DESC:FIELD OF INVENTION
The present invention relates to a stable herbicide formulation comprising pyrazosulfuron ethyl. The present invention also relates to a stabilising system for formulation comprising pyrazosulfuron ethyl and method of preparation the formulation.

BACKGROUND OF THE INVENTION
Pyrazosulfuron ethyl is a pyrimidinylsulfonylurea herbicide having IUPAC name 5-[(4,6 dimethoxypyrimidin-2-ylcarbamoyl) sulfamoyl]-1-methyl pyrazole-4-carboxylic acid and chemical structure as follows:

Pyrazosulfuron ethylis a systemic herbicide used to control annual and perennial broad-leaved weeds and sedges, pre- or post-emergence, wet sown and transplanted rice crops.

Various agrochemical compositions comprising pyrazosulfuron ethyl as active ingredient are available in the market, but they are known to be degrading during the shelf life of the product. The degradation of the active ingredient is not suitable for formulation and will result in ineffective dose application when applied in the field thus resulting in poor control of weeds.

Hence, there is an urgent and unmet need of the stable formulation comprising pyrazosulfuron ethyl which is stable prevent degradation during its shelf life.

OBJECT OF THE INVENTION
It is an object of the present invention to provide a storage stable composition comprising pyrazosulfuron ethyl.
It is another object of the present invention to provide a process for preparing a storage stable composition comprising pyrazosulfuron ethyl.

It is an object of the present invention to to provide a stable composition comprising pyrazosulfuron ethyl that does not undergo degradation.

SUMMARY OF INVENTION
In an aspect the present invention provides a storage stable agrochemical composition comprising:
a) pyrazosulfuron ethyl; and
b) astabilising system comprising silicaand china clay

In another aspect the present invention provides a process for preparation of storage stable composition comprising herbicidally effective amount of pyrazosulfuron ethyl and a stabilising system comprising silica and china clay, said process comprising:

Step-1: Pre-blending of pyrazosulfuron ethyl and stabilising system comprising silica and china clay optionally with agrochemically acceptable excipients;

Step-2: Milling; and

Step-3: Post-blending and/or drying to get a compositionwith predefined % moisture.

In another aspect the present invention provides a method of controlling undesired weeds, said method comprising applying to the weeds or to their locus an herbicidally effective amount of astorage stable agrochemical composition according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an agrochemical composition and in particular a storage stable agrochemical composition.

It is surprising to found that a stabilising system comprising silica and china clay, helps to increase shelf life of the product comprising pyrazosulfuron ethyl of formula-1.

Formua-1:

Surprisingly the present inventors found a stabilizing system which is effective in increasing stability and shelf life of agrochemical compositions comprising pyrazosulfuron ethyl.

In an embodiment there is provided a storage stable composition comprising:
a) pyrazosulfuron ethyl; and
b) astabilising system comprising silicaand china clay.

In another embodiment the storage stable compositions according to the present invention further comprises other agrochemically acceptable surfactants.

Thus, in an embodiment there is provided a storage stable composition comprising:
a) pyrazosulfuron ethyl;
b) astabilising system comprising silicaand china clay; and
c) optionally an agrochemically acceptable surfactant.

In an embodiment storage stable composition comprises pyrazosulfuron ethyl as anactive ingredient.

In another embodiment storage stable composition comprises herbicidally effective amount of pyrazosulfuron ethyl as active ingredient.

In another embodiment storage stable composition according to the present invention comprisespyrazosulfuron ethyl in the concertation of from about 0.1% to about 25%.

In another embodiment storage stable composition comprises herbicidally effective amount of pyrazosulfuron ethyl in combination with other agrochemically active ingredient.

In another embodiment, according to the present invention, degradation of pyrazosulfuron ethyl is controlled.
In another embodiment, according to the present invention, degradation of pyrazosulfuron ethyl is controlled to <5% of pyrazosulfuron ethyl present in the composition.

In an embodiment storage stable composition of pyrazosulfuron ethyl according to the present invention comprises a stabilising system.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl according to the present invention comprisessilica and china clay.

