DESC:FIELD OF INVENTION

The present invention relates to a novel crystalline modification of Pymetrozine and a process for preparation thereof. The present invention more particularly relates to the use of the said stable crystalline modification of Pymetrozine for preparing crop protection composition for controlling insects.

BACKGROUND OF THE INVENTION

Chemical substances have tendency to exist in more than one crystalline form (physical forms). Different crystalline forms exhibit different physicochemical properties such as solubility, dissolution rate, chemical stability, physical stability, melting point and many others. For long term storage and better handling of the products, the chemical compounds must have better stability under the defined storage conditions. Further, the different crystalline modification governs the bioavailability in the case of the drug substances and/or the agrochemical active ingredients. Polymorphism in pharmaceutical & agro chemical industries is of paramount importance as the existence of polymorphs is quite common and hence its thorough assessment is inevitable. Because of their crystalline stability and ease of handling, pharmaceutical & agro chemical industries prefer to use crystalline compounds for formulation development especially for solid formulations.

Pymetrozine (4,5-dihydro-6-methyl-4-((3-pyridinylmethylene)amino)-1,2,4-triazin-3(2H)-one) is an active ingredient which has been proven to be very effective agrochemical as insecticide selective against Homoptera, antifeedant. The structure is reproduced below:

Pymetrozine is an insecticide selective against Homoptera reported by C. R. Fluckiger et al. (Proc. Br. Crop Prot. Conf. Pest & Diseases 1992, 1, 43). Introduced by Ciba-Geigy in 1993. Pymetrozine is an active used to control of aphids and whitefly in vegetables, potatoes, ornamentals, cotton, deciduous and citrus fruits; also used to control of plant hoppers in rice. Pymetrozine is an antifeedant which interacts with chordotonalsensillae through-out the insect muscular system, results in death by starvation.

Pymetrozine is known from US4931439 and can be prepared by following the experimental procedure described in the example P.3 of US4931439. The product is precipitated out during the course of the reaction which is isolated by filtration, washed with ether and dried to give Pymetrozine in 90% yield.

US2002/0099053A1 (Indian counterpart IN224651 (IN/PCT/2001/1538/CHE)) describes various physical/chemical forms of Pymetrozine such as solvates (methanolate in particular), dihydrate and two different physical forms, ß- and a -modifications.

Various physical forms can exhibit different physical properties. Handling of amorphous or semi crystalline compounds can lead to various unforeseeable technical problems leading to difficulties in various process parameters such as filtration rate, stirring profile (crystal volume), surface activity (foaming), rate of drying, solubility, quality, packing, formulation ability and storage stability specially hygroscopicity.

The present inventors have developed a novel stable crystalline form of Pymetrozine, hereinafter referred as the Crystalline Modification III.

The Crystalline Modification III of Pymetrozine is easy for handling, with enhanced filtration rate, better stirring profile (crystal volume), faster drying rate, and overall improved quality of the product.

The present inventors have observed that when Pymetrozine prepared using the protocol as given in US4931439 (Example P.3) tested for various solid state characterizations and for the stability studies and compared with the Crystalline Modification III, the Crystalline Modification III proven to be different with characteristic and distinctly different 2? values. It was repeatedly observed that the rate of absorption of water is slower by manyfolds compared to the various Pymetrozine samples having different crystalline modifications other than the Crystalline Modification III.

The Crystalline Modification III of Pymetrozine exhibit excellent “flow properties” and can be handled with ease and formulations can be prepared without any difficulty such as solid formulations. Further, the Crystalline Modification III of Pymetrozine has characteristic and sharp melting point. The observed melting point of the Crystalline Modification III is about 235-238oC and is highest as compared to the various literature reports; example melting point of the Crystalline Modification III of Pymetrozine is higher as compared to reported melting points in P3 example of US4931439 (227-228°C) and Asian Journal of Chemistry, 2012, 24, 6, 2541-2545 (228-229°C). This gets supported by the DSC analysis (Figure 2) that explicitly shows sharp peak corresponding to the melting endotherms at 237.2-237.7°C of the Crystalline Modification III.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a novel stable Crystalline Modification III of Pymetrozine and a process for preparation thereof.

