Preparation And Properties Reaserch Of Methylene Bis Thiocyanate Suspension Concentrate

With the increasing scarcity of water resources, the recycled water is paid more and moreattention to be reused recently. Methylene bis thiocyanate (MBT) is an excellentbroad-spectrμm sterilization algaecide. It is one of the most widely used broad-spectrμmbactericidal drugs in the filed of circulating water domestic. However, solid dithionitrilemethane is hardly soluble in cold water. Solid dithionitrile methane is prone to precipitationwhen it is used in circulating water directly, and the bactericidal effect is difficult to get fullexhibition. Therefore, the preparation of liquid dithionitrile methane becomes the key factorto increase its bactericidal effect. The preparation of liquid dithionitrile methane not onlyovercomes the shortcomings of solvent-based agents about toxic, flammable, environmentalpollution, but also it is transported and used easily. Thus, it can be used wildly in the field ofpesticides, fungicides, etc. However, amount of suspension concentrate have poor stabilityand poor dispersion. In this paper, methylene bis thiocyanate suspension concentrate wasprepared with good stability and good dispersion in water, and combined with the research ofstability, dispersion and rheological characteristics of dithionitrile methane suspensionconcentrate. Rational materials selected, formulation design and grinding process design werecarried out at the same time. The shortcoming of poor stability and poor dispersion had beenovercomed by the method of surfactant complex. The rheological characteristics ofdithionitrile methane were also deeply studied in this paper.Methylene bis thiocyanate suspension concentrate was prepared by using MBT asdispersed phase, water as continuous phase, xanthan gum(XG) as thickener, magnesiumsilicate, aluminum(SB) as thixotropic agent, EFW and D425as surfactant, glycol as antifreeze,acetic acid as pH adjusting agent and Fomax805as defoamer. Then，the content effect ofsurfactants and other additives on the stability of methylene bis thiocyanate suspensionconcentrate were investigated. Grinding time, grinding process, and the original drug particlesize influence on the stability of methylene bis thiocyanate suspension concentrate had alsobeen studied. Finally, the optimal formulation and optimal process were worked out in thispaper. At the same time, the bactericidal capacity of industrial circulating water of methylenebis thiocyanate suspension concentrate using in industrious circulating water was studied in this paper. The results demonstrate that when the proportion of EFW/D425is1/1(the totalcontent were3%), XG content is0.5%, SB content is2%, glycol content is4%, prepared bygrinding for4h with sand mill, methylene bis thiocyanate suspension concentrate with goodstability and good dispersion would be prepared. At the50ppm concentration in industrialrecycled water, MBT suspension concentrate has a good effect on sterilizing anaerobicbacteria, reducing bacteria and iron bacteria.By changing the dosage of EFW and D425, effects of surfactants on particle surface zetapotential and properties of thixotropy and shear viscosity were studied with Fourier transforminfrared spectroscopy (FTIR), Zetasizer2000(Malvern) instrument and ARR550rheologicalinstrument. Results of Zetasizer2000(Malvern) instrument showed that under the conditionof diluted10-fold, in the system of SC-D, the absolute value of the Zeta potential increaseswith the dosage of surfactant D425increases; in the system of SC-E, with the increase of thesurfactant EFW, the absolute value of Zeta potential increases firstly and then decreases; inthe system of SC-ED, the absolute value of Zeta potential increases firstly and then decreases.The effects of surfactants on the thixotropy of methylene bis thiocyanate suspensionconcentrate are different. In the system of SC-D, under the condition of WD425＜3%，the shearviscosity increases with time increases firstly and then increases. When WD425=3%, therelationship between shear viscosity and shear time showed two thoughs and one peak. WhenWD425＞3%, the shear viscosity first decreases and then increases, and finally trended toequilibrium.While in the system of SC-E, when WEFW＜4%, the shear viscosity decreasesfirstly with time increases and then increases, when WEFW≥4%, the shear viscosity decreaseswith shear time increases. The fluid characteristics Eigen equation is good correlation withHerschel-Bulkley model. The effects of EFW, D425and both complex onmethylene bis thiocyanate suspension concentrate thixotropy are similar. As the surfactantconcentration increases, the system shear stress decreases firstly and then increases; when thetwo surfactants compound, the shear stress decreases firstly then increase with EFW andD425content ratio increases.