Field of the invention:

The present invention relates to granular formulations comprising pyrazosulfuron ethyl and pretiiachlor. More particularly, the present invention relates to storage stable herbicidal granular formulations comprising pyrazosulfuron ethyl and pretiiachlor.

Background of the invention: The use of herbicide combinations is a widespread and documented practice in the agricultural community. Herbicidal combinations offer significant advantages over individual applications including improved and extended weed control, reduced herbicide rates and application costs, shorter contact times for improved results in flowing water, less stringent use restrictions, improved selectivity, improved spectrum of weeds controlled, reduced cost and reduced residue problems. However, identifying appropriate herbicide application rates and combinations is essential to achieve synergistic weed control.

Indian Patent No. 210952, incorporated herein by reference in its entirety, discloses a synergistic herbicidal composition comprising a selective herbicide pyrazosulfuron ethyl in combination with at least another herbicide selected from butachlor, pretiiachlor and 2,4-D. This patent teaches several emulsifiable concentrate (EC) formulations comprising pyrazosulfuron ethyl in an amount of 3%, 1%, 1.4%, 2% and 50% in combination with pretiiachlor in an amount of about 35%, 40%, 40%, 50% and 50% respectively. Further, this patent teaches that pyrazosulfuron ethyl and pretiiachlor offer a remarkably synergistic weed control within a ratio of 1 :9 to about 1 :59. Moreover, this patent suggests preparation of the synergistic compositions of pyrazosulfuron ethyl in combination with pretiiachlor in either concentrated liquid or as a granular formulation. However, a stable granular formulation comprising pyrazosulfuron ethyl and pretiiachlor is not exemplified by this patent. In contrast, the present inventors have found that an emulsifiable concentrate formulation comprising pyrazosulfuron ethyl and pretiiachlor degraded by about 85% in pyrazosulfuron ethyl content and 60% in pretiiachlor content respectively subsequent to being stored at 54±2°C for 14 days. Moreover, a coated granular (CG) formulation prepared using bentonite, attapulgite or ceramic carrier granules as disclosed in this patent and comprising pyrazosulfuron ethyl and pretilachlor also degraded by 25-87% in pyrazosulfuron ethyl content and 15-55% in pretilachlor content respectively after storage at 54±2°C for 14 days when prepared using the conventional coated granules preparation process. Accordingly, despite the combination of pyrazosulfuron ethyl and pretilachlor being synergistic, there are no commercially viable formulations available in the market due to the notorious susceptibility of pyrazosulfuron ethyl to degradation on storage, which is aggravated due to the presence of pretilachlor. Thus, there exists a need in the art for a storage stable formulation comprising pyrazosulfuron ethyl and pretilachlor.

The granular formulations offer significant advantages over the liquid formulations such as ease of handling, ease of use, reduced work exposure, reduced toxicity, reduced spillage and waste disposal and less field drift. Moreover, it has been observed by the present inventors that pyrazosulfuron ethyl and pretilachlor are rendered more vulnerable to degradation when presented in a liquid formulation. Thus, there exists a need in the art for a storage stable granular formulation comprising pyrazosulfuron ethyl and pretilachlor.

However, the selection of the appropriate carriers for a granular formulation in order to retain the desired characteristics of the granules such as the liquid holding capacity, non-existent dust levels, high attrition resistance and chemical inertness is not reasonably predictable by a skilled formulator.

The liquid holding capacity measures the amount of liquid i.e. the active ingredient that could be absorbed by the granules without a significant loss of the flowability of the granule. A high liquid holding capacity of a carrier enables a formulator to prepare a concentrated formulation or allows him to accommodate more than one compatible pesticide within the same granule. Thus, there is a need in the art for a granular formulation comprising pyrazosulfuron ethyl and pretilachlor wherein the carrier material present within the granules possesses a high liquid holding capacity without compromising the flowability of the formulation. Preferably, a high attrition resistance ensures non-existence of dust within the formulation which reduces the work exposure thereby enhancing the desirability of the formulation. Another challenge to a formulator in preparing a granular formulation is the degree of chemical inertness of the granule towards the pesticide. Moreover, it is not always reasonably predictable to select a carrier material that is simultaneously inert to two different pesticides present in the preferred synergistic combination. It has been observed that even if the carrier surface is mildly reactive to one of the active ingredients of the combination, it results into a breakdown of the other pesticide thereby reducing the efficacy of the formulation thereby leading to less or no weed control. Thus, the choice of an appropriate carrier for a granular formulation is often an undesired compromise based on an informed consideration of these characteristics of the known carrier materials.

Another known method to reduce the reactivity of the carrier material to the pesticide is the incorporation of a deactivator such as glycols etc., which blocks the active sites on the carrier material thereby preventing their interaction with the active ingredient. However, the presence of a deactivator is disadvantageous for two primary reasons. The presence of a deactivator increases the load of liquid on the granules thereby reducing the flowability of the formulation. Another reason is that the presence of a deactivator significantly increases the formulation cost and yet cannot ensure the stability of a pesticide such as pyrazosulfuron ethyl that is notoriously susceptible to degradation, especially in the presence of pretilachlor. Moreover, pyrazosulfuron ethyl has been shown to be susceptible to degradation on the commonly used carrier materials with or without pretilachlor.

Accordingly, there exists a need in the art for selecting a stabilizing agent that would enable simultaneous loading of pyrazosulfuron ethyl and pretilachlor herbicides without compromising the stability of these herbicides. It is preferable that the selected stabilizing agent retains its stabilizing property even in the presence of a carrier having a sufficient or high liquid holding capacity, low surface activity, non-dustiness and attrition resistance.