In another embodiment,stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica selected from precipitated silica and fumed silica.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica in the concertation of from about 0.1% to about 10%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica in the concertation of from about 0.1% to about 7%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay.

In an embodiment china clay of stabilising system has water holding capacity of up to 75% by weight.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay in the concertation of 10% to 90%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises precipitated silica and china clay, in a ratio from about1:5 to about 1:30.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises precipitated silica and china clay, in a ratio from about 1:7 to about 1:20.

In an embodiment, the storage stable composition of pyrazosulfuron ethyl according to the present invention comprises an agrochemically acceptable surfactant.

Thus, in an embodiment, there is provided a storage stable composition comprising:
a) pyrazosulfuron ethyl;
b) astabilising system comprising silica and china clay; and
c) an agrochemically acceptable surfactant.

In an embodiment, the stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica selected from precipitated silica and fumed silica.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica in the concertation of from about 0.1% to about 10%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises silica in the concertation of from about 1% to about 7%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay in the concertation of from about 10% to about 90%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay in the concertation of from about 50% to about 90%.

In another embodiment stabilising system of storage stable composition of pyrazosulfuron ethyl comprises china clay in the concertation of from about 60% to about 80%.

In an embodiment of the present invention, agrochemically acceptable surfactant may be selected from dispersing agents, wetting agents, fillers and the like.

In stated embodiment, agrochemically accepted excipients may be selected from, but not limited to, following stated agrochemically accepted excipients:
Dispersing agents may include lignosulfonate, calcium lignin iodate, sodium lauryl polyoxyethylene ether sulfate, alkyl naphthalene condensate sulfonate, sodium dodecyl benzene sulfonate, sodium lauryl sulfate, Alkyl polyoxyethylene ether sulfonate, alkylphenol polyoxyethylene ether formaldehyde condensate, alkylphenol polyoxyethylene ether nonylphenol polyoxyethylene ether, polyoxyethylene polyoxypropylene ether block copolymer , pull-open powder, high molecular carboxylate, sodium methylene biguanide sulfonate, polyvinyl alcohol, modified naphthalene sulfonate, polycarboxylate, alkylnaphthalene sulfonate, alkylphenol polyoxyl Vinyl ether, EO/PO block polyether, JFC, unrolled powder, nonylphenol ethoxylate, octylphenol polyoxyethylene sulfate, fatty alcohol sulfate, alkylnaphthalene sulfonate, fatty amide N- Methanesulfonate, fatty alcohol sodium polyoxyethylene sulfate, fatty acid sulfate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, alkylbenzyldimethylammonium chloride, alkylamine oxide, etc. or mixture thereof.

Wetting agents may include alkyl sulfates, alkyl sulfonates, naphthalene sulfonates, sodium lignosulfonate, fatty alcohol polyoxyethylene ethers, alkylphenol ethoxylates, short chain EO/PO block polyethers , nonylphenol ethoxylate, nonionic ethoxylate, sodium alkyl sulfate, sodium dodecyl sulfate, TERSPERSE 2700, TERSPERSE 1004, sodium lignosulfonate, NNO, polyoxyethylene polyoxypropylene one or a combination of two or more of an ether block copolymer, an alkylphenol polyoxyethylene ether phosphate, or a water-soluble polymer compound CMC or PVA, etc. or mixtures thereof.

Fillers may includean organic or inorganic solid inert substance such as talc, clay, diatomaceous earth, magnesium aluminum silicate, white carbon black, pyrophyllite, light calcium carbonate, high clay, organic bentonite, etc. or mixtures thereof.

Surfactants may include sodium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, sodium alkyl sulfate, fatty alcohol sulfate, alkyl ethylsulfonate, Sodium methylnaphthalene sulfonate formaldehyde condensate, naphthalene sulfonate, formaldehyde condensate, polycarboxylic acid, lignosulfonate, alkylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether or a variety, etc. or mixtures thereof.

