GB2037585A - Herbicidal compositions - Google Patents

Abstract

A novel herbicidal formulation of improved stability and comprising known herbicides is described. The composition is in finely divided form and comprises in intimate mixture, a dinitroaniline compound of the formula <IMAGE> in which R<1> is C2-3 alkyl and R<2> is C3-4 alkyl or C4 alkenyl, (2) a urea compound of the formula: <IMAGE> in which R<3> and R<4> are each hydrogen, C1-4 alkyl, C1-4 alkoxy or halogen and R<5> and R<6> are each C1-4 alkyl or C1-4 alkoxy, provided that R<3> and R<4> are not both hydrogen and (3) a silica derivative selected from fumed silica and precipitated silica.

Description

Herbicidal compositions This invention relates to herbicidal compositions and in particular to a herbicidal composition in finely divided form.

In order to control a broad range of weeds in crops it is often necessary to employ more than one herbicide. Two widely known groups of herbicides can be described as dinitroaniline and urea herbicides, and amongst the former herbicides there are those of the following formula

in which R1 is 02-3 alkyl and R2 is C3--4 alkyl or C4 alkenyl. Such dinitroanilines include, for example, 2, 6 - dinitro - NN - dipropyl - 4 - trifluoromethylaniline (trifluralin), N - ethyl - N - (2 - methylallyl) - 2,6 dinitro - 4 - trifluoromethylaniline (ethalfluralin) and N-butyl-N-ethyl-2, 6-dinitro-4-trifluoromethylaniline (benfluralin).Both trifluralin and benfluralin are described in U.S. Patent 3,257,190 and ethalfluralin is the subject of British Patent 1,505,249.

Some of the more common ureas which have long been known for their herbicide properties are embraced by the following formula

in which R3 and R4 are each hydrogen, C1-4 alkyl, C,~4 alkoxy or halogen, and R5 and R6 are each Cur~4 alkyl or C,~4 alkoxy, provided that R3 and R4 are not both hydrogen.

It is often convenient to supply the farmer with a concentrated solid formulation which only requires dispersion in water before it can be directly applied to the crop area. Such solid formulations are safe to handle and their use is less likely to result in the farmer miscalculating the balance of herbicides to be applied, as can occur when the two ingredients are added separately to a large volume of water in a "tank mix". We have found that, owing to the particular characteristics of the above type of dinitroaniline and urea herbicides, solid compositions comprising them are frequently of poor quality tending to cake and form lumps, which in practice makes them difficult to use. These problems are particularly apparent when the product is stored for even quite short periods at elevated temperatures.Liquid formulations, for example, aqueous suspensions, also suffer from lack of stability when stored at temperatures above normal.

The solid herbicidal compositions of the invention comprise the active ingredients in association with certain silica derivatives which maintain the composition in free-flowing form. They possess excellent herbicide activity against a broad range of weeds and have the added advantage that they can be employed at a rate which gives good weed control whilst avoiding the known tendency of urea herbicides to exhibit phytotoxicity on the crop.

Accordingly the invention provides a herbicidal composition in finely divided form comprising, in intimate mixture, (1 ) a dinitroaniiine compound of the formula:

in which R' is 02-3 alkyl and R2 is C3-4 alkyl or C4 alkenyl, (2) a urea compound oftheformula:

in which R3 and R4 are each hydrogen, C,~4 alkyl, C1-4 alkoxy or halogen and R5 and R6 are each C,~4 alkyl or C,~4 alkoxy, provided that R3 and R4 are not both hydrogen, and (3) a silica derivative selected from fumed silica and precipitated silica.

Asuitable choice of silica derivative must be made in order to overcome caking in the formulation. Not all silicas can be employed for this purpose and the efficacy of the silica material appears not only to depend on its physical properties but also to be related to its chemical nature, the effect being limited to fumed or precipitated silicas. A mixture of fumed and precipitated silicas may, of course, be employed. Other silica materials which are widely used in herbicide formulations such as precipitated silicates and micronised silica are not effective for the purpose.