Mingelgrin, U., Saltzman, S. and Yaron, B. (1977) report the surface induced hydrolytic degradation of a number of pesticides over kaolin, which is predominantly hydrated aluminum silicate. This hydrolytic degradation was attributed to ligand water associated with the exchangeable cations on the kaolin surface. Thus, the choice of a selective carrier granule for both of pyrazosulfuron ethyl and pretilachlor with desirable storage stability and without compromising the desirable attributes of the formulation such as liquid holding capacity, non-existent dust levels, high attrition resistance and chemical inertness presents a formidable challenge to a skilled formulator. The magnitude of this formulation problem is corroborated by the absence of any commercially marketed formulation comprising pyrazosulfuron ethyl and pretilachlor despite the established synergistic correlation existing between these two herbicides. Moreover, kaolin is a readily available carrier material and its use in formulations is advantageous for commercial reasons. Thus, there is a secondary need in the art for a formulation that shows reduced degradation in the presence of kaolin.

CN 12876910 discloses a formulation comprising pretilachlor and pyrazosulfuron ethyl indicated for weed control in a paddy field. The disclosed formulations are grainy or wettable powder formulations comprising, apart from the active herbicides, (i) a bonding agent selected from polyvinyl alcohol, polyethylene acetate, starch and Arabic gum; (ii) stabilizers selected from sulfate and phosphate; (iii) auxiliary agents; and (iv) carriers such as kaolin, clay, china clay, diatomite, sand and bentonite. This patent does not indicate any particular preference for a preferred carrier granule, which is desirable to arrive at a stable formulation. This patent recognizes the stability problem of pyrazosulfuron ethyl and proposes to overcome the same by the addition of a stabilizer. However, despite repeated attempts of the present inventors to prepare a one-pot solid granular formulation of pyrazosulfuron ethyl and pretilachlor according to the teachings of this patent, a storage stable granular formulation cou.ld not be achieved. It was found that in such a one-pot formulation according to the disclosure of this Chinese patent, the content of pyrazosulfuron ethyl degraded by about 83-87% during storage at 54±2°C for 14 days.

In a further experiment, formulation made in accordance with the disclosure of this Chinese patent comprising 1.4% pyrazosulfuron ethyl, 40% pretilachlor, 29.3% sodium lignosulfonate and 29.3% ammonium sulfate was tested for pyrazosulfuron ethyl stability at elevated temperatures at 40°C and 54°C for 14 days. CN'910 discloses the use of a sulfate as a stabilizing agent. Therefore, it was expected to afford a stable formulation. In contrast, it was found that a stabilized formulation according to the invention disclosed therein was not possible, the results being tabulated below: Formulation % PSE active % PSE active % PSE content ingredients content at 0 day content after 14 days degraded after 14 at 54°C days at AHS, 54°C

1 .4 % PSE, 40% 1.79 1.47 17.88 (high pretilachlor, 29.3% degradation) ammonium sulfate

and 29.3% sodium

lignosulfonate

Thus, a need remains in the art to solve the storage stability problem inherent within the known combination of pyrazosulfuron ethyl and pretilachlor to arrive at a storage stable granular ^' formulation. A need remains in the art for a storage stable granular formulation comprising pyrazosulfuron ethyl and pretilachlor wherein the inherent degradation characteristics of both pyrazosulfuron ethyl and pretilachlor are not aggravated due to the presence of the other herbicide or any of the carriers.

It is further preferred that the desired granular formulation be substantially free from visible extraneous matter and hard lumps such that the formulation may be used by direct broadcasting for preventing, treating, diminishing or reducing the severity and incidence of yield reduction due to the presence of weeds in the crop field.

Another problem aggravating the degradation of pyrazosulfuron ethyl in the desired formulation is the mutual incompatibility between pyrazosulfuron ethyl, stable at a neutral pH and pretilachlor, which is generally stable at acidic pH. It is generally difficult to co-formulate two or more pesticides which are stable at different pH values. It is therefore desirable to provide granular formulations comprising pyrazosulfuron ethyl and pretilachlor wherein the two mutually incompatible active ingredients do not contact each other for a substantial period of time. It is furthermore desirable to provide a process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor wherein the process does not allow the two mutually incompatible active ingredients to contact each other for a substantial period of time thereby enhancing the storage stability of the formulations. It is further desired to provide granular formulations comprising pyrazosulfuron ethyl and pretilachlor which are capable of releasing the active ingredients slowly over an extended period of time after its soil application. Thus, a need remains in the art to solve the aforesaid problems, in particular the storage stability problem inherent within the known combination of pyrazosulfuron ethyl and pretilachlor to arrive at a storage stable coated granular or coated granular formulation. These and other objects of the present invention are met by the invention described hereinafter.

Advantages of the Invention:

The various embodiments of the present invention may, but do not necessarily, confer one or more of the following advantages and/or objects:

An object of the present invention is to provide a storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor.

Another object of the present invention is to provide a granular formulation of pyrazosulfuron ethyl and pretilachlor which offers significant advantages including improved and extended weed control, reduced herbicide rates and application costs, shorter contact times for improved results in flowing water, less stringent use restrictions, improved selectivity, improved spectrum of weeds controlled, reduced cost or reduced residue problems.

Another object of the present invention is to provide a storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor which displays reduced susceptibility of pyrazosulfuron ethyl to degradation, particularly in the simultaneous presence of pretilachlor.

Yet another object of the present invention is to provide storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor which offers significant advantages over liquid formulations such as safety of use, ease of handling, ease of use, reduced work exposure, reduced toxicity, reduced spillage, waste disposal or less field drift.

Yet another object of the present invention is to provide storage stable granular formulations of pyrazosulfuron ethyl, pretilachlor and including a carrier having a sufficient and beneficial liquid holding capacity, non-existent dust levels, high attrition resistance or chemical inertness.

Another object of the present invention is to provide a storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor such that the formulation is substantially free of a deactivator.

Still further object of the present invention is to provide storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor wherein said granular formulation is substantially free of visible extraneous matter and hard lumps.

Another object of the present invention is to provide a storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor wherein the two mutually incompatible active ingredients do not contact each other for a substantial period of time.

