CS210682B2 - Herbicides in microcapsule form - Google Patents

Abstract

Microcapsules of trifluro-2, 6- dinitro-N, N-dialkyl-p-toluidine dissolved in an aromatic solvent provide an improved herbicidal composition for large scale application to crop producing areas. The capsules are of a polyurea or amide-urea copolymer produced by the reaction of intermediates, at least one of which contains a polyfunctional reactant having amine, isocyanate, -COCL or SO2CL groups, to provide cross-linking. The capsules may be applied as an aqueous slurry.

Description

The invention relates to a selective herbicidal composition in the form of microcapsules. Capsule walls are precisely defined and the herbicide is dissolved in a certain amount of specific solvent. It relates mainly to microcapsules formed by a wall with a polycondensate structure (polyurea or amide-copolymer resin) and containing a suitable trifluoro-2,6-dinitro-N, N-dialkyl-p-toluidine dissolved in a specified solvent:

Trifluralin is a generic name for alpha, alpha, alpha-trffluoro-2,6-dinitro-N, N-dipioipyl-p-toliddihi, a product of Elanco Divisinn® of Eli Lilly and Oompany, marketed as a pre-emergence herbicidal mixture under the trademark Treflan. This product is one of the most commonly used herbicides today. As. the selective pre-emergence type of herbicide can be applied to many crops including cotton, soybeans, safflower, sunflower, beans, bro, sugarbeet, hop, general, rapeseed, ornamental plants, cabbage, cauliflower, cabbage, brussels sprouts, tomatoes, peppers; unserved vines; citrus trees; · Peanuts, carrots and potatoes. Its use for destroying germinated and seedlings of plevein grasses is protected by U.S. Patent No. 3,257,190.

Trifluralin as a pre-emergence herbicide is available either as an emulsifiable concentrate (E.C.) or as a 5% granule. In order to be effective, both forms must be incorporated into the soil after application. The granulated product is used at the recommended rate of 90 kg / ha, applied by conventional equipment. at the same time, it is fed into the top 5 to 8 centimeters of soil. In contrast, the emulsifiable concentrate is preferably applied by aerial spraying because a large area can be treated quickly and economically. Application of the emulsifiable concentrate must be followed by incorporation into the soil Beautifully four (4) hours after spraying (as described in the product instruction manual) to avoid losing the effect of this procedure. It has been shown that evaporation losses of unincorpolated trifluralin just three hours after spraying can be as high as 30 [Parochettf JV and Henn · ER, Weed Science, Volume 21, Number 5 (September) 1973). In this way, the great advantage of aerial spraying, which is the rapid coverage of large areas, is lost because the farmer is not able to inject the spray into the ground before it is dispersed by evaporation. It is evident that there is a need for such a sprayable form. trifluralin, which would not lose the active ingredients from steaming so rapidly. This would preserve the speed and economy of the air. applications while longer · pi ^ oi incorporation · '· ¹ would be more suitable for a farmer.

The microcapsule manufacturing process has been described as a method to prevent premature evaporation or other deterioration of the material in the microtip. (British Pat. No. 1,371,179). It is to be expected that the activity of the insecticides and herbicides in microcapsules should be greatly prolonged and accordingly this method of producing pesticides. and it is known to increase the stability of the treated product. (U.S. Pat. 3,577; U.S. Pat. 3,954,464; British Pat. 1,371,179; and W. A. Gentner et al., Publication, U.S.D.A. Effect of the use of microcapsules on the herbicidal activity of chlorpropham September 1976).

However, trifluralin and closely related derivatives are present. sufficiently stable after incorporation into soil and since their stability and selectivity in the treatment of crop plants is experimentally determined and confirmed. it is considered undesirable to increase or prolong their activity by incorporating into microcapsules or otherwise.

