Method for preparing polypropylene through body prepolymerization

Abstract

The invention discloses a method for preparing polypropylene through body prepolymerization. The method comprises the following steps: performing a prepolymerization reaction, namely, performing liquid-phase body copolymerization process of propylene and alpha olefin by taking Ziegler-Natta as a main catalyst so as to obtain a pre-polymer, wherein the mole ratio of the main catalyst, namely, a Ti metal, to the pre-polymer is 1:10; performing a polymerization reaction on a liquid-phase body+gas-phase fluidized bed multi-stage polymerization process device. According to the method disclosed by the invention, on the conventional basis that the prepolymerization reaction is independently implemented on a propylene monomer, ethylene is added to join in the prepolymerization reaction, the purpose of improving the strength and the pore volumes and pore gaps of catalyst granules can be achieved by controlling the ratio of the propylene to the ethylene in the pre-polymer, a copolymerization reaction base chain structure can be optimized, properties of an atactic copolymer can be finally improved, and the improvement lies to improvement of creep resistance of polypropylene of tubes, light transmittance of atactic transparent PP (Polypropylene), and the like.

Description

technical field [0001] The invention belongs to the field of polymer chemical industry, and in particular relates to a method for improving the polymerization effect of propylene and obtaining high-performance polypropylene products through prepolymerization. Background technique [0002] As the production and application of polypropylene become more and more extensive, the research on the polymerization process of its catalytic system and the processing and application of polymerization products has been deeply excavated. At present, the Z-N catalyst commonly used in industrial polypropylene production mainly consists of three components. The catalyst system for propylene polymerization is prepared during production. Generally speaking, the specific preparation of each production process is different, but it can be roughly divided into two methods: one is the catalyst preparation method of Mitsui Oil & Chemical; the other is the ring catalyst system. The catalyst preparatio...

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Problems solved by technology

[0011] The Institute of Resin Research Institute of Sinopec Yangzi Petrochemical Company conducted a comparative study on the catalyst preparation method of Mitsui's HYPOL production process and the current complexation method. The complexation is insufficient, the electron donor first contacts with the pre-polymerized catalyst, the fluctuation of the amount of the electron donor and the impurities in it have a negative impact on the Ti catalyst, and in addition, the amount of OF added in the actual polymerization of the industrial device is relatively large, which intensifies the Decrease in catalyst activity and adversely affect production and product quality

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