ASA Emulison Co-stabilized By Polyaluminum Sulfate And Inorganic Nanoparticles

In paper and board-making, internal sizing is a process for making the endproducts more resistant to liquid penetration. Alkaline/neutral reactive sizing agentssuch as alkyl ketene dimer (AKD) and alkenyl succinic anhydrides (ASA) are generallyadded to the papermaking process in the form of o/w emulsion. For traditional ASAemulsions, the most commonly used emulsifier and stabilizer are surface active agentsand cationic polymers, e.g., cationic starches in conjunction with lignosulfonates/naphthalene sulfonic acids. Unfortunately, using surfactants and polymer as stabilizerusually lead to a series of disadvantages such as interfering with sizing, causing foamproblem and complicating white water system. Solid stabilized emulsions, the so-calledPickering emulsions, can avoid the adverse effects of surfactants. It is well establishedthat solid particles adsorb to oil-water interface and develop strong lateral interactions,which results in the formation of a rigid film acting as a physical barrier to dropletcoalescence. The adsorption of solid particles on ASA-water interfaces may also reducethe hydrolysis of ASA. Therefore, the emulsification process and sizing performance ofASA emulsion co-stabilized by nanoparticles such as nano-TiO2or Laponite togetherwith polyaluminum sulfate (PAS) with different basicity were investigated in this work.ASA emulsions costabilized by nano-TiO2and polyaluminum sulfate (PAS) wereprepared by homogenizing the mixture of ASA and aqueous dispersion of TiO2and PAS.It was found that the interface tension between water and alkenyl succinic anhydride(ASA) was significantly reduced by polyaluminum sulfate (PAS), increasedconsiderably by TiO2nanoparticle. The morphology of ASA emulsions are significantlydepondent on the ASA-water interfacial tension, and thus can be adjusted by varying theratio of nano-TiO2to PAS. PAS with basicity of0.75(PAS-0.75) reduced the interfacetension to a larger extent than PAS with basicity of0.3(PAS-0.3). By reducing interfacetension with PAS-0.75, ASA-in-water emulsion bearing fusiform geometries wasconstructed. The emulsion stabilized by PAS-0.3and TiO2nanoparticle bore sphericalshapes with the exception when the mass fraction of TiO2nanoparticle was low, inwhich case fused non-spherical drops were formed. Both the lowering mechanism of theinterface tension and the formation mechanism of the fusiform emulsion were proposed.Meanwhile, the property of ASA emulsion co-stabilized by nano-TiO2and PAS withvarious ASA volume fraction, mass fraction of stabilizer and speed of revolution were also analyzed based on Pickering emulsion theory.ASA emulsions costabilized by Laponite and polyaluminum sulfate (PAS) wereprepared by homogenizing the mixture of ASA and aqueous dispersion of Laponite andPAS. The properties, sizing performance and hydrolysis resistance of the prepared ASAemulsions, were investigated. The results show that the introduction of PASsignificantly improves the stability, hydrolysis resistance, and sizing performance ofASA emulsions. The ASA emulsion stabilized by2%of Laponite (based on the mass ofASA) and2%of PAS (based on the mass of Laponite) shows high hydrolysis stabilityand high sizing efficiency on bleached chemi-thermomechanical pulp. At the additionlevel of0.3%based on bleached chemi-thermomechanical pulp, the sizing degree ofASA-sized paper can be as high as120s. Even when the storage time of the ASAemulsion exceeds3h, its sizing performance is hardly changed.