It is another object of the present invention to provide pymetrozine in a form which permits the preparation of agrochemical composition for crop protection with improved handling characteristics and stability.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a Crystalline Modification III of Pymetrozine which, in X-ray powder diffraction at 25°C., shows at least SIX of the following reflexes:
d = 9.50±0.01 ?A
d = 7.48 ±0.01 ?A
d = 5.98±0.01 ?A
d = 5.87±0.01 ?A
d = 4.07±0.01 ?A
d = 3.96±0.01 ?A
d = 3.49±0.01 ?A
d = 3.44±0.01 ?A
d = 3.31±0.01 ?A

According to an aspect of the present invention, there is provided a process for preparing a crystalline Modification III of Pymetrozine comprising the step of:
a) dissolving or suspending suitable Pymetrozine forms or the mixture of various forms in an organic solvent or mixture of the solvents or aqueous organic solvent in case of water miscible organic solvents at a temperature in the range from 5°C to 130°C;
b) efficient crystallization of Pymetrozine over a period in the range from 10 hours to 96 hours; optionally in the presence of ‘seed crystals’ of the Crystalline Modification III of Pymetrozine.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1: Illustrate X-ray powder diffraction of the Crystalline Modification III of pymetrozine.

Figure 2: Illustrate DSC of the Crystalline Modification III of Pymetrozine.
Figure 3: Illustrate X-ray powder diffraction of Pymetrozine prepared using the protocol as given in US4931439 (Example P.3).

Figure 4: Illustrate DSC of Pymetrozine prepared using the protocol as given in US4931439 (Example P.3).

Figure 5: Illustrate TGA of Pymetrozine prepared using the protocol as given in US4931439 (Example P.3).

Figure 6: XRPD of Crystalline Modification III of Pymetrozine formulation sample.

Figure 7: XRPD of Crystalline Modification III of Pymetrozine formulation sample after drying.

Figure 8: XRPD of Technical sample (Meta stable morph of Pymetrozine) before thermal treatment.

Figure 9: XRPD of Technical sample (Meta stable morph of Pymetrozine) after thermal treatment.

DETAILED DESCRIPTION OF THE INVENTION

Pymetrozine technical was prepared using the prior art, US4931439 (Example P.3) and analyzed for solid state characterization. The results of the solid-state characterizations XRPD, DSC and TGA are as shown in Fig 3, 4 and 5.

The data reveals that Pymetrozine technical prepared using the prior art (US4931439, Example P.3) has resembling XRPD pattern to that of the a & ß modifications as reported in the patent document (US2002/0099053A1 (Indian counterpart IN224651 (IN/PCT/2001/1538/CHE)).

In another embodiment of this study, Pymetrozine technical prepared using the prior art (US4931439, Example P.3) was subjected to crystallization and/or equilibrium suspension experiments in various solvents and conditions, and again subjected to solid state characterizations.

A careful comparison of the results of solid state analysis such as melting point, XRPD, DSC, and IR of the Crystalline Pymetrozine resulted from crystallization and/or equilibrium suspension experiments in the select solvents showed that there is the existence of a different crystalline form of Pymetrozine. This novel stable crystalline form of Pymetrozine is, hereinafter referred as the Crystalline Modification III.

XRPD pattern of the Crystalline Modification III is distinctly different as compared to Pymetrozine prepared using the prior art (US4931439, Example P.3).

Further, the Crystalline Modification III was compared for d-spacing values of a & ß modifications reported in (US2002/0099053A1 (Indian counterpart IN224651 (IN/PCT/2001/1538/CHE))) and observed that the Crystalline Modification III is distinctly different as compared to the a & ß modifications reported in the patent document (US2002/0099053A1 (Indian counterpart IN224651 (IN/PCT/2001/1538/CHE))).

