KR100481932B1 - Microencapsulated Compositions - Google Patents

Abstract

Particularly suitable polyurea microcapsules for the application of the leaves are prepared by an interfacial polymerization process, in which the polyurea has a weight ratio of polyisocyanate to diisocyanate (when two forms of isocyanate are present) from about 1: 100 to about Prepared from an aromatic diisocyanate of 1:15 and optionally an aromatic polyisocyanate having at least 3 isocyanate groups, the microcapsules have an average particle size of about 1 to 5 microns. Compared with conventional liquid (eg emulsifiable concentrate) compositions of agrochemicals, microcapsules provide a biological activity that is nearly comparable to conventional liquid compositions, allowing for convenient handling and high filling of the active ingredient.

Description

Microencapsulated Composition

The present invention relates to microencapsulated compositions, in particular pesticide compositions, in particular such compositions being useful for application to plants which have settled by the application of leaves.

Microencapsulation of pesticides and other pesticide chemicals has been performed for many years using a number of microencapsulation processes or techniques with respect to a number of other active ingredients. In general, the purpose of preparing the composition is to control the release of the active ingredient, and in particular to provide a release for long term efficacy in order for the ingredient to be released over a period of time and made available over the shelf life. This is particularly important for pesticides or other ingredients that degrade or degrade under relatively short periods or under certain environmental conditions. The use of microencapsulated compositions provides effective activity of the active ingredient over a long period of time since it is released into the environment more continuously than during one initial dosing (in the case of unencapsulated or uncontrolled release formulations such as solutions, emulsions, granules, etc.). do.

Microencapsulated pesticides are primarily used as preemergence pesticides, which can be used to kill or control newly occurring weed species or larval stage insects, which are applied to soil before plants appear or before insects appear. These applications require a relatively slow release rate to allow pesticides to be released into the environment over a period of time, usually at least weeks.

Generally, pesticides in microencapsulated form are prepared by one of three general methods: physical method, phase transfer method, and interfacial polymerization. In the third of these processes, interfacial polymerization, the microcapsule walls are formed of a polymeric material prepared by a polymerization reaction, which is generally a water-immiscible organic phase 2 It is preferred to occur at the interface between the phases. Generally, the two phases may be in the form of an oil-in-water emulsion, or may be a water-in-oil emulsion.

U.S. Patent No. 4,285,720 discloses a process for preparing materials which are not mixed with microencapsulated water, including pesticides and other pesticide chemicals, by interfacial polymerization techniques. The process generally involves the preparation of an aqueous phase comprising water, at least one surfactant and a protective colloid and an organic phase consisting of the substance to be encapsulated, preferably at least one solvent and at least one organic polyisocyanate. The substance or solvent to be microencapsulated may also serve as a solvent for the polyisocyanate.

The two phases are mixed for physical dispersion of the organic phase in the aqueous phase. This is usually done by adding the organic phase to the aqueous phase with stirring. Agitation and other conditions are adjusted to produce an O / W type emulsion in which the organic phase (in the form of droplets of the preferred size) is dispersed in the aqueous phase. The pH and temperature of the mixture prepared above are then adjusted to affect the condensation reaction of the polyisocyanate that occurs at the interface between the droplets of the organic phase and the aqueous phase to form the polymer or shell wall of the microcapsules containing the organic phase.

US Pat. No. 4,285,720 discloses a process that can produce microcapsules of about 0.5 to 4,000 micron droplet size using one or more polyisocyanates. Microcapsules prepared according to the examples of this patent and the general method thereafter are known to be very effectively controlled and to be released for a relatively long time (weeks).

However, different properties are required for the microencapsulated material used to be applied to the leaves of plants. In contrast to controlled release and release for relatively long periods of time, microcapsules for the application of leaves require the release of all substances relatively quickly in order to provide a rapid insecticidal effect.

