Patent Publication Number: US-5250502-A

Title: Method for enhancing the herbicidal activity of formulations containing solid imidazolinyl benzoic acid esters with bisulfate

Description:
This is a continuation of co-pending application Ser. No. 07/517,886, filed on Apr. 30, 1990 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Imidazolinyl benzoic acids, esters and salts, methods for the preparation thereof and use of such compounds as herbicidal agents is described in U.S. Pat. Nos. 4,188,487, 4,297,128 and 4,554,013. The patented compounds are effective for the selective control of a wide variety of undesirable monocotyledonous and dicotyledonous weed species in the presence of cereal crops such as barley, wheat and rye and have been used effectively in this manner in most wheat and barley producing countries around the world. Among the most effective of these compounds is an isomeric mixture of two positional isomers, namely, 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester. In graminaceous crops such as wheat, barley and rye, this isomeric mixture has provided excellent control of many important grasses and broadleaf weeds including: wild oats (Avena spp.), wind grass (Apera spicaventi), black grass (Alopecurus myosuroides), wild mustard (Brassica kaber), wild buckwheat (Polygonum convolvulus), field pennycress (Thlaspi arvense) and wild radish (Raphanus raphanistrum). However, as the use of the imidazolinyl benzoic acid esters has increased and spread to grain producing countries all around the world, it has become increasingly evident that the limited solubility of the above-said esters in aqueous solutions restricts the concentrations of ester obtainable in such solutions and hence their use in aqueous sprays. Thus, it was that Paserala et al U.S. Pat. No. 4,871,388 issued Oct. 2, 1989, devised a formulation which provided a water dispersible liquid concentrate of the ester containing 0.2 to 1 molar equivalents of polybasic acid and a water miscible organic solvent. In this formulation the imidazolinyl benzoic acid ester is dissolved in the water miscible solvent and remains in solution when the concentrate is diluted with water for spray application. Although this formulation is highly effective and extensively used it is not entirely satisfactory since crystalization of the ester may occur under adverse temperature conditions and the use of organic solvent is sometimes considered objectionable. 
     As viewed today, organic solvents are recognized as having a potential deletarious effect upon the environment. Moreover, the use of organic solvents in the preparation of pesticide formulations can be hazardous to workmen in the formulation and packaging plants and, likewise, to the farmer who is exposed to the formulations during pesticide application if the handling of such formulations is not adequately controlled. Additionally, it is well recognized that use of organic solvents in the preparation of pesticide formulations generally increases the cost of the product, both in manufacture and shipping of the finished formulation. 
     It would, therefore, be most advantageous if the imidazolinyl benzoic acid esters of this invention could be formulated in a manner which would be (1) free of organic solvents, (2) readily dispersed in water for application to the foliage of plants and soil and (3) exhibit enhanced biological activity over an equivalent amount of the ester suspension concentrate formulation applied alone. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows the percent of imidazolinyl benzoic acid ester in solution versus molar equivalents of NaHSO 4  added, as indicated in Tables VII and VIII, below. 
    
