Propylene polymer and preparation method thereof

Abstract

The present invention discloses a propylene polymer and a preparation method thereof. The method is as follows: under olefin polymerization conditions, in the presence of a catalyst, propylene or a mixture of propylene and ethylene and / or an alpha-olefin selected from C4-C8 are polymerized, the catalyst comprises a solid component, an alkyl aluminum compound and an optional external electron donor compound, the solid component comprises the following reaction product components: (i) a magnesium-containing compound; (ii) a titanium-containing compound; and (iii) an internal electron donor; wherein the internal electron donor is a combination of an internal electron donor compound a, an internal electron donor compound b and an internal electron donor compound c, the internal electron donor compound a is a diol ester compound of formula I, the internal electron donor compound b is a diether compound of formula II, and the internal electron donor compound c is an alkylene oxide compound of formula III. The propylene polymer prepared by the preparation method has high isotactic index and low ash content.

Description

technical field [0001] The invention relates to a propylene polymer and a preparation method thereof. Background technique [0002] It is well known that solid titanium-based catalyst components based on magnesium, titanium, halogen and electron donor compounds are used for olefin polymerization, especially for propylene polymerization, with high polymerization activity and stereospecificity. Among them, the electron donor compound is one of the essential components in the catalyst components, which plays a decisive role in important indicators such as polymerization activity, polymer isotactic index, molecular weight and molecular weight distribution. With the development of internal electron donor compounds, polyolefin catalysts are constantly updated. [0003] Catalysts with different internal electron donors have different characteristics, for example, some catalysts have higher polymerization activity, some catalysts have better hydrogen sensitivity, and some catalysts...

AI Technical Summary

Problems solved by technology

High ash content in polypropylene may cause the following defects: (1) easy fouling or even blockage in processing equipment, such as extrusion lines for film making and boards, production lines for fibers or non-woven fabrics; (2) affect the quality of products Strength, electrical properties, etc.: For example, fiber-grade polypropylene resin (PP resin) usually requires the mass fraction of ash to be below 0.0100%, and the ash mass fraction of PP resin for capacitors is usually required to be less than 0.0050%, preferably below 0.0030%; (3 ) affect the downstream production process

However, the effect of compounding is not a simple superposition of the properties of several electron donors.

For example, the isotacticity of polypropylene generally obtained from catalysts using monocarboxylic acid esters as internal electron donors is low, and the product needs to remove random substances.

And WO03002617 discloses a catalyst component and a catalyst for olefin polymerization obtained by using a monocarboxylic acid ester and a dicarboxylic acid ester in combination. The hydrogen adjustment sensitivity of the catalyst is good, but the stereospecificity and polymerization activity are still not very high

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