Pyrethroids are excellent pesticides used to protect plants from insects. In current pesticide experiments, compositions comprising pyrethroids for application of plant leaves are provided in unencapsulated form, typically emulsifiable concentrates and wettable powders, which are mixed with water and formed on the plant after the composition is formed. Sprayed.

However, handling of pyrethroids is known to cause harmful reactions on the skin. This reaction is expressed as a burn, discoloration, numbness or pain sensation, which is most pronounced in the face of the handler. This reaction, known as paraesthesia, is usually associated with the delivery of a small amount of pyrethroid to the face by the operator unconsciously touching the face with a contaminated hand. This problem can be particularly acute in solid formulations such as dust or granules.

Microencapsulation of pesticides can often improve the stability of pesticide handling to such an extent that the polymer walls of the microcapsules can minimize the contact of the handler with active pesticides. Microencapsulation of pesticides can also be used in the manufacture of agrochemicals by providing a relatively more concentrated form of the substance than the corresponding emulsifiable concentrates, wettable powders or flours, which are used in the manufacture of pesticides, surfactants, dispersants, It may offer advantages such as the possibility of reducing the amount of inert materials such as supports. However, typical sustained release microcapsules used to date for pesticides applied to soils are not satisfactory for applications where relatively fast and complete release is required.

Summary of the Invention

The present invention provides a weight ratio of aromatic polyisocyanate to aromatic diisocyanate comprising (a) an aromatic polyisocyanate which is not mixed with water, an aromatic diisocyanate and optionally three or more isocyanate groups, to prepare microcapsules. Preparing an organic phase having a maximum of about 1: 1.5, (b) introducing the organic phase into an aqueous phase optionally comprising water, protective colloids and surfactants, and (c) mixing under high shear stress to average size Forming an O / W emulsion having oil droplets having an oil droplet of about 1 to 5 microns and (d) causing the interfacial polymerization reaction to form the polyurea microcapsules comprising the organic phase to take place. And / or adjusting the pH as needed.

1-5 are graphs of insecticidal and herbicidal evaluation results for the compositions of the present invention.

It is known that microencapsulated pesticides suitable for relatively rapid release and application of leaves can be prepared by making two important changes and adjustments to the general process disclosed in US Pat. No. 4,285,720. These are monomers or mixtures of monomers that produce microcapsules with or without cross-linking on the walls as described herein and have an average particle size of about 1 to 5 microns, preferably 2 to 4.5 microns. It is associated with the formation of an oily O / W type emulsion with relatively small droplets. In addition, because of their relatively small size, the capsule of the present invention has a relatively thin wall. The contents of US Pat. No. 4, 285,720 are incorporated herein by reference.

Briefly, this process involves encapsulating a substance (in the present case preferably an organic phase comprising a pyrethroid insecticide) in the discontinuous capsule of polyurea. In this process, hydrolysis of the isocyanate monomer takes place to form an amine, and the amine subsequently reacts with other isocyanate monomers to form a polyurea. In general, this process involves two steps.

In the first step, the physical dispersion of the phase which is not mixed with water in the aqueous phase is prepared. Phases that are not mixed with water include pesticides to be encapsulated with other materials as described below. As is known, the dispersion is effected by a high shear stress device, and this step is carried out until the desired droplet size (as described below) is reached. Only mild stirring is required in subsequent processes.

In the second step, the dispersion is stirred under high shear stress at a temperature of about 20 ° C. to 90 ° C., where a reaction involving organic diisocyanate and organic polyisocyanate occurs at the interface between the organic phase and the aqueous phase to form polyurea. Adjusting the pH and temperature range of the mixture prepared during the second step promotes this condensation reaction.

