US3157486A - Pesticidal dispersion and method for preparing the same - Google Patents

Description

United States Patent 3,157,486 PESTlClDAL DISPERSION AND METHOD FOR FREPARING THE SAME Thomas S. Harrison, New Canaan, Conn, and Clarence A. Littler, Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Dec. 20, 1962, Ser. No. 246,021 '14 Claims. (Cl. 71-2.4)

This invention relates to fungicidal and insecticidal compositions and their preparation.

This application is a continuation-in-part of our copending US. patent applications Serial No. 782,396, filed December 23, 1958 (allowed November 30, 1962, and now abandoned), and Serial No. 782,386, filed December 23, 1958 (now abandoned), each of which is a continuation-in-part application of US. patent application Serial No. 629,796, filed December 21, 1956 (now abandoned), which is in turn a continuation-in-part of Serial No. 523,378, filed July 20, 1955 (now abandoned), which is in turn a continuation-in-part of Serial No. 374,448, filed August 14, 1953 (now abandoned).

The use of finely-divided water-insoluble solid fungicides is well known. These materials are commonly marketed as powders that are formulated into sprayable compositions by suspending them with mild agitation in water containing a dispersant. Many of such suspensions are said to be stable suspensions of the active ingredient in a highly dispersed non-fiocculatecl condition. Actually, however, they are flocculated to quite a substantial degree. On casual observation these compositions may appear non-flocculated but in practically every instance substantial flocculation will be evident on closer observation, such as against a black background. Insofar as we are aware, no dispersant is known that will give a completely non-flocculated aqueous suspension of a powdered solid merely by moderate agitation.

Furthermore, these suspensions are usually not as stable as is desirable in agricultural sprays and slurries. On standing quiescent the solids settle out in a relatively short period and cake in a layer on the bottom of the vessel. This layer ordinarily cakes so severely that it cannot be redispersed by ordinary means. Despite these deficiencies, the prior art dilute suspensions have found widespread acceptance, since they are sufficiently dispersed to have some practical effect.

Fungicidal and insecticidal compositions are most efiicient if they can be produced as concentrates containing the active ingredient in very finely divided state, and the particles are highly deagglomerated when diluted to spray concentrations. Such formulations in which the particles are as small in size as those in the instant invention were heretofore impossible to prepare commercially. Dry grinding as carried out by hammer mills, dry ball mills, air reductionizers, etc., to which present-day wettable powders are subjected, cannot yield distinct particles of much smaller size than has already been obtained because this type of grinding causes the particles to pack into tightly adhering agglomerates. A more severe grinding would result in even tighter agglomerates which are not readily dispersible and remain partly fiocculated when suspended in water.

It has been possible, by wet grinding a slurry of the water-insoluble ingredients in the presence of a dispersing agent, to obtain concentrated slurries of very finely-divided particles which upon dilution to spray concentrations require only conventional mild stirring to disperse the particles. However, these fungicidal and insecticidal aqueous concentrates were not stable in storage or on standing for extended periods of time. The highly dispersed, finely divided pesticide in the concentrate settled and formed an exceedingly hard cake at the bottom of the container which was very difiicult to resuspend.

We have now discovered pesticidal liquid concentrates substantially free from the aforementioned disadvantages. The concentrates are thixotropic suspensions which can be extended with water to yield highly stable dilute sprayable dispersions of substantially non-fiocculated, extremely finely divided pesticide particles.

Our concentrates are prepared by mixing finely-divided active ingredient, a thixotropic suspending agent, one or more dispersing agents and water in amounts to be described more fully hereinafter. This mixture is then wet-milled by ball milling or sand grinding. Sand mills and sand grinding are described in detail for example, in Hochberg Patent No. 2,581,414.

The wet-milling serves to comminute and deagglomerate the active ingredient. It is carried on until at least by weight of the active ingredient is of a particle size less than 10 microns, and preferably less than 5 microns in diameter. 7

A second essential function of the shearing action imparted by wet-milling is to coact with the dispersants to disperse the active ingredient homogeneously throughout the concentrate.

Still another essential function of the wet-milling is to impart the shearing action required to swell and deagglomerate the suspending agent so that the mixture thickens giving an intimately mixed homogeneous thixotropic suspension of extremely finely-divided deagglomerated active ingredient and deagglomerated and swelled suspending agent in water.

These critical functions performed by wet-milling ordinarily can be accomplished by sand grinding for 15-45 minutes on a batchwise basis. Of course, when the active ingredient and suspending agent are initially extremely finely divided and deagglomerated and the suspending agent is readily swelled, sand grind times as low as 5 minutes frequently are satisfactory. Likewise when the converse is true, sand grind times as long as 3 hours sometimes are required.

These times are given for batch grinding. It is also possible to use a continuous grinder in which a slurry is fed into one end and removed continuously from the other after grinding.

The optimum sand grind time can be readily ascertained by periodically checking the particle size of the active ingredient and the degree of thixotropy of the concentrate.

As aforementioned, the concentrates of this invention are true thixotropic suspensions, that is, the viscosity decreases upon application of shear. An illustration of what is meant by thixotropy is shown by measuring the apparent viscosity with a Brookfield viscometer at two difi'erent spindle speeds, e.g., at 6 r.p.m. and at 30 r.p.m. When doing so the sample is first agitated vigorously to establish a non-gelled, fluid state. The viscosity is then measured promptly at 30 r.p.m., followed immediately by a measurement at 6 rpm. The apparent viscosity at-6 r.p.m. is found to be substantially higher than that measured at 30 r.p.m. The ratio V /V has a minimum value of 1.5. A range of from 24.5 is preferred and the ratio is most desirable if it is in the range of 2.5 to 3.5.

