Emulsifiable Suspension Concentrate Compositions of Imidazolinyl Benzoic Acids, Esters and Salts Thereof, and Dinitroaniline Herbicides

Combination product containing imidazolinyl benzoic acids, or esters or salts thereof, such as imazamethabenz-methyl (an isomeric mixture of methyl 6-(4-isopropyl- 4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluate and methyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate), and dinitroaniline herbicides, such as pendimethalin (N-(1-ethylpropyl)-2,6-dinitrol3,4-xylidine), trifluralin (N,N-dipropyl-2,6-dinitro-4-trifluoromethylaniline) and the like, are effective herbicidal agents. However, it has been found that those combination products exhibit poor low temperature stability. Those products tend to thicken on storage at low temperatures and solid product remains in the container after use. The agriculturalist may experience difficulty, therefore, when using those products (e.g., during application of the herbicide, or with special storage requirements and limited application times).

Efforts to overcome the problems of the prior art are described in commonly assigned, copending U.S. patent application, Ser. No. 648,083, filed on Jan. 31, 1991.

The present invention overcomes the drawbacks of the prior art by providing a herbicidal emulsifiable suspension concentrate composition which exhibits low temperature stability. Such stable compositions also have desirable flow characteristics.

It is an object of the present invention, therefore, to provide an emulsifiable suspension concentrate composition of imidazolinyl benzoic acids, or esters or salts thereof, and dinitroaniline herbicides, which is stable at low temperatures.

The present invention relates to a herbicidal emulsifiable suspension concentrate composition comprising about 5% to 20% by weight of a imdazolinyl benzoic acid, or ester or salt thereof, about 10% to 30% by weight of a dinitroaniline herbicide, about 0.5% to 10% by weight of a mixture of an alkylarylsulfonate and an alkylarylsulfonic acid, about 5% to 15% by weight of a nonionic surfactant or mixture of nonionic surfactants, about 1% to 10% by weight of a suspending agent, up to about 1% by weight of an antifoaming agent, and an organic solvent or mixture of organic solvents.

It has been found that combinations of herbicidal imidazolinyl benzoic acids, or esters or salts thereof, and dinitroaniline emulsifiable suspension concentrate compositions thicken on storage at low temperatures and that large amounts of product are left in the container after the contents are poured out. Since those compositions may be used in areas where low temperature prevails, emulsifiable suspension concentrate compositions with low temperature stability are required. Surprisingly, it has now been discovered that the herbicidal emulsifiable suspension concentrate compositions of the present invention remain free-flowing at low temperatures and do not leave any significant amounts of product in the container after pouring.

The herbicidal emulsifiable suspension concentrate compositions of the present invention comprise about 5% to 20% by weight imidazolinyl benzoic acids, or esters or salts thereof, such as imazamethabenz-methyl, about 10% to 30% by weight of a dinitroaniline herbicide, such as pendimethalin or trifluralin, about 0.5% to 10% by weight of a mixture of an alkylarylsulfonate and an alkylarylsulfonic acid, about 5% to 15% by weight of a nonionic surfactant or mixture of nonionic surfactants, about 1% to 10% by weight of a suspending agent, up to about 1% by weight of an antifoaming agent, and an aromatic solvent or mixture of aromatic solvents to total 100%. Preferably, the ratio of the alkylarylsulfonate to the alkylarylsulfonic acid is about 0.1:1 to 8:1. Most preferably, the ratio of the mixture of the alkylarylsulfonate and the alkylarylsulfonic acid to imidazolinyl benzoic acid, or ester or salt thereof, is about 0.1:1 to 0.6:1.

Preferred emulsifiable suspension concentrate compositions of the present invention are those comprising about 10% to 15% by weight imidazolinyl benzoic acid, or ester or salt thereof, about 15% to 25% by weight of a dinitroaniline herbicide, about 2% to 6% by weight of a mixture of an alkylarylsulfonate and an alkylarylsulfonic acid, about 5% to 10% by weight of a polyoxyethylene phenyl ether, about 0.5% to 2% by weight of a polyalkylene glycol ether, about 1% to 6% by weight of a clay, up to about 1% by weight of an antifoaming agent, up to about 2% by weight xylene, and an aromatic hydrocarbon solvent having a distillation range of from about 135.degree. C. to 305.degree. C. The ratio of the alkylarylsulfonate to the alkylarylsulfonic acid is preferably about 0.1:1 to 8:1, more preferably about 0.3:1 to 3:1, and, most preferably, the ratio of the mixture of the alkylarylsulfonate and the alkylarylsulfonic acid to imidazolinyl benzoic acid, or ester or salt thereof, is about 0.1:1 to 0.6:1.

Advantageously, it has been found that the compositions of the present invention, which, in addition to all of the other necessary components, incorporate an alkylarylsulfonate salt-alkylarylsulfonic acid component, provide physically and chemically stable herbicidal emulsifiable suspension concentrate compositions of imidazolinyl benzoic acids, or esters or salts thereof, and dinitroaniline herbicides which remain free-flowing and homogeneous at low temperatures. Such compositions also remain physically and chemically stable after repeated freezing and thawing cycles without preciptating insoluble solids.

Imidazolinyl benzoic acids, esters and salts thereof suitable for use in the compositions of the invention include those described in U.S. Pat. No. 4,188,487, the disclosure of which is incorporated herein by reference. Imazamethabenz-methyl is preferred. Dinitroaniline herbicides suitable for use in the compositions of the present invention include those described in U. S. Pat. No. 3,920,742, the disclosure of which is incorporated herein by reference. Preferred are pendimethalin, trifluralin, benfluralin, isopropalin, ethalfluralin, oryzalin and the like with pendimethalin and trifluralin being most preferred.

