Preparation Of Polymeric Hollow Latex Particles And Investigation Of Their Morphology And Opacity Ability

With extremely strong optical opacity ability, the polymeric hollow latex particles havebeen widely applied in architectural coating, paperboard coating, leather retanning andcosmetic field. Besides, it is predicted that the hollow latex particles will also have vitalapplication prospect in fields of aerospace, damping material, biological medicine in thefuture. A series of technical problems need to be solved when preparing hollow latex particles.Several companies abroad have successfully produced high quality hollow polymeric productwhich meet the requirement of industrial applications. However, due to technology securityreasons, neither domestic companies nor scholars have produced such kinds of products.Furthermore, according to the published papers and patents, few scholars have paid muchattention to the research of morphology and opacity ability of the multi-stage hollow latexparticles. Therefore, this paper aimed at preparing polymeric hollow latex particles with alkaliswelling method and investigating their morphology and opacity abilities.This experiment was carried out in basis of research of predecessors. By applying thealkali swelling semi-continuous seeded emulsion polymerization method and layer by layerpolymer encapsulation technique, this paper firstly prepares core latex particles containingmuch carboxyl group, and then the intermediate layer with strong hydrophilicity and weakhydrophobicity was polymerized in the surface of the core latex particles. Finally, the totallyhydrophobic shell layer was prepared in the surface of the intermediate layer to producemulti-stage latex particles, and meanwhile, the alkali was charged to swell the multi-stagelatex particles. The results shows that the average diameter of the hollow latex particles is350-750nm, the void is30%-90%of the whole volume of the particles, and the solid contentof the emulsion is31wt.%.In this article, the FTIR spectrum and measurement of conversion rate proved that thereaction was carried out as expected, particle size and viscosity analysis method were appliedto investigate swelling degree of hollow latex particles, SEM and TEM analysis method wereused to characterize morphology of hollow latex particles, measurement of acid value was todemonstrate the full encapsulation of core latex particles by intermediate layer and theUV-Vis spectrophotometry characterization method was to quantify the opacity ability ofhollow latex particles.In this experiment, effect of thickness of intermediate and shell layer, crosslink monomerdosage, alkali swelling occasion and theoretical glass transition temperature of the intermediate layer on the morphology and opacity ability of the hollow latex particles wereinvestigated. The results showed that morphology of hollow latex particles, such as surfacesmoothness, the inner void size and weather the latex particles are collapsed or ruptured, isdetermined by its swelling degree. And the opacity ability of hollow latex particles isdetermined by its morphology. The hollow latex particles would show better opacity ability, ifthey possess more integrity structure and have fewer amounts of collapsed or rupturedparticles. Furthermore, the optimum intermediate/core is8, the optimum shell/coreencapsulated by intermediate layer is7-9; the optimum crosslink monomer dosage in the shellis6wt.%; the optimum alkali swelling method is30wt.%-50wt.%(shell preparation stage); thecore is prior to adopt surface crosslinking method and the optimum crosslink monomerdosage is1wt.%-3wt.%(the total weight of the monomer to prepare core latex particles); theintermediate layer should not been crosslinked and its optimum theoretical glass transitiontemperature is90℃.