Since the above measurements are made up on a freshly agitated sample, they still fail to show the state of gellation that can be obtained when a sample is allowed to rest undisturbed for a period of time. Since the act of measurement itself involves a shearing action which partially destroys the gelled state, there is no ideal way of measuring the viscosity when completely gelled. By allowing a viscometer spindle to stand immersed in the product for half an hour and then measuring the maximum viscosity reading appearing when the spindle starts to rotate at a speed of 6 r.p.m., one can get an" approximation to the gelled viscosity. Under these con-, .ditions the viscosity at 6 r.p.m. (gelled) is from 2 to 5 times the viscosity at 6 r.p.m..after agitation. For example, a sample showing a viscosity after shaking of 145 cps. at 30 r.p.m. and 440 at 6 r.p.m. gave a maximum viscosity at 6 r.p.m. of 1440 cps. after the spindle was herent in the handlingof pesticides in the form of wet-.

table powders and suspensions,

Our concentrates are easily dispersed in water with mild agitation to give compositions suitable for application using conventional spray equipment, say, for example, a spray containing 0.25% to 3% by Weight of the active ingredient. Such dilute spray compositions are in the form of substantially non-fiuocculated homogeneous mobile dispersions. Even at these dilute spraying concentrations, the compositions. are remarkably stable so that no agitation is ordinarily required in the spray tank to prevent settling unless application of the spray composition is to extend over a long period of time such as several days as contrasted with wettable powder particles which may settle out in as little as ten minutes if the spray tank is not agitated.

If settling doesoccur after long periods of standing, the settled material can be readily redispersed'using moderate agitation. No substantial caking takes place on the bottom of the spray tank. The reason for this is that the suspending agent which also tends to concentrate at the bottom of the vessel maintains the active ingredient in a highly dispersed suspended condition so that it can readily be redispersed with mild agitation. This is in contrast to the usual dilute suspension of well dispersed particles, which on settling, packs so tightly that the settled cake cannot be resuspended by ordinary means...

The difference between the dilute flocculated suspensions of wettabie powders and the highly dispersed dilute suspensions of the compositions of this invention can in:

example as determined by measurement in a light micro-' scope with the particle size distribution determined in the dispersion by conventional sedimentation techniques known to the art, as described by Andreasen, A. H. M., Thevalidity of Stokes Law for Non-sperical Particles,

Kolloid Zeitschrift, vol. 48, pp. 175-9 "(1929), and other similar methods described under Particle Dynamics in Perrys Chem. Eng. Handbook, 3rd edition, pp. 1017-21. If microscopic examination shows that the particles are significantly smaller than can be concluded from the rate of settling and the application of Stokes Law in the dispersion then obviously agglomeration into more rapidly settlingvfloccules must have taken place.

The solid pesticidal agents of our compositions must be Water-insoluble. By Water'-insolublewe mean that lessthan' approximately 0.1 gm. of the pesticidedissolves in approximately 99.9 gm. of water at 30 C.

Suitable fungicides are, for example, the well known tetraalkyl thiuram disulfides, such as bis(dimethylthiocarbamyl)disulfide, and dithiocarbarnates, such as manganese or zinc ethylenebisdithiocarb-amate, and ferric,

"son of :the size distribution of the ultimate particles, for

zinc, manganeseand other heavy metal salts of dimethyldithiocarbamic acid, ethylmethyldithiocarbamic acid, n-

butyldithiocarbamic acid and of other dithiocarbamic.

acids derived from primary and secondary amines. Other suitable'fungicides are derivatives of rhodanine, such as 3-(p-chlorophenyl)-5-methylrhodanine, Nettichloromethylmercapto-4-cyclohexene 1,2-dicarboximide (Cap-tan), N trichioromethylmercaptophthalimide (Phaltan),ethyl mercury p-toluenesulfonanilide, N,N- diphenyl p phenylenediarnine, 2,3 dichloro 1,4- naphthoquinone, tetrachloro p benzoquinone, 2,4 dichloro-G-(chloroanilino)-triazine and copper quinolinate. Also useful in dispersions of this type are insoluble inorganic fungicides such as copperoxide, and copper oxychloride.

Methoxychlor (1,1,1 trichloro 2,2 bis(p methox yphenyl)ethane) is a suitable water-insoluble, solid inseoticide which can be used as the active ingredient in our compositions. An insecticide such as Dieldrin (1,2,

3,4,10,10-heXachloro-6J epoxy 1,4,4a,5,6,7,8,8a octahydro-1,4,5,'8-dimethanonaphthalene) can'be present in seed treatment formulations along with an aforementioned fungicidal compound. More than one fungicide and/or insecticide may be present in the compositions.

Manganese ethylene -bis(dithiocarbamate) is an example of a preferred pesticide thatcan be used in our thixotropic formulations. As shown in US. Patent 2,504,404 this compound is precipitated, for example, by

the reaction between disodium ethylene bis(dithiocarbamate) and a manganous salt. In the slurry-produced the crystals of manganese ethylene bis(dithiocarbamate) contain two molecules of water of hydration per manganous' ion.. Some water of hydration is lost 'in drying the slurry and some decomposition of the 'manganese ethylene bis(dithiocarbamate) may also occur.v

, Our invention is particularly advantageous when applied to materials such as manganese ethylene bis(di= thiocarbamate). It permits the preparation of. a highly potentfungicide composition having" the desirable. prop-J erties of the compositions of the invention while avoiding the need for the slurry-drying step with its resultant partial dehydration and decomposition-eifects on the ac tive ingredient. Thus the washed, wet filter cake of the slurry can be milled with the suspending and dispersing ureas such as those disclosed in Todd Patents 2,655,444,

and 2,655 ,447. Alternatively, herbicides such as the solid water-insoluble substituted triazines can be used.

