MXPA99004410A - Endosulfan microcapsule dispersion - Google Patents

Abstract

Aqueous endosulfan microcapsule dispersions wherein the dispersed microcapsules contain endosulfan, an organic solvent or solvent mixture, and an isocyanate-prepolymer based capsule-forming material. The aqueous phase which constitutes the dispersion agent contains surface-active substances, a water-soluble inorganic salt and possibly further auxiliary formulation agents containing a relatively low proportion of capsule-forming material. Also disclosed is a method for the production thereof.

Description

DISPERSION OF MICROCAPSULES WITH ENDOSU FANO DESCRIPTIVE MEMORY In numerous patent applications, microencapsulation of pesticide active substances has already been described. Such formulations can, for example, release the encapsulated active substance in a delayed manner and thereby have a favorable influence on different undesired properties of the active substances, such as toxicity to users or leachability to ground and groundwater. For example, from the European patent document EP-A-134,674 it is known to decrease the cutaneous toxicity of the Difonate for rabbits, from the document EP-A-183999 it is known to decrease the toxicity of Permethrin for fish, from EP-A-368,576 it is known to decrease the toxicity of Chlorpyrifos for carps, from the Japanese patent document JP-A-6-256116 it is known to decrease the cutaneous toxicity of Fenobucarb and from the document PCT Patent WO-A-95/23506 toxicity to fish and ingestion toxicity to mice are known. Among the different variants of microcapsules encapsulated dispersions have been particularly well-established. These can be obtained by wrapping, for example, water-insoluble active substances with a thin layer of polymer in an aqueous medium, stabilizing the resulting dispersion, if appropriate with dispersing aids, and thereby obtaining formulations directly, as in all the other formulations. pluriphasic formulations, it is necessary to pay attention that when storing, no thickening, coagulation or sediment formations are reached; at least, the user must be able to make retrograde changes to these quality minimizing modifications, with a reasonable expense. It is inherent in the nature of the matter that the active substances with high density can therefore be processed in the most difficult manner to form dispersions of microcapsules. The requirements established in terms of physical stability are met by an appropriate composition of the aqueous support phase. Two other essential requirements affect from opposite directions on the capsule containing pesticides. On the one hand, by means of a sufficiently stable envelopment, it must be ensured that the intended purpose of the encapsulation is achieved, ie the fixation of the active substance inside the capsule. This means p. eg, in the case of insecticides that are toxic to warm-blooded animals, that the active substance can be released from its seal only after the user has typically diluted and spread the formulation, and that the sprayed coating or spray has dried on the target surface. On the other hand, the said wrapping must not be so firm that the active substance leaves too slowly after application. The lower limit for the rate of release is preset in this case by many factors, eg. ex. by physicochemical parameters, by the mode of biological action, by the type of the harmful organism to be combated, or by the tolerance of crop protection agent residues in the crop to be treated. The active substance insecticide endosulfan, because of its toxicity, is among the substances that have to be characterized in a corresponding manner according to the Ordinances on Materials Dangerous. However, endosulfan has a number of advantages, which is why it has been imposed and consecrated to a large extent as a type insecticide in different crops. Thus, for a long time, there is already a need for a commercial way of presenting endosulfan as a dispersion of microcapsules, which meets the aforementioned requirements. The most usual way for the constitution of said capsule wall around the active substance to be wrapped, consists of an interface polymerization in the presence of oil-in-water emulsions, the organic phase containing, together with the active substance, an oil-soluble prepolymer with free isocyanate groups. US Pat. No. 3,577,515 discloses how, after having added water-soluble polyamines, the surface of the droplets is completely hardened in such emulsions as a consequence of the addition reaction with the prepolymer containing the isocyanate groups. In this way an outer polyurea shell is formed.

