GRANULAR WATER SOLUBLE OR HYGROSCOPIC AGRICULTURAL FORMULATIONS AND METHODS OF MAKING THEM

Abstract: A pesticidal formulation in the form of dispersible granules comprising an effective amount of a salt of a water soluble or hygroscopic pesticide adsorbed onto an effective amount of a highly absorbent solid.

Description: Granular water soluble or hygroscopic agricultural formulations and methods of making them Description The present invention relates to dispersible granular formula¬ tions of salts of water soluble or hygroscopic pesticidal" compounds and to methods for making these granular formulations. Granular formulations of pesticides tend to be safer in application and environmentally, as they are more easily handled by the farmer. Dry, flowable formulations of silica and oil solu¬ ble pesticides are known. These formulations are generally ad- sorbed onto a solid carrier, milled and then granulated. However, this technique is generally unacceptable when used with water soluble or hygroscopic agricultural products. The plant growth regulator, known trivially as mepiquat chloride, is a water soluble pesticidal salt and is generally used to con¬ trol various aspects of cotton boll growth. See, for example, Khafaga, Angew. Botanik ∑L, 257-265 (1983); Sawan et al., J. Agronomy & Plant Science 154. 120-128 (1985); U.S. Patents 3,905,798 and 4,447,255. For example, mepiquat chloride has a high water solubility - in general, more than about 600 g/1. The substance is very hygro¬ scopic and readily absorbs moisture from humid air, so that the dry powder can turn to liquid when exposed to ambient humid air. Additionally, the solid material cakes rapidly in storage and sticks to container surfaces, even with initial water contents of less than 0.5%. These properties make it extremely difficult to granulate and disperse mepiquat chloride, for example. There is a need for methods of making dispersible, granular for¬ mulations for water soluble or hygroscopic pesticidal compounds which maintain the biological activity of the water soluble or hygroscopic pesticidal compound and eliminate milling. Hence, it was an object of the present invention to provide an agriculturally acceptable water soluble or hygroscopic pesticidal formulation in a dispersible granular form. Accordingly, dispersible granular formulations of water soluble or hygroscopic pesticidal compounds have been discovered. Also discovered was a method of making these dispersible granular for- mulations of salts of water soluble or hygroscopic pesticidal compounds. The method of the present invention uses highly aborbent solids to form a stable, dry product without the need for a milling step to attain an effective particle size of the dispersed product. The method involves adsorbing the pesticide onto a highly absorp¬ tive carrier. Thereafter, the adsorbed pesticide/carrier composi- tion is granulated by granulating means well known in the art. The granulated pesticide/carrier composition is then dried and the composition is sized to remove any oversize fines. The particularly preferred pesticides of the present invention are salts of water soluble or hygroscopic pesticides. These pre¬ ferred pesticides include, for example, plant growth regulators, including the group consisting of 1, l-dimethyl-3,4-dehydropiperi- dinium bromide, 4-chloro-l, 1-dimethylpiperidinium bromide, 1, 1-dimethylhexahydropyridazinium bromide, and 1, 1-dimethylpiper- idinium chloride; and herbicides such as sodium bentazon and so¬ dium acifluorfen. As used herein, the term "agriculturally acceptable" includes agricultural, industrial and residential use. As used herein, the terms "pesticide(s) " or "pesticidal" include plant growth regulators, insecticides, acaricides, nematocides, fungicides, miticides, herbicides, algicides, bactericides and molluscicides. As used herein, "plant growth regulator(s) " (hereinafter abbre¬ viated as "PGR") or "regulation" includes the following plant responses: inhibition of cell elongation, for example reduction in stem height and internodal distance, strenght ening of the stem wall, thus increasing the resistance to lodging; compact growth in ornamentals for the economic production of improved quality plants; promotion of better fruiting; increasing the num¬ ber of ovaries with a view to stepping up yield; promotion of senescence of the formation of tissue enabling fruit to absciss; defoliation of nursery and ornamental bushes and trees for mail¬ order business in the fall; defoliation of trees to interrupt parasitic chains of infection; hastening of ripening, with a view to programming the harvest by reducing the harvest to one to two pickings and interrupting the food-chain for injurious