CA2565490C

CA2565490C - Polyurethane encapsulated fertilizer, herbicide, insecticide or fungicide

Info

Publication number: CA2565490C
Application number: CA 2565490
Authority: CA
Inventors: Donald Charles Mente
Original assignee: BASF Corp
Current assignee: BASF Corp
Priority date: 2004-05-26
Filing date: 2005-05-11
Publication date: 2012-04-24
Anticipated expiration: 2025-05-11
Also published as: EP1768940A1; US7416785B2; US20050266245A1; BRPI0511539A; RU2006145856A; PT1768940T; EP1768940B1; JP2008500254A; WO2005118509A1; CN100567355C; CN1956938A; MXPA06013643A; ES2681892T3; RU2396237C2; CA2565490A1

Abstract

Disclosed is an encapsulated particle which includes a core particle. The core particle includes a fertilizer selected from the group of nitrogen, phosphate, potash, and sulfur, and combinations thereof. The core particle may also include herbicides, insecticides, and fungicides. The encapsulated particle also includes a polyurethane layer disposed about the core particle. The polyurethane layer includes the reaction product of an aromatic isocyanate component and a polyol that is reactive with the aromatic isocyanate component. The aromatic isocyanate component includes methylene diphenyl diisocyanate, toluene diisocyanate, and mixtures thereof. The polyol that is reactive with the aromatic isocyanate component is derived from an aromatic amine-based initiator and includes a toluene diamine. The aromaticity of the aromatic isocyanate component and the polyol serves to insure complete miscibility between the aromatic isocyanate and the polyol thereby forming the polyurethane layer without defects preventing water from permeating the polyurethane layer and dissolving the core particle.

Description

POLYURETHANE ENCAPSULATED FERTILIZER, HERBICIDE, INSECTICIDE OR FUNGICIDE

bACKGROUNb o1 THE INVENTION
1. Meld of The Ihvehtioh [0001] the subject Invention generally relates to an encapsulated particle.
More specifically, the subject Invention relates to an encapsulated particle that includes a polyurethane layer disposed about a core particle and that is Used as a controlled-release fertilizer.

2. bescriptloh of The Pelatpd Art [0002] Encapsulated particles that are used as controlled-release fertilizers are known in the art. Specifically, the encapsulated particles Include layers disposed about core particles. More specifically, the layers that are disposed about the core particles include polyurethane layers. A thickness and external Integrity of the polyurethane lay-ers limit a rate that the core particles dissolve Ih a soil that Includes water arid hiolstUte.

[0003] More specifically, prior art encapsulated particles include a core particle selected froth a group of fertilizer particles. The dlsadvahtages of Using the prior art ehcapsUlated particles include Inconsistent external Integrity and thickness of the poly-urethane layers resulting In a very fast rate that the core particles dissolve In the soil.
As Is known In the art, the very fast rate that the core particles dissolve in the soil leads to phytotoxicity. Additional disadvantages of Using the prior art encapsulated particles Include an inability to effectively customize the thickness of the polyurethane layer dis-posed about the core particle and the requirement of expehsive and perishable rnahU-facturing components, such as castor oil. Castor oil is. utilized for the production of the polyurethane layers serving as a polyoi that Is reactive with an Isocyahate to form the polyurethane layers.

[0004] Specifically, castor oil is subject to unpredictable market price fiuctuatiohs and unpredictable quality control. further, castot oil is perishable and thus Is hot suit-la able for long term storage and Use In Mass production of ehcapsUlated particles. Still further, castor oil contains double bonds In Its lipid structure and Is prone to Ilpid oxida-t1oh. Lipid oxidation occurs when the double bonds In the castor all react with oxygen to form peroxides and change the chemical nature of the castor oil. f=inally, castor oil Is hot aromatic. When serving as a polyol that Is reactive with an aromatic isocyanate to form the polyurethahe layers, castor oil Is hot completely hiisclble with the aromatic isocyahate due to a lack of aromaticity, and thus, is hot suitable tot use.