The aqueous phase is prepared from water, protective colloids and preferably surfactants. In general, the surfactant or surfactants of the phase may be an anionic or nonionic surfactant having an HLB of about 12-16. If more than one surfactant is used, each surfactant may have an HLB value of 12 or less or 16 or more, such that the total HLB value of the bound surfactant is in the range of about 12-16. Suitable surfactants include polyethylene glycol ethers of linear alcohols, ethoxylated nonylphenols, naphthalene sulfonates, long chain alkyl benzene sulfonate salts, block copolymers of propylene and ethylene oxide, anionic / nonionic blends, and the like. . Preferably the hydrophobic portion of the surfactant has similar chemical properties to the phase which is not mixed with water. Thus, when the latter comprises an aromatic solvent, one suitable surfactant is ethoxylated nonylphenol. In particular, the surfactant preferably comprises a block copolymer of propylene oxide and ethylene oxide and an anionic / nonionic blend.

Protective colloids present in the water (or continuous) phase must be strongly adsorbed to the oil droplets and must be polyacrylate, methyl cellulose, polyvinyl alcohol, polyacrylamide, poly (methylvinyl ether / maleic anhydride), polyvinyl alcohol and methyl Vinyl ether / maleic acid (hydrolyzed methylvinyl ether / maleic anhydride (see US Pat. No. 4,448,929, incorporated herein by reference)); And a wide range including materials such as alkali metal or alkaline earth metal lignosulfonates and the like. However, the protective colloid is preferably selected from alkali or alkaline earth metal lignosulfonates, most preferably sodium lignosulfonates.

The concentration range of the surfactant (when surfactant is used) in the process is about 0.01 to 3.0% by weight based on the aqueous phase, although higher concentrations of surfactant may be used. The protective colloid is generally present in the aqueous phase in an amount of about 0.1 to 5.0 weight percent. As long as there is sufficient amount to completely coat the surface of all oil droplets, the amount of protective colloid introduced is dependent on several factors such as molecular weight, compatibility and the like. The protective colloid may be added to the aqueous phase before being added to the organic phase or may be added to the whole system after the organic phase or the dispersion of the organic phase. Surfactants should be chosen so as not to remove the protective colloid from the droplet surface.

The organic phase comprises pesticides and / or other pesticide chemicals to be encapsulated in admixture with water, one or more solvents selected, aromatic diisocyanates and also preferably aromatic polyisocyanates. Suitable solvents include aromatic hydrocarbons such as xylene, naphthalene, or aromatic mixtures; Aliphatic or cycloaliphatic hydrocarbons such as hexane, heptane and cyclo hexane; Alkyl ethers including alkyl acetates and alkyl phthalates, ketones such as cyclohexanone or acetophenone, chlorinated hydrocarbons, vegetable oils, or mixtures of two or more such solvents.

The inventors have found that by adjusting the process of US Pat. No. 4,285,720 it is possible to obtain microcapsules which, when applied to an agricultural environment, release the encapsulated content relatively quickly.

Rapid release properties are achieved by providing microcapsules that have no correlation in the polymer walls, or have relatively small correlations, and have relatively small average particle sizes (as described below). The walls are formed of a mixture of aromatic diisocyanates or one or more aromatic diisocyanates with aromatic polyisocyanates having three or more isocyanate groups, wherein the weight ratio of polyisocyanate to diisocyanate in the mixture is from about 1: 100 to about 1: 1.5. , Preferably from about 1:50 to about 1:10.

The diisocyanates and polyisocyanates which may be used in the present invention are those described in US Pat. No. 4,285,720. Diisocyanates that may be used in the process of the invention include m-phenylene diisocyanate, p--phenylene diisocyanate; 1-chloro-2,4--phenylene diisocyanate; 4,4'-methylenebis (phenyl isocyanate); 3,3'-dimethyl-4,4'-biphenylene diisocyanate; 4,4'-methylenebis (2-methylphenyl isocyanate); 3,3'-dimethoxy-4,4'-biphenylene diisocyanate; 2,4-toliene diisocyanate; Isomeric mixtures of 2,6-toliene diisocyanate, 2,4- and 2,6-toylene diisocyanate and 2,2 ', 5,5'-tetramethyl-4,4'-biphenylene diisocyanate Include.