Fumed silica is the product of burning silicon tetrachloride (Si Cl4) in an atmosphere of oxygen and hydrogen. The average particle diameter of the resulting material is generally within the range of 2 to 50 millimicrons and the surface area between 175 and 400 square metres per gram, as measured by the Brunauer, Emmett and Teller equation (J. Amer.

Chem. Soc. 60,309(1938). Precipitated silica may be prepared by chemical reaction of an alkali metal silicate, such as for example sodium silicate, with mineral acid such as for example hydrochloric acid, followed by adjustment of the pH to cause precipitation. The precipitate is then separated, washed and dried. Its particle size is generally within the range of 5 to 50 millimicrons and its surface area between 50 and 350 square metres per gram. Both materials are well-known in the art of formulation. For example, fumed silica is available commercially as CAB-O-SIL H5 and CAB-O-SIL M5 and precipitated silica as HiSIL 233, SILICA K320, UTRASIL VN3, WESSALON S and ZEOLEX 39 and 39A. Preferably the silica derivative is present to the extent of from 2 to 40 percent by weight, more especially from 4 to 15 percent by weight.

Preferably the composition also comprises a solid inert carrier which can be any of the materials well known in the art for preparing solid herbicidalformu- lations and these include, for example, kaolin, talc, montmorillonite, attapulgite, diatomaceous earth and hydrated sodium silicoaluminate.Most suitably the average particle diameter of the solid carrier is within the range of from 1 to :O m microns and the quantity of carrier in the formulation may preferably vary within the limits of from 0 to 85 percent by weight, more especially from 5 to 50 percent by weight With respect to the herbicide components of the composition, a range of dinitroanilines can be util ised, preferred examples being trifluralin, ethalflura lin and benfluralin, trifluralin being of special signifi cance in this context. The dinitroaniline herbicide is generally present to the extent of from 10 to 50 per cent by weight, such as from 15 to 30 percent by weight.

With regard to the urea herbicide component it is chosen from compounds covered by formula Il above. When R3 or R4 is C1--4 alkyl it is for example, methyl, ethyl, propyl or butyl, and when R3 or R4 is alkoxy it is, for example, methoxy, ethoxy, propoxy or butoxy. When R3 or R4 is halogen it is chloro, bromo iodo orfluoro, and preferably chloro. R5 and R6 can take any of the values defined for R3 and R4 when they are alkyl or alkoxy. The urea herbicide is preferably chosen from metoxuron, chlortoluron, isoproturon, linuron and neburon, metoxuron being the most preferred of these herbicides, and there is conveniently from 10 to 75 percent by weight, such as from 20 to 60 percent by weight of the composi tion.

In the above formula ll (i) metoxuron has the values R3 methoxy, R4 chloro, R5 methyl and R8 methyl (ii) chlortoluron has the values R3 methyl, R4 chloro, R5 methyl and R6 methyl (iii) isoproturon has the values R3 is isopropyl, R4 hydrogen, R5 methyl and R6 methyl (iv) linuron has the values R3 chloro, R4 chloro, R5 methyl and R6 methoxy (v) neburon has the values R3 chloro, R4 chloro, R5 methyl and Rs butyl It will be understood that more than one dinit roaniline and / or urea herbicide can be employed in the composition of the invention.

Choice of the relative proportions of the active herbicides depends on the nature of the dinit roaniline and urea herbicide components but generally the herbicides are employed in a ratio range of from 5:1 to 1:20 by weight.

We have found that the composition of the invention has surprising stability and maintains its finely divided form on storage even at temperatures higher 'than those normally encountered. The finely divided particles of the solid carrier remain discrete despite the presence of the other ingredients of the composition adhered to then and the resulting formulations can very readily be diluted with water for direct application to crops by spraying.

