Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N43/00—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds
  • A01N43/72—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with nitrogen atoms and oxygen or sulfur atoms as ring hetero atoms
  • A01N43/80—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with nitrogen atoms and oxygen or sulfur atoms as ring hetero atoms five-membered rings with one nitrogen atom and either one oxygen atom or one sulfur atom in positions 1,2

Definitions

• the present invention relates to formulations of clomazone having reduced volatility relative to conventional emulsifiable concentrates of clomazone.
• it relates to microencapsulated formulations of clomazone in which the clomazone is encapsulated in a shell of polyurea.
• Clomazone the common name for 2-(2-chlorophenyl) methyl-4,4-dimethyl-3-isoxazolinone, a highly effective herbicide, is also highly volatile, so much so that clomazone applied to the soil in a target area may move to adjacent area s and there cause discoloration, most typically whitening or some degree of bleaching, of a variety of crops, trees, or decorative plants. While this bleaching, indicative of the mode of action of the herbicide, may be temporary when plants are exposed to sufficiently low concentrations, it is unwelcome, even when it does not result in the destruction of the plant.
• Herbicide an emulsifiable concentrate formulation in commercial use that contains four pounds of clomazone per gallon of formulation, lists a number of restrictions on how the product is to be used, including weather conditions, spray volume and pressure, and distance from areas where plants are in commercial production. For example, for preemergent applications clomazone is not to be applied within 1,500 feet of commercial fruit, nut, or vegetable production or commercial greenhouses or nurseries. Clearly, this is a severe limitation on the use of an herbicide.
• the process of the invention involves the following steps: (a) providing an aqueous phase containing an emulsifier, preferably a partially hydrolyzed polyvinyl alcohol; an antifoam agent, and optionally a xanthan gum viscosity modifier/stabilizer; (b) providing a water immiscible phase consisting of clomazone and polymethylene polyphenyl isocyanate, with or without a hydrocarbon solvent; (c) emulsifying the water immiscible phase in the aqueous phase to form a dispersion of water-immiscible droplets throughout the aqueous phase; (d) agitating the dispersion while adding to it, either neat or in aqueous solution, ethylenediamine, diethyltriamine, triethylenetetramine, 1,6-hexanediamine, or a mixture of the polyfunctional amines, thus forming a polyurea shell wall around the water-immiscible droplets.
• the suspension is cured by moderate heating, after which one or more stabilizing agents, such as propylene glycol, xanthan gum, smectite clay, or an ionic dispersing agent such as a sulfonate of an alkyl napthalene, may be added, as is well-known in the art.
• stabilizing agents such as propylene glycol, xanthan gum, smectite clay, or an ionic dispersing agent such as a sulfonate of an alkyl napthalene
• pH 8.9 pH 8.9
• the aqueous phase will ordinarily contain 0.3 to 3.0, preferably 0.8 to 2.0, weight percent of one or more emulsifiers, e.g., polyvinyl alcohol, 0.05 to 0.20, preferably 0.06 to 0.15, weight percent of the xanthan gum viscosity modifier/stabilizer, if it is used, and 0.1 to 1.0, preferably 0.4 to 0.9, weight percent of the antifoam agent.
• emulsifiers e.g., polyvinyl alcohol
• 0.05 to 0.20 preferably 0.06 to 0.15
• weight percent of the xanthan gum viscosity modifier/stabilizer if it is used
• 0.1 to 1.0 preferably 0.4 to 0.9
• the water-immiscible phase will ordinarily consist of 60 to 85, preferably 65 to 77, weight percent of clomazone, an amount of polymethylene polyphenyl isocyanate (PMPPI) such that the ratio of clomazone to PMPPI is in the range of 1:1 to 6:1, preferably 4.5:1 to 4.8:1, and an aromatic hydrocarbon solvent for the two solutes.
• PMPPI polymethylene polyphenyl isocyanate
• solvent is optional in the preparation of formulations containing more than about two pounds of clomazone per gallon of formulation. In such preparations a small amount of solvent may still be used to depress the melting point.
• the amine solution will ordinarily contain 10 to 100, preferably 30 to 40, weight percent of ethylenediamine, diethylenetriamine, triethylenetetramine, 1,6-hexanediamine, or preferably a mixture of the polyfunctional amines, with ethylene diamine being used only in a mixture.
• the emulsification step requires high shear mixing to give small droplets of the immiscible phase.
• Factors that influence droplet size, which determines the eventual size of the microcapsules, as well as the stability of the emulsion, include speed and length of mixing, the type and amount of surfactant, solvent, temperature, and viscosity, as well as the xanthan gum, when used.
• Selection of the appropriate microcapsule size to achieve the purposes of the invention requires a balance between competing factors. In general, increasing microcapsule size decreases volatility, but also decreases suspensibility of the particles, while decreasing size yields better suspensibility, but higher volatility.
• the average size of the microcapsules is 5 to 50 microns, preferably 5 to 30 microns.
