C1-Symmetric Metallocene Catalysts for Comonomer-Tolerant Polypropylene
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Solution Overview
Problem
Conventional catalyst systems for producing isotactic polypropylene suffer from deactivation in the presence of higher alpha olefins and dienes, leading to insufficient melt strength and increased production costs due to the need for post-reactor modifications and separation of racemic isomers.
Innovation Solution
The use of asymmetric bridged metallocenes containing indacenyl ligands in catalyst systems that tolerate higher alpha olefins and dienes, enabling in-reactor production of high molecular weight, high melting point, and long chain branched propylene polymers without the need for post-polymerization processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalyst systems are used to produce isotactic polypropylene, then high crystallinity and high molecular weight can be achieved, but the catalysts suffer from deactivation in the presence of higher alpha olefins and higher dienes
Solution Approach 1:
The patent employs C1-symmetric (asymmetric) metallocene catalysts instead of conventional C2-symmetric racemic catalysts. The asymmetric structure of the catalyst allows for differentiated interaction with propylene and comonomers, enabling the catalyst to maintain high activity while tolerating higher concentrations of alpha olefins and dienes without deactivation. This structural asymmetry resolves the contradiction by allowing the catalyst to be both reliable and adaptable to various comonomers simultaneously.
2Strength
If conventional catalyst systems are used, then production costs increase due to the need for separation of racemic isomers and post-reactor modifications, but the polymer produced has insufficient melt strength
Solution Approach 1:
The patent implements in-reactor production of long chain branched propylene polymers with high melt strength directly during the polymerization process. By using C1-symmetric metallocene catalysts that can incorporate dienes and alpha olefins during polymerization, the desired polymer structure and properties are achieved in the reactor itself, eliminating the need for subsequent post-reactor modification steps and costly separation processes. This preliminary action resolves the contradiction by achieving both high melt strength and cost-effectiveness simultaneously.
Solution Approach 2:
The patent merges the functions of polymerization, branching, and property enhancement into a single reactor process. The C1-symmetric metallocene catalyst system simultaneously performs propylene polymerization, incorporates comonomers to create branches, and produces the final high melt strength polymer product in one operation. This consolidation eliminates separate post-reactor modification steps and reduces overall production costs while achieving the desired strength properties.
3Strength
If post-reactor modifications are performed to increase branching and melt strength, then the polymer properties improve, but the production costs increase
Solution Approach 1:
The patent performs the branching and melt strength enhancement actions during the polymerization process itself rather than as subsequent post-reactor modifications. The C1-symmetric metallocene catalyst system incorporates dienes and alpha olefins during polymerization to create long chain branched structures with high melt strength, eliminating the need for time-consuming post-reactor modification steps. This preliminary action resolves the contradiction by achieving both improved polymer properties and reduced production time simultaneously.
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
The catalyst systems achieve high activity and comonomer incorporation, producing polymers with enhanced properties suitable for applications like foams and blown films, while reducing production costs by eliminating the need for post-reactor modifications.
Implementation Method 1
catalyst systems for the polymerization of olefins... catalyst compounds comprising asymmetric bridged metallocenes... catalyst systems including such
Data Source
AI summary
The present disclosure provides catalyst compounds comprising asymmetric bridged metallocenes containing a ligand having at least one saturated ring, catalyst systems including such compounds, and uses thereof. Catalyst compounds of the present disclosure can include indacenyl-type ligands. In another class of embodiments, the present disclosure is directed to polymerization processes to produce polyolefin polymers from catalyst systems including one or more olefin polymerization catalysts, at least one activator, and an optional support.