    
     SUMMARY OF THE INVENTION 
     The present invention relates to a method for enhancing the biological activity of aqueous herbicidal dispersions, suspensions, emulsions and the like, in which the herbicidal agent is present as a finely divided, particulate, imidazolinyl benzoic acid ester, by adjusting the pH of said aqueous dispersion, suspension, emulsion or the like upon dilution for spraying, to a pH of from 1.0 to 3.8 and preferably to a value between pH 2.0 and pH 3.5, with an alkali metal bisulfate ammonium bisulfate, or mixture thereof. 
     More particularly, the invention relates to aqueous herbicidal compositions as described above, wherein the herbicidal agent is an isomeric mixture of finely divided, particulate, 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester and the pH of the aqueous composition, when diluted with water for application, is adjusted to a pH value between pH 1.0 and pH 3.8 and preferably between pH 2.0 and 3.5 pH by addition thereto of from 1.0 to 3.0 molar equivalents of sodium bisulfate, potassium bisulfate ammonium bisulfate or mixtures thereof per mol of ester present in said aqueous composition. 
     The invention also relates to stable, non-aqueous, solid compositions comprising from 10% to 55% by weight of a mixture of solid particulate 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid methyl ester; and from 45% to 90% by weight of sodium bisulfate, potassium bisulfate, ammonium bisulfate or mixtures thereof. Preferred solid compositions are generally comprised of 45% to 55% by weight of the isomeric mixture of the imidazolinyl toluic acid methyl esters and about 55% to 45% by weight of the alkali metal or ammonium bisulfate. 
     Because of the limited solubility of imidazolinyl benzoic acid esters in water and many other solvents, such esters have been formulated for agricultural application as wettable powders, water dispersible granules, aqueous suspension concentrates and the like. These formulations are generally dispersed in water for application to plants, shrubs, soil or the locus of treatment in the form of an aqueous spray containing the imidazolinyl benzoic acid ester as finely divided solid particles. These aqueous sprays are highly effective for the control of a wide variety of weed species but would be of significantly greater value to the farmer if the herbicidal activity of said sprays could be enhanced. 
     Surprisingly, this invention achieves the above-said desirable biological enhancement of the ester-containing sprays. Moreover, the present invention eliminates use of organic solvents in the imidazolinyl benzoic acid ester formulations, thus avoiding problems frequently associated with the manufacture, handling or application of solvent-containing formulations. The compositions prepared by the method of the present invention also have the added advantage that they permit the application of lower dosages of the imidazolinyl benzoic acid esters while achieving the desired level of weed control and do not contaminate the environment with organic solvents. 
     Moreover, these advantages are obtained using innocuous alkali metal or ammonium bisulfates rather than strong acids which could be difficult and hazardous to handle at the application site. Importantly, it also appears that the use of alkali metal bisulfate and/or ammonium bisulfate with the aqueous formulations containing solid, particulate imidazolinyl benzoic acid ester unexpectedly increases the uptake of the imidazolinyl compound by the plants to which it is applied. 
     Typical suspension concentrate formulations which can be biologically enhanced, when diluted with water for spray application and pH adjusted in accordance with the present invention, have the following compositions: 
     
         ______________________________________                                    
Suspension Concentrates                                                   
Compound                % w/v                                             
______________________________________                                    
Imidazolinyl benzoic acid ester                                           
                        20.0-30.0                                         
Ethoxylated Nonyl phenol with 8-12 Mols                                   
                        12.0-20.0                                         
of ethoxylation (Nonionic surfactant)                                     
Oxyethoxylated polyaryl phosphate                                         
                        1.0-4.0                                           
neutralized with triethanolamine                                          
(Dispersing Agent)                                                        
Butyl capped ethylene oxide/propylene                                     
                        1.0-3.0                                           
oxide block copolymer (Nonionic                                           
surfactant)                                                               
Propylene glycol        0.75-3.0                                          
Silicone antifoam       0.50-1.0                                          
Preservative-aqueous dipropylene glycol                                   
                        0.1-0.2                                           
solution of 1,2-benzisothiazolin-3-one                                    
water q.s. to           100.00                                            
______________________________________                                    
 
    
     The tradenames and descriptions the ingredients employed in the preparation of the above-identified formulations are listed below along with the names of the manufacturers marketing such chemicals. 
     
         ______________________________________                                    
            Chemical                                                      
Tradenames  Description       Manufacturer                                
______________________________________                                    
Arkopal N-080                                                             
            8 mole nonyl phenol                                           
                              Hoechst                                     
            ethoxylate                                                    
N-110       11 mole nonyl phenol                                          
                              Hoechst                                     
(Nonionic sur-                                                            
            ethoxylate                                                    
factant)                                                                  
Soprophor FL                                                              
            Oxythoxylated polyarl                                         
                              Rhone-                                      
(Dispersing phosphate neutralized                                         
                              Poulenc                                     
Agent)      with triethanolamine                                          
Silcolapse 5000                                                           
            Silicone antifoam I.C.I. Ltd.                                 
Silica FK 320                                                             
            Precipitated amorphous                                        
            silica                                                        
Proxel GXL  Aqueous dipropylene                                           
                              I.C.I. Ltd.                                 
(Preservative)                                                            
            glycol solution of 1,2-                                       
            Benzisothiazolin-3-one                                        
Witconol NS 500K                                                          
            Nonionic surfactant: a                                        
                              WITCO S.A.                                  
(Dispersing butyl capped ethylene                                         
Agent)      oxide/propylene oxide                                         
            block copolymer                                               
EMCOL 4061  butyl capped ethylene                                         
                              WITCO S.A.                                  
            oxide/propylene oxide                                         
            block copolymer/propylene                                     
            glycol ratio = 1/3/1.29                                       
            (70% in propylene glycol)                                     
______________________________________                                    
 
