Crystalline modifications to pyraclostrobin
The present invention relates to novel crystalline modifications of pyraclostrobin, to processes for their preparation and to the use of the novel modifications for preparing crop protection compositions.
1. A crystalline modification IV of pyraclostrobin which, in an X-ray powder diffractogram at 25° C., shows at least three of the following reflexes:
d= 6.02±0.01 Å
d= 4.78±0.01 Å
d= 4.01±0.01 Å
d= 3.55±0.01 Å
d= 3.01±0.01 Å.
2. The crystalline modification IV according to claim 1 having a melting point in the range from 62 to 72° C.
3. The crystalline modification IV according to claim 1 having a pyraclostrobin content of at least 98% by weight.
4. A process for preparing a crystalline modification IV of pyraclostrobin according to any of the preceding claims, comprising:
i) dissolving a pyraclostrobin form different from modification IV in an organic solvent or solvent mixture, where the organic solvent or solvent mixture comprises at least 70% by volume of at least one fully water-miscible organic solvent L1 and up to 30% by volume of water; and
ii) effecting crystallization of pyraclostrobin over a period of at least 10 hours and/or in the presence of seed crystals of modification IV.
5. The process according to claim 4 , where the pyraclostrobin is dissolved at a temperature above 50° C.
6. The process according to claim 5 , wherein the solution is cooled to crystallize the pyraclostrobin.
7. The process according to claim 4 , wherein the crystallization of the pyraclostrobin is effected by adding water to the pyraclostrobin solution.
8. The process according to claim 4 , wherein seed crystals of modification IV are added during or prior to the crystallization of the pyraclostrobin.
9. The process according to claim 4 , where the fully water-miscible organic solvent L1 is selected from C 1 -C 4 -alkanols, acetone and butanone.
10. The process according to claim 9 , where, in step i), methanol, ethanol or a solvent mixture comprising at least 70% by volume of methanol and/or ethanol is used for dissolving the pyraclostrobin.
11. The process according to claim 4 , wherein after a partial amount of the pyraclostrobin is crystallized in the solution, water is added to bring the crystallization of the pyraclostrobin to completion.
12. A process for preparing a crystalline modification IV of pyraclostrobin according to claim 1 , comprising:
i) preparing a suspension of a pyraclostrobin form different from modification IV in an organic solvent;
ii) optionally, adding seed crystals of modification IV to the suspension;
iii) agitating the suspension until at least 90% of the pyraclostrobin comprised therein is present in the form of modification IV.
13. The process according to claim 12 , where the organic solvent used in step i) to suspend the pyraclostrobin comprises at least 50% by volume of at least one C 1 -C 4 -alkanol.
14. The process according to claim 13 , where the organic solvent used in step i) to suspend the pyraclostrobin comprises at least 70% by volume of methanol, isopropanol and/or ethanol.
15. A composition for crop protection, comprising pyraclostrobin in the form of modification IV, carriers, and/or auxiliaries.
16. The composition according to claim 15 in the form of an aqueous suspension concentrate.
17. A method for controlling phytopathogenic fungi comprising contacting a plant, seed, or soil in need of treatment with a crystalline form of modification IV of pyraclostrobin.