insects. As used herein, the formulations of the present invention may be used to form both package and tank mix compositions.. The present invention comprises salts of water soluble or hygro- scopic pesticidal compounds comprising an agriculturally and plant growth regulating effective amount of a salt of a hygro¬ scopic pesticidal compound, and more preferably, of a salt of a plant growth regulator (PGR) or a salt of a herbicide. Specific preferred examples include N,N-dimethyl-piperidinium salt, bentazon salt or sodium acifluorfen as a dry flowable highly concentrated powder. Preferred PGRs include salts of the formula: where R is methyl or ethyl; X is the anion of an inorganic or organic, but not phytotoxic acid, preferably bromide or chloride, and A is a chain of 4 or 5 methylene groups, which chain may be substituted by chloro, bromo, methyl, chloromethyl, bromomethyl, hydroxymethyl, and methylene, or which chain containing one or two double bonds, or A is the chain -(CH ) n -NH-, where n is 3 or 4, disclosed in U.S. 3,905,798. Preferred specific examples of PGRs include 1, l-dimethyl-3 ,4-de- hydro-piperidinium bromide, 4-chloro-l,1-dimethylpiperidinium bromide, 1, 1-dimethyl-hexahydropyridazinium bromide and 1, 1-dime¬ thylpiperidinium chloride. The most preferred plant growth regu¬ lator is 1,1-dimethylpiperidinium chloride (also known as N,N-di- methylpiperidinium chloride, mepiquat chloride or as PIX®) . Preferred herbicides include, for example, the sodium salt of bentazon (BASAGRAN®) , the sodium salt of acifluorfen (BLAZER®), the sodium salt of sethoxydim, the dimethylamine salts of 2,4-D, difenzoquat methyl sulf te (AVENGE®) and mixtures thereof. The granules of the present invention may be prepared by adsorb¬ ing the active ingredients onto highly absorptive solid carriers. Thereafter, optional ingredients or additives may be added. The wet powder is then granulated by means well known in the art, in- eluding, but not limited to, extrusion, pan granulation and Schugi agglomeration. The process of the instant invention eliminates the need for a milling step. The elimination of this step reduces the cost and time of production, and avoids worker exposure to respirable dust associated with most commercial milling processes. The granule size is determined by the end application; however, the granule diameter is preferably about 0.7 mm to about 1.5 mm for extrusion and about -8 to about +30 mesh for other granula¬ tion techniques. The wet granules are then dried by means well known in the art, including, but not limited to, oven drying and fluid bed drying. Drying generally takes about 4 to about 60 minutes. After the drying step is completed, the granules are then sized to eliminate fine and dust. The final granule particle size is preferred to be a mixture of about < 1.0 wt% +8 mesh, < 3.0 wt% -30 mesh and < 0.2 wt% -100 mesh. The preferred median dispersed particle diameter size is about < 40 micron after 5 minutes with dissolution without sonics. The loose bulk density is about 0.34 to 0.50 g/ml. A packed bulk density is preferred to be about 0.36 to 0.54 g/ml. When the final granules are suspended, they are preferred to have a solids suspendability content of greater than about 50%, by standard test means of the art. When the granules are suspended, the amount of active pesticide present should be greater than about 90%. The final granule has a preferred nominal diameter of about 1.5 mm. It is preferred to have minimal extraneous materials or contaminants in the product. Absorptive solid carriers may be synthetic or natural, and in¬ clude, for example, synthetic silicas, mineral earths such as si¬ licic acid, silica gels, silicates, talc, kaolin, Attaclay, lime- stone, lime, chalk, bole, loess, clay, dolomite, diatomaceous earth, synthetic calcium silicate (available commercially as i- crocel E) , calcium sulfate, magnesium sulfate, magnesium oxide, and mixtures thereof. The most preferred absorptive solid carrier is synthetic calcium silicate. The synthetic calcium silicate provides significant ab¬ sorption of the active onto the carrier with minimal agglomera¬ tion. This combination has superior tolerance of the varying shear intensity during agitation in the end use tank. In general, the formulations of the present invention contain from about 0.1 to about 95%, and preferably from about 5 to about 50% by weight of active ingredient. The ratio of carrier to active (pesticide plus granulation water) is about 0.1 to about 2.0, and more preferably about 0.2 to about 1.0 percent by weight. While the ratios of the concentrations of the various components of the present invention hereinafter suggested, those skilled in the art will recognize