Effect of Important Precipitation Process Parameters on the Redispersion Process and the Micromechanical Properties of Precipitated Silica

摘要

In the past, the importance of the industrial mass production of high-quality products and specialty chemicals by precipitation increased rapidly. In the industry, usually larger aggregates are produced and in order to produce colloidal systems with the desired properties, a more or less intense dispersion of the precipitated particles is necessary. The micromechanical properties such as the maximum indentation force, the plastic and elastic deformation energy, and the strength can give information on the product and the efficiency of the dispersion process. Generally, the temperature, as one of the most important parameters of the semi-batch precipitation process of silica, was varied in order to change the structure, the primary particle size, the aggregate size, and the primary particle interactions in the aggregates. Dispersion of the precipitated silica in a stirred media mill and a dissolver show that the higher the precipitation temperature, the higher is the product fineness and, thus, the smaller is the strength of the aggregates. The reason for this effect is the increase of the primary particle size and the decrease of the solid bonds with increasing precipitation temperature. Because of higher stress intensities, the product fineness in a stirred media mill is considerably higher than in the dissolver. In principal, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with decreasing particle strength and maximum indentation force. Besides the maximum indentation force, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with increasing quotient of plastic and elastic deformation energy.