Aromatic polyisocyanates that may be used in the present invention include polymethylene polyphenylisocyanates (available from ICl or Bayer), tetraphenylethane triisocyanate (“Desmodur R”) and 1 mole of trimethylolpropane, having at least 3 isocyanate groups; Addition product formed between 3 moles of toliene diisocyanate (“Desmodur TH”) (available from Desmodur available from Bayer AG).

Whether a polyisocyanate is needed to provide the required wall properties, and, if necessary, the relative amount, will depend on the active ingredient or composition of the composition and the use in which the composition is used. For example, for microencapsulated compositions containing herbicide fluaziphop-P-butyl for the application of leaves, satisfactory capsules can be made using only mixed isomers of tolyene diisocyanate free of polyisocyanates. In this mixture, the weight ratio of polyisocyanate to diisocyanate may be as high as about 1: 1.5. However, in compositions comprising the insecticide lambda-cyhalothrin, some polyisocyanate is needed to provide correlation in the capsule wall. Wherein the weight ratio of polyisocyanate to diisocyanate should be about 1: 100 to about 1: 3, preferably about 1:50 to about 1:10.

U.S. Patent No. 4,285,720 discloses the use of mixtures of these two types of isocyanates, in particular toluene diisocyanate (TDI) (many isomers) and polymethylene polyphenylisocyanate (PPI), examples of which are PPI: Although the use of these two isocyanate mixtures having a weight ratio of TDI of about 2: 1 to about 1: 1 is described, this patent does not provide any other information on the use of such mixtures.

The total amount of organic isocyanate used in the process will determine the contents of the formed microcapsule walls. In general, isocyanates (and corresponding microcapsule walls formed therefrom) contain from about 2.0 to 15%, most preferably from about 5 to 10% by weight of the microcapsules.

The encapsulated material is a material suitable for the application of agrochemicals, preferably pesticides, preferably leaves. Pesticides that may be applied to the present invention include insecticides (particularly pyrethroids), herbicides and fungicides. Other pesticides such as plant and insect growth regulators may be included instead. The encapsulated material can be a combination of two or more such ingredients.

A second important change in the process of US Pat. No. 4,285,720 is the size of the microcapsules produced, which corresponds to the droplet size of the organic phase present in the O / W emulsion. The patent discloses that the preferred droplet size is about 0.5 to 4,000 microns, preferably about 1 to 100 microns for most pesticidal applications. However, in carrying out the process according to the invention, the average particle size should be small, ie about 1 to 5 microns, preferably about 2 to 4.5 microns. Droplet size can be controlled by stirring speed and time and the form and amount of surfactant used, as is generally known in the art.

In order to obtain a suitable emulsion, the organic phase is added to the water phase with stirring. Suitable dispersing means are introduced to disperse the organic phase in the aqueous phase. This means may be a high shear stress device, which is operated to obtain a desired droplet (corresponding microcapsule particle) size of about 1 to 5, preferably 2 to 4.5 microns. Once a suitable droplet size is obtained, the dispersing means is stopped and only gentle stirring is required for the rest of the process.

To form the microcapsules, the temperature of the biphasic mixture is raised to about 20 ° C. to 90 ° C., preferably about 40 ° C. to 90 ° C. at ambient temperature. Depending on the system, as described in US Pat. No. 4,285,720, the pH value can be adjusted to a suitable level.

In addition to liquid pesticides or other pesticide chemicals, the organic phase may also comprise suspended biologically active solids as described in PCT Application No. 95/13698; For example, the organic phase can include a second solid pesticide in the liquid pesticide. In contrast, if encapsulated pesticides are sensitive to and controlled by UV or actinic degradation, Serial No. 08 / 430,030 filed April 1995 contains a suspension of "biologically active compounds and sunscreens. Microcapsules may also include suspended solid sun protection agents selected from titanium dioxide, zinc oxide and mixtures of titanium dioxide and zinc oxide, as currently patented.

