Claims:1. A stable granular formulation comprising effective amounts of propanil and MCPA or an agrochemically acceptable salt thereof.

2. The formulation as claimed in claim 1 comprising an adjuvant blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt.

3. The formulation as claimed in claim 1 wherein propanil is present in an amount of about 60.00% by weight of the formulation.

4. The formulation as claimed in claim 1 wherein MCPA or an agrochemically acceptable salt thereof is present in an amount of about 7.5% by weight of the formulation.

5. The formulation as claimed in claim 2 wherein the polycarboxylate salt is selected from sodium carboxylate or potassium polycarboxylate.

6. The formulation as claimed in claim 2 wherein the polyoxyalkylene aryl phenyl ether sulphate salt is selected from polyoxyalkylene styryl phenyl ether, polyoxyalkylene styryl phenyl ether, a polyoxyalkylene benzyl phenyl ether, a polyoxyalkylene benzyl phenyl benzene diphenyl ethers and polyoxyalkylene ether and salts thereof.

7. The formulation as claimed in any one of the preceding claims comprising at least one additional ingredient selected from a wetting agent, a dispersing agent, an antifoam, a carrier, a lignosulfonate salt and combinations thereof.

8. A granular formulation comprising;
a. propanil;
b. MCPA or an agrochemically acceptable salt thereof;
c. adjuvant blend of copolymer of maleic anhydride and isobutylene and potassium salt of polyoxyethylene aryl phenyl ether sulfuric acid ester.

9. A process for the preparation of a granular formulation comprising:
a. dry blending and milling propanil and at least one adjuvant to obtain a homogenous powder;
b. adding MCPA to the premixed powder and blending the mixture;
c. passing the powder through shear mixer / kneader with simultaneous spray of water to obtain dough;
d. extruding the dough through extruder to obtain granules;
e. drying the granules in fluidized bed dryer at maximum inlet temperature 55-65°C till the moisture content is reduced below 2 % w/w.

10. The process as claimed in claim 9 wherein the adjuvant in step (a) is a blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt.
, Description:FIELD OF THE INVENTION:

The present invention relates to a granular formulation comprising propanil and MCPA. More particularly, the present invention relates to a granular formulation comprising propanil and MCPA having superior stability, suspensibility and dispersibility.

BACKGROUND OF THE INVENTION:

Propanil is a widely used contact herbicide. With an estimated use of about 8 million pounds in 2001, it is one of the more widely used herbicides in the United States.

However, propanil is also prone to hydrolysis in addition to having a relatively low melting point. The formation of a paste containing water may lead to further difficulties in stability during processing if the energy input during the paste formation is too high. Thus, there are a number of constraints on the ingredients that could be used for preparing the granules of propanil. These constraints limit the choice of available components to those which are not heat sensitive due to the physical or chemical nature of those ingredients. In particular, the energy input required in the formation of the dough or paste may degrade certain low-melting, or temperature-sensitive, active materials.

MCPA or 2-methyl-4-chlorophenoxyacetic acid is a powerful, selective, widely used phenoxy herbicide. The pure compound is a brown-colored powder.

The use of herbicidal 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 herbicides application rates and costs, shorter contact times for improved results, less stringent use restrictions, improved selectivity, improved spectrum of weed controlled, reduced cost and reduced residue problems. However, identifying appropriate herbicide application rates and ratio of the combinations is essential to achieve efficacious weed control. Hitherto, the combination of Propanil and MCPA is known. However, the problem of incompatibility of these herbicides to liquid formulations is yet to be addressed satisfactorily.

Moreover, it has been found by the present inventors that the known formulations comprising propanil in combination with MCPA suffer from very poor suspensibility and are known to often fail the wet sieve test and low shelf life. These products display a considerable amount of sedimentation with time, often forming hard rock type lumps at the bottom of the storage containers. The increased sedimentation further aggravates the problem of nozzle clogging during the spraying application by a farmer. It is observed that when such a formulation is prepared as a diluted liquid or a solution to be sprayed, the same does not remain sprayable after the passage of a certain amount of time because of the high insoluble content. This can sometimes lead to a farmer rejecting an otherwise good product, which is certainly undesirable.