From US-A-4,140,516 it is known that, even without water-soluble external amines, microcapsules can be obtained with a thin outer layer of the polyurea type, allowing partial hydrolysis of the prepolymer to be carried out in the emulsion. carrier of isocyanate functions. In this way, a part of the amino groups is reconstituted from the isocyanate groups, and by means of an internal polyaddition reaction with subsequent total hardening, the desired capsule shell is also produced. The use of toluylene diisocyanate, hexamethylene diisocyanate, methylenediphenyl diisocyanate and its higher homologs is described. In the case that it has to be hardened with an external polyamine, it comes most of the time from the group consisting of ethylene diamine, propylene diamine, hexamethylene diamine, diethylenetriamine and tetraethylene pentaamine. Various formulations with microencapsulated endosulfan have already been described in various ways in the patent literature. German patent document DE-A-2,757,017 relates to internally structured microcapsules whose wall material has the nature of a mixed polymer, which is crosslinked for reasons of urea and urethane. Inside the capsule, the active substance is dissolved in an organic solvent. Typically, 10% of the prepolymer, based on the total formulation, is needed in the constitution of the wall of a capsule. There is no indication about the decrease of acute oral toxicity by means of this type of formulations.

The same prepolymer is also used in WO-A-96/09760 for the encapsulation of endosulfan. Certainly, good insecticidal activity is described, but no advantage is mentioned in relation to an undesired toxic effect. WO-A-95/23506 concerns polyurea microcapsules loaded with endosulfan, in which the active substance is presented as a cooled melt. A mixture of methylenediphenyl diisocyanate and its higher homologs is described as a prepolymer; the amount of prepolymer employed, referred to the total formulation, is greater than 6%. This is hardened with a mixture of polyamines. Along with the data about a strongly diminished toxicity of this type of formulations, there is no indication in this document about advantages in biological activity and in relation to waste. There remained, therefore, the desire to have an insecticidal formulation with microencapsulated endosultane, which fulfilled the following conditions. present a possibility of simple and safe preparation having a good stability in storage have a reduced toxicity for users and useful organisms present a good initial biological effect not harbor any risk of increased residues of active substance not released on the treated parts of the plants.

It was finally found, surprisingly, that a dispersion of microcapsules prepared according to the interface polymerization process, known per se, with up to 30 and more% by weight of endosulfan, preferably with approximately 300 to 330 g of endosulfan / 1, meets the aforementioned requirements if comparatively minor amounts of a isocyanate-containing prepoiimer (in the order of magnitude of about 1% by weight) are used for the preparation together with a water-soluble diamine optionally necessary. By means of the very small amount of the prepolymer forming the wall of the capsule, the effect of the insecticidal effect is not delayed under the conditions of practice. By adding a sufficiently large amount of a water-soluble inorganic salt, such as calcium chloride, to the aqueous phase, and by means of an increase in the density which is bound thereby, the microcapsules can be prevented, after a certain period of time, sediment and eventually form a sediment hardly redispersabie. Such dispersions of microcapsules make possible because of their favorable acute toxicity to warm-blooded animals the toxicological classification "dangerous = harmful" and in the case that they contain calcium chloride as a density-increasing agent surprisingly present a toxicity for the fish significantly smaller than that of the dispersions of microcapsules that does not contain any calcium chloride. Water-soluble emulsifiable concentrates have, as is known, toxicity to fish still much greater. The invention concerns aqueous dispersions of microcapsules with endosulfan, in which the dispersed microcapsules contain endosulfan, an organic solvent or a mixture of solvents of this type, and a capsule-forming material based on isocyanate prepolymers, and the aqueous phase, which constitutes the dispersing agent, contains surface-active substances and optionally other formulation aids, and which, based on the total dispersion, contains 20-40% by weight of endosulfan, 35% by weight of an organic solvent or of an organic solvent. mixture of solvents 1 of this type, a capsule-forming material based on 0.5-5% by weight of socianate prepolymers, 0.2-5% by weight of one or more surfactant substances taken from the group of emulsifiers and dispersants, and a water-soluble inorganic salt, the content of the salt being chosen in such a way that the density of the aqueous phase is between 1.05 and 1.45 kg / l. In the dispersions of microcapsules according to the invention, organic solvents or their mixtures, taken from the group of N-alkyl-amides of fatty acids, N-alkyl-lactams, fatty acid ethers and aromatic hydrocarbons can be used, the derivatives being especially suitable. of naphthalene substituted with lower alkyl. Commercially available solvents suitable according to the invention are, for example, Solvesso 200 (1), butyl diglycol acetate, © Shellsol RA (2), Acetrel 400 (3), Agsolex 8 (4), © Agsolex 12 ( 5), © Norpar 13 (6), ®Norpar 15 (7), © Isopar V (8), © Exsol D 100 (9), © Shellsol K (10) and © Shellsol R (11), which are composed in the following way: (1) Mixtures of alkylated naphthalenes, boiling range 219-282 ° C, manufacturer: Exxon. (2) Mixtures of alkylated benzenes, boiling range 183-312 ° C, manufacturer: Shell. (3) Mixture of high boiling point aromatic compounds, boiling point range: 332-355 ° C, manufacturer: Exxon. (4) N-octyl-pyrrolidone, boiling point (at 0.3 mm Hg) 100 ° C, manufacturer GAF. (5) N-dodecyl-pyrrolidone, boiling point (at 0.3 mm Hg) 145 ° C, Manufacturer: GAF. (6) Aliphatic hydrocarbons, boiling point range: 228-243 ° C, manufacturer: Exxon. (7) Aliphatic hydrocarbons, boiling point range: 252-272 ° C, manufacturer: Exxon. (8) Aiiphatic hydrocarbons, boiling point range 278-305 ° C, manufacturer: Exxon. (9) Aliphatic hydrocarbons, boiling range: 233-263 ° C, manufacturer: Shell. (10) Aliphatic hydrocarbons, boiling point range: 192-254 ° C, manufacturer: Shell. Mixtures of these solvents with each other are also suitable.