The XRPD patterns were recorded on a PANalytical Empyrean XRD machine operating at 45kV and 30mA with a step size of 0.020 in the range 2? = 3 to 60° and a total data collection time of 1Hour. The indexing was done using FULLPROF suite using the program DICVOL.

The Pymetrozine sample of the Crystalline Modification III was analyzed for XRPD pattern. Based on comparison of the XRPD pattern, particularly by comparison of the d-spacing values observed for Pymetrozine sample of the Crystalline Modification III with that of the reported d-spacing values reported in the US patent (US 2002/0099053 A1), it is evident that the XRPD pattern of the Crystalline Modification III is different than the reported a and ß modifications that confirms the Crystalline Modification III as altogether different morph /crystalline modification supporting to the claim of the present inventors.

In yet another embodiment of this invention, Pymetrozine prepared using the prior art (US4931439, Example P.3) and the Crystalline modification III were exposed to the same relative humidity, one set of experiment at 65±5%RH and another set of experiment at 90±5%RH, and observed that the rate of absorption of water of Pymetrozine of the Crystalline Modification III was found to be manyfold slower than Pymetrozine prepared using the prior art (US4931439, Example P.3). This clearly indicates that the Crystalline Modification III has an advantage over the rest of the physical forms of Pymetrozine in terms of unique crystallinity, faster filtration and drying rates and a slower rate of water absorption (less hygroscopic). Due to this, the Crystalline Modification III of Pymetrozine exhibit excellent “flow properties” and can be handled with ease and formulations, such as solid formulations can be prepared without any difficulty.

The present invention relates to the novel Crystalline Modification of Pymetrozine, a method of producing them, composition containing the Crystalline Modification III of Pymetrozine, a method of producing this composition and to the use of said novel modification for preparing crop protection composition.

The Crystalline Modification III of Pymetrozine typically has the melting point in the range from 235 to 238°C.

The Crystalline Modification III of Pymetrozine has a sharp melting point by DSC in the range from 236 to 238°C.

The Crystalline Modification III of Pymetrozine has Pymetrozine content of at least 98% by weight.

In a preferred embodiment of the present invention, the Crystalline Modification III of Pymetrozine shows the reflexes listed in Table 1 in the X-ray diffraction pattern (Figure 1), wherein d represents the interplanar spacing and I/I0 the relative intensity.

Table 1:
Pos. [°2Th.] d-spacing [Å] Rel. Int. [%]
7.5902 11.64758 26.79
9.3082 9.50135 84.12
11.8272 7.48273 83.60
12.8289 6.90064 4.87
13.3946 6.61045 4.16
14.0305 6.31225 6.94
14.8130 5.98054 93.17
15.0856 5.87307 89.96
15.8343 5.59701 44.42
17.0608 5.19730 36.59
18.7991 4.72045 34.32
19.9717 4.44588 20.94
20.2145 4.39302 17.21
20.5522 4.32160 11.35
21.8073 4.07562 74.86
22.4512 3.96017 100.00
22.7274 3.91267 42.44
23.5694 3.77476 15.43
24.0333 3.70295 6.48
25.0886 3.54953 20.31
25.5213 3.49031 50.90
25.8322 3.44902 61.20
26.9027 3.31415 86.92
27.5943 3.23264 6.93
28.5579 3.12572 52.58
29.3497 3.04317 9.43
29.9306 2.98542 36.16
31.0037 2.88449 19.22
31.4435 2.84515 7.66
32.1467 2.78450 10.69
32.7509 2.73449 11.61
33.7392 2.65662 5.32
34.6220 2.59088 9.58
35.5483 2.52547 2.80
36.5470 2.45871 1.38
36.9622 2.43204 1.74
38.0907 2.36255 1.26
38.7425 2.32428 1.34
40.4914 2.22784 6.39
40.9065 2.20619 2.19
41.9349 2.15443 0.98
42.5949 2.12257 1.78
43.1395 2.09702 1.91
43.9272 2.06123 2.56
45.3414 2.00018 7.43
46.5423 1.95133 1.45
47.3853 1.91856 3.36
48.3951 1.88087 1.92
49.2231 1.84962 1.47

