Multistage polymerization method and device of propylene

Abstract

The invention relates to a multistage polymerization method and device of propylene. After prepolymerization reaction, liquid phase polymerization reaction is conducted and then gas phase polymerization reaction is conducted; and two-step reaction is adopted in the gas phase polymerization reaction, and material composition and reaction systems in two reaction regions are the same or different, sothat molecular weight distribution can be widened. By the method and the device, homo-polypropylene, binary random co-polypropylene, ternary co-polypropylene or impact-resistant co-polypropylene withhigh rubber content can be produced; and the prepared polymer is uniform in particle size distribution, has low volatile organic matter content, wide molecular weight distribution and excellent mechanical property and processing property.

Description

technical field [0001] The invention belongs to the field of polymer material production, and in particular relates to a multi-stage polymerization method and device for propylene. Background technique [0002] In the existing propylene polymerization process, the number of reactors is relatively small, and the difference in monomer composition between each reactor is small. Even in a single reactor operation, the control difference is not obvious, and the mechanical properties and processing properties of the polymer are limited. [0003] When producing impact copolymerized polypropylene, a gas phase reactor must be used. In the existing process, a polymerization process of double horizontal gas phase reactors in series is used. Using this process, although the particle size of the polymer is uniform, it is suitable for the production of impact resistance Copolymerization of polypropylene, however, in this process, limited by the condenser, the content of hydrogen and ethyl...

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Problems solved by technology

[0002] In the existing propylene polymerization process, the number of reactors is relatively small, and the difference in monomer composition between each reactor is small. Even in a single reactor operation, the control difference is not obvious, and the mechanical properties and processability of the polymer are limited.

[0003] When producing impact copolymerized polypropylene, a gas phase reactor must be used. In the existing process, a polymerization process of double horizontal gas phase reactors in series is used. Using this process, although the particle size of the polymer is uniform, it is suitable for the production of impact resistance Copolymerization of polypropylene, however, in this process, limited by the condenser, the content of hydrogen and ethylene in the reactor is not high, and the impact performance and processing fluidity of the polymer are not outstanding;

[0004] Using the polymerization process of two gas-phase fluidized bed reactors in series, the particle size distribution of the produced polymer particles is not uniform, and the impact resistance of impact copolymerized polypropylene is poor.

[0005] Moreover, the catalyst is directly added to the pure gas phase polymerization reactor, and the initial activity of the catalyst is high, which is prone to breakage and local overheating due to uneven dispersion, which affects the long-term operation of the device.

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