[0005] Most importantly, the primary disadvantage of the prior art encapsulated particles Includes a tendency to exhibit polyurethahe layers that Include defects. be-fects in the polyurethane layers result from an incomplete miscibility between an Isocy-ahate and a polyol that Is reactive with the Isocyahate to form the polyurethane layers.
Pot example, when an organic, hon-aromatic polyol is combined with an aromatic Iso-cyahate, miscibility may hot be complete. Rather, the organic, hon-aromatic polyol could react with the aromatic Isocyahate only at their Interface.

tOO061 Incomplete miscibility between the aromatic Isocyahate and the hoh-aromatic polyol subsequently leads to polyurethane layers that Include defects such as pits and depressions. When the polyurethane layer that Includes defects is disposed about the core particle, the pits and depressions allow water and other liquids to per-meate the polyurethahe layer and rapidly dissolve the core particle. To cure the de-fects, multiple polyurethahe layers must be disposed about the core particle resulting in a time cohsuming and expensive process.

100071 Many different layers can be disposed about core particles. U.S. Pat.
No.
5,536,531 to Hudson discloses a plurality of water Insoluble, abrasion resistant layers disposed about a core particle that Includes a controlled-release fertilizer.
A first layer is disposed about the core particle and includes a polyurethahe derived from the reaction product of an aromatic Isocyahate and a hoh-aromatic polyol that Is reactive with the aromatic Isocyahate. A second layer, formed from an organic wax, Is disposed about the first layer to cover any defects in the first layer and prevent water and other liquids from permeating the first layer and rapidly dissolving the core particle. the 531 patent does not disclose the use of a polyol derived from an aromatic amihe-based initiator.
t0O08l Similarly, U.S. Pat. No. 6,663,686 to Geiger and U.S. Pub. Nos.
2004/0020254 and 2004/0016276 to Wyhhyk, all assigned to AgriumO' Inc. of Calgary, Alberta, also disclose a polyurethane layer disposed about a core particle.
The '686 patent and the '254 and '276 publications disclose the use of aromatic isocyahates Including diphehylmethahe diisocyahate, toluene diisocyahate, and mixtures thereof.
Additionally, the '686 patent and the '254 and '276 publications disclose the use of noh-aromatic polyols Including castor oil and hydrogenated castor oil. Yet, neither the '686 patent hot the '254 and '276 publications disclose the use of a polyol derived from an aromatic amine-based Initiator.

t0009] Yet, the controlled-release fertilizers disclosed in the '686 patent and the '254 and '276 publications are not the sole prior art. U.S. Pat. No. 3,475,154 to kato discloses a polymer layer disposed about a coated pellet. The polymer layer Includes the reaction product of active hydrogen, In the form of polyols and polyamihes, and an aromatic Isocyahate. The '154 patent does not disclose the use of a polyol derived from an aromatic amine-based initiator.

t00010] :lnally, U.S. Pat. No. 3,264,089 to Hansen and U.S. Pat. No. 4,711,659 to Moore disclose a plurality of polyurethane layers disposed about a core particle. The polyurethahe layers Include the reaction product of an aromatic isocyanate and a polyol. In both the '089 and '659 patents, the aromatic Isocyanate Includes methylene diphenyl diisocyahate, toluene dilsocyahate, and mixtures thereof.
Additionally, In both the '089 and '659 patents, the polyol Includes polyether diols and polyols.
f=urther, in the '659 patent, the polyol Involves reactions with amine-terminating groups.
Yet, hel-ther the '089 patent hot the '659 patent disclose the use of a polyol derived from an aromatic amine-based initiator. Specifically, in the '659 patent, the polyol reacting with the amine-terminating groups Is not equivalent to a polyol derived from an aromatic amine-based Initiator. Namely, in the '659 patent, the polyol that includes amine terml-natlhg groups is hot aromatic and therefore Is hot completely miscible with aromatic isbcyahates. Cohversely, the polyol derived from an aromatic amihe-based ihitiator Is tetmlhated In an alkyl group and hot ah amihe group. Additionally, the polyol derived from an aromatic amihe-based initiator includes amine functionality at the beginning of the alkyl chain. Therefore, the polyol derived from an aromatic amihe-based initiator is fully miscible with aromatic Isocyahates and Is unlike any polyol disclosed in either the '089 patent or the '659 patent.

