CH629074A5 - Compositions containing herbicidal derivatives of 2,6-dinitroaniline, process for preparing them and their application - Google Patents

Description

The present invention relates to herbicidal compositions in the form of aqueous emulsions containing high concentrations of herbicidal derivatives of 2,6-dinitroaniline such as trifluralin; the invention also extends to a process for the preparation of these compositions.

The herbicidal derivatives of 2,6-dinitroaniline typically exhibit a melting point which is less than 200 ° C and a solubility in water at 25 ° C which is less than 100 parts per million, expressed by weight. These herbicidal derivatives have so far been presented in the form of a concentrated solution in an organic solvent which is essentially immiscible with water such as xylene, also containing an emulsifying agent. These concentrated compositions are dispersed in large volumes of water before being sprayed onto the cultivation grounds.

The preparation of 2,6-dinitroaniline derivatives such as trifluralin and their activity as preemergence herbicides are described, for example, in British Patent No. 917253.

Although the concentrated compositions of herbicidal derivatives of 2,6-dinitroaniline have been found to be particularly effective in allowing the storage of large quantities of pesticides in a relatively compact form while allowing relatively easy dispersibility in large volumes of water during the preparation for spraying, these compositions have the disadvantage that their bulk storage is associated with the inevitable fire risks resulting from the presence of organic solvents and that the price of the preparation is relatively high due to the high cost of organic solvents. Up to now, it has not been possible to develop aqueous pesticidal compositions containing a high concentration of a herbicidal derivative of 2,6-dinitroaniline whose characteristics of storage stability are satisfactory.

The present invention relates to a herbicidal composition in concentrated form which consists of an aqueous emulsion comprising:

- 10 to 75% by weight of a herbicide consisting of at least one herbicidal derivative of 2,6-dinitroaniline having a solubility in water at 25 ° C of less than 100 parts per million by weight and a melting point of between —10 and 150 ° C,

0 to 60% by weight of a solvent essentially immiscible with water, the herbicide and the solvent forming a homogeneous dispersed phase,

0.5 to 10% by weight of an emulsion agent, and

- 15 to 70% by weight of an aqueous solution of an inorganic salt, the concentration of this salt in the aqueous solution being at least 5% by weight.

The herbicide may be a single herbicidal derivative of 2,6-dinitroaniline or a mixture of two or more of these derivatives.

In the case where the herbicide is a mixture of 2,6-dinitroaniline derivatives, the mixture must meet the conditions for melting point and solubility in water indicated.

Similarly, the inorganic salt can be a single salt such as sodium chloride or a double salt such as sodium alum or a mixture of salts. The salt must be such that the aqueous solution is practically neutral, that is to say that it does not have a pH greater than 9. Examples of salts which have appeared useful are constituted by sodium chloride, chloride potassium, ammonium chloride, calcium chloride, magnesium chloride, ammonium nitrate, sodium acetate, ammonium carbonate, copper sulfate, magnesium sulfate, sodium, aluminum sulfate, double ferric and sodium sulfate, potassium dihydrogen phosphate. Salts producing strongly alkaline aqueous solutions, i.e. solutions with a pH above 9, such as sodium carbonate, potassium carbonate and potassium monohydrogen phosphate should in principle be avoided.

The emulsion agent can consist of a single emulsion agent or can also be a mixture of these agents. It can be a nonionic, anionic or cationic surfactant, a mixture of two or more of two nonionic surfactants, a mixture of nonionic and anionic surfactants or a mixture of surfactants non-ionic and cationic. Nonionic surfactants are preferred. The hydrophilic-lipophilic balance of the emulsion agent must be at least 12.