In an embodiment of the present invention, there is provided the Crystalline Modification III of Pymetrozine which, in X-ray powder diffraction at 25°C, shows at least SIX of the following reflexes:
d = 9.50±0.01 ?A
d = 7.48 ±0.01 ?A
d = 5.98±0.01 ?A
d = 5.87±0.01 ?A
d = 4.07±0.01 ?A
d = 3.96±0.01 ?A
d = 3.49±0.01 ?A
d = 3.44±0.01 ?A
d = 3.31±0.01 ?A

In another embodiment of the present invention, there is provided a process for the preparation of the Crystalline Modification III of Pymetrozine comprising the step of:
a) dissolving and/or suspending suitable Pymetrozine forms or the mixture of various forms in an organic solvent or mixture of the solvents or aqueous organic solvent in case of water miscible organic solvents;
b) efficient crystallization of Pymetrozine with/without the use of ‘seed crystals’ of the Crystalline Modification III of Pymetrozine;
c) efficient crystallization of Pymetrozine over a period in the range from 10 hours to 96 hours;
d) efficient crystallization of Pymetrozine by dissolving and/or suspending suitable Pymetrozine forms or the mixture of various forms in an organic solvent or mixture of the solvents or aqueous organic solvent in case of water miscible organic solvents at a temperature ranges from 5°C -130°C, more preferably in the range of 50°C -100°C.

Suitable pymetrozine forms different from the Crystalline Modification III are, for example, amorphous pymetrozine or Pymetrozine solvates (in particular Pymetrozine methanolate) or Pymetrozine dihydrate or ß modification of Pymetrozine or a modification of Pymetrozine or mixture thereof.

Solvent used in step a) is selected from group consisting of C1 to C4 alkanols such as methanol, ethanol, n-propanol, isopropanol (Isopropyl alcohol), n-Butanol, t-Butanol or iso-butanol, acetonitrile, toluene, dichloromethane, dichloroethane, Tetrahydrofuran (THF), 2-Methyltetrahydrofuran (2-Me-THF), Dimethoxyethane (DME), 1,4-dioxane, acetone, ethyl acetate, Methyl tert-butyl ether (MTBE), Di-isopropyl ether (DIPE).

The amount of solvent used is in the present invention is in the ranges of 5 to 150 times by volume, preferably in the range of 10 to 35 times by volume.

In a preferred embodiment of the present invention, the solvent used is C1 to C4 alkanols either as a whole solvent or aqueous solutions in the range of 5 to 50 times by volume, preferably in the range of 10 to 35 times by volume.

In a preferred embodiment of the present invention, the preferred solvent used is methanol, in the range of 5 to 50 times by volume, preferably in the range of 10 to 35 times by volume.

In an embodiment of the present invention, the Crystalline Modification III can be achieved by dissolving and/or suspending Pymetrozine of any other form/s or the mixture of various forms at high temperature with/without the use of ‘seed crystals’ of the Crystalline Modification III of Pymetrozine.

To achieve a conversion into the Crystalline Modification III which is as complete as possible, the crystallization and/or equilibrium suspension process is carried out over a period (duration of crystallization) in the range from 10 hours to 96 hours in the presence/absence of seed crystals of the Crystalline modification III. Duration of crystallization and/or equilibrium suspension process is understood by the person skilled in the art as meaning the period of time between the beginning of the measure which initiates crystallization and the isolation of Pymetrozine by separating the crystalline material from the mother liquor.

In step b) crystallization is effected in the following ways:

i. efficient crystallization of Pymetrozine over a period in the range from 10 hours to 96 hours in the absence of seed crystals of the Crystalline Modification III.
ii. efficient crystallization of Pymetrozine over a period in the range from 10 hours to 96 hours in the presence of seed crystals of the Crystalline Modification III.
iii. efficient crystallization of Pymetrozine in the presence of seeds crystals of the Crystalline Modification III.