CN103027036 (A) discloses a phytocidal composite containing MCPA and propanil. The composite uses the MCPA and the propanil as active ingredients in the mass ratio of 1-80 to 80-1. However the patent fails to address the problem of incompatibility between propanil and methoxone salt, particularly in a liquid formulation.

It is thus desirable to present a storage stable granular formulation comprising a combination of propanil and MCPA, preferably in its free acid form, which is an unmet need in the art.
OBJECT OF THE INVENTION:

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

An object of the present invention is to provide a granular formulation comprising propanil and MCPA.

Another object of the present invention is to provide a granular formulation comprising propanil and MCPA having superior stability, suspensibility and dispersibility.

Yet another advantage of the present invention is to provide a wettable granular formulation of propanil and MCPA offering several advantages such as ease of handling, ease of use, reduced work exposure, reduced toxicity, reduced spillage and waste disposal, less field drift, free-flow and significant reduction in dust hazards.

SUMMARY OF THE INVENTION:

Therefore, in an aspect, the present invention provides a stable granular formulation comprising propanil and MCPA.

In another aspect, the present invention provides a stable wettable granular formulation comprising:
a) propanil;
b) MCPA or an agrochemically acceptable salt thereof;
c) an adjuvant blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt.

In yet another aspect the present invention provides a process for the preparation of a granular formulation comprising:
(a) dry blending and milling propanil and MCPA or an agrochemically acceptable salt thereof and at least one adjuvant to obtain a homogenous powder, wherein the adjuvant is either a salt of polyoxyalkylene aryl phenyl ether sulfate or its blend with at least one polycarboxylate salt;
(b) passing the powder obtained in step (a) through a shear mixer or a kneader with simultaneous spray of water to obtain dough;
(c) extruding the dough to obtain granules; and
(d) drying the granules in fluidized bed dryer at maximum inlet temperature of about 55-65°C till the moisture content is reduced below 2 % w/w.

DETAILED DESCRIPTION OF THE INVENTION

Therefore, in an aspect, the present invention provides a stable granular formulation comprising effective amounts of propanil and MCPA or an agrochemically acceptable salt thereof.

In yet another embodiment, the present invention describes a stable granular formulation comprising;
a) propanil;
b) MCPA or an agrochemically acceptable salt thereof; and
c) an adjuvant blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt.

In an exemplary embodiment, which is not to be construed as limiting, propanil is present in an amount of about 60% by weight of the formulation and MCPA or an agrochemically acceptable salt thereof is present in an amount of about 7.5% by weight of the formulation.

It has been surprisingly found that the combination of propanil and MCPA or an agrochemically acceptable salt thereof showed superior stability when mixed with the adjuvant blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt.

The adjuvant blend according to the present invention provides AHS stability for propanil in the presence of MCPA or an agrochemically acceptable salt thereof. It is believed that the alkaline nature of the adjuvant blend neutralizes the acid moiety of MCPA and the in-situ salt generation stabilizes the formulation.

It was further surprisingly found that the granular formulation comprising propanil, MCPA and the adjuvant blend of the present invention was storage stable and exhibited excellent suspensibility, dispersibility and passed the wet sieve test.

The present inventors have further surprisingly found that the presence of a carboxylate salt as an adjuvant, either individually or as a blend, imparts increased rainfastness on the herbicides as well as improved performance, which has hitherto not been seen with this combination.

The composition according to the present invention contains polycarboxylate salts, which unexpectedly serve as rainfastness enhancing agent.

The polycarboxylate salts include alkali metal salts such sodium and potassium. Potassium polycarboxylate of the present invention comprises a polymer of maleic acid potassium salt. Sodium polycarboxylate of the present invention comprises a polymer of maleic acid sodium salt.