The essentially water-immiscible solvent can be a single organic solvent or a mixture of two or more of these. It is important that the solvent is chosen so as to be able to dissolve the herbicidal compound of the composition and so that it is essentially immiscible with the aqueous phase of the emulsion. Advantageously, the solvent should not be soluble in the aqueous phase in a ratio greater than 0.2% by weight, and preferably the solubility of the solvent in the aqueous phase is therefore 0.2% by weight or less. The solvent may have a melting point equal to or greater than normal room temperature. However, if this is the case, it is preferable that the mixture of herbicides and solvents in relative proportions equal to the relative proportions in the herbicidal composition is liquid at room temperature. Examples of suitable solvents are aromatic hydrocarbons, such as xylenes, trimethyl-benzenes and polycyclic aromatic hydrocarbons such as naphthalene, alkylnaphthalenes and anthracene, halogenated aromatic hydrocarbons such as o-chlorotoluene, aliphatic hydrocarbons such as decane and other organic solvents such as camphor as well as miscible mixtures of two or more of these solvents. In the case where the herbicide is a liquid such as isopropalin and in other particular circumstances, the herbicidal composition according to the invention may contain no water-immiscible solvent other than the herbicide itself.

Preferred compositions according to the present invention contain from 15 to 70% by weight of herbicide, from 0 to 45% by weight of solvent, from 0.9 to 6% by weight of emulsifying agent and from 20 to 40% by weight of an aqueous solution, in which the concentration of inorganic salt varies from 10 to 20% by weight.

Examples of suitable 2,6-dinitroaniline derivatives include: trifluralin, benfluralin, isopropalin, ethylfluralin, dinitramine, dipropalin, oryzalin, 4-methylsulfonyl-2,6-dinitro-N, N-dipropylaniline, fluchloralin , penoxalin, profluralin and dibutalin. These derivatives fall under general formula I:

NO

R *

in which R1 represents hydrogen, C2_4 alkyl or chloroethyl, R2 represents C2_5 alkyl, chloroethyl, 2-methallyl or cyclopropyl-methyl, R3 represents hydrogen, methyl or amino and R4 represents trifluoromethyl, C ^ alkyl, —S02NH2 or - S02CH3.

The herbicidal compositions according to the present invention advantageously have one or more of the following characteristics:

a) the herbicide is a 2,6-dinitroaniline derivative of formula II:

(Formula on next page)

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R1 R2 II

CF3

in which R1 represents C2_4 alkyl or chloroethyl, R2 represents C2_4 alkyl, chloroethyl or 2-methallyl and R3 represents hydrogen or amino,

b) the herbicide is a 2,6-dinitroaniline derivative of formula II in which R1 represents ethyl or propyl, R2 represents propyl, butyl or 2-methallyl and R3 represents hydrogen,

c) the herbicide is trifluralin,

d) the herbicide constitutes from 15 to 65% by weight of the composition,

e) the herbicide constitutes at least 40% by weight of the composition,

f) the herbicide constitutes at least 45% by weight of the composition,

g) the herbicide does not constitute more than 60% by weight of the composition,

h) the solvent does not constitute more than 50% by weight of the composition,

i) the solvent constitutes from 10 to 45% by weight of the composition, j) the solvent constitutes at least 15% by weight of the composition, k) the solvent does not form more than 25% by weight of the composition,

1) the solvent is an aromatic hydrocarbon,

m) the solvent is xylene or a mixture of xylene or naphthalene,

n) the emulsion agent constitutes at least 0.9% by weight of the composition,

o) the emulsion agent constitutes at least 2% by weight of the composition,

p) the emulsion agent constitutes at least 3% by weight of the composition,

q) the emulsion agent does not constitute more than 7% by weight of the composition,

r) the emulsion agent does not constitute more than 6% by weight of the composition,

s) the emulsion agent is a nonionic surfactant or a mixture of two or more than two nonionic surfactants,

t) the emulsion agent has a calculated hydrophilic-lipophilic balance which is at least equal to 12,

u) the emulsion agent has a hydrophilic-lipophilic balance calculated in the range from 14 to 18,

v) the emulsion agent has a hydrophilic-lipophilic balance calculated in a range of 15 to 17,

w) the emulsion agent has a calculated hydrophilic-lipophilic balance of the order of 16,

x) the aqueous solution does not constitute more than 50% by weight of the composition,

y) the aqueous solution does not constitute more than 40% by weight of the composition,

z) the aqueous solution does not form more than 35% by weight of the composition,

aa) the aqueous solution does not constitute more than 25% by weight of the composition,

ab) the aqueous solution constitutes at least 10% by weight of the composition,

ac) the aqueous solution constitutes at least 15% by weight of the composition,

ad) the aqueous solution constitutes at least 20% by weight of the composition,

ae) the aqueous solution also comprises urea at a concentration of up to 25% by weight of the aqueous solution,

ai) the inorganic salt is chosen from sodium chloride, potassium chloride and calcium chloride,

s ag) the inorganic salt is sodium chloride.

