带电纳米颗粒对烯基琥珀酸酐乳液形态和施胶机制的调控

Paper sizing is a typical problem of colloid and interface science. For a paper sizing agent, emulsification to form fine emulsion and spreading on fiber surfaces at a right moment, both of which correlate with the sizing agent and water interfacial properities, are prerequisites for adequate sizing development in paper manufacture. Akenyl succinic anhydride (ASA), a high reacitive sizing agent, would be apt to spread on water-wetted paper surface when the interfacial tension of ASA-water is excessively reduced by surface-active substances in ASA emulsions, resulting in significant hydrolysis and reduction of the sizing performance of ASA. This not only leads to the dependence of ASA sizing efficiency on alum but also causes considerable controversy in its sizing mechanism. In this project, charged nanoparticles are used to stabilize ASA emulsions in order to avoid the adverse effect of surface-active substances. The effects of charged nanoparticles, including Laponite, titania and silica either alone, two of them used together or respectively together with polyaluminum sulfate, urea, and alanine, on the ASA-water interfacial tension, ASA hydrolysis, ASA emulsion morphology and properites are investigated. By designing appropriate nanoparticle stabilizing systems, the ASA-water interfacial tension, ASA emulsion morphology and properties will be controllable. Consequently, the spreading of ASA drops on paper surfaces can be controlled and regulated to let the ASA drops spread out on dried paper surfaces and hydrolyze to a minimum extent. By analyzing the influences of ASA-water interfacial tension on chemical composition and sizing degree of paper fiber surfaces sized by using ASA emulsions with various ASA-water interfacial tensions, the sizing mechanism of ASA emulsion can be clarified. This will provide a fundation for developing environment-friendly paper size emulsions with high sizing efficiency and enrich the thoeries of colloid and interface science.

纸张施胶是典型的胶体与界面化学过程，施胶剂通过适当乳化与适时铺展于纤维表面才能充分发挥其施胶潜力。反应型施胶剂烯基琥珀酸酐（ASA）常因乳化中引入表面活性物质，使其施胶时发生过早铺展，不仅加速其水解、降低其施胶效率、导致其施胶对铝盐的过分依赖，也引起有关ASA施胶机理的争议。为避免表面活性剂的不利影响，本项目拟以带电纳米颗粒稳定ASA乳液，研究各种带电纳米颗粒及带电纳米颗粒之间、带电纳米颗粒与聚合硫酸铝及与尿素、丙氨酸联合时，对ASA－水界面性质、ASA水解和ASA乳液形态与性质的影响；通过合理设计带电纳米颗粒稳定体系，调整ASA－水界面张力、乳液形态与性质，达到调控ASA液滴在纤维表面铺展的目的；通过分析不同铺展行为的乳液在纤维表面铺展和施胶后化学成分、施胶度的差异，阐明不同界面张力下ASA的施胶机制。这对发展环境友好的高效施胶剂乳液、丰富胶体与界面化学理论具有重要意义。

烯基琥珀酸酐（ASA）是一种高反应活性的造纸施胶剂，常以阳离子淀粉作乳化剂现场乳化，以减少因ASA水解引起的施胶性能恶化。然而，阳离子淀粉稳定的ASA乳液存在乳化剂用量大、ASA含量和施胶效率低等问题。本项目以锂皂石与、纳米二氧化钛、淀粉纳米晶作为主要带电纳米颗粒，以聚合硫酸铝、纳米氧化铝、纳米二氧化硅和碳量子点作为辅助带电纳米颗粒，以不同组合方式联合稳定ASA乳液，研究各种纳米颗粒浓度对ASA-水界面张力及其乳液形态、乳液性质、乳液贮存稳定性及施胶性能的影响，发现聚合硫酸铝与ASA通过配位作用大幅度降低ASA-水界面张力，与纳米二氧化钛和锂皂石联合，皆在界面张力低于0.6 mN/m时引发非球形乳液的形成，而形成球形乳液是ASA获得良好施胶性能的前提。利用聚合硫酸铝与锂皂石联合稳定的ASA球形乳液作为施胶剂，研究了ASA乳液在纤维素膜上的铺展和与纤维素纤维之间的反应，提出了ASA乳液的施胶机理。纳米二氧化钛与锂皂石联合可提高ASA乳液稳定性，减小乳液粒径，提高乳液施胶性能，而纳米二氧化硅与锂皂石联合虽然也可略微改善ASA乳液性能但却降低了ASA的施胶性能。具有两亲性的碳量子点与淀粉纳米晶纳联合也可显著降低ASA-水界面张力，但所稳定的ASA乳液却为球形，且界面张力的降低有助于提高乳液稳定性和减小乳液粒径，提高乳液施胶性能，并赋予乳液荧光性。利用尿素、丙氨酸、三聚氰胺、四烷基氯化铵、乙胺、二乙胺和三乙胺等小分子活性物质及聚乙烯吡咯烷酮、淀粉等长链聚合物和十二烷基胺、十二烷基三甲基氯化铵等长链表面活性剂改性锂皂石，研究各种改性剂与锂皂石的作用对ASA－水界面张力、乳液形貌、性质、施胶性能和ASA水解的影响，发现小分子活性物质和表面活性剂改性锂皂石稳定的ASA乳液稳定性、粒径和施胶性能均在ASA-水界面张力最小处得到优化，而长链聚合物与锂皂石联合对提高ASA稳定性、减小乳液粒径和提高ASA乳液施胶性能则具有协同作用。该研究这不仅对制备高效、高浓ASA乳液提供了理论依据，也丰富了Pickering乳液的稳定理论。