Catalyst System for Bimodal Olefin Copolymers
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Solution Overview
Problem
Existing catalyst systems struggle to produce bimodal olefin copolymers with controlled molecular weight distributions, leading to poor processing characteristics and difficulty in regulating mechanical properties.
Innovation Solution
A catalyst system comprising a metal complex with a cyclopentadienyl-type ligand and a boron-containing activator, where the molar ratio of boron to metal is greater than 2.5, allowing for the tuning of higher and lower molecular weight components in the polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high molecular weight monomodal olefin copolymers are produced using conventional catalyst systems, then desirable strength and toughness are achieved, but poor processing characteristics result
Solution Approach 1:
The invention segments the polymer molecular weight distribution into two distinct populations (high molecular weight and low molecular weight components) using a single catalyst system with controlled activator-to-metal ratio. This segmentation allows the polymer to simultaneously exhibit the strength and toughness of high molecular weight material while gaining the processability of low molecular weight material, resolving the contradiction between mechanical properties and processing characteristics.
2Manufacturing precision
If multiple reactors or multiple precatalysts/activators are used to produce bimodal polymers, then molecular weight distribution control is improved, but process complexity increases
Solution Approach 1:
The invention merges the functions of multiple catalyst systems or multiple reactors into a single catalyst system comprising a group 4 metal complex with specific ligands and an activator. By controlling the activator-to-metal ratio to be greater than 2.5, the system generates two distinct active site types in situ, achieving bimodal molecular weight distribution control without requiring multiple reactors or complex multi-catalyst procedures, thus simplifying the overall process while maintaining manufacturing precision.
3Reliability
If conventional activation of precatalyst is used, then activation is achieved, but uncontrolled multimodal behavior results from serendipitous generation of multiple active sites
Solution Approach 1:
The invention changes the critical parameter of activator-to-metal ratio to a specific range (greater than 2.5) to control the generation of active sites. This parameter control transforms the serendipitous and uncontrolled multimodal behavior into a controlled and predictable bimodal distribution. The specific ratio ensures reliable activation while precisely controlling the proportions of high and low molecular weight components, resolving the contradiction between activation reliability and manufacturing precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the production of bimodal polymers with enhanced mechanical properties by adjusting the molecular weight distribution, increasing productivity and comonomer affinity, and improving processing characteristics.
Implementation Method 1
a catalyst system for olefin polymerisation comprising: an organometallic complex of a group 4 metal comprising a guanidine ligand, a cyclopentadienyl ligand (preferably substituted); and an activator
Data Source
Figure 1~3
Figure 4
AI summary
A catalyst system comprising a) a metal complex of the formula CyLMZp, wherein M is a group 4 metal Z is an anionic ligand, p is number of 1 to 2, preferably 2 Cy is a cyclopentadienyl-type ligand and, L is a guanidinate ligand of the formula wherein each A is independently selected from the group consisting of nitrogen and phosphorus and R1, R2, R3 and R4 are independently selected from the group consisting of hydrogen, unsubstituted or substituted hydrocarbyl, unsubstituted or substituted silyl and unsubstituted or substituted germyl residues, and b) a boron containing activator, characterized in that the molar ratio of the boron of the activator and M of the metal complex is greater than 2.5.