Preparation And Sizing Performance Of ASA Emulsions Stabilized By Short Amine Modified Laponite

Solid stabilized emulsions hold many advantages such as reducing/avoiding detrimental effects of surfactant, enhancing emulsion stability, preparing emulsion with high discontinuous phase volume fraction. In this paper, we employ nano-sized Laponite particles as stabilizers and short amines such as ethylamine, n-propylamine and n-butylamine as modifiers of the Laponite particles to prepare fine emulsions of industrially specific ASA, reagent grade ASA and partly hydrolyzed ASA. It is found that, the unmodified Laponite particles cannot stabilize fine emulsions of the commercial ASA and the partly hydrolyzed ASA, while can stabilize fine emulsions of the reagent grade ASA. The emulsification effect of Laponite on three kinds of ASA?water system are all improved when Laponite particles are modified by short amines. Generally, just 1~3% of Laponite particles based on ASA mass fraction can stablize ASA emulsions with high content of ASA, fine particle size and high shelf stability.The emulsification effect of modified Laponite particles, the stability of the ASA emulsions largely depend on the charge amount of Laponite particles and amines, initial volume fraction of oil, pH of water phase, stirring speed and time and the initial location of the Laponite particles. Moderately increasing the charge level of the Laponite particles can improve the emulsion stability and reduce the emulsion drop size while superfluous Laponite particles interfere with the emulsification of ASA resulting in emulsions of larger drops. ASA emulsions with higher initial volume fraction of ASA show higher stability, but too high a initial volume fraction of ASA may induce catastrophic phase inversion of ASA emulsion. The ASA emulsions invert from O/W to W/O at lower initial volume fraction of ASA when the Laponite particles dispersed in water. It is most favorable to obtain fine ASA emulsions when Laponite dosage, initial volume fraction of oil, stirring speed and time are 1~3%, 25~33%, 8000~10000 r/min, and 3~4 min (Laponite particle dispersed in ASA), respectively, while the pH of water phase is 4 (Laponite particle dispersed in ASA) or 6 (Laponite particle dispersed in water).The modification of Laponite particles with short amines can improve the affinity of Laponite dispersion to ASA, reducing the average diameter of ASA emulsions and improving the emulsion stability. However, the short amines can induce the aggregation of Laponite particles and increase the viscosity and conductivity of Laponite dispersion as well. Superfluous amines thus may interfere with the emulsification of ASA. Short amines can reduce the emulsion drop diameter and increase the stability of commercial ASA and the partly hydrolyzed ASA emulsions. The introduction of short amines can reduce the required charge level of Laponite particles in stabilizing fine reagent grade ASA emulsions, but lower the stability of the prepared emulsions. Free short amines increase the emulsion drop diameter and decrease the stability of partly hydrolyzed ASA emulsions. The short amines with longer hydrocarbon chain show stronger modification effect on Laponite particles and influence more drastically on properties of ASA emulsions. Laponite modified by 2% of n-butylamine can stabilize emulsions of fine industrially specific ASA. It is most favorable to obtain stable emulsions of reagent grade ASA when the addition levels of ethylamine, n-propylamine and n-butylamine based on Laponite are 7~8×10~-4mol/g, 5×10~-4mol/g and 3×10~-4mol/g, respectively. The stable emulsions of partly hydrolyzed ASA are obtained when the addition level of ethylamine, n-propylamine and n-butylamine based on the mass fraction of Laponite are 12~14%, 8~10% and 6~8%, respectively.The modified Laponite stabilized emulsions of industrially specific ASA show good sizing effect on BCTMP. The sizing degree is as high as 150s with only 0.3% of the industrially specific emulsions based on the mass fraction of BCTMP (oven dry). However, the sizing performance of the emulsions decreases drastically within 60 min of emulsion standing. Partly hydrolyzed ASA emulsions can also provide good sizing effect on BCTMP. The addition of aluminum sulfate can boost the sizing degree of both the industrially specific ASA and the partly hydrolyzed ASA emulsions. Neither free ASA nor ester bond formed between ASA and cellulose hydroxyl groups is detected in the oven-dried mixture of CMC and partly hydrolyzed ASA emulsions. Most of the ASA sizing agent exist in a hydrolyzed form. It may be the reaction of alum and hydrolyzed product of ASA imparts sizing effect of PH-ASA on paper while the existence of amine, especially free amines can promote the reaction of hydrolyzed ASA and alum, improving the sizing efficiency of PH-ASA emulsions.