Viscosity of kaolin slurries: Effects of dispersant and urea-intercalation

Abstract

Good fluidity (low viscosity) of highly concentrated kaolin is highly needed in paper-coating industry. We put forward an effective route to improve the viscosity concentration of Beihai kaolin slurries. The effects of various factors such as solid content, pH, dispersant content, and urea-intercalation on the viscosity of kaolin slurries were investigated. The results revealed that the viscosity of kaolin slurries significantly decreased with decreasing solid content or with increasing pH and dispersant content. It was worth noting that urea-intercalation was proven to be an efficient method for promoting the dispersion of highly concentrated kaolin as compared with adding dispersant. The intercalation ratio of urea-intercalated kaolin was increased from 17.36% with 2% of urea addition to 81.30% with 6% of urea addition. Meanwhile, the viscosity concentration of raw kaolin slurry was improved from 65.0% to 70.13% after the intercalation of urea with 6% addition, which was attributed to finer particle size, increased pH value and more negative charges of urea-intercalated kaolin. Therefore, the route is effective to improve the dispersion of highly concentrated kaolin for paper-coating.