CS235047B2 - Chemically stable herbicide - Google Patents

Description

The invention describes stable herbicidal compositions, in particular herbicidal compositions containing m-bis-carbamates, which have been shown to be stable over the long term due to the presence of surfactants belonging to the class of polyoxyethylated alkylphenolphosphoric acids.

Herbicides, referred to as m-bis-carbamates, are compounds that exhibit good herbicidal activity and have long been used to control weeds in important crops. These m-bis-carbamates can be described by formula (I)

Representative examples of herbicides belonging to · this group include preparation phenmedipham (generic name of the compound of formula I wherein R ¹ is hydrogen, R ² is 3-tolyl and R 3 is a methyl group), and · preparation desmedipham (common name · a compound of formula I wherein R1 is hydrogen, R ² represents a phenyl group and R ³ represents an ethyl group).

These herbicides are generally used in the form of liquid preparations which are diluted with water before application and contain the active ingredient, an organic solvent and a surfactant.

Examples of organic solvents useful in the above compositions include aromatic hydrocarbons, alicyclic ketones (cyclohexanone, isophorone), esters, dimethylsulfoxide, dimethylformamide and the like, and examples of useful surfactants include polyethoxylated alkylphenols, alcohols, carboxylic acids, and amines. as well as salts of alkylbenzenesulfonic acids or naphthalenesulfonic acids.

These conventional compositions have the disadvantage that the active ingredient tends to decompose upon storage, even to a large extent, thereby reducing the concentration of the active ingredient in the composition and reducing the herbicidal activity of the composition.

Such compositions are also often physically unstable because the active ingredient, especially at high and low temperatures, tends to crystallize, so that deposits are formed and solid materials are formed from the composition.

Various solutions have been studied to overcome these disadvantages, but have consisted in introducing complex mixtures (containing no less than four components) of solvents, stabilizers and surfactants into the above compositions.

U.S. Pat. No. 3,898,075 discloses a process for stabilizing a herbicide in liquid formulations comprising admixing from 0.05 to 5% by weight of an organic acid selected from the group consisting of aliphatic dicarboxylic acids, aliphatic hydroxycarboxylic acids , monocarboxylic nitroaromatic acids, dicarboxylic aromatic acids, aliphatic and aromatic sulfonic acids.

It is also mentioned in the above cited patent that other acids, including phosphoric acid, are not suitable for stabilizing the herbicides of the general formula I.

In Belgian Patent Specification No. 884,482, Montedison S.p.A. Herbicidal compositions containing Phenmedipham as active ingredient are described. These compositions exhibit long-term physical stability at both high and low temperatures.

In further research on the compositions described in the Belgian patent cited above. It has been found that a composition as exemplified in the above-mentioned patent, consisting of Phenmedipham (40% by weight), dimethylformamide (30% by weight) and xylene (20% by weight), containing 10% by weight of a surfactant 'Rolfen 10 D' (a mixture of mono- and diesters of phosphoric acid with nonylphenol, polyoxyethylated 10 moles of ethylene oxide per mole of substrate), is characterized by the chemical stability mark of the active substance, since Phenmedipham undergoes only slight decomposition during storage.

It has also been found that a number of known phosphoric acid surfactants mono- and diesterified alkylphenols which are polyoxyethylated, however, contain at least one free acid functional group as defined below, impart m-bis-carbamate herbicides in the compositions for use. remarkable chemical stability in agriculture.

The fact that these phosphoric acid-derived surfactants and containing at least one free acidic functional group is capable of stabilizing m-bis-carbamate herbicides is particularly surprising given that U.S. Patent No. 3,898,075 explicitly states that phosphoric acid is unsuitable for this purpose.

Accordingly, the present invention provides a herbicidal composition based on .alpha.-bis-carbamates which is chemically stable and comprises, in a weight ratio of from 90: 1 to 1:40, surfactants belonging to the group of phosphoric acids mono- and diesterified with alkylphenol and polyoxyethylated, corresponding to formula II ° (О-С ^ -СН ^ О

in which

X represents a hydroxyl group or a radical of formula

m and n are independently from 1 to 80, the sum of m n being less than or equal to 80, p being a number from 1 to 4, preferably 1, and

R represents a straight or branched (C 4 -C 12) alkyl group, a bis-t-phenylethyl group or a benzyl group.

The use of surfactants of the general formula II as stabilizers in herbicidal compositions containing m-bis-carbamates avoids the need for additional additives and brings considerable advantages in providing stable m-bis-carbamate-based compositions consisting only of the active ingredient, organic a solvent and a surfactant selected from the group above.