SUMMAIRY OP THL INVENTION ANb AbVANTAGES

[00011] The subject invention as broadly disclosed provides an encapsulated particle. The encapsulated particle includes a core particle and a polyurethane layer. The polyurethane layer is disposed about the core particle and includes the reaction product of an isocyanate component and a polyol. The polyol is derived from an aromatic amine-based initiator.
The invention as claimed is more specifically directed to an encapsulated particle comprising:
A a core particle comprising a fertilizer selected from the group of nitrogen, phosphate, potash, sulfur, and combinations thereof, a herbicide, an insecticide or a fungicide;
B a polyurethane layer disposed about said core particle and comprising the reaction product of:

3a (1) an isocyanate component wherein said isocyanate component comprises an aromatic isocyanate component, and (ii) a polyol derived from an aromatic amine-based initiator.
Preferably, the aromatic amine-based initiator is of the formula:
hs 112 k3 wherein lR, Includes one of ah alkyl group, ah amine group, ahd a hydrogen ahd each of k2-IR6 ihdepehdehtly ihclude one of an amine group ahd a hydrogeh, so lohg as at least ohe of ki-IRe Is ah amihe group.

CO0O12] The aromatic amihe-based ihitiator provides a polyol that Is completely miscible with the isocyahate cohipoheht. The complete miscibility of the Isocyahate component ahd the polyol that is derived from ah aromatic amihe-based Initiator Is the result of two primary effects. Hrst, the complete miscibility is due to Lohdoh forces that create momentarily induced dipoles between similar aromatic moieties of the polyol arid the Isocyahate compoheht. The momentarily Induced dipoles allow the isocyanate component and the polyol to mix effectively. secondly, the complete miscibility Is due to the planar geometry of the aromatic moieties of the polyol and the Isocyahate com-pohent that allow for complementary stacking of the polyol ahd isocyanate component.
The complementary stacking of the aromatic moieties also allows the Isocyahate com-poheht ahd the polyol to mix effectively.

t000131 The complete miscibility of the Isocyahate component ahd the polyol de-rived from the aromatic amine-based initiator yields Multiple advantages. The complete miscibility results in an ability to Use various techniques for applying the polyol ahd the Isocyahate compoheht onto the core particle. The techhiques include, but are hot lim-ited to, pah coating, fluidlzed-bed coating, co-extrusion, spraying ahd spihhlhg disk ehcapsulatloh. In commercial appllcatioh, practitioners of each of these techniques will experiehce the advantages described by this Invention.

t000141 Specifically, spraying the polyol ahd the Isocyahate component onto the core panicle results in a Uniform, complete, ahd defect-free polyurethane layer dis-posed about the core particle. Spraylhg also results In a thihher and less expehslve polyurethane layer disposed about the core particle. furthermore, the polyol is shelf-stable thereby allowing for More effective storage ahd subsequent Usage.

t000151 The uniform, complete, ahd defect-free polyurethane layer disposed about the core particle allows for slow, controlled dissolution of the core particle in the soil and alleviates a heed for a second layer to be disposed about the polyurethane layer to cover any defects In the polyurethahe layer. because there are ho defects Ih the poly-urethahe layer disposed about the core particle, water and other liquids cannot perme-ate the polyurethane layer and rapidly dissolve the core particle, thus preventing phyto-toxicity.
bETAILbb bbsCIRIlTIoN o1 A pKl=1blIlkbb EMboblMi=NT

