COMPLETE AFTER PROVISIONAL

THE PATENTS ACT, 1970 As amended by the Patents (Amendment) Act, 2002


COMPLETE SPECIFICATION
(See Section 10; Rule 13)
TITLE
MICROENCAPSULATING A PLANT PROTECTING AGENT
APPLICANTS
UNITED PHOSPHORUS LIMITED, a company incorporated under the Companies Act, 1956 having its registered office at 3-11, GIDC, Vapi-396 195, State of Gujarat, India and its corporate office at Uniphos House, llth Road, C. D. Marg, Khar (West), Mumbai - 400 052, State of Maharashtra, India, an Indian Company.

The following specification particularly describes the invention and the manner in which it is to be performed :

Field of Invention :
The present invention relates the field of microencapsulating plant protecting agents, and more specifically to the production of microencapsulated plant protecting agent in aqueous suspension or dispersion in order to produce aqueous plant protecting compositions which can be diluted with water and can be applied by conventional spray technique. The present invention more specifically relates to microcapsules containing a plant protecting agent, insoluble in water. The microencapsules produced are safe during handling and during use and can be applied to the substances that are incompatible with each other.
Background of Invention :
Encapsulation and more specifically micro-encapsulation of plant protecting agents are increasingly being used to target specific insects. The microencapsules are prepared to maintain the active substance in inert stage until the time it is required to perform a given function.
The microencapsulation of plant protecting agents provides a number of benefits:
a) to protect active substance against chemical and physical degradation;
b) to allow separation of substances which are harmful upon contact with each other;
c) to mask an original odour, colour or taste of a substances;
d) to prevent undesirable release of an encapsulated substance to the formulation that contains it;
e) to provide means for controlled release of active material;
f) to prevent crystallization or flocculation of active ingredients;
g) to increase the biological activity of the active ingredients;
h) to enables the conversion of liquid to powder/solid form or vice versa;
i) to isolate substances that are otherwise detrimental when in contact with each
other; j) to protect sensitive substances from degradation process; k) to prevent excessive loss from dripping during and after application; 1) to help in reduction of required application dosage; m) to reduce the number of application of sprays.
In agrochemical industry pesticides/insecticides are formulated as dust, emulsifiable concentrates, suspension concentrates, wettable powders or wettable granules, water dispersible granules, depending on the properties of the active ingredient, and the target pest species and market. In Insecticides such as Endosulfan etc which are moderately toxic in the technical form, but have a high skin irritant property and in some cases may provoke an adverse skin reaction such as burning, tingling, numbness or prickling sensation or generally known as paraesthesia, during application of the insecticide, which is most pronounced in areas of operator's face, hand, neck etc. For delivering such agriculturally active materials at the target, encapsulation or microencapsulation is one of the safe modes. Encapsulation or more specifically microencapsulation is increasingly
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being used to target specific insects, as it also provides a safer handling of toxic fungicides and insecticides.
Microencapsules are being used as carrier for many different ingredients such as inks, dyes, pharma preparation, chemical reagents and the like and also attempts have been made repeatedly to use plant protecting ingredients in microcapsules. Microencapsulation of plant protecting agents becomes important with regard to the safety of handling. Another advantage of the encapsulation of active ingredients is the possibility to combine substances that cannot be blended or are incompatible with one another.
As Defined in "WIKIPEDIA" the Micro-encapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules with many useful properties. In its simplest form, a microcapsule is a small sphere with a uniform wall around it. The material inside the microcapsule is referred to as the core, internal phase, or fill, whereas the wall is sometimes called a shell, coating, or membrane. Most microcapsules have diameters between a few micrometers and a few millimeters.Many microcapsules however bear little resemblance to these simple spheres. The core may be a crystal, an emulsion, a suspension of solids, or a suspension of smaller microcapsules. The microcapsule even may have multiple walls.
A "microcapsules" as used herein, may generally refer to a droplet of material synthetically encased with an outer protective shell having a diameter ranging from sub-micron dimensions to a few hundred microns. In contrast, a "microparticle", as used herein, may generally refer to a solid or liquid particles having a diameter ranging from sub micron dimensions to a few hundred microns. Consequently a microcapsule is a microparticle, however, a microparticle is not necessarily a microcapsules. A microcapsule is a 10"3 m to 10"9 m diameter particle, composed of a core material and an outer wall (Tsuji, 1993).
Microencapsulation of a number of different agriculturally active materials and pesticides has been known for many years by using various processes or techniques for microencapsulation. The general technology for forming microcapsules is divided into two classifications known as physical methods and chemical methods. The physical methods are spray coating, spray drying, pan coating, rotary disk atomization etc. The chemical microencapsulation methods are phase separation, interfacial polymerization, simple and complex coacervation method etc.
The process of microencapsulation covers three separate steps on a time scale. The first step consists of forming a wall material to encapsulate the core material. The second step involves keeping the core inside the wall material. Also the wall material must prevent the entrance of undesirable materials that may harm the core material. And finally in third step, during application it is necessary to get the core material out at the right time and at a desired rate.
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Microcapsules may be produced by enveloping the active ingredient in an aqueous environment with a polymer film, with dispersant and producing a water dilutable concentrate. These microcapsule dispersions are stored and used like other liquid formulations. With these microcapsule dispersions care must be taken to ensure that thickening, coagulation, flocculation or sediment formation does not occur during storage, the user must at least, with reasonable effort, be able to reverse these changes which diminish quality. Requirements of physical stability must be complied with by suitable composition of the aqueous carrier phase. A sufficiently stable and effective coating must ensure that goal of encapsulation is achieved. Coating must on no account be so strong that the active ingredient exits too slowly after application.
Microcapsules are available usually in powder form and consist of spherical particles, which contain an encapsulated entrapped substance. The spherical particle usually consists of a polymeric shell and the encapsulated substance is located within the shell. The polymeric shell is frequently applied as a wall-forming material and serves as a membrane for the encapsulated substance. This membrane may be semi-permeable or degradable, and therefore it allows the microcapsule to be an efficient tool for controlled release applications.
In comparison to Emulsifiable Concentrates (EC), the microcapsules helps to retard the release of active ingredient, reduces toxicity to mammals, more favourable leaching behaviour, reduced evaporation rates and the like. These formulations will limit the number of applications and the overall quantity of active ingredient to be applied, for crop protection, can be reduced.
Microencapsulation is suitable for a large variety of materials including insecticide, fungicide, herbicide and accaricides, since this process is adaptable by varying the solvents and/or the polymers. Microencapsulation technologies may yield microcapsules having desirable size, spherical shape and smooth surface properties important for controlled release, for chemical stability of the core material, and homogeneous delivery of stable active substances to the target area.
A solvent used is able to efficiently dissolve the plant protecting agent to be encapsulated. Solvent has to be insoluble in water.
The nature of encapsulated substance and the type of polymer to be used are the basis of microencapsulation technique selected. For encapsulation of water insoluble substance within water insoluble polymer requires a solvent removal method. In this process the polymer is dissolved in a suitable organic solvent, followed by addition of desired substance (either dissolved or dispersed in organic solvent) to be encapsulated. The resulting organic solution or dispersion is dispersed in an aqueous phase to obtain an oil-in-water emulsion where oily microparticles are dispersed in the aqueous phase. Upon complete removal of solvent from the microparticles, the microcapsules are formed. The removal of solvent requires the use of vacuum distillation, evaporation, heating the aqueous dispersion or by reducing its pressure, by extraction with water etc.
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The use of chlorinated solvents are not applicable and are quite in appropriate for insecticidal, fungicidal, herbicidal and accaricidal products since they do not meet the regulation due to the presence of residual amount of chlorinated solvent in the microcapsules. Simple vacuum or heat do not result in a sufficiently low chlorinated solvent content and thus creating a necessity for a method of encapsulating pesticides by a non-chlorinated solvents.