In another embodiment, there is provided agricultural compositions comprising propanil; MCPA or an agrochemically acceptable salt thereof and an adjuvant blend of a salt of polyoxyalkylene aryl phenyl ether sulfate and at least one polycarboxylate salt selected from sodium polycarboxylate and potassium polycarboxylate.

The polyoxyalkylene aryl phenyl ethers are those containing two or more aromatic rings, and ethers of non-ionic surfactants in the molecule, wherein at least one aromatic ring has a polyoxyalkylene group. Typical examples of polyoxyalkylene aryl ethers include a polyoxyalkylene styryl phenyl ether, polyoxyalkylene styryl phenyl ether, a polyoxyalkylene benzyl phenyl ether, a polyoxyalkylene benzyl phenyl benzene diphenyl ethers and polyoxyalkylene ether and salts thereof. Polyoxyalkylene moiety is typically a polyoxyethylene, polyoxypropylene or polyoxyethylene and polyoxypropylene block copolymers. Typical examples are polyoxyalkylene tristyryl phenyl ether (e.g., polyoxyethylene tristyryl phenyl ether, polyoxyethylene polyoxypropylene tristyryl phenyl ether) and polyoxyalkylene distyrylbenzene ethers (polyoxyethylene styryl phenyl ether).

The adjuvant blend of the present invention includes at least one salt of polyoxyalkylene aryl phenyl ether and at least one alkali or alkaline earth metal salt of an organic polyacid salt in an amount of from about 0.1% to about 25% by weight of the formulation.

In an embodiment, the preferred organic polyacid salt is a polycarboxylate, preferably selected from sodium or potassium polycarboxylate.

The present formulation may further comprise adjuvant selected from at least one wetting agent, at least one dispersing agent, at least one antifoam, at least one carrier, a lignosulfonate salt and combinations thereof.

The wetting agent may be present, in an embodiment, in an amount of 3.5% by weight of the formulation and may be selected from sodium lauryl sulfate, dialkyl naphthalene sulphonate formaldehyde condensate, dialkyl naphthalene sulphonate sodium salt and sodium naphthalene sulfonate - formaldehyde condensate.

The dispersing agent may be present, in an embodiment, in an amount of 11.5% by weight of the formulation and may be selected from modified styrene acrylic polymers, potassium polycarboxylates, salts of polystyrenesulphonic acids, salts of polyvinylsulphonic acids, salts of naphthalenesulphonic acid/formaldehyde condensates, salts of condensates of naphthalenesulphonic acid, phenolsulphonic acid and formaldehyde, and salts of lignosulphonic acid, polyethylene oxide/polypropylene oxide block copolymers, polyethylene glycol ethers of linear alcohols, reaction products of fatty acids with ethylene oxide and/or propylene oxide, polyvinyl alcohol, polyvinylpyrrolidone, copolymers of polyvinyl alcohol and polyvinylpyrrolidone and copolymers of (meth)acrylic acid and (meth)acrylic esters, alkyl ethoxylates and alkylarylethoxylates selected from sodium, calcium and ammonium salts of ligninsulfonates which may be optionally polyethoxylated; salts of maleic anhydride copolymers, salts of polyacrylic acids; salts of condensed phenolsulfonic acids.

The antifoam agent may be present in an amount of 0.5% by weight of the formulation and may be selected from blend of maltodextrin, and methylated silica, silicone oil or magnesium stearate.

The carrier may be present in an amount of 10.5% by weight of the formulation and may be selected from precipitated Silica, kaolin, titanium dioxide, bentonite, soapstone, talc, attapulgite, ceramic, montmorillonite, pumice, sepiolite, diatomaceous earth, sand, clay, dolomite, calcite, magnesium oxides, magnesium carbonates, sucrose, corn starch, citric acid and its salts, and mixtures thereof.