The mixture of an alkylarylsulfonate and an alkylarylsulfonic acid is most preferably present in an amount such that its ratio to the imidazolinyl benzoic acid, or ester or salt thereof, is about 0.1:1 to 0.6:1 to ensure that the compositions remain free-flowing at low temperatures. Further, the ratio of the alkylarylsulfonate to the alkylarylsulfonic acid is preferably about 0.1:1 to 8:1, more preferably about 0.31 to 3:1. Alkylarylsulfonates suitable for use in the compositions of the present invention include C.sub.8 -C.sub.18 alkylbenzenesulfonates, with calcium dodecylbenzenesulfonate being most preferred. Alkylarylsulfonic acids suitable for use in the compositions of the invention include C.sub.8 -C.sub.18 alkylbenzenesulfonic acids, with dodecylbenzenesulfonic acid being most preferred.

Nonionic surfactants suitable for use in the compositions of the present invention include polyalkylene glycol ethers such as butoxypolypropylenoxy polyethylenoxyethanol and the like, and polyoxyethylene phenyl ethers such as polyoxyethylene nonylphenyl ethers, polyoxyethylene dinonylphenyl ethers, polyoxyethylene dodecylphenyl ethers, polyoxyethylene octylphenyl ethers, polyoxyethylene tridecylphenyl ethers and the like, with polyoxyethylene nonylphenyl ethers with about 11 moles of ethylene oxide per molecule being preferred.

Suspending agents suitable for use in the compositions of the present invention include clays such as attapulgite clays, montmorillonite clays, kaolin clays, zeolite, silicas and the like, with attapulgite clays being most preferred.

Organic solvents suitable for use in the compositions of this invention include aromatic hydrocarbon solvents such as toluene, xylenes, polynuclear aromatic hydrocarbons such as naphthalenes and alkylnaphthalenes and mixtures thereof, many of which are available from the fractionation of crude oil and in general have distillation ranges in the temperature range of from about 135.degree. C. to 305.degree. C., with those having a distillation range of from about 183.degree. C. to 290.degree. C. being most preferred, and are commercially available under a variety of tradenames.

The herbicidal emulsifiable suspension concentrate compositions of the present invention may conveniently be prepared by admixing a dinitroaniline herbicide with a mixture of the desired alkylarylsulfonate, alkylarylsulfonic acid, nonionic surfactant or mixture of nonionic surfactants, anti-foaming agent and aromatic solvent or mixture of aromatic solvents until a homogeneous mixture is obtained, then imazamethabenz-methyl, or other imidazolinyl benzoic acids, or esters or salts thereof, and the desired suspending agent are added to the homogeneous mixture, and mixing is continued followed optionally by milling to obtain the desired herbicidal suspension concentrate composition of the present invention.

The following examples are provided to further illustrate the compositions of the present invention but are not intended to limit the invention described herein.

Preparation of Emulsifiable Suspension Concentrate Compositions

An aromatic hydrocarbon mixture (C.sub.10 -C.sub.13) aromatics having a distillation range of from about 229.degree. C.-284.degree. C. (SOLVESSO.RTM. 200, Exxon) (31.89 kg, 50.2% on a weight basis), xylene (0.64 kg, 1.0% on a weight basis), a nonylphenolethoxylate with an average 11 moles of ethylene oxide (ARKOPAL.RTM. N110, Hoechst) (4.80 kg, 7.5% on a weight basis), calcium dodecylbenzene sulfonate (SOPROPHOR.RTM. 70, Rhone-Poulenc) (1.27 kg, 60% in isobutanol, 2.0% on a weight basis), dodecylbenzenesulfonic acid (ARYLAN.RTM. SC Acid, Lankro Chemicals Ltd.) (1.27 kg, 2.0% on a weight basis), a butoxypolypropylenoxy polyethylenoxyethanol (TERGITOL.RTM. XD, Union Carbide) (0.60 kg, 0.9% on a weight basis) and a silicone antifoam (SILCOLAPSE.RTM. 431, ICI) (0.18 kg, 0.3% on a weight basis) are stirred together to obtain a homogenous mixture. Molten pendimethalin (technical material, 92.3%, 13.44 kg, 21.1% on a weight basis) is added to the homogenous mixture and stirring is continued. Imazamethabenz-methyl (technical material, 92.9%, 8.01 kg, 12.6% on a weight basis) and attapulgite clay (ATTAGEL.RTM. 50, Engelhard) (1.50 kg, 2.4% on a weight basis) are added to the pendimethalin mixture and stirring is continued. The resultant mixture is stirred with a high-shear mixer and milled to obtain the desired emulsifiable suspension concentrate composition identified as composition 1 in Table I.

Using essentially the same procedure, the emulsifiable suspension concentrate compositions identified as compositions 2-20 in Table I are obtained.

Low Temperature Stability of Emulsifiable Suspension Concentrate Compositions of the Invention

Several samples of composition 1 from Example 1 and a comparative control composition containing on a weight basis 12.7% imazamethabenz-methyl (92.9% real), 20.4% pendimethalin (92.3% real), 7.6% ARKOPAL.RTM. N110, 4.5% SOPROPHOR.RTM. 70, 0.9% TERGITOL.RTM. XD, 0.3% SILCOLAPSE.RTM. 431, 2.4% ATTAGEL.RTM. 50 and 51.2% SOLVESSO.RTM. 200, prepared according to the procedure described in Example 1, are placed in plastic bottles and stored at 4.degree. C. After 4, 8 and 12 weeks the samples are inspected for evidence of gel formation. The results of these experiments are summarized in Table II.