    
     Typical aqueous flowable formulations that can be enhanced by the method of the present invention are described below: 
     
         ______________________________________                                    
Aqueous Flowable Concentrates                                             
______________________________________                                    
Compound              % w/v                                               
______________________________________                                    
Imidazolinyl Benzoic Acid Ester                                           
                      20-40                                               
Polyethoxylated nonylphenols                                              
                      12-20                                               
ethoxylated with 8-12 Mols of                                             
ethoxylation (Nonionic surfactant)                                        
Polyethoxylated polyarylphenol                                            
                      3-5                                                 
phosphate, neutralized with                                               
triethanolamine (dispersing agent)                                        
Silicone antifoam agent                                                   
                      0.5-1.0                                             
Water q.s. to         100.0                                               
______________________________________                                    
Polyoxyethylene nonylphenols suitable for use in                          
flowable concentrate compositions of the invention                        
Average      Kinematic viscosity                                          
Ethoxylation (25% aqueous solution)                                       
(moles)      centistokes                                                  
______________________________________                                    
 9.5         102                                                          
 9.5         87                                                           
10.0         53                                                           
10.0         43                                                           
10.0         22                                                           
10.5         18                                                           
11.0         30                                                           
12.0         13                                                           
______________________________________                                    
 
    
     To prepare effective aqueous flowable concentrates, free of clays and soluble gums and containing 20% to 40% by weight of finely divided, solid, particulate imidazolinyl benzoic acid ester, said ester is dispersed in an aqueous solution containing from 15% to 35% by weight of surfactant which has a kinematic viscosity of about 10 to 100 centistokes at 25% aqueous solution. Surfactants giving kinematic viscosities in the above range permit the use of sufficient quantities of said surfactants to obtain aqueous flowable concentrate compositions containing on a weight to volume basis 20% to 40% of solid, finely ground, imidazolinyl benzoic acid ester, 1.0% to 5.0% of wetting/dispersing agents, about 0.5% to 1.0% of antifoam agents, and 0.1 to 0.5% of a preservative and generally having a viscosity of from 1,000 to 3,500 centipoises as measured by a Brookfield viscometer, with a number 2 spindle at 6 rpm at 20° C. These compositions resist settling of the solid components and they do not gel. The kinematic viscosities of these surfactants measured as a 25% aqueous solution, allows the incorporation of high levels of surfactants in the final aqueous flowable compositions, without causing them to become too viscous to process and use easily. The incorporation of high levels of surfactant in the formulation provides the additional benefit that surfactants need not be incorporated during dilution of the flowable composition in a spray tank prior to application, making the compositions of this invention easier and safer to apply. 