They have the added advantage over concentrated liquid formulations in possessing good low temperature stability.

Conveniently the composition of the invention is in the form known as a "wettable powder" and comprises a surfactant such as a dispersing agent.

Examples of suitable anionic surfactants are the alkyl and aryl sulphonates, sulphates and sulphosuccinates such as isopropylnaphthalene sulphonates, dodecyl benzene sulphonates, dioctyl esters of sulphosuccinic acids, dinonyl sulphosuccinates, lauryl polyglycol ether sulphosuccinates, lauryl sulphates and cetostearyl sulphates.Examples of suitable nonionic surfactants are polyoxyethylene sorbitan esters of mixed fatty and resin acids such as polyoxyethylene sorbitan-monolaurates, -monopalmitates, -monostearates, -mono-oleates, -tri-stearates and -trioleates, alkyl aryl polyethoxy ethanols such as nonyl- and iso-octyl-phenyl polyethoxy ethanols, glyceride esters such as diglyceryl mono-oleate, glyceryl dioleate and glyceryl dilaurate, and ethoxylated alkyl phenols and cresols such as ethoxylated octyl phenol, ethoxylated nonyl phenol and ethoxylated octyl cresol.

A preferred formulation of the invention is one comprising from 5 to 40 percent by weight of trifluralin, from 5 to 75 percent by weight of metoxuron, from 2 to 25 percent by weight silica derivative, from 1 to 10 percent by weight of wetting agent and from 0to 10 percent by weight of dispersing agent, the remainder to 100 percent by weight being inert filler.

An object of the invention is to provide a formulation, which on dilution with water has useful herbicide properties. The dinitroaniline component is especially effective against grass weeds such as for example, Poa annua, Apera spica-venti and Alopecurus myosuroides, whereas the urea component is more active against broadleaf weeds such as for example, Capsella bursa-pastoris, Sinapis arvensis and Matricaria spp. This combination allows the useofurea herbicides at a rate which avoids their known tendency to exhibit phytotoxicity on the crop, whilst giving excellent weed control.

A combination of the two types of herbicide will allow control of a broad spectrum of weeds in the context of cereal crops such as for example, wheat, barley, oats and rye, and especially wheat and barley.

As a further aspect of the invention there is included a method of controlling weeds in a crop area which comprises applying to the crop area an aqueous dispersion prepared by mixing a composition according to the invention with water Application of the dispersion can be by any of the well known techniques of spraying, and at a pre or postemergence stage depending mainly on the urea herbicide employed and its preferred mode of use. In general the compositions are best used in postemergence treatments. As a particular instance, a composition comprising trifluralin and metoxuron, may be applied pre- or post-emergence but it is preferably employed in a post-emergence context, for example, in cereal crops at the stage when the crop is between the two-leaf state and jointing.

Oonvenientlythe aqueous dispersion prepared from the formulation of the invention is utilised at such a rate that the dinitroaniline herbicide is applied at a rate of 200 to 1500 g/hectare. With regard to the urea herbicide, the application rate is preferably chosen as follows : linuron in the range of from 200 to 1000 g/hectare, neburon in the range of from 2000 to 4000 glhectare, chlortoluron in the range of from 1000 to 3000 g/hectare, isoproturon in the range of from 450 to 2000 g/hectare and metoxuron in the range of from 1000 to 3500 glhectare. At such appli cation rates the active ingredients are generally diluted with 100 to 600 litres water for applications per hectare.

In preparing the composition of the invention a blend is first made by adding the urea compound and silica derivative and, optionally, a surfactant, inert carrier and other excipients to, for example, a ribbon blender or orbital screw blender. The dinitroaniline compound is then added to this mixture, preferably by spraying the molten material on to it. It is then cooled and preferably milled in, for example, an air mill, disc mill or hammer mill, to give a material having an average particle diameter of from 0.5 to 50 microns, preferably from 1 to 15 microns.