SUMMARY OF THE INVENTION The present invention provides a process for the preparation of a microcapsule herbicidal composition which comprises dissolving trifluoro-2,6-dinitro-N, N-dialkyl-p-toluidine in at least 20% to 60% of an aromatic naphtha solvent. (calculated on the weight of the solution) and said solution is formed into microcapsules, the wall of which is formed by a polycondensated resin selected from the group consisting of urea and amine urea copolymers, the larger of which. part of said microcapsules has a size ranging from. about ten microns. approximately a hundred · microns · and · mentioned. polykondenzioiraamá. the wall is prepared by indicating it. . dd reaction. . the first and second, the intermediate forming the urea polymer or urea. kopclym ^, wherein at least one of said. first · · a. Second. contains from · zero. Up to one hundred percent (based on the weight of the intermediate). · Polyfunctional; Reactants which are (a) complementary to the latter of said intermediates and which are effective for. A crosslinking reaction; and. at least three reactive groups that are effectively functional in said reaction, said reactive groups being rolled from. a class consisting of an aminoscupine, an isocyanate group, -COCl. and · SO2C1 ^! group. Alkyl groups · toluidine compounds include, for example. methyl, ethyl, n-propyl, isopropyl, n-batty: isoamyl, 1-methylisobutyl, and the like.

The term cross-linking as used. here, it refers to an intranolecular linkage or a bond between surfaces of linear polymer molecules resulting from a plurality of functional reactants having at least three). Efficiently functional reactive groups that exchange at least a part of one or. several similarly · · · reactive. . difunctional condensation reactants in polycondensation. · Regulation. For example, when the entire amount of a difunctional acid derived component is replaced by a polyfunctional reaction, for example a polyfunctional isocyanate in a polycondensation recipe, which may normally consist of) a difunctional amine, and an acid-derived difunctional component, resulting in polycondensate is. considered to be 100% crosslinked by urea. When only 50% of the difunctional component is replaced by a polyfunctional reagent, the polycondensate is considered to be 50% crosslinked.

Although how-first. thus, the latter of said intermediates may consist entirely (100%) of the polyfunctional reactants as described above, thereby rendering the individual reactant capable of cross-linking with a complementary cross-linking group. neighboring. . the polymer chain so that a polycondensated wall is obtained. which may be. called. 200% cross-linked, it is preferred that only one of said first and second intermediates contain up to 100% of said polyfunctional reactants. When only one of the intermediates contains a polyfunctional reactant and the polyfunctional reactant constitutes 100% of said intermediate, the polycondensed · resin is considered to be 100 ^! % 'cross-linked.

In general, the manufacturing process as used herein for preparing microcapsules is described in U.S. Pat. 3 429 827 and US Pat. No. 3,577,515 and comprises an interfacial polymerization process for producing polycondensed capsule wall material, which is preferably crosslinked. Important variables in this production process - which they can influence. Evaporation rate netxouvoliování trif luBaltaUéZzkrkrMitobolek, jsou. degree of cross-linking of the soldered wall; the polycondenate is the particle size. capsules. The method of manufacture consists in forming (by stirring) a dispersion of droplets of the first of said intermediates. which is to be converted into microcapsules in the liquid-liquid phase, the tin phase and is. Immiscible with droplets and contains substantially no reactant complementary to said first intermediate and (.2) and thereafter, the low-yielding of said intermediates, i.e., ancillary · k. the first intermediate into the liquid liquid. phase so that the first ·· and the second intermediate react. . at the interface between the droplets and the continuous phase, they form capsules in which the droplets are within the layer. . said polycondensate.

When it is . desire. Cross - linking,. . at least one of the above. Intermediate products must · contain at least in part. a polyfunctional reactant which is (a) complementary to the other of said intermediates and is effective cross-linking. reaction and. (b) it has at least three reactive groups that are non-existent. selected from the group consisting of amino groups, isocyanate groups, SO 2 and SO 2 Cl groups, said first t-a

21068 2nd. Intermediate. mutual. reactions. microcapsules · closing. inside the above · ^: said layers. cross-linkedthis pdiycondensate.drops. of active solution.