In another embodiment the surfactant is selected from sodium alkyl sulfate, formaldehyde condensates, sodium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, fatty alcohol sulfate, alkyl ethylsulfonat, Sodium methylnaphthalene sulfonate, naphthalene sulfonate formaldehyde condensate, polycarboxylic acid, lignosulfonate, alkylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether, etc. or mixtures thereof.

In another embodiment there is provided a process for preparation of storage stable composition comprising herbicidally effective amount of pyrazosulfuron ethyl and astabilising system comprising silica and china clay.

In an embodiment the composition is formulated as a solid composition.

In a preferred embodiment the composition is formulated as powder (WP).

lInan embodiment there is provided a process for preparation of storage stable composition comprising herbicidally effective amount of pyrazosulfuron ethyl and a stabilising system comprising silica and china clay, said process comprising:

Step-1: Pre-blending of pyrazosulfuron ethyl and stabilising system comprising silica and china clayoptionally with agrochemically acceptable excipients;

Step-2: Milling; and

Step-3: Post-blending and/or drying to get a composition with predefined % moisture.

In another embodiment there is provided a process for preparation of storage stable composition comprising herbicidally effective amount of pyrazosulfuron ethyl and a stabilising system comprising silica and china clay, said process comprising:

Step-1: Pre-blending of pyrazosulfuron ethyl and stabilising system comprising silica and china clay optionally with agrochemically acceptable excipients;

Step-2: Milling;

Step-3: Post-blending and/or drying to get a composition with predefined % moisture; and
Step-4: Formulating to a suitable form using a suitable equipment

In above stated embodiment, in step-1, the term ‘stabilising system’ refers to stabilising system comprising silica and china clay, in stabilizing effective ratio.

In above stated embodiment, in step-1, the term ‘agrochemically accepted excipients’ refers to additives of the composition that may be selected from dispersing agents, wetting agents, fillers, surfactants, etc.

In above stated embodiment, in step-1, agrochemically accepted excipients may be selected from, but not limited to, following stated agrochemically accepted excipients:

Dispersing agents may include lignosulfonate, calcium lignin iodate, sodium lauryl polyoxyethylene ether sulfate, alkyl naphthalene condensate sulfonate, sodium dodecyl benzene sulfonate, sodium lauryl sulfate, Alkyl polyoxyethylene ether sulfonate, alkylphenol polyoxyethylene ether formaldehyde condensate, alkylphenol polyoxyethylene ether nonylphenol polyoxyethylene ether, polyoxyethylene polyoxypropylene ether block copolymer , pull-open powder, high molecular carboxylate, sodium methylene biguanide sulfonate, polyvinyl alcohol, modified naphthalene sulfonate, polycarboxylate, alkylnaphthalene sulfonate, alkylphenol polyoxyl Vinyl ether, EO/PO block polyether, JFC, unrolled powder, nonylphenol ethoxylate, octylphenol polyoxyethylene sulfate, fatty alcohol sulfate, alkylnaphthalene sulfonate, fatty amide N- Methanesulfonate, fatty alcohol sodium polyoxyethylene sulfate, fatty acid sulfate, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, alkylbenzyldimethylammonium chloride, alkylamine oxide, etc. or mixture thereof.

Wetting agents may include alkyl sulfates, alkyl sulfonates, naphthalene sulfonates, sodium lignosulfonate, fatty alcohol polyoxyethylene ethers, alkylphenol ethoxylates, short chain EO/PO block polyethers , nonylphenol ethoxylate, nonionic ethoxylate, sodium alkyl sulfate, sodium dodecyl sulfate, TERSPERSE 2700, TERSPERSE 1004, sodium lignosulfonate, NNO, polyoxyethylene polyoxypropylene one or a combination of two or more of an ether block copolymer, an alkylphenol polyoxyethylene ether phosphate, or a water-soluble polymer compound CMC or PVA, etc. or mixtures thereof.

Fillers may include an organic or inorganic solid inert substance such as talc, clay, diatomaceous earth, magnesium aluminum silicate, white carbon black, pyrophyllite, light calcium carbonate, high clay, organic bentonite, etc. or mixtures thereof.