Yet another object of the present invention is to provide a storage stable granular formulation of pyrazosulfuron ethyl and pretilachlor which is capable of releasing the active ingredients slowly over an extended period of time in field after its soil application. Another object of the present invention is to provide a process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor wherein the process does not allow the two mutually incompatible active ingredients to contact each other for a substantial period of time.

Yet another object of the present invention is to provide a process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor wherein the process substantially improves the storage stability of the resultant formulations.

These and the other advantages may be realized by reference to the remaining portions of the specification.

Summary of the invention:

A storage stable granular formulation comprising:

(a) a herbicidally effective amount of pyrazosulfuron ethyl;

(b) a herbicidally effective amount of pretilachlor; and (c) a stabilizing effective amount of sodium lignosulfonate, optionally in combination with sodium salt of a sulfonated aromatic polymer, said sodium lignosulfonate being substantially free of a reducing sugar. A process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor, said process comprising:

(a) dissolving a stabilizing effective amount of sodium lignosulfonate in a sufficient quantity of water, said sodium lignosulfonate being substantially free of a reducing sugar and optionally being present in combination with sodium salt of a sulfonated aromatic formaldehyde condensate polymer;

(b) adding a herbicidally effective amount of pretilachlor slowly to the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce an emulsion;

(c) adding a herbicidally effective amount of pyrazosulfuron ethyl to said emulsion to obtain a first mixture; and

(d) granulating said first mixture to obtain the storage stable granular formulations.

A storage stable granular formulation comprising:

(a) a herbicidally effective amount of pyrazosulfuron ethyl;

(b) a herbicidally effective amount of pretilachlor; and

(c) a stabilizing effective amount of sodium lignosulfonate, optionally in combination with sodium salt of a sulfonated aromatic polymer, said sodium lignosulfonate being substantially free of a reducing sugar;

wherein said herbicidally effective amounts of pyrazosulfuron ethyl, pretilachlor and stabilizing effective amount of sodium lignosulfonate are emulsified; and said emulsion is co-extruded or sprayed with a carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof or sprayed on provided blank granules selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite.

A process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor, said process comprising: (a) dissolving a stabilizing effective amount of sodium lignosulfonate in a sufficient quantity of water, said sodium lignosulfonate being substantially free of a reducing sugar and optionally being present in combination with sodium salt of a sulfonated aromatic formaldehyde condensate polymer;

(b) adding a herbicidally effective amount of pretilachlor slowly to a portion of the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce a first emulsion;

(c) adding a herbicidally effective amount of pyrazosulfuron ethyl slowly to the remaining portion of the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce a second emulsion;

(d) separately granulating said first and second emulsions to obtain first and second granules comprising pretilachlor and pyrazosulfuron ethyl respectively; and

(e) mixing said first and second granules homogenously in a predetermined ratio.

In another aspect, the present invention provides a storage stable granular formulation comprising:

(a) first granules, said first granules prepared by granulating a first emulsion comprising a herbicidally effective amount of pyrazosulfuron ethyl in a sufficient quantity of water in the presence of a stabilizing effective amount of sodium lignosulfonate, said sodium lignosulfonate being substantially free of a reducing sugar and being optionally in combination with sodium salt of a sulfonated aromatic polymer formaldehyde condensate;

(b) second granules, said second granules prepared by granulating a second emulsion comprising a herbicidally effective amount of pretilachlor in a sufficient quantity of water in the presence of a stabilizing effective amount of sodium lignosulfonate, said sodium lignosulfonate being substantially free of a reducing sugar and being optionally in combination with sodium salt of a sulfonated aromatic polymer formaldehyde condensate; wherein said storage stable formulation comprises said first and second granules admixed in a predetermined ratio.

Additional features and advantages of the proposed invention will be apparent from the detailed description that follows, which illustrates by way of example, the most preferred features of the proposed invention which are not to be construed as limiting the scope of the invention described herein.

Detailed description of the preferred embodiments):

It has surprisingly been found that it is possible to stabilize pyrazosulfuron ethyl, even in the presence of pretilachlor, by co-formulating these two incompatible herbicides in the presence of sodium lignosulfonate, wherein the sodium lignosulfonate is substantially free of a reducing sugar and is optionally present in combination with sodium salt of a sulfonated aromatic formaldehyde condensate polymer. Another advantage of the present invention is in providing an improved process for the preparation of the storage stable formulations of the present invention. In this aspect, it has been found that further improvement in the stability of the desired formulations comprising pyrazosulfuron ethyl and pretilachlor could be achieved by emulsifying both the herbicides prior to granulating the pre-formed emulsions. Hitherto, it has not been possible to stabilize · pyrazosulfuron ethyl, which is known to be notoriously susceptible to degradation, and which is further aggravated due to the presence of pretilachlor.

It has been surprisingly found that enhancement in stability of pyrazosulfuron ethyl could be achieved by formulating pretilachlor and pyrazosulfuron ethyl in sodium lignosulfonate that is substantially free of a reducing sugar. Surprisingly, the stability of both pyrazosulfuron ethyl and pretilachlor demonstrated a strong correlation to the level of reducing sugars found in the sodium lignosulfonate that was utilized in the formulation. It has been further surprisingly found that further enhancement in the stability of the formulations of the present invention could be achieved by emulsifying pyrazosulfuron ethyl and pretilachlor, either together or individually, prior to being granulated. Without wishing to be bound by theory, it is believed that the formation of an emulsion prior to the granulation causes micellar encapsulation of the herbicides, which prevents pretilachlor from contacting pyrazosulfuron ethyl for a substantial period of time thereby leading to a substantial improvement in the stability of the formulation.