t00018J Ah encapsulated particle, according to the present ihvehtioh, ihclUdes a core particle. The core particle preferably includes a fertilizer selected from the group of hitrogeh, phosphate, potash, sulfur, and combinations thereof. Most preferably, the fertilizer is hitrogeh based ahd commercially available from AgriuM Inc. of Calgary, Alberta under the trade name of ESNe Controlled Release Nitrogeh.
Specifically, a fer-tilizer that Is hitrogeh based includes, but is hot limited to, ahhydrous ammonia, Urea, amMohium hitrate, urea ammonium Nitrate, calcium ammohiurn Nitrate, and combina-tlohs thereof. A fertilizer that Is phosphate based includes, but Is hot limited to, phos-phoric acid, mono-ammonium phosphate, ammonium polyphosphate, arnmoniuM
phosphate sulfate, ahd combihations thereof. A fertilizer that Is potash based includes, but Is hot limited to, potash, ammonium nitrate, and combinations thereof. A
fertilizer that is sulfur based includes, but is hot limited to, ammonium sulfate and sulfuric acid, and combinations thereof.

5 t00017] It Is to be understood that alternative forms of core particles can also be used, I.e., core particles that are hot fertilizers. Examples of such alternative forms of core particles Include, but are hot limited to, herbicides, Insecticides, and fungicides.
t00018] The encapsulated particle additionally Includes a polyurethane layer.
The polyurethane layer Is disposed about the core particle. It Is to be Understood that the terminology "disposed about" encompasses both partial and complete covering of the core particle by the polyurethane layer. The polyurethane layer Includes the reaction product of an isocyahate component and a polyol that Is reactive with the Isocyahate component. The Isocyahate compoheht Includes an aromatic isocyahate component.
preferably, the aromatic isocyahate component Includes, but is hot limited to, mono-meric and polymeric methylene diphehyl diisocyahate, monomeric and polymeric tolU-ehe dilsocyahate, and mixtures thereof. Most preferably, the Isocyahate component is commercially available from IBASI= Corporation of Wyandotte, Michigan under the trade name of Luprahatee M20S.
t00019] Polymeric methylehe diphehyl diisocyahates such as Luprahate M20S
offer high crosslihk density and moderate viscosity. Alternatively, monomeric methyl-ene diphehyl dilsocyahates such as Lupranate M Isocyahate offer low viscosity and high NCO content with low nominal functionality. Similarly, toluene diisocyahates such as Luprahate TIJI also offer low viscosity and high NCO content with low nominal functionality. Those skilled In the art will choose a suitable Isocyahate component based on economics and suitability.

t000201 Preferably, the aromatic Isocyahate compoheht has a viscosity from 1 to 3000, more preferably from 20 to 700, and most preferably from 50-300 centlpolse at 25 C. Preferably, the aromatic Isocyahate component has a nominal functionality from 1 to 5, more preferably from 1.5 to 4, and most preferably from 2.0 to 2.7.
Preferably, the aromatic Isocyahate component has an NCO content from 20% to 50%, more pref-erably from 25% to 40% and most preferably from 30% to 33%.
t000211 The aforementioned viscosity, nominal functionality, and NCO content of the aromatic Isocyahate component are preferred because of specific properties that each gives to the aromatic isocyahate. Specifically, the most preferred viscosity of the aromatic Isocyahate component Is from 50 to 300 cehtlpoise at 25 C to allow the aro-matic isocyahate to be sprayed onto the core particle. The most preferred nominal functionality of the aromatic isocyahate component is from 2.0 to 2.7 to allow for effec-tive reaction of the aromatic isocyahate with the polyol and for cost effectiveness. IFl-Wally, the most preferred NCO content of the aromatic isocyahate component is from 30% to 33%. The NCO content provides a high molecular crosslihk density of the aro-matic isocyahate that aids In the formation of a defect free polyurethane layer. The NCO content also provides an aromatic isocyahate with more chemical bonds per unit of mass to improve cost efficiency.

