Catalyst system for preparing broad-peak/dimodal polyethylene in single reactor

Abstract

The invention relates to a catalyst system for preparing broad-peak / dimodal polyethylene in a single reactor, wherein the catalyst system belongs to a polymerization catalyst which is used for the macromolecular compound preparation and is obtained only through a carbon-carbon unsaturated bond reaction. The catalyst system is characterized in that the catalyst comprises a main catalyst and an assistant catalyst, wherein the main catalyst comprises a component a or a component b; the component a is a transition metal-containing complex with the molecular formula of R1R2R3MX, R1 is selected from C1-20 alkyl, R2 is selected from C1-20 alkoxy, R3 is selected from C1-20 aryl or arlyoxy, M is Ti or Zr, and X is a halogen atom; the component b is a transition metal compound with the general formula of MXn or MXn(OR)4-n, M is a transition metal Ti or Zr, X is halogen, and n is between 1 and 4; and the assistant catalyst is methyl siloxane (MAO) or triethyl aluminum (TEAL). The catalyst system for preparing broad-peak / dimodal polyethylene in the single reactor provided in the invention has the advantages of easily controlled production technology, realization of the obtaining of broad-peak / dimodal polyethylene resin products with uniform molecular weight distribution, saved investment of equipment for the polyethylene production, and low production cost.

Description

technical field [0001] The present invention is a catalyst system for the production of broad / bimodal polyethylene in a single reactor. It belongs to the polymerization catalyst for the preparation of polymer compounds obtained only by the reaction of carbon-carbon unsaturated bonds. Background technique [0002] There are three main production methods for producing polyethylene resins with broad molecular weight or bimodal molecular weight distribution: melt blending method, multi-reactor method, and single-reactor method. The melt blending method is to produce polymers with relatively large molecular weight and relatively small molecular weight in parallel reactors, and then melt blend them in proportion to control the molecular weight distribution of the polymers. The main disadvantage of this method is that the mixture is difficult to mix evenly, the content of gel particles is high, and the product quality is difficult to be uniform. The multi-reactor method uses two ...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that the catalyst activity is low

The polyethylene prepared with this catalyst has bimodal or trimodal molecular weight distribution, and the melt flow rate is 20-70. The disadvantage is that the molecular weight distribution is narrow

The melt flow ratio of polyethylene products obtained by this method is about 20-45, the disadvantage is that the melt flow ratio is low and the molecular weight distribution is narrow

The Ziegler-Natta catalyst is difficult to control the physical properties of the synthesized polymer, and the activity is much lower than that of the metallocene catalyst, and the problem with the metallocene catalyst system is that the ratio of the alkylaluminoxane cocatalyst to the metallocene is high, and the use of metallocene Catalyst-produced polymers are difficult to handle and lack many desirable physical properties due to a single identical polymerization site

It is difficult to obtain polyethylene products with uniform molecular weight distribution, which in turn affects the quality of polyethylene products

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