In particular, butyl diglycol acetate, Acetrel 400, Agsolex 8 and Agsolex 12 are particularly useful. Solvesso 200 is particularly preferred. In this solvent, the active substance sulfan is present in the dissolved state, and in particular in amounts such that concentration of active substance, referred to the total formulation, has values between 20 and 40% by weight, preferably between 20 and 35% by weight. Especially preferred are about 300 to 330 grams of endosulfan / liter of the total formulation. The capsule-forming material, on the basis of which the microcapsule shells are constituted, is preferably obtained starting from oil-soluble prepolymers, containing isocyanate groups, in which case it is a group of mixed technical products, consisting of in each case of polyisocyanates based on aniline and formaldehyde condensates. These mixed technical products differ from each other in the degree of condensation and possibly in chemical modifications. Important characteristics for users are the viscosity and the content of free isocyanate groups. Commercially typical products are in this case the © Desmodur brands (from Bayer AG) and the © Voranate brands (from Dow Chemicals). It is essential for the invention that the amount of prepolymer containing isocyanate groups used is < 5% by weight, based on the total formulation; 0.5 - 5% by weight, especially 1 - 2% by weight is preferred. The capsule-forming material is formed by hardening the isocyanate prepolymer either in the presence of water at 0-95 ° C, preferably at 20-65 ° C or, also preferably, with the necessary amount of a diamine. In the case where the microcapsules are formed including diamines, such as, for example, alkylene diamines, dialkylene triamines and trialkylene tetraamines, whose carbon chain units contain between 2 and 8 carbon atoms, are suitable. Hexamethylene diamine is preferred. In this case, it is possible to use either amounts which are in the stoichiometric ratio with respect to the amount used of the isocyanate prepolymer or preferably in an excess of up to three times higher, especially up to twice as high. In the aqueous phase of the formulations according to the invention, formulation-forming surfactants, taken from the group of emulsifiers and dispersants, are present. These come from a group, which encompasses p. ex. the families of substances of polyvinyl alcohols, of polyalkylene oxides, of condensation products of formaldehyde with naphthalenesulfonic acids and / or phenols, of polyacrylates, of copolymers of maleic anhydride with alkylene -alkyl ethers, of the ligninsulfonates, and of the poly (vinyl pyrrolidones). These substances are used in proportions of 0.2 to 5% by weight, preferably 0.5 to 2% by weight, based in each case on the total dispersion. In the case of poly (alkylene oxides), block copolymers are preferred, in which the center of the molecule is formed by a block of poly (propylene oxide) and, on the contrary, the periphery of the molecule is formed by blocks of poly (ethylene oxides). Substances are particularly preferred in this case, in which the polypropylene block has a molar mass of 2,000-3,000, and the poly (ethylene oxide) blocks constitute a proportion of 60 to 80% in the total molar mass. Such substance is sold p. ex. by the BASF Wyandotte entity under the designation © Pluronic F 87. Other suitable dispersants are calcium ligninsulfonate, sodium lignin sulfonate, which is highly ennobled (eg © Vanisperse CB from Borregard), the Dispersing Agent SI and the Dispersing Agent. SS from the entity Hoechst AG, the sodium salt of the condensation product of naphthalene sulfonic acid and formaldehyde (eg © Morwet D 425 from DeSoto or © Tamol - NN 8906 of the BASF entity), sodium polycarboxylate (eg © Sopropon T 36 of the Rhône Poulenc entity). Suitable polyvinyl alcohols are prepared by partial saponification of polyvinyl acetate. These have a degree of hydrolysis of 72 to 99 mol% and a viscosity of 2 to 18 cP (measured in a 4% aqueous solution at 20 ° C, corresponding to DIN 53 015). Preferably, partially saponified poly (vinyl alcohols) with a degree