Examples of suitable diarnines · A. poíyaminomin,. toluene diamine, hexamethylenediamine, diethyl-1-one; Piperazine,. 1,3,5-benzentria. .min ·: trihydrochloride. 2,4,6 - Г] .шш tri tri tri tri tri tri tri tri tri tri tri tri tri. tetraethylenpentanlin,. pentaethylenehexamine, polythyienamine, 1,3,6-triaminonaphthalene, 3,4,5D-thiaminaminaphthalene. non. . Příkiady. difunctional. ; and. . polyfunctional derivatives of acids providing. -COC1 and -SO.2C1 reactive. groups. are. chloride. acid. sebakové,. ethylene-bis-chloroformate, phosgene,. chiorid. azeioic acid, chioride. adipic acid, terephthalic acid chloride. . . dodecanedioic acid chioride, chio. ridy. ' dimeric acids, 1,3,5-benzene trischioroformate. . Intermediates. useful for providing reactive isocyanate. groups are represented by compounds such as para-phenylene diisocyanate, metaphenylene diisocyanate, naphthalene-1,5-diisocyanate, 2,6-toluene diisocyanate, 4,4-diphenyldiisocyanate, dichlorobiphenylmethane diisocyanate, diphenyidoisocyanate, diphenyidoisocyanate, diphenyidoisocyanate, diphenyidoisocyanate, diphenyidoisocyanate. diphenyl ether diisocyanates, diphenyldimethyldiocyanates, polymethylene polyisocyanates, triphenylmethane. . iso-propypylene-zen-alpha-dhsot cyanate and the like.

When amplification is desired, it is. sufficient quantity added. A polyfunctional reactant (ie, a trifunctional or higher), i.e. a reactant having at least three functional groups as previously described, so as to produce a microtoboic in which the polycondensed wall may be cross-linked up to 100% (i.e. up to 100 of one of the polycondensate reactants) is polyfunctional. The preferred method. The embodiment consists in that the polycondensated wall is prepared with - about. 5 to 50 ^! % of the polyfunctional reactant as. components . one of said i-termiediates. The polycondonates from the polycondonsate without cross-linking were, to illustrate, composed of fibers of the linear type of molecules. that are not connected to each other. By crosslinking the polymer, these are bound. together in different places. according to the history and creates so. a much tighter network structure.

^; The ratio of 'wall polymers to active ingredients controls the' wall strength '. microcapsules. Scope. for a wall weight it is preferably from 5 to 15%, but. the product is. functional with walls from 2.5% to 40% calculated on the weight of the microtoboics. Most economical is the use of lower weight! . a wall ratio, although the price ratio may be more favorable for a product with a higher concentration of active ingredient.

The particle size of the microcapsule (the largest linear dimension) also affects the wall thickness and hence the release rate. effective siožky. 'Larger. parts of said micnotobot can. measuring from less than 10. microns to. several hundred microns. However, a preferred particle size is from 25 microns to 25 microns. .50 microns. Particles. larger than 100 microns cause sieve clogging. and particles less than 10 microns in diameter. increasing dispersion throughout. aerial .applications. Maié ^; particles. release effective. substance faster,. . than '. larger particles because the thickness: the wall of the small particle is ^: smaller. than. strong . walls with larger particles.

A slurry or slurry. mixture. mi- krotoholek-a. water. Yippee . normal. -form 'for transportation, storage. .-.-and finally . . for. application. herbicidal field composition. A suitable aqueous dispersion, suspension,. or a slurry of the herbicide in microtobics. for .transport and. . storage consists of. about 10 to about. 30 why,. % by weight, preferably about 25% by weight, of the herbicide, which is diluted to about 0.5% to 2% by application. This. slurry,

·. suspension. or a dispersion of microts in water. can. include. suspendační. agents such as cross-linked acrylic acid copolymers as discussed; U.S. Pat. No. 3,426,004, xanthate resin, as illustrated. U.S. Pat. 4,107,292; other. suspending agents such as hydroxyethyl cellulose, resins, clays, silica gel, with a grain size below one micron and other inorganic material; wetting and dispersing agents. agents such as detergents, polyvinyl alcohols, gelatin, methylcellulose, casiein and clays.

