GB2176108A - Stabilised liquid herbicidal compositions - Google Patents

Abstract

Liquid herbicide compositions comprising a biscarbamate of formula <IMAGE> in which X denotes a hydrogen atom or an alkyl radical containing 1 to 3 carbon atoms and R denotes an alkyl radical containing 1 to 3 carbon atoms, which compositions comprise: 5 to 500 g/l of active substance of formula (I), preferably from 100 to 250 g/l; 100 to 700 g/l of tributyl phosphate; 50 to 300 g/l of a water-miscible organic solvent which is a good solvent for the carbamate of formula (I); and 50 to 300 g/l of non-ionic surfactant(s).

Description

SPECIFICATION Stabilised liquid herbicidal compositions The present invention relates to stabilized, liquid herbicide compositions based on m-bis-carb-amates. It relates more particularly to compositions in the form of emulsifiable, concentrated solutions.

The term "m-bis-carbamates" refers to herbicides'corresponding to formula (I) below:

in which X represents a hydrogen atom or an alkyl radical containing 1 to 3 carbon atoms and R represents an alkyl radical containing 1 to 3 carbon atoms.

Examples representing this class of herbicides are: phenmedipham: common name of the compound of formula (I) in which X and R represent the methyl radical.

desmedipham: common name of the compound of formula (I) in which X represents a hydrogen atom and Ran ethyl radical.

These compounds are generally available in the form of liquid compositions, which are diluted with water1 before use, so as to obtain spraying mixtures containing the required concentration of active substance.

Numerous types of formulation of phenmedipham have already been proposed. One of the most common formulations is an emulsifiable concentrate which uses isophorone as solvent according to French Patent 1,536,108, an acid type stabilizer according to French Patent 2,028,876 and a surfactant.

The disadvantage of these concentrates is related to the presence of isophorone which involves drawbacks, especially on account of its toxicity and odour problems and also due to the fact that these concentrates have a strong tendency to give rise to crystal deposits on dilution with water.

Additionally, isophorone-based concentrates cannot have a very high phenmedipham concentration.

Formulations which are stabilized both from physical and chemical standpoints (French Patents 2,462,101 and 2,530,122) and contain dimethylformamide or dimethylacetamide and a surfactant such as a phosphate of a polycondensate of ethylene oxide with an alkylphenol have also been proposed. These compositions are presented as ensuring the chemical stability of the active substance and the physical stability during storage in the concentrated form.

It is known that the formation of micro-crystals of a size greater than or equal to 40 microns during dilution with water is harmful, especially in that it tends to block the slurry-spraying equipment used by farmers; it can also be detrimental to the herbicidal activity.

The object of the present invention is to provide compositions which are stable, including during storage in the concentrated form and on dilution with water; and which lead to good herbicidal results, at the same time employing lower doses of the active substance.

Another object of the invention is to make it possible to attain concentrates of high phenmedipham content.

The present invention provides a homogeneous liquid composition which comprises: 5 to 500 g/l of a biscarbamate of formula (I) wherein X and R are as hereinbefore defined, preferably from 100 to 250 g/l; the active substance is preferably, phenmedipham; 100 to 700 g/l of tributyl phosphate; 50 to 300 g/l of a water-miscible, organic solvent which is a good solvent for the carbamate of formula (I) 50 to 300 g/l of non-ionic surfactant.

Suitable organic solvents include dimethylformamide, cyclohexanone, dimethylsulphoxide and acetophenone; N-methylpyrrolidone is preferably used. The non-ionic surfactant generally has emuisioning (or emulsifying) properties; other surfactants, especially anionic emulsifying adjuvant surfactants in an amount of not more than 50% of the total non-ionic surfactant, may be added.

In this specification and the accompanying claims. grams per litre (g/l) denote grams of the substance under consideration per litre of the liquid composition. In practice the compositions according to the invention are homogeneous solutions at least at room temperature (20"C).

Among non-ionic surfactants which can be used in the invention, polyethers and especially polycondensates of ethylene oxide and/or propylene oxide with alkylphenols or polyalkylphenols or polyarylalkylphe nols (especially derivatives with an alkyl group containing 8 to 12 carbon atoms), polycondensates of ethylene oxide and/or propylene oxide with aliphatic alcohols (especially C6to C20 and in particular oleic and cetyl), polycondensates of ethylene oxide and/or propylene oxide with fatty acid esters (especially C6 to 020), polycondensates of ethylene oxide and/or propylene oxide with esters of anhydro8orbitol (= sorbitan), polyoxypropyleneglycols, polycondensates of ethylene oxide with polyoxypropyleneglycols and copolymers of alkylene oxide and the esters of these polyethers may be mentioned.In most of these products, the ethylene oxide polycondensate chains or polyalkylene chains generally contain 2 to 30 ethoxy or oxyalkylene groups.