Numerous processes are known in the art for producing microencapsulated materials. Various proposals have been made in recent years for the microencapsulation of various pesticidal or plant protecting materials. For example :
U.S. Pat. No. 5,160,530 Missekbrook John et al (Griffin Corp.) discloses a process for encapsulating pesticides (for example trifluralin), by melting the active material, and combining the melted material with a film-forming polymer. The materials are then emulsified together and spray dried.
U.S. Pat. No. 4,244,836 Frensch Heinz et al (Hoechst) discloses a similar method of encapsulating pesticidal materials, by spray drying a dispersion of the active material and a polymer.
Although for some systems, the processes disclosed by these references are useful, they suffer from a number of disadvantages, for example that the active material can diffuse within the product leading to crystallisation of the active material in polymer matrix, and also (particularly in the Griffin method) that undesired polymorphs of the molten active material may he produced upon cooling to ambient temperature.
U.S. Pat. No. 4,936,901 Surgant Sr John M et al (Monsanto) discloses an alternative method of encapsulation, in which microcapsules containing the active material are formed by means of an interfacial polycondensation reaction, involving an isocyanate/polyamine reaction. The resulting interfacially polymerised microcapsules are subsequently spray dried. This reference mentions that polymer (e.g. PVA) may be used as a suspension adjuvant in the spray drying step. Again, this method results in the production of microcapsules with uncontrollable release characteristics. Also, some active materials show a tendency to diffuse out of the interfacially polymerised microcapsules during storage, thus producing crystallisation (in the case of actives normally solid at ambient temperatures). Another difficulty with this method is that the products which result all have slow release characteristics, because of their large particle size distribution and thick polymer wall.
One particular problem which this reference does not address, is the production of microcapsules which provide rapid release of the active material, rather than sustained or delayed release. Often a controlled release formulation will be required to produce a rapid biological effect followed by a sustained release of the active. Rapid release capsules are generally required to be small in size (typically with a volume mean diameter (VMD) less than 5 micrometers) or have extremely thin polymer shell walls. None of the systems prepared in U.S. Pat. No. 4,936,901 have the small particle size normally required to
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provide rapid knock-down. The only information about particle size giver in the reference is that the size distribution (not the VMD) is from 1-50 microns.
U.S. Pat. No. 4,861,627 Mathiowitz Edith et al (Massachuesetts Inst technology) describes a method for preparation of microspheres from a mixture of any two or three polymers. The mixture is suspended in an aqueous solution followed by slow spray-drying of volatile solvent, creating microspheres with an inner core formed by one polymer and an outer layer formed by a second polymer.
U.S. Pat. No. 4,534,783 Beestman George B (Monsanto Co) discloses a process for encapsulating aqueous materials using two monomers or prepolymers.
U.S. Pat. No. 4,285,720 Scher Herbert B (Stauffer Chemical Co) involves production of microcapsules of a polyurea material.
US. Pat No. 4,956,129 Scher Herbert B et al (ICI America Inc) involves production of microcapsules of an etherified urea-formaldehyde polymer.
U.S. Pat. No. 4,157,983 Golden Ronald (Champion Int Corp) describes a water-in-oil microencapsulation process. In this process, a mixture is formed which contains an emulsifier, a water-immiscible liquid, a urea-formaldehyde prepolymer, a water-dispersible material to be encapsulated, and water. The mixture is agitated to produce a water-in-oil emulsion. The emulsion is then cured or treated to produce microcapsules by solidification of the urea-formaldehyde prepolymer resin to form a matrix encapsulating the droplets and permitting the separation of solid polymeric capsules containing the water-dispersible material. The curing or polymerization is instituted by use of an amphiphatic catalyst, that is, a catalyst which is soluble in both the water and oil phases of the emulsion. However, the products of this process are not true microcapsules but rather comprise a matrix of the urea/formaldehyde polymer containing the water dispersible material.
Microencapsulation of Endosulfan has been reported in U.S Patent no. 4230809, U.S Patent no. 5,549,903 and U.S. Patent no. 6294570.
U.S. patent no 4,230,809 Heinrich Rudolf et al (Hoechst AG) teaches about a process for the manufacture of microcapsules of active substances, especially for plant protection by using polyurethane-polyurea particles with textured internal mass and containing isocyanate prepolymer.
U.S Patent no. 5,549,903 Marcus Arie (Ben Gurion University of Negev Research & Development Authority) teaches about a microencapsulated chlorpyrifos or endosulfan composition comprising a polyurea shell and one or more photostable UV and visible light absorbent compound.
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U.S. Patent no. 6,294,570 Krause Hans-Peter (Aventis Crop Science GmbH) teaches about aqueous endosulfan microcapsule dispersions where capsule-forming material is based on isocynate prepolymer.
In case of microencapsulating insecticides such as endosulfan as described in above mentioned prior arts, wall forming material/prepolymer is Urea Formaldehyde modified by using alcohol like butanol to enhance the stability of prepolymer which may on cross-linking release alcohol in the formulation, eventually that may add pollution in the environment.
Few patents discloses the technique for obtaining microencapsulated plant protecting agent (Endosulfan) in aqueous suspension or dispersion in order to produce aqueous plant protecting compositions which can be diluted with water and can be applied for plant protection purpose by using the conventional spray application technique; to produce the microcapsules without using alcoholic and/ or chlorinated solvents, and which do not need the solvent removal method, or without using spray drying technique or without a second polymer, without using the inorganic salts to minimize the density difference of organic and aqueous phase.
In summary, none of the method known in the art meets the requirement for a considerable protection factor of the encapsulated substance without using the alcoholic and/ or chlorinated solvents, and which do not need the solvent removal method, or without using spray drying technique or without a second polymer, by using modified polymer and for obtaining microcapsulated plant protecting agent (Endosulfan) in aqueous suspension or dispersion in order to produce aqueous plant protecting compositions which can be diluted with water and can be applied for plant protection purpose by using the conventional spray application technique. This process prevents the degradation and controls the ability to release the encapsulated substance. Hence there is still a need for a method which do not uses alcoholic and/ or chlorinated solvents, and which do not need the solvent removal method, or without using spray drying technique or without a second polymer, by using modified polymer to produce the product in the form of aqueous suspension for stable encapsulation of active substance that simultaneously affords control of its release from microcapsules only after application.
It has also been observed that there none of the referred prior art offered microcapsules with at least 90 % of microencapsulation and with a free active ingredient not more than 10 % of total active content, present in the formulation/composition, as offered by the present invention.
The present invention provides microcapsules of plant protecting agent and a process of microencapsulation of a plant protecting agent. The plant protecting agent is substantially water-insoluble and the wall forming material is water soluble prepolymer, modified with an amide, preferably Urea Formaldehyde modified with acrylamide.
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OBJECT OF THE INVENTION:
It is an object of the present invention to provide microencapsulated plant protecting agents.
It is another object of the invention is to provide a process of microencapsulation of plant protecting agents.
It is further object of the invention is to provide microencapsulated plant protecting agent without using alcohol and/ or chlorinated solvent.
It is yet another object of the invention is to provide microencapsulated water insoluble plant protecting materials where encapsulating agent is a modified polymer.
It is another object of the invention is to provide a process of microencapsulation of plant protecting materials by using modified prepolymer of Urea Formaldehyde.
It is yet another object of the invention is to provide microencapsulated water insoluble plant protecting materials where Urea Formaldehyde is modified with alkylamine group compounds such as acrylamide and others.
It is yet another object of the invention is to provide a process of encapsulation of insecticides such as Endosulfan.
It is other object of the present invention to provide microencapsules of a plant protecting agent in which the encapsulated active ingredient in the inner core is stable throughout the preparation of the microcapsules, their storage and transportation.
