catalyst

Abstract

A catalyst in solid particulate form free from an external carrier material comprising(i) a complex of formula (I)whereinM is zirconium or hafnium;each X is a sigma ligand;L is a divalent bridge selected from —R′2C—, —R′2C—CR′2—, —R′2Si—, —R′2Si—SiR′2—, —R′2Ge—, wherein each R′ is independently a hydrogen atom, C1-20-alkyl, tri(C1-20-alkyl)silyl, C6-20-aryl, C7-20-arylalkyl or C7-20-alkylaryl;R2 is a C1-20-hydrocarbyl radical;R2′ is a C1-20-hydrocarbyl radical;R6 is a linear or branched aliphatic C1-20-hydrocarbyl group, SR9 or OR9;R6′ is a linear or branched aliphatic C1-20-hydrocarbyl group, SR9′ or OR9′;with the proviso that neither R6 or R6′ represents a group having a quaternary carbon atom directly attached to the indenyl ring;R9 is a C1-20-hydrocarbyl group;R9′ is a C1-20-hydrocarbyl group;Ar is a C6-12-aryl or C5-12-heteroaryl group optionally carrying one or more substituents R8;Ar′ is a C6-12-aryl or C5-12-heteroaryl group optionally carrying one or more substituents R8′;each R8 is a C1-20-hydrocarbyl group;each R8′ is a C1-20-hydrocarbyl group; andwherein at least two of R2 and R2′; R6 and R6′; or Ar and Ar′ are the same;and (ii) a cocatalyst comprising a compound of a group 13 metal, e.g. Al or boron.

Description

FIELD OF INVENTION[0001]This invention relates to new bisindenyl catalysts, in particular, solid particulate racemic symmetrical metallocene catalysts containing such bisindenyl ligands. The invention also relates to the use of such new bisindenyl metallocene catalysts for the production of polypropylene at excellent catalyst activities to give polypropylene with high molecular weight, and high melting point even at industrially relevant polymerization temperatures.BACKGROUND OF INVENTION[0002]Metallocene catalysts have been used to manufacture polyolefins for many years. Countless academic and patent publications describe the use of these catalysts in olefin polymerisation. Metallocenes are now used industrially and polyethylenes and polypropylenes in particular are often produced using cyclopentadienyl based catalyst systems with different substitution patterns.[0003]The two most important physical properties of isotactic polypropylene (iPP) are its average molecular weight and it...

AI Technical Summary

Benefits of technology

The invention provides a new catalyst for olefin polymerization that is solid in form without an external carrier material. The catalyst includes a complex of formula (I) and a cocatalyst of formula (III). The catalyst is obtained by a process involving the formation of a liquid / liquid emulsion system and solidification of the dispersed droplets. The use of this new catalyst results in improved polymerization efficiency and the production of isotactic polypropylene with a melting point of at least 152°C.

Problems solved by technology

When the polymerization temperature is increased to 30° C., the melting point of the resulting polypropylene decreases to 158° C. A polymerization temperature of −30° C. is however, far too low for polypropylene manufacturing in commercial plants, which need to be operated above 60° C. When used at industrially useful polymerization temperatures, this same metallocene yields low molecular weight polypropylenes with relatively low melting point.

One of the limitations of metallocene catalysts for polypropylene is the relative low melting of the homopolymer.

However, often the increased melting point is obtained at the expense of activity, or catalyst cost, or both.

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