of added thickener - suspending agents to a shearing action, said shearing action comprising the application of force to the particles in said liquid medium, said methylene urea polymers in said liquid medium including methylene diurea particles in an amount greater than the solubility limit of methylene diurea in the liquid medium and in an amount sufficient, upon subjecting said methylene diurea particles in said liquid medium to said shearing action, to provide a gel structure for suspending the amount of methylene diurea above the solubility limit and insoluble particles in said gel structure, and said methylene diurea particles being subjected to sufficient force by said shearing action to cause a reduction of the size of the methylene diurea particles to molecular size whereby the methylene diurea enters into solution and subsequently recrystallizes from said liquid medium substantially in crystalline form to form said gel structure with said liquid medium.

6. The controlled release nitrogen fertilizer gel compo-sition as defined in claim 5 wherein said liquid medium is selected from the group consisting of water, water and urea, aqueous urea ammonium nitrate solution, aqueous ammonium poly-phosphate solution, aqueous ammonium nitrate solution, aqueous ammonium polyphosphate solution, aqueous ammonium thiosulfate solution, aqueous ammonium nitrate solution, aqueous ammonium sulfate solution, phosphoric acid, superphosphoric acid, and mixtures therof.

7. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition as defined includes at least one agriculturally active ingredient suspended in said gel composition, said ingredient being insoluble in said liquid medium.

8. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition in-cludes at least one methylene urea polymer in addition to methylene diurea and which is at least substantially insoluble in said liquid medium.

9. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition in-cludes at least on agricultural potassium source guspended therein.

10. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition in-cludes at least one agricultural phosphorous source suspended therein.

11. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition in-cludes at least one secondary elemental agricultural nutrient-suspended therein.

12. The controlled release nitrogen fertilizer gel composition as defined in claims 5 wherein said composition in-cludes at least one agricultural micronutrient suspended therein.

13. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein said composition in-cludes at least on pesticidal component incorporated therein.

14. The controlled release nitrogen fertilizer gel composition as defined in claim 5 wherein the amount of methylene diureau is sufficient to provide a pourable gel upon agitation of said gel composition.

15. A process for producing a gel composition comprising:
subjecting a dry methylene urea composition in particulate form to a shearing action in a liquid medium in the absence of added thickener - suspending agents to form a gel structure, said dry methylene urea composition including an amount of methylene diurea greater than the solubility limit of methylene diurea in the liquid medium and in an amount sufficient to provide said gel structure for suspending insoluble particles therein, said shearing action comprising the application of force to the particles in said liquid medium including the application of sufficient force to the methylene diurea particles in said liquid medium to cause a reduction of the size of the methylene diurea particles to molecular size whereby the methylene diurea enters into solution and subsequently recrystallizes from said liquid medium to form said gel structure with the liquid medium.

16. The process as defined in claim 15 wherein the amount of methylene diurea in said dry methylene urea composition is sufficient to provide a pourable gel upon agitation of said gel composition.

17. The process as defined in claim 15 wherein said dry methylene urea composition contains particles which are insoluble in said liquid medium.

18. The process as defined in claim 15 where said dry methylene urea composition contains at least one component in addition to methylene diurea and which is at least substantially insoluble in said liquid medium.

19. The process as defined in claim 15 wherein at least one agriculturally active ingredient which is at least substan-tially insoluble in said liquid medium is added to said methylene urea composition and said liquid medium while said methylene urea composition is being subjected to said shearing action.

20. The process as defined in claim 15 wherein at least one agriculturally active ingredient which is at least substan-tially insoluble in said liquid medium is added to said dry methylene urea composition and said liquid medium prior to said methylene urea composition being subjected to said shearing action.

21. The process as defined in claim 15 wherein the amount of methylene diurea comprises an amount greater than the solubility limit of methylene diurea in the liquid medium and less than the amount which provides a solid composition upon subjecting said methylene urea composition to said shearing action in said liquid medium.

22. The gel composition as defined in claim 1 wherein said shearing action is combined with heating of the liquid medium to promote formation of the gel structure.

23. The fertilizer gel composition as defined in claim 5 wherein said shearing action is combined with heating of the liquid medium to promote formation of the gel structure.

24. The process as defined in claim 15 wherein said shearing action is combined with heating of the liquid medium to promote formation of the gel structure.