It is another object of the present invention to provide microencapsulated plant protecting agent with an optimal controlled release system that deliver a high content of the active ingredient only upon application.
In one embodiment, the present invention provides a method for the production of microencapsulated plant protecting agent, wherein the microcapsules consist of a core made of an encapsulated active ingredient and an outer modified polymeric shell.
In other embodiment, the present invention provides a method for the production of microencapsulated plant protecting agent, wherein the outer modified polymeric shell is made by using modified prepolymer.
In another embodiment, the present invention provides a method for the production of modified pre-polymer.
In another embodiment, the present invention provides a method for using the modified pre-polymer during the production of microencapsules of plant protecting agent.
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In another embodiment, the present invention provides a method for the production of microencapsulated plant protecting agent.
One of the advantages of the method of the present invention increases the stability of highly sensitive substances against degradation and prevent the undesirable release of the encapsulated substance into the formulation that contains it.
The active ingredient for encapsulation according to the invention may be insecticide, fungicide, herbicide and accaricides or a combination thereof, substances such as, but not limited to, Endosulfan only.
Also provided by the present invention are microcapsules obtained by the methods of the invention and compositions for pest control purpose in public and/or agriculture field application comprising said microcapsules.
STATEMENT OF THE INVENTION
A process for microencapsulating a plant protecting agent comprising the following steps:
a) dissolving or dispersing a plant protecting agent (active ingredient) to be encapsulated in an organic solvent (of a kind that is immiscible with water and is capable of dissolving or dispersing the said plant protecting agent) in the presence of at least one surfactant, to form an organic solution or dispersion;
b) homogenizing the organic solution or dispersion obtained in step (a) to get a clear transparent liquid free, from suspended and extraneous matter which gives a stable good thick emulsion when diluted with water, in the form of organic phase;
c) preparing a modified prepolymer comprising the steps of:
i) adding a required quantity of Urea to the required quantity of formalin and water in a vessel having a high speed stirrer;
ii) stirring the mixture of Urea and formalin obtained in step (i) to have a homogenous liquid;
iii) while stirring, pouring the required quantity of an acid catalyst into the homogenous liquid obtained in step (ii), to adjust the pH between 6 to 6.5;
iv) maintaining the temperature of the mixture obtained in step (iii) at 55 to 65 °C, to obtain a solution;
v) while stirring adding a required quantity of an acrylamide into the solution obtained in step (iv);
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vi) cooking the reaction mass obtained in step (v) at a temperature between 55 to 65 ° C for at least 15 minutes;
vii) adding a required quantity of an alkali catalyst to the cooked product of step (vi) to adjust the pH between 7 and 8;
viii) stirring the mass of step (vii) fori to 20 minutes to obtain the modified pre polymer;
d) preparing an aqueous phase comprising of water, a dispersing agent, an antifreezing agent, a defoamer, a stabilizer, a biocide and a modified prepolymer;
e) stirring the material of step ( d) with high shear to get a clear liquid having a pH of 7.0 to 7.5 in the form of aqueous phase;
f) while high shear mixing, slowly pouring the organic phase obtained in (b) into the aqueous phase obtained in (e), to form a white thick oil-in-water emulsion/ dispersion with a droplet size of less than 10 urn;
g) adding acidic catalyst with slow stirring at a specific temperature of 20 to 60°C to the oil-in-water emulsion / dispersion obtained in (f);
h) adjusting the pH of the system of step (g) from 1 to 7 preferably 3 to 6.5 to initiate polymerization reaction;
i) heating the product obtained in step (h) at 40 to 80 ° C with continuous stirring for at least 15 minutes;
j) cooling the product obtained in step (i) at a temperature of 20 to 45 ° C;
k) adding an alkali catalyst to the mass obtained in (j), with slow stirring, at a specific temperature of 20 to 40 ° C, to adjust the pH of the reaction mass obtained in (i) to 6 to 8 as neutral;
1) stirring the mass obtained in step (k) for 1 to 30 minutes;
m) while slow stirring, adding a structuring agent to the mass obtained in step (1);
n) homogenizing the product obtained in step (m) for at least 2 minutes to obtain the microcapsules of plant protection agent.
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DETAILED DESCRIPTION OF THE INVENTION
We have found that by using a modified prepolymer in aqueous phase for producing the microcapsules shows improved storage stability, lower level of free content and higher amount of encapsulated active content and controlled release rate of the encapsulated plant protecting agents like pesticides, insecticides, fungicides, herbicides and accaricides in aqueous suspension/dispersion form of resulting microcapsules, particularly when the microcapsules are prepared by following the invented method.
The invention therefore provides microcapsules and a process of microencapsulating a plant protecting agent in a water-based mixed-phase system is carried out by a procedure in which prior to the formation of the microcapsules, the water insoluble, non continuous phase comprises an active ingredient with a solvent and at least one surfactant to obtain a clear solution, this solution is emulsifiable and /or dispersible in water. This process produces microcapsules of materials contained in a water-immiscible or insoluble material and are produced by what is termed oil-in-water microencapsulation processes. These in general involve the production of a emulsion and/or dispersion of "oil" or organic, substantially water-immiscible liquid droplets (discontinuous phase) in an aqueous medium (continuous phase) containing modified prepolymer and microcapsules are formed by subjecting the emulsion to conditions such as temperature and/or pH and/or agitation to cause polymerization of the modified prepolymers present in the aqueous phase to produce microcapsules having a polymeric shell enclosing the water-immiscible droplet phase. The modified polymeric agent which forms the capsule wall may alternatively be insoluble in water, and after application to the targeted area(s) get dried and able to release the plant protecting agent to control the insect/pests. This modified polymer accordingly be present in the continuous dispersion phase.
The invention therefore provides microencapsules which encloses a water insoluble solid plant protecting agent i.e. active ingredient and which are composed of solid plant protecting agent for encapsulation, organic solvents, surfactant and modified prepolymer.
The process of microencapsulation maintains the original activity of the microencapsulated plant protecting agent and enable the timely release at the desired rate of the active ingredient when used to target specific insect pests.
The term "microcapsules" refers to a microparticle consisting of an inner core and outer polymeric shell of non reactive carriers which surround the plant protecting agents thereof. In the course of microencapsulation, the plant protecting agent are introduces to the polymer dispersion and promote the formation of polymeric shell which is converted to a structured shell of microcapsules.
The term "inner core " refers to the inner part of the microcapsule as defined above and consisting of the plant protecting agent (active substance) in the center of the microcapsule.
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The term "plant protecting agent" or " active ingredient' or active substance are used herein interchangeably and refers to the material located within the inner core of microcapsule, which material may include plant protecting agents such as insecticides, fungicides, herbicides and accaricides etc. The substance to be encapsulated are preferably solid which are soluble in organic solvents, whose water solubility is low and which do not react with the agent which forms the capsule wall. Such substance are preferably understood to include active plant protecting agent such as Endosulfan.
The term "polymeric shell" constitutes a wall consist of polymeric structures made from modified prepolymer which contains for example urea, formaldehyde, acrylamide or compounds of alkylamine groups which form a component of the external wall or shell of the microcapsules.
The term "water insoluble" should be understood as relating to the property of being able to be dissolved in water in concentrations while lower than a certain critical concentration, while the concentration thereof increases above a certain critical value, there is a separation and the water and the plant protecting agent form two separate phases. An example of such plant protecting agent is Endosulfan.
The term "stirring" should be understood as referring to agitation, shaking, vibrating and in general to any process whereby mechanical energy is transferred to the material preferably liquid to cause some turbulence in it.