of hydrolysis of 83 to 88 mol% and low viscosity, in particular 3 to 5 cP, are used. The aqueous phase of the formulations according to the invention optionally contains at least one other auxiliary agent. of formulation, taken from the series of wetting agents, frost protection agents, thickening agents, preservation agents and density-increasing constituents. Suitable wetting agents are, for example, representatives of the groups of substances formed by the alkylated naphthalene sulphonic acids, the N-acyl fatty acid-N-alkyl-taurides, the fatty acyl-amido-alkyl-betaines, the alkyl polyglycosides, alpha-olefin-sufonates, alkylbenzene sulphonates, ethers of sulfo-succinic acid and alkyl fatty sulfates (optionally modified with alkyleneoxy groups). The proportion is in this case between 0 and 5% by weight, preferably between 0 and 2% by weight, based on the total formulation. Appropriate commercial products are for example © Darvan n ° 3, © Vanisperse CB, © Luviskol K30, Reserve C, © Forlanit P, © Sokalan CP 10, © Maranil A, © Genapol PF40, © Genapol LRO, tributylphenol-polyglycol ethers, such as the marks © Sapogenat T (Hoechst), nonylphenol-polyglycol ethers, such as the marks © Arkopal N (Hoechst) or the derivatives of tristyrylphenol-polyglycol ethers. As preservatives, the following agents can be added to the aqueous formulations: formaldehyde or hexahydrotriazine derivatives such as p. ex. © Mergal KM 200 of the Riedel de Haen entity or © Cobate C of the Rhône Poulenc entity, derivatives of siathiazolinone, such as p. eg ®Mergal K9N from Riedel de Haen or © Kathol CG from Rohm and Haas, 1, 2-benzisothiazolin-2-one, such as p. ex. © Nipacide BIT 20 of the entity Ñipa Laboratorien GmbH or © Mergal K10 of the entity Riedel de Haen or 5-bromo-5-nitro-1, 3-dioxane (© Bronidox L of the entity Henkel). The proportion of these preservatives is a maximum of 2 % by weight, based on the total formulation. Suitable frost protection agents are, for example, univalent or plurivalent alcohols, glycol ethers or urea, especially calcium chloride, glycerol, isopropanol, propylene glycol monomethyl ethers, di- or tri-propylene glycol monomethyl ethers or cyclohexanol. The proportion of these frost protection agents is a maximum of 20% by weight, based on the total formulation. Thickening agents can be inorganic or organic in nature; They can also be combined. They are appropriate p. ex. those based on aluminum silicate, xanthan, methylcellulose, polysaccharides, alkaline earth metal silicates, gelatins and polyvinyl alcohols, such as for example © Bentone EW, © Veegum, © Rhodopol 23 or © Kelzan S. Su ratio is 0 - 0.5% by weight, based on the total formulation. As an increasing constituent of the density of the aqueous phase, water-soluble salts of alkali and alkaline-earth metals as well as ammonium salts or mixtures thereof can serve; Calcium chloride is preferred. The amount of salt is oriented to the specific weight, which the aqueous phase must adopt, namely densities between 1.05 and 1.45 kg / l, preferably between 1.10 and 1.40 kg / l and especially preferred 1.15 and 1. 35 kg / l. Amounts are preferred by the addition of which the density of the aqueous phase approaches the density of the organic phase. The invention also relates to a process for the preparation of the microcapsule dispersions according to the invention, which is characterized in that first a rough emulsion based on an organic and aqueous phase is prepared (without diamine) and this is then subjected to shear forces, preferably pouring it through a mixing device that works in a continuous regime, for example a static mixer, a toothed mill of colloids or the like. By this step only, the fineness of particles is necessary for the subsequent formation of microcapsules from the emulsified oil droplets. Finally, eventually after adding a diamine, it hardens by polymerization reaction throughout the volume of the substance. The process can be carried out in semi-continuous mode on a technical and preparation scale. The following Examples serve to explain the invention, without it being limited thereto.