The present invention also provides a stable m-bis-carbamate herbicidal composition comprising

A. herbicidally active m-bis-carbamate of the formula I in an amount of from 0.5 to 45% by weight,

B. a surfactant of the formula II in an amount of from 0.5 to 20% by weight; and

C. an organic solvent selected from the group consisting of aromatic or alkylaromatic hydrocarbons, alicyclic ketones, carboxylic acid esters, dimethylsulfoxide, dimethylformamide, glycol monoesters or mixtures thereof in amounts up to> 100%, provided that when the herbicide of formula I is Phenmedipham , the surfactant is "Rolfen 10 D" and the solvent is a mixture of dimethylformamide and xylene, these components are present in a weight ratio different from the 40: 10: 30: 20 ratio, since such a composition has already been described in Belgian patent specification 884,482 .

The compositions according to the invention are stable in the long term because, as is apparent from the examples, the herbicide undergoes only slight decomposition, whereas in conventional compositions this decomposition is very considerable.

The compositions of the invention are generally self-emulsifiable in water due to the presence of a compound of formula (II) which acts both as a stabilizer and as a surfactant.

However, if the selected solvent is poorly soluble in water and when the compound of formula (II) is used in an amount around the lower limit (e.g. less than 4% by weight), the addition of a conventional surfactant of a different chemical group may be useful. facilitating the emulsifiability of the compositions of the invention in water.

Some examples of organic solvents useful in the compositions of the present invention include: benzene, toluene, xylene (also in the form of a commercial mixture of isomers), C 9 -C 12 alkylbenzenes (also in the form of commercial mixtures), cyclohexanone, isophorone, ethyl acetate, butyl or octyl phthalate , methylcellosolve, cellosolve acetate and the like.

The amount of the herbicide of the formula I in the composition according to the invention depends on the solubility of the herbicide in the chosen organic solvent.

The compounds of formula (II) are known as surfactants, also as far as their use in agriculture is concerned, however, as far as we do not know their use to stabilize herbicides to the m-bis-carbamate group.

The surfactants of formula (II) are readily available commercially either as individual compounds or as mixtures, both in terms of the number of moles of ethylene oxide per mole of the phosphoric acid derivative and in terms of the phenolic residue substituents. Mixtures of mono- and diesters of phosphoric acid of the formula II, ethoxylated to various degrees, are also commercially available.

An optional compound of formula (II) which is not currently on the market can be synthesized by known techniques.

For example, a phosphoric acid mono- or dihalide may be reacted with one or two moles of the alkali metal salt of the corresponding alkylphenol. The resulting product is then polyoxyethylated in a conventional manner.

As is well known, ethoxylation is largely controllable, but due to the nature of the reaction, it produces product mixtures containing a certain number of moles of ethylene oxide per mole of substrate within a relatively narrow range, so that the term "degree of ethoxylation" refers to mole of ethylene oxide per mole of substrate.

The compositions of the invention are prepared by mixing the components in predetermined amounts.

Practical use and results are quite analogous to known formulations containing the same herbicides.

The invention is illustrated by the following non-limiting examples. In these examples, the following shortcut abbreviations are used to denote some components:

Surfactants of formula II:

Tens II-A phosphoric acid monoesterified with nonylphenol and polyoxyethylated (10 moles of ethylene oxide per mole of substrate), commercially available under the trademark "Rolfen 10".

Tens II-B is a mixture of nonylphenol diesterified phosphoric acid and polyethoxylated with 10 moles of ethylene oxide per mole of substrate and Tens Π-A (a product commercially available under the trademark "Rolfen 10 D" is used).

Tens II-C phosphoric acid monoesterified with bis-α-phenyl-ethylenelenol and polyoxyethylated with 10 moles of ethylene oxide per mole of substrate (using a product commercially available under the trademark "Rolfen 40").

Tens II-D phosphoric acid monoesterified with nonylphenol -and polyoxyethylated with 80 moles of ethylene oxide per mole of substrate (a product commercially available under the trademark "Rolfen 80" is used).

Surfactants for comparatives:

OR-25 ETO castor oil polyoxyethylated with 25 moles of ethylene oxide per mole of substrate.

DBS-Ca calcium dodecylbenzenesulfonate.

The term "xylene" refers to a commercial mixture of isomeric xylenes.

He did.

Dissolve 5 g of Phenmedipham in 90 g of cyclohexanone and add 5 g of Tens II-A surfactant to the solution to prepare the composition of the invention (composition 1.1). The resulting mixture was stirred at room temperature for homogenization.

The composition 1.1 is placed in a thermostat at 54 ° C for 14 days. Upon completion of this long-term heating, the composition of the Phenmedipham preparation is determined directly by high pressure liquid chromatography.

In this case, a degradation of less than 0.5% was found.

Example 1 a. D 2

In accordance with the procedure of Example 1, the compositions of the present invention are summarized in Table 1. At the same time, comparative compositions are prepared which either contain no surfactant or contain a surfactant belonging to another chemical group. These comparative means are shown in Table 2.

Table 1

Compositions of the Invention (b)

1.1

Resource no.