The term "surfactant" should be understood as referring to suitable emulsifiers such as ehtoxylated alcohols, ehtoxylated vegetable oils, ethoxylated propoxylated products, stearic monoethanolamide, phosphate esters, cationic surfactant, anionic surfactant, nonionic surfactants, polyethylene oxide-polypropylene oxide block copolymers (such as Pluronic L122, Pluronic P123 produced by BASF-Wyandotte Co.), ethylene diamine derivatives of polyethylene oxide-polypropylene oxide block copolymers (such as Tetronic 1501, Tetronic 1502, produced by BASF-Wyandotte Co.), lanolin derivatives, sorbitol derivatives and other surfactants commonly used to promote the formation of similar emulsions.
The term "organic solvent" is used for water-immiscible liquids either aliphatic or aromatic low viscosity hydrocarbons, or derivatives thereof such as aliphatic naphthas, such as Shell Sol 70, toluene, xylene, and the like. The other solvents includs aromatic hydrocarbans like Shell chemicals (Exxon) aromatic 100, aromatic 150, Solvesso-200, other group of solvents can be used such as Ethers, Esters, Alcohols, ketones will be used either individual or mixture of these.
The term "acidic catalyst" should be understood as referring to the use of sulfuric acid, Phosphoric acid, Citric acid , Nitric acid, Hydrochloric acids and other organic or inorganic acids which helps to bring maintain the pH of the system in the desired range.
The term "alkali catalyst" should be understood as referring to the use of Sodium hydroxide, Pottasium hydroxide, Triethanol amine, Trisodium phosphate, Ammonia,
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Ammonium hydroxide, Triethyl amine, and the like as such or in diluted form to maintain the pH of the system in the desired range.
The term "dispersing agent" should be understood as reffering to suitable dispersing agents form Phosphate Esters, Tristyrylphenol Ethoxylate, Potassium Salt (Soprophor FL or FLK), sodium lignosulphonates, sodium naphthalene sulphonate formaldehyde condensates, tristyrylphenol ethoxylate phosphate esters salts, aliphatic alcohol ethoxylates, alkylphenol ethoxylates etc.
The term "antifreezing agent" should be understood as referring to suitable glycol ethers, urea, glycols, glycerol, propylene glycol, moehtylene glycol, poly ethylene glycol, alcohols, cellosolves etc.
The term "defoamer" should be understood as referring to defoamers which are based on polyoxyalkylene copolymers (for example, triblock copolymers of ethylene oxide ("EO"), propylene oxide ("PO") and EO or of EO, butylene oxide ("BO") and PO), polydimethyl siloxane emulsion, agnique DFM 11 IS, Rhodosurf 426 R. The defoamer is a conventional defoamer.
The term "biocide" should be understood as referred to biocides include methanal (formaldehyde), ethanal (acetaldehyde), propanal, butanal, pentanal, glucose, benzaldehyde, glyceraldehydes, malonic acid dialdehyde, potassium N-hydroxymethyl-N-methyl thiocarbamate, 2-thiocyanomethylthio benzothiazole, propiconazole, 2-bromo-4'-hydroxyacetophenone, sodium 2-mercaptobenzothiazole, Methyl paraban, ethyl paraban and mixtures thereof.
The term "modified prepolymer" refers to a product obtained from processing a mixture of Urea, formalin, an acid catalyst, mono alkylamine compounds (methyl, ethyl, butyl amine or acrylamide to enhance the prepolymer stability) preferably acrylamide and an alkali catalyst. The mixture in various stages is subjected to conditions of maintaining temperature and/or pH and/or agitation to obtain the product termed as modified pre polymer which is water soluble amino resin and is stable and does not releases the organic solvent.
The term "structuring agent" refers to structuring agents include xanthane gum, guar gum, arabic gum, HPMC, CMC, others or a combination thereof.
The term "free active ingredient content" should be understood as referring to the free content expressed as the percentage by mass of total active ingredient present in the microencapsulated product of the present invention. The quantity of free active ingredient content" can be easily detected when the product obtained from this invention (equivalent to 60 -70 mg of active ingredient strength) is mixed with 5.8 ml of analytical grade water and 50 ml of toluene in a 60 ml volume glass bottle. This bottle is then sealed tightly and made revolved at an approximately rate of 70 rpm for at least 5 minutes.
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Thereafter the sample is drawn from toluene layer is analysed and the results obtained are expressed as the percentage by mass of total active ingredient present in the microencapsulated product
The term "total active ingredient content" should be understood as referring to the total amount of active ingredient present in the microencapsulated product of the present invention. This "total active ingredient content" can be easily detected by following method: a) preparation of internal standard (IS) : 1.5 g of DOP (dioctyl phthalate) is diluted up to a volume of 100 ml by toluene to obtain a 15,000 ppm solution of internal standard, b) preparation of reference standard solution (Std): 0.15 g of a reference standard of known purity was quantitatively transferred to a 25 ml volumetric flask having 5 ml of ethanol and 10 ml of IS and the volume is make up to the mark with toluene, c) preparation of sample solution (Spl): sample quantity having equivalent to 0.15 g of active ingredient is transferred quantitatively to a 25 ml volumetric flask having 5 ml of ethanol and 10 ml of IS and the volume is make up to the mark with toluene. These solutions are stirred properly and analysed to find out the total active content present in the microencapsulated product of the present invention.
The term " release rate of active ingredient" should be understood as referring to the amount of active ingredient released from the microencapsulated product of the present invention at the end of 15 minutes ad 30 minutes when the solution of microencapsulated product (equivalent to 0.15 g of active content) with 5.8 ml of water, 90ml of toluene, 10 ml of ethanol is rotated at 70 rpm. These solutions are then analysed to find out the "release rate of active ingredient" within 15 and 30 minutes from the microencapsulated product of the present invention.
The microencapsulation method of the present invention is based on the use of modified prepolymer. The modified prepolymer is prepared by using Urea , formaldehyde and acrylamide by subjecting the mixture to conditions such as temperature and/or pH and/or agitation to obtain the modified prepolymer.
A process for microencapsulating a plant protecting agent comprising the following steps:
a) dissolving or dispersing a plant protecting agent (active ingredient) to be encapsulated in an organic solvent (of a kind that is immiscible with water and is capable of dissolving or dispersing the said plant protecting agent) in the presence of at least one surfactant, to form an organic solution or dispersion;
b) homogenizing the organic solution or dispersion obtained in step (a) to get a clear transparent liquid free, from suspended and extraneous matter which gives a stable good thick emulsion when diluted with water, in the form of organic phase;
c) preparing a modified prepolymer comprising the steps of:
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i) adding a required quantity of Urea to the required quantity of formalin and water in a vessel having a high speed stirrer;
ii) stirring the mixture of Urea and formalin obtained in step (i) to have a homogenous liquid;
iii) while stirring, pouring the required quantity of an acid catalyst into the homogenous liquid obtained in step (ii), to adjust the pH between 6 to 6.5;
iv) maintaining the temperature of the mixture obtained in step (iii) at 55 to 65 °C, to obtain a solution;
v) while stirring adding a required quantity of an acrylamide into the solution obtained in step (iv);
vi) cooking the reaction mass obtained in step (v) at a temperature between 55 to 65 ° C for at least 15 minutes;
vii) adding a required quantity of an alkali catalyst to the cooked product of step (vi) to adjust the pH between 7 and 8;
viii) stirring the mass of step (vii) fori to 20 minutes to obtain the modified pre polymer;
d) preparing an aqueous phase comprising of water, a dispersing agent, an antifreezing agent, a defoamer, a stabilizer, a biocide and a modified prepolymer;
e) stirring the material of step ( d) with high shear to get a clear liquid having a pH of 7.0 to 7.5 in the form of aqueous phase;
f) while high shear mixing, slowly pouring the organic phase obtained in (b) into the aqueous phase obtained in (e), to form a white thick oil-in-water emulsion/ dispersion with a droplet size of less than 10 um;
g) adding acidic catalyst with slow stirring at a specific temperature of 20 to 60°C to the oil-in-water emulsion / dispersion obtained in (f);
h) adjusting the pH of the system of step (g) from 1 to 7 preferably 3 to 6.5 to initiate polymerization reaction;
i) heating the product obtained in step (h) at 40 to 80 ° C with continuous stirring for at least 15 minutes;
j) cooling the product obtained in step (i) at a temperature of 20 to 45 ° C;
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k) adding an alkali catalyst to the mass obtained in (j), with slow stirring, at a specific temperature of 20 to 40 ° C, to adjust the pH of the reaction mass obtained in (i) to 6 to 8 as neutral;
1) stirring the mass obtained in step (k) for 1 to 30 minutes;
m) while slow stirring, adding a structuring agent to the mass obtained in step (1);
n) homogenizing the product obtained in step (m) for at least 2 minutes to obtain the microcapsules of plant protection agent.