In the case where the herbicide is isopropalin, it preferably constitutes 60 to 75% by weight of the composition, no solvent being added, and the emulsion agent constitutes from 2 to 6% by weight of the composition and the aqueous solution constitutes from 19 to 38% by weight of the composition.

According to a particularly preferred aspect of the present invention, the herbicidal composition in concentrated form consists of an aqueous emulsion comprising:

- 45 to 60% by weight of trifluralin,

i - 15 to 25% by weight of an aromatic hydrocarbon solvent essentially immiscible with water, trifluralin and the solvent forming a homogeneous dispersed phase,

- 3 to 6% by weight of a nonionic surfactant or a mixture of these surfactants, having a hydrophilic balance-

20 lipophilic calculated in a range between 15 and 17, and

- 22 to 32% by weight of an aqueous solution of sodium chloride, the concentration of sodium chloride in the aqueous solution being within a range of 10 to 18% by weight, the aqueous solution comprising, in addition, 0 to 5% urea expressed by weight

25 compared to the solution.

The invention also relates to a process for the preparation of a herbicidal composition in concentrated form, characterized in that a homogeneous organic phase is stirred together containing from 10 to 75% by weight of the composition of the herbicide which is at minus one 2,6-dinitroaniline herbicide having a solubility in water at 25 ° C less than 100 parts per million by weight and a melting point in a range between -10 and 150 ° C, with 0 to 60% by weight of the composition of an essentially water-immiscible solvent and an aqueous phase forming 15 to 70% by weight of the composition of an aqueous solution of an inorganic salt, the concentration of the inorganic salt in the solution aqueous being at least 5% by weight, as well as 0.5 to 10% by weight of the composition of an emulsion agent, until a stable emulsion is formed from these constituents.

In the process of the present invention, it is desirable that at least a portion of the emulsion agent is dissolved in the organic phase before proceeding to the agitation of the organic phase with the aqueous phase. The herbicide is preferably dissolved in the solvent, the resulting solution is filtered and the emulsion agent is dissolved in the filtrate before adding thereto the aqueous phase and stirring. The stirring is preferably continued until the mean diameter of the droplets of the aqueous phase is, on observation, within a range of 8 to 14 [a. Urea can be dissolved in the aqueous solution at a value of 50 up to 25% by weight of the aqueous solution before the organic phase and the aqueous phase are stirred.

The invention also extends to the use of the herbicidal composition for inhibiting the growth of weeds, this process comprising the dispersion in a large volume of water 55 of the herbicidal composition according to the present invention and the application of the dispersion thus formed on the medium in which it is desired to inhibit the growth of weeds.

The invention will be described below, by way of nonlimiting illustration, with reference to examples of putting the invention into practice. In these examples, certain emulsion agents and certain solvents are described by their trade names. The solvents mentioned are: Remcopal NP 30, Remcopal PONF, Remcopal 25, Remcopal 0.11, Remcopal 273, Temsagex DP24, Stepan agent 555-66A, Stepan agent 555-66B, Ethomeen T. 25, Renex 650, Brij 72 and Brij 78 The solvents are Aromasol H and Solvesso 100. The chemical nature of these commercial products as far as known to the holder is as follows:

Remcopal NP30 - ethoxylated nonylphenol containing on average

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30 ethoxy groups and having a hydrophilic-lipophilic balance index (HLB = hydrophilic-lipophilic balance) of 17.5;

Remcopal PONF - ethoxylated nonylphenol containing an average of 11 ethoxy groups and having an HLB index of 13.7;