The herbicidally active aryl aliphatic ureas employed in the compositions of the invention can be represented by the formula where X is halogen; n is a cardinal number up to 3; R

is methyl or ethyl; and R" is hydrogen or alkyl or alkenyl of one to four carbon atoms. 4

Illustrative of specific preferred aryl aliphatic ureas employed in the compositions of the invention are:

3 (p-chlorophenyl) -1,1-dimethylurea 3-( 3 ,4-dichlorophenyl) 1, l-dimethylurea 3-(3,4-dibromophenyl)-1,1-dimethylurea 3-(3,4-dich1orophenyl)-1-methylurea 3 .--(p chlorophenyl)-1-methylurea 3- (p-chlorophenyl) -.1-methyll-isopropylurea 3- (p-chlorophenyl) -1-methyl-1-allylurea 3- (m-chlorophenyl) -1 l-dimethylurea 3- (3 ,4-dichlorophenyl)-1,1-diethylurea 3- (3 ,4-dichlorophenyl) -1-methyl-1-isopropylurea 3 ('3 ,4-dichlorophenyl -1-methyl-l-butylurea 3 3 ,4-dichlorophenyl) .-1-methyl-1-sec.butylurea 3- (p-chlorophenyl) -1-methyl-l-ethylurea 3- (p-bromophenyl) -1, l-dimethylurea 3- p-iiuorophenyl) -1,1-dimethylurea 3-(p-chlorophenyl)-1-methyl-1-n-propylurea 3-(p-chlorophenyl -1-methyl-1-sec.butylurea 3- (p-iodophenyl) 1 l-dimethylurea 3 t 3 ,4-dichlorophenyl) -l-methyl-1-ethylurea 3-( 3 -bromo-4-chlorophenyl) -1, 1-dimethylurea 3- 2,4,5 -trichlorophenyl) 1 -methylurea 3- p-bromophenyl) -1-methyl-1-isopropyiurea 3- (p-chlorophenyl) 1, l-diethylurea 3 (2,4,5-trichlorophenyl) -i l-dime-thylurea 3- (m-chlorophenyl) -1-methylurea 3'- (p-bromophenyl) -1-methylurea 3 (pchlorophenyl) -1-ethylurea 3 (m-chlorophenyl) l-methyl-1-isopropylurea The herbicidally active triazines which are particularly useful in the compositions of this invention can be represented by the following formula:

where R and R are the same or diiferent and are selected from the group consisting of alkyl of less than 4 carbons and -(CH OCH n is an integer selected from the group consisting of 2 and 3.

Illustrative of the herbicidally active tn'azines are:

2,4-bis (methylamino) -6=chloro-1,3 ,5 -triazine 2,4-bis(ethylamino)-6-chloro-1,3,5-t1iazine 2,4-bis (propylamino -6-chloro- 1,3,5 -triazine 2-.chloro 4-isopropylamino-fi-methylamino-1,3 ,5 -tri azine 2,4-bis (Z-methoxyethylarnino -6-chloro- 1,3 ,5 -triazine 2,4-bis 3-methoxypropylamino) -6-chloro-1,3 ,5 -triazine 2-chloro-4- Z-methoxyethylamino) -6- 3 -methoxypropylamino -1,3,5-triazine 2-chloro-4-ethylamino-6-( 3 -rnethoxypropylamino 1,3,5-triazine The suspending agents of the invention when subjected to the shearing force of our methods are responsible for the thixotropic nature of the novel compositions. That is, the compositions become more viscous and gel upon standing quiescent, but they are readily reversed to mobile fluids merely by the application of mechanical shear. Compounds such as sodium silicate, which forms an irreversible gel with water, and agar and the natural gums, which form heat-reversible gels with water, are not encompassed within the term thixotropic suspending agent as used herein.

The preferred suspending agents which give to the concentrates of this invention the desirable combination of properties of thioxotropy in the concentrate and very high dispersion in the dilute spray are the water-swellable hydrous colloidal mineral silicates. These water-swellable minerals are clays that are classified into two groups based on their particle configuration. One group consists of the plate or lath-like clays of the expanding latticetype, such as bentonite and similar minerals of the montmorillonite group such as montrnorillonite, beidellite, nontronite, hectorite, saponite and sauconite. The other group is fibrous or rod-like minerals such as attapulgite.

The water-swellable hydrous colloidal mineral silicates for use in the preparation of the compositions of the invention can be refined according to known; practices to remove gritty materials, impurities such as carbonates, or otherwise treated to provide a higher quality product. Commercial grades of montmorillonite and attapulgite type clays available in the market give satisfactory performance. Care should be taken, however, to avoid the use of attapulgite which has been subjected to relatively high temperatures since such treatment tends to destroy the swelling properties of the mineral. It is preferred that attapulgite, ifused as the water-swellahle silicate, be in such state of hydration that it will lose at least 10% of its weight aswater upon heating at C. at atmospheric pressure to. constant weight. Such attapulgitewill be referred to hereinafter as hydrated attapulgite.