Accordingly, in one aspect, the present invention provides a storage stable granular composition comprising a herbicidally effective amount of pyrazosulfuron ethyl together with a herbicidally effective amount of pretilachlor in the presence of sodium lignosulfonate surfactant, wherein said sodium lignosulfonate surfactant is substantially free of a reducing sugar. Preferably, in an embodiment, said pyrazosulfuron ethyl and pretilachlor are emulsified in the presence of sodium lignosulfonate prior to being granulated.

Accordingly, in an aspect, the present invention provides a storage stable granular formulation comprising:

(a) a herbicidally effective amount of pyrazosulfuron ethyl;

(b) a herbicidally effective amount of pretilachlor;

(c) a stabilizing effective amount of sodium lignosulfonate, optionally in combination with sodium salt of a sulfonated aromatic polymer, said sodium lignosulfonate being substantially free of a reducing sugar.

In a preferred embodiment of this aspect of the invention, said herbicidally effective amount of pyrazosulfuron ethyl, pretilachlor and stabilizing effective amount of sodium lignosulfonate are emulsified; and said emulsion is co-extruded or sprayed with a carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof or sprayed on provided blank granules ^' selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite.

In this embodiment, the pre-formed emulsion comprising pretilachlor and pyrazosulfuron ethyl may be either (i) admixed with an inert carrier selected from soapstone, kaolin, talc and mixtures thereof and prepared a dough therefrom, the dough being extruded and dried to afford the target granules; or (ii) sprayed on blank granules selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite and dried to afford the target granules. It has been found that irrespective of the process used to granulate the pre-formed emulsion, whether by extrusion or spraying, the resultant granules always displayed enhanced stability of pyrazosulfuron ethyl when the solution presented for granulation was an emulsion comprising either pyrazosulfuron ethyl or pretilachlor or both.

In yet another embodiment, the pre-formed emulsion comprising pyrazosulfuron ethyl and pretilachlor may alternately be admixed with an inert carrier selected from soapstone, kaolin, talc and mixtures thereof and spray dried in a spray dryer or a fluid bed spray dryer (FBD) to afford the target granular formulation.

In another embodiment, the pre-formed emulsion comprising pyrazosulfuron ethyl and pretilachlor may be sprayed on blank granules prepared from soapstone, kaolin, talc and mixtures thereof using conventional methods. The sprayed granules may thereafter be dried in a fluid bed dryer to afford the target granular formulation.

Thus, in another aspect, the present invention provides a process for the preparation of storage stable granular formulations comprising pyrazosulfuron ethyl and pretilachlor, said process comprising:

(a) dissolving a stabilizing effective amount of sodium lignosulfonate in a sufficient quantity of water, said sodium lignosulfonate being substantially free of a reducing sugar and optionally being present in combination with sodium salt of a sulfonated aromatic formaldehyde condensate polymer;

(b) adding a herbicidally effective amount of pretilachlor slowly to the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce an emulsion;

(c) adding a herbicidally effective amount of pyrazosulfuron ethyl to said emulsion to obtain a first mixture; and

(d) granulating said first mixture to obtain the storage stable granular formulations.

In an embodiment of the instant aspect of the present invention, the step of granulating the first mixture (emulsion) is not particularly limiting. In a preferred embodiment, granulating the instant emulsions may be carried out using a process selected from:

(a) admixing the pre-formed emulsion with an inert carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof and preparing a dough therefrom, extruding the prepared dough and drying the extruded product;

(b) spraying the pre-formed emulsion on blank granules selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite and drying the granules; and

(c) admixing the pre-formed emulsion with an inert carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof and spray dried in a spray dryer or a fluid bed spray dryer (FBD) to afford the target granular formulation.

The term "herbicidally effective amount" of either pyrazosulfuron ethyl or pretilachlor is that quantity of pyrazosulfuron ethyl and/or pretilachlor which when applied in that quantity will provide the required control of weeds. The particular amount is dependent upon many factors including, for example, the crop, weeds sought to be controlled and the environmental conditions. The selection of the proper quantity of pyrazosulfuron ethyl and/or pretilachlor to be applied, however, is within the expertise of one skilled in the art and is not considered particularly limiting.

In an embodiment of the present invention, the herbicidally effective amount of pyrazosulfuron ethyl comprises from about 0.01% to about 5% by total weight of the formulation. Still more preferably, the storage stable granular formulations according to the present invention comprise about 0.05% to about 4.0% by weight of pyrazosulfuron ethyl.

In another embodiment, the herbicidally effective amount of pretilachlor comprises from about 1% to about 50% by total weight of the formulation. Still more preferably, the storage stable granular formulations according to the present invention comprise about 2% to about 45% by weight of pretilachlor. In a further preferred embodiment, the herbicidally effective amount of pyrazosulfuron ethyl comprises about 0.15% or about 1.4% or about 1.5% by total weight of the formulation.

In further preferred embodiments, the herbicidally effective amount of pretilachlor is equivalent to about 6% by weight of the formulation or about 40% by weight of the formulation.

In a further preferred embodiment, the granular formulation according to the present invention comprises about 0.15% of pyrazosulfuron ethyl together with about 6% of pretilachlor or about 1.4% of pyrazosulfuron ethyl together with about 40% of pretilachlor by total weight of the formulation.

The granular formulation according to the present invention further comprises a stabilizing effective amount of sodium lignosulfonate. The term "stabilizing effective amount" used in reference to the amount of sodium lignosulfonate in the granular formulation of the present invention means an amount such that not more than 7% by weight of pyrazosulfuron ethyl in the granular formulation is degraded upon exposure to 54°C. It may be noted that stability measurements according to the present invention were directed in majority to the stability measurement of pyrazosulfuron ethyl instead of pretilachlor owing to (i) the greater effective amount of pretilachlor included within the formulations of the present invention; and (ii) the greater susceptibility of pyrazosulfuron ethyl towards degradation. However, this should not be construed to mean that the stability of pretilachlor is not a concern for a person skilled in the art. The present invention achieves acceptable stability for pretilachlor in addition to the achievement of superior stability for pyrazosulfuron ethyl.

