The grinding effect of zirconia beads with different particle sizes on the suspension agent
When using sino zirconia beads as the sanding medium in the sand mill, select sino zirconia beads with a smaller particle size, proper bead ratio and sufficient sanding time to obtain a suspension product with a narrow particle size distribution .
Choosing the appropriate sanding medium is an important means to improve the dispersion efficiency of the sand mill, and it is also a weak link in the current use of the sand mill. There are many types of sanding media. In addition to glass beads, there are currently ceramic beads, steel beads, alumina beads and zirconia beads. Although alumina beads and zirconia beads are superior to ordinary glass beads in terms of hardness, compressive strength and wear resistance, their prices are relatively high and only a few manufacturers use them. In addition, there are different opinions on how to use sanding media to obtain better grinding efficiency.
For example, when Hearst Company came to China for a discussion in 1977, it was introduced that the sanding media should be matched in size. In 1979, Natzsch, which produced sand mills in West Germany, believed that the sanding media should be of the same size. The ball is pushed away to reduce the wear effect. In this paper, sino zirconia beads are used as the sanding medium, and the particle size distribution of chlorothalonil and emamectin benzoate suspensions under different sanding conditions are discussed in order to provide a reference for the preparation process of the suspension .
Based on the formula of 40% chlorothalonil suspending agent and 5% emamectin benzoate suspending agent, a sand mill is used with zirconium beads as the sanding medium, and the sanding is changed during the sanding process. The process parameters such as the size of the medium, different ratios (different ratios of zirconium beads and different mass ratios of zirconium beads to the original drug), sanding time and other process parameters are used to prepare a series of suspensions.
Three zirconium beads with diameters of 0.4～0.6, 1.0～1.2, 1.8～2.0mm are selected as the sanding medium. The initial dosage is determined to be 60g, the formula material is selected as 50g, and the speed of the sand mill is controlled at 1900r/min. , The sanding time is controlled to 90min. After the sanding is completed, the particle size distribution of this series of suspensions is measured with a BT-1995 laser particle size distribution meter.
Zirconium beads of different particle sizes were mixed with a certain mass ratio as the sanding medium, the dosage was determined to be 60g, the formula material was selected as 50g, the speed of the sand mill was controlled at 1900r/min, and the sanding time was controlled at 90min. Determine the particle size distribution of this series of suspensions.
The amount of zirconia beads is determined to be 60g, the formula material is selected to be 50g, the speed of the sand mill is controlled at 1900r/min, and the sanding time is controlled at 30, 45, 60, 75, and 90 min. The particle size distribution of the suspension was measured in different sanding time periods.
The zirconia beads formula material is selected as 50g, the speed of the sand mill is controlled at 1900r/min, the sanding time is controlled at 90min, and the mass ratio of the sanding medium to the formula material is set to 1:1, 1.1:1, 1.2:1, respectively. 1.3:1 and 1.4:1. Determine the particle size distribution of the suspension prepared under different bead ratio conditions.
Results and discussion:
Using sanding media of different particle sizes, the sanding effects obtained are different.
Three kinds of zirconium beads with diameters of 0.4～0.6, 1.0～1.2, 1.8～2.0mm were selected as the sanding medium, and the zirconium beads were used as the dispersion medium, whether it was chlorothalonil or emamectin benzoate suspension. , The dispersion effect of small-diameter zirconium beads is obviously better than that of large-diameter zirconium beads. Among them, the dispersion effect of Zirconium beads with a diameter of 0.4～0.6mm is the best. In general, the sanding media used by sand mills are mostly round balls. The smaller the diameter, the more the number of media filled in the unit volume, and the more contact points between the sanding media. When the sanding time is the same With lower energy consumption, materials with fine particles and narrow distribution can be quickly obtained. Therefore, the finer the dispersion of the suspension agent product is required, the smaller the diameter of the sanding medium used. From the principle of sanding dispersion, the smaller the diameter of the sanding medium, the greater the probability that it will collide with each other in the sand mill cylinder and cause shearing, and the sanding dispersion efficiency is also improved. But this does not mean that the sphere can be reduced indefinitely, because the shear force generated when the spheres collide with each other is proportional to the diameter of the sphere. When the diameter of the sphere is reduced to a certain value, the shear force will drop to insufficient Disperse the aggregates of the original drug well, which makes the dispersion rate of the original drug drop sharply.