Further illustration of the process ..uveden polycondensed resin microcapsule wall constituting the f trifiuralin containing ¹ to mites in organic.! x moles (where x is equal to 0 ^: 1) are reacted. polyfunctional isocyanate. as· . is, for example, polymethylene polyphenyl isocyanate under the tradename PAPI; 1-mole of chloride. an acid (such as chloride of self-acid) or a difunctional isocyanate (such as toluene isocyanate); m, where n is equal to 1 to 3; a difunctional amine (such as ethylenediamine); y moles, where y. it is equal to zero to 1.5, a dysfunctional polyamine (such as diethyl lentriamine); case. add bases such as. eg, hydroxide. sodium to neutralize the hydrochloric acid formed during the polycondensation reaction. Excess amine may be used in the process. The diacid chloride and / or isocyanate are added to a solution of trifluralin which serves as a water-insoluble organic solvent, the organic mixture is dispersed in water and the amine is added to the reaction mixture. in the form of an aqueous solution.

In addition to the decisive importance of the wall of the micrototo was. found it necessary ^{: to} use a solvent that would dissolve triflurailin. prior to the formation of the micnOt ^ oboiek, and; which would allow a suitable release rate. It has been found that the choice of solvent used, and. its amount has a profound effect on. the rate of release of trifluralin from the capsule.

The number of solvents, which may be ^one of nodes for this invention is greatly reduced for three reasons. First, it must be shown that the solvent is · an inert ingredient for use in agriculture and as such · is listed in US Federal Regulations, title 40 part 180 ^: 1001. Second, the solvent must be compatible with the active ingredient and must dissolve it without affecting the selectivity of its herbicidal activity. Third, the microcapsule manufacturing process requires it to be insoluble in water. Typical aromatic petroleum solvents that are useful in the present invention include xylene, toluene, naphtha, and the like. The amount of solvent in the solution is from about 20 to about 60 percent, preferably from 30 to 50 percent, based on the weight of the solution.

In the description of the invention, microcapsules are sometimes referred to by a group of numbers and may also include letters. For example, in group 5 (10) SX 50, number 5 indicates a microcapsule with a wall weight of 5 percent (calculated on the weight of the microcapsule), number 10 indicates the use of a 10 percent polyfunctional reactant to replace the difunctional reactant in the recipe prepared by polycondensation of · sebacic acid chloride and the letter X with the number X 50 indicates a solution of trifluralin in xylene inside the microcapsule at a concentration of 50% by weight.

The effect of the solvent on the volatility of triflurahn in microcapsules can be demonstrated by the following data (Table 1).

The data in the above table was obtained by a test procedure in which the product in microcapsules or E. C. (trifluralin emulsifiable concentrate) was placed on filter paper in a thermostat heated to 54 ° C, which had the usual forced air extraction.

Table 1

Number Method Solvent type Quantity of sample preparation

Volatility:% evaporated trifluralin (hours) 1 2 19 24

1 AND xylene 30% 2 AND Panasol AN-2 30% 3 (B) xylene 80% 4 (B) Panasol AN-2 ^a 30% 5 E. C. -

a) Panasol AN — 2 is a registered trademark of Amoco Chemicals Corporation for Aromatic Petroleum Solvent (Heavy Petrol).

(b) value after 5 hours

The microcapsule tripleuralin used to obtain the above data was prepared in accordance with the microcapsule production method in the following: Except that the method of preparing wall A was derived using 50% polymethylene polyphenylisocyanate (PAPI), calculated on weight the water insoluble reactants and the wall weight were adjusted using the amount of reactants (relative to the trifluralin solution) to form a wall of 10 percent of the total weight of the microcapsule (10/50 / SP 70 where P = Panasol AN-2). The method of preparing wall B was also derived: in accordance with the same procedure, except that the amount of reactants was chosen to produce microcapsules with a wall of 10 percent calculated on the total weight of the microcapsules (10 / / 5 / SP 70). Samples 1 and 3 were prepared with xylene: instead of: Panasol AN-2 at the indicated amount.

