Process for producing a flowable fungicide formulation

Disclosed is a process for producing a flowable fungicide formulation comprising the steps of: PA1 (a) heating sufficiently a mixture of at least one solid active fungicidal compound with a hydrocarbon solvent and surfactant to form a melt; PA1 (b) adding sufficient aqueous solution to said melt to form a water-in-oil emulsion; PA1 (c) thoroughly mixing said emulsion in the presence of sufficient thickening agent to form a stable flowable fungicide formulation.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process for producing a flowable fungicide 
formulation. 
2. Description of the Prior Art 
In the art of fungicide formulation, three types of commercial products are 
commonly available today. These types of products are as follows: 
1. True liquid solutions--made by dissolving an active fungicidal compound 
in a suitable solvent (e.g., xylene); 
2. Wettable powders--made by grinding an active fungicidal compound with a 
selected inert clay (e.g., silica-containing material) in air mill, roller 
mill, ball mill or the like to obtain a fine powder having a particle size 
of about 1 to about 5 microns; 
3. Flowable formulations--made by grinding an active fungicidal compound 
with a clay to obtain a small particle size either before or after forming 
a suspension of solids in water by a thorough mixing step (e.g., in a high 
shear mixer). 
Because of handling problems and lack of ease in application with solid 
materials like wettable powders, farmers have favored liquid application 
of fungicides to soil, seeds and agricultural vegetation. Moreover, 
because true liquid solutions generally can be made more cheaper than 
flowables, fungicide manufactures have generally favored the making of the 
former type of formulation. 
However, for certain kinds of applications, true liquid solutions of 
fungicidal material are not preferred. For example, the employment of 
flowable formulations has been favored over true solutions for the 
fungicidal treatment of agricultural seeds. A principal reason for this 
favorism is that seeds which have been treated with a fungicide are 
normally required by governmental regulations to be dyed an unnatural 
color (e.g., bright red or violet) to disassociate treated seeds from 
untreated seeds. Accordingly, fungicide formulations employed in seed 
treatment also contain a minor amount of a dye. It has been found that 
flowables are better able to transfer that dye to the seeds than 
conventional true solutions. 
Another obstacle which prevents the universal use of true solutions of 
fungicides has to do with the selection of a suitable solvent. Such 
solvents must possess several properties. They must be inert to the active 
fungicidal material so as to not inactive its fungicidal properties. 
Furthermore, the solvent must still be able to dissolve it; and yet be 
harmless to the crops and agricultural environment being treated. Xylene, 
because it generally possesses such suitable properties, has been the 
solvent of choice for many fungicial applications. But, there are problems 
associated with xylene. This solvent possesses an odor which is 
objectionable, causing complaints from handlers and farmers. Also, the 
solvent has a flash point of about 80.degree. F., causing the products to 
carry a flammable label for transportation, which means higher freight 
rates and more restrictions on transportation, storage and use. 
Furthermore, distributors and farmers who employ xylene may have their 
insurance rates raised because of its "flammable" property. Further, 
because xylene is an aromatic petroleum product, its supply is 
increasingly smaller. Still further, when xylene-dissolved products are 
used in seed treatments, the presence of xylene appears to dull the 
brightness of the dyed color on the seeds, thus making it more difficult 
to disassociate treated seeds from untreated seeds. 
With such problems surrounding true liquid solutions of fungicides, farmers 
are increasingly turning to the use of flowable formulations, especially 
in the treatment of seeds. However, in the past, the production of 
flowable formulations has been relatively time consuming and expensive, 
mainly because of the grinding step that is necessary to reduce the size 
of solid fungicidal compounds. This size reduction is necessary to allow 
the fungicide materials to remain in the suspension. But, such grinding 
steps require relatively expensive equipment and are carried out at a slow 
rate. Thus, until now, it has been normally uneconomical to make flowable 
fungicide formulations starting with solid, as opposed to liquid, active 
fungicidal compounds. 
Therefore, there is a need in the art to find a new process for producing 
flowable fungicide that can economically utilize solid fungicidal 
compounds without grinding. The present invention is directed to a process 
that eliminates such unwanted grinding steps. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly, the present invention is directed to a process for producing a 
flowable fungicide formulation comprising the steps: 
(a) heating sufficiently a mixture of at least one solid active fungicidal 
compound, hydrocarbon solvent and surfactant so as to form a melt; 
(b) adding sufficient aqueous solution to said melt to form a water-in-oil 
emulsion; 
(c) thoroughly mixing said emulsion in the presence of sufficient 
thickening agent to form a stable flowable fungicide formulation. 