The use of the improved aspects of the present invention results in the preparation of microencapsulated pesticides that have the safe advantages of microcapsules in handling, which, when applied, perform equally well in liquid formulations such as emulsifiable concentrates of such pesticides. In addition, the use of the microcapsules of the present invention allows the emulsifiable concentrates used previously to be replaced with equally effective microencapsulated formulations, which have high concentrations of pesticides and correspondingly low concentrations of solvents, surfactants. And the like, thereby reducing the amount of the latter released to the environment. Because of the potential for pesticides to be crystallized from the composition in storage, handling and other situations, this latter improvement may not be suitable for the use of the same concentration of emulsifiable concentrates, but it may not be suitable for high saturated solutions or suspensions of pesticides in organic solvents. This is possible because microcapsules having them can be prepared. Microcapsules can also be prepared as water-based formulations, ie, aqueous suspensions of capsules, which further reduce the relative amounts of solvents in the formulations, further reducing the amount of solvent introduced into the environment relative to emulsifiable concentrates. Results in a decrease.

Capsules of the invention have been shown to provide nearly the same biological activity as emulsifiable concentrates. Thus, they are generally suitable for use in place of emulsifiable concentrates not only for the application of plant leaves, but also for other applications such as in soil or in buildings or around buildings.

The invention is illustrated by the following examples.

The general procedure for the preparation of microencapsulated lambda-cyhalothrin products is as follows.

The organic phase was prepared by dissolving technical grade lambda-cyhalothrin in a solvent (88% purity). If titanium dioxide was contained, as in Example 3, a dispersant was first added to the solution, followed by titanium dioxide. Finally organic isocyanate was added.

The aqueous phase was prepared by dissolving certain components in water. The organic phase and the water phase were combined with stirring with a high speed stirrer to form an O / W emulsion. Stirring was continued until the oil droplet size was 3.0 ± 1 micron. Thereafter, the emulsion temperature was raised to 50 ° C. over 30 minutes while maintaining gentle stirring, and maintained at this temperature for 3 hours to form a microcapsule shell.

The suspension prepared above was cooled to room temperature. A more stable suspension was made by adjusting the pH value to 5.0 with sulfuric acid while adding additional ingredients. The capsule size corresponded to the original oil droplet size. Microscopic observations showed suitable discontinuous particles.

The components used in the following examples are as follows:

Lambda-Sihalothrin, technical grade (88% purity)

Solvesso 200 aromatic solvent (available from Exxon)

Titanium dioxide-USP328-0.3 micron particle size (available from Whittaker, Clark & Daniels Ltd.)

Hypermer LP1, Hypermer LP5 and Atlox 4912 dispersants (available from ICI)

Reax 100M protective colloid (sodium salt of lignosulfonic acid in 40 wt% solution in water, available from Westvaco Chemicals)

Tergitol NP7 and XD surfactants (available from Union Carbide)

Whitconate 90 surfactant (available from Witco)

Kelzan (xanthan gum, available from Monsanto)

Proxel GXL (biocide, available from ICI)

Example 1

Example 2

Example 3

Example 4A-4F

Fluaziphop-P-Butyl

The general procedure for preparing microcapsules is as follows:

148 g of technical grade Fluaziphop-P-Butyl (90.7% purity), 12.0 g of toluene diisocyanate (TDI, 80% 2,4-isomer and 20% 2,6-isomer mixture) and polymethylene polyphenylisocyanate (PPI) were mixed together as indicated to prepare an organic phase.

A water phase was prepared by dissolving 3.72 g of Reax 100M (40 wt% aqueous solution) and 3.32 g of tergitol XD (20 wt% aqueous solution) in water. The organic phase was poured into the water phase with stirring and stirring continued until the oil droplet size was 4.1 to 4.7 microns. With continued gentle stirring, the emulsion temperature was raised to 50 ° C. and maintained at this temperature for 3 hours.