     A typical stable, non-aqueous, composition of the invention comprises about 50% by weight of a isomeric mixture of solid particulate 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester and 50% by weight of sodium bisulfate. 
     In accordance with this invention, formulations containing an imidazolinyl benzoic acid ester as a finely divided particulate solid when dispersed in water, are herbicidally enhanced by admixture of the diluted aqueous formulation with from 1 to 3 molar equivalents of an alkali metal bisulfate, ammonium bisulfate or mixtures thereof. Such admixture generally results in adjustment of the pH of the dilute aqueous composition to a value between pH 1.0 to pH 3.8. 
     Among the imidazolinyl benzoic acid esters that are effectively enhanced by the method of the present invention are those represented by the structure: ##STR1## wherein X is hydrogen, alkyl C 1  -C 3 , halogen or nitro; R 1  is alkyl C 1  -C 4  ; R 2  is alkyl C 1  -C 6  , cycloalkyl C 3  -C 6 , or when R 1  and R 2  are taken together with the carbon to which they are attached they may represent cycloalkyl C 3  -C 6  optionally substituted with methyl; R 3  is alkyl C 1  -C 12  optionally substituted with one C 1  -C 3  alkoxy group or one C 3  -C 6  cycloalkyl group or one phenyl group, alkenyl C 3  -C 5  optionally substituted with one or two C 1  -C 3  alkyl group(s) or one phenyl group or with one to two halogen substituent(s), alkynyl C 3  -C 5  optionally substituted with one or two C 1  -C 3  alkyl group(s) or one phenyl group or with one to two halogen substituent(s), benzyl, cyclohexenylmethyl, ethynylcyclohexyl, ethynylallyl or pentadienyl, cycloalkyl C 3  -C 6  optionally substituted with one or two C 1  -C 3  alkyl group(s); when R 1  and R 2  are not the same the optical isomers thereof, and the isomeric mixtures thereof. 
     Other imidazolinyl benzoic acid esters that are herbicidally enhanced by the method of this invention are: 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, 2-propynyl ester; 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, n-propyl ester; 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, 1,1-dimethylallyl ester; 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, allyl ester; 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, octyl ester; 
     (+)-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, ethyl ester; 
     (+)-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, 2-chloroallyl ester; 
     (-)-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, -2-propynyl ester; and 
     2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)benzoic acid, 1-methyl-2-butenyl ester. 
     The present invention is further illustrated by the examples set forth below. 
     EXAMPLES 1-2 
     Preparation of Suspension concentrate Formulations Containing an Imidazolinyl Benzoic Acid Ester 
     To a suitable vessel fitted with a propeller mixer and high shear agitation add 500 L of water. Turn on the mixer and add 7.5 kg of silicone antifoam agent, 1.5 kg of aqueous dipropylene glycol solution of 1,2-benzisothiazolin-3-one perservative and 42.9 kg of a mixture of butyl capped ethylene oxide/propylene oxide block copolymer and propylene glycol having a 1 to 3 to 1.29 ratio and 10 kg of oxythoxylated polyaryl phosphate neutralized with triethanolamine dispersing agent. 
     Stirring is continued to dissolve and/or disperse all the additives. Thereafter, the high-shear agitator is switched on and 250 kg of an isomeric mixture of an imidazolinyl benzoic acid ester is added. High-shear mixing is continued until a fluid, mobile slurry is achieved with retentions of less than 0.25% on 150 μ sieve. Avoid air entrainment during mixing. The thus formed slurry is then wet, milled to give a product with a particle size distribution of 90% less than 8μ and 50% less than 3μ. Thereafter the remaining water added. To this mixture 200 kg of 11 mole nonyl phenol ethoxylate is gradually introduced and stirring is continued to obtain a smooth, uniform aqueous suspension concentrate. 
     Compositions prepared by this method are reported in Table I below. 
     