Any one or more of the materials known in the art to act as dispersants for finely-divided solids in water can be used as the dispersing agent in the compositions and methods of the invention. Many such materials are known, illustrative of which are the products based on lignin sulfonic acid such as goulac and the dispersing agents sold under the proprietary names of Marasperse and palconate; the sodium salts of polymerized alkyl aryl and aryl alkyl sulfonic acids such as those sold under the proprietary names of Daxad, Lomar and Darvan; polyvinyl alcohol; methyl cellulose; methylhydroxyethyl cellulose; carboxy methyl cellulose, and polyoxyethylene compounds such as the reaction products of ethylene oxide with mixtures of resin and fatty acids (.Renex) or with sorbitol-fatty acid esters (Tweens). Dispersing agents of the high fomning type such as sap-. onin and glue while usable are not preferred since foaming is a hindrance in preparation and use of the compositions.

Considering now the. relative proportions of the several essential ingredients of our compositions, the amount of active ingredient can be varied from about 2*065% by weight of the composition without destroying either the stability obtained through thixotropy or the fluidity; of the concentrate on agitation. Lesser amounts of active ingredient can be used if larger amounts of the sus-. pending agent are employed to maintain the thixotropic property of the composition. However, compositions containing less than about 20% of the active ingredient are commercially less attractive because of increased; shipping costs per pound of active ingredient.

The suspending agent makes up from about /2 to 10% by. weight of the concentrate compositions of the invention. The optimum amount within this range depends upon the exact properties of the particular suspending agent used, the concentration of the active ingredient and the effectiveness of the dispersing agent. In general, less suspending agent is required with increased concentrations of the active ingredient. On the other hand, greater amounts. of suspending agent are needed in compositions containing the more efiective dispersing agents.

The amount of the dispersing agent in the compositions can be varied from about 0.5% to 25% by weight of the composition depending upon the efiectiveness of the dis: persant used. With highly effective dispersing agents such as materials sold under the proprietary names of Marasperse CB, and Methocel H.G., amounts as low as 0.5% by weight are satisfactory. With less efliective materials such as goulac, amounts from about 2% up to as much as 25% can be used.

Some preferred compositions of these novel pesticidal thixotropic suspensions are freeze stable, that is after repeated freezing and thawing, the suspensions can be readily redispersed by stirring and are then free of granules, This goal can frequently be obtained by using higher amounts of dispersing agents.

If desired, methanol, ethylene glycol, and other freezing point depressants can be included in the compositions. Liquid depressants in which the active ingredient has appreciable solubility should be avoided because of the tendeasy to induce crystallization of the active ingredient in the compositions upon aging. It may also be desired to should not exceed about 70% by weight of the compositions; and in general, the compositions should contain at least about 30% by weight of Water.

Preferred compositions contain from 2550% of the active ingredient, 10-20% goulac and 14% bentonite or attapulgite.

In the preparation of our liquid concentrates, it is essential that the suspending agent be present during the wetmilling since satisfactory swelling and deagglomeration of the suspending agent can seldom be obtained without extremely vigorous shear action such as is imparted by sand milling.

Likewise, the dispersant and the active ingredient must be present during the Wet-grinding. It is found that sand milling grinds the active ingredient to optimum particle size distribution. Furthermore, even if the active ingredient is in sufficiently finely-divided form so that further comrninution is not required, satisfactory dispersion of the active ingredient cannot be obtained without the application of vigorous shear action to the suspended active ingredient in the presence of the dispersant dissolved in the water. a

Simple stirring of the agglomerated suspending agent and active ingredient in water containing a dispersing agent using conventional or moderate agitation such as with a paddle-type agitator effects neither the desired deagglomeration and swelling of the suspending agent nor the deagglom eration, grinding and dispersing of the active ingredient.

Additional ingredients such as the anti-foaming agents, corrosion inhibitors, dyes, pigments, preservatives, or other additives can also be included in these liquid concentrates.

To describe our methods and compositions, the following examples in addition to those above are given:

Example 1 324 grams of the listed mixture is mixed with 277 cc. of 30 mesh Ottawa sand. This mixture is agitated for 30 minutes at an agitator speed of 2700 rpm. in a I I sand mill of a kind described in US. Patent 2,581,414. The sand mill employed in the process of this example consists of a vertical cylindrical stainless steel vessel of four-inch diameter provided with an agitator means and agitator shaft containing two flat three-inch diameter stainless steel discs spaced about one and one-half inches apart on the shaft.

. Percent Tetramethylthiuram disulfide (fungicide) 40.0 Attapulgite, hydrated 2.0 Goulac (sodium lignin sulfonate) 5.0 Water 53.0

' The resulting composition after separation from the sand by centrifuging is a thixotropic liquid having an apparent viscosity, Brookfield, of 743 cps. at 30 r.p.m. using a No. 2 spindle.

Portions of this composition are extended with water to form substantially non-fiocculated' highly stable suspensions containing 0.2% and 0.4% by weight of the fungicidally active ingredient.

.These sprayable compositions are applied to apple trees for the control of apple scab (V enturia inaequalis). Other apple trees are treated with sprayable suspensions of the same concentrations made up from a typical commercial tetramethylthiuram disulfide wettable powder.

8" The following shows the results of these treatments after exposure of all the apple trees to apple scab.

Whereas the wettable powder suspensions give no control of apple scab in these tests, the sand-ground suspensions give noticeable control.

Further portions of the sand-milled concentrates of this example are extended with water to various concentrations and sprayed on bean plants. Additional sprayable compositions of the same concentrations consisting of finely-divided dry tertamethylthiuram disulfide suspended with mild agitation in water plus a dispersant are also sprayed on bean plants. The treated bean plants are then exposed to bean rust (Uromyces appendiculams).