If seed crystals of the Crystalline Modification III were added, the crystallization of Pymetrozine was achieved by adding seeds of the desired Crystalline Modification III in an amount in the range of 1 to 5% by w/w more preferably 2-3% by w/w. The duration of crystallization ranges for the period of from 10 hours to 96 hours more preferably 24 hours to 40 hours.

If the crystallization is carried out in the absence of seed crystal, the duration of crystallization is generally at least 24 hours and will generally not exceed 96 hours more preferably 36 hours to 48 hours.

In an embodiment of the present invention, wherein in step b), after crystallization of a partial amount of the Pymetrozine comprised in the solution, the solvent used is partially distilled-off to bring the complete crystallization of the Pymetrozine.

In another embodiment of the present invention, wherein in step b), the Crystalline Modification III can be obtained by agitating the suspension until at least 90% of the Pymetrozine comprised therein is present in the form of the Crystalline Modification III of Pymetrozine.

The Crystalline Modification III is isolated using conventional techniques by separating a solid component from the liquid, for example by filtration, centrifugation or decanting. In general the isolated solid will be washed for example with the solvent used for the crystallization and/or equilibrium suspension process. The resulting Crystalline Modification III is then dried and subjected to further processing.

In an embodiment of the present invention, the Crystalline Modification III is isolated by filtration and washing with the same solvent which was used for crystallization or equilibrium suspension process and thereafter drying at 65-75°C for about 5-6 h or till water content not more than (NMT) 0.5% by weight is achieved.

In another embodiment of the present invention, Pymetrozine in the form of the Crystalline Modification III is used for controlling insects.

The examples below serve to illustrate the invention and are not to be understood as limiting it.

Examples:

Examples 1: Preparation of the Crystalline Modification III by suspension in Isopropyl alcohol (IPA) without seed crystal.

5 g of Pymetrozine technical in about 100 ml of IPA was heated to 80-85°C. The mixture was kept at 80-85°C for about 9-10 hour. Thereafter, the mixture was gradually cooled to room temperature and stirred for 15-16 hour at the room temperature. The Crystalline solid was isolated by filtration, washed with IPA (20 ml) and dried at 60-70°C for about 5-6 hour or till water content NMT 0.5 % is achieved. Yield: 4.5 g (90%) of the Crystalline Modification III of Pymetrozine.

Examples 2: Preparation of the Crystalline Modification III by crystallization in Isopropyl alcohol (IPA) without seed crystal.

5g of Pymetrozine technical in about 600 ml of IPA was heated to 80-85°C. The mixture was kept at 80-85°C until the material is fully dissolved about 2-3 hour. After complete dissolution, the mixture stirred for 48 hours with gradual cooling to room temperature. Crystals obtained were isolated by filtration, washed with IPA and dried at 60-70°C for about 5-6 hour or till water content NMT 0.5% by weight is achieved. Yield: 4g (80%) of the Crystalline Modification III of Pymetrozine.

Examples 3: Preparation of the Crystalline Modification III by crystallization from Methanol without seed crystal.

10 g of Pymetrozine technical in about 350 ml of methanol was heated to 60-70°C. The mixture was kept at 60-70°C until the material was fully dissolved about 1-2 hour. After complete dissolution, the mixture stirred for about 24 hours with gradual cooling to room temperature. The resultant Crystalline Modification III of Pymetrozine was isolated by filtration. The product was dried at 60-70°C for about 5-6 hour or till water content NMT 0.5 % was achieved. Yield: 7.5 g (75%) of the Crystalline Modification III of Pymetrozine.

Examples 4: Preparation of the Crystalline Modification III by crystallization from Methanol with seed crystal.