Remcopal 25 - ethoxylated oleocetyl alcohol containing on average 25 ethoxy groups and having an HLB index of 16.2;

Remcopal 0.11 - ethoxylated octylphenol containing an average of 10.5 ethoxy groups and having an HLB index of 13.8;

Remcopal 273 - ethoxylated tridecyl alcohol containing on average three ethoxy groups and having an HLB index of 8.6;

Stepan agents

555-66A and 555-66B - mixture of calcium dodecylbenzenesulfonate and alkylphenoxypolyoxyethylene-ethanols;

Ethomeen T. 25 - condensation product of ethylene oxide on primary fatty amines containing on average 15 ethoxy groups;

Renex 650 - alkylarylether having an HLB number of 17.1;

Brij 72 - polyoxyethylenestearyl ether having an HLB index of 4.9;

Brij 78 - polyoxyethylenestearyl ether having an HLB index of 15.3;

Aromasol H - aromatic hydrocarbon solvent consisting essentially of isomeric trimethylbenzenes and having a specific density of 0.879 and a distillation range of 168 to 220 ° C;

Solvesso 100 - aromatic hydrocarbon solvent consisting essentially of C9 hydrocarbons, but also containing certain C8 and C10 hydrocarbons, and having a specific density of 0.872 and a distillation range of 156 to 180 ° C.

Example 1:

Trifluralin, technical (purity 96%) 500 g

Xylene 230 g

Emulsion agent (mixture of 24.4 g of Remcopal NP30

and 15.6 g Remcopal PONF) 40 g Aqueous solution of sodium chloride

(15% w / w) 310 g

Total 1080 g (11)

The trifluralin is dissolved in xylene while carefully heating to 50 ° C and the solution obtained is filtered through a fine filter paper (Whatman No. 42). The emulsion agent is added to the solution of trifluralin in xylene and dissolved by heating carefully to 50 ° C. The aqueous sodium chloride solution is added to the xylene solution with stirring. The resulting emulsion was opaque and yellow-orange in color.

Example 2:

Trifluralin 500 g

Xylene 180 g

Naphthalene (technical grade) 60 g

Emulsion agent as in Example 1 40 g Aqueous solution of sodium chloride

(15% w / w) 310 g

Total 1,090 g (11)

The trifluralin and the naphthalene are dissolved in the xylene with careful heating to 50 ° C. and the subsequent stages of formation of the emulsion are identical to those of Example 1. The emulsion is opaque and yellow-orange in color.

The compositions of Examples 1 and 2 were studied to assess their stability by storage for one month at a temperature of -10 ° C, -2 ° C, ordinary temperature, 40 ° C and 50 ° C. No significant loss of property of the compositions is observed under these conditions. The two compositions retain their flowability at -18 ° C., which constitutes the lowest temperature that has been studied.

Both emulsions flow easily and can be easily dispersed with gentle agitation in large volumes of water.

Example 3:

A composition was prepared in an identical manner to that of Example 1, except that the emulsion agent used consisted of 40 g of Tensagex DP 24 produced by the company Tensia SA The emulsion agent was a surfactant anionic active. The composition obtained was a stable opaque yellow-orange emulsion.

Example 4:

A composition was prepared as in Example 3, except that the emulsion agent used consisted of 40 g of a mixture of 75% by weight of Stepan agent 555-66A and 25% by weight of Stepan agent 555 -66B produced by Stepan Chemical Company. These two compounds are mixtures of anionic and nonionic surfactants. The opaque emulsion obtained was stable and yellow-orange in color.

Example 5:

A composition was prepared as in Example 3, except that the emulsion agent used consisted of 40 g of Ethomeen T.25 produced by Armor Hess Chemicals Limited. The emulsion agent is a cationic surfactant. The emulsion obtained was stable, opaque in appearance and yellow-orange in color.

Example 6:

A composition was prepared as in Example 2, except that the aqueous solution consisted of 310 g of an aqueous solution of sodium chloride (17% w / w).