As anionic surfactant acting as emulsifying adjuvant, phosphates of a polycondensate of ethylene oxide with a (1-monophenylethyi)phenol of formula (II)

in which: m is an integer of from 1 to 80, each-Ar, which may be the same or different, denotes a 1 -phenyl-ethyl radical, which itself is optionally substituted, and advantageously contains 8 to 16 carbon atoms, z is an integer equal to 1,2 or 3 Y denotes an- OH radical or the group: -(OCH2 - CH2)m - 0 ~ C6Hs z(Ar)z in which m, Ar and-z are as defined above, may be mentioned.

Preferably, this surfactant is the monoester or diesterformed by phosphoric acid with the polycondensate of ethylene oxide with bis or tris(1 -monophenylethyl)phenol. The monoester of the polycondensate of ethylene oxide with this tris (1-monophenylethyl) phenol hasthe formula:

in which m is as defined above.

As other anionic surfactants (emulsifying adjuvant). aliphatic monoester salts of sulphuric acid, e.g.

sodium laurylsulphate, sulphonated aromatic acid salts such as calcium or sodium dodecylbenzene sulphonate and calcium alkylarylsulphonates may also be mentioned.

Other common anionic or non-ionic surfactants can also be used.

The quantities of surfactants may vary within very broad limits.

The compositions according to the invention are prepared in the form of emulsifiable concentrated solutions. It suffices then to dilute them with a defined quantity of water to obtain the slurries which are ready for use.

In addition to the constituents mentioned above, the compositions according to the invention may contain, if appropriate, various other ingredients or additives from the field of agricultural product formulation, e.g.

other solvents, other surfactants, penetrants, corrosion inhibitors, and adhesives.

The present invention also relates to a method of weed control at the locus of a crop, particularly of a beet crop, and especially of a sugar beet crop, which comprises the post-emergence application to the locus, e.g.

a field planted with a beet crop, of an effective quantity of a composition according to the invention diluted with water to form-a spraying mixture. According to this method, the slurry employed contains, in general, 1 to 10 g of active substance per litre of the slurry applied (diluted with water), preferably 1.1 to 6 girl. According to this weed control method according to the invention, 120 to 2,000 glha of active substance offormula (I) and preferably 250 to 1,000 g/ha are generally applied.

The following Examples illustrate the invention.

Examples 1 to 5 Liquid compositions in the form of emulsifiable concentrated solutions which have the following compositions in-grams per litre of solution (each of the compositions below has a volume of one litre) are prepared: Composition No. 1: Phenmedipham 160g Tributyl phosphate 375g N-methylpyrrolidone 100 g Cyclohexanone 200g Phosphated polycondensate of ethylene oxide (16-18 units per mole of phenol) with tris (1phenylethyl) phenol (monoester with two acidic groups remaining free) 20 g Copolycondensate of nonylphenol with ethylene oxide and propylene oxide (in respective proportions of 3:1; 42 oxyalkylene units) 130 g Calcium dodecyl-benzene sulphonate 45g Composition No. 2: Phenmedipham 200 g Tributyl phosphate 530 g N-Methylpyrrolidone 100 g Phosphated polycondensate of ethylene oxide with tris (1 -phenylethyl) phenol (similar to that of composition No.1) 20g Copolycondensate of nonylphenol similar to that of composition No.1 130g Calcium dodecyl benzene sulphonate 45 g Composition No. 3: Phenmedipham 200 g Tributyl phosphate 580 g N-Methylpyrrolidone 50 g Phosphated polycondensate of ethylene oxide with tris (1-phenylethyl) phenol (similar to that of composition No. 1) 20 g Copolycondensate of nonylphenol similar to that of composition No.1 130 g Calcium dodecyl benzene sulphonate 45 g Composition No. 4:: Phenmedipham 225g Tributyl phosphate 550g N-Methylpyrrolidone 100g Phosphated polycondensate of ethylene oxide with tris (1-phenylethyl) phenol (similar to that of composition No.1) 20 g Copolycondensate of nonylphenol similar to that of composition No.1 130g Calcium dodecyl benzene sulphonate 45 g Composition No. 5: Phenmedipham 160g Tributyl phosphate 395g N-Methylpyrrolidone 100g Cyclohexanone 200 g Copolycondensate of nonylphenol similar to that of composition No.1 130 g Calcium dodecyl benzene sulphonate 45 g The isophorone-based emulsifiable concentrate sold under the name of Bétanal and containing 157 g/l of phenmedipham is used as composition No.6. This concentrate complies with French Patents 1,536,108 and 2,028,876.