1.2 1.3 1.4 1.5

1.6 1.7

Folder ^ '

herbicide of formula I: Phenmedipham Desmedipham 5 15 Dec solvent: cyclohexanone isophorone dimethylformamide dimethylsulfoxide xylene dioctyl phthalate methyl cellulose surfactant of formula II: 90 80 Tens II-A Tens II-B Tens II-C Tens II-D 5 5

30 30 30 15 Dec 45 60 60 45 80 10 10 10 10 5

Component*' 1.8 1.9 1.10 Resource no. 1.11 1.12 1.13 1.14 herbicide of formula I: Phenmedipham Desmedipham 15 Dec 15 Dec 15 Dec 30 30 30 30

solvent:

cyclohexanone isophorone 65

dimethylformamide 5 20 May 20 May 30 30 30 30 dimethylsulfoxide xylene 5 55 55 15 Dec 15 Dec 15 Dec 15 Dec dioctyl phthalate 15 Dec 15 Dec 15 Dec methylcellosolve 15 Dec

surfactant of formula II:

Tens II-A

Tens II-B

Tens II-C

Tens II-D

10

10

Legend:

(a) the amount of each -složky is reported as weight% ^f 'means 1.1 is described in Example 1

Table 2

Comparative means Component ' ³ '

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 herbicide of formula I: Phenmedipham Desmedipham solvent: 5 15 Dec 30 15 Dec 15 Dec 15 Dec 30 30 15 Dec 15 Dec cyclohexanone isophorone 95 85 77 65 65 dimethylformamide 70 20 May 30 45 5 5 xylene dimethylsulfoxide surface 85 5 65 40 15 Dec 5 5 active agent: OR-25 ETO DBS-Ca 3 10 10 10

Legend:

^and * the amount of each component is given in% by weight

Example 3

Determination of chemical stability of herbicide in formulations

100 g of each of the compositions according to the invention (see Table 1 in Example 2) and the comparative compositions (see Table 2 in Example 2) are each placed in a glass container, which is placed in a thermostat, maintaining a temperature of 54 ° C.

After 14 days, the amount of herbicidally active ingredient was determined directly in the sample by high pressure liquid chromatography.

The results, expressed as% herbicide decomposition, are shown in Table 3 below.

Table 3

Chemical stability of m-bis-carbamate herbicides in various formulations after 14 days storage at 54 ° C

Resource No (see Tables 1 and 2) Herbicide decomposition ' ³ ' (%) 1.1 <0.5 1.2 <0.5 1.3 <0.5 1.4 <0.5 1.5 <0.5 1.6 <0.5 1.7 <0.5

Resource No (see Tables 1 and 2) Herbicide decomposition ' ³ ' (%) 1.8 <0.5 1.9 <0.5 1.10 <0.5 1.11 <0.5 1.12 <0.5 1.13 <0.5 1.14 <0.5 2.1 8.3 2.2 7.8 2.3 69.0 2.4 38.0 2.5 12.3 2.6 49.0 2.7 53.1 2.8 27.2 2.9 9.5 2.10 7.8

Legend:

^(a ''<'' means 'less than' and '<0,5' means that no degradation was detected within the sensitivity of the analytical method used.

From the data in Table 3, it can be seen that in the compositions of the invention, the herbicidally active ingredient is chemically stable even at long-term storage at higher temperatures.

Claims (3)

1. Chemically stable herbicidal composition based on m-bis-carbamates, characterized in that it contains a surfactant or a mixture of surfactants belonging to the group of polyoxyethylene mono- and diesters of phosphoric acid with a weight ratio of from 90: 1 to 1:40. alkylpheinols corresponding to the general formula P in which X is a hydroxyl group or a moiety in man-z each independently represents a number from 1 to 80, with the sum of m + n being less than or equal to 80, p being a number from 1 to 4, preferably 1, and R represents a straight or branched (C 4 -C 12) alkyl group, a bis-α-phenyl-ethyl group or a benzyl group. 2. A composition according to claim 1, wherein the m-bis-carbamate herbicide is Phenmedipham or Desmedipham. 3. The composition of Claim 1 comprising: A. m-bis-carbamate herbicide in an amount of 0.5 to 45% by weight, B. a surfactant of the above formula (II) in an amount of 0.5 to 20% by weight; and C. organic solvent selected from the group consisting of aromatic or alkylaromatic hydrocarbons, alicyclic ketones, carboxylic acid esters, dimethylsulfoxide, dimethylformamide, glycol monoethers or mixtures thereof, up to 100%, provided that when the herbicide is Phenmediphaim, a surfactant a mixture of phosphoric acid mono- and diesters with nonylphenol, polyoxyethylated with 10 moles of ethylene oxide per mole of substrate, and a solvent mixture of dimethylformamide and xylene, these components are present in a weight ratio different from 40: 10: 30: 20.