A. EXAMPLES OF FORMULATION Examples 1-5 (technical-scale experiments) A solution of 27 kg of technical endosulfan and 23 kg of © Solvesso 200 was prepared in a vessel with a 200 I capacity agitator with anchor stirrer mechanism and emptied into a reserve vessel. After that, an aqueous phase was prepared in the same vessel with stirring system (about the composition for the individual Examples, see below in Table 1), with water previously being prepared and the respective adjuvants being incorporated with stirring. It was continued stirring slowly until the total dissolution. After that, the stirring speed was increased to 70 rpm and the freshly prepared mixture of the organic phase prepared as above was quickly added with 1 kg of © Voranate M220. After further stirring briefly, the stirring mechanism was stopped and the resulting yellowish coarse emulsion was allowed to exit through a cogged toothed mill into a reserve vessel, forming a thin, light-colored emulsion whose droplets, depending on the setting of the mill teeth of colloids, had a diameter of 2-15 μm. This fine emulsion was added back to the stirred vessel and the stirring mechanism was started again at 70rpm. 2.5 Kg of a 40% aqueous solution of hexamethylene diamine was added and stirring was continued for 4 hours at 30 rpm.

TABLE 1 Examples (Quantitative data in each case in Kg). 1.2 3.4 5 ®MowioI 3/8 2.00 2.00 1.00 © Pluronic F87 1.80 1.80 1.80 © Morwet D425 0.50 © Galoryl DT120 0.50 © Soprofor FL 2.00 ®Rhodopoi 23 0.10 0.10 0.10 © Mergal K9N 0.10 0.10 0.10 © Antimussol UP 0.10 0.10 0.10 CaCl2 anhydrous 12.20 11.00 Technical glycerol 4.00 4.00 Water 25.70 26.90 41.4 ( The microcapsules contained in the dispersion have an average diameter, which depends, in addition to the composition of the recipe, also on the speed of rotation of the rotor in the mill and on the adjustment of the distance between the rotor and the stator ( say, of the "friction slit"). Table 2 explains this in more detail. The indicated values of the viscosity were determined in a rotating viscometer.

TABLE 2 Speed Viscosity Slice / mPa.s Diameter of friction rotation capsules Example (rpm) to 144 s "1 (μm) 1 3,000 3 840 2.8 2 1,500 3 1,100 5.1 3 1,500 1 500 9.0 4 1,500 1 510 8.7 5 3,000 3 140 2.5 EXAMPLE 6 As in Examples 1-5, a dispersion of microcapsules was prepared, with the difference that no continuous mixing step was anticipated. The aqueous phase was made up of 2.1 kg. from © Mowiol 3/83, 1.8 kg of © Pluronic F 87, 0.5Kg. from © Morwet D 425, 4Kg. of technical glycerol (86.5%) as well as in each case 100 g of © Rhodopol 23 and © Mergal K9N in 36.8 kg. of water. This aqueous phase was previously arranged in a vessel with agitation system provided with an anchor stirrer and the organic phase based on 27 kg of technical endosultane, 24 kg. of Solvesso 200 as well as 1Kg. of the prepolymer © Voranato M220, was added through a barrel dumper while stirring at room temperature. After stirring for 30 min 2.5 Kg of a 40% aqueous solution of hexamethylene diamine was added and stirring was continued for 4 h. In this way microcapsules with an average diameter of 14.9 μm were obtained.