that minor variations may be necessary to accommmodate particular characteristics of acceptable actives which may be employed in this invention. Optionally, dispersing agents may be incorporated into the gran¬ ule in the same manner as the active. Suitable examples of dis¬ persing agents include nonionic or anionic surfactants. Specific suitable examples include condensed sulfonate sodium salt (available commercially as Morwet D-425 from Desoto, Inc., Des Plaines, Illinois), polyvinylpyrrolidone (available commer¬ cially as Polyplasdone XL-10 from International Speciality Products, Wayne, New Jersey or as Kollidon CI M-10 from BASF Cor¬ poration, Parsippany, New Jersey) , organosilicones such as poly- alkylene oxide modified polydimethylsiloxane (available commer¬ cially as Silwet 7607 from Union Carbide Corporation) , alcohol ethoxylates such as 2,6,8-trimethyl-4-nonyloxypolyethyleneethanol (available commercially as Tergitol TMN6 from Union Carbide Chemicals and Plastics Company, Inc.), lignosulfonic acids such as Reax 88A or lignosulfonic acid formulations with wetting agents such as Reax 45DTC (both available commercially from Westavco, Charleston Heights, South Carolina). The most preferred dispersing agents are lignosulfonic acid for- mulations or condensed sulfonate sodium salts. It is most pre¬ ferred to use a mixture of either lignosulfonic acid formulations or condensed sulfonate sodium salts with polyvinylpyrrolidone (PVP) . The dispersing agent may be present in the present inven¬ tion in an amount of from 0 to about 15.0 wt% and more preferably from about 0.5 to about 15.0 wt%. The PVP dispersing agent is preferably present in an amount of 0.0 to 5.0 wt%, and more pre¬ ferably in an amount of about 0.2 to about 2.0 wt%. A wetting agent may also be used in the present invention. Suit- able examples include nonionic and anionic surfactants, and more specifically, mixtures of alkyl carboxylates and sulfonated alkyl naphthalene, and their sodium salts (available commercially as Morwet EFW from DeSoto, Inc., Des Plaines, Illinois). A wetting agent is preferably present in an amount of about 0.0 to 10.0 wt%, and more preferably about 0.5 to about 10.0 wt%. In addition, absorptive filler/binders may be incorporated into the composition of the present invention. Suitable examples of absorptive filler/binders include micas or clays such as kaolin, attapulgite, montmorillonite or bentonite, and mixtures thereof. The most preferred filler/binder is kaolin, in particular delami- nated kaolin (available commercially as Englehard ASP-NC from Englehard Chemical Corp.). Filler/binders may be present in the present invention in an amount of from 0 to about 60 wt%, and more preferably, from about 1.0 to about 40 wt%. In addition to the above-described components, the compositions of the present invention may also include other ingredients or adjuvants commonly employed in the art. Examples of such ingredients include drift control agents, de- foaming agents, preservatives, surfactants, fertilizers, phyto- toxicants, adherents, trace elements, synergists, antidotes, mix¬ tures thereof and other such adjuvants well known in the pesticide art. However, it is preferred to employ the compositions of the pres¬ ent invention along with sequential treatments with these other components for optimal effect. The formulations of the present invention have good storage sta¬ bility. The compositions of the present invention may be applied to above ground portions of plants. The application of liquid and particu- late solid compositions to above ground portions of plants may be carried out by conventional methods, for example, boom and hand application, including sprayers or dusters. The compositions may be applied aerially as a spray, if desired. The mixtures of the present invention are preferably used in the form of aqueous dispersions. The mixtures are applied in a conventional manner, for example, by spraying, atomizing, watering or disinfecting seed. The forms of application depend entirely on the purpose for which the compositions are being used. At all events, they should en¬ sure a fine distribution of the active ingredients in the com¬ position. The above plant growth regulator formulation may then be dis¬ persed in water and sprayed onto plants according to the method of the present invention. The action of the compositions of the present invention are opti¬ mal even at low application rates. For a given composition, the skilled artisan will readily arrive by routine experimentation at a composition having the optimum ratio of the ingredients. Examples Example 1 The following components were used: technical grade (yellow) At 1.5 wt% water in the product