PROCESS FOR THE PRODUCTION OF CHLOROTHALONYL

Abstract: Process for the production of 2,4,5,6-Tetrachloro-isophtalonitryl, with formula (I), having a crystallographic structure suited for producing fungicide compositions remaining stable throughout time and having a high biological activity, wherein a thermal and/or mechanical treatment is carried out on the non-suited crystallographic structre, both by gradually decreasing the temperature during the de-sublimation phase, subsequent to industrial synthesis, and by supplying thermal energy - in static or dynamic conditions - and/or mechanical energy to the industrial technical product having a non-suited crystallographic structure eventually during the phase of preparation or of micronization of said product.

Description: "PROCESS FOR THE PRODUCTION OF CHLOROTHALONYL" TECHNICAL FIELD This invention relates to a process for the production of chlorothalonyl. BACKGROUND ART Chlorothalonyl (2,4,5,6-Tetrachloro-isophthalonitryl) with formu¬ la CN is a fungicide widely used as anticryptogamic in agricultural cultiva¬ tions and as antifungus for paints of various types. After carrying out studies, the Applicant has been able to establish the existence of various crystallographyc structures of Chlorothalonyl, showing different physical behaviours and being more or less suited for producing compositions ready for use. In particular, it has been established that there exists a crystallographyc structure - hereinafter called type I - which is composed of suitable surface-active and suspending agents - as known to the expert in the art - and which allows to obtain flowables as well as water wettable powders, having optimal physical characteris¬ tics, remaining stable throughout time and having a high biological activity. The X-ray diffraction spectrogram of said type I crystallographic structure shows some typical bands, as reported in Table 1. Table 1 X-ray diffraction spectrogram of Chlorothalonyl with type I crystallo¬ graphic structure, in a decreasing order of intensity: Diffraction Intensity Interreticular angle (degrees) distances (A) 51.2 100 3.48 56.0 60 3-19 28.8 35 6.15 62.3 35 2.87 63.6 35 2.8l 40.1 30 4-42 40.7 30 4-37 It has moreover been established that there is another crystallo¬ graphic structure of Chlorothalonyl - hereinafter called type II - which is not suited, as it is, for producing compositions ready for usej in fact, various tests carried out on compositions including this type of Chlorothalonyl have showed the following: 1. On preparing flowables, the fluid mass undergoes an irreversible hardening, which can take place either after a few hours from preparation, or even after a few months, when the composition, initially deemed suitable for use, has already been delivered to the final users. 2. Whereas, in the case of wettable powder compositions, their capacity to be suspended in water may be greatly reduced, determining the formation of coarse flocculates and giving rise to difficulties of distribution when they are used. The compositions produced starting from technical Chlorothalonyl with a type II crystallographic structure have also evidenced - pa- rallely to a physical decay - a reduced biological activity in respect of similar compositions produced starting from Chlorothalonyl with a type I crystallographic structure. The X-ray diffraction spectrogram of the type II crystallographic structure, widely differing from that of the type I structure, is reported in Table 2. Table 2 X-ray diffraction spectrogram of Chlorothalonyl with type II crystal¬ lographic structure, in a decreasing order of intensity: Diffraction Intensity Interreticular o angle (degrees) distances (A) 53 -3 100 3-34 28.8 50 6.15 46.8 30 3-80 63.2 30 2.83 58.1 25 3-07 40.8 20 4-35 DISCLOSURE OF THE INVENTION To eliminate the drawbacks of Chlorothalonyl with a type II crys- tallographic structure, various production processes have been studied to obtain Chlorothalonyl having a type I structure, namely changing the type II crystallographic structure into a different structure, more suited for producing active compositions which remain stable throughout time. It has unexpectedly been found that the type II crystallographic structure of Chlorothalonyl can be changed into a different more suitable structure, by supplying an appropriate amount of thermal and/or mechanical energy to said Chlorothalonyl, being distributed over a sufficient period of time. BEST MODES FOR CARRYING OUT THE INVENTION In particular, it has been found that, by heating the type II Chlorothalonyl, its crystallographic structure can be changed more quickly into a type I structure if operating while the product is being stirred, or else by simultaneously applying mechanical energy, for instance by forced milling (micronization). With the product in static conditions, it has been found necessary to heat the type II Chlorothalonyl for at least 8-36 hours at 200°-8θ°C, while less hours are sufficient, at the aforespecified temperatures, if the type II Chlorothalonyl is kept stirred. On the other hand, if the type II Chlorothalonyl is heated already dispersed in an aqueous phase, and eventually micronized, only a few hours are sufficient at relatively low temperatures (eg. 6θ°-90°C), to change said Chlorothalonyl into a different one of more suitable type. Moreover, it has unexpectedly been found that a Chlorothalonyl of suitable type can be produced directly in the industrial synthesis plant, if care is taken to check that, during the de-sublimation phase, the temperature of Chlorothalonyl decreases gradually, thereby preventing a rapid fall of temperature which would lead to the forming of a type II crystallographic structure, not suitable for producing stable compositions having a high biological activity. To prevent this drawback already in the phase of industrial syn- thesis, the processing chambers, starting from the de-sublimation chambers, can be suitably prearranged, for instance by supplying proper insulation and/or hot air current and/or adequate mechanical stirring, so as to allow gradual de-sublimation of the Chlorothalonyl, at a temperature lower than the melting temperature (approx. 250°C) and gradually decreasing over a period of time sufficient to guarantee its crystallization at a suitable energy level (for instance, by keeping the temperature at 250°-8θ°C for 4-24 hours). INDUSTRIAL APPLICABILITY Thanks to the aforedescribed process, it is possible to produce Chlorothalonyl having a type I crystallographic structure, fit for use in stable compositions which are particularly active as fungicides. While carrying out the searches, the Applicant has also found that, if the energy level of the heretofore specified thermal and mechanical treatments is not optimal, it could give rise to the production of a Chlorothalonyl with a crystallographic struccure defined as type III, namely having a diffraction spectrogram which partly differs from those of the other types, but has at times bands which are typical of the type I or type II Chlorothalonyl. Table 3 reports the diffraction spectrogram of said type III Chlorothalonyl. Table 3 X-ray diffraction spectrogram of Chlorothalonyl with type III crys¬ tallographic structure, intermediate between type I and type II, in a decreasing order of intensity: Diffraction Intensity Interreticular o angle (degrees) distances (A) of type III structure 53.0 100 3-36 28.2 40 6.28 61.7 30 2.90 47.8 20 3-72 67.2 20 2.67 B) Typical angles and distances of type I structure (found at times) 51.2 20 3.48 C) Typical angles and distances of type II structure (found at times) 53-3 30 3-34 46.8 20 3.80 58.1 17 3.07 28.8 15 6.25 It has moreover unexpectedly been found that, when use is made - in various compositions - of said Chlorothalonyl with a type III crystallographic structure, having also some diffraction angle and some interreticular distance typical of the type I structure, the mechanical and thermal energy produced with said process - during micronization in an aquyous phase (with colloidal mills) or in a dry state (with suitable micronizers) - is sufficient to change the crystallographic structure of Chlorothalonyl from type III into the more suitable type I structure, thereby allowing to produce stable and particularly active compositions. Said phenomenon is above all quite apparent when using Chlorothalonyl with a type III structure for preparing flowables, wherein the wet micronization of the active substance is carried out into a colloidal sand (or pearl) mill, in that the rise in temperature and the kinetic/mechanical energy produced by the friction between the siliceous particles and the solid active substance cause the desired crystallographic transformation, and this is particularly evident especially with a double passage into two colloidal mills placed in direct succession.

