Pesticide formulations and process for the manufacture thereof

Details Pesticide formulations and process for the manufacture thereof Pesticide formulations and process for the manufacture thereof

1997-12-23

1999-06-15

Pak, John

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Ester doai

514531, 514770, 514772, 514937, 514941, 514949, 514970, 424405, A01N 5300, A01N 5314, A01N 2504, A01N 2530

Patent

active

059122676

DESCRIPTION:

BRIEF SUMMARY
The invention relates to pesticide aqueous suspensions containing beta-cypermethrin as insecticide active ingredient in 0.1 to 20% by mass beside physical and chemical stabilizers. Further subject of the invention is a process for the preparation of these suspensions.
Beta-cypermethrin (The Pesticide Manual 9th Edition p 212-213) is approximately a 2:3 mixture of the following enantiomer pairs: (S)-.alpha.-cyano-3-phenoxy/benzyl-(1R)-cis-3-(2,2-dichlorovinyl)-2,2-dime thyl/cyclopropane/carboxylate and (R)-.alpha.-cyano-3-phenoxy/benzyl-(1S)-cis-3-(2.2-dichlorovinyl)-2,2-dime thyl/cyclopropane/carboxylate with (S)-.alpha.-cyano-3-phenoxyvbenzyl-(1R)-trans-3-(2,2-dichlorovinyl)-2,2-di methyl/cyclopropane/carboxylate and (R)-.alpha.-cyano-3-phenoxy/benzyl-(1S)-trans-3-(2,2-dichlorovinyl)-2,2-di methyl/cyclopropane/carboxylate in the form of trielin cristalls. It is a well known very effective insecticide introduced to the market by CHINOIN Pharmaceutical and Chemical Works Co. Ltd. in 1989 under the name of CHINMIX. Beta-cypermethrin, its synthesis and compositions containing beta-cypermethrin as active ingredient are described in Hungarian patent specification Nr. 198.612. European patent specification Nr. 0208758, USA Pat. specifications Nos. 5,192,739 and 5,153,349 and in the British patent specification Nr. 2,251,621.
The above mentioned patents describe procedures for the formulation of beta-cypermethrin where the active ingredient is dissolved in organic solvent(s), preferably in the presence or without the presence of emulsifiers. The product thus obtained will be sprayed out preferably emulsified in water. The manufactured and marketed preparations are all organic solutions of the active ingredient (Chinmix 5 EC, Chinmix ME, Cyperyl-S ULV).
Such preparations have beside their indisputable advantages (simple manufacturing, good stability and easy handling) several disadvantageous characteristics resulting mainly from the use of organic solvents. These are: fire and explosion danger, high toxicity, expensive packaging.
All these disadvantages can be eliminated if the active ingredient is formulated in an aqueous suspension. This way the easy handling and by using the appropriate formulation technology the biological effectiveness of the product equivalent to that of the solvent formulations can be preserved.
In aqueous suspension concentrates (known in plant protection as FW or SC formulations) the active ingredient is present in a fine (usually in a few .mu.m size) colloidal state. Physical stability of the system is ensured by surface active substances, antifreeze substances, thickeners and other auxiliaries substances. The extremely low particle size is achieved by wet grinding with the help of pearl mills.
To prepare a stable aqueous suspension is not an easy task even for a technician. The colloid system is in a very sensitive equilibrium and can be influenced by several factors such as temperature, interactions among the elements of the system, etc. Physical and chemical characteristics of the suspendable substance (active ingredient) have a great significance and therefore there is no universal formulation recipe which could be applied for any active ingredient. Technicians generally accept it as a basic requirement that the substance to be formulated should be practically water insoluble, should have a relatively high melting, point and should be resistant to hydrolysis.
Beta-cypermethrin meets partly these requirements because its water solubility at 20.degree. C. is 0.01 mg/liter and with addition of certain substances (e.g. maleinic acid, malonic acid, phthalic acid) its chemical stability can also be insured.
The difficulty had lain in its relatively low (60 to 65.degree. C.) melting point which caused the failure of the early formulation trials. Although the temperature of the suspension during usual grinding, processes did not quite reach 60.degree. C. (generally it was between 35 to 50.degree. C.) the active ingredient partly still melted or recrystallized.
The reason for this phenomenon

REFERENCES:
patent: 4607050 (1986-08-01), Kieran et al.
patent: 4997642 (1991-03-01), Curtis et al.
patent: 5153349 (1992-10-01), Zoltan et al.
patent: 5192793 (1993-03-01), Szekely et al.
The Pesticide Manual, 9th Edition, pp. 212-213 (No Date Available).
Gubelmann-Bonneau, I. et al., Tristyrylphenol Surfactants in Agricultural Formulations: Properties and Challenges in Applications, ASTM, SuperTech. Publ. (Pestic. Formulations and Applied Systems, 14th Col., pp. 119-136 (1995).
Derwent Abstract Accession No. 76-02668 (1976), Abstracting JP 50-83268 (Jul. 5, 1975).

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