Analysis of Properties of Synthetic Mineral Microparticles for Retention and Drainage System.

Abstract

Over the past 20 years, nano- or macro-sized particles have been used revolutionary as a component of drainage and retention systems for paper making. More recently a group of patented technologies called Synthetic Mineral Microparticles (SMM) has been invented. This system has potential to further promote the drainage of water and retention of fine particles than bentonite during papermaking as shown in the prior research. In spite of the demonstrated advantages of this SMM system, the properties of SMM particles in the aqueous state haven't been elucidated yet.

Streaming current and potentiometric titration were employed to characterize the charge behavior of SMM, depending on the synthetic conditions, including variation of the Al⁄Si ratio, partial neutralization of aluminum, salt addition and shear rate. Surface area of SMM and the distribution of SMM particle size were investigated with scanning electron microscopy in order to elucidate the relationship between the morphology and coagulation behavior of SMM, versus the pre-stated synthetic conditions, as well as to estimate the optimal conditions to produce SMM as a retention and drainage aid for papermaking.

Streaming current titration experiments showed that pH variation, caused by the change of Al⁄Si ratio and partial neutralization, profoundly affects the charge properties of SMM, on account of the variation of Al-ion speciation and the ionizable groups on the Si-containing particle surfaces. The relationship between Al/Si ratio and isoelectric pH, measured by potentiometric titration, was estimated through statistical estimation, using a factor, the OH⁄Al ratio. This procedure permits estimation of the Al/Si ratio values at which the SMM particles are expected to have negative net charges, as required for promotion of retention and dewatering during papermaking.

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.