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Method for preparing polypropylene with high melt strength

A high melt strength, polypropylene technology, applied in the field of propylene polymerization, can solve the problems of low hydrogen susceptibility, molecular weight can not be done, affect the mechanical properties of products, etc., and achieve high performance.

Active Publication Date: 2013-12-04
CHINA PETROLEUM & CHEM CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, there are great limitations in such a method. When using an external electron donor with lower hydrogen modulation sensitivity in the catalyst system, although it is possible to make the molecular weight of the polymer higher when producing a higher molecular weight fraction, the When producing lower molecular weight fractions, due to the insensitivity to hydrogen adjustment, a very high hydrogen content is required to meet the actual requirements
However, when an external electron donor with high hydrogen tuning sensitivity is used in the catalyst system, although the amount of hydrogen used to produce lower molecular weight fractions is less, the molecular weight cannot be sufficient when producing higher molecular weight fractions. Large, thus affecting the mechanical properties of the final product

Method used

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  • Method for preparing polypropylene with high melt strength
  • Method for preparing polypropylene with high melt strength
  • Method for preparing polypropylene with high melt strength

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0056] The polymerization reaction was carried out on a polypropylene pilot plant. Its main equipment includes prepolymerization reactor, first loop reactor and second loop reactor. Polymerization method and steps are as follows:

[0057] (1) Prepolymerization reaction:

[0058] The main catalyst (titanium-containing solid catalyst active component) is obtained by the method described in Example 1 of Chinese Patent CN93102795, its Ti content: 2.4wt%, Mg content 18.0wt%, di-n-butyl phthalate content: 13wt %.

[0059]The main catalyst, co-catalyst (triethylaluminum), and the first external electron donor (dicyclopentyldimethoxysilane, DCPMS) were pre-contacted at 10°C for 20 minutes, and then continuously added to the pre-polymerization reactor for pre-polymerization. In the polymerization reactor, the pre-polymerization is carried out in the environment of the propylene liquid phase body, the temperature is 15°C, and the residence time is about 4 minutes. Under this conditio...

Embodiment 2

[0068] Same as Example 1, except that a small amount of hydrogen is added to the make-up propylene feed of the first loop reactor, and the hydrogen concentration detected by online chromatography is 230 ppmV. The hydrogen feed amount in the make-up propylene feed to the second loop reactor was adjusted to 8500 ppmV. By adjusting the feed amount of the external electron donor, the Al / Si-I was adjusted to 45 (weight ratio), and the Al / Si-II was adjusted to 4.2 (weight ratio). The addition amount of cocatalyst triethylaluminum is unchanged.

Embodiment 3

[0070] Same as Example 2, except that the Al / Si-I is adjusted to 85 (weight ratio) by adjusting the feed amount of the external electron donor. The addition amount of cocatalyst triethylaluminum is unchanged. .

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Abstract

The invention provides a method for preparing polypropylene with high melt strength by using a direct polymerization method. By the method, the polypropylene with wide molecular weight distribution and extremely high molecular weight fraction is prepared by controlling the variety and proportion of external electron donor components in a Ziegler-Natta catalyst system according to the different molecular weight fraction requirements in different propylene polymerization stages of cascade operations. The polypropylene has good mechanical property, and especially has high melt strength.

Description

technical field [0001] The present invention relates to a process for the polymerization of propylene, and more particularly to a multi-step propylene polymerization process for preparing polypropylene with high melt strength. technical background [0002] The main factor affecting the melt strength of polypropylene is the structure of the polymer molecule, including molecular weight, molecular weight distribution, whether there are long chain branches on the molecular chain, the length and distribution of long chain branches, etc. Generally, the larger the average molecular weight of the propylene polymer, the greater its melt strength, but the larger the molecular weight, the more unfavorable the post-processing performance of polypropylene. Therefore, considering the practical application of materials, it is necessary to make polypropylene have a wider molecular weight distribution. In addition, producing long-chain branched structures in polypropylene molecular chains ca...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C08F110/06C08F4/646C08F2/34C08F2/04
Inventor 宋文波张师军郭梅芳魏文骏于鲁强胡慧杰于佩潜张晓萌
Owner CHINA PETROLEUM & CHEM CORP