1000221 In addition to the aromatic isocyahate component, the polyurethahe layer is also the reaction product of a polyol that is derived from an aromatic amlhe-based Ini-tiator. The polyol includes alkylehe oxide substituehts. examples of suitable alkylehe oxides substituehts Include ethylene oxide, propylene oxide, butylehe oxide, amylehe oxide, mixtures thereof, alkylehe oxide-tetrahydrofurah mixtures, epihalohydrihs, and aralkylehe styrene. Most preferably, the polyol is commercially available from SASI=
Corporation of Wyandotte, Michigan under the trade Name of Pluracolo IDolyol 824.

t00023J preferably, the polyol has a viscosity'from 4,000 to 20,000, more preferably from 5,000 to 17,000, and most preferably from 10,000 to 15,000 cehtlpolse at 251)C.
To maximize efficiency, the polyol can be stored at and heated in the temperature ran-ge of from 60 to 80 C. Preferably, the polyol also has a nominal fuhctiohality from 1 to 7, more preferably from 2 to 6, and most preferably from 3 to 4. Ireferably, the polyol has an OH Number from 300 to 600, more preferably from 350 to 500, and most preferably from 380 to 450. Additionally, the polyol may also be derived from a dipro-pylehe glycol Initiator. In other words, the polyol may be co-Ihitiated with dipropylehe glycol.

t000241 the aforementioned viscosity, homihal functionality, and OH Number of the polyol are preferred because of specific properties that each gives to the polyol. Spe-cifically, the most preferred viscosity of the polyol Is from 10,000 to 15,000 cehtipolse at 25bC to allow the polyol to be sprayed onto the core particle. The most preferred homi-hal functionality of the polyol Is from 3 to 4 to allow for effective reaction of the polyol with the aromatic isocyahate and to reduce the cost of the polyol. l lhally, the most pre-ferred oH number of the polyol Is from 380 to 450 to maximize crosslinking density of the polyurethane layer.

t000251 As described above, the polyol is derived from the aromatic amine-based initiator. The aromatic amine-based initiator is of the formula:

h~ \ kZ
~2g ~ rt3 wherein k, Includes one of an alkyl group, an amine group, and a hydrogen and each of k2-k6 independently Include one of an amine group and a hydrogen, so long as at least one of ki-K6 is an amine group. Therefore, It is to be understood that P'i can be any one of an alkyl group, an amine group, or a hydrogen, or any compound Including combinations thereof. It Is also to be Understood that I'2-P6 do hot have to be Identical and each can include an amine group or a hydrogen. It Is also to be understood that the terminology "an amine group" refers to a-N-H and NH2 throughout.

000026] The aromatic amine-based initiator includes, but Is hot limited to a toluene diamihe. The toluene diamihe preferably Includes, but Is not limited to, the following structures:

H3 cH3 H3 ~ NHZ NH2 NN2 I I I

NHZ
2,3-tolUehe diahiihe 2,4-toltiehe diahilhe 2,5-toltiehe dithiihe cH3 CH3 CH3 NHZ NHZ
I

3,5-tolttetie diahiihe 2,6-toltiehe dlatiihe 3,4-tolUehe diat6ie wherein the toluehe diamihe Includes, but Is not limited to, 2,3-toluehediamihe, 2,4-toluehediamihe, 2,5-toluehediamihe, 2,6-toluehediamine, 3,4-toluehediamihe, 3,5-toluehediamihe, and mixtures thereof.

x000271 The reaction product of the isocyahate component and the polyol derived from the aromatic amine-based Initiator may include a pigment for coloring the reaction product. The pigment allows the completehess of the polyurethane layer to be visually evaluated and can provide various marketing advantages.

x000281 The aromatic amine-based Initiator provides a polyol that is completely miscible with the Isocyahate component. The complete miscibility of the isocyahate componeht and the polyol that Is derived from an aromatic amine-based Initiator Is the 26 result of two primary effects. Hrst, the complete miscibility Is due to London l7orces that a create momentarily Induced dipoles between similar aromatic moieties of the polyol and the isocyahate component. The momentarily Induced dipoles allow the isocyahate component and the polyol to mix effectively. Secondly, the complete miscibility Is due to the planar geometry of the aromatic moieties of the polyol and the isocyahate com-portent that allow for complementary stacking of the polyol and isocyahate component.
The complementary stacking of the aromatic moieties also allows the isocyahate com-poheht and the polyol to mix effectively.

t000291 The complete miscibility of the isocyahate component and the polyol de-rived from the aromatic amine-based Initiator yields multiple advantages. the complete miscibility results In an ability to use various techniques for applying the polyol and the Isocyahate compoheht onto the core particle. The techniques include, but are hot lim-ited to, pan coating, fluidized-bed coating, co-extrusloh, spraying and spihhing disk encapsulation. In commercial application, practitioners of each of these techniques will experience the advantages described by this Invention.

