An improved phase‐inversion process for the preparation of silica/poly[styrene‐ co ‐(acrylic acid)] core–shell microspheres: synthesis and application in the field of polyolefin catalysis

Spherical and well‐dispersed silica/poly[styrene‐ co ‐(acrylic acid)] (SiO 2 /PSA) core–shell particles have been synthesized using an improved phase‐inversion process. The resulting particles were successfully used as supports for polyolefin catalysts in the production of polyethylene with broad molecular weight distribution. Through the vapor phase, instead of the liquid phase in the traditional process, a non‐solvent was introduced into a mixture of micrometer‐sized SiO 2 and PSA solution. The core–shell structure of the resulting SiO 2 /PSA microspheres was confirmed using optical microscopy, scanning electron microscopy, Fourier transfer infrared spectrometry, thermogravimetric analysis and measurement of nitrogen adsorption/desorption isotherms. In order to avoid agglomeration of particles and to obtain a good dispersion of the SiO 2 /PSA core–shell microspheres, the non‐solvent was added slowly. As the concentration of PSA solution increased, the surface morphology of the core–shell particles became looser and more irregular. However, the surface area and the pore volume remained the same under varying PSA concentrations. The SiO 2 /PSA core‐shell microspheres obtained were used as a catalyst carrier system in which the core supported ( n ‐BuCp) 2 ZrCl 2 and the shell supported TiCl 4 . Ethylene/1‐hexene copolymerization results indicated that the zirconocene and titanium‐based Ziegler–Natta catalysts were compatible in the hybrid catalyst, showing high activities. The resulting polyethylene had high molecular weight and broad molecular weight distribution. Copyright © 2010 Society of Chemical Industry