The following table shows the results obtainable from this type treatment, as measured by percent disease when observed seven days after treatment.

Concen- Percent Type of Suspension tration, Disease percent Sand-milled 0. 12 0. 2 Mild agitation 0.12 9.0 Sand-milled 0. 004 10. 3 Mild agitation 0. 004 31. 5

It is to be noted that the sand-milled 0.004% spray has about the same activity as the mildly agitated spray of 0.12% concentration.

Example 2 In a manner similar to that described in Example 1, the following composition was prepared:

Thiram is a technical form of tetramethylthiuram disulfide, approximately 99% of the latter as active material. 7

After sand grinding as in Example 1, the product had a viscosity of centipoises as measured with the Brookfield viscometer at 30 rpm. using a No. 3 spindle. Upon dilution with water the concentrate gave a highly dispersed suspension which remained suspended without settling for many hours. Upon standing in a container, this thixotropic suspension would gel but the fluidity could be restored by mild agitation or shaking. After freezing and thawing this thixotropic suspension could be rendered homogeneous by mild stirring and was then free of granules.

Example 3 481 grams of the listed mixture is mixed with 318 cc. of 20-30 mash Ottawa sand and is sand ground for 30 minutes in accordance with Example 1.

The resulting composition after separation from the sand by centrifuging is a thixotropic liquid having an apparent viscosity, Brookfield, of above 2000 cps. at 30 rpm. using aNo. 3 spindle.

In accordance with the procedure of Example 1, portions of this composition are extended with water to form fungicidally-active sprays.

These sprays, and also sprayable-suspensions of the same concentrations made up from a typical commercial zinc ethylenebisdithiocarbamate wettable powder, are sprayed upon apple trees for the control of apple scab. The following table shows the results of these treatments after exposure of the apple trees to apple scab.

Concen- Percent Type of Suspension tration, Apple Scab percent Sand-ground 0. 04 6 o 0.2 3 Wettable powder 0. 04 29 o 0. 2 100 No treatment control 100 Further portions of the sand-milled concentrate of this example are extended with water to various concentrations and sprayed on bean plants. Other bean plants are treated with sprayable compositions of the same concentrations consisting of finely-divided zinc ethylene-bisdithiocarbamate suspended in water plus a dispersant. The treated bean plants are then exposed to bean rust Uroymces appendz'culatus) The following table shows the results obtainable from this type treatment, as measured in percent disease when Example 4 The following thixotropic fungicide concentrates are prepared by mixing the ingredients and said milling the mixture in accordance with the procedures of Examples 1, 2, and 3. These concentrates, when extended with water, form sprayable dilute compositions which are ideal for use in conventional spraying equipment.

Percent Manganese ethylenebisdithiocarbamatedihydrate 30 Methyl cellulose, low viscosity cps.) 0.5 Hydrated attapulgite 1.75 Water 67.75

Zinc dimethyldithiocarbamate 3O D'axad l1 (formaldehyde-naphthalene sulfonic acid condensate 2.0 Bentonite 1.0 Water, 67.0

Ferric dimethyldithiocarbamate 30 Marasperse C.B. (modified sodium lignin sulfonate 0.5 Bentonite 1.0

Water 68.5

10 Example 5 The following thixotropic fungicidal concentrate is prepared by mixing the ingredients and then sand milling with a volume of 2030 mesh Ottawa sand equal to the volume of the liquid pre-mix.

The total sand milling time is approximately 30 minutes and the mixture is maintained at approximately room temperature by circulating cooling water through the jacket of the mill:

Percent N trichloromethylmercapto-4-cyclohexene-1,2-dicarboximide (Captan) 35.0

Goulac (sodium lignin sulfonate, dispersing agent) 15.0 Attapulgite, hydrated 1.5 Disodium phosphate (anhydrous) 0.9 N-octyl alcohol (antifoam agent) 0.1 Water 47.5

The resulting mixture, when extended with water to a spray concentration of, for example, 1 lb. of Captan per 100 gallons of spray suspension forms a substantially non-flocculated dilute spray composition which is suitable as a fungicidal foliar spray for apple trees.

Example 6 325 grams of a mixture containing the listed ingredients were mixed with 445 grams of 22-30 mesh Ottawa sand to give a mixture containing about 50% sand by volume.

. Percent N,N'-diphenylparaphenylenediamine, 31.6 Sodiumlignin sulfonate 5.0 Attapulgite, hydrated 2.0 Water 61.4

This mixture was agitated for 30 minutes at an agitator speed of 2700 rpm. in a sand mill of the kind described in Example 1.

The resulting composition, after separation from the sand by centrifuging, was a mobile liquid having an apparent viscosity of 400 cps. as determined by a Brookfield viscometer at 30 r.p.m. with a No. 2 spindle. The product gelled on standing and was readily fluidized with slight agitation.

Example 7 The following thixotropic insecticide concentrate is prepared in accordance with the procedure of Example 3.

Manzate is a proprietary commercial product containing approximately 70% manganese ethylene bisdithiocarbamate, approximately half of which is present in the dihydrate crystal form, the rest being anhydrous. Florigel is a type of fullers earth, a hydrated attapulgite clay mined in Florida, and is known for the stability of its dispersions in the presence of electrolytes. Methocel 15 is a low viscosity methyl cellulose.

The mixtures were ground in a sand grinder with an equal volume of 20-30 mesh Ottawa sand for approximately minutes.