The prepared suspension of microcapsules was cooled to room temperature. The capsules are shown in Table 1 below.

Biological efficacy assessment

The biological activity of the products of Examples 1-3 in field tests was compared for the activity of standard emulsifiable concentrates (EC) of lambda-sihalothrin. As shown below, the level of insect control achieved by the products of the present invention in these tests was comparable to the use of unencapsulated products even on the day of application.

Cotton weevil from cotton ANTHONOMUS GRANDI Adjustment of

The products were applied four times in random complete blocks. Each product was applied at three ratios of 0.01, 0.02 and 0.03 lb / acre of lambda-sihalothrin. Activity was assessed by determining the level of weevil-harmed (% unflowered flower buds) (%) in each test complex, which was 50 erasure sized from each test complex on days 3 and 7 after treatment. This was done by collecting (eraser sized) squares and evaluating them for the weevil sea. The data were subjected to factorial analysis. The overall results are shown in FIG.

Velvet bean moths in beans ANTICARSICA JEMMATALIS Adjustment of

The products were applied four times in random complete blocks. Each formulation was applied at three ratios of 0.01, 0.02 and 0.03 lb / acre of lambda-sihalothrin. Activity was determined by the number of larvae per 12 row feet on days 3 and 7 after application. The data was subjected to factorial analysis. The results are shown in FIG.

Tobacco Caterpillar (BUDWORM) in cotton ( HELIOTHIS VIVESCENS Adjustment of

Activity in this test was determined by biological quantification of laboratory leaves on cotton grown outdoors. Each formulation was applied at three ratios of 0.0025, 0.005 and 0.01 lb / acre of lambda-sihalothrin. The treated leaves were collected outdoors and transferred to the laboratory and placed in Petri dishes with 1-3 instar caterpillar larvae (5 larva per leaf). Evaluations were made on days 0 and 1 after treatment, respectively, and the results are shown in FIGS. 3 and 4.

All three tests did not show satisfactory results between formulations applied at comparable ratios.

Example 4a-4f The biological efficacy of the product was compared against the biological efficacy of standard emulsifiable concentrates (EC) of herbicides in greenhouse tests.

The emulsion of the sprayable test substance was applied to four weed species (Green foxtail ( Setaria viridis ), broad leaf signalgrass at application rates of 0.016, 0.031 a and 0.125 lb / acres of Fluaziphop-P-butyl). ( Bracharia platphylla ), crabgrass ( Digitaria sanguiralis ) and giant antler ( Setaria faberi ) were applied after post emergence.

Weed control rates were assessed 14 and 21 days after treatment (“DAT”). 5 shows the grade of test material averaged over all four ratios of applications. As shown in FIG. 5, compositions prepared using only PPI or using a PPI: TDI ratio greater than 1: 1 (Examples 4b and 4c) did not perform well when compared to emulsifiable concentrates, but the present invention The composition of (Examples 4d-4f) showed a weak control rate compared to EC.

Toxicological Evaluation of Mammals

Tests for skin and eye irritation of mammals were performed on the products of Examples 2 and 3. For comparison, samples of emulsifiable concentrates (“ECs”) containing 12.5% by weight lambda-shihalothrin and sustained-release microencapsulated lambda-shihalothrin (10% by weight) (“SR”) Was used. The test procedure is as follows:

Eye irritation

The test was carried out on a group of six New Zealand white rabbits. Body weight was measured on the day of application. All rabbits weighed more than 2 kg. The product was applied to all rabbits. However, emulsifiable concentrates in all rabbits resulted in paralysis that prevented complete evaluation in these tests. Therefore, diluted aqueous spray of EC (0.5% w / v) was also applied.

