Laponite Modification And The Impact Of Modification On The ASA Emulsion Performance

Alkenyl succinic anhydride has the advantages of high sizing efficiency, highaluminum tolerance and good suitability to different pulps. However, it is easy tohydrolysis, which has adverse effect on sizing development of ASA. It is, therefore,nessecery to emulsify ASA in situ and improve the sizing performance andhydrolytic stability of ASA emulsion. In this paper, Laponite was used as particlestabilizer of ASA emulsion. By using sodium alginate or chitosan to co-stabilize ASAemulsion together with Laponite or modifying Laponite with melamine orpolyvinylpyrrolidone (PVP), the stability, sizing performance and hydrolysis resistanceof Laponite stabilized ASA emulsion are expected to be significantly improved.According to the experiment, ASA emulsion stabilized by Laponite and chitosan showsno improvement on emulsion stability to coalescence, but the addition of chitosan canimprove the creaming stability and sizing performance of Laponite stabilized ASAemulsions. The emulsion sizing performance gets its greatest improvement when thechitosan addition level based on Laponite reach to4%. When using sodium alginate toco-stabilize ASA emulsion,0.3%of addition level can improve the stability and sizingperformance of Laponite stabilized ASA emulsions.Melamine can adsorb on the Laponite, which reduces the extent of hydration, buthardly affect the zeta potential of Laponite and turbidity of its aqueous dispersion. Themodification of melamine on Laponite makes the apparent interfacial tension betweenthe ASA and the Laponite aqueous dispersion exist a minimum value. When using themelamine-modified Laponite to stabilize ASA emulsion, the stability and sizingperformance of ASA emulsion are significantly enhanced while the emulsion dropletsize is decreased. As the charge level of melamine based on Laponite reaches to3%, theASA emulsion reaches to the best stability, smallest droplet size and highest sizingperformance. More importantly, the modification of Laponite with melamine can reducethe hydrolysis of ASA when it is used as ASA emulsion stabilizer. After the storage timeof the melamine-modified Laponite stabilized ASA emulsion exceeds120minutes, thesizing effect of the emulsion is only reduced by10%. Increasing the volume fraction ofASA leads to the rapid increase of the viscosity of ASA emulsion. At the ASA volumefraction of25%, the as-prepared emulsion stabilized by melamine-modified Laponitehas the smallest droplet size and highest sizing performance. When the dosage of melamine based on Laponite is fixed at3%, the largest volume fractions of ASA in ASAemulsions stabilized by1%,1.5%and2%of Laponite are60%,50%and40%,respectively. The emulsion with the largest ASA volume fraction shows lower sizingperformance but better hydrolytic stability than that with25%of ASA volume fraction.PVP can modify the Laponite by adsorbing on its surfaces. The modification ofLaponite byPVP only slightly enhances the turbidity of Laponite aqueous dispersionand reduces the interface tension between Laponite aqueous dispersion and ASA. Whenusing PVP-modified Laponite to stabilize ASA emulsion, the stability and sizingperformance of ASA emulsion can be remarkably improved, while the droplet size thehydrolysis of ASA can be largely reduced. When the charge level of PVP based onLaponite reaches35%for1%Laponite stabilized ASA emulsion while25%for2%Laponite stabilized ASA emulsion, the ASA emulsion reaches its best stability, smallestdroplet size and highest sizing performance. The modification of Laponite by PVP canalso reduce the hydrolysis of ASA in ASA emulison. When the storage time of the ASAemulsion is over120minutes, the sizing degree is only reduced by16%.