EXAMPLE 7 As in Example 6, a dispersion of microcapsules was prepared, with the difference that instead of the anchor agitator a propeller-propeller stirrer was used. Under otherwise equal conditions, microcapsules with an average capsule diameter of 4.1 μm were then obtained.

EXAMPLE 8 (comparative example) For this microencapsulation experiment, a substance was used as a prepolymer, which was obtained by reacting 8 mol of toluylene diisocyanate with the hexane-1 mixture., 2,6-triol: butane-1,3-diol: polypropylene glycol 100 in the molar ratio 3: 1: 1, and for further use was dissolved in a 1: 1 mixture of n-butyl acetate and xylene , in which a 50% solution of the prepolymer was presented (described in DE-A 2,757,017). As described in Example 1, a dispersion of microcapules was prepared, with the difference that 36.4 parts of water and 3 parts of the aforementioned prepolymer solution were used, dispensing with the diamine for total hardening. For this, stirring was continued for 15 h at room temperature.

The microcapsules of the obtained dispersion had an average diameter of 17 μm, and the viscosity in the rotation viscometer was located in 350 mPa.s. with a shear rate of 144 s "1.

EXAMPLE 9. 10 AND 11 At the laboratory scale, with the recipes of Examples 1, 3 and 5 in each case dispersions of microcapsules were prepared, previously providing 46.5 parts of the aqueous phase described above and 51 parts of the complete organic phase were incorporated in the aqueous phase. stirring at 300 rpm. After that, the stirring mechanism was adjusted to 2,000 rpm and shaken first for 30 s at 2,000 rpm. Then the number of revolutions was reduced to 300 rpm, 2.5 parts of a 40% aqueous solution of hexamethylene diamine were added and stirring was continued for 1 min. The number of revolutions was finally further reduced to 50 rpm, and stirring continued for 4 h. The results are reproduced in table 3.

TABLE 3 Viscosity / Example Diameter mPa.s the capsules Example at 144 s "1 (μm) 9 1 870 8.1 10 3 560 7.8 11 5 150 8.4 B. BIOLOGICAL EXAMPLES EXAMPLE 12 Initial and permanent effects in the case of Aphis fabae Common bean plants were sprayed in each case until they were wet dripping with an aqueous dilution of the indicated formulation, and immediately or 3 days after desiccation they were infected with leaf aphids.

Assessment: mortality (in%) at 7 days after infestation (see table 4).

TABLE 4 EXAMPLE 13 Initial and permanent effects in the case of Heliothis virescens Cotton plants were sprayed in each case corresponding to an amount consumed of 200 I of liquid to spray per hectare (ha), with an aqueous dilution of the formulations indicated. After desiccation it was infected, immediately or after 4 and 7 days, with larvae of the borer of the cotton capsules. (Results see in the box). (Evaluation: mortality (%) at 4 days after infestation) TABLE 5 Infestation after Formulation g / h 0 days 4 days 7 days Endosulfan EC35 300 100 100 50 (commercial article) 100 100 70 20 30 80 30 40 10 10 0 10 Formulation Example 10 300 100 100 100 100 90 100 100 30 10 80 100 10 20 30 90 The greenhouse experiments demonstrate that a microcapsule formulation according to the invention is at least equivalent to an EC formulation (concentrate for emulsifying) usual in the trade in terms of the initial and permanent effects.

C. TOXICOLOGICAL EXPERIMENTS EXAMPLE 14 Microcapsules with a mean capsule diameter of 14.9 μm, produced as described in Example 6. Value of the LD50 in the case of a female rat: 530 mg / Kg. of body weight.

EXAMPLE 15 Microcapsules with an average diameter of capsules of 4.1 μm, produced as described in Example 7: Value of the LD50 in the case of a female rat: 315 mg / Kg. of body weight.

EXAMPLE 16 Microcapsules with a mean diameter of 7.8 μm capsules, produced as described in Example 10: Value of the LD50 in the case of a female rat: Greater than 200 mg / Kg. of body weight.

EXAMPLE 17 Microcapsules with a mean diameter of 17 μm capsules, produced as described in Example 8: Value of the LD 50 in the case of a female rat: 173 mg / Kg. of body weight. The toxicological experiments demonstrate the most favorable oral toxicity of the formulations according to the invention in the case of warm-blooded animals, over a wide range of diameters D. TOXICITY FOR FISH The examples presented in Table 6 show that the toxicity to fish of the formulation of microcapsules containing calcium chloride, according to the invention, is substantially lower than that of the dispersions of microcapsules without calcium chloride.