DETAILED DESCRIPTION 
Flowable fungicide formulations (sometimes referred to hereafter as 
"flowables") are generally known in the art as a suspension of solid 
materials such as clays and the like mixed with an active fungicidal 
material in water. Flowables have a creamy consistency which may or may 
not necessarily be added with more water just prior to application. 
Flowables may contain minor amounts of other ingredients such as 
surfactants, antifreezes such as propylene glycol, dyes to further improve 
the properties of the flowables. The active fungicidal ingredient or 
ingredients may originally be either liquid or solid in nature when 
formulated into the flowables. In the past, commercial flowables, to the 
best knowledge of applicant, did not contain any hydrocarbon solvents. And 
as stated above, prior art processes for making flowables required the use 
of a grinding step when solid fungicidal materials were used. 
The present process for making flowables does not require this costly and 
slow grinding step. Specifically, the melting step (a), of the present 
process, mentioned above, effectively reduces the particle size of solid 
fungicides so that the solid fungicidal compounds will remain in the 
formulation and not readily precipitate out. Further, the employment of 
hydrocarbon solvent in making a flowable is considered novel by the 
applicant. Still further, the combination of processing steps as described 
herein helps ensure that a stable and thoroughly mixed formulation is 
produced. 
The first step of the present process is to heat a mixture of at least one 
solid active fungicidal compound, at least one surfactant and at least one 
hydrocarbon solvent sufficiently as to form a melt of this mixture. In 
other words, the heating is carried on for sufficient time and at 
sufficient temperatures to melt or dissolve the solid fungicidal material 
in the solvent and surfactant. However, the time and temperatures employed 
in this step should preferably not be too great so as to decompose or 
inactive the fungicidal compound or surfactant or to evaporate a major 
portion of the solvent (i.e., more than 50% by weight of the solvent). Of 
course, the optimum heating temperatures and times will vary with the 
particular fungicidal compound, surfactant and solvent employed. Heating 
temperatures in the range from about 50.degree. C. to about 110.degree. 
C., and preferably about 90.degree. C. to about 105.degree. C., and 
heating times from about 1 to 60 minutes, preferably about 15-45 minutes, 
are generally suitable. 
The present invention contemplates that any active solid fungicidal 
compound may be dissolved during this melting step. 
Pentachloronitrobenzene, a well known soil and seed fungicide, sold under 
the trademark TERRACLOR.RTM. by the Olin Corporation, is one especially 
suitable solid material that may be dissolved by this melting procedure. 
Normally, pentachloronitrobenzene has a relatively large crystalline 
structure at room temperature and, in the past, required the use of a 
grinding procedure in order to use it as a flowable. 
Other examples of solid fungicides which may be made into flowable by the 
present process include 
cis-N-((trichloromethyl)thio)-4-cyclohexane-1,2-dicarboximide (sold under 
the common name captan); the sulfate or acetate salt of 
9-aza-1,17-diquanidinoheptadecane (sold under the common name guazatine); 
and 1-hydroxy-2-pyridinethione and its zinc salt (sold by Olin Corporation 
under the trademark Omadine.RTM. and zinc Omadine.RTM., respectively). Of 
course, mixtures of different solid fungicide compounds may be employed. 
Besides utilizing just solid fungicide products, it may be desirable to 
utilize mixtures of both solid and liquid fungicide compounds. For 
example, it is one preferred embodiment of the present invention to 
utilize mixtures of the forementioned solid pentachloronitrobenzene and 
the liquid fungicide, 5-ethoxy-3-(trichloromethyl)-1,2,4-thiadiazole (sold 
under the trademark TERRAZOLE.RTM. by the Olin Corporation). While this 
latter compound is usually liquid in nature at room temperatures and, 
thus, does not require grinding to be made into a flowable; it does react 
with water to a slight degree and, therefore, will lose some of its 
fungicidal activity if put directly into an aqueous solution. Accordingly, 
by first encapsulating this liquid fungicide in a hydrocarbon solvent 
before adding water as is done by the present invention, it is protected 
from hydrolysis. 