The method of manufacturing microcapsules according to the invention is explained in more detail in the following example.

22 30—

0.4 0.7 —8.5 - ——

68 68 ¹ '-

90.3 94.5 —'—

Exemplary embodiment

Production of trifluralin in microcapsules

For the production of trifluralin in. microcapsules having: a 15% wall with 5% crosslinking, i.e. 5% difunctional reactants are replaced by a polyfunctional crosslinking reactant and in which 70% trifluralin is dissolved in Panasol AN — 2: (15 / / 5 / SP 70) was used the following regulation:

10 g of trifluralin was heated with 4.3 g of Panosole AN-2 and stirred until the mixture was homogeneous (70% concentration of trifluralin solution). To this solution was added sebacic chloride (2.43 g) and PAPI (0.14 g), i.e., 5 V, calculated on the weight of the water-insoluble reactants to prepare a solution containing all water-insoluble organic components.

This organic mixture was then dispersed with a high speed stirrer into: an aqueous solution of 0.25% Gelvatol (polyvinyl alcohol) for 15 seconds.

To achieve: polymerization, a mixture of ethylenediamine (0.64 g) was added; diethylenetriamine (0.74 g) and sodium hydroxide (0.82 g) in: 10 mL of water.

The slurry was stirred for two hours, neutralized with concentrated hydrochloric acid to pH 7.0 and passed through a 50 mesh screen to remove too large particles. Some of the water was decanted and the resulting mixture was concentrated with xanthate gum to prevent settling. The finished mixture has a concentration of 22%, or about 225 kg per m ^{3 of} active ingredient.

In order to obtain a composition suitable for field application, for example by aerial spraying, water is added to the composition up to the desired concentration.

The following table shows volatility and herbicidal activity data for several trifluralin samples in microcapsules. different wall thickness. These samples were prepared according to the previous embodiment except that 1) the amount of reactants was chosen such that the walls of the microcapsules in samples C, D, and E were 10, 20 'and 30 why, calculated on the total weight of the microcapsules 2], the addition of polymethylene phenyl isocyanate was used to. polycondensated wall crosslinking increased (25% PAPI calculated on the weight of water insoluble reactants) and 3) adipic acid chloride was used instead of sebacic chloride. Volatility data was obtained in the same manner as in Table 1. Values related to herbicidal activity were obtained by field trials in which the herbicidal composition was sprayed at a rate of 0.58 kg per hectare and then incorporated (incorporated) into the vrchních

2.5 to 7.5 cm. of land in a given, number of days.

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These data show the reduced volatility of the trifluralin samples in the microcapsules, as well as the dependence of the evaporation rate on the capsule wall type as compared to the emulsifiable concentrate (E. C.) of trifluralin. The second table shows the decreasing herbicidal activity of the emulsifiable concentrate with an increasing interval between application and incorporation, while the trifluralin samples in the microcapsules, especially the sample D (20/25 / A) do not show such a trend. The data also show that the activity of the microcapsule form and the emulsifiable concentrate is substantially the same when incorporated into the soil immediately after application.

As mentioned, for an effective release rate, it is necessary to use a solvent to form a trifluralin solution prior to preparation of the microcapsules. The amount of solvent in the solution may range from about 20 to about 60 percent, preferably from 30 to 50 percent, calculated on the weight of the solution. Thus, the solution is allowed to contain from about 80 to about 40 percent dissolved trifluralin. However, it can be assumed that a minor proportion of trifluralin can be exchanged for another active pesticide, whereby a dual, additive or even synergistic effect can be obtained.

