Propylene polymer production method

Abstract

The invention relates to a propylene polymer production method which comprises the following steps: i) prepolymerization, namely prepolymerizing propylene in the presence of a catalyst to obtain a propylene prepolymer; and ii) polymerization in multiple temperature zones, namely introducing the propylene prepolymer obtained in step i) and propylene (or alpha-olefin containing propylene) together into one polymerization reactor or more polymerization reactors connected in series, introducing hydrogen into the polymerization reactor(s), and performing propylene homopolymerization or propylene and alpha-olefin copolymerization to obtain a propylene polymer. At least two continuous reaction zones exist, different reaction zones have different reaction temperatures, and the reaction temperatures are selected from 50-150 DEG C and preferably selected from 60-130 DEG C; and at least one high-temperature reaction zone exists among the reaction zones, and the reaction temperature of the high-temperature reaction zone is selected from 70-150 DEG C and preferably selected from 80-130 DEG C.

Description

technical field [0001] The invention belongs to the technical field of propylene polymer production, and in particular relates to a method for producing propylene homopolymers and copolymers by adopting gas-phase multi-temperature zone technology, and using the method for in-situ regulation of the properties of propylene polymers. Background technique [0002] Processes for the manufacture of propylene polymers are well known and include solvent processes, bulk processes, and the more efficient gas phase process. The gas phase polymerization process includes horizontal and vertical stirring sub-fluidized bed reactors, fluidized bed reactors and multi-zone circulation reactors. At present, the production equipment of the Inovene process technology adopted in China is basically a horizontal tank with a single reactor or a series of double reactors. For a single reactor, when producing random copolymer products, due to the small content of crystalline polypropylene segments, h...

AI Technical Summary

Problems solved by technology

However, when using hydrogen to adjust the molecular weight of the polymer, there is a certain limit to the increase of the hydrogen concentration in the reactor. For example, in the liquid phase propylene polymerization process, when the hydrogen concentration in the reactor is too high, bubbles are likely to be generated, which will affect the device. Stability and safety of operation; another example is in the gas-phase propylene polymerization process, when the hydrogen content is too high, the non-condensable gas components increase, which makes the heat transfer effect of the system worse, and reduces the dew point of the circulating gas, which leads to the circulation Significantly increased energy consumption during air cooling / condensing

In addition, the addition of a large amount of hydrogen has other obvious disadvantages: the catalyst activity is greatly reduced, and the stereoregularity of the polymer is reduced.

Chinese patent CN200980157329.6 also produces products with a wide molecular weight distribution by changing the hydrogen content of different polymerization zones. The temperature difference between the polymerization zones is not wide enough, so it has little effect on the regulation of product performance, and the molecular weight regulation is still mainly based on the hydrogen content

[0014] In summary, there are many shortcomings and deficiencies in the prior art methods for producing propylene polymers, which cannot solve the problems in actual production and improve the drawbacks in the prior art

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