Manufacture and use of herbicide chlorinated phenoxy formulation

[0002] This application claims priority to U.S. Provisional Application Ser. No. 60/118,254, filed Feb. 2, 1999.

[0003] As early as 1988, Henkel Corporation began marketing a line of methylated fatty acids, and more specifically, methylated soybean oil, as a replacement for commonly used organic solvents used in pesticide formulations. These methyl esters were and still are, promoted as being safer solvents because of their high flash point, relative to more commonly used aromatic hydrocarbons. In 1986, F. A. Manthey, et. Al., published a paper showing their work on various alkylated esters of different natural oils (soybean and sunflower). This work demonstrated that alkylated esters of soybean oil and sunflower oil can enhance the uptake of oxime herbicides (commonly referred to as “dims” or graminicides, i.e. sethoxydim, clopropoxydim.), and 2-(4-aryloxyphenoxy)alkanoic acid herbicides (commonly known as “fops”, i.e. diclofop, quizalofop, fluazifop). In 1989, Hazen, et.al. demonstrated the effectiveness of a methylated sunflower oil adjuvant on the uptake of sethoxydim. Furthermore, it was reported that methylated sunflower oil could actually increase the stability of sethoxydim in direct sunlight. Also in 1989, Manthey, et.al. reported that alkylated vegetable oils such as soybean oil and sunflower oil, could increase the realtive wax solubility of pesticide sprays. In 1991, more work was done by Urvoy, et Al. That demonstrated the effectiveness of alkylated fatty acids in enhancing the uptake of gramincides. In 1993, Serre, et.al. reported that alkyl esters of oleic acid could enhance the efficacy of quizalofop-ethyl, a 2-(4-aryloxyphenoxy)alkanoic acid herbicide, and phenmedipham, a bis-carbamate herbicide. In 1995, McMullan, et.al. demonstrated the effectiveness of methylated fatty acids in enhancing the efficacy of tralkoxydim, another graminicide herbicide.

[0004] Chlorinated phenoxy acid compounds comprise a family of herbicides that are used in the form of their parent acids, and more commonly as their salts and esters. The most common member of this herbicide family is 2,4-D [(2,4-dichlorophenoxy)acetic acid]. Two other commonly used compounds in this family are 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and MCPA[[(4-chloro-o-tolyl)oxy]acetic acid]. Additional herbicides in this family are 2,4-DB [4(2,4-dichlorophenoxy)butyric acid], MCPB [4-[(4-chloro-o-tolyl)oxy]butyric acid], silvex [2-(2,4,5-trichorophenoxy)propionic acid], dichlorprop [2-(2,4-dichlorophenoxy)propionic acid], mercoprop [2-[(4-chloro-o-tolyl)oxy]propionic acid]. These herbicides are plant growth regulator compounds with hormone-like activity.

[0005] The ester forms of these compounds are represented by the alkyl esters (mainly methyl, isopropyl, butyl, and octyl) and the low-volatile esters (butoxyethanol, propyleneglycolbutylether, and iso-octyl).

[0006] The major controllable factors of chlorinated phenoxy herbicides have been reported by Ashton and Crafts as being pH, concentration, and additives (i.e. surfactants). Absorption of chlorinated phenoxy herbicides is reported to be optimal at low pH ranges. While surfactants have been reported to enhance the activity of chlorinated phenoxy herbicides in some instances, no one surfactant could be selected which consistently enhanced the uptake of the herbicide. The authors cite work done by Bukovac in 1976 showing that foliar penetration is generally linearly related to the external herbicide concentration.

[0007] Recently, the family of 2,4-D herbicides has come under regulatory scrutiny due to the potential of spray mixes to drift to off-target areas. This drift is caused by volatilization of both sprays and of spray deposits. Therefore, it would be beneficial if the per acre use rate of these compounds could be reduced, thereby affording a reduction in driftable herbicide. Any attempt to reduce herbicide drift, however, must not demonstrate a reduction in herbicide efficacy.