As a further embodiment of the invention there is provided a method of preparing a herbicide composition which comprises mixing a finely divided inert solid carrier with a silica derivative selected from fumed silica and precipitated silica, and a urea compound of formula II, spraying a molten dinitroaniline compound of formula I at a temperature of from 4500 to 10000 on to the resulting mixture whilst continuing a thorough blending action, cooling the blend thus formed and subjecting it to milling at a temperature of from 1000 to 40"C to produce a product having an average particle diameter of from 1 to 15 microns.

The invention is illustrated by the following Examples: EXAMPLE 1 Kaolin was added to a ribbon blender which was set in motion. Precipitated silica, metoxuron, sodium alkyl sulphate and sodium lignin sulphonate were added, in the quantities set out below, and, a thorough blend achieved. Molten trifluralin at a temperature of approximately 75"C was sprayed on to the rotating blend of materials.

When the addition was completed the mixer was stopped, the blend collected and allowed to cool.

This coarse powder was subjected to the action of an air mill, the through-put being adjusted to provide a finely divided powdered formulation having an average particle diameter of 5 microns.

%by weight Trifluralin 20 Metoxuron 50 Precipitated silica 8 Sodium alkyl sulphate 2 Sodium lignin sulphonate 6 Kaolin to 100 Formulations prepared in a similarway to that described above were made employing the ingredients set out in Examples 2 to 12 below:: EXAMPLE2 % by weight Trifluralin 16 Metoxuron 45 Fumed silica 4 Sodium alkyl ether sulphate 4 Sulphonated lignin 2 Talc EXAMPLE 3 %by weight Ethalfluralin 18 Metoxuron 50 Precipitated silica 10 Ethoxylated alkyl phenol 2 Sodium salt of condensed napthalene 4 sulphonic acids Montormillonite to 100 EXAMPLE4 % by weight Benfluraiin 14 Metoxuron 42 Fumed silica 7 Sodium tridecyl sulphate 3 Sulphite lye powder 5 Attapulgite to 100 EXAMPLE 5 % by weight Trifluralin 20 Chlortoluron 25 Precipitated silica 10 Sodium alkyl ether sulphate 4 Sodium lignin sulphonate 2 Kaolin to 100 EXAMPLE 6 % by weight Trifluralin 20 Chlortoluron 46 Fumed silica 6 Sodium lauryl sulphate 3 Sulphite lye powder 5 Attapulgite to 100 EXAMPLE 7 %by weight Trifluralin 20 Neburon 40 Precipitated silica 8 Ethoxyiated alkyl phenol 2 Sulphonated lignin 3 Attapulgite to 100 EXAMPLES % by weight Trifluralin 18 Neburon 45 Fumed silica 6 Sodium lauryl sulphate 3 Sulphite lye powder 5 Talc to 100 EXAMPLES 9 %by weight Trifluralin 24 Linuron 12 Precipitated silica 12 Sodium lauryl sulphate 2 Sulphonated lignin 4 Attapulgite to 100 EXAMPLES 10 % by weight Trifluralin 24 Linuron 6 Fumed silica 8 Sodium tridecyl sulphate 5 Sodium lignin sulphonate 3 Kaolin to 100 EXAMPLES Ii % by weight Trifluralin 20 Isoproturon 20 Precipitated silica 6 Sodium lauryl sulphate 6 Sulphite lye powder 2 EXAMPLES 12 % by weight Trifluralin 25 Isoproturon 37.5 Fumed silica 10 Sodium dioctylsulphosuccinate 2 Sodium lignin sulphonate 6 Attapulgite to 100 COMPARA TI VE EXAMPLE In this Example a number of silica materials were employed in preparing formulations containing the two active herbicide ingredients trifluralin and metoxuron.

The ability af the formulation to resist caking and the formation of lumps when kept at elevated temp eraturessimulating conditions of storage was measured by means of a sieve having a mesh size of 45 microns.

