Propylene homopolymer having high melt strength and preparation method thereof

摘要

The present invention provides a process for preparing high melt strength propylene polymer by direct polymerization, comprising that a propylene polymer with wide molecular weight distribution and containing “very high molecular weight fraction” can be prepared by controlling the species and ratios of the external electron donors in the Ziegler-Natta catalyst system at different reaction stages according to the requirement for different molecular weight fractions in the different propylene polymerization stage of the series operation, and said polymer has excellent mechanical properties, especially with very high melt strength. The present invention also provides a propylene homopolymer with high melt strength, comprising the following features: (1) the MFR is 0.2-10 g/10 min at 230° C. with a load of 2.16 kg; (2) the molecular weight distribution Mw/Mn is 6-20; (3) the content of the fraction with a molecular weight higher than 5,000,000 is higher than or equal to 0.8 wt %; (4) Mz+1/Mn is higher than or equal to 70. Said homopolymer can be used in the preparation of foam products, thermoforming products, biaxial stretching films, blown films and blow-molded products.

主权项

1. A process for preparing propylene homopolymer with high melt strength, comprising carrying out a propylene homopolymerization reaction of two or more stages in two or more reactors connected in series, wherein
the first stage comprises carrying out a propylene homopolymerization reaction in the presence of a Ziegler-Natta catalyst comprising a first external electron donor component, under a polymerization temperature of 50-100° C., and controlling the MFR of the polymer obtained within a range of 0.01-0.3 g per 10 min, and the second stage comprises adding, based on the resulting material from the first stage, a second external electron donor component to further carry out the propylene homopolymerization in the presence of hydrogen, and controlling the MFR of the polymer finally obtained within a range of 0.2-10 g per 10 min, and wherein the hydrogen response of the first external electron donor is lower than that of the second external electronic donor.