                       TABLE I                                                     
______________________________________                                    
                    % w/v                                                 
Compound              Ex. I   Ex. 2                                       
______________________________________                                    
6-(4-isopropyl-4-methyl-5-oxo-2-                                          
                      30.0    25.0                                        
imidazolin-2-yl)- .sub.-- m-Toluic acid,                                  
methyl ester and 2-(4-isopropyl-4-                                        
methyl-5-oxo-2-imidazolin-2-yl)- -p-                                      
Toluic acid, methyl ester                                                 
Ethoxylated nonyl phenol 11 mols                                          
                      15.0    20.0                                        
of ethoxylation                                                           
Oxyethoxylated polyaryl phosphate                                         
                      1.0     1.0                                         
neutralized with Triethanolamine                                          
Propylene glycol      1.3     1.3                                         
Butyl capped ethylene oxide/                                              
                      3.0     3.0                                         
propylene oxide block copolymer                                           
Aqueous dipropylene glycol                                                
                      0.15    0.15                                        
solution of 1,2-benzisothiazolin-                                         
3-one (preservative)                                                      
Silicone antifoam     0.75    0.75                                        
Water q.s. to         100.0   100.0                                       
______________________________________                                    
 
    
     EXAMPLES 3-14 
     Preparation of stable aqueous flowable concentrates 
     The preparation of stable aqueous flowable concentrates that can be biologically enhanced by the method of the present invention when they are tank mixed in the field for dilute aqueous spray application, are generally prepared by a two step procedure as described below. 
     The first step involves the preparation of a ground, particulate, aqueous slurry which requires the calculation of the quantities of each ingredient required and mixing as follows: To a suitable vessel with fitted agitation, add all the water, then the antifoam agent if desired, followed by the wetting and/or dispersing agents and then the isomeric mixture of 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl5-oxo-2-imidazolin-2-yl-p-toluic acid, methyl ester. Gradually add this isomeric mixture with vigorous high-shear agitation until a mobile slurry results. Continue high shear-mixing until the particle size is suitable for milling, avoiding air entrainment during mixing. 
     Then pass the slurry through a wet-mill to give a suspension with particle size essentially 98% less than 5 microns and sample the milled slurry and analyse for active ingredient (% w/w). 
     The second step involves preparation of the aqueous flowable concentrate. 
     Calculate the weight of milled slurry required for the final product and add it to a suitable vessel fitted with efficient agitation. 
     Calculate the extra quantities, if any, of wetting and/or dispersing agents, the antifoam and the antifreeze required in the final product and add them to the slurry. Agitate the mixture until the mixture is homogeneous. 
     Calculate the quantity of extra water required and add it to the vessel and mix until homogeneous. 
     Gradually add and dissolve the required amount of surfactant, which as a 25% aqueous solution has a kinematic viscosity of 5 to 100 centerstokes, and mix with vigorous agitation, avoiding air entrainment. 
     Mix thoroughly until all the surfactant is dissolved and a smooth, uniform product is obtained. 
     Utilizing the above procedure yields the stable aqueous flowable compositions listed in Tables II, III and IV below. 
     
                                           TABLE II                                
__________________________________________________________________________
Aqueous Flowable Formulations Containing an Imidazolinyl Benzoic Acid     
Ester                                                                     
                   Formulations                                           
                   Ex. 3                                                  
                       Ex. 4                                              
                           Ex. 5                                          
                               Ex. 6                                      
                                   Ex. 7                                  
Compound           % w/v                                                  
                       % w/v                                              
                           % w/v                                          
                               % w/v                                      
                                   % w/v                                  
__________________________________________________________________________
6-(4-isopropyl-4-methyl-5-oxo-2-                                          
                   30.0                                                   
                       25.0                                               
                           30.0                                           
                               25.0                                       
                                   20.0                                   
imidazolin-2-yl)- .sub.-- m-Toluic acid,                                  
methyl ester and 2-(4-isopropyl-4-                                        
methyl-5-oxo-2-imidazolin-2-yl)- -p-                                      
Toluic acid, methyl ester                                                 
Arkopal N 110 - Nonionic                                                  
                   12.0                                                   
                       16.0                                               
                           15.0                                           
                               20.0                                       
                                   20.0                                   
surfactant - Ethoxylated nonyl                                            
Phenol 11 moles EO                                                        
Soprophor FL - Dispersing Agent-                                          
                   4.0 4.0 4.0 4.0 4.0                                    
oxyethoxylated polyaryl ethoxylate                                        
neutralized with triethanolamine                                          
Silcolapse 5000 - Silicone antifoam                                       
                   0.75                                                   
                       0.75                                               
                           0.75                                           
                               0.75                                       
                                   0.75                                   
Proxel GXL - Preservative - aqueous                                       
                   0.15                                                   
                       0.15                                               
                           0.15                                           
                               0.15                                       
                                   0.15                                   
dipropylene glycol solution of 1,2-                                       
benzisothiazolin-2-one                                                    
Water, to make     100%                                                   
                       100%                                               
                           100%                                           
                               100%                                       
                                   100%                                   
Density            1.04                                                   
                       1.03                                               
                           1.03                                           
                               1.03                                       
                                   1.03                                   
__________________________________________________________________________
 
    
     
                       TABLE III                                                   
______________________________________                                    
Aqueous Flowable Formulations Containing an                               
Imidazolinyl Benzoic Acid Ester                                           
                     Ex. 8   Ex. 9                                        
Compound             % w/v   % w/v                                        
______________________________________                                    
6-(4-isopropyl-4-methyl-5-oxo-2-                                          
                     25.0    25.0                                         
imidazolin-2-yl) .sub.-- m-Toluic acid,                                   
methyl ester and 2-(4-isopropyl-4-                                        
methyl-5-oxo-2-imidazolin-2-yl) -p-                                       
Toluic acid, methyl ester                                                 
Arkopal N 100 - Nonionic                                                  
                     15.0    20.0                                         
surfactant - Ethoxylated nonyl                                            
Phenol 11 moles EO                                                        
Dispersing Agent -   4.0     4.0                                          
Soprophor FL/Witconol NS 500K/                                            
Propylene glycol 1/3/1.3                                                  
Silicone antifoam    0.75    0.75                                         
Preservative - Proxel GXL                                                 
                     0.15    0.15                                         
Water, to make       100.0%  100.0%                                       
______________________________________                                    
 
    
     