The amount of each fungicide desired in the final formulation will 
determine to a large degree the relative concentrations of the other 
ingredients present in the formulation. Once the amount of such active 
ingredient has been selected, the amounts of each of the other ingredients 
in the formulation may be determined. The amount of each active fungicide 
compound for each formulation will vary over a great range depending, of 
course, on the particular fungicide, or mixtures of fungicides, used; the 
particular result desired; and a great many other factors. Generally, the 
total amount of active fungicide compounds in the final formulation will 
preferably range from about 1% to about 50% by weight of a flowable 
formulation; more preferably, from about 10% to about 30% by weight. 
Any hydrocarbon solvent in which solid fungicide compounds will melt or 
dissolve and is compatible with the crops and agricultural environment may 
be employed herein. Suitable examples of such solvents include xylene, 
kerosene, naphtha and isoparaffinic hydrocarbons. Isoparaffinic 
hydrocarbons are particularly favored because they are relatively 
odorless, have a relatively high flash point and are relatively 
inexpensive as compared to xylene. Accordingly, fungicide distributors and 
farmers would favor this solvent over xylene because of its better 
handling properties and ease of application. 
One particularly suitable example of isoparaffinic solvents is an 
essentially odorless, relatively high-boiling, narrow cut isoparaffinic 
solvent having a typical flash point of 77.degree. C. (170.degree. F.) 
sold under the trademark Isopar.RTM. M by the Exxon Corporation of 
Houston, Texas. Isopar.RTM. M is a preferred solvent because it is 
odorless and has a flash point above about 100.degree. F. 
The amount of solvent in the formulation is not critical to the present 
invention. The optimum amount will depend upon many factors including the 
amount of active fungicidal compounds present. Generally, it is preferable 
that the amount of solvent be sufficient for the solid fungicide compounds 
to melt or dissolve Normally, the amount of solvent is the flowable 
fungicide formulation will range from about 15% to about 40%, more 
preferably from about 25% to about 38%, by weight. 
Besides the hydrocarbon solvent, it is necessary to add at least one 
surfactant to the melt-forming mixture. A surfactant must be added before 
addition of the water is in step (b), discussed below, in order that a 
stable water-in-oil emulsion be formed. The present invention encompasses 
the use of any surfactant that is compatible with the active fungicidal 
compounds and solvent employed and will form a stable water-in-oil 
emulsion. Organophosphate ester surfactants have been found to be 
particularly suitable when using an isoparaffinic hydrocarbon solvent like 
Isopar.RTM. M. Specifically, one organophosphate ester surfactant that is 
preferred for the present invention is a high viscosity (i.e., about 
30,000 centistokes@25.degree. C.) monoester sold under the trademark 
ATPHOS.TM. 3220 by ICI Americas, Inc., of Wilmington, Delaware. Moreover, 
ATPHOS.TM. 3220 has a high flash point (over 200.degree. F.) and is 
compatible with nitrogen-containing fertilizers, and antifreezes such as 
propylene glycol and metals such as molybdenum which may be added to 
flowables. 
The amount of surfactant in the formulation is not critical to the 
invention and the optimum amount to be employed would vary according to 
the particular surfactant and other ingredients employed and the 
particular result desired. Generally, the amount of the surfactant may 
range from about 2% to about 10%, more preferably, from about 4% to about 
8%, by weight. 
The surfactant may be added anytime during the heating step including right 
up to the end of that step. Because its presence is necessary to form a 
stable water-in-oil emulsion, it should be added before the water-addition 
step. 
The best operating procedure for carrying out this heating step and 
apparatus employed therein are also not matters of criticality to the 
present invention and are believed to be within the skill of ordinary 
artisans. Preferably, it is desirable to add the solid fungicidal compound 
and the surfactant into the solvent while slowly increasing the heating to 
the desired melting temperature. Preferably this heating is accomplished 
by gentle agitation to keep the heat transfer even throughout the 
solution. It may be preferred to employ a nitrogen gas blanket over the 
solution to prevent any fires. The construction of the heating apparatus 
may be any conventional chemical reactor or tank which has heating coils 
attached or is jacketed. The melting temperature employed will vary with 
each combination of fungicidal material and solvent used; however, it 
usually is preferred to keep the melting temperatures in most cases in the 
range of from about 70.degree. C. to about 100.degree. C., more preferably 
from about 80.degree. C. to about 90.degree. C. Melting temperatures in 
excess of the boiling point of water may be undesirable because the excess 
amounts of the water added in step (b) may turn to steam immediately upon 
addition. 