Surfactants may include sodium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, sodium alkyl sulfate, fatty alcohol sulfate, alkyl ethylsulfonate, Sodium methylnaphthalene sulfonate formaldehyde condensate, naphthalene sulfonate, formaldehyde condensate, polycarboxylic acid, lignosulfonate, alkylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether or a variety, etc. or mixtures thereof.

In another embodiment the surfactant is selected from sodium alkyl sulfate, formaldehyde condensates, sodium dodecylbenzenesulfonate, calcium dodecylbenzenesulfonate, fatty alcohol sulfate, alkyl ethylsulfonat, Sodium methylnaphthalene sulfonate, naphthalene sulfonate formaldehyde condensate, polycarboxylic acid, lignosulfonate, alkylphenol polyoxyethylene ether phosphate, fatty alcohol polyoxyethylene ether, etc. or mixtures thereof.

In yet another embodiment, in step-1, pre-blending is carried out in a time period of about 15 minutes to 2 hours by charging pyrazosulfuron ethyl,stabilising system comprising precipitated silica and china clay and agrochemically accepted excipients if any simultaneously.

In anembodiment, step-2 provides a process for milling of pre-blended mixture of Step-1.
In another embodiment, Step-2 comprises grinding of the pre-blended mixture of Step-1 at pressure 6 to 8 Kg / cm2 to obtain ground material with specific particle size.

In the present invention, the term ‘specific particle size’ refers to D90 - less than 15 micron and/or wet sieve - 99.8 % passing through 500 BSS test.

In another embodiment, step-3 provides a process for post-blending of ground pyrazosulfuron ethyl, stabilising system and agrochemically accepted excipients if any, obtained as product of step-2.

In another embodiment, step-3 comprises blending of ground pyrazosulfuron ethyl, stabilising system and agrochemically accepted excipients if any, obtained as product of step-2 for a time period of about 15 min to 2 hours in order to facilitate complete homogenisation of resulting powder composition.

In another embodiment, step-3 comprises drying of the blended mixture to get a product with predefined % moisture.

In another embodiment, step-3 comprises drying of the blended mixture to get a product with % moisture <2%.

In a preferred embodiment, step-3 comprises drying of the blended mixture to get a product with % moisture <1%.

In another embodiment, in step-4, the process of formulating is not particularly limiting.

In a preferred embodiment tin step-4 the composition according to the present invention is formulated in the form of powder.

The present invention provides a method of controlling undesired weeds, said method comprising applying to the weeds or to their locus an herbicidally effective amount of a storage stable agrochemical composition comprising:
a) Pyrazosulfuron ethyl; and
b) astabilising system comprising silica and china clay.

In an embodiment, the present invention provides a method controlling annual and perennial broad-leaved weeds and sedges, pre- or post-emergence, in wet-sown and transplanted rice crops, said method comprising applying to the weeds or to their locus an herbicidally effective amount of a storage stable agrochemical composition comprising:
a) Pyrazosulfuron ethyl; and
b) a stabilising system comprising silica and china clay.

The invention will now be described further by reference to the following examples, which are intended to illustrate, but not limit, the scope of the appended claims.
Example 1
Exemplary composition was prepared as follows:
Sr.no Ingredients Quantity (w/w)
1 Pyrazosulfuron ethyl 10.9
2 Precipitated Silica 4.00
3 China Clay 78.1
4 Sodium alkyl sulphate 3.00
5 Formaldehyde condensate 4.00

Process conditions:
Step-1 (Pre-Blending): Pyrazosulfuron ethyl, precipitated Silica,china Clay, sodium alkyl sulphate and formaldehyde condensate were charged in required quantities in pre-blender. Blending was carried out for 20 Minutes.

Step-2 (Milling): The pre-blended material was ground to desired particle size under grinding pressure

Step-3 (Post-Blending): The ground material was blended in post blender for 15 min to achieve complete homogenization and dried to get the product having a moisture content <1%.

