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Method for preparing double-peak or broad-peak polyethylene with adjustable molecular weight

A technology of molecular weight and polyethylene, applied in the field of preparation of polyethylene with adjustable molecular weight bimodal or broad-peak distribution, can solve the problems of high catalyst requirements, difficult to control product quality uniformity, and high cost

Active Publication Date: 2012-03-21
ZHEJIANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The first method uses parallel reactors. The resins in the two reactors have different molecular weights and are blended in a molten state according to a certain ratio. The cost of this method is high, and the uniformity of product quality is difficult to control
The second method uses reactors in series to generate polymers with different molecular weights in different reactors. This method is flexible in operation and easy to switch products, but the cost is high
The process cost of this method is relatively low, but the requirements for the catalyst are relatively high, and the development cycle of the catalyst is long

Method used

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  • Method for preparing double-peak or broad-peak polyethylene with adjustable molecular weight
  • Method for preparing double-peak or broad-peak polyethylene with adjustable molecular weight
  • Method for preparing double-peak or broad-peak polyethylene with adjustable molecular weight

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Effect test

Embodiment 1

[0019] Firstly, the reactor was replaced with nitrogen three times at a high temperature of 100°C, and then replaced with ethylene three times. Then, 250 ml of anhydrous and oxygen-free toluene was added under an ethylene atmosphere, and stirring was started. The stirring rate was 600 rpm, and the temperature was controlled at At 25 °C, the pressure was controlled at 0.1 MPa, 10 mmol of methylaluminoxane was added, and 5 μmol of bis(3-methylsalicylidene-pentafluorophenylphenylimine) titanium dichloride was added for polymerization. When the reaction lasted for 1 minute, 900 μmol of diethylzinc was added, the reaction was continued for 15 minutes, and 4 ml of acidified ethanol was added to terminate the reaction. GPC method measures the molecular weight distribution of sample, and the results are shown in attached table 1.

Embodiment 2

[0021] Firstly, the reactor was replaced with nitrogen three times at a high temperature of 100°C, and then replaced with ethylene three times. Then, 250 ml of anhydrous and oxygen-free toluene was added under an ethylene atmosphere, and stirring was started. The stirring rate was 600 rpm, and the temperature was controlled at At 25 °C, the pressure was controlled at 0.1 MPa, 10 mmol of methylaluminoxane was added, and 5 μmol of bis(3-methylsalicylidene-pentafluorophenylphenylimine) titanium dichloride was added for polymerization. When the reaction lasted for 5 minutes, 900 μmol of diethylzinc was added, the reaction was continued for 15 minutes, and 4 ml of acidified ethanol was added to terminate the reaction. GPC method measures the molecular weight distribution of sample, and the results are shown in attached table 1.

Embodiment 3

[0023] Firstly, the reactor was replaced with nitrogen three times at a high temperature of 100°C, and then replaced with ethylene three times. Then, 250 ml of anhydrous and oxygen-free toluene was added under an ethylene atmosphere, and stirring was started. The stirring rate was 600 rpm, and the temperature was controlled at At 25 °C, the pressure was controlled at 0.1 MPa, 10 mmol of methylaluminoxane was added, and 5 μmol of bis(3-methylsalicylidene-pentafluorophenylphenylimine) titanium dichloride was added for polymerization. When the reaction lasted for 1 minute, 450 μmol of diethylzinc was added, the reaction was continued for 15 minutes, and 6 ml of acidified ethanol was added to terminate the reaction. GPC method measures the molecular weight distribution of sample, and the results are shown in attached table 1.

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Abstract

The invention discloses a method for preparing double-peak or broad-peak polyethylene with adjustable molecular weight. The method comprises the following steps of: replacing a reactor with nitrogen for 3 to 4 times at the high temperature of 100 DEG C to 150 DEG C; replacing the reactor with ethylene for 3 to 4 times; adding 100-50ml of anhydrous and oxygen-free organic solvent in ethylene atmosphere and stirring, wherein the stirring rate is 400-1000 rpm, the temperature is controlled to be at 0 DEG C to 150 DEG C, and the pressure is controlled to be at 0.1MPa to 10.0MPa; adding 0.01mmol to 100mmol of cocatalysts; adding 5mumol to 20mumol of main catalysts for polymerization reaction; after reacting for 1 to 30minutes, adding 100mumol to 2000mumol of chain transfer agents for continuous reaction for 10 to 20 minutes; and adding 4ml to 10ml of acidified ethanol for termination reaction. In the method for preparing the double-peak or broad-peak polyethylene with adjustable molecular weight, a piecewise polymerization process is adopted, and two peak values in a molecular weight distribution curve of the obtained double-peak polyethylene or the molecular weight size and the distribution of the obtained broad-peak polyethylene are adjusted by adjusting the feeding time of the chain transfer agent and / or adjusting the stoichiometric ratio of the chain transfer agents to the cocatalysts.

Description

technical field [0001] The invention relates to a preparation method of bimodal or broad-modal distribution polyethylene with adjustable molecular weight. Background technique [0002] The polyethylene resin with unimodal narrow distribution of molecular weight often has contradictory mechanical properties and processability. Increasing the molecular weight of polyethylene can enhance its mechanical properties, such as toughness, cracking strength, etc., but it will also make its processing performance worse. The polyethylene with bimodal or broad molecular weight distribution can just balance these two properties. The high molecular weight part can ensure its good mechanical properties, and the low molecular weight part can improve its processing performance. At present, there are three main production methods of bimodal polyethylene. The first method uses parallel reactors. The resins in the two reactors have different molecular weights and are blended in a molten state ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C08F10/02C08F2/38C08F4/659
Inventor 李伯耿刘伟峰范宏郭松王轶
Owner ZHEJIANG UNIV
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