After the melting is substantially complete, a sufficient amount of an 
aqueous solution is added to the melt to form a water-in-oil emulsion. The 
amount of aqueous solution added is not a primary critical parameter of 
the present invention, but the amount of water added should usually be in 
the range from about 10 to about 50% of the final flowable formulation, 
preferably, from about 25% by weight to about 35% by weight to form a 
flowable. 
Besides water, the added aqueous solution may contain other substances. For 
instance, it is preferred to add a minor portion of propylene glycol and 
its like with water for antifreeze and emulsion-improving properties. 
Normally, the amount of propylene glycol, when added, will range from 
about 1.0% to 10% by weight of the final formulation. 
It may be also desirable to add aqueous solutions of metals or fertilizers 
into the formulation. For example, it may be desirable to add sodium 
molybdate with the water as a source of the trace mineral molybdenum for 
the soil. Also, it may be desirable to add an aqueous solution of a 
nitrogeneous material like urea, ammonium nitrate and the like. The 
preferred amounts of each of these additional substances besides water 
must be determined for each particular use. Normally, the melt is added to 
the tank before the aqueous solution in order to protect the entrapped 
fungicidal compounds in the melt from being easily hydrolyzed by the 
water. The ratio of solvent-to-water in most situations will range from 
about 2:1 to about 0.5:1, more preferably about 1.25:1 to about 0.75:1, by 
weight. 
After the water-in-oil emulsion is formed, it is thoroughly mixed to be 
substantially homogenized. This mixing step is preferably accomplished by 
mixing the emulsion in a high shear dispersator or other equivalent mixing 
equipment. A preferred high shear dispersator is the Premier Series 8000 
Dispersator manufactured by the Premier Mill Corporation of New York, N.Y. 
The time of mixing will depend upon the particular formulation being 
mixed, the mixer and the specific RPM's employed. Generally, the length of 
mixing on the Premier Series 8000 Dispersator for most flowable 
formulations will be from about 1 minute to about 20 minutes at about 
7000-8000 RPMs. 
It has been found that it is necessary to add a thickening agent to the 
emulsion during this mixing step in order to form a stable flowable. If a 
sufficient amount of thickening agent is not added, then the flowable will 
break apart into different phases during storage. The present invention 
contemplates that any thickening agent conventionally used in this type of 
agricultural field may be employed herein. Of course, the optimum 
thickening agent and its optimum amount in the formulation will depend 
upon many factors including compatibility with other ingredients in the 
flowable. A preferred group of thickening agents that have been found to 
be useful for the present invention are those clays made up mainly of 
silica. Particularly one commercial silica product found to be useful is 
sold under the trademark Aerosil.RTM. COK 84 by Degussa Inc. of Tetraboro, 
New Jersey. This product contains from about 82%-86% silica (SiO.sub.2) 
and about 14%-18% aluminum oxide (Al.sub.2 O.sub.3). Generally, this 
product is employed in amounts ranging from about 0.25% to about 3.0% by 
weight of the final formulation, more preferably from about 0.4% to about 
2.0% by weight. Note that such amounts are far less than utilized in 
conventional flowables. 
It is also preferred to add a dye (e.g., purple) during the mixing step to 
import an unnatural color to the flowable. As state above, the reason for 
adding the dye is because government regulation requires any agricultural 
seeds treated with a fungicide to be dyed an unnatural color. In this 
process, any water- or oil-soluble dye of any unnatural color (e.g., red 
or violet) may be employed. Normally, the amount of dye added may range 
from about 0.1% to about 2% of the final formulation. 
After mixing, the stable flowable may be packaged or immediately mixed with 
seed or added to soil. The above formulation may be diluted further by the 
farmer by addition and mixing in of more water. Of course, the formulation 
can be employed as made without dilution. 
While this invention is discussed only in terms of making flowable 
fungicidal formulations, it may equally be applicable for making other 
pesticidal applications including herbicides, insecticides and the like.