described above, the amount of active ingedient (ai) in the formulation is 35.2 wt%. If the product moisture reaches 2 wt%, the formulation will then contain 35.0 wt% of ai. Synthetic calcium silicate (Microcel E, a crystalline silica free (CSF) form of diatomaceous earth) was used as a carrier. A mix¬ ture of alkyl carboxylate and sulfonated alkyl naphthaline, so¬ dium salt (Morwet EFW) was used as a wetting agent. A binder and dispersing agent of condensed naphthalene sulfonate sodium salt (Morwet D-425) was also used. Feed preparation - batch The batch size was computed to give a full charge to the blender to be used. Weighed amounts of each solid raw material were charged to the blender. A stainless steel ribbon blender, paddle mixer, kneader, or other suitable blender was used for homogeniz¬ ing the materials. After liquids (active ingredient and granula¬ tion water) were added to the batch, it contained about 34% water and the bulk density of the extruder feed went up to around 0.55 g/ml. The blender was equipped with spray nozzles for the active ingredient and for water and have appropriate air extrac¬ tion. Blend time for a properly filled ribbon or paddle mixer was about 20 minutes. The Micro-Cel ® E and then the clay were added to the blender. Weighed amounts of mepiquat chloride technical and water were added to a polyethylene or stainless steel liquid mixing vessel with agitator, and stirred for 5 minutes. This is sprayed onto the premixed solids. Blend time after all the liquid is added was about 5 to 10 minutes. Feed preparation - semi-continuous Solid raw materials are blended per the feed preparation described above. A solution of mepiquat chloride and water were prepared using about half of the calculated, theoretical amount of water. This mixture was stirred for about 5 minutes. The blended solids were metered to a continuous mixer with a gravimetric feeder. For this rate of solids, the liquids rate was calculated to give a dry product of about 35 wt% mepiquat chloride. A positive displacement metering pump was calibrated to deliver this flow rate. The liquid is appropriately sprayed onto the mixing solids in the continuous blender. A second liquid stream of water alone was also sprayed onto the mixing solids in the continuous blender. This stream was used to control the consistency of the wet solids which were charged to the extruder. Its rate was adjusted as needed. SUBSTITUTESHEET ISA/EP Extrusion and drying The solids wetted with active ingredient and water were fed to a Luwa basket type extruder*) of appropriate size. The product was extruded with a 1.5 mm die. The extrudate was discharged to a stainless steel fluid bed dryer where the water content was reduced to below 2 wt%. Drying air temperatures up to 75°C were employed without damage to the product. Screening A vibratory screen apparatus equipped with 8 and 30 US Sieve screens to separate oversize and fines from the product were used. The product was screened to about (-8) in a +30 mesh US Sieve. The +8 oversize fraction was extremely small and was reworked into the system manually. The (-30) fines ranged from 2 to 8 wt% of the dryer discharge. These may be added to dry ' solids blender (along with any recycled dust). An adjustment in the water rate may be needed, which is why the semi-continuous process is preferred. Hygroscopicity tests Hygroscopicity tests were conducted which showed that the product absorbed water at a rate dependent upon the relative humidity. At 76% relative humidity, the product gained only 5 wt% after 2 hours' exposure and completely maintained its granular struc¬ ture. Particle size determination The method of evaluating performance of the formulation was to determine the medium dispersed particle size (diameter) . A Cilas Granulometre Model 715 was used. A sample was added to water, which is stirring at about 50% power. After about five minutes, the median particle size was determined. The sample was then sonicated for thirty seconds and another median particle size was determined. Sonication or use of sonic energy provides very significant agitation. *) = LCI basket type extruder: very low pressure extruder; wet powder is fed to the top of the extruder and a blade wipes it through a screen; extrudate, wet noodles, are collected and later dried. SUBSTITUTESHEET ISA/EP The most preferred formulations include the ones with substan¬ tially the same median dispersed particle size values for both pre- and post-sonication. All of the following formulations were tested according to the above procedure. Table 1 Barden ® Fine Clay 22.6 20.0 27.5 21.0 24.9 ASP-NC 2 ) _ _ _ _ _ Residual Water 1.5 1.5 1.5 1.5 1.5 1 ) a finely milled, precipitated, synthetic amorphous silicon dioxide hydrate (Chemical Abstracts no. 112926-00-8) 2 ) delaminated kaolin clay (Chemical Abstracts no. 1332-58-7) SUBSTITUTE SHEET ISA/EP Table 2 Formulation No. 10 11 12 *) technical grade 5 The following examples used the methods described in the above examples but used salts of water soluble pesticides. As can be seen from the sonic testing, the pesticidal formulations gener¬ ated active products. 