In step (a) of the process of invention, an organic solvent that is capable of dissolving or dispersing a plant protecting agent (active ingredient) material chosen. The solvent shall be inactive with the dissolved material and surfactant. The solvent is water-immiscible liquids either aliphatic or aromatic low viscosity hydrocarbons, or derivatives thereof such as aliphatic naphthas, such as Shell Sol 70, toluene, xylene, and the like. The other solvents includes aromatic hydrocarbons like Shell chemicals (Exxon) aromatic 100, aromatic 150, Solvesso-200, other group of solvents can be used such as Ethers, Esters, ketones etc. will be used either individual or in mixture thereof excluding alcohol or chlorinated solvents. In a preferred embodiment the solvent is Solvesso 200, Solvesso 100, aromatic 100, aromatic 150 or xylene or mixture thereof.
The plant protecting agent to be encapsulated by the present invention, either solid or liquid preferably solid, is then dissolved or dispersed with a surfactant in the organic solvent to form an organic solution or dispersion.
In step (b) of the process of the invention, homogenizing the organic solution or dispersion obtained in step (a). This homogenization is required to get a clear transparent liquid free from suspended and extraneous matter. If necessary (i.e. the liquid is having suspended and /or extraneous matter) it can be filtered by any suitable technique, at this stage. This homogenized organic solution or dispersion is named as organic phase. This organic phase is in the form of a clear transparent liquid, which on dilution with water gives a good thick emulsion which is stable for at least 3 hours after the preparation of the emulsion in water. The water used to see the performance of this organic phase can be of desired hardness, preferably 342,500 and 1000 ppm hardness. The maximum active content / ingredient in this organic phase is 70% preferably to 65% by mass of the organic phase.
In step (c) of the process of the invention, a modified prepolymer is prepared by adding Urea to formalin (of a strength of 37%) and water in a vessel having a high speed stirrer. This stirrer is provided with a speed control arrangements. The mixture of Urea and formalin is stirred to obtain a homogenous liquid . An appropriate acid catalyst is added to the homogenous liquid. Such acid catalyst may be selected from sulfuric acid, Phosphoric acid, Citric acid , Nitric acid, Hydrochloric acids and other organic acids, inorganic acids or a mixture thereof as such / in diluted form. This acid catalyst should be chosen and adopted to the system in such a way that it helps to bring and maintain the
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pH of the system in the desired range. The preferred pH maintained is between 6 to 6.5. This mass is heated to a temperature at 55 to 65 °C to obtain a solution. During stirring, an appropriate alkylamine is added into the heated mass. Such alkyl amine may be selected from mono alkyl amine like Methyl, Ethyl, Butyl amine or Acrylamide to modify and enhance stability of pre polymer. Preferably the alkyl amine is acrylamide .This reaction mass is heated and maintained at 55 to 65 ° C for at least 15 minutes for cooking purpose. The preferable time of cooking this mass is at least 30 minutes. Thereafter an appropriate alkali catalyst is added to the cooked product . Such alkali catalyst may be selected from sodium hydroxide, Pottasium hydroxide, Triethanol amine, Trisodium phosphate, Ammonia, Ammonium hydroxide, Triethyl amine, and the like as such or in diluted form or a mixture thereof. This alkali catalyst, preferably triethanolamine, should be chosen and adopted to the system in such a way that it as such or in diluted form to adjust and maintain the pH of the system in the desired range. The preferred pH adjusted and maintain is between 7 and 8. It is advisable to stir, the obtained mass, for another additional 1 to 20 minutes, preferably for 5 to 15 minutes to obtain the modified pre polymer.This modified prepolymer is the wall forming material.
In step (d), an aqueous phase is prepared by taking the water in a vessel provided with a high speed stirrer. This stirrer is provided with a speed control arrangements. An appropriate dispersing agent is added to this water. Such dispersing agent may be selected from Phosphate Esters, Tristyrylphenol Ethoxylate, Potassium Salt (Soprophor FL or FLK), sodium lignosulphonates, sodium naphthalene sulphonate formaldehyde condensates, tristyrylphenol ethoxylate phosphate esters salts, aliphatic alcohol ethoxylates, alkylphenol ethoxylates etc or a mixture thereof. The preferred dispersing agent should be chosen and adapted to the system in such a way that it is able to keep the microcapsules in suspended/dispersed form in the final product.
An appropriate antifreezing agent is added to this water and dispersing agent. Such antifreezing agent may be selected from suitable glycol ethers, urea, glycols, glycerol, propylene glycol, moehtylene glycol, poly ethylene glycol, alcohols, cellosolves etc. or a mixture thereof. The preferred antifreezing agent should be chosen and adapted to the system in such a way that it is able to prevent the freezing of the final product at low temperature in storage, transportation and even at the time of use.
An appropriate defoamer is added to the above mixture of water, dispersing agent and antifreezing agent. Such defoamers may be selected from polyoxyalkylene copolymers (for example, triblock copolymers of ethylene oxide ("EO"), propylene oxide ("PO") and EO or of EO, butylene oxide ("BO") and PO), polydimethyl siloxane emulsion, agnique DFM HIS, Rhodosurf 426 R. The defoamer is a conventional defoamer. The preferred defoamer should be chosen and adapted to the system in such a way that it is able to prevent the foam generation and is able to serve the purpose of its selection during the processing, preparation, filling, storage, transportation and application time.
An appropriate stabilizer is added to the above mixture of water, dispersing agent, antifreezing agent and defoamer. The preferred stabilizer should be chosen and adapted
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to the system in such a way that it is able to stabilize the active content and the final product obtained from the process of the present invention.
An appropriate biocide is added to the above mixture of water, dispersing agent, antifreezing agent, defoamer and stabilizer. Such biocides may be selected from methanal (formaldehyde), ethanal (acetaldehyde), propanal, butanal, pentanal, glucose, benzaldehyde, glyceraldehydes, malonic acid dialdehyde, potassium N-hydroxymethyl-N-methyl thiocarbamate, 2-thiocyanomethylthio benzothiazole, propiconazole, 2-bromo-4'-hydroxyacetophenone, sodium 2-mercaptobenzothiazole, Methyl paraban, ethyl paraban and mixtures thereof. The biocide is a conventional biocide. The preferred biocide should be chosen and adapted to the system in such a way that it is able to prevent the fungus development and able to control the development of unwanted biological agent in the final product obtained from the invented process during the processing, preparation, filling, storage, transportation and application time
An appropriate modified prepolymer is added to the mixture of water, dispersing agent, antifreezing agent, defoamer, stabilizer and biocide. Such modified prepolymer needs to be prepared by following process of step (c).
In step (e), the mixture of water, dispersing agent, antifreezing agent, defoamer, stabilizer, biocide and a modified prepolymer is stirred, with high shear, for sufficient time to obtain a clear liquid in the form of aqueous phase. This aqueous phase is preferably having a pH of 7.0 to 7.5.