In an embodiment, the amount of sodium lignosulfonate present within the granular formulations according to the present invention varies from 0.5 % to a sufficient quantity (QS) % by total weight of the formulation. In another embodiment, the amount of sodium lignosulfonate within the granular formulations according to the present invention varies from about 1 % to about 95% by total weight of the formulation.

It has been surprisingly found that the degradation stability of pyrazosulfuron ethyl within the granular formulation of the present invention is intricately linked to the amount of reducing sugar present in the quantity of sodium lignosulfonate. The sodium lignosulfonate available commercially contains residual amounts of reducing sugar monomers, which are typically formed from wood cellulose during pulping. The reducing sugars typically found in sodium lignosulfonate include mannose, xylose, galactose, glucose, arabinose and rhamnose.

It was surprisingly found that the degradation of pyrazosulfuron ethyl content in the granular formulation of the present invention could be controlled to within 10% when sodium lignosulfonate was substantially free of reducing sugars. The term "substantially free of used in reference to the amount of reducing sugars in the sodium lignosulfonate means an amount of reducing sugars which is not more than 7%, preferably not more than 3% - 5% by weight of the total lignosulfonate used in the granular formulations of the present invention. In an embodiment, the amount of reducing sugars in the sodium lignosulfonate means an amount of reducing sugars which is from about 0.01% and not more than 1% by weight of the total lignosulfonate content of the formulations according to the present invention.

Lignosulfonates having varying degrees of sugar content and molecular weight are available in the art. Some of the lignosulfonates currently available along with their molecular weight ranges are tabulated below:

It should be understood that the preferred trade names listed above are only exemplary and any grade of sodium lignosulfonate having reducing sugar content less than 7%, preferably less than 3% - 5% and more preferably less than 1% may be conveniently used in embodiments of the present invention, irrespective of its manufacturing origin. In a preferred embodiment, lignosulfonates substantially free of reducing sugar, are preferably selected such that the preferred molecular weight ranges are within from about 5000 D to about 50000 D. Preferably, ultra-filtrated grades of lignosulfonates are selected which are substantially free of sugar content and have preferred medium molecular weights.

In an embodiment, the lignosulfonate is preferably used in a mixture with a dispersant component comprising a sodium salt of sulfonated aromatic formaldehyde condensate polymer. A preferred dispersing component comprises sodium naphthalene sulfonate formaldehyde condensate. The ratio of admixing a lignosulfonate and the dispersing component is not particularly limiting and may be conveniently selected by a person skilled in the art. A preferred admixing ratio is 1 :10 to 10:1 , more preferable being 1 :1.

The granular formulations according to the present invention comprise a carrier selected from soapstone, kaolin, talc, titanium dioxide and admixtures thereof in any ratio. The carrier may be present in an amount of from about 0% to sufficient quantities (q.s.) by total weight of the formulation to a total of 100% weight of the formulation. Preferably, the carrier may be admixed in any suitable ratio with the lignosulfonate prior to being included within the formulations of the present invention. A preferred admixing ratio for the lignosulfonate, including the dispersing component, to the carrier is 1 : 1.

In a preferred embodiment, the preferred surfactant sodium lignosulfonate may be combined with titanium dioxide as the only adjuvants to provide the storage stable granular formulations of the present invention. In this embodiment, sodium lignosulfonate may be present in an amount of about 40%, about 50% or about 60% of the total adjuvant content of the formulations while the remaining may be titanium dioxide.

Comparative tests

Exemplary formulations were prepared according to the following general compositions and evaluated for AHS stability at 54°C for 7 and 14 days. General Composition

Processing conditions

Water used to prepare dough: 22.5 g

Extruder: Fuji Paudal/ Dome

Diameter of perforation: 1.0 mm

Drying equipment: FBD

Temperature of drying: 65-75°C 8 grams sodium lignosulfonate was dissolved in 22.5 g water, to which 6.5 gram pretilachlor was added. The mixture was stirred vigorously to obtain an emulsion to which 0.20 gram pyrazosulfuron ethyl was added. The resulting emulsion was sprayed on inert carriers, either on blank granules (bentonite or attapulgite) or was blended with inert carriers like soapstone, kaolin and/or powder silica and/or talc and/or titanium dioxide and the resultant blend was either extruded or sprayed to obtain granules. The resulting granules were dried to remove the excess water content to obtain the granular formulations.

The following examples illustrate embodiments of the proposed invention that are presently best known. However, other embodiments can be practiced that are also within the scope of the present invention. All of the agrochemical formulations, according to the scope of the present invention and exemplified below had excellent storage stability properties.

The stability results of the exemplary formulations prepared according to the above general formula are: S No. Surfactant/Carrier Pyrazosulfuron Degradation Pretilachlor Degradation /Example ethyl content (%) content (%) No. Amb AHS Amb AHS

1 Ultrazine NA 0.1821 0.1802 1.04 6.06 5.97 1.48

Talc

2 Ufoxane 3A 0.1945 0.1898 2.45 6.12 5.63 8.00

Talc

3 Borresperse NA 0.1846 0.1840 0.35 6.25 5.95 4.8

Talc

4 Calcium 0.1859 0.1629 12.39 6.05 5.95 1.65

lignosulfonate

Talc

5 Ammonium 0.1910 0.1495 21.75 Not analyzed due to heavy lignosulfonate degradation in

Talc pyrazosulfuron ethyl

6 Surfactant (0%) 0.1953 0.1737 11.05 5.24 4.97 5.15

Talc QS

7 Ultrazin NA 0.2043 0.1948 4.65 5.80 5.63 2.93

Kaolin

8 Surfactant (0%) 0.2066 0.0333 83.88 6.00 5.84 2.66

Kaolin (QS)

9 Surfactant (0%) 0.2058 0.0502 75.607 6.25 6.08 2.72

Kaolin (QS)

10 Vanisperse CB 0.1922 0.1886 1.87 4.00 3.98 0.5

Talc

11 Vanisperse CB 0.1961 0.1927 1.73 6.93 6.41 7.5

Talc

12 Borresperse 3A 0.221 0.201 9.04 6.02 5.68 5.64

13 Norlig SA 0.4340 0.4016 7.05 6.22 6.14 1.29 Comparative example 14

Pyrazosulfuron ethyl and pretilachlor were granulated separately in magnesium silicate only using the process described in general composition example above, without any surfactant being dissolved initially into water. The stability of individual granules and in combination was evaluated in magnesium silicate (90-95% constituent in talc).