The product was a thixotropic mixture which formed a stifi gel upon standing. In spite of its apparently solid nature the fluidity of the suspension could be restored by simple shaking or agitation, and after such shaking the viscosity, as measured by a Brookfield viscometer at 30 r.p.m. using a No. 3 spindle, was 705 centipoises. This low Viscosity made it entirely possible to pour the suspension easily from container to container. Upon standing, the formulation would again gel, become more rigid, and no settling out would'occur. This same mixture when frozen and subsequently thawed still retained the thixotropic properties of the original gel and'during the freeze-thaw cycle no granules would form that could not be dispersed with very mild stirring. In spite of the highly thixotropic nature of the concentrated gel, the material could be diluted to spray concentration (approx. A%, for example) and at this spray concentration would disperse easily into a dispersion that remained suspended without settling for several hours.

The spray dispersion prepared from the thixotropic concentrate contains both anhydrous manganous ethylene bisdithiocarbamate as well as the dihydrate. Such spray dispersions are outstandingly useful as foliar fungicides, for example on tomatoes and beans.

Example 9 90.7 lbs. of water and 27.07 lbs. of tech-Mangam, a commercial product containing manganous sulfate, were mixed. In another vessel 108 lbs. of water was mixed with 149 lbs. of a 23% solution of disoduim ethylene bisdithiocarbamate and the pH was adjusted to 8.87 with 600 ml. of 10% sulfuric acid. The two solutions were mixed by adding the manganous sulfate solution to the disodium ethylene bisdithiocarbamate solution over a one hour period. The resulting slurry was filtered and the filter cake was washed three times with cold tap water. The resultant wet cake was not quite uniform, and contained between 36 and 40% of manganese ethylene bisdithiocarbamate.

77 lbs. of this wet filter cake was mixed with 349 grams of goulac and 698 grams of Florigel and the mixture was ball milled for 16 hours. The product containing 43.4% manganous ethylene bisdithiocarbamate dihydrate was a thixotropic non-settling suspension which dispersed readily upon dilution to spray concentration. The maneb particles in the suspension were small and discrete, averaging approximately 3 /2 microns as measured on a dried sample by the air permeability with the instrument known as the Fisher Sub-Sieve Sizer. Microscopic examination confirmed this measurement of the particle size of the fungicide particles in this suspension. a

The product was applied to apple trees to combat apple scab by standard spray applications of suspensions containing 0.5, 0.75 and 1.0 lb. of manganous ethylene bisdithiocarbamate, with results as follows:

Average percentage control of apple scab Spray concentration (lbs. active ingredient/ 100 gal.)

Rome McIntosh variety variety 12 fungicide were defoliated in the amount of 9.3% due to the ravages of the disease.

Example 10 I The type of manganous ethylene bisdithiocarbamate dihydrate wet cake described in Example 9 was formulated as follows:

7 Percent Maneb dihydrate wet cake 70 Goulac 7.5 Methocel, 15 cps. 1.0 Disodium phosphate heptahydrate 1.0 Florige 0.5 Paisley Defoamer 630 (a sulfonated tallow) 0.1 Water 19.9

The wet cake was added to the mixture of the other ingredients and mixed in by stirring with a paddle stirrer for about 10 minutes. This pre-mix was then sand milled for 30 minutes with approximately 4 lb. of sand per pound of premix. The product was a thixotropic mixture, as evidenced by the fact that the viscosity, using a Brookfield viscometer with a No. 3 spindle was 6680 centipoises at 6 r.p.m. of spindle and 2530 centipoises when the spindle was rotated at 30 r.p.m. Thus the thixotropy factor for this composition is 2.64. In spite of this thixotropic nature the product could be dispersed in'water to yield a highly dilute spray suspension for application as a foliar fungicide. In another test the product proved freeze-stable, i.e., remained homogeneous,

dispersible, non-granulated, and hence sprayable through agricultural spray nozzles after freezing and, thawing followed by very gentle agitation upon dilution with water.

Example 11 The following inorganic fungicide concentrate can be prepared by methods analogous to those in Example 4:

Percent Copper A 30.0 Goulac 10.0' Florigel 1.5 Atlas 68916 P 0.5 n-Octanol 0.1 Water 57.9

Copper A is a commercial inorganic funigicide containing 45% (metallic) copper, present as tetra copper calcium oxychloride, (4Cu(OH) CaCl -4H O).

Example 12 The following seed treatment concentrates are prepared in accordance with Example 3:

These compositions are diluted with water and then applied to seed in standard seed treatment equipment.

Example 13 A composition having the ingredients shown below is prepared.

Two hundred thirteen grams of the above mixture is mixed with 425 grams of 20-30 mesh Ottawa sand to give a mixture containing about 60% sand by volume. This mixture is agitated for 15 minutes at an agitator speed of 2700 r.p.rn. in a sand mill of a kind described in US. Patent 2,581,414. The sand mill employed in the process of this example consists of a vertical cylindrical stainless steel vessel of four-inch diameter provided with an agitator means and agitator shaft containing two flat three-inch diameter stainless steel discs spaced about one and one-half inches apart on the shaft.

The resulting concentrate of the example after separation from the sand by centrifuging has an initial apparent viscosity of 700 cps. as determined by a Brookfield viscometer at 30 r.p.m. and an apparent viscosity of 2050 cps. when measured at 6 rpm. Thus the thioxtropy factor for this composition is 2.93. Substantially all of the active ingredient is less than 10 microns in particle diameter.

The concentrate gels on standing, is readily fluidized with slight agitation, and is easily dispersed in water by mild stirring to. form a homogeneous, stable, milky suspension that appears non-fiocculated even against a black background.

