Preliminary Study On The Application Of Four Organobentonite In Pesticide Suspension Concentrate

The hard control of physical stability had been an important cause that restricted the development and production of pesticide suspensions. In this study, the modified organic bentonites were respectively used to the pesticide aqueous suspension concentrate (SC) and oil flowable concentrate (OF), and their possibility and application potential in the stability improvement of pesticide suspension concentrate was determined.Four kinds of quaternary ammonium salt cationic surfactants (respectively numbered 1227, 1427, 1631 and 1831) were used into the organic modification of sodium bentonite, and the structure of prepared organic bentonite was characterized by infrared spectru (IR) and x-ray diffraction (XRD). The results indicated that the organic carbon chains of quaternary ammonium salt cationic surfactants had entered the lamellar structure of prepared bentonites, which demonstrated the four organic bentonites had been successfully prepared.The determination of suspension capability in water of test four organic bentonite indicated that 1831-bent had a comparatively better suspension. But the suspension of 1227-bent, 1427-bent and 1631-bent was not ideal. Especially, 1227-bent and 1427-bent could rapidly deposit and flocculate, and showed strong water repellency. Chose 5% hexaconazole SC as test system, and determined the sedimentation resist action. The results showed that the physicial stability of samples prepared by 1831-bent was better than that of the samples prepared by the other three bentonites. However, compared to the unmodified Na-bent, the advantage of its action was not obvious.The effect of different factors on the character of 1831-bent in aqueous suspension concentrate was determined. The results indicated that alkalescent and neutral environment benefited the suspension of 1831-bent in water. Different electrolytes and their dose also had great influence on the suspension of 1831-bent. Among the selected electrolytes, the effect of NaCl was the greatest and the effect of AlCl3 was the least. Besides, the suspension became more instability with the increase of molar concentration of electrolytes. There was great difference among different surfactants. The use of anionic surfactant and cationic surfactant could not only be adverse to the improvement of suspension stability, but also destroy the former stability and accelerated the sedimentation of 1831-bent. The nonionic surfactant had little influence on the system stability, and there was no obvious change to the stability before and after use. The effect of thickener on system stability showed that xanthan gum could benefit the stability, but tragantine exhibited worst effect. Considering the influencing factors and the application effect of 1831-bent in three pesticides SC, as well as its unobvious advantage and high production cost, we concluded that organic bentonites could not be applied to pesticide SC.The critical volume and swelling volume of test organic bentonites in different oil medium were determined. The results indicated that all the test organic bentonites were lipophilic, and their lipophilic character changed in different oil medium. Each organic bentonite showed better lipophilic character in biodiesel and palm oil, but worse lipophilic character in soybean oil and cotton oil. Chose the comparatively inexpensive and better emulsified biodiesel as oil medium, and determined the application effect of the four organic bentonites on the stability improvement of 4% nicosulfuron OF. The results indicated that the suspension percentage of OF prepared by 1227-bent kept above 95% before and after heated store, and the separated oil percentage kept below 3% after stored at 54℃for 14d or under room temperature for 30d to 60d. After long observation, the physical characters of preparations kept better, and no bottom clinging was obversed. Besides, the possible effect of 1227-bent on the chemical stability of active ingredient and on the control effect of preparation was respectively determined by HPLC and field efficacy trial. The results indicated that 1227-bent had no any adverse effect on the active ingredient and control effect. From that, we concluded that 1227-bent could be applied to 4% nicosulfuron OF with biodiesel as oil medium, but its applicability in other pesticide and oil medium need our further study.