Morphologies of synthetic mineral microparticles for papermaking as a function of synthetic conditions

Morphological characteristics were determined for a system of synthetic mineral microparticles (SMM), which have been developed to promote drainage of water and retention of fine particles during papermaking. Prior research, as well as our own preliminary research showed that the SMM system can have advantages in both of drainage and retention, compared with montmorillonite (bentonite), which is one of the most popular materials presently used in this kind of application.A partially gelled form of a silica-type microparticle additive is known to perform better than the corresponding sol form, in terms of fine-particle retention during papermaking. For this reason it was of interest to investigate the morphological behavior of SMM as a function of the conditions of synthesis. BET nitrogen adsorption was used to measure the surface area of SMM. The distribution of SMM particle size was investigated in the aqueous state, using a light-scattering technique. The coagulation behavior and morphology of SMM were analyzed using scanning electron microscopy (SEM). It was found that the structural characteristics of SMM particles could be explained in terms of the effects of ionic charges on colloidal stability of primary particles during formation of the SMM.