Stability during storage These 6 compositions are maintained for 7 days at -5 C without noticing any precipitate or crystal formation. No chemical degradation has been observed after 1 month at 50"C.

Stability on dilution with water A test is carried out to evaluate the crystal-forming characteristic on dilution with water, of the compositions, given that the formation of crystals of size greater than or equal to 40 microns is considered harmful.

The composition to be tested (20 ml) is added to water (980 ml) over 40 seconds, with stirring (to homogenize). Precipitate formation is initiated by adding solid phenmedipham (300 mg). Filtration is carried out after 24 h using a sieve with a pore size of 40 microns. The precipitate is washed for 1 minute with a jet of water. The precipitate is recovered, dried and weighed.

The test as described above is used for checking slurries obtained by dilution with water of compositions Nos.1 to 6. Tests on slurries were carried out by diluting these compositions to obtain a slurry containing 2.5 g/l of phenmedipham on the one hand and a slurry containing 1.5 g/l of phenmedipham on the other Such dilutions are approximately of the order of magnitude of the dilutions of the slurries used by farmers on crops in weed control treatments; whereas the concentrated compositions are those which are stored and manipulated before dilution to obtain a slurry.

The percentage by weight of phenmedipham which produced microcrystals of size greater than 40 microns is indicated below.

Composition Percentage of phenmedipham No. producing microcrystals dilution to dilution to l,5g11 2.5 girl 1 6 -4 2 0 0 3- 0.5 0.5 4 1.5 1 5 3 2 6 50 16 Composition No.6 is much poorer than the compositions according to the invention.

HerbicidalActivity (Exampje 6) Composition No.1 diluted with wafer was applied to two beet crops infested with various weeds. A comparison was made with composition No.6 and the percentage of destruction was measured.

The following results were obtained: Compo- Dose of Percentage of destruction compared sition active to an untreated control No. substance Effect on beet Overall effect on weeds inglha 1st 2nd 1st 2nd crop crop crop crop 6 1,000 0 5 70 50 officially recommen ded dose 1 750 0 5 70 50 6 500 0 0 70 40 1 375 1 3 70 40 It is ascertained that the composition according to the invention has an excellent herbicidal activity and it even makes it possible to reduce the dose of the active substance by about 25% compared to the doses of the known product which is on sale and especially compared to the normal dose officially recommended by national departments of agriculture. Selectivity (non-destruction of the crop) is perfectly satisfactory.

Claims (14)

1. A homogeneous liquid composition which comprises 5 to 500 g/l of a biscarbamate of formula:

in which X denotes a hydrogen atom or an alkyl radical containing 1 to 3 carbon atoms and R denotes an alkyl radical containing 1 to 3 carbon atoms, 100 to 700 g/l of tributyl phosphate; 50 to 300 gll of a water-miscible organic solvent which is a good solvent for the carbamate of formula (I); and 50 to 300 g/i of non-ionic surfactant.

2. A composition as claimed in claim 1 in which the organic solvent is dimethylformamide, cyclohexanone, dimethylsulphoxide, acetophenone or N-methylpyrrolidone.

3. A composition as claimed in claim 1 or 2 which comprises 100 to 250 g/l of a biscarbamate of formula (I)

4. A composition according to any one of claims 1 to 4 in which the biscarbamate is phenmedipham.

5. A composition according to any one of claims 1 to 4 in which the organic solvent is Nmethylpyrrolidone.

6. A composition according to any one of claims 1 to 5 which additionaily comprises an anionic surfactant in an amount of not more than 50% by weight of the total non-ionic surfactant

7. A composition according to claim 1 substantially as hereinbefore described with reference to Examples 1 to 5.

8. A method of weed control at the locus of a crop which comprises the post-emergence application to the locus of an effective amount of a slurry obtained by dilution with water of a composition according to any one of claims 1 to 7.

9. A method according to claim 8 in which the crop is a beet crop.

10. A method according to claim 8 or 9, in which the slurry comprises 1 to 10 g/l of biscarbamate of formula (I).

11. A method according to claim 10 in which the slurry comprises 1.1 to 6 g/l of biscarbamate of formula (I).

12. A method according to any one of claims 8 to 11 in which 120 to 2,000 g/ha of biscarbamate of formula (I) is applied.

13. A method according to claim 12 In which 250 to 1,000 g/ha of biscarbamate of formula I is applied.

14. A method according to claim 8 substantially as hereinbefore described with reference to Example 6.