The concentrated suspension is freeze-stable, that is, if frozen and subsequently thawed, the mixture can again be rendered homogeneous by mild stirring, and no hard granules form which would resist such redispersion upon mild stirring.

When applied at a rate of 25 lbs. of active ingredient per acre as a concentrate by airplane application, this composition produces a rapid top injury to foliage. It also gives an enduring sterility to the soil in the sprayed area.

Example 14 The following thixotropic herbicidal concentrates are prepared by mixing the ingredients and sand milling the mixture in accordance with the procedure of Example 13. These concentrates, when extended with water, form substantially non-flocculated syrayable dilute compositions which are ideal for use in conventional spraying equipment. The mixtures of Example 15 below, also are freezestable.

(A) Percent Tech. 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (95%) 30.6 Goulac (sodium lignin sulfonate) l .0 Attapulgite, hydrated 2.4 Sodium pentachlorophenate 0.5 Disodium phosphate anhydrous (corrosion inhibitor) 0.96 Dodecyl alcohol (tech) 0.005 Water 50.535

This composition is ideal for cotton preemergence spraying at concentrations of 0.32% active ingredient in equipment having nothing but pump bypass agitation.

l 4 (B) Percent Tech. 3-(3,4-dichlorophenyl) -l-methyl-1 n-butyl urea 3 1.6

Goulac l5 .0

Attapulgite, hydrated 2.0 Sodium pentachlorophenate 0.5 Disodium phosphate anhydrous 0.95 Octyl alcohol 0.005 Water 49.945

This composition is Well suited for home application to lawns for selective chickweed control.

(C) Percent Tech. 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (95%) 30.6 Goulac (sodium lignin sulfonate) 15.0 Hydrated attapulgite 2.0 Sodium pentachlorophenate 0.7 Disodium phosphate (anhydrous) 1.0 Octyl alcohol 0.005

Water 46.695

This mixture is sandmilled until at least of the active ingredient has a particle size less than 10 microns. Four parts of 10% sodium hydroxide solution are added and the slightly alkaline mixture is packed out.

Example 15 The following thixotropic herbicidal concentrates are prepared in accordance with the procedure of Example 13. These concentrates can be extended with water to form dilute non-fiocculated compositions suitable for use in conventional spraying equipment.

(A) Percent 2,4-bis(ethylamino)-6-chloro-1,3,5-triazine 30.0 Goulae (sodium lignin sulfonate) 5.0 Attapulgite, hydrated 2.0 Sodium pentachlorophenate 0.5 Octyl alcohol 0.005 Water 62.495

This formulation is used at a rate of 5 lbs./ acre of active ingredient to freshly worked soil for control of germinating annual broad leaf and grassy weeds in ornamen- Water 57.795

This formulation is used at rate of 2 lbs./ acre of active ingredient as a preernergence treatment for the control of germinating annual broad leaf and grassy weeds in corn.

The foregoing examples given to illustrate specific embodiments of the invention. It will be understood that the terms and expressions employed are used as terms of description and not of limitation. We have no intention in the use of such terms and expressions of excluding any equivalents of the features described or portions thereof, and recognize that numerous modifications are possible within the scope of the invention described and claimed.

We claim: r

1. In a process for producing a concentrated, substantially homogeneous, thixotropic, aqueous dispersion of substantially non fiocculated, finely divided particles of a pest control agent selected from the group consisting of water-insoluble solid fungicides, herbicides and methoxychlor, said dispersion having the characteristics of being substantially fiee of settling of the particles to a hard,

0 a crib diflicultly resuspendable cake upon standing and being extendible with water to form a dilute mixture wherein the particles settle only after prolonged standing and when settled are readily redispersible with mild agitation, the steps comprising mixing the pest control agent, water, a suspending agent which is a water-swellable, hydrous, colloidal mineral silicate of. the group consisting of hydrated attapulgite and montmorillonite group clays, and a dispersing agent of the group consisting of lignin sulfonic acid, sodium lignin sulfonate, sodium salts of polymerized alkylaryl and arylalkyl sulfonic acids, polyvinyl alcohol, methyl cellulose, methylhydroxyethyl cellulose, carboxymethyl cellulose, and polyoxethylene compounds which are reaction products of ethylene oxide with sorbitol-fatty acid esters and with mixtures of resin and fatty acids, in proportions to give a mixture containing, by weight, about from to 65 of pest control agent, 0.5% to 10% of suspending agent, and 0.5% to of dispersing agent, the total of said ingredients not exceeding 70% and at least of water, and wet-grinding the mixture under vigorous shear, said wet-grinding being continued until the suspending agent has been swelled and deagglomerated and at least 90% by weight of the pest control agent is of a particle size less than 10 microns.

2. A process of claim 1 wherein the wet grinding is sand-grinding.

3. A process of claim 1 wherein the wet-grinding is ball-milling. i

4. A concentrated, substantially homogeneous, thixotropic aqueous dispersion of substantially non-flocculated, finely divided particles of a pest control agent selected from the'group consisting of water-insoluble fungicides, herbicides and methoxychlor, said dispersion having the characteristics of being substantially free of settling of the particles to a hard, diflicultly resuspendable cake upon standing and being extendible with water to form a dilute mixture wherein the particles settle only after prolonged standing and when settled are readily redispersible with mild agitation, the dispersion comprising the pest control agent, water, a suspending agent which is a water-swellable, hydrous, colloidal mineral silicate of the group consisting of hydrated attapulgite and montmorillonite'group clays, and a dispersing agent of the group consisting of lignin sulfonic acid, sodium lignin sulfonate, sodium salts of polymerized alkylaryl and arylalkyl sulfonic acids, polyvinyl alcohol, methyl cellulose, methylhydroxyethyl cellulose, carboxymethyl cellulose, and polyoxyethylene compounds which are reaction products of ethylene oxide with sorbitol-fatty acid esters and with mixtures of resin and fatty acids, in the proportions, by Weight, of about from 20% to 65% of pest control agent, 0.5% to 10% of suspending agent, and 0.5% to 25% of dispersing agent, the total or" said ingredients not exceeding 70%,

and at least 30% of Water, the suspending agent being swelled and deagglomerated, and at least by weight of the pest control agent having a particle size less than 10 microns. I