000030] Specifically, spraying the polyol and the isocyahate component onto the core particle results In a Uniform, complete, and defect-free polyurethahe layer dis-posed about the core particle. Spraying also results In a thinner and less expensive polyurethane layer disposed about the core particle. iutthermore, the polyol Is shelf-stable thereby allowing for more effective storage and subsequent usage.

t000311 The following examples illustrate the nature of the Invention and are hot to be construed as limiting of the Invention. Unless otherwise Indicated, all parts are given as parts by weight.

EXAMI~LES
t000321 Ehcapsulated particles, according to the present Invention, were prepared in beakers. Specifically, 4g of a polyol derived from an aromatic amine-based Initiator were heated to 901)C and added dropwise to a beaker containing 1 OOg of commercial urea spheres to form a polyol-urea mixture. The polyol-Urea mixture was swirled gently Using a foam mix blade to ensure distribution of the polyol derived from an aromatic amihe-based initiator around the urea spheres. 5g of an aromatic Isocyahate preheated to 90 C was added to the polyol-urea mixture and manually swirled to ensure complete contact between the commercial urea spheres and the reaction product of the polyol derived from an aromatic amihe-based initiator and the aromatic Isocyahate.
The com-plete contact resulted in a polyurethahe layer disposed about the commercial urea spheres. The commercial urea spheres were subsequently stirred with a foam mix blade to minimize agglomeration resulting In a free flowing group of commercial urea spheres.

000033] Three examples of the polyurethahe layers disposed about commercial urea spheres used to represent possible controlled-release fertilizers are presented in Table 1 below. Example I represents the subject Invention including an aromatic iso-cyahate and a polyol that is derived from an aromatic amine-based initiator.
Specifi-cally, Comparative Examples One and Two illustrate attempts to create polyurethane layers disposed about core particles disclosed In the prior art. Comparative Example Ohe utilizes an aromatic isocyahate and a hoh-aromatic polyol that includes castor oil.
Similarly, Comparative E=xample Two Utilizes an aromatic isocyahate and a hoh-aromatic polyol that Includes glycerine.
TAf3LE 1 Component Example 1 Comparative Example I Comparative Example 2 Isocyahate 3.0 3.0 3.0 polyol A 3.0 N/A N/A
polyol g- N/A 3.0 N/A
polyol C N/A N/A 3.0 0000341 the results of miscibility measurements, dissolution time Measurements, and cute time Measurements of the three aforementioned examples of the polyure-thahe layers are presented In table 2 below. Example I represents the subject lhveh-tioh Including an aromatic isocyahate and a polyol that Is derived from an aromatic amihe-based Initiator. Specifically, Comparative Examples Ohe and Two illustrate at-tempts to create polyurethahe layers disposed about core particles disclosed in the prior art. Comparative Example Ohe utilizes an aromatic isocyahate and castor oil, which Is hot aromatic and Is hot miscible with the aromatic Isocyahate.
Therefore, the polyurethahe layer that Is disposed about the core particle Includes defects and allows water and other liquids to permeate the polyurethane layer and rapidly dissolve the core particle. Additionally, the Immiscibility of the castor oil and the aromatic isocyahate greatly increases cute time of the polyurethane layer. Similarly, Comparative Example Two also utilizes an aromatic isocyahate and a hoh-aromatic polyol that Is hot com-pletely miscible with the aromatic isocyahate and also results In a polyurethane layer that Includes defects. Additionally, the partial miscibility of the aromatic isocyahate and the hoh-aromatic polyol Increases the cure time of the polyurethahe layer.
Finally, the urea illustrates the dissolution time of a cote particle that does not include a polyure-thane layer.

