Solid Particles Stabilizers And The Performance Of ASA Pickering Emulsions

Alkenyl succinic anhydride(ASA),a reactive and hydrolysis-sensitive internal sizing agent,is widely used in the alkaline/neutral papermaking process as an oil-in-water(O/W)emulsion.Conventional stabilizers and emulsifiers,such as polymers and surfactants,give rise to a series of disadvantages,for example raising the addition levels of stabilizers,causing foam problem,decreasing the emulsion stability and improving the cost of emulsion preparation.Laponite particles have been widely used as the emulsifiers of ASA-in-water emulsions after being modified by short amines.However,whether amines with nitrogen connected by various alkyl groups show similar behaviors on modification of laponite and stabilization of ASA emulsions have not been investigated.In this paper,ethylamine,diethylamine and trimethylamine were selected as short amines while dodecylamine(DDA)and dodecyl trimethyl ammonium chloride(DTAC)were used to present the long amines for modification of laponite.The effects of various amines on the properties of laponite aqueous dispersion and ASA emulsions were investigated.The morphology,property and sizing performance of the amine stabilized emulsions were compared and analyzed.The results show that the laponite particles modified by ethylamine,diethylamine and trimethylamine can reduce the negative zeta potentials of laponite in absolute value,raise the turbidity of laponite aqueous dispersions,and further lower the interfacial tension between laponite aqueous dispersions and ASA at suitable amine-to-laponite mass ratios,in which the diethylamine exerts the largest while the trimethylamine exerts the smallest influences.The adequate modification of laponite particles by the three amines reduces the emulsion droplet size,makes the distribution of the emulsion droplet size narrower,and enhances the creaming stability of laponite stabilized ASA emulsions.ASA-in-water emulsions with their smallest droplet sizes and highest stability are obtained at the amine-to-laponite mass ratio of 1.5% for ethylamine and diethylamine,and 2.0% for triethylamine modified laponites.The ASA emulsions with the smallest droplet size show the highest sizing efficiency,i.e.,the diethylamine modified laponite stabilized emulsions show the highest while trimethylamine modified laponite stabilized emulsions show the lowest sizing performance at the amine-to-laponite mass ratio of 1.5% and 2.0%,respectively.However,the introduction of ethylamine,diethylamine,trimethylamine is not obvious in reducing the hydrolysis of ASA.DDA and DTAC are effectively adsorbed on the surface of laponite particles via the electrostatic interaction.Compared to the DDA,the modification of laponite particles with DTAC can exert larger influence on negative zeta potentials of laponite particles,and make an larger increase in the turbidity of laponite aqueous dispersions when the charge amount of the latter is far larger than the former.The modification of laponite particles with DDA or DTAC can reduce the droplet size of ASA emulsions,and increase the uniformity of ASA emulsions droplets at suitable modifier-to-laponite mass ratios,in which the DTAC exerts the larger while the DDA exerts the smaller influences at their optimized charge levels.ASA-in-water emulsions with their smallest droplet sizes(2.65 ?m,2.15 ?m)are obtained at the modifier-to-laponite mass ratio of 0.6% for DDA and 5.0% for DTAC modified laponite.With increasing the storage time,the droplet sizes of ASA emulsions become larger and the droplet size distribution becomes broader.The DTAC modified laponite stabilized emulsions show the higher while DDA modified laponite stabilized emulsions show the lower sizing performance at the modifier-to-laponite mass ratio of 5.0% and 0.6%,respectively.Compared to DTAC,the storage time have less influence on the sizing degrees of the handsheets sized by DDA-modified laponite stabilized ASA emulsions.