Binuclear Metallocene Catalysts for Polyolefin Molecular Weight
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Solution Overview
Problem
Current binuclear metallocene catalysts for polyolefin production face challenges in activity and molecular weight capability, particularly for polypropylene, due to alkyl/aryl substitutions in the 3-position, which interfere with polymer chain growth and lead to reduced catalyst performance.
Innovation Solution
Development of binuclear metallocene catalysts with indene linkages in the 4-position, using hydrocarbyl or aromatic linkers, which are symmetric or asymmetric, leading to improved mechanical properties and co-monomer incorporation in ethylene-propylene copolymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If alkyl/aryl substitutions are made in the 3-position of indene ligands, then catalyst structure is modified, but polymer chain growth is interfered with and molecular weight capability is reduced
Solution Approach 1:
The patent removes the problematic alkyl/aryl substitutions from the 3-position of the indene ligands, extracting the harmful structural feature that interferes with polymer chain growth. This allows the catalyst to maintain high molecular weight capability while preserving the beneficial 1,3-position substitution pattern for enhanced activity.
Solution Approach 2:
Instead of adding substitutions to the 3-position to modify catalyst structure, the patent inverts the approach by using unsubstituted 3-positions and placing substitutions at the 1 and 3-positions of the indene ligands. This inversion resolves the steric interference problem while achieving the desired structural modification.
2Productivity
If binuclear metallocene catalysts are designed with 1 or 3-position linkages, then catalyst activity is enhanced, but polypropylene performance deteriorates due to steric interference
Solution Approach 1:
The patent applies different substitution patterns to different positions of the indene ligands: 1,3-disubstitution is used to maintain high catalyst activity, while the 3-position is kept unsubstituted to avoid steric interference with polypropylene chain growth. This local differentiation allows simultaneous optimization of activity and polymer quality.
3Productivity
If substituted indenyl ligands are used in binuclear catalysts, then catalyst activity increases, but molecular weight capability decreases
Solution Approach 1:
The patent segments the indene ligand substitution pattern into two functional zones: the 1-position and 3-position are substituted to provide high catalyst activity, while the 3-position substitution is carefully controlled to avoid steric interference. This segmentation allows the catalyst to achieve both high activity and high molecular weight capability.
Data Source
AI summary
A catalyst compound and process for olefin polymerization. The catalyst can be represented by Formula (I):wherein: M is a transition metal selected from group 3, 4, or 5 of the Periodic Table of Elements; L is a linking group selected from any one or more difunctional C1-C20 hydrocarbyl, aryl or substituted aryl groups; T is an optional bridging group; each X is a univalent anionic ligand, or two Xs are joined and bound to the metal atom to form a metallocycle ring, or two Xs are joined to form a chelating ligand, a diene ligand, or an alkylidene ligand; R1 and R2 are each independently a hydrogen atom or substituted or unsubstituted C1 to C20 hydrocarbyl group; R3, R5, R6 and R7 are each independently a hydrogen atom or a substituted or unsubstituted C1 to C20 hydrocarbyl group, and, optionally, any two of R5, R6, and R7 can be joined to form a cyclic structure; R4 is a substituted or unsubstituted aryl group; and R8, R9, R10, and R11 are each independently a substituted or unsubstituted C1 to C6 hydrocarbyl group and, optionally, R9 and R10 are joined to form a cyclic structure.