TABLE 6 Toxicity to fish against blue sun perch EXAMPLE 18 Dispersion of microcapsules without CaCl2 (Formulation of Examples 5) Mortality after Concentration 24 h 48 h 72 h 96 h mg animals /% animals /% animals /% animals /% Formulation / 1 Control 0/0 0/0 0/0 0/0 0. 032 0/0 0/0 0/0 0/0 0. 1 3/100 3/100 3/100 3/100 EXAMPLE 19 Dispersion of microcapsules according to the invention (Formulation of Example 1) Mortality after: Concentration: 24 h 48 h 72 h 96 h mg animal /% animal /% animal /% animal /% Formulation / 1 Control 0/0 0/0 0/0 0/0 0.032 0/0 0/0 0/0 0/0 0.1 0/0 0/0 0/0 0/0 EXAMPLE 20 Dispersion of microcapsules according to the invention (Formulation of Example 3) Mortality after Concentration: 24 h 48 h 72 h 96 h mg animals /% animals /% animals /% animals /% Formulation / 1 Control 0/0 0/0 0/0 0/0 0.032 0 / 0 0/0 0/0 0/0 0.1 0/0 0/0 0/0 0/0

Claims (10)

NOVELTY OF THE INVENTION CLAIMS

1. - Aqueous dispersion of endosulfan microcapsules, in which the dispersed microcapsules contain endosulfan, an organic solvent or a mixture of solvents of this type, and a capsule-forming material based on isocyanate prepolymers, and the aqueous phase, which constitutes the dispersing agent, contains surface-active substances and optionally other formulation aids, and which, based on the total dispersion, contains: 20-40% by weight of endosulfan, 10-35% by weight of an organic solvent or a mixture of solvents of this type a capsule-forming material based on 0.5-5% by weight of isocyanate prepolymers, 0.2-5% by weight of one or more surface-active substances taken from the group of emulsifiers and dispersants, and a water-soluble inorganic salt , the salt content being chosen in such a way that the density of the aqueous phase is between 1.05 and 1.45 Kg / l.

2. Dispersion of microcapsules according to claim 1, in which the isocyanate prepolymer is a mixed technical product soluble in oil based on polyisocyanates constituted by condensates of aniline and formaldehyde.

3. Dispersion of microcapsules according to claim 1 or 2, in which the capsule-forming material was formed by hardening the socianate prepolymer in the presence of water at 0-95 ° C, preferably at: 20-65 ° C. or with the necessary amount of a diamine.

4. - Dispersion of microcapsules according to one of the claims 1 to 3, which, based on the total dispersion, contains 20-35% by weight of endolsulfan, 15-30% by weight of an organic solvent or a mixture of solvents of this type, a capsule-forming material based on 1 - 2% by weight of isocyanate prepolymers, and 0.5-2% by weight of one or more surface-active substances taken from the group consisting of emulsifiers and dispersants.

5. - Dispersion of microcapsules according to one of the claims 1 to 4, in which the capsule-forming material had been formed by total hardening of isocyanate prepolymer with up to three times the stoichiometric amount of a diamine.

6. - Dispersion of microcapsules according to one of claims 1 to 5, whose aqueous phase has a density of 1.05 to 1.45 Kg / l.

7. - Dispersion of microcapsules according to one of claims 1 to 6, whose aqueous phase has a density of 1.10 to 1.40 Kg / l.

8. Dispersion of microcapsules according to one of claims 1 to 7, whose aqueous phase has a density of 1.15 to 1.35 Kg / l.

9. - Dispersion of microcapsules according to one of the claims 1 to 8, which contains calcium chloride as an inorganic salt soluble in water.

10. Process for the preparation of a dispersion of microcapsules according to one of claims 1 to 9, characterized in that a rough pre-emulsion is prepared on the basis of an organic and aqueous phase, this is then subjected to shear forces and the emulsion Finely divided thus obtained is hardened, possibly after having added a diamine in the total volume of material.