In step (f), during high shear mixing, the organic phase obtained in step (b), which contains the active substance, organic solvent and at least one surfactant, is poured into the aqueous phase of step (e), forming an oil-in-water emulsion/dispersion. The pouring is done with the high shear mixing and the mixing is continued for a further period of time. The rate of mixing and the type of the mixer, and its duration affect, among other factors, the size of the formed droplets. The formed droplet size constitute the basis for the final size of microcapsules. The desired droplet size in interim emulsion which is initially, formed on combination of the organic and aqueous phase is from 1 to 100 microns, preferably less than 50 microns.
The water and /or the second agent which forms the aqueous dispersion phase then reacts at the interface with the agent which forms the capsule wall of the organic phase, to form envelope around the emulsion droplets.
A desired average droplet size can be achieved according to the invention, or smaller oil droplets are obtained to get narrow droplet size range. This is required because the microcapsule dispersion resulting from the emulsion has practically the same volume distribution in the dispersed microcapsules. The average droplet size is usually less than 10 microns, preferably 8 microns.
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A less volume or weight and improper selection of the surfactant leads to a wider volume distribution for the oil droplets in the oil-in water emulsion/dispersion. If necessary, addition of an oil soluble surfactant to organic phase results in the formation of required oil droplet size in oil-in water emulsion.
In step (g), an appropriate acidic catalyst is added to the oil-in water emulsion, obtained in step (f). This addition of acidic catalyst is to be done when the oil-in-water emulsion/dispersion is maintained at a temperature of 20 to 60 ° C. An appropriate quantity of this acidic catalyst needs to be added. The pH of the resulting oil-in water emulsion/dispersion is lowered to between 1 to 7, preferably 3 to 6.5 by the addition of acidic catalyst. Polymerization reaction is initiated and the temperature of this mixture is maintained at 40 to 80 ° C and continuously stirred for at least 15 minutes. Here the free active content in the mass will reduces at least by 5% by mass of the total active content present in the mass prior to initiation of polymerization reaction. This stirred mass is then cooled to a temperature of 20 to 45 ° C. After complete polymerization the pH of the system is neutralize by using an appropriate alkali catalyst. Alkali catalyst needs to be added with the slow stirring and needs to be done at a temperature of 20 to 40 ° C. This alkali catalyst, preferably triethanolamine, should be chosen and adopted to the system in such a way that it as such or in diluted form to adjust and maintain the pH of the system in the desired range. The preferred pH adjusted and maintain is between 6 and 8. It is advisable to stir, the product thus obtained, for another additional 1 to 30 minutes. It is also advisable to adjust specifically the pH of the aqueous phase according to the active substance, solvent properties and the requirements for the final product.
In step (m), an appropriate amount and an appropriate structuring agent is added to the neutralized product obtained above. The addition of structuring agent, is done as such or a formulation thereof. The preferred form of the structuring agent is in gel. This gel is prepared by dispersing the structuring agent, like xanthane gum in powder form, in water in the presence of biocide and aging this mixture for at least 4 hours to get the required gel form of the structuring agent.
In step (n), the mass of step (m) is homogenized for at least 2 minutes.
In this way, microcapsules of plant protecting agent are obtained. These microcapsules are present in an aqueous continuous phase and is dispersed thoroughly in the continuous phase. The polymeric shell is insoluble in water and therefore it provide a better protection for the encapsulated active substance. This system enables a controlled release of the encapsulated agent only after application. After application this polymeric shell get dried in the absence of water on the target surface and thereafter releases the active substance.
The final product obtained after the completion of the invented process shows the free active content in the final product will not be more than 5% by mass of the total active content present in the final microencapsulated product obtained after completion of the process of this invention. The encapsulated active content will be at least 95 % of the
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total active content present in the microencapsulated final product obtained by the process of this invention.
The final product obtained after the completion of the invented process is tested to determine the release rate of active content within 15 and 30 minutes of rotation of the sample preparation for the determination of release rate. The product obtained shows a release rate not more than 10 % by mass of the total active content present in the final microencapsulated product obtained after completion of the process of this invention.
In this invention the selection of every ingredient appropriately and the invented process and its operating conditions, avoid the use of inorganic salts during the processing. Generally the inorganic salts are used during the process to minimize the density differences between organic and aqueous phase. The presence of these inorganic salts at later stage adversely effect the stability after dilution in terms of layer separation, coagulation and performance failure of the microencapsulated product. Not only this the presence of inorganic salts adds the increase in hardness of dilution water at the time of addition of the product in the water used for dilution purpose.
The quantity of organic phase: aqueous phase is 1: 10 to 10 : 1, most preferable ratio is 1:1 to 5:1.
The invention also provides a microcapsules for plant protection application having an outer polymer shell obtained by the method of the invention wherein the microcapsulating polymer is Urea -formaldehyde modified with acrylamide and the active ingredient is an insecticide - Endosulfan.
In another embodiment the active ingredient of microencapsules is an insecticide such as Endosulfan, but not limited to Endosulfan, selected from organochlorine group pesticides.
In another aspect, the present invention relates to a method for the production of modified pre-polymer. In general the method for preparation of modified pre-polymer according to the present invention consist of the following steps:
i) adding a required quantity of Urea to the required quantity of formalin and water in a vessel having a high speed stirrer;
ii) stirring the mixture of Urea and formalin obtained in step (i) to have a homogenous liquid;
iii) while stirring, pouring the required quantity of an acid catalyst into the homogenous liquid obtained in step (ii), to adjust the pH between 6 to 6.5;
iv) maintaining the temperature of the mixture obtained in step (iii) at 55 to 65 °C, to obtain a solution;
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v) while stirring adding a required quantity of an acrylamide into the solution obtained in step (iv);
vi) cooking the reaction mass obtained in step (v) at a temperature between 55 to 65 ° C for at least 15 minutes;
vii) adding a required quantity of an alkali catalyst to the cooked product of step
(vi) to adjust the pH between 7 and 8;
viii) stirring the mass of step (vii) fori to 20 minutes to obtain the modified pre polymer.
The invention also provides aqueous microscopic dispersions which comprises microcapsules in at least 1.0 % by weight preferrably at most 95 % by weight of the plant protecting agent present in the dispersion.
The invention will now be illustrated by the following non-limiting Examples.
Example 1: A process to prepare modified prepolymer:
A modified prepolymer was prepared by adding 60 grams of Urea to 180 grams of formalin (of a strength of 37%) and 246 grams of water in a vessel having a high speed stirrer. The mixture of Urea and formalin is stirred to obtain a homogenous liquid . Thereafter an acidic catalyst, preferably 4 ml of 15% aqueous solution of sulfuric acid to maintained pH between 6 to 6.5. This mass is heated to a temperature at 55 to 65 °C to obtain a solution. During stirring, 8 grams of acrylamide is added. This reaction mass is heated and maintained at 55 to 65 ° C for 25 minutes for cooking purpose. Thereafter 2 ml of 20 % aqueous solution of alkali catalyst, preferably triethanolamineis added to adjust and maintain the pH of the system between 7 and 8. Then this mass was stirred for another additional 5 minutes to obtain the modified prepolymer. This modified prepolymer is the wall forming material.
Example 2 : A process to prepare modified prepolymer:
A modified prepolymer was prepared by adding 80 grams of Urea to 250 grams of formalin (of a strength of 37%) and 349.5 grams of water in a vessel having a high speed stirrer. The mixture of Urea and formalin is stirred to obtain a homogenous liquid . This mass is heated to a temperature at 55 to 65 °C to obtain a solution. During stirring, 18 grams of acrylamide is added. This reaction mass is heated and maintained at 55 to 65 ° C for 25 minutes for cooking purpose. Thereafter 2.5 ml of 20 % aqueous solution of alkali catalyst, preferably triethanolamineis added to adjust and maintain the pH of the system between 7 and 8. Then this mass was stirred for another additional 5 minutes to obtain the modified prepolymer. This modified prepolymer is the wall forming material.
