Regulating the monomers composition ratio inside the particle nanodomains with induced condensing agent and its impact on particle growth

Abstract

Induced Condensing Agent (ICA) is commonly employed to enhance heat removal of olefin polymerization in gas phase fluidized bed. It is well known that ICA significantly promotes the instantaneous rate of ethylene polymerization and improves the solubility of ethylene, but little is known about the effect of ICA on regulating olefin monomers composition ratio in the nanodomains of polypropylene particles and the particle growth. In this work, we investigated this matter by adjusting the concentration of ICA during the copolymerization stage of impact polypropylene. This method can alter the monomers composition ratio in the polypropylene particles effectively, which, in succession, provides a systematic study on the effect of particle growth. Here we demonstrated that the propylene/ethylene ratio in polypropylene particles rose with addition of ICA. However, the particle size analysis suggested the existence of ICA caused the biomodal size distribution, indicating that the condensation of ICA required an essential pressure gradient length about 250–500 μm. Differential EPR distribution between the surface and internal of the particle provided novel perspectives for producing HIPP with high rubber content. This work also offered new insight into the condensed mode cooling olefin copolymerization process.