20g of Pymetrozine technical in about 700 ml of methanol was heated to 60-70°C. The mixture was kept at 60-70°C until the material is fully dissolved about 1-2 hour. Stopped heating after the clear solution. Added seeds of the Crystalline Modification III (5x100mg) about every 2-5 minutes of time of interval till undissolved seeds was observed in order to get the visible seeding effect. Thereafter, the mixture was gradually cooled to room temperature and the slurry was stirred for about 16-17 hour at room temperature. The solvent was distilled-off partially to the extent of about 400 ml at the atmospheric pressure and the suspension was further stirred for additional 16 hours with gradual cooling to room temperature. The resultant Crystalline Modification III of Pymetrozine was filtered and dried at 60-70°C for about 5-6 hour or till water content NMT 0.5% is achieved. Yield: 16g (80%) of the Crystalline Modification III of Pymetrozine.

Examples 5: Preparation of the Crystalline Modification III by suspension in Methanol without seed crystal.

25g of Pymetrozine technical in methanol about 500 ml of methanol was heated to 60-70°C. The mixture was kept at 60-70°C for about 10-12 hour. Thereafter, the mixture was gradually cooled to room temperature and was stirred for 15-16 hour at room temperature. The crystalline solid obtained filtered and dried at 60-70°C for about 5-6 hour or till water content NMT 0.5 % is achieved. Yield: 22g (88%) of the Crystalline Modification III of Pymetrozine.

Examples 6: Preparation of the Crystalline Modification III by suspension in Methanol with seed crystal.

250g of Pymetrozine technical in about 3.75 lit of methanol was heated to 60-70°C. The mixture was kept at 60-70°C for about 4-5 hour. After the saturation level was achieved, added seeds of the Crystalline Modification III and continued stirring further for about 4-5 hour at 60-70°C. Thereafter, the mixture was gradually cooled to room temperature and was stirred for 15-16 hour at room temperature. The Crystalline Modification III of Pymetrozine was isolated by filtration, washed with methanol and dried at 60-70°C for about 5-6 hour or till water content NMT 0.5% is achieved. Yield: 214g (85%) of the Crystalline Modification III of Pymetrozine.
Example 7: Preparation of Pymetrozine 50% WG

Charged 50 kg of crystalline modification III of Pymetrozine technical, 16 kg of wetting agent and dispersing agent (lignosulfonic acid sodium salt, mixture of isomers of dibutyl-naphthalene sulphonic acid sodium salt), carriers (Urea, polymer with formaldehyde-12kg, silicium oxide-15kg, sodium sulphate-6kg) in a premixing blender for homogenization for 30 minutes. The pre-blended material was grinded through Jet mill/ air classifier mills. The grinded material was blended in post mixing blender till it became homogeneous. (For 30 minutes). Then, the post blended material was mixed with 100 gm water and an antifoaming agent (polydimethylsiloxane)-200 gm to made dough in the blender and mixed for at least 30 minutes. The wet mass was then extruded using Basket Extruder using a desired mesh size of the sieve and the feed rate and speed of the extruder were streamlined based on granules quality and output and finally, granules were collected in trays. These extruded granules were passed through Fluid Bed Dryer (Hot air temperature 55-65ºC) to remove excess moisture using in dough formation. Dried granules were sieved using sieve shaker to remove oversize and undersize material. The final product was analyzed and observed that content of pymetrozine is > 50%.

Crystalline modification III of Pymetrozine and its formulated product (50% WG) were kept for accelerated Stability test at 54 ± 2°C for 7 & 14 days. After the analysis, it was observed that both the active ingredient and its formulated product (50% WG) were stable.

Observed results are as given below.