• the operating conditions to yield microcapsules of a desired size will depend on the emulsifying equipment used, and the adjustment to determine the proper conditions is well within the skill of the art.
• agitation during the amine addition should be gentle. Stirring is continued while the suspension is cured by heating to a temperature of 35 to 60, preferably 45° to 50° C., for 3 to 10, preferably 4 to 5, hours.
• the amounts of post encapsulation additives to be added typically would be selected from one or more of 0.75 to 6.5 wt. % propylene glycol, 0.05 to 0.30 wt. % xanthan gum, 0.25 to 0.50 wt. % smectite clay, and 0.5 to 6.0 wt. % one or more surfactants, each weight percent relative to the weight of the formulation after addition of the stabilizers.
• formulations of the present invention are prepared by the methods exemplified in the following examples.
• a stock solution of aqueous 20% (weight/weight) partially hydrolyzed polyvinyl alcohol having an average molecular weight of 13,000 to 23,000 (Airvol® 203) was prepared by stirring and heating the appropriate amounts of polyvinyl alcohol and water at about 80°-90° C. for one hour. The cooled solution was stored for later use.
• the mixture was stirred at a moderate speed with an air-powered stirrer, and a solution of 19.0 grams of triethylenetetramine (TETA) in 35.0 grams of water was added in one portion.
• TETA triethylenetetramine
• the mixture was then stirred at 50° C. for four hours. After this time, 2.5 grams of a smectite clay containing magnesium aluminum silicate, titanium dioxide, and cristobalite (Veegum® Ultra), and 15.0 grams of aqueous 2% xanthan gum (Kelzan® M) were added to stabilize the formulation.
• the formulation was then stirred for about one hour and stored for later use.
• Formulation P a three pound per gallon formulation, the components of which are given in Tables 3 and 4, was prepared by the method of Example 2. In this preparation 0.133 pound of the sodium sulfonated naphthalene condensate was added to the aqueous phase during its preparation. The post encapsulation additives, including the remainder of the sodium sulfonated naphthalene condensate, was added after the curing period at about 35° C., while the formulation continued to mix and cool to ambient temperature. The hydrochloric acid was then added to bring the pH from 10.8 to 8.9.
• the currently preferred practice is to continue stirring the formulation until the temperature reaches about 35° C., and then to add the hydrochloric acid to bring the pH to about 7.8.
• the post encapsulation additives including the remainder of the sodium sulfonated naphthalene condensate, is added, and stirring of the formulation is continued for about 30 minutes to give a homogeneous mixture.
• Formulation L is the same as Formulation A of the present invention, except that the polymethylene polyphenyl isocyanate (PMPPI) was replaced with toluene diisocyanate (TDI).
• PMPPI polymethylene polyphenyl isocyanate
• TDI is more reactive in water than PMPPI, which causes undesirable side-reactions leading to foaming in the emulsification step of the preparation of this formulation.
• Formulation M was an attempt to copy the formulation used successfully in an effective, four pound/gallon, capsule suspension formulation of an insecticide, substituting clomazone for the insecticide.
• the microcapsules produced were too small, and here, too, TDI caused foaming problems.
• Formulation N is the same as Formulation A of the present invention, except that the xanthan gum viscosity modifier/stabilizer is not used in the emulsification step. Batches of Formulation N prepared in this way gave microcapsules that not only are somewhat small, but are not uniform in size and tend to aggregate. Moreover, the formulation has poor physical stability, resulting in phase separation.
• Formulations V and W were prepared by the method of U.S. Pat. No. 4,280,833, Example 8. The composition of these formulations is given in Table 5a. Both formulations separated on standing, forming in the bottom of the container a hard-packed layer, which could be redispersed by shaking. Each gave at least as much release of clomazone as the standard Command® 4 EC Herbicide, when subjected to the laboratory volatility test described below.
• the spray mix consisted of sufficient clomazone test formulation to provide 0.0712 gm of active ingredient in 20 mL of water.
• the clomazone test formulation was applied to the soil at a rate of 1.0 kg a.i. (active ingredient)/ha.
• the soil was enclosed in a glass jar, where it remained briefly until used.
• the polyurethane foam plug from each column was placed in a 20 mL plastic syringe.
• the polyurethane foam plug was thoroughly extracted by drawing 15 mL of methanol into the syringe and through the plug, forcing the methanol extract into a beaker, and repeating the process several times.
• a 0.04 mL aliquot of the 15 mL sample was diluted with 0.96 mL of methanol and 1.0 mL of water.
• a 0.1 mL aliquot of this solution was analyzed for clomazone content using an enzyme-linked immunosorbent assay (ELISA), a method reported by R. V. Darger et al. (J. Agr.
• Formulation M which gives excellent results when the active ingredient is a less water-soluble insecticide, is totally unacceptable for clomazone, giving volatility equal to that of the standard clomazone 4.0 EC.
• the difference between Formulations A and N in reducing the loss of clomazone through volatility is particularly surprising, inasmuch as the only difference is the absence of xanthan gum in the aqueous solution prior to encapsulation in Formulation N.