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of Polyehtylene glycol an anti-freezing agent, 0.3 g of Agnique DFM 11 IS a defoamer, 0.01 g of Methyl paraban a biocide and 5.0 g of modified Urea- formaldehyde prepolymer as a modified pre-polymer(prepared in Example 1). Adding the organic phase prepared above into said aqueous phase slowly with the high shear to form and oil-in-water emulsion/dispersion in which the oil droplets size is less than 10 microns. Adjusting the pH of the mixture of Aqueous and Organic phase by adding 0.5 g of 10% sulfuric acid an acidic catalyst with slow stirring at a temperature 40 ° C, to initiate the polymerization reaction. After completing the polymerization reaction, the pH of the reaction mass is adjust neutral by adding 0.5 g of Triethanolamine an alkali catalyst and the stirring of the same for 10 minutes and thereafter 1.0 g of Rhodopol - 23 (4% by weight in gel from) as a structuring agent is added to obtain dispersed microencapsulated Endosulfan active content in a strength of 15 % by weight.
The product obtained was analysed, at ambient (without heat treatment) on the same day of sample preparation, for total active ingredient content and found 15.02 % by weight basis. The free active content was 2.48 % by mass and encapsulated content was found to be (100-2.48) 97.52 % by mass. The release rate after 15 minutes was 7.82 % and after 30 minutes was found to 9.53 % by mass.
And when the same sample was analysed after the 15 days treatment at 54 ± 2 ° C the free active content was 4.03 % by mass and encapsulated content was found to be (100-4.03) 95.97 % by mass. The release rate after 15 minutes was 85.09 % and after 30 minutes was found to 100.00 % by mass.
Example 6 : A process for encapsulation of Endosulfan 40 % w/w.
An organic phase is prepared by mixing the 43.01 g of Endosulfan of purity 93%, in 20.45 g of solvent Solvesso 200 with 3.33 g of Rhodacal 60 BE surfactant and 3.33 g of Alkyl phenol ethoxylate as other surfactant. An aqueous phase is prepared by mixing with high shear stirrer 9.34 g of water, 5.0 g of Soprophor FL a dispersing agent, 3.33 g of Polyehtylene glycol an anti-freezing agent, 0.6 g of Agnique DFM 11 IS a defoamer, 0.01 g of Methyl paraban a biocide and 10.0 g of modified Urea- formaldehyde prepolymer as a modified pre-polymer (prepared in Example 2). Adding the organic phase prepared above into said aqueous phase slowly with the high shear to form and oil-in-water emulsion/dispersion in which the oil droplets size is less than 8 microns. Adjusting the pH of the mixture of Aqueous and Organic phase by adding 0.6 g of 10% sulfuric acid an acidic catalyst with slow stirring at a temperature 40 ° C, to initiate the polymerization reaction. After completing the polymerization reaction, the pH of the reaction mass is adjust neutral by adding 0.4 g of Triethanolamine an alkali catalyst and the stirring of the same for 10 minutes and thereafter 0.6 g of Rhodopol - 23 (4% by weight in gel from) as a structuring agent is added to obtain dispersed microencapsulated Endosulfan active content in a strength of 40.00 % by weight.
The product obtained was analysed, at ambient (without heat treatment) on the same day of sample preparation, for total active ingredient content and found 40.01 % by weight
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basis. The free active content was 3.7 % by mass and encapsulated content was found to be (100-3.7) 96.3 % by mass. The release rate after 15 minutes was 8.92 % and after 30 minutes was found to 10.25 % by mass.
And when the same sample was analysed after the 15 days treatment at 54 ± 2 ° C the free active content was 5.42 % by mass and encapsulated content was found to be (100-5.42) 94.48 % by mass. The release rate after 15 minutes was 40.48 % and after 30 minutes was found to 69.86 % by mass.
Example 7 : A process for encapsulation of Endosulfan 27.1 % w/w.
An organic phase is prepared by mixing the 29.44 g of Endosulfan of purity 93%, in 29.44 g of solvent Solvesso 200 with 3.33 g of Rhodacal 60 BE surfactant and 3.33 g of Alkyl phenol ethoxylate as other surfactant. An aqueous phase is prepared by mixing with high shear stirrer 19.02 g of water, 3.0 g of Soprophor FL a dispersing agent, 3.33 g of Polyehtylene glycol an anti-freezing agent, 0.5 g of Agnique DFM 11 IS a defoamer, 0.01 g of Methyl paraban a biocide and 7.0 g of modified Urea- formaldehyde prepolymer as a modified pre-polymer (prepared in Example 2). Adding the organic phase prepared above into said aqueous phase slowly with the high shear to form and oil-in-water emulsion/dispersion in which the oil droplets size is less than 10 microns. Adjusting the pH of the mixture of Aqueous and Organic phase by adding 0.5 g of 10% sulfuric acid an acidic catalyst with slow stirring at a temperature 40 ° C, to initiate the polymerization reaction. After completing the polymerization reaction, the pH of the reaction mass is adjust neutral by adding 0.5 g of Triethanolamine an alkali catalyst and the stirring of the same for 10 minutes and thereafter 0.6 g of Rhodopol - 23 (4% by weight in gel from) as a structuring agent is added to obtain dispersed microencapsulated Endosulfan active content in a strength of 27 .1 % by weight.
The product obtained was analysed, at ambient (without heat treatment) on the same day of sample preparation, for total active ingredient content and found 27.1% by weight basis. The free active content was 2.18 % by mass and encapsulated content was found to be (100-2.18) 97.82 % by mass. The release rate after 15 minutes was 40.27 % and after 30 minutes was found to 49.07 % by mass.
And when the same sample was analysed after the 15 days treatment at 54 ± 2 ° C the free active content was 2.95 % by mass and encapsulated content was found to be (100-2.95) 97.05 % by mass. The release rate after 15 minutes was 79.48 % and after 30 minutes was found to 99.86 % by mass.
Example 8 : A process for encapsulation of Endosulfan 15 % w/w.
An organic phase is prepared by mixing the 16.13 g of Endosulfan of purity 93%, in 16.13 g of solvent Solvesso 200 with 2.0 g of Rhodacal 60 BE surfactant and 2.0 g of Alkyl phenol ethoxylate as other surfactant. An aqueous phase is prepared by mixing
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with high shear stirrer 51.73 g of water, 1.7 g of Soprophor FL a dispersing agent, 3.0 g of Polyehtylene glycol an anti-freezing agent, 0.3 g of Agnique DFM 11 IS a defoamer, 0.01 g of Methyl paraban a biocide and 5.0 g of modified Urea- formaldehyde prepolymer as a modified pre-polymer (prepared in Example 2 ). Adding the organic phase prepared above into said aqueous phase slowly with the high shear to form and oil-in-water emulsion/dispersion in which the oil droplets size is less than 10 microns. Adjusting the pH of the mixture of Aqueous and Organic phase by adding 0.5 g of 10% sulfuric acid an acidic catalyst with slow stirring at a temperature 40 ° C, to initiate the polymerization reaction. After completing the polymerization reaction, the pH of the reaction mass is adjust neutral by adding 0.5 g of Triethanolamine an alkali catalyst and the stirring of the same for 10 minutes and thereafter 1.0 g of Rhodopol - 23 (4% by weight in gel from) as a structuring agent is added to obtain dispersed microencapsulated Endosulfan active content in a strength of 15 % by weight.
Example 9:Preparation of Prepolymer of Urea formaldehyde modified with acrylamide
In to the vessel having the string and heating arrangement charged 1 mole of urea and 2mole of formaldehyde (Formalin 37 %) heat the system to 55 to 65 °C for half an hour with continuous string , After that add acrylamide powder to the vessel and stir for next 0.5 to 1 hours to complete the reaction which is indicate by the free acrylamide content in the composition then adjust the pH of the solution to 7 to 7.5 by using triethanol amine and cool the system to room temperature and stored it for further use.