                                           TABLE IV                                
__________________________________________________________________________
Aqueous Flowable Concentrate Containing an Imidazolinyl Benzoic Acid      
__________________________________________________________________________
Ester                                                                     
                Ex. 10                                                    
                     Ex. 11                                               
                         Ex. 12                                           
                              Ex. 13                                      
                                  Ex. 14                                  
Isomeric mixture of                                                       
                (g/l)                                                     
                     (g/l)                                                
                         (g/l)                                            
                              (g/l)                                       
                                  (g/l)                                   
__________________________________________________________________________
6-(4-isopropyl-4-methyl-5-oxo-                                            
                340.0                                                     
                     283.3                                                
                         340.0                                            
                              283.3                                       
                                  226.7                                   
2-imidazolin-2-yl) .sub.-- m-tolic                                        
acid, methyl ester and 2-(4-                                              
isopropyl-4-methyl-5-oxo-2-                                               
imidazolin-2-yl-toluic acid,                                              
methyl ester                                                              
Polyethoxylated nonylphenol                                               
                120.0                                                     
                     160.0                                                
                         150.0                                            
                              200.0                                       
                                  200.0                                   
(11 Mol EO) viscosity 15                                                  
centerstokes as a 25% aqueous                                             
solution (Nonionic surfactant)                                            
Wetting/dispersing agent                                                  
                 40.0                                                     
                      40.0                                                
                          40.0                                            
                               40.0                                       
                                   40.0                                   
(polyethoxylated polyarylphenol                                           
phosphate, neutralized with                                               
triethanolamine)                                                          
Silicone antifoam agent                                                   
                 7.5  7.5                                                 
                          7.5  7.5                                        
                                   7.5                                    
Water (Balance) 532.5                                                     
                     539.2                                                
                         499.2                                            
                              499.2                                       
                                  555.8                                   
Stability:                                                                
                   Average percent recovery                               
Storage time                                                              
            Example No.                                                   
                   28° C.                                          
                           37° C.                                  
                               50° C.                              
One Month    8-12  100.0   98.0                                           
                               97.0                                       
Two Months  10-12   99.0   98.0                                           
                               98.0                                       
__________________________________________________________________________
 
    
     EXAMPLE 15 
     Biological enhancement of aqueous suspension concentrate formulations containing finely divided, solid, particulate imidazolinyl benzoic acid esters 
     In these biological evaluations test samples are prepared using the 300 SC (suspension concentrate) from Example 1. The test procedure is designed to provide and evaluate the equivalent of 200, 400, 500 or 600 grams per hectare of an isomeric mixture of 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl) -m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester, applied to wild oats (Avena fatua) in the 2 to 3 leaf stage. Formulations evaluated include 300 SC in water alone, 300 SC plus sodium bisulfate in water, 300 SC plus Nonionic surfactant (11 mole nonyl phenol ethoxylate) in water and 300 SC plus sodium bisulfate and nonionic surfactant (11 mole nonyl phenol ethoxylate) in water. 
     The test compositions are made up in water and sprayed on wild oat plants in the 2 to 3 leaf stage of development and the sprayed plants are then placed on greenhouse benches where they are cared for using normal greenhouse practices. The sprayer is designed and calibrated to deliver the equivalent of 100 liters per hectare of test solution. 
     Each composition is replicated four times and on days 10 and 20 after spraying, all plants are examined and the percent wild oat control determined for each treatment and recorded. The compositions evaluated and the results obtained are reported in Tables V and VI respectively. 
     
                                           TABLE V                                 
__________________________________________________________________________
Suspension Concentrate Formulations for Wild Oat Control Greenhouse       
Test Equivalent to Spray Volume of 100 L/ha                               
                               ml/ha                                      
           Equivalent     g/ha 50% 11 mole                                
           of     l/ha    Sodium                                          
                               nonyl phenol                               
Treatment  g/ha ai                                                        
                  Formulation                                             
                          Bisulfate                                       
                               ethoxylate                                 
__________________________________________________________________________
Example I                                                                 
       300SC                                                              
           600    2.00    --   --                                         
Example I                                                                 
       300SC                                                              
           500    1.66    --   --                                         
Example I                                                                 
       300SC                                                              
           400    1.33    --   --                                         
Example I                                                                 
       300SC                                                              
           200    0.67    --   --                                         
Example I                                                                 
       300SC                                                              
           500    1.66    --   100                                        
Example I                                                                 
       300SC                                                              
           400    1.33    --    80                                        
Example I                                                                 
       300SC                                                              
           200    0.67    --    40                                        
Example I                                                                 
       300SC                                                              
           500    1.66    316  100                                        
Example I                                                                 
       300SC                                                              
           400    1.33    253  --                                         
Example I                                                                 
       300SC                                                              
           200    0.67    126  --                                         
Example I                                                                 
       300SC                                                              
           500    1.66    316  100                                        
Example I                                                                 
       300SC                                                              
           400    1.33    253   80                                        
Example I                                                                 
       300SC                                                              
           200    0.67    126   40                                        
__________________________________________________________________________
 300SC = 30% w/v of an isomeric mixture of                                
 6(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl).sub.-- mtoluic acid,     
 methyl ester and 6(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-ptoluic 
 acid, methyl ester                                                       
 