0 5 SUBSTITUTE SHEET ISA/EP Example 2: Acifluorfen WG Acifluorfen (34.5 g/kg) 34.6% Micro-Cel ® E 25.6% Morwet ® EFW 3.2% Morwet ® D-425 5.3% Agrimer ATF 1.0% Sodium Citrate 14.8% Englehard ASP-NC 14.1% Residual Water 1.5% No Sonics - 20 micron median particle size Sonics - 17 micron median pariticle size Example 3: Bentazon WG Na Bentazon (400 g/kg) 40.1% Micro-Cel ® E 22.4% Morwet ® EFW 2.4% Reax ® 5DTC 6.5% Agrimer ATF 0.8% Barden ® Clay 26.3% Residual Water 1.5% No Sonics - 18 micron median particle size Sonics - 18 micron median pariticle size Whereas particular embodiments of the invention have been described above for purposes of illustration, it will be appreciated by those skilled in the art that numerous variations of the details may be made without departing from the invention as described in the appended claims. SUBSTITUTE SHEET ISA/EP

Claims: Claims 1. A pesticidal formulation in the form of dispersible granules comprising an effective amount of a salt of a water soluble or hygroscopic pesticide adsorbed onto an effective amount of a highly absorbent solid. 2. The formulation of claim 1 wherein the highly absorbent solid is selected from group consisting of synthetic calcium sili¬ cates, fumed silicas, precipitated silicas and diatomaceous earth. 3. The formulation of claim 1 wherein the formulation includes wetting agents, dispersing agents and filler/binders. 4. The formulation of claim 3 wherein the wetting agents are surfactants. 5. The formulation of claim 3 wherein the wetting agents are se¬ lected from the group consisting of mixtures of alkyl carb- oxylates and sulfonated alkyl naphthalene and their sodium salts. 6. The formulation of claim 3 wherein said dispersing agents are nonionic or anionic surfactants. 7. The formulation of claim 3 wherein said dispersing agents are selected from the group consisting of condensed sulfonate so- dium salts, polyvinylpyrrolidone, organosilicones, alcohol ethoxylates, lignosulfonic acids, lignosulfonic acid formula¬ tions with wetting agents. 8. The formulation of claim 3 wherein said dispersing agents are lignosulfonic acid formulations or condensed sulfonate sodium salts. 9. The formulation of claim 3 wherein said dispersing agent is a mixture of either lignosulfonic acid formulations or con- densed sulfonate sodium salts and polyvinylpyrrolidone. 10. A method of making a dispersible, granular formulation of a salt of a water soluble or hygroscopic pesticide comprising: a) adsorbing said pesticide onto a highly absorptive carrier; b) granulating the adsorbed pesticide/carrier composition by granulating means; c) drying the granulated pesticide/carrier composition by 5 drying means; and d) sizing the pesticide/carrier composition to remove any oversize fines. 10 11. The method of claim 10 wherein the highly absorbent solid is selected from the group consisting of synthetic calcium sili¬ cates, fumed silicas, precipitated silicas and diatomaceous earth. 15 12. The method of claim 10 wherein the formulation includes wet¬ ting agents, dispersing agents and filler/binders. 13. The method of claim 12 wherein the wetting agents are surfactants. 20 14. The method of claim 12 wherein the wetting agents are se¬ lected from the group consisting of mixtures of alkyl carb- oxylates and sulfonated alkyl naphthalene and their sodium salts. 25 15. The method of claim 12 wherein said dispersing agents are nonionic or anionic surfactants. 16. The method of claim 12 wherein said dispersing agents are se- 30 lected from the group consisting of condensed sulfonate so¬ dium salts, polyvinylpyrrolidone, organosilicones, alcohol ethoxylates, lignosulfonic acids, lignosulfonic acid formula¬ tions with wetting agents. 35 17. The method of claim 12 wherein said dispersing agents are lignosulfonic acid formulations or condensed sulfonate sodium salts. 18. The method of claim 12 wherein said dispersing agent is a 40 mixture of either lignosulfonic acid formulations or con¬ densed sulfonate sodium salts and polyvinylpyrrolidone. 45

Inventors: BYRNE THOMAS, FERSCH KEN, BYRNE, THOMAS, FERSCH, KEN
Applicants: BASF AG, BASF CORP, BYRNE THOMAS, FERSCH KEN, BASF AKTIENGESELLSCHAFT, BASF CORPORATION, BYRNE, THOMAS, FERSCH, KEN
Application year: 1993
Main classification: A01N25
IPC codes: A01N25, A01N33, A01N43, A01P21