Ethylene polymer and preparation method thereof

Abstract

The invention relates to an ethylene polymer and a preparation method thereof. The ethylene polymer has an average particle size of 50-3000 [mu] m, a bulk density of 0.28-0.55 g / cm < 3 >, a true density of 0.930-0.980 g / cm < 3 >, a melt index of 0.01-2500 g / 10 min under a load of 2.16 Kg at 190 DEG C, a crystallinity of 30-90%, a melting point of 105-147 DEG C, a comonomer molar insertion rate of 0.01-5 mol%, a weight-average molecular weight of 20,000-400,000 g / mol, and a molecular weight distribution of 1.8-10. In the preparation method, an alkane solvent with a boiling point of 5-55 DEG C or a mixed alkane solvent with saturated vapor pressure of 20-150KPa at 20 DEG C is used as a polymerization solvent, and under the condition that the molar ratio of hydrogen to ethylene is (0.01-20): 1, preferably (0.015-10): 1, and the molar ratio of hydrogen to a comonomer is (8-30): 1, preferably (10-25): 1, the polymerization reaction is carried out for 1-2 hours under the existence of a polyethylene catalytic system. A raw material comprising ethylene, hydrogen and a comonomer is subjected to kettle slurry polymerization to produce an ethylene polymer.

Description

technical field [0001] The invention relates to a high-density ethylene polymer and an ethylene slurry polymerization preparation method for preparing the ethylene polymer. Specifically, the present invention relates to a high-density ethylene copolymer, which uses an alkane solvent with a boiling point of 5-55° C. or a mixed alkane solvent with a saturated vapor pressure of 20-150 KPa at 20° C. as a polymerization solvent. Under the existence of the system, under the condition of ethylene slurry polymerization, the raw material containing ethylene, hydrogen and comonomer is subjected to still-type slurry polymerization to obtain the preparation method of ethylene copolymer. Background technique [0002] The production methods of polyethylene mainly include high-pressure polymerization, gas phase polymerization, slurry polymerization, solution polymerization and other processes and methods. Among them, ethylene slurry polymerization is one of the main methods to produce pol...

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Problems solved by technology

[0005] However, in the existing ethylene stirred tank type slurry polymerization process or polymerization method, as in the ethylene slurry polymerization CX process of Mitsui Chemicals and the Hurst process of Basel Corporation, hexane is the polymerization solvent, in this case , when 1-hexene is used as a comonomer, it is difficult to separate hexane and 1-hexene because of their similar boiling points (the difference is less than 2°C), so the ethylene stirred tank slurry polymerization process or polymerization method using hexane as a solvent Not suitable for polymerization with 1-hexene as a comonomer, which greatly limits the stirred tank slurry polymerization process and the development of high-performance products with 1-hexene as a comonomer

[0006] On the other hand, when ethylene slurry polymerization uses a solvent with a higher boiling point than hexane, such as n-heptane, isoheptane or its isomer solvents, due to the higher boiling point of polymerization, the energy consumption of gasification and condensation is higher. It is not suitable for the heat removal method of gas phase circulation condensation on the existing industrial production equipment, and the polymer powder after filtration or centrifugation has a high solvent content, so the cost of polymerization production and post-treatment drying is relatively high

[0007] In addition, the polymerization pressure of the existing ethylene slurry polymerization process is low, and the presence of hydrogen and comonomer partial pressure leads to low ethylene partial pressure. In addition, when producing high melt index and low density ethylene polymer, polyethylene main catalyst Low activity, large consumption of catalyst, high production cost

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