    
     
                                           TABLE VI                                
__________________________________________________________________________
% Wild Oat Control with Example I, 300SC formulation alone or in          
combination                                                               
with sodium bisulfate, additional 11 mole nonyl phenol ethoxylate or      
both                                                                      
sodium bisulfate and additional 11 mole nonyl phenol ethoxylate           
                              % Oat Control                               
                                      Average                             
                                      %                                   
Treatment                     1 2 3 4 Control                             
__________________________________________________________________________
Example I                                                                 
      300SC                                                               
          600                                                             
             --               75                                          
                                85                                        
                                  80                                      
                                    85                                    
                                      81.3                                
Example I                                                                 
      300SC                                                               
          500                                                             
             --               80                                          
                                80                                        
                                  75                                      
                                    80                                    
                                      78.8                                
Example I                                                                 
      300SC                                                               
          400                                                             
             --               50                                          
                                75                                        
                                  75                                      
                                    80                                    
                                      70.0                                
Example I                                                                 
      300SC                                                               
          200                                                             
             --               50                                          
                                55                                        
                                  50                                      
                                    60                                    
                                      53.8                                
Example I                                                                 
      300SC                                                               
          500                                                             
             100-(AR)         90                                          
                                90                                        
                                  90                                      
                                    85                                    
                                      88.8                                
Example I                                                                 
      300SC                                                               
          400                                                             
              80-(AR)         85                                          
                                90                                        
                                  85                                      
                                    85                                    
                                      86.3                                
Example I                                                                 
      300SC                                                               
          200                                                             
              40-(AR)         80                                          
                                80                                        
                                  75                                      
                                    80                                    
                                      78.8                                
Example I                                                                 
      300SC                                                               
          500                                                             
             316-Sodium Bisulfate                                         
                              98                                          
                                98                                        
                                  90                                      
                                    95                                    
                                      95.3                                
Example I                                                                 
      300SC                                                               
          400                                                             
             253-Sodium Bisulfate                                         
                              95                                          
                                95                                        
                                  95                                      
                                    85                                    
                                      92.5                                
Example I                                                                 
      300SC                                                               
          200                                                             
             126-Sodium Bisulfate                                         
                              50                                          
                                75                                        
                                  75                                      
                                    65                                    
                                      66.3                                
Example I                                                                 
      300SC                                                               
          500                                                             
             100 + 316-AR + Sodium Bisulfate                              
                              95                                          
                                95                                        
                                  95                                      
                                    90                                    
                                      93.8                                
Example I                                                                 
      300SC                                                               
          400                                                             
              80 + 253-AR + Sodium Bisulfate                              
                              95                                          
                                95                                        
                                  90                                      
                                    80                                    
                                      90.0                                
Example I                                                                 
      300SC                                                               
          200                                                             
              40 + 126-AR + Sodium Bisulfate                              
                              50                                          
                                75                                        
                                  85                                      
                                    80                                    
                                      71.3                                
__________________________________________________________________________
 AR = 11 mole nonyl phenol ethoxylate                                     
 
