A novel linear low-density polyethylene for urea tank and its preparation method

Abstract

The invention provides a novel linear low density polyethylene for urea tank and its preparation method, which is obtained by in-situ polymerization of ethylene under the catalysis of oligomerization catalyst, copolymerization catalyst and co-catalyst, wherein the oligomerization catalyst is supported iron series catalyst, the copolymerization catalyst is a supported zirconium series catalyst, and the cocatalyst is methylaluminoxane MAO. Therefore, it has the characteristics of low melting point, low density and excellent mechanical properties.

Description

technical field [0001] The invention relates to the technical field of polymer materials, in particular to a novel linear low-density polyethylene for urea tanks and a preparation method thereof. Background technique [0002] Vehicle exhaust emissions not only pollute the environment, but also endanger people's health. For this reason, selective catalytic systems are installed on vehicles, which use urea aqueous solution as a reducing agent to convert nitrogen oxides in diesel engine exhaust into nitrogen. A urea tank must be used to store urea aqueous solution. The urea tank is generally made of linear low-density polyethylene (LLDPE) through a rotational molding process. The quality of LLDPE affects the performance of the urea tank. [0003] Catalyst plays an important role in the preparation of LLDPE, which determines the polymerization behavior, polymer particle morphology, polymer structure and properties of LLDPE. In the invention patent of application number CN201010...

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Problems solved by technology

In the invention patent of application number CN201010515021.9, a linear low-density polyethylene is introduced, which uses ethylene as raw material, pyridine bis-imine iron and cobalt complexes as oligomerization catalyst main catalyst, and β-diimine titanium The complex is the main catalyst of the copolymerization catalyst, and the main group metal organic compound is the only co-catalyst, forming a bifunctional catalyst system, which is obtained by in-situ copolymerization in one pot. It does not need to add expensive α-olefins, which simplifies the production process; The preparation method of the main catalyst is simple, the reaction conditions are mild, and the cost of the catalyst is low; using a single co-catalyst, there is no mutual interference between the bifunctional catalysts, and the amount of co-catalyst is small; the catalytic activity of ethylene polymerization is high, but the catalyst is in the early stage of the reaction. The high activity is difficult to control, and there is a serious sticking phenomenon, which is not conducive to industrial application

In the invention patent of application number CN200510086486.6, a catalyst system for preparing linear low-density polyethylene by in-situ copolymerization is introduced. Alkyl aluminoxane co-catalyst) and copolymerization catalyst (titanium catalyst and alkyl aluminum or alkyl aluminoxane co-catalyst), the linear low density polyethylene catalyzed by it has low melting point, low density, high co-unit However, the LLDPE produced by this catalytic system does not have excellent mechanical properties, which affects its practical application.

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