Preparation Of Polymeric Hollow Latex And Investigation Of Their Modification By Nano-titanium Dioxide

Polymeric hollow latex is a special core-shell emulsion whose latex particles have hollow structure after drying. The particles of hollow latex have internal cavity and external hard-shell. After the latex particles drying, there is a two-phase interface between internal cavity filled with air and external polymer hard-shell. Due to the different refractive indices between the inside and outside, the effective scattering of incident light can occur in the two-phase interface, so the latex particles have light-shielding properties after drying. Because of special structure and unique properties, Polymeric hollow latex particles have broad application prospects in paint, paper, leather, cosmetics and other fields.In this paper, single-shell hollow latex and hollow latex with soft/hard double shells were prepared by core-shell emulsion polymerization and Alkali swelling treatment. Furthermore, hollow latex modified with nano-titanium dioxide was studied. The work was divided into three parts:(1) Core-shell polymer emulsion with P(MMA-BA-MAA) core and P(St-AN-DVB) shell was prepared by seed emulsion polymerization technique, then the latex particles were swelling-treated by sodium hydroxide solution. After that,opacity latex with hollow structure was obtained.In this article, FTIR analysis and measurement of conversion rate proved that the reaction was carried out as expected. Structure and morphology of the hollow latex particles were characterized by TEM and SEM analysis. Hollow structure and the degree of swelling of hollow latex particles were studied by DSC and particle size analysis. UV-Vis spectrophotometer analysis was to discuss opacity ability of hollow latex particles. Experimental results showed that, the hollow latex particles prepared had uniform distribution and average particle diameter of350--500nm. The latex particles had a hollow structure obviously, and the internal cavity was40%-60%. The coating had excellent opacity properties when hollow latex and film emulsion were used as composite emulsion. The optimum conditions for preparing hollow latex were, the amount of SDS in seed emulsion and shell emusion being1%of monomers respectly, seed/core monomer mass ratio being1:6, MAA amount of core monomer being30%, crosslinking monomer DVB of shell layer being2%, alkali-swellable solution being NaOH solution, and swelling temperature being95℃.(2) Soft/hard double shell hollow latex with intermediate soft shell was prepared by multi-step emulsion polymerization method on the basis of single-shell emulsion method and conditions. The results showed that, composite coating had minimum light transmittance and best opacity performance when Tg of intermediate soft shell was60℃and core:soft shell: hard shell was1:3:3.(3) Preparation of hollow latex with shell modified by nano-TiO2was carried by in-situ. Morphology and particle size distribution of modified latex particles were characterized by SEM and size analysis. Effect of nano-TiO2amount on emulsion stability and opacity properties was discussed. Studies had shown that, spherical regularity and monodisperse of latex particles did not change by nano-TiO2modification, and emulsion gel was lowest, opacity performance was best, heat resistance of emulsion improved when nano-TiO2amount was2%of monomers.