In another embodiment the present invention describes a stable granular formulation comprising;
a) propanil;
b) MCPA or an agrochemically acceptable salt thereof;
c) adjuvant blend of copolymer of maleic anhydride and isobutylene and potassium salt of polyoxyethylene aryl phenyl ether sulfuric acid ester.

In another aspect, the present invention provides a process for the preparation of a granular formulation comprising:
(a) dry blending and milling propanil and at least one adjuvant to obtain a homogenous powder;
(b) adding MCPA to the premixed powder and blending the mixture;
(c) passing the powder through shear mixer / kneader with simultaneous spray of water to obtain dough;
(d) extruding the dough through extruder to obtain granules;
(e) drying the granules in fluidized bed dryer at maximum inlet temperature 55-65°C till the moisture content is reduced below 2 % w/w.

Propanil in addition to having a relatively low melting point, is also prone to hydrolysis. The formation of a paste containing water may lead to further difficulties in stability during processing if the energy input during the paste formation is too high. Thus, the above described processes may impose a number of constraints on the ingredients by limiting the choice of available components to those which are not heat sensitive which may be included in the granules due to the physical or chemical nature of those ingredients. In particular, the energy input required in the formation of the dough or paste may degrade certain low-melting, or temperature-sensitive, active materials.

Various adjuvant blends were used to check the suspensibility and dispersibility of the WG composition comprising Propanil + MCPA:

Sr. No. Ingredients Amount in % Suspensibility Dispersibility Comment
1. Propanil 62 - - -
2. MCPA 8.21 - - -
3. Geropon SC 213 (copolymer of maleic anhydride and isobutylene and potassium salt of polyoxyethylene aryl phenyl ether sulfuric acid ester) 7.36 80.37 84.34 Good suspensibility and dispersibility
4. Morwet D 425 (Sodium salt of naphthalene sulphonate condensate) 7.36 81.07 27-28 Good suspensibility and fair dipersibility
5. Morwet D425 (Sodium salt of naphthalene sulphonate condensate)+ Supragil WP (dialkyl naphthalene sulphonate sodium salt) 15 +4 41 >40 Poor Suspensibility and fair dispersibility
6. Atlox Metasperse 550S (modified styrene acrylic polymer)+ Ufoxane 3A (modified sodium lignosulfonate) 6+4 51 22 Poor Suspensibility and dispersibility
7. Ufoxane 3A (modified sodium lignosulfonate) 6 84.83 >30 Poor dispersibility
8. Morwet D 425 +Aerosol OTB 7.36 + 0.96 49.05 60 Poor dispersibility and suspensibility

From the above it was concluded that copolymer of maleic anhydride and isobutylene and potassium salt of polyoxyethylene aryl phenyl ether sulfuric acid ester provided good suspensibility and dispersibility to the formulation of the present invention.

Example:
Example 1:
Propanil 60 % + MCPA 7.5 % WG
Propanil 60
MCPA 7.5
blend of copolymer of maleic anhydride and isobutylene and potassium salt of polyoxyethylene aryl phenyl ether sulfuric acid ester 7.36
Sodium Lauryl Sulfate 7.56
TiO2 8.78
Kaolin QS
Total 100

Example 2:

Wet sieve retention of composition disclosed in Example 1:

Packing material Dilaminated Aluminium Pouch HDPE Bottle
Parameters/Period 0 Day 31 Months 0 Day 11 Months 25 Months
Active content (%w/w) Propanil 61.46 61.27 61.35 61.22 60.92
MCPA 7.64 7.31 7.83 8.10 7.77
Suspensibility (%w/w) Propanil 80.35 75.48 70.74 79.50 74.81
MCPA 96.20 100.80 104.95 97.22 97.89
Wet sieve (retention on 200 BSS test sieve) (%w/w) 1.98 0.13 0.96 0.45 0.25

It was thus surprising that the wet sieve retention and the suspensibility of the formulation according to the present invention was found surprisingly improved with ageing after storage for 25 months – 31 months. This improvement in the physico-chemical properties of the formulation upon ageing was unexpected and surprising.