• the function of xanthan gum seems unpredictable, however, since the only difference between Formulations K and O is the presence of xanthan gum in the aqueous solution prior to encapsulation in K.
• These two formulations have the same volatility loss, but the viscosity of Formulation K is 3640 cps, while that of O is 6360! No discernible difference has been found between Kelzan® M and Kelzan S xanthan gum in the aqueous phase prior to encapsulation in their effect on the formulations.
• Formulations V and W were no better than the 4 EC formulation in controlling volatility.
• Tests to determine the volatility of clomazone CS formulations in the field relative to that of the standard, Command® 4 EC Herbicide were carried out as follows.
• One trial on Formulation A-1 was conducted in a field of two-week old sunflowers, a plant species susceptible to clomazone. Plots were established on a 12 ⁇ 14 meter grid. Each plot was prepared by removing the sunflower seedlings and other vegetation from areas about 60 cm in diameter located at the intersections of the grid lines.
• the grid lines were 12 meters apart in one direction and 14 meters apart in the perpendicular direction.
• the edge of one replicate was at least 12 meters from the edge of the next replicate, a distance sufficient to prevent interference between replicates.
• the test was evaluated at seven days after treatment by measuring the distance from the center of each plot to, first, the most distant point where discoloration of the sunflowers could be found, then at 45° intervals around the center of the plot. The area of discoloration of the sunflowers was calculated, and the area of the direct treatment was subtracted to provide the area affected by the volatility of clomazone.
• a second test on Formulation A-1 was carried out in the same manner in a second field of sunflowers, this time with a 44 cm barrel and on a 14 ⁇ 14 meter grid.
• the total areas affected by clomazone movement from each test site for each test formulation and the standard clomazone 4.0 EC formulation were determined. From these data a percent reduction of area discolored by clomazone as compared to the standard Command® 4 EC was calculated for each test formulation.
• Table 9 show relatively poor performance for Formulation E in the greenhouse. As shown below, performance of Formulation E in the field was excellent. The reason for the difference between greenhouse and field performance is not understood. However, the greenhouse performance of Formulation P was excellent, as was performance in the field, as shown below.”
• test formulations were sprayed onto the surface of the soil (preemergence) at an application rate of 1.0 pound a.i./acre in 12.7 ⁇ 30 foot plots planted with cotton and weed seeds. There were four replicate plots for each formulation tested.
• the test formulation was applied by means of a backpack sprayer, equipped with flat fan spray nozzles, at a delivery volume of 15-20 gallons/acre and at a spray pressure of 28-30 psi.
• the plots were evaluated for percent weed control at 15 and 30 days after emergence of the plant species in the test.
• the cotton plants were evaluated for bleaching, stunting, and stand reduction.
• test formulations were sprayed onto the surface of the soil (preemergence) at application rates of 0.125, 0.25, and 0.5 pound a.i./acre in 6.7 ⁇ 12 foot plots planted with eight different plant species. There were four replicate plots for each formulation tested.
• the test formulations were applied using a backpack sprayer, equipped with four flat fan spray nozzles, at a delivery volume of 20 gallons/acre and at a spray pressure of 25 psi. The plots were evaluated for percent control 20 days after treatment.
• Table 12 reports results of a field test of Formulation P and the 4 EC formulation in which both formulations were applied at 0.88 lb/A, preemergence. It is apparent that in most cases where the 4 EC formulation is giving commercial control, Formulation P is also. Again, the effect of the encapsulated formulation P on cotton is negligible.
• Table 13 reports another field test of Formulation P, again applied preemergence, that shows that at 0.5 lb/A the encapsulated formulation is controlling all species except shattercane.
• each formulation of this invention have a suspensibility of greater than 70%, a viscosity of 1700 to 3800 cps, and a 100 mesh wet screen analysis of greater than 99.95%.
• Xanthan gum - Kelzan ® M and Kelzan S xanthan gums differ in that S has been surface treated to improve ease of dispersion. M was used in all cases except post encapsulation in Formulations A, C, D, F, and H.
• Antifoam - Dow Corning ® 1500 is 100% polydimethyl siloxane. Dow Corning 1520 is a 20% solution; amount shown is active ingredient (a.i.). 1500 was used in Formulation A and C; 1520 in the others.
• Petroleum solvent - Aromatic 200 a mixture of C 9 -C 15 aromatice hydrocarbons, flash point 95° C. That used in Formulation A was naphthalene depleted.
• TETA triethylenetetramline.
• HDA 1,6-hexanediamine.
• EDA ethylenediamine.
• DETA diethylenetriamine.
• Average Particle Size of Microcapsules is Clomazone CS Formulations Average Particle Formulation Size ( ⁇ m) A 26 B 21 C 16 D 18 E 15 F 15 G 23 H 12 I 12 J 11 K 17 L 14 M 2 N 9 O 7 P 14 V 21 W 17 Particle size was determined using a Malvern Master Sizer MS 20.

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