[0008] The present invention is a homogenous agricultural liquid composition containing at least one chlorinated phenoxy herbicide and at least one alkylated fatty acid or natural oil, and optionally, at least one organosilicone surfactant. Such formulations have been seen to exhibit synergistic effects allowing a reduction of herbicide use rates on a per acre basis.

[0009] It has been surprisingly discovered that a chlorinated phenoxy herbicides can be formulated with alkylated fatty acids or natural oils, and that the effective use rate of the composition can be reduced dramatically. This is in opposition to prior knowledge that the uptake of chlorinated phenoxy herbicides is directly associated with the concentration of the herbicide on the plant leaf surface.

[0010] In example 1, the following formulations were tested:

[0011] The control formulation:

[0012] The new formulation listed as HM-9625-B

[0013] Aromatic 100 is a conventional organic solvent containing aromatic hydrocarbons and is sold by Exxon.

[0014] Sponto N-702/710 is a mixed emulsifier specially blended by Witco Corp. to provide stable emulsions of 2,4-D ester formulations.

[0015] Methylated soybean oil is a methylated natural oil derived from soybean oil. It is manufactured by several US producers by the reaction of methanol and soybean oil.

[0016] Silwet L-77 is an organosilicone surfactant manufactured by Witco Corp. It is generally used to enhance the spreadability of water based sprays. Silwet L-77 has also been reported to enhance the uptake of herbicides through stomatal infiltration.

[0017] In the chart below, HM-8802-A is a commercially available adjuvant containing methylated soybean oil and Silwet L-77.

[0018] The improvement of this formula was originally thought to be simply the increased flash point and thus enhanced product safety. The flash point went from about 100 degrees F. using Aromatic 100, to over 200 degrees F. using the methylated soybean oil. While this benefit is certainly useful, it is hardly suprising or original. Henkel has been touting their methyl esters for this characteristic for several years. We were surprised to discover that this formula provided herbicidal efficacy at low use rates. The data table above shows better weed control as compared to the control formulation at higher rates. Furthermore, it was discovered that the formulation containing methylated soybean oil and organosilicone surfactant was superior to the addition of a methylated soybean oil/organosilicone surfactant adjuvant to the control formulation.

[0019] In example 2, the same materials were tested for herbicide efficacy on a separate weed species, common lambsquarter.

[0020] The data table above shows equivalent weed control as compared to the control formulation at higher rates. Furthermore, it was discovered that the formulation containing methylated soybean oil and organosilicone surfactant was equal to the addition of a methylated soybean oil/organosilicone surfactant adjuvant to the control formulation. This is significant because lower herbicide use rates are more environmentally friendly. Also, these findings with the improved formulation are different from what was previously believed, that concentration was the largest single factor involved in chlorinated phenoxy herbicide uptake.

[0021] In example 3, the novel formulation is shown using ethylated sunflower oil as the alkylated fatty acid. Ethylated sunflower oil is made by reacting natural sunflower oil with ethyl alcohol.

[0022] In example 4, the chlorinated phenoxy herbicide of choice is MCPA, or specifically, the iso-octyl ester of MCPA.

[0023] In example 5, the formula contains a nonylphenol ethoxylate surfactant in place of the organosilicone surfactant

[0024] The preferred embodiment of the present invention includes chlorinated phenoxy herbicides. The most preferred embodiment of the present invention includes 2,4-dichlorophenoxyacetic acid and its' iso-octyl ester.

[0025] The preferred embodiment of the present invention includes alkylated fatty acids or natural oils, including but not limited to the following:

[0026] Alkylated soybean oil

[0027] Alkylated sunflower oil

[0028] Alkylated canola oil

[0029] Alkylated fatty acids including C_6-18saturated and unsaturated fatty acids.

[0030] The preferred embodiment of the present invention includes additional surfactants to enhance the spreading characteristics of the spray deposit. These surfactants preferably include those listed in the prior patents U.S. Pat. No. 5,393,791 and U.S. Pat. No. 5,580,567 which are incorporated by reference herein. The most preferred embodiment of the present invention includes organosilicone surfactants.