    
     From the above data it can be seen that the addition of sodium bisulfate to the dilute aqueous 300SC formulations of Example 1 increases the control of wild oats from 11.5% to 22.5% over the dilute aqueous 300SC formulations alone. The data also show that the addition of nonionic surfactant to the diluted suspension concentrate helps to increase the biological activity thereof. Moreover, the addition of sodium sulfate and added nonionic surfactant to the suspension concentrate containing imidazolinyl benzoic acid ester also enhances the biological activity over that obtained with the nonionic surfactant. 
     EXAMPLE 16 
     Chemical and Physical Stability of a 1:1 w/w blend of Solid Imidazolinyl Benzoic Acid Ester 
     In this evaluation technical grade samples 98% purity of a mixture of 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid, methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester are uniformly blended on a 50/50 % w/w basis with sodium bisulfate 96% purity and then stored in glass jars at room temperature and 370° C. After four months of storage the chemical and physical characteristics of the blends show no evidence of change. 
     EXAMPLE 17 
     Determination of the effect of alkali metal bisulfate on imidazolinyl benzoic acid ester solubility in different types of water using 0, 1, 2 or a molar equivalents of alkali metal bisulfate 
     In these evaluations the 300SC concentrates of Example I, containing isomeric mixtures of 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-m-toluic acid methyl ester and 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluic acid, methyl ester are dispersed in water and treated with from 0 to 3 molar equivalents of sodium bisulfate based on the amount of ester used. The pH of the water was determined before admixture with the 300SC, after admixture with the 300SC and again after treatment with sodium bisulfate. 
     Also, each sample is assayed for the presence of the isomeric mixture of the esters and likewise for the isomeric mixture of the corresponding acids to determine where the esters are undergoing any significant hydrolysis. 
     The results of these evaluations are reported in Tables VII and VIII below. 
     
                                           TABLE VII                               
__________________________________________________________________________
Determination of the effect of from 1 to 3 molar equivalents of           
alkali metal bisulfate on aqueous dispersions of Example I,               
300SC in different type water samples                                     
           Water                                                          
           Canada Canada Canada NJ                                        
Treatment  A      B      C      D                                         
__________________________________________________________________________
water pH   8.64   8.64   8.59   7.40                                      
Water + 300SC pH                                                          
           8.24   8.14   8.14   6.86                                      
           milky  milky  milky  milky                                     
           appearance                                                     
                  appearance                                              
                         appearance                                       
                                appearance                                
+ 1 molar Equiv.                                                          
           5.14   5.90   3.82   2.73                                      
NaHSO.sub.4                                                               
           No apparent                                                    
                  No apparent                                             
                         No apparent                                      
                                turned                                    
           change change change Hazy                                      
+ 2 molar Equiv.                                                          
           2.75   2.97   2.61   2.15                                      
NaHSO.sub.4                                                               
           Slightly                                                       
                  No apparent                                             
                         Essentially                                      
                                Essentially                               
           Hazy   change Clear  Clear                                     
+ 3 molar Equiv.                                                          
           2.12   2.32   2.10   1.67                                      
NaHSO.sub.4                                                               
           Essentially                                                    
                  Essentially                                             
                         Essentially                                      
                                Essentially                               
           Clear  Clear  Clear  Clear                                     
__________________________________________________________________________
 
    
     
                       TABLE VIII                                                  
______________________________________                                    
Analytical determinations for the presence of Imidazolinyl                
Benzoic acid ester and corresponding imidazolinyl benzoic                 
acid in filtered and unfiltered samples treated with 300SC                
from Example I and from 1 to 3 molar equivalents of NaHSO.sub.4           
                              % w/w                                       
Treatments   % w/w Imidazolinyl                                           
                              Imidazolinyl                                
containing 300SC                                                          
             Benzoic Acid Ester                                           
                              Benzoic Acid                                
______________________________________                                    
unfiltered Samples                                                        
A            0.422            0.039                                       
B            0.404            0.041                                       
C            0.428            0.014                                       
D            0.454            0.007                                       
filtered Samples                                                          
A            0.187            0.024                                       
B            0.183            0.034                                       
C            0.194            0.031                                       
D            0.214            0.009                                       
filtered Samples +                                                        
1 Molar Eq. NaHSO.sub.4                                                   
A            0.204            0.006                                       
B            0.206            0.006                                       
C            0.240            0.007                                       
D            0.457            0.007                                       
filtered Samples +                                                        
2 Molar Eq. NaHSO.sub.4                                                   
A            0.436            0.007                                       
B            0.365            0.004                                       
C            0.456            0.006                                       
D            0.450            0.004                                       
filtered Samples +                                                        
3 Molar Eq. NaHSO.sub.4                                                   
A            0.464            0.007                                       
B            0.459            0.007                                       
C            0.460            0.004                                       
D            0.461            0.004                                       
______________________________________