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Method for preparing bimodal polyethylene adjustable in molecular weight distribution by use of metallocene system

A molecular weight distribution, bimodal polyethylene technology, applied in the production of bulk chemicals, etc., can solve problems such as the reduction of metallocene catalyst activity, and achieve the effect of effective regulation and wide application

Active Publication Date: 2014-09-24
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There are many kinds of chain transfer agents used in olefin polymerization. Hydrogen is a commonly used chain transfer agent in olefin polymerization, which can be used to adjust the molecular weight and molecular weight distribution of polyolefins. However, its introduction usually leads to a significant decrease in the activity of metallocene catalysts.

Method used

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  • Method for preparing bimodal polyethylene adjustable in molecular weight distribution by use of metallocene system
  • Method for preparing bimodal polyethylene adjustable in molecular weight distribution by use of metallocene system
  • Method for preparing bimodal polyethylene adjustable in molecular weight distribution by use of metallocene system

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] Ethylene polymerization was carried out in a three-neck flask equipped with ethylene gas inlet, electromagnetic stirring and vacuum port. The dry three-necked flask was baked and exhausted, then introduced with ethylene gas, and then vacuumed, and the vacuuming and ventilation operations were repeated three times. Add toluene according to the requirements of the experiment, and start stirring. When the ethylene gas is dissolved and saturated in the toluene solution, add methylalumoxane (MAO) and rac-vinyl bis-indenyl zirconium dichloride (rac-Et(Ind) 2 ZrCl 2 ) The catalyst starts ethylene polymerization, and the total volume of the reaction solution V total = 50ml. The concentration of the metallocene catalyst of rac-vinyl bis-indenyl zirconium dichloride in the reaction solution is 30 μmol / L.

[0031] After the reaction was over, the aeration was stopped, and acidified ethanol was added to terminate the reaction. After the polymer product was filtered and washed, ...

Embodiment 2

[0034] The specific implementation is the same as 1, adding triethylaluminum solution (TEA) in the 15th minute of ethylene polymerization, so that the total volume of the reaction solution V total =50ml, wherein the concentration of the metallocene catalyst of rac-vinyl bis-indenyl zirconium dichloride in the reaction solution was 30 μmol / L, and the reaction was continued. After the reaction was over, the aeration was stopped, and acidified ethanol was added to terminate the reaction. After the polymer product was filtered and washed, it was vacuum-dried and weighed. The molar ratio of each component in the catalyst system is: Zr / Al MAO / TEA (all peers understand) = 1:1000:100.

[0035] The characteristics of the bimodal polyethylene obtained in the experiment are: number average molecular weight (M n ) is 20.08kg / mol, polydispersity index (PDI) is 3.96; Catalyst activity is 1.67 ' 10 6 g PE / (mol.h.atm).

Embodiment 3

[0037] The specific implementation steps are the same as in Example 2, and TEA is added in the 10th minute of ethylene polymerization.

[0038] The ratio of each component of the catalyst system is: Zr / Al MAO / TEA=1 / 1000 / 100. Synthetic polymers are characterized by: number average molecular weight (M n )=11.84kg / mol, PDI=5.24; Catalyst activity: 1.72'10 6 gPE / (mol.h.atm).

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Abstract

The invention discloses a method for preparing a bimodal polyethylene adjustable in molecular weight distribution by use of a metallocene system. The method comprises the following steps: introducing the ethylene gas into a reaction container containing a dry organic solvent without water and oxygen under an electromagnetic stirring condition; after the ethylene gas is in a dissolution saturation state in the organic solvent, firstly adding a cocatalyst to the reaction container, and then adding a metallocene catalyst to start an ethylene polymerization reaction and adding a chain transfer agent to continue the polymerization reaction, and adding enough an acidified ethanol after the total polymerization reaction to terminate the reaction. The method is characterized in that the composition of the product and the molecular weight of the low molecular weight polyethylene can be regulated and controlled by adjusting the addition concentration and the addition time of an alkyl aluminum, and therefore, the bimodal polyethylene different in molecular weight distribution can be prepared; the addition of the alkyl aluminum is capable of improving the catalytic activity of the metallocene.

Description

technical field [0001] The invention relates to a method for preparing bimodal polyethylene, in particular to a method for preparing bimodal polyethylene with adjustable molecular weight distribution by a metallocene system. Background technique [0002] Polyolefin has excellent physical and chemical properties, and is cheap, so it is widely used in many fields such as industry, agriculture, and daily life. When polyethylene is used as a material, high stiffness and strength are often required, and these properties are generally possessed by high molecular weight polyethylene. High molecular weight polyethylene is difficult to process due to its high melt viscosity. Bimodal polyethylene is composed of high-molecular-weight polyethylene and low-molecular-weight polyethylene, and has excellent mechanical properties and processing properties, so its preparation research has received extensive attention. [0003] Bimodal polyethylene can generally be prepared in two ways. The ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F10/02C08F4/6592C08F2/38
CPCY02P20/52
Inventor 赵玉来王立俞豪杰井光辉李超
Owner ZHEJIANG UNIV
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