Preparation Of Silica Filler Materials And Matting Materials By Microdispersion Reactor

Silica hydrated have been used as filler agent or densifying agent, which have been widelyused in rubber tyre，absorbent and toothpaste. Silica matting agent was used to change propertyof coating. Currently, the industrial preparation of silica hydrated nanoparticles utilizes theprecipitation method and fume method. However it has the disadvantages of the large diametersand the wide distribution of particle diameter, as well as poor dispersion. The typical reactor ofprecipitation operation process is a stirred tank. According to theories of crystallization kinetics,the particle diameters is dominated by the supersaturation ratio of the production. However, intypical stirred tanks, good mixing performance and a high supersaturation ratio are very difficultto obtain. Therefore, developing highly efficient mixing equipment is a key factor to solve thisproblem.The high surface area and large pore volume of silica hydrated was prepared by usingsodium silicate and sulfuric acid as raw materials in a membrane-dispersion microstructuredreactor. The initial concentrations of Na2SiO3and H2SO4, flow rate of Na2SiO3aqueoussolution and the final pH were investigated. It was discovered that the mass transfer rate andthe supersaturation ratio could reach very high in this novel reactor, which was suitable forobtaining the tiny primary particles. Through the TEM imges of silica hydrated, the averagediameter of silica primary particles was5.3nm, which was close to that of silica hydratedprepared by combustion of SiCl4in H2and O2. Beside this, there is no shear force in thisreactor, it is also suitable for loose aggregation of primary particles. The specific surface areaand pore volume of amorphous silica reached as high as402.0m2/g and2.5mL/g, respectively.Silica precipitation consisted by the diameter of10nm primary particles was preparedusing the feedstock of sulfuric acid and sodium silicate in the micro-dispersionmicrostructured reactor, the precipitation was dispersed again in ethanol, high fluffy silicaflatting agent with was obtained after spray drying. It was because that the high mass transferrateand the supersaturation ratio could reach very high in this microdispersionreactor, whichwas suitable for obtaining the formation of tiny primary particles. Spray drying can improvethe fluffy of silica matting agent, through rapidly evaporating solution of ethanol, the porousof flatting agent was preserved. When the final pH of this reaction was equal to8.5，porevolume and the average pore diameter of matting agent was2.14mL/g and34.07nm，respectively. Comparing this silica matting agent with commercial products prepared by fumemethod, it was found that the properties of these samples were close, however, this method ofprecipitation can greatly reduce the cost of preparation.High dispersed silica hydrated was prepared using sulfuric acid and sodium silicate as raw material in a micro-dispersion microstructured reactor, sulfuric acid was diluted by thesolution of ethanol. During the reaction process, organic solvents combined with silanolprevent primary particle from connecting with other silanol of particles, which can obtain theproduct with high dispersion. When the concentration of ethanol is60%, the diameter of20-30nm primary particles, packing into dispersed spherical particles, can be obtained throughthe method of my lab. A new method of preparing high dispersion silica was discovered,which was easy and simple for obtaining highly dispersed silica.