Example 7:

A composition was prepared as in Example 1, except that the aqueous solution consisted of 310 g of an aqueous solution of sodium chloride (13% w / w) and urea (4% w / w).

Example 8:

A composition was prepared as in Example 1, except that the aqueous solution consisted of 310 g of an aqueous solution of potassium dihydrogen phosphate (13% w / w).

Example 9:

A composition was prepared as in Example 1, except that the aqueous solution consisted of 310 g of an aqueous solution of double ferric sulfate and ammonium (13% w / w).

Examples 10 to 15:

Compositions were prepared as in Example 1, except that the following emulsifying agents were used:

Example

Emulsion agent

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Remcopal 25 (36.7 g) + Remcopal 0.11 (3.3 g)

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Renex 650 (36.4 g) + Brij 72 (3.6 g)

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Renex 650 (15.6 g) + Brij 78 (24.4 g)

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Remcopal NP30 (18.3 g) + Remcopal PONF (11.7 g)

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Remcopal NP30 (12.2 g) + Remcopal PONF (7.8 g)

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Remcopal NP30 (6.1 g) -1- Remcopal PONF (3.9 g)

Example 16:

A composition was prepared as in Example 1, except that 235 g of Solvesso 100 were used instead of xylene.

Example 17:

A composition was prepared as in Example 1, except that 240 g of Aromasol H were used instead of xylene.

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Example 18:

Trifluralin, technical (purity 96%) 625 g

Xylene 181 g Emulsion agent (36.7 g Remcopal 25

and 3.3 g of Remcopal 0.11) 40 g

Aqueous solution of sodium chloride (15% w / w) 266 g

Total 1,112 g (11)

The above composition was prepared in a similar manner to the process used in Example 1.

Example 19:

Trifluralin, technical (purity 96%) 688 g

Xylene 119 g Emulsion agent (24.4 g Remcopal NP30

and 15.6 g Remcopal PONF) 40 g

Aqueous solution of sodium chloride (15% w / w) 289 g

Total 1,136 g (11)

The composition was prepared in a similar manner to that used in Example 1.

The emulsions of Examples 6 to 19 all constitute stable emulsions, of opaque appearance and of yellow-orange color.

Example 20:

Benfluralin, technical (purity 95%) 190 g

Xylene 317 g

Naphthalene (technical grade) 104 g Emulsion agent (38.9 g Remcopal 25

and 1.1 g of Remcopal 273) 40 g Aqueous solution of ammonium chloride (15% w / w) 362 g

Total 1,013 g (11)

The above composition was prepared in a similar manner to that used in Example 1. The stable solution obtained was opaque and yellow in color.

Example 21:

Benfluralin, technical (95% purity) 190 g

Xylene 277 g

Cyclohexanone 130 g Emulsion agent (33.3 g Remcopal NP30

and 6.7 g of Remcopal 273) 40 g Aqueous solution of sodium chloride (15% w / w) 362 g

Total 999 g (11)

This composition was prepared in a similar manner to the process used in Example 1. The emulsion obtained was identical in appearance to that of Example 20.

Example 22:

Ethalfluralin, technical (purity 95%) 347 g

Xylene 361 g Emulsion agent (33.3 g Remcopal NP30

and 6.7 g of Remcopal 273) 40 g Aqueous solution of sodium chloride (15% w / w) 289 g

Total 1037 g (11)

The above composition was prepared by a process similar to that of Example 1. The stable emulsion obtained was opaque in appearance and yellow in color.

Example 23:

A composition was prepared as in Example 22, except that the aqueous solution consists of 282 g of an aqueous solution of potassium chloride (13% w / w). The solution obtained was similar in appearance to that of Example 22.

Example 24:

A composition was prepared as in Example 22, except that the aqueous solution used consisted of 289 g of an aqueous solution of calcium chloride (13% w / w). The emulsion obtained was similar in appearance to that of Examples 22 and 23.

