Reactive Sizing Agents Emulsions Stabilized By Montmorillonite Nanoparticles

Compared with conventional emulsions, microparticle stabilized emulsions havemany advantages, such as higher internal phase volume fraction, higher stability andless or no adverse effects from surfactants, which is every important to realize greenproduction for papermaking industry. In this paper, platelet clay, such as bentonite andLaponite, and nano-sized titanium dioxide were employed as solid particle stabilizerseither individually, combined with each other, or short amines while reactive sizingagents including ASA and AKD were employed as oil phase, to investigate theemulsification and stabilization effects of solid particles on the sizing agents.Meanwhile the properties of the clay and nano-TiO₂stabilized ASA emulsions withvarious ASA volume fraction were analyzed based on the Pickering emulsion theory.The results show that neither Na-bentontie nor butylamine modified Laponite canstabilize AKD emulsion with100%of emulsion phase, however, the AKD emulsion isstable when the Na-bentontie and butylamine modified Laponite are both employed asthe emulsifiers of AKD. The optimum emulsification conditions are as follows: thedosages of butylamine, bentonite and Laponite are6%based on Laponite,4%based onAKD and2.5%based on AKD, respectively. The prepared AKD emulsions show goodsizing performance.Stable ASA emulsion can be prepared using butylamine modified bentonite asstabilizer. According to the initial location of the bentonite particles and whether freebutylamine being removed or not after reacted with the bentonite, three particledispersed modes were designed, and their effects on ASA emulsion stability and sizingperformance were investigated. It is found that the optimum conditions for preparingstable ASA emulsion are different for the three particle dispersed modes. When thebentontie particles are dispersed in aqueous phase, and the free butylamine is notremoved, the most suitable dosages of butylamine and bentonite are0.205mmol/gbased on bentonite,5wt%based on AKD, respectively. However, when the freebulylamine is removed, the corresponding dosages are0.342mmol/g and5wt%,respectively. When the bentontie particles are dispersed in ASA, the most suitabledosages of butylamine and bentonite are0.479mmog/g and5wt%, respectively. For theASA emulsions prepared at their optimized conditions, the sizing degrees of their sizedpapers increase with increasing their charge levels. The ASA emulsions in the presenceof free amine show better sizing performance than that with free amine being removed. This indicates that the free butylamine promotes the sizing development of the ASAemulsion.When the nano-TiO₂is used to stabilize ASA emulsions alone, it is found thatemulsion with both w/o and o/w types are formed as the aqueous phase volume fractionexceeds50%, while complete w/o emulsion is prepared as the aqueous phase volumefraction is less than50%. The complete w/o the emulsion is not stable to sedimentationafter24h. Particle initial locations significantly affect the emulsion stability, emulsiondroplet size and emulsion type. Laponite and nano-TiO₂can be modified by ASAhydrolysate at the ASA-water interface, and the hydrophobicity of the modifiedLaponite and nano-TiO₂is enhanced. When the Laponite and nano-TiO₂particles areemployed as stabilizers together and initially dispersed in ASA and aqueous phase,respectively, the volume fraction of ASA for catastrophic phase inversion from o/wemulsion to w/o type is higher than that when the Laponite and nano-TiO₂particles areinitially dispersed in aqueous phase and ASA, respectively. The ASA emulsionsco-stabilized by nano-TiO₂and Laponite show good sizing performances.