Sixth-generation of ziegler-natta catalyst for homopolymer polypropylene polymerization: Effect to product properties and regulation

Abstract

Abstract The development of catalysts for polypropylene (PP) polymerization has begun since Ziegler-Natta (Z-N) discovered the catalyst for polyethylene polymerization. However, the first-generation catalyst which was a combination of TiCl3-AlEt2Cl (catalyst-co-catalyst) has low productivity and isotacticity. The modifications continue to be made to increase the productivity and isotacticity by combining the Z-N catalyst with MgCl2, internal donors, and external donors. The fourth-generation Z-N catalyst, TiCl4/Phthalate/MgCl2-AlEt3/Silane, has given satisfactory results with high productivity and isotacticity. Another concern arose when phthalate derivatives turned out to be able to initiate cancer formation. This problem has led catalyst development to the sixth-generation Z-N catalyst with a phthalate-free internal donor. This research intends to study the effects of sixth-generation catalysts to polypropylene properties when compared to the fourth-generation catalysts. We produced homopolymer polypropylene (HPP) by fourth- and sixth-generation of Z-N catalyst with the same polymerization technology. Then, the effects on product properties, namely melt flow rate (MFR), xylene soluble, residual catalyst, physical properties, optical properties, and rheological properties were observed. Sixth-generation catalyst exhibited a better stereoregularity and it made a better flexural modulus. The rheological properties showed the sixth-generation catalyst products have lower molecular weight and it generates fewer gels and lower impact strength. Sixth-generation catalyst also exhibited lower catalyst residue which allows lower dosage of an acid scavenger with comparable color performance. With increasingly strict restrictions on the use of phthalates, the sixth-generation catalyst is more convenient to use. In terms of the effect on the polypropylene properties, fourth-and sixth-generation catalysts have their respective advantages.