Effect of polyoxyl 40 hydrogenated castor oil solutions on the wet mass of colloidal silicon dioxide for extrusion/spheronization

摘要

The effect of aqueous solutions of polyoxyl 40 hydrogenated castor oil (HCO-40) on the formation of hydrophilic colloidal silicon dioxide (CSD) pellets has been investigated. Wet masses containing a 1:2 ratio of CSD to HCO-40 solutions with concentrations varying from 0 to 12.5% w/w were ram extruded and spheronized. For this ratio of solid to liquid, the results showed that the ability of CSD to form round pellets in the size range 0.71–1.4?mm was dependent on the HCO-40 concentration. The formation of round pellets was reproducible for concentrations of 2–3% w/w. The role of HCO-40 was identified by measurement of the dynamic viscoelasticity of CSD dispersions with a solid to HCO-40 solution ratio of 1:5.7. The storage modulus, G′, was shown to be sensitive to the HCO-40 concentration. It suggests that the addition of non-ionic surfactant is necessary in order to modify the viscoelasticity of the CSD wet mass through surfactant adsorption on to the CSD particle surface and that there is an optimum range of surfactant concentration for pellet formation.