To compare the herbicidal activity of the emulsifiable concentrate (EC) of trifluralin and the experimental formulation of trifluralin in capsules with different wall systems designed for delayed incorporation, a test procedure using a millet and oat bioassay was applied using herbicide to wet soil and incorporation immediately and or after seven days as described below:

The 7.5 cm metal dishes were filled with unsterilized medium-heavy hotbed ground and moistened with excess water. The individual herbicides tested, the emulsifiable concentrate (E. C.) and the active ingredient in capsules, diluted with water, were sprayed onto the ground surface of three different dishes at a rate of 0.87 kg per hectare. In one treatment with the E.C. form, incorporation into the soil was immediately performed, i.e. the ground for the three dishes was placed in a rotary mixer and the E. C. form was sprayed during mixing; upon incorporation, the treated ground was placed back on the dishes and moistened.

After treatment, the dishes were placed in a greenhouse where the conditions during growth of the seedlings were imitated and had a large air exchange capacity to increase the volatility of the applied herbicide formulations. The dishes were left in this greenhouse for several days during which no water was added to the soil. With the exception of the three dishes in which the E. C. formulation was immediately incorporated into the ground, the capsules were incorporated into the ground of each of the plates after seven days by mixing on a rotary mixer. Twenty-five (25) millet grains and twenty (20) bred oat grains were then sown, including untreated control dishes, the soil was moistened with an aqueous solution of soluble fertilizer, and the dishes were placed in a hotbed. On the fourteenth day after sowing, the resulting plants were harvested and their weight recorded. The percent inhibition of millet and oat growth compared to control are shown in Table 3.

An E. C. formulation that was directly incoirified (sample number 30) provides 10% of the growth inhibition of both millet and oats, while upon incorporation of the E. C. formulation after; Seven days (Samples Nos. 27, 28, and 29) were percent inhibition for millet 38, 52 and 69 and for oats 22, 27 and 59 percent, respectively. Trifluralin formulations in microcapsules that have exhibited more than 90 percent inhibition in both millet and oat are specimens of Nos. 3, 6, 8, 13, 16, 22 and 23. The remaining formulations in microcapsules except for samples of pure 1, 7, 20 and 25 also provided greatly improved outcomes in both millet and oat compared to the EC formulation.

Samples Nos. 1 and 7 show approximately the same extent of inhibition as the EC formulation. Formulations of Samples 1 and 7 are the same and can be expected to show similar inhibitory results. The polycondensed wall of these microcapsules is not crosslinked and has a low weight relative to the weight of the whole microcapsule. The percent inhibition of trifluralin in microcapsules is increased when the polycondensed wall is crosslinked, as in the example of preferred ¹ embodiment, or, as in the case of samples of numbers 10, 15, 17 and 22, when the walls have a greater weight relative to the microcapsule weight. . Sample No. 20 is a repetition of the sample of pure 19, which shows a relatively good inhibition of oats. The low efficiency of the specimen number · 20 is therefore unexplained. Sample # 25 represents a microcapsule product in which a sufficient amount of solvent for trifluralin, i.e. 10% solvent and 90% trifluralin, was not used.

When trifluralin in microcapsules is sprayed onto the soil surface (i.e., without incorporation), it does not cause greater damage to either the maize or cotton culture and also shows the same degree of growth control of the cervix, amaranth and foxtail as the E. C. formulation.

Table 3

Delayed incorporation test

Sample no.

Formulation

Percent inhibition of Proso Oats

1 5/0 / ST 50 45 41 2 5/10 / ST 50 87 84 3 5/10 / ST 50 97 95 4 5/10 / ST 50 100 ALIGN! 92 5 15/10 / ST 50 87 79 6 10/10 / SP 70 97 99 7 5/0 / ST 50 · 31 34 8 10/50 / SX · 70 109 98 9 15/5 / SP 60 74 92 10 15/0 / ST 50 85 85 11 15/5 SP 70 · 76 91 12 12.5 / 5 / SP 70 85 94 13 10/50 / SP 70 95 97 14 15/5 / SP. 70 87 93 15 Dec 15/0 / SP 70 83 94 16 10/5 / ST 70 98 98 17 15/0 / ST 50 88 85 18 10/25 / TP “50 97 96 19 Dec 15/10 / ST 50 82 91 20 May 15/10 / ST 50 61 65 21 10/50 / S (HMDA) ^b P70 79 86 22nd 15 / 07SX 70 92 99 23 10/5 / SP 70 98 98 24 15/5 / SX 70 78 79 25 15/10 / Wed ⁶ 90 67 93 26 10/100 / X 70 97 98 27 Mar: EC ^d 69 59 28 E. C. 52 22nd 29 E. C. 38 27 Mar: 30 E. C. (Immediately incorporated) 100 ALIGN! 100 ALIGN! 31 Control 0 0