Compositions

A. PSE granulation:

Processing conditions

Extruder: Fuji Paudal/ Dome

Diameter of perforation: 1.0 mm

Drying equipment: FBD

Temperature for drying: 65-75°C Results

Herein, ' ^* ' denotes the degradation for pretilachlor was not measured due to heavy degradation observed in pyrazosulfuron ethyl. It was thus concluded that pyrazosulfuron ethyl is unstable in magnesium silicate but surprisingly stable in talc. It is well known that 90- 95% constituent in talc comprises magnesium silicate. Hence, it was considered surprising that pyrazosulfuron ethyl was stable in talc but exhibited heavy degradation in magnesium silicate. Example 15

The following formulation was prepared using the same procedure as for the above examples.

Degradation data: The resultant formulation was found stable in both pyrazosulfuron ethyl and pretilachlor content. Example 16 (6.15G)

The following formulation was prepared using the same procedure as for the above examples.

Degradation data: The resultant formulation was found surprisingly stable pyrazosuifuron ethyl and pretilachlor content. It was thus concluded that stabilizing pyrazosuifuron ethyl required an effective amount of sodium lignosulfonate which is substantially free of reducing sugar in combination with a carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof. The resultant formulations were found stable when prepared from a pre-formed emulsion, which was granulated using any granulation technique discussed hereinabove.

In an embodiment, the granular formulation according to the instant invention additionally comprise from about 0.01 % to about 15% of a safener.

More preferably, the amount of a safener varies from about 0.01% to about 25% by total weight of the herbicidal component of the formulations according to the present invention. In an embodiment, the safener is fenclorim although other safeners are not excluded.

In another aspect, the present invention provides a storage stable granular formulation of pyrazosuifuron ethyl and pretilachlor wherein the two mutually incompatible active ingredients do not contact each other for a substantial period of time. In this aspect, the formulation comprises first and second granules of pyrazosuifuron ethyl and pretilachlor admixed in a predetermined ratio. In this aspect, the present invention provides a storage stable granular formulation comprising:

(a) first granules, said first granules being prepared by granulating a first emulsion comprising a herbicidally effective amount of pyrazosulfuron ethyl in a sufficient quantity of water in the presence of a stabilizing effective amount of sodium lignosulfonate, said sodium lignosulfonate being substantially free of a reducing sugar and being optionally in combination with sodium salt of a sulfonated aromatic polymer formaldehyde condensate; and

(b) second granules, said second granules being prepared by granulating a second emulsion comprising a herbicidally effective amount of pretilachlor in a sufficient quantity of water in the presence of a stabilizing effective amount of sodium lignosulfonate, said sodium lignosulfonate being substantially free of a reducing sugar and being optionally in combination with sodium salt of a sulfonated aromatic polymer formaldehyde condensate.

In an embodiment, pyrazosulfuron ethyl and pretilachlor granules comprise herbicidally effective amounts of the active ingredients that are emulsified in a sufficient quantity of water in the presence of a stabilizing effective amount of sodium lignosulfonate, said sodium lignosulfonate being substantially free of a reducing sugar and being optionally in combination with sodium salt of a sulfonated aromatic polymer formaldehyde condensate.

The two emulsions, comprising pyrazosulfuron ethyl and pretilachlor, may thereafter be co- extruded or sprayed with a carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof or sprayed on provided blank granules selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite.

The first and second granules are thereafter admixed in a predetermined ratio. The terms "herbicidally effective amount" in relation to pyrazosulfuron ethyl and pretilachlor, "stabilizing effective amount" in relation to sodium lignosulfonate component and "substantially free of in relation to the reducing sugar in this aspect of the invention is defined to be the same as defined in relation to the previous aspect hereinabove. In another aspect, the present invention provides a process for the preparation of granular formulation comprising separate granules of pyrazosulfuron ethyl and pretilachlor respectively. In this aspect, the process comprises:

(a) dissolving a stabilizing effective amount of sodium lignosulfonate in a sufficient quantity of water, said sodium lignosulfonate being substantially free of a reducing sugar and optionally being present in combination with sodium salt of a sulfonated aromatic formaldehyde condensate polymer;

(b) adding a herbicidally effective amount of pretilachlor slowly to a portion of the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce a first emulsion;

(c) adding a herbicidally effective amount of pyrazosulfuron ethyl slowly to the remaining portion of the solution obtained in step (a) and simultaneously homogenizing the resultant solution to produce a second emulsion;

(d) separately granulating said first and second emulsions to obtain first and second granules comprising pretilachlor and pyrazosulfuron ethyl respectively; and

(e) mixing said first and second granules homogenously in a predetermined ratio.

In an embodiment, the said step of adding a herbicidally effective amount of pretilachlor to a portion of the solution obtained in step (a) comprises simultaneously homogenizing the resultant solution till a first emulsion is obtained. Similarly, a herbicidally effective amount of pyrazosulfuron ethyl is added slowly to the remaining portion of the solution obtained in step (a) and the resultant solution is simultaneously homogenized till a second emulsion is obtained.