Example 10 : A process for encapsulation of Endosulfan 36 % w/v.
An organic phase is prepared by mixing the 29.60 g of Endosulfan x)f purity 93%, in 29.60 g of solvent Solvesso 200 with 4.0 g of Rhodacal 60 BE suifactant and 4.0 g of Alkyl phenol ethoxylate as other surfactant. An aqueous phase is prepared by mixing with high shear stirrer 11.80 g of water, 6.0 g of Soprophor FL a dispersing agent, 3.0 g of Polyehtylene glycol an anti-freezing agent, 0.5 g of Agnique DFM 11 IS a defoamer, 0.01 g of Methyl paraban a biocide and 9.0 g of modified Urea- formaldehyde prepolymer as a modified pre-polymer (prepared in Example 9). Adding the organic phase prepared above into said aqueous phase slowly with the high shear to form and oil-in-water emulsion/dispersion in which the oil droplets size is less than 10 microns. Adjusting the pH of the mixture of Aqueous and Organic phase by adding 0.6 g of 10% sulfuric acid an acidic catalyst with slow stirring at a temperature 40 ° C, to initiate the polymerization reaction. After completing the polymerization reaction, the pH of the reaction mass is adjust neutral by adding 0.49 g of Triethanolamine an alkali catalyst and the stirring of the same for 10 minutes and thereafter 1.4 g of Rhodopol - 23 (4% by weight in gel from) as a structuring agent is added to obtain dispersed microencapsulated Endosulfan active content in a strength of 36.05 % by volume.
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The product obtained was analysed, at ambient (without heat treatment) on the same day of sample preparation, for total active ingredient content and found 36.05% by volume basis. The free active content was 2.00 % by volume and encapsulated content was found to be (100-2.00) 98.00 % by volume. The release rate after 15 minutes was 10.67 % and after 30 minutes was found to 68.33 % by mass.
And when the same sample was analysed after the 15 days treatment at 54 ± 2 ° C the free active content was 2.95 % by mass and encapsulated content was found to be (100-2.95) 97.05 % by mass. The release rate after 15 minutes was 51.34 % and after 30 minutes was found to 99.86 % by mass.
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We claim : -
1. A process for microencapsulating a plant protecting agent comprising the following steps:
a) dissolving or dispersing a plant protecting agent to be encapsulated in a water immiscible organic solvent capable of dissolving or dispersing the said plant protecting agent in the presence of at least one surfactant, to form an organic solution or dispersion;
b) homogenizing the organic solution or dispersion obtained in step (a) to get an organic phase as a clear transparent liquid, free from suspended and extraneous matter;
c) preparing a modified prepolymer comprising the steps of:
i) adding required quantity of Urea to a required quantity of formalin and water in a vessel having a high speed stirrer;
ii) stirring the mixture of Urea and formalin obtained in step (i);
iii) pouring the required quantity of an acid catalyst with stirring into the product of step (ii), to adjust the pH between 6 to 6.5;
iv) maintaining the temperature of the mixture obtained in step (iii) at 55 to 65 °C, to obtain a solution;
v) adding a required quantity of an acrylamide with stirring into the solution obtained in step (iv);
vi) maintaining the reaction mass obtained in step (v) at a temperature between 55 to 65 ° C, for at least 15 minutes;
vii) adding a required quantity of an alkali catalyst to the product of step (vi), to adjust the pH between 7 and 8;
viii) stirring the mass of step (vii) to obtain the modified pre polymer;
d) preparing an aqueous phase comprising water, a dispersing agent, an antifreezing agent, a defoamer, a stabilizer, a biocide and a modified prepolymer;
e) stirring the material of step ( d) with high shear to get a clear liquid having a pH of 7.0 to 7.5 in the form of aqueous phase;
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f) slowly pouring with high shear mixing the organic phase obtained in step (b) into the aqueous phase obtained in step (e), to form a white thick oil-in-water emulsion/ dispersion with a droplet size of less than 10 um;
g) adding acidic catalyst with slow stirring at a temperature of 20 - 60°C to the oil-in-water emulsion / dispersion obtained in (f);
h) adjusting the pH of the system of step (g) from 1 to 7 preferably 3 to 6.5 to initiate polymerization reaction;
i) heating the product obtained in step (h) at 40 to 80 ° C with continuous stirring ;
j) cooling the product obtained in step (i) and adding an alkali catalyst to the mass obtained in (j), with slow stirring, at a temperature of 20 to 40 ° C, to adjust the pH of the reaction mass obtained in (i) to 6 to 8 as neutral;
k) stirring the mass obtained in step (j);
1) adding a structuring agent to the mass obtained in step (k)with slow stirring;
m) homogenizing the product obtained in step (1) to obtain the microcapsules of plant protection agent.
2. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein a plant protecting agent is an insecticide, fungicide, herbicide and or acaricide .
3. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 2, wherein a plant protecting agent is preferably an insecticide.
4. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 3, wherein the insecticide selected is Endosulfan.
5. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein the microcapsule consist of active ingredient within a wall forming modified prepolymer.
6. A process to manufacture the microcapsules of a plant protecting agent as claimed in claims 1 to 5, wherein the modified prepolymer is prepared by using Urea , formaldehyde and acrylamide and subjecting to conditions of temperature and/or pH and/or agitation as stated in claim 1(c).
7. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein the surfactant is selected from ehtoxylated alcohols, ehtoxylated vegetable oils, ethoxylated propoxylated products, stearic
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monoethanolamide, phosphate esters, cationic surfactant, anionic surfactant, nonionic surfactants, polyethylene oxide-polypropylene oxide block copolymers such as Pluronic L122, Pluronic P123 produced by BASF-Wyandotte Co., ethylene diamine derivatives of polyethylene oxide-polypropylene oxide block copolymers such as Tetronic 1501, Tetronic 1502, produced by BASF-Wyandotte Co., lanolin derivatives, sorbitol derivatives and other surfactants commonly used to promote the formation of similar emulsions.
8. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein the dispersing agent is selected from Phosphate Esters, tristyryl phenol ethoxylate phosphate esters salts like Soprophor FL or FLK, sodium lingo sulphonates, sodium naphthalene sulphonate formaldehyde condensates, aliphatic alcohol ethoxylates, alkylphenol ethox)dates and a mixture thereof.
9. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein the acid catalyst is selected from sulfuric acid, Phosphoric acid, Citric acid , Nitric acid, Hydrochloric acids and other organic or inorganic acids.
10. A process to manufacture the microcapsules of a plant protecting agent as claimed in claim 1, wherein the alkali catalyst is selected from Sodium hydroxide, Pottasium hydroxide, Triethanol amine, Trisodium phosphate, Ammonia, Ammonium hydroxide, Triethyl amine, and the like as such or in diluted form.
11. Microencapsules of a plant protecting agent is prepared by following the process as claimed in any of the above mentioned claims.
12. Microencapsules of a plant protecting agent as claimed in claim 11 wherein the plant protecting agent is endosulfan and the mofidied prepolymer is Urea-formaldehyde modified with acrylamide.
13. A microencapsulated plant protecting agent and a process for its preparation as
herein described and exemplified.
Dated this 17th day of June, 2005
M. B. TRIVEDI Company Secretary United Phosphorus Limited, UNIPHOS HOUSE, 11th Road. C. D. Marg, Khar (west), Mumbai-400052, India.
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ABSTRACT
The invention disclosed in this application relates to microcapsules of organochlorine compounds useful as insecticides using a prepolymer of urea -formaldehyde modified by acrylamide and the process for encapsulation.
30