Explanatory notes to Table 3:

(a) T = terephthalic acid chloride

b) HMDA - hexamethylenediamine, which replaces the usual amines in this formulation;

c) t = Tenneco solvent (aromatic petroleum solvent);

d) E. C 1 = emulsifiable concentrate.

The following solvents were used to make the formulation in capsules: Panasol AN — 2, designated P in the previous table, Xylene designated X, toluene designated T.

The data shown in the table above show that trifluralin in microcapsules with a wall weight in the range of 5 to 15 percent, calculated on the microcapsule weight, the amount of polyfunctional reactant replacing from 5 to 50 percent difunctional reactant in the polycondensation recipe, and ranging from 30 to 50 percent is a preferred embodiment of the present invention. Further, the data show that if a polyfunctional reactant is not used in the polycondensation recipe, the wall weight of the microcapsule should be about 15 percent of the weight of the whole microcapsule. Further, it is apparent from the data that generally trifluralin in microcapsules of the present invention unexpectedly exhibits reduced volatility outside the soil but substantially unchanged activity when incorporated into the soil as compared to trifluralin which is not in microcapsules.

Claims (11)

A microcapsule herbicidal composition comprising the active ingredient alpha, alpha, alpha-trifluoro-2,6-dinttro-N, N-di (C 1 -C 3 alkyl-p-toluidine, such as alpha, alpha, alpha-trifluoro-2,6- Dinitro-N, N-di-n-propyl-p-toluidine, characterized in that the active ingredient is dissolved in 20 to 60% of an aromatic naphtha solvent, based on the weight of the solution, and the microcapsule wall consists of a polycondensed resin selected from polyurea · and amldmočovinové copolymers, wherein at least the majority of the microcapsules in the size range from 10 to 100 ~ m polycondensate wall is formed by reaction of first and second intermediate forming polyurea or amidmočovinový copolymer, wherein at least one of said intermediates contains ^0-100!% based on the weight of the intermediate a polyfunctional reactant which is complementary to the second intermediate and is effective for the crosslinking reaction and which has at least three reactive groups that are effectively functional in said reaction, wherein the reactive groups include an amino group, an isocyanate group, a -COC1, and -50201 group. 2. A herbicidal composition according to claim 1, wherein only one of the first and second intermediates consists of 0 to 100. %, based on the weight of the intermediate, polyfunctional reactant. 3. The herbicidal composition of claim 1, wherein the microcapsule walls are formed of an amide urea copolymer. 4. The herbicidal composition of claim 1 wherein 5 to 50% of said intermediate is said polyfunctional reactant. 5. The herbicidal composition of claim 4, wherein the solvent is a heavy gasoline. 6. The herbicidal composition of claim 4, wherein the solvent is xylene. 7. The herbicidal composition of claim 4, wherein the solvent is toluene. 8. The herbicidal composition according to claim 4, wherein the weight of the microcapsule wall is in the range of 5 to 15% based on the weight of the microcapsule. 9. The herbicidal composition of claim 9, wherein the amide urea copolymer is an interfacial polycondensation product of the respective difunctional amine, sebacic acid chloride and polymethylene polyphenylisocyanate, wherein the polyphenylisocyanate replaces 5 to 50% sebacic chloride in the polycondensation reaction. 10. A herbicidal composition according to claim 9, wherein the weight of the microcapsule wall is in the range of 5 to 15% based on the weight of the microcapsule. 11. The herbicidal composition of claim 1, wherein the composition is in the form of an aqueous dispersion to be sprayed.