In this aspect, the first and second emulsions are separately granulated using a process described hereinabove by either spray drying, preferably in a spray dryer/fluid bed dryer or extruding a dough prepared therefrom, preferably through an extruder. Preferably, in any aspect or embodiment described hereinabove, granulating an emulsion according to the instant invention can be carried out using any of the processes selected from:

(a) admixing the pre-formed emulsion with an inert carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof and preparing a dough therefrom, extruding the prepared dough and drying the extruded product;

(b) spraying the pre-formed emulsion on blank granules selected from the group comprising bentonite, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, clay, sand, dolomite and calcite and drying the granules; and

(c) admixing the pre-formed emulsion with an inert carrier selected from soapstone, kaolin, talc, titanium dioxide and mixtures thereof and spray dried in a spray dryer or a fluid bed spray dryer (FBD) to afford the target granular formulation.

The present invention is thus based on the surprising finding that pyrazosulfuron ethyl content could be further stabilized by preparing the granular product by spray drying or extruding an emulsion comprising the instant herbicides in the presence of sodium lignosulfonate that is substantially free of a reducing sugar. In contrast, when a dry mixture of the instant herbicides in combination with sodium lignosulfonate (comprising substantial amount of reducing sugars) and carriers such as herein described was kneaded to a dough, without forming an emulsion, and the resultant dough was extruded and dried to obtain a granular formulation, the resultant granules exhibited heavy degradation of pyrazosulfuron ethyl content. It was also surprising that whep an emulsifiable concentrate formulation according to the disclosure of Indian Patent No. 210952 was used to prepare a dough, the resultant granulated product also exhibited heavy degradation in pyrazosulfuron ethyl content.

The terms "herbicidally effective amount" in relation to pyrazosulfuron ethyl and pretilachlor, "stabilizing effective amount" in relation to sodium lignosulfonate component and "substantially free of in relation to the reducing sugar in this aspect of the invention is defined to be the same as defined in relation to the previous aspect hereinabove.

In an embodiment of the above two aspects of this invention, said first and second granules are homogenously mixed in a ratio of from about 1-5:1-10. More preferably, the predetermined ratio is mixed within the ratio of from about 1:1 to about 2:8.

In any aspect or embodiment described hereinabove, the ratio of the amounts of pyrazosulfuron ethyl to pretilachlor in the formulations according to the present invention varies from about 0.01 :5 to about 5:60. More preferably, the ratio of pyrazosulfuron ethyl to pretilachlor varies from about 1 :9 to about 1 :59.

It was found that the separated granular formulations according to the instant invention allowed co-formulating two or more mutually incompatible agrochemicals without allowing the agrochemicals to contact each other for a substantial period of time. Accordingly, the chemical and physical stability of the mutually incompatible agrochemicals was substantially enhanced in the formulation of the present invention.

Examples 17, 18:

Pyrazosulfuron ethyl and Pretilachlor were granulated separately using the process described hereinabove. The stability of the individual granules and their stability in the formulation was evaluated. Composition of first granules

S No. Ingredient . Quantity (g)

1 Pyrazosulfuron ethyl technical 0.4

2 Ultrazine NA 8.0

3 Talc QS

Composition of second granules

S No. Ingredient Quantity (g)

1 Pretilachlor technical 13 2 Ultrazine NA 8.0

3 Talc QS

The individual pyrazosulfuron ethyl (0.3%) granules and pretilachlor (12%) granules after complete processing, were mixed homogenously in a ratio of 1:1 to obtain a formulation comprising pyrazosulfuron ethyl (0.15 %) + pretilachlor (6.0 %) in granular form.

Processing conditions

Water used to prepare dough: 30 g

Extruder: Fuji Paudal Dome or radial extruder

Diameter of perforation: 1.0mm

Drying: FBD

Temperature for drying: 65-75°C

Results

It was therefore concluded that pyrazosulfuron ethyl could be stabilized by mixing the individual granules of pyrazosulfuron ethyl and pretilachlor. A slight variation in the degradation percentage of pretilachlor was observed, which was due to incompletely homogenized mixing of the individual granules of pyrazosulfuron ethyl and pretilachlor. The formulations according to the present invention, described in any aspect or embodiment hereinabove, were found to possess superior herbicidal activity and especially for the control of resistant weeds. These formulations were highly effective for the protection of growing plants including cotton, paddy, rice forage crops, sugarcane, cole crops, leafy vegetables, tobacco, tomatoes, potatoes, flowering ornamentals, vines, crops and fruit trees.

Specifically, the formulations according to the present invention were found synergistically effective against a wide variety of weeds including, but not limited to, Echinochloa crusgalli, Digitaria senguinalis, Setria app., Commelina benghalensis, Fimbristylis miliacoa, Cyperus iria, Eleusine indica, Panicum spp., Cyperus difformis, Cyperus rotunds, Alternanthera sessile, Caesulia axillaris, Cynotis cucullata, Ludwigia parviflora, Marsilae quadrifoliata, Monochoria vaginalis, Echinochloa colonum, Eclipta alba and Sphenoclea zeylamica.

In a preferred embodiment, a composition comprising about 0.15% of pyrazosulfuron ethyl together with about 6.00% of pretilachlor was granulated as a "dry flowable, DF" formulation intended for direct application to the soil and another composition comprising about 1.4% of pyrazosulfuron ethyl together with about 40% of pretilachlor was granulated as a "water dispersible granule, WDG" formulation intended for foliar application were prepared according to the present invention.

Description of the preferred embodiments of the invention

Example 19: Pyrazosulfuron ethyl (PSE) + Pretilachlor ( 0.15 % + 6 % ) G

Part A

Component Weight (in grams)

Pretilachlor technical 6.39

Pyrazosulfuron ethyl technical 0.16

Sodium lignosulfonate 8.00

Water (processing aid) 20 Part B

Inerts : Powdery material selected from soapstone, talc, kaolin, titanium dioxide or mixtures thereof were taken as 85.45 g (to make 100.0 g)

Manufacturing Process : 8.0 g of sodium lignosulfonate was added to 20 g of water and mixed until all of the surfactant went into solution. 6.39 g of Pretilachlor technical was added slowly while homogenizing to produce emulsion. The emulsion was continuously mixed and 0.16 g of pyrazosulfuron ethyl technical was added to produce a mixture. The inert material were charged in the blender and mixed properly. The herbicidal portion was added to the inert portion and a dough was prepared. The dough was extruded using a basket or radial or dome or screw or cone or axial extruder and the resultant granules were dried and evaluated.

