SiO2 / Mg ( OEt ) 2 / Ethyl Benzoate / TiCl4 촉매에 의한 프로필렌 중합특성연구

Abstract

SiO₂/Mg(OEt)₂/ethyl benzoate/TiCl₄ catalysts need for propylene polymerization were prepared by using silica(Davison-952) as a support, which is known to produce polypropylene with spherical shape and narrow particle size distribution. Propylene polymerization was carried out with the silica supported catalyst cocatalyzed with triethylaluminum(TEA) in the presence of an external electron donor(EED), p-ethoxy ethyl benzoate(PEEB) at 8 atm. The effect of TEA, PEEB concentration and polymerization temperature on activity as well as stereospecificity was investigated. The maximum average polymerization rate during the initial first hour of polymerization was obtained at the mole ratio of [TEA]/[Ti]=200 and 70℃. The increase of TEA concentration decreased stereospecificity. As the polymerization temperature increased, the stereospecificity did not change. The polymerization activity in the absence of PEEB was 16.2 ㎏-PP/g-Ti·hr·atm and the isotactic index was 84% at the molar ratio of TEA to Ti of 200 and 70℃. However, the activity decreased to 12.4 ㎏-PP/g-Ti·hr·atm and isotactic index increased to 93% at the same polymerization condition except for the addition of PEEB of which amount is 17% of [TEA]. Further addition of PEEB([PEEB]/[Al]=0.25) decreased the activity to 5.2 ㎏-PP/g-Ti·hr·atm and increased isotactic index to 96%.