Example 25:

Isopropalin, technical (90% purity) 800 g Emulsion agent (33.3 g Remcopal NP30

and 6.7 g of Remcopal 273) 40 g

Aqueous solution of sodium chloride (15% w / w) 338 g

Total 1,178 g (11)

The emulsion agent is dissolved in isopropaline with gentle heating. The aqueous sodium chloride solution is added with stirring. The stable emulsion obtained was opaque and a dirty yellow-orange color.

It will be noted that the emulsion agent used in all of examples 1 to 25 has a hydrophilic-lipophilic balance calculated on the order of 16.

For the emulsions of Examples 1 to 25 above, it has been found that the average diameter of the droplets of the organic phase is in the range of 8 to 14 µm. It has appeared that the emulsions dissolve easily when 1 volume is added to 100 volumes of water and that it remains essentially in the dispersed state for several hours. These dispersions can be easily applied to cropland by practical means such as spraying and can therefore be used in a similar manner to known concentrated compositions.

The emulsions of Examples 1 and 2 as well as 4 to 25 have remarkable stability properties under different storage conditions. Coalescence of droplets and formation of upper or lower aqueous layers occurs very slowly and samples can be stored for at least one year at 25 or 40 ° C without appreciable coalescence. The emulsion of Example 7 has remarkable stability properties under high temperature storage conditions and the emulsion remains stable after storage for several weeks at 60 ° C. Towards the lowest part of the temperature scale, these emulsions are generally stable at temperatures from -2 to -10 ° C and have very good resistance to crystallization. In general, they do not freeze until the temperature drops to around -25UC.

The compositions of Examples 1 to 25 present a reduced fire risk when compared to the known concentrated emulsifiable compositions of herbicides derived from 2,6-dinitroaniline in organic solvents such as xylene.

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Claims (24)