Each formulation contained 10 percent by weight silica and was subjected to the same method of preparation and milling so that in each case at the start of the test less than 0.2% of the formulation was retained on the sieve. The formulations were stored for one day at 60"C and for one week at 50 C and the amount retained on the sieve measured. A value of less than 1 percent represents an acceptable product and it will be seen that in most instances the formulations of the invention, that is those containing fumed or precipitated silica, exhibited a much lower value.

Talc to 100 *% retained on 45,uU sieve iday lweek 60"C 50"C ALUSIL N Precipitated silicate 3.0 1.4 MICROCAL 160 Precipitated silicate 6.8 2.6 ZEOLEX 29 Precipitated silicate 2.0 1.4 GASIL 23 Micronised silica 1.2 2.0 GASIL 200 Micronisedsilica 30.2 18.6 CAB-O-SIL H5 Fumed silica 0.2 0.6 CAB-O-SIL M5 Fumed silica 0.2 0.2 KISIL 233 Precipitated silica 0.4 0.2 SILICA K320 Precipitated silica 0.2 0.2 ULTRASILVN3 Precipitated silica 0.2 0.2 WESSALON S Precipitated silica 0.2 0.2 ZEOLEX 39 Precipitated silica 0.4 0.2 ZEOLEX 39A Precipitated silica 0.2 0.6

Claims (14)

1. Aherbicidal composition in finely divided form comprising, in intimate mixture, (1) a dinitroaniline compound of the formula

in which R' is C33 alkyl and R2 is C34 alkyl or C4 alkenyl, (2) a urea compound of the formula

in which R3 and R4 are each hydrogen, C, 4 alkyl, C14 alkoxy or halogen and R5 and R6 are each C14 alkyl or C14 alkoxy, provided that R3 and R4 are not both hydrogen and (3) a silica derivative selected from fumed silica and precipitated silica.

2. A herbicidal composition according to Claim 1 in which the dinitroaniline compound is trifluralin.

3. A herbicidal composition according to either of Claims 1 and 2 in which the urea compound in metoxuron, chlortoluron, isoproturon, linuron or neburon.

4. A herbicidal composition according to Claim 3 in which the urea compound is metoxuron.

5. A herbicidal composition according to any of the preceding claims, comprising a solid inert carrier.

6. A herbicidal composition according to any of the preceding claims in which the dinitroaniline compound is present to the extent of from 15 to 30 percent by weight.

7. A herbicidal composition according to any of the preceding claims in which the urea compound is present to the extent of from 20 to 60 percent by weight.

8. A herbicidal composition according to any of the preceding claims in which the silica derivative is present to the extent of from 4 to 15 percent by weight.

9. A herbicidal composition according to any of the preceding claims having an average particle diameter of from 1 to 15 microns.

10. A herbicidal composition according to Claim 1, which comprises from 5 to 40 percent by weight of trifluralin, from 5 to 75 percent by weight of metoxuron, from 2 to 25 percent by weight silica derivative, from 1 to 10 percent by weight of wetting agent and from 0 to 10 percent by weight of dispersing agent, the remainderto 100 percent by weight being inert filler.

11. A herbicidal composition according to claim 1 substantially as described in any of Examples 1 to 12.

12. A method of controlling weeds in a crop area which comprises applying to the crop area an aqueous dispersion prepared by mixing with water a composition according to any of claims 1 toll.

13. A method according to claim 12 for control of weeds in cereal crops.

14. A method of preparing a herbicidal composition according to any of claims 1 to 10, which comprises mixing a finely divided inert solid carrier with a silica derivative selected from fumed silica and precipitated silica, and a urea compound, spraying a molten dinitroaniline compound at a temperature of from 45"C to 1 00'C on to the resulting mixture whilst continuing a thorough blending action, cooling the blend thus formed and subjecting it to milling at a temperature of from 10 C to 40"C to produce a product having an average particle diameter of from 1 to 15 microns.