The stability results of the exemplary composition prepared according to above formula are:
Sr. No Parameters AMB AHS 14 Days AHS 28 Days
1 Assay of pyrazosulfuron ethyl (% w/w) 10.77 10.63 10.55
2 Suspensibility (% w/w) 94.40 89.10 95.00
3 pH (1% Aq.) 5.35 5.55 5.58
4 Wet Sieve Test* 100 100 100
5 Wettability (s) 15 15 15
6 Moisture Content 0.64 0.53 0.51
7 Bulk Density 0.256 NA NA
*(material passing through 75-micron test Sieve) (% w/w)

% Degradationofpyrazosulfuron ethyl:
Sample AMB(0days) AHS 14 Days AHS 28 Days
Example 1 0.00 1.30 2.04

Compositions according to the present invention are listed in the below table (Example 2 and 3)
Sr.no Ingredients Example 2 Example 3
1 Pyrazosulfuron-ethyl 5.3 15
2 Precipitated Silica 4.27 3.8
3 Formaldehyde condensate 4 4
4 Sodium alkyl sulphate 3 3
5 China Clay 83.43 74.2

Total 100 100

% Degradation of pyrazosulfuron ethyl:
Sample AMB (0days) AHS 14 Days
Example 2 0.0 3.4
Example 3 0.0 4.1

Comparative example (Example 4): A comparative composition of pyrazosulfuron ethyl was prepared as follows:
Sr. no Ingredients Quantity (w/w)
1 Pyrazosulfuron-ethyl 10.9
2 arylsulfonic acid sodium salt 04.00
3 Anionic surfactant 04.00
4 Sodium Ligno sulphate 04.00
5 Pentab UF 01.00
6 Precipitated Silica 14.70
10 Kaolin 61.40

% Degradation of pyrazosulfuron ethyl:
Sample AMB (0 days) AHS 14 Days AHS 28 Days
Example 4 0.0 12.69 24.87

Example 1-3 demonstrates inventions according to the present invention. Example 4 is a comparative example in which stabilizing system according to the invention is absent. Zero timedata was generated for all the samples. Studied were conducted by keeping the samples at 54?C for 14 days and 28 days. The results indicate that the stabilization system according to the present invention provides significant chemical stability to pyrazosulfuron ethyl in the composition.
,CLAIMS:1. A storage stable agrochemical composition comprising:
a) pyrazosulfuron ethyl; and
b) astabilising system comprising silicaand china clay
2. A composition according to claim 1 wherein said pyrazosulfuron ethylis present in an amount from about 0.1% to about 25%by weight of the composition
3. A composition according to claim 1 wherein said silica is selected from precipitated silica and fumed silica
4. A composition according to claim 1 wherein said silica ispresent in an amount from about 0.1% to about 10% by weight of the composition.
5. A composition according to claim 1 wherein said china clay is present in an amount from about 10% to about 90% by weight of the composition.
6. A composition according to claim 1 wherein ratio of said precipitated silica and china clay varies from about 1:5 to about 1:30.
7. A composition according to claim 1 wherein degradation of pyrazosulfuron ethyl is controlled to <5% of pyrazosulfuron ethyl present in the composition
8. A process for preparation of storage stable composition comprising herbicidally effective amount of pyrazosulfuron ethyl and a stabilising system comprising silica and china clay, said process comprising:
Step-1: Pre-blending of pyrazosulfuron ethyl and stabilising system comprising silica and china clay optionally with agrochemically acceptable excipients;
Step-2: Milling;
Step-3: Post-blending and/or drying to get a composition with predefined % moisture; and
Step-4: Formulating to a suitable form using a suitable equipment
9. A process of claim 8 wherein said process provides said composition having a % moisture <2%.
10. A process of claim 8 wherein said process provides said composition in the form of powder.

11. A method of controlling undesired weeds, said method comprising applying to the weeds or to their locus an herbicidally effective amount of a storage stable agrochemical composition comprising:
a) Pyrazosulfuron ethyl; and
b) a stabilising system comprising silica and china clay.