Pymetrozine >99 % Stability Data
Batch No. 0 Days After 7 Days after 14 Days
# 2017GSPT005 99.78 99.62 99.65
# 2017GSPT006 99.65 99.50 99.45
Pymetrozine 50 % WDG Stability Data
Batch No. 0 Days After 7 Days after 14 Days
# 2017GSPF005 50.51 50.39 50.34
# 2017GSPF006 50.62 50.51 50.45

These Pymetrozine formulations (50% WG) samples were prepared using Crystalline Modification III of Pymetrozine and were analysed for XRPD pattern. XRPD pattern of all the formulation samples were identical and similar to the dihydrate form of Pymetrozine. This indicates that Pymetrozine is in the dihydrate form in the formulation samples which was further confirmed by water content analysis.
,CLAIMS:1. A Crystalline Modification III of Pymetrozine which, in X-ray powder diffraction at 25°C., shows at least six of the following reflexes:

d = 9.50±0.01 ?A
d = 7.48 ±0.01 ?A
d = 5.98±0.01 ?A
d = 5.87±0.01 ?A
d = 4.07±0.01 ?A
d = 3.96±0.01 ?A
d = 3.49±0.01 ?A
d = 3.44±0.01 ?A
d = 3.31±0.01 ?A

2. The crystalline Modification III of Pymetrozine as claimed in claim 1 having melting point in the range from 235-238oC.

3. The Crystalline Modification III of Pymetrozine as claimed in claim 2 having a sharp melting point by DSC in the range from 236 to 238°C.

4. The crystalline Modification III of Pymetrozine as claimed in any one of the claim 1 to 3 having Pymetrozine content in the range from 98% to 100% by weight.

5. A process for the preparing a crystalline Modification III of Pymetrozine comprising the step of:
a) dissolving or suspending suitable Pymetrozine forms or the mixture of various forms in an organic solvent or mixture of the solvents or aqueous organic solvent in case of water miscible organic solvents at a temperature in the range from 5°C to 130°C;
b) crystallization of Pymetrozine over a period in the range from 10 hours to 96 hours; optionally in the presence of ‘seed crystals’ of the Crystalline Modification III of Pymetrozine.

6. The process as claimed in claim 5, wherein seed crystals of modification III are added during or prior to the crystallization of the Pymetrozine.

7. The process as claimed in claim 5, wherein in step a) the Pymetrozine forms or mixture of various forms is dissolved or suspended in an organic solvent or mixture of the solvents or aqueous organic solvent in case of water miscible organic solvents at a temperature in the range from 50°C to 100°C.

8. The process as claimed in claim 7, wherein Pymetrozine forms is selected from amorphous pymetrozine or Pymetrozine solvates (in particular Pymetrozine methanolate) or Pymetrozine dihydrate or ß modification of Pymetrozine or a modification of Pymetrozine.

9. The process as claimed in claim 7, wherein the organic solvent is selected from C1 to C4 alkanols such as methanol, ethanol, n-propanol, isopropanol (Isopropyl alcohol), n-Butanol, t-Butanol or iso-butanol, acetonitrile, toluene, dichloromethane, dichloroethane, Tetrahydrofuran (THF), 2-Methyltetrahydrofuran (2-Me-THF), Dimethoxyethane (DME), 1,4-dioxane, acetone, ethyl acetate, Methyl tert-butyl ether (MTBE), Di-isopropyl ether (DIPE) or mixture thereof.

10. The process as claimed in any one of the claims 5 to 9, wherein the solution is cooled to crystallize the Pymetrozine.

11. The process as claimed in any one of the claims 5 to 9, wherein the suspension is cooled to crystallize the Pymetrozine.

12. The process as claimed in claim 11, wherein the suspension is agitated until at least 90% of the Pymetrozine comprised therein is present in the form of crystalline modification III of Pymetrozine.

13. A composition of Pymetrozine for crop protection comprising:

i) Pymetrozine in the form of crystalline modification III as claimed in claim 1;
ii) Wetting agent and dispersing agent selected from lignosulfonic acid sodium salt or mixture of isomers of dibutyl-naphthalene sulphonic acid sodium salt;
iii) Carriers selected from urea, polymer with formaldehyde, silicium oxide, sodium sulphate.

14. The composition as claimed in claim 13 is in the form of Wet granules wherein content of crystalline modification III of Pymetrozine is > 50%.