629074 2 1. Herbicidal composition in concentrated form, characterized in that it is in the form of an aqueous emulsion comprising: - 10 to 75% by weight of a herbicide consisting of at least one herbicidal derivative of 2,6-dinitroaniline having a solubility in water at 25 ° C of less than 100 parts per million by weight and a melting point of between —10 and 150 ° C, 0 to 60% by weight of a solvent essentially immiscible with water, the herbicide and the solvent forming a homogeneous dispersed phase, 0.5 to 10% by weight of an emulsion agent, and - 15 to 70% by weight of an aqueous solution of an inorganic salt, the concentration of this salt in the aqueous solution being at least 5% by weight. 2. Composition according to claim 1, characterized in that it contains from 15 to 70% by weight of herbicide, from 0 to 45% by weight of solvent, from 0.9 to 6% by weight of agent emulsion and from 20 to 40% by weight of an aqueous solution, in which the concentration of inorganic salt varies from 10 to 20% by weight. 3. Composition according to claim 1 or claim 2, characterized in that it does not contain a solvent, the herbicide being isopropalin which constitutes 60 to 75% by weight of the composition, while the agent emulsion constitutes 2 to 6% by weight of the composition and the aqueous solution constitutes 19 to 38% by weight of the composition. 4. Composition according to claim 1 or claim 2, characterized in that it contains 15 to 65% by weight of a herbicide which is a 2,6-dinitroaniline derivative of formula 02N NO CF3 in which R1 represents C2_4 alkyl or chloroethyl, R2 represents C2_4 alkyl, chloroethyl or 2-methallyl and R3 represents hydrogen or amino, as well as 10 to 45% by weight of solvent, 0.9 to 6% by weight of agent of emulsion and 20 to 40% by weight of aqueous solution. 5. Composition according to claim 4, characterized in that R1 represents ethyl or propyl, R2 represents propyl, butyl or 2-methallyl and R3 represents hydrogen. 6. Composition according to one of claims 1,2,4 or 5, characterized in that it contains 40 to 65% by weight of the herbicide, which is trifluralin, 10 to 25% by weight of solvent, 0 , 9 to 6% by weight of the emulsion agent and 20 to 35% by weight of aqueous solution in which the concentration of inorganic salt is at least 10% by weight. 7. Composition according to claim 6, characterized in that the herbicide constitutes 40 to 60% by weight of the composition, the solvent constitutes from 15 to 25% by weight of the composition and the emulsion agent constitutes 2 to 6 % by weight of the composition. 8. Composition according to claim 7, characterized in that the herbicide constitutes 40 to 50% by weight of the composition. 9. Composition according to one of claims 1 or 2 and 4 to 7, characterized in that the water-immiscible solvent is xylene or xylene with naphthalene. 10. Composition according to one of claims 1 to 9, characterized in that the emulsion agent is a nonionic surfactant or a mixture of two or more of two nonionic surfactants. 11. Composition according to one of claims 1 to 10, characterized in that the emulsion agent has a calculated hydrophilic-lipophilic balance index between 14 and 18. 12. Composition according to claim 11, characterized in that the hydrophilic-lipophilic balance index is between 15 and 17. 13. Composition according to claim 12, characterized in that the hydrophilic-lipophilic balance index is of the order of 16. 14. Composition according to one of claims 1 to 13, characterized in that the inorganic salt constitutes of the order of 15% of the aqueous solution. 15. Composition according to one of claims 1 to 14, characterized in that the inorganic salt is chosen from sodium chloride, potassium chloride and calcium chloride. 16. Composition according to claim 15, characterized in that the inorganic salt is sodium chloride. 17. Composition according to one of claims 1 to 16, characterized in that the aqueous solution contains, in addition, urea in a concentration reaching up to 25%, and preferably 5% by weight. 18. herbicidal composition according to claim 1, characterized in that it comprises: - 45 to 60% by weight of trifluralin, - 15 to 25% by weight of an aromatic hydrocarbon solvent essentially immiscible with water, trifluralin and the solvent forming a homogeneous dispersed phase, 3 to 6% by weight of a nonionic surfactant or a mixture of these surfactants, having a hydrophilic-lipophilic balance index calculated in a range between 15 and 17, and - 22 to 32% by weight of an aqueous solution of sodium chloride, the concentration of sodium chloride in the aqueous solution being within a range of 10 to 18% by weight, the aqueous solution additionally comprising 0 to 5% of urea expressed by weight relative to the solution. 19. Process for the preparation of a herbicidal composition in concentrated form according to claim 1, characterized in that a homogeneous organic phase is stirred together containing from 10 to 75% by weight of the composition of the herbicide which is at least a 2,6-dinitroaniline derivative, a herbicide with a solubility in water at 25 ° C of less than 100 parts per million by weight and a melting point in a range between —10 and 150 ° C, with 0 to 60 % by weight of the composition of a solvent essentially immiscible with water and an aqueous phase forming 15 to 70% by weight of the composition of an aqueous solution of an inorganic salt, the concentration of the inorganic salt in the solution aqueous being at least 5% by weight, as well as 0.5 to 10% by weight of the composition of an emulsion agent, until a stable emulsion is formed from these constituents. 20. The method of claim 19, characterized in that at least a portion of the emulsion agent is dissolved in the organic phase before the organic phase is stirred with the aqueous phase. 21. The method of claim 19 or 20, characterized in that the herbicide, which is trifluralin, is dissolved in an amount of 40 to 65% by weight of the composition in the solvent which constitutes 10 to 25% by weight of the composition, filters the solution formed to obtain the organic phase, dissolves the emulsion agent therein and adds the solution to the organic phase and agitates. 22. Method according to one of claims 19 to 21, characterized in that the stirring is continued until the average diameter of the droplets of the aqueous phase is, on observation, within a range of 8 to 14 (i. 23. Method according to one of claims 19 to 22, characterized in that urea is dissolved in the aqueous solution at a value reaching up to 25% by weight of the aqueous solution before the the organic phase and the aqueous phase are stirred. 24. Use of the herbicidal composition according to claim 1 for inhibiting the growth of weeds, characterized in that the herbicidal composition according to one of claims 1 to 3 is dispersed in a large volume of water. 18 and in that 5 10 15 20 25 30 35 40 45 50 55 60 65 3 629,074 that the dispersion thus formed is applied to the medium in which it is desired to inhibit the growth of weeds.