5. A composition of claim 4 wherein the pest control agent is tetramethylthiuram disulfide.

6. A composition of claim 4 wherein the pest control agent is methoxychlor.

7. A composition of claim 4 wherein the pest control agent is manganese ethylene bis(dithiocarbamate), the

dispersing agent is sodium lignin sulfonate, and the suspending agent is hydrated attapulgite.

8. A composition of claim 4 wherein the pest control agent is a mixture of tetramethylthiuram disulfide and methoxychlor, the dispersing agent is sodium lignin sul-' fonate, and the suspending agent is hydrated attapulgite.

9. A composition of claim 4 wherein the pest control agent is a water-insoluble, herbicidal active aryl alkyl substituted urea.

10. A composition of claim 4 wherein the pest control is 3- (p-chlorophenyl) -1,1-dimethylurea.

11. A composition of claim 4 wherein the pest control is 3-(3,4-dichlorophenyl) -1,1-dimethylurea.

12. A composition of claim 4 wherein said pest control agent is 3-(3,4-dichlorophenyl)-1,1-dimethylurea,

suspending agent is attapulgite and said dispersing agent is sodium lignin sulfonate.

13. A composition of claim 4 wherein the pest control agent is a water-insoluble, herbicidally active substituted triazine.

14. A composition of claim 4 wherein the pest control agent is 2,4-bis(ethyiamino)-6-chloro-1,3,S-triazine.

References Cited in the file of this patent UNITED STATES PATENTS 2,089,612 Kubelka Aug. 10, 1937 2,504,404 Flenner Apr. 18, 1950 2,523,316 McClenahan Sept. 26, 1950 2,529,682 Flenner Nov. 14, 1950 2,599,373 Chrzanowski June 3, 1952 2,704,245 Searle Mar. 15, 1955 2,726,150 Wolter Dec. 6,1955 2,773,757 Connell et al. Dec. 11,1956 2,870,058 Loder Jan. 20, 1959 2,891,855 Gysin et a1. June 23, 1959 2,992,161 Flenner July 11, 1961 FOREIGN PATENTS 851,250 Great Britain Oct. 12, 1960 7 OTHER REFERENCES The Pharm. 1., Dec. 23, 1939, p. 528.

Claims (1)

1. 4. A CONCENTRATED, SUBSTANTIALLY HOMOGENEOUS, THIXOTROPIC AQEUOUS DISPERSION OF SUBSTANITALLY NON-FLOCCULATED, FINELY DIVIDED PARTICLES OF A PEST CONTROL AGENT SELECTED FROM THE GROUP CONSISTING OF WATER-INSOLUBLE FUNGICIDES, HERBICIDES AND METHOXYCHLOR, SAID DISPERSION HAVING THE CHARACTERISTICS OF BEING SUBSTANTIALLY FREE OF SETTLING OF THE PARTICLES TO A HARD, DIFFICULTLY RESUUSPENDABLE CAKE UPON STANDING AND BEING EXTENDIBLE WITH WATER TO FORM A DILUTE MIXTURE WHEREIN THE PARTICLES SETTLE ONLY AFTER PORLONGED STANDING AND WHEN SETTLED ARE READILY REDISPERSIBLE WITH MILD AGITATION, THE DISPERSION COMPRISING THE PEST CONTROL AGENT, WATER, A SUSPENDING AGENT WHICH IS A WATER-SWELLABLE, HYDROUS, COLLOIDAL MINERAL SILICATE OF THE GROUP CONSISTING OF HYDRATED ATTAPULGITE AND MONTMORILLONITE GROUP CLAYS, AND A DISPERSING AGENT OF THE GROUP CONSISTING OF LIGNIN SULFONIC ACID, SODIUM LIGNIN SULFONATE, SODIUM SALTS OF POLYMERIZED ALKYLARYL AND ARYALKYL SULFONIC ACIDS, POLYVINYL ALCOHOL, METHYL CELLULOSE, METHYLHYDROXYETHYL CELLULOSE, CARBOXYMETHYL CELLULOSE, AND POLYOXYETHYLENE COMPOUNDS WHICH ARE REACTION PRODUCTS OF ETHYLENE OXIDE WITH SORBITOL-FATTY ACID ESTERS AND WITH MIXTURES OF RESIN AND FATTY ACIDS, IN THE PROPORTIONS, BY WEIGHT, OF ABOUT FROM 20% TO 65% OF PEST CONTROL AGENT, 0.5% TO 10% OF SUSPENDING AGENT AND 0.5% TO 25% OF DISPERSING AGENT, THE TOTAL OF SAID INGREDIENTS NOT EXCEEDING 70%, AND AT LEAST 30% OF WATER, THE SUSPENDING AGENT BEING SWELLED AND DEAGGLOMERATED, AND AT LEAST 90% BY WEIGHT OF THE PEST CONTROL AGENT HAVING A PARTICLE SIZE LESS THAN 10 MICRONS.