Claims: CLAIMS 1) Process for the production of 2,4,5,6-Tetrachloro-isophthalo- nitryl, with formula having a crystallographic structure suited for producing fungicide compositions remaining stable throughout time and having a high biological activity, characterized in that a thermal and/or mechanical treatment is carried out on the non-suited crystallographic structure, both by gradually decreasing the temperature during the de-sublimation phase, subsequent to industrial synthesis, and by supplying thermal energy - in static or dynamic conditions - and/or mechanical energy to the industrial technical product having a non-suited crystallographic structure, eventually during the phase of preparation or of microniza¬ tion of said product. 2)Process as in claim 1), carried out during the de-sublimation phase, wherein the processing chambers starting from the de-sublima¬ tion chambers are insulated and/or supplied with suitable hot air cur¬ rent and/or mechanical stirring, in order to preserve the crystals at a temperature of 250°-8θ°C for 4-24 hours. 3) Process as in claim 1), carried out on the industrial technical product with a non-suited crystallographic structure, both with the product in static conditions and while it is being stirred, by heating it at 8θ°-200°C for at least 36-8 hours. 4) Process as in claim 1), carried out on the industrial tech¬ nical product, already treated with the process according to claim 3), by operating a wet micronization into a colloidal pearl * mill, or a dry micronization into a suitable plant.

Inventors: EPIS GINO, QUERZOLA GIUSEPPE, EPIS, GINO, QUERZOLA, GIUSEPPE
Applicants: SIPCAM, S.I.P.C.A.M. SOCIETA' ITALIANA PRODOTTI CHIMICI E
Application year: 1986
Main classification: C07C121
IPC codes: A01N37, C07C67, C07C253, C07C255