Approximately 0.1 ml of each test substance was injected into the conjunctival sac of the left eye of each rabbit. The right eye was used as a control. Test and control eyes were examined about 1 hour and 1, 2 and 3 days after application. Grading for eye response was recorded using the Draize scale. If signs of irritation appeared on day 3, the observation period was extended to 4 days, 7 days and at least 1 week later until 21 days, or sooner, until anything was normal.

Skin irritation

Skin irritation was performed by the guinea pig flank test as follows:

The test was conducted on a group of six female guinea pigs weighing 250-350 g. Each flank area was cut approximately 6 cm x 5 cm. 100 μl of the test substance was applied to one side of each animal and a control (excipient only or blank formulation) was applied to the other side. About 15 minutes after application, each guinea pig was observed and the number of times the animal attempted to reach the flank of the applied side with the head turned fully was recorded for 5 minutes. The observation was applied and repeated for 5 minutes after about 30 minutes, 1, 2, 3, 4, 5 and 6 hours. Observation was performed using a video camera having a timing device set to record the number of times. The response was calculated as the difference in the number of turns of the head between the test and control flanks. Potential sensory ideal responses were verified according to the following guidelines:

The above results indicate, on the one hand, that the microencapsulated compositions of the present invention have comparable biological activity to unencapsulated compositions containing the same active ingredient. These results indicate that the composition is encapsulated, but provides for relatively rapid release and the availability of the active ingredient. On the other hand, properties related to eye and skin irritation were similar to unencapsulated products. This combination of properties is amazing.

Claims (14)

In the method for producing a microcapsule containing agriculturally active substance, (a) an organic phase containing a substance to be encapsulated in water-immiscible, an aromatic diisocyanate and optionally an aromatic polyisocyanate having optionally at least 3 isocyanate groups, wherein the organic phase comprises aromatic diisocyanates and aromatic polyisocyanates When the weight ratio of polyisocyanate to diisocyanate is from about 1: 100 to about 1: 1.5; (b) introducing the organic phase into an aqueous phase containing water, a protective colloid and optionally a surfactant to form a dispersion of the organic phase in the aqueous phase; (c) mixing the dispersion to form an oil-in-water (O / W type) emulsion having oil droplets of average size about 1 to 5 microns; And (d) adjusting the temperature and / or pH of the oil-in-water (O / W type) emulsion as necessary to cause a polymerization reaction to form the polyurea microcapsules comprising the organic phase. Method for producing a microcapsule comprising a. The method of claim 1, And wherein said organic phase does not contain aromatic polyisocyanates having three or more isocyanate groups. The method of claim 1, And wherein said organic phase contains an aromatic diisocyanate and an aromatic polyisocyanate having at least 3 isocyanate groups. The method of claim 3, Wherein the weight ratio of aromatic diisocyanate to aromatic polyisocyanate is from about 1:50 to about 1:10. The method according to any one of claims 1 to 4, The method of claim 1, wherein the oil droplets have an average size of about 2 to 4.5 microns. The method according to any one of claims 1 to 4, The aromatic diisocyanate is a toluene diisocyanate production method of a microcapsule, characterized in that. The method according to any one of claims 1, 3 and 4, The aromatic polyisocyanate is a polymethylene polyphenyl isocyanate manufacturing method of the microcapsule, characterized in that. The method of claim 7, wherein A method for producing microcapsules, wherein the aromatic diisocyanate is tolyene diisocyanate. The method according to any one of claims 1 to 4, The method for producing a microcapsule, characterized in that the encapsulated material contains a pyrethroid insecticide. The method according to any one of claims 1 to 4, And wherein said encapsulated material contains lambda-cyhalothrin. The method according to any one of claims 1 to 4, Method for producing a microcapsule, characterized in that the encapsulated material contains fluazifop-P-butyl. Microcapsules prepared by the method of claim 1 microcapsules. Microcapsules prepared by the method of claim 3 microcapsules. Microcapsules prepared by the method for producing a microcapsule according to any one of claims 1 to 4.