Pxample 1 Comparative Comparative Urea example 1 Example 2 Miscibility of Isocyahate ahd Complete Partial None N/A
Polyol Dissolution time > 1 day > 1 day > 1 day < 3 hiihutes of Core Particle Cure Time of Polyurethane 5 mihutes I hour 4 hours N/A
Layer t000351 Polyol A is a polyol derived from ah aromatic amine-based ihitiator ihcluding 5 propylehe oxide ahd ethylehe oxide ahd has a hydroxyl Number of 390, a nominal fuhc-tionality of 4, ahd a viscosity of 10,500 cehtipoise at 25 C. Polyol A Is commercially available from bASI= Corporatioh of Wyahdotte, Michigan, Uhder the trade Name lDlUra-cole Polyol 824.

10 0000351 lDolyol 13 is castor oil and has a hydroxyl humber of 162 ahd a homihal fuhc-tiohality of 3.

t000371 Polyol C Is a glycerihe-ihitiated, propoxylated polyol ahd has a hydroxyl num-ber of 399, a homihal fuhctiohality of 3, and a viscosity of 360 cehtipoise at 25 C. Polyol C
Is commercially available from 13ASIF Corporation of Wyahdotte, Michigah, under the trade hame i'luracolo iDolyol GI'430.

x000381 Isocyahate is a polymeric methylehe diphehyl dilsocyahate with a functionality of approximately 2.7, an NCO cohteht of 31.5, and a viscosity of 200 cehtipoise at 25 C.
Isocyahate is commercially available from 13ASI Corporation of Wyahdotte, Michigan under the trade hame of Luprahate M20S.

Claims

1. An encapsulated particle comprising:
A a core particle comprising a fertilizer selected from the group of nitrogen, phosphate, potash, sulfur, and combinations thereof, a herbicide, an insecticide or a fungicide;
B a polyurethane layer disposed about said core particle and comprising the reaction product of:
(i) an isocyanate component wherein said isocyanate component comprises an aromatic isocyanate component, and (ii) a polyol derived from an aromatic amine-based initiator.

2. An encapsulated particle as set forth in claim 1, wherein said aromatic amine-based initiator comprises the formula:

wherein R1 comprises one of an alkyl group, an amine group, and a hydrogen;
and wherein each of R2-R6 independently comprise one of an amine group and a hydrogen; so long as at least one of R1-R6 is an amine group.

3. An encapsulated particle as set forth in claim 1, wherein said aromatic amine-based initiator comprises a toluene diamine.

4. An encapsulated particle as set forth in claim 1, wherein said isocyanate component comprises methylene diphenyl diisocyanate.

5. An encapsulated particle as set forth in claim 1, wherein said isocyanate component comprises toluene diisocyanate.

6. An encapsulated particle as set forth in claim 1, wherein said isocyanate component has a viscosity of from 20 to 700 centipoise at 25°C.

7. An encapsulated particle as set forth in claim 1, wherein said isocyanate component has a nominal functionality of from 1.5 to 4.

8. An encapsulated particle as set forth in claim 1, wherein said isocyanate component has a NCO content of from 25-40%.

9. An encapsulated particle as set forth in claim 1, wherein said polyol has a viscosity of from 5,000 to 17,000 centipoise at 25°C.

10. An encapsulated particle as set forth in claim 1, wherein said polyol has a nominal functionality of from 2 to 6.

11. An encapsulated particle as set forth in claim 1, wherein said polyol has an OH number of from 350-500.

12. An encapsulated particle as set forth in claim 1, wherein said polyol is derived from a dipropylene glycol initiator in addition to said aromatic amine-based initiator.

13. An encapsulated particle as set forth in claim 1, wherein said polyurethane layer comprises a pigment for coloring said polyurethane layer.

14. An encapsulated as set forth in claim 1, wherein said isocyanate component comprises methylene diphenyl diisocyanate, and said polyol is derived from a toluene diamine.

15. An encapsulated particle as set forth in claim 14, wherein said toluene diamine is of the formula: