Improving Stability and Sizing Performance of Alkenylsuccinic Anhydride (ASA) Emulsion by Using Melamine-Modified Laponite Particles as Emulsion Stabilizer

Alkenylsuccinic anhydride (ASA) is commonly applied as oil-in-water (o/w) emulsions in the papermaking industry. Herein Laponite mineral nanoparticles were employed as a stabilizer of the ASA emulsions after being modified with melamine just before emulsion preparation. The emulsion was prepared by homogenizing the mixture of ASA and melamine-modified Laponite aqueous dispersion. The modification of melamine on the Laponite was characterized by infrared spectroscopy and X-ray diffraction, whereas the impacts of the modification on the morphology, wettability and ζ-potential of the Laponite, as well as the interfacial tension between ASA and Laponite aqueous dispersion, were also analyzed. It is found that the adsorption of melamine on Laponite particles neither causes the aggregation nor significantly changes the charge properties of the Laponite particles. However, the adsorption of melamine can significantly increase the wettability of Laponite by the ASA liquid, and adequately lower the apparent interfacial tension between ASA and Laponite aqueous dispersion when the melamine-to-Laponite mass ratio is less than 3%. This results in an improvement in emulsion stability, a reduction in emulsion droplet size and an enhancement in the sizing performance of the ASA emulsion when the emulsion is stabilized by melamine-modified Laponite particles. The ASA emulsion with the smallest droplet size and best sizing performance is produced at a melamine-to-Laponite mass ratio of 3%. By monitoring the variations of the emulsion with time, it is discovered that the modification of Laponite with melamine can restrain the growth of emulsion droplets and the hydrolytic action of ASA substantially, thus decreasing the loss in sizing performance of the ASA emulsion with time. This is particularly important for the wide application of ASA emulsions in the papermaking industry.