Example 20: PSE + Pretilachlor f 0.15 % + 6 % ) G Composition

Component Amount (in grams)

Pretilachlor 6.00 Pyrazosulfuron ethyl 0.15

Surfactant (sodium Iignosulfonate) 4.0 or 8.0

Water 16.0

Inert material (Bentonite) Q.S.

Process :

The required quantity (4.0 or 8.0 gram) of sodium Iignosulfonate was added to water and mixed until all of the surfactant went into solution. Added 6.0 g of Pretilachlor content slowly while homogenization to produce the emulsion. Thereafter, 0.15 g pyrazosulfuron ethyl content was added while continuous homogenization to produce homogenous stable mixture. The carrier granules were charged to the mixing equipment and mixing was started. The homogenous mixture was sprayed on the carrier granules (bentonite) uniformly and dried. The resulting formulation was evaluated.

Example 21: PSE + Pretilachlor ( 1.40 % +40.0 % ) WDG/WG/DF/G

Component Amount (in grams)

Pretilachlor 40.00

Pyrazosulfuron ethyl 1.40 Ultrazine NA 27.38

Water 100

Inert (for example : kaolin, talc , titanium Q.S. (maximum 31.22) to make 100.00 g dioxide or mixtures thereof)

27.38 g of Ultrazine Na® was added to water and mixed until all surfactant content dissolved in water. 40.0 g of pretilachlor was added slowly while homogenization to produce an emulsion. The homogenization was continued while 1.40 g of pyrazosulfuron ethyl was added to produce a homogeneous mixture. Thereafter, upto 31.22 gram of inert material was added in the homogeneous mixture and the mixture was stirred vigorously. The mixture was sprayed uniformly in a fluid bed processor to produce granular formulation comprising less than 5% moisture content.

Comparative formulations were prepared wherein the surfactant content sodium lignosulfonate was replaced with (i) Calcium salt of alkyl benzene sulfonate, and (ii) CO-40 ethoxylate. These formulations exhibited heavy degradation in pyrazosulfuron ethyl content of 70.59% and 56.25% respectively after 14 days AHS tests.

Furthermore, coating the bentonite granules (in the absence of surfactants i.e. without forming the pre-formed emulsion) with known coating agents such as rosin gum, stearic acid, PVP-K30 surprisingly led to a heavy degradation in pyrazosulfuron ethyl content. It was initially believed that coating the granules to prevent contact between pyrazosulfuron ethyl and pretilachlor could be expected to stabilize the pyrazosulfuron content. It was indeed surprising that stabilization could only be achieved by utilizing sodium lignosulfonate that is substantially free of a reducing sugar. It was further surprising that the stability could be further enhanced by emulsifying the herbicides in water in the presence of sodium lignosulfonate having reducing sugar content less than about 7%, preferably less than 3% - 5%, more preferably less than 1 %. It was indeed surprising that coating the granules to prevent the contact between pyrazosulfuron ethyl and pretilachlor did not lead to any substantial enhancement in stability while emulsifying the herbicides prior to their granulation led to a surprising enhancement in storage stability. Further surprisingly, it was found that granules made out of the same composition as in examples 18-20 without being granulated from a pre-formed emulsion exhibited degradation of pyrazosulfuron ethyl content by about 77.19%. Examples 22-28: Using the process described hereinabove, the following seven formulations were prepared and tested for the stability of pyrazosulfuron ethyl. It has been conventionally known that pyrazosulfuron ethyl degrades quickly when formulated and stored at elevated temperatures. The formulations below were tested for stability of pyrazosulfuron ethyl at elevated temperatures of 40°C and 54°C for 14 days.

Formulations:

Example No. % % pretilachlor % Excipient

pyrazosulfuron

ethyl

22 1.4 40 Sodium lignosulfonate (58.6%)

23 1.4 40 Sodium lignosulfonate (58.6%)

24 1.4 40 Sodium lignosulfonate (58.6%)

25 1.4 40 Sodium lignosulfonate (29.3%) + kaolin 29.3%

26 1.4 40 Sodium lignosulfonate (29.3%) + talc

29.3%

27 1.4 40 Sodium lignosulfonate (29.3%) + Ti0 ₂

29.3%

28 1.4 40 Sodium lignosulfonate (29.3%) + ammonium sulfate (29.3%)

Stability testing

Example No. PSE % % PSE AHS % degraded % PSE AHS % degraded

(initial) 40°C AHS 40°C

54°C AHS 54°C

22 1.51 1.55 -3 1.46 3

23 1.69 1.70 -1 1.65 2

24 1.73 1.73 0 1.69 2

25 1.62 1.63 0 1.60 1 6 1.92 1.96 -2 1.99 -4 7 .1.65 1.66 -1 1.64 1 8 1.79 1.77 2 1.47 18 It was thus found that sodium lignosulfonate alone, or in combination with kaolin, talc or titanium dioxide stabilized the granular formulations according to the present invention wherein the sodium lignosulfonate was substantially free of a reducing sugar. The presence of ammonium sulfate instead of kaolin, talc or titanium dioxide substantially degraded the pyrazosulfuron ethyl content. Thus, the formulations according to the present invention were found to possess greater shelf life and stability. Moreover, these formulations were solvent- free and are therefore environment friendly.

The invention has been described above with reference to the specific examples. It should be noted that the example(s) appended above illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. Other than in the operating examples provided hereinbefore or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions are to be understood as being modified in all instances by the term "about".